Biomass Gasification: A Comprehensive Demonstration of a ...

Biomass Gasification: A Comprehensive Demonstration of a Community Scale Biomass Energy System

Final Report

USDA Rural Development Grant 68-3A75-5-232

Section I: Project Report Contents Authors & Contributors .................................................................................................................................... i Executive Summary ......................................................................................................................................... 1 Chapter 1: Biomass Gasification at UMM: An Historical Overview ................................................................. 3 Chapter 2: Design in Response to the University’s Objectives and the Technology Market.......................... 9 1 Campus Characteristics .......................................................................................................................... 9 2 Natural Resources .................................................................................................................................. 9 3 Regulation ............................................................................................................................................ 10 4 Equipment............................................................................................................................................ 10 5 Strategy ................................................................................................................................................ 11 6 Planning ............................................................................................................................................... 12 7 Implementation ................................................................................................................................... 13 8 Moving the Plant From Design to Operational .................................................................................... 14 9 Construction......................................................................................................................................... 18 10 Energy Density ..................................................................................................................................... 19 11 Alkalinity .............................................................................................................................................. 20 12 Moisture............................................................................................................................................... 21 13 The Roadmap ....................................................................................................................................... 22 Chapter 3: Report on Feedstock Testing and Biomass Testing Activities ...................................................... 23 1 Preproject Testing at Carterville, IL ...................................................................................................... 23 2 Summary of Initial Findings.................................................................................................................. 23 3 Emissions Summary ............................................................................................................................. 24 4 Conclusion............................................................................................................................................ 26 5 Appendix .............................................................................................................................................. 30 Chapter 4: Report on MPCA Coordination .................................................................................................... 47 1 Preproject Testing................................................................................................................................ 47 2 Permitting Process and Procedures ..................................................................................................... 47 3 MPCA Process and Requirements........................................................................................................ 49 4 Performance Testing............................................................................................................................ 50 5 Option D Permittees ............................................................................................................................ 51 6 Reporting and Recordkeeping ............................................................................................................. 51 7 New Source Performance Standards (NSPS, 40CFR60, Subpart Dc) .................................................... 52 8 Continuous Emission Monitors (CEMS) ............................................................................................... 53 9 CEMS Recordkeeping/Ongoing Operations ......................................................................................... 54 10 Appendix .............................................................................................................................................. 55 Chapter 5: Report on Outreach Deliverables ................................................................................................ 63 1 Biomass Gasification Project Outreach and Education - Summary ..................................................... 63 2 Gasification in the Classroom .............................................................................................................. 64 3 Community Outreach........................................................................................................................... 68 4 Tours .................................................................................................................................................... 68 5 Conference Presentations.................................................................................................................... 68 6 Web Outreach...................................................................................................................................... 70 7 Outreach Deliverables Appendices ...................................................................................................... 71 Glossary…………………………………………………………………………………………………………………………………………………..82 Acronym Quick Reference List ………………………………………………………………………………………………………………..87

Authors & Contributors Executive Summary Lowell Rasmussen Chapter 1:

Biomass Gasification at UMM: A Historical Overview David Aronson

Chapter 2:

Design in Response to the University’s Objectives and the Technology Market Hammel, Green and Abrahamson, Project Engineers: Chapters 1 through 7 Lowell Rasmussen, Project Investigator (PI): Chapters 8 through 13

Chapter 3:

Report on Feedstock Testing and Biomass Testing Activities James Barbour Jane Johnson Matt Zaske Tina Didreckson Joel Tallaksen

Chapter 4:

Report on MN Pollution Control Agency Coordination James Barbour Tina Didreckson David Bordson Mike Vangstad Joel Tallaksen

Chapter 5:

Report on Outreach Deliverables Lowell Rasmussen James Barbour Mike Reese Joel Tallaksen

Project Team The work described in this report is from a collaborative effort of scientists, educators and facilities people. The authors would like to thank them and make sure that recognition is given to the team as a whole for its work. Lowell Rasmussen Michael Reese Dr. Jane Johnson Mike Vangstad Dave Aronson Dr. Joel Tallaksen Dr. James Barbour Matt Zaske Tina Didreckson

Cover Image Photo Credits: Clockwise from top left- Amy Rager, Joel Tallaksen, Matt Zaske

Biomass Gasification: A Comprehensive Demonstration of a Community Scale Biomass Energy System USDA Final Report

Executive Summary I am pleased to submit the final report for the Biomass Gasification: A Comprehensive Demonstration of a Community Scale Biomass Energy System. The following report is the summation of a three-year grant that was extended two years to allow the research to follow due process and the University to identify and address the issues associated with designing, building, and operating a state-of-the-art research and community-scale production facility. This report is a conclusion of the efforts to understand how a community can develop its own energy ecosystem. The grant turned out to be the catalyst that brought together the natural and human resources in a community setting to accomplish a vision of what a sustainable community might look like. The human resources aggregated in a college campus—the University of Minnesota, Morris, a university agricultural research center—the West Central Research and Outreach Center (WCROC), an agricultural research station—the North Central Soils Conservation Research Laboratory,and the University of Minnesota Initiative on Renewable Energy and the Environment (IREE), combined with a community with robust natural resources in the form of biomass and agricultural production, proved to be an alliance that simply could overcome the obstacles that faced the establishment of a community-scale gasification system. The narratives and data provided in this report accurately reflect the learning curves required and the processes that needed to be established and solved to bring this project to a successful conclusion. The scope of the project is unique as it encompasses everything from initial concepts through the final commissioning. It provides insight from designers, contractors, researchers, educators, managers, and operators. Each element required the grant team to address their unique perspectives and factor these into the final outcomes. It is the hallmark of this project to understand the cradle to grave implications of biomass as an alternative energy stream. A team effort was undertaken to understand the role of carbon, soil chemistry, plant physiology, plant production, nutrient analysis, agricultural cropping practices, harvesting options, economic analysis, collection and transportation, storage, thermal conversion platforms, material handling, energy production and combined heat and power options, emissions characteristics, outreach and undergraduate research and educational opportunities. This work was done in a rural community setting with the understanding that biomass was one of the most underrepresented sources of energy in the region. The project embodies Strategic Asset Allocation—with a goal to create an asset mix that will provide the optimal balance between expected risk and return for a long-term investment. The risk identified in this project was the unstable pricing of traditional fuel. The asset was the large supply of nontraditional carbon production associated with agricultural cropping systems. The balance was to try to find the right thermal conversion processes to utilize the nontraditional carbon in a way that provides usable energy in conventional power plant configurations.

Executive Summary

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The research was to identify the sustainable best practices to insure that biomass energy solutions did not just move us from one unsustainable fuel source to another. The challenges were numerous and complex. Designing and building a production scale research plant immediately created a constant dialog about how to be able to meet the deliverables of two functions that had quite different expectations. The first section of this report is focused on the planning, design, construction and commissioning of this plant. The second section is the toolbox for biomass development. Both sections offer insight into the strategic and real world development of a state-of-the-art combined heat and power plant as well as the research on previously untested biomass fuel sources in a production-scale setting. The budget was a constant source of concern with the dual outcomes as a necessary prerequisite for the success of the plant. The lack of data to understand how high mineral content biofuels could be converted to heat energy was a significant challenge. The lack of industry experience in these fuels compounded challenges of the selection process. The contractors were leery of building “serial number one.” The University of Minnesota struggled with project delivery methods. Fuel moisture content, storage, density, material handling, thermal properties, alkalinity, and ash characteristics all impacted how the project developed over the grant period. In retrospect, given the hurdles in bringing this project to closure, it’s doubtful that private enterprise would have been able, or could have afforded, to draw on the amount and number of resources and researchers that were required and available in a large public land grant university to address the issues as they were discovered. The combination of a forward looking community, a USDA grant with a public land grant university, and a robust agricultural resource was the right combination to push the envelope of understanding in rethinking how biomass can become simply a different form of our traditional carbon based fuel infrastructure. Understanding how biomass fits in rural communities is the end deliverable of this project. We are happy to say that we think there are many opportunities for the deployment of this technology that meets the triple bottom line—local energy, local jobs, local economy. On behalf of a dedicated team of researchers, technicians, engineers, contractors, and plant personnel, I am pleased to submit the final report. Lowell Rasmussen

Executive Summary

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Chapter 1: Biomass Gasification at UMM: A Historical Overview Administrators’ at the University of Minnesota, Morris (UMM) and the West Central Research and Outreach Center (WCROC) of the University of Minnesota began informal discussions relating to energy around the year 2000. UMM facilities management was concerned with the increasing costs of natural gas and also the environmental impact of continued expansion of the use of oil, coal and natural gas. Discussion began on what alternate forms of energy might be available within the natural resources of western Minnesota, have a more positive impact on the environment and support the growth of agriculture and rural economies. West Central Minnesota has an abundance of agricultural based biomass and also an abundance of wind resources. UMM/WCROC began exploring the possibilities of small-scale community based renewable energy systems that could utilize partnerships of a variety of entities in small rural communities. In September 2002 Oak Ridge National Laboratory published, “An Assessment of Options for The Collection, Handling, and Transport of Corn Stover.” In October 2002 the National Rural Electric Cooperative Association sponsored publication of “The Vision for Bioenergy and Biobased Products in the United States.” This represented the collective vision of the Biomass Technical Advisory Committee established by the Biomass R&D Act of 2000. About this same time the Agricultural Utilization Research Institute (AURI) published an article on biobased “Agricultural Renewable Solid Fuels Data.” The ideas and vision presented in these papers were synergistic with the ongoing discussions on campus and discussions with other leaders in agriculture and business in western Minnesota. Would work on the process of researching and demonstrating that renewable energy resources available in western Minnesota lead to revitalizing the rural economy improve national security by reducing dependence on foreign energy sources and provide energy sources that vastly improved the impact on the environment? In the late summer of 2002 UMM/WCROC contacted personnel at the Energy and Environmental Research Center (EERC) in Grand Forks, North Dakota. EERC was asked to provide a pre-design for a biomass cogeneration system for UMM. The goal was to provide one aspect of a larger step to bring community-scale renewable energy to Morris. WCROC had conducted three community committee meetings in 2002 - 2003 with the purpose of providing vision and direction for such a project. 2003 was a pivotal year in exploring the possibility of using biomass as a renewable fuel to supplement or replace natural gas as a fuel source for the campus. The EERC report was presented in March 2003 and this served as the basis for meetings in June and July to develop a request for quotation (RFQ) to solicit a design team to develop a biomass gasification system for the campus. On July 28, 2003 this team met and selected an architectural/engineering firm to begin work on pre-design. On July 31, 2003 a pre-design meeting was held at Morris with representatives of the engineering firm and a University project manager from Capital Planning and Project Management (CPPM). By late August an estimated budget of $5,200,000 was developed for the project. On August 22, 2003 WCROC organized and sponsored a “Community Renewable Energy Program”. University agricultural and energy officials made presentations and state legislatures from both the senate and house were present and made comments about renewable energy. The project would require state funding and this was one effort to garner both public and legislative support for the project.

Chapter 1: Biomass Gasification at UMM: A Historical Overview

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In 2002 and 2003, the local school district had passed a bond for $27 million to build a new elementary addition to the high school on property contiguous with the high school and UMM. Stevens Community Medical Center was just across the street and was also in initial planning for expansion. Consistent with the vision for looking at a new way to supply energy in small communities, UMM initiated discussion about the possibility of district energy. Perhaps the university, the public school and the county medical center could partner to share a source of renewable biomass and perhaps wind energy. Meetings continued throughout the fall. By the end of September, an estimated construction time line for the biomass facility was developed beginning on May 31, 2004 with completion by December 23, 2005. Simultaneous to the biomass planning meetings being held throughout the fall there were also meetings with representatives of the school district and their architect regarding the possibility of district heating for the new elementary school. Also in the fall of 2003 a UMM economics professor had an undergraduate assistant conduct research on the availability of corn stover from regional farms as a possible fuel source. On December 1, 2003 UMM received confirmation from the Initiative for Renewable Energy and the Environment (IREE) that UMM’s request for $500,000 was approved to proceed with a request for proposal (RFP) for a construction manager at risk (CMaR) to take the pre-design to the ready to construct phase. At the same time staff at CPPM were preparing documents to provide rationale for not going to the state architectural selection board for design for the biomass addition but rather to continue with the architectural/engineering firm already under contract for pre-design. Members of the working group had been exploring options for biomass gasifier manufacturers while pre-design was in progress. By January 2004 the project manager developed Design Guidelines to be presented by the University Architect to the Board of Regents in February in preparation for presenting a schematic design in March when requesting project approval. In January UMM received confirmation from Ottertail Power Company that they wanted to continue to be involved and would consider funding 30% of an additional $126,000 of engineering expenses that had been awarded. Ottertail management also pledged to contact the Minnesota Department of Commerce in support of the project and their lobbyist would be contacting the appropriate University personnel to coordinate support for the project with the Minnesota legislature. Drafts for specifications for a biomass boiler RFP were completed by the end of January 2004. University construction and project management (CPPM) received approval to proceed with the CMaR process with efforts to continue to refine an RFP. By February 2004 attorneys in the Office of General Counsel (OGC) had made their first review of the draft RFP. It soon became obvious that since there are a limited number of suppliers of this type of equipment in the world, and the plant in Morris was to be of modest size with the potential to use a variety of fuels, developing an adequate RFP would be challenging. By mid-February CPPM noted the schedule was slipping a bit. It was still hoped to issue an RFP for the boiler and RFP for CMaR by early April 2004. Legislative backlogs raised the possibility that we might lose the opportunity to start construction in 2004 and by late March issued a revised schedule of perhaps starting construction in February 2005. One of the many challenges was getting an air permit for the project. In February 2004 funding options for the project were also being reviewed and developed. The Regents on behalf of the University of Minnesota, Morris submitted a Legislative-Citizen Commission on Minnesota Resources (LCMR) proposal to the legislature for 2005 requesting $750,000. $500,000 of


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this would be for UMM to update instrumentation and $250,000 for WCROC for procurement of ag based plant material for fuel and a pilot study to return the ash to the soil. The total other spending for the project was $5,500,000 for the biomass plant and research platform, which included a $4,300,000 legislative request (funding decision in May 2004) and $200,000 from the University of Minnesota, Morris. Previous spending included $70,000 for a feasibility study in 2003 and $1,000,000 from IREE in 2004. The proposed project was presented to the Regents with a power point presentation at the May 2004 meeting. The Minnesota legislature took no action on the bonding bill in 2004 so there was no state funding for the project at that time. On June 15, 2004 CPPM reported that there was the only viable respondent to the RFP (754-03-1654, April 1, 2004) for a biomass gasification boiler. The U of MN began inquiries with the Environmental Compliance specialists at the U of MN regarding the cost of stack emissions test at the responder’s pilot plant. The U of MN received a quote of $22,000 for testing by an independent third party. UMM began developing plans to ship corn stover to the pilot plant to do test burns and emissions testing in the fall. The tests were scheduled for October 8 – 16, 2004. Representatives of UMM and their engineering consultants traveled to plant for the tests. An independent third party was contracted to do the certified stack emissions testing. The pilot gasifier had worked well with other biomass fuels but they had never attempted to burn corn stover. The fuel hopper had horizontal and vertical augers to feed the fuel into the gasification unit. As soon as they attempted to feed the corn stover into the unit the corn stover bound up on the augers and blew the circuit breakers for the motors. This was the first inkling of potential fuel feed problems with corn stover. A hammer mill was located that could chop the corn stover to alleviate the fuel feed problems. This met with limited success and strong rainstorms soaked the remaining fuel so it became apparent the tests would have to be canceled and rescheduled for a later date. Representatives from the Minnesota Project forwarded information regarding biomass harvesting to UMM. A biomass plant tour at the Iowa State research center in Harlan Iowa was scheduled for October 22, 2004. Representatives from UMM and WCROC visited Harlan Iowa for that demonstration. By November 2004 the pilot test was rescheduled for January 7-14, 2005. Students at UMM were a driving force in a move to sustainable energy. Students initiated the purchase of “green” electricity for the Student Center on campus from Ottertail Power Company. The students agreed to cover the additional cost by conserving an equivalent amount of energy and recycling materials. On January 7, 2005 the Morris and engineering consultant representatives again traveled to the pilot plant for another attempted test burn. On January 25, 2005 representatives from the pilot plant submitted a preliminary test report for the corn stover gasification test. This test did work well enough that stack tests were conducted and data collected to develop an emissions report. Detailed bound reports of the January tests were received by UMM on March 30, 2005. It was during these challenging efforts to develop an operational biomass gasification plant that a preapplication for a USDA/DOE grant was due February 15, 2005 with a focus on the development of demonstration projects that lead to commercialization. The grant opportunity seemed like a good fit for what UMM and WCROC were attempting to do with the development of a research/demonstration site for biomass gasification. UMM continued to look for potential gasification vendors based on the newly received data from the pilot plant tests.


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In mid-March 2005 CPPM noted that it appeared that the 2004 capital request to the legislature for a biomass plant would likely be funded in the 2005 session. At the same time the engineering firm was developing a new time line for the biomass gasification project. By April 2005 the full emissions report was available from the third party testing firm for the test burn at Carterville in January. These results were forwarded to MCPA for review to begin the permitting process for a biomass gasification unit to use fuels other than wood. The U of MN also began work on a new RFP for a biomass gasification manufacturer. The University anticipated receiving proposals from manufacturers for review by late July 2005. The University anticipated awarding of the contract so fabrication of a gasification boiler would occur from October 2005 to May 2006 with construction and commissioning by March 2007. In April 2005 the USDA/DOE published a report, “Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply.” The report emphasized the DOE and the USDA had a strong commitment to expanding the role of biomass as an energy source. Two of the principal authors, Robert D. Perlack and Anthony F. Turhollow, had been the principal authors of the 2002 Oak Ridge National Laboratory report on options regarding corn stover. The April 2005 report became known in short as, “The Billion Ton Report.” This just reinforced the fact that the University of Minnesota, Morris was very much in the forefront in an effort to develop biomass as a renewable energy source with a practical size research/demonstration plant. While work was progressing on plans for the gasifier in the spring of 2005, the Minnesota legislature was considering funding the bonding request to build the biomass gasification research/demonstration plant. Also during this same time UMM/WCROC and others were at work drafting a new USDA grant. On March 25, 2005 UMM/WCROC learned that , “The good news is that the USDA biomass pre-proposal we (UMM, WCROC, Soils Lab, CVEC, and others) submitted entitled “Biomass Gasification: A Comprehensive Demonstration of a Community-Scale Biomass Energy System” scored in the top 50 out of 670 pre-applications.” This came with an invitation to submit a full proposal. Full applications were due May 2 and for the proposal to get through the University system it needed to be completed by April 26, 2005. The grant was submitted by May 2, 2005. The UMM Grants Officer reported on October 18, 2005 “I spoke with Mark Peters from USDA this morning. They are still in the process of transferring the program from NRCS to Rural Development within USDA. Rural Development has not administered this type of award before. Mark cannot speak for Rural Development, but believes we should have an initial call from a grant-contracting officer by the end of October. The goal is to have agreements negotiated by the end of December.” In June 2005 the U of MN (Office of General Council) OGC was still reviewing and commenting on the RFP document. The U of MN did not want to refer to it as specifications since we were just providing requirements and the contractor should provide the specifications. Considerable correspondence and discussion occurred throughout June and early July trying to develop a usable RFP. Eventually by early September the revised RFP was issued. In mid-October UMM learned that we had just received one response to the RFP from the same vendor that submitted the first time. There were numerous meetings and conference calls throughout November and December 2005 trying to determine if there was a way to proceed with the limited response. There was a conference call on December 22, 2005 that included everyone working on moving the project forward including OGC and U of MN Purchasing. While working on getting the biomass gasification project moving along there was simultaneous activity relating to the USDA grant. The UMM grants officer was coordinating some meetings regarding setting up the particulars of the grant and in mid May 2006 announced that the Office of Sponsored Projects Administration had received and set up the new award to UMM/WCROC. By the end of May 2006 the UMM team was still discussing how to move forward with a gasification platform.


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Design for the building for the biomass addition continued as the team continued to work to resolve the issue of a provider of a gasification unit. A pre bid meeting for the construction of the addition was held in mid-July with proposals due on August 15, 2006. It was a CM at Risk proposal so selection would not be strictly on low bid. We learned Purchasing only received one proposal on August 15 that was from Regional Construction Company. A meeting was held on October 12, 2006 to review the proposal. CPPM noted the project came in 2 million dollars over budget. There was some speculation that these prices reflected the fact of a limited response and that the project involved new and untested technology with significant risks. CPPM noted we had to develop a plan to get back within budget and a timeline to get there. The University asked for a peer review by a third party construction company and perhaps to assist in developing a plan. The project costs appeared to be at 7.2M. Another large meeting was held on November 10, 2006 to attempt to find ways to move the project along. The regional construction company noted part of the problem was that contractors were very nervous about a project building model number one. At this meeting the group continued exploring the possibility of other gasifier manufacturers. UMM worked to provide revised numbers for the project so CPPM could report to the Regents in February 2007. The group met again on November 17, 2006 to continue to explore options to reduce the cost and get the project moving. It was decided to explore the possibility of other gasification vendors. The project planning team continued to have extensive discussions throughout December 2006. MPCA had granted a permit for a biomass plant based on the emissions tests provided by the independent testing firm from the pilot plant. If another manufacturer were to be selected we would have to demonstrate they could meet the emissions criteria that MPCA had established based on our tests. In early January the regional construction company and our engineering consultants were still working out how to get the project within budget and what modifications might be made to do so. At a January 5, 2007 meeting a representative of the engineering firm noted they had received a call from another vendor inquiring about the project. This vendor claimed to have some experience with corn stover and their emission test had low NOx. At this same meeting there was some discussion of the design of the addition to the existing heating plant to accommodate the new gasification unit. Should the addition be on grade or below ground? There were also discussions about the roofline and connections to the existing building. Obviously there were challenges to designing a building addition without knowing exactly what would be going into the space and without knowing just how the fuel feed system would work. The project team made plans to visit the most recent potential vendor and tour their facility on January 14 - 16, 2007. The CPPM noted that we were now focused on comparing the options of three gasification unit manufactures. He suggested we needed to develop a matrix of what we would be getting or not getting from each of the providers and for what price. At the same time the General Contractor (GC) was progressing with getting bids to construct the building. We still were having discussions on the appropriate design of the building. The GC representatives noted they would bid the original documents and negotiate modifications with the contractors as needed to fit the needs of whatever gasification unit to be selected. CPPM noted we had to prepare a report for the Board of Regents meeting in March 2007. After the visit to the third site on January 15 2007 we immediately began making plans to ship corn stover to the emissions testing facility. Since we had learned that fuel feed could be an issue with corn stover we made


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arrangements with WCROC to grind the corn stover prior to shipping to the test site. UMM had expected the second gasification supplier to have done some emissions testing on corn stover but learned in late January they were having some difficulty feeding the corn stover into their gasifier. We were learning that handling and processing corn stover as a fuel had some issues yet to be resolved. Planning on the gasification unit continued and work progressed simultaneously with the USDA Grant. A biomass coordinator was hired on grant funding and on February 7, 2007 he sent and introductory e-mail to the group. We coordinated the emissions test burn with the third vendor’s test facility for February 12 & 13, 2007. The new biomass coordinator and a representative of our consulting engineering firm flew to observe the tests. By the end of February 2007 the third vendor submitted a formal proposal for the biomass gasification project. By early March preliminary results of the emissions test were available and our engineering firm summarized the results. In early march the GC reported that the current total cost estimate was over 7M but was confident with work by the consulting engineers and UMM staff to develop a clear list of priorities the project construction cost could be held to 7M. The consulting engineers proposed Friday March 16, 2007 for a kickoff meeting for the redesign of the project. This would include all elements of the project from fuel handling, to building layout and ash handling and scope of work. Tangential to this the biomass coordinator began organizing some meetings relating to the feed stock supply issues as well as fuel handling and fuel preparation issues. By mid-April the GC was trying to move the project along. Meetings focused on pricing updates and the status of a gasification/boiler manufacturer. The selected gasification vendor had submitted a revised proposal to the GC. At this time UMM still needed the official report of the emissions testing from the third vendor. Vendor number two was still being pursued as a possible supplier of a bale breaker/chain drag fuel-handling unit but were no longer under serious consideration to provide a gasification unit. Similarly vendor number one had been removed from consideration as a provider of a gasification unit. Discussions relating to fuel supply, fuel storage and fuel handling increased as the project moved closer to fruition. By May 9, 2007 we had the official test results for emissions from vendor number three. UMM’s environmental consultant commented, “The test results are very similar to that for the original vendor, and do not materially change the University's permitting requirements.” This result removed one of the obstacles for the GC to formalize a contract with vendor number 3. The project was tentatively on the Board of Regents agenda for June but it became apparent this might need to be moved to July when more information would hopefully be available. The Regents were scheduled to meet in Morris in August 2007. The GC was receiving bids from subcontractors for construction of the building and targeted June1, 2007 as a date to provide a guaranteed maximum price (GMP). At a meeting on June 1, 2007 the GC presented an estimated GMP of $7.155. There was considerable discussion on a number of unresolved issues including fuel handling, gasifier warranty, ash handling, emissions and discussion of possible opportunities for more competitive pricing. By June 7 the environmental consultant informed MCPA that the University had changed vendors for a gasification unit but that the new vendor’s unit emissions test results were similar to the original vendor’s. By June 12, 2007 the GC reported they had received the latest proposal from vendor number three and had prepared a draft contract agreement for review. Approval of the contract would allow the project to proceed. The first on site construction meeting was held on Friday July 13, 2007 at the Morris biomass site. The official groundbreaking event was scheduled for 11:00 AM Friday July 27, 2007. Construction began shortly thereafter with a target completion date of spring 2008 with commissioning in April 2008 so that fuel tests for the USDA grant could begin in the summer of 2008.


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Chapter 2: Design in Response to the University’s Objectives and the Technology Market The University of Minnesota, Morris (UMM) began it efforts in 2001 to investigate the use of biomass to meet its energy requirements on campus. With the help of the local electric utility, Ottertail Power Company, the university explored how to produce electricity at a scale that matched the university’s consumption. The utility and university explored options with the help of the University of North Dakota’s Energy and Environmental Research Center (EERC) and focused its efforts on a system that included a high pressure steam boiler and a condensing turbine. This work was concluded in early 2003. Prior to seeking funding of this recommendation, UMM decided to execute a comprehensive energy Master Plan and examine how this recommendation might be modified or expanded to address long term planning objectives. The University of Minnesota Twin Cities Campus was familiar with renewable energy initiatives that were underway in Saint Paul, Minnesota and the work of other Twin Cities consultants who were investigating renewable energy projects in North America. An RFP was prepared, and Hammel, Green and Abrahamson (HGA) were selected, together with Sweden’s FVB, to develop the plan. The Master Planning effort included a comprehensive analysis of planning parameters. They include:

1 Campus Characteristics Operating pressure of the existing steam plant is 18 psig. The system was originally operated at 15 psig and the pressure was increased to overcome the limitations of the distribution system. Operators were trained in high pressure plant operation; however, their experience was with low pressure operations. Electricity consumption peaked at less than 4 MW and is supplied by Ottertail Power Company from one of two service entrances on campus. The energy consumption profile is unique from most perspectives but made sense when considering the academic calendar for the campus. Peak consumption often occurred in September, on an Indian summer day after the students returned. Occasionally, the peak occurred in August. The campus distribution system is owned and operated by the university and was in the process of being upgraded to 12.7KV. Ottertail’s rate structure reflected its reliance on coal fired generation and a load base that experienced a daytime winter peak. Nighttime power was priced very low and there was little cost associated with peak demand. Steam demand followed outdoor air temperatures and reflected the time of day. Morning warm-up, student shower and dining activities were all reflected in the daily steam demand profile. This profile was of interest in the Master Planning effort, knowing that combined heat and power (CHP) was a path toward developing cost effective energy assets on a campus with a consolidated thermal load. Chilled water was primarily produced at the central plant by two electric drive water chillers. The campus expected future remodeling projects to add to the central plant load. The consumption profile was dominated by the school calendar first and the weather conditions second.

2 Natural Resources A fuel survey identified the biofuel sources that would be available in the market, their quantities and their projected price over the planning period. Corn stalks, sunflower seed husks, grass, wood and

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distillers grain solubles were the dominant biofuels in the market. By simply driving to Morris through surrounding prairie, it was easy to observe the abundance of corn in the county when compared to wood. Wind was recognized as an important resource to include in the Master Plan. The reasoning was simple, wind turbine developers were completing projects in the region and another school had successfully implemented a utility scale project. It was broadly understood that it is less expensive to generate electricity using a wind turbine than it is to use a thermal biomass fueled system.

3 Regulation The use of biomass as an energy source is not a new concept. Examples of wood-fueled plants are abundant and Minnesota has more than ten plants that use municipal solid waste or refuse derived fuel (both are often considered biomass). During the implementation phase of the project, the Minnesota Pollution Control Agency decided that corn stover (corn stover is the stalk, leaves and cob of the corn plant) though similar to wood, was not well understood, and therefore, they decided to explore all implications of stover as fuel by classifying stover as municipal solid waste. While the USDA could not identify any jurisdictional authority, they raised concerns about the impact on soil quality if stover were harvested aggressively from the same field over multiple decades. Consideration was given to the harvesting process, the location of the nutrients in the dried plant, and the cost of adding soil amendments to the field if stover were harvested. Their work was primarily classified as interdisciplinary research that could serve as the basis for regulation in the event that the stover fuel market grew significantly. Minnesota has a regulated electric market which is managed through Public Utility Commission tariffs. While the Federal Energy Regulatory Commission (FERC) and the state support independent power production, there are a number of tariffs that make development expensive. The tariffs also require that customer generating assets be connected on the customer’s side of the meter. This becomes a design criterion that affects the location of the generating asset and can present challenges to locating renewable energy projects, where both solid fuel boiler operations and wind generation are normally accomplished in a setting that is more like a field than a town.

4 Equipment At the inception of the project, the team was tasked with identifying manufacturers that could produce energy using wood for fuel. Tried and true systems were available to make steam that could then be used to heat the campus, make electricity or make chilled water. Decisions regarding how the combustion process was controlled and the operating steam pressure were the primary consideration. The mission was expanded to look beyond combustion technology so the university could experiment with producer gas driven electric generation. Producer gas is a low energy density gas (when compared to natural gas). A variety of engines and turbine manufacturers were considering product offerings. This concept refocused our search for thermal technology to gasification systems that would deliver producer gas. We were unable to find a reliable engine manufacturer; however, this did not end the university’s interest in gasification. It was seen as a technology that may eventually tilt the energy production of biofuel plants toward electricity and away from steam. This shift to electricity from steam reflected the overall consumption patterns of the campus and our society.



Because of the scale of the project at Morris, the survey of gasification technologies focused on systems with the following characteristics: • • • •

Operated at near atmospheric conditions. Used air rather than oxygen. Were close coupled, where the producer gas is combusted before it is cooled or cleaned. Fed the fuel from the bottom as a means to limit the demands of fuel preparation.

With the goal of having many competitors, approximately 40 manufacturers, domestic and foreign were identified that could either supply a wood fired boiler or a gasification system. To maintain the broadest participation and to respect the scale of the plant, its first cost and its operating complexity, we also decided to limit our operating pressure to 280 psig. At the same time that the Master Plan was being completed, Morris further developed its understanding of sustainability and set goals for the project that would make it more valuable to rural America. It was also opportunistic and worked with the state’s Initiative for Renewable Energy and the Environment to develop one utility grade wind turbine in conjunction with the West Central Research and Outreach Center (WCROC), a branch of the university. The electrical utility facilitated the project by making its right-of-way available and the power was delivered on the university’s side of the meter. The economic impact of the turbine was evaluated with the other electricity generating assets that were being planned. This provided the university with a comprehensive understanding of how Ottertail’s rate structure affected the cost of power on campus. Renewable energy costs were also analyzed and it was clear that the efficiency of combined heat and power (CHP), where steam flows through a back pressure turbine to building loads, rather than to a condenser where the heat is rejected to the atmosphere was important to the overall operating cost of the system. Wind was the most economical way to produce electricity; however, there was little cost penalty associated with CHP.

5 Strategy The university realized it was on course to achieve carbon neutrality and student feedback on campus showed strong support for the initiative. In fact, the support was so strong that the administration felt that it was responding to student demand, rather than working toward its own initiative. The energy strategy was knit with the campus’ marketing strategy. The campus was working to create a clear identity for itself within the university system. Morris administration focused on delivering benefit to its students, its host community and its region. The project was charged with exploring energy technology that could make a real difference for communities in the region. Recalling the abundance of corn grown in the area, it asked the team to plan for using corn stover for fuel. It also set a course for developing a district energy system that would serve the school districts K-12 facilities and the hospital. The idea was that economy of scale and sharing a single labor pool to meet the thermal energy requirements of three institutions could demonstrate a repeatable model in neighboring towns. The campus began to survey the market for boiler and gasification system manufacturers that would be interested in working with the university to use stover for fuel. To meet this goal, the properties of corn stover became a central issue. There is a reason why corn stover is abundant beyond its low value compared to the grain itself. The leaves and the stalk of the corn plant have high silica content



and are stringy. Silica in a boiler normally translates to slag which is an impure glass. The slag forms on the coolest surfaces of a boiler and that is generally on the tubes where steam is produced. The slag acts as insulation and is difficult to remove. It is the enemy of a boiler. There are also other elements in stover present in varying quantities, which affect the melting point of the ash being produced. If the ash melts, then cools, clinkers are formed and can clog a boilers ash removal system. Given the chemical properties of stover, the number of manufacturers willing to take up the project went from 40 down to one. In addition to experiencing a tepid response on the supply side, the local school district decided to proceed with a conventional gas fired system in their own building, rather than relying on the university’s thermal energy plant. This cost the university its chance to share operating costs with other institutions in the community. The university entered into a process of qualifying the only proposal for the project. The key issues at the beginning of the qualification process were determining if the equipment could produce heat, and if it could limit stack emissions to levels below permit requirements. Testing was conducted on corn stover and Distillers, Grain and Solubles (DGS). Wood was determined to be a straight forward and tested option that had already been documented by the manufacturer. At the same time that the university was testing the equipment, a Fortune 500 company was also running tests. Their interests were similar. The testing was interrupted by the fuel handling systems inability to move corn stover into the gasification furnace. Recall that corn stover is stringy. Fuel handling system commonly used for wood chips use screws to move the chips from a conveying system into the boiler-furnace. The corn stover wrapped around the screws, clogging the system. The manufacturer processed the fuel by tub grinding it to reduce the length of the stalks. That allowed the tests to be conducted for heat production and emissions and a later test was conducted on a modified fuel handling system. Following completion of the testing, planning commenced to incorporate the manufacturer’s equipment into a boiler plant addition that would be built to house their equipment and other equipment that was part of the energy Master Plan.

6 Planning Work proceeded to incorporate the manufacturer’s proposal into a boiler plant addition. The university recognized a conundrum early in its development of the project and the lack of competition highlighted the issue. Using corn stover for fuel put the project beyond the cutting edge of manufactured products being offered to the market by established companies. At the same time, the university was determined to use its standard contracting forms that sought guaranteed performance. While the university wrestled with it contracting language, the design proceeded. The resulting documents produced bids well in excess of the budget. An evaluation of the bids suggested that the project was underfunded and that the scope would need to be reduced to achieve the primary goal, gasification of corn stover to produce steam. The university explored additional options to fund the project, including the use of Clean Renewable Energy Bonds being made available through the U.S. Department of Treasury to reduce the cost of debt and the use of a revolving energy conservation fund within the university system. None of the options offered real value to the university and additional funding was raised within the university system.



The project was reissued in two packages, the first for the gasification technology and subsequently the balance of the plant that would house the gasification technology and provide the interfaces with existing equipment. Like the first time, potential manufacturers were identified. The difference is that the definition of gasification was blurred to allow very close coupled systems to qualify. An additional step was taken to review the bid documents ahead of issue to accommodate the expectations of several suppliers regarding the terms under which they would supply equipment for this highly experimental project. Interest was expressed by several companies and the bid documents were issued. Unfortunately; again only a single bid was received. Others, who initially were interested in the project stepped back, and in general cited business reasons that included not wanting to sort through a research and development project in a public arena. Like the first round, the lone bidder was qualified through testing that focused on a test burn to demonstrate emissions characteristics and the quality of the ash. Fuel handling was met with a claim that they had experience using a hydraulic ram to move refuse derived fuel that was certain to work with corn stover. (There was no test facility available to demonstrate the claim was true.) Design of the balance of the plant proceeded and was bid. This time the project met its budget threshold and the general contractor accepted assignment of the technology partner and led the coordination of that supplier’s performance on the project.

7 Implementation Construction demands the coordination of manufacturers and site labor to assemble a building that meets the specifications prepared by architects and engineers. This project also knit the requirement that detailed drawings of the gasification system be produced in advance of final documentation of the balance of the plant, eliminating rework that is required to coordinate construction details of complex systems in the documents. A third tier contractor on the project was in a financially precarious position so the general contractor took additional steps to make sure products and work were delivered before money was paid, to minimize the risk that a party does not perform. This tactic worked reasonably well for the component goods associated with their work, but did not help in making sure that coordination drawings were produced in a timely manner. Materials were delivered to the site prior to shop drawings being produced, reviewed or accepted. This frustrated the team’s ability to coordinate the work and to resolve potential problems ahead of field labor being spent. The engineers reverse engineered the thermal process to gain confidence that the systems could meet the overall objectives of the project. The university’s project manager made the judgment to proceed with the work and solve issues during start-up. During startup of the system, several subsystems required modifications to meet operational requirements. •

The stoker system was not able to feed the unprocessed corn stover (like the stover that was tested) at a rate that allowed the boiler to reach its operating capacity. By processing the fuel, into pellets that physically resembled wood and making some other modifications the stoker system worked.



• •

• •

The step grate system in the gasification furnace did not manage the fuel flow rate until changes to the hydraulic system were completed. The control system was modified to make use of the full complement of sensors provided as part of the system to manage over-fire and under-fire air. This allowed the system to respond to both the demand for steam and the management of excess oxygen in the combustion process. A flue gas scrubber system was adjusted to manage flow and the injection of sodium hydroxide when Chlorine was present in the fuel. Experiments were also conducted in the gasification system to better understand how various opportunity fuels might behave in a commercial system. During the process of testing fuels it became clear that the more the fuel was processed to resemble wood, the better the gasification furnace and the balance of the system performed. Trouble was experienced when: o Fuel density was in excess of 25lb/ft3. o Fuel was crushed or had high powder content. This generated significant fly ash that clogged the heat recovery system.

Early in the design process, a gasification technology was observed in an outdoor commercial/industrial setting. The gasifier was located in a freezing outdoor climate, and dust was observed on the outside of the equipment. A design decision was made to locate the university’s gasifier outdoors. This was seen as benefit because it offered a means of controlling dust, or at least eliminating dust from entering the existing gas fired plant. When observing the dust on the outside of the equipment a judgment could be made that this was a good design decision. Conversely, due to the intermittent operation of the system and the wind and cold temperatures at Morris, this system has challenged the operators and issues have surfaced. • •

The opening at the stoker into the furnace is protected by water. This was true of the other system that was observed, nonetheless, the water at the opening freezes, even if the system is up for more than a day. This system relies upon recirculated flue gas to provide lower oxygen content blast under the fire on the grate. This flue gas is moisture laden and condenses in the duct that is routed outdoors. This results in a significant amount of water draining to the space directly below the grate and results in wet ash.

The system that is in operation at Morris is based on a system that is normally fueled with wood. In hind sight, a commissioning process that proved subsystems with this fuel would have reduced the amount of ambiguity associated with early problems and allowed the team to focus without as many distractions. With processed fuel that resembles the dimensional properties of wood, the university was able to complete its testing to learn more about how the chemistry of various fuels behave. Finally, the system has demonstrated that it can operate to meet the goal of trigeneration; the production of steam for heating, electricity and chilled water using renewable fuels.

8 Moving the Plant From Design to Operational The conceptual design and assumptions made about how biofuels could be managed to produce useable energy were put to the test during the construction and commissioning phase of this project.



Before we describe the process, it should be noted that it took some time for the University to understand how to manage this construction project. The typical project delivery methods included Design/Build, Design/Bid/ Build and General Contractor at Risk. There was vigorous discussion about what project delivery mechanism should be used. The basic issue was owners look to hedge risk by using contracts that either shift risk or develop risk sharing in a manner that all parties are comfortable with. In this particular hybrid research/demonstration/operational plant prototype had by its aggressive deliverables, posed significant risk. The University was used to doing research projects, but had not built research projects with long term operational expectations. Contractors were comfortable with fossil fueled combined heat and power plants (CHP), but had no experience in biofuels and gasification. Gasification contractors were comfortable with gasification of wood and wood by products but knew very little about how high mineral content biofuels would perform in their gasification platforms. Thus in trying to define and understand the elements of risk, it was important to understand that each segment of the project participants understood risk from a different perspective. Each project delivery method placed risk at a different part of the project team. The downside of placing risk at specific participant levels is that the participants may adjust their bid response to mitigate perceived or real risk. The final project delivery method selected was the General Contractor at Risk, with some significant exceptions in that risk assignment. The General contractor agreed to accept risk for the typical combined heat and power plant construction but made a condition of acceptance that the University must accept risk for the actual biofuel gasification process. The efforts to identify contractors and subcontractors who might have had some prior experience in gasification or biofuels handing was difficult. It was nearly impossible to find contractors who had experience with gasification in the Midwest. We did locate contractors who had experience in materials management and grain handling. The robust agricultural economy was a significant help in finding projects that could provide guidance and information in handling bulk materials. The concept of the walking floor and load cells came directly from the ag processing industries. They were proven concepts and we could find working projects to observe. We were also fortunate to attract a general contractor who had experience in heating plants and doing work for the U of MN system. Selecting a general contractor who could bring the right mix of subcontractors to the project was also important. The project was put out for bid in 2007 and was awarded for construction to complete in 2008. A brief description of the final plant configuration is as follows:


Biomass Gasification: A Comprehensive Demonstration of a Community Scale Biomass Energy System USDA Final Report Figure 2.1-Overhead view of Biomass Facility

The infeed system is an 8 ft. wide 60 ft. long walking floor conveyer that is sitting on load cells. It can hold up to 30 tons of fuel that can be transferred into the plant. At the interface between the walking floor and the gasifier is a hydraulically controlled piston ram that is 51 inches wide and 9 1/2 inches deep. The travel of this ram is 38 inches from fully retracted to fully extended. This fuel bunker is equipped with cameras and quench type water suppression systems to prevent fires. Figure 2.2-Simplified Drawing of Gasification Process

The ram pushes the biofuel into the first grate of the gasifier. The gasifier is an incline grate atmospheric pressure air blown gasifier. It is a simple configuration and was proposed for this project



because there was a goal to provide equipment that can be readily adapted to existing industrial applications. The ram is driven by the number of cycles in the gasifier grate system. The gasifier thermally converts biofuels into an intermediary gas made up of compounds of Hydrogen, Carbon Monoxide and Nitrous Oxides. This is a low quality synthetic gas that can be combusted to produce heat. The gasification process was selected as means to produce a lower temperature thermal conversion reactions at the fuel bed level and then add additional air above the fuel bed to maximize the temperature of the producer gas just prior to entering the boiler. The lower fuel bed temperatures are necessary to manage the higher mineral content biofuels. The gasifer is close coupled to a conventional fire tube boiler that is designed to use the low quality producer gas to convert the heat energy to steam. The boiler is connected to a high pressure backpressure steam turbine that is designed to use the steam from the boiler to produce electricity and then discharge low pressure steam to either heat or cool the campus. (CHP) The cooling is accomplished by using an absorption chiller that uses low pressure steam to provide chiller water for building cooling operations. Additional plant equipment includes a water based scrubber for flue gas clean up. The scubber was added to the plant design when trial runs at a test site confirmed that we were producing a slightly acidic flue gas with the conversion of biofuels. In early gasification tests that drove the pre design, the Chlorine in the mineral salts found in most biofuels, quickly volatized in the fuel bed and combined with hydrogen that existed in producer gas. This resulted in an HCL flue gas that mandated that the process temperatures need to stay above 240 F to keep the HCL from condensing and causing acid decomposition. These temperatures are maintained until the flue gas enters the scrubber which sequesters the HCl in the water spray. We use an alkaline water spray to neutralize the slightly acidic flue gas to give a neutral (PH 7) scrubber discharge. The USDA grant added a continuous emissions monitoring system and SCADA monitoring system. The data collection requirements of this system was not typical for production CHP plants. This required additional sensors, collection hardware and software. Real-time data on the operation of the gasifier, boiler, steam turbine, absorption chiller, scrubber, and emissions is collected, stored on UMM servers and available on the UMM Biomass website. Considerable time and effort was spent on emergency operations and emergency shutdown procedures. Since the gasifier is a non-pressurized vessel, the shutdown was driven by the emergency requirements of the boiler. The control system was designed to integrate the steam production with both the steam turbine and the gasifier. The boiler is the primary control mechanism and the steam pressure determines the control sequence for grate speeds and induction fan settings. This in turn controls the ram feed and the walking floor activity. The challenge was building a control program that can recognize the lead/



lag control characteristics of the boiler and the gasifier. Lead compensators helped increase the stability and speed of the systems response. Lag compensators helped reduce steady state errors. The coordination of both types of data for reporting purposes and adding the pressure requirements of the steam turbine only complicated the control algorithms. The operational safety of using this equipment for research also required strategically located master kill switches, and continuous gas scavenging fans to insure that any carbon monoxide leakage could not build up in low lying areas. The final portion of the plant is the ash discharge system. The ash collection occurs at multiple points in the process. The base of the gasifier has collection augers as well as the base of the boiler. The augers are run by a timed sequence to insure that all ash is removed from the process.

9 Construction Once awarded the project started towards a completion date in Fall of 2008. There were many progress meetings to continue the coordination of the traditional parts of this project (CHP) with the nontraditional gasification elements. Integrating the robust research and instrumentation systems provided by this grant was always a slightly different application then building a production plant. A lot of time was spent working to insure that sampling ports, thermal couple wells and sensor locations were located at the critical parts of the thermal conversion process. The construction process was impeded due to some production delays from one of the subcontractors. This proved to be problematic as the subcontractor did not provide for timely review of shop drawings and delivered equipment that later had to be field modified. The completion of the plant marked the end of the concept and the beginning of the testing phase. It should be note the plant received an AIA State of MN award for design excellence in 2009. Commissioning was started in Fall of 2008. Fuel was purchased, equipment tested and the required commissioning tests were started. Commission had to be completed before the U of MN would accept the plant. The fall was spent working to move the biofuel through the system and attempting to initiate thermal conversion. Initial efforts to get to any sustained level of steam production failed. The winter of 2009 was spent analyzing the preliminary test results and we tried to determine what was causing the production failures. The focus eventually got to the biofuel density and the ability to provide a consistent and uniform energy flow into the gasifier. Our original concept of using lower density fuels that had significant air entrainment in the fuel feed proved to be counterproductive in the gasification process which is purposefully attempting to restrict the amount of air that is available for thermal conversion. The air entrained spaces caused rapid thermal conversion leading to overheating the fuel bed and thermal conversion rates much faster than the control system was designed to handle.



The lower density (3 to 5 lbs. cu. Ft.) biofuels simply could not be pushed into the gasifier fast enough to achieve maximum steam production. The success of the gasification process is a matrix of grate area and time spent in the gasifier, and the energy density of the fuel source. Our low quality lower density fuel sources simply could not meet the performance specifications of the maximum steam required in the system that was installed and stay within the temperature ranges that we defined as critical to successfully gasify high mineral content biofuels. Our options were to either increase the grate area or increasing the energy density. We chose to explore the energy density as the most cost efficient means to increase the steam production capabilities. We understood that this decision could affect the economic price points as we were putting more costs in our biofuels Fortunately our infeed systems were robust enough that we could change density without needing to make major modifications to the infeed equipment. We did need to increase cylinders and pumping pressures to handle high density fuel sources. We brought in an internationally recognized gasification consultant to review our system and make suggestions on how to migrate to a new higher density fuel source. At the same time we made modifications to the grate system and replaced the PLC programs to accommodate the different performance of biofuels from more traditional wood gasification control systems.

10 Energy Density The target fuel density of 10 lbs. per cu ft. was set. That meant the density had to somehow be increased by a factor of at least two from the existing bulk fuel supplies. Grinding to reduce the aggregate size of the biofuels from the existing 1 to 6 inch lengths to something that was more uniform was looked at first. Bales were ground in our tub grinder to a uniform size using trials from 2 inch screens to down to ½ inch screens. The immediate outcome was that we created a significant amount of dust and fines that were susceptible to being windblown and difficult to capture. Trials with the ground biofuels were run next but while we could increase density, the thermal performance in the gasifier was just too difficult to control. The fuel bed temperatures also could not be kept within the ranges we had specified. We suspected that entrained air was still causing problems with the speed of thermal conversion. A more aggressive densification system was tried next. Using ground biofuels and compressing them in a mechanical piston compression system 70MM pucks that had densities that ranged up to 30 lbs. cu ft. were produced.



The higher density fuel was better managed in our infeed system and could now load enough fuel on our infeed floor to run for up to 16 hours vs. the 6 to 8 hour supply in the bulk fuels we originally tested. A discussion of the thermal stability of densified fuels is located in Chapter 3. Trials on the 70 mm densified pucks were marginal. We observed much better energy conversion and we could adequately supply the fuel bed in terms of energy density, but still experienced problems with core temperatures in the individual pucks getting too hot and starting to develop a soft slag in the ash. The 70 mm pucks were quartered to provide a more “wood chip” type product to the gasifier. Some of our target fuels performed well in the quarter configuration, but corn stover still showed sticky ash characteristics. We then moved to a much smaller densification process using commercially available pelleting systems. We densified several of our targeted biofuels to ¼ in diameter pellets. Our density again was approaching 30 lbs. cu ft. Our trials on ¼ inch pellets showed another tendency to develop a soft slag above the grates. The pellets would get sticky just above the grate and bridge over the grate movement thus blocking the flow of air through the grates. The smaller pellets tended to roll around the grate movement and not be moved down the incline. We can speculate that this promoted overheating the pellets and increased the probability of soft slag. A blended fuel mix of partially densified material and partially ground material was tried next. This allowed us to custom build the density that we wanted to achieve. It also resulted lower the overall fuel preparation costs as we were using a percentage of ground material in lieu of more costly processed material. We ran various trials of various ratios of densified/ground fuel mixes. Again, some of our targeted fuels performed well with blended fuel stocks but we did notice that the movement of the fuel down the grate system tended to segregate back into higher density pellets on the bottom and lower density ground fuel on top of the fuel bed. The fuel pellets would then have a layer of ground fuel on top and the air supply from the bottom which poised significant problems if the fuel was prone to slagging. We had difficulty in keeping the higher density fuels from overheating. We observed that changing the physical composition of any of the biofuels changes the thermal conversion properties of that fuel. We think much more needs to be tested on how the physical configuration of fuels affects the thermal performance. We also tried mixing dissimilar fuels such as wood chips and corn stover. The thermal conversion of the dry woodchips progressed much faster than the corn stover and lead to a concentration of cornstover at the lower end of the grate which tended to develop sticky ash characteristics.

11 Alkalinity With some consistent slagging occurring in several different density trials of the target biofuels, we turned our focus to the alkalinity indexes of the various fuels.



That led to additional changes in our fuel bed control programs to try and tighten the range of our fuel bed temperatures. Just as extracting energy is a function of grate area, time and energy density, controlling the fuel bed temp is a function of underfed supply air, induction air and flue gas return back to the gasifier bed. The control programs were modified to be more reactive to changes in fuel bed trends and to make adjustments to attempt to keep our bed temperatures under the known points that would cause slagging. With help from or HRSG (Heat Recovery Steam Generator) subcontractor, we looked at modifying the alkalinity numbers of the fuels we were running. Please refer to Chapter 3 for a discussion of the alkalinity measurements of the fuels we tested. Our primary target fuels tended to have alkalinity numbers above one. The higher that number went, the more slagging we observed on the grates. Several of our targeted fuels did not have the slagging problems that we saw in the corn based fuels. Specifically, native prairie grasses showed little slagging when we ran them through the new fuel bed control algorithms for controlling fuel bed temps. Native grasses in our samples showed alkalinity numbers of under .75 and did not seem to develop the sticky ash characteristic of the fuels that were 1 or above in alkalinity. A second corn based fuel that seemed to work well was corn cobs. Their size and natural moisture content seemed to work well with the gasification equipment. The alkalinity of corn cobs was less than 0.25 lb Alkali/MBtu in our tests. This level indicates a relatively low risk of slagging. The last fuel characteristic that we found that significantly affected thermal performance is moisture. Biofuels are going to have certain moisture levels depending on physical characteristics. See Chapter 3 for a discussion on time weighted degradation of unprocessed biofuels.

12 Moisture Field stored biofuels will maintain a certain level of moisture because of ambient conditions. Ambient moisture in the northern portions of the Midwest provide a window that can allow materials to be stored unprotected in the field for at least 6 months after the material is harvested in the fall. The winter conditions provide a limited time to keep the material in a steady state and avoid either ambient moisture increases or microbial activity. We found that material used within that window could be used with little concern for moisture levels above what the moisture was when it was harvested. The shape of the bales also affected the length of time the bale stayed stable. Round bales seemed to perform better at moisture resistance. Material stored into the summer months showed increase moisture levels and increased microbial activity. After extended storage in a northern climate, the material stored outside became unusable for thermal conversion.



Our gasification ranges for optimum performance seemed to be in the range of 18% to 20% Field stored bales for the first 6 months stayed in the 20 to 25% range. In field trials we tested material over one year of storage. By the time the material was stored outside for 36 months, it was unusable for thermal conversion.

13 The Roadmap The commission process was difficult and high mineral content fuels proved to be a challenge. The HRSG contractor proved to be the most important contractor in meeting these challenges. Their experience in thermal conversion systems helped us to establish a roadmap on how to work through the issues. The Heat Recovery Steam Generator (HRSG) manufacturer has a vested interest in the performance of everything upstream from his boiler. Our experience shows that this contractor is key to the success of the project. By identifying the areas of energy density, alkalinity, and moisture, UMM was able to selectively test and refine our understanding of the fuel characteristics of the target fuels in the grant deliverables. Since Fall of 2010, Morris has run all of the target fuel stocks, collected data and identified the best practices associated with these fuels. This information is contained in this report. In some cases we simply have learned that certain biofuels are not good candidates for thermal conversion in our gasification platform. Other fuels show definite promise and will continue to be used for research and production at the campus. We have also learned a great deal about blending fuels to minimize undesirable characteristics in either the thermal conversion or the end products of gas or ash. Conversely, we think there is great opportunity in blending fuels to improve performance. The following sections will provide detail on the tests, the successes, the failures and the lessons learned in this process. The University of Minnesota is grateful to the USDA for the opportunity to promote the use of biofuels as a viable fuel for community based gasification facilities like Morris.



Chapter 3: Report on Feedstock Testing and Biomass Testing Activities 1

Preproject Testing at Carterville, IL

A Corn Stover/Ethanol Mash Gasification test was commissioned from Coaltec Energy USA, Inc., Carterville, IL, in January of 2005 for Recovered Energy Resources, LLC (RER) on behalf of UMM. In the final report compiled by RER, dated March 30, 2005, several findings demonstrated the feasibility of the project and helped the MPCA permitting process move forward. The test system was a commercial-size gasifier rated at 25 mmBtu/hr (7.32 MW(th)). The following summary presents the results that we used to determine the expected emissions and ash quality from the system: The test and subsequent report included:

• • • • • •

Sustained operations using corn stover and corn stover mixed with ethanol mash Heat and mass balance to estimate system efficiency Emissions monitoring Fuel analysis Ash analysis Identification of issues, opportunities, and expected solutions and/or costs associated with those issues.

2 Summary of Initial Findings While it was not expected to answer all questions about project feasibility, the goals of the testing were to gather reliable emissions data, identify any fatal flaws in the project, and develop a list of issues to be addressed in the system design should the project move forward. A brief summary of the findings follows: •

• • • • • •

Gasification was sustained with all fuels tested. Fuel was fed at a rate of 3,500 lb/hr during preliminary testing on 8 Jan 2005 to determine the burn rate. The measured rate of burn was approximately 35 lbs. of fuel per square foot of available bed area, which was in the expected range for this fuel. Material handling of corn stover was successful. The stover was reduced in size in a tub grinder. A test in October of 2004 had shown that the infeed system could not handle the stover in larger, variable pieces. In subsequent testing of the feed system with an alternative vertical auger, corn stover was moved successfully in all size ranges. Control of harmful emissions was generally successful. While the overall results were excellent, there are still a few issues that must be addressed. The ash material did not clinker and caused no handling problems. The system operated at very high efficiency. The efficiency of corn stover gasification was 99.6%, calculated as the percentage of fixed and volatile carbon that was converted. The system operated easily with the different fuel mixtures, without constant adjustment of the air flow and fuel feed rates. Occasional changes in feed rate and moisture content of the fuel caused no major problems.

Chapter 3: Report on Feedstock Testing and Biomass Testing Activities

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• • •

•

•

•

The ash quality did not present any environmental concerns. The air flow into the gasifier must be better controlled. Wetter fuel required more air, but the gasifier lacked zonal air flow control, resulting in the addition of more air than was needed. The excessive air flow in the inner cone produced increased levels of particulate carryover. The fuel feed system handled the ground fuel for this test. The horizontal feed augers could not maintain the required feed rate with unprocessed stover. A smaller vertical auger with a square housing was able handle the unprocessed stover with no difficulty. A commercial system could use either the square-cased augers or a hydraulic ram system. Expected fuel throughput rates were achieved. It is apparent that commercial feed and ash handling systems can be designed and implemented. Some bridging occurred in the ash dumping system even though the ash was free of clinkers and was generally a fine powder. These results indicate that some sort of agitation in the ash handling system would be of benefit. A particulate plume was not visible at the stack, but the fine filters did capture some material. This particulate entrainment is thought to be the result of fines created by the hammer mill grinding and the high rate of air flow required by the high moisture content in the fuel. In commercial application, the feed system would be designed so the grinding of the fuel would not be required; therefore, the amount of fines would be much lower. Allowing for some seasonal variability, the moisture content of the fuels is likely to be lower in commercial application. The stack emissions contained a high concentration of HCl. Laboratory analyses showed that the corn stover contained slightly over 0.5% chlorine. We have since learned that corn stover typically contains high levels of chlorine. System design must consider the presence of chlorine and its removal. Minnesota regulations require us to control HCl.

3 Emissions Summary Emissions sampling and analysis were performed by GE Energy. The gas stream was tested for CO, NOx, SO2, HCl, particulates, CO2, and O2. The stack emissions throughout the test were generally very low. The CO and CO2 levels were very good, and the NOx levels were within operating parameters. It was noted by Coaltec that the NOx levels were dramatically reduced as the reaction temperature was lowered. The NOx emissions at 1800° F were 50% of the emissions at 2000° F. Please see Table 3.1 for the summarized data. The major issues with emissions were identified as particulate matter and HCl. These issues are discussed in Chapter 4, Section 2.4. See also Section 5 of this chapter.

3.1 Storage of Fuel Bales Change in the composition of mineral elements in 4 fuel stock was studied over a period of 268 days from August 2009 to May 2010. Separate studies were done for carbon losses over winter and over summer. The data are summarized below in Sections 3.1 and 3.2. In all cases, the sampling was done according to the Sampling protocol shown in Figure 3.1 in the Appendix.


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3.2 Mineral Element Changes Round bales of corn stover and prairie grass, square bales of soybean residue, and bulk wood chips were sampled according to protocol and analyzed for the following elements by Inductively Coupled Plasma Spectrometry (ICP) at the USDA-ARS laboratory. The elements: Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, Ti, V, Zn. For all elements, the data became increasingly variable over time. Indeed, the variability was so great that no reasonable fit of a regression line was possible. The best R-square value for any line was 0.6. Most were less than 0.1. The reason for this extreme variability is not readily apparent. We are dealing with small concentrations of these minerals (ppm ranges). Uneven weathering of the bales may be evident here. Sampling errors probably contribute some variability. Experimental error can also creep in from the laboratory. It is recommended that further research be undertaken to elucidate the fate of mineral elements in stored fuel stocks.

3.3 Carbon Losses in Storage The loss of carbon during storage is generally of highest interest in handling and storing biomass fuels. Carbon and its compounds represent the majority of the heating value of the fuel. Carbon losses to weathering and microbial action rob the energy contained in the fuel. We conducted a study of carbon loss in stored bales of corn stover over a summer. We also measured losses to Prairie grass over a winter. Corn stover bales were sampled and assayed for carbon content in March of 2010. The stover averaged 39.8% carbon at that time. Following storage over the summer, the stover was sampled again and showed an average carbon content of 36.9%. It would appear that little carbon was lost, but for each ton of stover, that 2.9 percentage points lost from the carbon concentration means that 58 lb of carbon was lost. Based on an HHV for carbon of 14,662 Btu/lb, a total of 850,396 Btu were lost. The stover assayed at 7575 Btu/lb, so the total heating value of one ton of stover would be 15.15 MBtu. In this study, the stover lost 5.6% of its heating value over 180 days from March to September. A similar study was done during the winter months with prairie grass bales. In January, the bales averaged 46.3% carbon. In April, 127 days later, the bales averaged 46.5% carbon. The difference is too small to be statistically significant. We conclude that no carbon was lost from the bales in a Minnesota winter. Minnesota has natural frozen storage for a good part of the year! Studies were done to measure the change in carbon concentration in soybean residue and wood chips over a 28 day period in late summer. The soybean residue lost 124 lb of carbon per ton, or 1.82 M Btu/ton. Wood chips were (not surprisingly) more stable, losing 42 lb of carbon per ton in 4 weeks. The heating value loss was 334,068 Btu/ton.

3.4 Ash Composition As explained in Chapter 4, UMM is beginning the process of applying for a beneficial use determination regarding our intended use of the ash from our gasification system for land application. At present, MPCA requires a total chemical compositional analysis of the ash, pH, and may request others. Following is a brief description of some characteristics of the ash from our fuel stocks. The ashes from corn stover, corn cobs, wood chips, and prairie grass generally have few characteristics that would render them unfit for application on agricultural land or managed grasslands. The primary


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problem is the high pH of all of the ashes. In our tests, the agricultural residues have, on average, had lower pH than wood chips. There is, however, great variability in the ash from given batches of biomass fuel and given operational setups in the gasifier. This variability may make even use as a liming agent difficult without blending ash and other agents to produce a uniform product. The same variability in the plant nutrients will likely make blending a necessity. Upon completion of our CaseSpecific Beneficial Use Determination from MPCA, we will begin negotiations with fertilizer and liming agent processors in the region. If we attain our goal, all of our ash will go back to the land, and none to a landfill. It should be pointed out that corn stover has consistently shown relatively high levels of lead (Pb) averaging 532 ppm overall. This level is above the 300 ppm lead limit set by MPCA for land application of industrial byproducts. Ash from unadulterated wood and agricultural biomass is not considered an industrial byproduct. It is, however, unclear exactly what the MPCA will set as the regulatory limits, if any, on these products. It is also unclear whether the state or US Departments of Agriculture will issue new regulations regarding fertilizers and liming agents containing ash from agricultural biomass. In any event, we hold fast to our goal of keeping the ash we produce out of landfills. If necessary, we will explore other potential beneficial uses.

4 Conclusion The project partners have completed the commissioning of the biomass-fired combined heat and power plant on the UMM campus. We expect to have the system in routine use in the fall of 2011, pending completion of our emissions permitting process. This project has met with delays and problems, but much has been learned in the process, and not merely in the deliverables of the grant. We entered the project rather naively, understanding that there is no established supply infrastructure for agricultural biomass such as corn stover, but with no idea of the problems associated with the actual utilization of the material. Our chosen primary fuel stock was to be corn stover. That is unlikely to be the case unless we can find a way to produce a densified product that will work well in our gasifier while holding both monetary and energy costs as low as possible. We have discovered other options, and eliminated some potential crop residues form consideration. Work on fuel type, supply handling, processing, and gasification is ongoing. Corn stover is a bulky, low density product that does not handle well at all. A typical large round bale of corn stover weighs about 1000 lb and has a density of about 10 lb/ft3. Once the bale is broken, the stover fluffs up to density of around 3 lb/ft3. At such low density it would be impossible for us to put the rated 3000 lb/hr of fuel through the gasifier. We found that corn stover will jam typical auger feed systems and even plug and stop a hydraulic ram system. Grinding the product did not help these problems much, and added the problems of increased particulates and entrained air being delivered into the gasifier’s reactor. Obviously, densification to produce a consistent, uniform fuel was the solution. We worked with several companies and researchers to find a pellet or brick or briquette that would meet our needs. But each size and shape of fuel particle had its own set of problems. One of the most critical is that most pellets were simply too dense. They would begin to burn or pyrolyze on the surface, but never were completely consumed. The temperatures on the grate of a gasifier are not as high as those in a standard combustor. At these lower temperatures, the slow reaction of the surface


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of the pellet heats the interior of the pellet to the fusion temperature of the ash. We then end up with clinkers and, if grate temperatures are not carefully controlled, slagging of the gasifier and boiler. Still, densification seems to be the only choice for using corn stover or prairie grass. At present, we are working with V. Morey and colleagues, engineers at the UofM Twin Cities campus, on developing and testing a roller press for compaction of materials such as corn stover and prairie grass. A full-scale prototype should be available for us to test by the fall. In our examination and testing of potential fuels, we tried corn stover, corn cobs, wood, prairie grass, soybean residue, and wheat straw. The last two were rejected quickly. Soybean residue has the lowest heating value of the fuels (7000 Btu/lb) we tested, and it is difficult to handle. But the main problem is the very low yield of residue per acre of land. Wheat straw has a very respectable HHV of 7700 Btu/lb, but caused excessive fine particulate emissions in our system. It also would require densification. The other four fuels remain viable options, with certain provisos. Corn stover must be successfully densified, and we must find a way to reduce the potential for slagging. This area of slagging reduction is a ripe area for research. Prairie grass has slightly less slagging potential, but still requires densification. Wood is an excellent fuel and works beautifully in our system, but is not a locally abundant fuel. We must pay to have it hauled from 100 miles away. This cartage uses diesel fuel and severely offsets the excellent HHV of 8000 Btu/lb. Corn cobs work as well as wood, with a lower HHV (7500 Btu/lb). They handle easily and gasify well with little slagging. But the equipment and infrastructure for collection and storage is not available yet. So, what is the best fuel? Wood, but… •

We live on the prairie. Large quantities of wood must be hauled at least 100 miles to us.

•

Drying and transportation make it expensive.

•

Our break-even point vs. natural gas is about $9.00 per dekatherm.

•

We believe that the future of biomass energy is local. Wood simply is not abundant on the prairie.

Corn cobs are the best local fuel. They require no processing and handle well. Although we give up about 100,000 Btu/ton relative to wood, it is likely our best fuel option if we can develop a supply chain. Prairie grass and corn stover are very abundant, but require densification and mitigation of their slagging potential. Research is underway to find the optimum form and density for our fuels. Densification changes thermal characteristics of the fuels. We must find the optimum relationship between shape and intrinsic density for the densified fuel. And we have found in tests blending fuels that a custom-blended densified fuel might be the best solution, especially if the cost of densification can be kept reasonable. The above-mentioned research by Morey, et al., is very promising in that it provides variable and precise control of density with the added feature of the lowest power consumption of all the densification methods we have tested. To close the cycle of nutrients that we interrupt by using the crop residues or grasses for fuel, we intend to return the ashes to the soil. It is also likely that the remaining fixed carbon in the ash can be valuable. This biochar can improve some soils, and may be an important way to capture and sequester atmospheric CO2. The carbon content of ash can range from