Fuel flexibility of the future combustion engine power plants

2016 | 070 Fuel flexibility of the future combustion engine power plants 08 Basic Research & Advanced Engineering

Päivi Aakko-Saksa, VTT Technical Research Centre of Finland Ltd Juha-Pekka Sundell, Wärtsilä Energy Solutions Lauri Pirvola, Gasum Oy Tuomas Niskanen, Gasum Oy Pekka Hjon, AGCO Power Sami Nyyssönen, VTT Technical Research Centre of Finland Ltd. Tuula Kajolinna, VTT Technical Research Centre of Finland Ltd. Raimo Turunen, VTT Technical Research Centre of Finland Ltd. Seppo Niemi, University of Vaasa Teemu Sarjovaara, Aalto University

This paper has been presented and published on the occasion of the 28th CIMAC World Congress 2016 in Helsinki. The CIMAC Congress is held every three years, each time in a different member country. The Congress programme centres around the presentation of Technical papers on engine research and development, application engineering on the original equipment side and engine operation and maintenance on the end-user side. The topics of the 2016 event covered Product Development of gas and diesel engines, Fuel Injection, Turbochargers, Components & Tribology, Controls & Automation, Exhaust Gas Aftertreatment, Basic Research & Advanced Engineering, System Integration & Optimization, Fuels & Lubricants, as well as Users' Aspects for marine and landbased applications. The copyright of this paper is with CIMAC.

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ABSTRACT Combustion engine power plant related technologies play a significant role in the energy industry. Today, global challenge over whole energy field is to reduce greenhouse gas emissions to combat climate change. This can be achieved by increasing energy efficiency, and by finding alternative and renewable options instead of conventional fossil energy sources. Work on fuel flexibility was conducted within the Future Combustion Engine Power Plant programme (FCEP) of the Cluster of Energy and Environment (CLEEN) in Finland. A number of fuel options, including challenging liquid biofuels and their treatment, as well as gaseous fuels, were explored for different engine concepts. LNG was found to be potential solution to oncoming environmental requirements in shipping. Biogas was studied as regards upgrading technologies, particularly siloxane removal, which is a weak spot for biogas from wastewater and landfills. Mediumspeed engine was tested by using different fuels. Some of the fuels were challenging, and therefore pre-treatment methods for difficult fuels were developed to enable their use in medium-speed engines. Combustion properties of various fuels were studied with special ignition test unit, with a medium-speed and with a high-speed engine. Some fuels yielded promising results when engine performance and emissions are considered. A special task devoted to development of a diesel-ignited dual fuel ethanol high-speed engine for non-road machinery. The developed engine can be switched from diesel to diesel-ethanol operation at any load without noticeable change in engine operating point. Work on fuel flexibility within the FCEP programme took steps towards increased fuel flexibility, and consequently, towards better energy security in Finland. In addition, the demand for lower environmental impact of the current combustion engines was sought for. The structure and form of FCEP programme supported close cooperation of the industrial and research partners. This kind of cooperation and further development in the field of fuel flexibility is still needed.

INTRODUCTION The most important challenges that the world faces today relate to the climate change and energy security. The objectives are challenging, for example, the greenhouse gases (GHG) of developed countries are proposed to be reduced by at least 80% by 2050 compared to 1990 [1]. Furthermore, the regulations for the other emissions are tightening. The new alternative and renewable fuels for the internal combustion engines can contribute in meeting the future targets. A spectrum of fuel options is available, including various liquid and gaseous fuels. Diesel engines, which are the leading power sources for medium and high speed engines basing on their high efficiency, offer an especially efficient platform for the further development towards increased fuel flexibility. Scenarios project that global primary energy supply increases from 550 EJ in 2011 to 700–900 EJ in 2050 depending on the assumptions [2]. Fossil energy reserves are substantial and long-lasting, even though economic feasibility is uncertain and regional differences are high. In addition, if fossil energy is considered as energy solution of the future, it should be decoupled from GHG generation. Estimates on bioenergy potentials vary substantially, for example from 10% to 30% of total energy supply. In addition, sustainability issues remain to be solved for biofuels. Can we use energy crops, if they take area from food crops directly or indirectly? Global renewable energy reserves are higher than the projected energy demand, solar representing the highest reserves. Question remains whether the costs or, for example, critical/rare metals, becomes a limiting factor for these technologies. Renewable energy has been growing strongly, and flexible power generation is increasingly needed to back-up variable renewable energy production and to cope in the field of increasingly complex fuel pool on market. [references in 3]. Gas is suitable for flexible power generation, it is competitively priced, and low carbon option when compared to coal, for example. Gas engines provide in many respect better performance compared to diesel engines. LNG is increasingly used in shipping to meet tightening emission requirements in the emission control areas. If biogas is considered as methane source, upgrading technologies are key issues. Multifuel power plants can use wide variety of liquid and gaseous fuels, both fossil and biofuels, and new fuel options arise. Sufficiency of energy reserves and feasibility of fuel production processes set boundary conditions for the quantity and costs of energy and fuels. On the other hand, engine, emission control technology and infrastructure set requirements on the quality of fuels that can be utilised in the internal combustion engines. Emission limits are tightening for medium-speed engines, and for the mobile machinery. Therefore CIMAC Congress 2016, Helsinki

emission control devices are needed, which in turn require sufficient fuel quality. Fuel can vary from very poor quality, such as heavy fuel oils, shale oil, crude vegetable oils, animal fats and plastic oils to moderate/ good quality, such as fatty acid esters (FAME), hydrotreated oils and fats (HVO), distillates, methane/ LNG, LPG, DME and alcohols. Ligno-cellulosic pyrolysis oil is currently regarded as non-applicable for engines. The question remains, how to find sufficient quantity of compatible fuels for each sector. The Future Combustion Engine Power Plant (FCEP) research program in Finland belongs to the Cluster of Energy and Environment (CLEEN Ltd., currently CLIC Innovation), which aims at maintaining and developing an open innovation platform for market-driven joint research between industry and academia. Work Package 4 (WP4) of FCEP focused on fuel flexibility in the combustion engines. FCEP program covered 17 partners, from which 5 partners contributed in WP4: Wärtsilä Energy Solutions, AGCO Power, Gasum Oy, VTT Technical Research Centre of Finland Ltd and the University of Vaasa. In this work, fossil, bio, and other alternative fuels, including gaseous fuels and pyrolysis oil, are considered for engine power plants, ships and high-speed engines at least for the next 40 years. A number of fuel options, including challenging liquid biofuels and their pre-treatment, as well as natural and biogases, were explored for different engine concepts. Quality of fuels was considered together in respect to needs of engine and emission control technologies. FCEP WP4 resulted in numerous reports and publications [4]. This article shows the main results of fuel flexibility related issues of FCEP WP4.

RESULTS LNG AND BIOGAS LNG logistic chain – Shipping sector is facing major challenges when new emission regulations come in force, such as sulphur limit of 0.1% from January 2015 in North sea and Baltic sea and global sulphur limit of 0.5% from today’s 3.5% in 2020 or 2025. The ECA requirements shifting from a fuel oil based to a LNG based shipping industry will have a potential to reduce CO2, NOx and SOx emissions. The main challenge is an insufficient LNG fuel infrastructure, which also conveys an uncertain price structure. The work at hand investigated the LNG logistics and bunkering solutions for the Finnish market [5]. The various steps in the LNG logistics chain and a number of attributes for each logistical component were analyzed: description, technology maturity and experience, references, economic aspects, space and site requirements, size, scalability, flexibility, limitations, feasibility and risks. The assessment of a possible LNG distribution system for the Finnish marine LNG market concludes that the development will most probably be phased but with a focus on the main RoPax and RoRo hubs in the western and southern coast of Finland. The main

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logistic components for a matured marine LNG market in Finland may include main storage in southern coast, feeder vessel with a cargo capacity of ca 10 000 m3, fixed land based intermediate storages quay side bunkering facilities, bunker vessels, truck and container solutions. Potential hazards in the LNG logistics chain for maritime applications were identified, hazards were ranked in terms of consequence and probability, and mitigating measures for the various hazards were mapped out. LNG supply chain and quality management – Comprehensive supply chain is the main challenge for LNG, which was studied by Riaz [6]. Natural gas harmonization, interoperability and interchangeability are the additional new focus areas for the Finnish natural gas market, currently based only on Russian gas. Until recently, the limits of natural gas properties, acceptable to LNG importers, had been lenient, as it was generally used for power production. However, new markets demand an LNG with quality compatible to their existing pipeline grid and clientele specifications. This raises natural gas harmonization, interoperability and interchangeability concerns in potential LNG importers. Production, liquefaction, storage, transportation, and regasification are among main components of LNG value chain besides many small constituents. A preliminary simulation was conducted for enhancing the LNG methane number through LPG extraction process by means of Aspen HYSYS software. Three interchangeability parameters of natural gas were taken into account: methane number, Wobbe index, and lower heating value. Methane number of natural gas increases with methane and inert (e.g., nitrogen and CO2) content, and decreases with higher hydrocarbons and sulphur contents. High methane number fuel substantially reduces engine-knock, improves the engine efficiency, and decreases the pollutants, especially NOx emissions. Wobbe index is the measure of heat flow to an appliance through a nozzle. Lower (or effective) heating value is the heat of combustion when the water, as the product of combustion, remains in vapour phase. On comparing the available and the required LNG quality, limited LNG sources for Finnish natural gas market were found without at least some processing before injecting to the Finnish natural gas grid. The strict criterion is based on the methane number requirement of 87 by the existing Finnish grid operated by Gasum. If this methane number is reckoned, the available LNG sources increase. Methane number 83 is required by the land traffic sector, which represents 0.2% of Finnish natural gas consumption while rest of the sectors demand methane number 80 and around 35% of consumers in Finland demanded methane number of 70 and less. If methane number minimum threshold is dropped to 75 and then to 70, 13 and 23

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out of 27 LNG export sources would comply with Finnish natural gas market specifications. With current methane number requirement (87) of natural gas grid in Finland, limited number of applicable LNG sources is found without at least some processing. Variety of technologies for LNG quality improvement and management are applicable at LNG receiving/import terminals. A basic simulation process for LNG quality management compares 3 preliminary methods to adjust the quality of imported LNG to reduced heating value [6]: Case I. Extraction of LPG Case II. Injection of nitrogen (nitrogen ballasting) Case III. Injection of CO2 (CO2 ballasting) As portrayed in Figure 1 of end-product quality, Case-II is the most energy intensive process among all three alternatives. For the same value of target parameter LHV, Case-II consumes 359.7 kW and has average yield and smallest methane number, whereas Case-I not only consumes the least energy (257.8 kW), but also generates energy in the form of extracted LPG, which is marketable or could be used for power production. Also, it gives highest methane content (95.7%) and methane number, though it gives slightly lower yield compared to other processes.

Figure 1. Quality parameters of end product obtained from different process alternatives [6]. Biogas upgrading – Biogas can reduce life cycle CO2 emissions, but quality of biogas is not sufficient for internal combustion engines without upgrading. No upgrading technology is suitable for all applications: case-by-case choices are needed to provide sufficient quality of biogas for the natural gas grid or other applications. Different upgrading technologies are favored depending on capacity and source-dependent biogas quality. “Biogas upgrading” means removal of CO2 from raw biogas to increase its methane content. Some of the upgrading technologies can also separate other components, however, the majority of the technologies require the reduction of high concentrations of the other components from raw biogas before upgrading (e.g. activated carbon filter). The current biogas quality requirement in Finland is at least challenging for most of the commercially

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available biogas upgrading technologies, if the biogas needs to be injected to the natural gas transmission system [7]. Another aspect for the technology selection is to find the most efficient, environmental friendly and economic set-up for different applications. Specific energy consumption and methane losses of biogas upgrading technologies vary a lot according to different sources [9, 10, 11]. It seems not possible to proclaim a single technology with the lowest or highest energy consumption. If only the electricity consumption is taken into account the chemical absorption (amine scrubbing) is one the energy efficient upgrading technologies due to the lower operating pressure. The reported results on the methane losses supported each other relatively well. In Germany, the max. allowable methane slip for new upgrading plants is limited to 0.5 % from 2011. Chemical absorption fulfills this criteria without a post-treatment of the off-gas. At the time of review, a simplified life cycle assessment showed that from the selected commercial technologies, water scrubbing and chemical absorption had the smallest environmental impacts [14]. Water scrubbing and chemical absorption had also low life cycle CO2 impact, whereas energy intensive pressure swing adsorption (PSA) and cryogenic separation had the highest impacts. However, here only the electricity consumption is considered and the possible heat demand is ignored. Chemical absorption, for instance, uses quite a lot of heat for the regeneration of the absorption liquid. In general all the upgrading technologies are under constant development and this is expected to have a positive effect on the cost levels. Significant increase in demand leads to more standardized upgrading units, which typically decreases the investment costs per m3/h. A computer program for estimating the investment and operational cost for an upgrading plant developed by Vienna University of Technology is free and it can be downloaded from http://www.bio-methaneregions.eu/. The total number of upgrading plants had increased according the updated IEA plant list (version 01/2013) and the plant data by Petersson and Wellinger [12]. Number of chemical absorption and water scrubbing had increased in the capacity range of 300–1000 nm3/h, whereas the peak in plant number for PSA increased in the capacity range of 1000–4000 nm3/h of raw biogas (earlier in 100–300 nm3/h) in the studied time period. There were significant differences on the data depending on the country where the plant was located. For example, size of the upgrading plants in Sweden fell into the lowest three capacity categories, whereas in the USA into the highest two categories. In Germany main source for biogas was energy corps, in Sweden sewage sludge, and in the USA landfills. Siloxane removal technologies – A special issue regarding biogas from wastewater and landfills are siloxanes, methylated silicon compounds, originating CIMAC Congress 2016, Helsinki

from hygiene, health care and industrial products. In the combustion, silicon dioxide (SiO2) is formed from siloxanes. This forms deposit in the combustion chamber and other stages leading to engine damage already at very low siloxane concentrations. The test bench for siloxane removal technologies was built up at VTT. Simulated biogas (nitrogen with injected impurities) is circulated through siloxane removal units and through passed trace compounds are analysed [13]. Three market leading siloxane removal adsorbents were tested: activated carbon, molecular sieve and silica gel based media. Siloxanes injected in nitrogen were globally the most used siloxane D5, and increasingly used D6 with the target concentrations of 166 mg/m3 and 26 mg/m3, respectively. Common impurities of landfill gas, limonene (target 140 mg/m3) and toluene (target 140 mg/m3) were also injected. The results showed that three commercial siloxane removal systems maintained a siloxane removal efficiency of 95% longer than estimated based on manufacturer's removal capacity data and injected impurities. The activated carbon and molecular sieve system had the highest siloxane removal efficiencies before the breakthrough of siloxanes occurred. The silica gel media had slightly lower siloxane removal efficiency than the other systems. Activated carbon and molecular sieve systems provided the lowest outlet siloxane concentrations: sum of siloxanes stayed well below 3 mg/m3 almost until the breakthrough point (Figure 2). The efficiency of silica gel was also high. Activated carbon efficiently removed toluene and limonene in addition to siloxanes, which was expected due to its feature to remove all organic compounds from the gas. The behaviour of the molecular sieve system was close to activated carbon, whereas silica gel was more selective by removing more efficiently limonene than toluene. Weak removal of other compounds than silicon atoms can be seen as a good feature as more capacity is reserved for siloxanes in the applications where removal of other impurities than siloxanes is not necessary.

Figure 2. Removal capacity results for silica gel, molecular sieve and activated carbon [11].

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Siloxane monitoring systems – It is essential to monitor on-line siloxane concentration to avoid unnecessary engine damages. All siloxane removal technologies will eventually experience a break-through of siloxanes, which is a signal for replacement or regeneration of material. At the moment, no technical standards for siloxane measurements exist. Siloxane monitoring systems were evaluated with emphasis on the capability for continuous monitoring, portability and measurement accuracy [16]. Cost-efficiency is also important due to the large number of gas filling stations. Both commercial systems and the systems under development were considered. Twelve potential siloxane monitoring systems were found. The detection limit values and specificity of monitors varies a lot and may also be affected strongly by the other impurities of the gas. No easily portable monitoring systems were available as the systems were relatively heavy and needed also external zero gases and pump units. The cost level of monitoring systems was between 30 000 and 100 000 euros. MODELLING FUEL PERFORMANCE IN AN ENGINE An attempt was given for modelling the performance and emissions of the engine using a particular fuel basing its chemical and physical properties. Two simulation softwares, GT-Power and Diesel-RK, were used to build models to predict the ignition and combustion of the fuels. Combustion of a new fuel could be predicted by using Computational Fluid Dynamics (CFD) calculation. For practical purposes, however, this way is slow and labour-consuming. The work leaned on the data gathered with Combustion Research Unit (CRU), and even more on the engine tests results. In GT-Power, it is possible to specify a number of fuel components out of which the fuel is composed, but the actual calculations will still be performed using averaged properties for the fuel composition specified. The simulation model takes into account the elementary composition of fuel (carbon, hydrogen, oxygen, nitrogen and sulfur). It was demonstrated that the characteristic changes in engine operation by fuel change could be simulated with the predictive tool. However, the simulation model required calibration for each case – thus making engine testing is a necessity [15]. Diesel-RK can handle spray and combustion chamber geometry unlike many 1D-simulation codes. Many alternative fuels like pyrolysis oils and alcohols have poor ignitability and need pilot injection in the engine. Dual spray systems, however, have complicated interaction and the geometry must be taken into account. Piston engine department in Bauman Moscow State Technical University has developed Diesel-RK software for thermodynamic engine simulation. It has CIMAC Congress 2016, Helsinki

multi zone diesel fuel spray combustion model united with detail chemistry model of combustion and emission formation. The fuel properties can also be set for the model. Though the software can handle engine geometry and the interaction of fuel spray with combustion chamber wall or other spray, it is not CFD code and thus quite quick. A model, which gives ignition delays and heat release curves reasonably well for the example case, was created [16], however, many parameters must be correctly set for each fuel to get right results. As a conclusion, Diesel-RK could describe the behavior of a fuel(s) in the engine, but not basing merely on chemical and physical properties of fuel. All in all, it is difficult to model combustion of a new fuel in the diesel engine, and the situation is even more difficult with medium and low speed engine fuels, for which real cetane number is not available. Calculated Carbon Aromatic Index (CCAI) is a characteristic (basing on density and viscosity) used for ignitability instead, but it has found to work only with old-type fossil heavy fuel oils. A new attempt to predict the ignition and combustion properties of a fuel in recent years is the combustion chamber (or bomb) tests. In those the fuel is injected to a heated and pressurized atmosphere and the pressure curve is analyzed. So called Estimated Cetane Number (ECN) can be calculated from the results, too. CIMAC has made a recommendation of ECN for different types of engines. However, even bomb results fail many times to predict fuel combustion behavior in a real engine. Apparently the discrepancy between chamber and engine results arise from such things like differences in geometry, environmental conditions, injection pressures, swirl, and time scales. The situation becomes even more tricky in the case of two-fuel engines. UNCONVENTIONAL AND DIFFICULT FUELS FOR MEDIUM-SPEED ENGINE Synthesis report on future fuels for power plants was prepared basing on literature and the seminar organized for this purpose. The report collects views on potential fuels for combustion engine power plants in relation to drivers, energy sources, sectorial aspects and technology breakthroughs [3]. Pre-treatment of difficult fuels and cold performance – Some difficult fuels cannot be used in engine without fuel pre-treatment. In this work, new pre-treatment methods were developed, for example washing methods and fuel filters. Remarkable success was achieved also with the theory behind the agglomerates also known as phosphate lipids (Figure 3) which is a challenge for fuel filters. Fibres were found from Crude Palm Oil (CPO), which will affect to the filters in a negative way. For the fibres mechanical manipulation tests were conducted. Different kind of washing methods for filters was developed [17].

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gained. All fuels tested were suitable for use even at cold condition in a containerized 9L20 (1.6 MW) power plant, however, chicken oil showed some troubles. Some fuels smelled; fox oil smelled particularly bad. Engine tests – Before the engine tests, laboratory size tests were conducted with CRU. This equipment is a special unit for research of fuel ignition properties. This research showed, for example, which fuels could be used with HFO to decrease emissions. When the CRU results were promising, it was reasonable to continue with engine size tests. Figure 3. Fibres from crude biofuel [17]. Water degumming is a process, which decreases the content of inorganic particles, fibers and gum forming oil components in crude vegetable oil. Main purpose was to produce oil that doesn’t form deposits during transportation, storage, and that process is simple. Methods were developed as laboratory size tests at Wärtsilä Energy Solutions fuel laboratory and continued at VTT as engine size tests. In the laboratory tests for continuous systems, preheated oil (~70°C) was treated with water and mixed in a reactor tank with continuous inline agitators. At engine size tests, different techniques of mixing water with CPO were tested at water concentrations of 1%, 3% or 10%. Batch, static and homogenizer type mixers were used. Mixing period was mainly 30 minutes at 60–95°C. Settling temperature was 50–85°C for 1–18 hours. Separators were used for water and fibre removal. For crude biofuels one major challenge is related to impurities and agglomerates. The quality of the liquid bio-fuel (LBF) is strongly dependent on the feedstocks, which affect electric chemistry and fiber size of LBF, for instance. Washing methods, as well as mechanical manipulation tests on fibres, are needed. A totally new kind on filter unit for LBF was developed. The deterioration of oils and fats is a sum of different factors, such as autoxidation, thermal oxidation or biodegradation, which all involve various chemical, physical and biological mechanisms. Study was performed on the stabilization of plant oils and animal fats in comparison with ester-type biodiesels. The studied bio-oils were animal fat, rapeseed oil, animalbased fat methyl ester and rapeseed methyl ester. Deterioration by auto-oxidation and biodegradation of plant oils, animal fats and biodiesels can be alleviated by antioxidants. Antioxidant additives need to be selected fuel-dependently, because source materials dictate the effectiveness of additives and esterification play a role, as well [18]. LBF fuels with poor cold properties were successfully used in winter conditions in Pieksämäki in a containerized 9L20 (1.6 MW) Power plant. Tests focused on the tests at winter conditions with fox oil, chicken oil, fish oil and rape seed oil. The acid number of chicken oil was high, and new information about the metallurgic challenges with aged chicken oil was CIMAC Congress 2016, Helsinki

With VTT’s Wärtsilä Vasa 4R32 engine, almost 20 combinations of fuels were studied including petrochemical products, blends with chemical fuels, waste fractions, biobased side products and alcohols [19]. Using fractions currently nominated as hazardous waste would allow recycling of fuels, for example, by finding a way how to avoid/minimize use of flare for condenses. Medium speed engine was used in two modes: LN configuration uses standard mechanical injection system and the GD injection system is a dual fuel arrangement. The injection pumps designed for GD operation were used in both cases. During the tests, temperatures, pressures, and mass flow rates of fuel and air were recorded at 1 Hz frequency. Sampling was synchronized to engine crank shaft angle encoder signal at the sampling interval of 0.2 degrees at crank shaft. Cylinder combustion chamber and fuel injection pressures were gathered with fast data acquisition from one cylinder. Pressures via indicating cock of each cylinder were monitored when there was risk of too high in-cylinder pressure. In some cases, GD fuel rail pressure and the electronic rail valve (ERV) control signal were measured. Needle lift was measured when LN injectors were installed. Rate of heat release curves were calculated according to the measured in-cylinder pressure. Engine performance, gaseous emissions and particulate matter (PM) emissions according to ISO 8178 were measured in all single fuel tests. The test sequence consisted usually of 5 loads between 100% and 10% of nominal load. With dual fuel tests, the PM measurements were excluded in most cases, and the loads were chosen case-specifically. Single fuel tests included light fuel oil (LFO), animal fat, shale oil, tyre pyrolysis oil and hexane fuels. LFO was used as a reference fuel in both LN and GD engine modes [19]. Actual test fuels were conducted into cylinder trough LN or GD (pilot side) standard injectors, except for two cases in which LN engine mode with modified W20 engine injector nozzle tips were used (reduced injector fuel hole diameter). Tyre pyrolysis oil, animal fat and shale oil were tested with standard LN injectors. After shale oil test, tribological analyses of injector nozzle tips were carried out at VTT.

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For dual fuel tests, the standard Wärtsilä GD-injection system was modified to accept liquid and liquefied fuels [19]. The modified GD gas fuel circuit consists of high pressure pump with piping, hydraulic unit for needle actuating, and injection nozzles with liquid (pilot) and gas injection holes. The pilot injection works in ordinary manner and the needle is opened by the fuel pressure. There are three gas injection needles per injector. The ERV controls the needles with hydraulic pressure produced by auxiliary high pressure oil unit. The needle lift timing and fuel rail pressure are controlled by programmable logic controller that is connected to the Wärtsilä operator’s interface system. Several fuel injection ways were possible during the tests. The fuel was conducted to normal mechanical system from LFO system or from booster unit. GD injection system was in use simultaneously with mechanical injection and it could be controlled independently. The standard GD fuel injection system is designed for gaseous fuel. Therefore, the standard nozzle tip fuel hole diameter was proved to be too wide for most liquid fuels. GD nozzle tips with narrower fuel injection holes were not available. Therefore, the standard GD nozzle tips were modified. The first set was modified by simply blocking some of the fuel injection holes, and for the other sets sleeve inserts were welded into the fuel injection holes. In one case the internal fuel flow path was enhanced. In one set, the pilot fuel injection holes were widened. Dual fuel test started with hexane as fuel [19]. The pilot fuel was always LFO. The standard GD-type injector was used with different injection parameters in some tests. Some holes of the nozzles were blocked in order to improve the sprays from the remaining holes or the GD injector gas holes were reduced. When the effects of two stage injection and different GD fuel rail pressures were studied in addition to injection timing, a better controllability and efficiency was gained, but the emissions were not sufficiently good. When hexane was mixed with chemicals, engine could run with less pilot fuel. With hexane, the maximum load achieved was slightly less than with LFO, due to the lower maximum capacity of injection pump elements with low density of hexane. For LPG, further modifications were needed. New fuel delivery system to GD high pressure fuel pump was built. At VTT, a flare unit was constructed for flushing the piping and for safe discard of fluid during overpressure and emergency stop situations. LPG container was acquired and piping from the container was build. LPG handling premises were equipped with several gas detectors and alarm system. A mixing equipment was built to dose extra substance into propane. Thus, there were three separately controlled flows into the engine. In one of the tests, oil drilling site condensate was simulated by mixing propane and hexane. Glycerine was tested with several fuel injection and delivery strategies. Dual fuel test setup was similar as with petrochemical fuels. One of the tested glycerine batches seemed to contain significant amount of methanol and/or fatty acid methyl CIMAC Congress 2016, Helsinki

ester (FAME) as a residue from the manufacturing process (glycerine was a by-product of FAME production). This fuel also proved to be demanding to filter and handle. The measured filter smoke number was low with waste glycerine batch, even though the particulate mass emission was very high. In this case colour of particulate matter was white, which indicates that particles consisted mainly of substances other than soot. MOBILE MACHINERY Biofuel B20 – Engine development may enlarge possibilities to utilise new alternative fuels. For conventional diesel engine of non-road machinery, the alternative fuel options cover basically an ester-type FAME biodiesel and paraffinic HVO-type renewable fuel. FAME is problematic as concerns fuel stability and compatibility with emission control devices. In addition, the quality of FAME varies regionally, which is difficult warranty issue for an engine manufacturer. HVO fuel is in commercial use and generally it has positive effects on engine performance and emissions. Interest in the use of FAME in mobile machinery exists, and thus this study covered how FAME affects the performance and reliability of exhaust aftertreatment systems. In machines with exhaust aftertreatment, AGCO Power only allows the use of FAME as blends in standard diesel fuels (EN 590 or ASTM D975). However, there is interest to introduce “B20” or “B30” blends in certain regions. Literature study showed that FAME fuels have been problematic as concerns storage stability [20]. In addition, phosphorus present in FAME is harmful for catalysts. The chemical composition of FAME varies quite considerably depending on the production site and raw material leading to regional variations in fuel composition. Exhaust aftertreatment systems are introduced today to non-road mobile machinery (EGR+DPF or DOC+SCR). AGCO Power selected SCR technology, because it gives clear benefits in fuel economy, base engine durability and cooling capacity. If an engine manufacturer gave an approval to use FAME fuel, it should be applicable in all regions where quality-controlled FAME is available. The literature study showed that there are risks of catalyst poisoning when FAME is used, especially if it is used neat. The 500 hour B20 test was conducted with a modern off-road diesel engine driven with a fuel blend of ordinary diesel fuel oil (DFO) and soybean methyl ester (SME) for a period of 500 hours [20]. The B20 blend was doped to contain Na+K 10 ppm, Ca+Mg 10 ppm and P 4 ppm before preparing the blend. The main target was to study how the fuel blend affects the performance of the DOC and SCR system. Thorough performance and emissions measurements were conducted at the beginning (baseline), after 250 hours of engine operation, and in the end or after 500 hours of engine operation. Based on the performed

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measurements, the following conclusions could be drawn:

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The NOx conversions decreased by 3–13% at an alpha ratio of 0.95 during the endurance test with B20 blend. The results indicate problems with catalyst poisoning due to certain alkali metals and alkaline earth metals concerned as typical residues from the production process. Based on the decrease in NOx conversion, problems in NTE area and NRTC cycle emissions are expected if B20 blend is being used instead of diesel with EN590 specification.

The risk of damage can be considered noticeable even though FAME quality would be controlled according to proper standards. The conclusion of this study was that 20% FAME blend cannot be recommended for the state-of-the art heavy-duty engines without revision of alkali and earth alkaline metals limits of EN14214 standard. Fish and animal fat esters – A turbocharged, intercooled high-speed non-road diesel engine, manufactured by AGCO Power Inc., was driven by the University of Vaasa (UV) at the engine laboratory of Technobothnia Research Centre with different fuels and injector tips [21, 22]. Fuels studied were HVO, biodiesel from fish wastes (FISH ME), and animal fat based methyl ester (AFME). The baseline fuel was low-sulphur diesel fuel oil (DFO). AFME and FISH ME contain oxygen leading to the lower heating value than that for DFO and HVO. The studied batch of AFME contained slightly more sulphur than other fuels. The cetane number of HVO was significantly higher than that of other fuels. AFME contained much more saturated fatty acids than FISH ME, whereas FISH ME contained more polyunsaturated fatty acids than AFME. AFME showed a much lower iodine value (79) than FISH ME (132) - the latter did not meet the limit of 120 in the European biodiesel standard (EN 14214, 2008). Measurements were conducted according to the test cycle C1 of the ISO 8178-4 standard or the Non-Road Steady Cycle (NRSC). With few exceptions, the injection parameters were kept constant for all fuels and injector tips. The NOx emissions were higher at high loads when the engine was operated on FISH ME or AFME instead of DFO or HVO (Figure 4). The lowest high-load NOx was measured with HVO.

DFO HVO

NOx, (g/kWh)

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Rated speed 5,5

FISH ME

4,5

AFME

3,5 2,5 1,5 0

2

4

6

8

10

12

BMEP, bar

Figure 4. NOx emissions versus load at rated speed with different fuels [21, 22]. The lowest smoke readings were recorded with AFME and FISH ME. Smoke was at its highest with DFO and the HVO results were between those of the esterified fuels and DFO. Particle size distributions were also determined. Generally, the use of esterified bio-diesels seemed to reduce ultra-fine and large particles (> 50 nm). At idle, HVO reduced nanoparticles drastically. In addition to the fuel tests, four different injector tips the from the engine manufacturer AGCO Power Inc. were investigated running the engine on DFO. Regarding exhaust smoke at part loads, some advantages were achieved with the eight-hole low-flow (LF) injection nozzles. With these nozzles at rated speed, the NOx emissions remained almost unchanged with the exception of the lowest load, where NOx increased. At intermediate speed, the high-flow (HF) nozzles reduced NOx emissions but smoke increased. Usually, the 8-hole LF tips also reduced the number of ultra-fine and large particles (> 50 nm), while the HF nozzles tended to increase the number of large particles consistently with the higher smoke readings. Slight modifications had to be made for injection parameters in case of 8-hole LF nozzles due to the low flow rate and long injection duration. This must be taken into account when ranking the studied tips. Diesel-ignited dual fuel engines – A pathway to use alternative fuels for non-road machinery is the development of a diesel-ignited dual fuel engines. Here, focus was on dual fuel engine using ethanol as the main fuel and diesel fuel for ignition. In Brazil, ethanol made of sugar cane is used extensively as fuel in passenger cars with spark ignition engines. Because ethanol is relatively cheap and plentiful on sugar cane farms and basic diesel-powered tractors are used, the objective here was to study if a standard diesel engine could be modified to run with ethanol as primary fuel, ignited with diesel. The aim of this dual fuel study was to determine if a standard nonroad diesel engine can be converted to use ethanol as main fuel and use the existing diesel injection system to ignite the ethanol. The first test


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engine was built with rather big modifications for ethanol combustion and limited possibilities to adjust diesel injection [25]. The results from the first test engine showed that dual fuel combustion is not very problematic, especially concerning knock. The work continued towards a less modified engine which could be used with 100% diesel fuel, too. The second dual-fuel test engine was built up by using a 6 cylinder 7.4 litre engine as basis, having a common rail system and 2-valve cylinder heads (Figure 5). The main modifications included intake manifold with individual ports for ethanol injectors and lower waste gate opening setting [24]. Separate but interconnected ECUs were used for diesel and ethanol control. It was possible to set different diesel injection parameters (timing, rail pressure, use of pilot injections) for dualfuel and 100 % diesel. The system calibration for ethanol fuelling / diesel replacement was based on cylinder pressure curves. Ethanol fuelling at each load was limited so that a sufficient margin for knocking could be maintained. The performance targets were met and the engine can be switched from diesel to dual-fuel at any time without any noticeable change in engine performance or driveability. The second test engine was optimized for typical tractor load factors. The diesel substitution rate was 20–70 % depending on speed and load. In addition, performance in 100 % diesel operation was not compromised. At full load, a moderate substitution was used to prevent knock. Typical tractor loading situations were considered, and reasonable substitution was reached in those conditions. Exhaust emission measurements showed that the premixed ethanol increases HC and CO comparable to SI engine level, whereas the dual-fuel combustion reduces NOx compared to 100% diesel. PM emissions are typically lower for ethanol than for diesel fuel. The emissions results are reported by Väisänen [25]. It was possible to reach Tier 3 level by making some modifications in the charging system and diesel parameters and adding an oxidation catalyst. Brazil will introduce Tier 3 level exhaust emission limits for tractors after 2017. A totally similar engine was built for installation on a tractor for field testing in sugar cane farms in Brazil.

Figure 5. Diesel-ignited dual fuel engine using ethanol as the main fuel [24].

SUMMARY AND CONCLUSIONS Potential alternative fossil fuels and biofuels, including gaseous fuels and pyrolysis oil, were considered for engine power plants, ships and high-speed engines. Challenges for future energy are huge, but opportunities are also high. There are rapid technology developments foreseen that allow creation of new solutions. Fuel flexible engines represent a pathway to cope in the field of increasingly complex fuel pool on market, to enlarge possibilities to utilise new alternative fuels and to serve as a back-up for renewable energy. The shipping industry is facing major challenges with the emission regulations in the emission control areas. LNG was found to be the potential fuel to respond to upcoming emission requirements, but insufficient infrastructure presents a weak spot for large scale use. Various steps to improve LNG logistics in Finland were explored. A suitable LNG distribution network was found to probably focus on the main RoPax and RoRo hubs along western and southern coasts of Finland. The challenges associated with the LNG supply chain relate to harmonization, interoperability and interchangeability. Production, liquefaction, storage, transportation, and regasification are among the main components of LNG value chain. The world LNG sources suitable for import to Finland were identified based on specifications set by national natural gas applications. Methane number was the most critical constraint and to be deciding factor for selection of appropriate LNG variety available worldwide. Technologies available for LNG quality improvement and management were also evaluated. Quality of biogas as such is not sufficient for internal combustion engines; carbon dioxide and different impurities need to be removed. Water scrubbing, PSA and chemical absorption are popular technologies for upgrading of biogas. Costs of upgrading are dependent on the technology and size of the plant. Siloxanes present in biogas from wastewater and landfills are harmful for engines even at low


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concentrations. Efficiencies of three market leading siloxane removal adsorbents were tested (activated carbon, molecular sieve and silica gel based media). Three siloxane removal systems performed well in the tests, but differences in efficiencies and cleanliness of purified biogas were observed. In the evaluation of the siloxane monitoring systems, twelve candidates were found capable to measure low siloxane concentrations. The detection limits and specificity varies substantially, and no easily portable monitoring systems were available. For difficult fuels, pre-treatment methods were developed and remarkable success was experienced with new washing methods and fuel filters. For plant oils, animal fats and esters, efficiency of antioxidants was shown to be fuel-dependent. Use of several liquid biofuels with poor cold properties performed well in winter conditions in a containerized 1.6 MW power plant. With medium-speed Wärtsilä Vasa 4R32 engine, various fuels were studied in standard LN configuration and with the modified GD injection system: almost 20 combinations of reference fuel, petrochemical products, blends with chemical fuels, biobased side products and alcohols. Improvements in injection system performance, controllability and efficiency were gained. For conventional diesel engine of non-road machinery, paraffinic HVO-type renewable fuel shows generally good performance, whereas ester-type FAME biodiesel is problematic as concerns fuel stability and compatibility with emission control devices. This work showed that 20% FAME blend cannot be recommended for the state-of-the art heavy-duty engines equipped with emission control device without revision of metal limits of EN14214. Tests with fish oil and animal fat esters were conducted with a turbocharged, intercooled common-rail high-speed engine. The NOx emissions were higher for esters than for diesel at high loads, whereas the lowest high-load NOx was measured for the paraffinic HVO. The lowest smoke readings were recorded for esters, but HVO also resulted in lower smoke than conventional diesel fuel oil. For non-road machinery, a diesel-ignited dual fuel ethanol engine was developed. The engine has separate control units for diesel and ethanol injection. Depending on speed and load, 20 to 70 % of diesel consumption can be replaced with ethanol without compromising 100 % diesel operation. It was possible to reach Tier 3 emission level by making some modifications and by adding an oxidation catalyst. A diesel-ignited dual fuel ethanol engine was built and installed in a demonstrator tractor for a field test in Brazil. As a summary, a wide scope of issues related to fuel flexibility of medium-speed engines and machinery were taken, including options for the future LNG CIMAC Congress 2016, Helsinki

logistics in Finland and solutions for biogas use for engine power plants, as well as challenging liquid and gaseous non-conventional and biofuels and their treatment. These steps pave the way towards increased fuel flexibility, and consequently, towards better energy efficiency. Lower CO2 emissions and environmental impact of the current combustion engines were sought for. The structure and form of FCEP program supported close cooperation of the industrial and research partners, which integrated different know-how and competences to reach maximum achievements and increased understanding on the fuel flexibility in the energy field. This kind of cooperation and further development is still needed.

ABBREVIATIONS AFME animal fat based methyl ester B20 20% bio-component blended in diesel Ca Calcium CCAI Calculated Carbon Aromatic Index CFD Computational fluid dynamics CO2, Carbon dioxide and CPO Crude Palm Oil CRU Combustion research unit DFO Diesel fuel oil DME Dimethyl ether DOC Diesel oxidation catalyst DPF Diesel particulate filter ECA Emission control area ECN Estimated Cetane Number ECU Engine control unit EGR Exhaust gas recirculation ERV Electronic rail valve FAME Fatty acid esters (biodiesel) FISH ME Biodiesel from fish wastes GD Gas diesel technology GHG Greenhouse gases HVO Hydrotreated oils and fats (renewable diesel) K Potassium LBF Liquid bio-fuel LPG Liquefied petroleum gas LFO Light fuel oil LNG Liquefied natural gas Mg Magnesium Na Sodium NOx Nitrogen oxides P Phosphorus PM Particulate matter PSA Pressure swing adsorption RoPax Vessels for wheeled cargo and passengers RoRo Roll-on/roll-off vessels for wheeled cargo SCR Selective catalytic reduction SiO2 Silicon dioxide SME Soybean methyl ester SOx Sulphur oxides

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ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support from Tekes (426/10) (the Finnish Funding Agency for Technology and Innovation) for the Future Combustion Engine Power Plant (FCEP) program, Work Package 4, Fuel Flexibility. The authors would also like to thank the personnel running the mediumspeed engine at VTT: Jarmo Kuusisto, Jarno Martikainen and Matti Niinistö.

REFERENCES [1] IEA, “Energy Technology Perspectives”, 2010. © OECD/IEA 2010. [2] IEA, “Energy Technology Perspectives”, 2012. © OECD/IEA 2012. [3] AAKKO-SAKSA, P. (Ed.) “Synthesis report on potential fuels for future combustion engine power plants” Cleen Ltd. FCEP WP4 Fuel flexibility, Research Report D4.3, 2014. [4] AAKKO-SAKSA, P., HJON, P., KAJOLINNA, T., NIEMI, S., NISKANEN, T., NYYSSÖNEN, S., TURUNEN, R., PIRVOLA, L., SALMINEN, H., and SUNDELL, J-P. ”FCEP WP4 Fuel flexibility – Final report” Cleen Ltd. Research Report D4.14, 2014. [5] BURNS, G., ANDERSSON, H., WOLD, M., and JOHANSSON, M. “LNG logistics and bunkering solutions for maritime applications” Cleen Ltd. Research Report D4.2 (in Finnish), 2011.

[11] TUW “Biogas to Biomethane Technology Review” Vienna University of Technology, Contract Number: IEE/10/130, Deliverable Reference: Task 3.1.1, 2012. [12] STARR, K., GABARRELL, X., VILLALBA, G., TALENS, L., and LOMBARDI, L. “Life Cycle Assessment Of Biogas Upgrading Technologies” Waste Management, 32, 2012, pp. 991-999. [13] KAJOLINNA, T., AAKKO-SAKSA, P., ROINE, J., and KÅLL. L. “Efficiency testing of three biogas siloxane removal systems in the presence of D5, D6, limonene and toluene”, Fuel Processing Technology, 139, 2015, pp. 242-247. [14] KAJOLINNA, T. in “FCEP WP4 Fuel flexibility – Final report” Cleen Ltd. Research Report D4.14, 2014. (Aakko-Saksa, P. et al.). [15] SALMINEN, H. J. ”Prediction method” Cleen Ltd. FCEP WP4 Fuel flexibility, Research report D4.5, 2011. [16] TURUNEN, R. “Ignition properties of fuels Combustion prediction by Diesel-RK”. Cleen Ltd. FCEP WP4 Fuel flexibility, Research report D4.13, 2014. [17] SUNDELL, J-P. in “FCEP WP4 Fuel flexibility – Final report” Cleen Ltd. Research Report D4.14, 2014. (Aakko-Saksa, P. et al.).

[6] RIAZ, M. K., “Supply chain analysis and upgrading of liquefied natural gas (LNG) to meet Finnish gas market specifications” Master’s thesis, Aalto University Schools of Technology, 2014.

[18] VAUHKONEN, V., SIRVIÖ, K., SVAHN, A., and NIEMI, S. ”A comparative study of the antioxidant effect on the autoxidation stability of estertype biodiesels and source oils” International Conference on Clean Electrical Power, Renewable Energy Resources Impact (IEEE), Ischia, Italy, 14th-16th June 2011. pp. 211–215.

[7] PIRVOLA, L. in “Periodic report of 3rd Year” Cleen Ltd. FCEP WP4 Fuel flexibility, Research report D4.12. 2013. (Aakko-Saksa, P. ed.).

[19] NYYSSÖNEN, S. “Single and dual fuel tests with medium-speed engine” Cleen Ltd. FCEP WP4 Fuel flexibility, Research Report D4.6, 2014.

[8] PATTERSON, T., ESTEVANS, S., DINSDALE, R., and GUWY, A. “An evaluation of the policy and techno-economic factors affecting the potential for biogas upgrading for transport fuel use in the UK” Energy Policy, Vol 39, 2011, pp. 1806-1816.

[20] HJON, P., RAUTANEN, I., and KATILA, T. “First Generation Biodiesel as Nonroad Fuel” Cleen Ltd. FCEP WP4 Fuel flexibility, Research Report D4.8. 2011 (rev. 2014).

[9] WEILAND, P. “Status of Biogas Upgrading in Germany. IEA Task 37 Workshop Biogas Upgrading” Johann Heinrich von Thünen-Institute (vTI), Federal Research Institute for Rural Areas, Forestry and Fisheries, 2009. [10] PETERSSON, A., and WELLINGER, A. “Biogas upgrading technologies – developments and innovations” IEA Bioenergy, 2009.


[21] HISSA, M. “High-speed engine results with various renewable fuels” M.Sc.Thesis. The University of Vaasa, 2014, 187 p. [22] NIEMI, S., HISSA, M., SIRVIÖ, K., and NILSSON, O. “Engine tests with high-speed engine” Cleen Ltd. FCEP WP4 Fuel flexibility, Research Report D4.7, 2014. [23] ALANTIE, J. “A study on combustion in an ethanol-fuelled diesel-injection-ignited engine”

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Master´s thesis, Aalto University Technology, 2012 (in Finnish).

Schools

of

[24] HJON, P. “Studies on high speed diesel-ethanol dual fuel engines” Cleen Ltd. FCEP WP4 Fuel flexibility, Research Report D4.9, 2014. [25] VÄISÄNEN, E. “Emission control of an ethanolfuelled diesel-injection-ignited engine” Master´s thesis, Aalto University Schools of Technology, 2013 (in Finnish).

CONTACT Päivi Aakko-Saksa, VTT Technical Research Centre of Finland, e-mail [email protected]


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