APPLICATION OF GAS PERMEATION FOR BIOGAS UPGRADE – OPERATIONAL EXPERIENCES OF FEEDING BIOMETHANE INTO THE AUSTRIAN GAS GRID M. Miltner, A. Makaruk, M. Harasek Institute of Chemical Engineering, Vienna University of Technology A-1060 Vienna, Getreidemarkt 9/166, Austria, Phone: 0043/1/58801-15929, Fax: 0043/1/58801-15999
[email protected] ABSTRACT: The process design, plant erection and operational experiences of a novel biogas upgrading plant that produces approximately 100m³(STP)/h of fully-fledged natural gas substitute from about 180m³(STP)/h of raw biogas will be presented. The upgrading is based on the membrane separation process Gas Permeation and allows low energy consumption as well as very low methane losses. The quality of the upgraded biomethane is controlled continuously regarding various unwanted or malicious substances to assure the agreement with the quality prescribed by Austrian laws. The produced biomethane is introduced to the natural gas grid and delivered to the households of the neighboring city Bruck/Leitha in Lower Austria. During the summer months the gas consumption in the local grid is far too small compared to the produced biomethane stream and the excessive biomethane is compressed to 60bar and fed into the regional natural gas grid. The process of Gas Permeation is continuous, stable and relatively easy to handle and to control; furthermore, no regeneration or chemicals are needed. Additionally, a dynamic process simulation model has been developed to gain knowledge of startup and shutdown procedures, as well as to test control strategies and parameterize the implemented PID controllers. Keywords: biogas, methane, operating experience 1
INTRODUCTION
Biogas is considered to be a renewable and sustainable energy source. It is produced in a large number of biogas plants all over Europe from a manifold of substrates like energy crops, organic wastes or agrarian residues. Besides the minor content of malicious components like ammonia or hydrogen sulphide, this gas mainly contains methane (45 to 70vol%) and carbon dioxide. The common technology to use this energy source nowadays is the combustion in gas-engines and generating electric power with an efficiency of 35 to 40%. Because of the rising prices of energy and resources the usage of the thereby incurred waste heat is of vital importance for an economically and ecologically efficient operation of the biogas plant (e.g. district heat production). These biogas plants have proven their feasibility, therefore, a considerable amount of them have been constructed in the recent decades and many are still planned. Biogas upgrading can be an alternative solution to the production of electrical energy and heat. Processed biogas could be used as a fully-fledged natural gas substitute in households or industry or as a fuel for transportation purposes (CNG-Engines). One could use the natural gas infrastructure, i.e. piping and accumulators, to supply the gas to the consumers. The introduction of upgraded biogas as an alternative to the imported natural gas would have three main advantages. Firstly, it would reduce the dependence of European economy on foreign suppliers. Secondly, it would help to fulfill the European policy on reduction of carbon dioxide coming from fossil fuels and thirdly, it would support local undertakings and increase the local added value. Natural gas is a very popular fuel in Europe. European industry, power generation and households depend mainly on this source of energy. Among its advantages are: low transportation costs by pipelines and low emission of carbon dioxide and other contaminants per unit of produced energy in comparison with other fuels.
As a consequence of the aforementioned facts, a need for a process emerges that would be capable of an effective biogas upgrading. Due to the fact that the production of renewable energy has usually low Energy Returned on Energy Invested index, it is crucial to reduce the operational and investment costs of the biogas processing to the lowest possible level. Additionally, the process should be automated and operated with ease since little personal supervision is desired for the operation of the relatively small plant. Within this work, the design and the operational experiences of the first industrial scale biogas upgrading plant in Austria are presented. The aim of the project was to construct a fully automated unit that would be able to process approximately 180m³(STP)/h of biogas and supply 100m³(STP)/h of biomethane to the natural gas grid. The upgrading is based on the gas permeation membrane process. 2 GAS COMPOSITION NECESSITIES
AND
UPGRADING
There are more than few differences between biogas and the gas that is supplied to the consumers. Table I compares the properties of biogas and natural gas defined by the Austrian norms OEVGW G31 [1] and OEVGW G33 [2]. The compliance of the upgraded biomethane to these norms is obligate for feed-in operation. It can be easily seen that in order to upgrade biogas to the quality of natural gas, many steps must be performed. The most important of them are the separation of malicious substances, drying and separation of carbon dioxide, nitrogen and oxygen, which results in the increase of combustion heat and Wobbe Index. A reasonable combination of separation methods is a key to the successful gas upgrading. The process needs to be cheap, reliable and have low energy consumption. The main process steps that have to be performed to reach the aspired product gas quality given in legislature are shown in Fig. 1. Independent of the applied technique, the biogas upgrading plant has to implement each of these
steps to ensure the production of a biomethane gasstream according to the prescribed quality limits. If any technology would be able to combine two or more of these steps into one separation process, this technology would probably gain the lead over others. Table I: Characteristic of typical biogas and natural gas defined by Austrian norm OEVGW G31 and G33
45-70
Natural Gas -
mol %
30-45
≤2
mol %
≤1 000
0
mg/m³(STP)
≤2 000
≤5
mg/ m³(STP)
≤2 ≤8 37 at 1bar
≤0.5 ≤5 ≤-8 at 40bar
mol % mol %
6.7-8.4
10.7-12.8
kWh/m³(STP)
6.9-9.5
13.3-15.7
kWh/m³(STP)
Biogas Methane Carbon dioxide Ammonia Hydrogen sulphide Oxygen Nitrogen Water (dew point) Combustion heat Wobbe index
Unit
°C
Biogas production
Desulphurisation (preliminary)
Compression
H2O/NH3Separation
Desulphurisation (complete)
Drying
Separation of other contaminants
CO2Separation
Grid supply (Odorisation)
Figure 1: Main steps of the biogas upgrading process necessary to reach aspired product gas quality 3
Biogas CH4 CO2 H2O H2S feed
NH3 N2
O2 CH4-rich Retentate CO2-rich Permeat
Membrane (aromatic polyimide)
Figure 2: Principle of gas separation using the membrane technique Gas Permeation The separation technique uses a dense polyimidemembrane with different solubilities and diffusivities for the various gas species contained in the raw biogas feed. As a result, the driving force for separation is the difference in the partial pressures of the various species between the feed phase and the permeate phase. A high flux through the membrane can be realized with high pressure on the feed side and a low pressure (near to atmospheric pressure) on the permeate side of the membrane. Using this membrane material, most unwanted gas species are quantitatively removed from the feed stream and transported through the membrane to the permeate stream. Only nitrogen shows similar behavior as methane and therefore cannot be removed by this technique but remains in the product gas stream, the so-called retentate. Sufficient product gas quality and quantity can easily be reached if only enough membrane area and adequate operation conditions are provided. The great advantages of this process compared to others are the continuity, compactness, simultaneous drying and the removal of the traces of hydrogen sulphide and ammonia. Since the mixture of NH3, H2S and very humid gas can jeopardize the membrane material, some gas processing before the gas permeation is necessary. The membranes are constructed as hollow fibres with the high pressure feed/retentate stream on the inner side of the tube and the low pressure (almost atmospheric) permeate on the outside of the tube. Many of these fibres are collected to form a membrane module that is fed with pressurized biogas.
PROCESS DESIGN AND PLANT ERECTION
The most important task of biogas upgrading is the separation of carbon dioxide from the product gas stream. This is because CO2 is the main unwanted contaminant in the raw biogas and therefore produces the highest waste gas stream. Several classical processes have been suggested to meet this task and some of them have already been engineered and implemented into existing biogas plants. Among others these processes comprise Pressure-swing Adsorption (PSA), Temperature-swing Adsorption (TSA), water scrubbing (with thermal regeneration), amine scrubbing (MEA, MDEA), and cryogenic separation. All named processes show different advantages and drawbacks. Within this work, a novel membrane separation technique named Gas Permeation has been applied for the main biogas upgrading steps. This process has its advantages in a stable and continuous operation and thus is easy to control. Furthermore, no expensive regeneration or chemicals are needed. The whole process becomes very simple, straight-forward and compact. A simplified scheme showing the principles of this separation technique is presented in Fig. 2.
Product gas (CH4 – rich) H2S Adsorber Cooler (Refrigerant Drying) Compressor Biogas Heater
Module 1 Module 2
Offgas (CO2 – rich)
H2O (NH3)
Figure 3: Process concept scheme for biogas upgrading using Gas Permeation Fig. 3 represents a basic scheme of the designed process as it has been realized at the demonstration plant in Bruck/Leitha, Lower Austria. The raw biogas from the fermentation vessels is mixed with the permeate of the second membrane stage, it is subsequently compressed and water is condensed at gas temperatures of lower than +7°C. Afterwards, the biogas is heated up again using waste heat from the compressor in order to obtain the optimum temperature for the subsequent separation steps. After that, the hydrogen sulphide is removed by means of adsorption and the pretreated gas is fed to the two-staged membrane separation process.
In order to minimize the methane losses, two stages of membrane modules have been suggested. The permeate stream from the second stage, which contains significantly higher amounts of methane compared to the permeate of the first stage, is brought back for recompression. Due to the recycling of this permeate, a nonlinear dynamic behavior of the process is expected. The methane quality of the produced gas from the retentate of the second stage is controlled by a proportional valve that is located at the retentate outlet of the second stage. The position of the valve is adjusted by a PID controller, which influences the pressure in the feed channels and, in the same time, the methane content of the produced gas. Using this control strategy a gas with various methane contents can be produced (e.g. from almost raw gas composition 70% to 99% or more). Additionally, the volume flow of the produced biomethane can easily be adjusted with an enhanced PID controller manipulating the rotating speed of the compressor using a frequency converter. Like any other separation technique, Gas Permeation cannot transfer all of the methane in the raw biogas feed to the produced biomethane. As a result, the carbon dioxide-rich Offgas still contains little amounts of methane (usually 2 to 3% of the produced biomethane) and other separated substances. In order to achieve a zero-emission strategy regarding methane the upgrading plant is perfectly integrated into the existing biogas plant and the Offgas is delivered back to the existing gas engines (CHP with raw biogas). Thus, the remaining methane is not emitted to the atmosphere, but is burned and its chemical energy is used to produce heat and power. A schematic depiction showing this process integration is given in Fig. 4. Biogas Production
Biological Desulfurisation
Compression
CHP (Gas Engine)
Freeze Drying
Permeate 2. Stage (Recycle)
Adsorptive H2S Removal
Two Stage Gas Permeation
Permeate 1. Stage (Offgas)
Local Gas Grid Bruck/Leitha
substances (liquid mixtures of metal salts) directly into the fermenter. As a result the produced biogas typically contains 100 to 150ppmv of hydrogen sulphide at the exit of the gas storage tanks. The second is the microbiological treatment of the gas by means of the chemoautotrophic bacteria Thiobacilli [3]. It results in reduction of hydrogen sulphide to around 50ppmv. The microorganisms use the H2S for their metabolism and convert the gas to water and elemental sulfur or sulfurous acid which is discharged and treated together with the waste water stream. The microorganisms need oxygen for this oxidative conversion of the hydrogen sulphide. Before the biogas upgrading plant was included this biological desulphurization has been operated with air as an oxidizer. Due to the fact that air consists to four fifth of nitrogen and nitrogen cannot be removed with the upgrading technique from the biogas stream, this desulphurization step has been retrofitted with a pure oxygen injection. Moreover, an enhanced controlling mechanism is currently under development to ensure adequate desulphurization together with minimized oxygen consumption even under fluctuating biogas volume flows. Operational experiences of nearly one year until now show constant desulphurization capacity after this oxidizer switch. The final decrease in hydrogen sulphide is done in the third stage where adsorption by means of iron oxide is implemented. Fig. 4 also shows the downstream pathways of the upgraded biomethane. After a concise online analysis of the relevant gas species (methane, carbon dioxide, oxygen, hydrogen sulphide, humidity) the produced gas is transported to the gas distribution station via a 2.8km long pipeline. If the quality of the gas regarding any parameter mentioned in the Austrian laws does not meet the statutory obligations for feed-in operation, the grid supply is interrupted immediately and the gas is transported back to the gas engines of the biogas plant. The control system will then try again to improve the quality of the produced gas and to readopt the supply to the grid.
Quality Control (Gas Analysis) Bio-Methane Pipeline (2.8km)
Odorisation
Gas Distribution Station
Regional Gas Grid (60bar)
High Pressure Compression
Figure 4: Process Integration of the biogas upgrading facility in Bruck/Leitha
Figure 5: Outside view of the biogas upgrading container
Fig. 4 also shows the second most important cleaning step, which is the removal of hydrogen sulphide. Due to its toxicity and corrosive effects only a very small amount of hydrogen sulphide is allowed in the gas. The current process incorporates three stages of desulphurization. The first one is the in-situdesulphurization by addition of special chemical
The supplied bio-methane is transported to the nearby city of Bruck/Leitha (Population: 7600) via the public natural gas grid having a pressure of up to 3bar. During the winter months the entire amount of biomethane is used to satisfy the gas demand of this city (additional natural gas is required). During the summer months the gas demand is only a fraction of the produced
gas and the excessive biomethane is compressed to 60bar and fed into the regional natural gas grid. This approach enables a constant operation of the biogas upgrading facility over the whole year and therefore optimized workload and cost structure. As mentioned above the described process concept has been realized at the biogas co-digestion plant Bruck/Leitha in Lower Austria (40km from Vienna). This plant was designed to process about 180m³(STP)/h of raw biogas and supply 100m³(STP)/h of biomethane. Parallel to this grid supply the fermentation capacity of the biogas plant is high enough to additionally operate two gas engines to produce electrical power (2 x 830kW) and district heat. The whole upgrading plant according to the scheme depicted in Fig. 3 has been mounted inside a standard 30foot-container by the plant constructor and has been transported as a whole to the final location in Bruck/Leitha. Fig. 5 gives an outside view of this container. Fig. 6 shows the interior of the biogas upgrading container where especially the compressor, heat exchangers and the membrane modules are visible.
raw biogas and pressure in the grid have an influence on the process behavior. Therefore, a special control and safety strategy had to be developed. The whole process, especially the quality control and the clearance of feed-in operation as well as all safety relevant aspects are completely automated. For this purpose a state-of-the-art industrial PLC (Programmable Logic Controller) has been implemented and programmed completely from scratch (see Fig. 6).
Figure 6: Programmable Logic Controller (PLC) used for the biogas upgrading plant Bruck/Leitha (GE Fanuc) Additionally to the Automation-PLC an industrial Panel-PC with touch-screen has been applied for process visualization, manual operation and monitoring of the plant and data storage purposes. As an example for the process visualization Fig. 7 depicts a detailed screen of the compressor and its surroundings.
Figure 5: Inside view of the biogas upgrading container showing compressor, heat exchangers (right) and membrane modules (left) The biogas upgrading plant in Bruck/Leitha works as an industrial scale technology demonstrator and has been officially opened in June 2007. Normal feed-in operation at nominal and partial loads has begun January 2008. This technology, though improvable, already is marketable and an upgrading plant like the one described herein can already be bought. 4
Figure 7: Process Visualisation of the upgrading plant, detailed view on the biogas compressor
PROCESS CONTROL AND SIMULATION
An interesting aspect that appeared during the process planning and implementation was the design of the process control. Since it is expected that this process will be employed in the plant with limited personnel, it needs to be relatively easy to start and operate. Moreover, it is required that the plant will constantly produce biomethane of high quality even under variable process conditions. Temperature, methane content in
Figure 8: Dynamic simulation environment and model of the biogas upgrading process
39.8 100
39.6 39.4
80
39.2 60
39.0 38.8
40 20
38.6
Volumetric flowrate
38.4
Upper heating value
38.2
0 38.0 17.02.2008 17.02.2008 18.02.2008 18.02.2008 18.02.2008 12:00:00 18:00:00 00:00:00 06:00:00 12:00:00
0.8 0.7 0.6
Figure 10: Volumetric flowrate and upper heating value (calculated according to EN ISO 6976) of the produced biomethane monitored over a period of 24 hours
0.5 0.4 0.3 0.2
0
50
100
150
200
250
300
350
400
450
500
Time [s]
Figure 9: Simulated methane volume fraction at startup of the biogas upgrading plant after flushing with pure nitrogen OPERATIONAL EXPERIENCES
Already during the first commissioning phase it became apparent, that the start-up procedure of the upgrading plant is comparatively fast. 3-5 minutes after the compressor start-up a relatively constant methane content of the processed product gas of 98vol% +/2vol% can be reached. After that period it takes another 5 minutes for the control system to stabilize the methane content at the desired value and within the desired boundaries. The control system is designed to guarantee a constant product gas quality according to the Austrian laws. After the product gas fulfills the requirements (normally within the first 10 minutes), it is supplied to the public grid. This short startup time usually appears after a normal plant start from warm standby. In this case the whole upgrading plant is filled with biogas or partly upgraded biomethane. Only in the uncommon case of certain replacement activities parts of the plant have to be flushed with nitrogen as an explosion prevention measure. A startup after this cold standby takes a little bit longer (about 20 minutes) as it has been discussed in Fig.
Fig. 11 shows the main components of the produced biomethane stream, named methane and carbon dioxide monitored over the same period of 24 hours. It can be seen that the quality-PID-controller is working very well, keeping both parameters almost exactly on the desired values (98.0vol% for methane, 1.80vol% for CO2). 100
5.0
98
4.5
96
4.0
94
3.5
92
3.0
90
2.5
88
2.0
86 84 82
1.5
CH4-content CO2-content
1.0
CO2-content of produced biomethane [vol%]
0.1 0.0
5
40.0
Upper heating value [MJ/m³(STP)]
0.9
120
CH4-content of produced biomethane [vol%]
CH4 volume fraction [-]
1.0
9. Depending on the ambient air temperature the optimal operating temperature of all plant components is reached within the first 50 minutes of operation (after a longer stop in winter this time may elongate to 2 hours). To give a short overview of the behavior of the biogas upgrading plant, trend plots of the most important plant parameters are given in the following Figures. Fig. 10 shows the volumetric flowrate and the upper heating value (calculated using EN ISO 6976) of the produced biomethane stream monitored over a period of 24 hours. During this phase, the volume flow controller has been switched of and the biogas compressor worked with a manual set constant load of about 86%. Therefore, the volume flow is not exactly constant but varies between 100 and 103m³(STP)/h. The upper heating value slightly fluctuates together with the methane content but permanently keeps higher than the legislative limit of 38.5MJ/m³(STP). Volumetric flowrate of produced biomethane [m³(STP)/h]
Since the process was unknown, it was advisable to check its behavior and feasibility before the plant would be built. For this purpose a dynamic simulation model has been developed. It uses the finite volume method to discretize the one-dimensional wave equation ([4], [5]), which is used to model the mass transfer in the piping and in the membrane modules. The solver was programmed in C++ and implemented in the Matlab® Simulink® environment. Fig. 8 shows a screenshot of this simulation environment and the implemented dynamic model of the upgrading plant. Many simulation runs were made to investigate the dynamic behavior of the system, to test the control approaches and to adjust the controller parameters for all used PID controllers. Figure 9 presents a result from this model when simulating the startup phase of the plant that was filled with nitrogen at the beginning. The simulation was performed using constant volume flow through the compressor and constant position of the proportional valve (that means no PID-control). The simulation results suggest that the high methane quality, which is required for the grid supply, is achieved within 10 minutes of operation. This very fast startup behavior has been confirmed by experimental results collected at the real upgrading plant.
0.5
80 0.0 17.02.2008 17.02.2008 18.02.2008 18.02.2008 18.02.2008 12:00:00 18:00:00 00:00:00 06:00:00 12:00:00
Figure 11: Methane content and carbon dioxide content of the produced biomethane monitored over a period of 24 hours It has been shown, that the produced biomethane does not contain any nitrogen or other inert gases and only contains a little amount of oxygen. Therefore, the content of CH4 has to be kept about 1 percent higher then prescribed by the norm OEVGW G31 (97.0vol% corresponding to the upper heating value of at least 10.7kW/m³(STP)) in order to meet the limit for carbon dioxide, which is 2.0vol%.
O2-content of produced biomethane [vol%]
0.50
5.0
0.45
O2-content
4.5
0.40
H2S-content
4.0
0.35
H2O-content
3.5
0.30
3.0
0.25
2.5
0.20
2.0
0.15
1.5
0.10
1.0
0.05
0.5
0.00 0.0 17.02.2008 17.02.2008 18.02.2008 18.02.2008 18.02.2008 12:00:00 18:00:00 00:00:00 06:00:00 12:00:00
H2S- and H2O-content of produced biomethane [ppmv]
Finally, Fig. 12 shows the trace components of the produced biomethane stream over the monitoring period of 24 hours. The oxygen content of the gas can completely be ascribed to the oxygen dosing for the biological desulphurization. The usage of the actual, quite rudimental oxygen dosing controller results in a remaining oxygen content of 0.1 to 0.2vol% compared to the legislative limit of 0.5mol%. This first inaccurate implementation of the controller is also responsible for the steps in oxygen content occurring during changes of the biogas volume flow through the biological desulphurization column. However, though the oxygen content can only be slightly lowered in the product gas stream by means of Gas Permeation, this parameter is no problem for the feed-in operation. The same is true for the moisture content. This value usually drops below 40ppmv after 30 minutes of operation and reaches (depending on the temperature of the surroundings) values of 2 to 10ppmv compared to the legislative limit of about 80ppmv. These extremely low water contents originate from the high dehumidifying potential of the polyimide membranes. The coarse drying of the gas is done by condensation (cryogenic cooling, high mass flows of condensate) and the fine drying down to only a few ppmv is accomplished by the membrane modules. The content of hydrogen sulphide usually varies between 0 and 1.0ppmv with a weak daily fluctuation caused by the temperature of the biological desulphurization, which mainly consists of a huge, black column. With all three instances of desulphurization working this parameter usually does also not obstruct the feed-in operation.
Figure 12: Oxygen content, hydrogen sulphide content and moisture content of the produced biomethane monitored over a period of 24 hours The main consumer of electrical power in the biogas upgrading plant is the biogas compressor with a connected load of 55kW and a nominal power consumption of around 33kW for a full load scenario. Together with all other power consumers in the plant like blowers, coolers, drives, sensors and electronics (no power for heating is needed) the total power consumption has been summed up and is given in Table II. Table II: Total consumption of electrical power for biogas upgrading plant for a raw biogas methane content of about 65 to 68vol% Product gas flow 65 m³(STP)/h 80 m³(STP)/h 100 m³(STP)/h
Total power consumption 23.5kW 28.6kW 37.8kW
This power consumption can be related to the thermal energy content of the produced biomethane of about 10.82kWth/m³(STP) (upper heating value). As a result, the upgrading of the biogas produced at the co-digestion plant in Bruck/Leitha to natural gas quality including grid supply consumes about 3.2% of the thermal energy content of the delivered gas based on the upper heating value. If this amount of electricity would be provided using a CHP-gas-engine with a standard efficiency of 38%, a biomethane amount of 8.4% of the delivered gas would be needed to run the biogas upgrading facility. Compared to other techniques, this value is remarkably low. 6
SUMMARY AND OUTLOOK
The process design, plant erection and some operational experiences of an innovative biogas upgrading plant have been presented. The plant produces approximately 100m³(STP)/h of fully-fledged natural gas substitute (biomethane) and delivers this stream to the public natural gas grid either on a local grid level (up to 3bar) or, during the summer months, to a regional grid level with up to 60bar. The upgrading is based on the membrane separation process Gas Permeation and allows low energy consumption as well as very low methane losses. The quality of the upgraded biomethane is controlled continuously regarding various unwanted or malicious substances to assure the agreement with the quality described by Austrian laws. The relevant legislative framework concerning the gas quality which is given by the Austrian laws OEVGW G31 and G33 has been presented and subsequently the upgrading necessities to produce such a gas have been developed. The requirements for a continuous online gas analysis system for several gaseous species have been shown. The biogas upgrading plant commissioned in Bruck/Leitha has been presented in detail and some information on the plant behavior has been given. It has been shown that the upgrading process is very stable and continuous concerning gas quality and quantity. Finally, some conclusions on electrical power consumption and energy efficiency of the biogas upgrading process have been made. Subsidiary, a dynamic process simulation model for the Gas Permeation plant has been developed to act as a test field for the planned control strategies. Together with some plant specific data even the parameterization of the implemented PID-controllers has been supported. Moreover, deeper insight into the dynamic phases of plant startup and shutdown has been generated. In the near future, reliable and well-founded data on overall performance parameters will be compiled. These parameters will include power consumption and electrical efficiencies for the whole range of possible product gas flows, methane slip in the plant Offgas for several load scenarios as well as a first estimation on membrane life expectancy. The last point might be one of the most interesting questions of this new process. The dynamic process simulation model will be further evaluated using experimental data from simple and small laboratory scale plants as well as from more complex upgrading plants like Bruck/Leitha. Additionally, a detailed scientific analysis of another Gas Permeation
biogas upgrading plant will be carried out. This plant is situated in Margarethen/Moos, comprising quite similar process technology, but has about a third the size of Bruck/Leitha. Besides, this plant does not feed the produced biomethane to the public natural gas grid but feeds its own Bio-CNG-fuelling station. The biomethane is compressed up to about 250bar and can be fuelled into any commercial CNG-vehicle as a 100% renewable automobile fuel. This might be a very interesting concept in times of huge discussions on the maximum blending percentages of renewable fuels to gasoline and diesel. Furthermore, the application of the presented technology to other gas separation tasks will be examined. 7
ACKNOWLEDGEMENTS
We gratefully acknowledge the support of the providers of funds for the project: FFG - Oesterreichische Forschungsfoerderungsgesellschaft, funding program ‘Energysystems of the future’, and Land Niederoesterreich (Federal province of Lower Austria). Additionally we gratefully acknowledge the technical cooperation and the financial support of our project partners OMV, EVN, Wien Energie, Energiepark Bruck, Biogas Bruck, University of Natural Resources and Applied Life Science Vienna, Axiom Angewandte Prozesstechnik, AVL-List, and LuPower Alternative Antriebstechnik. 8
REFERENCES
[1] Oesterreichische Vereinigung für das Gas- und Wasserfach, Natural Gas in Austria - Gas quality, Richtlinie G31 (2001), in german. [2] Oesterreichische Vereinigung für das Gas- und Wasserfach, Renewable Gases - Biogas, Richtlinie G33 (2006), in german. [3] A. B. Jensen and C. Webb, Enzyme Microb. Technol., 17, (1995) 2. [4] R. J. Leveque, Finite Volume Methods for Hyperbolic Problems, Cambrigde University Press, (2002). [5] J.D.Anderson, Computational Fluid Dynamics: The Basics with Aplications, McGraw Hill, (1995).
