european biogas initiative to improve the yield of agricultural biogas plants

Project no. 513949

Project acronym: EU-AGRO-BIOGAS

Project title: European Biogas Initiative to improve the yield of agricultural biogas plants Instrument: Specific targeted research or innovation project Thematic Priority: Priority 6, Sustainable Energy Systems

Deliverable 21: User manual on the biogas conversion through CHP

Due date of deliverable: 2009-11-30 Actual submission date: 2010-01-15 Start date of project: 2007-01-15 Duration: 36 months (2007-2009) Organisation name of lead contractor for this deliverable: Partner N° , GE Jenbacher (GEJ)

D21: User manual on the biogas conversion through CHP

GE Jenbacher Friedhelm Hillen, Günther Wall, Matthias Schulze, Susanne Chvatal

Table of Contents:

1 Introduction: ___________________________________________________ 4

2 Fuel Gas Quality and Gas Conditioning _____________________________ 6

3 Exhaust Gas Heat Exchanger (EGHE) Maintenance __________________ 12

4 Exhaust Treatment Technologies _________________________________ 15

5 Lube Oil Management ___________________________________________ 17

6 ORC Technology _______________________________________________ 19

7 Table of figures ________________________________________________ 20

8 References ____________________________________________________ 20

Document Description Deliverable D21 is the report on Task 6, performed by GE Energy Jenbacher gas engines. For a high efficient and reliable Biogas Utilization and Energy Conversion in Gas Engine CHP plants all related subsystems and their interaction have to be well engineered for optimized output and high availability. For the main systems Fuel Gas Quality, Exhaust Treatment, Exhaust Gas Heat Utilization and Lube Oil Management proven technologies with optimized inter-coordination should be considered. Plant operation and contemporary maintenance are also relevant factors. This manual gives an overview on important topics as well as suggestions for measures to be taken into account.

1 Introduction:

In order to optimise the conversion in gas engine plants of the chemical energy held in the biogas into heat and power for public utility networks, the entire biogas - gas engine - exhaust system must looked at and optimised. If the quantity of energy that can be obtained and utilised over time (electricity, waste heat) is taken into account, then plant availability is of major importance in addition to energy conversion efficiency.

Fig. 1: Biogas utilization in a CHP [1]

Some of the major aspects of operating a biogas engine system and specific courses of action to improve the energy conversion are discussed below. All the links in the chain, from biogas production to feeding in the energy recovered, must be considered. Optimal trouble-free continuous operation and a high energy yield can only be ensured by using advance technology for all components, and harmonising the overall system.

The individual components in the system, consisting of fuel gas, gas engine, lubricating oil and exhaust gas heat recovery, all interact with each other. For example, the exhaust gas dew point and economically-recoverable exhaust gas heat are determined by both the fuel gas sulphur content and the type of exhaust gas treatment system installed.

The following illustration shows the individual areas of gas engine applications and associated areas that need to be considered more closely to achieve an optimised complete gas system.

Fuel Treatment

Electricity

Heat Usage

Emissions

Fuel Quality (H2S, NH3)Fluctuations in quality

Water content

AvailabilityLube Oil Management

ORC - Efficiency

DepositsAcid Dew Point

EGHE Maintenance

Exhaust Treatment

Fuel Treatment

Electricity

Heat Usage

Emissions


Water content


ORC - Efficiency


EGHE Maintenance

Exhaust Treatment

Fig. 2: Overview Biogas utilization with Gas engine [2]

Attention needs to be paid to the following points when designing gas engine systems for using biogas:

• use of fully-developed and proven technology for all subsystem components; • design for stable long-term operation; • interactions between the individual subsystems (e.g. the influence of fuel gas quality on waste heat

recovery): if a subsystem design is less than optimal this generally shows itself in its effect on other components;

• process monitoring and operational control; • maintenance, operation and servicing; • training the operating staff; • plant safety (explosion protection, handling combustible gases).

Fuel Treatment

Electricity

Heat Usage

Emissions


Water content


ORC - Efficiency


EGHE Maintenance

Exhaust Treatment

Fuel Treatment

Electricity

Heat Usage

Emissions


Water content


ORC - Efficiency


EGHE Maintenance

Exhaust Treatment

2 Fuel Gas Quality and Gas Conditioning

As well as methane and carbon dioxide, biogas as a fuel contains a series of impurities such as hydrogen sulphide and ammonium, and as a rule is also saturated with water. Depending on the quantity of impurities and the amount of the water content, these impurities can adversely effect engine availability and lead to increased maintenance and servicing costs for the following reasons: Unlike other conversion technologies, use in gas engines is generally characterised by a high degree of robustness and insensitivity to fuel gas contamination and quality fluctuations. However, the following adverse effects on plant operation can occur:

• Water content, relative humidity: if the biogas temperature drops below the dew point, water condenses in the gas path to the engine and in the gas pressure control system. This results in increased corrosion and reduced gas filter service life. The condensate must be drained off from the gas system through gas-tight piping and disposed off in accordance with the regulations currently in force. Drainage and piping must comply with the state of the art as regards safety engineering and explosion protection regulations.

Fig. 3: Condensate in gas filter of gas train [3]

• Hydrogen sulphide H2S: hydrogen sulphide forms aggressive acids with water, and in conjunction

with condensate this results in corrosion in the fuel gas system. The formation of acids in the fuel gas system leads to corrosion of engine components (mixture cooler, connecting rod bearings). Furthermore, the sulphur brought in leads to acidification of the engine oil, which degrades its important corrosion-inhibiting property so that it must therefore be replaced earlier.

• Ammonia NH3: ammonia in conjunction with condensation in the mixture cooler leads to corrosion of the mixture cooler and under certain conditions can result in the formation of deposits in the fuel gas

system. The formation of deposits in the fuel gas line and on components results in component wear and reduced filter service life.

• Particles and droplets: result in deposits in the fuel gas line and reduced filter service life or degradation of components. Increased dirt contamination in the mixture cooler affects engine operation and the mixture cooler will need to be cleaned.

• Impurities brought into the engine affect the exhaust gas treatment systems and the exhaust gas emissions. For example, H2S in the fuel gas results in an increased SO2 value, while NH3 increases the NOx emissions. Oxidation catalysts are sensitive to impurities such as silicon or sulphur.

The effects set out here can be summarised as affecting the energy conversion in the engine as follows:

• increased engine downtimes due to maintenance work • shorter maintenance intervals and consequently higher maintenance costs • reduced service life of individual components

The following graph shows the link between water content, temperature and relative humidity in the fuel gas:

0

10

20

30

40

50

60

5 10 15 20 25 30 35 40 45 50Gas Temperature [°C]

wat

er c

onte

nt [

g / m

³]

Gas Preheating

Gas cooling

80% rel. humidity

50% rel. humidity

100% rel. humidity

Fig. 4: Correlation of water content and relative humidity dependent on gas Temperature [4]

Biogas is generally saturated with water (relative humidity of 100%) when it leaves the fermenter. As the graph shows, the water content of the gas is markedly higher at higher gas temperatures. This means that the water content is greater with plants using thermophilic (42°C to 55°C) than with mesophilic fermentation processes (32°C to 38°C). . The graph also shows that the relative humidity increases as the gas is cooled, until condensation occurs when the 100% line is reached. This temperature drop below the dew point leads to the formation of condensate. Consequently, condensate formation is especially to be expected with thermophilic plants. Although heating the gas reduces the relative humidity, the dew point of the gas mixture remains unchanged so that gas heating without gas drying is usually insufficient to prevent condensation in the gas system reliably.

The H2S and NH3 content in the biogas depend very much on the substrate used. Hydrogen sulphide and ammonia are produced by the decomposition of proteins or substrates with a high protein content in the biomass. Furthermore, the concentration in the gas phase in the fermenter depends very much on the fermentation process conditions such as temperature and pH value.

Depending the biogas quality, the availability and efficiency of engine operation can be improved by the appropriate gas pre-processing such as gas drying, desulphurisation or gas scrubbing. The specific requirements laid down by the engine builder must be taken into account here.

Recommendations / Best practice:

1. Checking the gas quality and impurities content: The following should be checked when analysing the biogas:

• H2S content • NH3 content • Gas-moisture content

Fluctuations in the gas quality should be taken into account when doing this, and it is recommended that the gas quality and impurities content be judged on the basis of more than one analysis, or best of all by means of continuous gas analysis. The analysis results should be compared with the relevant requirements laid down by the engine builder. If the stated limits are exceeded, appropriate gas pre-processing should be provided.

2. Designing a suitable gas pre-processing plant Gas pre-processing for biogas engine systems should adapt the gas to meet the engine requirements exactly. This should fulfil the following tasks:

• gas drying: reduction in the biogas water content; • removal of impurities: ammonia, hydrogen sulphide (see Section 3); • removal of dust particles: • setting the operating parameters necessary for engine operation such as gas pressure, temperature,

relative humidity.

Chiller

Blower

CondensateDrain

PreaheatingCondenserSeparator

Demister

Gas QualityControlCH4 / O2

Chiller

Blower

CondensateDrain

PreheatingSeparator

Gas QualityControl

CH4 / O2

Absorber

The following diagram shows the design of a gas drying plant in simplified form. In the case of biogas plants with renewable raw materials as a substrate and no ammonia content or other impurities to speak off, this standard gas drying solution can be employed.

Fig. 5: Design of a gas drying plant [5]

In the case of biogas plants with renewable raw materials as a substrate and no ammonia content or other impurities to speak of, this standard gas drying solution can be employed.

Fig. 6: Gas drying plant with absorber scrubber [6]

The preheating shown in Fig. 6 is unnecessary if the piping lengths between the blower and motor are short, since the heat of compression will give an adequate margin from the condensation temperature.

3. Removal of hydrogen sulphide / desulphurisation The following parameters must be considered when selecting a suitable desulphurisation method:

• H2S content in the raw untreated gas; • target H2S content in the treated gas - coarse / fine - desulphurisation; • fluctuations in the raw untreated gas quality and quantity (charge in the fermenter, changes in the

substrate); • necessary reliability and availability of the desulphurisation plant (assessment of the consequences

of a desulphurisation failure for engine operation and emissions); • maintenance measures and operational management; • investment costs, operating costs.

The following table gives a summary of desulphurisation methods and their areas of application.

Sulphide activated carbon Ferrous substances

precipitation internal Potassium Iron (III)

in the fermenter trickling biofilter bioscrubber iodide / carbonate hydroxide / oxideApplication Biogas Biogas Biogas Biogas, sludge gas Biogas

Sludge gasBiogas, landfill gas,

Sludge gas

Separation process Chemical binding Biological conversion AdsorptionMethod / technology Admixing of iron salts Wetted surface Packed column Packed column Solid bed

Chemical binding the substrate in the

fermenter

Creation of aerobic zones in the fermenter

gas space

Column with packing for growing thiobacilli

(aerobic)

Scrubber (absorption)bioreactor (biological separation, aerobic)

Adsorption on activated carbon with catalytic oxidation

Chemisorption on iron (III) oxide with formation of elemental

sulphur

Internal / external fermenter internal internal external external external external

Separable substances H2S, NH3 H2S H2S, NH3 H2S, NH3 H2S H2S

coarse coarse coarse coarse / fine fine coarse / fine

Operating conditionsContent in raw untreated gas [ppm] 500 to 30,000 30 to 30,000 up to 15,000 up to 30,000 up to 10,000 1,000 to 50,000

Achievable content in clean gas

[ppm] 100 to 150 ppm 200 - 500 ppm 50 to 100 ppm 5 to 50 ppm 5 ppm 1 to 100 ppm

Temperature [°C] >20℃ 25 to 37 ℃ 25 to 37 ℃ 25 to 70℃ 25 ℃

Air / O2 injection No 8 to 12 % by volume of the biogas

volumetric flow

2 to 12 % by volume of the biogas

volumetric flow

Air injection necessary into bioreactor

~1-2 % by volume - min. double stoichiometric

necessary for regeneration

Product FeSin the fermentation

substrate

Elemental sulphur in the fermentation

substrate

Elemental sulphur, sulphate in a nutrient

solution

Elemental sulphur,sulphur sludge

Elemental sulphur, depleted activated carbon

Elemental sulphur, spent cleaning compound

Waste disposal Discharged with fermenter effluent

(max. 5%)

Discharged with fermenter effluent

Purification plant Landfill, recycling Disposal / landfill Regeneration / landfill

Investment costs + + + + - - - + + + Operating costs - - + - - - - - -

Desulphurisation / area of application

Costs

Overview ofDesulphurisation Technologies

Absorption and biological conversion

external

Biological desulphurisation

Fig. 7: Overview Desulphurisation Technologies [7]

Sources: Profaktor GmbH: Desulphurisation Concepts Study for GE Jenbacher, Fraunhofer UMSICHT - Study of Analysis and Evaluation of Possible Uses of Biomass, GEJ own research based on manufacturers' information

For renewable-biomass fuelled plants, air injection into the fermenter has proved to be a simple and low-cost desulphurisation technique. However, the achievable desulphurisation performance is limited, and if sensitive exhaust gas treatment technologies are employed (e.g. special catalysts for reaching the formaldehyde emission targets in the German Renewable Energy Act, EEG), additional fine cleaning will be advisable or necessary, depending on the biogas sulphur content.

For plants based on biogenous waste matter (liquid manure/waste matter), the characteristically high sulphur content of the latter render the following external biological desulphurisation methods suitable:

• trickling biofilters plant dynamics are an important criterion • bioscrubbers discharge of scrubbing agent drops, formation of deposits.

Experience has shown that with biological processes, good mixing of the injected air with the biogas is generally absolutely essential to:

• assist the desulphurisation inclination of the bacteria, and • keep the gas compression costs low due to the nitrogen ballast.

Fluctuations in the hydrogen sulphide content are more difficult to compensate in biological methods due to the slow adaptation processes of the biological metabolism, which can lead briefly to high sulphur contents in the treated gas.

3 Exhaust Gas Heat Exchanger (EGHE) Maintenance

When recovering the energy content from the exhaust gas, the net heat yield can be raised by improving the way the engine exhaust heat is incorporated into the local heating network, and by increasing the heat extracted from the exhaust gas. However, the additional cooling resulting from this can lead to in problems in the exhaust gas heat exchanger due to deposits and acid corrosion. The design and operating point of the exhaust gas heat exchanger and the acid dew point of the exhaust gas are key factors here, with the acid dew point depending primarily on the sulphur content of the biogas.

Deposits on the exhaust-side surfaces of the exhaust gas heat exchanger have an insulating effect that adversely affects the heat transfer and increases the exhaust gas backpressure downstream of the gas engine. The deteriorated heat transfer results an increased exhaust gas exit temperature and consequently in reduced thermal output. A higher exhaust gas backpressure can result in reduced engine output.

Fig. 8: Sulphuric deposits due to the temperature dropping below the acid dew point [8]

The recoverable waste energy from an exhaust gas heat exchanger over a review period depends not only on the engine operation and the specified transfer capacity of the heat exchanger, but is also heavily influenced by the following factors.

• The actual transfer performance in operation: dirt contamination of the heat exchanger surfaces results in deteriorated heat transfer;

• heat transfer availability: if the heat exchanger is heavily contaminated with dirt, it must be cleaned, in which case the gas engine must be shut down while this maintenance operation is carried out. The maintenance interval depends on the tendency for dirt contamination to occur; the need for cleaning is indicated by an increase in the measured exhaust gas exit temperature and an increase in the pressure loss across the exhaust gas heat exchanger.

Exit temperature: appr. 75°C

Exhaust temperature: appr. 490°C

Biogas engine

Standard EHE

Design temperature: 180°C

Available in standard applications for heat recovery

Additional EHE

Additional source for heat recovery

Wat

er in

let:

80°C

Wat

er in

let:

65°C

Exit temperature: appr. 75°C


Biogas engine

Standard EHE



Additional EHE


Wat

er in

let:

80°C

Wat

er in

let:

65°C


Biogas engine

Standard EHE



Additional EHE


Wat

er in

let:

80°C

Wat

er in

let:

65°C

The tendency for dirt contamination to occur in exhaust gas heat exchangers depends on a number of factors:

• design of the heat exchanger: e.g. minimum tube diameter of the exhaust gas tubes • fuel gas quality and H2S content and consequently the amount of sulphur entering the exhaust

system • exhaust gas treatment system and resulting additional conversion of SO2 to SO3


1. Taking the fuel gas quality into account The fuel gas quality should be a factor when designing the operating any waste heat recovery system. Regular measurements of the fuel gas sulphur content indicate any changes in the dirt contamination behaviour of the heat exchanger. With high sulphur contents and standard exhaust gas heat exchangers, the exhaust gas should not be cooled to below 180°C. If temperatures below 180°C are reached, a corrosion-resistant material should be used for the exhaust gas heat exchanger.

2. Checking the operating point of the exhaust gas heat exchanger The current operating point and degree of dirt contamination of the heat exchanger should be monitored by regularly measuring the exhaust gas temperature and pressure loss. This allows the heat recovery to be kept as high as possible by optimising heat exchanger cleaning and maintenance.

3. Increasing the recoverable heat by installing an additional exhaust gas heat exchanger

One possibility for increasing the recoverable amount of heat is the installation of an additional special exhaust gas heat exchanger downstream of the standard heat exchanger. This can then cool the exhaust gas still further and extract further heat from it. The precondition for this is countering the above-mentioned problems of the acid dew point, corrosion and deposits.

Fig. 9: New EGHE concept [9]

To ensure optimum operation and to counter these problems, a number of factors must be considered: • The design and installation of the heat exchanger must ensure that condensate can drain from its

chamber. • An acid-resistant, corrosion-proof material must be used for the heat exchanger due to the increased

tendency for condensation to form. • The exhaust gas final temperature will depend on the return temperature in the public district heating

system and therefore on the heat exchanger water inlet temperature. The lower the return temperature, the greater the amount of thermal energy that can be transferred from the exhaust gas to the heating system.

The material of any additional heat exchanger should also be selected to meet the following characteristics:

• its thermal conductivity should be as high as possible to facilitate the heat transfer; • its chemical resistance should be as high as possible; • its thermal resistance must comply with the pertaining operating conditions in the exhaust gas heat

exchanger.

4 Exhaust Treatment Technologies

Depending on the emission requirements, an exhaust gas cleaning plant may need to be installed downstream of the engine. Catalytic oxidation and thermal regenerative post-combustion are both available as exhaust gas treatment methods, and should be considered when designing the exhaust gas system and waste heat recovery. The two concepts have different effects on the acid dew point and consequently on the amount of heat recoverable and the exhaust gas heat exchanger maintenance intervals. The key factor here is the conversion rate of SO2 to SO3 by the exhaust gas treatment.


1. Oxidation catalyst The main task of oxidation catalysts in the exhaust gas flow of biogas engines is to convert carbon monoxide into carbon dioxide. The oxidation catalyst encourages the oxidation of sulphur dioxide to sulphur trioxide. Since the formation of sulphur trioxide is low without a catalyst due to the low reaction rate, the influence of an oxidation catalyst is significant, as it reduces the activation energy and makes it easier for the reaction to take place.

If oxidation catalysts are used, an increase in the SO3 content in the exhaust gas must be expected. Consequently, the oxidation catalyst represents a standard solution for exhaust gas treatment in applications where the fuel gas has a relatively low sulphur content.

Fig. 10: Oxidation catalyst [10]

Fig. 11: SO2- conversion rate for different catalysts [11]

Typ A

Typ B

Typ C

Typ A

Typ B

Typ C

SO2 conversion rate for different catalysts

Type A Type B Type C

Space velocity [1/h]

2. CL.AIR® system The CL.AIR® system is a thermal exhaust gas treatment technology.

In heating up the exhaust gas in the CL.AIR® system to a temperature of about 800 °C the hydrocarbons (CH4 and NMHC) as well as the CO react with the residual oxygen in the exhaust gas and form H2O and CO2. The nitrogen oxides (NOx) remain unchanged. In the course of thermal post-combustion in the CL.AIR®, a far smaller conversation rate of SO2 to SO3 is achieved than in oxidation catalysts. Typical measured values are in the range of < 10%.

Due to the design the CL.AIR® system isn´t sensitive to any kind of catalyst poisons that maybe enter the engine with the fuel.

In combination with the lean-burn engine concept, the CL.AIR® system is able to achieve pollutant emission values which are clearly below the limits specified by the German “TA-Luft”

Fig. 12: technical layout of the CL.AIR® system [12]

The CL.AIR® system is therefore a simple and robust technology that reliably gives results below all current emission limits, and can potentially be used with lower limit values in the future.

Correlation of theoretic oil life time to sulfur input

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0,00 0,20 0,40 0,60 0,80 1,00 1,20 1,40 1,60 1,80

sulfur input per oil volume/ g/h/L

theo

retic

oil

oper

atio

n tim

e (i-

pH)

oil class A (TBN > 9)

oil class B (TBN 7 - 9)

5 Lube Oil Management

The engine oil has a considerable influence on engine availability. Trouble-free engine operation requires a specific oil quality for setting up the engine tribological system and for cooling in accordance with the Technical Instructions. This is ensured by prompt oil management, in which the oil condition at any one time is compared with the oil quality requirements laid down by the engine builder.

If the stated limit values are exceeded at any time, the properties of the oil are changed to such an extent that the associated corrosion inhibition can no longer be maintained. The criteria for assessing an oil are given in the form of limit values for the individual analysis parameters. If a limit value is exceeded, the engine oil must be replaced in compliance with the engine builder's requirements. If the limit values are frequently exceeded in operation, two countermeasures can be employed:

• shortening the oil change interval -> entails higher operating costs for the oil used; • change to a different oil product -> this may allow a longer service life to be achieved, but usually

also entails higher oil costs per litre of oil.

The fuel gas quality is one of the most significant factors influencing the oil quality, affecting the way it changes over time and therefore the oil change interval. A reduction in the fuel gas sulphur content increases the oil service life. The costs for any required desulphurisation must be compared with the savings yielded by oil management, and both will vary as a function of the fuel gas quality and sulphur content.

Fig. 13: Correlation of theoretic oil life time to sulphur input [13]


1. Diligent oil management Continuous and diligent oil monitoring ensures that the engine keeps its value. The time lapse between taking a sample and the oil analysis should be kept as small as possible - 3 days is the optimum, and the focus should be on taking the sample and sending it off. The oil condition should be monitored with particular care in cases where there is a high impurities (H2S) content. Fluctuations in the fuel gas quality have an effect on the changes in oil condition over time. The engine oil should be changed promptly once the oil change criteria have been met. Using the oil for too long can lead to engine damage. Routine trend determination is the only way of reacting in good time to massive sudden changes and preventing severe engine damage. 2. Use of special engine oils for biogas applications Oils specially formulated for operation with biogas should be used. These lubricating oils can give substantially longer oil change intervals by virtue of their base oil characteristics together with the action of the additives, thus giving higher plant availability. The rule "a higher acid buffer (TBN) prolongs the oil service life" no longer generally applies. Some recent developments in lubricating oils have shown that improved service lives can be achieved with the same degree of engine protection and lower potential deposits in the exhaust gas system.

6 ORC Technology

Biogas plants without all-year round heat recovery cannot take full advantage of the CHP potential. Recovering the waste heat for electricity generation in such cases can increase the overall electricity generation efficiency even further. One possibility of doing this is the use of ORC technology adapted for application with gas engine CHP stations.


1. Design of an ORC plant

Increased electricity yields can be obtained without expending additional energy by installing an ORC plant to recover waste heat from the exhaust gas for use in power generation. An additional electricity yield of 6% was demonstrated in a long-term test over 18,000 service hours, and potential average daily values in excess of 8% have been estimated.

Fig. 14: GEJ ORC concept [14]

A concept developed by GE Jenbacher uses both heat sources (exhaust gas heat and engine cooling water) in a cascaded system with two selected working fluids, the objective being to obtain a higher electrical output at the lowest possible specific costs.

cond. / evap.

Evap.

condenser

Thermo oil loop

perheater

LT ORC

HT ORC

Cond. / evap.

Evap.

Condenser

Thermo oil loop

Preheater

LT ORC

HT ORC

7 Table of figures

Fig. 1: Biogas utilization in a CHP [1] 4 Fig. 2: Overview Biogas utilization with Gas engine [2] 5 Fig. 3: Condensate in gas filter of gas train [3] 6 Fig. 4: Correlation of water content and relative humidity dependent on gas Temperature [4] 7 Fig. 5: Design of a gas drying plant [5] 9 Fig. 6: Gas drying plant with absorber scrubber [6] 9 Fig. 7: Overview Desulphurisation Technologies [7] 10 Fig. 8: Sulphuric deposits due to the temperature dropping below the acid dew point [8] 12 Fig. 9: New EGHE concept [9] 13 Fig. 10: Oxidation catalyst [10] 15 Fig. 11: SO2- conversion rate for different catalysts [11] 15 Fig. 12: technical layout of the CL.AIR® system [12] 16 Fig. 13: Correlation of theoretic oil life time to sulphur input [13] 17 Fig. 14: GEJ ORC concept [14] 19

8 References

[1] GE Jenbacher, Biogas Application, Product Information, 2009 [2] GE Jenbacher, internal report: Biogas utilization, 2009 [3] GE Jenbacher, field report [4] GE Jenbacher, internal report: Biogas utilization [5] GE Jenbacher, internal report: Biogas utilization [6] GE Jenbacher, internal report: Biogas utilization [7] GE Jenbacher, internal report: Desulphurization Technologies, 2009 [8] GE Jenbacher, field report [9] GE Jenbacher, internal report: Waste Heat Utilization, 2009 [10] GE Jenbacher, field report [11] GE Jenbacher, internal report: SO2/SO3 conversion on catalyst, 2008 [12] GE Jenbacher CL.AIR® Product Information, 2009 [13] GE Jenbacher, internal report: Impact of fuel gas quality on lube oil properties, 2008 [14] GE Jenbacher, ORC Product Information, 2009

european biogas initiative to improve the yield of agricultural biogas plants

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