Adding gas from biomass to the gas grid - SGC

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Removal of hydrogen sulphide by oxidation with airThe H 2 S content of the biogas can be reduced significantly by addition of 5 - 10% air to the biogasin a cleaning unit after the biogas production [lit.9,10,11]. The filter vessel is filled with plasticcarriers and a liquid made up from gas condensate and liquid from effluent slurry separation iscontinuously recirculated over the filter. A temperature of approximately 35 °C promotes the processin which the H 2 S is biologically converted to sulphur. The sulphur is retained in the liquid in the filter.After successful full-scale experiments at the Fangel plant in 1993, this method has been utilisedwidely in Danish biogas plants. The utilisation of the method is increasing because it is cheaperthan chemical cleaning. The method is also able to remove the ammonia content of the biogas. Withaddition of air in biological filters the H 2 S content can be reduced from 2000 - 3000 ppm to 50 - 100ppm. In other experiments the H 2 S content has been reduced from 800 ppm to 10 ppm.Limitations:· Aftertreatment might be required to obtain pipeline gas quality.· The addition of air may conflict with pipeline specifications for oxygen (and nitrogen) content.· The addition of 5 - 10% air might reduce the effectiveness or capacity of an upgrading processfollowing the H 2 S cleaning.Removal of hydrogen sulphide by adsorption on activated carbonH 2 S can be adsorbed on activated carbon. The sulphur containing carbon can then either bereplaced with fresh activated carbon or regenerated.The adsorption of hydrogen sulphide on activated carbon is catalytic and the carbon acts ascatalyst. The carbon is often impregnated with potassium iodide (KI) or sulphuric acid (H 2 SO 4 ) toincrease the reaction rate. The chemical reaction is:2H 2 S + O 2 ---> 2S + 2H 2 OOxygen is needed for the reaction and is usually added as air. This results in nitrogen being addedto the gas, but if the H 2 S content is low, only minor amounts of nitrogen will be present in thecleaned gas.If the carbon is regenerated, this is done with hot nitrogen (inert gas) or steam. The sulphur will bevaporised and, after cooling, liquify at approximately 130 °C. Regeneration requires two reactionvessels for continuous running. The most common way for utilising activated carbon adsorption iswithout regeneration of the carbon.page: 29
Parameter Unit Process Plant exampleLocation/nameNSR pilot plantCapacity rangewith regeneration15without regenerationm 3 biogas/hm 3 hydrogen sulphide/hm 3 biogas/hm 3 hydrogen sulphide/h0 - 50000 - 100 - 10000 - 10Inputhydrogen sulphide Ppm50 - 2000 15-35Outputhydrogen sulphide Ppm10 – 100 0-2Process conditions 4adsorbtion temperatureambientregeneration temperatureSupplier°C°CAmbient400 - 500Table 9: Removal of hydrogen sulphide by adsorption on activated carbonno regenerationNSR4.2.2 Removal of waterRemoval of water by refrigerationThe crude biogas is saturated with water. The absolute amount of water in the gas depends on thetemperature. At 35 °C the water content is approximately 5%. Water has to be removed from thegas before it can be fed into the gas grid. The removal of water can be done with different methodsand at various stages in the upgrading process, depending on the upgrading method. Condensedwater is usually separated from the gas flow before any compressing takes place. With a scrubbingupgrade system no further drying of the crude gas is done. An adsorption upgrade system normallyrequires the gas to be dried before upgrading. The most commonly used drying methods arerefrigeration and adsorption. Absorption with hygroscopic salts can also be used.A common method for the drying of gas is refrigeration. The gas is cooled in heat exchangers andthe condensed water is separated from the gas. Normally a chiller is utilised for the refrigeration.This method can normally only lower the dewpoint to 0.5 - 1 °C due to problems with freezing on theheat exchanger surfaces. To achieve lower dewpoints the gas has to be compressed before coolingand then expanded to the desired pressure.The method can be used for all possible flow rates. The input dewpoint ranges from 3 °C tosaturated. The output dewpoint is 0.5 - 1 °C at actual pressure. There are no specific examples.Thisis a commonly used method with many suppliers.4air added for stoichiometry between oxygen and H 2Spage: 30
Page 1 and 2: Report SGC 118Adding gas from bioma
Page 3 and 4: CONTENTS1 INTRODUCTION 32 IMPORTANC
Page 5 and 6: 2 IMPORTANCE OF ADDING GAS FROM BIO
Page 7 and 8: Incentives by eco-labelingBy adding
Page 9 and 10: is mixed with coal in a combustor p
Page 11 and 12: Comparing efficiency data is a diff
Page 13 and 14: Figure 1: Energy flow diagram and i
Page 15 and 16: The product revenues are the most u
Page 17 and 18: 3.1.2 Survey of technologiesThis pa
Page 19 and 20: 3.1.3 Table of biogas compositionsD
Page 21 and 22: Aspect Unit ValueManure M 3 /day 6B
Page 23 and 24: Technologies for syngas upgradingTh
Page 25 and 26: CompositionProcesscalorific value M
Page 27 and 28: 4 PIPELINE QUALITY GAS FROM BIOGAS4
Page 29: Removal of hydrogen sulphide with m
Page 33 and 34: Parameter Unit Process valueCapacit
Page 35 and 36: 600.9500.840Wobbe index [MJ/m 3 n]R
Page 37 and 38: Figure 4 illustrates reported inves
Page 39 and 40: 4.3.4 Upgrading by absorption of ca
Page 41 and 42: Removal of carbon dioxide by water
Page 43 and 44: Selexol from the flash tank is depr
Page 45 and 46: poisonous and aggressive liquid wit
Page 47 and 48: Parameter Unit ProcessCapacity rang
Page 49 and 50: gas system is maintained by a contr
Page 51 and 52: In the gasification process the fir
Page 53 and 54: A catalytic process requires a feed
Page 55 and 56: In all countries gas in a distribut
Page 57 and 58: 6 SUPPLYING GAS FROM BIOMASS TO THE
Page 59 and 60: In Europe only two kinds of natural
Page 61 and 62: Component or quality Unit Limit or
Page 63 and 64: The directive thus also provides po
Page 65 and 66: Figure 13: Maximum range of permitt
Page 67 and 68: Figure 16: Wobbe index for differen
Page 69 and 70: 6.2.5 Discrepancies between standar
Page 71 and 72: 6.2.7 Description of national or de
Page 73 and 74: Figure 17:Arrangement of the contro
Page 75 and 76: Measurement methodDetection tubes f
Page 77 and 78: Descriptioncalculation of propertie
Page 79 and 80: The possibility of adding off-spec
Page 81 and 82:
Europe among countries relying on e
Page 83 and 84:
7.1.3 FinlandBiogas is mainly produ
Page 85 and 86:
Figure 18: Distribution of capacity
Page 87 and 88:
Calorific Availability Market price
Page 89 and 90:
Many landfills are equipped with ga
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the type and volume of the respecti
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7.2.4 FranceThere are currently no
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7.2.7 SwedenBiogas as a fuel for ve
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Policy on renewable energyThe gener
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Danish energy policy is to contribu
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Carbon dioxide taxApplication€/to
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CHP FundThe CHP Fund is an incentiv
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Taxation and incentivesFeed-in tari
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Subsidies and fundingThere are seve
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Figure 20:Impact of the energy tax
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TargetsParallel with the target on
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Sweden has no actual program dedica
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Swedish energy taxesThe Swedish ene
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8 CONCLUSIONS AND RECOMMENDATIONSCo
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14 Upgrading Landfill Gas to Natura
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46 ISO 15971: “Natural gas - Meas
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APPENDIX 1:DefinitionsBiogasBiomass
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fixed bed gasification: BIONEERProc
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Final cooling is accomplished by me
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used for direct drying applications
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fluidised bed gasification:EISENMAN
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fluidised bed gasification:SELTECpr
Page 135 and 136:
The Battelle biomass gasification p
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Primary heat exchangerThe primary h
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active coal filter and cooled. The
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• Kärnten (Austria)pyrolysis:Pro
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Quality Value UnitComponents• Car
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Adding gas from biomass to the gas grid - SGC

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