Adding gas from biomass to the gas grid - SGC

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4.2 CLEANINGThe main components in biogas are methane and carbon dioxide, normally 90 - 95%. Additionalsubstances can be water, hydrogen sulphide, nitrogen and sometimes oxygen. When biogas isupgraded to natural gas quality, most of these additional substances have to be removed. This canbe done before the upgrading process, in the upgrading process or after the upgrading process.4.2.1 Removal hydrogen sulphideProteins and other sulphur containing materials produce hydrogen sulphide in the digestionprocess. Hydrogen sulphide is poisonous and corrosive, as well as environmentally hazardoussince it is converted to sulphur dioxide by combustion. Furthermore it contaminates some upgradingprocesses. Hydrogen sulphide can be removed either in the digester, from the crude biogas, or inthe upgrading process.In-situ reduction of the hydrogen sulphide concentrationHydrogen sulphide can be treated directly in the digester vessel. The sulphide is either reacted witha metal ion to form an insoluble metal sulphide or oxidised to elementary sulphur. Iron salts are themost used reactants for the in-situ reduction of hydrogen sulphide emissions.Iron, in the form of Fe 2+ , reacts with sulphide ions to form iron sulphide, FeS. The iron ion isnormally supplied as iron chloride, FeCl 2 , which is added to the digester. Hydrogen sulphide levelsof typically 100 to 150 ppm in the gas stream can be reached with this method.The in-situ removal of hydrogen sulphide is included in the turn key biogas plant or installed by theplant owner. The investment costs are rather low since the only equipment needed is a dosingsystem. The operational cost for this method depends on the amount of hydrogen sulphide that isformed by the digestion processes. When using raw materials that are rich in protein and othersulphur containing molecules, this method is rather expensive.Plant examplesParameter Unit Process Plant 1 Plant 2 Plant 3 Plant 4Location/nameLinköpingbiogasLaholmbiogasNSR 2 KalmarbiogasCapacity rangem 3 hydrogen no specificall 100 - 10,000sulphide/yearrangeInput· hydrogen sulphide Ppm500 – 300,000 In situ In situ In situ In situOutput· hydrogen sulphide Ppm50 - 150 50 - 100 100 - 150 15 - 35 115 - 400Process conditionsnormal digesterconditionsDigester40 °CDigester38 °CDigester36 °CDigesterNo temp availTable 7: In-situ reduction of hydrogen sulphide productionpage: 27
Removal of hydrogen sulphide with metal oxides and hydroxidesThe crude biogas can be cleaned from hydrogen sulphide by different methods. The most commonmethods are reaction with metal oxides or hydroxides, oxidation with air and adsorption on activatedcarbon.The most commonly used metal compound is iron oxide, but iron hydroxide and zinc oxide can alsobe used. Below is a description of a mixture of iron oxides, with the registered trademark SulfaTreat.SulfaTreat is based on a naturally occurring substance, which is processed to granules for use inreaction beds.The solid phase is packed in a circular reactor vessel. Biogas is fed into the reactor from the top.The reason for this is that the reaction is exothermic and water is used to cool the solid bed. With adownstream gas flow the water is better distributed in the bed. The gas flow is saturated with waterand excess water is added to the reaction bed. Reaction temperature is dependent on the hydrogensulphide content in the biogas. The reaction bed is not heated.With fresh SulfaTreat and moderate concentrations of hydrogen sulphide, all H 2 S is removed fromthe gas. The bed material is consumed by the reaction and this results in a rising H 2 S content in theoutlet stream. If it is important to keep the H 2 S content in the cleaned gas to virtually zero, gassampling can be done in the bed at some distance from the gas outlet. When the H 2 S contentincreases in the sample, the bed material is removed and the reactor is recharged with freshmaterial. For completely continuous running, two reactors can be installed and switched when theH 2 S content starts to increase.Parameter Unit Process Plant exampleLocation/nameLaholmCapacity range · m 3 biogas/h 0 - 2000· m 3 H 2S/h0 - 5 0 - 0.5Input· hydrogen sulphide Ppm50 - 2500 50 - 3000Output· hydrogen sulphide Ppm0 - 10 0 - 15Process conditions· adsorbtion pressure· adsorption temperature· regeneration pressureSupplierbar (abs)°Cmbar (abs)105030no regenerationSulfaTreat Co. MalmbergWater ABInvestment M€ Included in the turn keyupgrading plant. No specificcost is available.Operational costs k€/year 6 3Table 8: Removal of hydrogen sulphide with SulfaTreat23NSR: North West Scania Waste Treatment Co.This includes the reacting agent, SulfaTreat, energy costs for compression work and labour costs for recharging theabsorption reactor.page: 28
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: 4 PIPELINE QUALITY GAS FROM BIOGAS4
Page 31 and 32: Parameter Unit Process Plant exampl
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
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The possibility of adding off-spec
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Europe among countries relying on e
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7.1.3 FinlandBiogas is mainly produ
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Figure 18: Distribution of capacity
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Calorific Availability Market price
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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
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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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