Adding gas from biomass to the gas grid - SGC

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negative pressure. Depending upon the feed stock, the air blown system produces a syngas containing alow calorific value of 3.7 to 7.5 MJ/m 3 . A higher calorific value can be reached with the use of oxygeninstead of air.A complete PRME biomass gasification system includes a fuel metering bin, the reactor/gasifier, thecombustion tube and chamber, the gasifier cooling water system, water cooled ash discharge conveyors,multi-zoned combustion air supply, rotary feeders and instrumentation required to provide automatic controlover the process. The entire gasification/combustion process, from feed to ash discharge, is controlledmanually or by computer.The PRME gasifier is basically a vertical cylindrical steel shell, reduced in diameter in the upper portion andlined with a refractory capable of withstanding temperatures as high as 1560 ºC in a reducing atmosphere.The cross sectional area of the upper portion of the gasifier is reduced to provide the turbulence required toinsure proper mixing of the product gas and the combustion air introduced into the combustion tubes in thisarea of the gasifier.Fuel is metered to the gasifier from the fuel metering bin. This bin is equipped with an input conveyor and anoutput conveyor that delivers fuel to the gasifier. The speed of the output conveyor is automatically adjustedby the automatic control system to maintain a pre-set temperature in the first stage gasification zone.Discharge from the output conveyor is directed through an impact weigh metering device that providesprecise indication and control of the fuel feed rate.Fuel is introduced to the gasifier by a water-cooled screw conveyor that discharges into the drying andheating zone of the gasifier. The gasification process is controlled by the proportioned application ofgasification and combustion air in a manner that supports efficient gasification.Residence time in the gasifier is varied by a residence control system that is adjusted to achieve a targetcarbon content of the ash residue. In the gasification zone of the gasifier, approximately 10 to 12% of thestoichiometric air requirement is admitted into the gasification air distribution area. The application ofgasification air is multi-zoned and is controlled to maintain the proper temperature required to volatilise thebiomass and allow partial combustion of the fixed carbon. Temperatures in this zone is controlled between600 o C and 1300 o C, depending on the particular biomass fuel and the required ash quality. A lowgasification airflow rate (< 0.1m/s) through the gasification zone, coupled with a low feed stock entrypointand continuous ash discharge minimises the amount of particulate matter entrained in the gasifier exhaust.Combustion of the gases starts in the combustion tube assembly where the temperature of the gases isincreased to promote thermal cracking of tars and hydrocarbons that were liberated during gasification.Partial combustion of gases in the combustion tube assembly, the use of mechanical bed agitation andprecise control of the zoning of gasification air produces a clean, low energy content gas that can be burnedin the combustion tube and chamber for drying applications or in the radiant section of the boiler. Thegasification rate is controlled by demand from the dryer or boiler. The boiler exhaust is clean and may bepage: 127
used for direct drying applications, including food grains. Alternatively, when biomass destruction withoutenergy recovery is desired, the clean gases may be diverted to the atmosphere via the combustion tubevent.A 1,000 tons/day (800 tons/day dry) oxygen fed system designed to gasify processed municipal solid wastecontaining 10% or 20% moisture and a calorific value of 18 MJ/kg will produce the following clean syngaswith a composition as given in table 61.Quality Value UnitRDF with10%MoistureRDF with20%MoistureComponents• Carbon monoxide34 29 %• Hydrogen42 43- %• Carbon dioxide19 22 %• Nitrogen and argon22 %• Water33 %Calorific value 9.7 9.3 MJ/m 3Table 61: Syngas composition and properties from the PRME processTwo plants are on the program:• Tulsa, Oklahoma Demonstration plant• A 3.5 MW Biomass Fired Engine Generator system utilising olive residues as feed stock is scheduledfor start-up in August 2000.Data on costs are available for the 1,000 ton/day (800 tons/day dry) oxygen fed system designed to gasifyprocessed municipal solid waste. This system consists of two Model KC-320 gasifiers, each 19 M€ and one450 TPD Oxygen system at 11 M€. This 50 M€ budget comprises a turnkey plant for the production ofelectricity from municipal waste.page: 128
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Report SGC 118Adding gas from bioma
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CONTENTS1 INTRODUCTION 32 IMPORTANC
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2 IMPORTANCE OF ADDING GAS FROM BIO
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Incentives by eco-labelingBy adding
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is mixed with coal in a combustor p
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Comparing efficiency data is a diff
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Figure 1: Energy flow diagram and i
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The product revenues are the most u
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3.1.2 Survey of technologiesThis pa
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3.1.3 Table of biogas compositionsD
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Aspect Unit ValueManure M 3 /day 6B
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Technologies for syngas upgradingTh
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CompositionProcesscalorific value M
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4 PIPELINE QUALITY GAS FROM BIOGAS4
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Removal of hydrogen sulphide with m
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Parameter Unit Process Plant exampl
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Parameter Unit Process valueCapacit
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600.9500.840Wobbe index [MJ/m 3 n]R
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Figure 4 illustrates reported inves
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4.3.4 Upgrading by absorption of ca
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Removal of carbon dioxide by water
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Selexol from the flash tank is depr
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poisonous and aggressive liquid wit
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Parameter Unit ProcessCapacity rang
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gas system is maintained by a contr
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In the gasification process the fir
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A catalytic process requires a feed
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In all countries gas in a distribut
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6 SUPPLYING GAS FROM BIOMASS TO THE
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In Europe only two kinds of natural
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Component or quality Unit Limit or
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The directive thus also provides po
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Figure 13: Maximum range of permitt
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Figure 16: Wobbe index for differen
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6.2.5 Discrepancies between standar
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6.2.7 Description of national or de
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Figure 17:Arrangement of the contro
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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
Page 91 and 92: the type and volume of the respecti
Page 93 and 94: 7.2.4 FranceThere are currently no
Page 95 and 96: 7.2.7 SwedenBiogas as a fuel for ve
Page 97 and 98: Policy on renewable energyThe gener
Page 99 and 100: Danish energy policy is to contribu
Page 101 and 102: Carbon dioxide taxApplication€/to
Page 103 and 104: CHP FundThe CHP Fund is an incentiv
Page 105 and 106: Taxation and incentivesFeed-in tari
Page 107 and 108: Subsidies and fundingThere are seve
Page 109 and 110: Figure 20:Impact of the energy tax
Page 111 and 112: TargetsParallel with the target on
Page 113 and 114: Sweden has no actual program dedica
Page 115 and 116: Swedish energy taxesThe Swedish ene
Page 117 and 118: 8 CONCLUSIONS AND RECOMMENDATIONSCo
Page 119 and 120: 14 Upgrading Landfill Gas to Natura
Page 121 and 122: 46 ISO 15971: “Natural gas - Meas
Page 123 and 124: APPENDIX 1:DefinitionsBiogasBiomass
Page 125 and 126: fixed bed gasification: BIONEERProc
Page 127: Final cooling is accomplished by me
Page 131 and 132: fluidised bed gasification:EISENMAN
Page 133 and 134: fluidised bed gasification:SELTECpr
Page 135 and 136: The Battelle biomass gasification p
Page 137 and 138: Primary heat exchangerThe primary h
Page 139 and 140: active coal filter and cooled. The
Page 141 and 142: • Kärnten (Austria)pyrolysis:Pro
Page 143 and 144: Quality Value UnitComponents• Car
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Adding gas from biomass to the gas grid - SGC

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