Adding gas from biomass to the gas grid - SGC

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The process achieves a 97% conversion of biomass carbon to useful syngas without producing troublesometars, oils, or other contaminating effluents. The process is robust in its ability to handle feedstocks withvarying degrees of inherent moisture, ranging from dry wood (in which case moisture is actually added tothe feedstock) to organic sludge with moisture contents of over 60%. In traditional gasification systems anymoisture in the feedstock results in an energy efficiency penalty. This process utilises a part of the moistureto produce hydrogen and other combustible gases. At 40% moisture in the feedstock, the system achievesan efficiency of about 80%.Figure 22: Process Flow Diagram of the Brightstar process Feed SystemDepending on the size, consistency and nature of the biomass, the material is often routed through ahammer-mill or tub grinder/classifier before entering the plant’s metering bin located above the feed system.The material is fed by gravity into the metering bin where it enters a screw feed system. The material is thenconveyed through a proprietary sealing mechanism that serves as the pressure seal on the front end of thesystem, keeping air out of the reformer and keeping syngas from backing up into the feed system. Thematerial received from the screw feeder is then conveyed with recycled compressed syngas into the primaryheat exchanger.page: 135
Primary heat exchangerThe primary heat exchanger serves two functions. First, biomass is conveyed with syngas into theconvection section where pre-heating, devolitisation, and evaporation of water occurs. In addition, afterreforming, as the hot syngas leaves the primary reformer, it gives up its sensible heat energy to the primaryheat exchanger and is cooled to the desired process temperature before it exits to the gas filter.Primary reformerThe pre-heated, partially reformed (gasified) biomass and conveying syngas pass from the convectionsection of the primary heat exchanger into the radiant coil section of the primary reformer where hightemperature steam reforming takes place.Gas filterThis unit receives syngas from the primary heat exchanger. The syngas and any char (inorganic solids andany unreformed carbon) are routed through barrier type filter elements where the char is collected andremoved as a dry, innocuous residue. The char is delivered to a collection bin for reuse or disposal.Final syngas coolerThis air-cooled heat exchanger receives clean syngas from the gas filter and reduces the gas temperatureto the desired level for supplying power generation equipment, or other fuel uses.The gas composition resulting from various forms of biomass is extraordinarily similar. However, certain keyprocess variables can be altered to adjust the composition of gas produced by the process. The compositionof the syngas can be varied by control of key process parameters but is generally as given in table 68. Thesyngas is virtually free of particulates.Quality Value UnitComponents• Carbon monoxide27 %• Hydrogen30 %• Methane11 %• Carbon dioxide15 %• Nitrogen10 %Contaminants• Hydrogen sulphiden.a. ppm• Particulatesn.a. g/m 3• Condensaten.a. g/m 3Calorific value 11 MJ/m 3Table 68: Typical gas composition obtained by the Brightstar processThe Brightstar process is in operation at two plants:• A mill in East Texas, USA. Bark is gasified to replace natural gas used in thermal oxidisers. System with3 modules. Expanding to 20 modules in planning.page: 136
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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
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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
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 and 128: Final cooling is accomplished by me
Page 129 and 130: used for direct drying applications
Page 131 and 132: fluidised bed gasification:EISENMAN
Page 133 and 134: fluidised bed gasification:SELTECpr
Page 135: The Battelle biomass gasification p
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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