Thermal Gasification of Biomass Introduction

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few months of start up. Between 1985 and 1986, three more gasifiers, two in Sweden(25 MWth at Norrsundet Bruks, AB, Norrsundet and 27 MW th at ASSI, KarlsborgBruk, Karlsborg) and one in Portugal (15 MW th at Portucel, Rodao Mill), were builtand commissioned for firing lime kilns.ItalyThermie Energy Farm ProjectThe Thermie Energy Farm (TEF) Project byBioelettrica SpA employing the atmospheric LurgiCFB-gasifier is now under construction at Cascina,near Pisa. The 43 MW th capacity plant will produceabout 14 MW e . The air-blown gasifier will gasify upto 3.5 cm biomass feedstocks (poplar and Robiniawood chips, olive residues, grape residues, andsawdust) with about 5% moisture (after drying at theplant by the flue gases from the heat-recovery steamgenerator) at a temperature of about 800°C and 1.5bar(a) pressure. The raw LCV fuel gas is cleaned ofmost particulates in cyclones, cooled, scrubbed, andcompressed prior to producing electricity in a gasturbine and heat-recovery steam generation and steamturbine plant. The project is owned by Bioelettrica SpA,whose shareholders are USF Italia, Electricidade de Portugal-EDP, Lurgi, EnergiaVerde, and Fumagalli, and receives financial contribution from the EC under theThermie 1994 programme. The plant is expected tobe operational in the middle of 2002.Courtesy of Bioelettrica, ItalySAFI SpA RDF Gasification ProjectThe first commercial TPS CFB gasification processwas built for RDF gasification at Loc Testi, Passodei Pecorai, Greve in Chianti. RDF pellets, up to150 mm long, are fed into the lower section of a15 MW th capacity CFB gasifier, at a rate of about3 t/hour. The TPS gasifier operates at low (2500mm water) pressure and a temperature of about875°C, employing air as the gasification/fluidizingagent. Part of the air is injected at the bottom ofthe gasifier and the remainder is injected part wayup the vessel. This pattern of air distributioncreates a high-density bed in the lower part of thevessel, which allows the gasifier to handle relativelylarge-sized fuel particles. The CFB of sandparticles are maintained by a superficial gasvelocity of about 3-10 m/s.Courtesy of SAFI SpA Gasification Project, Italy11
The pellets are gasified within the 2-2.2 seconds residence time producing an LCV fuelgas of about 8 MJ/Nm 3 . The raw gas passes through two stages of solids separationbefore being fed to a furnace/boiler to generate steam for producing 6.7 MW e in acondensing steam turbine. The overall power generation efficiency is about 19-20%.Alternatively, part of the raw gas can be fired in a nearby cement kiln. The flue gasexiting the boiler is cleaned in a three-stage Research Cottrell scrubber before ventingthrough the stack. The plant has been operated intermittently due to difficulty inobtaining a continuous supply of RDF pellets.The NetherlandsKARA/BTG Co-current Downdraft Gasifier SystemThis 150 kW e system incorporates two special features:• The use of a low-speed (750 rpm), low-cost, robust engine made in China. Thismarine diesel engine is re-designed for use in connection with rice husk gasifiers. Theengine is less sensitive to impurities and its efficiency is lower than modern, lean-burnengines. Any loss due to the low engine efficiency is compensated by incorporation ofa roots blower to compress the fuel gas to enhance its volumetric heating value.• The fuel gas enters the engine at a temperature higher than thedew-point, thus avoiding any condensation.The system consists of a fuel feeding conveyor, gasifier, two cyclones, baffle filter, gascooler, bag-house filter, roots blower, and gas engine.The gasifier feed is either sized orbriquetted block-sized wood. The fuel gas has a heating value of about 4.5 MJ/Nm 3 ,with tar and dust content below 100 mg/Nm 3 .A demonstration plant is scheduled for early 2000 at abriquetting plant near KARA. Power will be delivered to the grid whilethe heat will be used for the drying system of the briquetting plant. Thedevelopers include a consortium of KARA Energy Systems BV, BTGbiomass technology group BV and CPS, CompackSys BV, with fundingsupport from Shell International Renewables and Novem.Stork Thermeq Co-current Downdraft Gasification SystemThis 400 kW e system consists of a double valve fuel feeder, a gasifier developed atEnergy Research Centre Netherlands (ECN), thermal catalytic tar cracker developedand patented by BTG, and an IC engine for producing electricity. A 400 kW edemonstration plant will be constructed during 2000 in Goor. The gasifier will befed partly with composted waste wood. The electricity will be supplied to the grid andsold to Essent as 'green' power and the heat will be used in the greenhouses in Goor.The main objective is to demonstrate and validate the technology for subsequent scaleupto a commercially viable, fully automated, turnkey biomass gasification installationproducing 2 MW electrical and 4 MW thermal power. The developers include aconsortium of Stork Thermeq, BTG and KARA.12
Page 2 and 3: AustriaThere are two gasification d
Page 4 and 5: CanadaBIOSYN Gasification and Gas C
Page 6 and 7: esidual char from the pyrolysis ste
Page 10 and 11: Amergas BV ProjectThis 30 MW e proj
Page 12 and 13: SwitzerlandPyroforce Gasification P
Page 15 and 16: MTCI ProcessThe MTCI gasification p
Page 17: Thermal TechnologiesThermal Technol

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