GASIFICATION PERFORMANCE OF AUSTRALIAN LIGNITES IN A PRESSURIZED FLUIDIZED BED GASIFIER PROCESS DEVELOPMENT UNIT UNDER AIR AND OXYGEN-ENRICHED AIR BLOWN CONDITIONS S. P. BHATTACHARYA  Cooperative Research Centre for Clean Power from Lignite, Mulgrave, Victoria, Australia T his paper discusses the gasification performance of a number of Australian lignites in a high temperature winkler (HTW) gasification process development unit (PDU) capable of running at a pressure, temperature, and feed rate of 10 bar, 10008C, and 250 kg h 21 respectively. The fuels include three Victorian lignites, one South Australian lig- nite, and a char derived from a Victorian lignite. All fuels were pre-dried to less than 20% moisture content. The tests were of 3 – 32 h duration. The majority of the tests were conducted at 8 bar(g) pressure, 125 – 240 kg h 21 feed rate, 750–9208C average bed temperature, and involved steam and air or steam and oxygen-enriched air as reactants for gasification. Carbon conversion ranged between 70 – 87%, with further improvement limited by elutriation of carbon-rich fines originating from a large fraction of fine particles present in the feed, and brittle nature of these lignites which generate fines through attrition. An acceptable calorific value of 4 MJ kg 21 of the fuel gas has been attained. An assessment of the reasons and the extent of loss of char through elutriation has been investigated through tests in a 1 : 1 scale cold model and characterization of the char. Keywords: gasification; lignite; fluidized bed; agglomeration. INTRODUCTION Gasification provides a pathway for generation of synthesis gas from coal. The gas can be used for power generation or as a raw material for production of chemicals, fertilizers and liquid fuels. Gasification also provides an opportunity to control and reduce gaseous pollutant emissions, and a lowest cost approach to concentrate the carbon dioxide at high pressure to facilitate sequestration (Trapp, 2005). Low temperature gasification, if used for power gene- ration, results in increased efficiency by allowing more of the coal energy to be converted to chemical energy rather than sensible heat. At low temperatures, however, hydro- carbons such as methane form to some extent, limiting the capture of carbon in the form of carbon dioxide. If power generation rather than chemical production is the primary focus, and less than hundred percent carbon dioxide capture (80%) is intended, then low temperature gasification has a cost and efficiency advantage over high temperature gasification (Holt, 2004). Fluidized bed gasifiers are low temperature gasifiers. These offer very good mixing and therefore good heat and mass transfer between the oxidants and the feed, ensur- ing even distribution of materials in the bed. Fluidized bed gasifiers are operated below the ash sintering temperatures, usually below 10008C to ensure that excessive sintered agglomerates are not formed, and do not disturb the even distribution of bed materials. This in turn requires bed materials to be drained continuously or periodically from the bed, and for a well-fluidized bed, that invariably means a loss of carbon with the drained bed material. Despite this, low temperature gasification as achieved in fluidized bed is well suited for lignites. This is because lig- nites are more reactive than high-rank coals, and hence reasonable carbon conversion is achieved at temperatures around 9008C. Use of low temperature also limits fouling caused by the volatilization of any alkali species in the coal and its subsequent condensation on heat transfer surfaces. In order to design any process based on fluidized bed gasi- fication it is necessary to have information on the influence of operating parameters, such as pressure, temperature and con- centration of reactant gas on the reaction rate, carbon conver- sion, tar and alkali formation and product gas composition. The behaviour of inherent inorganic species in the fuel and  Correspondence to: Dr S.P. Bhattacharya, Cooperative Research Centre for Clean Power from Lignite, 8/677 Springvale Road, Mulgrave, VIC 3170, Australia. E-mail: spbh2000@yahoo.com.au 453 0957–5820/06/$30.00+0.00 # 2006 Institution of Chemical Engineers www.icheme.org/psep Trans IChemE, Part B, November 2006 doi: 10.1205/psep06007 Process Safety and Environmental Protection, 84(B6): 453–460