Co-gasification of Lignite and RDF in Greece Emmanuel Kakaras 1,2 , Nikolaos Koukouzas 2 , Panagiotis Grammelis 1,2 , Karlopoulos Evaggelos 2 1 Laboratory of Steam Boilers and Thermal Plants, School of Mechanical Engineering, National Technical University of Athens, Athens, Greece Phone: +30-210-772.28.65, Fax: +30-210-772.36.63, E-mail: pgra@central.ntua.gr 2 Institute for Solid Fuels Technology and Applications / Centre for Research & Technology Hellas, Ptolemais, Greece Abstract The gasification technologies using blends of coal and waste/biomass were investigated aiming to examine their potential application in Greece. Following, a feasibility study for the installation of an IGCC system that exploits Greek brown coal with RDF in Western Macedonia, Greece was carried out. Among others, IGCC systems offer several benefits, such as the flexibility of fuel supply, environment friendly plant operation and commercial application of the process by-products, eg. gasification slag and the elemental sulphur from the desulphurisation unit. Co-gasification of coal and waste can be performed with direct or indirect gasification. Both technology concepts are now demonstrated and they seem to be the most promising energy exploitation options for solid fuels, especially residues. Since there are sufficient lignite deposits in W. Macedonia and an integrated system of Municipal Solid Waste (MSW) treatment already exists, the specific region was selected in order to examine the possibility of an IGCC system application. The gasifier is based on the British Gas Lurgi (BGL) technology, the gasification agent being steam and oxygen, producing a synthetic gas rich in CO, H 2 and CH 4 . Taking into account the total annual production of MSW in W. Macedonia, the maximum capacity of the unit was estimated up to 30 MWe. The investment cost at this capacity range is much higher and almost tripled compared to the reference case of brown coal, despite the lower fuel supply cost. This also applies to the operation cost, which is higher than the electricity sales price in Greece, on kWh e basis. The high investment cost of IGCC systems using coal/RDF blends, within the capacity range of 30-200 MWe, implies the modular construction of the unit near operating power plants. First, the gasifier is installed and the produced syn-gas is then supplied in an operating lignite-fired unit. The plant changes into a direct gasification application, when the flue gas treatment equipment and the power generation system are installed. The operation cost becomes significantly competitive in larger units and ranges at the same level compared to the lignite-fired power plants when the installed capacity exceeds 300 MWe. Keywords: IGCC, BGL gasifier, feasibility study, Municipal Solid Waste, slag. Introduction Gasification technology, having substantially increased in the period 1900-1940, was set aside after the end of World War II. Interest was revived during the 1980’s, mainly owing to the environmental problems but also to an apparent shortage of fossil fuels. From 1970 to 2000, the global installed capacity of gasifiers had an increase of 1,600 %, while the current annual increase is more than 7 % [1, 2]. The highest percentage of synthesis gas is used in chemical industry, but there is also a steadily increasing tendency for electricity generation. Specifically, the commercial- scale gasification projects represent a total of 446 million Nm 3 /day of synthesis gas and its conversion to electricity via IGCC systems equals to 33,280 MW el of power equivalent. Currently, coal and oil residues constitute the main feedstocks of the gasifiers. On a long-term basis, after the year 2010, coal, biomass, wastes and mainly the combination of all the above will constitute the main feedstock of the gasification systems. Taking into consideration the technological abilities and energy trends of the IGCC technology, a preliminary study was carried out concerning the possibility of installing and operating a combined co- gasification unit (30 MWe) fueled with lignite and Municipal Solid Wastes (MSW), in the region of W. Macedonia in Greece. Technological aspects of IGCC systems There are many different gasification processes on offer. Depending on their flow regime, gasifiers fall into three groups: entrained flow, fluidized bed and moving bed Figure 1, [3, 4, 5]. The key characteristics of entrained flow gasifiers are their very high and uniform temperatures and the very short residence time of the fuel within the gasifier. For this reason, solids fed into the gasifier must be very finely divided and homogenous. In the fluidized bed the use of air as oxidant keeps the temperature below 1000 0 C. This, in turn, means that fluidized bed gasifiers are best suited to relatively reactive fuels, such as biomass, lignite but also solid wastes properly treated. Moving bed gasifiers use pure oxygen as gasification agent, have liquid or dry ash exit and their use is recommended for the utilization of coal but also of all kinds of solid wastes. The most important representatives of the three types of gasifiers in a commercial scale are Prenflo and Destec for the technology of entrained flow, High Temperature Winkler (HTW) for fluidized bed and British Gas Lurgi (BGL) for moving bed gasifiers. The appropriate