Power boiler fuel augmentation with a biomass fired atmospheric circulating fluid-bed gasifier

The successful experience in developing the advanced Foster Wheeler atmosph eric circulating fluidized-bed (ACFB) combustion system subsequently led to the development of the ACFB gasification (ACFBG) Technology in the early 1 980s. The driving force for the development work was the dramatic increase in oil price during this period. The primary advantage of the ACFBG technol ogy is that it enables the substitution of expensive fuels (e.g. oil or gas ) with cheaper solid fuels. Prior to this Lahti project, Foster Wheeler had supplied four waste wood fired commercial scale ACFBGs in the mid-1980s to the pulp acid paper industry with capacities from 17 to 35 MWth based on f uel input. These units are still in successful operation today. Lahden Lamp ovoima Oy (LLOy) is a Finnish power company producing power and district he at for the City of Lahti. The company is jointly owned by the city of Lahti and by Fortum Oy, the largest utility power company in Finland. LLOy opera tes the Kymijarvi Power Plant located nearby the city of Lahti in Southern Finland. To keep the energy prices as low as possible, Plant personnel are continuously looking for the most economical fuel sources, and simultaneous ly, trying to improve the environmental aspects of the energy production. C urrently, about 300 GW h/a of different types of biofuels and refuse fuels are available in the Lahti area. On an annual basis, the available amount o f biofuels and refuse fuels is enough to substitute for about 15% of the fu els burned in the main boiler, equaling up to 30% of the coal typically use d. The aim of the LLOy Kymijarvi Power Plant gasification project is a comm ercial scale demonstration of direct gasification of wet biofuel and the us e of hot, raw and very low calorific gas directly in the existing coal fire d boiler. The gasification of biofuels and co-combustion of gases in the ex isting coal-fired boiler offers many advantages such as: recycling of CO2, decreased SO2 and NOx emissions, efficient way to utilize biofuels and recy cled refuse fuels, low investment and operation costs, and utilization of t he existing power plant capacity. Furthermore, only small modifications wer e required in the boiler and process upsets in the gasifier do not shut dow n the power plant. The first two years of operation (1998 and 1999) have be en excellent with good availability for the gasifier and its related compon ents. During 1998 several measurements and tests with different fuel combin ations were performed. This paper presents the project in detail as well as the most important results of the first measurements. The EU Thermie progr am has supported this project. (C) 2001 Foster Wheeler Energy Services Inc. Published by Elsevier Science Ltd. All rights reserved.