BIOMASS CFB GASIFIER CONNECTED TO A 350 MW_(TH) STEAM BOILER FIRED WITH COAL AND NATURAL GAS - THERMIE DEMONSTRATION PROJECT AT KYMIJARVI CHP POWER STATION IN LAHTI, FINLAND

摘要

The successful experience in developing the advanced Foster Wheeler Circulating Fluidized Bed combustion system subsequently led to the development of the CFB Gasification Technology in the early 80's. The driving force for the development work was the dramatic increase in oil price during the oil crises of that time. The primary advantage of CFB gasification technology is that it enables the substitution of expensive fuels (e.g. oil or gas) with cheap solid fuels. Prior to this Lahti project Foster Wheeler Energia Oy of Finland has supplied 4 commercial scale atmospheric CFB gasifiers in the mid 80's to the pulp and paper industry with capacities from 17 to 35 MW based on fuel input. These applications utilize waste wood as feedstock and the units are still in successful operation today. Lahden Lampovoima Oy is a Finnish power company producing power and district heat for the City of Lahti. The company is 50% owned by the city of Lahti and 50% by Fortum Oy, which is the largest utility power company in Finland. Lahden Lampovoima Oy operates the Kymijarvi Power Plant located nearby the city of Lahti in Southern Finland. To keep the energy prices as low as possible, Lahden Lampovoima is continuously looking for the most economical fuel sources, and simultaneously, trying to improve the environmental aspects of the energy production. At the moment, about 300 GWh/a of different types of biofuels and refuse fuels are available in the Lahti area. On an annual basis, the available amount of biofuels and refuse fuels is enough to substitute for about 15% of the fuels burned in the main boiler, equaling up to 30% of the coal typically used. The aim in the Lahden Lampovoima Oy Kymijarvi Power Plant gasification project is to demonstrate in commercial scale the direct gasification of wet biofuel and the use of hot, raw and very low calorific gas directly in the existing coal fired boiler. The gasification of biofuels and co-combustion of gases in the existing coal-fired boiler offers many advantages such as: recycling of CO_2, decreased SO_2 and NO_x emissions, efficient way to utilize biofuels and recycled refuse fuels, low investment and operation costs, and utilization of the existing power plant capacity. Furthermore, only small modifications are required in the boiler and possible disturbances in the gasifier do not shut down the whole power plant. The experiences of the first operation year 1998 have been excellent. The availability of the plant has been good and the results, as regards the product gas quality, gasifier bottom ash, main boiler filter ash and main boiler flue gas, fulfill the expectations. During 1998 several measurements and tests with different fuel combinations were performed. This paper presents the project in detail as well as the most important results of the first measurements. This project has been supported by the EU Thermie program.