New Ecologically Acceptable Methods for Fuel and Power Production from Biomass and Peat

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Abstract
The demand for clean fuels and electrical power is increasing in Finland and is expected to continue to do so in the near future. This calls for new methods for converting presently used fuels to ecologically more beneficial ones, or developing better processes for their utilization. Upgrading the quality of the fuel gas obtained by gasification of solid fuels, thermal treatment of pulp mill black liquor to fuel oil, and integrated gasification combined cycle power production are current research topics at the Technical Research Centre of Finland (VTT). This article describes some results of the work on biomass and peat utilization at VTT. Fuel gas produced from peat and wood chips is used at about 10 district heating boiler plants in Scandinavia. The gas has to be burned close to the gasifier because of its tar content. In order to make pipeline transport, engine use, and some industrial applications possible, further processing of the gas is necessary. Both catalytic and thermal cracking of the gas have been studied together with the manufacturers of the fixed bed gasifiers, the Ahlstrom-Bioneer Corporation. NOx emissions are also of great importance. Production of pulp is a highly energy-intensive process. The regeneration of pulping chemicals is presently integrated into the energy production, and these cycles cannot be optimized separately. By treating the used cooking chemicals (black liquor) thermally under pressure in a reducing atmosphere, a fuel oil can be produced. The cooking chemicals are separated from the oil and remain in the water phase. A project on pressurized gasification has also been initiated in 1988. At a later stage of the research the replacement of the soda boiler is envisaged. The boiler is the most expensive single unit within the pulp plant. Integrated Gasification Combined Cycle (1GCC) technology developed for coal utilization can also be applied to biomass and peat. Some modifications have to be done, however. The cleaning stage of combustion gas, especially alkali metals, being the critical part of the IGCC concept presently, has to be studied further before industrial applications. It has been shown that condensing power production from peat with IGCC could be competitive with conventional power production technology already today in Finland. In addition, IGCC has considerable development potential, while pulverized combustion technology cannot be developed much further. IGCC is being experimentally developed at VTT in cooperation with Helsinki University of Technology and IVO Corporation, with the financial support of the Finnish Ministry of Trade and Industry.

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