Feasibility of electricity production from biomass by gasification systems

The overall objectives of the EC Research Programme JOULE II were to evaluate the potential of advanced power production systems based on biomass gasification and to study the technical and economic feasibility of these new processes with different types of biomass feedstocks. This report was prepared as part of a larger R & D project within JOULE II. The objectives of this subtask were to design a number power production process concepts for evaluation in the following size classes: farm scale (100 - 300 kWe), small scale (5 - 10 MWe), medium scale (20 - 30 MWe), and large scale (40 - 60 MWe); to determine mass and energy balances for each of the process concepts, and to determine the technoeconomic feasibility of the proposed concepts in the appropriate size class. The following conclusions were drawn from the results of the study: 1) New power production systems based on pressurised gasification and gas tur-bine cycles may be feasible only in a relatively large size class. 2) The gasification-diesel concept has, in small size classes, a potential to reach higher power production efficiencies than those reached in conventional fluidized-bed boilers. 3) Fixed-bed downdraft gasification coupled to a diesel or spark-ignited engine is one of the very few technically possible alternatives to produce electricity from biomass on a "farm scale". The main technical uncertainties of the concepts can be listed as follows: 1) gasifiers requires fur- ther development work. 2) Simplified IGCC technology has so far been tested with woody biomass and coal on a pilot scale only, and the behaviour of different agricultural residues and energy biomasses is poorly studied. 3) Gas cleaning is considered to be the prime uncertainty of the concepts. 4) The number of gas turbines applicable for hot low-heating-value gases is very small, and none of the present turbines has been designed especially for this type of gas. 5) The technical feasibility of the "farm-scale" concept based on downdraft gasification is limited to high-quality biomass fuels