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ECN publication
Green power production by co-gasification of biomass and coal in coal-fired oxygen-blown entrained-flow based IGCC processes
Published by: Publication date:
ECN 1-11-1998
ECN report number: Document type:
ECN-RX--98-059 Article (scientific)
Number of pages:

Published in: Extended ECN contribution to: Power-GEN International, Orlando, Forida, December 9-11, 1998 (), , , Vol., p.-.

The use of coal for large scale power production meets a growingenvironmental concern. In spite of the fact that clean coal conversion technologies integrated with high-efficiency power production facilities, such as IGCC, are developed, the aim for sustainable development strives for a power production system based on renewable energy sources. One of the most promising renewable energy sources that can be used in the Netherlands is biomass, i.e. organic waste materials and/or energy crops. To accelerate the introduction of this material, in a technical and economically acceptable way, co-gasification with fossil fuels, in particular coal, in large scale IGCC processes is considered. In this paper the technical feasibility, economic profitability, and environmental acceptability of co-gasification of biomass in coal-fired oxygen-blown entrained-flow based IGM is discussed. Both a base-case coal-fired oxygen-blown entrained-flow based IGCC process - showing strong resemblance to the Puertollano IGCC plant in Spain - and three co-gasification concepts, viz.: (1) a concept with separate dry coal and biomass feeding systems, (2) a concept with a combined dry coal/biomass-derived pyrolysis char feeding system, and (3) a concept with parallel biomass pre-treatment/gasification and combined fuel gas clean-up/power production, were defined for further consideration. The base-case system and the co-gasification concepts as well are modelled in the flowsheet simulation package ASPEN". Steady-state integral system calculations resulted in an overall net electrical plant efficiency for the base-case system of 50. 1 %LHV (48.3 %HHV). Replacing about 10 % of the total thermal plant input (coal) by biomass (willow) resulted in a decrease of the overall net electrical plant efficiency of 1.4 to 2.1 %-points LHV, avoided specific CO2 emissions of 40-49 g/kWhe, and total avoided CO2 emissions of about 129 to 159 kt/a, all depending on the co-gasification concept concerned. The net electrical efficiency of the biomass part amounts 28.4 to 35.8 %LHV, and is even significantly higher (> 45 %LHV) in 'fully' optimised concepts presented. The costs per tonne CO2 avoided are calculated as 25 to 66 ECU/tonne, depending on the concept concerned, and will even become negative in case of the proposed optimised concepts. The Simple Pay Back Period for the necessary additional investment for these proposed optimised concepts is 5-13 years, the Net Present Worth negative (discount rate: 7.5 %), and the Internal Rate of Return lower than (0 - 3 %) the market interest. Co-gasification of Dutch organic waste materials, in the optimised co-gasification concepts, is very promising from an economic point of view, with a SPBP of the necessary additional investment of smaller than 4 years, and an IRR of the necessary additional investment of 5 to 50%, depending on the concept concerned. 18 refs.

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