Case Studies for Biomass/Coal Co-Gasification in IGCC Applications

Abstract

Employing biomass as a feedstock to generate fuels or power has the advantage of being carbon neutral or even becoming carbon negative, if carbon is captured and sequestrated. However, there are challenges facing the effective utilization of biomass wastes: (a) biomass supply is limited and varies with the seasons, (b) biomass density is low and expensive for long-distance transportation, and (c) due to a limited supply of feedstock, biomass plants are usually small, which results in higher capital and production costs. Considering these challenges, it is more economically attractive and less technically challenging to co-combust or co-gasify biomass wastes with coal. This paper focuses on discussing issues associated with coal/biomass co-gasification as well as an investigation into the effect of adding different amounts of biomass up to 50% (wt.) on a 250MW IGCC plant’s performance, although a smaller plant of 75MW using 100% biomass is also included for comparison. The Siemens SGT6-6000G and Alstom GT8C2 gas turbines are used in the larger and smaller plants respectively. The results show the plant’s efficiency increases first as 10% biomass is added; then decreases as the biomass is increased to 30%; and increases again once the biomass reaches 50%. The variation of efficiency is minor, only within one percentage between 38% and 39%. The advantage of adding biomass can be seen from the almost proportional reductions of SOx, ash, energy for H2S removal, water for scrubber, and the effective CO2 emission. The effective CO2 is calculated by subtracting the neutral CO2 that is theoretically produced by burning the added biomass.

The Properties and Suitability of Various Biomass/Coal Blends for Co-Gasification Purposes

“…However, biomass produces cleaner syngas than coal because of its lower sulphur and ash contents and neutral traces of carbon. There is also a greater degree of complexity involved in processing biomass before gasification starts [2]. Biomass is a world-wide available renewable energy resource.…”

“…The remaining carbon left in the feedstock is then gasified giving syngas as the product. The chemical form of syngas usually consists mostly of CO, H 2 and CH 4 as fuel and also CO 2 , N 2 , and water vapour as non-combustible gases [2]. The syngas also consists of H 2 S, COS, HCN, HCl, Hg, and other contaminants that will have to be removed before utilizing the syngas for power generation.…”

A comprehensive study on co-pyrolysis of bituminous coal and pine sawdust using TG

“…Co-gasified coal and biomass can be considered a potential fuel base for gasification and offer the advantage of a reduction in CO 2 emissions, and even a net reduction if CO 2 capture is incorporated as part of the process [4,5]. In addition, use of biomass could contribute to the reduction of fossil fuel dependency [6]. Gasification can be divided into two main stages: pyrolysis and char gasification.…”

Comparison of kinetic models for isothermal CO2 gasification of coal char-biomass char blended char

“…Given the consideration of the current situation of China rich in non-coking coal and biomass, the co-gasification of biomass and coal can be considered as potential feedstock for the supply of reducing gas used in direct reduction iron-making technology by gasification. Therefore, co-gasified coal and biomass are not only beneficial for the development of gas-based shaft furnace technology in China, but also contribute to the reduction of the fossil fuel dependency and CO 2 emissions [4].…”