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from coal. However challenges associated with co-firing with biomass such as changes in ash properties, fouling of heat exchanger, etc. still need to be addressed [56]. Biomass torrefaction is promising process that improves the usefulness of biomass as a fuel by heating the biomass in the absence of air under mild temperatures (230–300C). The resulting biomass fuel is a desirable feedstock for entrained-flow reactors or in pulverized coal fired boilers with co-

Arce et al., [58] studied the performance of the different types of biomass fuel combustion process in a counter-current fixed bed reactor in the temperature range of 740–1300C to check the effects of different factors and find the optimum condition. According to the study, the ignition front propagation speed and the highest temperature that is reached at the fixed bed

Oxy-combustion is an emerging technology that uses pure oxygen in the combustor. The advantage is that after the cooling of flue gas, nearly pure carbon dioxide is produced without any nitrogen or nitrogen oxides. However, the use of pure oxygen (or oxygen enriched air) results in higher capital and operating costs. This needs to be balanced against the cost/energy savings related to carbon dioxide capture. This technology is still in the research and demonstration stage. As more cost effective processes for oxygen production such as membrane separation are developed, oxy-combustion will presumably become a more attractive option

Energy sources from the renewable carbon are critical to address future energy needs, in the all energy consuming sector. Biomass is the largest and most widespread carbon source for producing renewable energy, fuels and chemicals and can be a constant, reliable resource compare to other renewable sources such as solar or wind energy. A wide range of biomass conversion processes are available and are under development. Among these, thermochemical processes offer several advantages, including product versatility, and high conversion rates and efficiencies, although challenges to commercialization still remain.

Wet thermochemical processes including hydrothermal conversion, supercritical gasification and steam hydrogasification are still under development, but have many attractive aspects for use in decentralized, low cost applications, especially for high moisture content biomass. Dry thermochemical conversion processes including direct combustion, gasification and pyrolysis have several specific technology options that are mature. However, economic viability issues and technical challenges related to tar formation and alkaline

New emerging approaches such as the bio-refinery concept which synergistically combines different conversion technologies and generate multiple products are expected to play a key role in addressing the technical and economic barriers of the current thermochemical bio-

firing of biomass [57].

36 Gasification for Low-grade Feedstock

combustor affects the combustion process most.

for both biomass and fossil feedstocks.

ash presence still need to be addressed.

mass conversion processes.

5. Conclusion

Chan Seung Park1 \*, Partho Sarothi Roy1 and Su Hyun Kim2

\*Address all correspondence to: cspark@cert.ucr.edu

1 College of Engineering - Center for Environmental Research and Technology, University of California, Riverside, CA, USA

2 Institute for Advanced Engineering, Yongin-si, Gyeonggi-do, Korea
