Читать книгу Synthesis Gas - James Speight G., James G. Speight - Страница 41

The gasification of biomass and municipal solid waste differ in many ways from the gasification of crude oil coke or conversion of natural gas to synthesis gas. While the gasification technologies used with biomass (Chapter 6) or municipal or municipal solid waste (Chapter 7) are relatively straightforward, performance depends greatly on the unique characteristics of the feedstock. These feedstocks have much higher moisture content and less heating value by volume than coal. In addition, the non-uniformity of the feedstocks and the variability of the specific compositions over time require flexible and robust gasifiers.

Co-gasification technology varies, being usually site specific and feedstock dependent. In fact, biomass and municipal solid waste feedstocks are highly variable feedstocks that present issues for feed systems as these feedstocks are largely heterogeneous in their delivered state. Some biomass, such as sawdust from lumber mills, can be in a condition suitable for many existing feed systems most municipal solid wastes require extensive preparation or feed system customization. Biomass and municipal solid waste may also have characteristics such as higher moisture content which may necessitate pre-gasification drying. The mineral matter content of each feedstock can also vary widely and the gasifier must be able to handle variable (even high) levels of mineral matter and the ensuing ash.

At the largest scale, the plant may include the well-proven fixed-bed and entrained-flow gasification processes. At smaller scales, emphasis is placed on technologies which appear closest to commercial operation. Pyrolysis and other advanced thermal conversion processes are included where power generation is practical using the on-site feedstock produced. However, the needs to be addressed are (i) core fuel handling and gasification/ pyrolysis technologies, (ii) fuel gas clean-up, and (iii) conversion of fuel gas to electric power (Ricketts et al., 2002).