Đang tải... (xem toàn văn)
Công nghệ và thiết bị trong quá trình khí hóa sản phẩm biomass, sản xuất năng lượng, thích hợp để ứng dụng tại vùng nông thôn, giảm chi phí và bảo vệ môi trường, góp phần phát triển kinh tế tại vùng nông thôn, trình độ kỹ thuật còn thấp
7, J [...]... pyrolysis 4.4.3 Operation of the Downdraft Gasifier Downdraft gasifiers have been very successful for operating engines because of the low tar content Most of the work reported in this book was performed on downdraft systems, and they will be the principal gasifier discussed in the balance of this book In the downdraft gasifier of Fig 4-5 (b), air contacts the pyrolyzing biomass before it contacts... beginning of World War II, there was a great deal of interest in all forms of alternative fuels (Egloff 1941, 1943) By 1943, 90% of the vehicles in Sweden were powered by gasifiers By the end of the war, there were more than 700,000 wood-gas generators powering 6 Fig 2-1 Vehicle gasifiers before 1950 (Source: NAS 1983) Handbook of Biomass Downdraft Gasifier Engine Systems regarded as only temporary... D.C.: U.S Bureau of Mines; Report of Investigations 7282 Source: Reed 1981 gas is because of charcoal's low volatile content At the beginning ofWorld War II, most gasifiers used charcoal However, charcoal manufacture wastes approximately 50% of the energy of biomass and usually requires hardwood biomass as a starting material By the end of World War II, most gasifiers used wood instead of char coal (Gengas... possibly densification before use in most gasifiers Handbook of Biomass Downdraft Gasifier Engine Systems 3.4.1 Densifying Biomass Fuels Biomass fuels usually have bulk densities from one half to one-tenth that of coal as shown in Table 3-11, presenting a drawback for shipping, storage, and gasification Biomass fuels also come in a wide range of sizes, many of which are not suitable for fixed-bed gasification... Figs 20-35, 20·36) 20 Handbook of Biomass Downdraft Gasifier Engine Systems 3'6" v- W.P Chapter 4 Principles of Gasification 4.1 Introduction Gasifiers are relatively simple devices The mechanics oftheir operation, such as feeding and gas cleanup, also are simple The successful operation of gasifiers, however, is not so simple No neat rules exist because the thermodynamics of gasifier operation are... depending on vari ables such as gasifier heat loss, biomass moisture content, and char removal at the grate Source: Modified from data in Reed 1981 Handbook of Biomass Downdraft Gasifier Engine Systems The ratio CO/COz (or Hz/HzO) is a measure of the producer gas quality Approximately 30% of the biomass is burned to provide the energy for gasification of the rest The exact amount of excess oxygen required... bustion (Complete oxidation of biomass with oxygen requires a weight ratio of 1.476 [mass of oxygen/mass ofbiomassl; with air, a ratio of 6.36.) A very low or zero oxygen use is indicative of pyrolysis, shown at the left ofthe figure; a of about 0.25 is typical ofthe gasifica tion region at the middle; and combustion is indicated by a :2 1 at the right The composition of the gas produced is shown... Federal Emergency Management Agency (FEMA) Gasifier Work The downdraft gasifier reached its highest develop ment during the emergency of World War II FEMA has taken interest in small-scale gasifiers because they could function during a period of breakdown in our oil supply due to atomic attack or other disruption of conventional fuels Handbook of Biomass Downdraft Gasifier Engine Systems With this i n... The most important types of fixed-bed gasifiers for this task are the updraft and downdraft gasifiers of Fig 4-5 These gasifiers will be discussed in greater detail in Chapter 5 but a brief introduction here will facilitate understanding of the fundamental principles involved The terms "updraft gasifier" and " downdraft gasifier" may seem like trivial mechanical descriptions of gas flow patterns In... areas One of our authors (Das) has developed a small gasifier suitable for firing a foundry The other author (Reed) is developing small batch-type gasifiers for cooking and lighting applica tions in third world countries History, Current Developments, and Future Directions 7 Fig 2.2 Vehicle gasifiers after OPEC (Source: NAS 1983) 8 Handbook of Biomass Downdraft Gasifier Engine Systems Chapter 3 Gasifier