How does a downdraft gasifier work?
In downdraft gasifier the fuel slowly moves down by gravity. During this downward movement, the fuel reacts with air, which is supplied by the suction of a blower or an engine and is converted into combustible producer gas in a complex series of oxidation, reduction, and pyrolysis reactions .
What is the advantage of downdraft gasifier over updraft gasifier?
Advantage of the downdraft fixed-bed gasifier is that the tars are cracked down in the oxidation zone, thus the producer gas has lower tar content compared to other types of gasifiers.
How does a gasifier work?
Gasification occurs in a gasifier, generally a high temperature/pressure vessel where oxygen (or air) and steam are directly contacted with the coal or other feed material causing a series of chemical reactions to occur that convert the feed to syngas and ash/slag (mineral residues).
Which is better gasification or incineration?
Gasification is able to generate energy which is cheaper and more efficient than the steam process used in incineration. Municipal solid waste can be reduced by as much as 75% through this process, reducing to the same degree the amount of potential emissions the waste would have created in a landfill.
What is a downdraft gasifier?
Downdraft Gasifier. A downdraft gasifier is a gasification reactor with four distinct zones: (a) upper drying zone, (b) upper-middle pyrolysis section, (c) lower-middle oxidation zone, and (d) lower reduction zone. A schematic of a downdraft gasifier is given in Figure 8.3. Figure 8.3. Schematic of a downdraft gasifier.
What are the issues with stratified downdraft gasifiers?
An important issue in the design of the stratified, downdraft gasifier is the prevention of fuel bridging and channeling. High-grade biomass fuels, such as wood blocks or chips, will flow down through the gasifier because of gravity and downdraft airflow.
Is downdraft gasiication the only option for small-scale power systems?
Although the handbook focuses on downdraft gasiication as the only method suitable for small-scale power systems, it also gives extensive detail on biomass fuels, gas testing and cleanup in strumentation, and safety considerations that will be of use to all those who work with gasiiers at whatever scale.
What is the typical kj/nm3 of a downdraft air gasifier?
from the gas composition, using a value of 13,400 kJ/Nm3 (330 Btu/sc for H2 and and .900 kJ/Nm3 (1030 Btu/sci) for methane. are typical values for downdraft air gasifiers, but they can vary between 4880 and 7320 kJ/Nm3 (120-180 Btu/scf). depending on vari