Dry layer
The uppermost layer of the gasification furnace is the drying zone. The materials added from above enter the drying zone directly, where the materials exchange heat with the hot gas products generated in the three reaction zones below to evaporate the moisture in the raw materials. The temperature of this layer isPyrolysis layer
The organic combustible dry materials run down into the pyrolysis layer, and the biomass is heated at the same time. When the organic combustible materials are heated, a pyrolysis reaction occurs. Most of the volatile matter in the fuel is separated from the solid by the pyrolysis reaction, which is basically completed at 500~600℃, leaving the carbon residue. The main products of the pyrolysis zone are charcoal, water vapor, carbon dioxide, methane, tar and other hydrocarbon substances.
Oxide layer
The remaining carbon residue from pyrolysis reacts violently with air, releasing a lot of heat. Because it is anaerobic combustion, the supply of oxygen is insufficient, so the incomplete combustion reaction occurs at the same time. At a high temperature of about 1000℃, through the action of water vapor, an oxidation-reduction reaction occurs to produce carbon monoxide (CO), hydrogen (H2), etc. flammable gas.
What is going on in the oxidation zone is combustion reaction and releases heat. It is this part of the reaction heat that provides a heat source for the reduction reaction, pyrolysis and drying of materials in the reduction zone. The hot gases (carbon monoxide and carbon dioxide) generated in the oxidation zone enter the reduction zone of the gasifier, and the ash falls into the lower ash chamber.
Reduction layer
There is no oxygen in the reduction zone. The carbon dioxide generated in the oxidation reaction undergoes a reduction reaction with carbon and water vapor here to generate carbon monoxide (CO) and hydrogen (H2). Since the reduction reaction is an endothermic reaction, the temperature of the reduction zone is also lowered accordingly, about 600~800℃. The main products in the reduction zone are carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H2).
Gasification is actually always combined with the dry cracking process of fuel. In the actual operation process, the above four areas have no clear boundaries, and they are mutually infiltrated and interlaced. Therefore, at the outlet of the gasifier, the output gas components are mainly carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4), tar and a small amount of other hydrocarbons, as well as water vapor and a small amount of ash. Gasification is actually always combined with the dry cracking process of fuel. In the actual operation process, the above four areas have no clear boundaries, and they are mutually infiltrated and interlaced. Therefore, at the outlet of the gasifier, the output gas components are mainly carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4), tar and a small amount of other hydrocarbons, as well as water vapor and a small amount of ash.