Operational Mechanism
After the raw biomass material was put into the gasifier, chemical
processes like pyrolysis reaction and deoxidization were taken place with the
burning, part of raw material was burned with the oxygen, provide heat for the
pyrolysis, but more biomass materials were pyrolyzed in high temperature, and
separate out volatile and char. The volatile reacted for the second time within
the high temperature region and the tar was pyrolyzed further into gas. At the
same time, reduction reactions were happened between the char and gas, and
between the gases themselves. In the end, gas phase tar and gas went to the
separator, accompanying with some small char particles and ash particles and gas
phase been separated, part of the char re-circulate to the gasifier to react
again, gas phase tar was cleaned by water after scrubber. And the clean gas
meets with the requirement of the gas engine to generate power.
Operational Parameters
This system is used air as gasification medium, and the operating
temperature should between 650-850
C? The components of fuel gas include:
N2 (nitrogen), O2 (oxygen), H2 (hydrogen), CO2
(carbon dioxide), CO (carbon monoxide), CH4 (methane) and
CnHm, etc. and the heat value of the gas in between
4600-6300kJ/Nm3.
Take an example of 1 MW rice hull gasification and power generation system.
After the successful ignition of the gasifier, the power generating system
begins to operate. Comparing with other kinds of biomass materials, rice hull
has a high ash content, as much as 20%,When the temperature is more than 850 C?
silica and potassium oxide in the ash will slag on the surface of the rice husk
particles, forming a glass-like barrier, which prevents the further reaction of
the remaining char and jams in exit of the ash; When the temperature is less
than 700 C? part of carbon in the fuel remains un-burnt and accumulates in the
reactor, resulting in lower efficiencies. Due to such characteristics of the
ash, the CFB gasifier is supposed to be a promising choice for rice husk, since
the bed temperature can be kept below the ash slagging temperature by
controlling its operating parameters properly. At general condition, the
reacting temperature inside the gasifier should be steadily kept around
750-850 C?
Credit to : web: china-power-contractor.cn
