Industry Biomass Coal Fired Steam Boilers Double Drum Chain Grate Combustion

1. The principle of biomass gasification

Biomass gasification is a process that under certain conditions of thermodynamic, to made the composition of the biomass of C-H compounds change to CO and H2 other flammable gases. The gas mix with the air and oxygen to made the biomass burning, if the gas mix with limited oxygen, the biomass will incomplete combustion in the furnace, it will be gasification to combustible gas-pneumatolytic gas. During the gasification process, just supply the necessary and limited oxygen and as far as possible to retain the power in the after reaction combustible gases. The H, CO and low-molecular-weight hydrocarbons of combustible gas are the product after gasification.

After gasification, the main ingredient for the production comprised nitrogen, CO, CO2, hydrogen, methane, tar anda small amount other hydrocarbon substances (CnHm), as well as a small amount of ash and water vapor. It is contains 79% of N2 in the air, it does not participate in gasification reaction, so in the gasification gas almost content 50% of N2. But it is diluted the combustible part in the pneumatolytic gas, so it is reducing the gasification gas heat value. Pure gasification process can produce gas that heat value is 1060kcal/Nm3, while the gas after actual gasification generated the heat value will higher than the theoretical heat value, according to the biomass raw material difference, generally difference is 1200 ~ 1400 kcal/Nm3.

Gas after gasification comprised the more dust, tar and water, it is must to be purified. Mainly is to removal the ash, solid particles, tar, condensate and etc in the combustion gas. Ash and tar will be ≤ 50mg/Nm3 after the gas purified. Tar is gaseity when it is high temperature, and it is completely mixture with combustible gas. When under low temperature (usually less than 200 ℃) condition, tar will be condensation liquid, so it is hard to separation and processing. The generally purification equipment have cyclone dust collector, spray towers, separator, the tar filter and so on. The purified gas can be supply to the combustion engine to use.

2. The technology of KWEE has those five innovations as following:

⑴ Used the structure of the cycle of circulating fluidized bed (XHL) biomass gasifier, do not have to add sand (no bed material) also can be stable operation. It is good adaptability, large process capacity, stronge loading adaptability and easy operation;

⑵ Gasifier blown the strong and upward movement air current from bottom to make the biomass material liquid boling like a floating, It is gas and solid mixed equably, Generally, reaction temperature is 750 ~ 850 ℃. Large range of gas production capacity, and will not reduce the efficiency of gasification evidently.

⑶ Moving bed tar cracking technology, reduce the tar content in gas effectively and increase the efficiency of gasification

⑷ Use Chinese diesel engine units to developed a low/middle speed and large-scale low calorific value of gas-fired generating units, it is reduce the gas requirments of power generation equipment (tar content and impurities content <50mg / N m3);

⑸ Use special bacteria, use good aerobe, anaerobic mixed technique to made waste water and tar treatment.

⑹ 　Large gasifier, low calorific value of gas combustion engine, waste heat recovery can constitute a combined cycle power generation systems. Under the low investment conditions, a substantial increase in the efficiency of power generation. Efficiency almost can be up to 30%