China is one of the countries with the richest coal resources in the world. Coal plays an important role in China's energy structure. The development and research of deep and clean coal resource utilization technology is in line with my country's energy security strategic requirements. NOx is one of the main harmful gases produced during the coal conversion process. At present, domestic and foreign scholars agree that NH3 and HCN are the main precursors of NOx during the coal conversion process, and the precursors are further oxidized to generate NOx. As an earlier clean coal technology applied in China, atmospheric fixed bed generator gasification technology has always been the main coal gasification and gas supply technology for industrial fuel gas. A systematic analysis of the generation of NOx and its precursors during its gas production process will help to take relevant measures to control the generation of NOx and its precursors in coal gas, so that the NOx generated during the coal gas combustion process can be effectively controlled.

 

Gas production process of gas generator

 

       The main reactions of coal in the gas generator include pyrolysis and gasification processes. The volatile matter in the coal is removed through the pyrolysis process in the generator furnace, and tar and carbonization gas mainly composed of CH4, H2, and CO are precipitated;Single stage generatorThe characteristics of the furnace type are that the furnace body is low, the retort layer area and drying layer area in the furnace are thin, and an empty layer of 1.5~2 m must be maintained at the top of the furnace during operation. The gas production process of the one-stage generator is as follows: coal is added into the gas generator furnace through a stoker, and is first dried and retorted for a short period of time; then it enters the gasification reaction layer. Air and water vapor as gasification agents are drummed into the furnace from the bottom of the furnace. Under high temperature conditions, an oxidation-reduction reaction occurs with the coal in the gasification reaction bed to form coal gas with CO and H2 as the main components.

 

 

   The NO generated in the oxidation layer combustion zone of the gas generator goes up to the reduction layer area along with other gases generated in this layer area. It is reduced to N2 by the CO, semi-coke, volatile matter and NH3 precipitated from the coal in the reduction layer area and enters the gas.