Characteristics of Preheating Combustion of Power Coal with High Coking Properties

Abstract

Yankuang coal with the high coking property is difficult to use through direct combustion. The main purpose of this paper is to study the combustion characteristics and NOx emissions of this type of coal using preheating combustion technology. The experimental results show that after the pulverized coal is preheated, the char residue characteristic is significantly reduced from 5 to 1. During the preheating process, the preheating temperature is stable at about 910°C, and the particle size of char after preheating is reduced, and the pore structure and specific surface areas are increased. The combustion temperature of preheated fuel is stable at around 1100°C, and the combustion efficiency can reach more than 99% under different conditions. Changing the structure of the secondary air nozzles during the preheating combustion process can influence the characteristics of emissions. The NOx emission of the central nozzle is about 112 mg/Nm3 lower than that of the annular nozzle. Changing the tertiary air distribution modes can reduce the final NOx emissions to 215 mg/Nm3 (@6%O2), and the corresponding conversion ratio of fuel N to the final NOx is 4.2%. The results of this experiment prove that the Yankuang coal can achieve stable combustion by preheating combustion technology, and this proposed a new way for the utilization of Yankuang coal.