Effect of raw material, moisture and high-temperature tertiary air on a coal gasifier for cement precalciation

Abstract

This paper proposes a new method of pulverized coal gasification using high-temperature tertiary air in a cement precalciner, in which an external hanging gasifier is added nearby. A full-scale model is established and simulated for the entrained flow gasifier. During the gasification process, the global reaction mechanism is used to model the release and reactions of volatiles from pulverized coal, and a particle surface reaction model is employed to calculate the fixed carbon content. The mechanism by which reducing gas reacts with NO is also considered. The results of the velocity, temperature, gas composition, NOx emissions, calorific value, volatile conversion ratio and char burnout ratio, are achieved in the simulation. The results show that the volatile conversion ratios were close to 100%, and the carbon conversion ratios ranged from 27.97% to 62.76% among all the tested conditions. The concentrations of NO at the outlet of the gasifier were 109, 98, 75, 91, 87, 76, and 90 mg/m3 separately in 7 conditions. These values are significantly lower than those of complete combustion. However, the addition of raw meal had the best temperature control effect, leading to a significant decrease in thermal NOx production and no side effects on the stability of the production line.

Keywords

• Pulverized coal gasification
• High-temperature tertiary air
• NOx reduction
• Cement precalciner