Numerical Simulation on the Effect of Burner Bias Angles on the Performance of a Two-Stage Entrained-Flow Gasifier.

Abstract

A 2000 t/day HNCERI (Huaneng Clean Energy Research Institute) entrained-flow pulverized coal gasifier suffers from the problem of a high ash–slag ratio. An appropriate bias angle of the burners is the key to solve this issue for the gasifier with a specific structure. A random pore model considering bulk and pore diffusion effects was extended by user-defined function to describe the gasification reactions. The simulation of the gas flow and char gasification characteristics under different bias angles (0, 1.5, 2.5, 3.5, and 4.5°) of the four burners in the first stage was conducted. The simulation results showed favorable agreement with the industrial data. The evaporation, devolatilization, and char oxidation mainly occurred in the first-stage jet zone, and the upflow and downflow zones are dominated by the gasification reactions. The bias angles of the burners mainly affect the scale of gasification reaction zones. As the bias angles increased from 0 to 4.5°, the gas temperature at the slag tap hole decreased from 1880 to 1500 K. The carbon conversion efficiency of the first stage decreases and that of the second stage increases with the bias angle increasing. An optimal bias angle of 2.5° is recommended for the HNCERI gasifier with a total carbon conversion efficiency of 98.16%.