Effect of coal particle size on gasification performance of two‐stage entrained‐flow coal gasifier

Abstract

To clarify the effect of coal particle sizes on gasification performance of an advanced two-stage entrained-flow coal gasifier for IGCC (integrated gasification combined cycle) application, a comprehensive three-dimensional numerical model is established by incorporating the shrinking core model combined with the Langmuir-Hinshelwood kinetic rate expression, which considers the inhibitory effect of CO on char-CO 2 reaction. The flow, temperature, and species distributions were obtained, and the results are consistent with the operating data. Results show that the helical flow and eight recirculation zones in the gasifier improve carbon conversion efficiency through extending the residence time of coal particles. Slow devolatilization of large particles caused by slow heating retards volatiles combustion, and thus char combustion and gasification. As a result, less char gasification and higher gas temperature appear in the injection region of the first stage. Higher inertia of larger particles produces higher slip velocity, which enhances heat transfer and mass diffusion to char particles and increases char consumption rate in diffusionlimited regions. The regions of high inner wall temperature spread from locations around burners to the whole inner wall of the injection and bottom regions in the first stage with increase of coal particle sizes.

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

“…To verify the accuracy of the numerical models, the simulation results including the gas composition and carbon conversion efficiency are compared with the industrial data. 19 Fan et al’s simulation results, 39 which used a simplified PDF model to describe the interaction of turbulence and gas-phase chemical reactions, are also compared. As presented in Table 6 , the predictions presented in this work show favorable agreement with the industrial data.…”

“…The second stage of the gasifier was set to “reflect”. The thermal conditions of the wall were set as “convection” with an equivalent convective heat transfer coefficient of 169 W/m 2 K in the first stage and 121 W/m 2 K in the second stage, assuming a free stream temperature of 473 K. 39 The internal emissivity of the refractory brick was set to be 0.6. The discrete ordinate (DO) radiation model coupled with the weighted-sum-of-gray-gases model (WSGGM) was adopted to calculate radiative heat transfer.…”

CFD‐DPM‐based numerical simulation for char gasification in an entrained flow reactor: Effect of residence time distribution

“…Hence, higher conversion is expected for smaller particles for a certain coal feed rate. [ 5 ] Fan et al [ 19 ] studied the effect of coal size on gasification performance and found that an eight recirculation zones observed in the two‐stage entrained flow gasifier increase the residence time of particles. Jayaraman et al [ 20 ] studied the effect of heating rate on the kinetics of steam and CO 2 gasification in high ash coal and found that with an increase in the heating rate, the reactivity of char gasification increases.…”