Visualization and modelling study of reaction and heat transfer during gasification of single coal/char particle on slag wall

Abstract

The part of particles inside gasifier is captured by the slag wall and then reacts on the wall. However, the reaction of coal particles on the slag wall surface is very complex and the corresponding mechanism has not been revealed systematically. The CH* distribution can be used to characterise the area of reaction of the coal particles for the devolatilization, and the time of devolatilization of the coal particles in the furnace can be assessed. In this study, the CH* releasing and temperature two-dimensional distribution of single coal/char particle on slag and non-slag walls during gasification were visualized using a high-speed camera with bandpass filters. Moreover, the particle temperatures were calculated by shrinking core model to explore the effect of the slag wall surface on the heat transfer of the particles and the reaction process. The results show that the particles are subjected to heat conducted by slag, accelerating heating, enhancing CH* release, and shortening gasification time. The calculated particle temperatures closely matched experimental values, indicating precise temperature predictions. Based on the variation of CH* peak intensity versus time, coal particle gasification was divided into preheating, volatile components releasing, and coal char reaction stages. For volatile components releasing stage, CH* peak intensity was mainly depended on particle temperature, which can be estimated from CH* intensity. For the coal char reaction stage, the change of particle temperature versus carbon conversion is consistent with the exponential function model.