Fuel reactor modelling in chemical-looping combustion of coal: 2—simulation and optimization

Abstract

Chemical-looping combustion of coal (CLCC) is a promising process to carry out coal combustion with carbon capture. The process should be optimized in order to maximize the carbon capture and the combustion efficiency in the fuel reactor, which will depend on the reactor design and the operational conditions. In this work, a mathematical model of the fuel reactor is used to make predictions about the performance of the CLCC process and simulate the behaviour of the system over different operating conditions. The mathematical model considers the fluid dynamic characteristics of the fuel reactor, being a high-velocity fluidized bed reactor. It also considers the chemical processes happening inside the reactor, and the effect of a carbon separation system on the char conversion in the process.A sensitivity analysis of the effect of the efficiency of the carbon separation system, the solids inventory in the fuel reactor, the temperature in the fuel reactor, ratio of oxygen carrier to fuel, oxygen carrier reactivity, coal reactivity and coal particle on the carbon capture and combustion efficiency is carried out. Also the relevance of the water–gas shift reaction (WGS) is evaluated. The most relevant parameters affecting the carbon capture are the fuel reactor temperature and the efficiency of the carbon separation system, ηCSS. A value for ηCSS as high as 98% should be necessary to reach a carbon capture efficiency of 98.6% when the solids inventory was 1000 kg/MWth. Regarding the combustion efficiency, to use highly reactive oxygen carrier materials are desirable. In any case, additional actions or a modified design for the fuel reactor should be implemented to reach complete combustion of coal.