Quantitative evaluation of radiative heat transfer from reactor surface to multiphase reaction medium in a supercritical water gasification reactor for coal

Abstract

Supercritical water gasification (SCWG) of coal is a clean coal utilization technology, which converts organic matter in coal into hydrogen-rich gases through a series of thermo-chemical reactions. In this process, thermal radiation is an important heat transfer mechanism and significantly affects thermal efficiency and gasification performance. This paper aims to develop a comprehensive numerical model integrating with solving radiative transfer to precisely simulate the process of SCWG of coal, and quantitatively evaluate non-grey radiative heat exchange between reactor surface and multiphase reaction medium. The simulation results are validated against experimental data. It is shown that under practical operating conditions, thermal radiation accounts for 30 % – 42 % of total heat exchange in the reactor. More than 94 % of radiant energy lies in the spectral range of 1.99 – 50.0 μm, which just covers the three most important radiation bands of supercritical water. Because both coal particles and supercritical water participate in radiative heat transfer, enhancing radiative heat transfer can effectively improve reaction medium temperature and gasification rate. On average, for every 20 % increase in the proportion of radiative heat transfer in the reactor, fluid medium temperature increases by around 7.1 K, and the gasification reaction rate rises by 9.5 %. These findings would provide valuable guidance for reactor design and optimization in practice.