Optimal design of heat exchanger header for coal gasification in supercritical water through CFD simulations

Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercritical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers (A, B, C, D, E, F and G), which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water (SCW) to evaluate the uniformity of the velocity distribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-mm inlet pipe diameter.