Sangbin Park

Modeling and analysis of a syngas cooler with concentric evaporator channels in a coal gasification process

Coal gasification offers a flexible and efficient conversion of the solid fuel into CO- and H2-rich synthetic gas (syngas) for production of various chemicals and energy products. Since the hot syngas leaving a gasifier contains various impurities such as acidic gases and particulates, it needs to be cooled down for cleaning prior to conversion into the final product. A dedicated heat exchanger called a syngas cooler (SGC) is used to lower the gas temperature while recovering the thermal energy. This study investigated the heat transfer characteristics in a commercial-scale SGC consisting of a series of concentric helical coil channels. First, the detailed flow and heat transfer pattern in the unique heat exchanger were analyzed using computational fluid dynamics (CFD) for various operating loads and fouling conditions. The predicted heat transfer rate was used to derive correlations for Nusselt number for the channel sections of the SGC. Second, a one-dimensional model of the equipment was proposed for fast-response process simulations. In terms of heat transfer rate and gas temperature, the process model showed a reasonable accuracy compared to the CFD results for the tested cases.

Effect of Operating Pressure on the Heat Transfer and Particle Flow Characteristics in the Syngas Quench System of an IGCC Process

In a coal gasifier for IGCC, hot syngas leaving the gasifier at about 1550oC is rapidly quenched by cold syngas recycled from the gas cleaning process. This study investigated the flow and heat transfer characteristics in the gas quench system of a commercial IGCC process plant under different operating pressures. As the operating pressure increased from 30 bar to 50 bar, the reduced gas velocity shortened the hot syngas core. The hot fly slag particles were retained within the core more effectively, and the heat transfer became more intensive around the hot gas core under higher pressures. Despite the high particle concentrations, the wall erosion by particle impaction was estimated not significant. However, large particles became more stagnant in the transfer duct due to the reduced gas velocity and drag force under higher pressures.