Solar Assisted Gasification: Systematic Analysis and Numerical Simulation

Abstract

Hybrid solar thermo-chemical conversion process is a viable route to produce clean fuel using any carbonaceous material as feedstock and solar radiation to provide energy for endothermic reactions. The steam gasification of carbonaceous material under high energy solar flux provides a thermo-chemical pathway to produce syngas fuel i.e. hydrogen (H2) and carbon monoxide (CO). Therefore, in this study a steady state model of entrained flow gasifier is simulated utilizing direct solar irradiation as process energy for endothermic reactions inside reactor. Lagrangian approach is used to inject coal particulates in the reactor which immediately undergoes devolatalization and finally steam (H2O) gasified. Species transport equations are solved for the concentration of H2, CO2, CO, H2O and nitrogen (N2) as well as the heterogeneous reaction of char (C/fixed carbon) with steam. DO radiation model is applied to simulate 5KW of solar radiation through an optical window inside the reactor. Steady state mass and energy balance are solved to determine the reactor temperature and the composition of product syngas. The resulting problem is then simulated by finite volume method to solve governing mass, momentum, energy and species transport equation. Validation is accomplished by comparing the trends of simulated results with systematic analysis and experiment. The resultant H2: CO and CO: CO2 ratios are computed to be 1.83 and 9.42 respectively. The cold gas efficiency is calculated, which is found to be 105.21% showing the upgraded heating value of product gases by virtue of direct solar radiation.