Coal-Direct Chemical Looping Gasification for Hydrogen Production: Reactor Modeling and Process Simulation

TLDR

The CDCL process uses an iron‑oxide oxygen carrier to indirectly gasify coal into separate H₂ and CO₂ streams. The study presents a novel coal‑direct chemical looping (CDCL) gasification scheme that captures CO₂ in situ for hydrogen production. ASPEN Plus reactor simulations incorporating thermodynamic and kinetic limits were employed to model individual CDCL reactors, evaluate performance under various mass and energy management schemes, and assess steam oxidation of the reduced oxygen carrier, pollutant fates, and conversion effects. Reactor modeling demonstrates that a moving‑bed reducer can convert coal while reducing the oxygen carrier, and process simulation predicts that the CDCL process can achieve ~78 % HHV thermal efficiency with >90 % CO₂ capture—about 30 % higher than conventional hydrogen production.

Abstract

A novel process scheme for hydrogen production from coal with in situ CO2 capture, known as the coal-direct chemical looping (CDCL) gasification process, is discussed in this article. The CDCL process utilizes an iron oxide based oxygen carrier as a chemical looping medium to indirectly gasify coal into separate streams of H2 and CO2. ASPEN Plus reactor simulation models based on both thermodynamic equilibrium limitations and kinetic limitations are developed to analyze individual CDCL reactors. Process simulations are subsequently performed to estimate the performance of the CDCL process under various mass and energy management schemes. Reactor modeling results indicate that a moving bed reducer can effectively convert coal while reducing the oxygen carrier. The reduced oxygen carrier can in turn be oxidized by steam to produce hydrogen in a moving bed oxidizer. The fates of pollutants as well as the effects of various process operating parameters such as carbon and iron oxide conversions are also evaluated. Process simulation indicates that, even under a set of conservative assumptions, the CDCL process has the potential to convert coal to hydrogen at a thermal efficiency of nearly 78% (HHV) while capturing >90% CO2, which is 30% higher, on a relative basis, than conventional hydrogen generation processes.