Clean Hydrogen Production from Low Rank Coal: Novel Integration of Drying, Gasification, Chemical Looping, and Hydrogenation

Abstract

State-of-the-art integrated processes for hydrogen production from low rank coal (LRC) consisting of drying, gasification, chemical looping, and hydrogenation is proposed based on enhanced process integration (EPI). This paper focuses mainly on the performance of drying module, especially related to energy efficiency during drying. EPI, which is a combination of exergy recovery and process integration, in developed in order to minimize the total exergy destruction throughout the integrated processes. Each process module is designed initially based on exergy recovery to maximize the recirculated heat amount in each process module. Furthermore, the developed process modules are integrated based on process integration, hence the exergy destruction throughout the integrated processes can be minimized. LRC is initially dried in drying module employing exergy recovery and utilizing steam as drying medium. Hot dried- LRC is fed directly to gasification module for conversion producing syngas. The produced syngas is then flowing to chemical looping module to produce hydrogen, CO₂ and power. Finally, the produced hydrogen is then stored in liquid organic hydrogen carrier (toluene-methylcyclohexane). On the other hand, the separated CO₂ can be sequestered to achieve a clean coal conversion. From process calculation, the proposed drying module shows very high energy efficiency, which is about one sixth to which is required in drying with conventional heat recovery.