Energy-efficient Co-production of Hydrogen and Power from Brown Coal Employing Direct Chemical Looping

Abstract

An integrated system for co-production of H2 and power from brown coal having high energy efficiency is proposed. The integrated system consists of drying, coal direct chemical looping, hydrogenation, and power generation. To minimize the exergy destruction occurs throughout the integrated system, enhanced process integration technology is applied, first in each single process, and second among the involved processes to recover the unrecoverable energy/heat from any single process. Coal direct chemical looping is adopted to convert the brown coal to H2 and CO2, and the rest of produced heat is recovered for power generation through gas and steam turbines. The produced hydrogen is then hydrogenated with toluene producing methyl cyclohexane which is ready for storage and transportation. The effects of target moisture content in drying and carbon conversion in reduction to H2 production, power generation, and total energy efficiencies are evaluated. From modelling and process calculation, the proposed integrated-system shows very high values of the above mentioned efficiencies, which are about 68.9, 21.0 and 90.0 %, respectively. Although higher carbon conversion in reduction leads to lower power generation, higher H2 production efficiency and higher total energy efficiency can be achieved. In addition, no significant influence of target moisture content in drying to each efficiency could be observed.