Investigation of coal gasification hydrogen and electricity co-production plant with three-reactors chemical looping process

Abstract

This paper analyzes a novel process for producing hydrogen and electricity from coal, based on chemical looping combustion (CLC) and gas turbine combined cycle, allowing for intrinsic capture of carbon dioxide. The core of the process consists of a three-reactors CLC system, where iron oxide particles are circulated to: (i) oxidize syngas in the fuel reactor (FR) providing a CO 2 stream ready for sequestration after cooling and steam vapor condensation, (ii) reduce steam in the steam reactor (SR) to produce hydrogen, (iii) consume oxygen in the air reactor (AR) from air releasing heat to sustain the thermal balance of the CLC system and to generate electricity. A compacted fluidized bed, composed of two fuel reactors, is proposed here for full conversion of fuel gases in FR. The gasification CLC combined cycle plant for hydrogen and electricity cogeneration with Fe 2O 3/FeAl 2O 4 oxygen carriers was simulated using ASPEN ® PLUS software. The plant consists of a supplementary firing reactor operating up to 1350 °C and three-reactors SR at 815 °C, FR at 900 °C and AR at 1000 °C. The results show that the electricity and hydrogen efficiencies are 14.46% and 36.93%, respectively, including hydrogen compression to 60 bar, CO 2 compression to 121 bar, The CO 2 capture efficiency is 89.62% with a CO 2 emission of 238.9 g/kWh. The system has an electricity efficiency of 10.13% and a hydrogen efficiency of 41.51% without CO 2 emission when supplementary firing is not used. The plant performance is attractive because of high energy conversion efficiency and low CO 2 emission. Key parameters that affect the system performance are also discussed, including the conversion of steam to hydrogen in SR, supplementary firing temperature of the oxygen depleted air from AR, AR operation temperature, the flow of oxygen carriers, and the addition of inert support material to the oxygen carrier.