A multi-dimensional feasibility analysis of coal to methanol assisted by green hydrogen from a life cycle viewpoint

Abstract

Incorporating renewable hydrogen (green H2) in the coal to methanol process plays a significant role to achieve the reduction of carbon intensity and improve energy efficiency and economic performance of the coal chemical industry. This study proposed a coal to methanol process assisted by the green hydrogen generated from three pathways of water electrolysis by wind, solar or wind-solar hybrid power (GH-CTM). The GH-CTM process was established, modeled and validated based on the industrial data, and the key operating parameters that have significant effects on the system were investigated and optimized. Additionally, a comparative analysis based on techno-economic evaluation and life cycle assessment of GH-CTM and the traditional coal to methanol (CTM) is investigated. Results show that carbon utilization efficiency (CUE, 68.14 %), hydrogen utilization efficiency (HUE, 75.57 %), energy efficiency (57.16 %) and exergy efficiency (52.48 %) of GH-CTM is 28.91 %, 19.65 %, 3.82 % and 4.03 % superior to that of CTM. Carbon emission intensity (CEI, 1.39 t/t), water consumption (WC, 1.21 t/t), energy consumption of methanol production (ENC, 11.62 MWh/t) of GH-CTM process are 39.83 %, 20.92 % and 6.74 % lower than that of CTM process. GH-CTM processes (GH-CTM-1, GH-CTM-2 and GH-CTM-3) have outstanding economic performance, in which IRR is 5.68–16.33 % greater than that of the CTM process (15.9 %), and CMP is 23.17–39.86 % lower than that of CTM (334.20 $/t). With the same methanol production, the life cycle cost of methanol production (LCCMP, 235.75 $/t), life cycle carbon emission intensity (LCCEI, 1.88 t/t), life cycle water consumption (LCWC, 2.73 t/t) and life cycle energy consumption of methanol production (LCENC, 11.68 MWh/t) of GH-CTM-3 process are 40.26 %, 41.25 %, 35.46 % and 7.0 % lower than that of CTM process, respectively. These findings demonstrate that the GH-CTM process, which converts unstable renewable power into stable methanol molecules and solves the problem of intermittent and inter-seasonal renewable energy utilization, shows good feasibility in terms of the environment, economy, and technique.