Preliminary feasibility study for hydrogen storage using several promising liquid organic hydrogen carriers: Technical, economic, and environmental perspectives

Abstract

Liquid organic hydrogen carriers (LOHC) are promising alternatives to conventional H2 media owing to their novelty in the storage and transportation of H2. Herein, a comprehensive feasibility study is reported for hydrogenation processes using several promising LOHC systems: N-ethylcarbazole (NEC)–perhydro-NEC (12H-NEC), dibenzyltoluene (DBT), perhydro-dibenzyltoluene (18H-DBT), toluene (TOL)–methylcyclohexane (MCH), and CO2–methanol (MeOH). Detailed process simulation using Aspen Plus® reveals a considerable amount of stored H2 for DBT–18H-DBT (7.20 kmolH2 h−1) and the lowest unit cost of H2 storage (7.00 $ kgH2-1) by itemized cost estimation. In addition, the effects of operating temperature, recycle ratio of unreacted H2, and scale of H2 storage on economic feasibility are investigated, and the expected cost reductions to 2.83, 4.21, 3.84, and 2.37 $ kgH2-1 are evaluated for NEC–12H-NEC, DBT–18H-DBT, TOL–MCH, and CO2–MeOH, respectively. The sensitivity analysis quantifies the variation in the total unit cost of H2 storage and identifies the costs of the H2 reactant and labor as key economic parameters in LOHC hydrogenation. Furthermore, 0.16–0.43, 0.78–1.72, 1.25–1.73, and 1.12–5.52 kgCO2 kgH2-1 of unit CO2 emissions are evaluated by integrative carbon footprint analysis.