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 H-2 media owing to their novelty in the storage and transportation of H-2. 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 (R) reveals a considerable amount of stored H-2 for DBT-18H-DBT (7.20 kmolH(2) h(-1)) and the lowest unit cost of H-2 storage (7.00 $ kgH(2)(-1)) by itemized cost estimation. In addition, the effects of operating temperature, recycle ratio of unreacted H-2, and scale of H-2 storage on economic feasibility are investigated, and the expected cost reductions to 2.83, 4.21, 3.84, and 2.37 $ kgH(2)(-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 H-2 storage and identifies the costs of the H-2 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 kgCO(2) kgH(2)(-1) of unit CO2 emissions are evaluated by integrative carbon footprint analysis.