An innovative high energy efficiency-based process enhancement of hydrogen liquefaction: Energy, exergy, and economic perspectives

Hydrogen liquefaction can be one of the effective and viable solutions to enhance its energy contents for storage and transportation purposes. However, liquefaction of H-2 is highly energy intensive where precooling is the most significant energy consumption section (similar to 50% of overall process) due to huge reduction in temperature (25 to-159.4 degrees C). In this context, in proposed study the precooling cycle is split into two cycles for reducing the energy consumption, 1) Hydrofluoroolefin-based mixed refrigerant stream which reduces the H-2 temperature to -30 degrees C and 2) Mixed refrigerant stream which tends to reduce the H-2 temperature up to-159.4 degrees C. This is the first study which utilizes the four refrigeration cycles with unique selection of HFO-based mixed refrigerants in precooling section to reduce the gaseous H-2 temperature. Results of proposed study reveal that the specific energy consumption of proposed process was reduced by 55.2 % and 29.5%, as compared to base case-I (10.15 kWh/kgLH(2)) and base case-II (6.45 kWh/kgLH(2)), respectively. The exergy efficiency of the proposed process was increased by 67%. In addition, results of economic evaluation depicted that the total annualized cost of proposed process was obtained as $1.89 x 10(6)/y where the CAPEX has share of similar to 71.7% in total cost of project. The estimated unit production cost was recorded as $5.18/kg of LH2 at the capacity of 1TPD. The simplicity and less energy consumption of proposed model built a basis for its development to commercial scale adoption.

Automated summary

Hydrogen liquefaction is an effective and viable solution to increase energy contents for storage and transportation. This study proposes a precooling cycle that reduces energy consumption by using unique HFO-based mixed refrigerants to lower the temperature of gaseous H-2. The results show a significant reduction in specific energy consumption and an increase in exergy efficiency compared to the base cases. The economic evaluation also demonstrates the feasibility of the proposed process.