Pinch and exergy assessment of an innovative hydrogen and methane purification process configuration based on solar renewable energy

Abstract

Energy recovery from waste sources and developing new high-performance systems are essential to minimize energy consumption. A novel purification structure is developed to produce hydrogen and liquid natural gas (LNG) using exhaust gases from various industries, mixed refrigeration system, organic Rankine cycle (ORC), and solar energy sources. Solar parabolic trough collectors are used to supply energy in the low-temperature ORC. The proposed system produces 1.922 kg/s hydrogen with purity of 94.25 mol% and 1.777 kg/s LNG as the main product by consuming 10.56 kg/s crude hydrogen feed gas. The LNG and pure hydrogen specific power consumption (SPC) are 0.4111 and 0.3803 kWh/kg, respectively. The SPC of the sum of both products is obtained at 0.1975 kWh/kg. The methane and hydrogen recovery factors are 94.80% and 98%, respectively, indicating maximum methane and hydrogen absorption of the crude hydrogen feed gas. The exergy analysis indicates that the total exergy destruction of the integrated system is calculated at 5561 kW, and its exergy efficiency is obtained as 28.56%. The heat exchanger networks for the HE1, HE2, HE3, HE4, and HE6 multi-stream heat exchangers are extracted through the pinch strategy. The multi-stream heat exchangers have 8, 13, 6, 8, and 2 simple heat exchangers. The outcome results obtained from the parametric study is a 25.88% increase in the production rate of the main products (LNG and pure hydrogen). In addition, when the ratio of LNG to fuel gas increases by 48.08%, the ratio of main product to by-product increases from 54 to 62 mol%. By performing parametric analysis, it can be concluded that increasing the hydrogen content of the crude feed improves the performance of the system.