Cryogenic biogas upgrading process using solar energy (process integration, development, and energy analysis)

Biogas upgrading is a process that increases methane content to an acceptable percentage is compared with natural gas and reduces impurities such as CO2 and H2S in the biogas. Several methods for biogas upgrading are used. The selection of biogas upgrading methods depends on the type of biogas and the facilities' requirement according to local circumstances. This paper presents a study on an integrated process of cryogenic biogas upgrading by using renewable energy resources for sustainable development. Parabolic trough solar collector (PTC), organic Rankine cycle (ORC) power system and absorption refrigeration cycle are used in this process to separate the impurity of raw biogas. PTC supplies the required heat for the ORC, and absorption refrigeration cycles. Inlet biogas contains 61.10%, 36.93% and 0.01% (mole percent) CH4, CO2 and H2S. After purification, upgraded biogas contains 92.67% CH4 and 4% CO2. The results of the exergy analysis of the process show that the overall exergy efficiency of the integrated process and solar collector are 71.62% and 51.37% respectively. Also, the cryogenic heat exchangers have the highest exergy efficiency while the most exergy destruction occurs in the solar collector and afterward in the column. Sensitivity analysis on the effective parameters such as wind speed, ambient temperature, and auxiliary energy ratio is investigated. (C) 2020 Elsevier Ltd. All rights reserved.