Energy, exergy, and sensitivity analyses of a new integrated system for generation of liquid methanol, liquefied natural gas, and crude helium using organic Rankine cycle, and solar collectors

Abstract

The increasing growth of helium consumption in industries and the limited resources of this element are the challenges that industries will face in the future. One way to reduce the energy consumption in producing crude helium is to integrate it with low-temperature cycles. Also, using solar energy as a source of energy production in areas that receive adequate solar energy is an important strategy for energy supply in terms of environmental compatibility and sustainable development. In this paper, a novel integrated structure for producing liquid methanol, liquefied natural gas, and crude helium gas using the process of separating helium from natural gas, methanol synthesis process, organic Rankine cycle, and solar dish collectors is developed and analyzed. This hybrid system produces 3590 kmol h−1 liquid methanol, 3590 kmol h−1 liquefied natural gas, and 18.91 kmol h−1 crude helium. The feed gas extracted from the process of separating helium from natural gas is fed to the steam-natural gas reforming unit, which produces syngas with an amount of 16,015 kmol h−1. To supply the input heat to the reforming, solar dish collectors with the climatic conditions of Tehran in Iran are used. The produced syngas along with carbon dioxide is fed into the methanol synthesis unit. The energy and exergy efficiencies of the developed integrated structure are 88.48% and 93.79%, respectively. The exergy analysis of the integrated structure shows that the maximum exergy destruction corresponds to the heat exchangers (56.23%) and reactors (13.83%). The sensitivity analysis illustrates that with an increase in the outlet flow temperature of the methanol reactor from 100 to 200 °C, the energy and exergy efficiencies are increased by 9.939% and 9.257%, respectively. Besides, by increasing the amount of carbon dioxide feeding to the methanol production process from 100 to 1200 kmol h−1, the net power consumed and its thermal efficiency are increased by 8.489% and 2.855%, respectively.