Exergy analysis of flare gas recovery processes using steam and power generation systems

The protection of the environment is considered to be a major concern of industrial units today. Flare gas combustion systems are inappropriate as a disposal solution or safety measure to decrease pressure. The oil, gas, and petrochemical industries are also concerned about reducing greenhouse gas emissions. Flare gases are associated with non-renewable fossil energies, which have also increased due to the ever-increasing need to harvest underground sources of flare gases. Accumulation of these gases is caused by other reasons such as unburned process gas, excess gas, exhaust gas from units during repairs, technical defects, change of feed, shutdown, and start-up, etc. Research is necessary to collect information regarding revisions to the prevention of burning gases. Identifying the location of energy quality losses, both quantitatively and qualitatively, is the first step in optimizing industrial units. The term “exergy quality” is used to express the amount of exergy loss resulting from exergy analysis. It is possible to determine the critical point of energy loss in a unit by measuring the energy loss in each device, which contributes to increased efficiency. The purpose of this study is to use exergy analysis in order to optimize the recovery of flare gas, which is a form of non-renewable energy. To analyze the exergy of all process equipment, high-pressure steam generation, steam turbine, heat and power generation, and combined cycle processes are selected. According to the literature review, the combined cycle provides the highest rate of electricity recovery. In addition, the exergy analyses of the four processes above are compared, and necessary modifications are made to improve them and the results of economic calculation are presented. The results represented that the highest exergy loss of heat exchangers is equal to 25,776 (kj/kgmole), 26,538.5 (kj/kgmole), 25,776 (kj/kgmole), and 625,828.5 (kj/kgmole) in the processes, respectively.