Iranian Journal of Oil and Gas Science and Technology

Abstract In recent years, the issue of burning fossil fuels and the resulting carbon dioxide (CO₂) emissions have become a major concern. Various methods, including the synthesis of dimethyl ether (DME), have been proposed to address this issue. DME is considered a clean and sustainable fuel and is being regarded as an alternative to fossil fuels that can help reduce the emissions of harmful pollutants. This study assesses the cost of coproduction of dimethyl ether and electricity from the CO₂ flue gas of power plants. Producing this alternative fuel can reduce the power plant’s fuel consumption and environmental impacts while generating electricity. A feasibility study was conducted to integrate CO₂ recovery and utilization units from the flue gas of power plants for the synthesis of DME fuel using economic calculations in both direct and indirect methods. The total capital cost of establishing a DME production unit  was 2% higher through the direct method than the indirect method, due to the higher cost of equipment. Further, the cost of raw materials and utility was about 19% and 78% higher in the direct method than the indirect method, respectively, increasing the annual cost of DME production in this method by 52%.

Abstract Flaring of gas often having high heating value results in considerable economic and energy losses in addition to significant environmental impacts. Power generation through combined gas and steam turbine cycles may be considered as a suitable flare gas recovery process. Thermal sea-water desalination is a process that requires a considerable amount of heat; hence it may be used in downstream of power generation cycles. Energy is the largest section of the water generation cost of all desalination processes. The energy cost of thermal distillation sea-water plants is close to 50-60% of water generation costs. In the current study, the generation of power and desalinated water through the gas turbine cycle, steam cycle, and multistage flash (MSF) method using flare gas of cheshmeh khosh are investigated. The economic parameters related to the different scenarios considered for the production of power and water are evaluated in the current research. According to the economic evaluation carried out, the most economically profitable scenarios for the investigated co-generation plant is generating as much as possible power in the steam turbine and using the remaining heat in the low-pressure outlet steam in the MSF desalination process. The results show that by increasing steam turbine outlet pressure from 3 bar to 78 bar, power and water generation is changed from 697 to 581 MW and 1557 to 2109 m3/h, respectively. Also, by increasing the outlet pressure of the steam turbine from 3 to 78 bar, the total capital cost is changed from 1177 to 1192 MUSD, and the operating cost is changed from 117.85 to 117 MUSD/year. Finally, operating profit will decrease from 300 to 50 MUSD/year, and payback time will change from 3.92 to 4.75 years.

Abstract In Iran, power plants use liquid fuels such as heavy fuel oil (HFO) or mazut to prevent disruption in power generation. The high percentage of sulfur compounds in HFO and the lack of efforts to remove it, causing significant damage to the environment. The purpose of this research is performing a techno-economic analysis on the Hydrodesulfurization (HDS) process of HFO. The results showed that for removing 85% of sulfur compounds from HFO with a volume flow rate of 250 m3/h that includes 3.5% wt sulfur compounds, the total capital investment and the net production cost are 308.9 million US$ and 114.5 million US$/year, respectively. Besides, the sensitivity analysis indicates that with a 100% increase in the catalyst loading, the mass percentage of sulfur compounds in the HFO will be decreased by 15% more. Also, 6.4% and 32% will add to the total capital investment and net production cost, respectively. With a 100% increase in the gas to oil ratio, the mass percentage of sulfur compounds in the HFO will be decreased by 15.3% more. Also, 43.8% and 6% will be added to the total capital investment and net production cost, respectively. With a 100% increase in the pressure of the HDS process, the mass percentage of sulfur compounds in the HFO will be reduced by 20.75% more. Also, 43% and 6.75% will be added to the total capital investment and net production cost, respectively. Ultimately, with a 100% increase in the inlet temperature of beds, the mass percentage of sulfur compounds in the HFO will be reduced by 5% more. Among the effective operational parameters, hydrogen consumption has the greatest impact on net production cost and payback period, and the pressure of the Hydrodesulfurization process has the greatest impact on increasing the total capital investment of the process.