نشریه مهندسی گاز ایران
پیاپی 15 (بهار و تابستان 1401)

In the present study, brief review of the introduction of LNG, processes and equipment for its production and conversion to gas were done. Then mini LNG units were introduced and its maximum capacity (300 tons/day) was selected as the base unit. In the economic section, based on the selected scale and selection of the liquefaction process by the nitrogen expansion cycle method, price of the equipment was estimated and then updated according to the cost index for 2019. After that, the fixed and operating investment costs and finally total investment were estimated. According to assessments, the investment cost of the mini LNG unit with a capacity of 300 tons/day and a volume of 20,000 m3 of tanks is estimated at 101 MMUSD. Based on the calculations and according to the capacity of the proposed storage tanks and the consumption of a power plant, this mini LNG unit can supply gas for power plant for 60 hours of operation at its maximum power generation capacity. With the assumptions used for the price of electricity generated at peak times, the rate of return on investment was calculated and finally, based on the technical and economic evaluation, the feasibility of implementing this project was investigated.

Cathodic protection using an anode is one of the common methods for preventing the corrosion of metals in the oil and gas industry. In Golestan province, in some cities, the ground bed has been used for cathodic protection. In this research, with a monitoring method and using a novel- research tool, 14 anodic water wells in the cities of Golestan Province were investigated and the water of wells was analyzed. The breakage of the well wall, broken rope, irregularity of cables, and ground drift were observed at the well`s internal. Water hardness varied from 800 to 5200 ppm, chlorine from 5 to 86, and current from 0.21 to 3.6 in different wells. Wells No. 3, 11, and 12 have a pH lower than 6.5 and therefore have an acidic environment that is prone to corrosion. Wells 1, 4, 5, and 6 had TDS higher than 3000 mg/l, wells 1 to 3 had high water hardness, and the sodium adsorption ratio in well No. 6 was reached 23 indicating saline-sodium soil. Most wells also had low electrical conductivity. Based on the results of this research, it has become clear that during the design and operation of the anodic wells, soil characteristics, the probability of penetration of detergents into water wells, and other environmental issues should be considered. Moreover, It is suggested that the chemical and electrical properties of water and wells should be measured the during annual inspections and, that a standard be established in this field.

Thanks to its petrological and geochemical characteristics, the Pabdeh Formation has been acknowledged as a probable source rock across the Dezful Embayment, southwestern Iran. The present research investigates the hydrocarbon generation potential of the Pabdeh Formation through studying the distribution of the organic matter (OM) content in terms of quantity, quality, and maturity over the study area. For this purpose, Rock-Eval pyrolysis was conducted on a total of 330 samples taken from 15 fields in the study area, with the results subjected to geochemical evaluations. Our findings show that, in the Dezful Embayment, the Pabdeh Formation contains Type-II, Type-III, and mixed-type (II and III) kerogens and exhibits poor to very good oil generation potential. In terms of the OM maturity, the kerogens were found to be immature to early oil generation window. Investigation of organic facies reflected variable conditions of the depositional area and frequent changes in the mean sea level. To sum up, the results show that, as far as the Dezful Embayment is concerned, the Pabdeh Formation is yet to achieve an adequate degree of maturity for generating hydrocarbon.

Methanol is one of the four basic chemicals that is used beside ethylene, propylene and ammonia to produce other chemicals. Industrial production of methanol is dependent on synthesis gas (a mixture of CO, H2 and CO2). One of the approaches of producing hydrogen from renewable and organic sources is green hydrogen, and researches in this field is being developed as a renewable fuel. Carbon dioxide (CO2) is a greenhouse gas and the main reason of global climate change, which is being studied and recycled to valuable products and fuels. Methanol production is one of method for decreasing CO2. In this study, using an experimental method of nano-photocatalyst and UV light (renewable method), synthesis gas by combining water and hydrocarbons was produced. Experimental results show that with the degradation of 85.3% of hydrocarbons in water, the efficiency of titanium oxide-based copper chromate nano-photocatalyst in the production of synthesized gas is about 14% higher than that of titanium oxide nano-photocatalyst. In addition, the crystalline phase and material structure, morphology and chemical composition were tested and analyzed using the measurements of XRD, SEM/EDS, TEM/EDS and XPS. This catalytic technique can be important in producing a clean fuel due to the reduction of greenhouse gas emissions and environmental effects. One of the applications of methanol in MTBE feed is to increase the octane number of gasoline. It is also proposed, with the reduction of methanol prices in the global market in the future and the growing importance of environmental issues, through appropriate incentives, efforts should be made to invest in the conversion of methanol to propylene.

Sulfur is one of the most important products in the processing of oil and gas, which is used in important industries such as sulfuric acid production and agriculture. Hence, the improvement of the efficiency of sulfur production processes at the industrial scale has paid a lot of attention. Due to some process problems such as the presence of heavy aromatic compounds and inappropriate temperature, the efficiency of this unit decreasesTherefore, in this paper, the steady state simulation of the modified Claus process of the Sulphur Recovery unit of the first refinery of the South Pars Gas Complex using Aspen Plus software has been done. The dynamics of CO2 concentration and furnace temperature were also studied. The simulation accuracy is desirable in the stable and dynamic state, so that the average error for the simulation flow data compared to the industrial data is 2.52% and 2.11% for the dynamic and dynamic mode, respectively. In addition, the results indicate an increase for sulfur produced by increasing the furnace temperature and reducing the concentration of CO2.

Energy and the environment are two important parameters in the development of countries. The flaring system is the main way to waste energy in refineries and operation units, which emits the highest amount of environmental pollutants. Large volumes of associated gases are of high fuel value. Therefore, paying attention to this section's reuse, performance, and modification is of great importance. In this study, Aspen HYSYS software was used. The combination of incoming gas to flare from the Ahvaz refinery was considered. Sweetening was done with methyl diethanolamine and piperazine. Then, the dehydrate was performed with triethylene glycol. Sweetened gas sent to LNG unit. The results of the output of the software show that the separation of carbon dioxide by 99.99% and hydrogen sulfide by 99.94% has been done. When the gas enters from the bottom of the absorption tower, i.e. tray number 20, it has severe temperature changes from 33.6 °C to 54.5 °C, which can be due to the selective absorption of H2S in the presence of CO2 by MDEA and the polarity of H2S. The movement of gas to the top of the tower is accompanied by an increase in temperature up to tray 19, whose temperature has reached 57.7 °C, which is due to the greatest absorption and mass transfer that has occurred in this tray. From tray 19 to tray 13, absorption and temperature decrease until the system reaches equilibrium. As a result, exhaust gas can be considered sweet gas. LNG production capacity in the liquefy unit is 386,700 kg/h, which economically can have a net profit of 32136,000 $ per year.