Journal of Gas Technology
Volume:6 Issue: 2, Spring-Summer 2021

On review of skid-mounted LNG technology providers, single mixed refrigerant (SMR), ni-trogen expander and self-refrigerated processes have been used for LNG production in skid scale. However, SMR processes are more efficient and have lower rotating equipment. By RIPI comparative study on commercialized SMR processes and more than 100 patents in this topic, the SMR process with one phase separator (by 43% sharing in SMR processes), has been selected for skid LNG plant. Regarding to process complexity of multi-phase separators in SMR loop, these types of cycles were not selected. Otherwise SMR process without phase separator was not selected for skid LNG plant because of the freezing possibility of heavy hydrocarbon refrigerants in this configuration. Several single-phase separator SMR processes can be used based on arrangement of equipment in liquefaction and refrigeration sections. By extensive study and according to skid design limitations (e.g., the minimum number of fixed and rotating equipment, minimum process complexity and dimension and etc.), two process arrangements has been selected, simulated and optimized. Also, a sensitivity analysis on the feed pressure and temperature as well as the composition of MR and feed was done. Energy consumption of these two configurations was calculated and the complexity of them was compared. According to the results obtained in this study and considering lower total annualized cost of LNG unit and the necessity of pro-cess simplicity in the skid scales, the best case was recommended for LNG skid-mounted packages.

In this study, in order to increase the heat transfer rate in the heaters of the City Gas Station(CGS), a classic type of a tube insert was placed into its heating coils. The use of the inserts will lead to increase in the pressure drop that maybe treated as disadvantage of using inserts in some heat exchangers. However, in this case pressure drop is quite favor phenomenon as pressure should be reduced in city gas transfer line. The type of the given insert is spiral, and is made of seamless steel in accordance with the gas pipe production standard. The inserts are embedded in eight coil paths in the heater of Mavian pressure reducing station of in Kamyaran city of Kurdistan Province with capacity of 2500 m3/h. Heat transfer enhancement up to 47% obtained, which is quite important from energy saving and environmental pollution control point of view.

It is well known that burning flare gases and releasing them into the atmosphere has become one of the problems of the oil, gas, and petrochemical industries. If these industries can produce energy or valuable materials from flare gases, it will be very profitable and less harmful to the environment. The purpose of this investigation is to design, simulation and economic evaluation the process of converting flare gas to dimethyl ether (DME) for the production of gasoline, Liquefied petroleum gas (LPG), and hydrogen by Aspen HYSYS v.11 software. The flare gas to gasoline (FGTG) process can be indirect or direct DME production (two scenarios). In the economic comparison of these scenarios, the total product sales, operating profit, total capital cost, desired rate of return (ROR), and payoff period (POP) will be calculated. The economic evaluation results show that using the FGTG process with direct DME production (second scenario) instead of the FGTG process with indirect DME production (first scenario), increases the product sales and operating profit by about 55% and 65%, and also the total capital cost and utility cost is decreased by about 30% and 50%, respectively. Finally, the desired ROR in the FGTG process with direct DME production and indirect DME production is 52 percent/year and 33 percent/year, and the POP for the second scenario is approximately 1.1 years earlier than the first scenario.

Natural gas transmission processes in the pipeline encounter many problems, such as the high cost of purchasing and maintaining compressors in pressure boosting stations, the formation of gas hydrates, the formation of two-phase fluid, noise pollution, and service and maintenance costs of the pipeline. To solve these problems, natural gas transmission in the supercritical state (dense phase state) is recommended. Unfortunately, there is limited information on the transmission of natural gas in the dense phase. In this research, the natural gas transmission of Iran’s fourth national pipeline in the supercritical state has been studied, and the results have been compared with the normal state. By performing this process in the dense phase mode, the number of pressure stations was reduced from 10 stations in the normal mode to 4 stations in the dense phase mode. The results of this study also showed that the pressure drop and energy of compressors in the dense phase state were reduced by 59% and 60%, respectively.

In recent years, recovering waste heat to reduce energy consumption and provide the energy needs has become a promising method to solve the energy crisis. In this study, the waste heat from gas pressure reducing stations is used to produce fresh water using a humidificationdehumidification desalination unit. Using Aspen HYSYS to model the proposed system, the effect of different parameters on the fresh water production rate is evaluated. The results show that optimum saline water and air flow rates are 0.165 kg/s and 0.2 kg/s, respectively, for a gas pressure reducing station by a capacity of 50,000 standard cubic meters per hour. It is also found that by decreasing the gas inlet pressure from 1000 psi to 400 psi, the fresh water production rate is decreases by about 52.2%. The increase of the fresh water production rate by increasing the capacity of the pressure reducing station from 10,000 to 50,000 standard cubic meters per hour is about 62%. Furthermore, the fresh production rate at gas pressure reducing station with 10,000 SCMH increases 4.4% by increasing the saline water temperature entering the humidifier from 40ºC to 80ºC.

Reliability is one of the most important performance evaluation indicators in maintenance and repair filed. The present study is a mixed design attempting to identify the antifragility components and their effect on the system reliability using the system dynamics. In the qualitative section, using by the thematic analysis method, with the participation of 10 organizational and academic experts, antifragility factors were identified in the form of 254 open codes, 18 organizing codes and two global codes with the review of literature and using Maxqda 2020 software. In the quantitative part of the research, the relationship between the antifragility factors with the system reliability was investigated using multiple regression method. The three criteria of learning, redundancy and exploratory discussions were identified and selected as the factors that have the highest impact on system reliability. The effect of these indicators on system reliability in a dynamic environment was simulated using the Vensim software, DDS version. The results show the positive effect of all three criteria of learning, redundancy and exploratory discussions on improving the reliability of the system in the area in gas transmission Company-zone 10. Also, the redundancy index had the highest effect and learning components and explorative discussions were in the next classes of impact on improving the system reliability.