Sharif Digital Repository

The natural gas liquid recovery is an important process in a gas plant to correct hydrocarbon dew point and earn profit. In this study, a natural gas liquid recovery unit operated based on the Joule–Thomson process was investigated and its performance was optimized. To improve the system performance, the plant configuration and intermediate pressure ratio were defined as the variables and maximization of the natural gas liquid recovery rate and maximization of exergy efficiency were defined as the objective functions. To improve the plant performance, the amount of natural gas liquid recovery rate should be increased. To achieve this goal, several scenarios for the intermediate pressure... 

A general investigation of the viscosity of natural gas as a function of temperature, pressure and composition was carried out to develop a generalized correlation. The model obtained was based on 3231 data points of 29 multicomponent mixtures in wide ranges of pressures (0.1-137.8MPa), temperatures (241-473K) and specific gravities (0.573-1.337). Correction terms for non-hydrocarbons of hydrogen sulfide, carbon dioxide and nitrogen were up to 70, 54.4 and 15.8 of mole percent, respectively. The arithmetic average of the model's absolute error was found to be 5.05%, which is acceptable in engineering calculations and has superiority over other methods in its class  

One of the most promising methods for transporting natural gas and overcoming its low energy density is adsorbed natural gas (ANG) technology. ANG technology is highly dependent on the perfect conception of adsorption isotherms in different operational conditions and on different adsorbents. In this study, the utilization of a novel mathematical model of least squares support vector machine (LSSVM) for accurate prediction of adsorption isotherm has been examined. The considered variables were temperature, pressure and type of adsorbents. A data set containing 670 experimental data points of methane adsorption on 10 different adsorbents in a broad range of temperature and pressure were used... 

Optimization of ethane recovery in Phases 4 and 5 of Assalouyeh was studied. The influence of some parameters on the ethane recovery and the sensitivity analysis were determined. The effect of the parameter variation on the neighboring unit showed that a significant energy saving for compressor power consumption could be achieved. Some of the operating conditions of this unit were modified, including columns pressure, split fraction, minimum approach temperature, and expander power. This led to a 6% increase in ethane yield. This is an abstract of a paper presented at the 18th International Congress of Chemical and Process Engineering (Prague, Czech Republic 8/24-28/2008)  

The purpose of this study was to investigate the natural gas hydrate promotion capabilities of the hydrotrope Toluene Sulfonic Acid (TSA) isomers as an additive. The capabilities of TSA isomers were measured with different concentrations. The optimum additive concentration for hydrate formation was determined for the given pressure, temperature, mixing condition, and cooling time. The natural gas hydrate promotability of para-TSA was found to be 20% and 35% more than meta-TSA and ortho-TSA respectively at the optimum concentration. Beyond the optimum TSA concentration, the hydrate formation declined as the ice formation reduced the overall gas-to-water volume ratio in the hydrates  

This paper attempts to study the demand function of natural gas in Iran using smooth transition regression model (STR). To this end, gross domestic productions (GDP), real price of natural gas and temperature have been employed as variables explaining the natural gas demand from 1971 to 2009. The results indicate that natural gas demand follows an LSTR1 nonlinear two-regime model if the real price of natural gas is considered as the transition variable. Estimation results also indicate that the slope parameter approximately equals the high value of 10 and the threshold value is 31.82. Rials. 111 USD=24,700 Rials (IRR) at April 2013. per one cubic meter consumption of natural gas. The results... 

Impurities such as hydrogen sulfide, water vapor and heavy hydrocarbons in natural gas have considerable effects on the membrane performance. Small amounts of condensable and polymer soluble components in the feed gas cause swelling or plasticization of glassy membranes, leading to a reduction in membrane selectivity. In the present research the influence of ethane was investigated on the permeance and selectivity of two commercially available hollow fiber membranes, namely Cardo-type polyimide and PPO hollow fibers for CO 2/CH 4 separations. It was concluded that the gas mixture permeation rate was increased in the presence of C 2H 6. However, the CO 2/CH 4 separation factors remained... 

The Natural Gas Liquids (NGL) recovery unit is one of the processes that requires cooling. The sweetened gas enters this unit after the dehydration stage, and the final product called NGL Product is stored and ready for consumption or export. In this research, the first, one of the NGL units, is simulated with HYSYS software. Three types of processes with different cooling systems are studied using the exergy analysis method. Joule-Thomson's combination with the expander is selected for its high exergy efficiency, and the exergy efficiency function has been selected as the objective function 1 to optimize this process mathematically based on this study's findings. The critical term in this... 

Exhaust gas emissions from mobile sources and its importance in urban pollution have currently attracted lots of interests towards studying on alternative fuel systems for road vehicles usage. One of the best replacements is the natural gas/diesel dual fuel, which offers an alternative to standard compression-ignition diesel engines. In the dual fuel system the primary fuel is natural gas, which may replace as much as 90% of the diesel fuel with a small amount of diesel fuel required ensuring effective ignition. Methane, the main constituent of natural gas, has high combustion efficiency. Dual fuel engines produce lower NOx emissions and fewer particulates. However, at moderate engine loads,... 

In the natural gas transmission network, from supply points to demand nods there are various technological options that include processing, transportation, conversion and gas distribution. Comprehensive analysis of natural gas network requires evaluation of different chains of gas flow through various levels based on economical and environmental criteria subject to technical and operational constraints such as feasibility, operability and reliability of different alternatives. To aid decision-making process in the sector of natural gas, a generic optimization-based model has been developed for assessing long term energy issues related to planning and design of natural gas supply systems. The... 

The interdependencies of power systems and natural gas networks have increased due to the additional installations of more environmental-friendly and fast-ramping natural gas power plants. The natural gas transmission network constraints and the use of natural gas for other types of loads can affect the delivery of natural gas to generation units. These interdependencies will affect the power system security and economics in day-ahead and real-time operations. Hence, it is imperative to analyze the impact of natural gas network constraints on the security-constrained unit commitment (SCUC) problem. In particular, it is important to include natural gas and electricity network transients in... 

Here, a case study of natural gas network is conducted. We design an optimal distribution network of natural gas. Our proposed network is composed of stations reducing gas pressure to desirable pressure using consumer's viewpoint. By using minimum spanning tree (MST) technique, an optimal distribution network among stations and consumers is constructed. Our aim is to determine both locations and types of stations minimizing location-allocation costs in the network. A case study in Mazandaran Gas Company in Iran is made to assess the validity and effectiveness of the proposed model  

Transmission of natural gas from its sources to end users in various geographical locations is carried out mostly by natural gas transmission pipeline networks (NGTNs). Effective design and operation of NGTNs requires insights into their steady-state and, particularly, dynamic behavior. This, in turn, calls for efficient computer-aided approaches furnished with accurate mathematical models. The conventional mathematical methods for the dynamic simulation of NGTNs are computationally intensive. In this paper, the use of autoregressive neural networks for cost-effective dynamic simulation of NGTNs is proposed. Considering the length, diameter, roughness, and elevation as the main... 

This study presents economic and formation investigations on hydration effects by looking at natural gas hydrate (NGH) storage and transportation processes and formation conditions. The investigation includes experiments with methane. The obtained results show that the methane formation time increased linearly as the subcooling temperature decreased. Furthermore, the economic result indicates that the energy consumption parameter is appropriate for examining resource consumption for a system that, in turn, results in optimal capital investment through the storage and transportation process of NGH. The results also show that energy consumption increases logarithmically as the hydrate... 

The performance of commercially available poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and Cardotype polyimide (PI) hollow fiber membranes was investigated in removing hydrogen sulfide from methane in a series of bench-scale experiments. It was observed that in the concentration range of hydrogen sulfide in methane from 101 to 401 ppm, the methane permeability decreased in the presence of hydrogen sulfide for Cardo-type polyimide hollow fiber membranes, whereas the PPO membrane performance was not affected. The separation coefficients of hydrogen sulfide/methane were 6 and 4 for PI and PPO membranes, respectively. Effects of temperature on the performance of PI and PPO membranes were...