فهرست مطالب

Gas Processing Journal - Volume:5 Issue:2, 2017
  • Volume:5 Issue:2, 2017
  • تاریخ انتشار: 1396/09/24
  • تعداد عناوین: 6
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  • Abdolazim Rahimi, Mohamad Reza Talaie * Pages 1-12

    The accurate calculations of adsorption equilibrium for multicomponent gas systems are of great importance in many applications. In this paper, five two-dimensional equations of state 2D-EOS, i.e. Van der Waals, Eyring, Zhou-Ghasem-Robinson, Soave-Redlich-Kwong and Peng-Robinson, were examined to find out their abilities to predict adsorption equilibrium for pure and multi-component gas adsorption systems. Also, a new 2D-EOS named Rahimi-Talaie (RT) was developed for accurately predicting adsorption equilibrium of the gas mixtures having highly non-ideal behavior. The pure parameters of all these equations were obtained by fitting 2D-EOS into pure gas-adsorption equilibrium data, and then the mixture parameters were calculated by recommended mixing rules. It was concluded that all equations were capable of accurately predicting pure adsorption equilibrium. However, among the six above-mentioned 2D-EOSs, RT was more successful to provide more accurate prediction of gas-mixture adsorption equilibrium, especially for the mixture showing azeotrope behavior.

    Keywords: Equilibrium calculation, gas adsorption, two-dimensional equation of state, non-ideal mixture
  • Samaneh Bayati, Ali Mohebbi * Pages 13-32

    Natural gas usually contains significant amounts of acid gases when it is extracted from underground reservoirs. Therefore, it must be treated by appropriate processes to remove these acidic components. In this study, the simultaneous absorption of carbon dioxide and hydrogen sulfide from natural gas into diethanol amine solution was simulated using CFD. Absorption process was performed in a wetted-wall column with counter-current gas-liquid flow. A two-dimensional simulation based on the volume of fluid model was used. To investigate the hydrodynamics of the flow in the column, distribution of the volume fraction of phases along the column, the formation of liquid film and velocity profiles were studied. To validate the results for predicting the liquid film thickness, the column was simulated at different flow rates of water and air in laminar flow regime. Simulation results for liquid film thickness were compared with experimental data. Then by considering the mass transfer from the gas phase to liquid phase based on Higbie’s penetration theory, the concentration distribution of components in gas and liquid phases was calculated. The effect of temperature on absorption of and was also studied. The comparison of simulation results with the experimental data for the outlet concentrations in the gas phase showed that there was a good agreement between them. The developed model can also be used in further studies to determine the effective parameters on simultaneous absorption of and in a wetted-wall column. This helps to optimize the performance of the sweetening process in gas refineries.

    Keywords: Natural gas sweetening, Carbon dioxide, Hydrogen sulfide, CFD, DEA
  • Seyed Abootorab Moosazadeh Moosavi, Mostafa Mafi *, Abdolrazzagh Kaabi Nejadian, Gholamreza Salehi, Masoud Torabi Azad Pages 33-48

    One of the main components in combined cycles is the heat recovery steam generator (HRSG) which is responsible for energy recovery from gas turbine exhaust stream and produce superheated steam. In this paper, driving force plot and exergy analysis is used to study the behavior of heat exchangers of an HRSG in base case and off design conditions. The results indicated that performance of high pressure super heaters is far from their ideal operation. Based on this conclusion, a new configuration for the HRSG is proposed to boost its performance. This new configuration is based on split concept where it splits the hot flue gas to bypass the high pressure superheats. Therefore more energy is delivered to the high pressure evaporator and consequently steam production rate increases. Another advantage of this configuration is that it reduces start up time of the HRSG and consequently decreases start up time of the plant which results in higher flexibility of the system. To examine the applicability of the proposed approach, it is used to improve start up time in an existing combined cycle power plant. The results indicate that pressure and mass flow rate of HP stream reaches to its design point almost 20 minutes sooner. Finally, a sensitivity analysis is performed on the effect of split ratio on the power production. The results show that there is an optimum value for split ratio in which power production of steam turbine is maximized.

    Keywords: Combined cycle power plant, HRSG, Stream splitting, Start up time
  • Mohammad Rahimi *, Mohammad Hosein Hamedi, Majid Amidpour Pages 49-68

    This paper presents thermodynamic simulation, economic modeling and annual profit optimization of a multi generation system which produces both power and fresh water. The fuel of the combined system is natural gas plus synthesis gas which is produced in biomass gasification reactor. In order to evaluate thermodynamic performance of the biomass gasification reactor, visual simulation software was developed in C# programming language. The multi generation system is analyzed both with inlet air cooling and without inlet air cooling. The final results show that the total cost of produced power is 0.0286 $/kWh and total cost of produced water is 0.7408286 $/m3. Also the total annual profit which comes from selling power and water to the market is 35.103 M$ and the CHP efficiency is 67.08. Optimization of the configuration is carried out once the simulation phase is finished. The optimization results in 10.5% increase in total annual profit and 6.6% increase in CHP efficiency.

    Keywords: Synthetic gas, Desalination system, Power, water cost, Net annual profit, Gasification, ‎Genetic Algorithm
  • Hassan Khatamnejad*, Shahram Khalilarya, Samad Jafarmadar, Mostafa Mirsalim Pages 75-84

    Partially premixed dual fuel strategy has been suggested as a new strategy for Compression Ignition (CI) engines because it could be effective for simultaneous reduction in NOx and soot exhaust emission accompanied. This strategy uses premixed low reactivity fuel as main fuel and advanced injection of high reactivity fuel as pilot fuel to reach a Reactivity Controlled Compression Ignition (RCCI) in CI engines. The current paper presents results from a study about NG-Diesel RCCI combustion with variable intake charge temperature in a CI engine. The results from the developed CFD model with a reduced chemical kinetic mechanism verify that the model can simulate the in-cylinder process, accurately. Based on the results, intake temperature impact the engine operation at RCCI combustion, significantly. The high intake temperature could result in advanced combustion phasing and higher ringing intensity (RI) as well as enhanced combustion efficiency. It is due combustion improvement with higher heat release rate (HRR) and peak in-cylinder pressure. On the other hand, the results revealed that RCCI combustion in low intake temperature causes great HC and CO emissions accompanied with low NOx emission in part load condition.

    Keywords: RCCI, Natural gas, Diesel, Combustion, Emissions, CFD Simulation Coupled with Chemical ‎Kinetic, Intake Temperature
  • Mohammad Hassan Khoshgoftar Manesh *, Mojtaba Babaelahi Pages 85-102

    In this paper, Multi-Objective Optimization of a 160 MW combined cycle power plant has been performed from Exergetic, Economic, Environmental aspects simultaneously. In this regard, thermodynamic, exergetic and thermoeconomic modeling and simulation for this case have been done. The Multi Objective Evolutionary Algorithms (MOEAs) are used and evaluated by MINLP approach to find optimum design in view of exergetic, exergoeconomic and environmental impacts. In order to facilitate selecting optimum sets, the environmental impact objective function has been defined and expressed in cost terms and added to the economic objective. Furthermore, extended combined pinch and exergy analysis has been performed to demonstrate the system graphically for each case in the base case and the optimum case. So, the performance of a different component of the system can be demonstrated better. In addition, the feasible region for optimization problem has been indicated by extended combined pinch and exergy method. Results show overall exergetic efficiency increases about 7.5% through MOEA method. Finally, the exergetic product cost of electricity reduces to 0.0183 $/MJ consecutively

    Keywords: Pinch-Exergy, Multi-Objective, Thermoeconomic, Genetic Algorithm, Combined Cycle