فهرست مطالب

Gas Processing Journal - Volume:5 Issue: 1, Winter 2017

Gas Processing Journal
Volume:5 Issue: 1, Winter 2017

  • تاریخ انتشار: 1396/01/25
  • تعداد عناوین: 6
|
  • Malek Shariati Niasar *, Majid Amidpour, Bahram Ghorbani, Mohammad-Javad Rahimi, Mehdi Mehrpooya, Mohammad-Hossein Hamedi Pages 1-23
    Using absorption refrigeration cycles instead of vapor compression refrigeration cycles can drastically decrease energy consumption. In these systems, high level of energy consumption is reduced due to the partially elimination of vapor compression refrigeration systems. On the other hand, utilization of waste heat of the plant, which is a very good opportunity for energy saving, is possible. In the present paper, a novel mixed fluid cascade natural gas liquefaction process is investigated by exergy and exergoeconomic analysis methods. In this process, one of the vapor compression cycles is replaced by water-ammonia absorption refrigeration cycle. The simulation results show that the compressors of this plant are responsible for 43.2% of total exergy lost. Decision variables of the system are consists of mass flow ratio of the tower’s bottom product (bottom feed ratio), number of trays, and compressor’s pressure ratio. Choosing appropriate values for these variables will result in 12% increase in exergetic efficiency of the plant. Exergoeconomic factor of water coolers, heat exchanger no.1 and tower no.1 shows that these components respectively impose a sizable capital cost to the entire system and does not result to a reasonable capital recovery. In this paper an integrated structure of producing liquid fuels from coal using Fischer-Tropsch synthesis and some equipment such as gas and steam turbines as well as HRSG heat exchanger for recovering of heat and power has been developed. Gasification method because of high efficiency and exothermic nature from energy consumption point of view is employed for producing synthesis gas.
    Keywords: Cogeneration, Natural Gas Liquids (LNG), Gasification, Exergoeconomic
  • Gholamreza Salehi *, Shahab Farzin Pages 24-33
    The POXR and SMR methods adopted in producing hydrogen from methane gas are simulated and exergy analysis of both the processes are run for comparison. The effective parameters of the feeding materials ratio and the system temperature for maximizing hydrogen production and increasing efficiency are assessed here. Influenced by the changes in these parameters the unit efficiency is increased up to 76%. The efficiency of POXR and SMR processes are calculated for new ratios. The results indicate that SMR process has higher exergy efficiency than POXR process. Exergy efficiency of SMR and POXR processes are obtained as to 73.2 and 66.9, respectively, where the SMR efficiency process is increased by 2.6% because of the changes in the feeding material ratio and temperature. Highest destruction of exergy in methanator reactor in SMR process is due to high temperature of reaction caused by irreversibility from chemical reactions. Exergy destruction is reduced at high temperature and unit molar ratio.
    Keywords: Hydrogen production unit, exchange reaction of methane, steam, partial oxidation, Modeling, Simulation, Exergy
  • M. Bayat * Pages 35-42
    In the first part (Part I) of this study, a novel fluidized bed reactor was modeled mathematically for methanol synthesis in the presence of in-situ water adsorbent named Sorption Enhanced Fluidized-bed Reactor (SE-FMR) is modeled, mathematically. Here, the non-dominated sorting genetic algorithm-II (NSGA-II) is applied for multi-objective optimization of this configuration. Inlet temperature of gas phase (Tg), temperature of saturated water (Tshell), total molar flow rate (Ft), diameter of solid adsorbent (ds), mass adsorbent solid to mass catalyst ratio (Mratio) and inlet pressure are selected as the decision variables. The production rate of methanol and selectivity is maximized as two objective functions. The Shannon’s Entropy, LINMAP and TOPSIS methods as the three decision making approaches are applied to select the final solution of Pareto front. The optimization results approved by about 203.63 and 276.65 ton/day methanol production rate and CO2 consumption, respectively, based on LINMAP methods compared with the conventional methanol configuration. The results recommend that consuming optimized-SE-FMR for improvement of methanol production could be feasible and beneficial.
    Keywords: Multiobjective optimization, NSGA, II, Decision, making method, LINMAP, Pareto front
  • Farid Sadeghian Jahromi, Masoud Beheshti * Pages 43-54
    The exergetic analysis is a tool that has been used successfully in many studies aiming a more rational energy consumption to reduce the cost of processes. With this analysis, it is possible to perform an evaluation of the overall process, locating and quantifying the degradation of exergy. This paper applies exergy approach for analyzing the heat exchanger network design and refrigeration of MTP process. For this purpose, the behavior of some industrial processes and refrigeration cycle with propylene refrigerant has been investigated by exergy method. The equations of exergy destruction and exergetic efficiency for main components such as compressors, heat exchangers and expansion valves were studied. A specified section of propylene recovery unit with its refrigeration cycle has been simulated to perform the exergy analysis. Adding a new valve with optimum pressure drop according to process constraints and an expander results in high performance of multi-stream heat exchanger, saving cold utility consumption, using excess heat of the process section, and low required compression power (in the refrigeration section) which are the most important characteristics of the proposed configuration. Results show that the annual profit reaches 4.3 %.
    Keywords: MTP process, Refrigeration system, Energy saving, Exergy analysis
  • Mohsen Gholami * Pages 55-64
    In this study, the performance of an adsorbent coated finned tube exchanger for carbon capture was investigated numerically. The results showed that this structure has a great potential for being applied as a medium for CO2 capture by rapid indirect thermal swing adsorption. By using this structure, the recovery of 96%, and purity of 98% were achieved with a simple cycle consisting of two steps, including adsorption and regeneration. To assess the effect of operating parameters, the cooling water temperature, hot water temperature and feed flow rate were selected as varying parameters, and the recovery and purity were selected as objective functions. The results showed that by increasing the cooling water temperature from 25 C to 45 C the recovery decreases from 65% to 61% while the reduction of purity is almost negligible. The heating temperature has a more intense effect on the recovery and purity. By increasing the heating temperature form 80 to 120 the recovery increases from 16% to 65% and purity increases from 92% to 98%. The variation of feed flow rate showed that by increasing the feed from 2 to 6 (STP CM/min) the recovery decreases from 98.5% to 65% and the purity increases from 96% to 98%. It should be noted that finned tube exchangers are well developed to create minor pressure drop. Thus, they are suitable structures for getting coated by adsorbent for the purpose of gas separation by Rapid Thermal Swing Adsorption.
    Keywords: Finned tube, Coated exchanger, Rapid Thermal Swing Adsorption, CO2 capture
  • Parisa Naeiji, farshad varaminian * Pages 65-74
    In this study, the effects of sodium dodecyl sulphate (SDS) on gas hydrate formation kinetics of methane and ethane mixture has been investigated experimentally and also the thermodynamic natural path has been used for modeling of the hydrate formation rate in a constant volume process. Different mole fractions of methane 0.1, 0.2, 0.3, 0.5, 0.68 and 0.8 have been studied. All experiments have been carried out at a constant temperature of 277.15 K, approximately initial pressure of 3.6 MPa and a stirrer speed of 800 rpm, with and without the presence of SDS with concentration of 500 ppm. The results show that SDS increases the hydrate formation rate by means of decreasing the gas liquid surface tension, so that the initial rate of hydrate formation and the model kinetic parameter of Ar/RT are increased about 3 and 1.2 times, respectively. Besides, SDS transforms two-step process of methane-ethane hydrate formation to one-step of that. This surfactant also promotes the hydrate growth in the liquid phase and increases the moles of gas consumed, so that the highest amount of gas consumption for hydrate formation belongs to the mixture with 0.3 mole fraction of methane.
    Keywords: Methane, Ethane, Sodium Dodecyl Sulphate, Formation Kinetics, Gas Hydrate