فهرست مطالب

Gas Processing Journal
Volume:2 Issue: 1, Winter 2014,

  • تاریخ انتشار: 1393/03/15
  • تعداد عناوین: 6
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  • Mojtaba Masoudi, Nejad, Shohreh Fatemi * Pages 1-7
    The process of ethylene production from ethane dehydrogenation is one of the interesting processes in the field of conversion the petroleum light gases to the valuable products. In this process, the outlet gaseous product is a combination of ethylene, ethane and hydrogen. Effective separation techniques are required for separation of ethylene from unreacted ethane. Here a new adsorbent approach is introduced for separation of ethylene from ethane. The adsorbent is a kind of zeolitelike molecular sieve from silico-alumino-phosphate group (SAPO-34) which is previously synthesized and studied in the adsorption tests of ethane and ethylene. The equilibrium adsorption experiments are performed in a static batch adsorption apparatus at various moderate pressures and room temperature to evaluate the adsorption capacity and selectivity toward ethylene against ethane. A high tendency of SAPO-34 towards ethylene and the ethylene/ethane selectivity from 2 to 3 fold in the pressure range of 200 to 800 kPa is observed, confirming the potential application of SAPO-34 as an adsorbent in the adsorption process for separation of ethylene and ethane.
    Keywords: SAPO, 34, Equilibrium Adsorption, Isotherms, Selectivity, Ethylene and
  • Reza Azin *, Robab Chahshoori, Shahriar Osfouri, Ahmad Lak, Mohammad Hossein Heidari Sureshjani, Shahab Gerami Pages 8-18
    Understanding the flow behaviour in a gas well is crucial for future production strategies, obtaining bottomhole conditions from wellhead production data, analyzing production data and estimating reservoir properties. In this work, the pressure profile and flow regime are studied on four wells of a multi-well, multi-layer gas-condensate reservoir, producing at high rate. The wells are deviated and cased-holes, with the gas flowing through tubing to the wellhead. Here, a comprehensive quality assessment of data is presented. An algorithm is proposed to model wellhead chokes and determine production rates of individual wells from overall, commingled daily flow rates. The pressure profile and flow regime were determined in each well through back-calculation and nodal analysis. The bottomhole pressure is predicted. The best correlations are selected by comparing the model results with reported production logging tool (PLT) data. The rates of produced condensate and water (equivalent to gas) and their PVT properties, e.g. API of condensate, had little impact on choke calculations, which is due to high flow rate gas. The flow is shown to be gas-like at the bottom, which turns to mist flow near the wellhead. Liquid holdup is subject to the wellhead pressure and well flow rate. It decreases with an increase in wellhead pressure and gas flow rate. The findings here can be extended to other wells in the same reservoir, which can introduce guidelines for gascondensate well modeling.
    Keywords: Gas Condensate, Gas Well, Choke Modeling, Well Flow Modeling, Flow Regime
  • Masoumeh Moheb Shahrestani, Amir Rahimi * Pages 19-31
    A model is developed for separation of multicomponent gas mixtures in a countercurrent hollow fiber membrane module. While the model’s solution in countercurrent module usually involves in a time consuming iterative procedure, a proper initial guess is proposed for beginning the calculation and a simple procedure is introduced for correcting the guesses, hereby the CPU time is decreased essentially. The model’s predictions are compared with the experimental data and a good agreement is achieved. By using data taken from a LAB unit in Isfahan, the proposed model is applied to investigate the feasibility of membrane process for hydrogen separation in this unit. It is revealed that a high hydrogen purity and recovery could be achieved in the permeate stream, while the required area increases at higher stage cut or higher permeate pressure.
    Keywords: Membrane, Gas Separation, Modeling, Hydrogen Separation
  • Mostafa Mafi *, Bahram Ghorbani, Gholam Reza Salehi, Majid Amidpour, Seyed Mojtaba Mousavi Nayenian Pages 32-39
    A refrigeration cycle is a chain of various pieces of equipment including compressors, condensers, evaporators, and expansion devices each of which takes on a particular thermodynamic process duty in the cycle that eventually results in the production of the required refrigeration. The results of optimized mixed refrigerant cycles (MRCs) in Part I show that the configuration of MRC is an effective parameter in power consumption. In spite of simplicity of MRCs machinery configuration in comparison with a conventional cascade cycle, it is possible to imagine different configurations, providing the process required refrigeration, for these cycles. But the question here is how to find a configuration taking advantage of the existing complicated interactions between low temperature process and refrigeration cycle so that the maximum efficiency and the best functionality will be guaranteed. In this paper, based on the success of the systematic method proposed in part I for the optimal selection of refrigerant composition and operating pressures, the method is extended to give optimal arrangement of the cycle components. An illustrative example is presented to show how the proposed method can be utilized in order to achieve the optimal MRC configuration.
    Keywords: Mixed Refrigerant Cycle, Low Temperature Process, Optimal Arrangement
  • Shahriar Osfouri *, Reza Azin, Mahboobeh Kiani Zakheradi, Shahab Gerami Pages 40-50
    Finding a representative fluid in a hydrocarbon reservoir is crucial for integrated reservoir management. In this study, a systematic approach for screening and selecting consistent fluid samples in a reservoir was developed. The model integrated quality control (QC) of well conditioning before sampling, QC of PVT data, thermodynamic modeling and compositional gradient within a reservoir. Well and separator conditioning were examined as essential steps before sampling at equilibrium conditions. Sampling criteria were deduced according to available data, sampling standards, and tolerance of field measurement devices. Then, PVT data of consistent fluid samples were carefully screened for efficient phase behavior studies. This model suggests that thermodynamic modeling and equation of state (EOS) tuning be performed on screened fluids using only consistent experimental data. The proposed model was implemented on PVT samples of a supergiant gas condensate reservoir in the Middle East. Results show that only 10% of collected samples are at equilibrium, good candidates for PVT studies. Also, ±0.1% change in composition of C12+ causes ±300 psia change in dew point pressure, revealing no substantial difference between validated samples for the reservoir under study, and one representative fluid suffices throughout the reservoir.
    Keywords: Gas Condensate, Sampling, Well Conditioning, EOS Tuning, Compositional Gradient
  • Meysam Kamalinezhad *, Majid Amidpour, Seyed Mostafa Mousavi Naeynian Pages 51-68
    liquefied natural gas (LNG) is the most economical way of transporting natural gas (NG) over long distances. Liquefaction of NG by using vapor compression refrigeration system requires high operating and capital cost. Due to lack of systematic design methods for multistage refrigeration cycles, the conventional approaches of determining optimal cycle configuration are mostly based on trial-and-error and are very time consuming. Here a new Mixed Integer Non-Linear Programming (MINLP) model is introduced for selecting optimal synthesis of refrigeration system which would reduce both the OPEX and CAPEX of a LNG plant through Pinch technology. A superstructure of a complex refrigeration system is developed to select and optimize the key decision variables in refrigeration cycles (i.e. partition temperature, compression configuration, refrigeration features, refrigerant flow rate). This method reduces calculation time and increases design options that could be mounted over a multistage refrigeration cascade. Here a program (LNG-Pro) is developed that integrates the VBA, Refprop and Excel MINLP Solver to automate the methodology. Design of an LNG plant is described to illustrate advantages in adopting this method. Conceptual diagrams of pinch technology are shown to visualize the stepwise optimization procedure of compressor’s shaftwork. The proposed cascade by this method reduces compressor shaftwork of an LNG cascade from 1255 Kj/Kg to 1141.9Kj/Kg.
    Keywords: Cascade Refrigeration Cycle synthesis, Cryogenic, Liquefied Natural Gas, MINLP