Bandar-e Emam Khomeyni, Iran
Bandar-e Emam Khomeyni, Iran

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Akbari V.,Razi Petrochemical Company | Dehghani M.R.,Iran University of Science and Technology | Borhani T.N.G.,Imperial College London | Azarpour A.,Petronas University of Technology
Journal of Solution Chemistry | Year: 2016

Certain alkyl ammonium salts are called ionic liquids They can be used as green solvents without toxicity, effects on the ozone layer depletion, effects on climate change, and any other significant environmental impacts; in this regard knowledge about their thermo-physical properties are really important. In this work activity coefficients of aqueous solutions of alkyl ammonium salts at 298.15 and 293.15 K are modelled using the Extended UNIQUAC (Universal Quasi Chemical) thermodynamic model. Adjustable parameters of the Extended UNIQUAC thermodynamic model were obtained by non-linear regression between experimental data and the results calculated from the model. The results of the model are in good agreement with the experimental values in most cases, the average absolute deviation of the model being less than 2 %, which is acceptable considering the uncertainty of the experimental data. Additionally, the results gained from the Extended UNIQUAC model are also compared with the results obtained from Electrolyte NRTL and Pitzer thermodynamic methods. © 2016, Springer Science+Business Media New York.


Borhani T.N.G.,Imperial College London | Afkhamipour M.,National Iranian Gas Company | Azarpour A.,Petronas University of Technology | Akbari V.,Razi Petrochemical Company | And 2 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2016

This study presents a rate-based model of an absorber packed column for simultaneous absorptions of acid gases into methyldiethanolamine (MDEA) aqueous solution. The model is in good agreement with experimental data. The parametric study showed that the concentration of acid gases in the sweet gas stream increases by decrease in the specific surface area of packing. The peak of selectivity factor decreases with the increase in the mole ratio of CO2/H2S in the gas feed along the packed column. The sensitivity analysis reveals that selecting the accurate correlations of the gas-side mass transfer coefficient and specific surface area is vital. © 2015 The Korean Society of Industrial and Engineering Chemistry.


Borhani T.N.G.,University of Technology Malaysia | Azarpour A.,Petronas University of Technology | Akbari V.,University of Technology Malaysia | Akbari V.,Razi Petrochemical Company | And 2 more authors.
International Journal of Greenhouse Gas Control | Year: 2015

The potassium carbonate (PC) solution is an important chemical solvent to reduce CO2 emissions due to its advantages of low cost, little toxicity, ease of regeneration, slow corrosiveness, low degradation, and its high stability as well as CO2 absorption capacity. As a result, the PC process has been applied in more than 700 plants worldwide for CO2 and hydrogen sulphide removal from streams like ammonia synthesis gas, crude hydrogen, natural gas, and town gas. This paper provides a state-of-the-art review on the research works on CO2 capture using the PC solution. The studies related to the PC solution comprise three main areas: process, thermodynamics, and kinetics. Important experimental studies as well as modeling and simulation studies are reviewed. Future research directions on CO2 absorption by aqueous PC solution are highlighted and discussed. © 2015 Elsevier Ltd.


Shamiri A.,University of Malaya | Shamiri A.,Razi Petrochemical Company | Hussain M.A.,University of Malaya | Mjalli F.S.,Sultan Qaboos University | Mostoufi N.,University of Tehran
Chemical Industry and Chemical Engineering Quarterly | Year: 2013

A comparative study describing gas-phase propylene polymerization in fluidized- bed reactors using Ziegler-Natta catalyst is presented. The reactor behavior was explained using a two-phase model (which is based on principles of fluidization) as well as simulation using the Aspen Polymers process simulator. The two-phase reactor model accounts for the emulsion and bubble phases which contain different portions of catalysts with the polymerization occurring in both phases. Both models predict production rate, molecular weight, polydispersity index (PDI) and melt flow index (MFI) of the polymer. We used both models to investigate the effect of important polymerization parameters, namely catalyst feed rate and hydrogen concentration, on the product polypropylene properties, such as production rate, molecular weight, PDI and MFI. Both the two-phase model and Aspen Polymers simulator showed good agreement in terms of production rate. However, the models differed in their predictions for weight-average molecular weight, PDI and MFI. Based on these results, we propose incorporating the missing hydrodynamic effects into Aspen Polymers to provide a more realistic understanding of the phenomena encountered in fluidized bed reactors for polyolefin production.


Shamiri A.,University of Malaya | Shamiri A.,Razi Petrochemical Company | Hussain M.A.,University of Malaya | Mjalli F.S.,Sultan Qaboos University | And 2 more authors.
Chinese Journal of Chemical Engineering | Year: 2013

A two-phase dynamic model, describing gas phase propylene polymerization in a fluidized bed reactor, was used to explore the dynamic behavior and process control of the polypropylene production rate and reactor temperature. The open loop analysis revealed the nonlinear behavior of the polypropylene fluidized bed reactor, justifying the use of an advanced control algorithm for efficient control of the process variables. In this case, a centralized model predictive control (MPC) technique was implemented to control the polypropylene production rate and reactor temperature by manipulating the catalyst feed rate and cooling water flow rate respectively. The corresponding MPC controller was able to track changes in the setpoint smoothly for the reactor temperature and production rate while the setpoint tracking of the conventional proportional-integral (PI) controller was oscillatory with overshoots and obvious interaction between the reactor temperature and production rate loops. The MPC was able to produce controller moves which not only were well within the specified input constraints for both control variables, but also non-aggressive and sufficiently smooth for practical implementations. Furthermore, the closed loop dynamic simulations indicated that the speed of rejecting the process disturbances for the MPC controller were also acceptable for both controlled variables. © 2013 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP).


Shamiri A.,University of Malaya | Shamiri A.,Razi Petrochemical Company | Azlan Hussain M.,University of Malaya | Sabri Mjalli F.,Sultan Qaboos University | And 2 more authors.
Chemical Engineering Science | Year: 2011

A new model with comprehensive kinetics for propylene homopolymerization in fluidized bed reactors was developed to investigate the effect of mixing, operating conditions, kinetic and hydrodynamic parameters on the reactor performance as well as polymer properties. Presence of the particles in the bubbles and the excess gas in the emulsion phase was considered to improve the two-phase model, thus, considering the polymerization reaction to take place in both the bubble and emulsion phases. It was shown that in the practical range of superficial gas velocity and catalyst feed rate, the ratio of produced polymer in the bubble phase to the total production rate is roughly between 10% and 13%, which is a substantial amount and cannot be ignored. Simulation studies were carried out to compare the results of the improved two-phase, conventional well-mixed and constant bubble size models. The improved two-phase and well mixed models predicted a narrower and safer window at the same running conditions compared with the constant bubble size model. The improved two-phase model showed close dynamic behavior to the conventional models at the beginning of polymerization, but starts to diverge with the evolution of time. © 2010 Elsevier Ltd.


Shamiri A.,University of Malaya | Shamiri A.,University of Tehran | Hussain M.A.,University of Malaya | Mjalli F.S.,Razi Petrochemical Company | Mostoufi N.,Sultan Qaboos University
Computers and Chemical Engineering | Year: 2012

An improved model for the production of polypropylene in a gas phase fluidized bed reactor was developed. Comparative simulation studies were carried out using the well-mixed, constant bubble size and the improved models. The improved model showed different prediction characteristics of polymer production rate as well as heat and mass transfer behavior as compared to other published models. All the three models showed similar dynamic behavior at the startup conditions but the improved model predicted a narrower safe operation window. Furthermore, the safe ranges of variation of the main operating parameters such as catalyst feed rate and superficial gas velocity calculated by the improved and well mixed models are wider than that obtained by the constant bubble size model. The improved model predicts the monomer conversion per pass through the bed which varies from 0.28 to 5.57% within the practical ranges of superficial gas velocity and catalyst feed rate. © 2011 Elsevier Ltd.


Akbari V.,University of Technology Malaysia | Akbari V.,Razi Petrochemical Company | Borhani T.N.G.,University of Technology Malaysia | Godini H.R.,TU Berlin | Hamid M.K.A.,University of Technology Malaysia
Powder Technology | Year: 2014

A two dimensionally Eulerian-Eulerian multiphase flow model coupled with a population balance modeling (CFD-PBM) simulation was implemented to investigate the fluidization structure in an industrial scale gas phase polymerization reactor (FBR). Direct quadrature method of moments (DQMOM) was employed in this model to solve the PBM. Two cases including perforated distributor and complete sparger have been applied to examine the flow structure through the bed. A simulation of the reactor with perforated distributor was performed first to validate and evaluate the impact of distributor's characteristics on the fluidization behaviors. The predicted results were in good agreement with the industrial data in terms of pressure drop and bed height. The results showed that different heterogeneous flow patterns were created in a perforated distributor, due to more kinetic energy and jet formation above the distributor. A dead zone is expected to be formed near the corners of the perforated distributor. In addition, the cluster formation is expected to be decreased in comparison with the complete sparger plate distributor. Furthermore, the results predicted bigger bubble diameter in the case of the perforated distributor by using an image processing technique. The information obtained from this study could be important to assure efficient industrial operations of FBRs. © 2014 Elsevier B.V.


Akbari V.,University of Technology Malaysia | Akbari V.,Razi Petrochemical Company | Borhani T.N.G.,University of Technology Malaysia | Shamiri A.,University of Malaya | And 5 more authors.
Chemical Engineering Research and Design | Year: 2015

In an industrial fluidized bed polymerization reactor, particle size distribution (PSD) plays a significant role in the reactor efficiency evaluation. The computational fluid dynamic (CFD) models coupled with population balance model (CFD-PBM) have been extensively employed to highlight its potential to analyze the industrial-scale gas phase polymerization reactor (FBRs) utilizing ANSYS Fluent software. The predicted results reveal an acceptable agreement with the observed industrial data in terms of pressure drop and bed height. Courant number independent study has been carried out to record the mesh and time step independent results for large scale FBRs. Furthermore, the minimum fluidization velocity (Umf) and size-dependent particle growth rate have been assessed to emphasize the impact of PSD along the reactor. The results show transient regime in the case of minimum fluidization velocity. The simulation results signify that in order to improve the polymerization yield, the amount of gas velocity can be increased without change in the fluidization regime, i.e. segregation. Hence, the 2D CFD-PBM/DQMOM coupled model can be used as a reliable tool for analyzing and improving the design and operation of the gas phase polymerization FBRs. © 2015 The Institution of Chemical Engineers.


Faraji A.H.,Razi Petrochemical Co.
Ammonia Plant Safety and Related Facilities | Year: 2010

This paper provides case histories of failures in ammonia converters and their exchangers, different failures occurred in tubes, tubesheets, basket, thermowell and thermal barrier, two failed samples were as brittle as a glass. Investigation on samples which were in services between 3 -25 years, showed that the main reason of failures was Nitridation due to presence of high pressure, high temperature and nitrogen environment. By increasing the Nickel content in the steel, the Nitriding rate decrease but doesn't stop. By the way, the Nitrated layer increased as the plant aged, subsequently ductility decreased sharply.

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