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Naphtha stabilizer

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Using Hysys to simulation Naphtha Stabilizer Column
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  • MAY 2014 JULY 2014, Vol. 4, No. 3; 1851-1865. E- ISSN: 2249 1929

    Journal of Chemical, Biological and Physical Sciences An International Peer Review E-3 Journal of Sciences

    Available online atwww.jcbsc.org

    Section A: Chemical Sciences

    CODEN (USA): JCBPAT Research Article

    1851 J. Chem. Bio. Phy. Sci. Sec. A, May 2014 July 2014; Vol.4, No.3; 1851-1865.

    Enhance C5+ Recovery Predicting and Maximizing The Reformate Production in Naphtha Stabilizer Using HYSYS

    Ahmed Raheem Hashim* and Alaa Abdulrazaq Jassim

    * 1, 2Department of Chemical Engineering, Basra University, Basrah, Iraq

    Received: 19 April 2014; Revised: 28 April 2014; Accepted: 05 May 2014

    Abstract: The naphtha stabilizer in Al-Basrah Refinery was subjected to simulation and optimization to find the optimum operating conditions by using Aspen HYSYS V7.1. A steady state simulation model is utilized to study the behaviour of multi-component non-ideal mixture in the naphtha stabilizer distillation. Optimization results showed that, its possible to increase the recovery of C5+ in the reformate from 97 % in actual unit to 99.6 %, also the reformate production increases about (2.383%) from the actual reformate production by changing the design variables and operating conditions. A sensitivity analysis has been used to determine which variable can be used in the optimization tool.

    Keywords: Refinery, Stabilizer, Optimization, HYSYS, Sensitivity Analysis.

    INTRODUCTION

    Naphtha is a generic term applied to refined, partly refined or unrefined petroleum products and liquid products of natural gas which distill below1 240oC. Naphtha contains varying amounts of its constituents paraffins, naphthenes, aromatics and olefins in different proportions in addition to potential isomers of paraffin that exist in naphtha boiling range. Naphtha is used as automotive fuel, engine fuel, and jet-B (naphtha type). Broadly, naphtha is classified as Light Naphtha and Heavy Naphtha. Light naphtha is used as rubber solvent, lacquer diluent, while heavy naphtha finds its application as varnish solvent, dyers naphtha, and cleaners naphtha2. Naphtha is transformed into reformate by catalytic reforming. This process involves the reconstruction of low-octane hydrocarbons in the naphtha into more valuable high-

  • Comprehensive Hashim and Jassim.

    1852 J. Chem. Bio. Phy. Sci. Sec. A, May 2014 July 2014; Vol.4, No.3; 1851-1865.

    octane gasoline components without changing the boiling point range. Naphtha and reformate are complex mixtures of paraffins, naphthenes, and aromatics in the C5-C12 range. In the refineries the crude oil feedstock is a complex multi-component mixture which has to be separated into groups of compounds. The complexities of feeds and products made the development of simulating such processes are important. Simulation is a key step in distillation column optimization problems. Accuracy, speed and convergence properties are three important factors in selection of proper simulation method. Accuracy depends mainly on the distillation column modeling assumptions followed by the termination criteria in simulation steps. Simulation of the chemical processes and unit operations such as distillation column are an integral part of optimization. As plant problems to be simulated increased in complexity, like safety problems, feed fluctuations in composition and flow rates temperature fluctuation according to the heat exchanger load and so on, thats led to further focus on the simulation programs. One example of these simulators is HYSYS software, which is simulation software developed at Hyprotech Ltd which is being used to compare the result with simulation program and the actual data for the distillation column. The simulation program will be the core of the optimization program; it shall be used to simulate the actual distillation column.

    In 2000, Vaughan .M3 simulated a steady state multicomponent multistage distillation column by using HYSYS software. The thermodynamic properties calculated using Soave-Redlich-Kwong equation of state. A good working knowledge of HYSYS was concluded and its operation was realized. An understanding of the benefits, as well as, the idiosyncrasies of HYSYS was also obtained through a lot of trial and error and reading the help menus and manuals. In 2003, Okeke and Akofe4 optimized gasoline production in crude oil distillation and naphtha stabilizer unit, where maximizing the yield of gasoline and its intermediates will directly impact positively on total pool gasoline production. Steady state simulation of the fractionator and the stabilizer was done by using HYSYS. The operating conditions were depended for optimizing the fractionator and the stabilizer. The optimization was done by using Hysys software with using Sequential Quadratic Programming. The effect of the gasoline yield was studied with respect to the return temperature of the reboiler, where found that decreasing reboiler return temperature lead to increase the gasoline yield.

    In 2005, Vasconcelos et al.5 simulated the debutanizer column of a fluid catalytic cracking unit by using Hysys software, where the feed was naphtha mixture. The results and the top and bottom temperatures were analyzed to maintain the appropriate values of the LPG and the gasoline Reid Vapor Pressure. The reboiler duty and the reflux flow rate were used as manipulated variables. The multi-variable steady state HYSYS optimizer was used in the optimization, which the net profit is used as the objective function. It was used the SQP optimization method and the RVP of gasoline as the constraint. In 2009, Saghatoleslami et al.6 simulated the distillation column of 31 trays with a condenser, two side strippers and a reboiler in HYSYS software by using Modified Hysim Inside Out method . The distillation was optimized using Hysys software. To obtain this objective, a nonlinear SQP (Sequential Quadratic Program) model has been adopted for the optimization purposes. The objective function was chosen in a way that it would maximize the annual income. In 2010, Begum et al.7 studied the quality of three products of a fractionation column considering different design conditions of the column using natural gas condensate as column feed. The whole simulation study and analysis was done on ASPEN HYSYS V7.1. Design basis for simulation used are: fluid package Peng-Robinson, method of simulation pseudo-component, generation and plate by plate calculation, solver HYSIM Inside-Out, properties generation HYSYS properties. In 2010, Moghadassi et al.8 carried out the simulation of the atmospheric distillation unit of an existing petroleum refinery by using Hysys software. Optimization was performed on the

  • Comprehensive Hashim and Jassim.

    1853 J. Chem. Bio. Phy. Sci. Sec. A, May 2014 July 2014; Vol.4, No.3; 1851-1865.

    prepared simulation through the use of a sequential quadratic programming approach (SQP) by using Hysys optimizer. The objective function consisted of energy minimization and production level maximization. The results obtained from optimization were implemented on the real process and it was demonstrated that the suggested changes increased overhead production levels and maintained product quality. In 2010, Nawaz and Jobson9 simulated a demethanizer by using HYSYS 2006.5 software to determine the process power requirement and its sensitivity to selected variables. The process separates ethane and heavier components, from natural gas (NG). The optimization problem solved by the SQP algorithm is carried out in MATLAB using the function fmincon. The objective function is to minimize the total power requirement for the process. The results after optimization were the operating pressure is 36 bar and the reflux ratio is 0.6. In 2011, Sharifzadeh and Thornhill10 simulated and optimized a sequence of three distillation towers that separate C5, C6, C7+ and heavy-ends products. The first column, depentanizer, has three products. The required computational effort of simulating the process is relatively high because the pyrolysis gasoline must be estimated by 34 components. The modified Peng- Robinson equation of state is applied for thermodynamic calculation. The simulation is performed using Aspen-HYSYS V7.1 and the optimization algorithm is GA toolbox of MATLAB which is linked to Aspen HYSYS. In 2012, Jibril et al.11 simulated an atmospheric crude distillation tower by using HYSYS software, the column consist of 29 trays plus a partial condenser. The simulation results showed that the column needed to be optimized in order to convert more of the atmospheric residue into other premium products like diesel, kerosene and naphtha.

    In 2012, Moghadam et al.12 investigated condensate stabilization using two methods of multistage flash vaporization and distillation (fractionation) by using HYSYS simulation software, where a distillation column with a reboiler and without any condenser (non-refluxed column) was used. The scope of this process is to separate very light hydrocarbon gases, methane and ethane in particular, from the heavier hydrocarbon components (C3+). Peng Robinson equation of state was applied for thermodynamic calculations of both gas and liquid phases. It was found that heat duty in multistage flashing is much higher than distillation while liquid recovery is less than the stabiliz

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