Abstract
An HYSYS model for the crude distillation unit of the Port Harcourt Refining Company has been developed. The HYSYS model developed includes 3 mixers, 3 heaters, 1 heat exchanger, 1 desalter (3-phase separator), 2-phase separator and the main fractionating column. The raw crude was characterized using Aspen HYSYS version 8.8 and the developed model was simulated with the industrial plant data from the Port Harcourt Refining Company. The HYSYS model gave component mole fractions of 0.2677, 0.1572, 0.2687, 0.0547, 0.2517 for Naphtha, Kerosene, Light Diesel Oil (LDO), Heavy Diesel Oil (HDO) and Atmospheric Residue and when compared to plant mole fractions of 0.2710, 0.1560, 0.2650, 0.0530, 0.2550 gave a maximum deviation of 3.2%. The HYSYS model was also able to predict the temperature and the tray of withdrawal for Naphtha, Kerosene, Light Diesel Oil (LDO), Heavy Diesel Oil (HDO) and Atmospheric Residue as follows: tray 1 (120°C), tray 12 (206°C), tray 25 (215°C), tray 35 (310°C) and tray 48 (320°C) which was also compared with plant data and gave a maximum deviation 23.2%. The HYSYS model was then optimized using Sequential Quadratic Programming (SQP) with the industrial plant data as starting values of operating conditions. The optimization increased the mass flow rate of Naphtha product from 7.512E+004 kg/hr to 7.656E+004 kg/hr, Kerosene product from 5.183E+004 kg/hr to 5.239E+004 kg/hr, Light Diesel Oil (LDO) product from 1.105E+005 kg/hr to 1.112E+005 kg/hr, Heavy Diesel Oil (HDO) from 2.969E+004 kg/hr to 2.977E+004 kg/hr while the last product being Atm Residue remained at 3.157E+005 kg/hr. The new optimum mole fraction values for the five products were as follows: 0.2713, 0.1540, 0.2635, 0.0528, and 0.2584 while corresponding optimum temperature values were as follows: 129°C, 221°C, 257°C, 317°C and 327°C.
Highlights
Refining is the process by which the temperature of a liquid mixture is raised and separated into numerous cuts or fractions through the process of condensation and selective boiling
3) Process optimization: this is carried out to ensure the optimum mole fraction of the simulated model is obtained using the method of sequential quadratic programming (SQP) which is shown in Figure 3 and Figure 4 respectively
The HYSYS model developed included 1 mixer, 3 heaters, 1 heat exchanger, 1 desalter, a 2-phase separator and the main fractionating column which was modeled as a refluxed absorber in Aspen HYSYS
Summary
Refining is the process by which the temperature of a liquid mixture is raised and separated into numerous cuts or fractions through the process of condensation and selective boiling. In the processing of raw crude, the temperature of the components is raised inside which is a fired furnace and transferred into a distillation column. As the liquid flows down the column, the components with low boiling point are separated as it rises from the top part of the tower [1]. Condensation begins with the liquid sliding down from the top part of the column enriched and the less volatile parts begin to condense [2]. Products leaving at the top part of the column are those with a low boiling point and are found to have high relative volatility
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