Abstract
Currently, Indonesia is still experiencing a fuel deficit, so it is necessary to build a new oil refinery and a process optimization at an existing refinery. A vacuum distillation unit (VDU) is used to process the atmospheric residue products from crude distillation unit (CDU). A multivariable model predictive control (MMPC) is proposed to improve a control performance in VDU because of the interaction between variables in the unit. Therefore, it is necessary to find the variables that interact with each other. In this study only two variables are discussed. Set point (SP) and disturbance changes are used to test the control performance with integral of square error (ISE) as the indicator. The results are compared with the control performance of the PI controller and a single MPC. As a result, the feed flow rate and bottom-stage temperature are strongest interactions so that both are determined as controlled variables in MMPC. The control performance of MMPC is better than the PI controller and the single MPC with control performance improvement of 48% to the PI controller and 21% to MPC on for Feed Flow Rates, and 98% to the PI controller and 27% to MPC on Bottom Stage Temperature. While on disturbance changes the enhancement is 35% for the Bottom Stage Temperature.
Highlights
IntroductionVacuum Distillation Unit (VDU) is a secondary process unit in refinery
Vacuum Distillation Unit (VDU) is a secondary process unit in refinery. This unit is very important for fractionating atmospheric residue residue, bottom product of Crude Distillation Unit (CDU), which has boiling point more than 350oC [1]
After performing sensitivity testing of CV changes to MV changes, the strongest inter-variable interaction is between feed atmospheric residue flow rate (CV 1) and bottom stage temperature (CV 2) with the MVs of both are the feed flow rate (MV 1) and the heat duty of the reboiler (MV 2), respectively
Summary
Vacuum Distillation Unit (VDU) is a secondary process unit in refinery This unit is very important for fractionating atmospheric residue residue, bottom product of Crude Distillation Unit (CDU), which has boiling point more than 350oC [1]. VDU operates in 20-65 mmHg. As the pressure of the columns is reduced, the component’s boiling point will be decreased as well. As the pressure of the columns is reduced, the component’s boiling point will be decreased as well That, it doesn’t need high temperature to fractionate the atmospheric residue into lighter fraction. VDU produces Light Vacuum Gas Oil (LVGO), Medium Vacuum Gas Oil (MVGO), and Heavy Vacuum Gas Oil (HVGO). These products can be processed further into gasoline and diesel product blending
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