Platform for Implementing Advanced Controls

We implement a variety of basic and traditional advanced controls on the DCS, including:

• Cascade
• Feedforward
• De-coupling
• Inferential and constraint controls

Advanced Control Applications:

• Inferential calculations and Model Predictive Control (MPC) applications, including data acquisition and dynamic simulation, will be executed on a host engineering PC interfaced with the DCS.

Engineering Computer Interface

• The engineering computer will interface with the DCS and a separate PC for bi-directional file transfers.
• Custom schematics will be provided for operator monitoring of laboratory data.
• Application programs on the engineering computer will access laboratory data via the DCS Database.

Typical Scope of Crude (CDU) Unit Project

The scope includes integration with any underlying site-wide DCS system, ensuring seamless operation and control across all facets of the process.

CDU Advanced Control Objectives

1. Maximize Charge Rate:
   Operate the crude unit at maximum throughput while honoring all unit constraints, particularly during favorable economic conditions.
2. Maximize Lifting of Products:
   • Enhance lifting of Atmospheric Residue to Heavy Diesel (HD) and Light Diesel (LD).
   • Increase lifting of Vacuum Residue to High-Value Gas Oil (HVGO).
3. Reduce Quality Giveaway:
   • Minimize quality giveaway on Naphtha ASTM End Point (EP) to allow for increased Naphtha yield without violating ASTM EP constraints.
4. Improve Separation:
   • Reduce variability in Flash Zone Pressures and operate at minimum pressures dictated by tower constraints to enhance separation efficiency in CDU towers.
5. Minimize Giveaway During Crude Switching:
   Ensure product quality is maintained during transitions between crude types.
6. Reduce i-C5 Losses:
   • Minimize losses in the LSRN Stabilizer Overhead and reduce giveaway on Stabilizer bottoms Reid Vapor Pressure (RVP).
7. Reduce Energy Consumption:
   • Lower excess O2 levels in Fuel Gas F1101A and F1101B.
   • Maintain equal preheat trains and heater pass outlet temperatures.
   • Optimize pump-around heat duties to decrease overall energy usage.
8. Improve Fuel Oil Viscosity:
   Reduce the giveaway in Fuel Oil viscosity.
9. Increase Naphtha Splitter Throughput:
   • Maximize throughput within tower constraints while lowering operating pressure to enhance separation and decrease energy consumption.
   • Maximize i-C6 yield in Naphtha Splitter overhead and n-C6 in Splitter bottoms.

MOD Blending Unit Advanced Control Objectives

1. Optimize Blending:
   Enhance the blending of CDU Kerosene, LD, HD, VDU LVGO, and HDC Diesel to maximize MOD production and minimize Vacuum Residue output.
2. Reduce Quality Giveaway:
   Implement online blending to improve MOD product quality by integrating CDU Kerosene, LD, HD, VDU LVGO, and HDC Diesel.

Unifier Unit Advanced Control Objectives

1. Reduce Sulfur Variability:
   Minimize the variability in Unifier product sulfur content to improve hydrotreated Naphtha yield and overall unit throughput.
2. Maximize Throughput:
   Increase Unifier Unit throughput while adhering to constraints such as reactor temperature, H2 availability, circulation, and heater loading to process additional feed due to increased Naphtha production.
3. Maintain H2-to-Oil Ratio:
   Keep the H2-to-Oil ratio within specified limits to optimize Reformate catalyst aging and minimize H2 recycle compressor power consumption.
4. Reduce RVP Giveaway:
   Allow for more butane in the Naphtha Stabilizer bottoms, respecting RVP specifications to minimize giveaway.
5. Reduce i-C5 Losses:
   Focus on reducing i-C5 losses in the Naphtha Stabilizer overhead to maximize Naphtha yield.
6. Optimize Stabilizer Pressure:
   Lower Naphtha Stabilizer pressure within condenser capacity to enhance yield and reduce energy consumption.
7. Maximize Unifier Throughput:
   Continuously strive to maximize throughput of the Unifier unit.
8. Process More High-Sulfur Low-Cost Crude:
   Equip the refinery with the ability to efficiently process higher volumes of low-cost, high-sulfur crude.

• Isomerization Unit Advanced Control Objectives

  1. Maximize Throughput and Yield:
     Enhance unit throughput, yield, and product octane primarily by:
     • Monitoring isomer rate yield, feed composition, and charge rate.
     • Adjusting SAFE CAT reactor and adsorption section temperatures to maintain sulfur content in the hydrotreated product between 0.1 to 0.2 wt%.
  2. Optimize Total Isomerization Process (TIP):
     Fine-tune TIP reactor temperature and adsorber section cycle timer settings to balance yield and product octane improvement.
  3. Enhance Feed Processing Capability:
     Equip the refinery to process larger volumes of high-sulfur low-cost crude feed.

Utility Boilers and Steam and Electricity Distribution Advanced Control Objectives

1. Improve Boiler Efficiency:
   • Enhance the efficiency of steam and utility boilers, addressing high excess O2 levels in some heaters to further improve efficiency.
2. Optimize Steam Generation and Distribution:
   • Conserve energy by minimizing losses in let-down stations, optimizing load distribution across boilers, and lowering steam header pressures.
3. Electricity Distribution Efficiency:
   • Implement optimal electricity distribution to maximize the efficiency of turbo generators and reduce grid electricity consumption.

CDU, VDU, HDC, and MOD Blending Advanced Control Applications

Step-by-Step Implementation Plan:

1. Initial Advanced Controls Installation:
   Install traditional and inferential Advanced Controls on the CDU, VDU, HDC, and MOD blending units before implementing Model Predictive Control (MPC) controls.
2. MPC Controllers for CDU and VDU:
   • Install three MPC controllers: one for the LSRN Stabilizer, one for the Naphtha Splitter, and one for both the CDU and VDU.
   • Benefits: Immediate reduction in RVP giveaways, decrease in i-C5 losses to LPG, and maximization of n-C6 in Naphtha Splitter bottoms and i-C6 in the Splitter overhead.
3. MPC for HDC Fractionation Section:
   • Implement three stand-alone controllers: one for the product Fractionator, one for the debutanizer, and one for the Naphtha Splitters.
   • Benefits: Reduction in Naphtha and Diesel quality giveaways, improved lifting of PF bottoms to Diesel, decreased energy consumption in the HDC Fractionation section, and minimized RVP giveaway.
4. MPC Reactor Temperature Controllers for HDC:
   • Apply a single controller for both the 1st and 2nd stage reactors to stabilize operations and maximize throughput while respecting equipment constraints and hydrogen availability.
5. MOD Online Blending and Optimization Controls:
   • Install online blending and optimization controls for MOD to enhance performance.

2.1 Overview of Traditional and Inferential Control Applications

This section outlines the Traditional and Inferential Advanced Control applications for maximizing the yield of MOD and Naphtha, minimizing energy consumption, and maximizing unit throughput. Detailed discussions are available in Section 5.7 of this document.

Implementation Overview

The applications will primarily be integrated into the client’s Yokogawa DCS, with inferential calculations executed within the engineering WSPCr. Key controls include:

Atmospheric Crude Unit Controls

1. Desalter Pressure Control
2. Crude Preheat Train Temperature Balancing
3. Crude Charge Pump Speed Control
4. Crude Charge Flow Control and Heaters’ Pass Balancing
5. Combustion Control for Crude Heaters:
   • Using available stack O2 analyzers
   • Future application using stack O2 and CO analyzers
6. Crude Heaters’ Outlet Temperature Control
7. Pump Around Duty Control:
   • Top Pump Around
   • Mid Pump Around
8. Steam-to-Oil Ratio Control:
   • Kerosene Stripper
   • Light Diesel Stripper
   • Heavy Diesel Stripper
9. Naphtha ASTM End Point Control
10. ASTM BP Control:
    • Kerosene 95%
    • Light Diesel 95%
    • Heavy Diesel 95%
11. Overflash Control
12. CDU Overhead Pressure Minimization Constraint Pushing Control
13. Product Quality and Pump-Around Control During Crude Switches

• Vacuum Unit Controls

  1. VDU Charge Flow Control and Heaters’ Pass Balancing
  2. Combustion Control for Vacuum Heaters:
     • Using available stack O2 analyzer
     • Future application using stack O2 and CO analyzers
  3. Vacuum Heater Outlet Temperature Control
  4. Pump Around Duty Control:
     • Top Pump Around
     • Mid Pump Around
  5. ASTM BP Control:
     • LVGO 95%
     • HVGO 95%
  6. Overflash Control
  7. Overhead Pressure Minimization Constraint Pushing Control

HDC Unit Controls

1. HDC Charge Control and Heaters’ Pass Balancing
2. Combustion Control for HDC Charge Heaters:
   • Using available stack O2 analyzer
   • Future application using stack O2 and CO analyzers
3. HDC Charge Heaters’ Outlet Temperature Control
4. PF Charge Control and Heaters’ Pass Balancing
5. Combustion Control for HDC PF Charge Heaters:
   • Using available stack O2 analyzer
   • Future application using stack O2 and CO analyzers
6. HDC PF Charge Heaters’ Outlet Temperature Control
7. HDC NS Reboiler Flow Control and Heaters’ Pass Balancing
8. Combustion Control for HDC NS Reboiler:
   • Using available stack O2 analyzer
   • Future application using stack O2 and CO analyzers
9. HDC NS Reboiler Outlet Temperature Control
10. Pump Around Duty Control:
    • Top Pump Around
    • Mid Pump Around
11. Steam-to-Oil Ratio Control:
    • Kerosene Stripper
    • Diesel Stripper
12. ASTM End Point Control:
    • HDC Naphtha
    • HDC Kerosene 95%
    • HDC Diesel 95%
13. Hydrogen-to-Oil Ratio Control
14. HDC Hydrotreating Reactor Bed Inlet Temperature Control
15. Inferential Calculations:
    • HSRN Stabilizer and HDC Dehumanizer Bottoms RVP
    • CDU and HDC Naphtha Splitter Overhead I-C6
    • CDU and HDC Naphtha Splitter Bottoms n-C5

MOD Blending Controls Simulation Results Using ACSC Technology

• Online Blending of:
  • CDU Kerosene
  • Light Diesel
  • Heavy Diesel
  • VDU Light Diesel
  • HDC Kerosene and Diesel
• Utilization of:
  • Online Diesel 95% BP Analyzer
  • Laboratory Cold Properties Data
• MOD Blending Optimization Results

Simulation Results – Base Case

Refer to Table 5.2.1 for detailed simulation results pertaining to CDU, VDU, HDC, and MOD blending.