SS OPTIMZ-04 SimSci Advanced Control: Maximizing Utility Loading with an Inter-Unit APC Application

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2 SS OPTIMZ-04 SimSci Advanced Control: Maximizing Utility Loading with an Inter-Unit APC Application October 16, 2013 Paul Kesseler Manager NA APC Consulting / #SoftwareRevolution /InvensysVideos /InvensysOpsMgmt /Group/SimSci 2013 Invensys. All Rights Reserved. The names, logos, and taglines identifying the products and services of Invensys are proprietary marks of Invensys or its subsidiaries. All third party trademarks and service marks are the proprietary marks of their respective owners.

3 OVERVIEW Recent History of APC at this Refinery Hydrogen System Overview Hydrogen Producer Single Unit APC Single Unit Benefits/Results Multi-Unit Hydrogen System Producer/Consumer APC Multi-Unit Benefits/Results Slide 3

4 Refinery Background US refinery Crude capacity between 150,000 and 200,000 barrels/day Produces a high percentage of motor fuels Completed a control system modernization project in 2008 that added a centralized control room and a Foxboro I/A DCS MESH network Slide 4

5 Recent History of APC at Refinery Connoisseur Applications running on typical, larger units Crude Units (yield benefits) FCC/Gas Plant (yield benefits) DCU/Gas Plant (yield benefits) Hydrocracker (catalyst life) Also, one smaller hydrogen consuming unit, possible because of the presence of an online analyzer (difficult otherwise) Then we thought about the hydrogen system. Slide 5

6 Hydrogen System Units H2 Producer 1 PC Producer 2 Producer 3 (offsite) Fuel Gas Consumer 1 Consumer 3 Consumer 5 Consumer 7 Consumer 2 Consumer 4 Consumer 6 Slide 6

7 Hydrogen Producer APC Units H2 Producer 1 (APC1) PC Producer 2 Producer 3 (offsite) Fuel Gas Consumer 1 Consumer 3 Consumer 5 Consumer 7 Consumer 2 Consumer 4 Consumer 6 Slide 7

8 Hydrogen Producer 1 Unit Functions as a utility unit. Generates hydrogen into a hydrogen header Hydrogen is used as feed to multiple hydrogen consuming units Hydrogen is generated with two independent furnaces Multiple gas streams of various compositions are fed to the unit Unit must produce the correct amount of hydrogen at the target purity Slide 8

9 Producer 1 Operating Challenges Hydrogen user demand/consumption is constantly changing Feed quality also changes Operators attempt to only make what s required but must err on the conservative side Excess hydrogen product is vented to fuel gas on pressure control; wasteful and has negative impact on fuel gas heating value Must also control hydrogen purity with frequently varying charge rates Many operating constraints: multiple furnace constraints, multiple downstream constraints Constraints require loading between the two furnaces to shift, or unit total charge may have to be reduced causing H2 header pressure to sag Slide 9

10 Producer 1 APC Project Goals APC 1 was to vary unit charge rate continuously to directly control back end H2 pressure - operator to be relieved of this constant task - H2 vent to fuel gas to stay closed Second APC goal was to increase the overall hydrogen produced APC 1 would push the multiple operating constraints in Producer 1 unit Hydrogen consumers could then increase their production rates and make more final product Slide 10

11 Producer 1 APC Design APC 1 to move both furnace feed flows, steam flows, and fuel pressures, along with several other unit variables: - 9 manipulated variables (MV s) APC 1 to control H2 product pressure, H2 product purity, multiple furnace constraints, and multiple unit back end constraints: - 26 controlled variables (CV s) Slide 11

12 Producer 1 Performance Pre-APC Slide 12

13 H2 Producer 1 Performance Post-APC Slide 13

14 Producer 1 Backend Constraints on APC Slide 14

15 H2 Vent Flow Reduction APC On APC OFF Dec-12 Feb-13 Mar-13 May-13 Jul-13 Aug-13 Slide 15

16 Producer 1 APC Results Hydrogen venting to fuel gas was virtually eliminated Hydrogen production capacity increased by ~2.5% Hydrogen header pressure became more stable, less severe pressure dips Hydrogen product purity controlled at target value Unit back end equipment far more stable Furnace steam flows minimized Operators load greatly reduced Slide 16

17 How to Consume Extra Hydrogen? APC 1 on Producer Unit 1 provides additional hydrogen product Significant economic benefit to using this additional hydrogen in consuming units Identify which hydrogen consuming units to increase capacity Prioritize: Which units take the hydrogen first? Slide 17

18 Hydrogen Consuming APC Units H2 Producer 1 (APC1) PC Producer 2 Producer 3 (offsite) Fuel Gas Consumer 1 (APC1) Consumer 3 Consumer 5 Consumer 7 Consumer 2 (APC2) Consumer 4 Consumer 6 Slide 18

19 H2 Consumer APC Goals Adjust operation of Consumer 1 and Consumer 2 units to use all available hydrogen capacity Stabilize hydrogen consumption in Consumer 2 Prioritize which unit takes or gives back hydrogen first Slide 19

20 Multi-Unit APC Design Considerations Centralized control room allows APC application to be applied across multiple units MESH network technology also critical to this design Consumer 1 to run at variable charge rates Consumer 2 to run at variable reactor temperatures Producer 1 and Consumer 1 on adjacent operating boards APC1 Independent application APC 2 to cover Consumer 2 Prediction of available hydrogen is key Use DCS supervisory logic to link APC 2 and APC 1 Slide 20

21 Hydrogen Production Capacity LP Use custom Connoisseur LP to calculate the maximum hydrogen production capacity of Producer 1 unit Link custom LP with real APC LP Connoisseur LP Producer 1 MV/CV ON/OFF Status MV/CV Limits Online Models Capacity LP Producer 1 Max. H2 Production Capacity Connoisseur MVC Producer 1 Setpoint Moves To DCS PID s Slide 21

22 DCS Supervisory Block logic flow Slide 22

23 Consumer 2 Performance Before APC Slide 23

24 Consumer 2 Performance Before APC Slide 24

25 Consumer 2 APC Disturbance Rejection Slide 25

26 Consumer 2 Reactor Control on APC Slide 26

27 Multi-Unit APC Header Pressure Control Slide 27

28 Consumer 2 H2/Feed Ratio APC 7/30 8/4 8/9 8/14 8/19 Slide 28 28

29 Multi-Unit Benefits/Results Typical APC benefits push unit operating constraints and lessen operator load. This is accomplished with APC 1 Multi-unit APC actually assists with one level higher up: shift supervisor Automates setting unit charge rates and reactor conditions Also directly implements some goals from the economic planning group Results: - Increased feed rate in Consumer 1 - Increased hydrogen consumption and product quality in Consumer 2 - Further stabilized hydrogen header pressure Slide 29

30 Further Scope Expansion Hydrogen header appears to have additional H2 capacity due to steady operation Shift supervisors then make charge rate increases to another hydrogen consuming unit and the hydrogen supply cannot maintain the header pressure Customer decided to also add this unit s charge rate to the hydrogen system APC. APC will make correct move sizes and coordinate with the other hydrogen system units Slide 30

31 Slide 31 Questions?

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