Advanced Process Control A Real World Example Jim

Advanced Process Control A Real World Example Jim English UT Graduate, Ch. E ‘ 04 April 27, 2006

Introduction • Who am I? • Who is Air Liquide?

Why am I here? • “Real World” example • Some notes from industry

So what’s the story? • Hy. CO = Hydrogen + Carbon Monoxide • How does the Hy. CO work? (Go to PFD) • Amine System (Go to Amine)

Hy. CO Process Flow Natural Gas + Steam Reformer (Reactions) Hydrogen PSA Amine System Dryers (Details) Cold Box CO Membranes

Reformer Reactions Natural Gas Reforming: – CH 4 + H 2 O ↔ 3 H 2 + CO Water Shift Reaction – CO + H 2 O ↔ H 2 + CO 2 • Back to PFD ~60’

Amine System Process Gas Outlet CO 2 Reboiler Amine System Stripper Process Gas Inlet Absorber (Inside) Heat Exchanger

Pictures Inside Top Wall Reboiler X Stripper Reboiler

Pictures Inside Downcomer Tray X Stripper Reboiler Missing Clips

Pictures Inside Steam Deflector Plate Stripper X Reboiler

So What Next?

Form the Team • Research & Development • Engineering & Design • Process Control Experts • Plant Operations • Hy. CO Personnel

What’s our Goal? • Reduce corrosion in the stripper… • While maintaining absorber’s CO 2 removal

But Why? • If we have to replace stripper packing… – $50, 000 for packing – Plant shutdown = lost product revenue – Packing degradation ruined 2 pumps ($$$)

What’s Important? . . . • Constraint Variables • Manipulated Variables • Disturbance Variables

Which Allows Us To… CV Target CV Value MVPC MV History Controller DV History MV Setpoint

Amine System Revisited Process Gas Outlet CV CO 2 CV CV Reboiler CV MV Stripper Absorber Process Gas Inlet DV Heat Exchanger CV CV MV

How do these guys interact? MVs Stripper Reboiler Amine Recirc Total CO 2 Flow Stripper Ovhd Temp ? ? ? CO 2 Slip ? ? ? Rich Liquid Loading ? ? ? Stripper Top DP ? ? ? Stripper Bottom DP ? ? ? Absorber DP ? ? ? CVs

Next came the tough part • Test & collect process reaction curves • Import to Excel & Matlab • Fit First Order plus Time Delay models

Example Step Response (0. 5) G = 0. 5 τ = 4. 5 θ = 3. 0 θ (3. 0) τ (7. 5)

Now we Know CVs MVs Stripper Reboiler Stripper Ovhd Temp Modeled CO 2 Slip Modeled Rich Liquid Loading Amine Recirc Total CO 2 Flow Modeled Stripper Top DP Modeled Stripper Bottom DP Modeled Absorber DP Modeled

Inserting Models into MVPC…

Overall Results Corrision Temperature Post Implementation • Reduced average temperature by 5°F (225°F to 220°F) • Decreased standard deviation by to 4°F) Tavg = 225 ± 10°F Tavg 60% = 220 (10°F ± 4°F

Miscellaneous • Project Updates • Tools used • Tasks performed

Conclusions • Important Factors: – ENTIRE team – We reduced the risk of corrosion! – Project’s success is leading to further MVPC around the plant’s reformer

Thanks! Questions?