Plant-wide Control Example Ref.: Sieder et al, Product and Process Design Principles, 2nd Edition, Wiley, 2004, Chapter 20.

Plant-wide Control Example: Vinyl Chloride Production First Reaction: Chlorination of Ethylene At 90oC , 1.5 atm and about 100% conversion Second Reaction: Thermal cracking of Dichloroethane At 500oC , 26 atm and about 60% conversion of DCE Products specifications: Main product: VC (Liquid) with more than 99% purity By product: HCl (Gas) with more that 99% purity After preliminary design, the PFD and Mass & Energy balance Table are as follows

Plant-wide Control Example: Vinyl Chloride Production

Plant-wide Control Example: Vinyl Chloride Production

Plant-wide Control Example: Vinyl Chloride Production Step 1: Design a control system to produced 100,000 lb/hr VCM with more than 99% purity Step 2: Twenty control valves have been positioned in the PFD (DOF determination)

Plant-wide Control Example: Vinyl Chloride Production Step 3: Establish the energy-management system: V-3, V-6, V-5, V-7, V-8, V-20

Plant-wide Control Example: Vinyl Chloride Production Step 4: Set the production rate: V-1

Plant-wide Control Example: Vinyl Chloride Production Step 5: Control product quality (V-11, V-16, V-13, V-18), and safety, environmental, and operational constraints

Plant-wide Control Example: Vinyl Chloride Production Step 6: Fix recycle flow rates (V-4) and vapor and liquid inventories (R-100, V-19, V-17, V-15, V-14, V12, V-10.

Plant-wide Control Example: Vinyl Chloride Production Steps 7 & 8: Check component balances and control individual units (V-2)

Plant-wide Control Example: Vinyl Chloride Production Steps 9: Optimize economics and improve dynamic controllability: The setpoints of recycle flow and T-100 feed flow controllers are set in proportional to the feed flow rate.