Process controls play an important role in how a plant process upset can be controlled and subsequent

emergency actions executed. Without adequate and reliable process controls, an unexpected process

occurrence cannot be monitored, controlled, and eliminated. Figure 1 shows a simplified process flow

diagram for natural gas sweetening (using hot potassium carbonate) and dehydration (using molecular

sieves) process.

Based on the simplified PFD given in Figure 1, devise any five (5) suitable control strategies for these

processes. State the type and explain the objective of each control strategy proposed.

In the explanation, identify the manipulated variable and control variable for each control strategy proposed.

(Ensure that there is no conflict or contradiction between the control strategies proposed).

REGENERATION GAS Sweet Gas REGEN GAS COMPRESSOR WATER KNOCKOUT Acid Gas 230 to 315C 110C 200-400 psi REGEN GAS COOLER WATER Absorber INLET SEPARATORI Stripper WET FEED GAS Lean Solution REGENERATING & COOLING ADSORBING 115-120C 2-10 psi Sour Gas Steam REGENERATION GAS 315C Rich Solution REGEN GAS HEATER DRY GAS X- VALVE OPEN VALVE CLOSED