Distillation column The studies on distillation column suggest the following objectives: 1. Product quality control to m
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Distillation column The studies on distillation column suggest the following objectives: 1. Product quality control to maintain either the overhead or bottom composition at a specified value 2. Material balances control to maintain its column hold-up and overhead and bottom inventories between maximum and minimum limits. 3. Constraints. The column should not flood. Pressure should be high enough to maintain effective column operation and the temperature difference in the reboiler should not exceeded critical temperature difference. HAZOP Studies on Distillation Column Guide word NO
Deviation No flow
Possible causes Pipe blockage Control valve shut Valves fail Tube leakage and blocking Pump failure
Consequences
Column dry out Possible dangerous concentration No operation
LESS
Less Flow
MORE
More flow
Pipe blockage Control valve shut Valves fail Tube leakage and blocking Pump failure
Control valve is fully opened Increase pumping capacity Control valves failure
Column dry out Changes in product quality
Flooding in the column Changes in product quality Temperature decrease Rise in bottom
Action required Install low level alarm Check maintenance procedure and schedule Make bypass Emergency plant shut down Install low level alarm Check maintenance procedure Make bypass Emergency plant shut down Install high level alarm Check maintenance procedure and schedule Install control
liquid level
HIGH
High pressure
High Temperature
LOW
Low pressure
Vapor pressure high Pressure indicator controller fail
Instrumentation failure More steam flow Exchanger tube failure High steam pressure Cooling water in condenser failure. Reboiler control failure Heating medium leak into process Vapour line leakage
Low temperature
Instrumentation failure Less steam flow Loss of heating (steam leakage) Low steam pressure and temperature Ineffective isolation
Low efficiency of separation Rupture of column or other related equipment Product loss Separation cannot be done Changes in product quality Column flooding Film boiling in column and reboiler Phase effect Pressure changes Low efficiency of separation Loss of products Pressure change Product loss Changes in product quality Ineffective separating process Phase effect
valves Install flow indicator Make bypass Install high pressure alarm Install pressure relief valve
Install temperature indicator controller Instruct operator on procedure Attention to heat input and output control
Install pressure indicator
Install temperature indicator Instruct operator on procedure Upgrade isolation Attention to heat input and out control