QUESTION 2 Consider the reactor system shown below. The reaction is exothermic s

Question

QUESTION 2 Consider the reactor system shown below. The reaction is exothermic so a cooling system is provided to remove the excess energy of the reaction. in the event that the cooling function is lost, the temperature of the reactor would increase. This would lead to an increase in reaction leaing to an abashinnergy reasThe resut wouer be a y reascion win pressures exceeding the bursting pressure level of the reactor vessel. The temperature within measue ae Perform a HAZOP study on this unit to improve the safety of the process. Use as a study node the cooling coil (process parameters: flow and temperature) and the stirrer (process parameters: agitation) [20] Reactor Monomer Feed Cooling Coils Cooling Water Out Cooling Water In TC Thermocouple

Explanation / Answer

This reaction is exothermic, and a cooling system is provided to remove the excess energy of reaction. If the cooling flow is interrupted, the reactor temperature increases, leading to an increase in the reaction rate and the heat generation rate. The result could be a runaway reaction with a subsequent increase in the vessel pressure possibly leading to a rupture of the vessel. The temperature within the reactor is measured and is used to control the cooling water flow rate by a control valve.

Performing a HAZOP on this process with the assigned task of considering runaway reaction possibilities would lead to a completed HAZOP form shown below in table. Three study nodes are cooling water line, stirring motor, cooling water temperature.

The HAZOP analysis would reveal the following potential process modifications:

1. Control valve fails closed

2. Plugged cooling coils

3. Cooling water service failure

4. Controller fails & closes valve

5. Air pressure fails, closing valve

1. Loss of cooling, possible runaway

2. As above

3. As above

4. As above

5. As above

1. Select valve to fail open

2. Install filter with maintenance procedure. Install cooling water flow meter and low flow alarm. Installa high temperature alarm to alert operator.

3. Check and monitor reliability of water service

4. Place controller on critical instrumentation list

5. Same as Point A.

1. Control valve fails open

2. Controller fails and opens valve

1. Reactor cools, reactant concentration builds, possible runaway on heating

2. As above

1. Instruct operators and update procedures

2. Same as A.4 above

1. Partially plugged cooling line

2. Partial water source failure

3. Control valve fails to respond

1. Diminished cooling, possible runaway

2. As above

3. As above

1. Same as A.2

2. Same as A.2

3. Same as A.2

1. Failure of water resulting in backflow

2. Backflow due to high back pressure

1. Loss of cooling, possible runaway

2. As above

1. Same as A.2

2. Installation of check valve

1. Stirrer motor malfunction

2. Power failure

1. No mxing, possible accumulation of unreacted materials

2. Monomer feed continues, possible accumulation of unreacted material

1. Interlock with feed line

2. Monomer feed valve must fail closed on power loss

Sr No. Study NodeP Process Parameters Deviations (Guide words) Possible causes Possible consequences Action required Assigned to: Reply Date No Action: Completed A Cooling Coils Flow No

1. Control valve fails closed

2. Plugged cooling coils

3. Cooling water service failure

4. Controller fails & closes valve

5. Air pressure fails, closing valve

1. Loss of cooling, possible runaway

2. As above

3. As above

4. As above

5. As above

1. Select valve to fail open

2. Install filter with maintenance procedure. Install cooling water flow meter and low flow alarm. Installa high temperature alarm to alert operator.

3. Check and monitor reliability of water service

4. Place controller on critical instrumentation list

5. Same as Point A.

B High

1. Control valve fails open

2. Controller fails and opens valve

1. Reactor cools, reactant concentration builds, possible runaway on heating

2. As above

1. Instruct operators and update procedures

2. Same as A.4 above

C Low

1. Partially plugged cooling line

2. Partial water source failure

3. Control valve fails to respond

1. Diminished cooling, possible runaway

2. As above

3. As above

1. Same as A.2

2. Same as A.2

3. Same as A.2

D As well as Contamination of water supply 1. Not possible in this case 1. None E Part of 1. Covered under C F Reverse

1. Failure of water resulting in backflow

2. Backflow due to high back pressure

1. Loss of cooling, possible runaway

2. As above

1. Same as A.2

2. Installation of check valve

G Other than 1. Not conssidered possible H Sooner Than 1. cooling normally started early 1. None I Later than 1. Operator error 1. Temperature rises, possible runaway 1. Interlock between cooling flow and reactor feed J Where else 1. Not considered possible K Temperature Low 1. Low water supply 1. None-controller handles 1. None L High 1. High water supply temperature 1. Cooling system capacity limited, temperature increases 1. Install high flow alarm and/ or cooling water high temperature alarm M Stirrer Agitation No

1. Stirrer motor malfunction

2. Power failure

1. No mxing, possible accumulation of unreacted materials

2. Monomer feed continues, possible accumulation of unreacted material

1. Interlock with feed line

2. Monomer feed valve must fail closed on power loss

N More 1. Stirrer motor controller fails, resulting in high motor speed 1. None

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---