ERT 322 SAFETY & LOSS PREVENTION HAZOP. Prepared by; Miss Syazwani Mahmad Puzi School of Bioprocess Engineering. I suppose that I should have done that HAZOP Study!. A scenario….
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Miss Syazwani Mahmad Puzi
School of Bioprocess Engineering
should have done that
You and your family are on a road trip by using a car in the middle of the night. You were replying a text message while driving at 100 km/h and it was raining heavily. The car hits a deep hole and one of your tire blows.
You hit the brake, but due to slippery road and your car tire thread was thin, the car skidded and was thrown off the road.
What was the cause of the accident?
What was the consequence of the event?
What can we do to prevent all those things to happen in the first place?
What other possible accidents might happen on the road trip?
Can we be prepared before the accident occurs?
1. Remove hazard (use public transport)
2. Reduce the frequency (follow rules, car in good conditions, physically alert, route selection)
3. Consequence – prepare for hazard (airbag, seat belt)
1. Process hazard checklist
2. Hazard surveys
3. Hazard and operability (HAZOP) studies
4. Safety review
1. Dow Fire and Explosion Index (F&EI)
2. Dow Chemical Exposure Index (CEI)
Your plant is considering the installation of a new railcar tank unloading facility. The facility will unload nominal 25,000-gal tank cars containing either pure butadiene or cyclohexane. The unloading system will be equipped with an emergency shutdown system with remotely operated block valves. The unloading operation will be done by computer control. The railcars are inerted with nitrogen to a pressure of 40 psig, and the railcar relief system has a set pressure of 75 psig. The unloading operating instructions are written and have been reviewed by the corporate technical staff. A reactive chemicals review has already been completed on the proposed facility. Combustible gas detectors will be located at the unloading station. A deluge system will be installed at the unloading site with an excellent water supply. A diking system will surround three sides of the facility, with any spills directed to a covered impounding area.
Determine the Dow F&EI for this operation, and determine the minimum spacing from adjacent units.
Diammonium Phosphate (DAP) Production
Study line 1
Phosphoric acid delivery line
Consider the reactor system shown in Figure 10-8. The reaction is exothermic, so a cooling system is provided to remove the excess energy of 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 rate, leading to additional energy release. The result would be a runaway reaction with pressures exceeding the bursting pressure of the reactor vessel. The temperature within the reactor is measured and is used to control the cooling water flowrate by a valve.
Perform a HAZOP study on this unit to improve the safety of the process. Use as study nodes the cooling coil (process parameters: flow and temperature) and the stirrer (process parameter: agitation).
2. Raw material & products
3. Equipment setup
5. Safety checklist
The hydrolysis of acetic anhydride is being studied in a laboratory-scale continuously stirred tank reactor (CSTR). In this reaction acetic anhydride [(CH3CO)2O reacts with water to produce acetic acid (CH3COOH).
The concentration of acetic anhydride at any time in the CSTR is determined by titration with sodium hydroxide. Because the titration procedure requires time (relative to the hydrolysis reaction time), it is necessary to quench the hydrolysis reaction as soon as the sample is taken. The quenching is achieved by adding an excess of aniline to the sample. The quench reaction is
The quenching reaction also forms acetic acid, but in a different stoichiometric ratio than the hydrolysis reaction. Thus it is possible to determine the acetic anhydride concentration at the time the sample was taken.
The initial experimental design is shown in Figure 10-14. Water and acetic anhydride are gravity-fed from reservoirs and through a set of rotameters. The water is mixed with the acetic anhydride just before it enters the reactor. Water is also circulated by a centrifugal pump from the temperature bath through coils in the reactor vessel. This maintains the reactor temperature at a fixed value. A temperature controller in the water bath maintains the temperature to within 1°F of the desired temperature.
a. Develop a safety checklist for use before operation of this experiment.
b. Perform a HAZOP study on the intention “reactant flow to reactor” for your analysis. What specific recommendations can you make to improve the safety of this experiment?