The presentation is about the chemical accident that occured in Bhopal in the year 1984.

1. Presentation - 1​
Course – CHE 402 : Process Design and Economics​
Name – Artina Deka​
Roll No – 19056​
Year – 4th year(8th sem)

2. BHOPAL GAS TRAGEDY(1984)
"HIROSHIMA" of the "CHEMICAL INDUSTRY "
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3. • Introduction
• Background
• The Leak
• Design
• Safety Consideration
• Disaster Response
• Lessons
• My point of View
Contexts
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4. INTRODUCTION
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5. 1. Bhopal Gas Tragedy is one of the worst commercial industrial disasters in history
2. In the night of 2nd-3rd December 1984 , in the city of Bhopal , a highly toxic cloud of methyl
isocyanate (MIC) vapor burst from the Union Carbide pesticide plant.
3. The tumultuous outcome of the accident was a cumulative effect of the following seven reasons.
 a. Large release of chemical from the plant.
 b. Release of colorless, odorless MIC, which is highly toxic.
 c. Heavily populated areas adjacent to the plant.
 d. Calm weather conditions, bringing the vapor cloud down
 e. Leak occurs at night when people are sleeping.
 f. Failure or late warnings
 g. Unqualified and unaware people working at the plant
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6. BACKGROUND
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7. 1. India witnessed Green Revolution in 1960s and 1970s.
2. Agricultural productivity increased and so did the use and demand for Pesticides.
3. The Indian Government invited Union Carbide Corporation to set up a plant in India ,which at
that time was the largest manufacturer of pesticides and insecticides in the world .
4. UCC is the parent company and UCIL was the Indian subsidiary which held 50.9% stock .
5. The plant opened in 1969 in Bhopal to produce pesticides and later on in 1977 started
producing Sevin (pesticide - brand name for Carbaryl).
6. Despite initial expectations of producing 2000 tons of carbaryl, the plant was actually producing
much less due to the decreasing demand .
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8. 1. Sevin/Carbaryl was produced by a chemical reaction for which MIC , phosgene and carbon monoxide
was used.
2. Isocyanates : R‐N=C=O
3. Methyl isocyanate is highly reactive due to the cumulative action from the presence of adjacent double
bonds.
4. Having a boiling point of 39.1°C, MIC vaporizes at room temperature and exists as an odorless, colorless
gas.
5. The effects of MIC can be detected by contact, resulting in watering of the eyes and irritation of the
throat.
6. MIC reacts with water exothermically, generating heat above its boiling point and thus turns from liquid
to vapor. Hence the existence of even a small amount of water can be sufficient to produce enough heat
to cause and ruptures and leaks.
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9. Methyl Isocyanate
At 25 °C, in excess water, half of the MIC is consumed in 9 min. If the heat is not efficiently removed from the reacting
mixture, the rate of the reaction will increase and rapidly cause the MIC to boil. Such a reaction triggered the Bhopal
Disaster after that water was accidentally introduced in a MIC storage tank during cleaning operation of an adjacent
pipe without closing the proper Isolation Valve of the reservoir.
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10. THE LEAK
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11.  8‐9 pm: The MIC plant supervisor was ordered to wash out several pipes running from the phosgene system to t
he scrubber system through the MIC storage tanks
.The maintenance department is responsible for inserting the slip bind (a solid disk) into the pipe above the wate
r washing inlet. However, the MIC unit workers were not aware that the installation of these slip blinds is a requir
ed safety procedure, and the slip bind was not installed .
 9:30 pm: The water washing begins. One of the bleeder valves (overflow device) was blocked so water did not co
me out as it was supposed to. It was collected in the pipes. The plant supervisor ordered that the washing contin
ue .
 11 pm: The operator in the control room noticed pressure gauge connected to Tank E610 had risen from 2 psi to
10 psi. The rise in pressure didn’t arouse any concerns to the operator since 10 psi is within the normal 2‐25 psi r
ange. However, the control room lacked monitoring the temperature of the tank.
 11.30 pm: The unit workers in the area noticed MIC’s smell and saw an MIC leak near the scrubber.
The workers then set up a water spray to neutralize the leaking of MIC and the people in the control room were a
lso informed of the situation and their corresponding actions.
2nd December
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12. used for the purpose of positive shut
off of a piping system where mere
shut off using valves is not sufficient
as valves are prone to leakage.
SLIP BINDS
Their purpose is to prevent accidental flow through a pipeline to a
vessel.
A Bleed Valve is a screw-type valve that allows
trapped vapor or liquid to escape from a system.
BLEEDER VALVE
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13.  12.15‐12:30 am: The control room operator noticed that control room pressure indicator for Tank E610 reads 25‐
30 psi .
One of the safety valves popped out and clouds of lethal gas were discharging from the plant stack vent scrubber
and spreading rapidly through Bhopal.
 12.40 am: The plant supervisor turned on the in‐plant and external toxic gas sirens. The operators also turned on
the fire water sprayer. However, water could not reach the gas cloud formed at the top of the scrubber stack. M
oreover, attempts to cool the tank with the refrigeration system failed because the Freon had been drained.
 1 am: Plant supervisor realized that the spare tank, E619, was also not empty, so workers failed to reduce the pr
essure in E610 by transferring any MIC to E619.
 8 am: Madhya Pradesh governor ordered closure of the plant and arrest of the plant manager and 4 other emplo
yees .
3rd December 12

14. a) The design of the vent gas scrubber was constructed to handle a flowrate of 88 Kilograms of MIC per hour.
However, the actual flowrate was 20,000 Kg/hr during the time of the accident.
b) The storage systems were designed to carry 5 tons on a daily basis. However, during the accident, there were
three storage tanks and 55 tons of MIC was stored. Large scale storage without a proper safety system was a
major hard error.
c) The piping system had no bleeders or flanged joints.
FAULT IN DESIGN
Vent gas scrubber is a responsible gas flare
system by keeping liquids out of your flare stack.
A flange joint is a connection of pipes, where the connecting
pieces have flanges by which the parts are bolted together.
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15. Some of the equipment failure present at the Union Carbide plant prior to the incident :
1. Storage of MIC for a period longer than permissible.
2. Non-functional and nonexistent detection and warning devices.
3. Temperature and pressure gauges at various parts of the plant were extremely faulty and were genera
lly ignored by workers .
4. Insufficient and untrained staff that results in faulty pipe washing.
5. Shutdown of MIC refrigeration unit .
6. Shutdown of caustic soda spray system .
7. Out of order flare towers .
8. No valves to prevent water entering the tank ; it was
also not prepared to handle the high pressures reached during the tragedy.
Operational and safety failures:
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16. Management failure :
1. Management neglect of general plant operations .
2. Lack of investment in plant safety .
3. Cost cutting:
• Employee training and factory maintenance were radically cut.
• Skilled employees were replaced with lower paid workers.
• Stainless valving and pipes were replaced with Carbon Steel
4. No on‐site emergency plan .
5. Locating the plant in a densely populated area .
6. Indian government’s acceptance of the plant for political reasons without any safety analysis .
7. The lack of written reference manuals/instructions for the workers’ reference.
8. Data logging of both technical and general activities was not enforced by management.
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17. Disaster Response 16

18. Death rates:
• For the first two days after the disaster, the death rate in some affected areas reached 20 per thousa
nd of population.
• Of the more than 200,000 people exposed to the gas, the death rate exceeded 2,500 after 1 week of t
he accident .
• In November 1989, the Department of Relief and Rehabilitation, Government of Madhya Pradesh, pl
aced the death toll at 3,598, and by 1994 the toll was estimated at 6,000.
Health Effects:
• The exposure of MIC resulted in a severe eye irritation and blindness. Most symptoms included burni
ng sensations of the eyes and throat and coughing.
• The health -care staffs also have no idea of proper medication.
• Unavailability of beds in nearby hospitals in Bhopal
• Estimations showed that born children in Bhopal after the accident face twice the risk of dying as do c
hildren in other areas.
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19. 1. Management System.
2. Location/Site
3. Emergency Plans.
4. Control Building near major hazards.
5. Keeping protective equipment in use.
6. Shouldnot ignore unusual readings.
7. Carrying out hazops on new study.
Lessons : 18

20. 19

21. • Stix G. Bhopal: A Tragedy in Waiting. IEEE Spectrum. 1999.
• CommonDreams“Bhopal: The Hiroshima of the Chemical Industry” WWW URL: http://www.com
mondreams.org/headline/2009/07/12‐3 (November, 2009)
• Methyl Isocyanate. Union Carbide F‐41443A ‐ 7/76. Union Carbide Corporation, New York (1976)
REFERENCES
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