AMA I 1 Conference on Chemical (Industrial) Disaster Management, Pipelines, Storage & Medical...

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AMAI

Conference on Chemical (Industrial) Disaster Management, Pipelines,

Storage & Medical Preparedness February 11-13, 2009, FICCI, New Delhi

Chlorine Production Process Safety

HARISARAN DAS, JOINT DIRECTOR (SHE)ALKALI MANFACTRERS’ ASSOCIATION OF INDA

3RD FLOOR, PANKAJ CHAMBERS, PREET VIHAR COMMERCIAL COMPLEX, VIKAS MARG

NEW DELHI-110092

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AMAI Chlorine is a very useful but

Hazardous Chemical

Chlorine finds versatile application in our daily life starting from drinking water chlorination to sanitation, insecticides, pesticide, agriculture, drugs, pharmaceuticals, automobiles, paper, textiles, plastic and many more.

Chlorine is a very useful & indispensable chemical. Chlorine is also very hazardous & toxic because of

its properties.

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Properties of Chlorine Chlorine is a gas because its boiling points is -340 C which is less

than ambient temperature. Due to low boiling point (-340 C) It rapidly volatilizes when released from storage tanks and Tonners to the atmosphere.

Chlorine is liquefiable under pressure, because its critical temperature is1440 C

Vapour Pressure of chlorine at 550 C: About 16 Bars (absolute) and increases to about 20 Bars (absolute) at 650 C.

Toxic and Corrosive when water / moisture is present due to formation of Hypochlorous acid which further dissociates to Hydrochloric acid and nascent oxygen.

Yellow chlorine Hydrate (Cl2..8 H2O) may crystallize below 9.40 C at atmospheric Pressure and therefore chlorine pipe lines may choke in cold weather.

Chlorine has ill effect on the human health.

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AMAI Physiological effects of various concentrations of

Chlorine Gas on Human Beings.

S.no.

Effects Chlorine Concentration by Volume (ppm)

(1) (2) (3)

i) Least amount required to produce slight symptoms after several hours of exposure

1.0

ii) Least detectable odour 3.5

iii) Maximum amount that may be inhaled for 1 hour without serious disturbances

4.0

iv) Noxiousness, impossible to breathe for several minutes 5.0

v) Least amount required to cause irritation of throat 15.1

vi) Least amount required to cause coughing 30.2

vii) Amount dangerous in 30 minutes to 1 hour 40 to 60

viii) Amount likely to be fatal after few deep breaths 1000.0

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Release of chlorine is usually a flashing (two-phase) jet with small liquid aerosols drops embedded since when liquid chlorine is released, it flashes off more and more and simultaneously expand to vapour creating a turbulence, which causes the remaining liquid to be broken up into an aerosols (small drops) and is carried along with the flashed vapour.

The aerosol usually evaporates within a short period, leaving a cold dense cloud of chlorine gas.

Usually no significant liquid pool is formed under the Chlorine container.

Hazards Associated with Chlorine usage (contd…)

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A liquid pool may form if ambient temperatures are cold and/or the chlorine is semi refrigerated.

For holes with diameters larger than a few mm, the contents of a Tonner are released very fast and thus very less time is available for emergency response.

Develops high hydraulic pressure in overfilled tonners or overfilled bullets or in liquid full pipelines. This hydraulic pressure is sufficient to cause bursting of tonners or bullets or pipelines with 1 to 3 degree C temperature rise.


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AMAI Hazards Associated with Chlorine

usage (contd…)

Chlorine reacts violently with substance such as oils, greases, paints, some solvents etc. it will also react with steel wool, oil filings or pipe cuttings. It is, therefore, essential that foreign material be removed from chlorine lines and containers before allowing chlorine to enter them.

Wet chlorine gas may be handled in Titanium equipment. However, dry chlorine reacts violently with titanium.

Dry Chlorine will react violently with hot steel. For this reason, welding should only be done on Chlorine lines that have been isolated, depressurized and made free from chlorine gas. Welding leads should not be attached to such lines.

Contd…..

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Dry chlorine does not react with steel at normal temperatures. Under these conditions, steel is suitable for handling and storing Cl2.

Chlorine and hydrogen mixture can react violently in equivalent mixture and the rate of reaction increase in presence of oxygen. Ultra violet light can start this reaction.

Methyl Chloroform and other organic solvents should not be used to clean equipment where large amounts of Chlorine and its residues are present.


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We must remember that Chlorine dissipates more rapidly on a warm, windy day than on a cold, calm one.

Causes inhalation health effects at relatively low concentrations.

Vapour pressure increases considerably with increase in Temperature.

Liquid chlorine inside tonner and bullet expands more and more with considerable increase in storage pressure with rise in Temperature.


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Hydrogen is a Co- product in the manufacture of chlorine. Mixture of Hydrogen becomes explosive as per the properties

of mixtures of Hydrogen with chlorine, Hydrogen with air and Hydrogen with oxygen as tabulated.

Chlorine is also explosive with Hydrogen

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The properties of mixtures of Hydrogen with chlorine, Hydrogen with air and Hydrogen with oxygen

Properties of Hydrogen/oxygen mixture

Hydrogen/ Air Hydrogen / Chlorine

Hydrogen / Oxygen

Lower Flammability Limit (LFL)

P=1 bar a, T=20. C

4.0% V/V 3.0% V/V 4.0% V/V

Lower detonation Limit (LDL)

(atmospheric condition)

18.2% V/V 17.5% V/V 9.0% V/V

Ignition (Auto ignition) temperature

5600 C 2070 C

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Chlorine Production & Use in India

Chlorine is a Co-Product in the manufacture of Caustic Soda. Present installed capacity of Caustic Soda in India is around

28 lakh MT and the production is around 22 lakh MT (year 2007-2008) in 36 Plants.

The production facilities are spread through out India. 8 Plants in East Zone, 15 Plants in West Zone, 4 Plants in

North Zone & 9 Plants in South Zone.

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S. No.

Zone No. of Units

Installed Capacity Production

Membrane Mercury Total Membrane Mercury Total

1. EAST 8 185410 171940 357350 136267 128734 265001

2 WEST 15 1283545 10800 1294345 1038296 8572 1046868

3 NORTH 4 409960 0 409960 303958 0 303958

4 SOUTH 9 620700 59400 680100 449012 95492 54404

TOTAL 36 2499615 242140 2741755 1927533 232798 2160331

Chlorine Production & Use in India (contd…)

Installed capacity & Production of Caustic Soda in India

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In India, 91% of the total installed capacities of Caustic Soda/ Chlorine are based on Membrane Cell Technology which is environmental friendly & energy efficient

Balance 9% is based on Mercury Cell Technology. No production is based on Diaphragm Cell Technology Out of 19 Lakh MT of Chlorine Produced approximately 8.5

lakh MT Chlorine was captively used (Year 2007-2008) Approximately 10.5 lakh MT of Chlorine was transported

from manufactures to end users. Chlorine is filled in small containers (900 kgs) & transported

through trucks.


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Sector wise use of Chlorine in India-Vinyls (including PVC) - 18%Organic Chemicals - 20%, Inorganic Chemicals - 23%, Pulp & Paper - 8%,CPW - 11%,Water Treatment - 2.0%,Pesticides/ Insecticides/ Weedicides - 5%, Pharmaceuticals - 0.53%, Dye & Inks - 0.40%, Textiles - 0.60%, Exports - 0.4% Other Uses - 11%.


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AMAI KEY TO ACCIDENT FREE PRODUCTION &

HANDLING OF CHLORINE There is a potential danger during manufacture, storage, filling, transportation and use of chlorine (as discussed) and therefore necessary control & safety measures needs to be adopted.

Key FactorsTechnical Up-gradation and Innovation.Inclusion of all safety & control measures at the plant deign

stage Following safe operating procedures, safe handling and

transport procedures.Training of operating personnel.Training of Drivers and TransportersLearning from Past incidents

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Compliacence to regulation, such as: Gas cylinders Rule, 2004 Static & Mobile Pressure Vessels (Unfired) Rules, 1981

[SMPV (U) Rules, 1981] Factories Act, 1984 Manufacture, storage and import of hazardous chemical

Rules, 1989. The Chemical Accidents (Emergency Planning,

Preparedness and Response) Rules, 1996 The Environment (Protection) Act, 1986 The Public Liability Insurance Act, 1991, amended in

1992 Central Motor Vehicles Rules 1989 (amended 95)

KEY TO ACCIDENT FREE PRODUCTION &

HANDLING OF CHLORINE

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AMAI Caustic Soda/ Chlorine Production Process

(Common to all Technologies) Chlorine is a by product in the manufacture of caustic soda

Technologies used for manufacture of caustic soda / chlorine Mercury Cell Technology Diaphragm Cell Technology Membrane Cell Technology

The Caustic Soda – Chlorine production & process can be sub grouped as:

brine treatment Electrolysis sodium hydroxide production, storage and handling chlorine production, storage and handling waste chlorine gas neutralization and production, storage and

handling of sodium hypochlorite hydrogen production, storage and handling (chlorine filling)

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AMAI Caustic Soda – Chlorine Production

Process (Contd…)

SALT WATER

DISSOLVING

PRICIPITATION

FILTRATION

ION EXCHANGE(Membrane only)

DECHLORINATIONMERC / MEM

ELECTROLYSIS

PURGE

Depleted Brine & Chlorine

CAUSTIC SODA & HYDROGEN

Flow Diagram of Brine Treatment and Electrolysis

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MERCURYY DIAPHRAGM MEMBRANE

47-50% CAUSTICLOW CHLORIDE

9-12% CAUSTICHIGH CHLORIDE

30-33% CAUSTICLOW CHLORIDE

MERCURY REMOVAL EVAPORATION

STORAGE

USERSUSERS

Flow Diagram of Sodium hydroxide Production, Storage and Handling

Caustic Soda – Chlorine Production Process (Contd…)

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LIQUIFICATION

DIAPHRAGM MEMBRANE

COOLING (Ist stage/2nd stage) (400C) (160 C)

DEMISTER

DEMISTER

DRYINGSULPHURIC ACID

COMPRESSION

MERCURY

STORAGE

USERS

Flow Diagram of Chlorine Production, Storage and Handling


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MERCURY DIAPHRAGM

LIQUEFACTION

STORAGE

MEMBRANE

SODIUM HYDROXIDE STORAGE

CHLORINE ABSORPTION

FILLING

SODIUMHYPOCHLORITE

STORAGE

USERS

Chlorine

Chlorine

Chlorine

NaoH

Flow Diagram of Waste Chlorine Neutralization & Production of Bleach Liquor (Sodium Hypochlorite/ Calcium Hypochlorite)


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DIAPHRAGM MEMBRANE

COOLING

DISTRIBUTIONTO USERS

HIGHCOMPRESSION

MERCURY

STORAGE

USERS

COOLING COOLING

Flow Diagram of Hydrogen Production, Storage and Handling


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Control & Safety Measures in chlorine production

Control & Safety Measures in Brine treatment

Pure brine is the heart of Caustic Soda and Chlorine plant operation

In order to maintain control over the brine purification, a number of key process variables, such as brine concentration, (as Nacl,) brine Volume (flow), brine temperature, brine pH, chlorine content in brine, caustic soda concentration in brine, etc. are monitored at different stages of brine treatment.

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To maintain Nacl concentration in brine between 300 to 310 g/I salt crystallization may occur in the cold spots, at higher concentration.

To maintain feed brine temperature so that the products are at temperatures which will not affect materials of construction of electrolysers.

Control & Safety Measures in Brine Treatment Process (Contd….)

CONTROLS ARE PROVIDED / CONTINUOUS MONITORING DONE

Control & Safety Measures in chlorine production (Contd…)

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To maintain pH of the feed brine. No acidic brine should enter the cell.

To maintain brine flow to electrolysers. Low brine flow can lead to excessive temperatures and boiling explosion hazard.

Raw material (salt) Tested to ensure absence of ammonia compounds as presence of ammonia in brine may lead to formation of Nitrogen Trichloride, which is explosive in nature.

Control & Safety Measures in chlorine production (Contd…)

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AMAI Control & Safety Measures in production of

Chlorine (Contd…)

Control & Safety Measures in Operation of Electrolysers

Hydrogen content in chlorine in the cell gas is monitored to avoid formation of explosive mixture of Hydrogen & Chlorine.

Electrolysers are shut off in case of high hydrogen concentration in the cell gas of the electrolysers.

In case of high chorine pressure on the electrolysers, control is provided to switch off and shut down.

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Control & Safety Measures in Operation of Electrolysers (contd..)

In the event of emergency shut down, Chlorine is released to the chlorine absorption unit through emergency relief valves. Emission of chlorine to the atmosphere is prevented.

Formation of combustible & explosive mixture of hydrogen & chlorine in the operation of electrolysers are prevented by suitable Instrument contorl and safe operation procedure.

Air must be excluded from the hydrogen stream so that it can not combine with hydrogen to form an explosive mixture of hydrogen and oxygen.

Control & Safety Measures in production of Chlorine

(Contd…)

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AMAI Control & Safety Measures in

production of Chlorine (Contd…)Safety and control measures in Sodium Hydroxide Production, Storage & Handling

All the caustic tanks are provided with in built facilities to prevent overflow or spillage of caustic soda. Such facilities include containment and mitigation.

It should be noted that hydrogen gas can be released into the vapour space above the liquid in storage tanks. Tanks are normally vented from the highest point.

Testing for an explosive mixture of hydrogen in air normally precedes any maintenance activity in the area.

Storage tanks may be lined to minimize iron contamination of the prouduct and to avoid stress corrosion cracking of the tank.

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AMAI Control & Safety Measure in

production of Chlorine (Contd…)Control & Safety aspects in Chlorine Compression (contd…)

Concentration of the H2SO4 in compressor to be monitored by analysis on daily basis to avoid corrosion. Higher moisture content in chlorine gas (due to inadequate drying) will corrode the chlorine compressor

Sulphuric acid mist is to be removed with glass wool candle filters to avoid chocking in liquefier & pipeline.

Continuous PH monitoring of the chilled water of individual chlorine compressor coolers are to be done to detect any tube leakage. If the tube leakage of chlorine compressor cooler goes unnoticed, it will affect the entire chilled water cycle.

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Control & Safety aspects in Chlorine Compression

Automatic control valves and check valves are to be provided to prevent the back flow of chlorine (in case of compressor tripping) in to the low pressure system.

Chlorine Compressors are fitted with mechanical seal to prevent any leakage of CL2.

Acid temp of the chlorine compressor is to be maintained below 400 C to avoid corrosion.

Control & Safety Measure in production of Chlorine (Contd…)

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AMAI Control & Safety Measure in

production of Chlorine (Contd…)

Control & Safety aspects in Chlorine Cooling, Drying &Liquification

As titanium is used as a tube material for heat exchanger. Dry chlorine reacts violently with titanium. Back flow preventor is provided to prevent contact of Dry Chlorine with titaniunm.

Careful control with adequate failure warning, of the gas temperature from the second coolers is provided to prevent the formation of solid chlorine hydrate (9.60 C.). The chlorine hydrate formation may completely plug the heat exchanger or gas piping which will create a big hazard in the cell room.

Contd……

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Control & Safety aspects in Chlorine Cooling, Drying &Liquification Facilities for periodic or continuous washing of the demisters provided to prevent excess salt crystallization due to carryover from the cell room. This can lead to high pressure drops and stoppage of gas flow. To take care of high temp of Cl2 before cooling, the FRP line between electrolysers to chlorine cooler should be of proper quality (Alpolite (797) resin instead of Atlac 382 (Bis-phenol resin) Hydrogen is continuously monitored in the sniff gas to maintain below the explosive limit. (less than 4%) Make sure that refrigerant used for liquefaction does not react with Cl2 if there is a leak


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Control & Safety aspects in Chlorine Cooling, Drying &Liquification (Contd..)

Under pressure safety seal is to be provided in the system. Alignment of the compressor & motor should be proper as vibration

damages seals and results gas/ acid leakage. Provision to run the compressor with closed discharge valves in case

of startup/ stoppage/ maintenance (local by pass valve). Centrifugal compressor leads to unstable operation at high pressure

and low volume. It can also occurs at low chlorine density. This results surging. Speed control/ by pass control is required to ensure stable operation.

Initiations for trips of the chlorine compressors are provide, In case of abnormal chlorine temperature, chlorine pressure, oil pressures shaft vibration & axial movements etc. since the chlorine is at the peak pressure level at the compression stage. Contd…..


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The chlorine gas having moisture less than 150 ppm by volume of water is considered to be dry chlorine.

Concentrated sulphuric (98%) has to be dosed continuously to ensure proper drying. Maintain outlet concentration (of chlorine drying Tower ) at 78% (Min)

The use of H2SO4 requires specific attention. Velocities must be kept low at 1 m/sec to prevent excessive erosive wear. Due to corrosive nature of dilute H2SO4, seals or rotating parts rapidly deteriorates.

Contd..

Control & Safety Measure in Production of Chlorine (Contd…)

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AMAI


Flange guards to be provided on H2SO4 pipe lines to avoid splashing of H2SO4.( saturated with Chlorine)

Hot work permit to be issued for maintenance work on dilute sulfuric acid containing vessels/ pipe lines etc. since H2 generates in dilute H2SO4 system can lead to explosion with hot work. Such systems containing dilute sulfuric acid are to be washed & dried before undertaking maintenance work

Re use the chlorine condensate generated in the chlorine cooling.


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The moisture content in Cl2 gas after drying has to be detected by on line measurement Instrument/ or by Analysis to ensure chlorine gas dryness since wet chlorine is corrosive.

Instrumentation to monitor acid flow, acid concentration, acid temperature, for detection of restriction of flow with in the drying system.

Chlorine outlet from the drying tower should be at the top or immediately in line with the top portion to avoid accumulation of hydrogen at the top to avoid explosion due to electrostatic charge.


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Control & Safety Measures during Production of Liquid Chlorine

An important control parameter is moisture content in dried chlorine in relation to the materials of construction as wet chlorine is highly corrosive. The moisture content is measured before liquefaction.

Care needs to be taken about nitrogen trichloride (NCI3) as it is explosive. Procedures for maintaining levels of NCI3 below the explosive limit is available.

In addition, care needs to be taken to avoid high temperatures which could lead to a chlorine / iron reaction.


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AMAI Safety & Control Measures in Chlorine

Storage and chlorine filling (contd…) Design aspects and Material of Construction of chlorine

storage Tanks. Liquid chlorine is generally stored in horizontal pressure

vessels. Adequate distance between two storage tanks is to be

maintained. Chlorine storage tanks to be located away from hazardous

processes or storage with potential fire/explosion risk to minimize risk of damage.

Dyke wall and impervious flooring with 1:100 slope are to be provided in the storage area.

Tanks are to be designed as per IS 2825. Design pressure for chlorine storage tonner is 19.9 kg/

cm2 at 650 C.

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Corrosion allowance of 3 mm is to be provided. 100% stress relieved and X-rayed. Material of Construction (MOC) of chlorine storage

Tanks is low temperature carbon steel SA 516 grade 60/70 (-350 C to 550 C).

Valves are of forged carbon steel, spindle of monel metal or SS 316 and bellows are of hastalloy C 276.

Pressure Gauges with Haste alloy C diaphragm, Haste alloy C/ SS316 dip pipe.

Bolts, nuts & studs of proper MOC is used. Stud- 320 L7_, ( Nut – A194 grade -4)

Safety & Control Measures in Chlorine Storage and chlorine filling (contd…)

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Control & Safety measures for storage of liquid chlorine (contd…) Provide Low and high level alarm, 20% low & 80% high. Provide High & low pressure alarm, 2.5 Kg/ cm2 low and

11.5 Kg/ cm2. Provide Temperature alarm -150 C low and 300 C high. Provide Double Rupture disc, 13.5 Kg/ cm2. Provide Double Safety valve which opens at 13.0 Kg /cm2

& closes at 12.7 Kg/ cm2.

Safety & Control Measures in Chlorine Storage and chlorine filling (contd..)

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Control & Safety measures for storage of liquid chlorine (contd…) Provide Double valve of international standards quality of

each line. Provide Remote type valve in liquid chlorine line. Always one tank is to be kept empty for emergency

transfer of liquid chlorine. Connection of the emergency release line with the

neutralize system. Provide adequate number of CI2 detector in the storage

area.


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Control & Safety measures for storage of liquid chlorine (contd…) Transfer of liquid CI2 to empty tank. Time for transfer – 2

hrs by compressed dry air at 10.8 Kg cm2. Tank volume – 100 NM3.

Foam is used to contain chlorine, leakage. Chilled water below 100C can be used to control liquid

CI2 spillage. Liquefied gas pool can also be controlled by covering

with a large sheet of poly ethylene. Vapor evaporating from pool below the cover can be withdrawn by large bore hose to a neutralization system with on line connected vacuum hose.

Provision for Neutralization of chlorine with caustic soda (3 stage system).


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Prevent passage of liquid chlorine into drainage system/ effluent.

Dyke wall kept dry during rainy season. To avoid percolation, a steep slope is provided leading to a

sump with provision of small pumps or airlifts for recovery.

Provision for prevention of free access of wind and airflows to pool area.

The storage tanks may be fitted inside a close room with emergency exhaust blower. Which is connected to neutralization system.

Provide high capacity blowers in the storage and bottling area connected to the neutralizing system.


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SAFETY MESAURES FOR CHLORINE STORAGE TANKS

REQUIREMETNT UNDER SMPV – RULE 1981 License under SMPV Rules must be obtained by the

producers. Level or weight, pressure and temperature indicator will

be provided on each chlorine storage tank with proper alarm system.

Provision for release of excess pressure with rupture disc will be provided at chlorine storage tanks.

It will be provided with safety valve and safety valve will be connected to Hypo System. Pressure indication between rupture disc and safety valve will be given to detect any damage in rupture disc. Alternately, two Nos. Safety Relief Valves to be provided on each storage tank.

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REQUIREMETNT UNDER SMPV – RULE 1981 Provision of emergency suction hose for evacuation of

chlorine leakage to hypo system will be provided. Provision of On – line Breathing Apparatus and Self

contained Breathing Apparatus at different locations for emergency operation will be available at storage site.

Dew point of padding air will be monitored. Dew point should not be more than -450 C

Emergency Response Plan for Chlorine leakage is to be developed as per statutory guide lines and to be made operational.

The operation will be done by trained and experienced persons.

SAFETY MESAURES FOR CHLORINE STORAGE TANKS

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AMAI Safety & Control Measures in the Waste Chlorine

Neutralize (Sodium Hypochlorite Production, Storage, Handling)

The control parameters used in the chlorine neutralization process are generally redox monitoring and temperature measurement to ensure that the absorption capacity exists at all times, that the solution is not saturated with chlorine, and that the formation of salt does not occur in the reaction, beyond a manageable concentration.

Temperature monitoring ensures that the controlled heat exchange process is functioning at all times.

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