1

Internship Report on

"Global Heavy Chemicals Limited"

Submitted to:

Dr. Sayem Ahmed (PhD)

Head of Human Resources

Opsonin Pharma Limited

Submitted by:

Md Mahdi Salehin Feroze

Student ID - 260549713

Department of Chemical Engineering

McGill University

Date of Submission: 9 August 2014

2

Acknowledgement

At first, I would like to express my humble gratitude towards my Creator for the blessings He

has bestowed upon me. Next I would like to thank Dr. Sayem Ahmed (PhD), Head of HR,

Opsonin Pharma Limited for giving me the opportunity to pursue this internship at Global

Heavy Chemicals Limited, Hasnabad, Keranigonj, Dhaka despite of my inexperience and

shortcomings. I would like to pass my gratitude to Mr. Ahadur Rahman, Asst. Manager,

Corporate HR at Opsonin Group for his continued support throughout my internship period. I

am highly indebted to Muhammad Masudur Rahman, Deputy Manager, Production, GHCL

for watching over me during my short stint at the factory. I would like to thank all production

executives working at the DCS Control Unit of GHCL specially Shaikat Sumit, Executive -

Production, GHCL ; Yugesh Das, Executive - Production, GHCL for mentoring me. I am also

grateful to all the operators and workers of GHCL for helping me when I needed to learn

something. Lastly, nothing could have been possible without the help of my family. Thank you

all.

3

Description of the Process Raw Material

The raw material used is in this plant is a solid salt bought from India. The composition of the

salt is -

Ingredient Percentage

Ca2+ 0.227%

Mg2+ 0.049%

SO42- 0.645%

Total Iron 13.2 ppm

NaCl 95.43%

Moisture 3.649%

The composition of this salt is better than that of the salt available in Bangladesh.

There are 2 identical plants in total; situated side by side. The equipments described below are

for one plant only.

Salt Washer Unit

There is a fully automated Salt Washer Unit to purify the imported salt. Initially, the raw salt

is put into the hopper by a pay loader. A bucket elevator pulls it up into the screw conveyer.

The salt is then dissolved in a Salt Saturator and saturated brine is obtained. This saturated

brine is then passed through a plate filter to remove floating substances and impurities that

come from the salt feeding. Then the solution is fed into the dosing unit.

(In the salt saturator, there is a continuous process pumping of return brine solution at about

85oC from the Return Brine Tank which is extracted from the cell. This brine solution was not

converted into Caustic Soda.

Also, the impurities that come from the salt gather at the bottom of the salt saturator and thus

decrease the efficiency of the salt saturator. The saturator needs to be cleaned after 3-4 months

for this reason.)

Dosing

To remove the impurities, chemical dosing is done. For example, BaCl2 is dosed to remove the

SO42-. In GHCL, 5 different dosing is performed and they are -

1. Soda Ash(Na2CO3) dosing

4

2. Barium Chloride(BaCl2) dosing

3. Sodium Sulphite(Na2SO3) dosing

4. Caustic Soda(NaOH) dosing

5. Flocculants dosing

Calculation of Chemical Dosing:

Ca2+ in raw materials = 6385.774 𝑘𝑔 𝑠𝑎𝑙𝑡

ℎ𝑟∗

0.227 𝑘𝑔 𝐶𝑎2+

100 𝑘𝑔 𝑠𝑎𝑙𝑡

= 14.49 kg/hr

For removing Ca2+, Na2CO3 needed:

CaCl2 + Na2CO3 = CaCO3 + 2NaCl

Na2CO3 needed = 106∗14.49 𝑘𝑔

111 ℎ𝑟

= 13.83 kg/hr

Amount of Mg2+ = 6385.774 𝑘𝑔 𝑠𝑎𝑙𝑡

ℎ𝑟∗

0.049 𝑘𝑔 𝑀𝑔2+

100 𝑘𝑔 𝑠𝑎𝑙𝑡

= 3.129 kg/hr

NaOH needed for removing Mg2+:

MgCl2 + 2NaOH = 2NaCl + Mg(OH)2

NaOH needed = 80∗3.129 𝑘𝑔

95 ℎ𝑟

= 2.634 kg/hr

Amount of SO42- =

6385.774 𝑘𝑔 𝑠𝑎𝑙𝑡

ℎ𝑟∗

0.645 𝑘𝑔 𝑆𝑂42−

100 𝑘𝑔 𝑠𝑎𝑙𝑡

= 41.18 kg/hr

BaCl2 needed for removing SO42-:

Na2SO4 + BaCl2 = 2NaCl + BaSO4

5

BaCl2 needed = 208∗41.18 𝑘𝑔

142 ℎ𝑟

= 60.32 kg/hr

Procedure of making Dosing:

1. Barium Chloride (BaCl2):

Desired concentration- 0.15% by weight

Required composition:

1. 475 kg BaCl2

2. 2000-2500 Liter H2O

3. 500 kg HCl

Chemical Reaction:

BaCO3+HCl = BaCl2 + CO2 + H2O

In this reaction pH of HCl is 3.5 to 4 but pH should be maintained at level 6. This is done by

adding 10 to 12 kg excess NaOH.

2. Soda Ash (Na2CO3):

Desired concentration-0.14%

Required composition:

1. Soda Ash (Na2CO3)

2. 1400 liter H2O

3. Flocculent:

Required composition:

1. 500 gm floccal

2. 1000 liter H2O

Chemical Reaction:

500gm floccal+1000L H2O

6

Main function of flocculent is to hold up the moisture.

4. Sodium Sulphite (Na2SO3):

Desired concentration- 7% by weight.

Required composition:

1. 100L Na2SO3

2. 200L H2O

Reactor:

Reactor used in GHCL is mainly a CSTR. In this reactor the following reaction occurs:

Na2SO4 + BaCl2 → NaCl + BaSO4 ↓

Na2CO3 + Ca2+ → CaCO3 ↓ + 2 Na2+

2 NaOH + Mg2+ → Mg(OH)3 ↓

After the mixing of the brine and dosing solution is complete, a flocculent named Megna floc

is added to the solution. Then the solution is sent to the clarifier in order to remove the

precipitate of the solution and also to increase the turbidity of the solution.

In reactor concentration range of brine is 310-315gpl and is continuously monitored by a

Hydrometer. Reactor temperature is 60-65oC and is continuously monitored by a Thermometer.

Clarifier:

In the clarifier, mud (carried by the saturated brine solution) which was produced from the

dosing is precipitated at the bottom of the clarifier. From the bottom of the clarifier, the thick

mud solution of the saturated brine is pumped into the decanter. Mud is separated and collected

for disposal as waste product. The brine solution driven from the clarifier is stored in the

Clarified Brine Tank and then is sent to Anthracite Filter for further removal of floc particles.

Anthracite filter:

Filter medium of the Anthracite Filter is mainly the anthracite. In Anthracite Filter, solid-solid

adsorption occurs. Three types of carbon: large, small and medium lies in the anthracite filter.

When the brine solution is passed through the fine anthracite filter medium, the floc particles

cannot pass through the medium and get trapped in the anthracite medium. Then the solution

is stored in the anthracite filter tank to make the process continuous.

7

The solution is then sent to the Filtered Brine Tank, only later to be sent to the Candle Filters.

Candle filter:

Candle filter is a special type of filter in which the filter medium is activated carbon and the

filter aid is the alpha cellulose. This alpha cellulose blocks the micro level particles from the

brine solution. To maintain the layer of the alpha cellulose (which is externally exerted in the

upper surface of the activated carbon filter) 1-2 atmospheric pressure is maintained

continuously. If the pressure drops, there will be no alpha cellulose layer above the activated

carbon filter. To maintain the efficiency of the filter aid, alpha cellulose is continuously added

in the candle filter. Brine solution is fed at the bottom of the filter and mud free solution comes

out from the top of the filter. After filtering in the candle filter the turbidity becomes -3 or -4

and brine solution is therefore 3 to 4 times transparent than water.

The candle of the alpha cellulose is washed by using the back flow of the air. The new alpha

cellulose is added from the pre-coat tank.

Ion Exchanger:

In the ion-exchanger, multivalent ions are exchanged with the Iminodiacetic acid of ion

exchange resin. But sodium is a monovalent ion so it is not exchanged with this resin. Na+ ion

is replaced by Ca2+ and Mg2+. The resin used in ion-exchanger passes only Na+ and as it is a

cation exchanger, Na+ and Cl- enter into cell house. The Iminodiacetic acid formula is as

follows:

HN (CH2CO2H)2

Resin can work very well when its efficiency is high or moderate. When the concentration of

Ca2+ is less than 10 ppm and concentration of Mg2+ is 2-3 ppb the bed needs to be regenerated.

The regeneration process is as follows:

Wash 1:

At first the resin bed is washed by demineralised (DM) water at constant flow rate of 1600

L/hr and is continued for 1 hour. By this time, all ash and dust get washed.

Back wash:

Back wash is done by DM water at a flow rate of 1.6m3/hr for over 30 minutes. DM water is

supplied from the bottom of the tower and resin gets circulated with the tower. Water flow is

maintained at a constant rate so that resin does not overflow. After ensuring that all brine has

washed away, back wash is completed.

8

HCl regeneration:

18% concentrated HCl is then supplied at 600L/hr flow rate for over 30 to 50 minutes. By

adding DM water at the rate of 1000L/hr, 5% concentrated HCl is made. When the pH of HCl

becomes 1, HCl supply is stopped. During HCl regeneration, Na of Iminodiacetic acid gets

replaced by Cl2 and the media becomes acidic.

Wash-2:

To remove the acidic media again DM water is supplied at a flow rate of 1600L/hr for over 1

hour. Consequently all Cl2 is replaced by H+ ion of water.

NaOH regeneration:

Then 32% NaOH is passed through the bed at a rate of 200L/hr with DM water of rate

1400L/hr for over 40 to 50 minutes. As a result, COOH of Iminodiacetic acid is converted to

COONa and resin regeneration is completed.

Wash-3:

Again the bed is washed by DM water at a flow rate of 1600L/h for over 1 hour to maintain

the pH level 10. When pH 10 is obtained, water supply is stopped.

Brine filler:

Next the resin bed is filled up by 30% NaCl at 1.8m3/h flow rate for over 1 hour.

Brine feed:

At last feed brine is fed into the ion-exchange column as the bed is fully regenerated and

ready to use with 100% efficiency.

9

Cell House:

Membrane technology used in GHCL is a unique Single Element, which comprises an anode

half shell, a cathode half shell and an individual sealing system with external flanges. The

Single Elements are suspended in a frame and are pressed against each other by a clamping

device to form a "Bipolar stack”. Each Single Element can be replaced quickly and easily. The

elements are assembled in the Electrolyser workshop, where tightness tests are also carried out.

Exit Brine + Cl2(g) Exit Caustic(32%)+H2(g)

Feed Brine(30%) Feed Caustic(28%)

Figure: Cell House.

Important Features of the Membrane:

Perfluro Sulphonate Polymer act as a anode coating.

Perfluro Carboxylate Polymer act as a cathode coating.

High caustic flow is maintained as coating cannot attach with the membrane body.

Hence chlorine is a heavy gas so it gets pulled from the separator by a compressor.

This membrane is only permeable to Na+ ion.

This membrane is imported from Asai Kasai Company Japan.

Basic cell reaction:

Anode: 2Cl- - 2e- Cl2

Cathode: 2H+ + 2e- H2

Anode(Ti) Na+ Cl-

Cathode(Ni) H+

OH-

10

Figure: Assembling parts of a single cell.

All this ensures:

• Highest possible operational reliability.

• Easy maintenance.

• Timely cost-optimized membrane replacement and electrode recoating.

• No additional investments needed for back-up electrolysers.

• Minimal loss of production.

Chlorine production, storage and handling:

Generally, Chlorine production and storage are comprised of four basic section. These are

follows:

1. Drying section

2. Compression section

3. Liquefaction section

4. Storage

11

The excess chlorine gas generated at the cell house is sent to Chlorine Unit. Chlorine gas

leaving the electrolyser is at approximately 80-90ºC and saturated with water vapour. It also

contains brine mist, impurities such as N2, H2, O2, CO2 and traces of chlorinated hydrocarbons.

Electrolysers are operated at essentially atmospheric pressure with only a few milli-

atmospheres differential pressure between the Anolyte and the Catholyte.

Short description of the sections are as follows -

Drying section:

Drying of chlorine is carried out exclusively with 78% concentrated Sulphuric Acid. Drying is

accomplished in counter-current Sulphuric Acid contact towers. H2SO4 acts as a adsorber and

it adsorbs almost all moisture present in chlorine. 98% H2SO4 is charged from the top side of

the tower which always keeps the downward pressure constant. Dry chlorine leaving the top of

the drying tower passes through highly efficient demisters to prevent the entrainment of

Sulphuric Acid droplets. 78% H2SO4 gets out at the bottom of the tower and is continuously

collected at the jar.

Compression section:

After drying, chlorine gas is scrubbed with liquid chlorine or treated with ultra violet irradiation

to reduce levels of nitrogen trichloride. The dry chlorine is compressed in a centrifugal

compressor to maintain the outlet pressure at 8 bar.

Liquefaction section:

Liquefaction can be accomplished at different pressure and temperature levels, at ambient

temperature and high pressure (for example 18 ºC and 7-12 bar), at low temperature and low

pressure (for example -35 ºC and 1 bar) or any other intermediate combination of temperature

and pressure in a reciprocating compressor. Freon-22 is used as refrigerator. After liquefaction,

gaseous chlorine is converted to liquid chlorine and liquid Freon is converted to gaseous Freon.

Storage section:

Liquid chlorine gas is then sent to storage tank at 8 bar in four tank. Four tank is assembled so

that one is in production, one is in storage, one is in cleaning and other is in delivery.

12

Process Block Diagram

13

Material Balance

Overall material balance:

Area of a cell = 2.9 m2

= 2.9 * (100 cm)2

= 29000 cm2

Current density = 0.4 A/cm2

Total current needed for one cell = 0.4 𝐴

𝑐𝑚2 * 29000 cm2

= 11600 A

= 11.6 kA

From faraday’s law

1 F ≡ 1 mole NaOH

40 gm NaOH ≡ 96500 C

1 gm NaOH ≡ 96500

40 C

100 MT NaOH ≡ 96500∗100∗1000∗1000

40 C

= 2.4125 * 1011 C

From Faraday’s first law of electrolysis,

Q = It

I = 𝑄

𝑡

= 2.4125∗1011

24∗3600 A

= 2792245.37 A

= 2792.25 kA

So total cell needed for 100 MT NaOH plant

= 2792.25

11.6

= 240

14

Capacity of the plant = 100 MT NaOH/day

= 100∗1000 𝑘𝑔

24 ℎ𝑟

= 4166.67 kg/hr

= 104.17 kmol/hr

The principle chemical reaction is

2NaCl + H2O = 2NaOH + H2 + Cl2

Flow rate at Anode side:

From the reaction

1 kmol/hr NaOH ≡ 1 kmol/hr NaCl

104.17 kmol/hr NaOH ≡ 104.17 kmol/hr NaCl

At 600C temperature specific gravity of 30% NaCl = 1.2

And density ρ = 1.2 * 103 𝑘𝑔

𝑚3

NaClin = 1.2∗103𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

𝑚3 ∗0.3 𝑘𝑔 𝑁𝑎𝐶𝑙

1 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

= 360 kg NaCl/m3 solution

= 6.154 kmol/m3 solution

At 850C temperature specific gravity of 20% NaCl = 1.111375

And density ρ = 1.111375 * 103 𝑘𝑔

𝑚3

NaClout = 1.111375∗103𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

𝑚3 ∗0.2 𝑘𝑔 𝑁𝑎𝐶𝑙

1 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

= 222.275 kg NaCl/m3 solution

= 3.8 kmol/m3 solution

NaClin - NaClout = (6.154- 3.8) kmol/m3

= 2.354 kmol/m3

15

Flow rate in anode side = 104.167 𝑘𝑚𝑜𝑙

ℎ𝑟∗

𝑚3

2.354 𝑘𝑚𝑜𝑙

= 44.25 m3/hr

Material balance at Anode side:

NaClin = 1.2∗103𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

𝑚3∗

0.3 𝑘𝑔 𝑁𝑎𝐶𝑙

1 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 *

44.25 𝑚3

ℎ𝑟

= 15930.72 kg/hr

= 272.32 kmol/hr

NaClout = NaClin – NaClconsumption

= (272.32 – 104.17) 𝑘𝑚𝑜𝑙

ℎ𝑟

= 168.15 𝑘𝑚𝑜𝑙

ℎ𝑟

= 9836.775 𝑘𝑔

ℎ𝑟

H2Oin = 15930.72 kg NaCl

ℎ𝑟∗

0.7 𝑘𝑔 H2O

0.3 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

= 37171.68 𝑘𝑔𝐻2𝑂

ℎ𝑟

= 2065.09 𝑘𝑚𝑜𝑙𝐻2𝑂

ℎ𝑟

H2Oout = H2Oin

= 2065.09 kmolH2O/hr

Production of Cl2:

From reaction, Cl2produce = 1

2 * (104.16 kmol NaOH/hr)

= 52.08 kmol/hr

= 3697.68 kg/hr

16

Flow rate of Cathode side:

for 28% NaOH at 600C ρ = 1.284 * 103 kg/m3

NaOHin =1.284∗103 𝑘𝑔

𝑚3 ∗0.28 𝑘𝑔 𝑁𝑎𝑂𝐻

1 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛∗

1 𝑘𝑚𝑜𝑙

40 𝑘𝑔 𝑁𝑎𝑂𝐻

= 8.988 kmol NaOH/m3 solution

for 32% NaOH at 850C ρ = 1.3097 * 103 kg/m3

NaOHout = 1.3097∗103 𝑘𝑔

𝑚3 ∗0.32 𝑘𝑔 𝑁𝑎𝑂𝐻

1 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛∗

1 𝑘𝑚𝑜𝑙

40 𝑘𝑔 𝑁𝑎𝑂𝐻

= 10.4776 kmol NaOH/m3 solution

NaOHproduced = NaOHin - NaOHout

= (10.4776 – 8.988) kmol/ m3

= 1.4896 kmol/ m3

Flow rate of cathode side = 104.16 𝑘𝑚𝑜𝑙

ℎ𝑟∗

𝑚3

1.4896 𝑘𝑚𝑜𝑙

= 69.92 m3/hr

Material balance at Cathode side:

NaOHin = 1.284∗103 𝑘𝑔

𝑚3 ∗ 0.28 𝑘𝑔 𝑁𝑎𝑂𝐻

1 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛∗

1 𝑘𝑚𝑜𝑙

40 𝑘𝑔 𝑁𝑎𝑂𝐻 * 69.92 m3/hr

= 628.84 kmol/hr

= 25153.6 kg/hr

NaOHout = NaOHin + NaOHproduced

= (628.84 + 104.16) kmol/hr

= 733 kmol/hr

= 29320 kg/hr

H2Oin = 25153.6 kg NaOH

ℎ𝑟∗

0.72 𝑘𝑔 H2O

0.28 𝑘𝑔 𝑁𝑎𝑂𝐻

= 64680.68 kg H2O/hr

= 3593.37 kmol/hr

17

H2Oout = H2O in

= 3593.37 kmol/hr

H2 produced = 1

2 * NaOH kmol/hr

= 1

2 * 733 kmol/hr

= 366.5 kmol/hr

= 733 kg/hr

NaCl needed = (15930.72 – 9836.775) kg/hr

= 6093.945 kg/hr

So raw salt needed = 6093.945 kg

ℎ𝑟∗

100 𝑘𝑔 𝑟𝑎𝑤 𝑠𝑎𝑙𝑡

95.43 𝑘𝑔 𝑁𝑎𝐶𝑙

= 6385.774 kg raw salt/hr

Table: Material Balance at a glance

Anode in m3/hr Kmol/hr Kg/hr

NaCl 44.25 272.32 15930.72

H2O 2065.09 37171.68

Anode out NaCl 168.15 9836.775

H2O 2065.09 37171.68

Cl2 52.08 3697.68

Cathode in NaOH 69.92 619.63 24785.35

H2O 3593.37 64680.68

Cathode out NaOH 733 29320

H2O 3593.37 64680.68

H2 366.5 733

18

HAZOP Analysis

The hazard and operability study, commonly referred to as the HAZOP study is a systematic

approach for identifying all plant or equipment hazards and operability problems. In this

technique all segments are carefully examined and all possible deviations from normal

operating conditions are identified.

Hazard assessment is a vital tool in loss prevention throughout the life of a facility. A through

hazard and risk assessment of a new facility is essential during the final design stage.

A hazard assessment during the prestart-up period should be a final check rather than an initial

assessment.

The major hazards usually include toxicity, fire, and explosions. However various

environmental concerns like thermal radiation also need to be considered.

Hazard in a Chlor-Alkali Industry:

1. Chlorine Hazard:

A. Hazards associated with breathing of Chlorine:

Chlorine is a severe nose, throat and upper respiratory tract irritant. People exposed to chlorine,

even for a short period of time, can develop a tolerance to its odour and irritating properties.

Concentrations of 1 to 2 ppm produce significant irritation and coughing, minor difficulty in

breathing and headache. Concentrations of 1 to 4 ppm are considered unbearable. Severe

respiratory tract damage including bronchitis and pulmonary edema (a potentially fatal

accumulation of fluid in the lungs) have been observed after even relatively low, brief

exposures (estimates range from 15 to 60 ppm). However, long-term respiratory system

disorder and lung disorder have also been observed following severe short-term exposures to

chlorine.

B. Hazard associated when Chlorine comes into contact with skin:

Direct contact with liquefied gas escaping from its pressurized cylinder can cause frostbite.

Symptoms of mild frostbite include numbness, prickling and itching in the affected area. The

skin may become waxy white or yellow. Blistering, tissue death and gangrene may also develop

in severe cases. In addition, the airborne gas may irritate and burn the skin.

19

C. Hazard associated when Chlorine hurt eyes:

Chlorine gas is a severe eye irritant. Stinging, a burning sensation, rapid blinking, redness and

watering of the eyes have been observed at concentrations of 1 ppm and higher.

Health effects of exposure to Chlorine:

Despite design limitations, the small number of human population studies conducted have not

shown significant respiratory system effects in workers with long-term, low-level (typically

less than 1 ppm) chlorine exposure and 1.42 ppm (0.15 ppm average) for an average exposure.

Chlorine workers reported a higher incidence of tooth decay (based on medical history).

First Aid Measures:

Inhalation: Remove to fresh air. Get medical attention for any breathing difficulty.

Ingestion: If large amounts were swallowed, give water to drink and get medical advice.

Skin Contact: Wash exposed area with soap and water. Get medical advice if irritation

develops.

Eye Contact: Immediately flush eyes with plenty of water for at least 15 minutes, lifting upper

and lower eyelids occasionally. Get medical attention if irritation persists.

2. Bleaching Hazard:

Chlorine bleach contains chlorine, a toxic gas, combined with sodium and oxygen as sodium

hypochlorite. Hazards arise when the chlorine is released from this bond. The U.S. Food and

Drug Administration reports that chlorine bleach is also a common food tampering adulterant.

A. Gastrointestinal Damage

Excluding deliberate beverage tampering, accidental ingestion is relatively unlikely because

this strong-smelling, caustic liquid induces the gag reflex. However, when it is swallowed,

bleach causes corrosive damage to the throat and stomach linings. At domestic concentrations,

severe tissue damage or systemic poisoning are unlikely. Both toxicity levels and causticity are

more hazardous in industrial-strength bleach products.

20

B. Skin Damage

Undiluted bleach is corrosive. Even domestic bleach damages skin tissues and removes

essential fats. During extended contact, small amounts of toxic chlorine may enter the body

through the skin. Industrial bleach carries a much greater corrosive hazard, and protective

clothing and eye protection are required.

C. Lung Damage

It is relatively easy to accidentally mix bleach, used in cleaning, with other cleaning products.

Mixing bleach with ammonia is particularly hazardous, releasing chlorine gas, ammonia gas

and chloramines.

These gases are caustic and irritating, and inhalation damages the lungs and nasal passages.

Exposure to high concentrations of ammonia gas for longer than 15 to 30 minutes can lead to

irreversible damage, even death. As chlorine gas is water-soluble, it forms hydrochloric or

hypochlorous acid upon meeting moisture in the mucus membranes, eyes and mouth. In the

lungs, acid damage results in pulmonary edema (release of fluid into the tissues), causing

breathing difficulties. Chloramines cause similar breathing difficulties and irritation to the eyes,

nose, throat and skin. These are the compounds that cause irritation in swimming pools.

D. Explosion

More likely to occur in an industrial than a domestic setting, ammonia mixed with bleach in

higher proportion may form nitrogen trichloride or hydrazine, both of which are explosive.

Exposure to hydrazine causes burning pain in the eyes, nose and throat.