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Gujarat Clea CLEA OP CAUSTIC S aner Production Centre – ENVIS CENTRE ANER PRODUCTION PPURTUNITIES IN SODA /CHLOR-ALKA INDUSTRIES 1 ALI

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Gujarat Cleaner Production Centre

CLEANER PRODUCTION

OPPURTUNITIES

CAUSTIC SODA /CHLOR

Gujarat Cleaner Production Centre – ENVIS CENTRE

CLEANER PRODUCTION

OPPURTUNITIES

IN

CAUSTIC SODA /CHLOR-ALKALI

INDUSTRIES

1

ALKALI

Gujarat Cleaner Production Centre

Introduction to Caustic soda / Chlor Alkali Industry

The Chlor-Alkali industry in India forms an important component of basic chemicals industry,

comprising around 74% of the basic chemicals production in India. Caustic soda, soda ash,

chlorine alongside hydrogen and hydrochloric acid comprise the

components. These chemicals find their applications in a number of industries such as textiles,

chemicals, paper, PVC, water treatment, alumina, soaps & detergents, glass, chlorinated paraffin

wax, among others. The demand for the two sub

increased significantly registering a

respectively, over the past five years.

The Chlor-Alkali Industry in the country produces mainly Caustic Soda, Chlorine and Soda Ash.

The products of the industry are of vital importance and their uses are:

a) Caustic Soda

• Soaps and Detergent Industry

• Pulp and Paper Industry

• Textile Processing Industry

• Aluminum Smelting

• Dyes and Dyestuff Industry

• Plastic Polymers

• Rayon Grade Pulp

• Pharmaceuticals

• Electroplating

• Adhesives/Additives.

b) Chlorine, By-product of Caustic Soda Industry is very important for manufacturing of

PVC, one of the five major Thermoplastic Commodity Plastics. Besides this, it is used in

disinfection of drinking water, pharmaceutic

industries. Because of the strong oxidizing properties of Chlorine, it is effectively used to

control bacteria and viruses in drinking water that can cause devastating illness such as

Cholera. Use of Chlorine is very

of floods. 85% of the pharmaceuticals rely on Chlorine Chemistry including medicines

that treat heart disease, cancer, AIDS and many other life threatening diseases. Chlorine

tablets are also used by public health workers in rural areas.

c) Soda Ash is used in Glass Industry, Soaps & Detergents, Silicates and various other

Chemical Industries.

Gujarat Cleaner Production Centre – ENVIS CENTRE

Caustic soda / Chlor Alkali Industry

lkali industry in India forms an important component of basic chemicals industry,

comprising around 74% of the basic chemicals production in India. Caustic soda, soda ash,

chlorine alongside hydrogen and hydrochloric acid comprise the Chlor-alkali industry

components. These chemicals find their applications in a number of industries such as textiles,

chemicals, paper, PVC, water treatment, alumina, soaps & detergents, glass, chlorinated paraffin

wax, among others. The demand for the two sub-segments – caustic soda & soda ash, has

increased significantly registering a compound annual growth rate (CAGR) of 5.6% and 4.7%

respectively, over the past five years.

Alkali Industry in the country produces mainly Caustic Soda, Chlorine and Soda Ash.

oducts of the industry are of vital importance and their uses are:-

Soaps and Detergent Industry

Pulp and Paper Industry

Textile Processing Industry

Dyes and Dyestuff Industry

Adhesives/Additives.

product of Caustic Soda Industry is very important for manufacturing of

PVC, one of the five major Thermoplastic Commodity Plastics. Besides this, it is used in

disinfection of drinking water, pharmaceutical industry and various other chemical

industries. Because of the strong oxidizing properties of Chlorine, it is effectively used to

control bacteria and viruses in drinking water that can cause devastating illness such as

Cholera. Use of Chlorine is very important for the Countries like India especially in case

of floods. 85% of the pharmaceuticals rely on Chlorine Chemistry including medicines

that treat heart disease, cancer, AIDS and many other life threatening diseases. Chlorine

by public health workers in rural areas.

is used in Glass Industry, Soaps & Detergents, Silicates and various other

2

lkali industry in India forms an important component of basic chemicals industry,

comprising around 74% of the basic chemicals production in India. Caustic soda, soda ash,

alkali industry’s

components. These chemicals find their applications in a number of industries such as textiles,

chemicals, paper, PVC, water treatment, alumina, soaps & detergents, glass, chlorinated paraffin

stic soda & soda ash, has

CAGR) of 5.6% and 4.7%

Alkali Industry in the country produces mainly Caustic Soda, Chlorine and Soda Ash.

product of Caustic Soda Industry is very important for manufacturing of

PVC, one of the five major Thermoplastic Commodity Plastics. Besides this, it is used in

al industry and various other chemical

industries. Because of the strong oxidizing properties of Chlorine, it is effectively used to

control bacteria and viruses in drinking water that can cause devastating illness such as

important for the Countries like India especially in case

of floods. 85% of the pharmaceuticals rely on Chlorine Chemistry including medicines

that treat heart disease, cancer, AIDS and many other life threatening diseases. Chlorine

is used in Glass Industry, Soaps & Detergents, Silicates and various other

Gujarat Cleaner Production Centre

As stated above the growth of Caustic Soda and Soda Ash Industry is very important for the

Nation and if competitiveness of this Industry is maintained, it can certainly grow at a much

faster rate.

Highlights of processes for Chloralkali/

The Chloralkali process (also chlor

electrolysis of sodium chloride

besides hydrogen can be produced. If the products are separated,

(caustic soda) are the products; by mixing,

depending on the temperature.

There are three basic processes for the electrolytic production of chlorine, the nature of the

cathode reaction depending on the specific process. These three processes are the diaphragm cell

process(Griesheim cell, 1885), the mercury cell process (Castner

membrane cell process (1970). Each process represents a different method of keeping

chlorine produced at the anode separate from the caustic soda and hydrogen produced, directly or

indirectly, at the cathode.

The basic principle in the electrolysis of a sodium chloride solution is the following:

- At the anode, chloride ions are o

- At the cathode: In the mercury process a sodium/mercury amalgam is formed and hydrogen

(H2) and hydroxide ions (OH-) are formed by the reaction of the sodium in the amalgam with

water in the denuder. In membrane and

(H2) and hydroxide ions (OH-) at the cathode.

For all processes the dissolving of salt, sodium chloride, is:

NaCl → Na+ + Cl-

The anode reaction for all processes is:

2 Cl-(aq) → Cl2(g) + 2 e

-

The cathode reaction is:

2 Na+(aq) +2 H2O + 2e

- → H2(g) + 2 Na

The overall reaction is:

2 Na+(aq) + 2 Cl

-(aq) + 2 H2O →

Gujarat Cleaner Production Centre – ENVIS CENTRE

As stated above the growth of Caustic Soda and Soda Ash Industry is very important for the

mpetitiveness of this Industry is maintained, it can certainly grow at a much

Highlights of processes for Chloralkali/ caustic soda

chlor-alkali and chlor alkali) is an industrial process for the

solution (brine). Depending on the method, several products

can be produced. If the products are separated, chlorine and sodium hydroxide

(caustic soda) are the products; by mixing, sodium hypochlorite or sodium chlorate

There are three basic processes for the electrolytic production of chlorine, the nature of the

pending on the specific process. These three processes are the diaphragm cell

process(Griesheim cell, 1885), the mercury cell process (Castner–Kellner cell, 1892), and the

membrane cell process (1970). Each process represents a different method of keeping

chlorine produced at the anode separate from the caustic soda and hydrogen produced, directly or

The basic principle in the electrolysis of a sodium chloride solution is the following:

At the anode, chloride ions are oxidised and chlorine (Cl2) is formed.

At the cathode: In the mercury process a sodium/mercury amalgam is formed and hydrogen

) are formed by the reaction of the sodium in the amalgam with

water in the denuder. In membrane and diaphragm cells, water decomposes to form hydrogen

) at the cathode.

For all processes the dissolving of salt, sodium chloride, is:

reaction for all processes is:

H2(g) + 2 Na+(aq) + 2 OH

-(aq)

→ 2 Na+(aq) + 2 OH

-(aq) + Cl2(g) + H2(g)

3

As stated above the growth of Caustic Soda and Soda Ash Industry is very important for the

mpetitiveness of this Industry is maintained, it can certainly grow at a much

) is an industrial process for the

). Depending on the method, several products

sodium hydroxide

sodium chlorate are produced,

There are three basic processes for the electrolytic production of chlorine, the nature of the

pending on the specific process. These three processes are the diaphragm cell

Kellner cell, 1892), and the

membrane cell process (1970). Each process represents a different method of keeping the

chlorine produced at the anode separate from the caustic soda and hydrogen produced, directly or

The basic principle in the electrolysis of a sodium chloride solution is the following:

At the cathode: In the mercury process a sodium/mercury amalgam is formed and hydrogen

) are formed by the reaction of the sodium in the amalgam with

diaphragm cells, water decomposes to form hydrogen

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(Flow diagram of the three main

Gujarat Cleaner Production Centre – ENVIS CENTRE

Flow diagram of the three main Chlor-alkali processes)

4

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(Simplified scheme of chlorine electrolysis cells)

The main characteristics of the three electrolysis processes are presented in Table

Mercury

Caustic quality

High, <30 ppm NaCl

5-150 µ

treatment the Hg level

is between 2.5

Hg/l)

Caustic

concentration

50%

Chlorine quality Contains low levels of

Gujarat Cleaner Production Centre – ENVIS CENTRE

chlorine electrolysis cells)

The main characteristics of the three electrolysis processes are presented in Table

Mercury Diaphragm Membrane

High, <30 ppm NaCl

150 µg Hg/l (Before

treatment the Hg level

is between 2.5-25 mg

1.0-1.5% by weight

NaCl (Before

treatment the NaCl

content is about 18%)

0.1% NaClO3 Not

suitable for some

applications

High, <50 ppm NaCl

12%, requires

concentration to 50%

for some applications

33%, requires

concentration

for some applications

Contains low levels of Oxygen content Oxygen content

5

The main characteristics of the three electrolysis processes are presented in Table

Membrane

High, <50 ppm NaCl

, requires

concentration to 50%

for some applications

Oxygen content

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oxygen

hydrogen

Brine feedstock

Some

required

but depends on purity

of salt or brine used

Variable electric

load performance

Good variable

electricity load

performance, down to

30 %

possible for some

cell rooms, which is

very important in

some European

countries

Auxiliary processes

There are various auxiliary processes attached to all the three technologies, which are listed

below:

• salt processing; unloading/storage

• brine purification and re-saturation

• chlorine processing

• caustic processing

• hydrogen processing

Caustic Processing

Process for Caustic Soda

Sodium hydroxide (caustic soda) is produced in a fixed ratio of 1.128 tonnes (as 100% NaOH)

per tonne chlorine produced.

The caustic soda solution from the three technologies is treated in slightly different ways due to

the difference in composition and concentration.

In the mercury cell process, 50% caustic soda is obtained directly from the decomposers. The

caustic soda is normally pumped through a cooler, then through a mercury removal system and

then to the intermediate and final storage sections. In some cases the caustic is heated before

filtration. The most common method for removal of mercury from caustic soda is a plate (or leaf)

Gujarat Cleaner Production Centre – ENVIS CENTRE

oxygen (< 0.1%) and

hydrogen

between 1.5-2.5%

between

2%, depending on

whether an acidified

electrolyte is used

Some purification

required

but depends on purity

or brine used

Some purification

required but depends

on purity of salt or

brine used

Very high purity brine

is

impurities affect

Membrane

performance

ood variable

electricity load

performance, down to

of full load

possible for some

cell rooms, which is

important in

some European

countries

Tolerates only slight

variation in electricity

load and brine flows

in order to maintain

diaphragm

performance

Variable electricity

load performance less

than for

60% depending

on design load),

affects

quality, and

efficiency at lower

loads

There are various auxiliary processes attached to all the three technologies, which are listed

salt processing; unloading/storage

saturation

Sodium hydroxide (caustic soda) is produced in a fixed ratio of 1.128 tonnes (as 100% NaOH)

The caustic soda solution from the three technologies is treated in slightly different ways due to

the difference in composition and concentration.

In the mercury cell process, 50% caustic soda is obtained directly from the decomposers. The

caustic soda is normally pumped through a cooler, then through a mercury removal system and

te and final storage sections. In some cases the caustic is heated before

filtration. The most common method for removal of mercury from caustic soda is a plate (or leaf)

6

between 0.5% and

2%, depending on

whether an acidified

electrolyte is used

Very high purity brine

required as

impurities affect

Membrane

performance

Variable electricity

performance less

than for mercury (40-

60% depending

on design load),

affects product

quality, and

efficiency at lower

There are various auxiliary processes attached to all the three technologies, which are listed

Sodium hydroxide (caustic soda) is produced in a fixed ratio of 1.128 tonnes (as 100% NaOH)

The caustic soda solution from the three technologies is treated in slightly different ways due to

In the mercury cell process, 50% caustic soda is obtained directly from the decomposers. The

caustic soda is normally pumped through a cooler, then through a mercury removal system and

te and final storage sections. In some cases the caustic is heated before

filtration. The most common method for removal of mercury from caustic soda is a plate (or leaf)

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filter with carbon precoat. Under normal operating conditions, mercury

100% NaOH) contains 20-100 ppm of sodium chloride and 40

In the case of diaphragm and membrane technologies the caustic soda is concentrated by

evaporation before final storage.

(The flow to storage of caustic soda from the diff

Emissions in Chlor Alkali Industry

Emission from Mercury cell process

Air Emission

Releases of mercury are

specific to the amalgam

technology. Air emissions

consist of mercury vapour

coming from:

- cell-room ventilation

- process exhausts

- brine purification

- stack of caustic evaporators

Gujarat Cleaner Production Centre – ENVIS CENTRE

filter with carbon precoat. Under normal operating conditions, mercury-cell caustic s

100 ppm of sodium chloride and 40-60 µg Hg/kg NaOH.

In the case of diaphragm and membrane technologies the caustic soda is concentrated by

(The flow to storage of caustic soda from the different technologies)

Emissions in Chlor Alkali Industry

Emission from Mercury cell process

Water emissions

- the process: bleed from brine purification,

condensate from hydrogen drying,

condensate from caustic soda concentration

units, brine leakage, ion-exchange eluate

from process water

Treatment.

- the wash water from the cell cleaning

operations: inlet and outlet boxes

- the rinsing water from the electrolysis hall:

7

cell caustic soda (as

g Hg/kg NaOH.

In the case of diaphragm and membrane technologies the caustic soda is concentrated by

Solid Waste

- Solids from brine

purification

- Solids from

caustic filtration

- Graphite and

activated carbon

from treatment of

gaseous streams

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- hydrogen burnt or vented to

atmosphere

- mercury retorting

-maintenance outside cell

room

Emission from Diaphragm cell process

Air Emission

Three sources of asbestos

emission can be identified in

the cell room maintenance

area:

- from the off-gas compressor,

- from the off-gas drying

oven,

- from the off-gas asbestos

weighing room

Emission from the Membrane Cell Process

Air Emission

Water emissions

- Waste water from the membrane cell process

originates from

- caustic evaporation,

- chlorine

- Wash

used to purify the brine.

Environmental Issues in Chlor alkali/

• Implementation of cleaner processes and pollution prevention measures can yield both

economic and environmental benefits. In MBCP (membrane process), the chlorine (at the

anode) and the hydrogen (at the cathode) are kept apart by a selective polymer membra

allows sodium ions to pass into the cathodic compartment and react with the hydroxyl ions to

form caustic soda. The depleted brine is de

major waste stream from the MBCP consists of brine mud

purification step, which may contain magnesium, calcium, iron, and other metal hydroxides,

depending on the source and purity of the brine.

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cleaning of the floors, tanks, pipes and

dismantled apparatus

- the rinsing water from maintenance areas

outside the electrolysis hall, if they are

cleaned with water

Emission from Diaphragm cell process

Water emissions

Waste water streams from the diaphragm cell

process mainly originate from

- the condenser

- caustic soda evaporation,

- chlorine drying,

- brine purification of salt recovered

from

The evaporators.

Emission from the Membrane Cell Process

Water emissions Solid Waste

Waste water from the membrane cell process

originates from

caustic evaporation,

chlorine drying and

Wash water from the ion exchange resin

used to purify the brine.

- precoat and body feed

material made of cellulose

- Spent membranes and

gaskets from membrane

cells

Environmental Issues in Chlor alkali/ caustic soda Industry and CP options

Implementation of cleaner processes and pollution prevention measures can yield both

economic and environmental benefits. In MBCP (membrane process), the chlorine (at the

anode) and the hydrogen (at the cathode) are kept apart by a selective polymer membra

allows sodium ions to pass into the cathodic compartment and react with the hydroxyl ions to

form caustic soda. The depleted brine is de-chlorinated and recycled to the input stage. The

major waste stream from the MBCP consists of brine mud - the sludge from the brine

purification step, which may contain magnesium, calcium, iron, and other metal hydroxides,

depending on the source and purity of the brine.

8

Solid Waste

- Bagged asbestos

from scrap

diaphragms

Solid Waste

precoat and body feed

material made of cellulose

Spent membranes and

gaskets from membrane

Industry and CP options

Implementation of cleaner processes and pollution prevention measures can yield both

economic and environmental benefits. In MBCP (membrane process), the chlorine (at the

anode) and the hydrogen (at the cathode) are kept apart by a selective polymer membrane that

allows sodium ions to pass into the cathodic compartment and react with the hydroxyl ions to

chlorinated and recycled to the input stage. The

ludge from the brine

purification step, which may contain magnesium, calcium, iron, and other metal hydroxides,

Gujarat Cleaner Production Centre

• The pollution emission target namely wastewater generation target of 0.1 m

1. Having an emergency preparedness and response plan for potential uncontrolled chlorine

and other releases.

2. Using carbon tetrachloride with levels below 4% to avoid explosion.

3. Using metal rather than graphite anodes in DCP to reduce lead and chlorinated organics.

4. Re-saturate brine in closed vessels to reduce the generation of salt sprays.

5. Use non-contact condensers to reduce the amount of process wastewater.

6. Scrub chlorine tail-gases to reduce chlorine discharges and to produce hypochlorite.

Scrub chlorine tail-gas using suitable quantity of water for preparation of caustic solution

for pH maintenance to reduce chlorine discharge and to produce sodium hypo chloride

7. Recycle condensates and waste process water to the brine system, if possible.

8. Recycle brine wastes, if possible

9. Preferable use of substitutes for carbon tetrachloride as this is hazardous

10. chlorine produced can be achieved by adopting preventive measures such as:

• Indian Chlor-alkali plants have achieved huge benefits through

Technology shift from Mercury cell to Membrane cell, which are tabulated below:

1. Given the fact that Chlor

technology, approximately 70

costs in case of mercury cell based technology. On the other hand in case of membrane cell

technology, there is a significant reduction in energy consumption and the total energy cost

only constitutes 60% of the production cost. Therefore, immediate reduction of produ

cost of about 24% can be achieved by technology shifts.

2. The membrane cell plant is an environment friendly and energy efficient technology. Any

end products or gas, generated

chances of mercury contamination to the soil or water;

3. The membrane cell based plant would ensure no emission of mercury into the air;

4. No chances of negative impacts on humans as well as the environment remains as the

mercury itself is a toxic element;

5. Net energy saving of about 24 percent, thereby reducing the amount of carbon foot print

• Mercury cell Chlor-alkali plants are subject to special regulations due to the use of mercury.

the case of mercury as well as membrane cell process, the initial investment on pollution

control measures remains unchanged; thereby the conversion in technology did not envisage

any additional investment. Converting to a mercury free process will lead

several relevant costs, which in approximate order of economic significance include:

1. Avoiding costs of recycling, retorting, transporting, inventorying and/or disposing of

mercury wastes;

2. Elimination of the mercury wastewater treatment facility;

3. Reduced labor costs due to reduced need for maintenance;

Gujarat Cleaner Production Centre – ENVIS CENTRE

The pollution emission target namely wastewater generation target of 0.1 m3 per ton of

an emergency preparedness and response plan for potential uncontrolled chlorine

Using carbon tetrachloride with levels below 4% to avoid explosion.

Using metal rather than graphite anodes in DCP to reduce lead and chlorinated organics.

saturate brine in closed vessels to reduce the generation of salt sprays.

contact condensers to reduce the amount of process wastewater.

gases to reduce chlorine discharges and to produce hypochlorite.

using suitable quantity of water for preparation of caustic solution

for pH maintenance to reduce chlorine discharge and to produce sodium hypo chloride

Recycle condensates and waste process water to the brine system, if possible.

possible

Preferable use of substitutes for carbon tetrachloride as this is hazardous

chlorine produced can be achieved by adopting preventive measures such as:

alkali plants have achieved huge benefits through technology shift i.e.

y shift from Mercury cell to Membrane cell, which are tabulated below:

Given the fact that Chlor-alkali production relies on energy intensive electrochemical

technology, approximately 70-75% of the production cost primarily comprises of energy

e of mercury cell based technology. On the other hand in case of membrane cell

technology, there is a significant reduction in energy consumption and the total energy cost

only constitutes 60% of the production cost. Therefore, immediate reduction of produ

cost of about 24% can be achieved by technology shifts.

The membrane cell plant is an environment friendly and energy efficient technology. Any

gas, generated from this plant are completely free of mercury with no

ontamination to the soil or water;

The membrane cell based plant would ensure no emission of mercury into the air;

No chances of negative impacts on humans as well as the environment remains as the

mercury itself is a toxic element;

about 24 percent, thereby reducing the amount of carbon foot print

alkali plants are subject to special regulations due to the use of mercury.

the case of mercury as well as membrane cell process, the initial investment on pollution

control measures remains unchanged; thereby the conversion in technology did not envisage

Converting to a mercury free process will lead to the savings of

several relevant costs, which in approximate order of economic significance include:

Avoiding costs of recycling, retorting, transporting, inventorying and/or disposing of

Elimination of the mercury wastewater treatment facility;

Reduced labor costs due to reduced need for maintenance;

9

per ton of

an emergency preparedness and response plan for potential uncontrolled chlorine

Using metal rather than graphite anodes in DCP to reduce lead and chlorinated organics.

saturate brine in closed vessels to reduce the generation of salt sprays.

contact condensers to reduce the amount of process wastewater.

gases to reduce chlorine discharges and to produce hypochlorite.

using suitable quantity of water for preparation of caustic solution

for pH maintenance to reduce chlorine discharge and to produce sodium hypo chloride

Recycle condensates and waste process water to the brine system, if possible.

chlorine produced can be achieved by adopting preventive measures such as:

technology shift i.e.

y shift from Mercury cell to Membrane cell, which are tabulated below:

alkali production relies on energy intensive electrochemical

75% of the production cost primarily comprises of energy

e of mercury cell based technology. On the other hand in case of membrane cell

technology, there is a significant reduction in energy consumption and the total energy cost

only constitutes 60% of the production cost. Therefore, immediate reduction of production

The membrane cell plant is an environment friendly and energy efficient technology. Any

from this plant are completely free of mercury with no

The membrane cell based plant would ensure no emission of mercury into the air;

No chances of negative impacts on humans as well as the environment remains as the

about 24 percent, thereby reducing the amount of carbon foot print

alkali plants are subject to special regulations due to the use of mercury. In

the case of mercury as well as membrane cell process, the initial investment on pollution

control measures remains unchanged; thereby the conversion in technology did not envisage

to the savings of

several relevant costs, which in approximate order of economic significance include:

Avoiding costs of recycling, retorting, transporting, inventorying and/or disposing of

Gujarat Cleaner Production Centre

4. Reduced labor costs due to reduced need for monitoring mercury emissions and

occupational exposures, health testing, reporting and abatemen

5. Avoidance of costs of storage of residual mercury;

6. Elimination of mercury monitoring equipment, as well as equipment for cleaning mercury

from product streams, flue exhausts, other clean

7. This cannot be easily quantified; however, at least 5% of the total benefits listed above, can

be achieved, which include, improved community relations, decreased legal liability,

improved public/investor image of the company, improved attractiveness of the company

as a place to work (employee satisfaction), reduced energy demand during the time of

raised energy consciousness, reduced CO

8. Reduced costs on medical testing of workers and relevant insurances as well as costs

related to potential need of rehabilitation in case workers had to take time off.

• Fundamental research programmes related to mercury technology are not being developed

since it is very unlikely that any new mercury plants will be built. The only recent

improvements in mercury cells concerns the anode geometry with the aim of improving gas

release in order to decrease electrical energy usage and increase anode coating life. In

diaphragm technology, with the exception of non

improvements are minor and related to reducing power consumption in the cell. An interesting

example is a specific development of activated cathode technology which is the pre

concept.

• Oxygen depolarized cathodes in membrane cells have the potential to save

kWh/tonne of chlorine produced and are now being tested at the industrial scale.

• The membrane is being developed that can produce high concentration (50%) caustic soda

and believes that it could be available at an acceptable cost within a fe

• For MBCP (membrane technology) the cleaner options include:

1. Minimizing the discharge of chlorate and bromate to water by applying: acid conditions in

the anolyte (pH: 1-2) to minimize the formation of chlorate (ClO3

chlorate destruction in the brine circuit to remove chlorate before purging.

2. The acidity of the anolyte is a design parameter of membrane cell plant and cannot be

adjusted without affecting the operation of the membrane cell. If this is not the chosen

option, a chlorate decomposer may be necessary to remove chlorate before purging.

3. The chlorate level associated with BAT in the brine circuit is 1

bromate level is 2-10 mg/l (note that the bromate level depends on the bromide level in the

salt).

4. Appropriate handling of spent membranes and gaskets.

Environmental Issues in Caustic Soda Manufacturing

• Steam is used as the source of evaporative energy. The presence of salt in the diaphragm cell

liquor requires that the evaporator is

the precipitated salt. This high quality sodium chloride can then be used to enrich depleted

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Reduced labor costs due to reduced need for monitoring mercury emissions and

occupational exposures, health testing, reporting and abatement measures;

Avoidance of costs of storage of residual mercury;

Elimination of mercury monitoring equipment, as well as equipment for cleaning mercury

from product streams, flue exhausts, other clean-up related costs (spillages) etc;

quantified; however, at least 5% of the total benefits listed above, can

be achieved, which include, improved community relations, decreased legal liability,

improved public/investor image of the company, improved attractiveness of the company

to work (employee satisfaction), reduced energy demand during the time of

raised energy consciousness, reduced CO2 emissions related to energy demand etc.

Reduced costs on medical testing of workers and relevant insurances as well as costs

ntial need of rehabilitation in case workers had to take time off.

Fundamental research programmes related to mercury technology are not being developed

since it is very unlikely that any new mercury plants will be built. The only recent

rcury cells concerns the anode geometry with the aim of improving gas

release in order to decrease electrical energy usage and increase anode coating life. In

diaphragm technology, with the exception of non-asbestos technology referred earlier,

s are minor and related to reducing power consumption in the cell. An interesting

example is a specific development of activated cathode technology which is the pre

Oxygen depolarized cathodes in membrane cells have the potential to save

kWh/tonne of chlorine produced and are now being tested at the industrial scale.

The membrane is being developed that can produce high concentration (50%) caustic soda

and believes that it could be available at an acceptable cost within a few years

For MBCP (membrane technology) the cleaner options include:

Minimizing the discharge of chlorate and bromate to water by applying: acid conditions in

2) to minimize the formation of chlorate (ClO3-) and bromate (BrO3

destruction in the brine circuit to remove chlorate before purging.

The acidity of the anolyte is a design parameter of membrane cell plant and cannot be

adjusted without affecting the operation of the membrane cell. If this is not the chosen

lorate decomposer may be necessary to remove chlorate before purging.

The chlorate level associated with BAT in the brine circuit is 1-5 g/l and the associated

10 mg/l (note that the bromate level depends on the bromide level in the

Appropriate handling of spent membranes and gaskets.

Caustic Soda Manufacturing and CP options

Steam is used as the source of evaporative energy. The presence of salt in the diaphragm cell

liquor requires that the evaporator is equipped with scraper blades or other devices to draw off

the precipitated salt. This high quality sodium chloride can then be used to enrich depleted

10

Reduced labor costs due to reduced need for monitoring mercury emissions and

t measures;

Elimination of mercury monitoring equipment, as well as equipment for cleaning mercury

up related costs (spillages) etc;

quantified; however, at least 5% of the total benefits listed above, can

be achieved, which include, improved community relations, decreased legal liability,

improved public/investor image of the company, improved attractiveness of the company

to work (employee satisfaction), reduced energy demand during the time of

emissions related to energy demand etc.

Reduced costs on medical testing of workers and relevant insurances as well as costs

ntial need of rehabilitation in case workers had to take time off.

Fundamental research programmes related to mercury technology are not being developed

since it is very unlikely that any new mercury plants will be built. The only recent

rcury cells concerns the anode geometry with the aim of improving gas

release in order to decrease electrical energy usage and increase anode coating life. In

asbestos technology referred earlier,

s are minor and related to reducing power consumption in the cell. An interesting

example is a specific development of activated cathode technology which is the pre-cathode

Oxygen depolarized cathodes in membrane cells have the potential to save around 500-600

kWh/tonne of chlorine produced and are now being tested at the industrial scale.

The membrane is being developed that can produce high concentration (50%) caustic soda

w years

Minimizing the discharge of chlorate and bromate to water by applying: acid conditions in

) and bromate (BrO3-) −

The acidity of the anolyte is a design parameter of membrane cell plant and cannot be

adjusted without affecting the operation of the membrane cell. If this is not the chosen

lorate decomposer may be necessary to remove chlorate before purging.

5 g/l and the associated

10 mg/l (note that the bromate level depends on the bromide level in the

Steam is used as the source of evaporative energy. The presence of salt in the diaphragm cell

equipped with scraper blades or other devices to draw off

the precipitated salt. This high quality sodium chloride can then be used to enrich depleted

Gujarat Cleaner Production Centre

brine, sometimes it is used as a raw material for an amalgam or membrane process. The

residual level of sodium chloride in sodium hydroxide from diaphragm cell is about 1% and

sodium chlorate 0.1%. For this reason, it is unsuitable for certain end applications such as the

manufacture of rayon.

• Salt and sodium chlorate in the caustic soda from diaphragm cells

extraction to increase marketability, but at increased cost.

• The caustic soda from membrane cells is of high quality, although the caustic soda produced

(usually around 33% NaOH) needs concentration to 50% NaOH for some applicatio

salt content of the membrane-cell caustic soda lies between 20

is on average slightly higher than mercury cell caustic

• In some plants the caustic soda is further concentrated to a 73% solution and to 100% as solid

caustic prills or flakes.

• Some Chlor-alkali production facilities can combine the caustic production process from

mercury and membrane cells in order to

caustic from the membrane cells to the decomposer to produ

for evaporation.

Bibliography

Books

1. Kirk-Othmer, Encyclopedia,

2. Lindley Encyclopedia, 1997,

3. Ullmann’s Encyclopedia1996

4. Research and Markets: Indian Chlor

hydrogen December 08, 2011 09:28 AM Eastern Standard Time

5. Pre-Budget Memorandum

6. Technical EIA guidance manual for Chlor Alkali Industry Prepared for The Ministry of

Environment & Forests Government of India

7. Chlorine Industry: Economics Of Conversion In India Study By: Toxics Link, New

Delhi Supported By Zero Mercury, 2012

8. BREF document on Chlor Alkali Manufacturing Industry

9. Cost Benefit Analysis for Changeover of Hg

Alkali Industry, by Central Pollution Control Board (CPCB);

10. The effects of Environmental Regulation on Technology Diffusion: The Case of Chlorine

Manufacturing, by Lori Snyder, Nolan Miller, Robert Stavins, Aug, 2003: Resources

The Future;

Gujarat Cleaner Production Centre – ENVIS CENTRE

sometimes it is used as a raw material for an amalgam or membrane process. The

odium chloride in sodium hydroxide from diaphragm cell is about 1% and

0.1%. For this reason, it is unsuitable for certain end applications such as the

Salt and sodium chlorate in the caustic soda from diaphragm cells can be reduced by ammonia

extraction to increase marketability, but at increased cost.

The caustic soda from membrane cells is of high quality, although the caustic soda produced

(usually around 33% NaOH) needs concentration to 50% NaOH for some applicatio

cell caustic soda lies between 20-100 ppm (in 100% NaOH), but

average slightly higher than mercury cell caustic.

In some plants the caustic soda is further concentrated to a 73% solution and to 100% as solid

alkali production facilities can combine the caustic production process from

mercury and membrane cells in order to minimize energy costs. It is possible to feed 33%

caustic from the membrane cells to the decomposer to produce 50% caustic without the need

Encyclopedia,1991,

, 1997,

1996

Research and Markets: Indian Chlor-Alkali Industry: caustic soda, soda ash, chlorine and

December 08, 2011 09:28 AM Eastern Standard Time

Budget Memorandum 2012-2013 by Alkali Manufacturers’ of India

Technical EIA guidance manual for Chlor Alkali Industry Prepared for The Ministry of

Environment & Forests Government of India by IL&FS Ecosmart Hyderabad

Economics Of Conversion In India Study By: Toxics Link, New

Delhi Supported By Zero Mercury, 2012

BREF document on Chlor Alkali Manufacturing Industry.

Cost Benefit Analysis for Changeover of Hg-Cell to Membrane Cell technology in Chlor

Alkali Industry, by Central Pollution Control Board (CPCB);

The effects of Environmental Regulation on Technology Diffusion: The Case of Chlorine

Manufacturing, by Lori Snyder, Nolan Miller, Robert Stavins, Aug, 2003: Resources

11

sometimes it is used as a raw material for an amalgam or membrane process. The

odium chloride in sodium hydroxide from diaphragm cell is about 1% and

0.1%. For this reason, it is unsuitable for certain end applications such as the

can be reduced by ammonia

The caustic soda from membrane cells is of high quality, although the caustic soda produced

(usually around 33% NaOH) needs concentration to 50% NaOH for some applications. The

100 ppm (in 100% NaOH), but

In some plants the caustic soda is further concentrated to a 73% solution and to 100% as solid

alkali production facilities can combine the caustic production process from

energy costs. It is possible to feed 33%

ce 50% caustic without the need

Alkali Industry: caustic soda, soda ash, chlorine and

Technical EIA guidance manual for Chlor Alkali Industry Prepared for The Ministry of

Ecosmart Hyderabad , 2010

Economics Of Conversion In India Study By: Toxics Link, New

e Cell technology in Chlor-

The effects of Environmental Regulation on Technology Diffusion: The Case of Chlorine

Manufacturing, by Lori Snyder, Nolan Miller, Robert Stavins, Aug, 2003: Resources For

Gujarat Cleaner Production Centre

Website

1. http://www.adityabirlachemicals.com/products/chlor_alkali/companies_producing_chlor_

alkalis.html

2. http://www.businesswire.com/news/home/20111208005754/en/Research

Indian-Chlor-Alkali-Industry

3. http://www.ama-india.org/

4. http://www.greenbuildingcongress.com/site/superdirectory/suppliers.jsp?sector=3&

er=3

Gujarat Cleaner Production Centre – ENVIS CENTRE

http://www.adityabirlachemicals.com/products/chlor_alkali/companies_producing_chlor_

http://www.businesswire.com/news/home/20111208005754/en/Research

Industry-caustic-soda#.UrvzyvtgCho

india.org/

http://www.greenbuildingcongress.com/site/superdirectory/suppliers.jsp?sector=3&

12

http://www.adityabirlachemicals.com/products/chlor_alkali/companies_producing_chlor_

http://www.businesswire.com/news/home/20111208005754/en/Research-Markets-

http://www.greenbuildingcongress.com/site/superdirectory/suppliers.jsp?sector=3&suppli