CHLOR-ALKALI INDUSTRYPRESENTED TO:

Dr.KHURRAM

PRESENTED BY: ANDALEEB YASEEN

ANUM ASLAMKHANSA GULSHADNOOR-UL-AIN(022)

SUNBLA ALMAS

THE CHLOR ALKALI INDUSTRYThe Chlor- alkali industry is the industry that produces chlorine(Cl2) and alkali, sodium hydroxide(NaOH)or potassium hydroxide(KOH),by electrolysis of a salt solution.

The main technologies applied for chlor-alkali production are mercury, diaphragm and membrane cell electrolysis.

History of Chlor-alkali IndustryThe diaphragm cell process and the mercury cell process were both introduced in late 1800s.

The membrane cell process was developed much more recently (1970).

Each of these processes represents a different method of keeping chlorine produced at the anode separate from caustic soda and hydrogen produced at the cathode.

Currently 95% of world chlorine production is obtained by chlor- alkali process.

The geographic distribution of chlor-alkali processes world-wide differs appreciably:

Western Europe, predominance of mercury cell process (June 2000):55%

United States, predominance of diaphragm cell process: 75%

Japan predominance of membrane cell process: >90%

The chlor-alkali sector in Europe has developed over time and is scattered geographically.

Europe is approximately balance in chlorine, and has traditionally been the world’s second largest exporter of caustic.

During the last half of 19th century, chlorine,used almost exclusively in the textile and paper industry.

It was made by reacting manganese dioxide with hydrochloric acid.

Recycling of manganese improved the overall process economics, and the process became known as Weldon process

Sodium hydroxide is usually supplies as a 50% aqueous solution and can be stored for long periods and reality transported (rail, road and ship). The main areas of application of sodium hydroxide today are:

•Chemicals; synthesis of organic or inorganic compounds •Metallurgy , alumina/ aluminum industry •Pulp and paper industry •Textile industry •Soaps, surfactants •Water treatment •Consumer products

SODA ASH Soda Ash also known as sodium carbonate. Na2CO3, is a sodium salt of

carbonic acid.

Sodium carbonate is domestically well known for its everyday use as a water softener.

It can be extracted from the ashes of many plants or seaweed.

It is synthetically produced in large quantities from salt (sodium chloride) and limestone by a method known as the Solvay process.

MANUFACTURING OF SODA ASHSOLVAY PROCES

The Solvay process, also called ammonia soda process, uses salt (NaCl) and limestone (CaCO3) as raw materials.

The raw material of this process is found every where in the world.

The Solvay process produces “light soda ash”, which is used for the detergent market and certain chemical intermediates.

Recrystallization of light soda ash produce dense “soda ash”.

MAIN CHEMICAL REACTIONSThe two main components: sodium chloride and calcium carbonate.

2 NaCl + CaCO3 → Na2CO3 + CaCl2

In practice this direct way is not possible and it needs the participation of other substances and many different process steps to get the final product: soda ash.

NaCl + H2O + NH3 NaCl + NH4OH (1)2 NH4OH + CO2 (NH4)2 CO3 + H2O (2)

(NH4)2CO3 + CO2 + H2O 2 NH4HCO3 (3)2 NH4HCO3 + 2 NaCl 2 NaHCO3 ↓ + 2 NH4Cl (4)

Sodium bicarbonate crystals are separated from the mother liquor by filtration. sodium bicarbonate is decomposed thermally into sodium carbonate, water and carbon dioxide (5).

2 NaHCO3 → Na2CO3 + H2O + CO2 (5)

The ammonium chloride filtrate (4) is reacted with alkali, generally milk of lime (6), followed by steam stripping to recover free gaseous ammonia:

2 NH4Cl + Ca(OH)2 → CaCl2 + 2 NH3 ↗ + 2 H2O (6)

Carbon dioxide and calcium hydroxide originate from limestone calcination (7)

CaCO3 → CaO + CO2 ↗ (7)

CaO + H2O → Ca(OH)2 (8)

Brine (NaCl) has to be treated before the input in the process to remove impurities : calcium and magnesium. If not removed they would react with alkali and carbon dioxide to produce insoluble salts contributing to scale formation inside equipment.

Ca2+ + CO3 2- → CaCO3 ↓ (9)

Mg2+ + 2 OH- → Mg(OH)2 ↓ (10)

Sodium carbonate formed (equation 5) is called "light soda ash" because its bulk density is approximately 0.5 t/m3. A subsequent operation called densification enables this value to be doubled by crystallisation into sodium monohydrate, by adding water (equation 11) then followed by drying (equation 12). Final product is "dense soda".Na2CO3 + H2O -------- > Na2CO3.H2O (11) Na2CO3.H2O --------- > Na2CO3 + H2O ↗ (12)

ADVANTAGES OF SOLVAY PROCESS Can use low-grade brine Less electric power Less corrosion problems No co-products to dispose of Does not require ammonia plant investment

DISADVANTAGES OF SOLVAY PROCESS Higher salt consumption Higher investment in ammonia recovery unit verses crystallization units for ammonium

chloride Waste disposal of calcium chloride brine stream More steam consumption Higher capacity plant for economic break-even operation With current fertilizer shortage, all of the ammonium chloride will be used as a mixed

chemical fertilizer ingredient, so co-product disposal no problem.

HANDLING AND STORAGE

Handling: Do not breathe dust, vapor, mist, or gas. Do not get in eyes, on skin, or on clothing. Use only in a chemical fume hood.

Storage: Store in a cool, dry place. Store in a tightly closed container.

EXPOSURE POTENTIAL Workplace exposure - Exposures can

occur at a sodium carbonate (soda ash) manufacturing facility or a manufacturing, packaging or storage facility that handles soda ash. Exposure may also occur in the event of a transportation incident. Persons involved in maintenance, sampling and testing activities, or in the loading and unloading of sodium carbonate containers are at greater risk of exposure.

Environmental releases- Spills of sodium carbonate should be contained and isolated from waterways and sewers or drains. Spills should be swept up and placed in a compatible container. Any residue that cannot be swept up should be diluted with large amounts of water

Fires – Sodium carbonate is not flammable or combustible.

HEALTH INFORMATIONSodium carbonate typically found in consumer products may pose a risk of symptoms due to skin or inhalation exposure. Sodium carbonate can produce the following adverse health effects: Contact - Skin exposures can cause symptoms ranging from minor skin irritation or

itching to redness and swelling. Eye exposure to sodium carbonate may result in redness, tearing or severe eye irritation. In severe exposures, irreversible eye damage may result.

Inhalation - The inhalation of sodium carbonate dusts can cause nose and throat irritation or coughing. Repeated or prolonged exposures may cause sore throat or nosebleeds.

Ingestion - The ingestion of sodium carbonate may cause severe irritation of the mouth and throat, nausea, vomiting, abdominal irritation and diarrhea.

Other Effects - The International Agency for Research on Cancer (IARC) has not classified sodium carbonate as a carcinogen (cancer causing).

CHLOR-ALKALI INDUSTRY PROCESSES

The chlorine-alkali (chlor-alkali) industry is an important part of the chemical industry, and produces chlorine and sodium hydroxide through

the electrolysis of table salt (NaCl).

Cl2 and NaOH can be produced through a number of different reactions Problem occur when Cl2 and NaOH are produced together

Cl2 combines with the NaOH to form ClOˉ and Clˉ ions. This produces NaClO3, NaClO, a component of household bleach.

TYPES OF CELLS IN ELECTRYLOSIS

Three industrial processes and all three methods involve electrolytic cells:

The Diaphragm Cell (Griesheim cell, 1885) The Mercury Cell (Castner–Kellner cell, 1892) The Membrane Cell (1970)

RAW MATERIAL

Brine which is a saturated solution of sodium chloride (NaCl) that is obtained from natural salt deposits.

Electricity Water

THE MERCURY CELL

𝑁𝑎𝐶𝑙→𝑁𝑎+¿+𝐶𝑙−¿

PRIMARY ELECTROLYSER

DECOMPOSER

2𝐶𝑙(𝑎𝑞 )→𝐶𝑙2(𝑔)+2𝑒−

2𝑁𝑎(𝑎𝑞)+¿ +2𝑒−→2𝑁𝑎(𝐻𝑔)¿

+ 2Hg+ 2NaOH

At Anode:

At Cathode:

Overall Reaction:

ADVANTAGES

The products are pure. The chlorine, along with a little oxygen, generally can be used without further purification.

Efficient separation of Cl2 and NaOH

Reducing the level of impurities of (NaClO), oxygen and (NaClO3)

DRAW BACK

Only produces a fraction of the chlorine and sodium hydroxide

Requires a pure brine solution with little or no metal contaminants.

Mercury is expensive and toxic.

In the past effluent was released into lakes and rivers.

About 100 to 200 g mercury were lost for each 1000 kg chlorine produced.

THE DIAPHRAGM PROCESS FOR ELECTROLYSIS OF BRINE

The diaphragm process was developed in the 1880s in the USA . In North America, diaphragm cells are still the primary technology,

accounting for roughly 70% of all USA production.

Flow Sheet for the whole process of production of NaOH and Cl gas by electrolysis of brine with the help of

diaphragm cell

ADVANTAGES AND DISADVANTAGES OF DIAPHARGM PROCESS

The advantage of this process is that large quantities of sodium hydroxide can be produced and chlorine, which are two high-demand industrial chemicals, at reasonable costs .

The disadvantages are:

A small amount of chloride in the NaOH produced. There are health and environmental problems with small losses of asbestos in

making and using diaphragms. There may be hypochlorite, a strong oxidant, in the waste brine solution.

THE MEMBRANE PROCESS FOR ELECTROLYSIS OF BRINE

In the 1970s, the development of ion-exchange membranes enabled a new technology to produce chlorine: the membrane electrolysis process.

The first industrial membrane plant was installed in Japan in 1975 due to the pressure of Japanese environmental regulations.

Non-chlor-alkali related mercury pollution in Minamata drove the authorities to prohibit all mercury processes.

Most promising and fast-developing technique for the production of chlor-alkali .This can be deduced from the fact that since 1987 practically 100% of the new chlor-alkali plants world-wide apply the membrane process.

Flow Sheet for the whole process of production of NaOH and Cl gas by electrolysis of brine with the help of membrane cell

ADVANTAGES OF MEMBRANE CELL

Pure sodium hydroxide (only contains about 0.02% of sodium chloride at most) being produced

No contamination by chloride No oxidant in the spent brine There is no working hazard of working with asbestos or mercury.

CHLORINE PROCESSING

CHLOR ALKALI INDUSTRY IN ECONOMY OF PAKISTAN

Chemical industry plays a vital role in the economic development of Pakistan.

The chlor-alkali business can be described as a subsector of the chemical industry which produces liquid chlorine, hydrochloric acid, sodium hypochlorite, bleaching earth, whereas, Caustic Soda (Sodium Hydroxide- NaOH) is the key product of this sector.

Presently, there 4 major players in the market with a production capacity of more than 500,000 MT of caustic soda and chlor alkali based products. These plants are

SCIL Ittehad Chemicals Limited (ICL) Engro Polymers Chemicals Limited (EPCL) NIMIR Industrial Chemicals Limited (NIMIR). However, NIMIR produces

caustic soda for its internal usage only

Uses of products form in chlor alkali industry

Chlorine Disinfectant and purifier, in plastics and polymers,

bleach, solvents, agrochemicals and pharmaceuticals, as well as an intermediate in manufacturing other substances where it is not contained in the final product.

Chlorine is used worldwide to purify water supply as the ultimate defense against waterborne microbiological infection.

Chlorine is used in pools and drinking water because it is a great disinfectant. It is able to kill bacteria and algae, among other things

HYDROGEN

Hydrogen and Fuel CellsThe element is often used as fuel because of its high calorific

value. Combustion generates plenty of energy

Because hydrogen is light, scientists are able to use it with weather balloons.

Other uses of hydrogen are in the fertilizer and paint industries. It is also used in the food and chemical industries

This element is used for producing several chemical compounds. Apart from ammonia, hydrogen can be harnessed in other ways. It can be used to make fertilizers, hydrochloric acids etc

Sodium hydroxide

DISADVANTAGES

Electricity Is the Largest Energy SourceElectricity fuels the electrolysis process and represents the primary

energy source.Energy in the form of fuels or steam is used primarily for

evaporation of the sodium hydroxide solution to a useable state.Among the three types of chlorine cells, the mercury cell is the

most energy-intensive, with electricity requirements of nearly 3600 kWhr per metric ton of chlorine.

Air Emissions

Chlorine Gas and Freon Are Primary Air Emissions from Brine Electrolysis. Air emissions from brine electrolysis include chlorine gas and freon emissions (both fugitive and point source) and other vapors

These emissions are controlled through leak-resistant equipment modifications, source reduction, and programs to monitor such leaks

Effluents

Wastewater Is Treated To Remove Chlorine and Acids Prior to Discharge Wastewater from diaphragm and membrane cells originates from caustic evaporation, chlorine drying, washing of the ion-exchange resin, and from purification of salt recovered from evaporators.

Hazardous Wastes and Byproducts

Brine Mud Constitutes the Largest Solid Waste Stream from Chlor-Alkali Production Brine purification results in brine mud, one of the largest waste streams from the chlor-alkali industry

The sludge or brine mud containing impurities must be disposed of in a landfill

Health effect

The chlor-alkali industry is also a major source of industrial mercury pollution

The central nervous system is considered the critical organ for mercury toxicity. A wide variety of respiratory, cardiovascular, gastrointestinal, reproductive, hepatic, renal, thyroid disorders has been associated with mercury exposure

Environmental Issues Within the Chlor/Alkali Industry

There are several environmental concerns that have made a significant impact on the growth of the chlor-alkali industry. These issues are highly debated, and the associated "chemophobia" is likely to adversely affect the chlorine consumption profile in the future

Pollution Prevention and Control

• Use metal rather than graphite anodes to reduce lead

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

• Use noncontact condensers to reduce process wastewater quantities.

• Scrub chlorine tail gases to reduce chlorine discharges and to produce hypochlorite.

THANK YOU