Skip navigation

Tag Archives: Chlorine

There is a great deal of misconception about desalination of seawater and the word ‘desalination’ is taken literally as a method of separating  fresh water from seawater but not the separation of salt from seawater. The main focus here is only about recovery of fresh water from seawater or from any saline water sources but not salt. In fact separation of salt from seawater is also known as desalination or desalting. The reason for this misconception is because fresh drinking water is in demand and people are concerned only with fresh water and not the salt. There is a huge demand for fresh drinking water all over the world. Increasing population, large scale usage of fresh water by industries, pollution of fresh water by domestic and industrial effluents, failure of monsoon or seasonal rains due to climate change are some of the factors that contributes to water shortage. There is also a demand for water by agriculture industry both in terms of quality and quantity. Bulk of the ground water is used as a main source of fresh water by agriculture industries in many countries.

But sea water also contains number of minerals or salts which have greater economic and commercial value. In terms of quantity their presence is small, only 3.5% and the rest 96.5% is fresh water. For example Chemical industries such as Caustic soda and Soda ash plants use salt as their raw material. But they also use de-ionized water to dissolve salt to produce brine which is their feed stock.

Therefore Chemical plants are the largest users of seawater in terms of salt as well as fresh water. Power plants mainly located on seashore also use large quantity of de-ionized or desalinated water for boilers and for cooling towers.

Sea is now becoming a great source of fresh water as the inland water supply is becoming scarcer due to dwindling water table by drought or flooding by too much rains, pollution by industries etc. In earlier days seawater was the only source of common salt known as Sodium chloride produced by solar evaporation. Bulk of the salt is till used by this method. Therefore it is logical to locate a chemical plant and a power plant side by side so that seawater can be utilized efficiently.

CEWT (Australian company) has developed a new desalination technology called ‘CAPZ desalination technology’ that can generate fresh water as well as Sodium chloride brine simultaneously which is suitable for Caustic soda/Soda ash production. They can integrate such a facility with a skid mounted Chlorine plant of smaller capacities. This plant can generate large volume of drinking water (WHO standard) as a by-product that can be supplied to municipalities and agriculture industries.

Locating large scale solar salt pans near such a facility will be a problem because it requires a huge area of arid land with good wind velocity and it takes nearly a year to harvest the salt.

Using CAPZ desalination technology one can generate saturated Sodium chloride brine of 315 gpl concentration as well as fresh drinking water directly from seawater. The brine is purified to meet the specifications required by membrane Electrolysis for the production of Caustic Soda. The same brine can also be used for the production of Soda ash using Solvay process.

It is no longer necessary to produce brine from solar salt. Solar salt requires vast area of arid land with good wind velocity and least rain fall and large manual labour force to work under harsh conditions; it is a very slow process and takes almost a year to harvest the salt, which is full of impurities and requires elaborate purification process during the production of Caustic Soda. Such purification process generates huge volume of solid waste for disposal. Chlor-alkali industry is one of the most polluting industries in the world. In fact these impurities can be converted into more value added products such as recovery of Magnesium metal or recovery of Potassium salts. CAPZ technology is developing a ZLD (zero liquid discharge) desalination process where the effluent containing the above impurities such as Calcium, Magnesium and Sulphates are converted into value added products. By recovering more such salts from seawater one can recover additional fresh water. Therefore desalination of sea water is now emerging as an integral part of Chlor-alkali industry. By such integration Chlor-alkali can become a major player is meeting fresh drinking water of a nation.

skid mounted Chlorine plantSkid mounted Cl2 planElectrolysis plant by Thyssen krupBy careful integration and co-location of a desalination plant, Caustic soda plant, Food and pharmaceutical grade salt plant and a power plant  on a sea shore will be a win situation for everybody involved.

Let us take a specific case study of setting up a Caustic soda plant, a captive power plant and a desalination facility.

A typical skid mounted Chlorine plant will have the following configuration:

Capacity of Caustic Soda: 50.7 Mt/day (100% basis)

Capacity of Chlorine        : 45.00 Mt/day (100% basis)

Hydrogen production        : 14,800m3/day (100% basis)

A typical usage of Vacuum salt for such skid mounted Chlorine plant will be about 76.50 Mt/day with a power consumption of 2.29 Mwhr/Mt of NaOH (100%).

A captive power plant of capacity 200Mw will be able to supply necessary power for both Desalination facility as well as Caustic soda plant.

The CAPZ desalination facility can supply a saturated sodium chloride brine (315gpl concentration) 245 Mt/day and 9122 m3/day of fresh drinking water from the desalination plant. This water can be used for boiler feed in the power plant. Surplus water can be supplied as drinking water meeting WHO specifications.

The Hydrogen gas the by-product from caustic soda plant with capacity of 14,800 m3/day can be used to generate clean power using a Fuel cell. The power generated from Fuel cell will be about 20 Mwhr/day that can be supplemented for the Caustic soda production thereby reducing the power consumption from 2.29Mwhr to 1.46 Mwhr/Mt of NaOH (100%)

By careful integration of a large (ZLD) desalination facility with caustic soda plant and power plant it will be possible in future to generate a clean energy using Hydrogen, a by-product of Caustic soda plant and solar thermal plant to produce chemicals in a clean and environmentally sustainable manner.

For further information on CAPZ technology, please contact




Chemistry has revolutionized human life and it has affected each and every one of us in some way or other for the past several decades. We were happily using these chemicals in our everyday life without really understanding their side effects.Individuls and companies who invented and commercialized chemical products were keen to offer end products to consumers often without explaining the side effects of such chemicals.They themselves were not fully aware of long-term consequences of such chemicals. Classical examples are Chlorine and its derivatives.

Chlorine is a common chemical that is used even today in many countries to disinfect drinking water in water treatment plants. Their usage is sill continued though they found that Haloethanes, which are formed by the action of Chlorine on decayed organic leaves in water storage, causes cancer (carcinogenic). DDT is another chemical that was used widely as a pesticide, known as “atom bomb of pesticides”,  until their side effects proved deadly for human beings and to the environment. It was officially banned in USA in 1972 by EPA, though it is still continued in some third world countries. Bleaching powder in another example of powder disinfectant ( a popular form of disinfectant used on roads in India when  prominent political leaders visit municipalities; though they are only chalk  powder with no traces of residual Chlorine).

A whole range of dyes known as coal-tar dyes derived from coal  were used in many applications including ‘food colors’, later substituted by petroleum-based organic chemicals. These ‘food colors’ are now substituted with ‘natural organic colors’ such as vegetable colors derived from vegetables and fruits. Industrial chemicals, both organic and inorganic have caused serious environmental damages all over the world for several decades, but Governments, companies and EPA did not realize the deadly consequences of some these chemicals for a long time. The ‘Bhopal Gas tragedy’ in India is one such grim reminder of such consequences.

Chemicals are not natural products even though one can separate them into various organic chemical molecules but some of the consequences of such separation and usage are not fully understood. Many natural herbs have outstanding medicinal values and when consumed in a Natural form, it has absolutely no side effects and they show tremendous therapeutic values. But when you isolate certain molecules from such herbs (Alkaloids) and used as a drug, they can cure a disease but at the same time, they create many side effects. Nature offers such drugs in a diluted form that is quite compatible to human beings. One such example is ‘Vinblastine’ and “Vincristine’, anti-cancer drugs derived from a herb called ‘vinca rosea’.

Of late there is awareness among companies, people and Governments about Green technologies that can help protect the environment. Greenhouse gas and global warming is one such issue. When Petrol or Diesel, an organic chemical known as Hydrocarbon is burnt, it not only generates power but also emits greenhouse gases such as Carbon dioxide and oxides of Nitrogen, that cause globe to warm. We were happily burning away such fossil fuels until scientists raised an issue on emission of ‘greenhouse gases’ in recent past. When we deal with chemicals and chemical reactions, the molecule is transformed into a new molecule and often such reaction cannot be reversed.It is not a physical change but a chemical change. When we convert water into steam, we can get back water by condensing steam; but when you convert Chlorine into PVC (Poly vinyl chloride) plastic, there are environmental consequences and reversing PVC into Chlorine gas in not easy, though it is technically possible with environmental consequences.

One has to observe and learn from Nature what is good and what is bad when developing a new technology, because such development will not only affect the environment but also many generations to come. When Nature teaches how to turn sugar into Alcohol by fermentation using air-borne microorganisms, we should follow Nature to make alcohol. We know how to turn Alcohol into PVC, but we do not know how to make biodegradable PVC from Alcohol. Companies call it ‘Green Chemistry’, but not until we can make a biodegradable PVC. Human knowledge is imperfect and we can learn ‘Green chemistry and Clean Technologies’ only from Nature and not by deviating from the path of Nature.

Those who studied chemistry and conducted laboratory experiments in universities will be familiar with precautionary measures we take to avoid  accidents. Aprons, gloves, goggles and fume cub-boards with exhaust fans are some few examples of protective measures from flames, hot plates and fumes. The blue color of the flame represented the degree of hotness of the flame from Bunsen burner; the pungent smell pointed to the ‘Gas plant’ that generated ‘water gas’ for Bunsen burners. The familiar smells of chemicals would bring ‘nostalgic memories’ of college days. Each bottle of chemicals would display a sign of warning ‘Danger or Poison’. We could recognize and identify even traces of  gases or fumes or chemicals immediately. Those memories embedded deeply in our memories and I vividly remembered even after few decades I left university.

I could smell traces of Chlorine in the air even at a distance of 20 miles from a Chloroalkali plant in sixties, when air pollution controls were not stringent. People who lived around the factory probably were used to live with that smell for generations. Many families had not breathed  fresh air in their life time, because they have not breathed air without traces of chlorine.They lived all their lives in the same place because agriculture was their profession. Many people developed breathing problems during  their old ages and died of asthma and tuberclosis.The impact of these fumes cannot be felt in months and years but certainly can be felt after decades especially at old ages, when the body’s immune system deteriorates. Bhopal gas accident in India is a grim reminder of  such tragedy of chemical accidents and how they can contaminate air, water and earth and degrade human lives. But we learnt any lessons from those accidents?

During experimental thermonuclear explosion in the desert of Australia by then British army, people were directly exposed to nuclear radiation. Many of those  who saw this explosion developed some form of cancer or other later in their life .They were treated as heroes then. After several decades of this incident, many exposed to this experiment are now demanding compensation from current British government. But have we learnt any lessons from those incidents? Many politicians still advocate ‘Nuclear energy as a safe and clean energy’. Yes, until we meet with an another accident!

We human beings identified the presence of  chemicals in Nature and used them for our scientific developments. We identified fossil fuels as ‘Hydrocarbons’ and burn them to generate power and to run our cars. We emit toxic gases and fumes every second of our lives, when we switch our lights on or start our cars.Imagine the amount of gases and fumes we emit everyday all over the world by billions of people for several decades. It is a simple common sense that we are responsible for these emissions and we contaminate the air we breathe. Nature does not burn Hydrocarbons everyday or every month or every year. In fact Nature buried these Hydrocarbons deep down the earth like we bury our dead.

Can people who breathed Chlorine for decades and died of asthma or tuberculosis prove that they died due constant inhalation of Chlorine emitted by the Chloroalkali plant? The Court and Authorities will demand ‘hard evidence’ to prove that Chlorine emitted by Chloroalkli plants caused these diseases. We use science when it suits us and we become skeptics when it does not suit us. They know it is almost impossible to prove such cases in our legal system and they can get away scot-free. The same argument applies to our ‘Greenhouse gas emission’ and ‘Global warming’.

We contaminate  our air, water and earth with our population explosion, industrialization and our life styles. Yet, major industrialized countries are not willing to cut their emissions but want to carry on their ‘economic growth’. But these countries got it completely wrong. In chemical experiments, one can draw conclusions by ‘observations’ and ‘Inference’. Inference is a scientific tool and not a guess work. From overwhelming evidences of natural disasters occurring around the world one can ‘infer’ that human activities cause these disasters. Nature is now showing this by devastating ‘the business and economic’ interest of nations because that is the only way Governments can learn lessons. They don’t need ‘harder evidence’ than  monetary losses. According to recent reports:

“The monetary losses from 2011’s natural catastrophes reached a record $380 billion, surpassing the previous record of $220 billion set in 2005. The year’s three costliest natural catastrophes were the March earthquake and tsunami in Japan (costing $210 billion), the August-November floods in Thailand ($40 billion), and the February earthquake in New Zealand ($16 billion).

The report notes that Asia experienced 70 percent, or $265 billion, of the total monetary losses from natural disasters around the world—up from an average share of 38 percent between 1980 and 2010. This can be attributed to the earthquake and tsunami in Japan, as well as the devastating floods in Thailand: Thailand’s summer monsoons, probably influenced by a very intensive La Niña situation, created the costliest flooding to date, with $40 billion in losses.”

%d bloggers like this: