Bhavnagar-based Central Salt Marine and Chemical Research Institute (CSMCRI) has standardised and internationally patented a novel process of converting the discharge emanating from soda ash and salt-making units into value-added products (VAP).

“A novel cost-effective process that helps derive three times more gypsum from the distellar waste, emanating from the soda ash and salt-making units, using the solvay process for production, has been standardised and granted US patent,” Dr Pushpito Ghosh, Director of CSMCRI, a laboratory of Council for Scientific and Industrial Research (CSIR), told PTI.

Solvay process

The distellar waste (calcium chloride), which is a by-product of landmark solvay process, is currently being discharged directly into the sea by the industry.

“But once this waste is added with brine to forcibly precipitate out gypsum, the common salt derived is much purer compared to the traditional salt, currently drawn by the industry using conventional methods,” Dr Ghosh claimed.

Salt itself is required for soda ash manufacturing, which makes the invention especially more significant.

“If adopted by the industry, the process shall help reduce the discharge of distellar waste into the sea, besides reducing expenses involved in the purification of salt for manufacturing of soda ash, chlor alkalies or even for edible applications,” he claimed.

“In addition, one could realise the value from the additional amount of gypsum obtained,” Dr Ghosh said.

“Once the salt is produced, the leftover sulphate-free bitten would also be ideal for recovery of low sodium salt,” he said, adding that separate international patents have been granted to the institute for this.

In a more recent development, the gypsum, derived from using this process, can further be value-added. Even though, it is on a very small scale currently, efforts are underway to scale it up, he said.

“It can be converted into ammonium sulphate which is a fertiliser,” Dr Ghosh said.

Merferberg process

The gypsum can be value-added, using the merferberg process to obtain ammonium sulphate fertiliser and calcium carbonate.

Interestingly, calcium carbonate, too, is required in the solvay process to manufacture soda ash, and this can help reduce quarrying of lime stone, a natural resource, Dr Ghosh claimed.

CSMCRI is in dialogue with the Gujarat Pollution Control Board (GPCB) on how this novel technology can be put to use in the state, which is a major manufacturing hub for soda ash and salt.

The major players into soda ash or salt manufacturing in the state are Gujarat Heavy Chemicals Ltd, Tata Chemicals, Nirma and Gujarat Alkalies and Chemicals Ltd.

(This article was published on January 9, 2012)
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