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Regeneration of Na-Cation Exchangers

#G-725


Regeneration of Na-Cation Exchangers with Sulphate–Natrium Solution and Recycling of Spent Regenerating Solution

Tech Area / Field

  • CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry

Status
8 Project completed

Registration date
15.05.2001

Completion date
17.10.2008

Senior Project Manager
Mitina L M

Leading Institute
Shota Rustaveli State University, Georgia, Batumi

Collaborators

  • Iowa State University of Science and Technology, USA, IA, Ames

Project summary

In water treatment technology for industrial boiler installations, softening water in Na-cation exchangers has become widespread. Today Na-cation exchangers are usually regenerated with concentrated solutions of sodium chloride. Owing to this process, chloride wastewater is formed, which contains an ample quantity of calcium chloride and magnesium with good solubility. The reuse of such water is possible after being treated with sode-lime. For this purpose, an equivalent quantity of calcium chloride and magnesium is required. This is economically unprofitable. Therefore, such wastewater is discharged into reservoirs, but this causes an increase in salt content. The constant increase in the salt content changes the chemical and physical composition of the water and causes ecological changes and changes in technology for enterprises using such a kind of natural water.
This project is devoted to the development of the technology for a Na-cation exchanger with a sodium-sulphate solution, which makes it possible to reuse spent regenerating solution and to prevent the discharge of highly mineralised wastewater into reservoirs. The regeneration of a Na-Cation exchanger by sodium-sulphate solution causes the formation of sulphate wastewater, which contains weak-soluble calcium-sulphate. The salt content is 3-4 times higher than its solubility. Therefore, it loses three quarters of its volume without the use of a calcium reagent. Using sode-lime or a thermochemical method could precipitate the remaining quantity of calcium-sulphate. In this case the discharge of technical soda is to be 4 times less than the discharge needed for chloride wastewater treatment.
To date, the regeneration of Na-Cation exchangers with sodium sulphate solution has yet to become widespread because of the weak solution strength (up to 0.5%), which considerably increases both the volume and the duration of the regeneration process. The use of a heightened concentration of regenerated solution causes the danger of sulphate-calcium precipitation directly into the filter, which renders it inoperable.
This problem could be avoided by adding a small amount of stabiliser into the regenerated solution, which will not exert a detrimental effect on the operation of the Na-cation exchanger.
The process of regeneration of a Na-cation exchanger is the most important and expansive in the technology of water softening. Therefore, to study it with contemporary methods, a mathematical model of the regeneration process is to be created and optimum parameters of the process are to be determined.
Development of the proposed technology will make it possible to reduce expenditure both on regeneration of Na-cation exchangers and on wastewater treatment for its recycling. All this is to prevent the discharge of wastewater into reservoirs, which facilitates protection of the environment.
The applied research results will be as follows:
- the development of new regeneration technology for Na-cation exchangers with sodium-sulphate solutions and their recycling after thermochemical treatment of spent regenerating solution;
- development of a mathematical regeneration model and a new program for estimating optimal parameters of the process;
- a proposal for a new method for assessment of damage to the environment caused by wastewater discharge. A new technical and economic comparison of regeneration methods for cation exchangers and the utilization of spent solutions will be made.
Sphere of application .The developed technology could be used for:
- chemical water treatment for industrial boiler plants;
- water treatment in steam power plants;
- water treatment in thermal power.
- design of new and the reconstruction of existing water softening plants.
Implementation of ISTC objectives. This project will provide Georgian specialists, who were previously employed in the “closed” sectors, with the opportunity to use their professional skills, knowledge, and experience in peaceful activities. These activities include chemical water treatment technology for boiler plants, the reclamation of chemical production waste and the prevention of wastewater discharge into water reservoirs, providing security for the environment. This project gives them the opportunity to establish co-operation with scientists and specialists from the international scientific community, to exchange experience, take part in conferences, meetings, and publish both inpidual and joint publications.


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The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.

 

ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

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