Liquid purification or separation – Processes – Preventing – decreasing – or delaying precipitation,...
Patent
1998-06-15
2000-03-14
Simmons, David A.
Liquid purification or separation
Processes
Preventing, decreasing, or delaying precipitation,...
210710, 210721, B01D 2100
Patent
active
060368675
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the qualitative and quantitative reduction of the content of precipitable ions in aqueous or other solutions and to the use of these solutions.
The invention more particularly applies to the desalination and to the demineralization of water, in particular of potable water or of process water, for the purpose of satisfying potability restrictions or restrictions related to the use of water and to the recycling of waste water in industry.
BACKGROUND OF THE INVENTION
Various desalination or demineralization or crystallization processes are currently known. The main processes will be restated hereinbelow with the disadvantages which are associated with them: from the treated water by settling or filtration. Thus, French Patent FR-A-2,339,575 discloses a process and a plant for the treatment of water by crystalline precipitation and settling which consists in producing a homogeneous dispersion of water to be treated, of reagents necessary for the crystalline precipitation and of sludges separated from the water to be treated and in settling this dispersion, the crystalline precipitation reaction being completed during the settling. The disadvantage of this known technique lies in the use of reagents which can be very expensive for the purpose of reducing their contents of salts of very slight solubility below their solubility; replace all or part of the ions by other ions. This solution exhibits the disadvantage of high consumption of chemical reagents and that of the production of saline, indeed highly saline, regeneration eluates; selective with respect to certain salts and which concentrate them in a fraction of the treated flow. The disadvantage of this technique lies in the production of a filtration concentrate which represents a significant fraction of the flow of the water to be treated (of the order of 10 to 70%, depending on the initial salinity and the degree of conversion adopted); vapor produced and which concentrates the salinity into a brine. This solution leads to very high energy consumption and the production of a saline brine which has to be either discharged or crystallized, the latter stage resulting in a very high investment cost; extract the inorganic salts from the solutions and to concentrate them into a brine, the purified water flow being separated from the brine flow by the said ion-exchange membranes.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides for the introduction of a process for desalination or demineralization with the possibility of crystallization which does not exhibit the disadvantages of the currently known solutions briefly restated hereinabove.
The desalination and demineralization process according to the present invention mainly relates to solutes, the solutions of which can be supersaturated by addition of chemical reagents.
The solutes can be, inter alia, inorganic or organic acids and their salts.
Consequently, the subject-matter of the present invention is a process for the desalination, demineralization and optionally crystallization of solutions containing acids and/or metal salts, characterized in that it comprises the following successive stages: reagent which is an inhibitor of the precipitation of salts, optionally followed by a filtration; fraction of the flow of between 5 and 80% of the flow of the solution to be treated; precipitation inhibitor and precipitating the crystallizable supersaturated salts in the concentrated fraction.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the dr
REFERENCES:
patent: 4175100 (1979-11-01), Schiller et al.
patent: 4634532 (1987-01-01), Logan et al.
patent: 4956157 (1990-09-01), Nasu
patent: 5685980 (1997-11-01), Patapoff et al.
Jogand Henri Louis Armand
Peron Pierre-Alain Jean Henri
Degremont
Morrison Betsey J.
Simmons David A.
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