Method for selectively removing calcium ions from concentrated water byproduct of sea water desalination process and other high-calcium-magnesium-content concentrated brines
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A concentrated brine, selective technology, applied in concentrated water decalcification, high calcium and magnesium concentrated brine in the field of selective removal of calcium ions, can solve the problem of unsuitable for selective decalcification treatment, low calcium removal rate, high operating cost, etc. problem, to achieve the effect of reducing operating cost, low operating cost and long stirring time
Inactive Publication Date: 2013-02-20
天津凯铂能膜工程技术有限公司
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[0008] Use Na 2 SO 3 When dealing with seawater or low-concentration calcium-magnesium aqueous solution, CaSO 3 Most of them exist in supersaturated state, and part of calcium and magnesium exist in the form of double salt, the removal rate of calcium is extremely low
Instead use Na 2 SO 3 There is no relevant report on the treatment of concentrated seawater or high calcium and magnesium concentrated water
And use NaF, Na 2 C 2 o 4 、Na 3 PO 4 As a precipitant, the effect is the same as that of Na 2 CO 3 , the removal rate of calcium is low, the loss rate of magnesium is high, and the operation cost is high, so it is not suitable for selective decalcification of high calcium and magnesium concentrated water
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Embodiment 1
[0040] Concentrated water by-product of a multi-stage flash seawater desalination plant, 5.4°Bé, pH=8.2, [Ca 2+ ]=650mg / L, [Mg 2+ ]=2000mg / L, heated to 85°C in a closed container with stirring, and then added the theoretical equivalent (n Ca2+ :n Na2SO3 =1:1.2) 20% (wt) of Na 2 SO 3 Solution, stirred for 40min, filtered after standing for 5min, according to [Ca 2+ ] to calculate Ca 2+ The removal rate is 90.5%, Mg 2+ The loss rate is 0.45%;
Embodiment comparative example 2
[0044] Concentrated water quality is the same as in Example 1, 20% (wt) Na is used at 25°C 2 SO 3 Solution processing, other operating conditions are with embodiment 1, after processing Ca 2+ The removal rate is 72.5%.
[0045] In addition, add concentrated hydrochloric acid to the filtrate obtained in Example 1 to adjust the pH to 6.2, then use an evaporator to evaporate and concentrate, and no precipitation occurs when the concentration is 25 ° Bé; or the concentrated water after decalcification is aerated for 30 minutes, and then use an evaporator Concentrated by evaporation, no precipitation occurs when the concentration is 25°Bé.
Embodiment 2
[0047] Concentrated water by-product of reverse osmosis seawater desalination in a factory, 6°Bé, pH=7.0, [Ca 2+ ]=871mg / L, [Mg 2+ ]=2680mg / L, heated to 85°C in a closed container with stirring, and then added the theoretical equivalent (n Ca2+ :n Na2SO3 =1:1.2) 20% (wt) of Na 2 SO 3 solution, stirred for 40min, filtered after standing for 5min, measured Ca 2+ The removal rate is 92.5%, Mg 2+ The loss rate is 0.40%.
[0048] The comparative example of embodiment 2:
[0049] Concentrated water quality and operating conditions are the same as in Example 2, and the precipitant is changed to 20% (wt) Na 2 CO 3 solution, after treatment Ca 2+ The removal rate is 81.5%, Mg 2+ The loss rate was 12.5%.
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Abstract
The invention relates to a method for selectively removing calcium ions from a concentrated water byproduct of a sea water desalination process and other high-calcium-magnesium-content concentrated brines, which comprises the following steps: regulating the pH value of the concentrated water to 7.0-8.5, and then heating to a certain temperature; introducing the concentrated water into a heat-insulating apparatus capable of realizing sealed stirring, adding a sodium sulfite or sodium carbonate solution having a certain concentration while stirring, reacting for 1-40 minutes while sufficiently stirring, standing for 5-10 minutes, and then filtering to remove calcium sulfite or calcium carbonate precipitate; and adding hydrochloric acid into the filtrate to regulate the pH value back to 6. According to the invention, the problems of low calcium removal rate, high magnesium loss rate, long stirring time and the like during the concentrated water treatment based on the traditional normal-temperature sodium carbonate precipitation method are overcome, the operation is convenient, the investment is low, and the operation cost is low; and the concentrated water liquid subjected to decalcification treatment can be further deeply concentrated through a membrane method or hot method, thereby improving the fresh water recovery rate and realizing the reutilization and zero discharge of the resources. The method provided by the invention is suitable for selectively removing calcium ions from sea water, sea water or brackish water subjected to other treatment processes such as reverse osmosis or multiple-effect evaporation and concentration, underground salt brines and concentrated water of industrial waste water subjected to reverse osmosis treatment.
Description
technical field [0001] The invention belongs to the technical field of chemical feed liquid or wastewater pretreatment, and relates to concentrated water decalcification, in particular to a method for selectively removing calcium ions from concentrated water by-produced in a seawater desalination process or other concentrated brines high in calcium and magnesium. Background technique [0002] my country's fresh water resources are scarce, and the time and geographical distribution are uneven. In recent years, due to the aggravation of pollution, the contradiction between supply and demand of fresh water has become more prominent, and the lack of fresh water resources has become a restrictive factor for the sustainable development of economy and society. The advanced treatment and reuse of industrial wastewater such as seawater desalination plants, refineries, steel plants and power plants has become an effective means to solve the problem of water shortage in our country. H...
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