WO2000007945A1 - Method for processing mineralised water - Google Patents

Abstract

The present invention relates to a method for processing mineralised water containing sulfates and chlorides and in which the ratio between the chloride and sulfate concentrations does not exceed 1:6. This method comprises different steps such as water preparation, concentration, crystallisation and centrifugation. The crystallisation is carried out at a total salt content of between 50 and 100 g/l, while the concentration is carried out according to a reverse osmosis method under a working pressure of between 1.5 and 4.0 Mpa. During the concentration process, the ratio between the sulfate and chloride concentrations increases at least 2.5 times. Due to the feedback into the processing cycle of the residual solutions obtained from the crystallisation and the centrifugation, it is possible to further increase the ratio between the sulfate and chloride concentrations before the concentration step. When mixing the residual solutions with the starting water, the ratio between said concentrations can be increased by at least 18 %. When mixing the residual solutions with the starting water and with the water after each water preparation step, this same ratio can be increased by at least 3 % in the starting water and by at least 17 % in the water to be concentrated. The preparation step of the present method may for example include the elimination of heavy metals and of calcium- and magnesium-containing solids.

Description

Processing method for mineralized water

Field of technology

The invention relates to the field of processing mineralized sulfate-chloride waters with a concentration ratio of chlorides and sulfates of less than 1:6 and can be used in mining, coal, energy, chemical, oil and gas industries. industry.

Previous level of technology

A number of variants are known for processing mineralized waters of the chloride-sulphate class with a relatively low salt content with the aim of their complete utilization and obtaining the components contained in them in the form of marketable salt products.

In the multi-stage processing method of mineralized waters, evaporation is carried out at the first stage with the release of sodium sulfate crystals, the residual solution is cooled at the second stage with the release of sodium sulfate decahydrate crystals, and the mother liquor is The third stage is evaporated with the release of sodium chloride crystals. In this case, the process of cystalization of particles proceeds at high concentration levels and is characterized by high energy intensity (patent RF ZhYu865P, IPC С02Р9/00, 10.08.97). The technological scheme of processing mineralized waters and chloride-sulphate class brines with a high concentration of hardness salts and a ratio of chloride to sulphate concentrations less than one (Maksin V.I., Vakhnin I.G., Skorobogach E.G., Standritschuk O.Z. Processing of mineralized waters chloride-sulfate class // Chemistry and technology of water - 1992-14, XЬб-С.428-433). In this way, the initial solution is softened with the release of carbonate calcium, the residual solution is concentrated by evaporation with the release of sodium sulfate, the residual solution of the paste after evaporation is salted to a ratio of sulfates and chlorides of 1:3 and a sodium chloride concentration of 18-21%, sodium sulfate dehydrate is crystallized by cooling, The uterine paste is drained until the clod natrium remains dry.

This method at all stages involves the release of salts from highly concentrated pastes with a total salt content of 200-240 g/l. Such concentration of chloride-sulfate solution can be achieved only by using evaporation, which is implemented in this way. To evaporate 1 ton of water, it is necessary to save from 500 to 2500 MJ of thermal energy. Meanwhile, the costs of concentrating by reverse osmosis are 2-3 orders of magnitude lower, but the use of reverse osmosis in this technological system is possible only at the preliminary stage and does not exclude subsequent concentration by evaporation. In this method, sodium sulfate decahydrate is released at the stage of maximum total salt content of the solution, when the concentration of sodium chloride is 3-6 times greater than the concentration of sulfate and is 18-21%. This is a direct result of the fact that the resulting mytabilities contain a significant amount of ploids and the following cleaning. In addition, when the ratio of chlorides and sulfates is less than 1:6, practically all of the obtained sodium chloride is used to salt the system to the required concentrations.

Discovery of inventions

The objective of the present invention is to develop a method for processing low-mineralized waters containing chlorides and sodium sulfates in a ratio of less than 1:6, whereby virtually all of the original solution is converted into drinking-quality water and sodium sulfate decahydrate. In this case, it is necessary to obtain a high-quality salt product, to achieve a significant reduction in energy costs due to 3

carrying out the crystallization process at lower concentration levels and at concentration ratios of chlorides and sulfates of no more than 1:20.

This result is achieved through a step-by-step processing of the source water, including successive stages of water preparation, concentration, crystallization and centrifugation. The distinctive features of the proposed method are the crystallization of sodium sulfate dehydrate at a total salt content in the solution of 50-100 g/l, the use of the reverse osmosis method at the concentration stage with working pressures in the range of 1.5-4.0 MPa with an increase The ratio of sulfate and chloride concentrations at this stage is not less than 2.5 times.

In this case, due to the return to the processing cycle of residual solutions obtained after crystallization and centrifugation, the ratio of sulfate and chloride concentrations is additionally increased before the concentration stage. Mixing residual solutions with the original water allows increasing the concentration ratio by at least 18%. Mixing the residual solutions with the initial water, as well as with water after each stage of water preparation, allows increasing the concentration ratio by at least 3% in the initial water and at least 17% in the water before concentration.

In addition, the water treatment stage of the proposed method may include the removal of heavy metals, as well as the removal of calcium hardness. In the other case, add caustic soda to the original paste with a polyacrylamide-type filoculant, and so on Pasta is brought to 8-9, and in the middle - soda ash and the same filoculants, brought to 9-11.

In addition, the proposed method can include, if necessary, the removal of magnesium hardness. It is removed from the residual solutions after crystallization and centrifugation directly before returning to the recycling cycle. To do this, add calcined soda and a flocculant such as polyacrylamide to the solution, bringing the pH solution to 13-14. The concentration of magnesium ions in the solution after the crystallization and centrifugation stage reaches its maximum value. Therefore, the release of magnesium hydroxide at this moment is most beneficial, because allows to reduce the time of its precipitation, especially when the concentration of magnesium ions in the source water is low.

In addition, it is possible to obtain anhydrous sodium sulfate from Glauber's salt upon melting the latter, and the crystals of sodium sulfate decahydrate do not require additional washing. The resulting sodium sulfate suspension is centrifuged to release the salt, and the cumate is returned to the processing cycle.

A distinctive feature of the proposed method of processing mineralized waters is the implementation of the process of crystallization of sodium sulfate dehydrate at a low total salt content of the solution of 50-100 g/l and a high ratio of sulfate concentrations and chlorides. The specified range of values of total salt content allows the use of the reverse osmosis method for concentrating. Moreover, carrying out this process at an operating pressure of 1.5 to 4.0 MPa and the specified salt content allows increasing the ratio of sulfate and chloride concentrations by at least 2.5 times. This is explained by the fact that with such working parameters the proportion of chloride ions that go into the permeate is much greater than the proportion of sulfate ions that go. For weakly mineralized waters with a ratio of chlorides and sulfates less than 1:6 under the specified process conditions, the amount of chloride ions in the permeate does not exceed the values established by the standards for drinking water. The return of residual particles after crystallization into the metabolism cycle allows for an almost significant increase in The ratio of concentrations of sulfates and clopiids is reduced by a concentration block of no less than 18%, i.e. the specified ratio of concentrations in the residual solutions of the city is higher than in the original water. In addition, it is possible to reduce energy consumption in the cycle, and also additionally increase the ratio of concentrations, if you return residual solutions are fed into the processing cycle in stages. In this case, residual solutions after crystallization and centrifugation are mixed and then divided into several streams. One is added to the source water, another is added to the solution after removing heavy metals, a third is added to the solution after removing calcium hardness, with the ratio of sulfate and chloride concentrations increasing in the source water by at least 3%, and in the solution after removing heavy metals by no more. less than 7.5%, in a sand solution after removal of calcium hardness - not less than 9%. In this case, the ratio of concentrations of these substances in water before concentration increases by not less than 17%. The distribution of the residual solution between the stages of water treatment allows for regulation of the degree of concentration of heavy metals and calcium in the circuit, as well as the reduction of sulfates and chlorides along with them.

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Fig. 1 shows the flow-scheme of mineralized water processing according to the invention.

The best option for implementing the invention

The method of processing mineralized waters is described below. The initial solution enters the water treatment unit 1, which may include stages of heavy metal removal 1a and calcium hardness 1b with the production of iron-containing pigment and calcium carbonate, respectively. Heavy metals (iron, manganese, chromium, etc.) are removed from the solution by adding _cast soda and a flocculant. The resulting suspension is dehydrated with the release of the iron-containing pigment as a commercial product. The clarified solution is sent to reagent softening 1v, where calcium hardness is removed. adding _^ m of calcined soda and a flocculant such as polyacrylamide. The resulting solution is clarified, the suspension is dehydrated to obtain calcium carbonate as a commercial product. The clarified solution is filtered and neutralized by adding sulfuric acid, after which it is fed to the reverse osmosis unit of concentration 2. The process of water treatment in the reverse osmosis unit is carried out at an operating pressure in the range of 1.5-4.0 Mpa to a total salt content in concentration of 50-100 g/l. As a result, the ratio of chloride and sulfate concentrations at the outlet increases by at least 2.5 times compared to the solution entering the concentration. The concentrated solution after reverse osmosis is crystallized by cooling, and the resulting suspension is centrifuged to isolate _^ m of sodium sulfate dehydrate.

Thus, the reduction of the concentration of contaminants in solutions before crystallization due to the use of concentration by the method of reverse osmosis with the specified parameters of operation allows to reduce the total energy consumption at the stages concentration and crystallization, and also to obtain a pure finished product - Glauber's salt with the amount of dry impurities no more than 0.3%.

Below is an option for processing mine water with the chemical composition indicated in the table.

Table. Composition of source and drinking water

Β κачесτве гοτοвыχ προдуκτοв τρебοвалοсь ποлучиτь вοду πиτьевοгο κачесτва, сτандаρτ на κοτορую τаκже уκазан в τаблице, железοсοдеρжащий πигменτ, κаρбοнаτ κалъция, глаубеροву сοль. Ρасχοд исχοднοй шаχτнοй вοды, ποсτуπающей на πеρеρабοτκу, сοсτавил 3,1 м7час. Пοсле смешения ее с ποτοκοм οсτаτοчнοгο ρасτвορа сτадии κρисτаллизации ρасχοд увеличился дο 3,13 м³/час, οбщее сοлесοдеρжание дοсτиглο 4,7 г/л, сοοτнοшение χлορидοв и сульφаτοв - не бοлее 1 :34. Β блοκе вοдοποдгοτοвκи на πеρвοм эτаπе с целью удаления τяжелыχ меτаллοв ποсτуτιающий ρасτвορ οбρабаτывали едκим наτροм с дοбавлением ποлиаκρиламида, дοвοдя ρΗ ρасτвορа в зοне ρеаκции дο значений 8..9. Пοсле οсвеτления и οбезвοживания ποлучили железοсοдеρжащий πигменτ в κοличесτве 0,53 κг на 1 м^" исχοднοй вοды с массοвым сοдеρжанием οснοвнοгο вещесτва - οκсида железа δοлее 90%.

As for the quality of the prepared products, you were concerned about obtaining drinking water, the standard for which is also indicated in the table, iron-containing pigment, calcium carbonate, glaucous salt. The consumption of the initial mine water entering the processing plant was 3.1 m7/hour. After mixing it with the flow of the residual solution from the crystallization stage, the flow rate increased to 3.13 ^m3 /hour, the total salt content reached 4.7 g/l, the ratio of chlorides and sulfates was no more than 1:34. In the water treatment unit, at the first stage, in order to remove heavy metals, the final solution was treated with caustic soda with the addition of polyacrylamide, bringing the pH of the solution in the reaction zone to values of 8..9. After clarification and dehydration, an iron-containing pigment was obtained in the amount of 0.53 kg per 1 ^m3 of initial water with a mass content of the main substance - iron oxide - of more than 90%.

A clarified solution with a residual iron ion content of no more than 0.02 mg/l was mixed with a flow of the residual solution from the crystallization stage. The resulting solution in the amount of 3.19 m3/hour with a total salt content of 4.8 g/l and a ratio of chlorides and sulfates of no more than 1:37 was fed to the stage of removing calcium hardness. At this stage, calcined soda and a floxulant - polyacrylamide - were added to the solution, bringing the pH in the reaction zone to 9..10. After separating the sediment and dehydrating it, 1.3 kg of calcium carbonate per 1 ^m3 of source water with a mass content of polluting impurities of less than 5% of the mass of dry sediment is obtained.

The clarified solution with a residual hardness of no more than 1 mg-eq/l was mixed with a flow of the residual solution from the crystallization stage, neutralized with sulfuric acid to ρΗ values equal to 6..7, and then filtered on ceramic membrane filters with a size πρ no more than 1 μm. The resulting solution with a flow rate of 3.26 m3/hour, a total salt content of 5.3 g/l, a ratio of chlorides and sulfates of no more than 1:40 was fed to the reverse osmosis concentration unit. The reverse osmosis concentrating process included two stages with workers pressures of 2.06 and 3.75 MPa, respectively. The permeate flow rate was 3.3 m3/hour, and the concentration was 0.16 m3/hour. The total salt content of the permeate after mixing the flows from the two stages did not exceed 370 mg/l, of which no more than 100 mg/l of chloride ions were detected. In the concentration, the ratio of chloride to sodium sulfate was maintained at a level of 1:100 with a chloride concentration of no more than 450 mg/l and a _total salt content of 90 g/l.

From the reverse osmosis unit the concentrate was sent for crystallization. The process proceeded while cooling the solution to a temperature of 0..1°C. The resulting suspension was left to settle, after which the thickened residue was fed to centrifugation, where glaucine salt was isolated in the amount of 92 kg per 1 m3 of concentrate with a content of the main substance in terms of dry weight of at least 99%. The amount of chlorides in dry Glauber's salt was no more than 0.1%. The fagate was mixed with the mother liquor after settling and fed into the feed water, into the solution after the precipitation of heavy metals, into the solution before the reverse osmosis unit in a ratio of 1:2:2.3, respectively.

The obtained results of the experimental studies show that the method of reverse osmosis with the specified working parameters allows to concentrate sodium sulfate to a greater extent than all other compounds present in the solution before crystallization and, thereby reducing the amount of contaminating impurities in the finished sodium sulfate dehydrate by at least 4 times compared to known methods.

Industrial applicability

The proposed method is applicable for the disposal of mineralized waters, which are by-products in the mining, coal, energy, chemical, oil and gas industries, and obtaining drinking-quality water and commercial salt products. The method concerns waters of the sulfate-chloride class with a relatively low salt content and a ratio of chlorides and sulfates of less than 1:6.

Claims

10 principles of invention 1. A method for processing mineralized waters, including the stages of water treatment, concentration, crystallization and centrifugation, characterized in that crystallization is carried out at a total salt content of 50-100 g/l, and concentration is carried out by the reverse osmosis method at an operating pressure of 1.5 - 4.0 μη, and the ratio of sulfate and chloride concentrations in the concentration process increases by at least 2.5 times. 2. Method according to paragraph 1, characterized in that the residual solutions obtained after crystallization and centrifugation are mixed and returned to the processing cycle. 3. The method according to item 2, characterized in that the residual solutions obtained after crystallization and centrifugation are mixed with 15 source water, whereby the ratio of sulfate and chloride concentrations in the source water increases by at least 18%. 4. The method according to item 2, characterized in that the residual solutions obtained after crystallization and centrifugation are mixed with the initial water after each stage of water preparation, and the ratio 20 The concentration of sulfates and chlorides increases in the original water by no less than 3%, and in the water before concentration - by no less than 17%. 5. Any method from steps 1-4, characterized by the fact that the water treatment stage includes the removal of heavy metals Processing of the original pasta with caustic substances with the addition of a filoculant type 25 polyamide, and this brings the paste to 8-9. 6. Method according to any of steps 1-5, differing in that the water treatment stage includes the removal of hard salts. 7. . The method according to item 6, characterized in that the removal of hardness salts includes the removal of calcium hardness by adding to the solution before 30 by concentrating soda ash and filoculant like polypylamide, and this is achieved by pasta until 9-10. 8. The method according to item 6, characterized in that the removal of hardness salts includes the removal of magnesium hardness by adding calcined soda and a flocculant such as polyacrylamide to the solution after crystallization and centrifugation, while the pH of the solution is brought to 13-14. 9. The method according to any of paragraphs.1-8, characterized in that the sodium sulfate decahydrate obtained after centrifugation is melted with the release of sodium sulfate crystals, the suspension obtained upon melting is centrifuged with the release of anhydrous sodium sulfate, and the product obtained after The centrifuged concentrate is mixed with the concentrate obtained by the reverse osmosis method.