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CN-122006417-A - Method for mineralizing and carbon fixing of concentrated brine

CN122006417ACN 122006417 ACN122006417 ACN 122006417ACN-122006417-A

Abstract

The invention discloses a method for mineralizing and solidifying carbon by using concentrated brine, which comprises the following steps of introducing a carbon dioxide gas source into pure water, stirring under pressure until carbon dioxide is dissolved in the pure water to obtain a carbonic acid solution, dropwise adding alkali into the carbonic acid solution under the pressure, regulating pH to obtain a high-pressure carbonic acid alkali solution, mixing the high-pressure carbonic acid alkali solution with the concentrated brine containing calcium ions under normal pressure, curing at 25-40 ℃ to obtain reaction slurry, carrying out solid-liquid separation, washing, drying and collecting calcium carbonate. The method can lead the removal rate of calcium ions in the concentrated brine after nanofiltration separation to reach 97%, obviously reduce the hardness of calcium in the effluent, create favorable conditions for recycling the effluent, realize the fixation of about 0.4 ton of carbon dioxide per 1 ton of calcium carbonate product produced, realize the high-valued mineralization utilization of carbon dioxide in flue gas, and synchronously solve the multiple problems of calcium resource waste, high energy consumption, limited carbon dioxide utilization in the carbon capture field and the like in the treatment of the concentrated brine.

Inventors

  • ZHANG XIAOJING
  • YUE XIN
  • GAO JIAN
  • MA JIAN
  • SONG YULONG
  • ZHANG KAI

Assignees

  • 凌源钢铁股份有限公司

Dates

Publication Date
20260512
Application Date
20260402

Claims (10)

  1. 1. A method for mineralizing and solidifying carbon by using concentrated brine, which is characterized by comprising the following steps of: Step 1, high-pressure carbon dioxide dissolution, namely introducing a carbon dioxide gas source into pure water, and stirring under the pressure of 2-5 MPa until the dissolution amount of carbon dioxide in the pure water reaches 2.76-6 g/L to obtain a carbonic acid solution; step 2, alkalizing and converting, namely dropwise adding alkali into the carbonic acid solution under the pressure condition in the step 1, and regulating the pH value to 10.2-10.5 to obtain high-pressure carbonic acid alkali solution; step 3, precipitation reaction, namely uniformly mixing high-pressure alkali carbonate solution with concentrated brine containing calcium ions at normal pressure, and curing for 30-60 minutes at 25-40 ℃ to obtain reaction slurry, wherein the concentrated brine is calcium-enriched side concentrated solution obtained by separating salt from concentrated water of a reverse osmosis device through a nanofiltration membrane; And 4, post-treatment, namely solid-liquid separation, washing, drying and collecting to obtain the calcium carbonate.
  2. 2. The method of claim 1, wherein the carbon dioxide source comprises carbon dioxide produced by a pressure swing adsorption carbon capture process of flue gas, the pure water comprises reverse osmosis produced water, the conductivity of the reverse osmosis produced water is less than 10 μs/cm, and the volume concentration of carbon dioxide in the carbon dioxide source is greater than or equal to 95%.
  3. 3. The method according to claim 1, wherein a carbon dioxide gas source is introduced into pure water for 10-30 minutes to fully dissolve carbon dioxide in the pure water, and the dissolution amount is 2.76-6 g/L; The pure water temperature is 15-25 ℃.
  4. 4. The method according to claim 1, wherein the concentration of CO 3 2- in the high-pressure carbonic acid alkali solution is 1.7-5 g/L.
  5. 5. The method according to claim 1, wherein the liquid alkali is a mixture of alkali metal hydroxide and water, the concentration of the alkali metal hydroxide in the liquid alkali is 30-40 wt%, and the alkali metal hydroxide comprises sodium hydroxide or potassium hydroxide.
  6. 6. The method of claim 1, wherein the concentration of calcium ions in the strong brine is 800-1000 mg/L.
  7. 7. The method according to claim 1, wherein the high-pressure alkali carbonate solution is depressurized to normal pressure and mixed with the concentrated brine containing calcium ions, and reacted at 25-40 ℃ for 30-60 minutes.
  8. 8. The method according to claim 1, wherein the operation of mixing the high-pressure alkali carbonate solution with the concentrated brine containing calcium ions is that the total volume of the needed concentrated brine is calculated according to a chemical reaction equation of calcium carbonate, the high-pressure alkali carbonate solution and the concentrated brine accounting for 30-35% of the total volume of the concentrated brine are uniformly mixed, and then the rest of the concentrated brine is slowly added dropwise; the slow dropwise adding time is 20-30 min, and the stirring speed is 100-150 rpm.
  9. 9. The method according to claim 1, wherein the reaction slurry is subjected to solid-liquid separation by a centrifugal separation device, and the filtrate after the solid-liquid separation contains sodium carbonate as an alkalizing agent for the alkali liquor in step 2; The centrifugal separation equipment is a horizontal decanter centrifuge or a disk centrifuge, and the separation factor of solid-liquid separation is controlled to be 150-300.
  10. 10. The method according to claim 1, wherein the washing is three-stage countercurrent washing, the first stage washing liquid used in the three-stage countercurrent washing is filtrate collected after solid-liquid separation, the second stage washing liquid and the third stage washing liquid are all pure water, and the mass ratio of the total mass of the first stage washing liquid, the second stage washing liquid and the third stage washing to the solid precipitate is 3:1; And the filtrate after solid-liquid separation and the washing liquid generated after washing are returned to the circulating water system for recycling.

Description

Method for mineralizing and carbon fixing of concentrated brine Technical Field The invention relates to the technical field of technology, energy technology and energy water treatment, in particular to a method for mineralizing and solidifying carbon by using concentrated brine. Background With the development of the steel industry and the acceleration of the urban process, the treatment of high-salinity strong brine (total dissolved solids (TDS)) generated in the sewage treatment process is generally more than 10,000 mg/L, and the hardness (calculated by CaCO 3) can reach 500-2000 mg/L, which becomes an industrial problem. At present, strong brine is mainly treated by adopting modes such as evaporative crystallization or deep well recharging, so that the energy consumption is high (usually 20-60 kWh/m 3), the cost is high, and the produced mixed salt is difficult to recycle, so that the waste of calcium resources is caused. Meanwhile, carbon dioxide trapped by the carbon trapping technology in the iron and steel enterprises is mostly used for a coal gas utilization way, so that the recycling of strong brine and the development of carbon trapping at the tail end of the iron and steel enterprises are restrained. Therefore, development of a treatment method combining strong brine treatment and carbon dioxide emission reduction is urgently needed to solve the problems of calcium resource waste, generation of mixed salt and waste liquid, high cost, limited carbon capture path and the like in the prior art. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a method for mineralizing and fixing carbon by using concentrated brine. According to the method, the calcium carbonate is prepared by utilizing the hardness of the strong brine and the carbon dioxide in the flue gas to cooperatively fix carbon, and the high-efficiency removal and recycling of calcium ions in the strong brine and the high-value carbon fixation utilization of CO 2 in the flue gas are realized through a high-pressure carbon dioxide dissolution-alkalization conversion-chemical precipitation process route. In order to achieve the above object, the present invention is achieved by the following means. A method for mineralizing and solidifying carbon by using concentrated brine, which comprises the following steps: Step 1, high-pressure carbon dioxide dissolution, namely introducing a carbon dioxide gas source into pure water, and stirring under the pressure of 2-5 MPa until the dissolution amount of carbon dioxide in the pure water reaches 2.76-6 g/L to obtain a carbonic acid solution; In the step 1, the carbon dioxide gas source comprises carbon dioxide produced by flue gas through Pressure Swing Adsorption (PSA) carbon capture engineering, and the pure water comprises reverse osmosis produced water, wherein the conductivity of the reverse osmosis produced water is less than 10 mu S/cm. In the step 1, the volume concentration of carbon dioxide in the carbon dioxide gas source is more than or equal to 95 percent. In the step 1, a carbon dioxide gas source is introduced into pure water for 10-30 minutes so as to enable carbon dioxide to be fully dissolved in the pure water, wherein the dissolution amount is 2.76-6 g/L. In the step 1, the pure water temperature is 15-25 ℃. Step 2, alkalizing and converting, namely dropwise adding alkali into the carbonic acid solution under the pressure condition in the step 1, and regulating the pH value to 10.2-10.5 to obtain high-pressure carbonic acid alkali solution; In said step 2, a base is added dropwise to the carbonic acid solution to convert CO 2（H2CO3、HCO3- in dissolved form into CO 32-. In the step 2, the concentration of CO 32- in the high-pressure alkali carbonate solution is 1.7-5 g/L. In the step 2, the liquid alkali is a mixture of alkali metal hydroxide and water, wherein the concentration of the alkali metal hydroxide in the liquid alkali is 30-40 wt%, and the alkali metal hydroxide comprises sodium hydroxide and potassium hydroxide. Step 3, precipitation reaction, namely uniformly mixing high-pressure alkali carbonate solution with concentrated brine containing calcium ions at normal pressure, and curing for 30-60 minutes at 25-40 ℃ to obtain reaction slurry, wherein the concentrated brine is calcium-enriched side concentrated solution obtained by separating salt from concentrated water of a reverse osmosis device through a nanofiltration membrane; in the step 3, the concentration of calcium ions in the strong brine is 800-1000 mg/L. In the step 3, the high-pressure alkali carbonate solution is decompressed to normal pressure and mixed with the strong brine containing calcium ions, and the mixture is reacted for 30 to 60 minutes at a temperature of between 25 and 40 ℃ so that CO 32- in the high-pressure alkali carbonate solution and Ca 2+ in the strong brine react to generate calcium carbonate. In the step 3, the operation of mixing the high-pressure a