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CN-122010155-A - Method for recycling calcium chloride wastewater

CN122010155ACN 122010155 ACN122010155 ACN 122010155ACN-122010155-A

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a calcium chloride wastewater recycling treatment method. Adding quick lime or slaked lime into calcium chloride wastewater to adjust the pH of the system to 10-12, then adding a flocculating agent to perform flocculation treatment, carrying out solid-liquid separation, wherein the liquid phase is a solution after impurity removal, adding an ammonium carbonate solution into the solution after impurity removal, stirring to perform precipitation reaction, carrying out solid-liquid separation, washing and drying the solid phase to obtain nano-scale calcium carbonate, crystallizing the liquid phase, and recycling ammonium chloride crystals. The method has the advantages of simple process, low energy consumption, low cost and high recycling utilization rate, and can obtain the high-whiteness and nanoscale calcium carbonate product and the high-purity ammonium chloride product.

Inventors

  • ZHOU MINGPU

Assignees

  • 厦门正元环境科技有限公司

Dates

Publication Date
20260512
Application Date
20260309

Claims (10)

  1. 1. The method for recycling the calcium chloride wastewater is characterized by comprising the following steps of: (1) Adding quick lime or slaked lime into the calcium chloride wastewater to adjust the pH of the system to 10-12, then adding a flocculating agent to perform flocculation treatment, carrying out solid-liquid separation, wherein the liquid phase is a solution after impurity removal; (2) Adding ammonium carbonate solution into the solution after impurity removal, stirring for precipitation reaction, carrying out solid-liquid separation, washing and drying a solid phase to obtain nano-grade calcium carbonate, crystallizing a liquid phase, and recovering ammonium chloride crystals.
  2. 2. The method for recycling calcium chloride wastewater according to claim 1, wherein the pH of the calcium chloride wastewater in the step (1) is 1-3, the concentration of calcium ions is 20000-50000 ppm, and the total concentration of impurity ions of iron, aluminum and silicon is 3000-5000 ppm.
  3. 3. The method for recycling calcium chloride wastewater according to claim 1, wherein the flocculant in the step (1) is an inorganic or organic flocculant, and comprises at least one of polyaluminium chloride, polyaluminium sulfate and polyacrylamide.
  4. 4. The method for recycling calcium chloride wastewater according to claim 3, wherein the adding amount of the flocculant is 50-150 mg/L.
  5. 5. The method for recycling calcium chloride wastewater according to claim 1, wherein the concentration of the ammonium carbonate solution in the step (2) is 0.5-2 mol/L.
  6. 6. The method for recycling calcium chloride wastewater according to claim 5, wherein the ammonium carbonate solution is prepared by the following steps: Ammonia and carbon dioxide are simultaneously or sequentially introduced into the water phase through a micro-nano bubble generator, so that the ammonia and the carbon dioxide are fully dissolved and reacted in the water to generate an ammonium carbonate solution.
  7. 7. The method for recycling calcium chloride wastewater according to claim 1, wherein the adding amount of the ammonium carbonate solution in the step (2) is controlled to be (1-1.2) in terms of the molar ratio of the ammonium carbonate to calcium ions in the solution.
  8. 8. The method for recycling calcium chloride wastewater according to claim 7, wherein the addition amount of the ammonium carbonate solution is controlled to be 1-1.1:1 in terms of molar ratio of ammonium carbonate to calcium ions in the solution.
  9. 9. The method for recycling calcium chloride wastewater according to claim 1, wherein the stirring rate of the stirring in the step (2) for precipitation reaction is 500-3000 rpm, the temperature is 10-35 ℃, and the average particle size of the nano-sized calcium carbonate is 10-200 nm.
  10. 10. The method for recycling calcium chloride wastewater according to claim 1, wherein the crystallization treatment in the step (2) is cooling crystallization treatment and/or evaporation crystallization treatment.

Description

Method for recycling calcium chloride wastewater Technical Field The invention belongs to the technical field of wastewater treatment, and particularly relates to a calcium chloride wastewater recycling treatment method. Background In industrial processes such as chlor-alkali chemical industry, inorganic salt production, metallurgy, surface treatment, hydrochloric acid-containing washing and the like, a large amount of acid wastewater containing calcium chloride is often generated. The waste water has the characteristics of high acidity, high calcium salt concentration and high impurity ion (such as iron, aluminum, silicon and the like) content, and if the waste water is directly neutralized and discharged or is simply evaporated and crystallized, the waste water has high energy consumption and is difficult to realize high value-added resource recovery. In the prior art, ammonia salt (such as ammonium bicarbonate or ammonium carbonate) is adopted to react with calcium chloride solution to generate calcium carbonate and recycle ammonium chloride, but the following defects generally exist: (1) The influence of impurity ions in the acid wastewater on the crystallization behavior of calcium carbonate and the quality of products are not fully considered; (2) Most of the obtained calcium carbonate is micron-sized or agglomerated particles, so that the application requirements of the nano calcium carbonate are difficult to meet; (3) The utilization efficiency of ammonia is low, and loss and secondary pollution are caused by easy volatilization; (4) The recovery mode of the ammonium chloride has higher energy consumption or insufficient crystallization purity. Therefore, a new method for recycling the calcium chloride wastewater is needed, which can effectively remove impurities, improve the utilization efficiency of ammonia and carbon dioxide, stably prepare nano calcium carbonate and realize efficient recovery of ammonium chloride. Disclosure of Invention Aiming at the defects and shortcomings of the prior art, the invention aims to provide a method for recycling calcium chloride wastewater. The invention aims at realizing the following technical scheme: a method for recycling calcium chloride wastewater comprises the following steps: (1) Adding quick lime or slaked lime into the calcium chloride wastewater to adjust the pH of the system to 10-12, then adding a flocculating agent to perform flocculation treatment, carrying out solid-liquid separation, wherein the liquid phase is a solution after impurity removal; (2) Adding ammonium carbonate solution into the solution after impurity removal, stirring for precipitation reaction, carrying out solid-liquid separation, washing and drying a solid phase to obtain nano-grade calcium carbonate, crystallizing a liquid phase, and recovering ammonium chloride crystals. Further, in the step (1), the pH of the calcium chloride wastewater is 1-3, the concentration of calcium ions is 20000-50000 ppm, and the total concentration of impurity ions of iron, aluminum and silicon is 3000-5000 ppm. The method comprises the steps of (1) converting free hydrochloric acid in wastewater into calcium chloride by adding quicklime or slaked lime, wherein impurity ion components are not introduced, and adjusting the pH value of a system to 10-12, and under the pH value condition, impurities such as iron, aluminum, silicon and the like in the wastewater are separated out in the form of hydroxide or composite precipitation, so that the influence on calcium carbonate precipitation in the follow-up process is reduced, and the quality of calcium carbonate products is improved. Further, the flocculant in step (1) is a conventional inorganic or organic flocculant, including polyaluminum chloride (PAC), polyaluminum chloride (PFC), polyaluminum sulfate (PAS), polyaluminum sulfate (PFS), polyacrylamide (PAM), more preferably a combination of polyaluminum chloride and cationic polyacrylamide. Further, the adding amount of the flocculant in the step (1) is 50-150 mg/L. And (3) performing flocculation treatment to obtain a solution with Ca 2+ and Cl - as main components after removing impurities. Further, the concentration of the ammonium carbonate solution in the step (2) is 0.5-2 mol/L, and the ammonium carbonate solution is prepared by the following method: Ammonia and carbon dioxide are simultaneously or sequentially introduced into the water phase through a micro-nano bubble generator, so that the ammonia and the carbon dioxide are fully dissolved and reacted in the water to generate an ammonium carbonate solution. Further, the adding amount of the ammonium carbonate solution in the step (2) controls the molar ratio of the ammonium carbonate to calcium ions in the solution to be (1-1.2): (1-1.2), and more preferably 1-1.1:1. Further, in the step (2), the stirring speed of stirring for precipitation reaction is 500-3000 rpm, the temperature is 10-35 ℃, and the average particle size of the nano-grade