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EP-4741345-A1 - HIGH-PURITY POTASSIUM CHLORIDE PREPARATION METHOD USING DUST, AND HIGH-PURITY POTASSIUM CHLORIDE PREPARED THEREBY

EP4741345A1EP 4741345 A1EP4741345 A1EP 4741345A1EP-4741345-A1

Abstract

The present invention relates to a method for preparing potassium chloride, the method capable of obtaining high-purity potassium chloride which may be used for fertilizers and industrial purposes by successively performing purification, two-stage evaporation and concentration, and cooling and crystallization on dust obtained from an exhaust gas generated during cement firing, and high-purity potassium chloride prepared by the preparation method.

Inventors

  • KIM, GYU SUN
  • LEE, HYUN MIN
  • AHN, SEONG YONG
  • SUN, KYUNG BOK
  • BAE, HEUNG KWON
  • CHOI, YUN SEOK

Assignees

  • LG Chem, Ltd.

Dates

Publication Date
20260513
Application Date
20240705

Claims (12)

  1. A method for preparing potassium chloride, the method comprising the steps of: (S10) preparing a potassium chloride aqueous solution by removing heavy metals from a dust aqueous solution; (S20) performing two-stage evaporation and concentration on the potassium chloride aqueous solution obtained in the step of S10; (S30) obtaining a potassium chloride slurry by cooling and crystallizing the potassium chloride aqueous solution obtained in the step of S20; and (S40) obtaining potassium chloride powder by dehydrating and drying the potassium chloride slurry obtained in the step of S30, wherein: primary evaporation and concentration in the step of S20 is performed at 85 °C to 97 °C; secondary evaporation and concentration in the step of S20 is performed at 60 °C to 70 °C; and the difference between the saturation concentration of the potassium chloride aqueous solution at the temperature at which the primary evaporation and concentration is performed and the potassium chloride concentration of the potassium chloride aqueous solution formed after the primary evaporation and concentration is 2.5 wt% or greater.
  2. The method of claim 1, wherein the step of S10 is to introduce carbon dioxide to the dust aqueous solution to precipitate and remove heavy metals.
  3. The method of claim 2, wherein the step of S10 comprises a primary mineralization step (S11) and a secondary mineralization step (S12), wherein the weight ratio of carbon dioxide introduced in the step of S11 and the step of S12 is 100:1 to 100:10.
  4. The method of claim 1, further comprising a step of (S13) removing sulfate from the potassium chloride aqueous solution between the step of S10 and the step of S20.
  5. The method of claim 4, wherein the step of S13 is to allow the potassium chloride aqueous solution to pass through a filter membrane including a polyamide nanofiber layer.
  6. The method of claim 1, wherein the difference between the saturation concentration of the potassium chloride aqueous solution at the temperature at which the secondary evaporation and concentration is performed and the potassium chloride concentration of the potassium chloride aqueous solution formed after the secondary evaporation and concentration is 0 wt% to 0.8 wt%.
  7. The method of claim 1, wherein the step of S30 is to perform the cooling at a rate of 5 °C/10 min to 15 °C/10 min.
  8. The method of claim 1, wherein the step of S30 is to perform stirring at a rate of 50 RPM to 350 RPM.
  9. The method of claim 1, wherein the step of S30 is to terminate the cooling at a temperature of 10 °C to 30 °C.
  10. The method of claim 1, wherein the moisture content of the potassium chloride powder is 0.5 wt% or less.
  11. The method of claim 1, wherein the dust is obtained from an exhaust gas generated during a cement firing process.
  12. High-purity potassium chloride having a purity of potassium chloride of 96.5 wt% or greater, and satisfying at least one of the following conditions i) to iii): i) the content of sulfate is 0.050 wt% to 0.300 wt% ii) the content of bromine is 400 weight ppm to 800 weight ppm iii) the content of aluminum is 200 weight ppb to 10,000 weight ppb.

Description

TECHNICAL FIELD Cross-reference to Related Applications This application claims the benefit of Korean Patent Application Nos. 10-2023-0088481, 10-2023-0088482, and 10-2023-0088484 filed on July 7, 2023, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. Technical Field The present invention relates to a novel method for preparing potassium chloride, the method capable of preparing high-purity potassium chloride by utilizing dust obtained from an exhaust gas generated during cement firing, and high-purity potassium chloride prepared by the preparation method. BACKGROUND ART Cement is the most commonly used building material in the modern world, and is manufactured through a process of firing a raw material including limestone in equipment such as a rotary kiln. Since the raw material needs to be heated to a high temperature of 1,000 °C or higher during the firing process, a large amount of energy needs to be supplied, and to this end, a large amount of fuel is used. However, when natural gas or petroleum is used as a fuel in the above process, there is a problem in that process cost is greatly increased, so that in recent years, waste plastics or the like have been used as the fuel to achieve two purposes of reducing the process cost and smoothly disposing waste. However, in the waste plastics, there is a large amount of harmful components, such as heavy metals derived from various additives added during a process of manufacturing plastics, or chlorine derived from plastics such as polyvinyl chloride, and the harmful components are included as they are in a dust component generated during a combustion process. Although such a dust component has typically been processed through landfill, there is a limitation in processing using the landfill, so that there is ongoing research on a method capable of efficiently processing the dust. As an example, since a large amount of chlorine is included in the dust, there are various studies on recovering the same in the form of potassium chloride. However, the purity of recovered potassium chloride is not high in the prior art, so that there is a limitation in utilizing the recovered potassium chloride for agricultural use or industrial purposes, and energy used in the process is not small, so that it is also not advantageous in terms of cost. Accordingly, the present invention is to provide a novel method for preparing potassium chloride, the method capable of efficiently preparing high-purity potassium chloride from dust. DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM An aspect of the present invention is to provide a method for preparing potassium chloride, the method capable of preparing high-purity potassium chloride at a high yield from dust in an exhaust gas generated during a cement firing process, and high-purity potassium chloride prepared by the preparation method. TECHNICAL SOLUTION According to an aspect of the present invention, there are provided a method for preparing potassium chloride and high-purity potassium chloride. More specifically, (1) the present invention provides a method for preparing potassium chloride, the method including the steps of S10 preparing a potassium chloride aqueous solution by removing heavy metals from a dust aqueous solution, S20 performing two-stage evaporation and concentration on the potassium chloride aqueous solution obtained in the step of S10, S30 obtaining a potassium chloride slurry by cooling and crystallizing the potassium chloride aqueous solution obtained in the step of S20, and S40 obtaining potassium chloride powder by dehydrating and drying the potassium chloride slurry obtained in the step of S30, wherein primary evaporation and concentration in the step of S20 is performed at 85 °C to 97 °C, secondary evaporation and concentration in the step of S20 is performed at 60 °C to 70 °C, and the difference between the saturation concentration of the potassium chloride aqueous solution at the temperature at which the primary evaporation and concentration is performed and the potassium chloride concentration of the potassium chloride aqueous solution formed after the primary evaporation and concentration is 2.5 wt% or greater. (2) In (1) above, the present invention provides a method for preparing potassium chloride, wherein the step of S10 is to introduce carbon dioxide to the dust aqueous solution to precipitate and remove heavy metals.(3) In (1) or (2) above, the present invention provides a method for preparing potassium chloride, wherein the step of S10 includes a primary mineralization step S11 and a secondary mineralization step S12, wherein the weight ratio of carbon dioxide introduced in the step of S11 and the step of S12 is 100:1 to 100:10.(4) In any one among (1) to (3) above, the present invention provides a method for preparing potassium chloride, wherein the method further includes a step of (S13) removing sulfate from the potassiu