A potassium chloride production process

Abstract

This invention discloses a production process for potassium chloride using carnallite as raw material. The process includes a crystallization unit and a flotation unit. First, pretreated carnallite is transported to the crystallization unit. The flotation unit includes a direct flotation unit and a reverse flotation unit. This process improves the yield and purity of potassium chloride products and avoids the drawbacks of existing single direct or reverse flotation processes requiring multiple (at least three) flotation operations. Furthermore, it reduces the washing steps after flotation while maintaining high purity, simplifying the experimental procedures, reducing energy consumption, and avoiding the reduction in potassium chloride crystal particle size caused by washing operations.

Description

Technical Field

[0001] This invention belongs to the field of chemical production, specifically relating to a production process for producing potassium chloride using carnallite as raw material. Background Technology

[0002] Potassium chloride is a very important chemical raw material with significant applications in fields such as potash fertilizer production. The main raw materials for producing potassium chloride include sylvite and carnallite.

[0003] Existing potassium chloride production processes mainly include "cold decomposition-positive flotation-washing method" and "cold crystallization-positive flotation-washing method". The "cold decomposition-positive flotation-washing method" involves adding fresh water and saturated brine during the grinding process, decomposing the ore while grinding. The "cold crystallization-positive flotation-washing method" for potassium chloride production is a novel process invented by Qinghai Salt Lake Yuantong Company and is currently one of the main methods for producing potassium chloride. It utilizes controlled supersaturation of the carnallite decomposition system to achieve the growth of potassium chloride crystal particles under room temperature conditions. The principle of cold crystallization is to control the rate of decomposition and crystallization of carnallite under room temperature conditions. This mainly involves controlling the decomposition conditions of carnallite to control the supersaturation of potassium chloride in the solution, reducing the number of potassium chloride crystals, and achieving the goal of growing potassium chloride crystals at room temperature. The emergence of the "cold crystallization-positive flotation-washing method" has gradually replaced the "cold decomposition-positive flotation-washing method" for producing potassium chloride. The production process of the "cold crystallization-positive flotation-washing method" mainly includes six steps: cold crystallization, flotation, separation, filtration, washing, centrifugation, and drying. The flotation process mainly involves primary roughing, primary scavenging, and secondary cleaning. After secondary cleaning, the concentrate is washed, dehydrated, and dried to obtain the potassium chloride product.

[0004] Currently, energy consumption, potassium chloride yield, and particle size are all important production indicators in the potash fertilizer production process, which are related to the company's cost control and product quality. Therefore, there is an urgent need to develop a potassium chloride production process with low energy consumption, high potassium chloride yield, and large particle size. Summary of the Invention

[0005] The purpose of this invention is to provide a potassium chloride production process with high yield, large particle size, low energy consumption, and high purity using carnallite as raw material. The production process includes a crystallization unit and a flotation unit. First, pretreated carnallite is transported to the crystallization unit. The flotation unit includes a forward flotation unit and a reverse flotation unit.

[0006] This invention employs a direct flotation-reverse flotation process, which improves the yield and purity of potassium chloride products. It also avoids the drawbacks of existing technologies where a single direct flotation or reverse flotation process requires multiple washing steps. While maintaining high purity, it reduces the washing steps after flotation, simplifies the experimental procedures, reduces energy consumption, and avoids the defect of potassium chloride crystal particle size reduction caused by washing operations.

[0007] According to a specific embodiment of the present invention, the production process sequentially passes through a positive flotation unit and a reverse flotation unit; the filtrate 1 obtained after filtration of the slurry in the positive flotation unit is transported back to the positive flotation unit, the filtrate 2 obtained is transported back to the crystallization unit, and the resulting foam filter cake is directly transported to the reverse flotation unit.

[0008] This invention employs a specific positive flotation-reverse flotation self-circulation process, which avoids the mutual influence between positive and reverse flotation reagents and improves the purity and yield of the product.

[0009] By sending a portion of the filtrate 1 from the positive flotation unit back to the positive flotation unit, and sending the resulting filtrate 2 back to the crystallization unit, the particle size of the potassium chloride product can be increased, thereby improving the purity and yield of the potassium chloride product.

[0010] According to a specific embodiment of the present invention, the volume of the filtrate 1 accounts for 75%-95% of the total volume of the filtrate 1 and the filtrate 2.

[0011] According to a specific embodiment of the present invention, the filtrate 3 obtained after filtration of the slurry processed by the reverse flotation unit is entirely transported back to the reverse flotation unit.

[0012] According to a specific embodiment of the present invention, the slurry after passing through the reverse flotation unit is filtered to obtain potassium chloride product without further washing.

[0013] According to a specific embodiment of the present invention, the positive flotation reagent is a fatty amine cationic collector or an alkyl sulfonate anionic collector, preferably one or more of dodecylamine and octadecylamine.

[0014] According to a specific embodiment of the present invention, the anti-flotation reagent is a carboxylic acid, an amide, or a morpholine; the carboxylic acid anti-flotation reagent is a saturated or unsaturated carboxylic acid, or a long-chain or short-chain carboxylic acid; the morpholine anti-flotation reagent is an alkylmorpholine or a morpholine fatty acid ester, preferably an alkylmorpholine, and more preferably an alkylmorpholine whose alkyl functional group contains 10 to 18 carbon atoms.

[0015] According to a specific embodiment of the present invention, the slurry at the outlet after being processed by the crystallization unit is passed through a solid-liquid separation device to obtain underflow and overflow; the underflow is transported to the flotation unit, and the overflow is transported back to the crystallization unit.

[0016] According to a specific embodiment of the present invention, the crystallization unit includes a fine crystallizer, and the overflow is processed in the fine crystallizer before being transported back to the crystallization unit.

[0017] According to a specific embodiment of the present invention, the chemical composition of the carnallite is KCl·MgCl2·6H2O.

[0018] Beneficial effects

[0019] This invention employs a specific process using carnallite as raw material, combining direct flotation and reverse flotation with a self-circulating mechanism. This improves the yield and purity of potassium chloride products and avoids the drawbacks of existing single direct or reverse flotation processes that require multiple (at least three) flotation steps. Furthermore, while maintaining high purity, it reduces post-flotation washing steps, simplifies experimental procedures, reduces energy consumption, and avoids the reduction in potassium chloride crystal particle size caused by washing operations. The specific self-circulating process also prevents interference between the direct and reverse flotation reagents, further improving product purity and yield. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the flotation process in Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the flotation process for Comparative Example 1. Detailed Implementation

[0022] Typical embodiments embodying the features and advantages of this invention will be described in detail in the following description. It should be understood that the invention can have various variations in different embodiments without departing from the scope of the invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the invention. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0023] Example 1

[0024] One ton of Lao carnallite obtained from mining is transported to the crushing unit, where it is crushed and then transported to the rod mill unit. From there, it is continuously transported in batches to the crystallization unit. The crystallized slurry is then transported to the direct flotation unit, where octadecylamine is used as the flotation reagent. The filtrate 1 obtained from the direct flotation unit is returned to the direct flotation unit, and the filtrate 2 is returned to the crystallization unit. Filtrate 1 accounts for 80% of the total volume of filtrate 1 and filtrate 2. The resulting froth filter cake is directly transported to the reverse flotation unit, where dodecylmorpholine is used as the flotation reagent. The filtrate 3 obtained from the reverse flotation unit is then entirely returned to the reverse flotation unit. The filter cake obtained from the slurry after filtration in the reverse flotation unit yields potassium chloride, which requires no further washing. The yield of the obtained potassium chloride product is 78%, the purity is 97.5%, and 70% of the particles have a diameter greater than 0.17 mm.

[0025] Comparative Example 1

[0026] Other conditions are the same as in Example 1, except that all the filtrate from the positive flotation unit is returned to the crystallization unit, see [link to example]. Figure 2 The yield of the obtained potassium chloride product was 66%, the purity was 95.5%, and 70% of the particles had a diameter of 0.12 mm or larger.

[0027] A comparison of Comparative Example 1 and Example 1 shows that by sending a portion of the filtrate 1 from the positive flotation unit back to the positive flotation unit and filtrate 2 back to the crystallization unit, the particle size of the potassium chloride product can be increased, and the purity and yield of the potassium chloride product can be improved.

[0028] Comparative Example 2

[0029] Other conditions were the same as in Example 1, except that a reverse flotation unit was not used. The product was washed three times after passing through a filtration unit to achieve the same purity as in Example 1. The yield of the obtained potassium chloride product was 65.5%, the purity was 97.5%, and 70% of the particles had a diameter of 0.09 mm or larger.

[0030] A comparison of Comparative Example 2 and Example 1 shows that, using the process of this application, under the condition of obtaining the same product purity, the product yield and particle size are improved, the number of product washings is reduced, the experimental steps are simplified, and energy consumption is reduced.

[0031] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for producing potassium chloride using carnallite as raw material, characterized in that, The production process includes a crystallization unit and a flotation unit; firstly, pretreated carnallite is transported to the crystallization unit; the flotation unit includes a direct flotation unit and a reverse flotation unit, and the production process passes through the direct flotation unit and the reverse flotation unit in sequence; the filtrate (1) obtained after filtration of the slurry in the direct flotation unit is transported back to the direct flotation unit, the filtrate (2) obtained is transported back to the crystallization unit, and the resulting foam filter cake is directly transported to the reverse flotation unit. The volume of the filtrate (1) accounts for 75%-95% of the total volume of the filtrate (1) and the filtrate (2).

2. The production process according to claim 1, characterized in that, The filtrate (3) obtained after the slurry processed by the reverse flotation unit is all transported back to the reverse flotation unit.

3. The production process according to claim 1 or 2, characterized in that, The slurry after passing through the reverse flotation unit is filtered to obtain potassium chloride product, which does not require further washing.

4. The production process according to claim 1 or 2, characterized in that, The positive flotation reagent is a fatty amine cationic collector or an alkyl sulfonate anionic collector; and / or The anti-flotation reagent is a carboxylic acid, amide, or morpholine; the carboxylic acid anti-flotation reagent is a saturated or unsaturated carboxylic acid, or a long-chain or short-chain carboxylic acid; the morpholine anti-flotation reagent is an alkylmorpholine or a morpholine fatty acid ester.

5. The production process according to claim 4, characterized in that, The positive flotation reagent is one or more of dodecylamine and octadecylamine.

6. The production process according to claim 4, characterized in that, The morpholine-based reverse flotation reagent is an alkylmorpholine.

7. The production process according to claim 6, characterized in that, The alkylmorpholine is an alkylmorpholine with an alkyl functional group containing 10 to 18 carbon atoms.

8. The production process according to claim 1 or 2, characterized in that, The slurry at the outlet of the crystallization unit is processed by a solid-liquid separation device to obtain underflow and overflow; the underflow is sent to the flotation unit, and the overflow is sent back to the crystallization unit.

9. The production process according to claim 8, characterized in that, The crystallization unit includes a fine crystal tank, and the overflow is processed in the fine crystal tank before being transported back to the crystallization unit.

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