Method for separating potassium and sodium in phosphate mother liquor

Abstract

The application provides a method for separating potassium and sodium in a phosphate mother liquor, comprising the following steps: firstly, potassium in the phosphate mother liquor containing potassium and sodium is precipitated from the phosphate mother liquor in the form of potassium dihydrogen phosphate to obtain a potassium-removed mother liquor; and then, sodium in the potassium-removed mother liquor is crystallized and separated to realize the separation of potassium and sodium; specifically, the method comprises the following steps: S1. potassium removal: adjusting the pH value of the phosphate mother liquor to 4.0-5.0, then cooling and crystallizing, and centrifugally separating to precipitate potassium dihydrogen phosphate crystals, and obtaining the potassium-removed mother liquor; S2. sodium removal: adjusting the pH value of the potassium-removed mother liquor to 7.5-8.5, then cooling and crystallizing, and centrifugally separating to precipitate ammonium sodium phosphate crystals, and obtaining the sodium-removed mother liquor; the separation method separates potassium and sodium in the mother liquor, removes sodium impurities in the system, purifies the mother liquor, improves the quality of the circulating mother liquor, ensures the normal operation of the production system, and achieves the purposes of improving the product quality and improving the production capacity.

Description

Technical Field

[0001] This invention relates to the field of phosphate mother liquor treatment technology, and more specifically, to a method for separating potassium and sodium from phosphate mother liquor. Background Technology

[0002] Many chemical companies generate large amounts of phosphate mother liquor during their production processes. In potassium phosphate production, sodium, as an impurity, accumulates in the mother liquor, and when it reaches a certain level, it severely impacts the production process. Potassium and sodium salts are both soluble salts and always coexist in nature. The separation of sodium and potassium in the chemical industry is mainly achieved by utilizing their different solubilities at different temperatures. However, with the development of production and the economy, it is difficult to achieve complete separation of sodium and potassium using ordinary recrystallization methods.

[0003] Existing technologies for sodium-potassium separation include: Chinese patent CN102448885A discloses a sodium and potassium separation and extraction device and method, which uses a combination of multi-stage cooling crystallization and conversion absorption to separate potassium chloride and sodium bicarbonate. This technology is applied to mixed solutions containing sodium, potassium, and chlorine, but the process is lengthy, energy-intensive, costly, and produces products with insufficient purity, which greatly reduces the production efficiency of enterprises. Summary of the Invention

[0004] The purpose of this invention is to provide a method for separating potassium and sodium in phosphate mother liquor, which separates potassium and sodium in the mother liquor, removes sodium impurities from the system, purifies the mother liquor, improves the quality of circulating mother liquor, ensures the normal operation of the production system, and achieves the goal of improving product quality and increasing production capacity.

[0005] The embodiments of the present invention are achieved through the following technical solutions:

[0006] A method for separating potassium and sodium from phosphate mother liquor includes the following steps: First, potassium in the potassium- and sodium-containing phosphate mother liquor is precipitated from the phosphate mother liquor as potassium dihydrogen phosphate to obtain a depotassium-treated mother liquor; then, sodium in the depotassium-treated mother liquor is crystallized to separate potassium and sodium; specifically, the method includes the following steps:

[0007] S1. Potassium removal: Adjust the pH of the phosphate mother liquor to 4.0-5.0, then cool and crystallize. After centrifugation, potassium dihydrogen phosphate crystals are precipitated to obtain the potassium removal mother liquor.

[0008] S2. Sodium removal: Adjust the pH of the potassium removal mother liquor to 7.5-8.5, then cool it to crystallize. After centrifugation, sodium ammonium phosphate crystals are precipitated to obtain the sodium removal mother liquor.

[0009] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0010] This invention's separation method can solve the problem of sodium impurity accumulation in the mother liquor during phosphate production, effectively purifying the mother liquor, improving product quality, and stabilizing yield. Furthermore, the mother liquor after potassium-sodium separation can be returned to the system for reuse, potassium salt crystals can be returned to the potassium salt production system, and ammonium sodium crystals can be used to produce sodium phosphate, achieving resource utilization of the phosphate mother liquor and bringing greater production benefits to enterprises. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0012] The following is a detailed description of a method for separating potassium and sodium from phosphate mother liquor provided by an embodiment of the present invention.

[0013] A method for separating potassium and sodium from phosphate mother liquor includes the following steps: First, potassium in the potassium- and sodium-containing phosphate mother liquor is precipitated from the phosphate mother liquor as potassium dihydrogen phosphate to obtain a depotassium-treated mother liquor; then, sodium in the depotassium-treated mother liquor is crystallized to separate potassium and sodium; specifically, the method includes the following steps:

[0014] S1. Depotassium removal: Adjust the pH of the phosphate mother liquor to 4.0-5.0, stir at a rate of 50-100 r / min, and cool at a rate of 0.1-0.25℃ / min to 15-30℃ for crystallization, so that the potassium in it precipitates out of the phosphate mother liquor as potassium dihydrogen phosphate, thereby achieving partial potassium separation. The potassium dihydrogen phosphate crystals and depotassium removal mother liquor are obtained by centrifugation.

[0015] S2. Sodium Removal: Ammonia gas is then introduced into the potassium-removed phosphate mother liquor to adjust the pH to 7.5-8.5. The liquor is stirred at a rate of 150-200 r / min and cooled to 5-20℃ at a rate of 0.1-0.15℃ / min for crystallization. The crystallized sodium ammonium phosphate is then centrifuged and washed to separate potassium and sodium, ultimately yielding the sodium-removed mother liquor. The obtained sodium-removed mother liquor can be returned to the system for reuse, the potassium salt crystals can be returned to the potassium salt production system, and the sodium ammonium phosphate crystals can be used to produce sodium phosphate, achieving resource utilization of the phosphate mother liquor.

[0016] During the separation process, ammonia reacts with sodium dihydrogen phosphate in the phosphate mother liquor to form sodium ammonium phosphate double salt, which has low solubility. Potassium in the phosphate mother liquor is only carried away during crystallization separation through liquid retention. High-purity sodium ammonium phosphate can be obtained by washing the crystallized sodium ammonium phosphate, thus achieving the separation of potassium and sodium from the phosphate mother liquor containing both potassium and sodium. The separation method of this invention yields Na₂O ≤ 1.50% in the phosphate mother liquor. The reaction formula is as follows: Na + +H2PO4 - +NH3+4H2O→NaNH4HPO4.4H2O.

[0017] This invention's separation method can solve the problem of sodium impurity accumulation in the mother liquor during phosphate production, effectively purifying the mother liquor, improving product quality, and stabilizing yield. Furthermore, the mother liquor after potassium-sodium separation can be returned to the system for reuse, potassium salt crystals can be returned to the potassium salt production system, and ammonium sodium crystals can be used to produce sodium phosphate, achieving resource utilization of the phosphate mother liquor and bringing greater production benefits to enterprises.

[0018] Example 1

[0019] The phosphate mother liquor in this embodiment has the following characteristics: pH 4.8, P2O5 content 26.21%, K2O content 17.51%, Na2O content 3.36%, N content 1.31%, and temperature 55℃.

[0020] A method for separating potassium and sodium from phosphate mother liquor includes the following steps:

[0021] a. Potassium removal process: Take 1500g of the above phosphate mother liquor, stir at a rate of 70r / min, cool to 25℃ at a cooling rate of 0.2℃ / min, and then centrifuge to obtain potassium removal mother liquor and 196g of potassium salt crystals (potassium dihydrogen phosphate crystals). The potassium salt crystallization index is: pH 4.7, P2O5 content 50.33%, K2O content 33.62%, Na2O content 0.21%, and N content 0.19%. The obtained potassium salt crystals are returned to the potassium salt production system of the production line.

[0022] b. Sodium removal process: Take 1200g of the potassium removal mother liquor obtained in the previous step, with the following specifications: pH 4.8, P2O5 content 22.53%, K2O content 15.05%, Na2O content 3.88%, and N content 1.45%. Then, introduce gaseous ammonia into the potassium removal mother liquor to adjust the pH to 8.1 and the temperature to 75℃. Further stir the slurry at a rate of 180r / min and cool it to 15℃ at a cooling rate of 0.12℃ / min. Then, centrifuge to obtain 260g of sodium ammonium phosphate crystals with the following specifications: pH 8.0, P2O5 content 33.19%, K2O content 1.29%, Na2O content 13.75%, and N content 6.29%. At the same time, obtain 955g of sodium removal mother liquor with the following specifications: pH 7.7, P2O5 content 19.28%, K2O content 18.45%, Na2O content 1.06%, and N content 1.81%.

[0023] Example 2

[0024] The phosphate mother liquor of this embodiment has the following characteristics: pH 4.8, P2O5 content 26.21%, K2O content 17.51%, Na2O content 3.36%, N content 1.31%, and temperature 55℃.

[0025] A method for separating potassium and sodium from phosphate mother liquor includes the following steps:

[0026] a. Potassium removal process: Take 1500g of the above phosphate mother liquor, stir at a rate of 90r / min, cool to 20℃ at a cooling rate of 0.23℃ / min, and then centrifuge to obtain potassium removal mother liquor and 260g of potassium salt crystals. The potassium salt crystallization index is: pH 4.7, P2O5 content 50.18%, K2O content 33.51%, Na2O content 0.22%, and N content 0.19%. The obtained potassium salt crystals are returned to the potassium salt production system of the production line.

[0027] b. Sodium removal process: Take 1200g of the potassium removal mother liquor from the previous step, with the following specifications: pH 4.8, P2O5 content 21.18%, K2O content 14.15%, Na2O content 4.02%, and N content 1.54%. Then, introduce ammonia gas into the mother liquor to adjust the pH to 8.2 and the temperature to 75℃. Further stir the slurry at a rate of 160r / min and cool it to 10℃ at a cooling rate of 0.14℃ / min. Then, centrifuge to obtain 304g of sodium ammonium phosphate crystals with the following specifications: pH 8.1, P2O5 content 32.99%, K2O content 1.22%, Na2O content 13.65%, and N content 6.29%. Obtain 912g of sodium removal mother liquor with the following specifications: pH 7.7, P2O5 content 16.83%, K2O content 18.01%, Na2O content 0.76%, and N content 1.79%.

[0028] Example 3

[0029] The phosphate mother liquor of this embodiment has the following characteristics: pH 4.8, P₂O₅ content 26.32%, K₂O content 17.32%, Na₂O content 3.66%, N content 1.35%, and temperature 55°C.

[0030] A method for separating potassium and sodium from phosphate mother liquor includes the following steps:

[0031] a. Potassium removal process: Take 1500g of the above phosphate mother liquor, stir at a rate of 60r / min, cool to 20℃ at a cooling rate of 0.16℃ / min, and then centrifuge to obtain 254g of potassium salt crystals with the following properties: pH 4.8, P2O5 content 50.22%, K2O content 33.52%, Na2O content 0.25%, and N content 0.20%. The obtained potassium salt crystals are returned to the company's potassium salt production system.

[0032] b. Sodium removal process: Take 1200g of the potassium removal mother liquor from the previous step, with the following specifications: pH 4.8, P2O5 content 21.46%, K2O content 14.05%, Na2O content 4.38%, and N content 1.57%. Then, introduce ammonia gas into the mother liquor to adjust the pH to 8.0 and the temperature to 75℃. Further stir the slurry at a rate of 190r / min and cool it to 20℃ at a cooling rate of 0.1℃ / min. Then, centrifuge to obtain 292g of sodium ammonium phosphate crystals with the following specifications: pH 8.0, P2O5 content 33.25%, K2O content 1.17%, Na2O content 13.75%, and N content 6.36%. Obtain 921g of sodium removal mother liquor with the following specifications: pH 7.7, P2O5 content 17.24%, K2O content 17.85%, Na2O content 1.29%, and N content 1.71%.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for separating potassium and sodium in a phosphate liquor, characterized in that, The method comprises the following steps: firstly, potassium in a potassium-sodium-containing phosphate mother liquor is precipitated from the phosphate mother liquor in the form of potassium dihydrogen phosphate to obtain a potassium-removed mother liquor; then, sodium in the potassium-removed mother liquor is crystallized and separated to realize separation of potassium and sodium; and the method comprises the following steps: S1. Potassium removal: the pH value of the phosphate mother liquor is adjusted to 4.0-5.0, then the temperature is reduced to 15-30℃, and cooling crystallization is performed, and potassium dihydrogen phosphate crystals are precipitated through centrifugal separation to obtain a potassium-removed mother liquor; in this step, the cooling rate during cooling crystallization is 0.1-0.25℃ / min, and stirring is further included during cooling crystallization, and the stirring rate is 50-100r / min; S2. Sodium removal: ammonia gas is introduced into the potassium-removed phosphate mother liquor, the pH value of the potassium-removed mother liquor is adjusted to 7.5-8.5, then the temperature is reduced to 5-20℃, and cooling crystallization is performed, and sodium ammonium phosphate crystals are precipitated through centrifugal separation to obtain a sodium-removed mother liquor; in this step, the cooling rate during cooling crystallization is 0.1-0.15℃ / min, and stirring is further included during cooling crystallization, and the stirring rate is 150-200r / min; S3. The obtained sodium-removed mother liquor is returned to S1.