Method for producing monopotassium phosphate through organic extraction of crude phosphoric acid

Abstract

The invention discloses a method for producing monopotassium phosphate by organic extraction of crude phosphoric acid, which comprises the following steps: carrying out desulfurization and defluorination on wet-process crude phosphoric acid, then removing heavy metals, adding the heavy metal removed crude phosphoric acid and extract liquor into a crude phosphoric acid extraction clarification tank, carrying out crude phosphoric acid extraction reaction, and carrying out phase separation to obtain an extraction phase and raffinate acid; washing the extract phase with purified phosphoric acid, feeding into a homogeneous pre-reaction tank, adding a potassium chloride solution, fully and uniformly mixing, feeding into a hydrochloric acid extraction reaction clarification tank for phase separation to obtain monopotassium phosphate slurry and a hydrochloric acid-containing extract phase, and performing solid-liquid separation on the monopotassium phosphate slurry to obtain monopotassium phosphate clear liquid; concentrating and crystallizing the monopotassium phosphate clear liquid to obtain a monopotassium phosphate product; the extract liquor is an alkylamine type extractant added with a diluent. The method is high in comprehensive economic value, the used extraction agent is excellent in comprehensive performance, and the prepared monopotassium phosphate product is good in quality.

Description

Technical Field

[0001] The invention belongs to the technical field of potassium dihydrogen phosphate production, and particularly relates to a method for producing potassium dihydrogen phosphate by an organic extraction method using crude phosphoric acid. Background Art

[0002] Traditional methods for producing potassium dihydrogen phosphate, such as Figure 1 As shown, crude phosphoric acid is desulfurized and defluorinated before heavy metals are removed to obtain H3PO4 still containing a large number of cationic impurities, and then KCL solution is added and phases are separated after extraction with hydrochloric acid to obtain potassium dihydrogen phosphate slurry. The slurry has a high concentration of impurity ions and contains potassium dihydrogen phosphate solution and potassium white fertilizer. After filtering the potassium white fertilizer, potassium dihydrogen phosphate clear liquid is obtained. In the traditional process, only sulfate, fluoride and other anions in wet phosphoric acid are removed. The wet crude phosphoric acid containing a large number of cations is directly mixed with potassium chloride solution. After extracting hydrochloric acid, the pH of the mixed solution increases, and the cations in the crude phosphoric acid are precipitated to form phosphates. The phosphates carry potassium dihydrogen phosphate and extractants to form a large amount of potassium white fertilizer, which also causes a high content of impurities in the product. Due to the large amount of potassium white fertilizer produced, the yield of phosphorus pentoxide and potassium in potassium dihydrogen phosphate products is low. Phosphorus pentoxide and potassium in potassium white fertilizer are both depreciated. The amount of extractant carried by potassium white fertilizer is positively correlated with the amount of potassium white fertilizer, and the price of extractant is expensive. These factors lead to the low comprehensive economic value of traditional processes. Therefore, the industry has been exploring how to produce potassium dihydrogen phosphate clear solution with low impurity ion content in order to obtain a process method with better product quality.

[0003] In addition, the product quality obtained by the traditional extraction method for producing potassium dihydrogen phosphate is difficult to meet the fine phosphate standard. In addition, the traditional production method only focuses on the extraction ability of the extractant for hydrochloric acid. The standard for screening the extractant is strong extraction ability for hydrochloric acid. The screening standard is single, ignoring the extraction ability of the extractant for phosphoric acid and the selectivity of impurities in phosphoric acid. For the traditional extraction method for producing potassium dihydrogen phosphate, the hot research focus in the industry has always been on how to reduce the amount of potassium white fertilizer, increase the yield of phosphorus pentoxide and potassium, maintain the value of phosphorus pentoxide in wet phosphoric acid, find an extractant with better comprehensive performance, and enhance the overall economic value. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and provide a method for producing potassium dihydrogen phosphate with high comprehensive economic value, good comprehensive performance of the extractant and better quality of the prepared product.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid. The method is to first desulfurize and defluorinate wet-process crude phosphoric acid, then remove heavy metals, and then add the heavy-metal-removed crude phosphoric acid and extraction liquid into a crude phosphoric acid extraction clarifier for a crude phosphoric acid extraction reaction, and phase separation is carried out in the crude phosphoric acid extraction clarifier to obtain an extraction phase and raffinate acid; the extraction phase is washed with purified phosphoric acid and then sent into a homogeneous pre-reaction tank and potassium chloride solution is added and mixed evenly, and then sent into a hydrochloric acid extraction reaction clarifier, and phase separation is carried out in the hydrochloric acid extraction reaction clarifier to obtain potassium dihydrogen phosphate slurry and hydrochloric acid-containing extraction phase, the potassium dihydrogen phosphate slurry is subjected to solid-liquid separation to obtain solid potassium white fertilizer residue and potassium dihydrogen phosphate clear liquid, and the potassium dihydrogen phosphate clear liquid is concentrated and crystallized to obtain potassium dihydrogen phosphate product; the extraction liquid is an alkylamine-type extractant added with a diluent.

[0006] Further, the alkylamine-type extractant is one of primary amine, secondary amine, tertiary amine, and quaternary amine; the diluent is a saturated alkane diluent.

[0007] Further, the mass concentration of P2O5 in the wet-process crude phosphoric acid is 45% - 54%.

[0008] Further, the hydrochloric acid-containing extraction phase is subjected to back extraction to obtain an extraction liquid, and the extraction liquid is returned to the crude phosphoric acid extraction clarifier.

[0009] Further, the wash residue acid generated after washing the extraction phase with purified phosphoric acid is returned for desulfurization and defluorination of the crude phosphoric acid.

[0010] Due to the heterogeneous reaction between the washed extraction phase and potassium chloride solution, the extractant and purified phosphoric acid will form a complex that hinders the purified phosphoric acid from entering the potassium chloride solution in an ionic state. In the method of the present invention, a homogeneous pre-reaction tank is set in the previous process before the hydrochloric acid extraction reaction clarification, and the washed extraction phase and potassium chloride solution are sent into the homogeneous pre-reaction tank and mixed evenly, which is beneficial to the purified phosphoric acid entering the potassium chloride solution in an ionic state, and the phosphoric acid concentration in the potassium chloride solution increases, which is beneficial to improving the hydrochloric acid extraction rate in the hydrochloric acid extraction reaction clarifier.

[0011] The method of the present invention changes the precipitation process of cation impurities in wet-process phosphoric acid, adds an extractant extraction wet-process phosphoric acid process, and cleverly uses the alkylamine-type extractant to selectively separate impurities in wet-process phosphoric acid, so that most impurities enter the raffinate acid, reducing the amount of potassium white fertilizer precipitated during the hydrochloric acid extraction reaction, and converting a large amount of potassium white fertilizer with low economic added value into raffinate acid. The raffinate acid is essentially crude phosphoric acid with slightly higher impurities, and the raffinate acid has higher economic added value and more available ways. The method of the present invention has high comprehensive economic value, the prepared potassium dihydrogen phosphate product has good quality, the used extractant not only has the extraction ability for hydrogen chloride, but also has excellent extraction ability for wet-process crude phosphoric acid, and has good selectivity for impurities in wet-process crude phosphoric acid, and has excellent comprehensive performance. Description of the Drawings

[0012] Figure 1 It is a process schematic diagram for producing potassium dihydrogen phosphate by traditional extraction method; Figure 2 It is a process schematic diagram for producing potassium dihydrogen phosphate by the method of the present invention. Detailed implementation manners

[0013] The content of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0014] Example 1 A method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid, the process flow of which is as Figure 2 shown. First, 2222 kg of wet-process crude phosphoric acid (containing 1000 kg of P2O5) from the phosphoric acid workshop is desulfurized and defluorinated by the existing technology method, and then heavy metals are removed. The desulfurization method is to add barium carbonate or phosphate rock powder and react at 40°C for 1-2 hours. The defluorination method is to add microsilica powder, sodium carbonate or liquid caustic soda and react at 80°C for 2-3 h. The method for removing heavy metals is to add sodium sulfide or phosphorus pentasulfide and react at 80°C for 2 h.

[0015] The analysis indexes of the crude phosphoric acid are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> F% <![CDATA[SO4%]]> Crude phosphoric acid 45.00 0.92 1.73 0.59 1.89 0.25 0.09 Then, the heavy-metal-removed crude phosphoric acid and the extractant are added into the crude phosphoric acid extraction clarification tank for crude phosphoric acid extraction reaction, and phase separation is carried out in the crude phosphoric acid extraction clarification tank. The upper layer is the extract formed by the organic phase and the purified phosphoric acid with less impurity content, called the extraction phase, and the lower layer is the raffinate acid with more impurities. The extractant is an alkylamine-type extractant added with a diluent. The extraction rate of cation impurities in the wet-process crude phosphoric acid by this type of extractant is only 3-5%. And the cations form potassium white fertilizer during the hydrochloric acid extraction reaction, so the production amount of potassium white fertilizer can be reduced. The alkylamine-type extractant is one of primary amine, secondary amine, tertiary amine, and quaternary amine, and the diluent is a saturated alkane diluent. The alkylamine-type extractant used in this example is primary amine, and the diluent is 200# solvent oil.

[0016] Subsequently, the extraction phase is washed with purified phosphoric acid to obtain 2000 kg of washed extraction phase. The analysis indexes of the washed extraction phase are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> F% <![CDATA[SO4%]]> Washed extraction phase 20 0.002 0.001 0.0009 0.005 0.01 0.004 Next, in the homogeneous pre-reaction tank, the washed extraction phase and the potassium chloride solution containing 413 kg of potassium chloride are mixed (the volume ratio of the extraction phase to the potassium chloride solution is controlled at 3:1, the extraction rate of P2O5 in the wet-process crude phosphoric acid is controlled at 40%, and the extraction rate of cationic impurities is 3%). 98% of the purified phosphoric acid in the washed extraction phase enters the potassium chloride solution, and then the mixed solution is sent to the hydrochloric acid extraction reaction clarification tank. In the hydrochloric acid extraction reaction clarification tank, a hydrochloric acid extraction reaction occurs. The hydrochloric acid-containing extraction phase is in the oil phase, and the main component of the aqueous phase is potassium dihydrogen phosphate. The aqueous phase contains a small amount of potassium white fertilizer, and the aqueous phase is called the potassium dihydrogen phosphate slurry. Phase separation begins under the action of gravity. Since the density of the hydrochloric acid-containing extraction phase is less than that of the potassium dihydrogen phosphate slurry, the upper layer is the hydrochloric acid-containing organic phase, and the lower layer is the potassium dihydrogen phosphate slurry. After that, the potassium dihydrogen phosphate slurry is subjected to liquid-solid separation to obtain 54.7 kg of potassium white fertilizer residue and 2945 kg of potassium dihydrogen phosphate clear liquid with low impurity content. The analysis indexes of the potassium dihydrogen phosphate clear liquid are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> <![CDATA[SO4%]]> <![CDATA[K2O%]]> Cl% pH <![CDATA[KH2PO4 clear liquid]]> 12.9 0.07 0.0 0.0 0.0 0.02 8.59 0.08 3.0 The potassium dihydrogen phosphate clear liquid is concentrated and crystallized to obtain 730 kg of potassium dihydrogen phosphate product. The analysis indexes of the product are shown in the following table:

[0017] The water-insoluble matter in the above table refers to the mass percentage of solid substances that are insoluble in water at room temperature in the potassium dihydrogen phosphate product.

[0018] The hydrochloric acid-containing extraction phase can be subjected to back-extraction and then returned to the crude phosphoric acid extraction clarification tank.

[0019] The washing residue acid generated after washing the purified phosphoric acid extraction phase can be returned for desulfurization and defluorination of the crude phosphoric acid, which can further reduce the content of impurity ions in the extraction phase and reduce the output of potassium white fertilizer.

[0020] Example 2 A method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid. First, 2222 kg of wet-process crude phosphoric acid (containing 1000 kg of P2O5) from the phosphoric acid workshop is desulfurized, defluorinated, and then heavy metals are removed by the same method as in Example 1. Then, the heavy-metal-removed crude phosphoric acid and the extractant are added to the crude phosphoric acid extraction clarification tank for crude phosphoric acid extraction reaction, and phase separation is carried out to obtain the extraction phase and the raffinate acid. In this example, the alkylamine-type extractant used is primary amine, and the diluent is 200# solvent oil.

[0021] Subsequently, the extraction phase is washed with purified phosphoric acid to obtain 2000 kg of washed extraction phase. The analysis indexes of the washed extraction phase are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> F% <![CDATA[SO4%]]> Washed extraction phase 20 0.002 0.001 0.0009 0.005 0.01 0.004 Mix the washed extraction phase with a solution containing 379 kg of potassium chloride (the volume ratio of the extraction phase to the potassium chloride solution is controlled at 3:1, the extraction rate of P2O5 in wet-process crude phosphoric acid is controlled at 40%, and the extraction rate of cationic impurities is 3%), and feed it into the hydrochloric acid extraction reaction clarifier. 90% of the purified phosphoric acid in the washed extraction phase enters the potassium chloride solution, and a hydrochloric acid extraction reaction occurs in the hydrochloric acid extraction reaction clarifier. The hydrochloric acid-containing extraction phase is in the oil phase, and the main component of the aqueous phase is potassium dihydrogen phosphate. The aqueous phase contains a small amount of potassium white fertilizer, and the aqueous phase is called potassium dihydrogen phosphate slurry. Phase separation begins under the action of gravity. Since the density of the hydrochloric acid-containing extraction phase is less than that of the potassium dihydrogen phosphate solution, the upper layer is the hydrochloric acid-containing organic phase, and the lower layer is the potassium dihydrogen phosphate slurry. Then, the potassium dihydrogen phosphate slurry is subjected to liquid-solid separation to obtain 50.2 kg of potassium white fertilizer residue containing 7 kg of K2O and 3490 kg of potassium dihydrogen phosphate clear liquid with low impurity content. The analysis indexes of the potassium dihydrogen phosphate clear liquid are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> <![CDATA[SO4%]]> <![CDATA[K2O%]]> Cl% pH <![CDATA[KH2PO4 clear solution]]> 10 0.07 0.0 0.0 0.0 0.02 6.6 0.08 3.0 Concentrate and crystallize the potassium dihydrogen phosphate clear liquid to obtain 670 kg of potassium dihydrogen phosphate product. The analysis indexes of the product are shown in the following table: <![CDATA[KH2PO4%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> Cl% Insoluble in water % pH 99.81 34.61 0.15 0.28 0.03 4.4 Ca (ppm) Mg (ppm) Fe (ppm) Al (ppm) As (ppm) Pb (ppm) Na (ppm) <![CDATA[SO4 (ppm)]]> F (ppm) 27.8 16.7 3.1 10.9 5.6 0.4 100 156 10

[0022] Example 3 A method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid. First, 2222 kg of wet-process crude phosphoric acid (containing 1000 kg of P2O5) from the phosphoric acid workshop is desulfurized and defluorinated by the same method as in Example 1, and then heavy metals are removed. Then, the heavy metal-removed crude phosphoric acid and the extraction liquid are added into the crude phosphoric acid extraction clarifier for crude phosphoric acid extraction reaction, and phase separation is carried out to obtain the extraction phase and the raffinate acid. The alkylamine-type extractant used in this example is tertiary amine, and the diluent is 260# solvent oil.

[0023] Subsequently, the extraction phase is washed with purified phosphoric acid to obtain 1818 kg of washed extraction phase. The analysis indexes of the washed extraction phase are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> F% <![CDATA[SO4%]]> Washed extraction phase 22 0.003 0.002 0.001 0.009 0.01 0.005 In the homogeneous pre-reaction tank, the washed extraction phase is mixed with a solution containing 723 kg of potassium chloride (the volume ratio of the extraction phase to the potassium chloride solution is controlled at 4:1, the extraction rate of P2O5 in wet-process crude phosphoric acid is controlled at 70%, and the extraction rate of cationic impurities is 4%). 98% of the purified phosphoric acid in the washed extraction phase enters the potassium chloride solution. The mixed solution is fed into the hydrochloric acid extraction reaction clarifier, and a hydrochloric acid extraction reaction occurs in the hydrochloric acid extraction reaction clarifier. The hydrochloric acid-containing extraction phase is in the oil phase, and the main component of the aqueous phase is potassium dihydrogen phosphate. The aqueous phase contains a small amount of potassium white fertilizer, and the aqueous phase is called potassium dihydrogen phosphate slurry. Phase separation begins under the action of gravity. The upper layer is the hydrochloric acid-containing organic phase, and the lower layer is the potassium dihydrogen phosphate slurry. Then, the potassium dihydrogen phosphate slurry is subjected to liquid-solid separation to obtain 95.25 kg of potassium white fertilizer residue and 5000 kg of potassium dihydrogen phosphate clear liquid with low impurity content. The analysis indexes of the potassium dihydrogen phosphate clear liquid are shown in the following table: <![CDATA[P2O5%]]> CaO% MgO% <![CDATA[Fe2O3%]]> <![CDATA[Al2O3%]]> <![CDATA[SO4%]]> <![CDATA[K2O%]]> Cl% pH <![CDATA[KH2PO4 clear liquid]]> 13.3 0.07 0.0 0.0 0.0 0.02 8.8 0.08 3.0 The potassium dihydrogen phosphate product of 1270 kg can be obtained by concentrating and crystallizing the potassium dihydrogen phosphate clear solution. The product analysis indexes are shown in the following table:

[0024] If the Figure 1 shown traditional process method is adopted, first desulfurize and defluorinate 2222 kg of wet-process crude phosphoric acid with a P2O5 mass concentration of 45% in the same way, then remove heavy metals, and then add the heavy-metal-removed crude phosphoric acid and 1049 kg of potassium chloride solution to the hydrochloric acid extraction reaction clarifier to extract hydrochloric acid. After phase separation, a potassium dihydrogen phosphate slurry and a hydrochloric acid-containing extraction phase are obtained. Filter the potassium dihydrogen phosphate slurry to obtain 1300 kg of potassium white fertilizer containing 406 kg of K2O, and obtain 3023 kg of potassium dihydrogen phosphate clear solution with high impurity content. The analysis indexes of the potassium dihydrogen phosphate clear solution are shown in the following table: If the Figure 1 shown traditional process method is adopted, first desulfurize and defluorinate 2222 kg of wet-process crude phosphoric acid with a P2O5 mass concentration of 45% in the same way, then remove heavy metals, and then add the heavy-metal-removed crude phosphoric acid and 1049 kg of potassium chloride solution to the hydrochloric acid extraction reaction clarifier to extract hydrochloric acid. After phase separation, a potassium dihydrogen phosphate slurry and a hydrochloric acid-containing extraction phase are obtained. Filter the potassium dihydrogen phosphate slurry to obtain 1300 kg of potassium white fertilizer containing 406 kg of K2O, and obtain 3023 kg of potassium dihydrogen phosphate clear solution with high impurity content. The analysis indexes of the potassium dihydrogen phosphate clear solution are shown in the following table:

[0025] Concentrate and crystallize the potassium dihydrogen phosphate clear solution to obtain 750 kg of potassium dihydrogen phosphate product, and the analysis indexes are shown in the following table:

[0026] By comparing the components of the potassium dihydrogen phosphate clear solution and the potassium dihydrogen phosphate product obtained by the method of the present invention and the traditional process method, it can be seen that the impurity content of the potassium dihydrogen phosphate clear solution obtained by the method of the present invention is significantly reduced, and the purity of the prepared potassium dihydrogen phosphate product is higher.

[0027] The following is the P2O5 material balance table of the embodiment:

[0028] The following is the K2O material balance table of the embodiment:

[0029] Compared with the traditional potassium dihydrogen phosphate production process, in the present invention, a unique alkylamine extractant is used to carry out a crude phosphoric acid extraction reaction on crude phosphoric acid, effectively reducing the impurities in the subsequent potassium dihydrogen phosphate slurry and greatly reducing the production amount of potassium white fertilizer. Calculated based on the production of 1 ton of KH2PO4 product, the traditional process will produce approximately 1733 kg of potassium white fertilizer, resulting in a phosphorus pentoxide loss of 61% and a potassium loss caused by potassium white fertilizer of 60%. In contrast, the present invention only produces approximately 75 kg of potassium white fertilizer, with a phosphorus pentoxide loss of only 2% - 4% and a potassium loss caused by potassium white fertilizer of only 1% - 3%. The potassium dihydrogen phosphate product prepared by the traditional process is only a qualified product, while the potassium dihydrogen phosphate product prepared by the present invention is a superior product. At the same time, the present invention can also produce raffinate acid with wide applications and high utilization value.

[0030] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the protection scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid, characterized in that: The method comprises the following steps: firstly desulfurizing and defluorinating wet crude phosphoric acid, and then removing heavy metals; then adding the crude phosphoric acid from which the heavy metals have been removed and an extracting liquid into a crude phosphoric acid extraction clarification tank for crude phosphoric acid extraction reaction, and performing phase separation in the crude phosphoric acid extraction clarification tank to obtain an extracting phase and a raffinate acid; washing the extracting phase with purified phosphoric acid, sending it into a homogenizing pre-reaction tank, adding a potassium chloride solution and mixing it evenly, and then sending it into a hydrochloric acid extraction reaction clarification tank, performing phase separation in the hydrochloric acid extraction reaction clarification tank to obtain potassium dihydrogen phosphate slurry and a hydrochloric acid-containing extracting phase; performing liquid-solid separation of the potassium dihydrogen phosphate slurry to obtain solid potassium white fertilizer slag and potassium dihydrogen phosphate clear liquid; and concentrating and crystallizing the potassium dihydrogen phosphate clear liquid to obtain a potassium dihydrogen phosphate product; and the extracting liquid is an alkylamine type extracting agent with a diluent added thereto.

2. The method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid according to claim 1, characterized in that: The alkylamine extractant is one of primary amine, secondary amine, tertiary amine and quaternary amine; the diluent is a saturated alkane diluent.

3. The method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid according to claim 1 or 2, characterized in that: The P2O5 mass concentration of the wet-process crude phosphoric acid is 45% to 54%.

4. The method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid according to claim 1, characterized in that: The hydrochloric acid-containing extract phase is stripped to obtain an extract, which is returned to the crude phosphoric acid extraction clarification tank.

5. The method for producing potassium dihydrogen phosphate by organic extraction of crude phosphoric acid according to claim 1, characterized in that: The residual acid produced after washing the extract phase with purified phosphoric acid is returned for desulfurization and defluorination of crude phosphoric acid.

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