A production process of potassium dihydrogen phosphate

Abstract

The invention discloses a production process of potassium dihydrogen phosphate, specifically comprising the following steps: step 1: adding raffinate phosphoric acid and filtrate G to 1# neutralization tank, adding pH adjusting agent, and sending slurry into concentration tank after reaction to be concentrated to slurry density 1.32-1.40, and filtering slurry to obtain filtrate A and filter residue B; step 2: sending filtrate A in step 1 into crystallization tank to cool and precipitate crystals, separating to obtain crystals and filtrate C, and obtaining potassium dihydrogen phosphate product after crystals are dried; step 3: sending filter residue B and filter residue H in step 1 into 2# neutralization tank, adding potassium liquid I to react, adding pH adjusting agent, filtering after reaction, obtaining filtrate D, washing filter cake to obtain washing liquid E, and washing filter cake F to compound fertilizer or general calcium device for use as additive. The present invention solves the technical problem that the neutralization method adopts industrial grade purified phosphoric acid and potassium hydrogen potassium to obtain the reaction in the prior art, resulting in high raw material cost.

Description

Technical Field

[0001] The invention relates to the technical field of potassium dihydrogen phosphate preparation, and in particular to a production process of potassium dihydrogen phosphate. Background Art

[0002] Potassium dihydrogen phosphate (chemical formula: KH2PO4) is sealed and stored, stable in the air, loses water at 400°C and becomes metaphosphate, which is used to prepare buffer solutions, determine arsenic, antimony, phosphorus, aluminum and iron, prepare phosphorus standard solutions, prepare culture media, and determine inorganic phosphorus and alkaline phosphatase activity in serum;

[0003] Physical properties: colorless tetragonal crystals or white crystalline powder. Relative density 2.338, melting point 252.6℃, soluble in water (83.5g / 100ml water at 90℃), aqueous solution is acidic, pH value of 1% potassium dihydrogen phosphate solution is 4.6, insoluble in alcohol, deliquescent, melts into transparent liquid when heated to 400℃, solidifies into opaque glassy potassium metaphosphate after cooling.

[0004] Existing methods for producing potassium dihydrogen phosphate include extraction, ion exchange, double decomposition, direct and neutralization methods. Among them, the neutralization method is characterized by simple process flow, low energy consumption, high product purity, few equipment required for production, and small one-time investment. It is currently the mainstream method for industrial production applications. However, the neutralization method is usually produced by the reaction of industrial-grade purified phosphoric acid and potassium hydrogen, and the raw material cost is relatively high. Summary of the invention

[0005] The purpose of the present invention is to provide a production process of potassium dihydrogen phosphate, which solves the technical problem in the prior art that the neutralization method adopts industrial-grade purified phosphoric acid and potassium hydrogen phosphate to react, resulting in high raw material costs.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A production process of potassium dihydrogen phosphate specifically comprises the following steps:

[0008] Step 1: Add raffinate phosphoric acid and filtrate G to the 1# neutralization tank, add a pH adjuster, control the reaction pH at 4.2-4.8, the reaction time is 0.5-2 hours, the reaction temperature is 70-90°C, the slurry after the reaction is sent to a concentration tank to be concentrated to a slurry density of 1.32-1.40, and the slurry is filtered to obtain filtrate A and residue B;

[0009] Step 2: The filtrate A in step 1 is sent to a crystallization tank to cool and precipitate crystals, and the crystals and filtrate C are separated and dried to obtain potassium dihydrogen phosphate product;

[0010] Step 3: Send the filter residue B and filter residue H in step 1 to the 2# neutralization tank, add potassium solution I for reaction, add pH regulator, control the reaction pH at 8-10, reaction time 0.5-2 hours, reaction temperature 80-90°C, filter after reaction to obtain filtrate D, wash filter cake to obtain washing liquid E, and send the washed filter cake F to compound fertilizer or general calcium device for use as additive;

[0011] Step 4: Send the filtrate D obtained in step 3 and the filtrate C obtained in step 2 to the 3# neutralization tank, add a decolorizing agent and a pH adjuster, control the reaction pH to 5-7, the reaction time to 0.5-2 hours, the reaction temperature to ≦90°C, filter the slurry after the reaction to obtain a filtrate G and a filter residue H;

[0012] Step 5: feeding the washing liquid E obtained in step 3 into a potassium liquid preparation tank, adding potassium hydroxide to prepare potassium liquid I, wherein the amount of potassium hydroxide used is such that the molar ratio of potassium in potassium hydroxide as K2O to phosphorus in the residual phosphoric acid in step 1 as P2O5 is 1:0.9-1.2;

[0013] Wherein, the filtrate G in step 1 and the filter residue H in step 3 are the filtrate G and filter residue H described in step 4, and the potassium liquid I in step 3 is the potassium liquid I obtained in step 5.

[0014] Among them, the raffinate phosphoric acid is a by-product after the wet-process phosphoric acid is purified by solvent extraction.

[0015] According to further optimization, the mass percentage of P2O5 in the raffinate phosphoric acid is 40% to 50%, and the mass of iron, magnesium, aluminum and calcium elements contained in the raffinate phosphoric acid is 6% to 15% of the mass of P2O5 contained in the raffinate phosphoric acid.

[0016] The decolorizing agent is one or both of hydrogen peroxide and activated carbon, and the added amount thereof is 0.05%-0.5% of the mass of the slurry in step 4.

[0017] It is further defined that the pH adjuster is one or both of raffinate phosphoric acid and potassium hydroxide.

[0018] Among them, the residual phosphoric acid can be replaced by desulfurized fertilizer-grade phosphoric acid, the mass percentage of P2O5 in the fertilizer-grade phosphoric acid is 40% to 50%, and the mass of iron, magnesium, aluminum and calcium elements contained in the fertilizer-grade phosphoric acid is 3% to 7% of the mass of P2O5 contained in the fertilizer-grade phosphoric acid.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] Compared with the prior art, the present invention adopts raffinate acid or fertilizer-grade wet phosphoric acid, and the raw material cost is low; by adding potassium hydroxide and a raffinate acid pH regulator to adjust the pH to a suitable range, the main metal impurity ions such as iron, magnesium, aluminum and the like in the acid are removed, and a qualified potassium dihydrogen phosphate product is produced. The process has a good raw material cost advantage; after the impurities are removed, a phosphate-containing filter cake is obtained, which is used to prepare a compound fertilizer product, recovers the lost phosphorus and potassium resources, and improves the utilization rate of the elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is the overall principle diagram of the present invention. DETAILED DESCRIPTION

[0023] In the following, only some exemplary embodiments are briefly described. As those skilled in the art can realize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present invention.

[0024] Embodiment 1

[0025] See also Figure 1 This embodiment discloses a production process of potassium dihydrogen phosphate, which specifically includes the following steps:

[0026] Step 1: Add raffinate phosphoric acid and filtrate G to the 1# neutralization tank, add a pH adjuster, control the reaction pH at 4.2-4.8, the reaction time is 0.5-2 hours, the reaction temperature is 70-90°C, the slurry after the reaction is sent to a concentration tank to be concentrated to a slurry density of 1.32-1.40, and the slurry is filtered to obtain filtrate A and residue B;

[0027] In step 1 of this embodiment, the pH is 4.5, the reaction time is 1 hour, the reaction temperature is 80°C, and the slurry after the reaction is sent to a concentration tank and concentrated to a slurry density of 1.32;

[0028] Step 2: The filtrate A in step 1 is sent to a crystallization tank to cool and precipitate crystals, and the crystals and filtrate C are separated and dried to obtain potassium dihydrogen phosphate product;

[0029] Step 3: Send the filter residue B and filter residue H in step 1 to the 2# neutralization tank, add potassium solution I for reaction, add pH regulator, control the reaction pH at 8-10, reaction time 0.5-2 hours, reaction temperature 80-90°C, filter after reaction to obtain filtrate D, wash filter cake to obtain washing liquid E, and send the washed filter cake F to compound fertilizer or general calcium device for use as additive;

[0030] In step 3 of this embodiment, a pH adjuster is added to control the reaction pH at 9, the reaction time is 1 hour, and the reaction temperature is 80°C;

[0031] Step 4: Send the filtrate D obtained in step 3 and the filtrate C obtained in step 2 to the 3# neutralization tank, add a decolorizing agent and a pH adjuster, control the reaction pH to 5-7, the reaction time to 0.5-2 hours, the reaction temperature to ≦90°C, filter the slurry after the reaction to obtain a filtrate G and a filter residue H;

[0032] In step 4 of this embodiment, a decolorizing agent and a pH adjusting agent are added to control the reaction pH to 6, the reaction time is 1 hour, and the reaction temperature is 85°C.

[0033] Step 5: feeding the washing liquid E obtained in step 3 into a potassium liquid preparation tank, adding potassium hydroxide to prepare potassium liquid I, wherein the amount of potassium hydroxide used is such that the molar ratio of potassium in potassium hydroxide as K2O to phosphorus in the residual phosphoric acid in step 1 as P2O5 is 1:0.9-1.2; preferably 1:1.1;

[0034] Wherein, the filtrate G in step 1 and the filter residue H in step 3 are the filtrate G and filter residue H described in step 4, and the potassium liquid I in step 3 is the potassium liquid I obtained in step 5.

[0035] Among them, the raffinate phosphoric acid is a by-product after the wet-process phosphoric acid is purified by solvent extraction.

[0036] According to further optimization, the mass percentage of P2O5 in the raffinate phosphoric acid is 40% to 50%, and the mass of iron, magnesium, aluminum and calcium elements contained in the raffinate phosphoric acid is 6% to 15% of the mass of P2O5 contained in the raffinate phosphoric acid.

[0037] Among them, the P2O5 mass percentage of the raffinate phosphoric acid is 46%. The P2O5 mass percentage of the raffinate acid is in the range of 40% to 50%, which can meet the production requirements of potassium dihydrogen phosphate by neutralization method. Generally, the phosphoric acid percentage of the acid is required to be not less than 50%, and the corresponding P2O5 content is not less than 36.23%. When concentrated, it can reduce the evaporation of water during concentration and reduce energy consumption.

[0038] The decolorizing agent is one or both of hydrogen peroxide and activated carbon, and the amount added is 0.05%-0.5% of the mass of the slurry in step 4, preferably 0.3%; the decolorizing agent is used to remove colored impurities in the raffinate acid to ensure the appearance quality of the potassium dihydrogen phosphate product.

[0039] It is further defined that the pH adjuster is one or both of raffinate phosphoric acid and potassium hydroxide; in actual use, the mass of potassium hydroxide added can be 10%-20% of the mass of filtrate A, preferably 15%; the mass of raffinate acid added can be 30%-40% of the mass of filtrate A, preferably 35%; the mass of both can be 40%-60% of the mass of filtrate A, preferably 50.

[0040] This embodiment uses raffinate acid, and the raw material cost is relatively low. By adding potassium hydroxide and a raffinate acid pH regulator to adjust the pH to a suitable range, the problem of removing major metal impurity ions such as iron, magnesium, and aluminum in the acid and producing a qualified potassium dihydrogen phosphate product is solved. The process has a good raw material cost advantage. After the impurities are removed, a phosphate-containing filter cake is obtained, which is used to prepare a compound fertilizer product and recover the lost phosphorus and potassium resources.

[0041] Embodiment 2

[0042] This embodiment is basically the same as the first embodiment, except that, in this embodiment, the raffinate phosphoric acid in step 1 is replaced by desulfurized fertilizer-grade phosphoric acid (fertilizer-grade wet-process phosphoric acid), the mass percentage of P2O5 in the fertilizer-grade phosphoric acid is 40% to 50%, preferably 45%, and the mass of iron, magnesium, aluminum and calcium elements contained in the fertilizer-grade phosphoric acid is 3% to 7% of the mass of P2O5 contained in the fertilizer-grade phosphoric acid, preferably 5%.

[0043] Compared with raffinate acid, fertilizer-grade wet-process phosphoric acid contains fewer impurity ions, and less phosphorus loss is caused when impurities are removed.

[0044] The present invention uses raffinate or fertilizer-grade desulfurized wet phosphoric acid raw material and the filtrate G of step 4 to react with potassium hydroxide to generate a precipitate of potassium dihydrogen phosphate and salts such as iron phosphate and aluminum, which is not directly filtered, but heated and concentrated to a specific gravity of 1.32-1.4, filtered and impurities removed, to obtain a filtrate A and a filter cake B (step 1);

[0045] Filtrate A is crystallized to obtain potassium dihydrogen phosphate product (step 2);

[0046] Step 3: Process the filtrate C of step 2, adjust the pH to 8-10 by adding potassium solution I to generate a precipitate, deeply remove impurities such as magnesium, filter the precipitate, wash the precipitate and use it to prepare compound fertilizer, and use the washing water to prepare potassium hydroxide (step 5).

[0047] The filtrate is added with a decolorizing agent and a pH adjusting agent to control the pH at 5-7 to generate a precipitate, which is filtered to remove impurities and returned to step 1 (step 4).

[0048] The current mainstream production method uses industrial-grade purified phosphoric acid and potassium hydroxide to neutralize the reaction, control the pH to about 4.2-4.6, filter, evaporate and concentrate, and finally produce potassium dihydrogen phosphate products through a crystallization process.

[0049] The advantage of this process is that the phosphoric acid used is raffinate or fertilizer-grade wet phosphoric acid, and the raw material cost is greatly reduced. Although wet phosphoric acid contains impurities such as iron, aluminum, and magnesium, which cause phosphorus loss and have a great impact on the production of potassium dihydrogen phosphate, the raffinate or fertilizer-grade desulfurized phosphoric acid raw materials are much cheaper than industrial-grade phosphoric acid, which can greatly reduce production costs. The phosphate precipitate generated in the process can be used to prepare compound fertilizers, which will not cause a complete loss of phosphorus and potassium resources. There is only a discount loss when phosphorus and potassium resources are used to produce low-value compound fertilizers.

[0050] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A production process of potassium dihydrogen phosphate, It is characterized in that The specific steps include: Step 1: Add raffinate phosphoric acid and filtrate G to the 1# neutralization tank, add a pH adjuster, control the reaction pH at 4.2-4.8, the reaction time is 0.5-2 hours, the reaction temperature is 70-90°C, the slurry after the reaction is sent to a concentration tank to be concentrated to a slurry density of 1.32-1.40, and the slurry is filtered to obtain filtrate A and residue B; Step 2: The filtrate A in step 1 is sent to a crystallization tank to cool and precipitate crystals, and the crystals and filtrate C are separated and dried to obtain potassium dihydrogen phosphate product; Step 3: Send the filter residue B and filter residue H in step 1 to the 2# neutralization tank, add potassium solution I for reaction, add pH regulator, control the reaction pH at 8-10, reaction time 0.5-2 hours, reaction temperature 80-90°C, filter after reaction to obtain filtrate D, wash filter cake to obtain washing liquid E, and send the washed filter cake F to compound fertilizer or general calcium device for use as additive; Step 4: Send the filtrate D obtained in step 3 and the filtrate C obtained in step 2 to the 3# neutralization tank, add a decolorizing agent and a pH adjuster, control the reaction pH to 5-7, the reaction time to 0.5-2 hours, the reaction temperature to ≦90°C, filter the slurry after the reaction to obtain a filtrate G and a filter residue H; Step 5: The washing liquid E obtained in step 3 is sent to a potassium solution preparation tank, and potassium hydroxide is added to prepare potassium solution I. The amount of potassium hydroxide used is the amount of potassium in potassium hydroxide as K 2 The phosphorus in the residual phosphoric acid in step 1 is calculated as P 2 O 5 The molar ratio of the formula is 1:0.9-1.2; Among them, the raffinate phosphoric acid has a good raw material cost advantage, and after the impurities are removed, a phosphate-containing filter cake is obtained, which is used to prepare compound fertilizer products, recover the lost phosphorus and potassium resources, and improve the utilization rate of the elements; the filtrate G in step 1 and the filter residue H in step 3 are both the filtrate G and the filter residue H in step 4, and the potassium liquid I in step 3 is the potassium liquid I obtained in step 5; Raffinate Phosphoric Acid P 2 O 5 The mass percentage is 40% to 50%, which can meet the production requirements of potassium dihydrogen phosphate by neutralization method. The phosphoric acid percentage of the raffinate is not less than 50%, and its corresponding P 2 O 5 When the content is not less than 36.23%, the amount of water evaporation during concentration can be reduced, and energy consumption can be reduced; the mass of iron, magnesium, aluminum and calcium elements contained in the residual phosphoric acid is P contained in the residual phosphoric acid 2 O 5 6% to 15% of mass; The pH adjuster is potassium hydroxide, or raffinate phosphoric acid and potassium hydroxide.

2. A production process for potassium dihydrogen phosphate according to claim 1, Features: Raffinate phosphoric acid is a byproduct of wet-process phosphoric acid purification by solvent extraction.

3. A production process for potassium dihydrogen phosphate according to claim 1, Features: The decolorizing agent is one or both of hydrogen peroxide and activated carbon, and the added amount is 0.05%-0.5% of the mass of the slurry in step 4.

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