A kind of production method of high-purity dipotassium hydrogen phosphate

Abstract

The present invention specifically discloses a production method of high-purity dipotassium hydrogen phosphate, the method includes, low-grade phosphate ore is ground and sieved to a finer powder below 160 mesh, then the obtained phosphate ore is mixed with boiler ash in a mass ratio of 1:1, then sent to a rotary kiln for combustion, the rotary kiln temperature is controlled to be 350-450°C, thereby burning to generate phosphorus pentoxide, the phosphorus pentoxide is absorbed by a potassium carbonate solution cycle, to a solution neutralization end point of pH value 8.5-9.0, phenolphthalein indicator just shows red, then, fine powdered activated carbon is added, adsorption time 0.5-1h, adsorption temperature above 80°C, neutralization solution is concentrated to 120-124°C and then filtered out insoluble matter, then cooled to crystallization below 20°C, centrifuged, dried to obtain product, and mother liquor is sent to neutralization program for reuse. The inventive method has the advantage of environmental protection, and the obtained dipotassium hydrogen phosphate has the advantage of high purity.

Description

Technical Field

[0001] The present application relates to a method for producing high-purity dipotassium hydrogen phosphate, and more specifically, to a method for producing environmentally friendly high-purity dipotassium hydrogen phosphate. Background Art

[0002] Potassium hydrogen phosphate is a white hygroscopic granule or crystalline powder, which is very soluble in water. Its aqueous solution is slightly alkaline to phenolphthalein and soluble in ethanol. It is mainly used as a corrosion inhibitor for antifreeze, a nutrient for antibiotic culture medium, a phosphorus and potassium regulator for the fermentation industry, and a feed additive. At present, there are many methods for manufacturing potassium hydrogen phosphate, including neutralization method, urea phosphate method, etc.

[0003] Preparation by neutralization method: solid caustic potash is prepared into a 30% aqueous solution, clarified, filtered to remove impurities, and then added to a corrosion-resistant reaction tank after measurement. An appropriate amount of 50% phosphoric acid solution is slowly added under stirring, and the neutralization reaction is carried out at 90-100°C. The pH of the reaction end point is controlled to be 8.5-9.0 (until phenolphthalein is used as an indicator and just turns red), and the solution is heated to 120-124°C for concentration. After the solution concentration reaches the required range, the insoluble matter is filtered to remove. The clarified filtrate is cooled to below 20°C to precipitate crystals, and then centrifuged and slightly air-dried to obtain the finished product of dipotassium hydrogen phosphate.

[0004] CN2014102138887 discloses a method for producing dipotassium hydrogen phosphate, which uses urea phosphate to react with potassium hydroxide, controls the reaction temperature to be 50°C-90°C, stirs the reaction for 20-70 minutes, controls the endpoint pH value to be 8-9.5, and produces a dipotassium hydrogen phosphate product. This preparation method is relatively costly, corrosive to equipment, and has no environmental value.

[0005] In the prior art, phosphoric acid is widely used to react with potassium hydroxide or potassium carbonate to produce the product during the preparation of dipotassium hydrogen phosphate. In this process, phosphoric acid corrodes the equipment, so the material requirements for the equipment are relatively strict. At the same time, a large amount of water is required in the production process, and the high-temperature concentration product is used, which consumes a lot of energy, making the production process of the entire dipotassium hydrogen phosphate product costly and polluting. At the same time, the dipotassium hydrogen phosphate produced in the prior art is not pure enough and contains many impurities, which is difficult to meet the application scenarios of high purity.

[0006] Phosphate resources in my country are widely distributed, with large quantities in Guizhou, Yunnan, Sichuan, Hunan, Hubei and other provinces. More than 90% of my country's phosphate resources are medium and low-grade phosphate ores. The current utilization of medium and low-grade phosphate ores mainly includes making them into phosphate fertilizers or phosphoric acid, and the use of rotary kilns for phosphate combustion has gradually become the focus of industrial research, because the phosphoric acid produced by the rotary kiln method has high purity and is more environmentally friendly. However, the ratio of its raw materials has become a difficulty that restricts its industrial application.

[0007] In view of the problems existing in the preparation technology and the problem that the purity of dipotassium hydrogen phosphate produced by the prior art is not enough, the present invention seeks a method with mild preparation conditions, easy control of process conditions and parameters, low energy consumption and simple subsequent treatment for promotion and application. Summary of the invention

[0008] The present invention provides a method for producing high-purity dipotassium hydrogen phosphate, which specifically comprises the following steps:

[0009] Low-grade phosphate rock is ground and sieved to a finer powder below 160 mesh, and then the obtained phosphate rock is mixed with boiler ash in a mass ratio of 1:1, and then sent to a rotary kiln for combustion. The rotary kiln temperature is controlled at 350-450°C, thereby burning to generate phosphorus pentoxide, which is absorbed by a potassium carbonate solution circulation until the solution is neutralized to a pH value of 8.5-9.0, and the phenolphthalein indicator just turns red. Then, fine powdered activated carbon is added, the adsorption time is 0.5-1h, the adsorption temperature is above 80°C, the neutralized solution is concentrated to 120-124°C, the insoluble matter is filtered out, and then cooled to below 20°C for crystallization, centrifuged, and dried to obtain the product, and the mother liquor is sent to the neutralization process for reuse.

[0010] Among them, in the potassium hydrogen phosphate concentration process, when a large amount of material is precipitated during concentration and the concentrated material is in a thick and flowing state, the concentration can be stopped. While ensuring the yield, the impurities can be effectively retained in the mother liquor and removed in the dehydration process.

[0011] Among them, low-grade phosphate ore includes P2O5 15-21%, SiO2 19-25%.

[0012] Among them, boiler ash can be the smoke deposited in the furnace of a power plant.

[0013] Wherein, the content of potassium carbonate solution is controlled at 0.05-0.06 g / ml.

[0014] Among them, the adsorption temperature of activated carbon is 80-100℃

[0015] Among them, kiln slag can be used as fertilizer.

[0016] The dipotassium hydrogen phosphate produced by this production method has the advantages of being environmentally friendly, greatly reducing equipment corrosion, and having extremely high purity.

[0017] The potassium hydrogen phosphate produced by this process fully meets the requirements of HPLC, has a simple reaction process, high product quality, low energy consumption, safety and environmental protection. The specific effects are as follows:

[0018] The present invention achieves the optimal raw material ratio for phosphoric acid production by reasonably designing the particle size of phosphate rock and obtaining a suitable ratio of phosphate rock to boiler ash through multiple tests. At the same time, the equipment of the present invention does not directly contact phosphoric acid, thereby avoiding corrosion of the equipment by phosphoric acid, greatly reducing environmental risks and equipment damage risks.

[0019] Adding adsorbent: After the neutralization reaction is completed and before filtering, add fine powdered activated carbon so that during the filtering process, the activated carbon fills the gaps in the filter bag and effectively reduces the penetration of impurities. Its porous structure can effectively adsorb impurities in the solution, and the chemical properties of activated carbon are stable and it is not easy to react chemically with the adsorbed substances. The length of the activated carbon soaking time and the temperature during soaking will also affect the adsorption of activated carbon. If the soaking time is too short and the temperature is too low, the activated carbon adsorption will be incomplete. If the soaking time is too long, the activated carbon adsorption reaches saturation, wasting time and cost. Experiments show that when the temperature is controlled at 80-100℃ and the soaking time is 0.5-1h, the product treated with activated carbon adsorption can meet the quality standards.

[0020] Control the concentration end point: In the potassium hydrogen phosphate concentration process, when a large amount of material is precipitated and the concentrated material is in a thick and flowing state, the concentration can be stopped. While ensuring the yield, the impurities can be effectively retained in the mother liquor and removed in the dehydration process.

[0021] 4. Compared with the traditional purification method, the introduction of activated carbon adsorption and the effective control of the concentration endpoint will effectively remove impurities and improve the purity of potassium hydrogen phosphate. The purity obtained can reach the special grade (more than 99%). This method meets the production concept of high product quality, low energy consumption, safety and environmental protection.

[0022] Further illustrate the technical effects of the present invention:

[0023] The present invention effectively removes relevant impurities and improves product purity by adjusting process parameters. The specific method is as follows:

[0024]

[0025] The boiler ash used in the present invention can generally be smoke deposited in the furnace of a power plant. DETAILED DESCRIPTION

[0026] In order to better illustrate the technical solution of the present invention, a specific implementation method is disclosed below to specifically explain the technical features of the present invention, and the explanation is not restrictive.

[0027] Embodiment 1:

[0028] A method for producing high-purity dipotassium hydrogen phosphate specifically comprises the following steps:

[0029] Low-grade phosphate rock is ground and sieved to a finer powder below 160 mesh, and then the obtained phosphate rock is mixed with boiler ash in a mass ratio of 1:1, and then sent to a rotary kiln for combustion. The rotary kiln temperature is controlled at 400°C, thereby burning to generate phosphorus pentoxide, which is circulated and absorbed by a potassium carbonate solution with a content of 0.05g / ml until the solution is neutralized to a pH value of 8.7, and the phenolphthalein indicator just turns red. Then, fine powdered activated carbon is added, the adsorption time is 0.5h, the adsorption temperature is 85°C, the neutralized solution is concentrated to 122°C, the insoluble matter is filtered out, and then cooled to below 20°C for crystallization, centrifuged, and dried to obtain the product, and the mother liquor is sent to the neutralization process for reuse.

[0030] Among them, in the potassium hydrogen phosphate concentration process, when a large amount of material is precipitated and the concentrated material is in a thick and flowing state, the concentration can be stopped. While ensuring the yield, the impurities can be effectively left in the mother liquor and removed in the dehydration process. The purity of the obtained potassium hydrogen phosphate is measured by quantitative method, and its purity is 99.8%.

[0031] In order to better illustrate the technical effect of the present invention, an experimental comparison is carried out based on Example 1.

[0032] Comparison 1: The effect of adding different types of adsorbents on the absorbance of potassium dihydrogen phosphate. Three adsorbents and no adsorbent were selected. After keeping in a water bath at 85℃ for 30 minutes, the absorbance of the material is as follows:

[0033] Absorbance No activated carbon added Granular activated carbon Honeycomb activated carbon Fine powder activated carbon raw material 230nm≤0.15 0.586 0.486 0.567 0.212 240nm≤0.12 0.554 0.442 0.501 0.156 250nm≤0.11 0.503 0.413 0.501 0.143 310nm≤0.05 0.433 0.338 0.436 0.089 500nm≤0.02 0.278 0.234 0.268 0.032

[0034] The data show that under the experimental conditions, fine powdered activated carbon has the best adsorption effect and reduces the absorbance the most because fine powdered activated carbon has a larger specific surface area, thus providing more adsorption sites.

[0035] Comparison 2: The effect of adding fine powdered activated carbon at 85°C and different adsorption times on the absorbance of potassium dihydrogen phosphate. The results are as follows

[0036]

[0037]

[0038] The data show that under the experimental conditions, in a short time (10 minutes), the adsorption effect of fine powdered activated carbon on the solution is limited, and the absorbance decreases little. After 60 minutes, the decrease in absorbance tends to be stable, indicating that the adsorption has reached an approximate equilibrium state. Although the absorbance decreases further with time, from the perspective of efficiency and economy, a longer adsorption time is not required.

[0039] Comparison 3: The effect of adding fine powdered activated carbon and adsorbing for 30 minutes at different temperatures on the absorbance of potassium hydrogen phosphate. The results are as follows:

[0040]

[0041] The data show that: under experimental conditions, the adsorption effect of fine powdered activated carbon increases with the increase of temperature, but it basically reaches a maximum value after the temperature reaches 80°C, ensuring that the maximum adsorption effect can be achieved when the adsorption temperature of activated carbon is around 80°C, thereby avoiding energy waste and saving resources.

[0042] Comparison 4: Add fine powdered activated carbon before filtration of the synthetic liquid, adsorb for 30 minutes in a water bath at 85°C, control the concentration endpoint at different levels, and the effect on the absorbance and yield of potassium dihydrogen phosphate. The results are as follows:

[0043]

[0044]

[0045] The data show that: under the experimental conditions, different concentration endpoints have a great influence on the absorbance of potassium dihydrogen phosphate. After concentrating to the point of peeling, cooling and crystallizing, although the absorbance data is very good, the yield is too low, wasting resources; when concentrating to a whole block of material, the material is discarded while hot, the yield is good, but the absorbance does not meet the standard; therefore, the material is concentrated to a large amount of material precipitated, and then the material can be discarded, which not only ensures that the absorbance meets the standard, but also controls the yield and saves costs.

[0046] The present invention may also have other specific implementation parameters, and any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the scope of protection required by the present invention.

Claims

1. A method for producing high-purity dipotassium hydrogen phosphate, comprising the following steps: The low-grade phosphate rock is ground and sieved to a finer powder below 160 mesh, and then the obtained phosphate rock is mixed with boiler ash in a mass ratio of 1:1, and then sent to a rotary kiln for combustion. The rotary kiln temperature is controlled at 350-450°C, thereby burning to generate phosphorus pentoxide, which is absorbed by a potassium carbonate solution circulation until the solution is neutralized to a pH value of 8.5-9.0, and the phenolphthalein indicator just turns red. Then, fine powdered activated carbon is added, the adsorption time is 0.5-1h, the adsorption temperature is 80°C-100°C, the neutralized solution is concentrated to 120-124°C, and then the insoluble matter is filtered out, and then cooled to below 20°C for crystallization, centrifuged, and dried to obtain the product. The mother liquor is sent to the neutralization process for reuse, wherein, In the potassium hydrogen phosphate concentration process, when a large amount of material is precipitated and the concentrated material is in a thick and flowing state, the concentration can be stopped. While ensuring the yield, impurities can be effectively retained in the mother liquor and removed in the dehydration process. Among them, the low-grade phosphate ore includes P2O5 15-21%, SiO2 19-25%. The purity of the obtained potassium hydrogen phosphate is determined by quantitative method, and its purity is 99.8%.

2. The method for producing high-purity dipotassium hydrogen phosphate according to claim 1, wherein: Boiler ash is the soot that settles in the furnace of a power plant.

3. The method for producing high-purity dipotassium hydrogen phosphate according to claim 1, wherein: Control the content of potassium carbonate solution to 0.05-0.06g / ml.

4. The method for producing high-purity dipotassium hydrogen phosphate according to claim 1, wherein: Kiln slag can be used as fertilizer.

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