CN114956025A - Preparation process of feed-grade monocalcium phosphate - Google Patents

Abstract

The invention belongs to the field of phosphorus chemical industry, and in particular relates to a process for preparing feed-grade calcium dihydrogen phosphate. I neutralize the calcium hydrogen phosphate slurry that generates with milk of lime, obtain calcium hydrogen phosphate semi-finished product after the calcium hydrogen phosphate slurry is carried out solid-liquid separation, dry first, obtain the calcium hydrogen phosphate that moisture content is less than 4%; (2) Phosphate II with a concentration of more than 50% is obtained by using phosphate rock with a grade higher than 29% through semi-water-diwater extraction, concentration, defluorination and dearsenic; (3) The phosphoric acid II obtained in step (2) is the same as that in step (1). The calcium hydrogen phosphate obtained in ) reacts to generate a semi-finished product of calcium dihydrogen phosphate, which is dried after curing, and then sieved to obtain a finished product of calcium dihydrogen phosphate. The invention can use a large amount of low-grade phosphate rock that is difficult to use in traditional processes, reduce the use ratio of high-grade phosphate rock, and save about 45% of coal consumption per unit product.

Description

A kind of preparation technology of feed grade calcium dihydrogen phosphate

technical field

The invention belongs to the field of phosphorus chemical industry, and in particular relates to a process for preparing feed-grade calcium dihydrogen phosphate.

Background technique

(1) Energy saving and carbon reduction

Based on the new development stage, fully, accurately and comprehensively implement the new development concept, build a new development pattern, adhere to the system concept, properly handle the relationship between development and emission reduction, overall and partial, short-term and medium-term, coordinate and stabilize growth and adjust the structure, and Carbon peaking and carbon neutrality are included in the overall economic and social development. Adhere to the general policy of “national overall planning, conservation priority, two-wheel drive, internal and external smoothness, and risk prevention”, and effectively, orderly and effectively do a good job in carbon peaking. The goals and tasks of various fields and industries, accelerate the realization of green changes in production and lifestyle, promote economic and social development on the basis of efficient use of resources and green and low-carbon development, and ensure that the carbon peaking goal by 2030 is achieved as scheduled.

(2) Industry status quo:

The calcium powder method (also known as one-step method or concentration one-step method) is generally used to produce calcium dihydrogen phosphate. The main process is as follows: using higher-grade phosphate rock to obtain wet Phosphoric acid; then concentrate it (if the dihydrate method is used, the concentration of the finished phosphoric acid is low, and the energy consumption during concentration is large); the concentrated concentrated phosphoric acid is purified; the purified phosphoric acid and calcium carbonate are reacted to make a slurry ; Obtain filter cake and filtrate after filtration; Continue to add phosphoric acid to the filter cake, and then generate feed grade calcium dihydrogen phosphate semi-finished product, and obtain the finished product after spray drying.

(3) Dilution of phosphate rock

According to the data on pages 64-65 of the "Latest Phosphorus Chemical Technology Manual" published by China Knowledge Publishing House in August 2013, "According to preliminary statistics, only 1.298 billion tons of grade I rich ore with a phosphorus pentoxide content of more than 30% in my country's phosphate rock is only 1.298 billion tons. , accounting for 6.4% of the national reserves; 1.5 billion tons of grade II medium ore with a phosphorus pentoxide content of 24-30%, accounting for 7.4% of the national reserves; 14.8 billion tons of grade III lean ore with a phosphorus pentoxide content of 14-24% , accounting for 72.9% of the national reserves”.

(4) Policy orientation

The "Investment Guidelines for Technological Transformation and Upgrading of Industrial Enterprises (2019 Edition)" encourages "enhancing the utilization of medium and low-grade phosphate rock and associated resources of phosphate rock", and the "Plan for Industrial Transformation and Upgrading of Yunnan Province (2016-2020)" "supports the hierarchical utilization of phosphate rock resources. Encouraging comprehensive utilization of low- and medium-grade phosphate rock", "Industrial Structure Adjustment Guidance Catalogue (2019 Edition)" "Encouraged Category/Eleven, Petrochemical Chemicals/2/Utilization of Low- and Medium-Grade Phosphate Rocks". In order to effectively utilize medium and low grade phosphate rock and realize the purpose of energy saving and carbon reduction, it is urgent to study a method for preparing calcium dihydrogen phosphate using medium and low grade phosphate rock under the condition of energy saving and carbon reduction.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the present invention provides a preparation process of feed-grade calcium dihydrogen phosphate, which effectively utilizes medium and low grade phosphate rock to prepare calcium dihydrogen phosphate under the condition of energy saving and carbon reduction.

The specific technical scheme is: a preparation process of feed-grade calcium dihydrogen phosphate, comprising the following steps:

(1) Phosphate ore with a grade of 14-25% in terms of phosphorus pentoxide is used to obtain phosphoric acid I after extraction with dihydrate, and then the calcium hydrogen phosphate slurry generated by the neutralization of phosphoric acid I and lime milk, and the calcium hydrogen phosphate The slurry is subjected to solid-liquid separation to obtain a semi-finished product of calcium hydrogen phosphate, which is first dried to obtain calcium hydrogen phosphate with a moisture content of less than 4%;

(2) Using the phosphate rock whose grade is higher than 29% in terms of phosphorus pentoxide, and after concentration, defluorination and dearsenic through hemi-water-dihydrate extraction, phosphoric acid II with a concentration of more than 50% in terms of phosphorus pentoxide is obtained. ;

(3) The phosphoric acid II obtained in step (2) reacts with the calcium hydrogen phosphate obtained in step (1) to form a semi-finished product of calcium dihydrogen phosphate, which is dried after being aged, and then sieved to obtain a finished product of calcium dihydrogen phosphate.

Further, in step (1), the concentration of phosphoric acid I prepared by purification after dihydrate extraction is 16-18% in terms of phosphorus pentoxide.

Further, in step (1), after the calcium hydrogen phosphate slurry is subjected to solid-liquid separation, the water content of the semi-finished calcium hydrogen phosphate obtained is less than 20%. Feed grade calcium dihydrogen phosphate is the traditional name, and the professional name is feed grade additive calcium dihydrogen phosphate (GB22548-2017).

Further, in step (3), the generated semi-finished calcium dihydrogen phosphate has a moisture content of 9-11%, and is then dried after being aged.

Further, the phosphate rock with a grade of 14-25% is selected from the grade III phosphate rock with a phosphorus pentoxide content of 14-24% or a grade II phosphate rock with a phosphorus pentoxide content of 24-25%, that is, it is selected from the grade III phosphate rock. Or a grade II phosphate rock slightly higher than grade III.

Further, the phosphate rock with a grade higher than 29% is selected from the grade I phosphate rock with a phosphorus pentoxide content of more than 30% or a grade II phosphate rock with a phosphorus pentoxide content of 29-30%, that is, it is selected from the grade I phosphate rock or Class II phosphate rock close to Class I.

Beneficial effects:

Under the background of carbon peaking in 2030, energy saving and emission reduction, and "double control" of energy consumption, as well as the orientation of many national industrial policies, enterprises are required to develop towards the utilization and energy saving of medium and low-grade phosphate rock. The present invention is based on the requirements of such an era background, and the company independently developed a set of production processes that can utilize medium and low grade phosphate rock, save energy and reduce carbon.

(1) In this process, the moisture content of each semi-finished product of calcium dihydrogen phosphate is calculated according to the median of 11.5%. 0.12994 tons; about 0.65 tons of calcium hydrogen phosphate is needed to produce one ton of calcium hydrogen phosphate, the moisture content of semi-finished calcium hydrogen phosphate is about 23%, and the moisture content required for drying 0.65 tons of calcium hydrogen phosphate is 0.65/(1-23 %)*23%=0.1942 tons; then in this process, the moisture required for drying per ton of calcium dihydrogen phosphate semi-finished products is 0.1942+0.1299=0.324 tons. The water required for drying calcium hydrogen is reduced by 0.494 tons, which can theoretically reduce coal consumption by about 80%. However, due to the fact that the exhaust gas takes away part of the heat and the heat dissipation of the system is similar, the coal consumption per unit product in the actual production process is reduced from 124kgce/t to 68kgce/t , saving 56kgce/t, which is equivalent to saving about 45% of coal consumption.

(2) Theoretical calculation: CaHPO ₄ + H ₃ PO ₄ =Ca(H ₂ PO ₄ ) ₂ , 50% of the phosphorus comes from calcium hydrogen phosphate. According to the data since production started from May to October 2021, dihydrogen phosphate 50% of phosphorus in calcium products comes from phosphoric acid, but in the actual production process, 55.51% of phosphorus pentoxide consumption comes from phosphoric acid, and 44.49% comes from calcium hydrogen phosphate. Compared with high-grade phosphate rock, using the production process of this patent, 55.51% of the phosphate rock is medium and high-grade phosphate rock, 44.49% of the phosphate rock is low-grade phosphate rock, and a large amount of low-grade phosphate rock is used, which is in line with the guidance of the national industrial policy. , but also in line with the actual needs of enterprise development.

(3) Economic analysis: the current market price of phosphate rock with 32% grade is 950 yuan/ton, the market price of phosphate rock with about 29% grade is 780 yuan/ton, and the market price of phosphate rock with about 23% grade is 310 yuan/ton. Compared with the calcium powder method, the cost of producing raw phosphate rock by the hydrogen calcium method is reduced by more than 440 yuan/ton, the coal consumption is saved by 56 kilograms of standard coal (about 94 yuan/ton), and the electricity consumption is reduced by about 10 yuan/ton. The annual output per ton is calculated, which is equivalent to saving 200,000 tons* (440+94+10) ≈ 100 million yuan. At the same time, the use of calcium hydrogen production reduces the links of pulping, pulping, spraying and exhaust gas circulation washing, which greatly reduces the process and also reduces the investment (taking the 200,000-ton plant as an example, the investment is saved by about 24 million yuan) and the energy consumption of the above-mentioned links in the traditional process; especially in the traditional process, in order to achieve spray granulation, it is necessary to add a large amount of water to adjust the slurry to a concentration of 45 to 50%, and finally evaporate a large amount of water; The powdered calcium dihydrogen phosphate prepared by preparing calcium hydrogen phosphate and then adding high-concentration phosphoric acid can avoid the operation of adding water first and then evaporating, saving most of the energy consumption.

The method can use a large amount of low-grade phosphate rock that is difficult to apply in traditional processes, reduce the use ratio of high-grade phosphate rock, and save about 45% of coal consumption per unit product, and can achieve better economic benefits.

Description of drawings

Fig. 1 is the contrast schematic diagram of the present invention and traditional technology.

Detailed ways

A preparation process of feed-grade calcium dihydrogen phosphate, comprising the following steps:

(1) Phosphate ore with a grade of 14-25% in terms of phosphorus pentoxide is used to obtain phosphoric acid I after extraction with dihydrate, and then the calcium hydrogen phosphate slurry generated by the neutralization of phosphoric acid I and lime milk, and the calcium hydrogen phosphate The slurry is subjected to solid-liquid separation to obtain a semi-finished product of calcium hydrogen phosphate, which is first dried to obtain calcium hydrogen phosphate with a moisture content of less than 4%;

(2) Using the phosphate rock whose grade is higher than 29% in terms of phosphorus pentoxide, and after concentration, defluorination and dearsenic through hemi-water-dihydrate extraction, phosphoric acid II with a concentration of more than 50% in terms of phosphorus pentoxide is obtained. ;

(3) The phosphoric acid II obtained in step (2) reacts with the calcium hydrogen phosphate obtained in step (1) to form a semi-finished product of calcium dihydrogen phosphate, which is dried after being aged, and then sieved to obtain a finished product of calcium dihydrogen phosphate.

Further, in step (1), the concentration of phosphoric acid I prepared by purification after dihydrate extraction is 16-18% in terms of phosphorus pentoxide.

Further, in step (1), after the calcium hydrogen phosphate slurry is subjected to solid-liquid separation, the water content of the semi-finished calcium hydrogen phosphate obtained is less than 20%.

Further, in step (3), the generated semi-finished calcium dihydrogen phosphate has a moisture content of 9-11%, and is then dried after being aged.

Further, the phosphate rock with a grade of 14-25% is selected from the grade III phosphate rock with a phosphorus pentoxide content of 14-24% or a grade II phosphate rock with a phosphorus pentoxide content of 24-25%, that is, it is selected from the grade III phosphate rock. Or a grade II phosphate rock slightly higher than grade III.

Further, the phosphate rock with a grade higher than 29% is selected from the grade I phosphate rock with a phosphorus pentoxide content of more than 30% or a grade II phosphate rock with a phosphorus pentoxide content of 29-30%, that is, it is selected from the grade I phosphate rock or Class II phosphate rock close to Class I.

Example (because the "calcium" in the calcium dihydrogen phosphate product is derived from calcium hydrogen phosphate, referred to as "hydrogen calcium method")

(1) Select the grade III phosphate rock or the grade II phosphate rock with a grade of 14-25% slightly higher than the grade III, enter the ball mill, and add water or process circulating water to the ball mill, adjust the amount of water added to make the water content of the pulp Phosphate slurry between 40-42%;

(2) Phosphate slurry reacts with sulfuric acid in the extraction tank:

Ca ₅ F(PO ₄ ) ₃ +5H ₂ SO ₄ +mH ₂ O==3H ₃ PO ₄ +5CaSO ₄ .m/5H ₂ O+HF, the reaction is actually carried out in two steps, the first step: Ca ₅ F (PO ₄ ) ₃ +7H ₃ PO ₄ ==5Ca(H ₂ PO ₄ ) ₂ +HF, the second step is:

5Ca(H ₂ PO ₄ ) ₂ +5H ₂ SO ₄ +mH ₂ O==10H ₃ PO ₄ +5CaSO ₄ .m/5H ₂ O, the reacted slurry is subjected to solid-liquid separation, and the liquid phase is dilute phosphoric acid, which enters Dilute phosphoric acid storage tank; solid-liquid separation solid-phase treatment: the solid phase enters the extraction tank and reacts with the phosphoric acid and sulfuric acid returned by filtration. After the reaction is completed, the solid phase is filtered and washed to obtain phosphogypsum, and the liquid part is returned to the extraction tank. .

(3) The prepared dilute phosphoric acid reacts with calcium slurry: 2H ₃ PO ₄ +CaCO ₃ =Ca(H ₂ PO ₄ ) ₂ +CO ₂ +H ₂ O after the reaction, after passing the qualification, it enters the precipitation device to settle and clear. The liquid overflows to the buffer storage tank for secondary purification treatment; after the solid phase separation of the thick slurry at the bottom, the solid phase is a fertilizer grade calcium hydrogen phosphate product (available for sale).

(4) The clear liquid after the primary purification and precipitation enters the secondary purification reaction tank to react with the lime milk slurry, and the pH value of the reaction end point is controlled to be 2.8-3.0. After the secondary purification reaction, after the purification is qualified, the slurry enters the precipitation device for precipitation. The clear and supernatant liquid is phosphoric acid I (phosphorus-fluorine ratio>240) to three-stage neutralization, and the solid phase of the bottom thick slurry is separated into a fertilizer grade calcium hydrogen phosphate product (available for sale).

(5) The phosphoric acid I qualified for the secondary purification treatment reacts with the ash milk of the ash-dissolving process in the neutralization reaction tank, and the pH value of the reaction end point is controlled to be between 5.7-6.0. After neutralization, it is used in the ash process. The thick slurry is separated by a centrifuge, and the solid product is filtered and transported to drying. A part of the mother liquor pool of the clear liquid in the three-stage precipitation device is returned to the pump for recycling. After the thick slurry is separated, the semi-finished product of hydrogen calcium is obtained. The moisture content is required to be less than 20%, and it is transported to the drying section through the belt, and dried to a moisture content of less than 4% to obtain calcium hydrogen phosphate with a moisture content of less than 4%.

(6) Select the grade I phosphate rock or the grade II phosphate rock close to the grade I, that is, the phosphate rock powder with a grade higher than 29% reacts with sulfuric acid in the hemi-water extraction tank to generate phosphoric acid and hemihydrate gypsum slurry, which is passed through the belt type. Filter and wash to obtain concentrated phosphoric acid with a concentration of about 39%.

(7) Concentrated phosphoric acid is concentrated and defluorinated and reacted in the purification reaction tank under the condition of adding steam and purifying agent. The main principle is that the fluorine in the wet phosphoric acid mainly exists in the form of HF and H ₂ SiF ₆ . Under the conditions of: 6HF+SiO ₂ = H ₂ SiF ₆ + 2H ₂ O, H ₂ SiF ₆ =SiF ₄ +2HF, the generated SiF ₄ is brought out of the liquid surface in the collision of steam and acid, and enters through the negative pressure of the system The washing tower is in countercurrent contact with water in the washing tower to generate a fluorosilicic acid solution: 3SiF ₄ +(n+2).H ₂ O=2H ₂ SiF ₆ + SiO ₂ .n H ₂ O. The slurry that has passed the reaction is filtered through the plate and frame, and the purified phosphoric acid II (phosphorus pentoxide concentration > 50%) enters the storage tank, and the sludge is transported to the white manure for drying and can be sold.

(8) Phosphoric acid II and calcium hydrogen phosphate (moisture content less than 4%) are reacted in biaxial stirring, 1 ton of calcium hydrogen phosphate is controlled to add 0.5 m³ phosphoric acid, and the returned material after crushing is 2 tons, and then according to the material moisture content and The production index is to adjust the amount of returned material and the amount of phosphoric acid added, and control the moisture content of the semi-finished product to be between 9-11%; After sieving, the under-sieves are packaged to obtain calcium dihydrogen phosphate finished products, and the over-sieves are crushed and returned to the calcium dihydrogen phosphate production process.

Note: Phosphate I with a grade of 14-25% can be adjusted to 16-18% after purification to produce phosphoric acid I concentration by dihydrate extraction. The phosphoric acid I concentration of 16-18% is due to the production needs of the reaction with phosphoric acid II; The phosphoric acid II produced by the phosphate rock with a grade higher than 29% through the semi-aqueous-diwater extraction process can be adjusted to more than 50% because of the concentration process, and the concentration of phosphoric acid II is greater than 50% because of the production needs of the reaction with phosphoric acid I.

Claims (6)

1. A preparation process of feed-grade monocalcium phosphate is characterized by comprising the following steps:

(1) extracting phosphate ore with a grade of 14-25% by using dihydrate, purifying to prepare phosphoric acid I, neutralizing the generated calcium hydrophosphate slurry by using the phosphoric acid I and lime milk, performing solid-liquid separation on the calcium hydrophosphate slurry to obtain a calcium hydrophosphate semi-finished product, and drying to obtain calcium hydrophosphate with the moisture content of less than 4%;

(2) utilizing phosphorite with the grade higher than 29 percent, and obtaining phosphoric acid II with the concentration higher than 50 percent through semi-hydrated-dihydrate extraction, concentration, defluorination and dearsenification;

(3) and (3) reacting the phosphoric acid II obtained in the step (2) with the calcium hydrophosphate obtained in the step (1) to generate a calcium dihydrogen phosphate semi-finished product, curing, drying, and screening to obtain a calcium dihydrogen phosphate finished product.

2. The process for preparing feed-grade monocalcium phosphate as claimed in claim 1, wherein in step (1), the concentration of phosphoric acid I obtained by diaextracting and purifying is 16-18%.

3. The process for preparing feed-grade monocalcium phosphate as claimed in claim 1, wherein in step (1), the water content of the calcium hydrophosphate semifinished product obtained by performing solid-liquid separation on calcium hydrophosphate slurry is less than 20%.

4. The process for preparing feed-grade monocalcium phosphate as claimed in claim 1, wherein in step (3), the produced monocalcium phosphate semi-finished product has a moisture content of 9-11%, and is dried after being cured.

5. The process for preparing feed-grade monocalcium phosphate as claimed in claim 1, wherein the grade of 14-25% phosphorus ore is selected from grade III phosphorus ore with phosphorus pentoxide content of 14-24% or grade II phosphorus ore with phosphorus pentoxide content of 24-25%.

6. The process for preparing feed-grade monocalcium phosphate as claimed in claim 1, wherein the phosphate ore with grade higher than 29% is selected from grade i phosphate ore with phosphorus pentoxide content higher than 30% or grade ii phosphate ore with phosphorus pentoxide content 29-30%.

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