CN100500553C - A kind of method of producing calcium dihydrogen phosphate - Google Patents

Abstract

The production process of calcium dihydrogen phosphate features that excessive phosphoric acid is used to decompose phosphate rock powder and the decomposed product is separated to obtain phosphoric acid solution containing calcium dihydrogen phosphate and impurity slag containing metals including RE metals. After partial calcium dihydrogen phosphate is crystallized and separated, the residual calcium dihydrogen phosphate in the mother liquid is decomposed with sulfuric acid, and the mother liquid is separated to obtain white gypsum and phosphoric acid, which is used in the next production. The present invention utilizes calcium element in phosphate rock powder, has saving in sulfuric acid, and can also obtain side products white gypsum and available metal impurity slag.

Description

A kind of method of producing calcium dihydrogen phosphate

The invention is a method for producing calcium dihydrogen phosphate.

The current method of producing calcium dihydrogen phosphate is to prepare phosphoric acid first by wet method or thermal method, and then neutralize it with bone meal or milk of lime. No matter whether wet method or thermal method is used to produce phosphoric acid, the calcium element in the phosphate rock is completely unused, and the wet method consumes sulfuric acid. Also high, thermal law energy consumption is very high, the current process is obviously unreasonable, so the production cost is very high.

The purpose of the present invention is to provide a method for directly producing calcium dihydrogen phosphate with phosphate rock powder and sulfuric acid. The calcium element in the calcium dihydrogen phosphate comes completely from phosphate rock, so no bone powder or milk of lime is needed, and the consumption of sulfuric acid is also low. The consumption is also very low, and the production cost is greatly reduced.

The concept of the present invention is: use excess phosphoric acid to decompose phosphate rock powder, separate phosphoric acid insoluble slag to obtain phosphoric acid solution of calcium dihydrogen phosphate, cool to room temperature after cooling or concentration, part of calcium dihydrogen phosphate crystallizes out, and obtains the quantity after separation Calcium dihydrogen phosphate not greater than 30% of the total amount of calcium dihydrogen phosphate produced by the reaction is used as the product, and the rest of the calcium dihydrogen phosphate is left in the mother liquor, and sulfuric acid is added to decompose it. After the white gypsum is separated, phosphoric acid is used to decompose the next batch of phosphorus Mineral powder.

The specific process is as follows:

Using excessive phosphoric acid to decompose phosphate rock powder, the reaction formula is as follows:

7H ₃ PO ₄ +Ca ₅ F(PO ₄ ) ₃ →5Ca(H ₂ PO ₄ ) ₂ +HF

The molar ratio of reactants: H ₃ PO ₄ :Ca ₅ F(PO ₄ ) ₃ =20～50:1, the concentration of phosphoric acid is 20～60%, the reaction temperature is controlled at 50～100℃, and the reaction is completed within 1～3 hours under stirring , the fluorine-containing waste gas produced in the reaction is absorbed by water, alkali or salt solution, and then made into fluorine products. The obtained slurry is separated by filtration, and the filter residue can be further used after washing because it is rich in various metals and rare earth metals. Because the filter residue is nearly black in color, it is called black residue, and the washing water of the black residue can be returned to the process for use. The filtrate is the phosphoric acid solution of calcium dihydrogen phosphate. After cooling or concentrating, it is cooled to room temperature. Part of the calcium dihydrogen phosphate crystallizes out. After filtration and separation, calcium dihydrogen phosphate is obtained, and it is the product after drying. The amount of calcium is not more than 30% of the total amount of calcium dihydrogen phosphate generated by the reaction, and the rest of the calcium dihydrogen phosphate remains in the mother liquor and is decomposed by adding sulfuric acid. The reaction formula is as follows:

3.5H ₂ SO ₄ +3.5Ca(H ₂ PO ₄ ) ₂ →3.5CaSO ₄ +7H ₃ PO ₄

The molar ratio of reactants: H ₂ SO ₄ :Ca(H ₂ PO ₄ ) ₂ =3.5:3.5, sulfuric acid concentration 60-98%, normal temperature or heating temperature control below 100°C, stirring reaction for 1-3 hours to complete, after filtration White gypsum is obtained by separation, and then washed and dried to obtain gypsum powder as a by-product. The washing water of white gypsum can also be returned to the process for use, and the filtrate is phosphoric acid solution, which is all returned to decompose the next batch of phosphate rock powder.

Accompanying drawing 1 is the technological process schematic diagram of producing calcium dihydrogen phosphate.

Embodiment 1 of the present invention is described below in conjunction with accompanying drawing 1:

In the decomposition tank, add phosphoric acid solution 18 obtained from separation 6 and water 28 after washing black slag obtained by washing 10, add phosphate rock powder 11 to decompose 1, obtain slurry 12 through separation 2 to obtain black slag 26, wash 10 with water 29 Obtain black residue 27 after washing. The filtrate obtained from separation 2 is the phosphoric acid solution 13 containing calcium dihydrogen phosphate. Part of calcium dihydrogen phosphate crystals are separated out through crystallization 3. The crystal slurry 14 is separated 4 to obtain calcium dihydrogen phosphate 24, and the product dihydrogen phosphate is obtained through drying 9. Calcium 25. The mother liquor 15 containing calcium dihydrogen phosphate obtained from separation 4 is decomposed 5, adding the water 19 after washing the white gypsum from washing 7, and adding sulfuric acid 23 to decompose, and the decomposed slurry 16 is separated 6 to obtain the filtrate as a phosphoric acid solution 18 to decompose 1, the filter residue white gypsum 17 is washed 7 with water 20, and the water 19 after washing the white gypsum is decomposed 5, and the washed white gypsum 21 is dried 8 to obtain by-product white gypsum powder 22.

In the production of calcium dihydrogen phosphate, not only the phosphorus element but also the calcium element come from phosphate rock, thereby reducing the consumption of sulfuric acid, the process is more reasonable, and no waste phosphogypsum is produced, but white gypsum and metal-rich metals for further use are produced by-product , The black slag of rare earth metals fully utilizes raw material resources, which not only eliminates pollution but also improves economic benefits.

Claims (1)

1, a kind of method of producing monocalcium phosphate is characterized in that reaction formula is as follows with excessive phosphorolytic cleavage ground phosphate rock:

7H ₃PO ₄+Ca ₅F(PO ₄) ₃→5Ca(H ₂PO ₄) ₂+HF

Reaction consumption mol ratio: H ₃PO ₄: Ca ₅F (PO ₄) ₃=20-50:1, phosphoric acid concentration is 20-60%, 50-100 ℃ of reaction temperature control, stirring down, reaction finished in 1-3 hour, the waste gas containing fluoride water that produces in the reaction, alkali, or salt solution absorbs, make the fluorine product again, the gained slip separates after filtration, and filter residue is owing to be rich in multiple metal, rare earth metal can be done further utilization after washing, this filter residue is because color is closely black, claim black slag, the washing water of black slag can return technology and use, and filtrate is the phosphoric acid solution of monocalcium phosphate, through the cooling or concentrated postcooling to room temperature, the crystallization of part monocalcium phosphate is separated out, and promptly obtains monocalcium phosphate after separating after filtration, is product after the drying, the quantity that should control the product monocalcium phosphate is not more than 30% of monocalcium phosphate total amount that reaction generates, remaining monocalcium phosphate is stayed in the mother liquor, adds sulfuric acid and decomposes, and reaction formula is as follows:

3.5H ₂SO ₄+3.5Ca(H ₂PO ₄) ₂→3.5CaSO ₄+7H ₃PO ₄

Reactant consumption mol ratio: H ₂SO ₄: Ca (H ₂PO ₄) ₂=3.5:3.5, sulfuric acid concentration 60-98%, normal temperature or heating temperature control are below 100 ℃, stirring reaction 1-3 hour finishes, obtain white gypsum after filtration, obtain the by-produced gypsum powder through washing drying again, the washing water of white gypsum also can return technology and use, and filtrate is that phosphoric acid solution all returns and is used for branchs and takes off and criticize ground phosphate rock.

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