A kind of method utilizing crystal seed and returning material to produce large crystal calcium hydrogen phosphate

Abstract

The invention provides a method for producing large dicalcium phosphate crystals by utilizing seed crystals and a returned material. The method comprises the following steps: returning a part of slurry in a second neutralization reaction tank into a first neutralization reaction tank, and controlling the pH value of the neutralization reaction tank; causing the slurry reacted in the second neutralization reaction tank to enter a third neutralization reaction tank, and adding lime milk to regulate the pH value; fractionating the slurry in the third neutralization reaction tank, concentrating coarse grains with grain sizes of more than 150 [mu]m to obtain a dicalcium phosphate semi-finished product, performing solid-liquid separation to obtain solids, drying the solids to obtain the large dicalcium phosphate crystals, and causing discharged fine crystals with grain sizes of smaller than 150[mu]m to enter the first neutralization reaction tank as the reaction seed crystals. According to the method, the moisture content of a separated solid phase can be reduced without reducing the phosphorus yield, a drying system and procedures of packaging and the like are greatly improved, coal power consumption is reduced, the packaging environment is improved, and packaging labor is reduced.

Description

technical field [0001] The invention relates to a method for producing large-crystal feed-grade calcium hydrogen phosphate with wet-process phosphoric acid, in particular to a method for producing large-crystal calcium hydrogen phosphate by using crystal seeds and returning materials. Background technique [0002] The current method of producing calcium hydrogen phosphate is to react phosphoric acid pulp with sulfuric acid to generate phosphoric acid, and then separate the liquid and solid after filtration to obtain phosphoric acid, then add limestone powder for rough adjustment, and finely adjust lime milk to control the neutralization pH value, so as to meet the standard for producing feed grade calcium hydrogen phosphate For the required phosphoric acid, after clarification and removal of impurities, lime milk is added to neutralize the pH to 6-6.3 to generate calcium hydrogen phosphate. In this process, there are two reaction tanks, and they are single-connected, without...

AI Technical Summary

Problems solved by technology

In this process, there are two reaction tanks, and they are single-connected, without returning materials (such as figure 1 ), resulting in fine crystals with an average particle size of 130µm, and those below 60µm accounted for 30%, which brought difficulties in the solid-liquid separation process, and the moisture content was as high as 28%, and the phosphorus yield was 98.3%. The large proportion of crystals increases the labor intensity of the packaging, and the unit weight is difficult to control

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