Improved process for producing spherical and granulated nitrogen-phosphorus-potassium mixed fertilizer based on nitrophosphate fertilizer device

Abstract

An improved process for producing spherical and granulated nitrogen-phosphorus-potassium mixed fertilizer based on a nitrophosphate fertilizer device comprises the following steps: firstly, mixing a calcium nitrate filter cake in a working procedure of calcium nitrate crystallization with potassium nitrate in proportion, drying, and crushing to obtain a potash-lime fertilizer; drying and crushing NP slurry in a working procedure of mother liquor evaporation to obtain a nitrophosphate fertilizer; feeding both of the potash-lime fertilizer and the nitrophosphate fertilizer in proportion into a stock bin at the top of a high tower, stirring and mixing in the stock bin, heating up and fusing through a smelt tank of the high tower, and finally, granulating by a granulation sprayer of the high tower to obtain the spherical and granulated nitrogen-phosphorus-potassium mixed fertilizer. According to the process, element calcium in by-products is fully used, and effective components in the fertilizer are increased while the temperature of nitrophosphate fertilizer slurry in the smelt tank of the high tower is lowered by calcium nitrate as a by-product. Because the slurry is granulated by mixing in a molten state, the product has uniform nutrients. The method not only improves the physical and chemical properties and the appearance of the nitrophosphate fertilizer, but also simplifies the production process, reduces the production cost and offers a new approach for nitrophosphate fertilizer production.

Description

technical field [0001] The invention relates to a production process of nitrophosphate fertilizer, in particular to a nitric acid which combines high tower granulation technology with an existing nitrophosphate fertilizer production process, and effectively utilizes by-product calcium nitrate to produce spherical particle nitrogen, phosphorus and potassium compound fertilizer. Phosphate fertilizer production improvement process. Background technique [0002] Existing nitrophosphate fertilizers are NP / NPK compound fertilizers obtained by using nitric acid, phosphate rock and ammonia gas as raw materials, and by freezing method to produce nitrophosphate fertilizers and adding potassium salts. The production process mainly includes acid hydrolysis of phosphate rock, acid insoluble matter Precipitation and separation, freeze crystallization, calcium nitrate filtration, mother liquor ammonia neutralization, neutralization slurry evaporation, biaxial granulation, drying and coolin...

AI Technical Summary

Problems solved by technology

[0004] Problem 1. With the year-by-year decline of phosphate rock grade, the impurity content in phosphate rock is getting higher and higher, and the content of by-product calcium nitrate is also increasing. Sometimes, 0.8-1.0 tons of by-product calcium nitrate can be produced per ton of product. Moreover, the relative humidity of the prepared calcium nitrate tetrahydrate is low, the hygroscopicity is strong, and the nitrogen content is very low, only 11.86%, so it is generally not suitable to be sold directly as a chemical fertilizer.

[0008] Problem 2: The fertilizers produced by the existing biaxial granulation technology have shortcomings such as uneven particle size, no spherical particles, high return rate, unsightly appearance, poor fluidity, and inconvenient practical application.

[0010] However, in the process of producing spherical granular NPK compound fertilizer based on the existing nitrophosphate fertilizer plant using high-tower granulation, due to the complex composition and relatively viscous composition of NP slurry, it is easy to block the pipeline and equipment, so that the slurry is sent into the Granulation at the top of the tower is difficult to achieve

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