Method for preparing long-acting slow-release compound fertilizers by one-step pulp spraying granulation

Abstract

The invention relates to a method for preparing long-acting slow-release compound fertilizers by one-step pulp spraying granulation, which comprises the following steps: heating and mixing urea and formaldehyde solution according to a mol ratio of (2 to 7)/1 to be prepared into mixed material pulp with the temperature between 40 and 90 DEG C; introducing N, P and K fertilizers or filling materials and the like into a granulation device; after the mixed material pulp and ammonium sulphate are mixed in a pipeline according to a weight ratio of (5 to 30)/1, spraying the mixture on solid materials in the granulation device for mixed granulation; simultaneously introducing ammonia for neutralization during the granulation; and obtaining the grain compound fertilizers, wherein the weight ratio of the mixed material pulp to the sulphuric acid is (5 to 30)/1, the addition of the mixed material pulp sprayed on the solid materials accounts for 10 weight percent to 50 weight percent of the total material weight, and the quantity of the introduced ammonia accounts for 1 weight percent to 5 weight percent of the total material weight.

Description

technical field [0001] The invention relates to a preparation method of a compound fertilizer, in particular to a method for preparing granular long-acting slow-release compound fertilizer by one-step spraying and granulation. Background technique [0002] Traditional urea-based slow-release compound fertilizers generally adopt a two-step method to produce compound fertilizers, that is, firstly, a certain proportion of urea and formaldehyde are used to react to form urea-formaldehyde, and then urea-formaldehyde is mixed with other phosphorus-containing and potassium-containing raw materials to granulate, and then granulated After the material is dried, cooled and sieved, the qualified product can be obtained. The production process is long and the production cost is relatively high. [0003] Chinese patent CN1307550A discloses a production method of compound fertilizer granules. Although this method omits the drying process after granulation in the traditional method, the t...

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Problems solved by technology

[0003] Chinese patent CN1307550A discloses a production method of compound fertilizer granules. Although this method omits the drying process after granulation in the traditional method, the temperature of the hot air introduced into the raw materials during granulation is as high as 200-300°C, and the melting of solid urea The temperature is 135°C. At such a high granulation temperature, the residence time of the material is slightly longer, and the production of biuret will increase significantly. Biuret will cause damage to crops when fertilizer is applied.

The production process of this production method is too long, and the setting of the process is not reasonable, that is, let the urea react with formaldehyde first, then dry it into a white solid, and then mix it with other solid materials to granulate it and then dry it. The process is long and wastes energy seriously.

In the first step of preparing urea-formaldehyde fertilizer, after heating, cooling, drying and other processes, the heat energy loss is very large, which increases the production cost of fertilizer, and the economic benefit is not obvious.

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