Production method of tower type prilling slow release fertilizer

Abstract

The invention relates to a method for making a slow-release fertilizer through tower granulation, which comprises: heating and mixing solid urea or a urea solution and a formaldehyde solution to form mixed slurry, wherein the mol ratio of the urea to formaldehyde is 1-8:1, and the temperature of the mixed slurry is between 40 and 80 DEG C; mixing a phosphorus fertilizer preheated to a temperature of between 50 and 80 DEG C, one or more selected from a nitrogenous fertilizer, a potassium fertilizer or solid filler, and a urea-formaldehyde solution; and adding a small amount of dilute sulfuric acid solution into the mixed slurry, spraying the mixed slurry from the top of a tower, and making the granular compound fertilizer. The method utilizes the principle that condensation reaction of the urea and the formaldehyde in an acid solution is exothermic reaction to achieve the aim of flash evaporation of moisture, reduces the height of the granulation tower, simultaneously reduces the temperature of the mixed slurry, and can produce composite fertilizers with various formulas. The compound fertilizer is slowly released and difficult to agglomerate.

Description

technical field [0001] The invention relates to a method for manufacturing slow-release fertilizers by tower granulation, in particular to a method for manufacturing nitrogen-containing or nitrogen-phosphorus or nitrogen-phosphorus-potassium slow-release fertilizers by tower granulation. Background technique [0002] In recent years, tower granulation has been rapidly popularized in my country due to its good sphericity, good surface gloss and high yield. However, because this method is limited to high nitrogen, the production formula is limited, and it can only produce high nitrogen, low phosphorus and medium potassium, which is not suitable for the needs of most enterprises in my country to produce multiple formulas. [0003] Chinese patent CN1546441A discloses a method for manufacturing compound fertilizer by tower granulation of molten slurry, the melting temperature is (130°C-145°C), and the tower height is 60m-100m. At such a high granulation temperature, the residenc...

AI Technical Summary

Problems solved by technology

The tower body of this method is too high, and the cost of each meter of the granulation tower is about 100,000, and the cost of 100 meters is about 10 million. For most small and medium-sized enterprises, the investment in the production of a single formula is too large to be worth the candle.

[0004] Chinese patent CN147380A discloses a new oil-cooled spray granulation process for producing compound fertilizers. Oil-cooled granulation consumes about 4% of the oil, which increases the production cost of the enterprise. In addition, the oil is applied to the Farmland has caused pollution to the soil. At present, few companies are using this method

[0005] Chinese patent (application number 2006101590915) discloses a kind of production method of high-tower slow-release compound fertilizer, and it is to add the urea-formaldehyde of making in advance in the mixed slurry, then carries out high-tower granulation, although this method has made slow-release compound fertilizer Release fertilizer, but did not make full use of urea and formaldehyde to react under acidic conditions and release heat, thereby reducing tower height

[0006] Chinese patent CN1880286A discloses a production method of compound fertilizer without drying process. It is urea and formaldehyde to generate mixed slurry, which is then sprayed on other heated solid materials, and some materials are returned. Although it is an economical production method method, but compared with the tower granulation, it is not economical enough, and the appearance of the particles is not round enough and has no luster