Method for granulating urea by using melt marble cutting technology and obtained urea granules

Abstract

The invention discloses a method for granulating urea by using a melt marble cutting technology, which comprises the following steps: by using industrial urea powder and omniphobic urea melt powder asraw materials, coating the surface of urea melt with the omniphobic urea melt powder in a melting coating or premixing melting mode to form urea melt marbles; and then cutting the urea melt marble ona superomniphobic urea melt cutting table surface which is higher than the melting point of urea and lower than the decomposition temperature of urea to obtain independent urea melt particles, and condensing the independent urea melt particles after cooling to obtain urea particles. By using the granulation method disclosed by the invention, urea particles with different particle sizes can be conveniently prepared as required, the cost can be reduced, the pollution to the environment can be alleviated, the prepared urea particles have excellent moisture degradation resistance and slow releaseperformance, the compressive strength of a single urea particle can reach 6.36 N / mm, and the urea particles are high in compression resistance and not easy to break.

Description

technical field [0001] The invention belongs to the technical field of urea granule preparation, in particular to a urea granulation method. Background technique [0002] At present, the industrial urea granulation methods mainly include tower spray granulation process, steel belt granulation process and fluidized bed granulation process. [0003] The urea spray tower granulation process is mainly used to produce small granule urea products. First, urea melt is prepared from urea powder, and then the urea melt needs to be transferred to the top of the prilling tower, and sprayed out through the nozzle to produce urea liquid. drop. This process requires the design of a heating and heat preservation system for the nozzle to prevent urea crystallization from clogging the nozzle; at the same time, it is necessary to prevent the sprayed urea droplets from colliding with each other or contacting and bonding with surrounding equipment. [0004] Steel strip granulation process, fi...

AI Technical Summary

Problems solved by technology

The production method of this process is simple, but there are the following problems: 1) urea granules are easy to bond with the plate, and the plate surface needs to be cleaned regularly; 2) the obtained granules have poor sphericity and fluidity, and are not suitable for mechanical fertilization; 3) the obtained urea granules The specific surface area is large, and it is easy to absorb moisture and deliquescence, and the dissolution rate is fast when fertilization is applied, resulting in increased nutrient loss

Although the fluidized bed method has produced large granular urea and has become the mainstream preparation method of large granular urea, there are the following problems: 1) The granulation characteristics of the encapsulated crystals cause the particle size of the urea particles prepared by the fluidized bed method to be uneven , it is necessary to separate the small particle urea through the screening process to obtain the required large particle product, and use the small particle urea as the return material, and the return material reduces the production capacity; 2) because the urea melt needs to be atomized into fine droplets, the product needs After sieving, a large amount of urea dust will be brought, causing environmental pollution and affecting the health of the operator; 3) When granulating, urea molten droplets are sprayed into the bed through the nozzle, and there are problems of nozzle clogging and corrosion, and the structure of the equipment 4) Since formaldehyde additives are added to the urea melt to increase the hardness of the product, large-grain urea will cause pollution during the preparation process, and will pollute the environment such as soil and water during use

Although this method can obtain large-grained urea with uniform particle size distribution and strong pressure resistance, and reduces the cost and environmental pollution, the method is to drop or spray the urea melt on the superhydrophobic surface to form a dispersed urea solution. Therefore, the nozzle or nozzle of the feeder (device) still has the problem of clogging and corrosion, and the dispersed droplets are prone to roll and coalesce on the superhydrophobic surface

[0007] To sum up, the existing urea granulation process needs to use mechanical energy or / and thermal energy to obtain the required urea droplets, and the formation of urea droplets needs to be realized through small-diameter structures such as nozzles or drop holes, which not only requires high investment Ratio and energy consumption, and it is easy to cause the nozzle or drop hole of the equipment to be blocked and corroded, and the dispersed droplets are easy to coalesce, etc.

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