Urea Granulation Cooling via Fine Atomized Water
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Solution Overview
Problem
The existing process for preparing urea granules in a fluid bed granulator results in significant fine urea dust being blown out with the fluidization air as water evaporates, leading to economic and environmental concerns.
Innovation Solution
The process involves using fluidization air with very finely atomized water and a urea melt concentration higher than 97 wt.%, ensuring rapid water evaporation for cooling without forming large amounts of dust, and allowing flexible introduction of water into the granulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water is sprayed to cool the urea melt during granulation, then cooling effect is achieved, but fine urea dust is generated and blown out with fluidization air
Solution Approach 1:
The invention changes the parameter of water droplet size from conventional larger droplets to very fine atomized droplets with a diameter of less than 10 micrometers. This parameter change enables rapid evaporation that provides effective cooling while preventing dust generation, as the fine droplets evaporate before urea particles can be entrained in the fluidization air
Solution Approach 2:
The invention utilizes the phase transition of water from liquid to vapor through rapid evaporation. The very fine atomized water droplets undergo complete or near-complete evaporation when contacting the urea melt, providing latent heat of vaporization for cooling while the water transitions to vapor phase that mixes with the fluidization air without carrying urea particles
2Quantity of substance
If urea melt concentration is increased above 97 wt.% to reduce water content in final product, then product quality improves, but cooling requirement increases
Solution Approach 1:
The invention applies parameter change by using extremely fine atomization of water (droplet diameter < 10 μm) to achieve rapid evaporation. This enables the system to handle higher urea melt concentrations (>97 wt.%) by providing intense cooling through the large surface area to volume ratio of the atomized droplets, allowing complete evaporation before the cooled granulate is discharged
3Temperature
If conventional water spraying is used for cooling, then cooling is achieved, but granulator capacity is limited due to dust formation
Solution Approach 1:
By changing the water application parameter from conventional spraying to very fine atomization (droplet diameter < 10 μm), the invention achieves rapid evaporation that provides superior cooling efficiency. This enables increased granulator capacity by allowing higher urea melt concentrations and faster processing rates without the limitation of dust formation that constrains conventional water spraying systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces urea dust in the off-gas, increases granulator capacity, and allows for more efficient cooling, enabling 10-50% higher urea granulate production in the same size granulator with reduced water content in the final product.
Implementation Method 1
the water can evaporate very rapidly, so achieving the desired cooling by evaporation of water
Implementation Method 2
achieving the desired cooling by evaporation of water without the formation of large amounts of fine dust
Implementation Method 3
a distribution plate above which the fluid bed is present and sprayers that are mounted in the distribution plate, from which the urea melt is sprayed on or over the urea particles present in the fluid bed, which particles are kept in motion by the fluidization air
Data Source
AI summary
Process for the preparation of urea granules in a fluid bed granulator comprising at least one inlet for fluidization air, a distribution plate above which the fluid bed is present and sprayers that are mounted in the distribution plate, from which the urea melt is sprayed on or over the urea particles present in the fluid bed, which particles are kept in motion by the fluidization air, characterized in that the fluidization air contains very finely atomized water and in that the urea concentration of the urea melt is higher than 97 wt. %.