Urea Granulation Recovery Loop Ammonium Salt Control
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Solution Overview
Problem
Existing urea granulation processes face issues with ammonium salt precipitation, leading to clogged equipment and high water content in the urea solution, which hampers continuous operation and product quality.
Innovation Solution
A method that includes a granulation step, recovery step, ammonium salt concentration adjustment, concentration step, and mix step to control the ammonium salt concentration in the urea solution, using an aqueous solution with a low ammonium salt concentration to prevent precipitation and optimize water content, involving neutralization and control of the ammonium salt concentration based on temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the aqueous recovered-urea solution is concentrated to remove water, then the water content is reduced, but the ammonium salt concentration becomes high causing precipitation
Solution Approach 1:
The patent applies preliminary action by adjusting the ammonium salt concentration before concentration. Specifically, urea melt is added to the aqueous recovered-urea solution prior to concentration, which dilutes the ammonium salt concentration and prevents precipitation during the subsequent concentration step. This preliminary adjustment ensures stable composition throughout the concentration process.
Solution Approach 2:
The patent changes the concentration parameter of urea melt to control ammonium salt precipitation. By adjusting the amount of urea melt added (controlling its concentration parameter), the system prevents ammonium salt precipitation while achieving the desired water removal. This parameter adjustment allows continuous operation without equipment clogging.
2Stability of the object's composition
If urea melt is added to the aqueous recovered-urea solution before concentration, then ammonium salt precipitation is prevented, but the water content in the solution increases
Solution Approach 1:
The patent optimizes the parameter of urea melt addition amount to balance two conflicting requirements: preventing ammonium salt precipitation and minimizing water content increase. By controlling the concentration and quantity of urea melt added, the system achieves stable ammonium salt concentration while limiting the water content increase to acceptable levels for continuous operation.
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
Prevents ammonium salt precipitation, allowing for long-term continuous operation and reducing water content in the urea solution supplied to the granulation step, thereby improving product quality and process efficiency.
Implementation Method 1
a concentration step of concentrating the aqueous recovered-urea solution which is obtained from the ammonium salt concentration adjustment step by vaporizing water which is contained in the aqueous recovered-urea solution
Data Source
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AI summary
When recovering and utilizing the urea and NH3 contained in a gas that contains urea dust and NH3 and has been discharged from a urea granulation step, an aqueous urea solution to be fed to the urea granulation step is prevented from suffering the precipitation of an ammonium salt while inhibiting the solution from increasing in water content. The method for granulating urea comprises: a granulation step in which granular solid urea is produced from a feed aqueous urea solution using air, a recovery step in which urea dust and NH3 are recovered, using an acid-containing aqueous solution, from the air discharged from the granulation step, thereby obtaining a recovery liquid containing urea and an ammonium salt, a salt concentration regulation step in which an aqueous urea solution having a lower ammonium salt concentration than the recovery liquid is mixed with the recovery liquid to regulate the ammonium salt concentration in the recovery liquid, a concentration step in which water contained in the liquid obtained in the salt concentration regulation step is vaporized to concentrate the liquid obtained in the salt concentration regulation step, thereby obtaining a concentrated recovery liquid, and a mixing step in which the concentrated recovery liquid is mixed with the feed aqueous urea solution, the concentrated recovery liquid being regulated so as to have an ammonium salt concentration of 7 mass% or less.