Urea Pellet Granulation via Spouted Bed Control
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Solution Overview
Problem
Existing methods for producing urea granulates for diesel engine denitrification fail to achieve the necessary high standards of grain size uniformity, sphericity, and low residual moisture, leading to inhomogeneous products that do not meet the specifications required for effective exhaust treatment in the automotive industry.
Innovation Solution
A spouted bed apparatus is used to spray urea-containing liquids at controlled temperatures into a high-density particle flow, allowing for controlled heat and material transfer, resulting in urea pellets with a narrow grain size distribution, high sphericity, and low residual moisture, while avoiding agglomeration and dust formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If urea-containing liquids are sprayed into a fluidized bed, then granulation occurs, but agglomeration cannot be avoided and homogeneous structure cannot be achieved
Solution Approach 1:
The invention extracts the problematic fluidized bed environment and replaces it with a spouted bed system. This separation allows the granulation process to occur in a different flow regime where particles are transported in discrete streams rather than being suspended together, preventing agglomeration while maintaining homogeneous structure through controlled particle circulation.
Solution Approach 2:
The invention changes the fundamental flow parameters of the gas-solid system by transitioning from fluidized bed conditions (where gas velocity exceeds minimum fluidization velocity) to spouted bed conditions (with specific gas velocity profiles and particle circulation patterns). This parameter change fundamentally alters particle-particle and particle-gas interaction modes, enabling precise control over granulation while avoiding agglomeration.
2Productivity
If gas and liquid are introduced at a common place in spouted bed granulator, then fluidized bed is created, but inhomogeneous particle concentrations develop and dust formation occurs
Solution Approach 1:
The invention segments the gas and liquid introduction points in the spouted bed granulator, placing them at different locations rather than a common place. This spatial segmentation prevents direct mixing of gas and liquid streams at the introduction point, avoiding localized inhomogeneities in particle concentration and reducing dust formation while maintaining overall granulation efficiency through the spouted bed's natural circulation patterns.
3Reliability
If high air flow speeds are used to maintain fluidized bed, then stable processing conditions are achieved, but dust is generated and surface quality is reduced
Solution Approach 1:
The invention changes the gas velocity profile and flow regime parameters by transitioning from fluidized bed operation to spouted bed operation. This parameter change allows processing to occur at lower overall gas flow speeds while maintaining stable processing conditions through the spouted bed's characteristic particle circulation and suspension zones, thereby reducing dust generation and preserving surface quality.
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
The method produces urea pellets with a narrow grain size range, high sphericity, and low residual moisture, ensuring they are dust-free, freely flowing, and meet the specifications for diesel engine exhaust denitrification, while also allowing for large-scale production with high operational security and ease of cleaning.
Implementation Method 1
a spouted bed apparatus is used to spray urea-containing liquids at controlled temperatures into a high-density particle flow
Implementation Method 2
spray urea-containing liquids at controlled temperatures into a high-density particle flow
Implementation Method 3
allowing for controlled heat and material transfer, resulting in urea pellets with a narrow grain size distribution, high sphericity, and low residual moisture
Data Source
AI summary
A method for producing urea pellets having a narrow range of grain sizes and a sphericity >75% and a defined residual moisture ≦0.5% is provided. The method provides urea pellets having the properties required which meet the requirements of the automotive industry for use thereof in reducing emissions from diesel engines. The method includes spraying a urea-containing liquid having a temperature between ambient temperature and above the melting point of the urea into the high particle density region of the spray zone of a near circular gas, material flow of a spouted bed apparatus and onto the particle surface of the material, which is dried and granulated in the gas flow at a temperature of not more than 130° C. at a controlled heat and mass transfer rate while being separated.