Urea Solution Purification via Flash Evaporation
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Solution Overview
Problem
Conventional processes for producing urea solutions for selective catalytic reduction are energy-intensive and result in impure solutions due to the use of deionized water and common fertilizer urea, which contains heavy metals and oils, leading to shortened catalytic converter lifetimes and failure to meet high quality standards.
Innovation Solution
A continuous process that purifies process water from conventional urea synthesis using multiple cleaning columns to remove NH3, CO2, and biuret, then mixes it with urea to create a solution meeting ISO 22241 standards, with less than 0.2% NH3 and 0.3% biuret, achieving the desired 32% urea concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deionized water is used to produce urea solutions, then the purity of the solution is improved, but the energy consumption increases
Solution Approach 1:
The invention changes the parameters of process water through temperature-controlled purification steps (heating to 80-100°C, flash evaporation at specific pressures) to remove impurities, transforming waste water into a purification medium that meets quality standards without requiring energy-intensive deionization processes
Solution Approach 2:
The invention converts harmful process water containing NH3, CO2, and biuret into a beneficial purification medium by using it as the basis for producing pure urea solution through controlled heating and flash evaporation, eliminating the need for separate deionization steps
2Ease of manufacture
If conventional fertilizer urea is used, then the cost is reduced, but the lifespan of catalytic converters is shortened due to heavy metals and oils
Solution Approach 1:
The invention extracts and removes harmful impurities (heavy metals, oils, biuret) from the urea solution through flash evaporation and controlled heating processes, retaining only the beneficial urea and water components needed for SCR catalyst operation
Solution Approach 2:
The invention changes the chemical composition parameters of the urea solution by controlling temperature and pressure during flash evaporation to selectively remove volatile impurities while maintaining urea concentration within the required 31.8-33.2 wt% range
3Manufacturing precision
If energy-intensive crystallization and drying processes are used, then pure urea solution is produced, but the energy consumption increases significantly
Solution Approach 1:
The invention utilizes phase transitions (liquid to vapor) through flash evaporation at controlled temperatures and pressures to separate impurities from the urea solution, achieving purification without the energy-intensive crystallization and drying processes
Solution Approach 2:
The invention employs periodic flash evaporation steps at different pressures and temperatures to progressively remove different types of impurities, achieving high purity through multiple rapid cycles rather than continuous energy-intensive processing
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 process efficiently produces a pure urea solution suitable for SCR, extending catalytic converter lifespan and meeting ISO 22241 quality criteria, reducing energy consumption and impurities, and ensuring compliance with environmental standards.
Implementation Method 1
a first purification column (5) for purifying the process water, in which the process water is heated to 100 to 150 °C by introducing steam or, preferably, flash gases consisting of ammonia, carbon dioxide, and water vapor from purification columns 2 and 3, and then condensed
Implementation Method 2
the process water is heated to 100 to 150 °C by introducing steam or, preferably, flash gases consisting of ammonia, carbon dioxide, and water vapor from purification columns 2 and 3, and then condensed
Implementation Method 3
a mixing device (10) for mixing the purified process water with the urea solution obtained from the urea process
Data Source
Figure 1
AI summary
The invention relates to a process for producing pure urea solutions and in particular a pure urea solution with the quality characteristics of AUS 32 according to ISO 22241, in which a urea solution produced according to a conventional urea synthesis process is mixed with process water produced stoichiometrically during the synthesis and purified by a purification process by means of desorption in such a way that a pure urea solution is obtained which is free of urea synthesis-typical impurities and contains less than 0.2 wt% NH3 and 0.3 wt% biuret, based on the total solution.