Water-Selective Membrane Concentration of Urea Solution
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Solution Overview
Problem
Current methods for concentrating urea solutions from urea plant recovery sections, such as vacuum evaporation and crystallization, are inefficient in terms of energy use and require large, expensive equipment, posing maintenance challenges and inefficient heat management.
Innovation Solution
The use of selective membrane separation to differentiate between water and urea, allowing for the concentration of urea solutions using water-selective membranes that are permeable to water but impermeable to urea, potentially replacing or complementing traditional concentration methods like evaporation or crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If vacuum evaporation is used to concentrate urea solution, then high urea concentration is achieved, but large and expensive equipment is required with poor energy efficiency
Solution Approach 1:
The patent replaces the mechanical vacuum evaporation system with a membrane separation system. The semi-permeable membrane selectively transports water molecules from the urea solution through concentration stages, eliminating the need for vacuum equipment, steam heating, and complex mechanical systems while achieving the same concentration goal with minimal energy input.
Solution Approach 2:
The patent changes the operating parameters from high-energy vacuum evaporation to low-energy membrane separation. By using multiple concentration stages with progressively tighter membranes, the system achieves high urea concentration without requiring the extreme conditions (vacuum, high heat input) needed by traditional evaporation methods.
2Quantity of substance
If vacuum evaporation is used to concentrate urea solution, then high urea concentration is achieved, but large and expensive vessels are required
Solution Approach 1:
The patent replaces large vacuum evaporation vessels with compact membrane modules. The membrane separation process requires minimal space compared to the large vessels needed for vacuum evaporation, as the separation occurs across thin membrane surfaces rather than requiring large-volume heating chambers.
Solution Approach 2:
The patent employs multiple concentration stages nested within each other, where each stage uses progressively tighter membranes to achieve incremental concentration. This nested multi-stage approach achieves high final concentration in a compact configuration, similar to how nested dolls achieve complex functionality in limited space.
3Quantity of substance
If crystallization is used to concentrate urea solution, then high urea concentration is achieved, but big and complex equipments requiring significant maintenance efforts are required
Solution Approach 1:
The patent replaces the complex mechanical crystallization equipment with a simple membrane separation system. The membrane modules have no moving parts, no mechanical complexity, and require minimal maintenance compared to crystallization equipment which involves complex mechanical systems for crystal formation, separation, and handling.
Solution Approach 2:
This principle is not directly applicable to the urea concentration process described in the patent.
4Quantity of substance
If vacuum evaporators are used, then urea concentration is achieved, but sealing problems arise to avoid infiltration of air from the outside
Solution Approach 1:
The patent replaces the vacuum system with an atmospheric pressure membrane separation system. Since the process operates at or near atmospheric pressure, there is no vacuum seal required, eliminating the sealing problems and air infiltration issues inherent in vacuum evaporators.
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 achieves high urea concentrations (95-99.5% wt.) with reduced energy input and eliminates the need for costly vacuum equipment, enhancing energy efficiency and simplifying maintenance, while allowing for flexible integration with existing concentration processes.
Implementation Method 1
A membrane for carrying out the invention has a first permeability for the transport of water and/or for the transport of other contaminants, and a second and different permeability for the transport of urea
Implementation Method 2
water is collected from the discharge side, thus increasing the concentration of the solution at the feed side
Data Source
Figure 1
AI summary
A process and a related plant for the synthesis of urea, where a solution (13) comprising urea is obtained in a synthesis section (10), said solution is treated in a recovery section (14), and an aqueous solution (15) comprising mainly urea and water, which is obtained from said recovery section, is concentrated by means of contact with a water-selective membrane.