CO2-Stripping Synthesis Section for Urea Plant Revamping
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Solution Overview
Problem
Existing self-stripping urea plants face challenges in increasing production capacity due to limited margins in high-pressure and medium-pressure sections, requiring expensive revamping and additional equipment, and are constrained by site space and energy costs from compressing CO2 to high pressures.
Innovation Solution
A new CO2-stripping synthesis section is installed, operating in parallel to the existing self-stripping section, redirecting a portion of the liquid ammonia and carbamate solution to this new section, which produces a low-ammonia urea solution that bypasses the high-pressure and medium-pressure sections, directing it to the low-pressure section for increased capacity without overloading existing equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a new CO2-stripping synthesis section is installed to increase production capacity, then urea production capacity increases, but device complexity increases
Solution Approach 1:
The urea plant is divided into distinct operational sections: existing self-stripping HP/MP sections, a new CO2-stripping synthesis section, and a common LP section. This segmentation allows independent operation and optimization of each section while sharing common infrastructure, thereby increasing capacity without proportionally increasing overall system complexity
Solution Approach 2:
The low-pressure section serves multiple functions: it processes urea solution from both the existing HP section and the new CO2-stripping synthesis section. This multi-functionality allows the LP section to handle increased total flow without requiring duplication of equipment, thus increasing capacity while limiting complexity growth
2Productivity
If CO2 is compressed to high pressure for the synthesis reaction, then urea production is enabled, but energy consumption increases
Solution Approach 1:
The invention changes the pressure parameter at which CO2 is introduced into the synthesis loop. Instead of compressing CO2 to full HP section pressure (140-160 bar), the new section operates at a lower pressure (80-120 bar), reducing the compression energy requirement while maintaining effective urea synthesis through adjusted operational parameters
3Productivity
If existing HP and MP sections are revamped to increase capacity, then production capacity increases, but investment cost increases
Solution Approach 1:
The invention merges the output of the new CO2-stripping synthesis section with the existing plant's low-pressure section, creating a unified processing system. This merging allows the new capacity to be integrated into existing infrastructure rather than requiring separate complete processing trains, thereby reducing investment costs while achieving capacity increase
Solution Approach 2:
Rather than copying and expanding the entire HP-MP-LP train, the invention creates a parallel CO2-stripping synthesis section that feeds into the existing LP section. This selective copying of only the synthesis portion while sharing the recovery section reduces the scope and cost of revamping compared to duplicating the entire process train
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 increases urea production capacity without additional duty on the HP and MP sections, improves conversion yield by adjusting the nitrogen-to-carbon ratio, reducing water consumption and by-product formation, and is cost-effective by utilizing existing equipment and reducing energy costs.
Implementation Method 1
at least a portion of the process stream from the reactor is stripped in a CO2 stripper in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas
Implementation Method 2
The stripping process takes place with the help of heat furnished e.g. by hot steam (thermal stripping)
Implementation Method 3
a vapour phase containing ammonia and CO2 produced in the stripper is condensed in the high-pressure condenser
Data Source
Figure 1
Figure 2
AI summary
A method for revamping a self-stripping urea plant comprising the installation of a new CO2-stripping synthesis section (6), wherein at least part of the aqueous urea solution (10) leaving said new section (6) is directed to the existing low pressure recovery section (4)of the self-stripping plant, by-passing the existing self-stripping high-pressure section (2) and medium pressure treatment section (3).