Vertical Submerged Condenser for Urea Plant Revamping
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Solution Overview
Problem
Urea production plants using the thermal stripping process face inefficiencies in ammonia removal and limited condensation unit capacity, leading to high energy consumption and increased investment costs when attempting to increase production capacity.
Innovation Solution
Transforming horizontal condensation units into vertical submerged units with simultaneous and independent feeding of ammonia and carbon dioxide vapors and carbamate liquid within the tubes, and using carbon dioxide as a stripping agent in the stripping unit, enhancing mixing and heat exchange efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal stripping process is used in conventional plants, then urea production can be maintained, but ammonia removal efficiency is insufficient and requires additional medium pressure treatment section
Solution Approach 1:
The invention extracts and eliminates the medium pressure treatment section from the conventional urea production process. By optimizing the thermal stripping unit to achieve complete ammonia removal directly, the complex medium pressure treatment section (distillation column, rectifying column) is removed entirely, simplifying the overall process while maintaining high urea production capacity
Solution Approach 2:
The invention changes the operating parameters of the thermal stripping unit by introducing carbon dioxide as a stripping agent and operating at optimized temperature and pressure conditions. This parameter optimization enables complete ammonia removal in the thermal stripping unit alone, eliminating the need for additional medium pressure treatment section
2Productivity
If production capacity is increased in conventional plants, then more urea can be produced, but energy consumption increases and investment costs rise
Solution Approach 1:
The thermal stripping unit is designed to perform multiple functions simultaneously: heating the aqueous solution, stripping ammonia, and utilizing carbon dioxide for both stripping and subsequent urea formation. This multi-functionality increases production capacity while avoiding the need for separate energy-intensive treatment sections
Solution Approach 2:
The process uses carbon dioxide from the synthesis reactor outlet as a stripping agent in the thermal stripping unit, and the heat from vapor condensation in the condensation unit serves both cooling and heating purposes. This self-service approach reduces external energy input requirements while increasing production capacity
3Productivity
If conventional horizontal condensation units are used, then condensation can be performed, but mixing efficiency is limited and capacity is restricted
Solution Approach 1:
The invention transitions from horizontal condensation units to vertical condensation units. This dimensional change allows for improved mixing efficiency through better contact between vapor and liquid phases, increased condensation unit capacity through optimized flow patterns, and enhanced heat transfer efficiency while maintaining compact design
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 significantly increases urea production capacity, reduces ammonia content in aqueous solutions, and simplifies the process by bypassing the medium pressure treatment section, resulting in lower energy and maintenance costs while maintaining existing high-pressure synthesis section apparatuses.
Implementation Method 1
a thermal stripping unit for subjecting a reaction mixture comprising urea, carbamate and free ammonia in aqueous solution coming out from the reactor to a partial decomposition treatment of the carbamate
Implementation Method 2
at least one horizontal condensation unit for subjecting the flow comprising ammonia and carbon dioxide in vapour phase coming out from the stripping unit to substantially total condensation
Implementation Method 3
The condensation heat freed is removed by means of a liquid (normally water) running through the tubes of the tube bundle, said liquid being converted into vapour, by means of the heat exchange
Implementation Method 4
providing means for feeding at least one part of the carbon dioxide feed into said stripping unit for use as stripping agent of said reaction mixture
Data Source
AI summary
A method for revamping a urea plant of the type comprising a synthesis section (2) having a urea synthesis reactor (5), a thermal stripping unit (7) and at least one horizontal condensation unit (6), a treatment section (3) operating at medium pressure and a recovery section (4) operating at low pressure foresees the transformation of said at least one horizontal condensation unit (6) into a vertical condensation unit of the submerged type comprising a tube bundle and the provision of means (37, 41) for feeding a flow comprising ammonia and carbon dioxide in vapor phase and a flow of condensation liquid comprising carbamate simultaneously and independently in each of the tubes of said tube bundle with circulation inside said tubes in equicurrent from the bottom towards the top, and means (39, 50) for feeding at least one part of the feed carbon dioxide into said stripping unit (7) for use as stripping agent. Thanks to the present revamping method, the efficiency of the condensation unit (6) is substantially improved, consequently allowing an increase in its capacity and it is possible to leave out the medium pressure treatment section (3) thus obtaining a reduction in energy and maintenance costs.