Urea Production Heat Integration via Condenser Decomposer Wall
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing urea production processes face challenges in energy efficiency and equipment design, particularly in the high pressure section, where corrosive conditions and high energy consumption are issues due to the use of corrosive ammonium carbamate in heat exchangers.
Innovation Solution
The process involves subjecting ammonia and carbon dioxide to urea-forming conditions in a high pressure reaction zone, followed by high pressure stripping and heat recovery through multiple condensation stages, using heat integration between condensers to maximize energy reuse without the need for heat transfer fluids, and operating at lower stripping efficiencies to reduce equipment costs and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high pressure stripping is used to decompose carbamate, then urea conversion is improved, but steam consumption increases
Solution Approach 1:
The patent operates the high pressure stripper at lower temperatures (180-220°C) and optimized pressure conditions to achieve effective carbamate decomposition with reduced steam consumption. By carefully controlling the stripping efficiency parameter rather than maximizing it, the process achieves good urea conversion while minimizing energy input requirements
Solution Approach 2:
The patent utilizes phase transition of water from liquid to vapor in the stripper to carry out carbamate decomposition. The generated steam provides both the heat for decomposition and the stripping medium, achieving dual functionality that improves energy efficiency while maintaining conversion rates
2Loss of energy
If high pressure carbamate condenser operates at high temperature, then heat recovery is improved, but material corrosion increases
Solution Approach 1:
The patent operates the high pressure carbamate condenser at moderate temperatures (100-150°C) rather than high temperatures, which sufficiently recovers heat for process use while staying below the threshold where aggressive corrosion of carbon steel and lined equipment occurs. This parameter optimization balances energy recovery with equipment longevity
Solution Approach 2:
The patent employs composite construction with carbon steel shells and liners (such as rubber or plastic liners) in contact with corrosive carbamate solution. This composite material approach provides both mechanical strength from steel and corrosion resistance from the liner, enabling effective heat recovery at temperatures that would otherwise be too corrosive
3Loss of energy
If multiple effect heat integration is implemented, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The patent combines the high pressure carbamate condenser with the low pressure carbamate condenser in a single integrated vessel, allowing heat exchange between the two pressure stages without requiring separate equipment. This merging reduces the number of individual heat exchangers while achieving multiple-effect heat integration, thus improving energy efficiency without proportionally increasing device complexity
Solution Approach 2:
The integrated condenser performs multiple functions: it condenses carbamate from high pressure stripper gas, recovers heat from this condensation, transfers the recovered heat to evaporate water from low pressure decomposer gas, and handles liquid-liquid separation. This multi-functionality achieves N=2 or N=3 heat integration while using a single piece of equipment rather than multiple separate units
4Loss of energy
If direct heat exchange is used between condenser and decomposer, then heat transfer efficiency is improved, but equipment design difficulty increases
Solution Approach 1:
The patent uses a heat exchanger with walls as an intermediary between the hot carbamate-containing gas from the high pressure stripper and the cooler liquid from the low pressure decomposer. This intermediate heat transfer surface allows efficient heat transfer without direct contact between the two process streams, simplifying equipment design while maintaining high heat transfer efficiency. The heat exchanger walls act as the mediator that enables the heat integration
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 reduces steam consumption, increases urea conversion and yield, minimizes hydrolysis, and decreases biuret formation, while simplifying the high pressure section design and reducing equipment costs by using lower temperature, less corrosive conditions.
Implementation Method 1
subjecting said gas stream to condensation in a high pressure carbamate condenser, thereby forming a first carbamate-containing solution and releasing heat of condensation
Implementation Method 2
heating in a low pressure decomposer the urea solution containing carbamate using said heat of condensation from the high pressure carbamate condenser
Implementation Method 3
subjecting said first vapor to condensation in a first low pressure carbamate condenser, thereby obtaining a second carbamate-containing solution and second vapor and releasing additional heat of condensation
Implementation Method 4
heating said expanded third urea solution to decomposition of carbamate in a sub-atmospheric decomposer using said additional heat of condensation from said first low pressure carbamate condenser
Implementation Method 5
subjecting said expanded third urea solution to decomposition of carbamate in a sub-atmospheric decomposer, thereby obtaining a fourth urea solution and a third vapor
Implementation Method 6
subjecting said third vapor to condensation in a sub-atmospheric carbamate condenser, in indirect heat exchange with cooling fluid, thereby obtaining a fourth carbamate-containing solution
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention pertains to a urea production process using a high pressure stripper and a low pressure decomposer connected to a low pressure carbamate condenser which is in heat exchanging contact through a wall with a sub - atmospheric decomposer wherein urea solution obtained from the low pressure decomposer is processed.