Parallel MP Dissociator for Urea Plant Energy Efficiency
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Solution Overview
Problem
Current urea production processes face limitations in energy efficiency and CO2 emission reduction, particularly in large-scale plants, due to the high energy consumption and CO2 emissions associated with high-pressure stripping and condensation steps, which restrict the capacity expansion of existing facilities without significant modifications or equipment replacement.
Innovation Solution
The implementation of a urea production process that includes a medium-pressure treatment unit and dissociator, which receives the urea synthesis solution from the reactor and stripped urea solution from the high-pressure stripper, allowing for gas stream condensation in the medium-pressure condensation section, thereby improving CO2 recovery and reducing steam consumption in the high-pressure stripper, and integrating this with a low-pressure dissociator for further purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-pressure stripper is used for CO2 stripping in urea production, then stripping efficiency can be maintained, but steam consumption and energy usage increase significantly
Solution Approach 1:
The urea synthesis solution stream is divided into two parallel paths: one goes to the HP stripper for high-pressure CO2 removal, and the other goes to the MP dissociator for medium-pressure CO2 release through thermal dissociation of carbamate. This segmentation allows CO2 to be removed through two different mechanisms, reducing the burden on the HP stripper and thereby reducing its steam consumption while maintaining overall stripping efficiency.
Solution Approach 2:
The invention changes the pressure parameter from exclusively high-pressure to include medium-pressure treatment. By operating the dissociator at medium pressure (lower than HP stripper) and the condenser at even lower pressure, the system creates a pressure gradient that enables CO2 removal through dissociation rather than requiring high-pressure steam-driven stripping, thus reducing energy consumption.
2Productivity
If the capacity of an existing urea facility is expanded, then production volume increases, but modification or replacement of expensive high-pressure equipment is required
Solution Approach 1:
By adding the MP dissociator and MP condenser as separate parallel units to the existing HP stripper system, the invention enables capacity expansion without modifying the existing high-pressure equipment. The new MP units handle additional CO2 removal tasks, allowing increased production capacity while keeping the original HP stripper unchanged.
Solution Approach 2:
The MP dissociator and condenser units serve multiple functions: they remove CO2 from urea synthesis solution, condense CO2 for recycling, and can handle variable feed rates. This multi-functionality allows the system to accommodate different production capacities without requiring dedicated equipment for each capacity level, making the expansion more flexible and cost-effective.
3Manufacturing precision
If more CO2 is removed in the HP stripper, then urea solution purity increases, but CO2 emissions from downstream ammonium nitrate section increase
Solution Approach 1:
The MP condenser acts as an intermediary between the dissociator and the ammonium nitrate section. It condenses CO2 from the gas stream at medium pressure, separating it before the gas reaches the ammonium nitrate section. This allows CO2 to be recovered and recycled rather than being emitted, while still achieving the necessary CO2 removal from the urea solution.
Solution Approach 2:
Instead of discarding CO2 as a waste product from the ammonium nitrate section, the invention recovers CO2 through condensation in the MP condenser. The condensed CO2 can be recycled back to the urea synthesis process, transforming a harmful emission into a valuable recovered resource.
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 enhances energy efficiency by reducing steam consumption in the high-pressure stripper, allows for more efficient CO2 recovery, and decreases CO2 emissions from the ammonium nitrate section, enabling larger urea production capacity without extensive equipment modifications.
Implementation Method 1
The MP dissociator receives liquid directly from the urea reactor and a gas stream from the HP stripper
Implementation Method 2
an MP dissociator and an MP condensation section, wherein the reactor has an outlet for a urea synthesis solution connected to a first liquid flow line connected to the HP stripper, wherein said outlet is also connected to a second liquid flow line connected to the MP dissociator
Implementation Method 3
a gas flow line for a first MP gas stream from the MP treatment unit to the MP condensation section, and a gas flow line for a second MP gas stream from the MP dissociator to the MP condensation section
Implementation Method 4
The HP stripper is operated with a stripping efficiency of e.g. 80% and has a corresponding demand for steam as heating fluid
Implementation Method 5
US 2012/0302789A1 describes a urea production process with a HP CO2 stripper wherein the urea solution leaving the stripper is subjected to an adiabatic expansion, thus creating a vapor and a liquid
Data Source
AI summary
Some embodiments of the disclosure pertain to a plant and a process for producing a urea-containing product. The plant comprises a medium pressure dissociation unit and a high pressure CO2 stripper each receiving a part of the urea synthesis solution. Stripped urea solution is further treated in a medium pressure treatment unit.