Melamine Reactor CO2 Separation via Calm Zones
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Solution Overview
Problem
Current melamine production processes from urea at high pressure face inefficiencies due to the incorporation and dissolution of CO2, leading to reduced purity and increased costs, as well as the need for multiple high-pressure equipment, which complicates the separation of reaction gases from the liquid phase.
Innovation Solution
A reaction section comprising a reactor, a gas separator, and a post-reactor, where the liquid stream of raw melamine flows through two calm zones for effective separation of incorporated and dissolved CO2, allowing for minimal CO2 presence in the post-reactor, thereby enhancing the efficiency of the melamine synthesis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single homogeneous reactor is used for melamine synthesis, then the equipment structure is simple, but the reactor volume must be large and operation costs are extremely expensive due to the need to resist corrosive action under severe temperature and pressure conditions
Solution Approach 1:
The single homogeneous reactor is divided into two separate reactors: a first reactor for the main synthesis reaction and a second reactor (post-reactor) for completing the transformation and purifying the product. This segmentation allows each reactor to be optimized for its specific function, reducing the total volume and material requirements while maintaining high productivity.
2Productivity
If CO2 is present in the reaction system, then the reaction can proceed, but CO2 incorporation and dissolution reduce melamine purity and require additional separation steps
Solution Approach 1:
CO2 is actively removed from the reaction system by introducing a gas stream that selectively extracts CO2 from the liquid phase. This extraction process prevents CO2 incorporation into the melamine product, thereby maintaining high purity without compromising the reaction rate.
Solution Approach 2:
The partial pressure of CO2 is controlled by introducing inert or reactive gases that displace CO2 from the system. By changing the gas phase composition and partial pressures, CO2 is prevented from dissolving in the liquid phase and incorporating into the melamine, thus maintaining product purity.
3Manufacturing precision
If multiple high-pressure equipment are used for CO2 separation, then CO2 removal efficiency increases, but the device complexity and investment costs increase
Solution Approach 1:
The CO2 separation function is merged with the product synthesis process by implementing the separation directly in the second reactor where melamine is being formed. This integration eliminates the need for separate CO2 removal equipment, reducing device complexity and investment costs while maintaining high separation efficiency.
Solution Approach 2:
The second reactor serves multiple functions simultaneously: it completes the melamine synthesis reaction, separates CO2 from the liquid phase, and purifies the final product. This multi-functionality reduces the overall number of equipment units needed while achieving effective CO2 removal and high product purity.
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 configuration effectively separates CO2 from the melamine stream, increasing the efficiency of the post-reactor, reducing back-mixing, and allowing for a compact, cost-effective melamine production system with high purity (>99.9%) and reduced investment costs.
Implementation Method 1
a reaction section comprising a reactor, a gas separator and a post-reactor, where a liquid stream of raw melamine flows through two calm zones for effective separation of incorporated and dissolved CO2
Implementation Method 2
The (negative) reaction heat is transferred to the reacting mass via appropriate heat-exchange tubes, positioned inside the reactor, within which a heat-carrier fluid circulates at a temperature higher than the reaction temperature
Implementation Method 3
urea in the molten state, at temperatures ranging from 140 to 150° C., is introduced into a synthesis reactor, usually together with gaseous NH3, maintained at a temperature ranging from 360 to 420° C. using suitable heating means
Data Source
AI summary
The present invention relates to an apparatus for the production of melamine from urea at high pressure and the relative process.