Melamine Off-Gas Condensation for Low-Water Urea Integration
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Solution Overview
Problem
Existing urea and melamine production processes face challenges in achieving high energy efficiency and low water supply to the urea synthesis section, as the presence of water in the reaction mixture is detrimental to urea yield.
Innovation Solution
A process and plant design that integrates urea and melamine production by purifying urea streams at low pressure, condensing melamine off-gas at high pressure, and using carbamate solutions efficiently to minimize water input into the urea synthesis section, including steps like off-gas washing, condensation, and mother liquor treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If off-gas is condensed to aqueous carbamate solution for urea synthesis, then CO2 and NH3 are recovered, but water content increases which is detrimental to urea yield
Solution Approach 1:
The condensation process is divided into two distinct pressure zones: high pressure condensation (≥25 bar) producing carbamate solution with controlled water content, and low pressure recovery section for further processing. This segmentation allows optimization of water content in the synthesis section while maintaining CO2 and NH3 recovery.
Solution Approach 2:
The patent utilizes pressure parameter changes to control the condensation process. By operating the off-gas condenser at high pressure (≥25 bar) and the LP recovery section at lower pressure, the system achieves different carbamate solution compositions suitable for each section, thereby controlling water content in the final synthesis feed.
2Reliability
If conventional waste water treatment sections are used for melamine off-gas, then treatment is achieved, but energy consumption increases
Solution Approach 1:
The patent merges the melamine off-gas treatment with the urea recovery process by integrating the LP recovery section to handle both streams. This consolidation eliminates separate waste water treatment sections, reducing energy consumption while maintaining treatment effectiveness through the unified carbamate condensation and recovery system.
Solution Approach 2:
The LP recovery section is designed to perform multiple functions: recovering carbamate from urea stream, treating melamine off-gas, and producing synthesized feed. This multi-functionality replaces dedicated waste water treatment sections, achieving energy efficiency while maintaining comprehensive off-gas treatment.
3Productivity
If high pressure non-catalytic melamine synthesis is used, then melamine production is achieved, but water must be minimized in urea synthesis section
Solution Approach 1:
The patent extracts and removes excess water from the carbamate solution through the high pressure condensation process and LP recovery section before the solution enters the urea synthesis section. By taking out water in the form of separate liquid streams during condensation, the system maintains melamine production while minimizing water content in the final urea synthesis feed.
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 reduces energy consumption in waste water treatment and minimizes water supply to the urea reaction zone, enhancing urea conversion efficiency and yield.
Implementation Method 1
subjecting the washed off-gas to condensation in an off-gas condenser, which condenser is preferably comprised in the melamine production section, at a pressure of at least 25 bar to form off-gas condensate
Implementation Method 2
washing the anhydrous off-gas by contact with urea in a washing unit
Implementation Method 3
urea is formed by the reaction of CO2 and NH3 to form carbamate and dehydration of the carbamate
Data Source
AI summary
The disclosure pertains to melamine production coupled to urea production, using a melamine off-gas condenser operating at a pressure of at least 25 bar. In embodiment, carbamate solution from a recovery section of the urea production is supplied to the melamine off-gas condenser. In an embodiment, carbamate solution from melamine mother liquor treatment is supplied to the LP carbamate condenser of the recovery section.