Urea-Melamine Off-Gas Pressure Decoupling for Stable Integration

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Solution Overview

Problem

Integrated production of urea and melamine is prone to process disorders due to pressure fluctuations and increased energy consumption when off-gases from melamine plants are directly connected to urea plants, leading to instability and inefficiency.

Innovation Solution

Implement a pressure-reducing step between the melamine off-gas treatment section and the urea plant's medium pressure condensation section, controlling the pressure of the melamine off-gas to a range 2-10 bar lower than its original pressure, decoupling the processes while maintaining integration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If off-gases from melamine plants are directly connected to urea plants, then integration of production is achieved, but pressure fluctuations cause process disorders and instability

Engineering Contradiction:

Improveintegration of productionVSAvoidprocess stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

A pressure control device is introduced as an intermediary component between the melamine off-gas treatment section and the urea plant's condensation section. This device mediates the pressure connection, allowing off-gases to be utilized while preventing pressure fluctuations from propagating to the urea synthesis process, thus maintaining both integration and stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system is segmented into distinct pressure zones: the melamine off-gas section operates at its own pressure, the pressure control device manages the transition, and the urea condensation section operates at its required pressure. This segmentation allows each section to operate independently while maintaining overall integration

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If off-gases from melamine plants are directly fed to urea synthesis section, then process integration is improved, but energy consumption increases

Engineering Contradiction:

Improveprocess integrationVSAvoidenergy consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The pressure control device acts as an intermediary that enables energy optimization by allowing the urea plant to operate at its optimal pressure conditions while still utilizing the off-gases from the melamine plant, thereby avoiding excessive energy consumption associated with pressure adjustment

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If pressure in condensation section is increased to maintain positive flow, then off-gas utilization is improved, but melamine plant experiences process disorder and product losses

Engineering Contradiction:

Improveoff-gas utilizationVSAvoidmelamine plant operation

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Instead of increasing pressure in the condensation section to maintain positive flow (the conventional approach), the invention inverts the approach by using a pressure control device to regulate pressure from the off-gas side, ensuring stable flow to the urea plant without disrupting melamine plant operation

Inventive Principle:

Principle #13The other way round (Inversion)

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 stabilizes the operation of both plants, preventing pressure swings and reducing energy consumption by optimizing the urea plant's energy requirements, thus enhancing process economy.

Implementation Method 1

Methodology Applied

Scientific EffectPressure reduction: Pressure Drop

Implementation Method 2

a medium pressure condensation section adapted to receive said melamine off-gas

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 3

urea synthesis section comprising a high pressure urea synthesis section... introducing an ammonia excess together with carbon dioxide at a pressure between 12 and 40 MPa and at a temperature between 150°C and 250°C

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentEP3286165B2Method and system for the integrated production of urea and melamine

Publication Date: 2026.02.18 STAMICARBON BV

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AI summary

Disclosed is an integrated process for the production of urea and melamine, as well as a system for carrying out the process. The invention thereby pertains to an integrated process of the type wherein off-gas obtained from the production of melamine is entered into the process for the production of melamine, by condensation in the presence of water. A typical embodiment thereof is the condensation in the presence of an aqueous carbamate solution obtained from urea recovery. In accordance with the invention, said condensation takes place at a substantially lower pressure than the pressure at which the melamine off-gas is obtained. To this end, the pressure of the off-gas is reduced typically by 2-10 bar. In connection herewith, the system of the invention comprises a pressure reducing unit downstream of an outlet for the melamine off-gas, and upstream of a section for the condensation of the off-gas. The invention also includes a method for the modernization of an integrated system for the production of melamine and urea. This is accomplished by adding the aforementioned pressure reducing unit to a pre-existing system.