Shell-and-Tube Condenser for Urea Synthesis

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Solution Overview

Problem

The existing CO2-stripping process for urea synthesis is costly due to the need for expensive high-pressure vessels and inefficient ammonia recovery, with previous solutions either requiring elevated equipment installation or penalizing stripper efficiency.

Innovation Solution

The process involves feeding full fresh CO2 to the stripper, splitting stripper vapors to optimize efficiency, and using a shell-and-tube condenser where high-pressure fluids are confined in the tube side, reducing the pressure vessel's design costs and eliminating direct CO2 feed to the reactor, with optional use of an ejector for condensate recycling and mixing with reactor vent gas to enhance efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If the condenser is designed as a horizontal kettle apparatus with condensation in the shell side, then the elevation of equipment is reduced, but the entire pressure vessel must resist synthesis pressure making the condenser expensive

Engineering Contradiction:

Improveelevation of equipmentVSAvoidcost of condenser

Core Design Contradiction:

Length of stationary objectVSEase of manufacture

Solution Approach 1:

The condenser is divided into tube side and shell side, with the tube side containing the high-pressure process fluid and the shell side containing cooling water at atmospheric pressure. This segmentation allows only the tube side to be designed for high pressure, reducing the overall cost while maintaining the horizontal layout benefit

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the condenser are assigned different pressure ratings based on their function. The tube side is designed for high synthesis pressure to contain process fluids, while the shell side operates at atmospheric pressure for cooling water, optimizing material usage and cost

Inventive Principle:

Principle #3Local quality

2Device complexity

If part of fresh CO2 is diverted directly to the reactor, then the condenser design is simplified, but the stripper ammonia efficiency is penalized

Engineering Contradiction:

Improvecondenser designVSAvoidstripper ammonia efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The invention extracts the CO2 feed requirement from the reactor and supplies it entirely through the stripper. The stripper receives 100% of fresh CO2, and the process design ensures optimal ammonia efficiency is maintained by not diverting CO2 directly to the reactor

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If equipment are installed at different elevations to ensure proper circulation, then fluid flow is facilitated, but installation cost increases

Engineering Contradiction:

Improvefluid circulationVSAvoidinstallation cost

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The horizontal kettle condenser design creates a more level installation configuration, reducing the need for significant elevation differences between equipment. This equipotential approach facilitates fluid circulation while minimizing installation complexity and cost

Inventive Principle:

Principle #12Equipotentiality

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 equipment elevation and capital costs, maintains high stripper efficiency, and recovers ammonia and carbon dioxide, potentially halving steam consumption in the stripper, while minimizing inert gas accumulation.

Implementation Method 1

The condenser is a shell-and-tube apparatus wherein condensation of the stripper gas is performed in the tube side

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 2

the cooling water is fed to the tube side

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 3

optional use of an ejector for condensate recycling and mixing with reactor vent gas

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS12012372B2Process and plant for the synthesis of urea

Publication Date: 2024.06.18 CASALE SA

AI summary

A process for synthesis of urea from ammonia and carbon dioxide wherein: the urea synthesis is performed with a stripping process in a synthesis loop including at least a reactor (1), a stripper (2) and a condenser (3); the reactor effluent is treated in the stripper to remove unreacted ammonia and carbon dioxide; the urea solution (14) from the stripper is sent to a low-pressure recovery section (4); the stripper vapours are split into a first portion (151) directed to the reactor and a second portion (152) sent to the condenser; the condenser (3) is a shell-and-tube kettle condenser where condensation of stripper vapours is performed in the tube side (30); a carbamate-containing effluent (20) from the condenser is returned to the reactor.