High pressure strippers for use in urea plants
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Solution Overview
Problem
Scaling up high-pressure shell-and-tube strippers for urea-carbamate mixture decomposition leads to severe tube corrosion and inefficient stripping due to inhomogeneous heating, resulting in reduced stripper lifetime and operational inefficiencies.
Innovation Solution
The implementation of a shell-and-tube stripper design featuring a plurality of baffles and deflectors that create a multi-pass crossflow in the shell-side space, with deflectors positioned at oblique or right angles to the baffles, ensuring homogeneous heating and reducing corrosion by distributing the heating fluid flow uniformly across the tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the stripper is scaled up to manufacture large volumes of urea, then productivity increases, but tube corrosion becomes severe and stripping efficiency decreases
Solution Approach 1:
The shell-side space is segmented into multiple passes by arranging a plurality of baffles, creating a multi-pass crossflow configuration. This segmentation distributes the heating fluid flow more uniformly across different tube sections, preventing localized overheating and corrosion while maintaining high productivity in scaled-up strippers
Solution Approach 2:
Deflectors are positioned at oblique or right angles with respect to the baffles, introducing a dimensional element that redirects heating fluid flow across tube bundles. This angular arrangement ensures homogeneous heating distribution and prevents dead zones that would otherwise cause severe corrosion in large-scale operations
2Device complexity
If conventional baffle arrangements are used in scaled-up strippers, then device complexity remains manageable, but heating homogeneity deteriorates leading to inefficient stripping
Solution Approach 1:
Deflectors are positioned at asymmetric angles (oblique or right angles) with respect to the baffles, creating an asymmetric flow pattern that enhances heat distribution uniformity. This asymmetric arrangement prevents symmetric dead zones and ensures all tube surfaces receive adequate heating, improving stripping efficiency without significantly increasing device complexity
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 design significantly reduces tube corrosion and enhances stripping efficiency, extending the useful life of the strippers to around 20 to 30 years and improving the homogeneity of heat distribution, leading to uniform stripping gas flow and increased productivity.
Implementation Method 1
the urea/carbamate mixture is heated by means of a heating medium in the shell-side space, commonly steam
Implementation Method 2
The stripping gas and the urea/carbamate mixture run counter-current through the tube-side space while the urea/carbamate mixture is heated by means of a heating medium in the shell-side space
Implementation Method 3
a plurality of baffles are arranged in the shell-side space, the baffles defining a multi-pass crossflow in the shell-side space, wherein the deflectors are at oblique or right angles with respect to the baffles
Implementation Method 4
the ammonium carbamate in the urea and carbamate mixture decomposes to form gaseous NH3 and CO2
Data Source
AI summary
Shell-and-tube strippers for stripping a urea/carbamate mixture, related systems, methods, and uses. The stripper includes a shell and a plurality of tubes disposed within the shell. Baffles and deflectors offer improved homogeneity of heating fluid flow in the stripper's shell-side space.