Two-Part Connecting Piece for Ethylene Cracking Tube Retrofit
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Solution Overview
Problem
Existing ethylene cracking plants face challenges in replacing cooled transition pieces with uncooled ones due to the need for high-precision connections that can be retrofitted with minimal effort in existing systems, while maintaining thermal stability and avoiding thermal stresses.
Innovation Solution
A two-part connecting piece is developed, comprising a prefabricated unit with a transition piece and a feed chamber, where the critical weld seam is precision-welded in the workshop, and simpler manual welds are used for site connections, ensuring high-quality assembly without dismantling the entire cracked gas cooler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-part connecting piece with prefabricated unit is used, then manufacturing precision and quality of critical weld seams are improved, but device complexity increases
Solution Approach 1:
The connecting piece is divided into two separate parts: a prefabricated unit containing the transition piece and a separate feed chamber. This segmentation allows the critical weld seam between the transition piece and feed chamber to be prepared and welded with high precision in a workshop setting using automatic welding, while simpler manual welding is used for site connections. The segmentation thus resolves the contradiction by separating complex precision work from simple installation work.
2Reliability
If uncooled transition piece is used, then thermal stresses are reduced, but connection precision requirements increase
Solution Approach 1:
A connecting piece acts as an intermediary component between the uncooled transition piece and the cooled feed chamber. This intermediary design allows the two components with different thermal characteristics to be connected while maintaining proper alignment and clearance. The connecting piece includes clearance in radial and axial directions that accommodates thermal expansion differences, thus enabling the use of uncooled transition pieces without compromising connection precision.
3Loss of time
If retrofitting is performed in existing plants, then loss of time for plant shutdown is reduced, but ease of operation decreases
Solution Approach 1:
The feed chamber and transition piece are pre-assembled into a prefabricated unit in a workshop before being transported to the existing plant. This preliminary assembly allows complex welding and alignment work to be performed under controlled conditions, reducing the time and complexity of on-site retrofitting operations. The pre-prepared unit can be quickly installed by connecting it to the existing inner and outer tubes, minimizing plant shutdown time while maintaining high connection quality.
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 solution allows for efficient retrofitting of uncooled transition pieces in existing ethylene cracking plants, reducing conversion time and ensuring improved thermal management with reduced thermal stresses, thus enhancing the operational efficiency and reliability of the system.
Implementation Method 1
The space between the two sections is filled with a heat-insulating material
Implementation Method 2
The cooling takes place due to the phase transition from liquid to vapor
Implementation Method 3
the unsaturated hydrocarbons (also called cracked gases) are cooled from 775 - 875°C to around 350 - 450°C with the formation of high or low pressure steam
Implementation Method 4
The inner tube is welded into the bottom of the feed chamber, while the outer tube is welded to the part of the feed chamber lying outside the recess
Data Source
Figure 1~3
AI summary
The connector has an inner tube section (13) extending out of a supply chamber (6) and aligned in inner portion (15) of a transition piece (14). The inner tube section has thickness, inner diameter and outer diameter corresponding to an inner pipe (3). Half shells (18, 19) have thickness, inner diameter and outer diameter corresponding to that of an outer pipe (4). The half shells have axial length greater than length of a part of the inner tube section extending out of the supply chamber. An independent claim is also included for a method for connecting a reaction pipe of a reaction furnace with a cooling pipe of a reaction gas cooler using a connector.