Variable-Diameter Oligomerization Reactor with Pre-Cooled Solvent Recycling
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Solution Overview
Problem
The management of gaseous ethylene in two-phase gas/liquid reactors during oligomerization processes leads to significant ethylene loss and reduced productivity due to the piercing phenomenon, where gaseous ethylene passes from the liquid phase to the gaseous headspace, resulting in inefficiencies and increased costs.
Innovation Solution
A process utilizing a reactor with variable diameter zones and recycling a cooled solvent fraction from a downstream separation step to control exothermicity, enhancing the dissolution of gaseous ethylene in the liquid phase and minimizing the size of heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-phase gas/liquid reactor is used for oligomerization, then the reaction can be carried out with good selectivity, but significant ethylene loss occurs due to the piercing phenomenon
Solution Approach 1:
The patent changes the physical parameters of the reactor by implementing variable diameter zones along the reactor length. The diameter decreases from the bottom to the top, which modifies the hydrodynamic conditions and gas-liquid contact characteristics. This parameter change prevents the piercing phenomenon while maintaining good ethylene conversion and selectivity for linear alpha-olefin production.
Solution Approach 2:
The patent introduces a spatial dimension variation by using a reactor with changing cross-sectional area along its length. Instead of a uniform cylindrical reactor, the variable diameter creates different flow regimes and residence time distributions in different zones, which improves gas dissolution and prevents ethylene piercing to the headspace.
2Temperature
If external cooling is implemented to control the exothermic reaction, then temperature control is improved, but the size and cost of heat exchangers increase
Solution Approach 1:
The patent merges the cooling function with the reactor itself by implementing cooling zones directly within the reaction vessel. The variable diameter reactor includes integrated cooling sections where heat exchange occurs in-situ, eliminating the need for separate external heat exchangers and reducing both equipment size and capital costs.
Solution Approach 2:
The patent uses the reactor wall and internal structures as intermediary heat exchange surfaces. By incorporating cooling jackets or internal coils within the variable diameter reactor zones, heat is transferred from the reaction mixture to the cooling medium through the reactor structure itself, providing efficient temperature control without large external exchangers.
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 improves the saturation of gaseous ethylene in the liquid phase, reducing ethylene loss, enhancing productivity, and lowering operational costs by minimizing the size of heat exchangers and optimizing the reactor's liquid volume.
Implementation Method 1
a step of cooling a solvent fraction from said downstream separation step to a temperature lower than the temperature to which the fraction of the liquid phase is cooled in said recirculation loop(s), and a step of introduction into said reaction section of said cooled solvent fraction
Implementation Method 2
The implementation of a reactor with variable diameter zones according to the invention makes it possible to improve the dissolution of the gaseous olefinic feedstock and therefore to limit the piercing phenomenon
Implementation Method 3
The oligomerization reaction is highly exothermic; it is common to regulate the reaction temperature by implementing external cooling. A reactor can be coupled to one or more recirculation loops in order to withdraw a liquid fraction, cool it by one or more exchangers
Data Source
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Figure 3~4
AI summary
The present invention relates to a method for oligomerisation in a reactor comprising variable-diameter zones, including a step of recycling a pre-cooled solvent.