Process for removing light components from an ethylene stream
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Solution Overview
Problem
Current methods for producing ethylene from petroleum feedstocks face challenges in efficiently removing light components like CO, H2, and CH4, which can lead to ethylene loss, and often require caustic washes or multiple distillation steps to remove oxygenates, such as acetaldehyde, that can poison catalysts and cause fouling in purification units.
Innovation Solution
A process involving a stripper (demethanizer) with a refrigerant cooling system using liquid propane or propylene initially and then liquid ethane or ethylene to condense the overhead stream, reducing ethylene loss and eliminating the need for caustic washes or additional distillation columns, while optionally using CO2 adsorption to achieve pure ethylene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a very low temperature is required to separate light components from ethylene stream, then separation efficiency is improved, but a cold stream must be required which increases process complexity
Solution Approach 1:
The condensation process is divided into two stages: first condensing most light components at a higher temperature using available cooling, then performing a second condensation step at lower temperature to remove remaining light components. This segmentation avoids the need for a single complex cold stream system while achieving complete separation.
Solution Approach 2:
The first condensation step is performed as a preliminary action to remove the bulk of light components before the second condensation step. This preliminary condensation reduces the load on the low-temperature system and simplifies the overall process by handling most separation at more manageable temperatures.
2Manufacturing precision
If light components are removed from ethylene stream, then purity is improved, but ethylene loss occurs
Solution Approach 1:
The process utilizes parameter changes in the cooling system by switching between two different condensation temperatures. The first condensation operates at a higher temperature to remove most light components, while the second condensation operates at lower temperature to remove remaining light components. This staged approach optimizes the balance between purity and ethylene recovery by adjusting temperature parameters at different stages.
3Manufacturing precision
If caustic wash or wash column is used to remove oxygenates, then oxygenate removal is improved, but process complexity and cost increase
Solution Approach 1:
The process merges the light component removal and oxygenate removal functions into a single integrated condensation system. By performing two condensation steps in sequence, the system simultaneously removes both light components and oxygenates without requiring separate caustic wash or wash column units, thereby reducing overall process complexity.
Solution Approach 2:
The condensation system is designed with multi-functionality to perform both light component separation and oxygenate removal in a single integrated unit. This universal approach eliminates the need for dedicated oxygenate removal equipment, reducing the total number of processing units while maintaining effective removal of all contaminants.
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 effectively reduces ethylene loss and achieves high-purity ethylene production without caustic washes or additional distillation columns, making the process more efficient and cost-effective by minimizing the escape of ethylene with light components.
Implementation Method 1
the gaseous phase on top of the stripper is condensed in a heat exchanger cooled by a refrigerant stream to get a first gaseous phase and a first liquid phase
Implementation Method 2
the first gaseous phase is condensed in a heat exchanger cooled by liquid ethane or liquid ethylene to get a second gaseous phase referred to as the overhead stream comprising essentially ethylene CO, H2 and CH4 and a second liquid phase
Implementation Method 3
the gaseous phase on top of the stripper is condensed in a heat exchanger cooled by a refrigerant stream
Data Source
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AI summary
The present invention is a process for removing light components from an ethylene stream comprising : a) providing a dried ethylene stream (A) comprising essentially ethylene, ethane, CO, CO2, H2, CH4, C3+ hydrocarbons and optionally oxygenates, b) sending said stream (A) to a stripper (also referred to as a demethanizer) to produce - an overhead stream comprising essentially ethylene, CO, H2 and CH4, - a bottom stream comprising essentially ethylene,ethane, CO2, C3+ hydrocarbons and optionally oxygenates, wherein, the gaseous phase on top of the stripper is condensed in a heat exchanger cooled by a refrigerant stream to get a first gaseous phase and a first liquid phase, in a preferred embodiment the refrigerant stream consists of one or more C3 or C4 hydrocarbons advantageously it consists of liquid and gaseous propane or propylene the first gaseous phase is condensed in a heat exchanger cooled by liquid ethane or liquid ethylene to get a second gaseous phase referred to as the overhead stream comprising essentially ethylene CO, H2 and CH4 and a second liquid phase, the first and second liquid phases are the reflux of the stripper.