Ethylene Oxide Purification Bypass Strategy
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Solution Overview
Problem
The existing ethylene oxide recovery and purification processes in combined ethylene oxide/ethylene glycol plants are inefficient in terms of energy usage and complexity, particularly due to the need for high stripping steam consumption and the requirement for precise ethylene oxide concentrations in feed streams to achieve high purity ethylene oxide and fiber-grade ethylene glycol production.
Innovation Solution
The introduction of an additional lights stripper that allows a greater percentage of the ethylene oxide absorbate to bypass both the ethylene oxide stripper and reabsorber columns, with strategic mixing and dilution to achieve the necessary ethylene oxide concentrations for high-purity ethylene oxide distillation and glycol reactor feeds, thereby reducing stripping steam consumption and simplifying the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional ethylene oxide recovery processes are used with full stripping and reabsorption, then high purity ethylene oxide can be produced, but stripping steam consumption is excessively high
Solution Approach 1:
The invention divides the ethylene oxide absorbate stream into multiple portions: one portion bypasses both the stripper and reabsorber entirely, while another portion goes through the stripper only. This segmentation allows different streams to be processed differently, reducing overall steam consumption while maintaining product purity through selective processing paths.
Solution Approach 2:
Instead of stripping and reabsorbing the entire ethylene oxide absorbate stream, the invention applies partial action by allowing a significant portion (25-35%) to bypass the energy-intensive stripping and reabsorption processes. The bypass stream is mixed with the stripped stream to achieve the required concentration, thereby reducing steam consumption while maintaining product specifications.
2Ease of operation
If ethylene oxide absorbate is fully processed through stripper and reabsorber, then required ethylene oxide concentration is achieved, but process complexity increases
Solution Approach 1:
The process is segmented into multiple parallel pathways: a bypass line that avoids the stripper and reabsorber, a partial processing line that goes through the stripper only, and a full processing line. This segmentation simplifies operation by allowing independent control of each stream and reduces the burden on any single unit operation.
Solution Approach 2:
The ethylene oxide absorber serves multiple functions: it absorbs ethylene oxide from the reactor effluent, produces a concentrate stream for purification, and generates a bypass stream that can be directly mixed with the purified stream. This multi-functionality reduces the need for separate concentration control systems.
3Loss of energy
If more ethylene oxide is allowed to bypass the stripper, then steam consumption decreases, but maintaining precise ethylene oxide concentration becomes more difficult
Solution Approach 1:
The invention employs feedback control by monitoring the ethylene oxide concentration in the combined stream (after mixing the bypass stream with the stripped stream) and adjusting the split ratio between the bypass and stripped streams accordingly. This ensures the final product meets concentration specifications while optimizing steam consumption.
Solution Approach 2:
The invention changes the operational parameters by allowing variable proportions of the absorbate stream to bypass the stripper (25-35% range). This parameter adjustment enables optimization of steam consumption while the mixing process naturally buffers concentration variations, making precise control more achievable.
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 significantly reduces stripping steam usage by 25-35% and increases the amount of ethylene oxide that can bypass the stripper, enhancing energy efficiency and process simplification while maintaining the required ethylene oxide concentrations for high-purity ethylene oxide and glycol production.
Implementation Method 1
contacting the quenched and alkaline treated and water washed vaporous reaction stream with water in an EO absorber to produce a first absorbate stream
Implementation Method 2
feeding the first portion of the first absorbate stream to an EO stripper and contacting the first portion of the first absorbate stream with steam to produce a vaporous EO stream
Implementation Method 3
feeding the vaporous EO stream to an EO reabsorber and contacting the vaporous EO stream with the second portion of the first absorbate stream to form a reabsorber bottoms stream
Implementation Method 4
feeding the first portion of the reabsorber bottoms stream to a first lights stripper to remove dissolved carbon dioxide and feeding a second portion of the reabsorber bottoms stream to a second lights stripper to remove other light gases
Data Source
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AI summary
An improved process for the recovery of high-purity ethylene-oxide water feed streams to EO purification and MEG reaction units when both are operating in EO plants that incorporate EO Stripper bypass technology, by installing a second lights stripper to exclusively degasify the diluted EO feed to the MEG reactor, thus permitting the use of additional bypassed (gasified) EO absorbate as the diluent and resulting in a substantial increase in the total amount of EO absorbate that can bypass the EO Stripper.