Ejector-Driven Gas Recycle in Membrane Separation
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Solution Overview
Problem
Existing gas separation processes require significant energy for recompressing recycle gas, increasing operational costs and complexity due to the need for rotating equipment, especially when achieving high recovery and purity levels in multi-step processes.
Innovation Solution
A hybrid gas separation process utilizing a membrane separation step followed by a partial pressure-driven flow-through step, such as partial condensation, absorption, or pressure swing adsorption, with an ejector to recycle non-product gas, eliminating the need for recompression by converting pressure energy into velocity energy and back, using a device like an ejector with no moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a recycle compressor is used to repressurize recycle gas in multi-step membrane separation processes, then product recovery is improved, but energy consumption increases
Solution Approach 1:
The patent combines the compression function with the existing feed compressor by routing recycle gas through the feed compressor inlet, merging two compression needs into a single equipment operation and eliminating the requirement for a separate recycle compressor
Solution Approach 2:
The feed compressor is made multi-functional by designing it to handle both fresh feed gas and recycle gas, allowing a single piece of equipment to perform multiple compression tasks that would traditionally require separate compressors
2Productivity
If a recycle compressor is installed in the processing loop, then product recovery is improved, but device complexity increases
Solution Approach 1:
The patent merges the recycle gas compression function into the feed compressor system, combining multiple equipment functions into fewer units and simplifying the overall process flow configuration
Solution Approach 2:
The feed compressor is designed to serve dual purposes by compressing both feed gas and recycle gas, reducing the total number of equipment items and simplifying plant layout and operation
3Manufacturing precision
If a recycle compressor is used to repressurize recycle gas, then product purity is improved, but capital costs increase
Solution Approach 1:
The patent combines the compression capability needed for both feed and recycle streams into a single feed compressor unit, eliminating capital expenditure on an additional recycle compressor and associated balance of plant equipment
Solution Approach 2:
The feed compressor is designed with multi-functional capability to handle both fresh feed and recycle gas streams, reducing total equipment count and associated capital costs while maintaining required product purity
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 reduces energy consumption and capital costs by simplifying the equipment needed, enhancing the efficiency and effectiveness of gas separation while maintaining high recovery and purity levels, particularly when the total stage cut is at least 40%, thereby minimizing the recycle stream back to the ejector.
Implementation Method 1
an ejector to recycle the non-product gas and drive the gas flow in the loop
Implementation Method 2
a gas mixture is passed over a semi-permeable membrane. The back (permeate) side of the membrane is maintained at a considerably lower pressure than the feed side; as a result, a portion of the gas mixture permeates the membrane
Data Source
AI summary
A gas separation process that utilizes ejector recycle with a membrane separation step in combination with a second separation step. The second separation step may be a second membrane separation, or may involve a different type of separation process. At least a portion of the non-product (i.e. residue) stream withdrawn from the second separation step is directed back to the ejector to form a processing loop. The ejector drives the gas flow in the loop and recycles the non-product stream to the first separation step.