Membrane Gas Separation with Permeate Sweep for Feedstock Recovery
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Solution Overview
Problem
Current methods for treating off-gas streams from reaction processes are inefficient and often result in atmospheric pollution and resource wastage, as they fail to effectively recover unreacted components like petrochemical feedstocks, which are difficult to handle due to their mixture with inert components and contaminants.
Innovation Solution
A membrane-based gas separation process where an off-gas stream containing unreacted reagents is passed across the feed side of a membrane, and a sweep gas stream containing a second reagent is passed across the permeate side, allowing preferentially permeating components to be recovered and recirculated back to the reaction process, utilizing membranes with high permeance and selectivity for the target component over inert components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional methods are used to treat off-gas streams, then the process is simple, but unreacted feedstocks are wasted and atmospheric pollution occurs
Solution Approach 1:
A membrane separation unit is introduced as an intermediary device between the reactor off-gas stream and the feedstock recovery system. The membrane selectively permeates unreacted feedstock molecules while blocking inert components, enabling efficient separation and recovery without complex distillation or absorption systems.
Solution Approach 2:
The patent employs thin-film membrane structures with specific permeability characteristics to separate unreacted feedstock from inert gases in the off-gas stream. The membrane's selective permeability allows small hydrocarbon molecules to pass through while retaining larger inert components, achieving high recovery rates with a compact, flexible separation system.
2Use of energy by moving object
If total pressure difference is applied across membranes, then permeation driving force is increased, but energy consumption increases due to compression or vacuum requirements
Solution Approach 1:
The membrane separation system is designed to operate using the existing pressure differential between the reactor outlet and the permeate side, without requiring additional compression or vacuum equipment. The system self-regulates the permeation driving force based on process conditions, eliminating energy-intensive pressure control mechanisms while maintaining effective feedstock recovery.
Solution Approach 2:
The patent optimizes operating parameters such as temperature, pressure, and flow rates to maximize permeation efficiency without requiring external energy input for compression or vacuum. By adjusting these parameters within the existing process range, the system achieves high recovery rates while minimizing additional energy consumption.
3Loss of substance
If off-gas is vented or flared, then atmospheric pollution is avoided, but valuable feedstocks are wasted
Solution Approach 1:
The membrane separation system extracts unreacted feedstock molecules from the off-gas stream before disposal. By selectively removing permeable hydrocarbon components while blocking inert gases, the system recovers valuable feedstock for reuse while the non-polluting inert gas stream can be safely vented to the atmosphere.
Solution Approach 2:
The patent implements a dual-stream approach where the membrane separates the off-gas into a permeate stream containing recoverable unreacted feedstock and a retentate stream containing inert gases suitable for safe venting. This enables simultaneous recovery of valuable materials and environmentally safe disposal of non-harmful components.
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 process efficiently recovers unreacted reagents, reducing energy consumption and preventing the introduction of unwanted components into the reaction zone, making it suitable for energy-sensitive and pressure-ratio limited applications, such as petrochemical manufacturing, by achieving high recovery rates of organic feedstocks like propylene or n-butane while minimizing losses.
Implementation Method 1
Gas separation by means of membranes is a well-established technology. In an industrial setting, a total pressure difference is usually applied between the feed and permeate sides
Implementation Method 2
Membranes that may be used to carry out the separations should exhibit high permeance for the feedstock component that is to be removed and recovered, as well as high selectivity for that component over at least one other component of the stream to be treated
Implementation Method 3
a driving force for transmembrane permeation may be supplied by passing a sweep gas across the permeate side of the membranes, thereby lowering the partial pressure of a desired permeant on that side to a level below its partial pressure on the feed side
Data Source
AI summary
A gas separation process for treating off-gas streams from reaction processes, and reaction processes including such gas separation. The invention involves flowing the off-gas across the feed side of a membrane, flowing a sweep gas stream, usually air, across the permeate side, and passing the permeate/sweep gas mixture to the reaction. The process recovers unreacted feedstock that would otherwise be lost in the waste gases in an energy-efficient manner.