Polyimide Membrane Propylene Propane Separation
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Solution Overview
Problem
Current membrane-based separation systems for propylene and propane face challenges due to similar molecular sizes and condensability, leading to issues like plasticization, reduced selectivity, and increased capital costs, with existing membranes being difficult to fabricate into practical industrial forms that offer high selectivity and durability under industrial conditions.
Innovation Solution
A membrane-based separation process that minimizes temperature drop during separation by pressurizing the feed stream to reduce the Joule-Thompson coefficient, using a polyimide membrane with high propylene/propane selectivity, and optimizing feed pressure to maintain a constant temperature, thereby reducing the number of membrane modules and capital costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If membrane-based separation is used for propylene/propane separation, then capital costs and energy consumption are reduced, but selectivity and durability are compromised due to plasticization under high pressure and temperature
Solution Approach 1:
The patent changes the operating parameters by maintaining lower pressure and temperature conditions on the feed side of the membrane, preventing plasticization while still achieving effective separation. This resolves the contradiction by operating outside the harsh conditions that cause membrane degradation.
Solution Approach 2:
The patent utilizes phase transition by condensing the feed stream before membrane separation and condensing the permeate side to maintain liquid-phase operation throughout the membrane module. This eliminates the need for high-pressure gas-phase operation that causes plasticization, thereby improving membrane durability while maintaining separation efficiency.
2Productivity
If higher pressure is applied to increase permeation rate, then productivity improves, but temperature drop increases due to Joule-Thomson effect
Solution Approach 1:
The patent maintains liquid-phase operation by condensing both the feed and permeate streams, which eliminates the large temperature drops associated with gas-phase Joule-Thomson expansion. This allows higher pressure operation for increased productivity without the penalty of excessive temperature drop.
Solution Approach 2:
The patent changes the phase state parameter from gas to liquid throughout the membrane system, fundamentally altering the thermodynamic behavior and eliminating the Joule-Thomson temperature drop that limits high-pressure operation in gas-phase systems.
3Manufacturing precision
If distillation column with many trays is used to achieve high separation, then purity is improved, but capital cost increases
Solution Approach 1:
The patent replaces the mechanical distillation system with a membrane-based separation system that operates on different physical principles (solution-diffusion mechanism). This substitution achieves high separation purity with a simpler, more compact device that has lower capital cost and smaller footprint.
Solution Approach 2:
The patent uses thin-film membrane structures to achieve separation that would otherwise require many trays in a distillation column. The membrane's selective permeability provides high-purity separation in a compact configuration, reducing both device complexity and capital cost.
4Manufacturing precision
If reflux ratio is increased to improve separation with fewer trays, then operating cost increases
Solution Approach 1:
The patent replaces the energy-intensive reflux mechanism of distillation with a passive membrane separation process driven by pressure differential. This eliminates the need for large amounts of reflux and associated energy consumption while achieving equivalent or superior separation efficiency.
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 allows for efficient separation of propylene and propane with minimal temperature change, simplifying system design and operation, and achieving high propylene and propane recovery with reduced energy and capital costs compared to traditional methods.
Implementation Method 1
utilization of membrane separation has taken an important place in chemical technology for use in a broad range application. Gas separation has become a major industrial application of membrane technology
Implementation Method 2
A membrane-based separation process that minimizes temperature drop during separation by pressurizing the feed stream to reduce the Joule-Thompson coefficient
Data Source
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AI summary
A process for the membrane-based separation of propane and propylene, said process comprising the steps of feeding a feed stream (330) comprising propylene and propane to a first membrane (335), said first membrane comprising a feed port, a residue port, and a non-permeate port, at a temperature at or slightly above the dewpoint of propylene and a pressure between 2758 kPa and 4136 kPa, said first membrane (335) having a selectivity for propylene of at least 6.5, whereby at least a portion of a first non-permeate stream (340) condenses on or about said first membrane; and extracting a first permeate propylene enriched stream (390), wherein said permeate stream (390) is extracted at or the same temperature as said feed stream (330).