Three-Stage Gas Separation Process with Recycled Streams
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gas separation processes for mixtures, such as those involving biogas and natural gas, face challenges in achieving high purity of both permeate and retentate gases while minimizing energy consumption and maintenance costs, particularly in locations where energy is cheap, and often require multiple recompression steps or high-purity gas streams.
Innovation Solution
A three-stage membrane separation process that recycles the second permeate and third retentate streams to the feed stream, increasing the total gas volume recycled and membrane capacity in the retentate separation stage compared to the feed and permeate stages, with specific pressure ratio quotients to achieve high purity permeate and retentate streams without additional purification, using membranes with lower selectivity to reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple recompression steps are used to achieve high purity of both permeate and retentate gases, then gas purity is improved, but energy consumption increases
Solution Approach 1:
The gas separation process is divided into three distinct membrane separation stages, each with specific functions. Stage 1 performs initial separation, stage 2 further purifies the retentate stream, and stage 3 purifies the permeate stream. This segmentation allows each stage to operate optimally without requiring multiple recompression steps, achieving high purity of both product streams while minimizing energy consumption.
Solution Approach 2:
The invention optimizes pressure ratios across the three stages by adjusting operating parameters. Specifically, the pressure ratio in stage 1 is set lower than in stages 2 and 3, creating an optimized pressure distribution that enables high purity separation without additional recompression. This parameter optimization resolves the contradiction between achieving high gas purity and minimizing energy consumption.
2Device complexity
If high membrane capacity is used to reduce separation stage requirements, then device complexity is reduced, but maintenance costs increase
Solution Approach 1:
Instead of using uniformly high membrane capacity throughout, the invention applies different membrane capacities to different stages based on their specific requirements. Stage 2 (retentate separation) uses higher membrane capacity than stages 1 and 3, optimizing performance where it is most needed while controlling overall maintenance costs. This local optimization resolves the contradiction between reducing device complexity and controlling maintenance expenses.
3Manufacturing precision
If membranes with higher selectivity are used to achieve high purity streams, then gas purity is improved, but investment costs increase
Solution Approach 1:
The three-stage membrane separation process segments the purification task, allowing each stage to use membranes with moderate selectivity rather than requiring one high-selectivity membrane to perform all separation functions. This segmentation enables the use of more cost-effective membrane materials while achieving the same overall purity levels, resolving the contradiction between gas purity and investment costs.
Solution Approach 2:
The invention changes the operational parameters, specifically the pressure ratios across stages, to optimize the performance of membranes with lower selectivity. By setting the pressure ratio in stage 1 lower than in stages 2 and 3, the system maximizes the effectiveness of moderate-selectivity membranes, achieving high purity outputs without requiring expensive high-selectivity membrane materials.
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 simultaneously achieves high purity of both permeate and retentate streams with reduced overall membrane capacity, lowering investment and maintenance costs, and minimizes methane emissions, making it suitable for energy-cheap locations by optimizing membrane usage and recycling.
Implementation Method 1
gas mixtures can be separated by means of gas separation membranes because of different permeabilities of the individual gases
Implementation Method 2
polymers are processed to give hollow fibers or flat membranes. The membranes are characterized by a very thin separation layer so that the permeance of the membrane is as large as possible
Data Source
Figure 1
AI summary
The invention relates to a specific process and apparatus for separation of gas mixtures with reduced maintenance costs.