Core-shell composite adsorbent for PSA mass transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional adsorbents in PSA processes for hydrogen production are inefficient in reducing system size and cycle time, leading to higher adsorbent requirements and thermal swings, while existing core-shell composite adsorbents have limitations in volumetric performance and production complexity.
Innovation Solution
The development of core-shell composite adsorbents with a non-porous core and adsorbent shell, such as zeolite or activated carbon, which reduces diffusion path length, enhances mass transfer rates, and incorporates high heat capacity cores to minimize thermal swings, allowing for smaller bed heights and faster cycle times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional homogeneous beaded adsorbents are used, then the system is simple to manufacture, but the mass transfer rate is low and the bed height must be large
Solution Approach 1:
The adsorbent bead is segmented into two distinct functional parts: a non-porous inert core and a porous adsorbent shell. This segmentation allows the core to provide structural support and thermal mass while the shell provides adsorption functionality, enabling faster mass transfer rates without requiring excessive bed height.
Solution Approach 2:
The invention uses a composite material structure combining a non-porous inert core material with a porous adsorbent shell material. This composite approach leverages the advantages of both materials: the core provides thermal stability and structural integrity, while the shell provides adsorption capacity and selective mass transfer, resulting in enhanced productivity without proportionally increasing bed height.
2Productivity
If particle size is reduced to increase mass transfer rate, then the path length is shortened, but pressure drop increases and fluidization risk increases
Solution Approach 1:
By segmenting the bead into core and shell components with different functional properties, the invention maintains larger overall particle sizes that reduce pressure drop and fluidization risk while the shell structure itself provides the necessary mass transfer pathways for high productivity.
Solution Approach 2:
The porous shell structure provides localized high surface area and short diffusion paths specifically where mass transfer occurs, while the non-porous core provides structural stability. This local quality differentiation allows high mass transfer rates without requiring the entire particle to be small and porous, thus avoiding excessive pressure drop.
3Temperature
If high heat capacity core is used, then thermal swing is suppressed, but the core occupies volume that could be used for adsorption
Solution Approach 1:
The segmentation into inert core and adsorbent shell allows the core to be optimized for thermal properties (high heat capacity) while the shell is optimized for adsorption properties. This functional separation enables suppression of thermal swing without requiring the entire bead volume to be dedicated to adsorption material.
Solution Approach 2:
The non-porous core region is specifically designed for thermal management functions, while the porous shell region is designed for adsorption functions. This local quality differentiation allows the core to occupy volume without compromising overall adsorption capacity, as the shell provides the necessary adsorption functionality.
4Productivity
If core-shell composite adsorbent is used, then mass transfer rate is improved, but manufacturing complexity increases
Solution Approach 1:
The core-shell structure is formed by nesting the non-porous inert core within the porous adsorbent shell, creating a concentric configuration. This nesting approach simplifies manufacturing compared to more complex multi-layer or irregular composite structures, as it allows for straightforward core formation followed by shell coating or growth.
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 results in increased adsorbent productivity, reduced cycle time, and lower capital costs by achieving sharper mass transfer fronts and suppressing thermal swings, thereby intensifying the PSA process.
Implementation Method 1
By using a non-porous core, such composite adsorbents reduce the path length for diffusion of gas molecules
Implementation Method 2
it consists of two or more adsorption beds containing various layers of adsorbents which perform different purification functions
Implementation Method 3
higher heat capacity and dense cores can be used in our composite adsorbents, leading to suppression of the thermal swing during the PSA cycle
Data Source
AI summary
The invention relates to the intensification of hydrogen PSA processes through utilization of specifically engineered core-shell composite adsorbents. Different embodiments of core-shell adsorbents can be used with either high or low heat capacity cores, and different adsorbent shells (e.g. activated carbon, zeolite, silica gel, alumina etc.) resulting in higher mass transfer rates and hence sharper mass transfer fronts during the PSA process. The location of the limiting impurity front determines the product purity. Therefore, with sharper impurity fronts, lower height of adsorbent bed is required, and cycle time can be proportionally reduced. Also, thermal swing during the PSA can be reduced by use of such adsorbents. The use of a high heat capacity core to reduce the thermal swing, leads to higher overall working capacity of the adsorbent bed.