Core-in-shell carbon adsorbents for PSA mass transfer
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Solution Overview
Problem
Existing carbon adsorbents for PSA processes face limitations in achieving high mass transfer rates and physical strength while maintaining low pressure drop and attrition resistance, particularly due to the challenges of reducing particle size and high temperature carbonization processes.
Innovation Solution
The development of carbon adsorbents with a core-in-shell structure using a non-adsorbing inert core and an activated carbon shell, combined with an organic binder, which are processed at low temperatures to preserve the binding agent and achieve high sphericity and strength, thereby enhancing adsorption properties and heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If particle size of adsorbent aggregates is reduced to increase mass transfer rate, then adsorption/desorption kinetics is improved, but pressure drop increases and fluidization risk increases
Solution Approach 1:
The adsorbent is structured as core-shell particles with a porous adsorbent shell surrounding a non-porous core. This segmentation allows the shell to provide high mass transfer rate through its porous structure while the dense core reduces overall particle density and pressure drop, resolving the contradiction between fast kinetics and low pressure drop.
Solution Approach 2:
Different regions of the particle have different properties: the shell is highly porous for fast mass transfer, while the core is non-porous and dense for mechanical strength and reduced pressure drop. This local differentiation allows simultaneous optimization of mass transfer rate and pressure drop characteristics.
2Speed
If particle size is reduced to increase mass transfer rate, then adsorption kinetics is improved, but attrition resistance decreases
Solution Approach 1:
The core-shell structure separates the functions: the porous shell provides mass transfer pathways while the dense non-porous core acts as a mechanical strengthener. This segmentation allows small particle size for fast kinetics while the robust core maintains attrition resistance.
Solution Approach 2:
The particle combines two different materials with complementary properties: porous adsorbent material for mass transfer and non-porous mechanically strong material for attrition resistance. This composite structure enables simultaneous achievement of fast kinetics and high strength.
3Reliability
If high temperature carbonization is used to produce activated carbon, then adsorbent properties are achieved, but organic binder is degraded and sphericity is reduced
Solution Approach 1:
The organic binder is applied to form spherical particles before the carbonization step. The binding agent is pre-positioned to create the desired spherical shape, and subsequent low-temperature treatment preserves this shape while activating the carbon. This preliminary action ensures sphericity is established before any thermal processing that might degrade the binder.
Solution Approach 2:
The carbonization temperature is reduced from conventional high temperatures to a lower range (200-500°C) that is sufficient for activation but does not degrade the organic binder or destroy sphericity. This parameter change allows simultaneous achievement of adsorbent properties and shape preservation.
4Reliability
If conventional high temperature processing is used, then carbonization is complete, but binding agent is destroyed and particle strength is reduced
Solution Approach 1:
The processing temperature is changed from conventional high temperatures (>700°C) to a lower range (200-500°C) that provides sufficient carbonization and activation while preserving the organic binding agent. This parameter change enables complete carbonization without binder destruction, maintaining particle strength.
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 carbon adsorbents with superior mass transfer rates, heat capacity, and physical strength, improving the performance and efficiency of PSA processes while minimizing attrition and manufacturing costs.
Implementation Method 1
Activated carbons, which possess a wide range of pore structures and surface chemistry for adsorption of gases
Implementation Method 2
processed at low temperatures to preserve the binding agent
Data Source
AI summary
The present invention relates to a superior carbon adsorbent with or without a core. In one embodiment the carbon adsorbent of the present invention employs carbon adsorbent powder and an organic binding agent which are combined together with an appropriate solvent in an agglomeration step. In another embodiment the invention contemplates a core-in-shell adsorbent comprising an outer shell composed of a carbon and a non-adsorbing inert inner core. Low temperature processing of these agglomerates substantially preserves the binding agent within the final composition and allows one to prepare adsorbent products of high sphericity. The adsorbents of the invention possess superior characteristics such as higher mass transfer rate and CO2 working capacity for use in a H2PSA process.