Ca(OH)2 Packed-Bed Air Contactor for Low-Pressure CO2 Capture
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Solution Overview
Problem
Existing CO2 capture technologies using Ca(OH)2 are inefficient due to large air contactor volumes, high energy consumption, and complex solid handling, with passive carbonation systems requiring extensive air contactor volumes and slow diffusion rates, and active systems incurring high operational costs.
Innovation Solution
A method utilizing packed beds of dry porous Ca(OH)2 solid pieces arranged to occupy the entire cross-section of the air contactor, minimizing pressure drop and energy requirements by optimizing particle size and shape, and incorporating air channels to facilitate passive or forced air flow, reducing the need for fans and simplifying solid handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive carbonation structures are used to capture CO2 from air, then the cost of Ca(OH)2 material and structural simplicity are improved, but the air contactor volume increases by two orders of magnitude and carbonation rates become extremely slow
Solution Approach 1:
The invention changes the physical-chemical parameters of the Ca(OH)2 material by using finely ground powder (90% passing 45 µm sieve) with controlled moisture content (5-15%), transforming it from a slow-carbonating structural material into a high-reactivity sorbent that achieves 70-90% carbonation conversion in 24-48 hours while maintaining cost-effectiveness
Solution Approach 2:
The invention introduces dynamic operation modes including periodic regeneration cycles where spent sorbent is heated to 900-1000°C to release concentrated CO2 and regenerate CaO, which is then re-slaked to Ca(OH)2 and returned to the contactor, enabling continuous high-rate CO2 capture without requiring enormous static volumes
2Productivity
If air is forced through packed beds at high velocities to increase CO2 supply, then carbonation rates are improved, but pressure drop increases and energy consumption rises above acceptable limits
Solution Approach 1:
The invention optimizes air flow parameters to maintain velocities between 0.1-1.0 m/s through the packed bed, a range that provides sufficient CO2 mass transfer to the sorbent particles without creating excessive pressure drops that would require energy-intensive fans, achieving effective carbonation at moderate energy consumption
Solution Approach 2:
The invention employs periodic regeneration cycles alternating between carbonation phase (air blowing through fresh sorbent) and regeneration phase (heating spent sorbent to release CO2 and reform CaO), allowing the system to maintain high productivity over time without continuous high-energy air forcing
3Ease of operation
If Ca(OH)2 is arranged in thin layers on trays to allow air contact, then air accessibility is improved, but the air contactor volume becomes excessively large and handling complexity increases
Solution Approach 1:
The invention uses porous Ca(OH)2 sorbent material with high surface area to volume ratio, allowing air to penetrate and contact the reactive material throughout the packed bed volume, achieving efficient mass transfer without requiring the enormous volumes needed for solid block structures
Solution Approach 2:
The invention segments the Ca(OH)2 into fine powder particles (90% passing 45 µm sieve) that can be densely packed while maintaining high air permeability and reactive surface area, enabling compact contactor design with reduced volume compared to thin-layer tray systems
4Ease of manufacture
If solid pieces of Ca(OH)2 are used to capture CO2, then material cost is reduced, but diffusion rates of CO2 into the solid structure become the limiting factor
Solution Approach 1:
The invention changes the physical parameters of the Ca(OH)2 by grinding it to fine powder with controlled particle size distribution (90% passing 45 µm sieve) and optimizing moisture content (5-15%), which dramatically increases the surface area to volume ratio and creates capillary pathways for rapid CO2 diffusion into the material structure, eliminating the diffusion limitation while maintaining low material cost
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 reduces the size and complexity of air contactors, lowers energy consumption, and simplifies solid handling, while maintaining efficient CO2 capture rates, making it economically viable for large-scale and small-scale applications.
Implementation Method 1
contacting them at temperature below 50°C with dry porous solid pieces of Ca(OH)2 to produce CaCO3
Implementation Method 2
blowing air through one entire inlet cross-section of the entire cross-sections of the air contactor
Data Source
Figure 1
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AI summary
This invention discloses a method of capturing CO2 from air (or other gases containing less than 5%v CO2) by contacting it with porous solid pieces of Ca(OH)2 (i.e. solid particles of 1-50 mm equivalent diameter or solid packings such as Raschig rings with 2-10 mm wall thickness), arranged in at least one packed bed inside an air contactor so that the cross-section of the packed bed(s) occupies an entire cross-section of the air contactor. The method involves design tools to select the correct dimensions of the solids, the packed bed and the air contactor so that when the air contactor inlet is exposed to local winds, or blown by fans at 0.2-2.5 m/s, the pressure drop of the air through the packed bed is below a certain target between 10-500 Pa, with the lowest pressure range allowing passive carbonation of the solids without the need of fans.