Vacuum Swing Calcination for High Purity CO2 from CaCO3
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Solution Overview
Problem
Current calcium looping processes face challenges in achieving efficient and energy-effective calcination of CaCO3 to capture CO2 in high purity form, due to limitations in heat transfer and the need for external heat sources, especially in packed beds and calcium looping systems using CaO sorbents with low mechanical stability and reactivity.
Innovation Solution
A cyclic calcination process involving a heating step where fuel is combusted at atmospheric pressure to heat CaCO3 to 800-900°C, followed by a vacuum step at 0.05-0.5 atm to extract CO2, with the option of using oxygen-enriched air or O2/CO2 mixtures for combustion, and incorporating metal oxides like NiO or CuO as oxygen carriers for chemical looping processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vacuum pressure is applied to extract CO2 from CaCO3, then CO2 purity is improved, but energy consumption increases due to the need for external heat sources
Solution Approach 1:
The system uses the heat generated during the carbonation step (exothermic reaction) to provide the necessary heat for the subsequent vacuum calcination step, making the system self-sufficient and eliminating the need for external heat sources
Solution Approach 2:
The patent combines the carbonation and calcination steps into a single integrated system where the carbonation reactor serves dual purposes: capturing CO2 during carbonation and providing heat for vacuum calcination, thereby reducing overall energy consumption
2Quantity of substance
If CaO sorbents are used with low mechanical stability, then CO2 capture capacity is improved, but process reliability deteriorates
Solution Approach 1:
The patent operates at high pressures (10-100 atm) during carbonation to enhance CO2 capture capacity, while then reducing to vacuum pressure for calcination, using pressure as a controllable parameter to achieve both high capacity and reliability
Solution Approach 2:
The system employs cyclic operation alternating between carbonation (high pressure) and vacuum calcination (vacuum pressure) steps, allowing the CaO sorbent to be regenerated periodically and maintaining long-term process reliability despite using sorbents with lower mechanical stability
3Productivity
If cyclic operation is implemented, then CO2 capture efficiency is improved, but process complexity increases
Solution Approach 1:
The same reactor vessel performs multiple functions: CO2 capture during carbonation, heat generation through exothermic reaction, and CO2 release during vacuum calcination, simplifying the overall system despite cyclic operation
Solution Approach 2:
The heat generated during the carbonation step is immediately utilized in the subsequent vacuum calcination step, creating a continuous internal heat cycle that maintains process efficiency while managing the complexity of cyclic operation
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 enhances the energy efficiency and product quality of CO2 capture by maintaining or exceeding the efficiency of non-CO2 capture processes, allowing for continuous operation and high purity CO2 recovery from CaCO3 calcination in limestone kilns and calcium looping systems, while reducing the need for external heat sources.
Implementation Method 1
a first step of combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO3 heating them up to 800-900° C.
Implementation Method 2
heating them up to 800-900° C.
Implementation Method 3
a second step of application of a vacuum pressure between 0.05 and 0.5 atm to extract pure CO2 from the solids containing CaCO3
Implementation Method 4
cooling them by 30-200° C.
Implementation Method 5
the preferred method of combustion of the fuel used to heating up the bed of solids containing CaCO3 is a chemical looping process, that uses as oxygen carrier a second solid containing a metal oxide (preferably NiO or CuO)
Data Source
AI summary
This invention discloses a calcination process to produce high purity CO2 from solids containing CaCO3 which operates cyclically and continuously on the solids, arranged in a packed or a moving bed, and wherein each cycle comprises a first step where the combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO3 heats them up to 800-900° C. and a second step wherein a vacuum pressure between 0.05 and 0.5 atm is applied to extract pure CO2 from the solids containing CaCO3 while cooling them by 30-200° C. Said combustion can be carried out directly with air, oxygen enriched air or O2/CO2 mixtures when the process is applied to the calcination of a continuous flow of limestone in a moving bed shaft kiln. The process is also applied to calcine CaCO3 formed in reversible calcium looping processes comprising a carbonation reaction step to form CaCO3 from CaO.