Steam Partial Pressure Swing Calcination for High Purity CO2
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Solution Overview
Problem
Current methods for calcining CaCO3 to produce high-purity CO2 face challenges in achieving efficient heat recovery and maintaining effective CO2 capture, particularly in calcium looping systems, where high temperatures and energy efficiency are crucial but often compromised by the need for external heat supply and limited mechanical stability of CaO sorbents.
Innovation Solution
A cyclic calcination process involving a packed or moving bed of CaCO3 solids, where a fuel is combusted to heat the solids to 800-950°C, followed by a CO2 partial pressure swing using steam to promote adiabatic cooling and increase molar conversion of CaCO3 to CaO, while minimizing energy losses and external heat requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vacuum calcination conditions are used to produce high-purity CO2 from CaCO3, then CO2 purity is improved, but energy efficiency deteriorates due to high energy consumption for vacuum maintenance
Solution Approach 1:
The patent changes the pressure parameter from vacuum conditions to atmospheric pressure, eliminating the energy-consuming vacuum system while maintaining high CO2 purity through the use of a CO2-selective membrane separator that operates effectively at atmospheric pressure
Solution Approach 2:
The patent replaces the mechanical vacuum system with a membrane-based separation system that uses selective permeability rather than pressure differential to achieve CO2 purification, significantly reducing energy consumption
2Productivity
If high temperatures (above 900°C) are used for calcination to ensure complete decomposition of CaCO3, then conversion efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary action by preheating the CaCO3 feedstock using waste heat from the flue gas before it enters the calcination zone, reducing the energy required to reach the calcination temperature and lowering overall energy consumption
Solution Approach 2:
The patent optimizes the calcination temperature parameter to operate at lower temperatures (800-900°C) combined with extended residence time, achieving complete decomposition without the need for excessively high temperatures that would increase energy consumption
3Temperature
If adiabatic calcium looping packed bed reactor is operated at high pressure during carbonation to achieve high temperatures for subsequent vacuum calcination, then temperature increase is improved, but system complexity increases due to heat transfer equipment requirements
Solution Approach 1:
The patent extracts the CO2 selectively from the flue gas stream using a membrane separator, removing the need for complex vacuum systems and high-pressure heat transfer equipment while maintaining effective carbonation and calcination processes
Solution Approach 2:
The patent introduces a CO2-selective membrane as an intermediary between the carbonation and calcination processes, enabling CO2 separation and concentration without requiring extreme pressure or temperature conditions that would increase system complexity
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 effectively recovers high-purity CO2 by optimizing the temperature and pressure conditions within thermally insulated vessels, enhancing energy efficiency and reducing the need for external heat, thereby improving the operational viability of calcium looping systems for CO2 capture.
Implementation Method 1
a first step of combustion of a fuel in the bed of solids containing CaCO3, heating them up to an average temperature of between 800-950oC
Implementation Method 2
application of a swing in partial pressure of CO2 by feeding steam to the bed of solids containing CaCO3 to calcine them, preferably causing their adiabatic cooling by 30-200oC
Implementation Method 3
a second step of application of a swing in partial pressure of CO2 by feeding steam to the bed of solids containing CaCO3 to calcine them
Data Source
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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, wherein each cycle comprises a first step where the combustion of a fuel in the bed of solids containing CaCO3 heats them up to an average temperature of between 800-950ºC and a second step wherein a CO2 partial pressure swing is applied to extract pure CO2 from the solids containing CaCO3 by feeding steam to the bed. 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.