Scraped Heat Exchanger CO2 Removal Process
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Solution Overview
Problem
Conventional CO2 removal processes from exhaust gas are costly due to high energy and solvent requirements, and become less effective over time, especially at smaller scales, due to issues like water dilution and contaminant absorption.
Innovation Solution
A process involving staged cooling of exhaust gas using non-scraped heat exchangers followed by the addition of an antifreeze agent, minimizing ice formation, and subsequent treatment in a scraped heat exchanger to separate CO2, reducing the need for costly solvents and dehydration, and minimizing equipment size and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amine-treating process is used to remove CO2 from exhaust gas, then CO2 removal effectiveness is improved, but energy consumption increases significantly and net power generation decreases by approximately 30%
Solution Approach 1:
The patent employs phase transition of CO2 from gas to solid (dry ice) through cryogenic cooling. The exhaust gas is cooled to temperatures below -78.5°C, causing CO2 to sublimate directly from gas phase to solid phase, enabling separation without chemical reactions or high energy input for solvent regeneration
Solution Approach 2:
The patent changes the temperature parameter dramatically, cooling the exhaust gas from typical flue gas temperatures (100-200°C) to cryogenic temperatures (below -78.5°C). This parameter change enables direct physical separation of CO2 based on its phase transition point, avoiding the need for energy-intensive chemical absorption processes
2Reliability
If amine-treating process is used to remove CO2 from exhaust gas, then CO2 removal effectiveness is improved, but process costs increase due to high solvent requirements and dehydration needs
Solution Approach 1:
The patent extracts CO2 from the exhaust gas stream through cryogenic condensation and phase transition. By cooling the gas to below CO2's sublimation point, CO2 is extracted as solid particles that can be easily separated from the remaining gas stream, eliminating the need for expensive solvent systems
Solution Approach 2:
The patent uses inexpensive cooling media (such as expanded polystyrene beads or simple refrigeration systems) instead of expensive amine solvents. The cooling medium can be regenerated or replaced at low cost, making the overall process more economically viable
3Reliability
If amine-treating process is used to remove CO2 from exhaust gas, then CO2 removal effectiveness is improved, but the process becomes less effective over time due to contaminant absorption and water dilution
Solution Approach 1:
The patent converts the presence of water vapor and other contaminants in the exhaust gas from a harmful factor into a non-issue. By using cryogenic temperatures, water vapor condenses and freezes out along with CO2, and the scraping mechanism continuously removes these frozen contaminants, preventing any dilution or absorption problems that plague amine-based systems
Solution Approach 2:
The scraping mechanism automatically and continuously removes accumulated ice and contaminant deposits from the heat exchanger surfaces. This self-cleaning action maintains consistent heat transfer efficiency and CO2 removal effectiveness over time without manual intervention or solvent replacement
4Reliability
If scraped heat exchanger is used to cool the cooled mixed stream to a third temperature below which solid CO2 forms, then CO2 separation effectiveness is improved, but equipment complexity increases
Solution Approach 1:
The scraping mechanism uses mechanical motion (rotating scrapers or reciprocating blades) to physically remove frozen CO2 and ice deposits from the heat exchanger surfaces. This mechanical action prevents buildup that would insulate the cooling surfaces and maintain efficient heat transfer for CO2 separation
Solution Approach 2:
The system exploits the phase transition of CO2 from gas to solid at cryogenic temperatures. By cooling the mixed stream below CO2's sublimation point in the scraped heat exchanger, CO2 condenses as solid particles that can be easily separated from the gas stream, achieving high separation effectiveness
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 reduces energy requirements, operational pressures, and costs, maintaining effectiveness across varying scales without the drawbacks of contaminant absorption, resulting in a more cost-effective and efficient CO2 removal method.
Implementation Method 1
introducing a gas stream comprising CO2 to a non-scraped heat exchanger to cool the gas stream to a first temperature greater than about 0° C. and less than about 10° C.
Implementation Method 2
introducing an antifreeze agent to the gas stream downstream from the non-scraped heat exchanger to form a mixed stream
Implementation Method 3
introducing the mixed stream to at least one other non-scraped heat exchanger to cool the mixed stream to a second temperature greater than a freezing temperature of the mixed stream
Implementation Method 4
introducing at least a portion of the cooled mixed stream to a scraped heat exchanger to cool the cooled mixed stream to a third temperature below which solid CO2 forms
Implementation Method 5
cool the cooled mixed stream to a third temperature below which solid CO2 forms
Data Source
AI summary
Improved processes and systems for removing CO2 from exhaust gas to substantially prevent such greenhouse gas from being released to the atmosphere. The systems and processes use a) staged cooling of an exhaust gas stream, b) addition of an antifreeze, and c) a combination of non-scraped heat exchangers and scraped heat exchangers to separate CO2 from an exhaust stream while reducing or minimizing accumulation of ice on surfaces within the system.