CVI Cold Trap Recirculation for Hydrocarbon Tar Removal
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Solution Overview
Problem
Conventional chemical vapor infiltration and densification processes in the manufacturing of ceramic matrix composites result in byproduct deposits within system components, leading to increased downtime and reduced throughput due to the accumulation of reactive and pyrophoric substances, as well as non-pyrophoric hydrocarbon tars that clog plumbing systems.
Innovation Solution
A system and method for chemical vapor infiltration and densification that employs a recirculation path with a cryogenic-cooler or pressure swing absorption unit to condense and recycle hydrocarbon gases, utilizing an electric arc to break down heavier hydrocarbons and a plasma conduit to trap and condense hydrocarbons with six or more carbon atoms, thereby reducing system downtime and improving process efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemical vapor infiltration processes are used to densify porous substrates, then carbon deposition occurs within the pores, but byproduct deposits accumulate in system components leading to increased downtime and reduced throughput
Solution Approach 1:
The patent extracts and removes harmful byproduct deposits (hydrocarbon tars and condensable materials) from the exhaust gas stream using a cold trap positioned in the exhaust path. This prevents the deposits from accumulating in system components while maintaining the beneficial carbon deposition process in the substrate, thereby resolving the contradiction between manufacturing precision and productivity
Solution Approach 2:
The patent introduces an intermediary component (cold trap) between the reaction chamber and the vacuum pump system. This intermediary captures and retains harmful byproducts that would otherwise accumulate in the plumbing and cause shutdowns, allowing continuous operation while maintaining high-quality densification
2Manufacturing precision
If conventional CVI processes are used, then carbon is deposited in porous substrates, but reactive and pyrophoric byproduct deposits require manual cleaning and system shutdown
Solution Approach 1:
The cold trap extracts and retains pyrophoric and reactive byproduct deposits from the exhaust stream before they can enter the vacuum pump system. This prevents the need for manual cleaning and system shutdowns, eliminating downtime while preserving the quality carbon deposition process
Solution Approach 2:
The patent converts the harmful byproduct deposits into a beneficial situation by using the cold trap to capture them in a controlled manner. The trapped deposits are safely contained and can be removed during routine maintenance without requiring system shutdown or posing safety risks, thus converting a harmful accumulation problem into a manageable maintenance task
3Productivity
If recirculation of exhaust gas is implemented, then throughput is improved, but condensable hydrocarbon tars accumulate in plumbing systems
Solution Approach 1:
The cold trap is positioned in the recirculation line to extract and remove condensable hydrocarbon tars from the exhaust gas before it is recirculated back to the reaction chamber. This prevents tar accumulation in the plumbing while maintaining the high throughput benefits of gas recirculation
Solution Approach 2:
The patent applies preliminary action by removing harmful condensable tars from the exhaust stream before recirculation occurs. The cold trap预先 captures these tars, preventing them from entering the recirculation system and accumulating in the plumbing, thus enabling continuous high-rate recirculation without maintenance shutdowns
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
The recirculation of processed gases enhances the densification rate and efficiency of carbon deposition, allowing for faster and more effective densification of carbon fiber preforms and porous substrates, while minimizing the need for manual cleaning and reducing operational downtime.
Implementation Method 1
The cryogenic-cooler may be configured to condense hydrocarbon molecules comprised of six or more carbon atoms
Implementation Method 2
utilizing an electric arc to break down heavier hydrocarbons
Implementation Method 3
a plasma conduit to trap and condense hydrocarbons with six or more carbon atoms
Data Source
AI summary
A method of chemical vapor infiltration and deposition includes disposing a porous substrate within a reaction chamber, establishing a sub-atmospheric pressure within the reaction chamber, introducing a hydrocarbon reaction gas into a reaction zone of the reaction chamber to densify the porous substrate, withdrawing unreacted hydrocarbon reaction gas from the reaction chamber, the unreacted hydrocarbon reaction gas comprising hydrocarbon molecules having six or more carbon atoms, removing at least a portion of the hydrocarbon molecules having six or more carbon molecules from the unreacted hydrocarbon reaction gas by causing the portion of the hydrocarbon molecules having six or more carbon atoms to condense, and recirculating at least a portion of the unreacted hydrocarbon reaction gas back into the reaction zone.