Continuous Carbon Nanotube Production via Gas Recirculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for producing carbon nanotubes face challenges such as high production costs, limited productivity, excessive energy consumption, and environmental impact due to inefficient gas usage and waste gas emission, particularly in rotary kiln and fluidized bed reactors.
Innovation Solution
A continuous carbon nanotube production apparatus and method utilizing a fluidized bed chemical vapor deposition reactor with a hydrogen pressure swing adsorption (PSA) unit to recirculate filtered gases, reducing waste gas generation and enhancing carbon source conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional arc discharge or laser ablation methods are used to produce carbon nanotubes, then high purity carbon nanotubes can be obtained, but mass production capability is limited and preparation costs are excessively high
Solution Approach 1:
The patent replaces the mechanical/physical methods of arc discharge and laser ablation with a chemical vapor deposition process using a fluidized bed reactor. This substitution enables continuous mass production at lower costs by using chemical reactions rather than high-energy physical processes, directly addressing the contradiction between productivity and manufacturing ease.
Solution Approach 2:
The patent optimizes reaction parameters including temperature (700-900°C), gas flow rates, and catalyst composition to achieve high productivity. By carefully controlling these parameters in the CVD process, the system achieves mass production capability while maintaining cost-effectiveness, resolving the contradiction between production scale and manufacturing complexity.
2Productivity
If chemical vapor deposition is used with vapor dispersion catalyst to increase synthesis rate, then production speed improves, but CNT particles become excessively small and mass production is limited
Solution Approach 1:
The patent introduces a fluidized bed system as an intermediary between the carbon source and catalyst, enabling better control over particle growth. The fluidized bed environment allows CNTs to grow to appropriate sizes while maintaining high synthesis rates, resolving the contradiction between productivity and particle size control that plagues vapor dispersion methods.
3Productivity
If rotary kiln or fluidized bed reactors are used for mass production, then production capacity increases, but carbon source conversion ratio decreases to at most 80% and waste gas incineration increases costs
Solution Approach 1:
The patent implements a feedback mechanism by recirculating the mixed gas from the reactor outlet back to the inlet. This feedback loop allows unreacted carbon source to be reused, significantly improving the carbon source conversion ratio while maintaining high production capacity, thereby resolving the contradiction between productivity and material efficiency.
Solution Approach 2:
Instead of discarding the mixed gas containing unreacted carbon source as waste, the patent recovers and recirculates it back to the reactor. This recovery process improves carbon source utilization efficiency and reduces waste, directly addressing the contradiction between production capacity and substance loss.
4Productivity
If large scale reactors are used to increase production capacity, then mass production capability improves, but energy consumption increases due to excessive equipment scale
Solution Approach 1:
The patent employs a dynamic fluidized bed system where catalyst particles are continuously moved and suspended by gas flow. This dynamic operation allows for efficient heat and mass transfer, enabling high production capacity in a relatively compact reactor volume, thus resolving the contradiction between productivity and energy consumption that arises from oversized static reactors.
5Object-generated harmful factors
If conventional reactors directly incinerate mixed gas to dispose of reducing gas, then waste gas is eliminated, but production costs increase due to raw material loss and carbon dioxide emission
Solution Approach 1:
The patent uses feedback by recirculating the mixed gas containing reducing gas back to the reactor inlet rather than incinerating it. This approach eliminates waste gas emissions while recovering valuable materials, thereby reducing production costs and resolving the contradiction between environmental protection and manufacturing cost.
Solution Approach 2:
The patent converts the previously harmful reducing gas that required incineration into a beneficial recirculated reactant. By redirecting the mixed gas back to the reactor, the system eliminates waste gas disposal needs while improving carbon source utilization, thus converting a harmful factor into a benefit and resolving the contradiction between waste disposal and production 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
The apparatus achieves superior productivity, high carbon source conversion rates, reduced energy consumption, and minimized waste gas emission, resulting in cost-effective and environmentally friendly carbon nanotube production.
Implementation Method 1
a method for synthesizing CNT using a fluidized bed reactor including forming a fluidized bed, in which a fluid medium flows when heated, in a reactor, and synthesizing CNT in the fluidized bed
Implementation Method 2
reacting a reaction gas containing a carbon source, a reducing gas and an inert gas with a catalyst to synthesize carbon nanotubes
Implementation Method 3
a hydrogen pressure swing adsorption (PSA) unit including two or more adsorption towers and two or more flow direction control valves
Data Source
Figure 1~2
AI summary
Disclosed are an apparatus and method for continuously producing carbon nanotubes. More specifically, disclosed are an apparatus for continuously producing carbon nanotubes including i) a reactor to synthesize carbon nanotubes, ii) a separator to separate a mixed gas from the carbon nanotubes transferred from the reactor, iii) a filter to remove all or part of one or more component gases from the separated mixed gas, and iv) a recirculation pipe to recirculate the filtered mixed gas to the reactor for carbon nanotubes. Advantageously, the apparatus and method for continuously producing carbon nanotubes enable rapid processing, exhibit superior productivity and excellent conversion rate of a carbon source, significantly reduce production costs, reduce energy consumption due to decrease in reactor size relative to capacity, and generate little or no waste gas and are thus environmentally friendly.