Technical Principle

The system uses floating-catalyst or supported-catalyst chemical vapor deposition (CVD) for continuous CNT production. Catalyst precursors or catalyst-coated substrates are continuously conveyed into a multi-zone steel-belt furnace, where they are reduced and activated at elevated temperatures.

Carbon-source gases decompose on the catalyst surface, releasing carbon atoms that nucleate and grow on catalyst particles to form few-walled or multi-walled carbon nanotubes. The CNTs are then conveyed out of the furnace on the steel belt, enabling continuous production.

Key Equipment Components

The steel-belt furnace is a continuous, horizontal furnace with multiple independently controlled temperature zones.

1. Feeding and Preheating Section

- Continuous Conveying: The steel belt runs continuously at an adjustable speed of 0.1–5 cm/min.

- Inert Gas Purging: Argon (Ar) or nitrogen (N₂) is used to displace air.

- Preheating and Drying: The low-temperature zone operates at 200–400°C to remove solvents and moisture from the catalyst precursors.

2. Multi-Zone Reaction Chamber

The core reaction chamber typically contains 3–5 independently controlled temperature zones, providing precise temperature-gradient control across the reduction, activation, growth, and cooling stages.

3. Cooling and Discharge Section

The products are rapidly cooled under an inert atmosphere at temperatures of ≤600°C to help prevent CNT oxidation and structural defects.

4. Exhaust Gas Treatment System

Catalytic combustion and activated carbon adsorption are used to treat unreacted hydrocarbons and dust before discharge, supporting compliance with applicable emission requirements.

Continuous CNT Production Process

1. Catalyst Preparation and Feeding

Catalyst preparation and feeding are key factors in determining CNT wall count and diameter.

2. Continuous Reaction in the Furnace

The material passes through three main reaction stages within the multi-zone furnace: catalyst reduction and activation, CNT growth, and cooling.

3. CNT Growth Mechanism

- Catalytic Decomposition: Carbon-source gases decompose on the catalyst surface at high temperatures, releasing carbon species and hydrogen.

- Carbon Dissolution and Precipitation: Carbon atoms dissolve into the metal catalyst particles. Once saturation is reached, carbon precipitates from the particle surface or edges.

- Nanotube Formation: The carbon atoms assemble into curved graphitic layers that develop into carbon nanotubes.

4. Product Collection and Post-Processing

The resulting CNTs are collected after leaving the furnace and can undergo further processing as required by the production process.

Key Advantages and Applications

Key Advantages

1.Continuous Production: Supports production capacities at the kilogram-per-day scale, significantly exceeding those of batch-operated tube furnaces.

2.Consistent Product Quality: Precise temperature control across multiple zones helps maintain consistency in CNT diameter, length, and wall count.

3.Flexible Product Control: 

Process parameters can be adjusted to produce few-walled, multi-walled, or mixed CNT products.

4.Lower Production Costs: 

Large-scale production can significantly reduce raw material and energy costs.

Applications

Few-Walled Carbon Nanotubes

- Lithium-ion battery conductive additives

- Transparent conductive films

- Sensors

These materials offer high electrical and thermal conductivity and high mechanical strength.

Multi-Walled Carbon Nanotubes

- Composite reinforcement

- Electromagnetic shielding

- Thermally conductive fillers

These materials offer a cost-effective solution for applications requiring reinforcement, conductivity, or thermal management.