Vertical fluidized bed tube furnace with nitrogen gas supply

The use of nitrogen gas in a vertical fluidized bed tube furnace is a common and safe operation, which relies on the inert protection of nitrogen gas, uniform fluidization heating, and process adaptability. The following is a specific analysis:

1. The role of nitrogen in vertical fluidized bed tube furnace
Inert atmosphere protection
Nitrogen can effectively isolate oxygen and prevent material oxidation at high temperatures. For example, in metal powder sintering or high-temperature treatment of carbon materials, nitrogen gas can prevent material oxidation and ensure product quality.
In some scenarios where hydrogen embrittlement or surface oxidation needs to be avoided, such as material processing of titanium alloys, nitrogen can be used as a protective gas during the cooling stage to replace residual hydrogen gas.
fluidizing medium
Nitrogen, as a fluidized gas, is evenly distributed through a gas distribution plate to suspend and thoroughly mix particulate materials, eliminate temperature gradients, and achieve uniform heating.
For high viscosity or easily agglomerated materials, nitrogen fluidization can effectively disperse particles, avoid local overheating, and improve heat treatment efficiency.
Carrier gas function
In processes such as chemical vapor deposition (CVD), nitrogen can be used as a carrier gas to transport precursors to high temperature zones, achieving thin film growth or material synthesis.
Nitrogen can also carry volatile by-products to the exhaust gas treatment system, keeping the furnace environment clean.

2. Operation steps and precautions
Operation steps
Leak detection and preparation: Connect the nitrogen gas circuit, use soapy water to detect leaks, and ensure that there is no air leakage at each joint. Close all valves of the tube furnace and nitrogen cylinder.
Vacuum pumping and inflation: Open the main valve and outlet pressure reducing valve of the nitrogen cylinder to maintain the outlet pressure at 0.1 MPa. Connect the mechanical pump, open the outlet valve of the tube furnace and the gas path valve of the mechanical pump, and evacuate for 5 minutes to remove air. Afterwards, close the relevant valves and stop pumping.
Flow regulation and ventilation: Open the upper air control valve and adjust the flow meter knob to the desired flow rate (such as 20ml/min). Open the inlet valve of the tube furnace and the outlet valve of the nitrogen gas pipeline, and start to introduce nitrogen gas.
Heating preparation: After passing nitrogen gas for ten minutes, confirm that the atmosphere inside the furnace is stable before starting to heat the tube furnace.
precautions
Pressure control: The air pressure inside the furnace tube should not exceed 0.02MPa to prevent tube rupture. When the temperature of the furnace body is higher than 1500 ℃, the pressure inside the furnace tube needs to be maintained at atmospheric pressure.
Flow restriction: The gas flow entering the furnace tube must be less than 200SCCM to avoid the impact of cold air flow on the heating tube.
Safety monitoring: Install an environmental oxygen analyzer to monitor oxygen content in real-time. Once the oxygen content is too low, immediately initiate emergency response procedures to prevent suffocation accidents.
Equipment inspection: Regularly check the working status of pressure reducing valves, flow meters, and other components to ensure their accurate range, safety, and reliability.

3. Application scenarios
High temperature sintering and annealing
During the high-temperature sintering or annealing process of metals, ceramics, and other materials, nitrogen gas can prevent material oxidation and ensure product performance.
CVD film growth
Nitrogen is used as a carrier gas to transport the precursor to the high-temperature zone, achieving the deposition of thin films such as silicon nitride and aluminum oxide.
Pyrolysis and Gasification
During the pyrolysis or gasification process of biomass, plastics and other materials, nitrogen acts as an inert protective gas to promote the discharge of volatile matter and the collection of products.
Powder modification and coating
Nitrogen fluidization can uniformly disperse particles, achieving surface coating of nanoparticles or loading of catalysts.