Rotating inclined tube high-temperature furnace drying

The application of rotary inclined tube high-temperature furnace in the drying field significantly improves the uniformity and efficiency of material drying through dynamic drying process, especially suitable for high value-added materials or scenarios with strict requirements for drying quality. The following provides a detailed introduction from four aspects: drying principle, advantages and characteristics, application scenarios, and operating standards:

1. Drying principle
Rotating motion promotes uniform drying
The furnace tube rotates at a speed of 0-15rpm, driving the internal materials to form a spiral motion trajectory. This dynamic rolling continuously updates the surface of the material, avoiding the common “clumping” or “local overheating” phenomenon in static drying. For example, when drying nano alumina powder, rotational motion maintains stable interparticle porosity, unobstructed water vapor diffusion channels, and improves drying efficiency.
Tilt design optimizes material flow
The furnace body can be tilted at 0-45 degrees (some equipment supports a large tilt angle of 30 degrees), and the material is driven by gravity to flow along the axial direction of the furnace tube. This design is particularly suitable for drying viscous materials or easily agglomerated particles, such as aluminum hydroxide gel. The synergistic effect of tilt angle and rotation speed can achieve continuous flow of materials from the feeding end to the discharging end, while maintaining drying uniformity.
Multi temperature gradient drying
The furnace is divided into 2-6 independent temperature zones along the axial direction (such as preheating zone 100-200 ℃, drying zone 200-400 ℃, cooling zone 50-100 ℃), each equipped with independent heating elements and temperature control systems. This gradient temperature design can match the drying requirements of materials at different stages:
Preheating zone: Slowly raise the temperature to avoid material cracking due to excessive temperature difference;
Drying zone: high temperature for rapid removal of free water and bound water;
Cooling zone: Reduce material temperature to prevent moisture regain or degradation of heat sensitive components.
Atmosphere control to prevent oxidation or deterioration
Create a low oxygen or oxygen free dry environment by using a vacuum pump (capable of pumping up to 10 ⁻ Pa to 10 ⁻⁵ Pa) or by introducing inert gases such as nitrogen and argon. For example, when drying lithium-ion battery cathode materials (such as NCM811), an argon atmosphere can prevent the oxidation of metal elements such as cobalt and nickel, while suppressing the reaction of the material with water vapor to produce hydroxides.

2. Advantages and Characteristics
Significant improvement in drying uniformity
The dynamic drying process (rotation+tilt) continuously exposes the material surface to high-temperature airflow, reducing the diffusion resistance of water vapor.
Prevent material aggregation and cracking
The rotating movement destroys the capillary force between particles through mechanical force to avoid the formation of hard shell or cracking of viscous materials (such as aluminum hydroxide gel) during drying. The inclined design promotes material flow through gravity and prevents local excessive drying.
Energy saving and efficiency optimization
Multi zone temperature control technology can accurately match the drying needs of materials and reduce ineffective heating. For example, when drying graphene oxide, only centralized energy supply is required in the drying zone (300 ℃), reducing energy consumption in the preheating and cooling zones and making the overall process more energy-efficient.
Strong adaptability and support for complex processes
It can handle various forms of materials such as powder, particles, fibers, etc., and supports segmented drying (such as low-temperature dehumidification first, and then high-temperature de crystallization water). For example, when drying pharmaceutical intermediates, the “drying mixing” integrated process can be achieved by adjusting the tilt angle (15 degrees) and rotation speed (5rpm) to shorten the production cycle.

3. Application scenarios
new energy materials
Lithium ion battery materials: Dry positive electrode materials (such as NCM811, LFP) and negative electrode materials (such as graphite, silicon carbon composites) to prevent oxidation and agglomeration.
Hydrogen fuel cell materials: Dry proton exchange membrane (PEM) precursor to avoid membrane material deformation at high temperatures.
Ceramics and Glass
Advanced ceramics: Dry ceramic powders such as alumina and zirconia to enhance sintering activity.
Fiberglass: Dry glass raw materials (such as boric acid and sodium silicate) to prevent clumping and affect the quality of wire drawing.
Chemical Engineering and Catalysts
Molecular sieve catalyst: Dry ZSM-5, SAPO-34 and other molecular sieves to maintain the integrity of the pore structure.
Fine chemicals: Dry high-purity inorganic salts (such as lithium carbonate, sodium hydroxide) to prevent moisture absorption and agglomeration.
Metal Powder and 3D Printing
Metal Injection Molding (MIM): Dry metal polymer feed to enhance injection flowability.
3D printing sand mold: Dry resin bonded sand mold to prevent deformation during the printing process.
Food and Medicine
Pharmaceutical intermediates: Dry highly active pharmaceutical ingredients (such as APIs) to prevent degradation of thermosensitive components.
Functional foods: dry probiotics, dietary fiber, etc., to maintain biological activity.

4. Operating standards
Equipment inspection and pre-processing
Check if the sealing of the furnace body, heating elements, temperature control system, and vacuum system (if necessary) are functioning properly.
Clean the furnace to prevent residual materials from contaminating the new batch.
Pre start the rotation and tilt mechanism and confirm that it operates smoothly without any jamming.
Material loading and parameter setting
Choose loading methods based on material characteristics (such as boats or fluidized beds) to avoid accumulation or overflow.
Set drying parameters:
Heating rate: ≤ 10 ℃/min (to prevent material cracking);
Drying temperature: set according to the thermal stability of the material (such as ceramic powder 200-400 ℃, pharmaceutical intermediate 80-120 ℃);
Tilt angle: 15-30 degrees for viscous materials, 5-15 degrees for free flowing materials;
Rotation speed: powder 2-8rpm, particles 5-12rpm.
Drying process monitoring
Real time monitoring of furnace temperature, vacuum degree (if necessary), and material status (such as color and shape).
Regular sampling and testing of moisture content (such as Karl Fischer method) to ensure compliance with process requirements (such as ≤ 0.5%).
If material clumping or abnormal temperature is found, immediately pause the equipment and adjust the parameters.
Post processing and equipment maintenance
After drying, cool the material according to the process requirements (such as natural cooling or forced air cooling).
Clean up residual materials in the furnace and check if the heating elements and seals are damaged.
Regularly calibrate the temperature control system and vacuum gauge to ensure equipment accuracy.