Production Equipment and Precision Control Technology for Continuous Basalt Fiber

1. Main Production Equipment for Continuous Basalt Fiber 
Continuous basalt fiber production adopts a "one-step process", characterized by a simplified workflow but high technical barriers. Compared to carbon fiber production, continuous basalt fiber consumes significantly less energy (less than 1/10 of carbon fiber's energy consumption) and emits no CO₂, SO₂, or other harmful gases, making it an environmentally friendly and low-carbon production method. The primary thermal equipment for continuous basalt fiber production is the furnace, which is categorized into crucible furnaces and tank furnaces.  

(1) Crucible Furnace  
A crucible furnace typically operates with one furnace per bushing.  
Advantages: Compact size, low investment, flexibility for localized process adjustments, and suitability for small-batch or specialized production.  
Disadvantages: Low thermal efficiency, high energy consumption, inconsistent product quality, low production efficiency, and high overall costs.  
Currently, crucible furnaces dominate the continuous basalt fiber industry, with an annual production capacity of 100–300 tons. Due to electrode and refractory material degradation, crucible furnaces have a short lifespan of 6–12 months. During the early stages of industry development, crucible furnaces were ideal for small-scale production and equipment research.  
Types of Crucible Furnaces:  

• Flame Crucible Furnace: Heated by natural gas and air combustion.  
    Pros: Flexible flame control, quick start/stop capability.  
    Cons: Low flame temperature, poor melting capacity, energy waste due to nitrogen (78% of air) generating harmful NOₓ emissions, and uneven heating leading to inconsistent melt homogeneity.  
• All-Electric Crucible Furnace: Heated internally via plate or rod electrodes.  
    Pros: High thermal efficiency, uniform internal heating.  
    Cons: Short lifespan due to electrode wear, requiring full replacement after degradation.  

(2) Tank Furnace 
As demand for fiber quantity and quality grows, tank furnaces (one furnace with multiple bushings) have become critical for large-scale production. They enable strict temperature control, improved melt homogeneity, stable product quality, and high efficiency, with annual capacities reaching thousands to tens of thousands of tons.  
Types of Tank Furnaces:  

• All-Electric Tank Furnace: Uses rod electrodes (horizontally or bottom-mounted).  
    Pros: High thermal efficiency and uniform heating.  
    Cons: Electrode hotspots, uneven wear, and short lifespan (~1 year).  
• All-Flame Tank Furnace: Heated by natural gas with air or pure oxygen. Pure oxygen combustion is preferred for efficiency and reduced emissions.  
    Pros: Long lifespan (3+ years), energy-saving with pure oxygen.  
    Cons: Temperature gradients in deep melts, though shallow melts improve uniformity.  
• Hybrid Flame-Electric Tank Furnace: Combines top flame heating and bottom/side electrodes.  
    Pros: Enhanced melt homogenization.  
    Cons: Complex design, uneven surface heating, high energy loss from water-cooled electrodes, and short lifespan due to electrode wear.  

(3) Bushing
The bushing, typically made of platinum-rhodium alloy, is a core component for fiber forming. Large-scale production demands high-capacity bushings. Initial bushings had 200 holes; current standards include 400, 800, and 1,200 holes. Bushing technology advances synergize with tank furnace development.  

2. Precision Control Technology 
Basalt melt exhibits challenges such as high drawing/crystallization temperatures, rapid crystallization, narrow forming temperature windows, uneven fiber hardening, strong bushing wettability, and poor heat transparency. These factors cause instability during fiber drawing (e.g., breakage, flyaway, diameter variation). Stabilization relies on three aspects:  

• Melt Homogeneity and Stability: Achieved through precise raw material mixing, furnace temperature control, melt level regulation, and pressure management.  
• Bushing and Temperature Control: Ensures uniform bushing heating and avoids crystallization.  
• Drawing Process Optimization: Includes precise control of drawing speed, cooling parameters, and fiber tension.  

Key technologies involve advanced control systems for material blending, furnace temperature, melt level, chamber pressure, channel temperature, bushing temperature, and drawing speed. These ensure stable, high-quality continuous basalt fiber production.