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A pneumatic conveying system is an automated closed-loop system that uses airflow energy to transport materials. It is widely used in industries such as chemical, food, power, and environmental protection. Its core components include air supply systems, feeding systems, pipelines, separators/dust collectors, control systems, and discharge systems. Below, we focus on the role of the rotary discharge valve (also known as a rotary feeder or star valve) and its structural design
Air Supply System
Provides the airflow energy for conveying. Common equipment includes Roots blowers, centrifugal fans, or air compressors. The airflow velocity must match the material properties and system pressure (positive or negative)
Feeding System
Introduces materials into the pipeline. Key devices include rotary feeders, screw conveyors, or blow tanks. The rotary discharge valve is critical for positive-pressure systems and serves as the terminal discharge device in negative-pressure systems
Conveying Pipeline
Made of wear-resistant materials (e.g., seamless steel pipes) with optimized layouts to minimize wear and pressure loss
Separator/Dust Collector
Separates materials from airflow using devices like cyclone separators or bag filters
Control System
Adjusts airflow rate, feeding speed, and pressure via PLCs or inverters for automated operation
The rotary discharge valve performs three critical roles: feeding, discharging, and airlocking, ensuring system stability and efficiency
Continuous Feeding and Discharging
Transports materials from storage silos to pipelines (positive pressure) or discharges materials from separators (negative pressure).
Suitable for powders, granules, and small bulk materials (e.g., cement, grains). For fluidizable materials (e.g., aerated clay), rotor capacity must account for reduced bulk density
Air Locking and Pressure Isolation
A narrow gap (~0.15 mm) between the rotor and housing prevents gas leakage in positive-pressure systems or air ingress in negative-pressure systems
Structural reinforcement (e.g., thicker shafts, durable bearings) is required for high-pressure differentials to avoid rotor jamming
Adaptability to Complex Conditions
Anti-jamming design: Offset rotors or V-shaped blades reduce material blockage
Pressure-resistant design: Enclosed rotors handle high-pressure environments
Anti-adhesion design: Polytetrafluoroethylene (PTFE) coatings or scraper blades prevent sticky materials from adhering
A typical rotary discharge valve consists of the following components (textual illustration)
[Housing] │ ├─ **Inlet**: Connects to silos or separators; materials enter rotor chambers via gravity. ├─ **Star-shaped rotor**: 6–8 blades with wear-resistant edges (nylon, brass). ├─ **Drive unit**: Reducer motor controls rotor speed to adjust feeding rate. ├─ **Pressure-equalizing vent**: Releases trapped gas to ensure smooth material flow. ├─ **Outlet**: Connects to pipelines or downstream equipment. └─ **Sealing system**: Packing glands and bearings maintain airtightness under pressure.
Positive-pressure systems: Require pressure-resistant rotors and reinforced sealing
Negative-pressure systems: Use anti-jamming designs to prevent blockages
High-temperature/corrosive materials: Stainless steel housings or external bearings are recommended
The rotary discharge valve acts as the "gateway" of pneumatic conveying systems. Its design must align with material properties (e.g., bulk density, fluidity), pressure differentials, and operational demands. For detailed structural diagrams or customized solutions, refer to technical documentation from manufacturers.
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