The combined suction-pressure pneumatic conveying system, also known as positive-negative pressure combined powder conveying, integrates suction and pressure conveying in a single process. It is designed for continuous, dust-free, and efficient transfer of bulk powders and granular materials. This hybrid system is widely applied in chemical, food, building materials, metallurgy, mining, and pharmaceutical industries, offering outstanding adaptability and reliability.

The working process consists of two stages. In the suction stage, a vacuum pump or blower creates negative pressure in the line, drawing material from a hopper, truck, or silo through a suction nozzle into a separator. Then the pressure stage uses positive air pressure to push the separated material through the delivery pipeline to the target location. The entire process is totally enclosed and automatically controlled.

Key components include a roots blower, vacuum pump, cyclone separator, bag filter, rotary valve, pipelines, diverter valves, pressure gauges, and a PLC control cabinet. The PLC system enables precise control of start-up, shutdown, and fault handling. It also supports remote monitoring and parameter adjustment. Modular construction simplifies installation and future expansion, reducing site engineering costs.

The main advantages are multi-point pickup and single-point or multi-point discharge. The vacuum section prevents dust leakage and is particularly safe for toxic or explosive powders. The pressure section delivers material over long distances with high capacity. Compared with separate suction and pressure systems, the combined configuration saves energy, lowers investment, and occupies less space while reducing product degradation.

This system is suitable for conveying cement, fly ash, lime powder, calcium carbonate, titanium dioxide, flour, starch, sugar, plastic pellets, rubber powder, resin, graphite, alumina, and other non-sticky fine powders or granules. It is commonly used for unloading railway wagons or trucks, feeding packaging machines, distributing material from a central source to multiple silos, and elevating material from underground pits to overhead storage hoppers.

Technical parameters are determined by material properties and plant layout. Typical conveying capacity ranges from 1 to 100 tons per hour. Suction distance is usually up to 80-200 meters, while pressure conveying distance can reach 500-1000 meters. The conveying gas velocity is kept between 15 and 30 m/s, and the solid-to-gas mixing ratio is normally 5-25. Operating vacuum is up to -50 kPa, and positive pressure can be as high as 200 kPa.

Selection should consider the material's bulk density, particle size distribution, moisture content, abrasiveness, temperature, toxicity, and explosibility. The conveying route, horizontal length, vertical height, number of bends, and available space also influence the design. Environmental standards about noise and dust emission must be met. A material trial at the manufacturer's test facility is strongly recommended to verify the optimum operating parameters.

The system can be manufactured from carbon steel, stainless steel, or aluminum alloy to suit different product requirements. For abrasive materials, wear-resistant linings and long-radius elbows are used. Explosion-proof motors, valves, and control instruments are available for combustible dust environments. The PLC can be connected with DCS or SCADA for centralized control and data collection, which meets the demands of modern intelligent factories.

Regular maintenance is essential for reliable operation. Operators should check blower oil level, filter pressure difference, pipeline sealing, and valve operation daily. Filter bags should be cleaned or replaced periodically to maintain suction efficiency. Safety devices such as pressure relief valves, rupture discs, emergency stop buttons, and temperature sensors are installed. The PLC automatically issues alarms and stops the system in abnormal conditions, preventing equipment damage.

In conclusion, the combined suction-pressure pneumatic conveying system is a reliable, clean, and economical solution for bulk material handling. It brings together the benefits of negative and positive pressure transport, resulting in high efficiency, low energy use, and excellent adaptability. Whether you need to move powders or granules over short or long distances, this system can be customized to meet your exact requirements. Contact our engineering team for a free assessment and quotation.