What materials can be conveyed by a screw conveyor?

A screw conveyor is a conveying device that uses rotating helical blades to continuously move materials along a fixed casing or trough.  It has a simple structure, good sealing performance, and strong adaptability, and is widely used in industries such as grain, building materials, chemicals, metallurgy, environmental protection, and power generation. The types of materials it can convey are very broad, and can usually be classified and described based on the physical state, particle characteristics, chemical properties, temperature, and humidity of the material.

 
First, in terms of the physical form of the material, screw conveyors are mainly suitable for bulk materials. The most common are powdered materials, such as flour, cement, lime powder, coal powder, gypsum powder, talc powder, and pigment powders. These materials have good fluidity and can achieve stable and continuous conveying under the propulsion of the helical blades. At the same time, the sealed structure of the screw conveyor can effectively reduce dust, which has a positive effect on environmental protection.

 
Secondly, granular materials are also an important conveying object for screw conveyors. For example, grain materials such as wheat, corn, rice, sorghum, and beans, as well as plastic granules, fertilizer granules, and resin granules in the chemical industry. These materials have a certain particle size and good fluidity, and are not prone to caking or adhesion during the conveying process, making them suitable for horizontal or small-angle screw conveying. For these materials, by reasonably selecting the pitch, rotation speed, and blade form, the conveying volume can be effectively controlled to avoid crushing or blockage.

 
Thirdly, screw conveyors can also be used to convey small lump materials, such as coal lumps, coke, crushed ore, gravel, and slag. These materials have larger particles and higher hardness, requiring higher wear resistance from the equipment.  Thickened blades, wear-resistant liners, or special materials are usually required. Although the conveying resistance is greater, the screw conveyor can still function stably under short-distance or medium-volume conveying conditions.

In some special working conditions, screw conveyors can also be used to convey semi-fluid or paste-like materials. For example, sludge, oil residue, pulp, sauces in food processing, and fermentation residues. These materials have high water content and strong viscosity, and are prone to adhering to the blades and the inner wall of the casing. To adapt to these material characteristics, a shaftless screw structure or special blade forms are usually adopted to reduce entanglement and blockage and improve conveying reliability.

 
From a chemical perspective, screw conveyors can transport generally inert materials, and with appropriate protective measures, they can also transport materials with certain corrosive properties, such as fertilizers, salts, and some chemical raw materials. For corrosive materials, the service life is often extended by using stainless steel, corrosion-resistant alloys, or adding anti-corrosion coatings to the inner surface of the equipment. At the same time, for toxic, irritating, or volatile materials, the good sealing performance of the screw conveyor effectively prevents leakage and ensures operational safety.

 
Furthermore, in terms of temperature adaptability, screw conveyors can transport both normal temperature materials and high or low-temperature materials within the design limits. Examples include high-temperature materials such as hot ash, hot slag, and hot sand, or cooled powders and granules. For high-temperature conditions, the heat resistance of the materials, thermal expansion, and protection of bearings and sealing parts usually need to be considered.

 
It should be noted that although screw conveyors have a wide range of applications, not all materials are suitable for use. For example, oversized materials, long-fiber materials that are easily entangled, and highly adhesive and easily hardened materials can easily cause blockages, increased wear, or excessive energy consumption if the design is improper. Therefore, in practical applications, the structure and operating parameters of the screw conveyor should be reasonably selected based on the characteristics of the material, such as particle size, humidity, fluidity, and abrasiveness.

Overall, screw conveyors can transport powdery, granular, small lump, and some semi-fluid materials, covering various fields such as grain, building materials, chemicals, metallurgy, and environmental protection. Through optimized design tailored to different material characteristics, the conveying range and reliability can be further improved.