一.The basic principle and structure of the screw conveyor
Screw conveyor, as a kind of conveying equipment widely used in the industrial field, its working principle is that when the screw shaft starts to rotate under the driving device, the screw blade rotates with it, and the material moves forward along the surface of the screw blade as if it were an object pushed by a screw. In this process, the material is continuously conveyed along the set path.
Structurally, the screw conveyor is mainly composed of screw shaft, blades, casing, bearings, inlet and outlet, and other components. The screw shaft is the core component of the whole conveyor, which is usually made of high-strength steel pipe to ensure that it will not be deformed or damaged during long-time operation. The screw blade is the part that acts directly on the material, and the common blade forms are full-face type (solid type) and belt type. Full-face type blade is suitable for conveying dry and loose materials, such as grain, coal powder, etc., which can provide larger conveying thrust; belt type blade is commonly used for conveying viscous materials or materials with a certain degree of humidity, such as fertiliser, wet sand, etc., which can effectively avoid the sticking of materials on the blade.
The casing is the external protection structure of the screw conveyor, and also plays a role in guiding the flow of materials. The casing is generally made of welded steel plate with good sealing, which can prevent the material from leaking in the conveying process and reduce the pollution to the environment. At both ends of the casing, there are inlet and outlet ports, the material enters the conveyor through the inlet port, and is pushed by the screw blades and output from the outlet port.
The bearings are used to support the screw shaft to ensure that it can rotate smoothly. Common types of bearings are rolling bearings and plain bearings. According to the working conditions and load requirements of the conveyor, choose the right type of bearings to ensure the normal operation of the equipment.
二.The performance advantages of the screw conveyor
1.Structure and operation advantages
In the actual production process, the screw conveyor intermediate charging and discharging function shows great flexibility. Take chemical production as an example, in a continuous production line, it may be necessary to add all kinds of additives to the material being conveyed at different locations, and the intermediate feeding function of the screw conveyor can easily meet this demand. By opening a feeding port at a suitable position on the casing and using a special feeding device, the additives can be accurately added to the material being conveyed. The intermediate unloading function is also practical, in the material conveying process, if you need to take out part of the material in a specific location for subsequent processing, through the corresponding location of the discharge port, and equipped with a valve to control the discharge of the material can be realised to achieve the targeted unloading of the material.
It is worth mentioning that some screw conveyors also have two-way conveying function. This unique design makes the material can be in the same equipment according to the production demand in two opposite directions for conveying, greatly reducing the equipment footprint and investment costs.
2.Conveying Performance Advantages
Screw conveyor has significant advantages in conveying capacity and conveying efficiency. The size of its conveying capacity depends mainly on the diameter of the spiral blade, pitch, speed and material characteristics and other factors. Through reasonable design and adjustment of these parameters, the screw conveyor can achieve several tonnes or even dozens of tonnes of material conveying capacity per hour, which can meet the needs of different sizes of production enterprises. In some large cement factories, screw conveyor can convey a large amount of cement raw material and clinker per hour, which provides a strong guarantee for the efficient operation of the production line.
The conveying efficiency of screw conveyor is also very considerable. It can convey materials continuously, avoiding the waste of time caused by material loading and unloading and stopping. Moreover, because the material is moving along the surface of the screw blade in the conveying process, its trajectory is relatively stable, and there will be no accumulation or blockage of materials, thus ensuring the high efficiency of the conveying process.
In addition, the screw conveyor is also very adaptable to the material. Whether it is granular coal, ore, or powdered cement, flour, or small pieces of material, it can easily deal with. At the same time, according to different production requirements, the screw conveyor can be horizontal, inclined and even vertical conveying. In some factories or construction sites with complicated terrain, the installation angle of the screw conveyor can be flexibly adjusted to achieve precise conveying of materials at different heights and positions. In mining, it is often necessary to transport the ore from the shaft to the ground, vertical screw conveyor can play its advantage, the ore will be steadily lifted to the specified height.
三.The actual application of screw conveyor in various industries
1.Building materials industry
In the building materials industry, especially in the cement production process, from the preparation of cement raw materials to the packaging of finished cement, screw conveyor throughout. In the raw material preparation process, raw materials such as limestone, clay, iron ore and coal are crushed and then transported to the mill for grinding. By virtue of its stable conveying performance, the screw conveyor feeds these raw materials into the mill continuously to ensure the continuous grinding work.
In the cooling and conveying process of cement clinker, the high-temperature cement clinker is discharged from the rotary kiln, and then enters into the cooling machine for cooling, and then is conveyed to the clinker warehouse for storage through the screw conveyor. The sealing of the screw conveyor is particularly important in this process, which effectively prevents the clinker from coming into contact with the outside air too much during the conveying process, avoids the secondary oxidation of the clinker, and ensures the quality of the clinker.
When it is necessary to grind cement clinker with gypsum, mixing materials and so on in a certain proportion to make finished cement, the screw conveyor is responsible for precisely conveying these materials into the cement mill. In the packing of cement, the screw conveyor conveys the finished cement from the cement warehouse to the packing machine to achieve the automatic packing of cement. In the whole cement production process, the efficient operation of screw conveyor ensures the close connection of each production link and provides a strong guarantee for the stable production of cement.
2.Chemical industry
In the chemical industry, there are many kinds of materials with different properties, and the requirements for conveying equipment are also extremely strict. Take fertilizer production as an example, in the manufacturing process of fertilizer, it involves the conveying of various powdery and granular raw materials, such as liquid ammonia and carbon dioxide in the production of nitrogen fertilizers, phosphate rock and sulfuric acid in the production of phosphate fertilizers, as well as the mixing and conveying of various raw materials in the production of compound fertilizers. Screw conveyor can achieve stable conveying of these materials according to the characteristics of different materials by adjusting the shape of screw blades, pitch and other parameters.
In the production of plastic granules, from the batching and mixing of plastic raw materials to the conveying of granules after granulation, screw conveyor plays an important role. In the batching stage, different kinds of plastic raw materials and additives need to be mixed according to the precise proportion, the intermediate feeding function of the screw conveyor enables various raw materials to be accurately added to the conveying process, which ensures the uniformity of mixing. After granulation, the plastic granules are transported to the packaging equipment or storage warehouse through the screw conveyor. As the plastic granules have certain electrostatic adsorption, it is easy to produce agglomeration phenomenon in the conveying process, and the fully enclosed design and reasonable conveying speed of the screw conveyor effectively avoid this situation and ensure the conveying quality of plastic granules.
3.Grain industry
In the grain storage link, whether it is wheat, rice, corn and other grains into the warehouse, or in the warehouse dumping operations, screw conveyor can efficiently complete the task. When grain is harvested, it needs to be conveyed from the transport vehicle to the granary for storage. Screw conveyor can be flexibly arranged to convey the grain from different positions to the specified height and position in the silo, so as to realise the rapid storage of grain. Moreover, its good sealing performance can effectively prevent the grain from being contaminated by external dust and impurities in the conveying process, ensuring the cleanliness of the grain.
In the process of grain processing, screw conveyor is indispensable. From the cleaning of the original grain, in addition to impurities, to rice milling, milling and other processes, are inseparable from the screw conveyor material transport. The stable operation of the screw conveyor ensures the efficient and continuous operation of the grain processing production line, providing a reliable guarantee for the production of grain processing enterprises.
4.Power industry
In the electric power industry, especially in thermal power plants, screw conveyors are mainly used to handle fly ash, coal slag and other materials. Fly ash is a fine-grained material produced after coal combustion, which is characterised by large quantity and fine particle size. The screw conveyor can transport the fly ash collected by the electrostatic precipitator from each electric field to the ash depot for storage. Its fully enclosed conveying method effectively avoids the dust problem of fly ash in the conveying process and reduces the pollution to the environment.
Cinder is the solid residue after coal combustion, which needs to be conveyed from the bottom of boiler to the slag yard for treatment. With its strong conveying capacity and adaptability to lumpy materials, the screw conveyor can smoothly convey the coal slag from the bottom of the boiler to the designated place. In some power plants, the screw conveyor will also be used to comprehensively utilise the fly ash and coal slag, such as fly ash conveyed to the building materials factory as raw materials for the production of cement and concrete, and coal slag conveyed to the brick factory for the production of bricks and so on. Screw conveyor in the power industry, not only to achieve the effective treatment of waste, but also for the recycling of resources to provide a convenient condition.
5.Mining industry
In the mining industry, screw conveyor is often used to transport ore, concentrate and other materials. In the ore mining process, the ore mined from the underground needs to be transported to the ground for subsequent processing. Screw conveyor can be used for horizontal, inclined or vertical conveying according to the topography and mining layout of the mine, to lift the ore stably from underground to the ground, or to transfer materials between different workshops on the ground. Its sturdy structure and wear-resistant features enable it to adapt to the harsh working environment of mines and ensure the continuity of mine production.
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