How to avoid the problem of material hanging on the wall during pneumatic conveying?
During the pneumatic conveying process, some materials may adhere inside the pipeline, reducing the flow area of the pipeline and even potentially blocking it. The reasons for material adhesion in pipes can be roughly divided into the following six categories:
(1) Materials with low melting points or softening points, such as paraffin, thermoplastic resins, sulfur, etc., will melt, soften, and bond when heated or compressed during transportation.
(2) Plant seeds or other oily materials containing oil, when heated or compressed during transportation, will produce oil secretions that can cause adhesion to pipelines.
(3) Fine materials, especially those with particles smaller than 1um, such as lead, carbon black, titanium oxide, etc., are prone to adhere to the pipe wall.
(4) Materials with hygroscopicity or water solubility, such as salts, adhere to the pipe wall by relying on surface moisture.
(5) Charged materials, such as synthetic resin powder, grain powder, etc., have strong adhesion due to static electricity, and are prone to pipe wall sticking.
(6) The adhesion of materials that adhere to the pipe wall due to mechanical mutual restraint, such as fibers, is related to the surface shape of the particles themselves and the morphology of the pipe wall.
Based on the reasons for material adhesion inside the pipe, we can take some measures to prevent pipe wall sticking:
(1) Choose a reasonable air flow rate. The adhesion strength of different materials varies at different airflow speeds. Therefore, selecting a reasonable air flow rate based on the specific characteristics of the materials can help reduce the occurrence of material adhesion.
(2) Use smooth inner wall processing for conveying pipelines. The smooth inner wall of the pipeline can effectively reduce the restraint and friction between the material and the pipe wall, making it difficult for the material to adhere or quickly carried away by the airflow after adhesion.
(3) According to the pneumatic conveying requirements of different materials, specific requirements are proposed for the temperature, humidity, pressure value, static electricity content, etc. of pipeline conveying to reduce the possibility of material sticking to the wall.
(4) Different requirements should be put forward for the particle size and particle size distribution, physical and chemical properties of materials. For example, the above-mentioned ultra-fine materials may not be suitable for pneumatic conveying.
(5) Dry the material before pneumatic conveying. For materials with high moisture content, the drying process is very important.
(6) Use large-diameter and short distance conveying. When pneumatic conveying of materials that are prone to sticking is unavoidable, it is recommended to consider conveying pipelines with large diameters and choose short distance conveying as much as possible to reduce the number of bends and minimize the degree of material sticking to the wall.