Since the application range of the pneumatic conveyor is very closely related to the physical properties of the material being conveyed, the effects of several main material characteristics on the application range of the pneumatic conveyor are analyzed below.
(1) Granularity of materials. The particle size of the material is too large, and it is easy to be blocked in the feeding device, so that the material cannot automatically enter the feeding pipe. Therefore, the particle size is generally not greater than 50mm, or the particle size of the specified material should not exceed 0.3 to 0.4 times the diameter of the conveying pipe.
(2) Bulk density of materials. The bulk density of the material greatly affects the structural size and energy consumption of the pneumatic conveyor. Because with the increase of the material packing density, the air velocity in the pipe must be increased, so that the power consumption increases and the pipe wall wear is accelerated. Therefore, pneumatic conveyance is not suitable for materials with large bulk density.
(3) The humidity of the material. The humidity of the material has a great relationship with the reliability of the pneumatic conveyor. Excessive humidity will not only destroy the loose nature of the materials, but also the materials will adhere to the inner walls of the device components, which will lead to uneven supply, increased energy consumption, reduced transport capacity, and even block the entire system. Therefore, for various materials, it is necessary to determine the ultimate humidity that will not be damaged during transportation.
(4) Grindability of materials. The so-called abrasiveness refers to the abrasiveness of sports materials to other objects. The size of the abrasiveness depends on the hardness, surface characteristics and shape of the object particles, and it affects the power consumption and service life of the pneumatic conveyor.
(5) Material temperature. At a certain concentration and temperature, the combustible dust of the conveyed material will produce a dust explosion, causing serious accidents. Therefore, during pneumatic conveying, the temperature of the material must not exceed its ignition point (generally lower than 400 ° C, otherwise inert gas should be used instead).
At present, the port widely uses a pneumatic conveyor that uses a high-speed airflow at a speed of about 10-30m / s in the pipe to transport the material in a suspended state. However, its energy consumption is large, and the working members wear quickly. Therefore, increasing the mixing ratio of materials in the air and reducing the speed of the conveying airflow are effective ways to overcome the above disadvantages. Some new types of pneumatic conveyors are being developed. They are pneumatic conveyors that transport high-concentration materials under the conditions of high mixing ratio and low air velocity (usually only 4-6m / s).