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The wide application of pneumatic conveying

     Pneumatic conveying is used for conveying bulk materials. Compared with traditional mechanical and vehicle transportation, it has higher transportation efficiency. The device has a simple structure and is easy to maintain and manage.

Therefore, pneumatic conveying has been widely used in industries such as thermal power generation, steel smelting, cement loading and unloading, storage, transportation, and powder engineering unit operations. In addition, with the increasingly strict environmental requirements of the country, improving industrial dust pollution will greatly promote the sustainable development of the pneumatic conveying industry.

From the emergence of pneumatic conveying to its widespread application, it has undergone research changes from dilute phase to dense phase, promoting the sustainable development of pneumatic conveying. As for the research on powder pneumatic conveying at home and abroad, most of it still focuses on short distance dense phase pneumatic conveying, mainly to solve the problem of close distance pneumatic conveying within or between factories. Long distance pneumatic conveying systems, such as ash removal pneumatic conveying systems in power plants, are typically implemented using multi-stage relays or series connected systems due to technological limitations. However, in situations where on-site conditions are limited or land acquisition is difficult, it is still difficult to achieve long-distance pneumatic transportation. Therefore, there is an urgent need to develop new technologies for long-distance pneumatic conveying.

1. Research status of long-distance pneumatic conveying technology
The two key factors affecting remote pneumatic conveying of powders are energy consumption and stability. Energy consumption refers to the energy consumption of powder and transported gas in pipelines, i.e. pressure drop; Stability is the smoothness of the conveying process. Unstable transmission may cause blockages and prevent the transmission from proceeding. Therefore, studying long-distance pneumatic conveying of powders is to investigate how to reduce energy consumption and ensure the stability of conveying.

2. Energy consumption
Energy consumption refers to the energy consumption (pressure drop) during the pneumatic conveying process. Reducing energy consumption can reduce the pressure drop per unit of conveying length and extend the conveying distance. The pressure drop in pneumatic conveying is related to many factors, with the most complex and variable being the properties of the conveyed material. Different types, particle sizes, and powders have different pneumatic conveying rules. For the same powder, particle size and distribution, as well as moisture content, are the main factors affecting the flowability of the powder. The smaller the particle size, the wider the distribution, the higher the water content, and the poorer the flowability, making pneumatic transportation more difficult.
In long-distance pneumatic conveying pipes, the movement of solid particles is both rolling and suspended, and at the same time, solid particles collide with solid particles and wall surfaces. The rotation of solid particles also generates lifting force. Fully considering these issues is very complex. Therefore, many researchers have also studied the mechanism of pneumatic conveying through numerical simulations during the experimental process.

3. Stability
The apparent gas velocity during long-distance pneumatic transportation along the pipeline increases, and the gas-solid two-phase flow pattern also changes accordingly. When the speed of gas transportation exceeds the boundary of dense phase steady-state transportation, an unstable sand dune flow will be formed, characterized by increased pressure fluctuations and continued decrease in the speed of gas transportation. The material will accumulate along the pipeline until it is blocked. Therefore, studying the stability of powder pneumatic conveying and maintaining a stable state of the conveying system is of great significance for achieving long-distance pneumatic conveying.
The demand for long-distance transportation is increasing, therefore specialized research is needed for long-distance powder pneumatic transportation. To solve the long-distance pneumatic conveying of powders, it is necessary to comprehensively consider energy consumption and the stability of the conveying process, not only to meet the pressure requirements of the conveying, but also to ensure that the conveying is not blocked. Whether it is reducing energy consumption during transportation or ensuring stable transportation without blockage, the gas-solid two-phase flow mechanism and friction characteristics in pipelines should be thoroughly studied.
With the arrival of the era of environmental protection, dust pollution will become the main target of strict investigation. Therefore, in the production process, efforts should be made to minimize dust pollution and generate dust.