Air slide transportation has a history of more than 100 years as the transportation of bulk materials. Compared with conventional mechanical transportation and vehicle transportation, it has many advantages, such as high transportation efficiency, simple equipment structure, convenient maintenance and management, easy automation, and environmental protection. Unique advantages.
Therefore, air slide conveying has been widely used in the unit operation of loading, unloading, storage and transportation, and powder engineering in thermal power, steel smelting, and cement industries. In addition, with the increasingly strict environmental protection requirements in the world, improving the status quo of industrial dust pollution will greatly promote the continuous development of the pneumatic conveying industry.
Energy consumption of Air Slide conveying
One of the key factors affecting the long-distance pneumatic air slide transportation of powder is energy consumption. What is the energy consumption of air slide transportation: the energy consumption of air slide transportation is the energy consumption of the powder moving in the pipeline with the conveying gas, that is, the pressure drop.
Why reduce the energy consumption of Air Slide conveying
Energy consumption is the power consumption (pressure drop) in the pneumatic Air Slide conveying process. Reducing energy consumption can reduce the pressure drop per unit conveying length and extend the conveying distance.
Conveying material
The pressure drop of pneumatic air slide conveying is related to many factors, among which the most complex and changeable is the nature of the conveyed material.
- Different types, particle sizes, and moisture of powder have different pneumatic conveying laws. For the same powder, particle size, distribution, and moisture content are the main factors affecting the fluidity of the powder.
- The smaller the particle size, the wider the distribution, the higher the moisture, the poorer its fluidity, and the more difficult the pneumatic conveying.
Three types of materials conveyed by an air slide
The interaction between the material and the gas depends on the average particle size distribution and particle density of the material, and the material is divided into 3 categories:
- PC1: such as fly ash, cement, and pulverized coal, it can smoothly transition from dilute phase flow to dense phase flow;
- PC2: such as plastic balls, wheat, dilute phase, instability, and plunger flow may occur during transportation;
- PC3: (coarse concentrate), only dilute phase can be used.
Studies have shown that particles with a small average particle size are easy to move with the gas due to their strong followability; while particles with a large average particle size are easily deposited at the bottom of the tube due to gravity, increasing the friction with the tube wall. Therefore, under the same conveying pressure difference, the conveying solid-gas ratio decreases with the increase of the average particle size.
4 characteristics of air slide conveying different materials
- The fine particles and the gas have strong followability and are easy to be carried, while the coarse particles are easy to deposit to the bottom of the pipe due to the action of gravity, and more gas is required to transport the same amount of material;
- Influence of pulverized coal moisture content on pressure drop and transportation stability: when the moisture content increases to 6%, it is difficult to convey, and the pipe is often blocked, but the lower the moisture content, the greater the pressure loss;
- The effect of pipe diameter on the resistance of two-phase flow: the resistance p/L is inversely proportional to the pipe diameter Dn at a certain flow rate, that is, the larger the pipe diameter, the smaller the resistance loss; but the larger the pipe diameter, the higher the particle deposition rate and the more stable the transportation. reduce;
- Resistance characteristics: with the increase of apparent gas velocity at the same mass flow rate, the kinetic energy pressure loss of the elbow increases, and the frictional pressure loss decreases; under the same apparent gas velocity, the mass fraction of pulverized coal increases, and the frictional pressure loss increases; There is no obvious direct relationship between the average particle size of pulverized coal and the mass flow rate of pulverized coal, and it decreases slightly with the increase of superficial gas velocity.
Epilogue
The demand for long-distance transportation is increasing, so special research on long-distance pneumatic air slide transportation is required.
To solve the long-distance pneumatic air slide transportation of powder, it is necessary to comprehensively consider the energy consumption and stability of the transportation process, not only to meet the pressure requirements of transportation but also to ensure that the transportation is not blocked.
Whether it is to reduce the energy consumption of the conveying process or to ensure that the conveying process is smooth and not blocked, the mechanism of gas-solid two-phase flow in the pipeline and the friction characteristics in the pipeline should be deeply studied.