Air Transport Rquipment
Pneumatic conveying, also known as airflow conveying, is the use of the energy of the airflow, along the direction of the airflow in the closed pipe conveying granular materials, is a specific application of fluidisation technology. The main characteristics of pneumatic conveying are The main features of pneumatic conveying are large volume, long conveying distance and high conveying speed; it can be loaded in one place and then unloaded in many places. The structure of pneumatic conveying device is simple, easy to operate, and it can be used for horizontal, vertical or inclined direction conveying. In the process of conveying, the heating, cooling, drying and airflow classification of materials can also be carried out at the same time, such as physical operations or some chemical operations. Compared with mechanical conveying, this method consumes more energy, the particles are easy to be broken, and the equipment is also Easy to be abraded. Materials with high water content, adhesion or static electricity in high-speed movement are not suitable for pneumatic conveying.
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Air Transport Rquipment
Dilute-phase conveying: solids content is lower than 1-10kg/m³, operating gas velocity is high (about 18-30m/s), conveying distance is basically within 300m. As for the mature equipment material seal pump, the conveying operation is simple, no mechanical rotating parts, low conveying pressure, no maintenance.
There are no mechanical rotating parts, low conveying pressure, no maintenance and maintenance-free.
Dense-phase conveying: conveying processes with a solid content of 10-30kg/m³ or a solid-to-gas ratio of more than 25. The operating air speed is low, and the conveying is carried out with high air pressure. Now the mature equipment warehouse pump, conveying distance reaches more than 500m, suitable for long-distance conveying.
Suitable for long-distance conveying, but this equipment has more valves, pneumatic and electric equipment. The conveying pressure is high, and all pipelines need to be made of wear-resistant materials. Intermittent aerated tank type dense phase conveying. The particles are added into the pressure tank in batches, and then the tank is inflated and blown loose.
After air blowing, when the tank reaches a certain pressure, open the material valve and blow the granular material into the conveying pipe. Pulse conveying is a stream of compressed air into the lower tank, the material will be blown loose; another frequency of 20 ~ 40min-1 pulses.
20～40min-1 pulse compressed air flow blowing into the inlet of the conveying pipe, in the pipeline to form an alternating arrangement of small segments of the material column and small segments of the air column, through the air pressure to promote forward.
Negative pressure conveying: the pressure in the pipe is lower than the atmospheric pressure, self-absorption into the material, but must be unloaded under negative pressure, can be transported over a shorter distance; Advantages: equipment investment, load is small. Disadvantages: high flow rate, pipe wear
Serious wear and tear, wear holes can not be detected.
When thin-phase conveying is carried out in horizontal pipelines, the gas velocity should be high so that the particles are dispersed and suspended in the gas flow. When the air velocity decreases to a critical value, the particles will start to be deposited in the lower part of the pipe wall. This critical air velocity is called the deposition
Accumulation speed. It is the lower limit of the air velocity for horizontal transport of dilute phases. When the operating air velocity is lower than this value, a deposition layer occurs in the pipe, the cross-section of the flow path is reduced, and the air flow above the deposition layer still operates at the deposition velocity.
For upward pneumatic conveying in vertical pipes, the particles are dispersed and suspended in the gas stream at higher gas velocities. When the particle transport is constant, the gas velocity is reduced and the solids content in the pipe increases. When the gas velocity is reduced to a certain
When the gas velocity decreases to a certain critical value, the gas flow can not make the dense particles uniformly dispersed, the particles converge into a plunger, the phenomenon of surge, the pressure drop rises sharply. This critical speed is called choking speed, which is the lower limit of air speed when the dilute phase is transported vertically upwards.
This is the lower limit of gas velocity when the dilute phase is transported vertically upwards. For particles of uniform size, the deposition speed and the choking speed are roughly equal. But for materials with certain distribution of particle size, the deposition speed will be 2-6 times of the choking speed.
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