pneumatic conveying of solids
Pneumatic conveying of solids
- Solids conveying is a chemical unit operation that is important in chemical production. In chemical production, many kinds of raw materials, semi-finished products and finished products are in a solid state and need to be transported from one place to another.
- The transportation of solid materials must ensure efficiency and maintain the quality of the materials. In the solid conveying area, under the action of the rotating screw, the solid polymer material added from the hopper is transported and compacted forward through the friction between the inner wall of the barrel and the surface of the screw.
- In the solid conveying area, due to the lower temperature, the material still remains in a solid state and is gradually solidified.
- At the same time, the gas mixed in the loose material is eliminated.
pneumatic conveying of solids
Pneumatic conveyor working principle
- The working principle of the pneumatic conveyor is to use the energy of air flow to transport granular materials in the direction of air flow in a closed pipe.
- This process is a specific application of fluidization technology, which uses pressurized air as the transport medium to transport materials from one place to another.
- Basic Principle: Pneumatic conveyors use the energy of air flow to transport granular materials from one place to another through closed pipes.
- This conveying method can be carried out in horizontal, vertical or inclined directions, and during the conveying process, physical operations such as heating, cooling, drying and air flow classification of materials or certain chemical operations can be performed simultaneously.
- System composition: Pneumatic conveying system usually consists of feeder, conveying pipeline, separator and material warehouse.
- The feeder is responsible for feeding materials into the conveying pipeline, which is the main channel for material transmission.
- The separator is used to separate the transported gas and materials, and the material warehouse is the storage location of the materials.
pneumatic conveying of solids
Dilute phase pneumatic conveying system calculation
- The calculation of dilute phase pneumatic conveying system mainly involves the determination of parameters such as gas flow rate, pipe diameter, conveying speed and pressure drop.
- Gas flow calculation
- Definition: Gas flow refers to the flow of gas through the pipeline system, in cubic meters/hour.
- Key parameters: Q (gas flow rate), A (cross-sectional area), V (gas flow rate), Y (transport rate).
- Explanation: The calculation of gas flow rate is the basis for the design of dilute-phase pneumatic conveying system and directly affects the conveying efficiency and cost.
- Pipe diameter calculation
- Definition: Pipe diameter refers to the inner diameter of the delivery pipe, in millimeters.
- Key parameters: D (pipe diameter), Q (gas flow rate), V (gas flow rate).
- Note: The selection of pipe diameter requires comprehensive consideration of gas flow, transportation distance and speed, as well as cost factors.
- Conveying speed calculation
- Definition: Conveying speed refers to the average speed of materials in dilute phase pneumatic conveying, in meters per second.
- Key parameters: V (conveying speed), Q (gas flow rate), A (cross-sectional area), Y (conveying rate), ρ (material density).
- Note: The calculation of the conveying speed needs to consider the physical properties of the material and the gas flow rate, which has an important impact on the conveying efficiency and stability.
- Pressure drop calculation
- Definition: Pressure drop refers to the pressure drop caused by frictional resistance, pipeline bending and other factors in the gas transportation pipeline.
- Key parameters: ΔP (pressure drop), f (friction coefficient), L (pipe length), D (pipe diameter), Q (gas flow rate), A (cross-sectional area).
- Note: The calculation of pressure drop is crucial for evaluating the energy consumption and efficiency of the conveying system, and the comprehensive impact of multiple factors needs to be considered.
pneumatic conveying of solids
What are the different modes of pneumatic conveying?
- There are four main modes of pneumatic conveying: suction type, pressure type, mixed type and flow type.
- Suction pneumatic conveying: This mode uses air flow with a pressure lower than atmospheric pressure to convey materials. Its advantages include a simple feeder, the ability to convey from multiple places to one place, and the ability to convey from low and narrow places. However, the conveying distance and conveying volume of suction pneumatic conveying are limited, the sealing performance is required to be high, and the conveyed air needs to be processed before it can enter the fan and be exhausted.
- Pressure-feed pneumatic conveying: Contrary to suction conveying, pressure-feed pneumatic conveying uses air flow with a pressure higher than atmospheric pressure to transport materials. Its main advantages include the ability to transport from one place to multiple places, long transport distance, high height, large transport capacity and high efficiency. However, pressure-feed pneumatic conveying consumes a lot of power, has high sealing requirements, and has a complex feeder structure.
- Hybrid pneumatic conveying: This mode combines the characteristics of suction and pressure conveying. It can not only suck materials from multiple places, but also transport materials to multiple places, and the conveying distance is long. However, the hybrid pneumatic conveying device is more complex, and the passage of material-containing gas through the fan will accelerate the wear of the fan.
- Flow pneumatic conveying: This is a modified form of pneumatic conveying. The material exhibits fluid-like properties during the conveying process. Its advantages include good maneuverability, high speed and stability, good continuity, and efficient containerization. Streaming pneumatic conveying is suitable for conveying large quantities of materials.
