Fluidization of dilute phase pneumatic conveying
? ? ? In general, the flow states of gas-solid fluidization are divided into bubbling fluidization, slug fluidization, and turbulent fluidization. There is a type of fluidized dilute phase transportation in gas-solid vertical conveying operations. Its flow state includes dilute phase transport, rapid fluidization or turbulence, slug flow/gasBubble flow, bubble free dense phase flow, and packed bed flow. In actual circulating fluidized beds and conveying risers, due to equipment limitations, it is usually impossible to achieve a state lower than that of rapid fluidization.
? ? ? Actual flow diagrams, including homogeneous dilute phase flow and core ring dilute phase flow (with obvious differences)Lateral gradient but smaller axial gradient) and rapid fluidization (with both lateral and axial gradients). The boundary between rapid fluidization and fluidized dilute phase conveying is set by the flow velocity, at which uniformly suspended particles begin to settle at the bottom of the conveying lineThe mechanism of regional aggregation and the transition from rapid fluidization to dense phase flow is related to column and particle diameter.A fluidized bed consists of two phases: solid and fluid (gas or liquid). If the fluid flows through a stationary solid layer at sufficient velocity (fluidization velocity), the layer is released and individual solid particles enter a suspended state. This state is called fluidization. Formed in this wayFluidized beds are similar to liquids in terms of flow and thermodynamics. If the speed is too high, the particles are expelled from the liquefaction layer. Start hydraulic or pneumatic conveying.
?Fluidized bed transport may occur in the following forms:
1： Homogeneous fluidized bed
Fluidized dilute phase transportation
? ?As the fluid velocity increases, the volume tends to become uniform and the fluidized bed expands. Solid particles are uniformly distributed throughout the entire layer. In reality, this type of travel can only be observed when an equal amount of particles are used in the liquid.
2： Heterogeneous fluidized bed
? ? ? The grading or sorting process is carried out in a fluidized bed. Especially heavier particles gather in lower areas. When using gas as a fluid, a bubble liquefaction layer almost always occurs. There is no solid in the bubble. Smaller bubbles merge during the process of reaching the water surfaceAnd form larger bubbles. Break on their surface. The surface of a fluidized bed looks like boiling liquid. Fluidized dilute phase transport involves the transfer of heat and substances between particles due to the large contact surface between solids and fluids, as well as the flow of fluids and particles themselvesThe body has gained motivation. One application of it is in fluidized beds made by crushers, where the principle of fluidized beds is low nitrogen content and the emission limit of oxides can be reached.
? ? ? ?InPneumatic conveying systemIn the fluidization of a dilute phase pneumatic conveying systemThere are very complex conveying states involved. If you need pneumatic conveying equipment or design pneumatic conveying systems, please feel free to consult us!