Factors affecting adhesion in pneumatic conveying
Inpneumatic conveyingThe factors affecting adhesion in the process are divided into particle size, porosity and moisture, airflow velocity and roughness avoidance, flow field forces, and collision forces of obstacles.
1. The relationship between particle size and adhesion force. According to experience, the finer the powder, the easier it is to adhere. This is due to the increased adhesion force per unit mass and mechanical interaction effects when particles are small.
2. The porosity and moisture can be measured using the fracture method, and a decrease in porosity and an increase in moisture can increase adhesion.
3. In pneumatic conveying, sufficient separation caused by airflow velocity and well processed avoidance surfaces can reduce adhesion. Generally, the higher the airflow velocity, the greater the pressure on the avoidance surface, causing an increase in adhesion. At the same time, the separation force, namely the shear stress at the avoidance surface, increases almost with the quadratic relationship of the airflow velocity. The intersection of two lines is called the critical velocity. When the airflow velocity is below the critical value, adhesion persists. When the airflow velocity exceeds the critical point, the separation force is greater than the adhesion force, and adhesion is no longer produced.
For some low melting point oily materials, when the impact or friction is enhanced, the adhesion force caused by melting or oil spillage also increases sharply. Only within a certain range of airflow velocity, the separated gas is greater than the adhesion force and does not produce adhesion. When the airflow velocity increases, the adhesion phenomenon will become more severe due to the significant adhesion generated.
Pneumatic conveying system
4. The flow field force has a dispersing effect on the agglomeration between particles.
? ?(1) When accelerating rapidly in a uniform flow field, favorable dispersion interaction forces are generated between adjacent particles of different sizes in the condensed material.
? ?(2) In an uneven flow field with a velocity gradient, favorable dispersion interaction forces will be generated between adjacent particles in cohesive aggregates.
5. The conflicting force of obstacles, caused by the inertial force acting on a cluster of particles condensed by multiple particles, will collide with the obstacle with a certain conflict efficiency to achieve the goal of resolving the cluster.
influencePneumatic conveying systemThere are many factors that affect pneumatic conveying, and professional work still requires professionals to do it. If you have any questions about pneumatic conveying, please feel free to contact our experts and we will answer them one by one.