Difference between Centrifugal and positive displacement pulp pumps

The difference between Centrifugal pulp pumps and positive displacement pulp pumps are as followings:

Working principle

Centrifugal pulp pump: relying on high-speed rotation of the impeller to produce centrifugal force, so that the pulp in the impeller is thrown from the center to the outer edge, decelerating and pressurizing in the pump shell, the center of the impeller forms a low pressure area, so that the pulp is constantly sucked in. 

Positive displacement pulp pump: transport pulp through periodic changes in the working volume of the pump, such as reciprocating by the movement of the piston to change the volume to suck in pulp.

Structure characteristics

Centrifugal pulp pump: the structure is relatively simple, mainly composed of pump body, impeller, shaft seal and so on. The shape and size of the impeller are diverse, and the flow channel is generally large, but compared with the positive displacement pump, the passage of impurities such as fibers is slightly worse.

Positive displacement pulp pump: the structure is usually more complex, reciprocating piston, plunger, cylinder and other parts. Rotary Type has gear, screw and other rotating parts, and a sealed chamber is formed between these parts and pump body to transport pulp.

Features 

Flow characteristics: centrifugal pulp pump flow is related to pressure, when the pressure changes, the flow will change accordingly, and the pressure increases and the flow decreases within a certain range; positive displacement pulp pump flow is basically independent of pressure, as long as the speed is constant, the flow is more stable.

Head and pressure: centrifugal pulp pump can provide relatively low pressure, but the flow rate is large; positive displacement pulp pumps can produce high pressure, suitable for overcoming large resistance or in high pressure environments to transport pulp.

Application scenarios

Centrifugal pulp pump: in the pulping, washing and other links of the paper mill, it is commonly used in the scene where the demand for pulp flow is large and the pressure requirement is not particularly high, and it is also suitable for pulp transportation which is not sensitive to shear force.

Positive displacement pulp pump: In the need to accurately control the flow of pulp, such as metered addition, dosing and other links are more used, but also for high concentration, high viscosity pulp transport, such as the feeding pump of the high consistency crusher in the waste paper pulping.

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