What Is a Bulk Solid Flowmeter?
A bulk solid flowmeter is a device designed to measure the flow rate of aggregates (such as powders or grains).
Although each particle of powder is a solid, it can behave like a fluid when moving in large aggregates. A bulk solid flowmeter utilizes this property of powders to capture and measure the flow rate of moving powder, similar to how fluid flow is measured.
Bulk solid flowmeters find application in various situations, depending on the type of powder and the measurement site.
Uses of Bulk Solid Flowmeters
Situations involving the measurement of large quantities of powder or particles are encountered in various industrial fields.
Bulk solid flowmeters are employed across a wide range of industries to measure and control raw materials and products. They are used in the food industry for items such as flour, milk powder, cocoa, sugar, and salt; in the agriculture and livestock industry for agricultural chemicals, fertilizers, feed, wheat, and rice; in the construction and engineering industry for materials like cement, slaked lime, incinerated ash, and sand; and in the chemical industry for pigments, lead oxide powder, and calcium carbonate. Bulk solid flowmeters are used to measure, control, and proportionally blend materials in various industries.
Depending on the substance being measured, there are situations where volume flow rate control is required, and others where mass flow rate control is necessary. There are flowmeters capable of handling both types of measurements.
Principles of Bulk Solid Flowmeters
There are several types of bulk solid flowmeters, each operating on a different principle.
- Capacitance Type
Powder is allowed to fall freely between electrodes consisting of two opposing metal plates, which act as capacitors. As the insulating powder passes between them, the capacitance increases in accordance with the relative permittivity of the powder and the flow rate. By continuously measuring the capacitance between the electrodes, the flow rate of the powder can be measured in real-time. This type of flowmeter can only measure free-fall bulk solid flow. - Microwave Type
A bulk solid flowmeter that utilizes the Doppler effect. A sensor is installed in the conveying pipe, and it transmits microwaves while receiving the reflected microwaves. The frequency of the returned microwaves changes due to the Doppler effect caused by the powder particles passing through the pipe. The changed frequency is proportional to the number of particles, and the amplitude of that frequency is proportional to the average volume of the particles. Consequently, the powder flow rate can be calculated from the frequency and amplitude. This type can measure both free-fall and pneumatic powder flow rates. - Coriolis Type
When powder is placed in a weighing wheel rotating by a motor, centrifugal force causes the powder to move outward with the wheel. During this movement, a Coriolis force is generated in the circumferential direction opposite to the direction of rotation. This Coriolis force is proportional to the mass of the powder, allowing the mass flow rate of the powder to be determined by measuring the Coriolis force. This type can only measure pneumatically conveyed powders.