Application of Online Density Meter in Coal Preparation Plants

Differential pressure online slurry density meter has no radiation source, can directly measure and display the real-time density value of the medium. The liquid density meter has the characteristics of anti-vibration, small measurement error, simple maintenance, and so on. The traditional differential pressure liquid density meter utilizes Archimedes' principle, which works on the principle that the pressure generated by a liquid column of a certain height is directly proportional to the density of the liquid, i.e.: P = ρgh. P is the pressure of the liquid column; ρ is the liquid density; g is the acceleration of gravity for the measurement; and h is the height of the liquid column.

The pressure part of the online liquid density meter consists of two membrane box sealing devices and a differential pressure transmitter. Box sealing device from different heights of the pipeline through the pressure conduit directly on the pressure transmitter, and then the sensing element on the pressure transmitter will be the pressure difference into a voltage signal, the voltage signal through the terminal equipment according to the differential pressure value up to a certain vertical distance to calculate the density of the medium, and finally converted into 4 ~ 20mA current signal access to the PLC.

The coal beneficiation plant of heavy media suspension in the material pipe flow rate is generally very fast, will cause large measurement errors and instability, or even can not be measured. So, it is necessary to control the flow rate. To control the flow rate, you can consider the bypass installation, which facilitates the selection of a small pipe diameter digital chemical density meter and saves material costs. The liquid slurry density meter measuring chamber and diaphragm with a sufficient distance between the flared arc welding, the benefits of this structure will not only directly scour the diaphragm to ensure that the life of the digital density meter, but also prevent particles of the media or blistering set of errors brought about. During the installation of the digital density meter, to ensure the production operates normally and does not affect the use of the existing chemical density meter, the original measurement of the magnetic content of the pipeline needs to be removed. After measurement, production, and installation of a new pipeline, the differential pressure transmitter will be installed.

Differential pressure online liquid density meter is to measure the pressure difference of the measured medium, that is, △ P = ρg △ h, by the signal converter operation, was converted to 4 ~ 20mA signal output to the PLC. use PLC internal PID operation for automatic adjustment, by receiving the field density meter return 4 ~ 20mA current signal and external set density value for comparison, the output of the 4 ~ 20mA signal to drive the stepper valve electrical The actuator action controls the switch of the valve. When the density measured by the digital density meter is higher than the set density, the control stepping valve opens, the clean water enters 313 barrels, and the density decreases; when the density measured by the online digital slurry density meter is lower than the set density, the stepping valve operates, the valve closes, and the density rises to the set density to reach the automatic equilibrium. The automatic function of PLC realizes the automatic tracking of density without intervention, which ensures the qualified heavy medium suspension required for production.