Sludge

Microwave dry matter measurement Valmet - Metso

The Valmet Total Solids Transmitter (Valmet TS) sensor uses dry mass measurement microwave technology. The device is used to measure the total content of solids and thus contributes to easier control of technological processes. The basic technical parameter measured by the sensor is the time of flight of a wave of the appropriate frequency in the tested medium. The time of flight depends on the dielectric permittivity of the given medium. In the case of organic substances, it is practically constant, but changes with the change in water content. Therefore, the change in dielectric permittivity allows for conclusions about the content of solids in the tested medium. By performing measurements in the flow, it is possible to obtain higher accuracy and eliminate the risk of clogging the installation.

The sensor installation is extremely simple (between flanges) and does not require major modifications to the installation. The wide range of sensor sizes allows the device to be adapted to virtually any pipeline diameter.

Advantages of microwave measurement

Previously used optical sensors are easily contaminated and lose their accuracy due to calcium compounds being deposited on the sensors. Microwave technology has eliminated this drawback and is superior to other solids measurement methods in many ways:

high accuracy – in accordance with laboratory measurements,
changing the composition of solids does not affect the measurement results,
no moving parts, so no maintenance work is required,
resistance to contamination – any contamination on the ceramic measuring antenna does not affect the obtained results,
resistance to caustic and corrosive substances.

Scope of application

Valmet sensors enable the achievement of an optimal method of controlling wastewater treatment processes. Due to the possibility of achieving significant financial savings and the fact that within the framework of the technological processes carried out in the wastewater treatment plant, the aim is to achieve the assumed values of the dry mass level, Valmet sensors are used from the primary settling tank stage to the dewatered sludge.

Proven technology

Valmet microwave solids sensors have been used for over a decade in process measurements in the most demanding applications. The measurement data obtained is not only accurate but also repeatable. It is not affected by changes in process conditions, type of raw materials used or flow rates. Total solids measurement results obtained with microwave sensors are characterized by exceptional accuracy and stability.

Thanks to the use of reliable Valmet sensors for continuous on-line measurements of dry mass content, we can dispense with laboratory analyses as a basic measurement. Laboratory analyses are used only to verify the sensor's operation and are treated as supplementary measurements. Additionally, on-line measurement allows the use of current density data in control and SCADA systems, which significantly facilitates the setting of sewage treatment plants or incinerators.

For more information, please see the pdf file.