Dust Measurement

Multifunctional devices for continuous and mobile applications for industrial and public sectors

There is dust everywhere in our environment. Industrial processes are the reason for dust and because of the general population growth dust particles continue to increase. The permanent control of dust emissions is becoming more and more important. Especially considered worldwide the potential and the necessity are high. Country-specific, legal conditions specify the compliance with limit values for certain plants.
All dust monitors are developed by Dr. Födisch technical-team and all monitors are tested and calibrated in their own dust channel.

For emissions and pollution monitoring Dr. Födisch provides dust measurement technique for legally required and process-related measuring tasks for the following applications:

1. Fine Dust
2. Filter Monitoring
3. Dust Concentration
4. Mobile Dust Measurement

1) Fine Dust

The air is the elixir of life. However, the air contains impurities, whose composition and concentration vary depending on the location. Various researches have shown that the fine dust particles in the air are damaging to the heart, lungs and brain. For measurement is often used complex and expensive measurement technology. Thanks to the compact fine dust sensors of Dr. Födisch Umweltmesstechnik AG this is now history. These are a low cost measuring devices for industrial applications.

Whether the application is for outdoor, indoor, stationary or mobile - the device handling is easy, the measurements are precise and independent from the weather conditions. By means of preconditioned air the particulate matter content of the air is measured every two seconds. By WLAN, the the devices can be linked to other air quality / climate sensors to achieve an efficient, meaningful environmental monitoring. There are many benefiting advantages, for example the analysis of ambient air for particulate matters at workplaces.

2) Filter Monitoring

A qualitative dust measurement, for example by triboelectric filter monitoring, includes both the monitoring of the clean gas dust content after dust collectors as well as the evaluation of the status of the exhaust gas cleaning systems.The signal generation is based on the triboelectric measuring principle. In other words the charge exchange between the probe and the streaming as well as the bouncing dust particles is carried out.

According to the triboelectric measuring principle the filter monitoring device will be installed as in-situ measuring device in the clean gas pipes after the dust collectors. Devices are suitable for monitoring baghouse-, envelope- and cartridge filters and centrifugal separators (cyclones).There are more than 10,000 pcs of Dr. Födisch AG filter monitor devices operating worldwide i.a. in the food processing or cement industries, in the metal- and woodworking and chemical industries.

3) Dust Concentration

Devices used for the continuous dust measurement register in the wider sense the physical changes caused by the particles in the measuring system converting them into electrical signals. For that the measured object can be analysed directly in exhaust gas channel (in-situ measurement) or a partial volume flow is collected and fed into a measuring device (extractive sampling).

As result of the in-situ techniques, the measurement signals derive from the direct interaction of light or a triboelectric probe with the dust particles in the exhaust gas channel. For evaluation the scattered light or the absorbance of a transmitted light beam respectively triboelectricity can be used.

The in-situ measuring devices are only suitable for the measurement of dust in dry gases.

In case of wet or saturated with water vapour gases, the existing water droplets and aerosols create also light scattering effects, which distort the measurements results. Therefore in these cases the extractive measurement technique should be selected. The basis of the extractive methods constructs a preferably isokinetic partial flow extraction from the main gas flow. As measuring principles the scattered light measurement or the triboelectric measurement can be carried out.

The process-related restrictions have substantial influence over the choice of the measurement method.

Periodic dust concentration measurements are usually used as a standard reference method (gravimetric) for calibration of continuous dust concentration measuring devices.

4) Mobile Dust Measurement

The measuring of dust emissions can be carried out discontinuously or continuously depending on the requirements. 

Periodic measurements are applicable only to a limited sampling for the determination of emissions behaviour on site. However, it has to allow conclusions about the continuous behaviour of the system and take into account possible seasonal variations of the measured air pollution.

The reasons for this may be diverse:

• acceptance tests (warranty certificate)
• measurements made to verify compliance with the emission limits
• control measurements for the determination of the system status or when complaints are made
• measurements to initiate an approval process (for example extensions, remodifying etc.)
• measurements in the context of self-monitoring, in case of malfunctions, in the context of safety inspections
• measurements of the emission declaration
• measurements for functional testing or calibration of continuous emissions measurement systems
• measurements to analyse the cause of a particular emission behaviour
• measurements to forecast the emission behaviour in certain operating states