Incinerating plants for industrial and toxic waste are subject to strict exhaust emission standards. The emitted values of pollutants must be ascertainable and must not exceed specific limits. Hoechst AG and Hoechst Trevira GmbH & Co KG use Höntzsch vortex flow sensors in their Offenbach factory for determining the amount of flue gas. The vortex flow sensors are installed in a toxic waste incinerating plant for solid and liquid residues. Above all the anticorrosion properties of the flow sensors are challenged here. Another of their uses is in a toxic waste incinerating plant for liquid residues where their heat resistance is put to the test.

The principle of measurement

The probe records the velocity of the flue gases being discharged according to the vortex principle of measurement. It is based on vortices being shed at a strut in the probe whereby the vortex shedding frequency is a dimension for the flow velocity. The evaluation instrument calculates the rate of flow by means of the pipe diameter. This measuring data is entered on the emitting values computer. With the inclusion of the pollutant parameter the pollutant flow rate per ½ hour, per hour or rather per day can be determined.

Operating conditions

In toxic waste incinerating plants for solid and liquid residues flue gases arise out of the combustion process which are subject to various cleaning procedures which result in the cooling down of the flue gas.

The measuring probes of the vortex flow sensors are installed in the flue gas chimney behind a wet scrubber. Here the dew point of the flue gas falls short and as a consequence a highly saturated atmosphere prevails in the flue gas chimney. Without the anticorrosion properties of the flow sensors lengthy exposure times in these surroundings would not be possible. After three years of Höntzsch instruments being in constant use we can safely say that no evidence of corrosion has been reported. With the toxic waste incinerating plants for liquid residues the vortex flow sensors are subject to temperatures of up to 180 °C. Their maximum capacity is reached here. The flow sensors are installed in the exhaust emission pipe after the cleaning filter.

The exceptionally high heat and corrosion resistance of the vortex flow sensors ensure reliable measurement of the gas volume flow even under the most extreme conditions.

They are an essential part of the emission measurement in the above mentioned plants.