Figures:
A heat flux sensor is incorporated in the waterwall of a boiler.
By measuring the flux as a function of time, the process of soot accumulation can be monitored. The heat flux sensor functions as a slagging and fouling sensor.
The key element of the Intelligent Sootblowing system and for the measurement of fouling is a heat flux sensor. The sensor measures the exchange of energy (in Watts per square meter) from the flame to the steam inside the waterwall tubes. In addition this sensor also measures the temperature of the tube wall. In fact the combination of the heat flux and the temperature signal allows accurate calculation of the tube skin temperature. These data are again used for calculations of the tube lifetime. (in fact the sensor is specially calibrated for this application).
The heat flux sensor perfroms two functions:
- as a deposition probe (indication the degree of slagging and fouling)
- as a chordal thermocouple (offering the possibility to measure tube skin temperature)
More details about Heat Flux Sensors.
Figures:
A heat flux sensor incorporated in a boiler tube: cross section, normal situation on the left, with fouling / slagging on the right
Figure:
Signal of a heat flux sensor incorporated in a boiler tube: from the clean to the fouled condition, the output signal level (heat flux) drops, and also the spectral content of the signal changes (the fouling dampens the signal).
Figure:
Complete heat flux sensor, including lead out tube for the wiring and connection box for wiring.
