Dew Point Monitoring System

Dew point (DP) is a measure of the moisture composition in a furnace atmosphere. In the various zones of a sintering furnace, the atmosphere can vary widely from a relatively wet, oxidizing atmosphere in the pre-heat zone to a dry, reducing atmosphere in the hot and cooling zones. Maintaining the appropriate atmosphere composition in each zone is critical to achieving the desired delubrication and consistency of the sintered product.

Dew points of –35 to –45°C (–31 to –49°F) are typically desired in the hot zone to ensure carbon control and a good sinter. Continuous monitoring of the dew point in the hot zone can be challenging. Particulate and vapor-phase contaminants in the sample gas stream can potentially accumulate in filtering systems and on sensors. As a result, dew point readings can drift significantly, causing erroneous measurement and necessitating frequent cleaning, recalibration, and sensor replacement. Temperature variations within the sampling unit can also impact the accuracy of the sensors.

These issues can be mitigated by incorporating an automated self-cleaning and sensor calibration process. Temperature control of the sensor and the sampling system are also essential to maintain consistency. This can be achieved via various design features. Drifts and changes in dew point that are reported through local monitoring/alarms or remotely through cloud server access can also help to address furnace operational issues quickly and efficiently.

Continuous dew point monitoring helps manufacturers comply with CQI-9 and NADCAP requirements, and enables operators to plan ahead for shutdowns and preventive maintenance of their furnaces.

Air Products has recently developed a dew point monitoring system to address these issues.