There are two major types of oxygen analyzers found in the aluminum industry: extractive and in-situ sensors. Both types work in aluminum applications, but excessive maintenance limits the usefulness and reliability of the extractive units in many applications. Because of high moisture content and particulate in the combustion gas, cells and sample conditioning systems require continuous attention. Regular calibration services are a must. The filters used on the sensor must be cleaned periodically due to moisture and particulate in the hot gases.
Using a high temperature in-situ sensor solves these problems. In most cases, high temperature in-situ oxygen sensors do not require pumps, heaters, filter systems, calibration, etc. The sensors are located in the exhaust port or duct. Proper installation of the sensor will ensure its performance. Continuous oxygen monitoring improves efficiency, lowers emissions, provides higher metal yields, better metallurgical results, and improved through-put. While monitoring has its benefits, the true Return on Investment is realized when oxygen is accurately controlled for optimized combustion.
The recurring cost of sensors is low compared to the operating expense of the melt process. Continuous excess oxygen measurement provides a tighter, more responsive air/fuel ratio resulting in: