Redox-control in glass melting
ZrO2-Sensors for the continuous measuring in production
The colour is decisive for the appearance of glass. Viscosity, visco-elastic reaction and the voltage of the surface are defining its ability of processing. The refining function of the glass melt is responsible for the quality of the finished product. The common base of all these dimensions is the high dependence on the reaction of oxidation of the glass melt. On one hand there is a necessity to melt down recycling fragments and filter dust, on the other hand these are raw materials with high fluctuations on the reaction of oxidation. For that reason it gets more and more important, to register also the measuring on the oxidation reaction of the glass melt.
Kühnreich & Meixner offers an oxygen sensor for the continuos measuring in the glass melt (with technical support of the Hüttentechnische Vereinigung der Deutschen Glasindustrie „HVG“ (Research associaton of the German Glass Industry)
This new technique is having a number of advantages compared to conventional methods: The sensor position of the feeder channel enables the information on the reaction of oxidation much earlier. A costly preparation of samples is not necessary. The higher temporal density of measuring data makes it easier to make out trends.
Useful operational connections have been worked out in research projects: The sensor signal is closely combined with the composition of glass batch. If a lot of different fragments are added to the glass batch, organic soiling can be directly observed with an oxygen sensor. Bubble problems are appearing mainly in green glass, if the oxygen partial pressure is going down below 2 x 10-4 bar. A ZrO2-sensor helps to avoid these bubble problems. In brown glass the oxygen partial pressure for the most intensive colouring and the best refining is not identical. A ZrO2-sensor enables choosing the optimal time of service under the predominating conditions of productions, which means selecting the given contents of iron and sulphur of the glass melt.
The oxygen sensor is usually installed hanging in the feeder channel. An optimal cooling facility enables installing the sensor also in a different position. Main item of the sensor is a tip of Y2O3-stabilised ZrO2, being in contact with the glass melt. This cylinder is dissolving in service. According to the temperature in the feeder channel and the composition of glass the endurance of the sensor is 6 to 12 months.
