Online Sensors for Industrial Glass Production
In modern glass production, there are more and more limiting conditions, which can be tackled only with a quick access to process variables. Such conditions concern restrictions in respect of the noxious gas emissions due to environmental regulatory constraints, guarantee of a stable process in spite of varying raw material qualities for example when using cullet, and of a high product quality in particular with regard to further processing. The required process variables can be achieved in many cases by means of sensors designed in the last years. Electrochemical sensors developed to maturity at HVG for instance can measure properties of a glass melt online.
The properties of a glass depend significantly on the redox state of the polyvalent elements contained. Most obviously, the colour of the glass shows the redox state. Depending on the oxygen partial pressure of the melt, glasses containing iron and sulphur can be brown, blue or green.
The sensor shown in the picture alongside can measure the oxygen partial pressure of the glass melt as well as the concentrations of sulphur, chrome, iron and selenium. The best results could be achieved for the measurement of the sulphur concentration. The graph below the picture compares the sulphur concentrations measured online with the electrochemical sensor and the results of the chemical analyses carried out on simultaneously taken samples.
The properties of a glass depend significantly on the redox state of the polyvalent elements contained. Most obviously, the colour of the glass shows the redox state. Depending on the oxygen partial pressure of the melt, glasses containing iron and sulphur can be brown, blue or green.
The sensor shown in the picture alongside can measure the oxygen partial pressure of the glass melt as well as the concentrations of sulphur, chrome, iron and selenium. The best results could be achieved for the measurement of the sulphur concentration. The graph below the picture compares the sulphur concentrations measured online with the electrochemical sensor and the results of the chemical analyses carried out on simultaneously taken samples.
Renting Online Sensors for the Glass Melt
The operating conditions of electrochemical sensors in the glass melt are very different for the various methods of glass production in respect of fibre, container and flat glass. In the past, the sensors were mainly installed in the forehearth. With the aid of water-cooled mounts, they can also be used in working ends. The long-term stability of sensor types used up to now has not yet been satisfactory, however, so that further development work is necessary. In order to be able to estimate the possibilities of electrochemical sensors without large investments, HVG offers electrochemical sensors on a rental basis. Support in interpretation of the measurement results and development of adjustment are included in the services and based on HVG research work.
Electrochemical sensor for the combined measurement of oxygen partial pressure and concentrations of polyvalent elements. 1: Electrode for measurement of concentration, 2: Electrode for oxygen partial pressure measurement, 3: Counter electrode for concentration measurement, 4: Reference electrode from Y2O2 stabilised ZrO2.
Agreement between the results of measurement by means of sensor and chemical analysis. 1: Green container glass, 2: Colourisation of container glass from white to light green, 3: White container glass. (Click to enlarge)