INSTALLATION ET PROCEDE POUR LE CONTROLE DE PROCESSUS DE TRAITEMENTS THERMIQUES, NOTAMMENT LA NITRURATION, L'OXYNITRURATION EN PHASE GAZEUSE OU ANALOGUE

Heat treatment processes such as gas nitration are monitored by four sensors, preferably of solid electrolyte which determine the status of the gas atmosphere. Gas sensor I in the treatment gas measures the actual oxygen partial pressure in the atmosphere, while the gas sensor II in conjunction with a heated catalyst path 15 supplies a parameter characteristic of the remoteness of the gas phase state from the state of equilibrium. Gas sensor III supplies a value for the level of carbon in the treatment gas and the gas sensor IV provides an auxiliary value for controlling an oxidising gas dispensing arrangement (18) upstream of the gas sensor III to ensure complete oxidation of the gas reaching sensors III and IV. In sensor I the reference gas passes over a catalyst 7 and, sensor II uses either the same reference gas as sensor I (Figure 6) or oxidises the treatment gas in heated catalyst 15 to form the reference gas. Temperature measurement, and heating of the sensors is provided.