How Zirconia Oxygen Analyzer Works

According to different detection methods, zirconia oxygen probes are divided into two categories: sampling detection oxygen probes and in-line oxygen probes.

Sampling Detection Oxygen probe sampling detection method is through the guide tube, the measured gas is introduced into the zirconia detection chamber, and then through the heating element to heat the zirconia to working temperature (750 °C above). Zirconia is generally tubular and the electrode is a porous platinum electrode. The advantage is that it is not affected by the temperature of the detected gas. By using different diversion tubes, the oxygen content in various temperature gases can be detected. This flexibility is used in many industrial on-line inspections. The disadvantages are that the reaction time is slow; the structure is complex, and it easily affects the detection accuracy; when there are many impurities in the gas to be detected, the sampling tube is easy to block; the porous platinum electrode is vulnerable to corrosion by sulfur and arsenic in the gas and the clogging of fine dust; The heater is usually heated by electric wire, and the service life is not long.

When the temperature of the detected gas is low (0 °C ~ 650 °C), or when the measured gas is relatively clean, suitable sampling type detection methods, such as oxygen measurement by a nitrogen generator, oxygen measurement in a laboratory, etc.

In-line detection type oxygen probe In-line detection is to directly insert zirconia into the gas under high temperature and directly detect the oxygen content in the gas. This detection method is suitable when the gas temperature to be detected is 700°C～1150°C (special structure can also be For high temperatures up to 1400°C, it uses the high temperature of the gas being measured to bring the zirconia to operating temperature without the need for additional heaters. The technical key of the in-line oxygen probe is the high temperature sealing and electrode problems of the ceramic material.

Because the zirconium oxide needs to be directly inserted into the detection gas, there is a high requirement for the length of the oxygen probe. The effective length is about 500 mm to 1000 mm, and the special environment length can reach 1500 mm. And the detection accuracy, working stability and service life have very high requirements, so the in-line oxygen probe is difficult to adopt the traditional zirconia oxygen probe of the overall zirconia tubular structure, and take more technically demanding zirconia and oxidation Aluminum tube structure. Sealing performance is one of the most critical technologies of this zirconia oxygen probe. At present, the most advanced connection method in the world is the permanent welding of zirconia and alumina tubes. The sealing performance is excellent. Compared with the sampling detection method, the in-line detection has obvious advantages: zirconium oxide directly contacts the gas. The detection accuracy is high, the reaction speed is fast, and the maintenance amount is small. Zirconia Oxygen Sensor Schematic When measuring the flue gas temperature is higher than 700 °C, the sensor composition eliminates the need for a heater and temperature thermocouple.

In an ideal state, when the measured flue gas is the same as the reference gas, the output potential E is 0 mV. However, in practical applications, the actual conditions and field conditions of the zirconium tube are not ideal. Therefore, the de facto zirconium tube deviates from this value. In fact, the potential of the zirconium tube with a certain oxygen content is the sum of the theoretical value and the background potential. We call it the potential value of the zirconium tube output under no-concentration conditions, which is the background potential or zero potential, and the magnitude of this value. It also has different values ​​at different temperatures and changes with the prolonged use of the zirconium tube. Therefore, if you do not deal with this situation, it will seriously affect the accuracy of the entire oxygen meter and probe life.

The zirconia oxygen analyzer is mainly used to measure the oxygen concentration of the flue gas during the combustion process, and it is also suitable for the oxygen concentration measurement of non-combustion gases. It is also called zirconia oxygen analyzer, zirconia analyzer/zirconia oxygen meter/zirconia oxygen meter. An electrochemical cell (oxygen-rich cell, also called zirconium head) with a constant temperature inside the sensor generates a millivolt potential, which directly reflects the concentration of oxygen in the flue gas. The key component of the oxygen sensor is zirconium oxide. A porous platinum electrode is coated on both the inner and outer sides of the zirconia element to make an oxygen concentration difference battery. It is located at the top of the sensor. In order to keep the battery at the rated operating temperature, a heater is provided in the sensor. The temperature controller in the oxygen analyzer controls the zirconia temperature to be constant. Zirconia oxygen analyzer is composed of oxygen sensor (also known as oxygen probe, oxygen detector), oxygen analyzer (also known as transmitter, transmitter unit, converter, analyzer) and the connection cable between them Etc.