Oxygen analyzer is an industrial online process analysis instrument, not only widely used in heating furnaces, chemical reaction vessels, underground wells, industrial nitrogen production and other occasions in the detection of oxygen concentration in mixed gases, but also widely used in boiler water dissolved oxygen, sewage The detection of dissolved oxygen in the drainage outside the treatment device.
There are many types of oxygen analyzers, different detection principles, and strong pertinence. Therefore, appropriate instruments should be selected according to different use occasions and different process conditions.
Measuring principle: It is designed using the oxygen ion conductivity of stable zirconia ceramics in an environment above 650℃. Under certain temperature conditions, if there are different partial pressures of oxygen (ie oxygen concentration) in the gas on both sides of the zirconia bulk ceramic, a series of reactions will occur inside the zirconia ceramic, and oxygen ions Migration. At this time, through the lead electrodes on both sides of the zirconium dioxide, a stable millivolt level signal can be measured, which we call the oxygen potential. It obeys the Nernst equation: where E is the oxygen potential (mv) output by the oxygen sensor, Tk is the absolute temperature (K) in the furnace, and P1 and P2 are the oxygen partial pressures of the gas on both sides of the zirconium dioxide. . In practical applications, one side of the zirconium dioxide is passed into a gas source (usually air) with a known oxygen concentration, which we call the reference gas. On the other side is the gas to be measured, which is the atmosphere in the furnace that we want to detect. The signal output by the oxygen sensor is the oxygen potential signal. Through the Nernst equation, we can get the relationship between the oxygen partial pressure and the oxygen potential in the atmosphere of the measured furnace. When the reference gas is air, it can be expressed as: where E is the output oxygen potential of the oxygen sensor; Tk is the absolute temperature in the furnace; P02 is the partial pressure of oxygen in the furnace. Wuhan Huamin oxygen sensor product has a self-heating device, and the general temperature is guaranteed to be 700 ℃, so that the TK value is basically constant, so that the oxygen partial pressure concentration in the furnace can be directly measured by the above formula.
In practical applications, sometimes the oximeter measurement value may be deviated due to a long time after the instrument leaves the factory. The measured oxygen content of the air is about 19%, which is quite different from the actual situation. At this time, the oxygen content analyzer can be calibrated.
Zirconia Oxygen Analyzer: The zirconia oxygen content analyzer system has been rigorously tested and calibrated, and there is no need to re-calibrate when it is first installed on site. After the system has been running for a period of time, it is recommended to calibrate the system every 6 months. When conditions are available on site, a 2-point calibration can be carried out, that is, the zero point and full scale calibration of the system. When there is no condition on site, just perform single-point calibration, that is, full-scale calibration of the system. Air can be used as the system full-scale calibration gas, which is easy to obtain.
Here is a new type of oxygen content analyzer with simple structure, good qualitative properties, high sensitivity, fast response time and low price. It is a zirconia oxygen analyzer, which has been recognized by the industry in recent years. Wide range of applications.
The zirconia oxygen analyzer can not only analyze the oxygen purity of the oxygen product, but also analyze the trace oxygen in high-purity hydrogen and high-purity nitrogen. It is only necessary to adjust the analyzer to the corresponding range level according to the content of trace oxygen in the gas. When used for hydrogen analysis, the flowmeter reading is on the left; when used for nitrogen analysis, the flowmeter reading is on the right. When it is used to analyze high-purity hydrogen or high-purity nitrogen, if the range is placed in a small stop and the pointer is still parked on the left, it indicates that there is reducing gas in the gas, and it should be removed, otherwise it cannot be measured.
The working principle of zirconia oxygen analyzer:
It is designed based on the principle of concentration difference in electrochemistry. Zirconia is a solid electrolyte that only transfers different oxygen ions at high temperatures. Porous platinum electrodes are installed on both sides of the zirconia. One platinum electrode is in full contact with a gas with a known oxygen content (such as air), and the other platinum electrode The electrode is in full contact with the oxygen-containing gas on the waiting side. When the oxygen concentration in the gas on both sides is different, the oxygen molecules on the side with the higher concentration acquire electrons from the platinum electrode to become oxygen ions, making the platinum electrode the cathode of the battery.
Oxygen ions reach the low-concentration side through the zirconia dielectric and lose electrons to the platinum electrode, turning into oxygen, making the platinum electrode the anode of the battery. As a result, a concentration difference battery with zirconia as the electrolyte is formed, and an electromotive force will be generated between the two electrode plates. It can be seen from the experiment that when zirconia is heated to a certain temperature, the logarithm of the ratio of the oxygen concentration in the measuring gas to the reference gas is proportional to the electromotive force between the two plates. As long as the magnitude of the electromotive force is measured, the oxygen content in the measured gas can be known.
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