The direct reason why zirconia is easy to damage when the furnace is shut down and restarted is that the water vapor in the flue gas remains in the zirconia probe after being condensed after the furnace is shut down. It is easy to damage the ceramic zirconia head. Most people know that the zirconia probe cannot touch water when it is heated. The structure of the Nernst zirconia probe is different from the ordinary zirconia probe, so this kind of situation will not happen.
Nernst's zirconia probes have been used in dozens of power plants and dozens of steel plants and petrochemical plants in China, with an average service life of 4-5 years. In some power plants, zirconia probes were discarded and replaced after being used for 10 years. Of course, it has something to do with the conditions of power plants and the quality of coal powder and reasonable use.
When calibrating the gas, pay attention to the flow of the calibration gas, because the flow of the calibration gas will cause the local temperature of the zirconium to drop and cause calibration errors.Because the calibration gas may not be well controlled, the flow of the standard oxygen in the compression bottle may be too large. In addition, a similar situation can occur when compressed air is used for purging online, especially when the compressed air contains water. The temperature of different zirconia heads during online is about 600-750 degrees. The ceramic zirconia heads at this temperature are very fragile and easily damaged. Once local temperature changes or moisture is encountered, the zirconia heads will be generated immediately Cracks, this is the direct cause of the damage of the zirconia head.However, the structure of Nernst's zirconia probe is different from that of ordinary zirconia probes. It can be directly purged with compressed air online and has a large calibration gas flow rate without damaging the zirconium head.
Because any ceramic material is very fragile at high temperature, when the zirconium head touches water at high temperature, the zirconia will be destroyed. This is undoubtedly a common sense.Imagine what happens when you put a ceramic cup with a temperature of 700 degrees into water?But Nernst's zirconia probe can indeed do such an attempt. Of course, we do not encourage customers to do such tests. This shows that Nernst's zirconia probe is more resistant to water at high temperatures. This is also the direct reason for the longer service life of Nernst's zirconia probes.
Because the zirconia head is a ceramic material, all ceramic materials have to control the temperature change process according to the thermal shock of the material (the material expansion coefficient when the temperature changes)When the temperature changes too fast, the zirconia head of the ceramic material will be damaged.Therefore, the probe should be gradually put into the installation position of the flue when changing online.However, the Nernst zirconia probe has its superior thermal shock resistance. When the flue temperature is lower than 600C, it can be straight in and out without any influence on the zirconia probe.This greatly facilitates the online replacement of users. This also proves the reliability of the Nernst zirconia probe.
Because the structure of the Nernst zirconia probe is different from most common zirconia probes, it can still work normally when both sides of the probe are worn out. However, if the probe is found to be worn out, a protective sleeve can also be easily installed, so that the service life of the probe can be prolonged.Generally, when the coal quality of the power plant is relatively good, it can work for 5-6 years without adding a protective sleeve. However, when the coal quality in some power plants is not good or the flue gas flow is relatively large, the Nernst zirconia probe can be easily installed with a protective sleeve to delay the wear time. Generally, the delay wear time can be prolonged by about 3 times after adding a protective sleeve.
Because of the large amount of air leakage at the gas saver, if the zirconia probe is installed after the gas saver, the air leakage of the gas saver will cause errors in the accuracy of the oxygen measurement in the flue.In fact, power designers all want to install the zirconia probe as close to the front of the flue as possible.For example, after the trough of the flue, the closer to the front flue, the less the influence of air leakage, and the higher the accuracy of oxygen measurement. However, ordinary zirconia probes cannot withstand the high temperature of 500-600C, because when the temperature is high, the sealing part of the zirconium head is easy to leak (the reason for the large difference between the thermal expansion coefficient of metal and ceramic), and when the ambient temperature is higher than 600C , It will produce errors during measurement, and the zirconia head is also very easy to be damaged due to poor thermal shock.Usually, the manufacturers of zirconia probes with heaters require users to install the zirconia probes where the flue temperature is lower than 600C. However, the Nernst zirconia probe with heater can withstand a high temperature of 900C, which not only improves the measurement accuracy of the oxygen content, but also greatly extends the service life of the zirconia probe.
Urban garbage is the most scientific and energy-saving treatment method by burning to generate electricity. However, because the composition of garbage is very complex, in order to ensure its full combustion and reduce environmental pollution during the emission of flue gas, the oxygen content in the combustion process is higher than that of ordinary coal or oil fueled boilers, which makes various acidic components in the flue gas increase.In addition, there are more acidic substances and water in the garbage, so that a highly corrosive hydrofluoric acid will be produced after the garbage is burned. At this time, if the zirconia probe is installed at a position where the flue ambient temperature is relatively low (300-400C), the stainless steel outer tube of the probe will rot in a short time. In addition, the moisture in the flue gas can easily remain at the zirconia head and damage the zirconia head.
Nernst's zirconia probe can be used for oxygen measurement in various occasions. Its in-line zirconia probe can be used for a maximum furnace temperature of 1400C, and the lowest oxygen content that can be measured is 10 minus 30 powers (0.00000000000000000000000000001%) ) .Completely suitable for metal powder sintering furnace.