1. Application of glove box
Glove box is a general working platform to provide a very high purity inert gas environment, the inert gas concentration in this working platform can reach a very high level, some very sensitive to water or oxygen materials research, process or experiment can be achieved in the glove box.
Glove box has been increasingly used in scientific experiments, new materials research and development, biomedical, chemical, lithium batteries, solar cells, nuclear materials and nuclear industry, new lighting, special welding, vacuum coating and other industries and fields. As a universal platform, the glove box can provide working conditions for experiments or production that need to be realized in high purity inert gas protection, low water and oxygen content, or dust-free and sterile environments.
2. Application of trace moisture analyzer in the lithium industry glove box
1. lithium production, in the process of electrolyte injection, the electrolyte contains LiPF6, when encountering moisture will produce hydrogen fluoride (HF) gas, this corrosive gas will cause corrosion of the sensor of the trace moisture analyzer and the accuracy of the drift, will greatly reduce the service life of the trace moisture analyzer;
2. lithium production, the glove box water content value changes, depending on: whether the normal operation of drying equipment, glove box in the process of feeding and taking material how much and the frequency of access, etc. have a relationship, because some trace moisture analyzer response sensitivity is not fast enough to bring a lot of trouble to quality management.
3. the installation position of the trace moisture analyzer in the glove box is very important, because the production of lithium batteries will produce corrosive gases will directly affect the life and accuracy of the dew point meter.
3. Current market commonly used trace moisture analyzer and principle
3.1. Indirect measurement using a dew point meter
The so-called indirect measurement means that the dew point meter measures the dew point temperature of the sample gas and converts it to the water content concentration (PPM) through a formula. The difference between dew point measurement and direct measurement is that the dew point measurement of the temperature of the air when the humidity reaches saturation requires a formula or a table check to derive the volume concentration of moisture, while direct measurement directly obtains the volume concentration of moisture.
3.1.1 Cold mirror principle: High measurement accuracy, stable work and direct reading dew point temperature, long service life but high price, strict maintenance and use requirements, the mirror is also afraid of oil, dust and other pollution, and response time is relatively long, generally used as a measurement department as a standard, not resistant to hydrogen fluoride / hydrofluoric acid corrosion, not suitable for application in the lithium industry glove box.
3.1.2 Capacitance Principle (e.g. Vaisala, Michell, GE, MZD): low purchase cost, high cost of use and maintenance.
1) Metal oxide - alumina principle: due to the lack of corrosion resistance of alumina capacitive moisture-sensitive components, high environmental requirements, can not be suitable or exposed to high humidity environment; the existence of photoelectric failure, electrostatic failure phenomenon, alumina moisture-sensitive materials can not overcome its surface structure "natural aging", the impedance is unstable, there are Long-term operating stability is poor (every 6 months to 12 months need to be calibrated once) the weakness; higher cost of use (as a result of the need for frequent calibration), staff maintenance workload, slow measurement response speed, long response time; in addition, the sensor is not resistant to hydrogen fluoride / hydrofluoric acid corrosion, not suitable for long-term application in the lithium industry glove box.
2) Polymer film capacitor principle: polymer film capacitor products can be used normally in high humidity environment, even in the condensation environment will not damage the sensor, long-term use of better stability, calibration cycle up to 2 years long, but the lack of corrosion resistance. The polymer film will also be consumed with time and need to return to the factory for coating or replacement of new sensors, which is less time-sensitive and relatively expensive to use; in addition, the sensor is not resistant to the corrosion of hydrogen fluoride/hydrofluoric acid and is not suitable for long-term application in the glove box of lithium industry.
3.2. Direct measurement of ppm trace moisture by P2O5 electrolysis (e.g. MZD, Mbraun).
High measurement accuracy, stable operation, long service life, moderate price and low maintenance cost. Mbraun is equipped with ceramic sensor. And MZD can supply enhanced ceramic sensor which is resistant to hydrogen fluoride corrosion and hydrofluoric acid corrosion, low cost of use, low maintenance cost (no calibration, regular use of 40% phosphoric acid to regenerate the probe coating).