Laser oxygen content monitoring

It was used in 2008 on the electrostatic precipitator at a gas station; it was a domestic brand (appears to be made in Shanghai), with the transmitting and receiving units installed on either side of the inlet pipe of the electrostatic precipitator. The oxygen meter itself operates quite stably. However, the transmitting and receiving heads need to be pressurized with nitrogen to prevent dust and coal tar from sticking to the probes. We don’t have a nitrogen source; we use a molecular sieve nitrogen generator, whose operation is extremely unstable, and this system has never worked properly.

Yes, for this type of in-situ laser oxygen content analyzer, we also lack a nitrogen source to ensure its proper operation; moreover, our system does not allow nitrogen to enter

Mettler Toledo, sampling and analysis; price: 210,000 per unit. High humidity and high temperature require you to treat the sample gas.

I have used in-situ laser oxygen analyzers from Yokogawa, Focus, and Mettler Toledo. The first two brands are used for VOC treatment in exhaust gases, while the third is used in process conditions. Yokogawa’s price is around 200,000; the focused version is slightly cheaper at around 170,000. The price for Mettler is unknown. The measurement performance of all three brands is acceptable. The purging systems of the first two brands are relatively simple, while Mettler’s purging system is more complex and requires more installation space. The VOC treatment conditions did not encounter high humidity issues, and the measurements were less affected by these conditions. The humidity under operating conditions is very high, and water droplets form on the on-site transmitting/receiving mirrors, affecting measurements. Later, periodic purging was implemented, which reduced this impact significantly.

Mettler Toledo does indeed have laser oxygen content analyzers, but their main areas of use are as mentioned on the second floor: in-situ testing, in conjunction with nitrogen

In the third operating condition, when there is condensation on the mirror surface, does the displayed value fluctuate unpredictably or is it lower than normal? If the displayed stability is only slightly low, could a correction factor be considered? I asked many laser manufacturers, and all of them said that sample gas pretreatment (dehumidification and cooling) is required. A small number of people suggested that heat-resistant sensors could be used; in my opinion, this is theoretically feasible, as it helps to reduce condensation under high temperatures. Firstly, it prevents liquid droplets from forming on the mirror surface, and secondly, condensation can affect the relative proportions of the gases in the system. However, I am not aware of any actual cases where such sensors have been used!

I’ve used Siemens and FocusTech products, and both gave good results

Currently, domestic laser devices are used to measure oxygen content; they cost around 80,000 yuan each, and they don’t come with a purge function, which results in unstable readings!

The Chuanyi one works very well; we’re using it

According to the site, the measurement values during condensation are unstable and fluctuate. The manufacturer also recommended dehumidifying the sampling gas, but this is difficult to implement in actual projects (the specifics are unclear; it was a response from the engineering team). The manufacturer further suggested making the purge tube into a coiled shape and heating it, but this idea was not adopted due to the limited effect of temperature elevation. Finally, after consultation with the owner, the solenoid valve was programmed for multiple purges.