Problems with pure hydrogen sampling and testing
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When using pure hydrogen as a raw material, it is necessary to test the impurity content. Sampling is a major issue; sampling from steel cylinders requires multiple purging steps, otherwise air will mix into the sample, leading to inaccurate test results. However, if replacement is carried out multiple times, the hydrogen emissions become excessive, posing safety risks. I found out that many companies are doing online analysis. But pure hydrogen is our raw material, and the amount to be tested is small; due to cost considerations, we do not plan to implement online testing. Additionally, the material is delivered in large tank trucks, and testing is carried out upon arrival at the factory – I’m not sure whether it’s possible to conduct online testing in such cases If online operation is not used, how can the problem of sampling and replacing gas be solved?
This post was last edited by qqgd on 2025-4-11 at 16:19. Is the material for the tank cars also unloaded through pipelines on site? If so, then online pure hydrogen analysis can be used; but what is the impurity component you want to analyze? If the impurities are substances such as nitrogen, oxygen, and argon, then a large amount of pure hydrogen will be required for displacement; if it’s not these three components, it can still be detected through appropriate displacement methods along with the use of suitable carrier gases and detectors. You can consult manufacturers with experience in high-purity gas analysis, such as huapiaoxu521 Haiyou, who has extensive knowledge in the analysis of high-hydrogen gases. This requires high-purity carrier gases and some special detectors, as well as certain specialized equipment and methods for enriching trace impurities. @huapiaoxu521
Torpedo vehicles for hydrogen supply? 1. First, the hydrogen supplier can provide paper documents such as certificates of conformity and test reports (for each batch and each truck) ； 2. If a large amount is used, online monitoring can be added after the converger and after the buffer tank; the cost is not particularly high (laser oxygen analysis) ； 3. A oxygen analysis instrument should be installed in the hydrogen system; however, since hydrogen needs to flow through the system, the replacement cycle is quite long. The analysis instrument can be dual-channel or triple-channel, with a bypass line leading to it and a shut-off valve – this allows for an analysis to be performed when the vehicle arrives ； 4. If there is really no other option, then it is necessary to use a sealed sampler or a disposable bladder for sampling; set up sampling points in relatively open areas, install combustible gas detectors for early warning, and at least provide fire extinguishers.
We don’t unload the cargo, as the factory doesn’t have hydrogen storage tanks; once the long-distance tank truck arrives, it stays there and connects directly to the system for supply, with another truck being brought in after the supply is used up. Moreover, we need to conduct inspections before unloading, and it can only be used after passing the inspection. So, sampling can only be done by directly connecting to the long tank truck.
It is used to detect impurities such as nitrogen, argon, oxygen, carbon monoxide, and carbon dioxide; it is frequently employed for those substances that cannot be analyzed by other methods and for which DID chromatography is the only option
Therefore, a small sampling point should be designed at an appropriate location along the hydrogen delivery pipeline in the plant, and a portable high-purity hydrogen analyzer should be used for on-site analysis; this way, the sampling pipeline can be kept as short as possible to avoid excessive loss of sample during pipeline purging. Once the analysis is complete, the sampling line can be closed and the analyzer removed. The analyzer should be equipped with a chromatographic column and detector capable of detecting the components of the impurities being monitored.
We produce hydrogen gas ourselves and use a sealed sampler
It is used to detect impurities such as nitrogen, argon, oxygen, carbon monoxide, and carbon dioxide; it is frequently employed for those substances that cannot be analyzed by other methods and for which DID chromatography is the only option. Such chromatography is monitored continuously by an online chromatography system, while yours is a batch-type detection method that requires testing before unloading, and it can only be used after passing the test. So, sampling can only be done by directly connecting to the long tank truck. Contact manufacturers of closed-system sampling devices to have a closed sampling system designed for tank trucks, one that is safe and reliable; use gas cylinders for sampling and replacement, then bring it back to the laboratory for analysis using a DID chromatograph.
Thank you, that’s also how we design it at the moment
Wow, the moderator replied to me! I didn’t even notice :P