Online chromatographic analysis and sampling analysis using a sealed sampler?
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This post was last edited by guoxbo on 2020-8-23 at 22:30. Hello everyone, I work in the field of manufacturing processes, and I have a question regarding the design process that I hope experts can help answer. If the pressure of the medium (propylene, methanol, water, etc.) in a process pipeline is between 2–3 MPaG, and this medium is in a fully liquid state at operating pressure but in a gas-liquid two-phase state at atmospheric pressure, can an online chromatograph be installed directly on the process pipeline for component analysis? If there is no online chromatography, can the medium be sampled using a sealed sampler and then analyzed by chromatography? Can the sealed sampler be connected directly to the chromatograph, or is it necessary to first separate the gas and liquid phases before analyzing each one separately? Thank you!
Contact online chromatography manufacturers; they have complete sets of sampling, pretreatment, and testing methods. Generally, pressure reduction is required first, followed by chromatography ； There are also liquid-phase sampling valves. For example, ABB.
Online gas or liquid chromatography can be installed, but the sampling and pretreatment systems must be properly set up.
Whether it is online analysis or offline analysis via sampling, the key is that the sample being analyzed must be reliably representative. Since the sample medium is a pressurized mixed medium with a large difference in boiling points, partial vaporization occurs upon pressure reduction due to this significant difference in boiling points, leading to boiling point discrimination. To ensure the reliability of online analysis, an online analyzer needs to vaporize the sample continuously and rapidly, and then maintain the vaporized sample at a temperature above its dew point under conveying pressure through heating. In the case of offline analysis, a high-pressure sampler is required to obtain liquid samples, which are then injected for analysis using a liquid injector or a similar method that enables rapid vaporization of the liquid samples, as in online analysis. This is not a technical issue related to analysis; it is an issue with sampling and sample processing.