Natural gas water dew point
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Due to the development of a new process, municipal pipeline natural gas is required as a raw material for the chemical reactions; this is for non-combustion purposes, and there are specific requirements regarding its water content. Current external third-party testing shows that the water dew point of natural gas is +15°C, which corresponds to a water content of 17,000 ppm V. The measurement point is located at the inlet pressure regulation station, where the pressure is 0.15 Mpa (gauge pressure); the sampling point is situated on the vertical pipeline, as shown in the diagram. The measurement method follows GB/T 5832.1-2016 Gas analysis – Determination of trace moisture – Part 1: Electrolytic method. The municipal natural gas is sourced from the West-to-East Gas Transmission project; the nearest processing station upstream is about 40 kilometers away. Upon on-site inspection, it was found that the dew point of the gas pipeline during online monitoring was -8°C, the pressure was 8.0 Mpa, and the water content was very low, below 50 ppm. Why is there such a large difference between the dew point and water content measured in factory tests and those at the station? The cause has not yet been identified. Is it a problem with the testing method? Is there still water accumulated inside the pipe? (The pipeline has been in use for 5 years) or other reasons? There is a claim that a gas pipeline leak allowed external moisture to enter, resulting in a high water content, but I am still skeptical about this claim. Looking forward to everyone's answers, thank you!
Under the pressure and temperature conditions at the point of transfer, the water dew point of natural gas should be lower than the lowest ambient temperature; isn’t the water dew point of natural gas as determined by third-party tests supposed to be no higher than +15℃?
It is because the dew point measurement was +15°C, and it was thought that there was an issue with this value, but it wasn’t clear where the problem lay. The dew point shouldn’t be this high normally
The cause has been identified; upon opening the main natural gas pipeline at the intake pressure regulation station, significant water accumulation was found. The diameter of the main natural gas pipeline is 50 mm, while the gas-consuming equipment, namely the flare, has a diameter of 8 mm. Regarding the water remaining in the pipes, the reason is that the water was not completely drained during the first pressure test. With such a low amount of gas used, will it be insufficient to remove the water remaining in the pipes?