Why is the naphtha pipeline in the hydrocracking unit purged with N2 instead of steam?
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Why is that? Can’t figure it out
Light oil pipelines generally do not use steam to prevent water contamination； Also, the steam temperature is high.
It prevents oil from vaporizing instantly and causing overpressure in the pipelines. Additionally, it is strictly prohibited to use air for purging light oil pipelines, to avoid the formation of explosive mixtures that could explode when exposed to high temperatures. If steam must be used, it is possible to first apply water and then use steam.
Naphtha is a light petroleum product that tends to vaporize at high temperatures, leading to overpressure in pipelines and containers and posing a risk of danger. Since nitrogen is an inert gas, using nitrogen for purging can prevent the formation of explosive mixtures and thus avoid explosions. What was said on the 3rd floor is correct; if using steam for purging, the pipes must first be flushed with water before steam is used for purging. If purging reaches the naphtha pipeline in the tank area, after flushing with water, the flange in front of the tank should be disconnected and then purging should be carried out using steam.
Steam purging of naphtha can lead to water contamination in the naphtha, as well as pump cavitation.