Why is acetylene present in the liquid oxygen tank? ?

What is the amount? Is it on a ppm scale or a percentage scale? The latter can be quite dangerous. It must be the residue left inside the tank itself

Will acetylene remain in the liquid oxygen tank? ? ? Isn’t everything inside the liquid oxygen tank oxygen? ? ? ?

It might have been used to hold something other than liquid oxygen before

Liquid oxygen is obtained through air separation; during the liquefaction of air, small amounts of hydrocarbons remain and are incorporated into the liquid air. During air distillation, these liquid or even solid hydrocarbons still remain in the liquid oxygen, as its boiling point is lower. At the same time, these residual hydrocarbons are also enriched in liquid oxygen. In air separation units, trace amounts of hydrocarbons and acetylene in liquid oxygen must be monitored in real time; when the acetylene level exceeds a certain limit, an alarm should be triggered, and the liquid oxygen must be drained to prevent the accumulation of these trace hydrocarbons and acetylene, which could lead to explosion hazards. To detect trace hydrocarbons and acetylene in liquid oxygen, online chromatography is generally used.

As mentioned on the 5th floor, acetylene originates from trace amounts of acetylene present in the air drawn in during air separation, with concentrations at the ppm level or even lower. Due to continuous enrichment inside the tank, rising levels may pose a danger

During air separation, acetylene accumulates in liquid oxygen and settles at the bottom of the tank; when it reaches a certain concentration, there is a risk of explosion, so the liquid needs to be drained regularly

I once consulted someone who works in this industry, and he said that initially, it was small industrial gas suppliers who provided oxygen. The main users were those who needed welding gas; therefore, there were both systems for producing acetylene from calcium carbide and then bottling it, as well as systems for producing oxygen using small air separation units. In factory areas with unsuitable wind conditions, it’s inevitable that the air drawn into the air separation units will contain trace amounts of acetylene. Although the molecular sieves used in the air purification process can remove some of this acetylene, still some traces remain in the units. After passing through the air separation unit, it enters the liquid nitrogen and liquid oxygen systems in proportion. The normal dissolution amount is very low, thus well below the explosion limit. However, since the boiling point of acetylene is higher than that of liquid oxygen, after the liquid oxygen storage tanks are filled and emptied repeatedly over a long period of time, the high-boiling-point acetylene will gradually accumulate in the liquid phase of liquid oxygen, its concentration will increase steadily, and it will gradually approach the explosive limit. Therefore, standard specifications require regular analysis of the acetylene component. However, if there are no acetylene installations in close proximity to the gas supplier’s facility, then the period required for enrichment is longer.