Analysis of oxygen tube degreasing in the air separation process of coal chemical industry

Our oxygen tubes are also degreased, but it seems no degreasing analysis has been done. Oxygen tube degreasing involves acid-base cleaning, acetone, carbon tetrachloride degreasing, water washing, and then air blowing. It’s sufficient to measure the content of cleaning agents and oil components in the purge gas. How is it measured specifically? Chromatography. This post was last edited by chengjingbao on 2009-2-13 17:41]

We usually use carbon tetrachloride for degreasing, but the limit is 125 mg/m3, making it impossible to perform chromatography

We used carbon tetrachloride for degreasing; no testing was conducted.

I found the information regarding degreasing inspections in the acceptance procedure documents from the time we carried out degreasing; I hope it will be useful to everyone: Chapter 5 Inspections, Article 5.0.1 Equipment, pipes, fittings, and valves must be inspected and evaluated after degreasing. The inspection criteria shall be applied in accordance with Articles 5.0.2 to 5.0.5 of these specifications, based on the different roles of the degreased parts in production and the degree of risk or hazard caused by oil contamination. Article 5.0.2 For equipment, pipes, fittings, valves, etc. that are in direct contact or may come into contact with strongly oxidizing media such as oxygen, oxygen-enriched gases, and concentrated nitric acid, any of the following methods may be used for inspection: 1. Examine the surface of the degreased parts using ultraviolet light with a wavelength of 3200–3800 angstroms; no oil fluorescence indicates compliance ； II. Wipe the surface of the degreased parts with clean, dry white filter paper; it is considered acceptable if no traces of oil remain on the paper ； III. Blow clean the degreased parts with oil-free steam, collect the condensate, add a small particle of pure camphor (with a diameter of less than 1 millimeter), and it is considered satisfactory if the camphor keeps rotating continuously ； IV. For degreased parts that cannot be tested using the above methods, samples can be taken for inspection; a solvent and oil content of no more than 350 milligrams per liter is considered acceptable. Article 5.0.3 Equipment and pipelines cleaned with concentrated nitric acid shall have their total organic content in the acid analyzed, with a limit of 0.03% being considered acceptable. Article 5.0.4: Parts degreased with solvents must have any remaining solvent thoroughly blown away until no odor of solvent is present. Those who use alkali solution for degreasing must rinse thoroughly with oil-free water until the pH reaches neutral, and then dry it. For those using steam to blow off moisture, the degreased parts should be dried promptly. Oil-free water used for rinsing austenitic stainless steel shall have a chloride content of no more than 25 ppm. Article 5.0.5 Where the design specifies inspection standards, inspections shall be carried out in accordance with those standards.

Carbon tetrachloride can be used for degreasing. We have an infrared oil detector, and this is how we proceed in our factory: An appropriate amount of absorbent cotton is cleaned using carbon tetrachloride, and then the infrared oil detector is used to check whether any oil remains on the cotton. If there is a trace of oil, it is washed away until no oil is left. After that, this absorbent cotton is used to wipe the oxygen tubes. Subsequently, carbon tetrachloride is used to dissolve the substance to a certain volume, and the infrared detector is again used to measure the oil content. The presence of an absorption peak indicates the presence of oil, while its absence means no oil is present. The magnitude of the absorption peak allows for a qualitative assessment of the oil content.