Solving the chloride ion problem in hydrocracking
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In hydrocracking, denitration after refining leads to reactions between chlorine ions present in hydrogen and the feed oil, resulting in the formation of ammonium salts. This causes crystallization that blocks pipelines, such as those used for heat exchange. The oil products produced by our company contain high levels of chlorine, and hydrogen also contains hydrogen from reformation processes. I would like to know more about related issues – for example, what other harms can chlorine ions cause, and what problems might arise as a result of their presence in the processing equipment
Excessive chloride levels can cause cracking in austenitic stainless steel； Excessive chloride ions can also cause poisoning of the hydrogenation catalyst
Excessive chloride ions can affect the activity of the catalyst; in severe cases, as mentioned above, it may lead to catalyst poisoning. Dechlorination facilities can be installed at the inlet of the new hydrogen generator.
Furthermore, chloride ions can combine with ammonia in the system to form ammonium salts, and the crystallization of these ammonium salts can block the system’s pipelines, leading to an increase in the system’s differential pressure.
Thank you for the explanation. As mentioned on the 2nd floor, what exactly causes cracking in stainless steel? And what reaction leads to catalyst poisoning?
Water can be injected before air cooling; this is a commonly used method. Also, where does your oil come from, and what is the chlorine content?
Ammonium salt crystals clog the inlet filter of the cyclohydrogen compressor, causing an increase in system differential pressure
In the presence of “CI–”, austenitic stainless steels of types 18–8 are particularly sensitive to pitting corrosion. Pitting corrosion is very dangerous in production; it develops rapidly within a certain area and penetrates deeper, resulting in equipment damage due to localized failure. Or leakage may occur due to perforations in certain areas. The cause of pitting may be weak spots in the passivation film (oxide layer) on the surface of the stainless steel, or it may result from impurities or irregularities in certain areas. When active chloride ions (CI‑) are present in the liquid, they are easily adsorbed onto the surface of the purification membrane. In those areas where the passivation layer is thinner, the chloride ions displace oxygen atoms on the membrane and take their place. As a result, soluble chlorides are formed at the sites where the CI‑ ions are adsorbed, and small pores gradually develop in these areas. After the formation of these pores, an unfavorable situation arises: the pores act as the anode, while the passivated surface functions as the cathode. The cathode has a large area, whereas the anode area is very small. Such a corrosion cell accelerates the rate of corrosion; when the pitting holes connect with each other, cracks are formed, leading to severe damage to the steel. To prevent chloride ions from causing corrosion in austenitic stainless steel, the water used for cleaning or pressure testing of such equipment and pipelines must have a chloride content of less than 30 ppm. Ammonium chloride also corrodes heat exchangers
Thank you to all the students for their enthusiastic answers
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