Why is it necessary to limit chlorine content in hydrocracking?
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This post was last edited by linweihua6 on 2011-9-13 08:22. Why is it necessary to limit chlorine content in hydrocracking, even at trace levels?
Here’s a link to take a look: previous forum posts. http://bbs.hcbbs.com/viewthread.php?tid=502479
Reply to 1#: The columns are quite demanding in terms of operation; the main concern is that ammonium chloride salts crystallize at higher temperatures, which leads to an increase in system pressure. Therefore, most systems monitor chloride ion concentrations in order to adjust the process promptly.
Prevent the formation of NH4CL, ammonium salt crystals
The HCl generated by the hydrogenation of Cl in the raw materials can cause problems in the operation of the process; under high temperatures, it reacts with Fe and Ni present in the materials of containers or pipelines, leading to corrosion. 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 over a certain area and penetrates deeper, resulting in equipment damage due to localized failure or leakage as a result of perforations in specific areas. At the same time, HCL reacts with NH3 in the system to form NH4Cl, which deposits at temperatures below 350°C and thus blocks the system (significant precipitation generally begins at 180–200°C). Some refineries in the United States use only reforming hydrogen, and white NH4Cl crystals often accumulate at the compressor outlet valves. This is because trace amounts of chlorine are present in the reforming hydrogen; therefore, hydrocracking requires restrictions on the amount of chlorine in both the feed oil and the hydrogen.