It is not uncommon for refinery feedstocks to contain chloride salts, including chlorides of alkali and alkaline earth metals in amounts ranging from 1 to 2000 ppm. It is known that hydrocarbon streams containing these chloride contaminants, at elevated temperatures and in the presence of water, will hydrolyze to form hydrochloric acid, causing problems to processing equipment in the absence of any chemical treatment programs.
With crude feedstocks first treated in a desalter, much of the salts and other water soluble contaminants are removed prior to introducing the hydrocarbon stream through the refinery process, including heat exchangers, furnaces, distillation columns and the associated processing equipment such as pumps, valves, piping, etc.
The process stream exiting the desalter is typically introduced into an atmospheric distillation column together with steam to make a rough fractionation into generally four cuts that includes an overhead stream containing C1 to C8 hydrocarbons. It is common practice to stream strip the crude in the atmospheric column. Thus, any hydrochloric acid formed upstream of the atmospheric column will be carried over in the light fraction (C1 to C8) to be condensed with water. Subsequent treatment of this condensed fraction will result in the hydrochloric acid coming in contact with and causing corrosive damage to process equipment used to treat the condensed fraction.
The usual method for dealing with the overhead corrosion resulting from the hydrolysis reaction is to apply neutralizers and corrosion inhibitors, of which there are many available on the market. These inhibitors are costly and in many instances cause foaming and deposition problems, which can be more damaging than the corrosion problem.
According to information currently available from Nalco Champion, a method has been developed for reducing hydrolysis in a hydrocarbon stream wherein a hydrocarbon stream containing a chloride compound which undergoes hydrolysis at elevated temperatures and in the presence of water to form hydrochloric acid is treated with an effective amount of a treating agent comprising at least one overbase complex of a metal salt and an organic acid complexing agent. Details on the application of this novel technology are beyond the scope of this discussion and should instead be referred to the subject matter experts. According to information currently available, the treating agent is introduced into the hydrocarbon stream when the stream is at a temperature below which any substantial hydrolysis of the chloride containing compound occurs.
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