Napthenic acids

This input to design refers to the long-term stability of the raw material sources for the plant. It is only of importance where the raw materials can or do contain impurities which can have profound effects on the corrosivity of the process. Just as the design should cater not only for the norm of operation but for the extremes, so it is pertinent to question the assumptions made about raw material purity. Crude oil (where HjS, mercaptan sulphur and napthenic acid contents determine the corrosivity of the distillation process) and phosphate rock (chloride, silica and fluoride determine the corrosivity of phosphoric acid) are very pertinent examples. Thus, crude-oil units intended to process low-sulphur crudes , and therefore designed on a basis of carbon-steel equipment, experience serious corrosion problems when only higher sulphur crudes are economically available and must be processed. 

Note Typical agents of concern are amines, chlorides, cyanide, fluorides, and napthenic acid. 

The polars describe mainly the resins, asphaltenes, and the poryphyrins, as well as the trace nitrogen found in bases, the nonbasic poryphyrins, the oxygen in the phenols, the napthenic acids and esters, and the sulfur in sulfide and disulfide bonds. The polars and the metalloporphyrins are indicated as emulsifier species involved in stabilizing the emulsions (24, 25). Resins, which will be discussed later with asphaltenes, contain O, N, and S in the form of car-bazoles, fluor-enones, fluorenols, carboxylic acids, and sulfoxides. These are attracted to water interfaces. 

Some crude oils contain significant concentrations of organic acids, mainly napthenic acids, which are corrosive to carbon steel at temperatures above about 400 F (200°C), and may require the use of molybdeniun-containing austenitic stainless steels (i.e., AISI316 and 317). Determination of when to use alloys is done by analysis of the crude oil for acid content using ASTM D 974, Test Method for Acid and... 

Decahydronaphthalene Naphthalene, Molten Naphthalene, Molten Decahydronaphthalene Napthenic Acids 1-Naphthylamine 1-Naphthylamine Carbaryl... 

DTPA diethylenetriaminepentaacetic acid RCOOH napthenic acids ... 

Stainless steels are subjected to serious corrosion problems in oil refineries as they may encounter very corrosive fluids, such as hydrochloric acid and napthenic acids in the process streams. 

Most crude oils contain some napthenic acid. These acids tend to concentrate in those crude oil components that boil between kerosene and heavy gas oil. Naphthenic acid corrosion is characterized by a general thinning of stainless steel vessels and tower internals at temperatures between 450 to 750°F. Rates of corrosion are greatly accelerated in areas of high velocities. 

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