API PUBL 932-A:2002 pdf download.A Study of Corrosion in Hydroprocess Reactor Effluent Air Cooler Systems
1 Introduction
The treatment of crude distillation products with hydrogen to produce higher yields of gasoline and jet fuel became a major part of refinery technology with the introduction of hydrocracking in the 1950s. Later, other hydrofining pro- cesses for removal of impurities from products were intro- duced. These technologies all had similar corrosion experiences that eventually were identified as being associ- ated with the presence of hydrogen sulfide (H 2 S) and ammo- nia (NH 3 ), and their reaction product ammonium bisulfide (NH 4 HS), in the reactor effluents. Minor contaminants such as chlorides and oxygen were also believed to have an influ- ence on corrosion. But in general, corrosion was associated with salt deposition, concentrated solutions of ammonium bisulfide and the flow velocity. In 1976, R. L. Piehl (Standard Oil of California) conducted a survey for the National Association of Corrosion Engineers (NACE) on corrosion in Reactor Effluent Air Cooler (REAC) systems. Industry-wide experience was gathered and ana- lyzed to establish guidelines to minimize REAC corrosion. In 1996, Unocal/UOP conducted an extensive survey of their licensees world wide. Their conclusions confirmed the valid- ity of the original parametric guidelines and contributed to the importance of certain design features in avoiding corrosion problems. Since the earlier survey, failures have continued to occur and while it is believed that most have resulted from operation outside of the guidelines, there has been no system- atic study of the experience or open documentation of indi- vidual events.
2 Preamble
Information for this report has been gathered from open lit- erature, private company reports and interviews with represen- tatives of major refining companies. The terminology used by each of these sources to describe some of the corrosion events has varied slightly and may have introduced some double meanings. Every effort has been made in this document to maintain consistency and avoid confusion. Specifically, we have tried to differentiate between “localized corrosion” as a category of corrosion phenomena (e.g., pitting, crevice corro- sion or stress corrosion cracking) and corrosion that has been confined to a small area of the corroding surface at a specific location in the process equipment. For the most part, localized corrosion will refer to the latter, i.e., corrosion occurring on a small area, or at a specific location in the process. Where a specific type of corrosion has occurred the proper description, for example, pitting, or stress corrosion cracking, will be used. Throughout the report, reference is made to the effects of velocity on corrosion. It is commonly acknowledged that velocity induces accelerated attack by a mechanism involving the erosive effect of the high velocity liquid. The many con- tributors have frequently referred to this phenomenon as ero- sion. The consensus however appears to be that the mechanism is one of accelerated corrosion. This should more properly be categorized as erosion-corrosion. Thus, unless otherwise stated, the use of the term erosion-corrosion is meant to describe the severe corrosion experienced by high velocity fluid flow.
API PUBL 932-A:2002 pdf download
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