Investigation of Stress-Oriented Hydrogen-Induced Cracking (SOHIC) in an Amine Absorber Column of an Oil Refinery

Gregory N Haidemenopoulos,Panagiotis Dimitriadis,Kyriaki Polychronopoulou,Helen Kamoutsi,Ioannis Altanis,Michael Stiakakis,Panagiotis Papageorgiou

doi:10.3390/met8090663

Abstract

Stress-oriented hydrogen-induced cracking (SOHIC) of an amine absorber column made of a Hydrogen Induced Cracking (HIC) resistant steel and operating under wet H2S service was investigated. SOHIC was not related to welds in the column and evolved in two steps: initiation of HIC cracks in the rolling plane and through-thickness linking of the HIC cracks. Both the original HIC cracks as well as the linking cracks propagated with a cleavage mechanism. The key factors identified were periods with high hydrogen charging conditions, manifested by high H2S/amine ratio, and stress triaxiality, imposed by the relatively large thickness of the plate. In addition, the mechanical properties of the steel away from cracked regions were unaffected, indicating the localized nature of SOHIC.

Highlights

Amine absorber columns in oil refineries are columns where a downflowing amine solution absorbs H2 S from the upflowing sour gas stream
The results presented above indicated that the failure mechanism of the absorber column, which operated under wet H2 S conditions, was stress-oriented hydrogen-induced cracking (SOHIC)
(2) SOHIC proceeds in two steps: (a) initiation of small hydrogen-induced cracking (HIC) cracks lying in the rolling plane and stacked in a direction normal to the applied stress; (b) through-thickness linking of HIC cracks

Summary

Introduction

Amine absorber columns in oil refineries are columns where a downflowing amine solution absorbs H2 S from the upflowing sour gas stream. The H2 S-rich amine solution, when exiting the absorber, is routed to a regenerator to produce an H2 S-lean amine that is recycled for use in the absorber. Under specific operation conditions, where the ratio of H2 S/amine is high, H2 S corrosion of the steel shell can take place, producing hydrogen, which can enter the steel and cause hydrogen blistering and hydrogen-induced cracking. The local pressure increases and decohesion takes place, generating internal blistering or so-called hydrogen-induced cracking (HIC). The interconnected HIC cracks, which run through the thickness of the plate, form a significant through-thickness crack. This cracking is classified as stress-oriented hydrogen-induced cracking (SOHIC). Hydrogen is produced by a corrosion reaction, such as when steel is exposed to wet H2 S service

Results

Discussion

Conclusion