Occurrence of metal dusting – referring to failure cases

The mechanism of metal dusting of 9Cr-1Mo steel in CCR platforming unit, based on examinations of a charge heater tube, is presented. The tube operated for 10 years, and the metal skin temperature was about 600 8C. The feed was composed of hydrotreated naphtha and hydrogen gas. The mechanism of the corrosion was elucidated using scanning electron microscopy, electron probe microanalysis and X-ray diffraction technique. It has been found that the carbon deposition on the steel surface and its inward diffusion into the steel is accompanied by the outward diffusion of carbide forming elements, i.e. chromium and molybdenum. At an advanced stage of the metal dusting process a thin layer of fine chromium-rich carbides beneath the steel surface exists. The layer is followed by a porous zone composed of big degraded primary carbides and fine carbides instead of alloy ferrite, with chromium and molybdenum content higher than the ferrite inside the tube wall. On the steel surface, a layer of coke composed of graphite, iron and M 7 C 3 carbides is formed and the uniform wastage of the steel takes place. Possible influence of some sulphur additions to the CCR platformer feed during the future service on degradation of the subsurface material has been considered.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Sulphur in the catalytic reformer feed plays an important role in metal dusting [1][2][3]. It may protect the heater tubes against the corrosion.…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Metal dusting in CCR platforming unit

Dampc

Grzesik

Hucińska

2009

The influence of surface condition on the metal dusting behavior of cast and wrought chromia forming alloys

Hermse¹,

Asteman²,

IJzerman³

et al. 2012

The current work investigated the impact of surface condition on the metal dusting behavior of chromia forming alloys. Five commercial alloys were included in the study, wrought 800H, 353MA, and cast G4859, G4852 Micro, and ET45 Micro, these alloys have a chromium and nickel content in the range of 20-35 wt% and 32-45 wt%, respectively.The wrought alloys were tested in a pickled state and the cast alloys with a machined surface, all the alloys were tested using a laboratory ground surface condition for comparison. The exposures were performed using a gas with a composition of 44 vol% CO, 52 vol% H 2 , 2 vol% CO 2 , and 2 vol% H 2 O at a temperature of 600 8C and a pressure of 5.5 bar. The samples were periodically characterized by measuring the mass loss, pit density, pit size, and pit depth. The results show that the pickled surfaces were sensitive toward metal dusting attack while the machined and the ground surfaces had better resistance. This shows that the surface pre-treatment plays a crucial role.

The influence of alloying elements on metal dusting behavior of nickel chromium alloys and their statistical correlation

Hattendorf¹,

Hermse²,

IJzerman³

2019

The focus in this study is on very metal dusting resistant nickel chromium alloys with a high content of chromium (in the range of 22 to 33 wt.%), additions of aluminum (between 0 and 3 wt.%) and variable iron content (between 0.1 and 15 wt.%). All samples were exposed up to 5693 h at 600 °C in a 37 vol.% CO, 7 vol.% CO2, 46 vol.% H2, 9 vol.% H2O atmosphere at a total pressure 20 bar. The differences between the samples in terms of mass loss, pit depth and incubation time to first pit are evaluated by a statistical analysis and discussed in dependence of alloy composition. Only samples with combined chromium plus aluminum content of about 30 wt.% or more and an iron content of 0.6 wt.% or less do not show any pit formation during the exposure time, even on the edges. In contrast, samples with a similar combined chromium plus aluminum content, but with a higher iron content, do show pit formation due to metal dusting corrosion.