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51317--9784-High Temperature Coking Resistance of an Alumina Forming Alloy

Coking is carbon deposition from a gas phase that is encountered in many reforming, cracking and other high temperature processes. An experimental high temperature coking atmosphere was constructed and used to evaluate the effects of temperature, time and metal surface roughness on the carbon deposition of an alumina forming alloy.

 

Product Number: 51317--9784-SG
ISBN: 9784 2017 CP
Author: Benjamin Church
Publication Date: 2017
Industry: Petroleum Refining
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Coking is the process of carbon deposition from a gas phase that is encountered in many reforming cracking and other high temperature processes. Coking in certain petrochemical processes can lead to carbon build up causing reduced process efficiency corrosive attack and degradation of the alloy. Components used in these processes are fabricated from HP alloys that form a chromia-based oxide layer or more recent alloys that form an alumina-based oxide layer to help protect against coking.An experimental high temperature coking atmosphere was constructed and used to evaluate the effects of temperature time and metal surface roughness on the carbon deposition of an alumina forming alloy. Coking conditions were simulated with multiple atmospheres including CO-H2 mixtures at moderate temperatures (e.g. 650 °C) and ethane at higher temperatures (e.g. 900 °C). Carbon deposition was tracked using specific mass change of the samples as a function of exposure times and conditions. Results obtained with the alumina forming alloy were compared to a baseline HP alloy. The materials were analyzed using XRD SEM and optical microscopy to characterize the oxide layer formation carbon deposition layers and carbon attack and changes to base metal microstructure. Raman spectroscopy was used to characterize the carbon deposits. The overall resistance of the alumina-forming alloys relative to the traditional chromia forming composition will be described.

Key words: High temperature corrosion, carbon deposition, cyclic conditions, alumina forming alloy, chromia forming alloy.

Coking is the process of carbon deposition from a gas phase that is encountered in many reforming cracking and other high temperature processes. Coking in certain petrochemical processes can lead to carbon build up causing reduced process efficiency corrosive attack and degradation of the alloy. Components used in these processes are fabricated from HP alloys that form a chromia-based oxide layer or more recent alloys that form an alumina-based oxide layer to help protect against coking.An experimental high temperature coking atmosphere was constructed and used to evaluate the effects of temperature time and metal surface roughness on the carbon deposition of an alumina forming alloy. Coking conditions were simulated with multiple atmospheres including CO-H2 mixtures at moderate temperatures (e.g. 650 °C) and ethane at higher temperatures (e.g. 900 °C). Carbon deposition was tracked using specific mass change of the samples as a function of exposure times and conditions. Results obtained with the alumina forming alloy were compared to a baseline HP alloy. The materials were analyzed using XRD SEM and optical microscopy to characterize the oxide layer formation carbon deposition layers and carbon attack and changes to base metal microstructure. Raman spectroscopy was used to characterize the carbon deposits. The overall resistance of the alumina-forming alloys relative to the traditional chromia forming composition will be described.

Key words: High temperature corrosion, carbon deposition, cyclic conditions, alumina forming alloy, chromia forming alloy.

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Product Number: 51317--9682-SG
ISBN: 9682 2017 CP
Author: Faisal Al-Refai
Publication Date: 2017
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A failure in one of the de-salter relief lines of the crude distillation unit. This paper describes the probable causes and the adopted remedies for the localized corrosion observed in the insulated relief line. Circumstantial evidence and failure morphology were used in arriving at the root cause for this failure.