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Optimization of the in situ pretreatment of high temperature Ni-Cr alloys for ethane steam cracking

Stamatis Sarris (UGent) , Natália Olahová (UGent) , Kim Verbeken (UGent) , Marie-Françoise Reyniers (UGent) , Guy Marin (UGent) and Kevin Van Geem (UGent)
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Abstract
Coke inhibition of reactor materials is one of the major research areas in the field of steam cracking. Selecting the optimal in situ pretreatment of a steam cracking coil depends on many different aspects such as the reactor material composition, the process conditions, the pretreatment duration, the atmosphere, and the used additives. Therefore, the effect of eight different pretreatments on the coking resistance of a classical Ni/Cr 35/25 high temperature alloy is evaluated in a thermogravimetric setup with a jet stirred reactor under industrially relevant ethane steam cracking conditions (dilution 0.33 kg H2O/kg C2H6, continuous addition of 41 ppmw S/HC at T = 1160 K, equivalent ethane conversion 68%). Next to the sequence of the preoxidation and steam pretreatment, also presulfiding was evaluated. The coking results proved that a high temperature preoaddation, followed by a steam/air pretreatment at 1173 K for a duration of 15 min, has the best coking performance under ethane cracking conditions. This pretreatment results in a factor of 5 reduction of the coking rate compared to the standard pretreatment used as a reference case. SEM and EDX cross section and surface analyses show that the increased homogeneity of the oxide layer formed together with the Cr and Mn layer passivates the catalytic behavior of the alloy, while the presence of Fe and Ni on the surface leads to increased catalytic and pyrolytic coke formation, which was the case when presulfiding was applied. Optimization of the pretreatment clearly pays off; however, the optimum will be different depending on the starting material.
Keywords
SATURATED OXYGENATE COMPOUNDS, COMPUTATIONAL FLUID-DYNAMICS, FILAMENTOUS, CARBON FORMATION, COKE FORMATION, HYDROGEN ABSTRACTIONS, DIMETHYL, DISULFIDE, REACTION-KINETICS, THERMAL-CRACKING, SULFUR-COMPOUNDS, HYDROCARBONS

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Chicago
Sarris, Stamatis, Natália Olahová, Kim Verbeken, Marie-Françoise Reyniers, Guy Marin, and Kevin Van Geem. 2017. “Optimization of the in Situ Pretreatment of High Temperature Ni-Cr Alloys for Ethane Steam Cracking.” Industrial & Engineering Chemistry Research 56 (6): 1424–1438.
APA
Sarris, S., Olahová, N., Verbeken, K., Reyniers, M.-F., Marin, G., & Van Geem, K. (2017). Optimization of the in situ pretreatment of high temperature Ni-Cr alloys for ethane steam cracking. INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 56(6), 1424–1438.
Vancouver
1.
Sarris S, Olahová N, Verbeken K, Reyniers M-F, Marin G, Van Geem K. Optimization of the in situ pretreatment of high temperature Ni-Cr alloys for ethane steam cracking. INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH. Washington: Amer Chemical Soc; 2017;56(6):1424–38.
MLA
Sarris, Stamatis et al. “Optimization of the in Situ Pretreatment of High Temperature Ni-Cr Alloys for Ethane Steam Cracking.” INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 56.6 (2017): 1424–1438. Print.
@article{8542484,
  abstract     = {Coke inhibition of reactor materials is one of the major research areas in the field of steam cracking. Selecting the optimal in situ pretreatment of a steam cracking coil depends on many different aspects such as the reactor material composition, the process conditions, the pretreatment duration, the atmosphere, and the used additives. Therefore, the effect of eight different pretreatments on the coking resistance of a classical Ni/Cr 35/25 high temperature alloy is evaluated in a thermogravimetric setup with a jet stirred reactor under industrially relevant ethane steam cracking conditions (dilution 0.33 kg H2O/kg C2H6, continuous addition of 41 ppmw S/HC at T = 1160 K, equivalent ethane conversion 68%). Next to the sequence of the preoxidation and steam pretreatment, also presulfiding was evaluated. The coking results proved that a high temperature preoaddation, followed by a steam/air pretreatment at 1173 K for a duration of 15 min, has the best coking performance under ethane cracking conditions. This pretreatment results in a factor of 5 reduction of the coking rate compared to the standard pretreatment used as a reference case. SEM and EDX cross section and surface analyses show that the increased homogeneity of the oxide layer formed together with the Cr and Mn layer passivates the catalytic behavior of the alloy, while the presence of Fe and Ni on the surface leads to increased catalytic and pyrolytic coke formation, which was the case when presulfiding was applied. Optimization of the pretreatment clearly pays off; however, the optimum will be different depending on the starting material.},
  author       = {Sarris, Stamatis and Olahová, Natália and Verbeken, Kim and Reyniers, Marie-Françoise and Marin, Guy and Van Geem, Kevin},
  issn         = {0888-5885},
  journal      = {INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH},
  keywords     = {SATURATED OXYGENATE COMPOUNDS,COMPUTATIONAL FLUID-DYNAMICS,FILAMENTOUS,CARBON FORMATION,COKE FORMATION,HYDROGEN ABSTRACTIONS,DIMETHYL,DISULFIDE,REACTION-KINETICS,THERMAL-CRACKING,SULFUR-COMPOUNDS,HYDROCARBONS},
  language     = {eng},
  number       = {6},
  pages        = {1424--1438},
  publisher    = {Amer Chemical Soc},
  title        = {Optimization of the in situ pretreatment of high temperature Ni-Cr alloys for ethane steam cracking},
  url          = {http://dx.doi.org/10.1021/acs.iecr.6b04537},
  volume       = {56},
  year         = {2017},
}

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