Coke formation on polished and unpolished Incoloy 800 coupons during pyrolysis of light hydrocarbons

Crynes, Lawrence L.; Crynes, B.L.

doi:10.1021/ie00070a034

Cited by 21 publications

(21 citation statements)

References 8 publications

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“…The results in Table S.2 indicate that when changing the initial surface roughness of 0.15 to 2.6 μm, the amount of coke deposited in the first cracking cycle remains rather stable while for the initial surface roughnesses of 3.9–7.0 μm, the amount of coke is 20–30% higher. Qualitatively, these observations are in line with earlier work by Marek and Albright , and Crynes and Crynes . Although the pretreatment and operating conditions in these studies were strongly different from those in the current study, these authors also observed that polishing reduced coke deposition on Incoloy 800 , and aluminized Incoloy 800 coupons in the pyrolysis of light hydrocarbons.…”

Section: Results and Discussionsupporting

confidence: 93%

“…Qualitatively, these observations are in line with earlier work by Marek and Albright , and Crynes and Crynes . Although the pretreatment and operating conditions in these studies were strongly different from those in the current study, these authors also observed that polishing reduced coke deposition on Incoloy 800 , and aluminized Incoloy 800 coupons in the pyrolysis of light hydrocarbons. As stated previously, these authors did not measure the difference of roughness induced by polishing.…”

Section: Results and Discussionsupporting

confidence: 93%

“…To reduce coke formation, several technological innovations have been proposed encompassing application of high-performance alloys, − coatings, , and/or in situ or ex-situ pretreatments. − Steam cracking reactors are typically made of heat-resistant Fe–Ni–Cr alloys which resist coke formation by a chromium oxide surface layer. , Often aluminum and manganese are added to improve the coking resistance of the alloys aiming at the formation of a protective alumina (Al 2 O 3 ) or manganese chromite (MnCr 2 O 4 ) layer, respectively. ,,, Alternatively, a thin coating can be deposited on the reactor base alloy surface. There are two coating categories, namely barrier − coatings, which passivate the inner reactor wall, and catalytic coatings, , which aim at coke gasification.…”

Section: Introductionmentioning

confidence: 99%

“…Roughened catalytic and noncatalytic surfaces are found to promote coke formation from the gas phase and tar droplets. − Higher coking rates on rougher surfaces have also been associated with lower tube wall temperatures because a highly polished surface could operate at temperatures that are 50–100 K below that of an unpolished surface . Crynes and Crynes reported that polishing can reduce coke deposition over Incoloy 800 coupons during pyrolysis of different light hydrocarbons at 973 K by at most 80%. Marek and Albright , also studied coke deposition on polished and unpolished Incoloy 800 or aluminized Incoloy 800, and in all cases, less coke was deposited on the polished surfaces than on the rougher unpolished surfaces.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Impact of Initial Surface Roughness and Aging on Coke Formation during Ethane Steam Cracking

Sarris

Symoens

Olahová

et al. 2017

Ind. Eng. Chem. Res.

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Alloy composition and morphology of the inner wall of steam cracking reactors are well-known key factors that affect their coking tendency. The effect of surface roughness on the coking tendency remains uncharted to date and has been studied here for a 35/25 Ni/Cr wt % alloy in a quartz jet stirred reactor equipped with an electro-balance under coil outlet industrially relevant ethane steam cracking conditions: T gas phase = 1173 K, P tot = 0.1 MPa, and X C2H6 = 70%. Up to 6 times higher initial coking rates have been observed during cyclic aging in an R α surface roughness range of 0.15–7 μm, and cyclic aging proved to have an effect mainly on the catalytic coking behavior. No effect was observed on the asymptotic coking rates. Scanning electron microscopy, energy diffractive X-ray surface analysis, and cross section elemental mappings suggest that the effect of surface roughness and aging on the catalytic coking rate derives mainly from changes in the metal surface composition. The amounts of metallic Ni and Fe show an increasing tendency with increasing surface roughness, explaining the pronounced coke deposition. Using Ekvicalc, thermodynamic calculations were performed proposing that the amount of Cr2O3 gradually decreases followed by an increase of manganese chromite, MnCr2O4.

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Section: Results and Discussionsupporting

confidence: 93%

Section: Results and Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Impact of Initial Surface Roughness and Aging on Coke Formation during Ethane Steam Cracking

Sarris

Symoens

Olahová

et al. 2017

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

show abstract

“…With regard to the chemical composition, many studies have shown that some metals, such as Fe, Ni, and Mo, on the surface of the reaction channels have a catalytic effect for coking, while other metals, such as Cu, Si, Al, Cr, Ti, Nb, and Ta, are found to inhibit coking [18][19][20]. With regard to the surface roughness, Crynes et al [21] examined the effect of surface roughness on coke formation during the pyrolysis of light hydrocarbon feedstock using polished metal coupons of Incoloy 800. The results showed that the coking rate reduced sharply after polishing; the ratio of carbon formed on the unpolished coupons to the polished ones varied from 5.6 for iso-butane to 28.1 for ethene.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Growth Characteristics and Properties of CVD TiN and TiO2 Anti-Coking Coatings

et al. 2019

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Coating metals with anti-coking materials inhibit their catalytic coking and are especially beneficial in the pyrolysis of hydrocarbon fuels. It is believed that growth characteristics and properties may play a pivotal role in the anti-coking performance of chemical vapor deposition (CVD) coatings. In this study, TiN and TiO 2 coatings were obtained by CVD using TiCl 4 -N 2 -H 2 and TiCl 4 -H 2 -CO 2 systems, respectively. The effects of deposition time, residence time, and partial pressure were examined, and the coating microstructure was characterized by scanning electron microscopy (SEM). The results reveal that the effect of deposition parameters on the growth characteristics of TiN and TiO 2 coatings is very different. The growth of the TiN coating shows characteristics of the island growth model, while the TiO 2 coating follows the layer model. In general, the growth rate of the star-shaped TiN crystals is higher than that of crystals of other shapes. For the TiO 2 coating, the layer mode growth characteristics indicate that the morphology of the TiO 2 coating does not change significantly with the experimental conditions. Coking tests showed that the morphology of non-catalytic cokes is not only affected by the temperature, pressure, and coking precursor, but is also closely related to the surface state of the coatings. Both TiN and TiO 2 coatings can effectively prevent catalytic coking and eliminate filamentous cokes. In some cases, however, the N or O atoms in the TiN and TiO 2 coatings may affect common carbon deposits formed by non-catalytic coking, such as formation of needle-like and flaky carbon deposits.

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The role of the vapour phase in fluid coker cyclone fouling: Part 1. Coke yields

et al. 2000

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C yclone fouling in fluid cokers can lead to untimely shutdowns for oil sand upgrading operators. This problem was described extensively by Richardson (1 997). The cyclones, located above the fluid bed, are responsible for separating solid coke particles from the vapour stream before it enters the scrubbing section of the coker. Excessive buildups of coke have been noted to form in various parts of each cyclone, as shown in Figure 1. These coke formations lead to an increased pressure drop through the coker and a reduction in the overall efficiency of the cyclones. This problem worsens with the passage of time until, eventually, the coker must be shut down so that the coke formations in the cyclones can be removed. Richardson (1997) discussed a number of mechanisms which may be responsible for the production of these coke structures. It is possible that the vapour phase rising from the fluid coke bed may continue to thermally crack, forming smaller molecular species and coke. Since coke i s a byproduct of thermal cracking, the formations observed in the cyclones would be initially formed by reactions of the vapour phase. Deposition of the coke onto surfaces within the cyclones would initiate the surface formation mechanism. The growth of the coke surface may continue as a result of interaction of vapour phase free radicals and the coke deposited on the walls of the cyclones. The purpose of this study was to determine if coke could be produced from the vapour phase derived from the thermal cracking of Athabasca bitumen and to investigate the effects of reaction time and temperature on the vapour phase coke yield.Coke is composed mostly of carbon (more than 95 percent by mass) combined with small amounts of hydrogen (Speight, 1991). Much research has been performed in the field of gas phase carbon formation.

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Coke formation on polished and unpolished Incoloy 800 coupons during pyrolysis of light hydrocarbons

Cited by 21 publications

References 8 publications

Impact of Initial Surface Roughness and Aging on Coke Formation during Ethane Steam Cracking

Impact of Initial Surface Roughness and Aging on Coke Formation during Ethane Steam Cracking

Comparison of Growth Characteristics and Properties of CVD TiN and TiO2 Anti-Coking Coatings

The role of the vapour phase in fluid coker cyclone fouling: Part 1. Coke yields

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