Influence of Metal Surface and Sulfur Addition on Coke Deposition in the Thermal Cracking of Hydrocarbons

Reyniers, Marie-Françoise; Froment, Gilbert F.

doi:10.1021/ie00042a009

Cited by 112 publications

(164 citation statements)

References 18 publications

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“…This mechanism was previously described by Baker et al (1972Baker et al ( , 1973, Rostrup-Nielson and Trimm (1 977), Crynes and Crynes (1 987), Albright and Marek (1988), Rayniers and Froment (1995), and Snoeck et al (1 997). The catalytic mechanism forms coke only so long as the metal substrate is exposed to the gas phase.…”

Section: Moore@enchucaigarycasupporting

confidence: 57%

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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Section: Moore@enchucaigarycasupporting

confidence: 57%

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

et al. 2000

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“…The amount of TEOS used during the pretreatment in the pilot plant is 10 g, which can produce 2.89 g of SiO 2 . Assuming that all the SiO 2 is uniformly deposited on the inner surface of the cracking coil of the pilot plant setup, the thickness of the SiO 2 layer is 3.2 µm.…”

Section: Influence Of Teos On the Steam Cracking Of Ethane In A Pilotmentioning

confidence: 99%

“…32 The mechanism explaining the increase in coking rate with continuous addition of the higher amount of DMDS has been discussed in a previous paper. 2,32 It mainly originates from the interference of HS radical, derived from the decomposition of DMDS, with the heterogeneous noncatalytic radical reactions responsible for the growth of the coke layer in the asymptotic stage.…”

Section: Influence Of Si Pretreatment + Presulfidation + Continuous Amentioning

confidence: 99%

“…The reported effect is contradictory. 2,[26][27][28][29][30][31] Besides S-containing compounds, other chemicals have been proposed as additives to suppress coke formation in steam cracking. These mainly include phosphorus-containing compounds, [4][5][6][7][8][9][10] siliconcontaining compounds, [11][12][13][14][15][16][17][18] alkali and alkaline earth metal salt based additives, 19,20 and tin-and antimony-based additives.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Silicon and Silicon/Sulfur-Containing Additives on Coke Formation during Steam Cracking of Hydrocarbons

Wang

Reyniers

Geem

et al. 2008

Ind. Eng. Chem. Res.

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The influence of the combination of two Si-containing additives, BTMS and TEOS, with DMDS on coke formation during steam cracking has been evaluated both on a laboratory scale and in a pilot plant unit. Under the optimal presulfidation conditions (T ) 1023 K, H 2 O ) 20 g h -1, DMDS in H 2 O ) 750 ppm wt, duration ) 1 h), the combination of Si pretreatment + presulfidation + continuous addition of 2 ppm wt DMDS results in a decrease in the rate of coke formation up to 40% when hexane is cracked in the lab-scale unit. Under similar conditions in the pilot plant the coke formation is decreased by 70%, while the CO production decreases by more than 90%. Moreover, the suppressing effect on coke formation remains significant even after several coking/decoking cycles. Simulations of an industrial ethane cracker indicate that the application of Si-and S-containing compounds as additives for the suppression of coke formation can potentially double the run length of industrial steam crackers.

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“…The latter allows measurement of the kinetics of the cracking reactions (Van Geem et al, 2005) and of the coke deposition in both the radiant coil (Reyniers and Froment, 1995) and the transfer line exchanger [TLE] (Dhuyvetter et al, 2001). The pilot plant set-up consists of 3 parts: a feed section, the furnace containing the suspended reactor coil and the analysis section.…”

Section: Reactor Modelingmentioning

confidence: 99%

Challenges of Modeling Steam Cracking of Heavy Feedstocks

Reyniers

Marin

2008

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Les défis de la modélisation du vapocraquage des hydrocarbures lourdsActuellement les modèles cinétiques du vapocraquage des hydrocarbures, par événements constitutifs, permettent de simuler la conversion de fractions lourdes. Le principal défi pour modéliser le craquage de ces matières lourdes est leur reconstruction moléculaire. Celle-ci dépend du niveau de précision molécu-laire requis du réseau réactionnel et de la caractérisation/méthode de reconstruction de la charge, comme cela est illustré pour les condensats du gaz naturel par exemple. La comparaison entre les prédictions et les résultats obtenus dans une unité pilote montre comment les incertitudes au niveau de la reconstruction de la charge se propagent au niveau des résultats de la simulation. La combinaison du modèle cinétique par événements constitutifs et de la méthode de reconstruction basée sur la maximisation de l'entropie de Shannon, permet d'obtenir des résultats précis si la densité, la repartition en poids ou en volume des fractions PIONA, et les points d'ébullition initiaux, à 50 % et finals sont connus. Moins il y a d'indices spéci-fiés, moins il y a de correspondance entre les résultats simulés et ceux obtenus par expérimentation. La méthodologie développée peut être très simplement élargie à d'autres coupes pétrolières. Abstract -Challenges of Modeling Steam Cracking of Heavy Feedstocks -Today single event microkinetic (SEMK) models for steam cracking of hydrocarbons allow simulating the conversion of heavy fractions. The key challenge to model the cracking behavior of these heavy feedstocks is related to feedstock reconstruction. The latter depends on the required level of molecular detail of the reaction network and of the feedstock characterization/ reconstruction model. This is illustrated for gas condensate feedstocks. Comparison of yield predictions with yields obtained in a pilot

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Influence of Metal Surface and Sulfur Addition on Coke Deposition in the Thermal Cracking of Hydrocarbons

Cited by 112 publications

References 18 publications

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

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

Influence of Silicon and Silicon/Sulfur-Containing Additives on Coke Formation during Steam Cracking of Hydrocarbons

Challenges of Modeling Steam Cracking of Heavy Feedstocks

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