Influence of the Reactor Material Composition on Coke Formation during Ethane Steam Cracking

Gandarillas, AndreÌsE. MunÌoz; Reyniers, Marie Françoise; Marin, Guy

doi:10.1021/ie500391b

Cited by 57 publications

(160 citation statements)

References 54 publications

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“…It can be observed that for cycle 3, the coking rate reaches an asymptotic value of approximately 2 2 1 4 10 kg m s       . A similar tendency was observed 17 for the coking of an aluminium alloy during the decomposition of naphtha at 1098K. The decline in the coking rate as a function of time for the three cycles may be explained by the fact that the contact surface (and thus the catalytic surface) between the material and the n-dodecane reduces as the coke builds up in the thickness e 1 of the porous material.…”

Section: B Comparison Of Two Models: Linear and Exponentialsupporting

confidence: 71%

Modeling the spatio-temporal evolution of permeability during coking of porous material

Tabach¹,

Chetehouna²,

Gascoin³

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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International audienceTranspiration cooling is one of the most efficient cooling techniques, but one which generates complex phenomena that are difficult to model, and this all the more in that a reactive fluid such as an endothermic fuel is used. Above a certain temperature, such fuel is pyrolysed and, thanks to its endothermic behaviour, this ensures the active cooling of the hot walls of the combustion chamber. However, one of the consequences of this thermal decomposition is the unwanted formation of coke which blocks the porous material (both on the surface and in the interior). This gradual blocking reduces the material's permeability and thus the efficiency of the cooling system. Modelling the permeability distribution of porous materials is thus a key parameter in better understanding transpiration cooling. The present article shows several models intended to estimate the variation in time and space of the permeability of a material (stainless steel) during its coking. The fluid circulating in this porous material is n-dodecane that is maintained at a high temperature. Following a presentation of the measurement device and the measured experimental data of the mean permeability, two categories of model are studied, notably discontinuous mesh models (with 2 and 3 meshes) and continuous analytical models (linear and exponential). The results obtained show that discontinuous models with 2 and 3 meshes are very close in measuring the temporal evolution of the thickness of the coked zone of the porous material. They also revealed that the exponential model is more appropriate than the linear model in estimating the spatiotemporal evolution of the permeability. Additionally, the evolution of the coking rate in the porous material was determined as a function of time and the results show behaviour similar to that indicated in the literature. Lastly, the average Darcy permeability was linked to the mass of coke deposit in the porous material, the result of which reveals a quasi-linear decrease. Nomenclature Latin letters e = Sample thickness e j [m] = Thickness of each layer j K = Hydraulic conductivity tensor K D = Darcian's permeability K Davg = Average Darcian permeability K D0 = Initial Darcian permeability K F = Forchheimer's permeability K j = Darcian permeability of each layer j P = Pressure ΔP = Pressure drop t = time T = temperature V = Mean fluid velocity Greek Letters ε = Overall open porosity μ = Dynamic viscosity ρ = Fluid density ø = Diamete

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Section: B Comparison Of Two Models: Linear and Exponentialsupporting

confidence: 71%

Modeling the spatio-temporal evolution of permeability during coking of porous material

Tabach¹,

Chetehouna²,

Gascoin³

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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“…Numerous investigations have been conducted to reduce coke formation, including altering the inner surface compositions on the inner surface of the coils, adding compounds, and increasing steam dilution ratio of feedstock …”

Section: Introductionmentioning

confidence: 99%

Effect of selective oxidation and sulphur/phosphorus‐containing compounds on coking behaviour during light naphtha thermal cracking

Bao

Liu

et al. 2017

Can J Chem Eng

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The investigation was aimed at evaluating the effect of selective oxidation and sulphur/phosphorus‐containing compounds on coking behaviour at the surface of HP40 alloy during thermal cracking of light naphtha. The surface morphology and composition of the selectively oxidized alloy were characterized by SEM, EDX, and XRD. Coking tests show that the coking rate of blank alloy decreased with sulphur/phosphorus‐containing compounds, while the effect of sulphur/phosphorus‐containing compounds on coking rate for selectively oxidized alloy is complex, and a mass concentration of µg/g results in the lowest coking rate. The morphology and microstructure of cokes were investigated by SEM and Raman spectra. SEM and Raman spectra analyses indicated that either selective oxidation or sulphur/phosphorus‐containing compounds resulted in more disordered graphite structures and amorphous carbon.

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“…Over time, coke forms on the inner surface of the pyrolysis coils, especially in the radiant section where temperatures are highest, due to undesirable side reactions. Coke formation has a deleterious influence on the energy efficiency and economic viability of ethylene production processes . The coke layer on the coil surface reduces heat transfer to the process gas inside the coils due to low thermal conductivity of the coke layer.…”

Section: Introductionmentioning

confidence: 99%

“…The resulting higher furnace temperature increases coil surface temperatures, which may reach or exceed the maximum permissible value imposed by the metallurgy of the coil . Note that coke formation is also associated with the formation of local hot spots that can damage furnace coils . Furthermore, the coke layer on the inside of the coils reduces the cross sectional area, which increases pressure drop through the coils if a constant ethylene production rate is maintained .…”

Section: Introductionmentioning

confidence: 99%

“…To our knowledge, coke formation models in the literature account only for the pyrolytic mechanism of coke formation, however, the catalytic coke formation mechanism may be important because it can influence the initial rate of pyrolytic coke formation and consequently change the overall rate of coke formation. Recently, advanced alloys have been produced that reduce the rate of catalytic coke formation . Incorporating a catalytic coke formation model with a specific parameter to account for tube surface effect may aid in the accurate prediction of run length.…”

Section: Introductionmentioning

confidence: 99%

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Modelling coke formation in an industrial ethane‐cracking furnace for ethylene production

et al. 2019

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The development of a model for predicting coke formation in an industrial ethylene cracking furnace is described. Expressions for predicting the rates of catalytic and pyrolytic coke formation are developed and a differential equation is derived to predict changes in coke thickness with time and position. An expression is developed to account for a decline in the rate of catalytic coke formation with increasing thickness of the coke layer. The proposed coke model equations are used to extend a previously developed ethane pyrolysis furnace model that ignored coke. Three model parameters related to coke formation are estimated using industrial data to obtain reliable model predictions. Two of these parameters are coefficients that appear in the catalytic and pyrolytic coke formation rate expressions. The third is a characteristic‐length parameter used to reduce the rate of catalytic coke formation as the coke layer grows. The resulting dynamic model matches the industrial data well and can be used to simulate furnace operation and predict coke thickness profiles over a variety of the operating conditions, thereby helping process engineers who plan the decoking process.

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Influence of the Reactor Material Composition on Coke Formation during Ethane Steam Cracking

Cited by 57 publications

References 54 publications

Modeling the spatio-temporal evolution of permeability during coking of porous material

Modeling the spatio-temporal evolution of permeability during coking of porous material

Effect of selective oxidation and sulphur/phosphorus‐containing compounds on coking behaviour during light naphtha thermal cracking

Modelling coke formation in an industrial ethane‐cracking furnace for ethylene production

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