A prediction model for dry sludge formation in residue hydroconversion.

Takatsuka, Toru; Wada, Yusaku; Hirohama, S.; Fukui, Yoshio

doi:10.1252/jcej.22.298

Cited by 20 publications

(6 citation statements)

References 2 publications

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“…Of the various residue-upgrading processes, , ebullated-bed residue hydroconversion − is the only proven technology capable of obtaining high conversion levels of residue fractions and leading to high yields of light and middle distillates. In general, the severity of hydroconversion operations in ebullated-bed units is limited by the formation of sediments − and by subsequent fouling of downstream equipment in the fractionation section − rather than by a limit in catalyst activity or other constraints.…”

Section: Introductionmentioning

confidence: 99%

“…Unconverted species were found to be of lower molecular weight ( M w ) with a lower number and lower length of alkyl chains. ,− With lower steric hindrance, stronger intermolecular aromatic interactions might occur, leading ultimately to aggregation and sediment formation. At the same time, hydrogenation reactions occur, increasing the proportion of saturates in the oil matrix, affecting its compatibility …”

Section: Introductionmentioning

confidence: 99%

“…At the same time, hydrogenation reactions occur, increasing the proportion of saturates in the oil matrix, affecting its compatibility. 7 To avoid sediment formation during hydroconversion, one approach consists of increasing the aromatic content in the reactor to boost interactions between aromatics and asphaltenes, thereby avoiding asphaltene aggregation. A recent study 31 has shown that aromatic feeds, such as heavy cycle oils (HCOs) and light cycle oils (LCOs), derived from a fluid catalytic cracking (FCC) unit are indeed efficient inhibitors of sediment formation in high-temperature operation in a fixed-bed reactor.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of Ebullated-Bed Effluent Stability at High Conversion Operation

2011

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This work concerns the study of sediment formation in ebullated-bed hydroconversion of vacuum residues and investigates ways to avoid their formation at high conversion operation. Tests were carried out in a bench-scale unit at high temperature using a vacuum residue feedstock. Feeds and effluents were characterized to follow sediment formation, as well as conversion, yield structure, and hydrotreating performances. It was found that co-processing a vacuum residue feedstock with low amounts (<15 wt %) of heavy cycle oil from a fluidized catalytic cracking (FCC) unit can significantly improve the stability of the unconverted effluents. A detailed characterization of feedstock and products was carried out to understand the stabilization mechanisms. The effect of heavy cycle oil (HCO) on sediment reduction was attributed to the polycondensed tri-, tetra-, and pentaaromatics. It was also found that these species do not affect the hydroconversion performances and are refractory to conversion.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improvement of Ebullated-Bed Effluent Stability at High Conversion Operation

2011

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“… Initial accumulation of the highly aromatic asphaltene cores in the oil phase , stabilized in solution by the heavy maltenic fractions and prevented from forming higher molecular weight asphaltene cores by hydrogen donation from the heavy maltenic species which inhibits the combination reaction pathways. Phase separation of asphaltene cores triggered once the concentration of AS + in the oil phase exceeds a specific solubility limit, followed by rapid molecular weight growth of the asphaltene cores in the new phase lean in hydrogen donating and dispersing heavy maltenic solvent molecules, resulting in the formation of solid coke precipitated in the reactor , as illustrated in Figure 3. Owing to the above features, the Wiehe LR kinetics model 14,15 is able to capture important characteristics of the batch reactor experimental data for VR and heavy oil thermolysis like: (i) the coke induction period (wherein no solid coke precipitation is observed in the reactor until a specific reaction time instant) observed in both, Wiehe's extensive experimental work 14,15 as also in other earlier experimental studies reported in the literature, 17–24 and (ii) the maximum in asphaltene concentration in the reactor at the onset of coke formation. In fact, the hypothesis of coke formation triggered by phase separation was first postulated by Magaril et al 19,25,26 and was employed in earlier LR kinetic models for VR hydroconversion by Sosnowski et al 27 and Takatsuka et al 28 A detailed discussion of the important chemical pathways and characteristic features of the thermolysis of heavy oils and VR is taken up in Section 2 of Appendix S1. The details of the Wiehe model are elaborated in Section 2.2.1.…”

Section: The Tpsr Model: Formulation and Sub‐modelsmentioning

confidence: 99%

Inference of reaction kinetics for supercritical water heavy oil upgrading with a two‐phase stirred reactor model

Raghavan

Ghoniem

2021

AIChE Journal

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We present the development and application of a two‐phase stirred reactor model for heavy oil upgrading in the presence of supercritical water (SCW), with coupled phase‐specific thermolysis reaction kinetics and multicomponent hydrocarbon–water phase equilibrium. We demonstrate the inference of oil and water phase kinetics parameters for a compact lumped reaction kinetics scheme through the application of this model to two different sets of batch reactor experiments reported in the literature. We infer that, although SCW can suppress the formation of newer polynuclear aromatics (PNA) from distillate range species, it is broadly ineffective in deterring the combination of pre‐existing PNA fragments in the oil feed. Quantification of the conversion to distillate liquids before the onset of coke formation helps arrive at a clear conclusion on whether the use of SCW in the batch reactor leads to better product outcomes for different oil feeds and operating conditions.

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“…An increase in the conversion of vacuum residue increases the aromaticy of the asphaltenes and decreases the aromaticy of the maltenes (15). Consequently, the solubility of the asphaltenes in the maltenes decreases.…”

Section: Intermediate Catalyst Deactivationmentioning

confidence: 99%

Catalyst Deactivation in Commercial Residue Hydrodesulfurization

Koyama

Nagai

Kumagai

1996

ACS Symposium Series

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It has been proposed that, as an increase in the conversion of vacuum residue in the commercial fixed-bed reactors, a coke-controlled catalyst deactivation regime appears in the last bed, where coke blocks the active sites as well as decreases the diffusivity. The activity and diffusivity tests were conducted for aged and regenerated catalysts, which were used in the commercial reactors, to investigate mechanisms of the deactivation by coke and metal deposition. The effects of residue conversion, reactor position, and time on-stream on the deactivation were investigated, comparing the catalysts aged at different conditions.The Mizushima Oil Refinery of Japan Energy Corporation first implemented a high conversion operation of vacuum residue, versus a constant desulfurization operation, in the commercial residue hydrodesulfurization unit equipped with fixed-bed reactors, to produce more middle distillates as well as fuel oil with lower viscosity. The catalysts will be replaced when the sulfur content in the product oil reaches the allowable limit. Since we have believed that an increase in the residue conversion decreases the catalyst activity by coke deposition, we have been interested in controlling the coke deactivation to maximize the residue conversion during a scheduled operating period.Though a number of researchers have proposed deactivation mechanisms and models of the residue hydrodesulfurization catalysts, most of them are correlated with the amount and distribution of Ni and V deposited on the catalyst surface (1,2, 3, 4). Newson has proposed a semi-quantitative deactivation model accounting for pore plugging by both coke and metal sulfides (5). Bartholdy and Cooper studied the catalyst deactivation at a constant desulfurizarion operation and a high temperature operation (6). They suggest that a high temperature operation causes an initial larger activity loss due to coke deposition. Meyers et al. examined the effects of coke and metal sulfides on residue catalyst deactivation in three-stage expanded-bed reactors with a high residue conversion operation, and observed the largest deactivation in the

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A prediction model for dry sludge formation in residue hydroconversion.

Cited by 20 publications

References 2 publications

Improvement of Ebullated-Bed Effluent Stability at High Conversion Operation

Improvement of Ebullated-Bed Effluent Stability at High Conversion Operation

Inference of reaction kinetics for supercritical water heavy oil upgrading with a two‐phase stirred reactor model

Catalyst Deactivation in Commercial Residue Hydrodesulfurization

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