The Effect of Visbreaking Conditions on the Stability of Some Iraqi Long Residues

Savaya, Z.F.; Al-Soufi, H.H.; Mohammed, H.K.

doi:10.1080/08843758808915891

Cited by 5 publications

(12 citation statements)

References 2 publications

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“…For example, at 5.4 wt % residue conversion, the P-value decreased from 3.0 to 2.7 as the equivalent residence time at 427 °C was increased from 130 to 153 s. 14 (b) The relationship between the increase in phase instability and increase in visbreaking severity depended on the chemical nature of the residue feed. 7 Phase instability of asphaltic feed materials increased gradually with an increase in visbreaking severity, whereas a rapid increase in the instability of the more paraffinic feed was found at operating temperatures >460 °C. For example, as the visbreaking temperature was increased from 420 to 460 °C, the flocculation ratio of a more paraffinic residue increased from 23 to 28%, but as the temperature was increased from 460 to 480 °C, it increased from 28 to 92%.…”

Section: Introductionmentioning

confidence: 96%

“…For example, as the visbreaking temperature was increased from 460 to 480 °C, the flocculation ratio increased from 28 to 92%, 52 to 63%, and 46 to 49%, respectively, for three different residues. 7 Analogous observations were made using the P-value as a measure of phase stability. Even when there was little or no apparent change in the residue conversion, the Pvalue decreased with increasing severity.…”

Section: Introductionmentioning

confidence: 99%

“…For example, as the visbreaking temperature was increased from 420 to 460 °C, the flocculation ratio of a more paraffinic residue increased from 23 to 28%, but as the temperature was increased from 460 to 480 °C, it increased from 28 to 92%. 7 (c) It was shown that the increase in phase instability could be related to a change in the solubility parameter (δ) distribution of the visbroken product. 11 As visbreaking severity increased, there was a decrease in the lower solubility parameter material.…”

Section: Introductionmentioning

confidence: 99%

“…Stability of the visbroken product is important, and oil stability in general refers to the ability of the oil to resist change over time . Several studies on the topic of the stability of visbroken products were found in the literature. − …”

Section: Introductionmentioning

confidence: 99%

“…The observations about visbroken product stability from the literature were summarized using this descriptive framework. Phase instability of visbroken products increased as the visbreaking severity by which the products were produced was increased. − ,, The amount of xylene in a xylene–alkane mixture that just prevents formation of a second phase, i.e., flocculation ratio, or xylene equivalence, was reported in many studies as a measure of phase stability. With increasing visbreaking severity, an increasing amount of xylene was required to prevent second phase formation.…”

Section: Introductionmentioning

confidence: 99%

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Storage Stability of Products from Visbreaking of Oilsands Bitumen

2020

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Thermal conversion of bitumen by visbreaking is an important technology for partial upgrading of bitumen to pipeline transportable oil. The product from visbreaking of bitumen will likely spend a long time in storage or transport before being used, and due to cost considerations, postprocessing should be minimal. This study investigated the changes that take place over time during storage of visbroken bitumen (420 °C, 18–22 min) under nitrogen atmosphere in the dark. The study did not investigate phase instability, and it focused on chemical and physical changes taking place over a storage period of 20 weeks. With increasing storage time many properties of the visbroken liquid product changed; notably, refractive index, density, viscosity, microcarbon residue, and n-pentane insoluble content increased, while free radical content and aromatic hydrogen content decreased. The observed changes during storage are best explained by the formation of products with higher molecular mass. Although care was taken to limit the potential impact of oxidation, indirect evidence of the impact of oxidation due to dissolved oxygen was found during the initial 2 weeks of storage. Oxidation was not a prerequisite for free radical reaction during storage because the visbroken product already contained persistent free radicals, as is typical of high boiling petroleum fractions. Free radical termination reactions took place, but the extent of the changes in the properties with storage time was not consistent with simple radical–radical termination reactions as the only source of heavier products. Alkenes (olefins) formed during thermal conversion were likely involved in free radical propagation reactions by radical–alkene addition to form heavier products. The relationship between free radical content and storage instability, the nature of reactions taking place during storage, and the nature of the species in visbroken bitumen leading to storage instability were discussed. To reduce the formation of products with higher molecular mass during the storage of visbroken material, in addition to maintaining oxygen-free conditions, it is necessary to decrease the amount of free radicals and the amount of alkenes in the product.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Storage Stability of Products from Visbreaking of Oilsands Bitumen

2020

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Theoretical Approach to the Stability of Visbroken Residues

Rogel¹

1998

Energy Fuels

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A theoretical method to calculate solubility parameter distributions was used to study the main factors that affect the stability of residues and products of their visbreaking with respect to asphaltene deposition. With this method it was possible to analyze the changes observed on the solubility parameter distributions of asphaltenes due to visbreaking. The results obtained showed a decrease in easily soluble asphaltenes, while there is an increase in difficult-to-dissolve asphaltenes during processing. To evaluate the instability, a compatibility index between asphaltenes and resins/or aromatics is proposed using the theoretical solubility profiles. By use of this index, it was possible to identify the factors involved in instability and to establish their relative importance for each sample. Among all the factors studied, the characteristics of the asphaltene fraction seem to be the main one. For the group of fractions examined, it was found that the average solubility parameter calculated was directly proportional to the H/C atomic ratio.

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Petroleum Residue Upgradation via Visbreaking: A Review

Joshi

Pandit

Kataria

et al. 2008

Ind. Eng. Chem. Res.

155

124

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World petroleum residue processing capacity has reached about 810 MMTPA. In the present petroleum refining scenario, the viability of a petroleum refinery strongly depends on the flexibility of processing heavy crudes and, in turn, heavy residues. Visbreaking is one of the major residue upgrading processes and constitutes about 33% of the total residue processing capacity. In the present communication, the published literature pertaining to the visbreaking process has been extensively analyzed and a state-of-the-art review has been written that includes the following: (i) the effect of feed properties on fuel oil stability; (ii) reaction pathways, mechanism, and kinetics; (iii) parametric sensitivity of the operating variables such as temperature, pressure, and residence time; (iv) different visbreaker designs, viz. coil visbreaker, coil-soaker visbreaker, soaker with internals, and high conversion soaker; (v) coking and fouling; (vi) estimation of design parameters, viz. gas holdup in high-pressure bubble column (soaker), gas holdup in sectionalized bubble column (soaker with internals), liquid-phase mixing and axial mixing in high-pressure bubble column, liquid-phase mixing and axial mixing in sectionalized bubble column, and weeping; and (vii) mathematical modeling of visbreaker, which mainly includes the coil and the soaker. An attempt has been made to get the aforementioned aspects together in a coherent manner so that the information is available at a glance and is expected to be useful to researchers and practicing refiners.

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The Effect of Visbreaking Conditions on the Stability of Some Iraqi Long Residues

Cited by 5 publications

References 2 publications

Storage Stability of Products from Visbreaking of Oilsands Bitumen

Storage Stability of Products from Visbreaking of Oilsands Bitumen

Theoretical Approach to the Stability of Visbroken Residues

Petroleum Residue Upgradation via Visbreaking: A Review

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