Luba S. Kotlyar

Athabasca oil sands: effect of organic coated solids on bitumen recovery and quality

Abstract The Canadian oil sands deposits in northern Alberta contain about 1.3 trillion barrels of crude oil equivalent. The largest of the four major formations is found in the Athabasca region where bitumen is heterogeneously distributed throughout an unconsolidated mineral matrix. About one-tenth of the oil sands in this deposit is economically recoverable by conventional surface mining techniques. The Hot Water Extraction Process (HWEP) is used commercially to recover bitumen from surface mined oil sands ore. The viability of this process relies on the existence of a thin water film around each solid particle in the ore matrix. However, a completely water-wet mineral condition is not generally the case for oil reservoirs, including oil sands deposits. In the latter case, it has been shown that certain solid fractions are associated with significant amounts of toluene insoluble organic matter (TIOM), physically or chemically adsorbed onto particle surfaces. These fractions are generically described as ‘organic rich solids’ (ORS). In bitumen separation processes, the organic matter associated with various ORS fractions represents an impediment to optimum bitumen separation and upgrading. In this sense, these solids are considered to be ‘active’ relative to the ‘inactive’ water wetted quartz particles comprising the bulk of the oil sands ore. Preliminary results indicate that the ORS content of an ore appears to be a better predictor for ore processability than the traditional use of bitumen or fines (−44 μm) contents. Two types of ORS have received particular attention. The first is a coarser fraction, usually less than 44 μm but also occurring as particles greater than 100 μm in diameter. This material typically occurs as aggregates of smaller particles bound together by humic matter and precipitated minerals. During the bitumen separation process, these heavy aggregates carry any associated bitumen into the aqueous tailings, thus reducing overall bitumen recovery. The second important fraction comprises very thin, ultra-fine clay particles with a major dimension of

DISTRIBUTION AND TYPES OF SOLIDS ASSOCIATED WITH BITUMEN

ABSTRACT In the conventional Hot Water Extraction Process bitumen is separated as a froth that is then diluted with naphtha and subjected to two stages of centrifugation. The resulting bitumen solution still contains residual water, dissolved salts and mineral solids. Before upgrading the solvent and other volatile components are removed by topping at 524°C. The salts and mineral solids remain with topped bitumen; their presence can lead to serious operational problems in the bitumen upgrading process. In the present work the solids associated with bitumen (BS) have been identified as mainly ultra-fine (nano sized) aluminosilicate clays coated with strongly bound toluene insoluble organic material having “asphaitene characteristics”. It is proposed that these ultra-fine clays with their strong tendency to collect at oil-water interfaces, are the key component responsible for the presence of intractable water and associated salts in bitumen froth.

Molecular transformation of Athabasca bitumen end-cuts during coking and hydrocracking

Abstract The use of supercritical pentane, under increasingly severe conditions of temperature and pressure, allows residual oils to be separated into fractions with progressively higher molecular weight without significant chemical degradation. Characterisation of these individual fractions provides a more complete picture of bitumen resid chemistry than average values determined for the whole sample. In the work described here, this approach has been applied to resid samples taken from the bitumen upgrading units at the Syncrude Canada Ltd. plant in Northern Alberta (Oil Gas J, 20 (1997) 66; Rev Process Chem Engng, 1 (1998) 41). A significant amount of each sample was non-extractable under even the most severe conditions. These end-cuts from virgin bitumen pitch (P-EC), hydrocracking product resid (HC-EC) and coking product resid (CK-EC) were compared to pentane insoluble asphaltenes (ASP) from a conventional coker feed bitumen. In addition, the P-EC sample was subjected to further fractionation based on its solubility in different blends of toluene and pentane. The P-EC sample comprises about 55%(w/w) highly aromatic heavy molecules, rich in heteroatoms and metals. Smaller molecules, with much lower aromaticity and polarity, represent the remaining 45%(w/w). Owing to a their high heteroatom and metals content, the heavier molecules in this material are considered to be major coke precursors under thermal cracking conditions. However, in hydrocracking the free radicals generated by the cleavage of carbon–carbon and sulphur–carbon bonds are suppressed by hydrogen capping. As a result, the “difficult to crack” aromatic “cores” of the heavier components remain toluene soluble. Although these components do not form coke under hydrocracking conditions, they may cause fast catalyst deactivation. In existing commercial processes the residue from hydrocracking is recycled to extinction in a coker. Because of its intractable nature, this heavy resid may not be conducive to the production of lighter liquid products. It is suggested that, prior to hydrocracking, the heaviest portion of bitumen pitch be removed to avoid these problems.

Solids contents, properties and molecular structures of asphaltenes from different oilsands

Abstract As the Canadian supply of light crudes has diminished in recent years, refineries have necessarily been required to deal with difficult to process oilsands bitumens and heavy oils. Bitumen in particular exhibits unique behavior during upgrading; nearly 50% (w/w) of the feedstock is an intractable residuum. The fast catalyst deactivation and high coke forming propensity displayed by this feedstock have been attributed to the asphaltene and associated solids contents of extracted bitumen. The variability of these intractable components in bitumens from mined and in-situ Athabasca oilsands were examined and compared with bitumens from Nigerian and Utah oilsands. Except for the in-situ bitumen, all of the samples were found to contain significant amounts of fine solids. Unexpectedly, the in-situ bitumen also contained the least amount of asphaltene and the highest amount of the intractable heteroatoms nickel and vanadium. Solids-free asphaltene samples were characterized by several complementary analytical techniques to determine the relative abundance of different carbon types and to calculate their average three-dimensional molecular conformations. Even though the parent bitumens came from geographically diverse sources the corresponding asphaltene fractions had similar structures. Each sample comprised basic units, or ‘cores’, of condensed aromatic rings connected by bridges. The main differences relate to the number and complexity of the basic units.

CHARACTERIZATION OF COLLOIDAL SOLIDS FROM ATHABASCA FINE TAILS l

During processing of Athabasca oil sands, the finely divided solids form an aqueous suspension, which ultimately stabilizes as a gel-like structure retaining up to 90% of the process water. This gelling phenomenon is believed to be caused by colloidal inorganic components. Kaolinite and mica are the main crystalline minerals in these colloidal solids; swelling clays are present in only trace amounts. Non-crystalline components are more concentrated in the finer fraction of the solids. Although the surfaces of the colloidal solids are virtually free of Fe, some contamination with polar organic matter is observed.

Quantification of crystalline and noncrystalline material in ground kaolinite by X-ray powder diffraction, infrared, solid-state nuclear magnetic resonance, and chemical-dissolution analyses

The capabilities of X-ray powder diffraction (XRD), infrared absorption (IR), solid-state magicangle-spinning nuclear magnetic resonance (MAS-NMR), and chemical dissolution methods were assessed for estimating the amount of noncrystalline material in a ground kaolinite. The Georgia kaolinite was ground in a mechanical mortar for various lengths of time to produce a set of ground samples containing different amounts of the resulting noncrystalline material. In the XRD method, the intensities of characteristic reflections at 7.2 and 4.47 Å did not respond proportionally to the amount of crystalline kaolinite. Although a transmission-type X-ray diffraction method using the hk reflection gave a slightly better estimate than the reflection-type X-ray diffraction method using the basal reflection, both methods gave overestimated values for the amount of noncrystalline material. This overestimation may have been caused by a masking effect due to coaggregation. Using the characteristic IR absorption band at 3700 cm-1 underestimated the amount of the noncrystalline material, if the proportion of this material <50%.Extraction with NaOH gave estimations 15 to 20% greater than extraction with alkaline Tiron, except for the sample ground for 24 hr, for which both extractions indicated the presence of about 50% noncrystalline material. X-ray powder diffraction data of the residues after these extractions indicated that they consisted of crystalline kaolinite. 29Si NMR spectra of samples ground for » 30 hr suggested that SiO4 tetrahedra were considerably distorted.27 Al NMR spectra showed a signal for tetrahedral A1 for the sample ground for 10 hr, which increased with an increase in grinding time. Plots of the Al(IV)/[Al(IV) + Al(VI)] ratios vs. time were similar to those of chemical extraction curves. Inasmuch as extraction with hot 0.5 M NaOH is a rather harsh treatment, the composition of the noncrystalline material must have been similar to that of the crystalline kaolinite. The chemical dissolution using alkaline Tiron appeared to be superior to other methods, such as XRD, IR, and NaOH extraction, for estimating the amount of noncrystalline material in kaolinite.

Characterization of organic-rich solids fractions isolated from Athabasca oil sand using a cold water agitation test

Using a cold water agitation test (CWAT), different grades of oil-sand solids were separated into three fractions with respect to their insoluble organic carbon content (IOCC). Solids enriched with humic matter (IOCC ~36%) were present in association with bitumen, whereas solids with an IOCC of about 5% occurred suspended in the aqueous phase. The IOCC of the remaining solids was very low (<0.3%). Comparison of HC and OC atomic ratios of the different solid fractions rich in organic matter with corresponding results for different types of kerogen indicated that oil-sand organic matter has the same origin as kerogen type III. On the basis of 13C n.m.r. data the oil-sand humic matter was found to be of similar maturity as subbituminous coal. It has been shown that solids associated with bitumen have high concentrations of Ti, Zr and Fe. Solids occurring in the form of an aqueous suspension were enriched with alumina.

Non-crystalline inorganic matter-humic complexes in Athabasca oil sand and their relationship to bitumen recovery

Bitumen-free solids from different grades of Athabasca oil sand were fractionated according to particle size before and after treatment with sodium pyrophosphate (Na4P2O7) solution. All solids showed decreasing amounts of organic matter from coarse to fine fractions. The concentration of organic carbon retained in all size fractions after the treatment was found to be significantly lower as compared with that before the treatment. The mineralogy and some chemical properties of the material separated as a result of treatment were investigated. The data obtained indicate that treatment releases mostly non-crystalline compounds (possibly metal oxides in some kind of association with humic matter). A cold-water agitation test (CWAT) was used to correlate bitumen recovery with the amount of inorganic matter-humic complexes separated. It was observed that most of the bitumen was liberated when inorganic matter-humic complexes could be separated during the CWAT. For some oil sands complexes could not be isolated and in these cases most of the bitumen appeared to be associated with that fraction of solids consisting of globules of fine sand and clay particles cemented together with humic matter.

Adsorption of Pentane Insoluble Organic Matter from Oilsands Bitumen onto Clay Surfaces

Abstract The effectiveness of commercial oilsands separation processes relies on the water wettability of the solids. Consequently, the interaction between the mineral and organic matter types present in oilsands is of interest. In this work, we report results related to the adsorption of a pentane insoluble fraction from bitumen on kaolinite and illite, the major clay types present in oilsands. We determined adsorption from toluene solution by illite and kaolinite and use a combination of spectroscopic techniques to probe the organic coated clay surfaces to different depths. The results are compared with similar data for equivalent natural fractions from oilsands.

Impact of fines content on a warm slurry extraction process using model oilsands

Abstract Natural oilsands deposits are composed of a complex mixture of sand, silt, clay, water and bitumen. The bitumen content and silt fraction, or fines (