Francis V. Hanson

Supercritical fluid extraction of bitumens from Utah oil sands

Abstract The supercritical fluid extraction (SFE) of bitumens from four major Uinta Basin (Utah) oil sand deposits was studied with propane solvent. The deposits studied included Whiterocks, Asphalt Ridge, PR Spring and Sunnyside. The bitumens from these deposits differed widely in physical and chemical properties. The volatilities (components with boiling point n -pentane insolubles) were 2.9, 6.8, 19.3 and 23.6 wt.% for the Whiterocks, Asphalt Ridge, PR Spring and Sunnyside bitumens, respectively. The SFE experiments were carried out at five conditions, combinations of three different pressures (5.6 MPa, 10.4 MPa, and 17.3 MPa) and three temperatures (339 K, 380 K and 422 K). The cumulative extraction yield increased with increase in solvent density at all operating conditions for the four bitumens. A maximum yield of 45 wt.% was obtained at the highest solvent density with the Whiterocks bitumen. The extraction products were significantly upgraded liquids relative to the bitumens. Comparatively lighter fractions were extracted in the earlier stages of extraction for all the four bitumens, whereas heavier extracts were obtained at higher extraction-solvent densities. The asphaltene contents of the residual fractions were significantly higher than the asphaltene contents predicted on a prorated basis for all four bitumens. This trend was due to the extraction of cosolubilizing components that kept the asphaltenes in suspension in the bitumen. It was concluded that solute polarity played a significant role in the extraction yields of the four bitumens. The Whiterocks bitumen, which was the least polar bitumen based on asphaltenes content, gave higher extraction yields compared to the bitumens from the other three deposits at all five operating conditions. The Sunnyside bitumen with the highest asphaltene content gave the lowest extraction yield at all five conditions. The Asphalt Ridge and PR Spring bitumens with intermediate polarity (based on asphaltene content) gave intermediate extraction yields with the Asphalt Ridge bitumen extraction yields higher than the PR Spring bitumen. Preliminary modeling of the extraction process using the Peng–Robinson cubic equation of state and a pseudocomponent lumping scheme provided a reasonable match with the experimental data for Whiterocks and PR Spring bitumens.

Supercritical fluid extraction of a crude oil, bitumen-derived liquid and bitumen by carbon dioxide and propane☆

Abstract Extractions of a crude oil, a bitumen-derived liquid and bitumen were conducted at several temperatures and pressures with carbon dioxide and propane in order to assess the effect of the size and type of compounds in the feedstocks on the extraction process. The pure-solvent density at the extraction conditions was not the only variable governing extraction, and the proximity of the extraction conditions to the pure-solvent critical temperature affected the extraction yields and the compositions of the extract phases. Higher oil yields were obtained at lower solvent reduced densities when the extraction temperatures were in the vicinity of the pure solvent critical temperature. In the crude oil and native bitumen extractions, as the extraction time and/or the extraction pressure increased, heavier compounds were found in the extract phases. This preferential extraction was not observed with the bitumen-derived liquid. The non-discriminatory extraction behaviour of the bitumen-derived liquid was attributed to its thermal history and to the presence of olefins and significant amounts of aromatics. Phase behaviour calculations using the Peng-Robinson equation of state and component lumping procedures provided reasonable agreement between calculated and experimental results for the crude oil and bitumen extractions, but failed to predict the bitumen-derived liquid extractions.

The influence of carboxylic acid content on bitumen viscosity

Abstract Bitumens from six diverse tar sand deposits were obtained by toluene extraction. The viscosities of each of the bitumens were determined in the temperature range 60 to 90 °C and were found to be Newtonian in character. All bitumen samples were fractionated using a modified SARA (saturates, aromatics, resins and asphaltenes) type analysis. The separated fractions were examined by transmission and specular reflectance FT-i.r. spectrsocopy (SR-FT-i.r.). The FT-i.r. analysis indicated that carboxylic acid present in the bitumen accumulated in the polar fractions, particularly in the resin fraction. The carboxylic acid concentration was estimated from its characteristic FT-i.r. absorbance band by the band-fit method. The carboxylic acid in the resin fractions was also estimated by a potentiometric titration method using a mixed solvent. Although it was clearly indicated from the infrared analysis of the bitumen fractions that bitumens with higher viscosity generally contained larger amounts of carboxylic acid, a simple quantitative relationship between these two variables to the exclusion of others in a complex material such as bitumen was found to be difficult. The viscous nature of the bitumen is principally attributed to the internally suspended asphaltene particles. The fractional compositions of the various bitumens clearly indicated that the viscosity of a given bitumen cannot always be correlated with its asphaltene content alone. However, the introduction of another variable, namely the carboxylic acid content of the bitumen, together with asphaltene content can better account for the property of viscosity. The Athabasca sample was the least viscous of all the bitumens under study, although it contained an intermediate amount of asphaltenes. FT-i.r. analysis indicated that the Athabasca resin fraction contained only a small amount of acid and was explained to be inadequate to optimally engage the asphaltenes in suspension through hydrogen bonding. In addition, it was shown that the major oxygen functional group in Athabasca bitumen is an ester which was believed to be not as efficient as an acid in the hydrogen bond formation. The presence of esters in the Athabasca resin fraction was confirmed by the hydrolysis of the resin fraction and analysis of the hydrolysis products by SR-FT-i.r. The influence of carboxylic acid and asphaltene contents on bitumen viscosity is discussed with reference to the structural model developed by Nellensteyn.

Fluidized bed pyrolysis of a Uinta basin oil sand

Abstract The pyrolysis of the mined and crushed ore from the Whiterocks oil sand deposit was studied in a fluidized bed reactor. The reactor was designed to operate by pulling the fluidizing gas through the reactor rather than by pushing the gas through the bed. This was accomplished by reducing the pressure above the bed with a gas pump operating in the suction mode. This mode of operation resulted in smooth, stable fluidization without slugging at H D ratios up to 8. Pyrolysis energy was supplied by a propane burner, and the hot combustion gases were used to fluidize the bed. Operating the pyrolysis reactor without slugging allowed the reactor to be operated at lower temperatures than previously reported for equivalent liquid product yields. The bitumen-derived liquid yields ranged from 80 to 90 wt% based on bitumen fed to the reactor in the temperature range 720–773 K. Less than 1 wt% of the bitumen fed to the reactor was converted into a carbonaceous residue on the spent sand.

Crude Oil Characterization and Regular Solution Approach to Thermodynamic Modeling of Solid Precipitation at Low Pressure

Abstract Wax and asphaltene precipitation have caused many problems in the petroleum industry. One of the ways to mitigate the problems is to have a model that can predict the conditions at which the precipitation occurs and the amount of solids precipitated. Several models have been proposed in the past. However, the models are for either wax or asphaltene precipitation. Moreover, the previously proposed models usually involve the use of fitting parameters to match the calculated results to the experimental values. The incorporation of fitting parameters limits the predictive capability of the models. Therefore, it is useful to have a predictive model that can describe the precipitation of both wax and asphaltene. In addition to modeling, crude oil characterization is also important. Experimental data are needed for input to the model and for model validation. Hence, this study has focused on both experimental techniques for crude oil characterization and the modeling of solid precipitation from crude oils. This article will discuss the capability of a thermodynamic model, which uses regular solution theory to describe the precipitation of both wax and asphaltene at different conditions. The data for the model input were obtained using experimental techniques such as TBP distillation, solvent extraction, HPLC, HTGC, SEC, and RI measurement. A discussion on using the model for description of the solids precipitation caused by the addition of n-alkane to the crude oil will also be presented.

Fluidization of a multi-sized group B sand at reduced pressure

Abstract The fluidized bed pyrolysis of oil sand produces a spent sand which contains 1–2 wt.% carbonaceous residue. The rapid bitumen pyrolysis reactions indicate that the fluidized bed inventory is essentially spent sand. This spent sand has been shown to be a Group B sand according to the classification scheme of Geldart. A multi-sized Group B sand was smoothly fluidized with air by reducing the pressure above the surface of the bed to less than the pressure at the inlet of the distributor. Beds of sand with heights up to four times the reactor diameter were taken from the slugging regime to smooth fluidization by changing the effective distributor pressure drop while the reactor was operating at reduced pressure above the bed. The characteristics of reactor pressure drop versus superficial gas velocity were determined for the multi-sized particles under reduced pressure and compared to the fluidization behavior of multi-sized particles in the more common positive gas pressure systems. The shapes of fluidizing and defluidizing curves caused by pulling air from the reactor top were similar but not the same as curves obtained at atmospheric pressure by pushing air through the distributor. An ‘interpreted’ minimum fluidization velocity definition for multi-sized particles fluidized at reduced pressures is proposed and shown to be consistent with predictive correlations.

Re-examination of minimum fluidization velocity correlations applied to Group B sands and coked sands

Abstract Fourteen previously published variations of the Ergun equation were studied and found to be unreliable predictors of minimum fluidization velocity for some Group B sands, including coked sands, at ambient conditions. Three simplified versions of the Ergun equation were found to adequately correlate published fluidization data for over 25 Group B sands at ambient temperatures. A relationship between Umf and T was found and incorporated into a proposed method for predicting Umf at elevated temperatures.

Pyrolysis of bitumen-impregnated sandstones: a comparison of fluidized bed and rotary kiln reactors☆

Abstract A series of stationary-state pyrolysis experiments have been completed with the mined ore from the Whiterocks tar sand deposit. The C5+ hydrocarbon liquid yield decreased with increasing solids retention time at fixed operating temperatures in both fluidized bed and rotary kiln reactors. The liquid yield obtained with the rotary kiln was higher than that obtained with the fluidized bed at comparable operating conditions. The bitumen-derived hydrocarbon liquids produced in the rotary kiln reactor were significantly upgraded relative to the natural bitumen. The total asphaltene content as determined by gradient elution chromatography was reduced by 50–63%.

Hydrotreating the bitumen-derived hydrocarbon liquid produced in a fluidized-bed pyrolysis reactor

Abstract The pyrolysis of bitumen-impregnated sandstone produces three primary product streams: C 1 C 4 hydrocarbon gases, a C 5 + total liquid product, and a carbonaceous residue on the spent sand. The bitumen-derived hydrocarbon liquid was significantly upgraded relative to the native bitumen: it had a higher API gravity, lower Conradson carbon residue, asphaltene content, pour point and viscosity, and a reduced distillation endpoint relative to the native bitumen. The elemental composition was little different from that of the native bitumen except for the hydrogen content, which was lower. Thus, integration of the bitumen-derived liquid into a refinery feedstock slate would require that it be hydrotreated to reduce the nitrogen and sulphur heteratom concentrations and to raise the atomic hydrogen-to-carbon ratio. The bitumen-derived liquid produced in a fluidized-bed reactor (diameter 10.2 cm) from the Whiterocks tar sand deposit has been hydrotreated in a fixed-bed reactor to determine the extent of upgrading as a function of process operating variables. The process variables investigated included total reactor pressure (11.0–17.2 MPa (1600–2500 psig)); reactor temperature (617–680 K; (650–765 °F)) and liquid hourly space velocity (0.18-0.77 h −1 ). The hydrogen/oil ratio was fixed in all experiments at 890 m 3 m −3 (5000 scf H 2 /bbl). A sulphided Ni-Mo on alumina hydrodenitrogenation catalyst was used in these studies. The extent of denitrogenation and desulphurization of the bitumen-derived liquid was used to monitor catalyst activity as a function of process operating variables and to estimate the extent of catalyst deactivation as a function of time on-stream. The apparent kinetics for the nitrogen and sulphur removal reactions were determined. Product distribution and yield data were also obtained.

Pyrolysis of oil sand from the Whiterocks deposit in a rotary kiln

Abstract A rotary kiln reactor was evaluated for thermal recovery of oil from Utah oil sands. A series of continuous-flow pyrolysis experiments was conducted. Process variables investigated included temperature (748–848 K), solids retention time (10–27 min) and sweep gas flow rate (1.27–2.83 m s 3 h −1 ). The results indicated that the pyrolysis temperature and the solids retention time were the two most important variables affecting the liquid and gas yields. The liquid yield (C 5 + ]) decreased and the gas yield (C 1 –C 4 ) increased with increasing temperature. The liquid yield increased with decreasing solids retention time, while the gas yield decreased. No significant effect of the sweep gas flow rate on the product distribution and yields was observed. The quality of the bitumen-derived liquids was significantly better than that of the bitumen. A preliminary process kinetics model which conforms to the observed trends was proposed.