Milind D. Deo

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.

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.

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.

A model for the prediction of bubble size at a single orifice in two-phase gas-liquid systems

Abstract A new model for the prediction of volumes of bubbles generated from a single orifice in two-phase gas—liquid systems has been developed based on a rigorous bubble closure mechanism. The interaction between the primary bubble and subsequent bubbles formed at the orifice has been incorporated into the model at high gas flow rates. The distance traveled by the bubble from the orifice before it detaches is also calculated by the model. This has been validated by comparison with the available experimental data and it is found that this model represents an improvement over previous models.

Hydrotreatment process kinetics for bitumen and bitumen-derived liquids☆

Abstract Hydrodenitrogenation, hydrodesulfurization and resid conversion data for the Whiterocks bitumen and bitumen-derived liquid were analysed using a modified power rate law model. The data were obtained with a fixed-bed reactor in the upflow mode. A space velocity (WHSV α ) term was included to account for deviations from plug flow behaviour. The upflow mode was preferred to the trickle-bed mode to ensure complete wetting of the catalyst and nearly isothermal operation. The apparent kinetic parameters were obtained by combined non-linear regression and ODE solver techniques for the analysis of laboratory data. A simple n th-order power rate law expression for hydrodenitrogenation and hydrodesulfurization was examined. The higher than first-order kinetics for hydrodenitrogenation and hydrodesulfurization of the bitumen and bitumen-derived liquids were explained by invoking two parallel first-order reactions for the facile and refractory fractions or lumps. Parallel and consecutive reaction schemes were used to examine the extent of conversion of the resid fraction to middle distillate, gas oil and naphtha. The apparent kinetic parameters were also determined.

Characterization and utilization of hydrotreated products from the Whiterocks (Utah) tar sand bitumen-derived liquid

Abstract The bitumen-derived liquid produced in a fluidized-bed reactor from the Whiterocks tar sand was hydrotreated over a sulphided Ni-Mo/Al2O3 hydrodenitrogenation catalyst in a fixed-bed reactor. The process variables studied were temperature (617–680 K), pressure (11.0–17.1 MPa) and liquid hourly space velocity (0.18–0.77 h−1). The feed and the hydrotreated liquid products were analysed by gas chromatography-mass spectrometry analyses. The compounds identified in the bitumen included isoprenoids; bicyclic, tricyclic, and tetracyclic terpenoids; steranes; hopanes; and perhydro-β-carotenes. Normal and branched alkanes and alkenes and partially dehydrogenated hydroaromatics were identified in the bitumen-derived liquid. Comparison of the compounds identified in the bitumen and the bitumen-derived liquid indicated that the dealkylation of long alkyl side chains 0to form α- and isoolefins and the cleavage of alkyl chains linking aromatic and hydroaromatic clusters were the dominant pyrolysis reactions. Monoaromatic hydrocarbons were the predominant aromatic species in the hydrotreated product. The properties of the jet fuel fractions from the hydrotreated products met most of the jet fuel specifications. The cetane indices indicated that these fractions would be suitable for use as diesel fuels.