Anhydrous Extraction of Bitumen By Direct Heating
Authors: Moore R.G. , Donnelly J.K. , Bennion D.W. , Abdalla E.O. 
Published: March 2010

Anhydrous extraction of bitumen from mined oil sands offers potential advantages over the hot-water extraction process. A fluid-bed coker for extraction of bitumen by direct distillation has been constructed at the University of Calgary. The process is based on a direct heating concept in which one tower is utilized for vaporization of the volatile bitumen fraction and for burning of the resulting coked sand.

This paper describes the results from a typical test. The data show that a significantly upgraded liquid hydracarbon product was obtained. Produced oil had an average density of 0.943 gm/cm3 and an average viscosity 7.0 centipoise at 25 °C The average sulphur content of the produced oil was 3.62 weight per cent, as compared to 4. 71 weight percent/or the initial bitumen. Gas produced during the process had an upper heating value of 3778 KJ/m3(ST) and contained sulphur mainly in the form of hydrogen sulphide.

Introduction

The extraction of bitumen from mined oil sands by direct coking was first proposed by Gishler(l) and Peterson and Gishler2,3. Their concept was to feed oil sands directly to a fluid-hed coker in which cracking and distillation took place so that a light hydrocarbon product was recovered overhead and a coke deposit formed on the sand. Coked sand was then pneumatically conveyed to a fluid-bed burner in which the coke deposit was burned by contact with air. Hot sand generated by burning the deposited coke was recycled back to the coker in an approximate ratio of five parts hot sand to one part oil-sand feed. Hot sand in excess of that required for the coker fuel requirements was rejected as tailings.

Although the process described by Gishler(1) was not developed beyond the pilot stage, the concept is interesting in that it contains several potential advantages over the currently employed hot-water extraction technology. Some of these advantages are:process water requirements are greatly reduced;a dry tailing is produced which can be moistened and conveyed directly to the pit area or mixed with water and hydraulically transported to the pit area;the hydrocarbon product can be easily transported by pipeline for off-site upgrading at a central location; andretorting processes do not require water-wet oil sands, hence aging of the stockpiled water-wet oil sands is not a problem and those sands not amenable to hot-water extraction can be processed.

The process described by Peterson and Gishler is classified as an indirect-heated, direct coking process in that a solid heat carrier is utilized for transferring energy between a coke burner and the coker. Another direct-heated process, termed "Dry Distillation" or Lurgi-Ruhrgas(4), also utilizes hot spent sand generated by burning the residual coke as the energy source to the coker- The Lurgi-Ruhrgas process utilizes a mechanical screw mixer as the primary coker and burns the coke in an airlift pipe prior to mixing with the oil-sand feed. Underwood, McLellan and Associates and the Alberta Oil Sands Technology and Research Authority are currently constructing a pilot plant based on the "Taciuk Direct Thermal Processor"(5).