Operating Laboratory Oil Shale Retorts In An In-Situ Mode
Authors: Sandholtz Willis A. , Ackerman Jay F. 
Published: December 2007

To study and develop the modified in-situ oil-shale retorting process, LLL operates two laboratory oil-shale retorts. Experiment explore retorting parameters. Some results are compared with those of a predictive computer parameters. Some results are compared with those of a predictive computer model. Some features of in-situ processing are simulated in the laboratory by controlling heat losses and void fraction in the shale bed. A single computer system provides data acquisition and process control for both retorts. Control methods and algorithms are discussed. Experimental results with and without control of heat losses are compared. Reasonable agreement exists in retorting rates, temperature profiles, and yields between the experimental measurements and the computer model. These, as far as we know, are the first retorting data taken under heat-loss and void- fraction conditions similar to those expected in-situ. Retorting experiments on oil shale of uniform particle size have given yields of 99% of Fischer assay for inert gas, and of more than 90% for combustion retorting. Yield is decreased in packed beds with a wide range of particle sizes, similar to beds expected in-situ. particle sizes, similar to beds expected in-situ

Introduction

Technology applicable to retorting oil shale in a modified in-situ process is being developed at Lawrence Livermore Laboratory. This type of process is being developed at Lawrence Livermore Laboratory. This type of processing is also under laboratory study by Occidental Research processing is also under laboratory study by Occidental Research Corporation and laramie Energy Research Center. Basically, approximately 20% of the raw shale is mined for processing on the surface (Figure 1). The remaining shale is then rubblized with conventional explosives and the oil is extracted through vertical downward retorting. In the bed being retorted, a flame front, fed by air forced in from above, moves through the rubble bed decomposing kerogen into shale oil, char, and gases. Shale oil and gases are swept from the retort by gravity and gas flow, and the shale oil is pumped away as it accumulates at the bottom of the retort. To study the retorting process, we are performing tests at LLL. Ideally, we would like to isolate a segment of an in-situ retort for laboratory study, but practically, we must approximate in-situ conditions in surface retorts at the laboratory. The principal conditions simulated to date are (1) negligible lateral process-heat transfer and (2) low void fraction in the rubble bed. The effects of shale particle size are studied within the retorts size limitations. Experiments have been largely confined to a single grade of oil shale from the Anvil Points mine that averages about 24 gallons/ton (100 litre/tonne) Fischer assay oil yield.

RETORT SYSTEMS

A schematic overview of the LLL oil-shale system is shown in Figure 2. We operate two stainless steel retorts; both are electrically heated and insulated. The smaller vessel is 1 ft in diameter by 5 ft high (30 cm by 150 cm), the larger, 3 ft in diameter by 20 ft high (90 cm by 610 cm).