FACTORS AFFECTING PRODUCT YIELDS AND OIL QUALITY DURING RETORTING OF STUART OIL-SHALE WITH RECYCLED SHALE - A SCREENING STUDY

Seven process variables-retort temperature, solids recycle ratio, char content of recycle solids, recycle solids temperature, pretreatment o f recycle solids with ammonia, solids residence time and steam concent ration-were studied. The Plackett-Burman statistical experimental desi gn, highly effective for detecting main effects of large number of var iables with a minimum number of experiments, was used to screen these variables. Each variable was tested at low and high levels. The bench- scale integrated retorting-combustion oil shale (BIRCOS) facility at L ucas Heights was used to obtain product yields and compositions under realistic recycle shale conditions. The significance of the main effec ts of the variables on product yields and carbon conversions decreased in the order: retort temperature, solids residence time, steam concen tration, char content, solids recycle ratio, recycle solids temperatur e, and ammonia treatment. Retort temperature was the only variable to affect the H/C atomic and nitrogen content of the oil. The sulfur cont ent of the oil was independent of all variables.