Oil shale retorting in dense phase hot-solid recycle systems

Oil shale processing remains primitive despite more that a century of study and development. To expand the industry in China, and to develop an industry in the U.S.A., more efficient, environmentally acceptable oil shale retorting schemes are required. Rapid pyrolysis, solid-recycle retorts offer high throughput and improved oil yield compared to hot gas retorts currently in operation. At the Lawrence Livermore National Laboratory (LLNL), we are studying this class of retort, by combining laboratory and mathematical model development efforts with operation of a 1 tonne/day pilot-scale, solid-recycle retorting system. In this paper we first discuss hot gas and hot solid retorting methods. We then compare laboratory pyrolysis kinetic and yield results with those obtained using the LLNL pilot retort, processing both Western and Eastern U.S.A. shales. Sulfur chemistry important in solid-recycle retorting is discussed. Based on this experience, coupled with laboratory measurement for shales from Maoming and Fushun, China, we discuss the possibility of processing Chinese shales in rapid-pyrolysis, solid-recycle retorting systems.