Thermal decomposition of buddingtonite in oil shales

Abstract

Thermal decomposition of buddingtonite, an ammonium feldspar found in Green River Formation oil shales, was studied in order to determine its contribution to the total nitrogen released from oil shales. In an inert gas sweep, ammonia from buddingtonite evolves at temperatures between 400 and 900 °C. Ammonia also decomposes to form N 2 and H 2 in the same temperature range. The water evolution profile consists of several peaks. The water peak, which is associated with buddingtonite decomposition, occurs at the same temperatures as the nitrogen species evolution. The X-ray diffraction spectra show that solid products from decomposition are mainly quartz, with some potassium feldspar and mullite. Kinetic parameters for buddingtonite decomposition were derived from the total nitrogen evolution data. Pyrolysis of an ashed Green River Formation oil shale shows that buddingtonite in oil shale also decomposes at the same temperature range as the museum-grade buddingtonite. During oil shale processing, buddingtonite generates ammonia during combustion. Some of this ammonia is burned, yielding NO x , and some remains in the flue gas. This has implications for NO x control during retorted shale combustion.