Secondary Pyrolysis of the Products of the Thermal Destruction of High-Sulfur Oil Shale

Abstract

Secondary pyrolysis of products of Israeli oil shale processing was studied in a two-stage bench-scale unit. The gas and oil vapors generated from the primary pyrolysis were sent to the converter for the secondary pyrolysis at temperatures of 650−820 °C. The oil yield on kerogen decreased from 35.3% at the pyrolysis temperature of 500 °C to 15.4% at 820 °C. The gas yield increased in the same temperature range from 10.7 to 25.5%. The yields of hydrogen, methane, ethylene, and carbon monoxide increased with temperature, whereas yields of alkanes decreased. The secondary pyrolysis enables us to simplify substantially the composition of the primary shale oil. The higher the severity of the conversion, the higher the yield of the simplest homologuesthiophene, naphthalene, phenanthrene, anthracene, thionaphthene, and dibenzothiopheneand the lower the yield of alkyl derivativestoluene, methylthiophenes, styrene, etc. Maximal content of methyl and dimethyl derivatives was observed at a temperature of 730 °C. The total thiophenes yield may be as high as 6.4% on oil shale organic matter, and this can be of practical interest because thiophenes are an important source for the production of light- and photoemitting polymers, materials for semiconductors, electrochemical cells, films, sensors, and other high-tech devices.

Pyrolysis in indirectly heated fixed bed with internals: The first application to oil shale

“…In reactor A, the reaction of char with CO 2 (gasification) in the hightemperature annular zone is responsible for its obviously higher CO content. Being generated usually from oil secondary reactions [22], the C2 + C3 content was higher for reactor A. Corresponding to these gas compositions, the LHV of pyrolysis gas was higher for the pyrolysis in reactor A (f), and with raising the furnace temperature the difference in LHV became larger, as a result of the substantial formation of H 2 and CO when using reactor A.…”

“…Darrell [21] demonstrated that the components ranging from benzene to n-decane had great cracking activity in their contacting the pyrolyzed shale (char) at temperatures above 550°C. Valentin et al [22] found that the oil yield of kerogen was reduced with increasing temperatures of secondary reactions. It is conceptualized that the higher temperature would increase the secondary reactions occurring to the primary pyrolysis product and lower the oil yield.…”

Investigation of Behavior of Sulfur in Oil Fractions During Oil Shale Pyrolysis

“…Considering the reaction temperature in the GC−SCD experiment, thiophene, BT, and the corresponding derivatives did not decompose further, and high reaction temperatures were required to form hydrocarbons or hydrogen sulfide. 26 With respect to the composition of the sulfur-containing compound, essential differences were not observed. However, the relative contents of the products at different pyrolysis temperatures significantly changed.…”

“…With the thermal decomposition of sulfur-containing structures, organic sulfur is mainly present in shale oil in the form of thiophene derivatives, such as thionaphthene, alkylthiophenes, and dibenzothiophene (DBT). 26 In fact, the chemical composition of shale oil is extremely complex. Owing to the high degree of branching of hydrocarbons, the identification of the hetero compounds is hampered by a large amount of alkane or alkene products.…”

“…The conversion or pathway of sulfur mainly occurs during the secondary pyrolysis of kerogen. With the thermal decomposition of sulfur-containing structures, organic sulfur is mainly present in shale oil in the form of thiophene derivatives, such as thionaphthene, alkylthiophenes, and dibenzothiophene (DBT) . In fact, the chemical composition of shale oil is extremely complex.…”