High Temperature Thermal Cracking of Heavy Oils.

摘要

Thermal cracking of the vacuum residue fraction of bitumen and petroleum is an important feature of several refinery processes. At normal process temperatures, this fraction remains liquid, which favors coke formation. In order to understand the reaction yields and intrinsic reaction kinetics of this important material at temperatures above 600°C, innovative reactor designs and techniques were developed.;First, a microstructured mixer was used to rapidly heat reactants to nearly constant reaction temperatures in a few milliseconds. The reactor was tested by studying of the rate of the thermal cracking of n-hexadecane temperatures ranging from 600 to 750°C, at atmospheric pressure, and mean residence time of 110 to 170 milliseconds. The apparent activation energy and pre-exponential factor for the over all first order reaction was calculated as 235 kJ/mol and 1.1x1013 s-1 respectively, consistent with the majority of previous studies in the literature.;In order to minimize the role of the liquid phase in cracking of vacuum residue, an aerosol reactor was designed and constructed. Thermal cracking of Athabasca vacuum residue was studied at temperatures of 700 to 800°C at atmospheric pressure and residence time of 100 to 115 milliseconds. The feed was introduced as submicron droplets into the reactor. Alkenes were the dominant components among the gas products, with total yield of ethene and propene ranging from 5 to 18 wt %. The yield of coke was 6.3 wt% on average, and was insensitive to conversion of the vacuum residue. Both these observations were consistent with the predominance of vapour-phase reactions. The molar ratio of hydrogen to carbon decreased monotonically with conversion from 1.4 for unconverted feed to 0.98 at 78% conversion, consistent with high yields of hydrogen-rich gas products.