Analysis of Soot Formed during the Pyrolysis of Athabasca Oil Sand Asphaltenes

Abstract

Asphaltenes are formed during the primary upgrading process of bitumen. Gasification is considered as a good option for conversion of the low-value asphaltenes into syngas. Syngas can later be used in the generation of steam for steam-assisted gravity drainage, and the hydrogen from the syngas can be used for upgrading. Understanding the decomposition of asphaltenes, the subsequent formation of soot, and the properties of soot enables optimization of the process of asphaltene gasification. In this work, the effects of feed particle size, temperature, and residence time on the formation of soot particles during the pyrolysis of Athabasca oil sand asphaltenes were investigated. Morphological, structural, and elemental properties of collected soot were also investigated. The experiments were carried out in an atmospheric entrained-flow reactor that was electrically heated to a range of set temperatures between 800 and 1400 °C, and the residence time was varied between 5 to 12 s by controlling the carrier gas nitrogen flow rate. The pyrolysis products were air-cooled in the collection probe after the reactor and passed through a cyclone to separate out particles larger than 10 μm. The particles smaller than 10 μm were subsequently passed through a cascade impactor for segregation of soot and ash particles in the size range from 0.03 to 3 μm. It was found that asphaltenes devolatilize to produce char, light gases, and tar. The different feed particle size ranges used in this study had a negligible effect on the analyzed properties of the soot. The yield of soot formed increased with the pyrolysis temperature. It was observed that the average size of primary soot particles decreases with an increase in temperature. The sulfur and hydrogen contents of soot decrease with temperature as a result of the liberation of sulfur as hydrogen sulfide during the pyrolysis reactions. With increasing residence time, the average size of the primary soot particles increases.

Distribution of Vanadium, Nickel, and Other Trace Metals in Soot and Char from Asphaltene Pyrolysis and Gasification

“…This absence may be due to either the large quantity of amorphous carbon present in the sample or the V and Ni present as organometallic form in the soot. The TEM analysis of the pyrolysis soot, as shown in Vinoj et al, also could not detect V or Ni in the soot collected from the pyrolysis experiment.…”

“…Of the 13 stages available, it is possible that fine char particles and ash particles will enter the cascade impactor. The morphology of the soot particles collected are examined using scanning electron microscopy (SEM), and it is confirmed that the contamination is limited to the top few stages of the impactor . This may include one or two top stages or sometimes a maximum of five stages.…”

“…The pyrolysis and gasification experiments were carried out in an atmospheric entrained-flow reactor. The experimental setup used for this study is explained in previous papers, , and a schematic diagram is shown in Figure . The reactor furnace consists of an electrically heated vertical core of mullite tube (2.5 in.…”

“…Following the collection probe, the cooled stream was passed through a cyclone, where char and ash samples of a size larger than 10 μm were separated from the gas and collected. Then, the gas passes through the Dekati low-pressure cascade impactor to collect the fine soot particles of sizes ranging from 0.03 to 10 μm with 13 channels . The impactor is an inertial device classifying the particles according to their aerodynamic diameter.…”

“…Then, the gas passes through the Dekati low-pressure cascade impactor to collect the fine soot particles of sizes ranging from 0.03 to 10 μm with 13 channels. 19 The impactor is an inertial device classifying the particles according to their aerodynamic diameter. The operation principle of the impactor is based on inertial classification and gravimetric analysis of the aerosol particles.…”