Heavy oils C-grade

Figure 27.12 Sorption curves observed for the A- and C-grade heavy oils using exfoliated graphite with different bulk densities.

For the viscous C-grade heavy oil, the value of sorptivity was so small, about 0.2kg/m s, that its slight dependence on the bulk density of the two carbon sorbents — carbonized fir fibers and carbon fiber felts — was observed. 

A piece of exfoliated graphite was placed on the snrface of A-grade heavy oil directly it was picked up by using a stainless steel mesh after 2 h of immersion and then kept for 1 h to drain off the excess oil. In the case of viscous C-grade heavy oil, immersion for 15 h and draining-off for 3 h was employed. 

FIGURE 4.7 Dependence of heavy oil sorption capacity of exfoliated graphite on its bulk density, (a) A-grade heavy oil, (b) B- and C-grade heavy oils and crude oil. 

Sorption capacity of different sorbents for less viscous A-grade and more viscous C-grade heavy oil... 

The carbon fiber felt nsed also does not have a high sorption capacity for A-and C-grade heavy oils (Table 4.2), but it showed excellent cycling performance, as will be discussed in Section VI.C. 

FIGURE4.17 Time to reach 50% of mass increase saturation, f versus bulk density of exfoliated graphite, (a) A-grade heavy oil and (b) C-grade heavy oil. 

FIGURE 4.26 SEM images of the surface of wormlike particles of exfoliated graphite after sorption of heavy oil. (a) After sorption of A-grade heavy oil, (h) after recovering hy suction filtration, (c) after sorption of C-grade heavy oil, and (d) after suction filtration. 

In Figure 4.33 representative cycling performance with n-hexane washing is shown for A- and C-grade heavy oils. The recovery ratio is almost 100% in each cycle for both heavy oils. It was also possible to wash out the viscous C-grade heavy oil with the less viscous A-grade heavy oil, similar to the behavior of carbonized fir fibers. 

FIGURE 4.31 Changes in sorbed amount of C-grade heavy oil for fir fibers carbonized at 900°C with a bulk density of 11 kg/m and recovered amount by washing with A-grade heavy oil. 

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