Bottom, atmospheric

Metals, such as nickel, vanadium, and sodium, are present in crude oil. These metals are concentrated in the heavy boiling range of atmospheric bottoms or vacuum residue, unless they are carried over with the gas oil by entrainment. 

Fractionation of the heavier products by steam stripping resulted in different wax grades being produced. The soft wax and atmospheric bottoms (Gatsch) were typically air oxidized to produce oxygenated waxes. The medium, hard, and oxidized waxes all ended up as chemical products. 

The atmospheric bottom, also known as reduced oil, is then sent to the vacuum unit where it is further separated into vacuum gas oil and vacuum residues. Vacuum distillation improves the separation of gas oil distillates from the reduced oil at temperatures less than those at which thermal cracking would normally take place. The basic idea on which vacuum distillation operates is that, at low pressure, the boiling points of any material are reduced, allowing various hydrocarbon components in the reduced crude oil to vaporize or boil at a lower temperature. Vacuum distillation of the heavier product avoids thermal cracking and hence product loss and equipment fouling. 

Fig. 3.3 FT-IR spectra (in KBr) of fullerane C6ffH36 (top spectrum) and the soot formed by its thermal decomposition at 630°C under inert atmosphere (bottom spectrum). The four band pattern spectrum at the bottom of the figure at 6.99, 8.45, 17.39 and 19.05 pm is due to C60 fullerene. Thus, fullerane by thermal processing can form back quite easily fullerene which in its turn is able to react with atomic hydrogen forming back hydrogenated fullerene or fullerane...

Cince the first commercial H-Oil unit came on-stream at Lake Charles in 1963, a variety of feedstocks have been processed, including heavy cycle oils, atmospheric bottoms, vacuum bottoms, and cutback propane deasphalter bottoms. The unit has operated successfully with both microspheroidal and extrudate catalysts and has been expanded to 6000 bbl/day. 

Flocculation Point. Figure 4 shows that the flocculation point of a reactor effluent sample (cracked atmospheric bottom) is much lower than that of the reactor feed. Generally, the flocculation point decreases as the amount of solids in the sample increases. This has been confirmed by the Shell Hot Filtration Test IP/375/ASTM 4870 procedure. 

C-NMR. Table 2 shows C-NMR data [7] for liquid samples from the bottoms of the atmospheric and vacuum towers, and for side streams from and above the most seriously fouled vacuum tower trays. The data show the vacuum bottom to contain 12 % more aromatics than the atmospheric bottom, while the amount of paraffins is 6 % lower. This indicates that the vacuum residue has a greater "solubilizing power" than the atmospheric tower residue, which possibly accounts for the decreased amount of microscopic particulates in the vacuum bottom. In contrast, the side stream from the severely fouled trays contains only 25 % aromatics and 47 % aliphatics, suggesting a relatively low "solubilizing power" for the local reflux. 

Figure Bl.4.1. Top schematic illustration of the observing geometry used for limb sounding of the Earth s atmosphere. Bottom illustrative stratospheric OH emission spectra acquired by the SAO FIRS-2 far-infiared balloon-borne FTS in autumn 1989. The spectra are from a range of tangent heights h = tangent height in the drawing), increasing toward the bottom, where the data are represented by solid curves nonlinear least-square fits to the measurements, based on a combination of laboratory data, the physical structure of the stratosphere and a detailed radiative transfer calculation, are included as dashed curves. The OH lines are Fj 7/2 ...

First, crude oil is desalted, then it is separated into its various components, called fractions, by atmospheric distillation. As crude oil is heated, its different fractions vaporize at different temperatures and are removed separately. All fractions are processed further. The lightest fraction, distilled gas, is subjected to sulfur extraction. The heaviest fraction, called atmospheric bottom, undergoes vacuum distillation. Most distilled fractions undergo hydrotreatment, which is infusion of hydrogen to remove sulfur. 

Fig.6.52. Vertical absorption curve for the earth s atmosphere (bottom) and individual constituent absorptions [6.100]...

Fractionation equipment, a vacuum pipestill (VPS) or vacuum distillation unit (VDU) is used to distill atmospheric bottoms into gas oil or lube distillate cuts. 

Recently, major synthetic oil producers in Western Canada have switched from atmospheric bottoms to vacuum resids for processing bitumen. This raises the question of what impact this change might have on the coke induction period during thermal processing of these materials. To address this question, Athabasca bitumen (+343°C) was fractionated using Distact distillation into four distillates and resids.The selected boiling point cuts were 525°C, 575°C, 625°C, and 675°C. The coke induction periods of bitumen... 

The same reactor was used but with 100 cc charge. Catalyst sizes ranged from about 0.4 to 3 nim. A heavy vacuum bottoms, 22 reduced crude, and a lighter atmospheric bottoms, 36 reduced crude, were used for these tests. Figure 2.1.4 shows that for the smaller catalyst, the first order kinetic constant remains constant with increasing particle size and then decreases as would be expected from the onset of pore diffusion limitations. The data was interpreted with the model shown below ... 

The graph shows the global surface temperature (top) and the Sun s energy received at the top of the Earth s atmosphere (bottom). 

---