Simulated Atmospheric Residue

Considering the temperature limits in use in refinery processes a value of 100 % simulated atmospheric residue, SAR, is found in most of the samples of investigation. By this definition, the four atmospheric residues have not been fully distilled. The simulated vacuum residue, SVR, shows how far the samples are distilled. Since the SVR = 100 -AG300, exhibits higher values than the non-distiUable portion of the sample ND = 100 -AG400, the values of that part of the sample which is crackable in practice, PCR, exceed the more theoretical values, CR. The ratio PCR/SVR does not give a clear distinction of distillation residues from conversion products than it is possible using the ratio CR/ ND. 

Several of the commercial simulation programs offer preconfigured complex column rigorous models for petroleum fractionation. These models include charge heaters, several side strippers, and one or two pump-around loops. These fractionation column models can be used to model refinery distillation operations such as crude oil distillation, vacuum distillation of atmospheric residue oil, fluidized catalytic cracking (FCC) process main columns, and hydrocracker or coker main columns. Aspen Plus also has a shortcut fractionation model, SCFrac, which can be used to configure fractionation columns in the same way that shortcut distillation models are used to initialize multicomponent rigorous distillation models. 

Hydrodemetallation tests were conducted with Kuwait atmospheric residue feed at operating conditions selected to simulate the guard reactor in a typical residue processing service. In one such test, the temperature was initially held constant at a typical residue start-of-run (SOR) temperature condition for nearly three and one half months and then raised to a typical middle-of-run (MOR) temperature condition and maintained at that level for an additional equivalent length of time. In an another similar experimental run, SOR temperature was maintained for nearly two months and then the temperature was raised to a typical end-of-... 

The Conradson coke residue in the simulated vacuum residue ((CCR/SVR) 100) for the vacuum residues and bitumens has a mean value x2l.6%( y= 7.01% relative). For the atmospheric residues the mean amounts to x = 13.8 % ( + y = 8.7 % relative). The products from conversion processes (samples 19, 20, and 22) have extremely high values demonstrating that they have been distilled exhaustively, whereas the distillate of the residue of a cat-cracker, sample 25, exhibits the extremely low value of 4.4 %. 

The data from the simulated cracking process may also be assembled in groups. Statistical evaluation of the groups A vacuum residues and bitumens (samples 1-13), B atmospheric residues (samples 14-17), and C products from conversion processes which can be cracked under the given experimental conditions (samples 19-22) is shown in table 4-34 ... 

The relation of the different index numbers characterizing the coke residue to the simulated vacuum residue, SVR, does give useful results. The relation of the Conradson coke residue CCR to SVR results in ratios between 10.0 and 23.4 for vacuum residues and bitumens to ratios from 12.2 to 14.8 for atmospheric residues and the ratio for residues from conversion processes gives values of over 27 up to 43. 

Thermogravimedy in argon shows that the evaporation start temperatures of the extracts (T1 %, T5 %) increase with increasing solubility parameter 5, whereas the distillable fraction AG400 decreases and the residues J 600 and i 800 increase (Fig. 4-113). This is a consequence of the rising amounts of aromatic, coke-generating substances, whieh were extracted with solvents of increasing solubility parameter. The curves of the simulated distillation of the extracts correspond approximately to that of an atmospheric residue of a Middle East crude (for example AR Kirkuk). 

High-quality assay data for the atmospheric residue are always desirable in modeling a VDU. For VDU simulation, there are three ways to obtain assay data of the atmospheric residue (1) stream results of ADU simulation ifwe build the ADU and VDU models together (2) analysis of the atmospheric residue and (3) back-blending the assay data of VDU product streams if product analyses are available. 

However, we must pay more attention to correctly representing the atmospheric residue while using VDU operation and production data to build a VDU model. This follows because the atmospheric residue is an intermediate stream rather than a final product, and a detailed stream analysis is usually not available. Most likely, we can only have the analysis results of the distillation curve below 540 °C and the bulk density of the atmospheric residue. While using commercial simulators to construct the atmospheric residue based on an incomplete feed analysis, the resulting pseudocomponent distribution may not represent atmospheric residue well. 

Lababidi, H.M.S., Shaban, H.I., Al-Radwan, S., Alper, E. 1998. Simulation of an atmospheric residue desulfurization unit by quasi-steady state modeling. Chem. Eng. Technol. 21(2) 193-200. 

Finally, other methods are used to obtain simulated distillation by gas phase chromatography for atmospheric or vacuum residues. For these cases, some of the sample components can not elute and an internal standard is added to the sample in order to obtain this quantity with precision. 

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