Conradson coke

Conradson coke residue in the non-distillable part of the sample... 

Oil Field Geological Formation Specific Gravity at 20 °C (g/cm ) °API Molecular Weight (Mean) Petroleum Resins (% wt) Asphaltenes (% wt) Conradson Coke (% wt)... 

Sample No. Softening Point R B Cc) Penetration at 25 °C (0.1 mm) Viscosity at50°C atl00°C (mmVs) (mmVs) Conradson Coke Residue (% wt)... 

The / 800 is always smaller than the Conradson coke residue CCR (DIN 51 551). A linear dependence exists ... 

The Conradson coke residue CCR of samples 6, 7,10, and 11 is within the limits of the other samples of this group. The corresponding temperatures with values of... 

The data for the residue at the temperature clearly exceed the corresponding data of / 800. On the other hand the values are comparable to the corresponding Conradson coke residues The same is valid if the temperature is ascertained from the TGA... 

Thus the equivalence of and as well as of and G has been proved. The statistical evaluation of results in a mean x = 585.9 X with a coefficient of variaton +V= 14.34 %. It is well known, that measurement of the Conradson coke residue exhibits a large scattering. DIN 51 551 speaks of a repeatability of 10 % and a reproducibility of 15 % of the values. 

The Conradson coke residue in the non-distillable part of the samples (CCR/ND) 100 is in the limits from 23 to 33 % for vacuum residues, bitumens, and atmospheric residues. The statistics result in a mean x = 27.3 % and a coefficient of variation V = 9.6 % (relative). The products from conversion processes scatter from 33 to 58 %. The furfural extract (sample 24) stands out because it does not possess any coke residue. 

Conradson coke residue in the simulated vacuum residue (%) residue at 800 °C in the simulated vacuum residue (%) residue in the extrapolated point of inflexion of the TGA curve in the simulated vacuum residue (%)... 

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 %. 

Residue at the end of experiment, with the Conradson coke residue, CCR ... 

Correlation of the Conradson coke residue or R800 with the non-distillable part of the samples does not give significant results, nor does correlation of the reaction rate with the average molecular weight. 

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. 

The fact that the formation of coke is not complete at 600 °C in every case, has already been proved by other means. This is confirmed by comparing the data of / 600 and i 800, with the mean of the colloid component, but this calls in question to a certain extent the importance of the values of the Conradson coke residue. 

Conradson coke - hydrogen deficient, high coking tendency feed components which correlates directly with the basic nitrogen and average molecular weight of the feedstock, as well as the Conradson carbon analysis... 

Problems sulfur and nitrogen transferred to the products (and coke) Solutions feed hydrotreating, reduction of S, N, Conradson carbon, metals Results higher quality products reduction in pollution better yields of valuable products reduced post-treatment... 

It has been shown that coke yield as a fraction of feed does give a linear relationship with second-order conversion (13) indicating a positive coke yield at 2ero conversion. This coke yield at 2ero conversion is the additive coke contribution to the total coke yield and is related to feed properties, particularly Conradson carbon content. The amount of this additive coke is significantly less than the Conradson carbon value of the feed (14), probably in the range of 50% of the Conradson carbon. 

The Conradson test (ASTM D-189) measures carbon residue by evaporative and destructive distillation. The sample is placed in a preweighed sample dish. The sample is heated, using a gas burner, until vapor ceases to burn and no blue smoke is observed. After cooling, the sample dish is reweighed to calculate the percent carbon residue. The test, though popular, is not a good measure of the cokeforming tendency of FCC feed because it indicates thermal, rather than catalytic, coke. In addition, the test is labor intensive and is usually not reproducible, and the procedure tends to be subjective. 

The Micro-method uses an analytical instrument to measure Conradson carbon in a small automated set. The Micro-method (ASTM D4530) gives test results that are equivalent to the Conradson carbon residue test (D189). The purpose of this test is to provide some indication of relative coke forming tendency of such mat al. 

Hydroprocessing reduces the Conradson carbon residue of heavy oils. Conradson carbon residue becomes coke in the FCC reactor. This excess coke must be burned in the regenerator, increasing regenerator air requirements. 

Feed residue coke is the small portion of the (non-residue) feed that is directly deposited on the catalyst. This coke comes from the very heavy fraction of the feed and its yield is predicted by the Conradson or Ramsbottom carbon tests. 

Group 2 Coke imbalance. This grouping considers malfunctions leading to a difference between the rate at which coke accumulates on the catalyst and the rate at which it is burned off. A coke imbalance is associated with a reduction of oxygen, which can be caused by a loss of combustion air or through an increase in the conradson carbon in the gas oil feed to the unit. 

FIGURE 1.8 Effect of API gravity and Conradson carbon on catalyst to oil ratio and coke yield at 55% conversion. 

The third type is the additional coke related with the feedstock quality. FCC feedstock contains a dissolved carbon, polynuclear aromatic compounds, called Conradson carbon residue (CCR ASTM D-189). It is deposited over the catalyst surface during cracking reactions. In the FCC unit, this material is part of the coke remaining in the catalyst. Some researchers have investigated cracking of heavy feedstock and observed that, in particular cases, the amount of Conradson carbon is linearly related with the carbon-hydrogen ratio of the feedstock [3]. 

The TPO profiles obtained were analyzed by deconvoluting them using Gaussian peaks and GRAMS 32 software. The peaks obtained were assumed to represent the four different types of coke in the spent catalyst catalytic coke, contaminant coke, occluded coke, and additional coke (Conradson carbon). 

This coke has been related with feedstocks quality and more specifically with their carbon Conradson content. The catalyst used for this analysis was the sample without metals deactivated 20 hours, 30 cycles, and 80% steam. The MAT test was performed with feedstock of different quality gasoil, DMO, and mixture of gasoil-DMO. 

Figure 10.7 represents the TPO profile of spent catalyst tested with pure DM0. It can be noted that the area of the peak at 715°C has increased even more owing to this feedstock high-CCR content. It can be concluded that the coke related with the feedstock CCR is located between 700°C and 715°C. As expected, this coke increases with the feedstock Conradson carbon content. 

FIGURE 10.8 Conradson carbon versus coke related with the feedstock. 

Before TPO analysis it was necessary to Soxhlet extract the FCC samples to remove nonvaporized hydrocarbons and avoid their accumulation in the pores of the catalyst as carbonaceous residue with high hydrogen content. As a result, the interference during TPO analysis caused by the desorption and decomposition of these compounds at high temperatures was eliminated. In this study it was observed that this type of coke is directly related to the Conradson carbon content of the feedstock. 

The additional coke related with feed quality is a function of their Conradson carbon content. According to the literature, our results show that this coke is the most refractory and consequently is located in the highest temperatures range ( 700°C-716°C). Furthermore, it shifts to higher temperatures as the content of CCR of feedstock increases. 

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