Distillation Coke Residue

Feedstocks for this very flexible process are usually vacuum distillates, deasphalted oils, residues (hydrotreated or not), as well as by-products from other processes such as extracts, paraffinic slack waxes, distillates from visbreaking and coking, residues from hydrocracking, converted in mixtures with the main feedstock. 

Thermal Cracking. In addition to the gases obtained by distillation of cmde petroleum, further highly volatile products result from the subsequent processing of naphtha and middle distillate to produce gasoline, as well as from hydrodesulfurization processes involving treatment of naphthas, distillates, and residual fuels (5,61), and from the coking or similar thermal treatment of vacuum gas oils and residual fuel oils (5). 

The FCC process is used worldwide in more than 300 installations, of which about 175 are in North America and 70 in Europe. Figure 9.10 shows the principle of an FCC unit. The preheated heavy feed (flash distillate and residue) is injected at the bottom of the riser reactor and mixed with the catalyst, which comes from the regeneration section. Table 9.5 gives a typical product distribution for the FCC process. Cracking occurs in the entrained-flow riser reactor, where hydrocarbons and catalyst have a typical residence time of a few seconds only. This, however, is long enough for the catalyst to become entirely covered by coke. While the products leave the reactor at the top, the catalyst flows into the regeneration section, where the coke is burned off in air at 1000 K. 

Shell Stills. At the beginning of the period under review, large quantities of crude oil were processed in tower stills. These were cylindrical vessels 10 to 15 feet in diameter and about 40 feet long. The vessels were mounted horizontally and arranged so that a fire could be applied to the underside (10, 55). The stills were charged with crude oil and the appropriate fractions removed by distillation. The residue was then destructively distilled or coked. Heating was continued until the bottom of the still was at a dull red heat (55). 

Data calculated from that for composite synthetic crude obtained after coking and Unifining of extracted bitumen, from Bachman and Stormont [2]. Before Unifining (hydrogenation) mean density of the composite stream would be somewhat higher, and sulfur content would be about 3%. Proportions of distillate components are approximate carbon content quoted is the coke residue on pyrolysis of bitumen. 

High temperature flash distillation of residue oil and simultaneous coking of non-distillable asphaltenes in a unique mixing reactor... 

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

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. 

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 difference of 100 % minus the sum of the distillable firaction of the sample, AG400, and the coke residue, / 800 gives the percentage of the sample which can theoretically, be cracked, CR ... 

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. 

Data from colloid analysis show that the concentration of the dispersion medium may be related to the distillable fraction AG400, whereas the concentration of asphaltenes, or the total of asphaltenes and petroleum resins, determines the quantity of coke residue after pyrolysis. That portion of the sample which can be cracked, CR, will usually be determined from die concentration of petroleum resins. The aliphatic side chains of the alkylaromatic system of the asphaltenes have a small influence. The coke residue can be related to the data from structural group analysis which describe the aromatic character of the samples. 

A plot of the TGA curve versus the temperature of the distillation bitumen B80 (sample 6) and its colloidal components is shown in Fig. 4-37. The curves of the bitumen, the dispersion medium, and the petroleum resins difler very little from each other up to 450 °C. The differences shown by the curves in the temperature range above 500 °C represent the coke residue. The curve of the asphaltenes is shifted towards higher temperatures due to a higher particle mass and also has a considerably higher coke residue. 

In a statistical evaluation, decreasing coefficients of variation are indicative of a to more homogeneity substance (Table 4-63), The dispersion medium have the highest contents of distillable fractions (AG400) whereas asphaltenes supply (he highest coke residue (R800). 

Table 4-64 Means x of the coke residue for distillation bitumens ...

The total colloids (petroleum resins and asphaltenes) can be correlated quite well with the coke residues R600 and RSOO (Fig. 4-54 and 4-55). There is no difference between the distillation and the blown bitumens. Correlation of the maxima of the reaction rate DTG with the colloid content gives two straight lines for the distillation bitumens (independent of the origin of the samples) and a third line for the blown bitumens (Fig. 4-56). No other correlations with the colloid content were found, nor were any expected. 

The asphaltenes are responsible for the formation of coke residue due to their high content of condensed aromatic ring systems. This is shown by the correlation of the coke residues / 600 or RSOO with the contents of asphaltenes (Fig. 4-60). Independent of the origin of the samples, two straight lines result for the distillation bitumens, whereas the data of the blown bitumens fit a third line with a steeper slope. Correlation of the maxima of the reaction rate DTG upon the concentration of asphaltenes presents a similar picture (Fig. 4-61). 

The H/C ratio only correlates with the distillable fraction AG400. Neither the evaporation start temperatures T % and T5 %, nor the coke residues 7 600 and / 800 give a satisfactory coefficient of correlation with the H/C ratio. 

Coke Solid residue produced by heating bituminous coal and other carbonaceous materials, with the concomitant removal of volatile substances by destructive distillation coke is commonly used in making steel. 

Preparation. Most petroleum is refined to some extent before use, although small amounts are burned without processing. The refining of crude oil yields a number of products having many different applications. Those used as fuel include gasoline, distillate fuel, residual fuel, jet fuels, still gas, liquefied gases, kerosene, and petroleum coke. 

ISO 647 (1974) Brown Coals and Lignites Determination of the Yields of Tar, Water, Gas and Coke Residue by Low Temperature Distillation,... 

The Conradson carbon residue (CCR) results from ASTM test D189. It measures the coke-forming tendencies of oil. It is determined by destructive distillation of a sample to elemental carbon (coke residue), in the absence of air, expressed as the weight percentage of the original sample. A related measure of the carbon residue is called Ramsbottom carbon residue. A crude oil with a high CCR has a low value as a refinery feedstock. 

Influence of the feed coke produced from distillation residue is less structured, less crystalline than that from a cracking residue. If the residue feeding the unit is highly contaminated with sulfur and metals, it is still coke, but is disqualified for certain applications. 

Feedstocks are light vacuum distillates and/or heavy ends from crude distillation or heavy vacuum distillates from other conversion processes visbreaking, coking, hydroconversion of atmospheric and vacuum residues, as well as deasphalted oils. 

The feedstocks in question are primary distillation streams and some conversion products from catalytic cracking, coking, visbreaking, and residue conversion units. 

The specification requirements for electrode binder pitch, eg, high C/H ratio, high coking value, and high P-resin content, effectively ruled out pitches from gasworks or low temperature tars. The cmde tar is distilled to a medium-soft pitch residue and then hardened by heating for several hours at 385—400°C. This treatment increases the toluene-insoluble content and produces only a slight increase in the quinoline-insoluble (Ql) material, the latter by the formation of mesophase. 

---