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. 

As an example, consider heavy fuel oil (CH15, specific gravity, 0.95) atomized to a surface mean particle diameter of d, burned with 20 percent excess air to produce coke-residue particles having the original drop diameter and suspended in combustion products at 1204°C (2200°F). The flame emissivity due to the particles along a path of L m will be, with d in micrometers. 

S. Stapf, X. Ren, E. Talnishnikh, B. Bliimich 2005, (Spatial distribution of coke residues in porous catalyst pellets analyzed by field-cycling relaxometry and parameter imaging), Magn. Reson. Imag. 23, 383. 

There are several factors that may be invoked to explain the discrepancy between predicted and measured results, but the discrepancy highlights the necessity for good pilot plant scale data to properly design these types of reactors. Obviously, the reaction does not involve simple first-order kinetics or equimolal counterdiffusion. The fact that the catalyst activity varies significantly with time on-stream and some carbon deposition is observed indicates that perhaps the coke residues within the catalyst may have effects like those to be discussed in Section 12.3.3. Consult the original article for further discussion of the nonisothermal catalyst pellet problem. 

Deposition was performed using a vacuum system [1]. Before deposition of the alkoxlde, the sample was evacuated at 673 K for 2 hr, and the temperature was then lowered to 593 - 293 K for the deposition of silicon methoxlde. S1(0CH3)4 vapor was then admitted to the dried zeolite at a vapor pressure of 2.5 Torr. The resultant Increase of weight was measured by the quartz microbalance. After the deposition, the decatlonlzed zeolite was calcined Iji situ by oxygen at 673 K to remove the coke residue, while the Na-type mordenlte was treated with water vapor at 593 K. The amount of SI deposited was... 

Retorting of oil shales to produce shale oil results in wastes (condensate water and solid semi-coke residue) that are heavily contaminated with organic compounds, especially phenolic compounds. Semi-coke leachate is typically alkaline (Kundel Liblik 2000) and can contain several hundred mg/L phenol in Estonia, in addition to potentially toxic heavy metals and trace elements, for example, As, B, F, Mo, and Se, which might be mobilized during leaching by water. Volatilization of phenols from leachate lagoons can also impact atmospheric quality. 

Nitrogen physisorption of the Ge-ZSM-5 sample revealed a considerable contribution of mesopores to the total pore volume, accompanied by a drop in micropore volume of 20%. In a study of the catalytic activity of these materials it was found that the increased mesoporosity of Ge-ZSM-5 had a beneficial effect on the catalytic activity in a series of acid-catalysed reactions.1771 It was observed that the presence of germanium in the framework does not change the strength of the acid sites but, instead, decreases the extent of deactivation from coke residues formed upon reaction. The microporous domains only have short diffusional lengths, but the shape selectivity ascribed to the zeolitic channels is still fully... 

Possible pollution sources in the area include dust, ash, scum, slag, carbon coke residues, minerals, heavy oils, hydrocarbons, and combustion residues. The minerals used to produce cast iron and steel were imported mainly from Africa (Liberia and Mauritania), Canada, India, the former USSR, and from the American Continent (L Industria Mineraria, 1979a). 

Nalchikit-M, wt % Destruction temperature, °C Coke residue value at 600°C, %... 

It was found basing on TGA data that initial destruction temperature raises for all prepared nanocomposites containing up to 5%. In contrast to original PET all nanocomposites decompose producing coke residue, which number increases with higher content of layered silicate. Nanocomposite presence indicates on more complex behavior of nanocomposite thermodestruction process. It is likely that the layered silicate addition is an initiator of coking as a result of barrier effects to volatile products, formed in process of thermal destruction and other processes, concerned with change of macromolecular chains entropy in near-surface nanocomposite layers. 

In general, carbocyclic aromatic polymers yield more carbonized products than heterocyclic ones. Susceptibility of polymers to carbonization under pyrolysis conditions is characterized by the so-called coke number Van Krevelen concluded that the tendency for carbonization may be regarded as an additive resultant of the contributions of the individual functional groups in the monomer units. The contribution of a group is expressed in carbon equivalents contributed by each group to the coke residue, CR, per monomer unit ... 

For polymers whose pyrolysis products are not inhibitors for the flaming reaction, Van Krevelen established a simple empirical correlation between the limiting oxygen index and the coke residue ... 

The amino groups as well as oxygen and hydrogen are involved in the chelating of the metal ions. During combustion, this polymer produces Nj, COj, HjO, metal oxides, and a coke residue. The flammability of fibers from this polymer is r uced by chelated Ca, Zn, and Zr ions (LOI cs 40%), whereas Cu and Fe ions catalyze the complete combustion of the fibers, under the effect of a 1500 °C flame. 

The book also explores the application of various acidic catalysts, such as silica-alumina, zeolites (HY, HZSM-5, mordenite) or alkaline compounds such as zinc oxide. However, the main problem with catalytic cracking is that in the course of the cracking process all catalysts deactivate very quickly. Expensive zeolite catalysts increase the cost of waste plastics cracking process to the point where it becomes economically unacceptable since the catalyst becomes contained in coke residue and therefore cannot be recovered and regenerated. 

Chemical composition of waste plastic cracking products depends on shares of the individual polymers (PE, PP, PS) in the feed and process parameters. This fact decides the technological application of the final products. Important products of the cracking process, both petroleum fractions and waste plastics, are coke residues. Coke residue yield increases considerably, up to 10 wt%, in cracking of municipal and industrial waste plastics since they contain various inorganic impurities and additives. It can be applied as solid fuel, like brown coal. In the fluid cracking the solid residue is continuously removed from the process by combustion in a regenerator section. 

In the next reactor design [48] mixer arms have exactly the same dimensions and shape as the internal reactor part and in the course of the run coke residue is scraped by mixer arms from the heated reactor walls. Scraped coke falls down and is collected at the bottom of the reactor and removed with part of the reaction mixture by a suction pipe. The main process products are the gas fraction (used for heating purpose), gasoline and light gas oil and paraffin fractions. 

Both produce predominantly diesel, along with gasoline, some LPG and a coke residue. 

Gaseous products include LPG range gases liquid products include liquid hydrocarbons solids include coke/residue. The average composition and properties of the output products depend upon the following factors. 

When burning bio-oil is has been established that it is necessary to preheat the bio-oil to 60 - 70 °C. The pre-heating of the bio-oil leads to a decreased viscosity and enhances the atomisation of the oil. As a consequence, a stable flame was obtained. The condition of the flame tube after 20 minutes of bio-oil operation is shown in Figure 9. No coking residues were found and only a fine, H t greyish layer was formed by deposition. 

The coke residue is the result of the hydrogen-deficient stoichiometry of the process. With a proximate analysis (determination of the compounds, moisture, ash, etc., present) of carbon 80%, volatiles 10%, sulfur 6%, and ash 4%, the coke has a fuel value near that of high rank coals. It is burned in the site power plants to provide steam and electrical power for oil sands processing. However, the high sulfur content detracts from its wider utility as a fuel. Any coke in excess of the current fuel requirement is finely powdered and incorporated into the dyke walls to help trap any hydrocarbons present in water seepage through the wall. 

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. 

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