Coking resid processing

The reduced coke, gas and hydrogen make of these types of catalysts open the road to a significant increase in resid processing. 

It is also clear that in the case of FCC with heat removal, the frontier of resid processability can at a certain moment be determined by the coke selectivity of the catalyst, while on the other hand the conversion of resid in a unit without heat removal may also be limited by the metal resistance of a catalyst. 

As discussed in the previous sections any improvements in coke selectivity can be utilized to extend the frontiers of resid processing as several types of poisons in the resid feed, most of all the polar hydrocarbons will increase the coke formed. Also for fuel gas we can observe that non-optimal vaporization and cracking conditions with resid will strongly enhance gas formation. A low coke and gas catalyst is hence a big plus for resid processing. (Table XII.)... 

Further reduction of "catalytic" coke and fuel gas production in order to allow more room for resid processing... 

As reported by Ho [12], the types of delta coke formed in Resid FCC can be classified based on the length of time needed for their formation. CCR coke will form nearly instantaneously at the inlet of the reactor and is therefore also called entrance coke." The second type of coke is formed by the adsorption of highly aromatic and basic materials on even weakly acidic surfaces this process also occurs quite rapidly. Finally, reaction or catalytic coke will form in what is clearly the slowest coke formation process. 

Changing economic scenarios and available processing options often compel a refiner to pursue resid processing. Due to the varied properties of resid feeds, the refiner must carefully consider the choice of available FCC catalyst technology. This paper reviews novel matrix and zeolite technologies for resid processing applications to obtain better coke selectivity, gas selectivity and bottoms upgrading. Commercial experience and mechanism of separate particle vanadium traps to control vanadium deactivation is also reviewed. 

The loss in conversion is also partly caused by lower "effective catalyst activity" in the riser as a result of increased coke blockage of the catalyst pores with coke and higher vanadium and hydrothermal deactivation of the catalyst. The negative effects of resid processing on FCC yields can be reduced by adjusting the FCC process conditions (lower feed preheat, increased catalyst make-up, increased steam dispersion and stripping) and by the use of FCC catalyst formulations more suitable to such applications. 

Petroleiun coke, petcoke and liquid refinery resid feedstocks are used for gasification. Petcoke is made from heavy residues in refineries by the coking process (delayed coking). Resids and petcoke are characterised by a low C/H ratio of 7-10 wt/wt and high content of sulphur 1-7 wt%. 

I was called to Axxoco Oil Co. lo help increase the capacity of their delayed coker. The refinery was bottlenecked by resid processing capacity so that any incremental increase in coking capacity would permit the plant to increase crude runs substantially. 

Parallel passes (coking heater), 78 Partially coked resid, 40 Pass partition baffle, 27 Pass partition failure (heat transfer equipment), 433—435 Performance test planning, 486-497 strategy, 487-490 laboratory, 487 instruments, 487-488 interfacing units, 488 shift operators, 488 mechanical department, 488 flag sheet, 488-489 onstream analyzers, 488 day before test, 490-491 unit optimization, 490-491 test day, 491 data correlation, 491-496 capital projects, 495 checklist, 497 Performance testing (process unit), 482-483. See also Performance test planning. 

Polymerization, the reaction through which small hydrocarbon molecules are combined to form a single large molecule of high molecular weight. The result of this reaction is the formation of coke. This process is initiated in the liquid phase and continued in different steps. Polymerization reactions require long reaction time and the coke drums provide the necessary residence time for these reactions to proceed to completion. 

The quantity of coproduct acetylene produced is sensitive to both the feedstock and the severity of the cracking process. Naphtha, for example, is cracked at the most severe conditions and thus produces appreciable acetylene up to 2.5 wt % of the ethylene content. On the other hand, gas oil must be processed at lower temperature to limit coking and thus produces less acetylene. Two industry trends are resulting in increased acetylene output (/) the ethylene plant capacity has more than doubled, and (2) furnace operating conditions of higher temperature and shorter residence times have increased the cracking severity. 

Opera.tlon, Because of the long residence time of the materials (8—10 h), the blast furnace process can exhibit considerable inertia, and control is usually appHed where the goal is maintaining smooth, stable input conditions. One of the most important aspects of blast furnace control is supply of consistent quaUty raw materials, which is why there is a strong emphasis on quaUty control at coke plants, peUeti2ing plants, and sinter plants (see Quality ASSURANCE/QUALITY control). 

Manufacture and Processing. The largest volume of coal is carbonized in batch coke ovens to produce a hard coke suitable for blast furnaces for the reduction of iron ore. Oven temperatures, as measured in the flues, are between 1250 and 1350° and residence time varies between 17 and 30 h. The gas made in this process is mainly used as fuel and other appHcations in the steel works (see Fuels, synthetic). 

Thermal Cracking. Heavy petroleum fractions such as resid are thermally cracked in delayed cokers or flexicokers (44,56,57). The main products from the process are petroleum coke and off-gas which contain light olefins and butylenes. This stream also contains a considerable amount of butane. Process conditions for the flexicoker are more severe than for the delayed coker, about 550°C versus 450°C. Both are operated at low pressures, around 300—600 kPa (43—87 psi). Flexicokers produce much more linear butenes, particularly 2-butene, than delayed cokers and about half the amount of isobutylene (Table 7). This is attributed to high severity of operation for the flexicoker (43). 

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. 

To minimize coking, the reactor may be operated at short residence times, or hydrogen may be added to the process stream to convert gas-phase carbon into methane. It is also advantageous to minimize the temperature upstream of the catalyst bed, since gas-phase carbon is less readily formed at low temperatures. 

Other wastes that are typical of a refinery include (1) waste oils, process chemicals, and still resides (2) nonspecification chemicals and/or products (3) waste alkali (sodium hydroxide) (4) waste oil sludge (from interceptors, tanks, and lagoons) and (5) solid wastes (cartons, rags, catalysts, and coke). 

The manufacture of the xylenes is a dejk vu story of benzene and toluene—cat reforming, olefin plants, a small amount naturally resident in crude oil, and coke making. A small but rapidly growing amount of xylene comes from catalytic disproportionation, the process described in the ben-... 

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