Stripper coke

As discussed in Chapter 1, a portion of the feed is converted to coke in the reactor. This coke is carried into the regenerator with the spent catalyst. The combustion of the coke produces H2O, CO, CO, SO2, and traces of NOx. To determine coke yield, the amount of dry air to the regenerator and the analysis of flue gas are needed. It is essential to have an accurate analysis of the flue gas. The hydrogen content of coke relates to the amount of hydrocarbon vapors carried over with the spent catalyst into the regenerator, and is an indication of the rcactor-stripper performance. Example 5-1 shows a step-by-step cal culation of the coke yield. 

The hydrogen content of coke indicates the amount of hydrocarbon vapors carried through the stripper with the spent catalyst. 

If a reliable spent catalyst temperature is not available, the stripper is included in the heat balance envelope (II) as shown in Figure 5-4. The combustion of coke in the regenerator satisfies the following heat requirements ... 

Using the operating data from the case study. Example 5-5 shows heat balance calculations around the stripper-regenerator. The results are used to determine the catalyst circulation rate and the delta coke. Delta coke is the difference between coke on the spent catalyst and coke on the regenerated catalyst. 

The coke calculation showed the hydrogen content to be 9.9 wtVt. As discussed in Chapter 1, every effort should be made to minimize the hydrogen content of the coke entering the regenerator. The hydrogen content of a well-stripped catalyst is in the range of 5 wt% to 6 wt%. A 9.9 wt% hydrogen in coke indicates either poor stripper operation and/or erroneous flue gas analysis. 

Catalyst circulation coke is a hydrogen-rich coke from the reactor-stripper. Efficiency of catalyst stripping and catalyst pore size distribution affect the amount of hydrocarbons carried over into the regenerator. 

Reactor stripper. Operational and hardware changes to the stripper improve its performance by removing the entrained and adsorbed hydrocarbons. The benefits are lower delta coke and more liquid products. 

Check pressure profile around Feed Nozzles Track in Coke Survey the Stripper... 

Spent Catalyst is the coke-laden catalyst in the stripper. 

The type of oil-removing equipment used may be alum or caustic precoat coke filters, diatomaceous earth filters, or coalescing filters, sometimes employing oleophilic resins as oil strippers. Phenolic formaldehyde demulsifiers are also sometimes used. 

The spent, i.e. coked, cracking catalyst and the SOx catalyst then move to the FCCU stripper. In the stripper, they are treated with steam to flush out the volatile hydrocarbons. The steam also hydrolyzes the metal sulfide on the surface of the SOx catalyst to give metal oxide and release H S in the stripper (Equation 6). 

Add packing to top of stripper to insert oil to increase delta coke when processing very low delta coke feeds... 

The stripper performance may be evaluated by sampling the spent catalyst standpipe for both hydrogen in the coke on catalyst and the relative amounts of water and hydrocarbon leaving the stripper. If debris disrupting the catalyst and/or steam flow patterns is suspected, tracer scans can be used to identify the location of the blockage [5]. 

Catalyst mass flowrates exceeding about 1600 Ib/ft -min (7800kg/m -min) results in poor steam/catalyst contacting, flooded trays, insufficient catalyst residence time, and increased steam entrainment to the spent catalyst standpipe. This is reflected by the stripper efficiency and catalyst density shown in Figure 7.10. The primary concern is hydrocarbon entrainment to the regenerator leading to loss of product, increased catalyst deactivation, increased delta coke and potential loss of conversion and total liquid yield, and feed rate limitation. A rapid decrease in stripper bed density is an indication that... 

Occluded coke is a function of the operating conditions of the FCCU stripper, of catalyst pore volume and pore size distribution. This coke that has the higher content of hydrogen is the lowest refractory between the different kinds of coke produced in the FCC process. Althongh in this study it was not directly evalnated, it may be associated with the peak A at the lowest temperature ( 500°C-550°C). So once the... 

Fractionation Section. A typical fractionation section includes the coker fractionator and attendant heat exchange equipment, the light gas oil side stream stripper and the overhead system. The coke drum overhead vapors enter the fractionator under shed trays which are located below conventional wash trays. Hot induced gas oil reflux is pumped to the wash trays to condense recycle and to wash the product vapors. The light and heavy gas oil products are condensed as sidestream products. The light gas oil product is usually steam stripped in a sidestream stripper. The overhead vapors from the fractionator are partially condensed and the gas and gasoline products are directed to the vapor recovery unit. 

Fluid Coking and Cracking, Delayed Coking, Alkylation, Sulfur Plants, and Sour Water Strippers... 

Overall, evaluation of catalysts on resid feedstocks requires sophisticated and well integrated catalyst deactivation, catalyst stripping and cracking systems. It is important to determine not only the coke yield, but each of its components (Catalytic coke, contaminant coke, CCR coke and stripper (soft) coke). This paper provides details on how each of the components of the coke yield may be experimentally determined using catalyst metallation by cyclic deactivation, catalyst strippability measurements and modified catalytic cracking techniques. 

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