Fresh Feed Quality

The quality of the raw oil eharged to a Hydrocracker will affect the temperature required in the eatalyst bed to reach the desired conversion, the amount of hydrogen eonsumed in the process, the length of time before the catalyst is deactivated, and the quality of products. The effect of the feedstock quality on the performance of the unit is important and should be well understood, espeeially with regard to contaminants that can greatly reduce the life of the eatalyst. 

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Feeder management also plays an important role in delivering quality feed to poultry. Feed becomes stale and of reduced palatability if allowed to remain in feeders for long periods. Feeders should be filled often enough to provide fresh feed at all times, unless restricted feeding is being used. 

Carbon Residue. The carbon residue is one factor used to determine coke yield as a percentage of fresh feed, and is defined as the carbon residue remaining after evaporation and pyrolysis of the feedstock in a specified procedure. All other operating conditions being the same, as the carbon residue is increased, more coke will be produced. In recent years, as the quality of crudes has diminished, the carbon residue of vacuum residue feedstocks has increased from typical values of 10 to 20 weight % to 20 to 30 weight % and more. 

Three operating control variables in a delayed coker dictate the product quality and yields for a given feedstock. These variables are the heater outlet temperature, coke drum pressure and the ratio of recycle to fresh feed. 

Cs Fresh feed 0 Product stream 0 Self-regulating by product quality controller... 

Note that the changes in production rate occur more quickly when the toluene recycle flowrate handle is used, compared to the reactor inlet temperature handle. Fresh feed rates of toluene and hydrogen change more quickly, as does benzene product flowrate. So if rapid transitions in production rate are important, toluene recycle flowrate manipulation is better than reactor inlet temperature manipulation. If tight product quality control is more important, the opposite is true. 

In pressure agglomeration, it is preferable to meter recycle into the mixer. However, when product quality does not need to be tightly controlled, recycle can be added to the fresh feed in the agglomerator. The ratio of fresh feed to recycle should be kept constant, however, because variations in feed composition change the agglomerate quality which, in turn, influences the recycle rate. Therefore, a surge bin for the recycle must be provided from which the fines are metered back into the system. (Note This statement is valid for all agglomeration methods.)... 

Now let us apply the capacity-based approach. Positive and negative 10 percent disturbances are made in the fresh feed flow rate Fg and in the fresh feed composition Zq. Dynamic simulations (confirmed by frequency-domain analysis, to be discussed in Chapter 10) show that the variability in product quality xb is decreased by increasing reactor volume or by decreasing the number of trays in the stripper. 

Operational flexibility and reliability are excellent changes in feedstock quality and flows are easily handled. If the catalyst is deactivated by feed quality upsets, then fresh catalyst can be injected without a shutdown. 

An additional benefit of this development is increased feedstock flexibility, both for the SGP itself and for the refinery as a whole. The carbon recycle currently practised also recycles some of the ash, so that the charge pump, burner, and reactor system are exposed to a higher content of ash than that present in the fresh feed. Elimination of the recycle thus makes it possible to use feeds with considerably higher ash contents than previously. Current experience of >1000 pg/g vanadium at the reactor inlet would be directly applicable to residues of this quality. This is certainly an important feature when reviewing the possibility of introducing heavier (and cheaper) crudes into the refinery. 

However, consider the case when there is only one product the reaction A + B C. Now the column temperature information is not rich enough to use to balance the stoichiometry. This means that the measurement and control of an internal column composition must be used in this neat operation. An example of this type of system is shown in Figure 9.6. The production of ethyl tcrt-butyl ether (ETBE) from ethanol and isobutene produces a heavy product, which goes out of the bottom of the column. The C4 feed stream contains inert components in addition to isobutene. These inerts go out of the top of the column. The production rate is set by the flow controller on the isobutene feed stream. The ethanol concentration on a suitable tray in the column is maintained by manipulating the ethanol fresh feed. ReboUer heat input controls a tray temperature in the stripping section to maintain ETBE product quality. 

In the absence of a suitable commercially available artificial diet, five and fresh feed sources currently represent the most suitable vehicle for the administration of nutrition for the promotion of adequate growth and survival in phyllosomas. While phyllosomas will readily accept a variety of commercially available five and fresh feed sources, such as squid, mussel mantle and gonad, vlrfemia sp., oyster and clam, it is generally well accepted that Anemia sp. and mussel gonad, in combination, are the most common food sources for phyUosoma culture (Takeuchi and Murakami, 2007). However, fluctuations in the supply and nutritional quality of these feed sources results in an unreliable feed source, which potentially impedes the establishment of robust mass rearing protocols. 

Feeds are a significant biosecurity risk. There is no single pelletized feed that produces high quantities and quality of shrimp nauplii. Successful reproduction in marine shrimp requires the use of fresh feeds such as marine polychaetes, squid and shellfish. This daily addition of fresh feeds to the SPF broodstock is a large risk to biosecurity. Sourcing of the fresh feeds is important in trying to prevent any disease introduction. 

In the continuous shell still process, several shell stills are linked in series to form a battery. Fresh feed continuously enters the first still, which is kept at the lowest temperature for the lightest overload produa. The bottoms from the first still are fed to the second still, which is kept at the temperature for the next highest boiling overhead product, and so on. The number of stills required depends on the number of produas needed. If the feed and the temperature of each still remain constant, the finished product is of satisfaaory quality. Exhibit 10-3 depicts the continuous shell still process, which is an improvement over the batch shell still operation. 

Many industrial reactive distillation systems do not use stoichiometric amounts of reactants. An excess (10-20% above the stoichiometric amount) of one of the reactants is fed to the reactive column. There may be kinetic reasons for using an excess in some systems. These include suppressing undesirable side reactions, reducing catalyst requirements, and increasing conversion. However, even in the absence of kinetic reasons, the use of an excess of one of the reactants makes the control problem easier because the fresh feed flowrates of the components do not have to be precisely balanced in the reactive column. Achieving this exact balance may require the use of expensive and high maintenance on-line composition analyzers in some systems. In addition, the variability of product quality may be larger in the neat operation process because there arc fewer manipulated variables available and there is only one column to contain disturbances. 

Relaxing the requirement on BFW quality to few ppm s of ammonia and AN. In this case, recycle and interception techniques can be used to significantly reduce the fresh water feed to the boiler and, consequently, the net wastewater generated. 

The circulating catalyst in the FCC unit is called equilibrium catalyst, or simply E-cat. Periodically, quantities of equilibrium catalyst are withdrawn and stored in the E-cat hopper for future disposal. A refinery that processes residue feedstocks can use good-quality F-cat from a refinery that processes light sweet feed. Residue feedstocks contain large quantities of impurities, such as metals and requires high rates of fresh catalyst. The use of a good-quality E-cat in conjunction with fresh catalyst can be cost-effective in maintaining low catahst costs. 

In commercial operations, catalyst activity is affected by operating conditions, feedstock quality, and catalyst characteristics. The MAT separates catalyst effects from feed and process changes. Feed contaminants, such as vanadium and sodium, reduce catalyst activity. E-cat activity is also affected by fresh catalyst makeup rate and regenerator conditions. 

Plot properties of the fresh and equilibrium catalysts ensure that the catalyst vendor is meeting the agreed quality control specifications. Verify that the catalyst vendor has the latest data on feed properties, unit condition, and target products. Verify the fresh makeup rate. Check for recent temperature excursions in the regenerator or afterburning problems. 

A variety of molecular indicators of the freshness (and perhaps nutritional quality) of organic matter exists. For example, certain labile phytoplankton constituents, such as polyunsaturated fatty acids, are readily degraded in the environment or in herbivore guts, and are thus depleted in more degraded particles (de Baar et ak, 1983 Wakeham and Canuel, 1988). Preferential loss of labile algal fatty acids resulting in the enrichment of more stable components in the products of heterotrophic metabolism has been observed in both field studies and laboratory feeding experiments (Prahl et ak, 1985 Wakeham and Canuel, 1988 Harvey et ak,... 

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