Feed and catalysts

Often the catalysts described in the Hterature are not quite the same as those used in industrial processes, and often the reported performance is for pure single-component feeds. Sometimes the best quantitative approximations that can be made from the available Hterature are those based on reported kinetics of reactions with pure feeds and catalysts that are similar to but not the same as those used in practice. As a first approximation, one may use the pubHshed results and scale the activity on the basis of a few laboratory results obtained with reaHstic feeds and commercially available catalysts. 

Efficient contacting of the feed and catalyst is critical for achieving the desired cracking reactions. Steam is commonly used to atomize the feed. Smaller oil droplets increase the availability of feed at the reactive acid sites on the catalyst. With high-activity zeolite catalyst, virtually all of the cracking reactions take place in three seconds or less. 

Any mechanical revamp to improve the unit yields should always begin with installing an efficient feed and catalyst distribution system. This is the single most-important component of the FCC unit. An efficient feed and catalyst injection system maximizes gasoline yield and conversion at the expense of lower gas, coke, and decant oil and allows downstream technology to perform at its full potential. 

Ideally, a well-designed feed and catalyst injection system will achieve the following objectives ... 

The next series of experiments were run with the same feed and catalyst charge to assess the influence of the molar ratio MeOH/SA (10-30) at constant temperature of 83°C (Figure 32.5). 

In the butane route, a chemically complicated three-step process is needed to get from the feed to EDO. The two feeds, oxygen (air is used) and butane, are fed to a fluid bed reactor admixed with a catalyst. In a fluid bed reactor, the feeds and catalyst move continuously and, in this case, at a uniform temperature that allows optimum conditions for the catalyst to do its work. Butane and oxygen react to form maleic anhydride (MA), a cyclic compound. The fixed bed reactor effluent gases are taken off overhead, cooled, and filtered to remove entrained catalyst particles. The gases are then... 

As practiced today, FCC is a fluidized-bed process with continuous catalyst regeneration which reUes on short contact in a riser reactor between the feed and catalyst, fluidized with an inert gas, followed by disengagement and catalyst regeneration to burn off coke deposits and return the catalyst to near-fresh activity. 

The major problems in the engineering the ACC are the facts that (1) they must operate under transient conditions and (2) customers treat different cars very differently. The feed and catalyst temperatures vary widely, from ambient temperature upon startup (which can be -30°C in Minnesota) to >500°C during high-speed desert or mountain driving. 

Nonuniform mixing of feed and catalyst at the feed injection point... 

A feasibility study on the application of H-NMR petroleum product characterization to predict physicochemical properties of feeds and catalyst-feed interactions has been performed. The technique satisfactorily estimates many feed properties as well as catalyst-feed interactions to forecast products yield. There are, however, limitations that have to be understood when using the H-NMR method. The technique, in general, is not capable either to estimate the level of certain contaminants such as nitrogen, sulfur, nickel, and vanadium when evaluating feed properties or the effect of these contaminants on products yields while testing catalyst-feed interactions. 

In catalytic cracking, a large amount of heat needs to be supplied at the reactor inlet to vapourize the feed and provide the heat of reaction. In commercial units, this heat is provided by the hot catalyst recirculated from the regenerator. High heat transfer rates are achieved when the fluidized catalyst is mixed with the feed. In some experimental units, feed and catalyst are injected at reactor temperature. The heat of reaction must then be supplied by an external heating element, at much slower rates of heat transfer. The product selectivity from such laboratory units cannot be expected to simulate that of commercial units... 

Feed and catalysts. A regular Kuwait vacuum gasoil was used as a feed. Its characteristics can be found in Table II. Three commercial cracking catalysts with an increasing rare earth and alumina content, viz. A, B, and C, were tested. All catalyst were presteamed and deactivated to an equilibrium level by its supplier. Larger catalyst particles were removed with a 150 pm sieve. This step is followed by either a calcination or regeneration. Fresh, but pre-steamed catalyst was calcined at 773 K for 1 h, while coked catalyst was regenerated at 873 K for 2 h. 

This expcessLon then allows evaluation of coke levels for any given tlne fee i or hydrogen pressure and tenperacure, Variations due to the nature of the feed and catalyst can be grouped in the pre- exponential term empirically as single value factors, Ff and F. ... 

Several previous papers 2,3,4, 5) have reviewed the H-Oil process with respect to its principal characteristics and commercial performance. The major difference between H-Oil and the other processes for production of low sulfur fuels is a reactor system in which the oil and hydrogen are passed upflow through the reactor at a velocity suflBcient to maintain the catalyst in a suspended or ebullated state. This reactor system offers several advantages. It is isothermal, it is not susceptible to pressure drop buildup from suspended materials contained in the feed, and catalyst can be added and withdrawn during operation to maintain a constant level of catalyst activity. 

The usefulness of the of artificial neural networks as a modelling tool is apparent. A more general H-Oil product slate model can be developed by including the feed and catalyst properties. It can also easily be adapted to model the other aspects of the H-Oil process such the hydrotreating and hydrocracking reaction kinetics or coke lay down tendency in the separation units with the appropriate input and output patterns. 

Fig. 16.3 Reformer unit control based on reformate product octane rating setting the temperature of the reactor feed, and catalyst regeneration system. (O2, An), (H, An) and (O.N., An) are the oxygen, hydrogen and octane number analysers, respectively.

Ethylene feed and catalyst solution enter the bottom of the cylindrical reactor where the reaction proceeds at 125-130 C (255-265 °F) and 8-9 atm. (100-115 psig). The reactor contains internal distributors to insure good vapor-liquid distribution. Ethylene conversion is 96.7< 7o and selectivity to acetaldehyde is 9B.2 o. Even though there is a high exothermic heat of reaction, the reactor temperature is nearly isothermal because of the large quantity of catalyst solution circulated to the reactor. The reactor effluent is flashed adiabatically. Acetaldehyde product, unreacted ethylene, and flashed steam constitute the overhead vapor from the flash drum, and the catalyst solution is pumped from the bottom. 

In the case of cumene formation, the catalyst can be either AICI3 or supported phosphoric acid. In the second case the feed and catalyst have to be well purified, and moreover the catalyst has to be replaced each 6-9 months. Long chain alkylaromatics... 

Feed and catalyst information along with a brief overview of catalytic hydroprocessing (HDS in particular) will be presented to your group prior to beginning the project. 

We restrict our presentation to the case of a spherical bead of gel submitted to the BZ reaction performed with feed and catalyst conditions analogous to the above-mentioned experiments (bonded catalyst). Each point of the sphere is defined by a triplet of variables (r, 9, ), and furthermore, we shall assume that spherical symmetry is maintained during the volume oscillations, that is, the deformations are only radial as in Ref. [27,40-42]. 

It is hardly surprising that model developers have been compelled to drastically simplify model development along two lines. One is what may be called partition-based lumping, while the other total lumping. In the former case, the reaction mixture is represented by a finite number of lumps and the reactions among them are tracked. The lumped system aims to capture essential features of the real system so that it has sufficient predictive power and robustness over ever-changing feeds and catalysts. In the latter case, the... 

The basic problem lies in the fact that in the MAT unit the catalyst remains fixed while in a FCC riser reactor the catalyst moves along with the hydrocarbon vapours. Mott (1987) describes this in terms of the number of active sites. In the MAT unit the number of active sites is fixed while in real operation the number of active sites delivered to the riser per unit of feed is dynamic and will change according to the heat requirements and the combined coke-making tendencies of the feed and catalyst. Thus, the most effective FCC catalyst should be determined by the number of active sites it can bring to the reactor per mass of feed which may not necessarily be the catalyst with the highest MAT activity (Mott, 1987). 

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