Cracking cycle

Fresh activity, however, only partially determines the efficacy of these catalysts. Among other important factors, as we have seen, are how easily the catalyst releases SO2 during the cracking cycle and how resistant it is to deactivation by steam. 

Figure 10. Wojciechowski s mechanistic formalism for the catalytic cracking cycle for normal paraffins [38].

Experimental data from cracking cycles of 1 to 2 minutes at various temperatures indicate that the true activation energy for the catalytic cracking reaction is probably about 10,000 calories/mole (73). Higher apparent values of 15,000 to 20,000 calories/mole calculated from long-... 

Another variation of the partial-oxidation process is one in which a heavy-oil fraction is cracked in the presence of an inert solid and a hydrogen-rich gas under conditions which result in the saturation of olehns and diolefms. During the process some coke and residual material depoats on the inert solid. The latter then flows by gravity to a combustion aone where the coke is burned off the solid in the presence of oxygen and steam to produce the hydrogen-rich gas used in the cracking cycle. ... 

SCD Sulphur-containing compounds in light catalytically cracked cycle oil-heavy gas oil mixtures 800 50 [87]... 

Shear stress distribution Quality of part tendency to distort. Quality of part tendency to crack. Cycle time low stresses permit hotter demold temperature. 

After several cracking cycles, the major alkene product formed Is ethylene, the smallest possible alkene. 

Cycle type Indirect cycle intermediate loop of forced circulation molten salt. Ca-Br thermochemical water cracking cycle/ supercritical CO2 Bra54on cycle with a feed-forward multi-effect distillation bottoming cycle... 

See Fig. XXIV-4) water cracking cycle and a supercritical CO2 Brayton cycle (sized for on site needs). 

Given that the asymptotic states in response to ATWS initiators are safe, it remains to show that the dynamic transition to the asymptotic state will not engender damaging conditions on the in-core structures. A plant dynamic code, which can model the STAR-H2 balance of plant, was not available at the time when this report was prepared. Such a code is being developed first for the STAR-LM, which has a simpler (SC-C02 Bra)hon cycle) balance of plant. In the future, after further refinement of the Ca-Br water cracking cycle, that dynamics code will be modified for applicability to the STAR-H2. 

The essentials of the method proposed in Ref. 12 are that in carrying out cracking experiments in succession, in each successive cracking cycle enough raw material has to be added to make the amount of recycle material equal the working charge of the reactor. 

The main difference is that whereas in the method proposed in Ref. 12 the steady state is attained after about 2-3 cracking cycles, with our method, depending on the size of a, it is attained in 5-10 cycles. 

With this system, the recycle material from the primary cracking (cycle I) of the raw material g is supplied for cracking in cycle II. The recycle material produced in this cycle is supplied for cracking in cycle III, and so on. 

Here gn is the quantity of recycle material produced in the wth cracking cycle a is the yield of recycle material, expressed as a proportion of gn . 

If we suppose that the relative yields of the products in each cracking cycle do not change, then the above relations can be written as follows ... 

Thus, with respect to the available experimental data, we can write the following system of equations for the charges in cracking cycles I to n ... 

Theoretically, this is only attainable if n = 00. However, in practice a finite number of cycles is found to suffice. Therefore it is necessary to calculate the number of cracking cycles before the virtually steady state of the process is attained with the permissible degree of error /i, for which the following equation is valid ... 

Taking logarithms and solving (5.20) for n, we get an equation by means of which we can determine the practical number of cracking cycles in which the process will attain the steady state with a given degree of error ft ... 

We will now determine the steady-state parameters on the basis of the data from cycles I-IV, when p% const., and from cycles V-XV, when Pi = const. Here, as was stated earlier, the yield of the cracking products in cycles V-XV equals the yields of the Vth cracking cycle, i.e. 

From the data in this Table we can determine the total yield of all the products in the steady state (in XV cracking cycles) ... 

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