Specific Reactor Types

Although there are hundreds of tire pyrolysis processes, they all can be categorized as either oxidative or reductive. Table 8-2 contains a list of manufacturers of oxidative and reductive processes with capacities, operating temperatures, and product mixes. 

Steam injection is a variation of oxidative combustion because the predominant reactions involve cracking hydrocarbons to form carbon monoxide, carbon dioxide, and hydrogen. Because the gas products are not consumed as in the substoichiometric process, the steam injection process produces more combustible gas products than the oxidative process. In addition to the heat required to heat the reactor and contents, tne steam injection process requires an external source of heat to produce the steam. 

Process Km Capacity tpd Reaction Tamp, C Yields as a percent of Tires  

The reductive process is the more traditional process for tire pyrolysis. This process excludes all sources of oxygen and relies on the reactor heat alone to decompose the tires. Some processors pressurize the reactor with an inert gas such as nitrogen to prevent air from leaking into the reactor, while some inject hydrogen to react with the sulfur present in the rubber in the tires to form hydrogen sulfide. Hydrogen sulfide can be recovered and sold as a by-product. 

As mentioned earlier, a number of different types of reactors have been tried in tire pyrolysis. Almost any vessel that can be sealed can be used as a pyrolysis reactor. Reactor design has a significant effect on the quality of char produced, due to a uniform temperature gradient, and the abrasion of the particles with one another. Some of the reactor types that have been used are  

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Several different reactor types were used for catalyst evaluation, including a DCR pilot riser [3] an ACE fixed fluidized bed (FFB) reactor [7], a Riser simulator [4,9], and a specially designed extended residence time circulating pilot unit. The reaction conditions of each of the reactors will be reported in the sections dealing with the specific reactor type. Different grades of Brazilian Campos Basin derived VGOs were used in the experiments. Feed properties are presented in Table 2.1. 

Exploration for an acceptable or optimum design for a new reactor may require consideration of several feed and product specifications, reactor types, catalysts, operating conditions, and economic evaluations. Modifications to an existing process likewise may need to consider many cases. Commercial software may be used to facilitate examination of options. A typical package can handle a number of reactions in various ideal reactors under isothermal, adiabatic, or heat-transfer conditions in one or two phases. Outputs can provide profiles of composition, pressure, and temperature as well as vessel size. 

In the figure, a link type called PFRLink is defined. This example link type expresses that exactly one instance of the specific reactor type PFR (plug flow reactor) can be simulated by exactly one instance of the specific reactor block RPlug in the simulation model. The reactors in both documents can have an arbitrary number of ports which are mapped by the link as well. To assign corresponding ports, the link may have sublinks each mapping pairs of ports . Both reactors are referenced as dominant increments. This link type is rather specific, as it forms relatively tight constraints for all of its instances. 

An overall kinetic model for the cracking of gasoils to gasoline products was developed by Nace, Voltz, and Weekman [15]. The actual situation was a catalytic reaction and the data were from specific reactor types, but mass-action type rate expressions were used and illustrate the methods of this section. 

As already mentioned, the form of the fundamental continuity equations is usually too complex to be conveniently solved for practical application to reactor design. If one or more terms are dropped from Eq. 7.2.a-6 and or integral averages over the spatial directions are considered, the continuity equation for each component reduces to that of an ideal, basic reactor type, as outlined in the introduction. In these cases, it is often easier to apply Eq. 7.1.a-l directly to a volume element of the reactor. This will be done in the next chapters, dealing with basic or specific reactor types. In the present chapter, however, it will be shown how the simplified equations can be obtained from the fundamental ones. 

Criteria for acceptable values and uses of uncertainties in operation, instrumentation numerical requirements, limit settings for alarms or scram, frequency and extent of power distribution measurements, and use of excore and incore instruments and related correlations and limits for offsets and tilts, all vary with reactor type. Guidance will need to be developed for each specific reactor type. 

The specific reactor type used, and why it is needed, is described in Chapter 4. A number of worked problems, using AR theory, are given in Chapter 5. 

A reactor type constraint In this scenario, the construction of the AR is carried out by using PFRs alone. This approach is similar to that discussed in Chapters 2 and 3. This is done because situations might arise when only access or knowledge to a specific reactor type is available. We will be interested in how this constraint impacts construction of the AR, and ultimately how this influences what states are achieved. 

The second edition of this handbook contains some new and updated information including chapters on liquid metal cooled fast reactors, liquid fueled molten salt reactors, and small modular reactors that have been added to the first section on reactors. In the second section, a new chapter on fuel cycles has been added that presents fuel cycle material generally and from specific reactor types. In addition, the material in the remaining chapters has been reviewed and updated as necessary. The material in the third section has also been revised and updated as required with new material in the thermodynamics chapter and economics chapters, and also includes a chapter on the health effects of low level radiation. 

Major accidents, not limited to the specific reactor type (e.g. post-Chernobyl boron dilution concerns for PWRs) ... 

This leads to the obvious conclusion that changes in the nuclear part of power station design will have a great effect on the fuel cycle. A detailed analysis of future fuel cycle expenditures in relation to the different assumptions that can be made for the development and utilization of specific reactor types could therefore be of great importance for decisions on present day reactor development activities. In this article we have tried to analyze some of these assumptions, in particular, the effect on fuel cycle expenditures of the utilization of fast and thermal breeders in future nuclear strategies. 

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