Pyrolysis design data

When a reaction has many participants, which may be the case even of apparently simple processes like pyrolysis of ethane or synthesis of methanol, a factorial or other experimental design can be made and the data subjected to a re.spon.se. suiface analysis (Davies, Design and Analysis of Industrial Experiments, Oliver Boyd, 1954). A quadratic of this type for the variables X, Xo, and X3 is... 

Air pollution implications of pyrolysis are minimal with correct design and operation. VOC s in the gas can leak from pump seals, pipe flanges, valve stems, drains, and compressors. Particulate matter is generated from handling and processing the char. Emissions data from pyrolysis units are minimal, because many plants operate for short periods of time, and often only at pilot scale level. 

Figure 1 shows a computational framework, representing many years of Braun s research and development efforts in pyrolysis technology. Input to the system is a data base including pilot, commercial and literature sources. The data form the basis of a pyrolysis reactor model consistent with both theoretical and practical considerations. Modern computational techniques are used in the identification of model parameters. The model is then incorporated into a computer system capable of handling a wide range of industrial problems. Some of the applications are reactor design, economic and flexibility studies and process optimization and control. 

In conclusion, pseudo-kinetic models cannot be extrapolated beyond the range of the experimental data they are derived from, cannot incorporate the progress achieved in the whole field of fundamental chemical kinetics, both experimental and theoretical, and cannot be used for designing new reactors. In all these domains, mechanistic simulation is obviously superior, at least theoretically, and this seems also to be true in practice. Indeed, Goossens et al. [77—79] have carried out a comparison of the value for prediction of their mechanistic model and of the molecular reaction schemes proposed by Ross and Shu [55] and Sundaram and Froment [60]. Goossens et al. concluded that there is an actual superiority of the mechanistic model. Froment himself now seems to agree with this conclusion since, after having developed the molecular reaction schemes with co-workers [57—61], he and Sundaram [186] have lately proposed free radical schemes for pyrolysis reactions. 

The data form the basis of pyrolysis models consistent with both theoretical and practical considerations. The resulting models are integrated into a complete reactor simulation, which is then applied in design and optimization work. The simulation includes detailed models describing process-side heat and momentum transfer, thermophysical properties, and fired-side radiative heat transfer. 

Computer modeling of hydrocarbon pyrolysis is central to an optimum design of reactors for olefins production. Approaches to pyrolysis model development can be classified into four groups mechanistic, stoichiometric, semikinetic, and empirical. Selection of approaches to meet minimum development cost must be consistent with constraints imposed by such factors as data quality, kinetic knowledge, and time limitations. 

This chapter focuses attention on reactors that are operated isotherraally. We begin by studying a liquid-phase batch reactor to determine the specific reaction rate constant needed for the design of a CSTR. After iilustrating the design of a CSTR from batch reaction rate data, we carry out the design of a tubular reactor for a gas-phase pyrolysis reaction. This is followed by a discussion of pressure drop in packed-bed reactors, equilibrium conversion, and finally, the principles of unsteady operation and semibatch reactors. 

Heterogeneous kinetics of straw pyrolysis and straw gasification are essentia data for reactor design. Pyrolysis is a relatively fast process. In view of the poor heat conduction of straw and straw char, the pyrolysis time is the time which is required to heat the center of the particle to the decomposition temperature. This is a rather simplified model, but allows a reasonable time estimate in view of the order of magnitude. 

To examine the pyrolysis reaction of the scrap tires, pulverized scrap tires were heated in a quartz tube by an electric furnace (h). Then the continuous pyrolysis test plants in Table I were constructed to get the engineering data required for the design of an actual plant,... 

The present discussion is by no means exhaustive. It is designed to provide a summary of the most significant and reliable kinetic data, at least those that appear so to the author. There is a variety of methods for producing alkyl radicals, and, naturally, there will be certain restrictions on experimental conditions depending on the method chosen. Some of the common methods for generation of methyl radicals, for example, include photolysis of acetone, pyrolysis of di-ferf-butyl peroxide, photolysis of biacetyl, photolysis of azomethane and decarbonylation of acetaldehyde. In the majority of cases discussed here, the reactions were followed by product determinations, employing gas chromatography. 

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