Design of Reactor

The wide variety of reactor designs results from the possible combinations of  

However, in industrial practice a smaller number of reactor types are found, which can be classified according to the states of aggregation that they handle  

A good overview can be found in [Ullmann2]. In the following only the three most important reactor types - the stirred-tank, tubular, and fluidized-bed reactors - are discussed in detail, together with a more recent development, namely the microreactor. 

The classical apparatus for homogeneous liquid-phase reaction systems is the stirred tank, which is preferentially operated in batch mode, since for normal reaction kinetics (order 0) its continuous operation is disadvantageous an exception here is its use in a cascade. 

For smaller production quantities (mle of thumb 10 000 t/a) and/or frequent product changes, it has advantages over the tubular reactor. Very long residence times can readily be achieved, and reaction conditions such as temperature, pH value, and catalyst concentration can be changed and optimized during the reaction time. In batch mode, product quality is subject to certain variations, and hence continuous process control is necessary. 

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In the design of reactors for fluids in the presence of granular catalysts, account must be taken of heat transfer, pressure drop and contacting of the phases, and, in many cases, of provision for periodic or continuous regeneration of deteriorated catalyst. Several different lands of vessel configurations for continuous processing are in commercial use. Some reaciors with sohd catalysts are represented in Figs. 23-18 and 23-24. 

Analysis of thermal runaway reactions is reviewed in Chapter 12. Table 4-6 gives various guidelines for the design of reactors and Figure 4-26 illustrates various reactor configurations. 

Although this article focuses on design of reactors, keep in mind that the principles presented here can also he applied to other equipment through which process streams pass. 

Most earlier units around the world were BWR types, but modem units tend to be PWR types. The designs of reactors have been continuously improved upon since they were first installed in the early 1950s. 

The problem is of great significance in the design of reactors because a varying residence time will, in general, lead to different degrees of chemical conversion of various fluid elements, and this is discussed in some detail in Volume 3, Chapter 1. 

In this chapter, consideration will be given to the basic principles underlying mass transfer both with and without chemical reaction, and to the models which have been proposed to enable the rates of transfer to be calculated. The applications of mass transfer to the design and operation of separation processes are discussed in Volume 2, and ihe design of reactors is dealt with in Volume 3. 

The flow-dynamics and mass-transport processes can be expressed mathematically and realistic models obtained to be used in the predictions of a CVD operation and in the design of reactors. 

The design of the Pd-membrane reactor was based on the chip design of reactor [R 10]. The membrane is a composite of three layers, silicon nitride, silicon oxide and palladium. The first two layers are perforated and function as structural support for the latter. They serve also for electrical insulation of the Pd film from the integrated temperature-sensing and heater element. The latter is needed to set the temperature as one parameter that determines the hydrogen flow. 

Prepare a chemical engineering design of reactor (A) and either column (B) OR column (D). 

In summary, the negative perception about all four issues seems strong and is not easy to refute the differences between the pro- and anti groups are in differences of perception, not provable facts. As a result, there have to be doubts whether development, say, of safer designs of reactors or repositories will greatly affect public perception What can ... 

The problem with the flowsheet shown in Figure 28.5 is that the ferric chloride catalyst is carried from the reactor with the product. This is separated by washing. If a design of reactor can be found that prevents the ferric chloride leaving the reactor, the effluent problems created by the... 

Polymerization processes represent an extremely important aspect of the chemical processing industry. Since many of the properties of polymeric materials are markedly affected by their average molecular weight and their molecular weight distribution, the design of reactors for polymerization processes offers many opportunities for the use of the principles presented earlier in this chapter. 

Flow Column Reactor 5.3.1 General design of reactor... 

The characteristics of this kind of CL emission, design of reactors, CL reactions in gas phase, and applications as detection technique in gas chromatography (GC) and atmospheric research are extensively described in Chapter 13. 

Autoclaves provide reactors which can be used readily to acquire data from coal liquefaction studies but are less representative of likely commercial plant tyi reactors than small scale continuous bed-type reactors. Ideally comparisons between reactors are best made by carrying out experiments in various designs of reactors under similar reaction conditions, but, in order to cover the full range of designs adequately, a larger expenditure on equipment (beyond the budgets of most laboratories) would be necessary. However, steps can be taken to cover the... 

So far, the discussion has been in terms of an empty tubular reactor. Similar arguments can be applied to a reactor packed with catalyst particles. The design of reactors for carrying out solid-catalysed gas reactions is discussed fully in Chap. 4. 

The equations describing the concentration and temperature within the catalyst particles and the reactor are usually non-linear coupled ordinary differential equations and have to be solved numerically. However, it is unusual for experimental data to be of sufficient precision and extent to justify the application of such sophisticated reactor models. Uncertainties in the knowledge of effective thermal conductivities and heat transfer between gas and solid make the calculation of temperature distribution in the catalyst bed susceptible to inaccuracies, particularly in view of the pronounced effect of temperature on reaction rate. A useful approach to the preliminary design of a non-isothermal fixed bed catalytic reactor is to assume that all the resistance to heat transfer is in a thin layer of gas near the tube wall. This is a fair approximation because radial temperature profiles in packed beds are parabolic with most of the resistance to heat transfer near the tube wall. With this assumption, a one-dimensional model, which becomes quite accurate for small diameter tubes, is satisfactory for the preliminary design of reactors. Provided the ratio of the catlayst particle radius to tube length is small, dispersion of mass in the longitudinal direction may also be neglected. Finally, if heat transfer between solid cmd gas phases is accounted for implicitly by the catalyst effectiveness factor, the mass and heat conservation equations for the reactor reduce to [eqn. (62)]... 

The above analysis, which is exceedingly brief and simplified is designed to demonstrate how, even in a pre-mixed flame, the question arises as to what is the appropriate reaction volume (i.e. the flame thickness). In heterogeneous reactions, this is a question that will recur again and ain and the designer of reactors must not attempt to avoid it. It is interesting to note that, in the next but one example to be treated, the overall reaction rate (a flame speed cm s in the above) becomes a mass transfer coefficient (also cms" ) when considering the absorption of gas into a liquid with which it reacts quickly. Furthermore, exactly the same sort of analysis as the above leads to the dependence of the mass transfer coefficient fej on the reaction rate coefficient and the diffusivity, D, in the liquid phase, of ki o. (rD), cf. z a RKY above. 

This chapter deals with the design of reactors which do not conform to these ideal models its attention is restricted to constant volume, single phase, isothermal reactors which are operated in the steady state. It is not intended to be a state of the art review of non-ideal reactor design methods, but rather an introduction to basic ideas and techniques frequently, the reader will be referred to more extended or specific coverage of the material being considered. 

With such a large ratio, of course the design of reactors will be quite different in these cases. 

We discussed thermodynamic equilibrium previously in relating kinetics to reversible reactions. One should always estimate these quantities and keep them in mind before performing more detailed design of reactors and separation units. We also note that one must consider aU chemical reactions that may occur for a given feed, not just the one desired. 

Ultraviolet sources are chiefly mercury-discharge lamps in various forms. These lamps are fragile and quite inefficient. The design of reactors using these lamps is hampered by these considerations, and by the limited ultraviolet transmission, of common glasses and solvents. The transmission is further decreased by coatings of opaque materials which form... 

HA Duxbury A J Wilday, "Efficient Design of Reactor Relief Systems", International Symposium on Runaway Reactions, 373-393, CCPS/AIChE, 1989, ISBN 0-8169-0460-X... 

HA Duxbury A J Wilday, The Design of Reactor Relief Systems", IChemE Symposium Series No 115,125-139, 1989, IChemE, ISBN 0 82595 242 2... 

Thermal effects also are major factors in the design of reactors... 

The design of reactors, preparation of catalysts, control of tempera-tim and other topics of practical importance are summarized by Pokrovskii in excellent reviews1 84.1885 which encompass the literature up to 13o5. Reference should be made to these sources for numerous patent disclosures that will not be considered in the present disoussicn Among the significant problems examined by Pokrovskii from the standpoint of industrial technology are relative merits of fixed and fluidized catalyst beds, optimum composition of the reaction mixture in terms of both yield and safety, and properties of catalysts—selectivity, activity, durability, etc,—that arc vita] to the success of the enterprise. 

Non-isothermal and non-adiabatic conditions. A useful approach to the preliminary design of a non-isothermal fixed bed reactor is to assume that all the resistance to heat transfer is in a thin layer near the tube wall. This is a fair approximation because radial temperature profiles in packed beds are parabolic with most of the resistance to heat transfer near the tube wall. With this assumption a one-dimensional model, which becomes quite accurate for small diameter tubes, is satisfactory for the approximate design of reactors. Neglecting diffusion and conduction in the direction of flow, the mass and energy balances for a single component of the reacting mixture are ... 

The SEMICONDUCTOR, insulator, or conductor layers in microscale or larger scale electronic devices such as a photovoltaic cell are created in a reactor. The reactor needs to be designed and operated to produce materials that have the desired optical and electronic properties. The design of reactors is a nontrivial research and design problem. In this chapter, some of the theoretical and experimental framework for this research and for more-effective designs of physical-vapor-deposition-type reactors will be developed. 

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