Other Types of Reactors

There are many other reactors of various types not included among those discussed above. These include tower reactors (Chapter 24), which may be modeled as PF or modified PF reactors. We describe one further example in this section. 

The reactor is designed to provide sufficient residence time (for recirculating liquid) for the reaction producing chlorate (started in the electrolyzers) to be completed. This involves further reaction of intermediates formed by the complex reactions in the electrolyzer, such as hypochlorite and hypochlorous acid, to produce chlorate. The reactor receives weak chlorate liquor from a crystallizer (not shown), fresh brine feed (also not 

The following reactor problems illustrate some process calculations that involve material and/or 

11-2 Fora 1000-tonne day-1 sulturic acid plant (100% H2SO4 basis), calculate the total molar flow rate (mol s 1) of gas entering the SO2 converter (for oxidation to SO3), for steady-state operation, if the fractional conversion (/so2) in the converter is 0.98, and the feed to the converter is 9.5 mol % SO2. (1 tonne = 1000 kg.) 

11-3 Calculate the (total) volumetric flow rate (m3 s-1) of gas leaving the reactor of a 1000-tonne day-1 ammonia plant, if the gas originates from H2 and N2 in the stoichiometric ratio, and 20% conversion to ammonia occurs. T = 450°C, P = 300 bar, and the compressibility factor z = 1.09. (1 tonne = 1000 kg.) 

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Before we can explore how reactor conditions can be chosen, we require some measure of reactor performance. For polymerization reactors, the most important measure of performance is the distribution of molecular weights in the polymer product. The distribution of molecular weights dictates the mechanical properties of the polymer. For other types of reactors, three important parameters are used to describe their performance ... 

Its unique design suggests several accident scenarios that could not occur at other reactors. For example, failure to supply ECC to 1/16 of the core due to the failure of an ECC inlet valve. On the other hand, some phenomena of concern to other types of reactors seem impossible (e.g., core-concrete interactions). The list of phenomena for consideration came from previous studies, comments of an external review group and from literature review. From this, came the issues selected for the accident progression event tree (APET) according to uncertainty and point estimates. 

One other type of reactor allows this in principle. Dijferential reactors are so short that concentrations and temperatures do not change appreciably from their inlet values. However, the small change in concentration makes it very hard to determine an accurate rate. The use of dilferential reactors is not recommended. If a CSTR cannot be used, a batch or piston flow reactor is preferred over a dilferential reactor even though the reaction rate is not measured directly but must be inferred from measured outlet concentrations. 

For other types of reactors, three important parameters are used to describe their performance7 ... 

The process design of an LFR, like that of other types of reactors, may involve, for a specified throughput (q or FAo), calculation of the fractional conversion (/A) achieved at the outlet of a vessel of given size, or the size of vessel required for a specified /A. 

In the post-treatment of films or fibers, fluorine-containing gas is continuously injected into the reactor and gaseous by-products are removed. The other type of reactor for posttreatment is the batch process reactor, which consists of a suitably sized vacuum chamber provided with means of evacuation and injection. 

The results have shown that spinning/falling basket autoclaves can be used effectively for gathering data on coal hydroliquefaction, a single contact being representative of steady state conditions. As with other types of reactors for coal liquefaction, the catalysts were deactivated to a constant activity but the rate of deactivation was much more rapid in tiie autoclaves. 

For purposes of plant design and for optimum operation consistent with feed stock availability, it is necessary to be able to predict accurately the octanes of the alkylate produced under varying operating conditions. Such a correlation developed from several hundred pilot plant and commercial plant tests is presented in Figures 7, 8, and 9. This correlation is applicable to sulfuric acid alkylation of isobutane with the indicated olefins, and was developed specifically for the impeller-type reaction system, although it also appears to be satisfactory for use with some other types of reactors. 

Equation (45) can be solved by applying different photoreactor models. The literature reports several photochemical reactor models for both homogeneous and heterogeneous reactors [11,108,109]. In practice, annular photoreactors are often used (see Fig. 5) therefore, models for this type of reactor are considered here. For other types of reactors, attention should be given to other publications [109]. 

Other types of reactors, such as trickle bed or bubble (slurry) reactors, are used only in special cases for reactions of liquids with gases catalysed by solids. 

The major characteristic of a polymeric reactor that is different from most other types of reactors discussed earlier is the viscous and often non-Newtonian behavior of the fluid. Shear-dependent rheological properties cause difficulties in the estimation of the design parameters, particularly when the viscosity is also time-dependent. While significant literature on the design parameters for a mechanically agitated vessel containing power-law fluid is available, similar information for viscoelastic fluid is lacking. 

Similar forms of simplified expressions can be developed for back-mix tank reactors and other types of reactor systems.ft A typical example of the analysis used in developing the mathematical model for a reactor design is presented in the following section. 

The extent of axial mixing is typically small, compared with other types of reactors. 

Experimental. Figure 2 compares molecular weight data reported by Garden (J 0) for batch reactors and by Poehlein for CSTR reactors ( ), with the data obtained in this study for a tubular reactor. The solid lines are predicted by Garden s theory (10). The molecular weights obtained in this experimenTal study were predicted within a factor of 3 by Garden s theory. No direct comparison can be made with the data of other workers, yet this molecular weight data is consistent (at least within experimental error) with data obtained in other types of reactors. 

There are numerous other types of reactors (e.g., membrane reactors) that will not be discussed in this text. Readers interested in reactor configuration should look for references specific to the reactor configuration of interest. 

For gas-phase reactions in packed beds where there is a pressure drop, we need to proceed to level to evaluate the pressure ratio (F / in the concentration term using the Ergun equation (Section 4,5). In level , w e combine the equations for pressure drop in level w ith the infomiation in levels and to proceed to level where the equations are then evaluated in the appropriate manner (i.e.. analytically using a table of integrals, or numerically using an ODE. solver). Although this structure emphasize.s the determination of a reaction time or reactor volume for a. specified conversion, it can also readily be used for other types of reactor calculations, such as determining the conversion for a specified volume. Different manipulations can be performed in level to answer the different types of questions mentioned here. 

Mechanically stirred batch reactors are often used for the production of fine chemicals and pharmaceuticals. One might wonder why this is so. One important reason for the choice of this type of reactor is its widespread use in laboratory and pilot-scale research and development programs-the mechanically stirred batch reactor is, therefore, often the fii st reactor that comes to mind. Frequently, however, other types of reactor are preferable for reasons such as better reactant conversion, product selectivity, ease of catalyst separation, etc. 

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