Symbols, process reactors

Reactors are stationary vessels that are classified as batch, semi-batch, or continuous. Some reactors use mixers to blend the individual components. Reactor design depends on the type of service the reactor will be used in. Some of the reactor processes (among many others) include alkylation, catcracking, hydrodesulfurization, hydrocracking, fluid coking, reforming, polyethylene, and mixed-xylene. Figure 7-14 shows the standard symbols for reactors. 

This section is divided into three parts. The first is a comparison between the experimental data reported by Wisseroth (].)for semibatch polymerization and the calculations of the kinetic model GASPP. The comparisons are largely graphical, with data shown as point symbols and model calculations as solid curves. The second part is a comparison between some semibatch reactor results and the calculations of the continuous model C0NGAS. Finally, the third part discusses the effects of certain important process variables on catalyst yields and production rates, based on the models. 

Table 1.6 Characteristic quantities to be considered for micro-reactor dimensioning and layout. Steps 1, 2, and 3 correspond to the dimensioning of the channel diameter, channel length and channel walls, respectively. Symbols appearing in these expressions not previously defined are the effective axial diffusion coefficient D, the density thermal conductivity specific heat Cp and total cross-sectional area S, of the wall material, the total process gas mass flow m, and the reactant concentration Cg [114].

Figure 3.27 Conversion of NHj (open symbols) and selectivity to N2O (closed symbols) for the ammonia oxidation process on Pt catalyst. Micro reactors A1 (A), A2 ( ), A3 ( ), B ( ) and C ( ) were used (see Table 3.1) [98].

Figure 5.3-17. Flow-sheet of a batch process unit symbols E = heat exchanger, P = pump, R = reactor, T = storage tank, V = vessel controllers FC = flow controller, LC = level controller 0 stream number.

Using the symbolic calculation engine available in Matlab ,2 we obtained the following description of the intermediate dynamics of the reactor-condenser process ... 

Physical Processes. The formulation of the reaction engineering problem is best handled by characterizing separately the physical and chemical processes. The physical processes can be symbolized by an operator, R(Y), defining the differential accumulation, flow, and diffusion which characterize each type of reactor. These operators are generalizations of those proposed by Hulbert and Kim (32). The chemical processes are... 

The symbol Si indicates the initial organic compounds in the solution, S2 the intermediate form of organic compounds in the solution, and S3 is the final form of organic compound when they are eliminated from the solution. The first stage behaves as a zero-order reaction (4.41), as it is assumed that neither the pollutant nor the reagent controls the rate of the process. Consequently, for a discontinuous reactor the decrease in the pollutant concentration during this phase is proportional (4.42) to the time lapse (t). 

Fig. 12. The effect of zeolite loading in the TEOM reactor on the diffusion process for n-hexane diffusing into HZSM-5 at T = 298 K, total flow rate of 250 ml/inin and n-hexane partial pressure of 22.7 mbar. Symbols , 20 mg of zeolite O, 10 mg +, 5 mg.

When you are given process information like this and asked to determine something about the process, it is essential to organize the information in a way that is convenient for subsequent calculations. The best way to do this is to draw a flowchart of the process, using boxes or other symbols to represent process units (reactors, mixers, separation units, etc.) and lines with arrows to represent inputs and outputs. ... 

This example illustrates how the techniques used in an operability study can be used to decide the instrumentation required for safe operation. Figure 9.6a shows the basic instrumentation and control systems required for the steady-state operation of the reactor section of the nitric acid process introduced in Figure 4.2. Figure 9.6b shows the additional instrumentation and safety trips added after making the operability study set out in this section. The instrument symbols used are explained in Chapter 5. 

The next modification you will try allows phase equilibrium in the separator where most of the ammonia is condensed. For simplicity, though, you should set the conversion per pass in the reactor to 25 percent Change the separator so that it is a phase separation. The A -values are nitrogen, 4.8 hydrogen, 70 ammonia, 0.051 carbon dioxide, 0.32. (Remember that the symbol K value is used in both chemical reaction equilbria and phase equilibria, but K represents different things in those two cases.) The flow rates of nitrogen and hydrogen into the process are 1 and 3 mol per time unit, respectively, but there is also 0.01 mol per time unit of carbon dioxide. Because of the carbon dioxide,... 

Figure 5.18 Process scheme for combination of a hydrogenation reactor with an ultrafiltration module (1) reactant reservoir, (3) reactor, (5) ultrafiltration module, (6) product tank and (2), (4) are pumps as shown by symbols.

An endothermic continuous stirred tank reactor (CSTR) is shown schematically in Figure 15.2. The symbols used in the control schematics are listed in Table 15.1 The controlled variable is the temperature of the product leaving the reactor, and the manipulated variable is the flow rate of steam to the heat exchanger, which adds heat to the recycle line. The final control element is the control valve and associated equipment on the steam hue. The sensor is a temperature sensor/trans-mitter that measures the temperature of the product stream leaving the reactor. The controller compares the measured value of the product temperature with its desired temperature (setpoint) and makes changes to the control valve on the steam to the heat exchanger. The process is the... 

Figure 10.26. The reactor of the example process. For an explanation of the symbols, see Table 10.7.

Several months later, Fm was isolated as a product of reactor irradiation. In this case the neutron capture occurs over a long time and j3-decay processes compete with neutron capture depending on the t, (0 ) and the neutron flux. The reaction sequences are shown as the shaded area in Figure 16.4. Symbolically, for example the sequ ce Pu+3n, /3, + 8n, 2j8, +4n,j8 , +n,/3, -l-n produces j Fm. See dso Figures 16.2 and 16.3 for the production of various nuclides in the sequence as a limction of time for a reactor with a predominantly thermal neutron flux. 

Figure 12.4 Methane conversion against temperature for membrane reactor. Comparison between experimental data (symbols) and model results (lines) for a 40 SCCM sweep flow rate. Reprinted from G. Barbieri, G. Mar-igliano, E. Drioli, Simulation of steam reforming process in a catalytic membrane reactor, Ind. Eng. Chem. Res., 36, 6, 2001, with permission of American Chemical Society.

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