Reactor the first

Since process design starts with the reactor, the first decisions are those which lead to the choice of reactor. These decisions are among the most important in the whole design. Good reactor performance is of paramount importance in determining the economic viability of the overall design and fundamentally important to the environmental impact of the process. In addition to the desired products, reactors produce unwanted byproducts. These unwanted byproducts create environmental problems. As we shall discuss later in Chap. 10, the best solution to environmental problems is not elaborate treatment methods but not to produce waste in the first place. 

Choice of reactor. The first and usually most important decisions to be made are those for the reactor type and its operating conditions. In choosing the reactor, the overriding consideration is usually raw materials efficiency (bearing in mind materials of construction, safety, etc.). Raw materials costs are usually the most important costs in the whole process. Also, any inefficiency in raw materials use is likely to create waste streams that become an environmental problem. 

Figure A3.14.4. P-T ignition limit diagram for H2 + O2 system showing first, second and third limits as appropriate to a closed reactor. The first and second limits have similar positions in a typical flow reactor, for which there is also a region of oscillatory ignition as indicated.

A necessary feature of the alkylation reaction section is the use of two reactors the first-stage reactor completes the major part of the alkylation reaction, and in the second-stage reactor the last traces of unsaturated hydrocarbons react, and a sizable portion of the soluble polyaromatics is removed. Modem units with lower-diene-containing feeds employ a single alkylation reactor (79). 

Figure 7.4 illustrates some of the arrangements that can be used for liquid-liquid reactors. The first arrangement... 

Since there are 8 effective states for the overall problem, the resulting number of binary variables is 8 xf. Note that this number of effective states emanates from the fact that each of states s. 2, s6 and, v8 can be fed to any of the 2 reactors. The first set of effective states was chosen throughout the formulation. 

Figure 11.3 is the representation of the case study that is used to demonstrate the performance of the proposed model it is taken from directly from Chapter 10. To facilitate understanding, this case study is described in some detail in this chapter. The plant, which constitutes 30% of production and consumes 55% of utility steam in the multinational agrochemical facility of choice, involves the manufacture of an herbicide. The saturated steam is produced from a coal fired boiler at 10 bar absolute pressure and 3 t/h, although it is only used at 4 bar in the chosen process. The process entails 3 consecutive chemical reactions which take place in 4 reactors. The first reaction, which uses water as a solvent, takes place in reactors R1 and R2. 

Whether the first or the second factor dominates depends on the type of polymerization process involved. If the period during which the polymer molecule is growing is short compared to the residence time of the molecule in the reactor, the first factor dominates. This situation holds for many free radical and ionic polymerization processes where the reaction intermediates are extremely short-lived. Figure 9.11, taken from Denbigh (10), indicates the types of behavior expected for systems of this type. 

In a batch reactor, the first two terms in equation 12.2-1 are absent. In a semibatch reactor, one of these two terms is usually absent. In a semicontinuous reactor for a multiphase system, both flow terms may be absent for one phase and present for another. In a continuous reactor, the two terms are required to account for the continuous inflow to and outflow from the reactor, whether the system is single-phase or multiphase. 

In a typical polymerising experiment, a mixture of monomer, solvent and initiator is allowed to feed into a chain of three polymerising reactors. The first reactor is having three heating zones. 

Where the composition within the reactor is uniform (independent of position), the accounting may be made over the whole reactor. Where the composition is not uniform, it must be made over a differential element of volume and then integrated across the whole reactor for the appropriate flow and concentration conditions. For the various reactor types this equation simplifies one way or another, and the resultant expression when integrated gives the basic performance equation for that type of unit. Thus, in the batch reactor the first two terms are zero in the steady-state flow reactor the fourth term disappears for the semibatch reactor all four terms may have to be considered. 

Thus steam reforming is typically done in two or three staged chemical reactors, the first a reforming reactor operated at 850°C, and then one or two WGS reactors operated at temperatures as low as 200°C, where the equihhrium conversion to H2 is higher because the WGS reaction is exothermic. 

A reactant of bulk concentration Cao reacts on the external surface of catalyst spheres of radius 7 in a slurry reactor. The first-order surface reaction rate coefficient is k , and the diffiisivity of A in the solution is Da- Find fhe effective rate coefficient in terms of these quantities, assuming that stirring is sufficiently slow that fhe fluid around particles is stagnant. 

All isotopes of the element are synthesized in the nuclear reactor. The first isotope synthesized had the mass 241, produced by irradiation of milligram quantities of americium-241 with alpha particles of 35 MeV in a cyclotron ... 

There are two criteria which can be used to compare the performances of different types of reactor. The first, which is a measure of reactor productivity, is the output of product in relation to reactor size. The second, which relates to reactor selectivity, is the extent to which formation of unwanted byproducts can be suppressed. When comparing reactions on the basis of output as in the present section, only one reaction need be considered, but when in the next section the question of byproduct formation is taken up, more complex schemes of two or more reactions must necessarily be introduced. 

Since, by definition, there is no reactant flow into or out of the reactor, the first two terms are equal to zero. The remaining balance is... 

There are two factors that explain why aspect ratios between 1 and 2 are frequently used for reactors. The first is the capital cost. The weight of metal required to build a reactor of a fixed volume is minimized using an aspect ratio of 1. The second consideration is mixing. It becomes more difficult to achieve good mixing as the aspect ratio increases. More details are provided in Chapter 2. 

There are five fundamental differences between CSTRs and tubular reactors. The first is the variation in properties with axial position down the length of the reactor. For example, in an adiabatic reactor with an exothermic irreversible reaction, the maximum temperature occurs at the exit of the reactor under steady-state conditions. However, in a cooled tubular reactor, the peak temperature usually occurs at an intermediate axial position in the reactor. To control this peak temperature, we must be able to measure a number of temperatures along the reactor length. 

The structure of separations is determined by the composition and the thermodynamic properties of the mixture leaving the reactor. The first separation step is... 

Spherilene [Spherical polyethylene] A process for making polyethylene in the form of spherical granules. The catalyst combines a Ziegler-Natta catalyst with a silane. Developed by Montecatini, Italy. Spherilene C uses two reactors in series. Sperilene S uses a single reactor. The first plant was built by Himont, in Lake Charles, LA, in 1993. Fifteen plants had been licensed by 2007. The process is now licensed by Based Polyolefins. 

Two series of irradiations were made with the UCI 250-kW TRIG A Mark I reactor. The first run consisted of irradiation for 30 s at a thermal neutron flux of 4.8 X 109 neutrons cm-2 s 1 using the facility s pneumatic transfer system. Samples were permitted to decay for 1 min and then counted for 2 min on a Ge-Li detector (21% efficiency) at a distance of 1.3 cm from the crystal and a gain setting of 0.8 keV per channel. Elements determined in this run were Al, Mg, Mn, Si, Sn, V, and Zr. 

Ion, S. et al., Pebble Bed Modular Reactor The First Generation IV Reactor to Be Constructed, paper presented at the World Nuclear Association Annual Symposium, London, September 3-5. 

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