Maximize reactor productivity

Consecutive reactions, Ei = E2. The selectivity is temperature-independent. The highest allowable temperature should be applied to maximize reactor productivity. 

Consecutive reactions, E < Ei. The selectivity of the desired product decreases with temperature. However, a low temperature disfavours the reaction rate. A nonuniform temperature-time profile should be applied to maximize reactor productivity (see Fig. 5.4-72). At the start, no desired product is present in the reaction mixture. The temperature should then be as high as possible to keep the rate of P formation high. During the course of reaction, the amount of P in the reaction mixture increases. Therefore, the temperature should be lowered to minimize the rate of formation of the unwanted product from the desired product. 

The selectivity is also influenced by the length of period. The formation of ether requires the simultaneous presence of isopropanol adsorbed on S and on S2 sites, on the contrary to the formation of propene, which is accelerated by vacant S2 sites. It is interesting to note that at maximal reactor productivity the selectivity for propene reaches its maximal value as well. 

The secondary reactions are parallel with respect to ethylene oxide but series with respect to monoethanolamine. Monoethanolamine is more valuable than both the di- and triethanolamine. As a first step in the flowsheet synthesis, make an initial choice of reactor which will maximize the production of monoethanolamine relative to di- and triethanolamine. 

Shift Conversion. Carbon oxides deactivate the ammonia synthesis catalyst and must be removed prior to the synthesis loop. The exothermic water-gas shift reaction (eq. 23) provides a convenient mechanism to maximize hydrogen production while converting CO to the more easily removable CO2. A two-stage adiabatic reactor sequence is normally employed to maximize this conversion. The bulk of the CO is shifted to CO2 in a high... 

The gas-phase dehydrogenation of benzene to diphenyl (D) and further to triphenyl (T) is conducted in an ideal isothermal tubular reactor. The aim is to maximize the production of D and to minimize the formation of T. Two parallel, gas-phase reactions occur at atmospheric pressure... 

Use of bioflocs rather than supported film particles will maximize the effectiveness factor for a given particle, but uneven growth of floes can cause severe stratification in the bed. If stratification can be overcome by methods such as the use of a tapered bed to control porosity the removal, breaking up, and recycle of biomass at the bottom of the bed or, ideally, the use of microbial strains or species that will stop growing at a desirable floe size, such as a Zymomonas mobilis strain that stops growing at one millimeter in diameter (Scott, 1983), the use of bioflocs rather than support particles can improve reactor productivity. 

Mollah, A. H., and Stuckey, D. C., Maximizing the Production of Acetone-Butanol in an Alginate Bead Fluidized Bed Reactor Using Clostridium acetobutylicum, J. Chem. Tech. Biotechnol., 56 83 (1993)... 

For a feed stream AO = 4 mol/liter what size ratio of two mixed flow reactors will maximize the production rate of R Also give the composition of A and R leaving these two reactors. 

How should we operate a mixed flow reactor so as to maximize the production of R Separation and recycle of unused reactant is not practical. 

For the set of elementary reactions of Problem 10.6, with a feed of AO = 1 mol/liter and u = 100 liters/min we now wish to maximize the production rate of intermediate S (not the fractional yield) in a reactor arrangement of your choice. Sketch your chosen reactor scheme and determine Cs ax obtainable. 

We noted earlier that chemical engineers are seldom concerned with single-reaction systems because they can always be optimized simply by heating to increase the rate or by finding a suitable catalyst [You don t need to hire a chemical engineer to solve the problems in Chapter 3]. Essentially aU important processes involve multiple reactions where the problem is not to increase the rate but to create a reactor configuration that will maximize the production of desired products while rninirnizing the production of undesired ones. 

In general, an objective function in the optimization problem can be chosen, depending on the nature of the problem. Here, two practical optimization problems related to batch operation maximization of product concentration in a fixed batch time and minimization of batch operation time given amount of desired product, are considered to determine an optimal reactor temperature profile. The first problem formulation is applied to a situation where we need to increase the amount of desired product while batch operation time is fixed. This is due to the limitation of complete production line in a sequential processing. However, in some circumstances, we need to reduce the duration of batch run to allow the operation of more runs per day. This requirement leads to the minimum time optimization problem. These problems can be described in details as follows. 

For a highly exothermic reaction the optimization of the temperature profile is the key factor in maximizing the reactor productivity. For endothermic reactions maximizing the reaction temperature and employing a heat carrier is often the best solution. Table 2.11 summarizes the guidelines. 

The synthesis gas leaving the gasifier contains entrained particles of char and ash. Particulate removal is performed using cyclone separators and ceramic candle type hot gas filters. The coal gas is primarily comprised of H2, CO, C02, and H20. Since there is less than 0.1 mol% CH, reforming of the syngas is not necessary. However, in order to maximize hydrogen production, shift reactors will be needed to convert the carbon monoxide to hydrogen. 

The CO-hydrogenation reaction, or Fischer-Tropsch (F-T) synthesis reaction, has been thoroughly investigated since its discovery fn the 1920 s [1]. A range of catalysts has been shown to be active for hydrocarbon synthesis and iron [2] and cobalt [3] have found commercial applications in this field. A variety of reactors have been developed to optimize the synthesis reaction [4]. Variations of reactor conditions have been shown to maximize specific products from the broad range of products produced in the reaction [5). 

The manner in which a bioconversion is performed is dictated by the nature of the biocatalyst, the chemistry, involved, and process economics.16 The overall aims of a bioconversion are the same as for any process, to maximize the production of a given material at the lowest overall cost. In some cases this might mean maximizing the volumetric productivity (Qp in units of mol.m3 s l) of the reactor. Alternately, it might be most important to enable the more efficient recovery through maximizing the ratio of desired to undesired products. If the cost of the biocatalyst is limiting then the catalyst productivity (P ) must be maximized, a function of the intrinsic activity of the catalyst itself and the fashion in which it is used. 

Description Ammonia solution, recycled amines and ethylene oxide are fed continuously to a reaction system (1) that operates under mild conditions and simultaneously produces MEA, DEA and TEA. Product ratios can be varied to maximize MEA, DEA or TEA production. The correct selection of the NH3/EO ratio and recycling of amines produces the desired product mix. The reactor products are sent to a separation system where ammonia (2) and water are separated and recycled to the reaction system. Vacuum distillation (4,5,6,7) is used to produce pure MEA, DEA and TEA. A saleable heavies tar byproduct is also produced. Technical grade TEA (85 wt%) can also be produced if required. 

In the simplest case we seek to maximize the production of a particular species, say Ai. If q is the flow rate through the reactor, then... 

---