Reactor requirements

Incomplete conversion in the reactor requires a recycle for unreacted feed... 

Adiabatic operation. If adiabatic operation leads to an acceptable temperature rise for exothermic reactors or an acceptable fall for endothermic reactors, then this is the option normally chosen. If this is the case, then the feed stream to the reactor requires heating and the efiluent stream requires cooling. The heat integration characteristics are thus a cold stream (the reactor feed) and a hot stream (the reactor efiluent). The heat of reaction appears as elevated temperature of the efiluent stream in the case of exothermic reaction or reduced temperature in the case of endothermic reaction. 

Uranium production in 1992 of 36,246 t U was only about 63% of world reactor requirements of 57,182 t U the remainder, 20,950 t U, was met from inventory drawdown. The worldwide production shortfall has developed since 1990 when production exceeded reactor requirements by about 1000 t U (27). 

Supply Projections. Additional supphes are expected to be necessary to meet the projected production shortfall. A significant contribution is likely to come from uranium production centers such as Eastern Europe and Asia, which are not included in the capabihty projections (27). The remaining shortfall between fresh production and reactor requirements is expected to be filled by several alternative sources, including excess inventory drawdown. These shortfalls could also be met by the utili2ation of low cost resources that could become available as a result of technical developments or pohcy changes, production from either low or higher cost resources not identified in production capabihty projections, recycled material such as spent fuel, and low enriched uranium converted from the high enriched uranium (HEU) found in warheads (28). 

Typically, reactors require some type of catalyst. Reactors with catalyst can be of the fixed-bed style for fiuid-bed types. Fixed-bed reactors are the most common. The feed often enters the reactor at an elevated temperature and pressure. The reaction mixtures are often corrosive to carbon steel and require some type of stainless steel alloy or an alloy liner for protection. If the vessel wall is less than 6 mm, the vessel is constmcted of all alloy if alloy is provided. Thicker reactor walls can be fabricated with a stainless overlay over a carbon steel or other lower alloy base steel at less cost than an all-alloy wall constmction. 

The refluxing solvent provides a constant wash to the reactor and brings back reactants that had escaped from the reaction mixture. The reaction temperature is better controlled by the constant refluxing, and the viscosity of the reaction mixture is lower, which improves the effectiveness of the agitation. The product usually has better color and is more uniform than material made by the fusion process. Ordinarily, the reactor requires no more than... 

Processes involving oxygen and nitrogen oxides as catalysts have been operated commercially using either vapor- or Hquid-phase reactors. The vapor-phase reactors require particularly close control because of the wide explosive limit of dimethyl sulfide in oxygen (1—83.5 vol %) plants in operation use Hquid-phase reactions. Figure 2 is a schematic diagram for the Hquid-phase process. The product stream from the reactor is neutralized with aqueous caustic and is vacuum-evaporated, and the DMSO is dried in a distillation column to obtain the product. 

Fusion Reactors. The development of fusion reactors requires a material exhibiting high temperature mechanical strength, resistance to radiation-induced swelling and embrittlement, and compatibUity with hydrogen, lithium and various coolants. One aUoy system that shows promise in this appHcation, as weU as for steam-turbine blades and other appHcations in nonoxidizing atmospheres, is based on the composition (Fe,Co,Ni)2V (30). 

This part also briefly describes different types of power reactors required to control inrush currents or suppress the system s harmonic disorders, besides absorbing the excessive charging currents on an EHV system. 

The steady-state operation of any reactor requires that the heat removed should equal the heat generated ... 

The rate equation involves a mathematical expression describing the rate of progress of the reaction. To predict the size of the reactor required in achieving a given degree of conversion of reactants and a fixed output of the product, the following information is required ... 

The term V/F for flow reactors is used to evaluate the size of the reactor required to achieve the conversion of a reactant feed rate F. It is the numher of reactor volumes of feed at specified conditions that can he treated in unit time, where F is the molar flowrate (uC q) and V is the volume of the reactor. 

Determine the size of the reactor required to achieve 85% conversion of A. 

Pressurised water nuclear reactors require metals that will have a high degree of corrosion resistance to pure water at around 300°C. Laboratory testing of materials for this application have included potentiostatic polarisation experiments designed to clarify the active-passive behaviour of alloys as well as to establish corrosion rates. Since pressure vessels are used for this work, it is necessary to provide sealed insulated leads through the autoclave head . 

Neutralization of organic acid within 1 min after sulfonation reactor. A separate aging step is not needed under commercial reactor conditions Short residence time falling film reactor required to avoid thermal breakdown of R0S03H... 

Reaction temperature in short residence time reactor 90°C, cooling water — 80-85°C in lower part and 40-50°C in upper part Aging reactor post-falling film reactor required residence time 0.5 h at 90-95°C, plug flow conditions... 

The first of the relations in Equation (4.9) is valid for any flow system. The second applies specifically to a CSTR since p = pout- It is not true for a piston flow reactor. Recall Example 3.6 where determination of t in a gas-phase tubular reactor required integrating the local density down the length of the tube. 

Firstly, there are technical reasons concerning catalyst and reactor requirements. In the chemical industry, catalyst performance is critical. Compared to conventional catalysts, they are relatively expensive and catalyst production and standardization lag behind. In practice, a robust, proven catalyst is needed. For a specific application, an extended catalyst and washcoat development program is unavoidable, and in particular, for the fine chemistry in-house development is a burden. For coated systems, catalyst loading is low, making them unsuited for reactions occurring in the kinetic regime, which is particularly important for bulk chemistry and refineries. In that case, incorporated monolithic catalysts are the logical choice. Catalyst stability is crucial. It determines the amount of catalyst required for a batch process, the number of times the catalyst can be reused, and for a continuous process, the run time. 

Reaction class Batch or fed-batch reactor characteristics Representative reaction time Continuous reactor requirements/benefits... 

In any catalyst selection procedure the first step will be the search for an active phase, be it a. solid or complexes in a. solution. For heterogeneous catalysis the. second step is also deeisive for the success of process development the choice of the optimal particle morphology. The choice of catalyst morphology (size, shape, porous texture, activity distribution, etc.) depends on intrinsic reaction kinetics as well as on diffusion rates of reactants and products. The catalyst cannot be cho.sen independently of the reactor type, because different reactor types place different demands on the catalyst. For instance, fixed-bed reactors require relatively large particles to minimize the pressure drop, while in fluidized-bed reactors relatively small particles must be used. However, an optimal choice is possible within the limits set by the reactor type. 

Figure 5.4a compares the profiles for a mixed-flow and plug-flow reactor between the same inlet and outlet concentrations, from which it can be concluded that the mixed-flow reactor requires a larger volume. The rate of reaction in a mixed-flow reactor is uniformly low as the reactant is instantly diluted by the product that has already been formed. In a plug-flow or ideal-batch reactor,... 

The initial concentration of styrene is 0.8 kmol-m-3 and of butadiene is 3.6 kmol-m-3. The feed rate of reactants is 20 t-h-1. Estimate the total number of reactors required for polymerization of 85% of the limiting reactant. Assume the density of reaction mixture to be 870 kg-m-3 and the molar mass of styrene is 104 kg-kmol-1 and that of butadiene 54 kg-kmol-1. 

When deciding on the type of the reactor required for a particular chemical or physical transformation, the first question that needs to be addresses is whether the cavitation enhancement is the result of an improved mechanical process (due to enhanced mixing). If this is the case, then cavitation pretreatment of a slurry may be all that is required before the system is subjected to conventional type transformation scheme and the scale up of the pretreatment vessel would be a relatively simpler task. 

Calculate the volumes of a plug flow reactor and a laminar flow reactor required to process 0.5 m3/ksec of feed containing 1.0 kmole/m3 of species A to 95% conversion. The liquid phase... 

The ongoing work on sludge-blanket and draft-tube reactors requires demonstration of sufficient gas-liquid mass transfer to provide the necessary oxygen needed in high cell density reactors. 

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