Reactor sizing and design

The use of precision density measurements for monitoring polymerization reactions can be done rapidly and automatically using commercially available instrumentation. The method is independent of the reactor size and design but suffers from sampling difficulties. The examples of this paper show the rapidity of data collection and three distinct sampling problems pump failure from either monomer attack or polymer scale formation, monomer phase separation in the density cell, and the lag time for rapid polymerizations. Techniques have or can be devised to avoid or reduce the influence of these problems. 

Present Status of Our Approach to Reactor Sizing and Design 83... 

Research into reaction kinetics under well-defined conditions has been one of the most active areas of investigation, as this knowledge is directly applicable to optimized reactor sizing and design. Much of this work has been performed at the lab scale in universities and national laboratories around the world. The focus in these kinetic studies has typically been on model compounds rather than actual wastes. These compounds have been chosen because they are easier and... 

Tubular reactors often offer the greatest potential for inventory reduction. They are usually simple, have no moving parts, and a minimum number of joints and connections that can leak. Mass transfer is often the rate-limiting step in gas-liquid reactions. Novel reactor designs that increase mass transfer can reduce reactor size and may also improve process yields. 

Initiating events, in this study, initiate plant scram or setback. Other initiators, such as refueling discharge accidents, do not necessarily cause a reactor shutdown but may lead t< minor fuel damage and radioactive releases. The list of initiators for nuclear power plants has litf ance for HFBR because of size and design differences. A list of HFBR-specific initiators was developed from " st prepared with the HFBR staff, the FSAR, the plant design manual, the procedures manual, techn specifications, monthly operating reports, and the HFIR PRA (Johnson, 1988). 

The summation involves the effluent molal flow rates. This equation and equation 10.4.2 must be solved simultaneously in order to determine the tubular reactor size and to determine the manner in which the heat transfer requirements are to be met. For either isothermal or adiabatic operation one of the three terms in equation 10.4.7 will drop out, and the analysis will be much simpler than in the general case. In the illustrations which follow two examples are treated in detail to indicate the types of situations that one may encounter in practice and to indicate in more detail the nature of the design calculations. 

The choice of reactor type and its design for a particular reaction netw ork may require examination of trade-offs involving reactor size and mode of operation, product distribution (selectivity), and production rate. If, as is often the case, selectivity is... 

The scale-up of mechanically stirred gas-liquid reactors mainly involves reactor size and stirrer size, and is generally based on homothetic designs from pilot tests. The similitude in the scale-up means that the following parameters are - or at least should be - kept constant ... 

Aspects of coal liquefaction have been much researched, particularly with the re-emeigence of interest caused by the oil crisis in the 1970 s. The type of reactors used in the studies has been various, ranging from small bomb type microautoclaves through larger autoclaves and bench-scale reactors to larger scale pilot or demonstration plants. The use of differently sized and designed high pressure equipment for liquefaction studies further complicates an already complex system and allows only limited comparison of results. 

Temperature, composition, and reaction rate are uniquely related for any single homogeneous reaction, and this may be represented graphically in one of three ways, as shown in Fig. 9.2. The first of these, the composition-temperature plot, is the most convenient so we will use it throughout to represent data, to calculate reactor sizes, and to compare design alternatives. 

The steady-state economic design of a process with this type of reaction requires consideration of the effects of reactor size and temperature on the entire plant. High recycle flowrates of A and a large reactor operating at a low temperature will suppress the production of D. But this will require a large capital investment in the reactor and separation sections of the plant and consume significant energy. 

The design of tubular reactor systems is dominated by the classical tradeoff between reactor size and recycle flowrate. Gas phase systems are particularly affected because of the high cost of compression. 

These results indicate that a process change would probably be required to handle the dynamic problems. There are several alternatives. A cooled nonadiabatic reactor should reduce the sensitivity since more heat will be removed as temperatures increase. Probably a more practical solution would be to design for a lower concentration of one of the reactants. This mode of operation would prevent reaction runaways because the reaction rate would drop olf quickly as the concentration of the limiting reactant declined. The economic penalties would include requiring a larger reactor and more recycle than in the equimolar pure reactant feed mode of operation. Alternatively, the concentrations of both reactants could be reduced by recycling an inert substance (probably product C). This would also increase reactor size and recycle flowrate. 

The rate of steam consumption is equal to the steam flow rate times the steam conversion, and the rate of HBr formation is twice the rate of steam consumption. The formation of HBr at a given reaction time tR depends upon the melt composition. A second-order reaction of CaBr2 was found to match the experimentally measured reaction rates far better than a first-order reaction. The reaction constant is then derived from the rate of HBr formation, which is experimentally measured. The observed kinetic constant was 2.17 10-12 kmol s-1 m-2 MPa-1 (1.30 1CH g-mol min-1 cm-2 bar-1) for the hydrolysis reaction, which is 24 times greater than the constant reported for solid CaBr2 reaction. This higher rate promises to significantly reduce the size and design complexity of the hydrolysis reactor. 

The observed kinetic constant is 24 times greater than the constant reported for solid CaBr2 reaction. This higher rate promises to significantly reduce the size and design complexity of the hydrolysis reactor. 

Mass transfer is often the rate-limiting step in gas-liquid reactions. Novel reactor designs that increase mass transfer can reduce reactor size and may also improve process yields. 

Standard plant provides a build ratio of 1 8 but by special design can be 1 25 or even 1 50. A build ratio of 1 2 5 means 2 5 mol of ethylene oxide is added to 1 mol of alcohol or in round terms 4 tonnes of ethylene oxide is added to 1 tonne alcohol. If the plant had a build ratio of 1 12.5, it would mean the batch would have to be stopped half way, split in two, dried and recatalysed with attendant loss of production. It is a convenient measure of reactor size and recycle volume so that, at the start of the reaction, there is enough volume of alcohol to circulate round the plant and, at the end, enough volume to hold the finished product. 

SIZING AND DESIGN OF A SYSTEM OF STIRRED-TANK REACTORS 5.21... 

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