Reactor feed composition

Table 2.2 gives the compositions of the reactor feed and effluent streams. Calculate the conversion, selectivity, and reactor yield with respect to (a) the toluene feed and (b) the hydrogen feed. 

The conversion of fatty alcohols is approximately 99%. The reaction product is then condensed and sent to a distillation column to remove water and high boilers. Typically, a-olefin carbon-number distribution is controlled by the alcohol composition of the reactor feed. The process is currentiy used to produce a-olefins from fatty alcohols. A typical product composition is at <5%, at 50—70%, C g at 30—50%, C2Q at <2%,... 

The scheme of commercial methane synthesis includes a multistage reaction system and recycle of product gas. Adiabatic reactors connected with waste heat boilers are used to remove the heat in the form of high pressure steam. In designing the pilot plants, major emphasis was placed on the design of the catalytic reactor system. Thermodynamic parameters (composition of feed gas, temperature, temperature rise, pressure, etc.) as well as hydrodynamic parameters (bed depth, linear velocity, catalyst pellet size, etc.) are identical to those in a commercial methana-tion plant. This permits direct upscaling of test results to commercial size reactors because radial gradients are not present in an adiabatic shift reactor. 

Table 5.2 gives the compositions of the reactor feed and effluent streams. 

Ethylene is to be converted by catalytic air oxidation to ethylene oxide. The air and ethylene are mixed in the ratio 10 1 by volume. This mixture is combined with a recycle stream and the two streams are fed to the reactor. Of the ethylene entering the reactor, 40% is converted to ethylene oxide, 20% is converted to carbon dioxide and water, and the rest does not react. The exit gases from the reactor are treated to remove substantially all of the ethylene oxide and water, and the residue recycled. Purging of the recycle is required to avoid accumulation of carbon dioxide and hence maintain a constant feed to the reactor. Calculate the ratio of purge to recycle if not more than 8% of the ethylene fed is lost in the purge. What will be the composition of the corresponding reactor feed gas ... 

In normal operation of ebullated bed reactors, the reactor feed temperature is the control variable. The desired reactor feed temperature depends on both the feed rate and feed composition. The feed temperature is chosen such that the overall heat generation in the reactor is used to elevate the low temperature feed material to the bed temperature during... 

The reactor effluent is separated in a distillation column. The overhead is mostly excess reactant A which is recycled back to the reactor. The bottoms from the column is mostly product C. The reaction occurs in the liquid phase so the reactor feed streams are liquid. Reactant B is added directly to the reactor on flow control. The flow rate of the recycle stream is ratioed to the flow rate of the B feed stream. The composition of A in the column base sets heat input. The composition of C in the column overhead sets reflux. 

EOS models were derived for polymer blends that gave the first evidence of the severe pressure - dependence of the phase behaviour of such blends [41,42], First, experimental data under pressure were presented for the mixture of poly(ethyl acetate) and polyfvinylidene fluoride) [9], and later for in several other systems [27,43,44,45], However, the direction of the shift in cloud-point temperature with pressure proved to be system-dependent. In addition, the phase behaviour of mixtures containing random copolymers strongly depends on the exact chemical composition of both copolymers. In the production of reactor blends or copolymers a small variation of the reactor feed or process variables, such as temperature and pressure, may lead to demixing of the copolymer solution (or the blend) in the reactor. Fig. 9.7-1 shows some data collected in a laser-light-scattering autoclave on the blend PMMA/SAN [46],... 

Flow ratio control is essential in processes such as fuel-air mixing, blending, and reactor feed systems. In a two-stream process, for example, each stream will have its own controller, but the signal from the primary controller will go to a ratio control device which adjusts the set point of the other controller. Figure 3.17(a) is an example. Construction of the ratioing device may be an adjustable mechanical linkage or may be entirely pneumatic or electronic. In other two-stream operations, the flow rate of the secondary stream may be controlled by some property of the combined stream, temperature in the case of fuel-air systems or composition or some physical property indicative of the proportions of the two streams. 

Second activation energy E2 Heat of reaction A Feed flowrate FA0 Feed flowrate FBo Feed composition CAo Feed composition CBo Reactor volume VR... 

Run No. T w T Bax Composition of Reactor Feed (Mole Fraction) Overall propene conversion (%)... 

The possibility of improving selectivity or polymer molecular weight distribution by periodically changing the composition of the reactor feed was pointed out by Bailey and Horn and co-workers on one hand O, 2, 3) and by Douglas and Rippen (4,5) and others (6) in the late 1960 s and early 1970 s. Experimental investigations in the following years (T, 8) confirmed the predictions of these theoretical studies. In a series of contributions beginning in 1973 (9,10,11), our... 

Figure 2. Methane conversion versus residence time in two different cross sectional area reactors. Feed composition, 4/1 CH,/02 gas temperature, 298 K power, 5.2 watts. Calculated line is for 7.0 mm reactor based on 4.5 mm reactor data.

Selectivity is another catalyst attribute that is often considered when ranking catalysts. Selectivity may be defined as the ratio of the molar amount of key reactant converted to the desired product to the total molar amount of the key reactant converted. As such, selectivity is a measure of the efficiency of the catalyst in promoting the formation of the desired product as compared to other products. Since selectivity is a function of the relative rates of reaction with a given reaction system, selectivity will be a function of reaction temperature, space velocity, feed composition, reactor geometry, and degree of conversion. Comparing selec-tivities of different catalysts is therefore only meaningful when all the latter parameters are constant. 

The selectivity to MEG can be influenced by adjusting the glycol reactor feed composition. 

However, our column is connected via material flow with a reactor. In Chap. 4 we show that reactor control often boils down to two issues (1) managing energy (temperature control) and (2) keeping as constant as possible the composition and flowrate of the total reactor feed stream (fresh feed plus recycle streams). The latter goal implies that it may in fact be desirable to control the composition of the recycle stream. This minimizes the variablity in recycle impurity composition back into the reactor. This recycle composition is dictated by the economic tradeoffs between yield, conversion, energy consumption in the separation section, and reactor size. 

Starting with the HDA reactor, we find most of the needed information in Chap. 10. The feed temperature is llSOT, the heat of reaction -21,500 Btu/lb mol, and the mole fraction of toluene (limiting component) in the reactor feed is 0.0856. The molar heat capacity of the feed is computed from its composition and standard literature data ... 

We can make a similar classification around U and W. For instance, control valves belong to the set UB. whereas the regeneration of a packed-bed catalyst would be classified as JX,. Similarly, measurements of the reactor feed flow and temperature belong to W while a once-per-shift analysis of the reactor feed composition belongs to W,. 

We start by plotting the temperature rise in the reactor. This is done by integrating the steady-state differential equations that describe the composition and heat effects as functions of the axial position in the reactor. The adiabatic plug-flow reactor gives a unique exit temperature for a given feed temperature. This also means that we get a unique difference between the exit and feed temperatures. The temperature difference has to be less than or equal to the adiabatic temperature rise at a given, constant feed composition. Figure 5.20 show s the fractional temperature rise as a function of the reactor feed temperature for a typical system. 

If we select temperature, we would like the reactor flow and composition to be nearly constant and we are constrained by the upper reactor temperature limit of 1300°F. If we select toluene composition, we can control it either directly or indirectly. If directly, a reactor feed composition analyzer is needed and is used to adjust either the fresh toluene feed rate or the total reactor toluene feed rate. If indirectly, the separation section is used as an analyzer for toluene. This allows us to control the total flow of toluene to the reactor (recycle plus fresh). Fresh toluene feed flow is used to control toluene inventory reflected in the recycle column overhead receiver level as an indication of the need for reactant makeup. Controlling the total toluene flow sets the reactor composition indirectly and is advantageous because it is less complicated and does not require an on-line analyzer. 

Step 9. The basic regulatory strategy has now been established (Fig. 10.2). We have some freedom to select several controller setpoints to optimize economics and plant performance. If reactor inlet temperature sets production rate, the setpoint of the total toluene flow controller can be selected to optimize reactor yield. However, there is an upper limit on this toluene flow to maintain at least a 5 1 hydrogen-to-aromatic ratio in the reactor feed since hydrogen recycle rate is maximized. The setpoint for the methane composition controller in the gas recycle loop must balance the trade-off between yield loss and reactor performance. Reflux flows to the stabilizer, product, and recycle columns must be determined on the basis of column energy requirements and potential yield losses of benzene (in the overhead of the stabilizer and recycle columns) and toluene (in the base of the recycle column). Since the separations are easy, in this system economics indicate that the reflux flows would probably be constant. 

The overriding safety constraint in this process involves oxygen concentration in the gas loop, which must remain below 8 mole % to remain outside the explosivity envelope for ethylene mixtures at process conditions. The most direct manipulated variable to control oxygen composition at the reactor feed is the fresh oxygen feed flow. ... 

The most direct way to control the remaining levels would be with the exit valves from the vessels. However, if we do this we see that all of the flows around the liquid recycle loop would be set on the basis of levels, which would lead to undesirable propagation of disturbances. Instead we should control a flow somewhere in this loop. Acetic acid is the main component in the liquid recycle loop. Recycle and fresh acetic acid feed determine the component s composition in the reactor feed. A reasonable choice at this point is to control the total acetic acid feed stream flow into the vaporizer. This means that we can use the fresh acetic acid feed stream to control column base level, since this is an indication of the acetic acid inventory in the process. Vaporizer level is then controlled with the vaporizer steam flow and separator and absorber levels can be controlled with the liquid exit valves from the units. 

For a reactor feed composition of 10 mole % A, 30 mole % P and 60 mole % D and for one molecule of A converted into three molecules of P, for every place inside the reactor... 

The processes usually differ by the composition of the reactor feed gas. Some processes employ a large excess of ammonia with NH3/CO2 ratio ranging from 4 to 6. This achieves high conversion of carbon dioxide (75 to 80 per cent). Others use only a small excess or even operate with reactants in stoichiometric proportions. This leads to lower conversion (40 to 50 per cent) and requires recycling of the unconverted gases. 

The first step in the analysis is to determine if zero degrees of freedom exist in any process unit. In this case, the analysis will be simplified because of the reduction in the number of equations requiring simultaneous solution. After analyzing each process unit, we then combine the equations to determine if the process contains zero degrees of freedom. When analyzing each unit separately, we will repeat some variables and equations. For example, in line 3, the composition and flow rate variables, and the mole fraction summation, are the same for the mixer exit stream and the reactor feed stream. Later, when we combine the various processing units to determine the process degrees of freedom, we will take the duplication of variables and equations into account. 

The copolymer composition may drift during the course of an emulsion copolymerization because of differences in monomer reactivity ratios or water solubilities. Various techniques have been developed to produce a uniform copolymer composition. The feed composition may be continuously or periodically enriched in a particular monomer, to compensate for its lower reactivity. A much more common procedure involves pumping the monomers into the reactor at such a rate that the extent of conversion is always very high [>about 90%]. This way, the polymer composition is always that of the last increment of the monomer feed. 

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