The Feeding Composition

The third composition was obtained from a theoretical scale-up of the above-mentioned test facility (1MW, prototype). 

In the process, there are three heat exchangers for the isothermal and five heat exchangers for the adiabatic case in the former case, the entering gas coming from the gasifier is cooled from 850 to 300°C. This relatively high temperature has been chosen to avoid tar condensation, according to the ECN data reported earlier (400 C). 

Other heat exchangers are located downstream the compressors (7) and (9) and as intermediate cooling stages between two fixed-bed methanation reactors (for the adiabatic case only). Their exit stream temperature (300 C) and pressure (10 bar) are fixed, and the minimum water flow rate (at T = 25 C) required to cool down the gaseous stream is used. 

The inlet/outlet temperature difference of the compressed gases and the minimum amount of water flow rate required for stream II are reported in Table 8.4. 

A biodiesel scrubber for tar removal is placed downstream the heat exchanger. Naphthalene has been chosen as tar model compound, which is removed in the cold (T= 300°C) cleaning section. The choice of naphthalene as the most representative aromatic hydrocarbon of the complex tar mixture is supported by many studies in the field (see for instance [51]). On the other hand, the model compound 1-T bicyclohexyl has been used to simulate the biodiesel mixture, being representative of physical and chemical properties of the commercially produced biodiesel [52, 53]. 

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As the feed composition approaches a plait point, the rate of convergence of the calculation procedure is markedly reduced. Typically, 10 to 20 iterations are required, as shown in Cases 2 and 6 for ternary type-I systems. Very near a plait point, convergence can be extremely slow, requiring 50 iterations or more. ELIPS checks for these situations, terminates without a solution, and returns an error flag (ERR=7) to avoid unwarranted computational effort. This is not a significant disadvantage since liquid-liquid separations are not intentionally conducted near plait points. 

The criterion used for "too near the plait point" is that ratio of K s for the two "solvent" components is less than seven with the feed composition in the two-phase region. 

In addition, one other feature of the prefractionator arrangement is important in reducing mixing effects. Losses occur in distillation operations due to mismatches between the composition of the column feed and the composition on the feed tray. Because the prefractionator distributes component B top and bottom, this allows greater freedom to match the feed composition with one of the trays in the column to reduce mixing losses at the feed tray. 

Oxidation Step. A review of mechanistic studies of partial oxidation of propylene has appeared (58). The oxidation process flow sheet (Fig. 2) shows equipment and typical operating conditions. The reactors are of the fixed-bed shell-and-tube type (about 3—5 mlong and 2.5 cm in diameter) with a molten salt coolant on the shell side. The tubes are packed with catalyst, a small amount of inert material at the top serving as a preheater section for the feed gases. Vaporized propylene is mixed with steam and ak and fed to the first-stage reactor. The feed composition is typically 5—7% propylene, 10—30%... 

A typical slag (specific gravity 3.6) contains complex siUcates of iron, calcium, 2iac, magnesium, and aluminum oxides. The quantity of fluxes (compounds added to lower the melting poiat) added depends on the feed composition, and is calculated to ensure a fluid slag at the operating temperature. 

Intermediate Condenser. As shown in Figure 3, an intermediate condenser forces the operating line closer to the equiUbrium line, thus reducing the inherent inefficiencies in the tower. Using intermediate condensers and reboilers, it is possible to raise the efficiency above that for a simple reboder—condenser system, particularly when the feed composition is far from 50 50 in a binary mixture. 

The feed compositions and products of each of these strategic separations remain ill-defined. The unspecified 2-propanol—water mixture, the input to each strategic separation, could be but is not necessarily the original feed composition. The MSA composition (pure hexane in this case) is such that one of the products of the strategic separation is in region II, ie, the strategic separation crosses the distillation boundary. Two opportunistic distillations from... 

This deposit is composed of suspended particles similar to conventional filter cakes, and more importantly, a slime that forms as retained solutes exceed their solubility. The gel concentration 6 is a function of the feed composition and the membrane-pore size. The gel usually has a much lower hydrauHc permeabihty and smaller apparent pore size than the underlying membrane (27). The gel layer and the concentration gradient between the gel layer and the bulk concentration are called the gel-polarization layer. 

The production rate is 2—4 t/h, depending on the feed rate, monomer concentration in the feed, and conversion. The conversion of isobutylene and isoprene typically ranges from 75—95% and 45—85%, respectively, depending on the grade of butyl mbber being produced. The composition and mol wt of the polymer formed depend on the concentration of the monomers in the reactor Hquid phase and the amount of chain transfer and terminating species present. The Hquid-phase composition is a function of the feed composition and the extent of monomer conversion. In practice, the principal operating variable is the flow rate of the initiator/coinitiator solution to the reactor residence time is normally 30—60 minutes. 

Pressures can be specified at any level below the safe working pressure of the column. The condenser pressure will be set at 275.8 kPa (40 psia), and all pressure drops within the column will be neglected. The eqnihbrinm curve in Fig. 13-35 represents data at that pressure. AU heat leaks will be assumed to be zero. The feed composition is 40 mole percent of the more volatile component 1, and the feed rate is 0.126 (kg-mol)/s [1000 (lb-mol)/h] of saturated liquid (q = 1). The feed-stage location is fixed at stage 4 and the total number of stages at eight. 

When the feed composition oecomes enriched in water, as with Case B, the column profile changes drastically (Fig. 3S2b). At the same reflux and boil-iip, the column no longer meets specifications. The MIPK product is lean in MIPK and too rich in water. The profile now tracks generally up the left side of Region 11. Note also the dramatic change in the temperature profile. A pinched zone still exists... 

Continuous Countercurrent Systems Most adsorption systems use fixed-bed adsorbers. However, if the fluid to be separated and that used for desorption can be countercurrently contacted by a moving bed of the adsorbent, there are significant efficiencies to be realized. Because the adsorbent leaves the adsorption section essentially in equilibrium with the feed composition, the inefficiency of the... 

The distribution-coefficient concept is commonly applied to fractional solidification of eutectic systems in the ultrapure portion of the phase diagram. If the quantity of impurity entrapped in the solid phase for whatever reason is proportional to that contained in the melt, then assumption of a constant k is valid. It should be noted that the theoretical yield of a component exhibiting binary eutectic behavior is fixed by the feed composition and position of the eutectic. Also, in contrast to the case of a solid solution, only one component can be obtained in a pure form. 

Step 7. Make a flash calculation with the feed composition and the K-values from Step 6. 

The slope of a line from the intersection point of the feed composition, xp with the 45° line on Figure 8-2 is given by q/(q - 1) = - q/(l - q). Physically this gives a good approximation of the mols of saturated liquid that will form on the feed plate by the introduction of the feed, keeping in mind that tmder some thermal conditions the feed may vaporize liquid on the feed plate rather than condense any. 

Note This is not too accurate due to switched operating line equations before the feed compositions were reached, yet, one more calculation on the stripping line would have placed us below the feed plate composition. Hence a change in reflux ratio is necessary in order to split right at the feed composition. 

After an initial distillation to split the coproducts phenol and acetone, each is purified in separate distillation and treating trains. An acetone finishing column distills product acetone from an acetone/water/oil mixture. The oil, which is mostly unreacted cumene, is sent to cumene recovery. Acidic impurities, such as acetic acid and phenol, are neutralized hy caustic injection. Figure 10-7 is a simplified flow diagram of an acetone finishing column, and Table 10-1 shows the feed composition to the acetone finishing column. 

One final point should be made. The observation of significant solvent effects on kp in homopolymerization and on reactivity ratios in copolymerization (Section 8.3.1) calls into question the methods for reactivity ratio measurement which rely on evaluation of the polymer composition for various monomer feed ratios (Section 7.3.2). If solvent effects arc significant, it would seem to follow that reactivity ratios in bulk copolymerization should be a function of the feed composition.138 Moreover, since the reaction medium alters with conversion, the reactivity ratios may also vary with conversion. Thus the two most common sources of data used in reactivity ratio determination (i.e. low conversion composition measurements and composition conversion measurements) are potentially flawed. A corollary of this statement also provides one explanation for any failure of reactivity ratios to predict copolymer composition at high conversion. The effect of solvents on radical copolymerization remains an area in need of further research. 

The data in Example 1.2 are in moles of the given component per mole of mixed feed. These are obviously calculated values. Check their consistency by using them to calculate the feed composition given that the feed contained only para-xylene and chlorine. Is your result consistent with the stated molar composition of 40% xylene and 60% chlorine ... 

If the pilot reactor is turbulent and closely approximates piston flow, the larger unit will as well. In isothermal piston flow, reactor performance is determined by the feed composition, feed temperature, and the mean residence time in the reactor. Even when piston flow is a poor approximation, these parameters are rarely, if ever, varied in the scaleup of a tubular reactor. The scaleup factor for throughput is S. To keep t constant, the inventory of mass in the system must also scale as S. When the fluid is incompressible, the volume scales with S. The general case allows the number of tubes, the tube radius, and the tube length to be changed upon scaleup ... 

A continuous polymerization train consisting of two stirred tanks in series is used to copolymerize styrene, rx = 0.41, and acrylonitrile, vy = 0.04. The flow rate to the first reactor is 3000 kg/h and a conversion of 40% is expected. Makeup styrene is fed to the second reactor and a conversion of 30% (based on the 3000 kg/h initial feed) is expected there. What should be the feed composition and how much styrene should be fed to the second reactor if a copolymer containing 58 wt% styrene is desired ... 

There are four decision variables three different measures of the feed composition ( Ci, Zj, x ) and the value of an unspecified operating condition (.Z4). 

The feed composition chosen was 6 mol% n-hexane, 6 mol% ammonia, 12 mol% oxygen and remainder helium, with an overall gas residence time of 2.5 s. Due to the low temperature of n-hexane self-ignition (T 234°C), a relevant contribution of homogeneous, radical reactions was expected. Tests made in the absence of catalyst... 

Though the total degrees of freedom is seen to be (C + 4) some of the variables will normally be fixed by general process considerations, and will not be free for the designer to select as design variables . The flash distillation unit will normally be one unit in a process system and the feed composition and feed conditions will be fixed by the upstream processes the feed will arise as an outlet stream from some other unit. Defining the feed fixes (C + 2) variables, so the designer is left with ... 

In the manufacture of aniline from nitrobenzene the reactor products are condensed and separated into an aqueous and organic phases in a decanter. The organic phase is fed to a striping column to recover the aniline. Aniline and water form an azeotrope, composition 0.96 mol fraction aniline. For the feed composition given below, make a mass balance round the column and determine the stream compositions and flow-rates. Take as the basis for the balance 100 kg/h feed and a 99.9 percentage recovery of the aniline in the overhead product. Assume that the nitrobenzene leaves with the water stream from the base of the column. 

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