Inlet intermediate

Figure 13.1a shows two possible thermal profiles for exothermic plug-fiow reactors. If the rate of heat removal is low and/or the heat of reaction is high, then the temperature of the reacting stream will increase along the length of the reactor. If the rate of heat removal is high and/or the heat of reaction is low, then the temperature will fall. Under conditions between the two profiles shown in Fig. 13.1a, a maximum can occur in the temperature at an intermediate point between the reactor inlet and exit. 

A schematic illustration of a typical inlet apparatus for separating volatile hydrides from the analyte solution, in which they are generated upon reduction with sodium tetrahydroborate. When the mixed analyte solution containing volatile hydrides enters the main part of the gas/liquid separator, the volatiles are released and mix with argon sweep and makeup gas, with which they are transported to the center of the plasma. The unwanted analyte solution drains from the end of the gas/liquid separator. The actual construction details of these gas/liquid separators can vary considerably, but all serve the same purpose. In some of them, there can be an intermediate stage for removal of air and hydrogen from the hydrides before the latter are sent to the plasma. 

Pressures Turboexpanders ean be designed to operate at up to 3,000 psi and higher inlet pressures as required by eonditions. Expansion pressure ratios ean also be adjusted for eaeh proeess over a wide range. A majority of effieient expansion ratios are below 5 1, although pressure ratios up to 10 1 ean be aeeommodated with reasonable effieieney. Smaller, lower pressure units are popular for air separation and helium liquefaetion. Intermediate pressure (100-1,000 psi) and high pressure expanders (1,000-3,000 psi) are widely used in natural gas proeessing and industrial gas liquefaetion. 

In the case of nitrous acid plants, application of integrally geared process gas radial turbines and compressors are used in plants with capacities ranging from 120-600 t/day and higher. For air compression, up to three compressor stages are connected in series. To increase efficiency, the inlet temperature of the individual stages is reduced by using two external intermediate coolers. 

Turbine inlet temperature Highest Intermediate Lowest... 

Consider a series of eontinuous flow stirred tank reaetors of equal size with inlet and exit eonversions as Xg and X. The intermediate optimal eonversions Xj, Xj, X3. . . X . . . X i ean be determined, whieh will minimize the overall reaetor size. Levenspiel [1] has shown... 

The partial pressure at a given pressure and temperature is lower when there are more moles of other components in the gas phase. The lower the partial pressure the greater the tendency of the component to flash to gas. Thus, the higher the fraction of light components in the inlet fluid to any separator, the lower the partial pressure of intermediate components in the gas phase of the separator, and the greater the number of intermediate component molecules that flash to gas. 

In some cases, friction losses are difficult to quantify. If the pumped liquid is delivered to an intermediate storage tank, the configuration of the tank s inlet determines if it adds to the system pressure. If the inlet is on or near the top, the tank will add no back pressure. However, if the inlet is below the normal liquid level, the total height of liquid above the inlet must be added to the total system head. 

If the vibration analyzer permits acquisition of time-domain data, additional time-waveform data should be obtained from the intermediate guide as well as the inlet and discharge valves. The intermediate guide is located... 

At a fixed temperature, a single, reversible reaction has no interior optimum with respect to reaction time. If the inlet product concentration is less than the equilibrium concentration, a very large flow reactor or a very long batch reaction is best since it will give a close approach to equilibrium. If the inlet product concentration is above the equilibrium concentration, no reaction is desired so the optimal time is zero. In contrast, there will always be an interior optimum with respect to reaction time at a fixed temperature when an intermediate product in a set of consecutive reactions is desired. (Ignore the trivial exception where the feed concentration of the desired product is already so high that any reaction would lower it.) For the normal case of bin i , a very small reactor forms no B and a very large reactor destroys whatever B is formed. Thus, there will be an interior optimum with respect to reaction time. 

These boundary conditions are really quite marvelous. Equation (9.16) predicts a discontinuity in concentration at the inlet to the reactor so that ain a Q+) if D >0. This may seem counterintuitive until the behavior of a CSTR is recalled. At the inlet to a CSTR, the concentration goes immediately from to The axial dispersion model behaves as a CSTR in the limit as T) — 00. It behaves as a piston flow reactor, which has no inlet discontinuity, when D = 0. For intermediate values of D, an inlet discontinuity in concentrations exists but is intermediate in size. The concentration n(O-l-) results from backmixing between entering material and material downstream in the reactor. For a reactant, a(O-l-) [Pg.332]

Mass Spectrometry. The mass spectra were obtained on a CEC 21-llOB mass spectrometer with the batch inlet system maintained at 250°C to assure complete vaporization of the samples. Sensitivity factors for quantitative analysis were obtained from standards of di-, tetra-, hexa-, and octa-chlorodibenzo-p-dioxin. The factors for the intermediate chlorinated species were estimated by interpolation. The analyses were based... 

The intermediate storage between the reaction and separation system can also help dampen out variations in composition, temperature and flowrate between the two sections (for gases and non-viscous liquids, but not solids). Variations in the outlet properties from the storage are reduced compared with variations in the inlet properties. 

Figure 20.1b shows two possible thermal profiles for endothermic plug-flow reactors. This time, the temperature decreases for low rates of heat addition and/or high heat of reaction. The temperature increases for the reverse conditions. Under conditions between the profiles shown in Figure 20.1b, a minimum can occur in the temperature profile at an intermediate point between the inlet and exit. 

Consider now a two-stage compression in which the intermediate gas is cooled to a defined temperature T2 different from the inlet temperature T). For an ideal gas ... 

Thus, for a specified intercooler outlet temperature T2 for the gas and fixed inlet and outlet pressures Pi and P3, Equation B.53 predicts the intermediate pressure for minimum shaft work for compression of an ideal gas. The corresponding expression for a polytropic compression is given by replacing y by n in Equation B.53. Although Equation B.53 changes the intermediate pressure for an intercooler temperature different from the inlet temperature, the effect on the overall shaft work for compression is often insensitive to modest deviations of the intercooler temperature from the inlet temperature. 

The balance over a dedicated intermediate storage unit has to be modified because of the possibility of latent storage. Constraint (3.34), provides the link for the inlet and outlet mass balance between units, as shown in constraints (3.17) and (3.18). Constraints (3.35), (3.36) and (3.37), are similar to constraints (3.4), (3.5) and (3.6), however they apply to the case where the PIS operational philosophy is taken into account. 

Figure 4 Schematic of an oxygen uptake device. 1, sample 2, electrical oven 3, Hg manometer 4, intermediate vessel for pressure adjustment 5, drying vessel 6, control thermometer 7, outlet to vacuum pump and 8, inlet for gas feeding. Reproduced with permission from Zaharescu [10]. Springer 2001.

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