Stage temperature

In the low temperature process, the slurry is heated to 105—108°C and held at temperature for 5—10 minutes. The resulting 1—2 DE hydrolyzate is flashed to atmospheric pressure and held at 95—100°C for one to two hours in a batch or continuous reactor. Because the enzyme is not significantly deactivated at the first-stage temperature, a second enzyme addition is not needed. This process is used woddwide throughout the starch-based sweetener industry and has been judged the most efficient process for dextrose production. 

Metallic Diaphragm Compressors (Fig. 10-99) These are available for small quantities [up to about 17 mvh (10 ftVmin)] for compression ratios as high as 10 I per stage. Temperature rise is not a... 

The solution starts with an assumed arbitrary split of all the components to give estimates of top and bottom compositions that can be used to get initial end temperatures. The (Xj s evaluated at these temperatures are averaged with an assumed feed-stage temperature (assumed to be the bubble point of the feed) by using Eq. (13-36). The initial assumption for the split on i-Cs will be Dxp/Bxb = 3.15/16.85. As mentioned earlier, N usually ranges from 0.4N to 0.6N, and the initial value assumed here will be (0.6)(10) = 6.0. Equation (13-32) can be rewritten as... 

In general, values and molal enthalpies in these MESH equations are complex imphcit functions of stage temperature, stage pressure, and equilibrium mole fractions ... 

Using specified stage pressures, current estimates of stage temperatures, and current estimates of stage vapor- and liquid-phase... 

Example 4 Calculation of the BP Method Use the BP method with the SRK eqiiation-of-state for K values and enthalpy departures to compute stage temperatures, interstage vapor and hqiiid flow rates and compositions, and rehoiler and condenser duties for the light-hydrocarhon distdlation-coliimn specifications shown in Fig. 13-51 with feed at 260 psia. The specifications are selected to obtain three products, a vapor distillate rich in Cri and C3, a vapor side-stream rich in n-C4, and a bottoms rich in n-C and n-Cg. 

Example 5 Calculation of the SR Method Use the SR method with the PR equation of state for K values and enthalpy departures. The oil was taken as n-dodecane. To compute stage temperatures and interstage vapor and hquid flow rates and compositions for ahsorher-column specifications shown in Fig. 13-52. Note that a secondary ahsorher oil is used in addition to the main ahsorher oil and that heat is withdrawn from the seventh theoretical stage. 

Use the Naphtali-Sandholm SC method to compute stage temperatures and interstage vapor and liquid flow rates and compositions for the rehoiled-stripper specifications shown in Fig. 13-53. The specified hottoms rate is equivalent to removing most of the nCs and nCe and some of the nC in the hottoms. 

Calculations were made with the Grayson-Streed modification of the Chao-Seader method for K values and the Lee-Kesler method for enthalpy departures. Initial estimates for stage temperatures and flow rates were as follows, where numbers in parentheses are consistent with specifications ... 

From these tables, it is seen that the stage temperatures and total liquid flows are already close to the converged solution after only one outer-loop iteration. However, the composition of the bottoms product, specifically with respect to the lightest component, C, is not close to the converged solution until after two iterations. The inside-out method does not always converge so dramatically, but is usually quite efficient,... 

FIG. 13-95 Comparison of computed stage temperatures with plant data for the example of Fig. 13-94. 

Compute a new set of stage temperatures from Eq. (13-156). Calculate a corresponding set of vapor-phase mole fraclions from Eq. (13-155). 

Since 1,4-butanediol (BD) undergoes dehydration side reaction in the presence of acid resulting in THF formation, the hydroxy-ester interchange reaction is the preferred method for the preparation of PBT. The first stage of reaction is carried out at 150-200°C and consists of a hydroxy-ester interchange between DMT and excess butanediol with elimination of methanol. In the second stage, temperature is raised to 250°C and BD excess is eliminated under vacuum. Tetraisopropoxy-and tetrabutoxytitanium are efficient catalysts for bodi stages (Scheme 2.20). 

At constant pressure, the stage temperatures will be functions of the vapour and liquid compositions only (dew and bubble points) and the specific enthalpies will therefore also be functions of composition... 

The problem of determining the stage and reflux requirements for multicomponent distillations is much more complex than for binary mixtures. With a multicomponent mixture, fixing one component composition does not uniquely determine the other component compositions and the stage temperature. Also when the feed contains more than two components it is not possible to specify the complete composition of the top and bottom products independently. The separation between the top and bottom products is specified by setting limits on two key components, between which it is desired to make the separation. 

In each stage calculation it will necessary to estimate the stage temperatures to determine the K values and liquid and vapour enthalpies. The temperature range from top to bottom of the column will be approximately 120 — 60 = 60°C. An approximate calculation (Example 11.7) has shown that around fourteen ideal stages will be needed so the temperature change from stage to stage can be expected to be around 4 to 5°C. 

Estimation of stage temperature and outlet liquid composition (x )... 

Selection of values for the iteration variables for example, estimated stage temperatures, and liquid and vapour flows (the column temperature and flow profiles). 

If the time for the first stage (temperature below 250°) is shortened, the frothing is greater at this point, and the final yield is lowered. 

CUORE detectors will be cooled by a 3He-4He refrigerator with a cooling power of 3mW at 120 mK. Refrigerators with the required characteristics are technically feasible (see Section 6.1). A cryogenic configuration, which allows to keep the 4 K stage temperature constant for the whole duration of the experiment, is foreseen. This solution is based on new commercial pulse tube coolers (see Section 5.8). 

Three years experience with the Plastofrost technique indicate measurements are reproducible, provided the same observer makes the readings. However, sample preparation is slow and measurements have a subjective element because different observers obtain different stage temperatures from the same sample. 

Either the temperatures or flows could be adjusted first. The common choice is to correct the temperature. Correction of temperatures is usually done through either bubble-point or dew-point determinations on the calculated stage compositions. After correcting the stage temperatures, the liquid and vapor enthalpies may be obtained from the calculated compositions, and the flows corrected by solution of the now linear heat balance equations of Table I. 

The basic program performs the function of using the existing estimates of component flows and stream enthalpy values to predict a new stage temperature and the flows of components from the stage. This is accomplished partly by calculation in the basic program and partly by calling for calculation in various subroutines. 

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