Absorption calculation procedure

Example 2 Calculation of Kremser Method For the simple absorber specified in Fig. 13-44, a rigorous calculation procedure as described below gives results in Table 13-9. Values of were computed from component-product flow rates, and corresponding effective absorption and stripping factors were obtained by iterative calculations in using Eqs. (13-40) and (13-41) with N = 6. Use the Kremser method to estimate component-product rates if N is doubled to a value of 12. 

In concentrated wstems the change in gas aud liquid flow rates within the tower and the heat effects accompanying the absorption of all the components must be considered. A trial-aud-error calculation from one theoretical stage to the next usually is required if accurate results are to be obtained, aud in such cases calculation procedures similar to those described in Sec. 13 normally are employed. A computer procedure for multicomponent adiabatic absorber design has been described by Feiutnch aud Treybal [Jnd. Eng. Chem. Process Des. Dev., 17, 505 (1978)]. Also see Holland, Fundamentals and Modeling of Separation Processes, Prentice Hall, Englewood Cliffs, N.J., 1975. 

Alternatively the absorbance of the mixture can be measured at different wavelengths (usually one for each compound present) and, provided that the molar absorption coefficients for each compound at each wavelength are known, the concentration of each compound can be calculated. Procedure 2.2 illustrates such a calculation. 

Table 5d.O supplies the forms for the three terms needed to formulate (GSi)jj, with Ar substituted for As. If in addition, allowance is to be made for the gas not being gray, and are evaluated using values of the emissivity and absorptivity calculated using Table 5-8, and the procedure described in the previous subsection is followed with c.Jct, replacing Ec together with the addition of a clear-gas contribution, when SS is at issue. It is tempting to say that a surface As (or Ar) could be made radiatively adiabatic simply by assigning its reflectance p a value of 1, making the terms in the brackets of Eq. (5-173) much easier to evaluate and the result much simpler. This is valid only if the gas is gray. If it is not, A is a net absorber of radiation...

Assuming dilute solutions, Table 6.21 lists the equations for sizing absorbers and strippers in terms of a key component and Table 6.22 outlines the calculation procedure. In numbering the relationships in Table 6.21, A, S, P, and T means absorption, stripping, packed columns and tray columns, respectively. Processing dilute solutions implies that heat effects will be small, and therefore, the separation is essentially isothermal. If the column is both isothermal and isobaric, the equilibrium value will be constant. Also, dilute solution means that the gas and liquid flow rates will essentially be constant. In absorption, the gas flow rate is fixed and the liquid flow rate must be estimated, whereas in stripping the liquid flow rate is fixed and the gas flow rate must be estimated. 

The indirect molar absorptivity calculated from the change in absorbance produced by fluoride (F) under the conditions given below in the procedure is 2.7-10 (sp. abs., a = 1.4) at 540 nm. At this wavelength, the difference in the absorbance before and after reaction is greatest (at pH 1). 

The remainder of the development of the calculational procedure is ordered in the same sequence in which the calculations are carried out. The calculational procedure is initiated by the assumption of a set of temperatures 7 and a set of vapor rates Vj from which the corresponding set of liquid rates L, is found by use of the total material balances presented below. This particular choice of independent variables was first proposed by Thiele and Geddes.14 On the basis of the assumed temperatures and total-flow rates, the absorption factors Aji appearing in Eq. (2-18) may be evaluated for component i on each plate j. Since matrix A, in Eq. (2-18) is of tridiagonal form, this matrix equation may be solved for the calculated values of the vapor rates for component i [denoted by (i )cJ by use of the Thomas algorithm4 which follows. Consider the following set of linear equations in the variables xu x2,. .., xN-u xN whose coefficients form a tridiagonal matrix. 

Application of (12-104) requires iterative calculation procedures to establish values of necessary absorption factors, stripping factors, and recovery fractions. 

The proposed calculation procedure will be first tested by analysing in detail the effects of the solvent polarity on the structure and electronic spectra of the simple merocyanine Ml. Afterwards, the selected calculation procedure will be applied to the more complex dyes M2 and M3, characterized by equal length of the conjugated path connecting the donor and acceptor group, but exhibiting opposite solvatochromic effects. To be precise, the acyclic merocyanine M2 shows, like the simpler chromophore Ml, positive solvatochromism [25] (i.e. bathochromic shift of the first absorption band on increasing solvent polarity),... 

Several studies have been devoted to determine the COP and limitations of absorption system operating conditions [21-23]. In order to evaluate the refrigeration absorption system performance, relative to different previously presented configuration, we have developed a numerical program. The calculating procedures of the fluid thermodynamic properties and the performance coefficient were obtained using MAPLE computer tools. 

However, analytical procedures based on the absorption/stripping factor concept permit an integral number of stages or cells to be specified beforehand for each section. Furthermore, the calculations terminate at points and x, so determined after the fact by the calculation procedures and, in the process, automatically satisfying the material balances. These analytical methods are next developed in detail. 

The Absorption factor or Stripping factor chart, as it is sometimes known, is shown in Fig. 50.5. It provides simple calculation methods for hydrocarbons when considering either an Absorber tower or a Stripper tower in hydrocarbon service, but for combination Absorber-Stripper towers the calculation procedures become iterative and a lot more complex. So for a combination Absorber-Stripper tower it is best not to attempt to use this chart. It is actually better to resort to a computer simulation. In fact, as a point of historical interest, Norman tells me that it was when the idea of combined Absorber-Stripper towers was first invented that brought about the use of computer simulations so as to handle all the intricate and cumbersome calculations needed to design them. 

The calculation procedures discussed in this section are based on estimating the total vapor feed to the absorption section. This is followed by conventional calculations to determine lean oil and tray requirements for the desired separation. The final step calculates the temperature profile across the absorption section and estimates intercooler requirements. 

Figures 5.3(b) to (d) are ultraviolet spectra in the 250 to 418 nm region of synthetic solutions in the 5% sodium carbonate extractant of Uvitex OB (53 ppm), and up to three times this concentration of the other three polymer additives. Each of these additives would seriously interfere in the determination of Uvitex OB by evaluation of its absorption maximum at 378 nm. In the correction procedures, measurements are made at not only at this maximum but also at the two Uvitex OB minima at 275 and 418 nm (Figure 5.3(a)) Using suitable calibration and calculation procedures it is then possible to calculate the corrected optical density at 378 nm due to Uvitex OB alone, provided that in the region 275-418 nm, background absorption due to any other substances present is low, fairly linear, and not too steep.

The apphcation of microwave power to gaseous plasmas is also of interest (see Plasma technology). The basic microwave engineering procedure is first to calculate the microwave fields internal to the plasma and then calculate the internal power absorption given the externally appHed fields. The constitutive dielectric parameters are useful in such calculations. In the absence of d-c magnetic fields, the dielectric permittivity, S, of a plasma is given by equation 10 ... 

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