HETP correlation equation

An initial guess of kefr can be obtained from moment analysis (Section 6.5.3.1) or empirical correlations. For peak injections in the linear range of the isotherm kefr is calculated by Equation 6.139 if the axial dispersion coefficient is already known (Section 6.5.6.2). Another rough estimation is based on the slope C of the simplified HETP curve (Equation 6.143) ... 

As with distillation, the correlation for overall tray efficiency for absorbers, given in Equation 10.7, should only be used to derive a first estimate of the actual number of trays. More elaborate and reliable methods are available, but these require much more information on tray type and geometry and physical properties. If the column is to be packed, then the height of the packing is determined from Equation 9.64. As with distillation, the height equivalent of a theoretical plate (HETP) can vary... 

On the basis of analysis of published data on distillation operations with packed towers, Murch has presented the following empirical equation as a correlation to be used for estimating HETP f... 

Height Equivalent to a Theoretical Plate. Provided both the equilibrium and operating lines are straight, HETP values may be estimated by combining the HG and HL values predicted by the above correlations and by translating the resulting HQG into HETP by combining equations 47, 51, and 56 with equation 85, which is discussed under bubble tray absorption columns ... 

The van Deemter equation was developed in the 1950s to explain band broadening in chromatography by correlating HETP or plate height with linear flow velocity (V).16 Figure 2.18 shows a typical van Deemter curve (HETP vs. V),... 

When comparing the moments of Equations 6.62 and 6.63 with the definition of the number of stages given in Equation 2.37, a simple correlation between dispersion coefficient and the number of stages N or the HETP can be derived ... 

HPLC is a well-established analytical technique that has been used in laboratories globally over the past 35 years. One of the major drivers for the development of this method has been the evolution of packing materials used to effect the separation. The fundamental principles of this evolution are governed by the van Deemter equation, which is an empirical formula that defines the correlation between linear velocity (flow rate) and plate height (HETP or column efficiency). Since particle size is one of the variables, a van Deemter curve can be used to investigate chromatographic performance. 

However, there are a number of occasions where the designer is faced with developing a design HETP value without any actual experience. The designer then must rely on a calculated value obtained from some correlation. A model has been proposed by Onda et al to calculate Hqg by means of Equation 7-16 [24], This model evaluates Hq and Hl values from mass transfer coefficients ... 

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