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Estimating the HETP

Having determined the column packing height on the basis of equilibrium calculations and whatever mass transfer correlations, the capacity of the column to handle the required vapor and liquid flows hydraulically must be checked. The specific items of concern in this regard are the pressure drop across the packing and the tendency of the column to flood. These are the considerations that determine the required column diameter. [Pg.548]

The HETP depends on the type and size of the packing material, the column dimensions, the fluid properties, the operating conditions, and so on. It also depends on whether the packing is dumped or ordered. The HETP is usually supplied by the packing vendors or estimated based on experimental data or empirical correlations. [Pg.548]

Bolles and Pair (1979) estimate the HETP from vapor and liquid heights of transfer units (HTU). The vapor phase Hq and liquid phase are first calculated separately from empirical correlations. The overall HTU is then calculated as follows  [Pg.548]

Equations 15.30 and 15.31 are derived based on the assumption of constant operating line and equilibrium curve slopes (Vital et al., 1984). [Pg.548]


We can now put the whole van Deemter equation together, including the coefficients that we can use as a rule of thumb to estimate the HETP for a normal packed bed of porous particles ... [Pg.221]

Strigle [94] proposed this term to better describe the performance of a packed column at or near the previously described loading point. Kister [93] evaluated the limited published data and proposed using the MOC at 95% of the flood point. The flood point can be estimated by Equation 9-20 or from the plots in References 90 and 93. The data are reported to be within 15-20% of the prediction [93]. See Figure 9-22 for the identification of MOC on the HETP vs. Cg chart For more accurate information... [Pg.299]

The methods for estimating the heights of transfer units, HTU, given in Section 11.14.3 can be used for distillation. The relationship between transfer units and the height of an equivalent theoretical plate, HETP is given by ... [Pg.594]

One last contribution to HETP in this chapter is to establish tray efficiency by simply running one of the tray programs and inputting T for the tray method selection. The program will give you the well-proven tray efficiency two-film method [1]. Then refer to Table 3.10 and estimate your HETP minimum required. I always recommend adding at least 6 in to the HETP for a reasonable, safe design. [Pg.114]

Compare the HETP for the packing under consideration to the rule of thumb in Eq. (9.34). If different, estimate the magnitude of this packing effect from the data, and allow for it in the design. [Pg.654]

Estimate of the HETP intradiffusion coefficients, when based on HETP dependence on concentration, has been shown to be close in value to the quantity calculated with the theoretical formula obtained by using the model of centrosymmetrical diffusion in an ion-exchanger bead [89,90]. The values in this formula of r /D, where r is the effective particle radius, were determined in thin-layer kinetic experiments with the same ion-exchanger fraction. [Pg.83]

Thus, for multicomponent mixtures, the required number of theoretical stages N, is calculated, and the HETP for the key components is estimated from the approximate relationship. [Pg.428]

Moment analysis and HETP plots are described in Chapter 2. Here it will be shown how they can be used in estimating the model parameters. If the detector signal is a linear function of concentration, analysis can be carried out directly with the detector signal without calibration. Since the concentration profile is available as np discrete concentration vs. time values, the momentums have to be calculated by numerical integration. [Pg.257]

The next step is to determine the column packing height. The HETP is estimated using any of the methods described in Section 15.4.1. The column packing height is simply the number of equilibrium stages multiplied by the HETP. [Pg.551]

If we know the HETP, we can estimate the required column length. With an assumed HETP of 1 1/2 feet and an ideal number of trays in the rectifying section often, we need a rectifying section 15 feet tall. The HETP will determine the actual number of plates needed the number should not be doubled. [Pg.13]

Application of the sum-rates method developed in Chapter 15 for the equilibrium and flow rate calculation to estimate the number of theoretical equilibrium stages, coupled with some form of HETP calculation based on experience or available correlations. [Pg.725]

Whether we have used the first or the second approach, we can now proceed to determine the true HETP as a function of the velocity. An example of results obtained (26) using this procedure is shown in Figure 3.14. The HETP was measured for several proteins eluted under gradient conditions from a S-cm column packed with i-fita particles and a 10-cm column packed with 20-/im particles. The packing was a 300 A packing. In this case, we did not need to estimate the particle size from the permeability of the column, since the particle size was known. The results for both particle sizes line up quite nicely. This demonstrates that this procedure works well and that true r uced HEIT values data can be obtained even under gradient conditions. [Pg.46]

For the calculations of reduced velocities or the prediction of an HETP we need to know the diffusion coefficient of an analyte in the mobile phase. However, this information is seldom available. We therefore have to estimate the diffusion coefficient. There are several different approaches available, but the one most frequently used in the HPLC literature is the Wilke-Chang equation. It is claimed to be accurate for small to medium-sized molecules within 10%, which is sufficient for most purposes (9) ... [Pg.226]

The design of the equipment for the non-reactive sections should not pose too great a challenge since existing methods of estimating efficiencies or HETP that are based on key-components could be used. For the reactive section, however, the estimation of HETPS and efficiencies is more problematic. There is no easy way to identify key components. Chemical reactions influence component efficiencies in an unpredictable manner (Fig. 9.22 in [1]). Of course, like the rest of the RD community, we could behave like ostriches and bury our heads in the sand while assuming equal component efficiencies (say, 70%) for individual species and hope for the best ... [Pg.237]

D4. Example 10-4 and Problem 10.D17 sized the diameter of a packed column doing the separation in Example 11-1. Suppose a 15-foot diameter column is to be used. The 1-in Intalox saddles have an HETP of 0.37 m. Estimate the packing and tower costs. Pressure is 101.3 kPa. [Pg.466]

Remember, though, that the old concept of the HETP (height equivalent to a theoretical plate) can be evaluated as equal to around 25 times the nominal size of the packing. Thus, we can quickly gain a rough estimation of the height of a distillation colunm or even an isothermal absorption column. However, this way of working is imprecise, because there is no rational justification for the concept of the HETP. [Pg.114]


See other pages where Estimating the HETP is mentioned: [Pg.548]    [Pg.548]    [Pg.548]    [Pg.385]    [Pg.407]    [Pg.408]    [Pg.408]    [Pg.198]    [Pg.548]    [Pg.548]    [Pg.548]    [Pg.385]    [Pg.407]    [Pg.408]    [Pg.408]    [Pg.198]    [Pg.593]    [Pg.14]    [Pg.380]    [Pg.45]    [Pg.593]    [Pg.30]    [Pg.747]    [Pg.1479]    [Pg.1567]    [Pg.529]    [Pg.1476]    [Pg.1563]    [Pg.224]    [Pg.91]    [Pg.412]    [Pg.679]    [Pg.398]   


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