Experimental flooding point data

The constant numerical value of the exponent n = 3.5 also appHes to other packing elements, for which the experimental flooding point data uypi and ULas well as the liquid loads h° PI are available, e.g. [3,12, 22,36, 37]. 

Comparing Experimental Flooding Point Data and SBD Model Acc to Eq. (2-67)... 

Evaluation of Experimental Flooding Point Data for the Pressure Range... 

Figure 2-17e shows a comparison between the experimental flooding point data Uv,Fl,exp taken by Krehenwinkel [75], Mozenski et al. [39], and the calculation based on Eqs. (2-69) and (2-71) uv,Fi,calc- The experimental data is based on various test systems and an operating pressure of up to 100 bar. The experimentally derived gas velocities at the flooding point uv,fi are m the range of approx. 0.01 to 0.85 ms . ... 

The first term in Eq. (2-75) is used to determine the effective droplet velocity ut, based on the experimental flooding point data, if the values uy.FL and h pj as well as the void fraction 8 are known. Equation (2-75) therefore constitutes the full form of the correlation based on Eq. (2-24). The second term in Eq. (2-75) is important for various design tasks and constitutes the final equation for the falling velocity of droplets in packed columns. 

Based on the evaluation of approx. 1,200 items of experimental flooding point data, the model of suspended bed of droplets (SBD model), which is presented in this book, is applicable to any types of randomly filled packing elements, stacked packings, struc-... 

The evaluation of the experimental flooding point data acc. to Eq. (2-73) and/or (2-69) was based on roughly 1,200 items of experimental data for approx. 200 random and structured packings and tube columns. The columns, internals and operating parameters were varied within the foUowing ranges ... 

Table 2-2 contains a list of 32 mixtures with widely different physical properties, which were used for evaluating the experimental flooding point data. 

In 1990, a database was created for the purpose of evaluating aU experimental data, including literature data. It currently holds more than 1,200 experimental flooding point data, in excess of 1,100 Kquid hold-up data and more than 10,000 pressure drop data for irrigated random and structured packings. The number of test mixtures is 32. The result is a comprehensive data pool, which is constantly being updated with the addition of new experimental data. 

Table 2-6. Data relating to the experimental flooding point values, diagrammed in Fig. 2-17a, in columns with randomly filled metal packing elements. No. of test system acc. to Table 2-2...

Figure 7-17 [15] shows a comparison between the experiment and the calculated flooding point data, Eq. (7-21), with the parameter m= 1.9 for pure binary mixtures and ternary mixtures C D and for the mass transfer direction D C with the parameter m = 1.5. As can be seen from the comparison, the experimental data has been verified by calculation with an accuracy of less than 20 %. It was therefore possible to significantly consolidate and generalise the information available on the loading capacity of non-pulsed extractors, compared to Mersmann s flooding point diagram shown in Fig. 7-14. 

This work is based on more than 10,000 experimental pressure drop data, in excess of 1,100 liquid hold-up data and more than 1,200 flooding point data for approx. 160 different random and structured packings made of various materials commonly used in practice. The majority of this data was compiled by the author in an accurate and reproducible manner whilst working for the Institute of Thermal Separation Processes at Bochum University. This book exceeds all publications worldwide in terms of its volume of data, and the industry will be grateful to the author as well as Springer Publishing for its publication. 

Belles and Fair (55) compared flood-point predictions from the Eckert correlation to published experimental data for random packings. Their massive data bank consisted mainly of data for first-generation packings, but also included some data for second-generation packings. For the data compared, Bolles and Fair showed that Eckert s correlation gave reasonable flood-point prediction. Statistically, they showed that if a safety factor of 1.3 was applied to the correlation flood-point predictions, the designer will have 95 percent confidence that the column will not flood. 

Interpolation of experimental flood, pressure drop, and maximum operational capacity (MOC) data is the most reliable and accurate method available for predicting flood, pressure drop, and MOC. As pointed out in Secs. 8.2.6 to 8.2.9, use of correlations to predict these parameters can lead to poor and dangerously optimistic results in many situations frequently encountered in commercial practice. 

Many empirical equations for predicting pressure gradients in countercurrent flow of gas and liquid are available in the literature.17,31,36 The pressure drop in countercurrent flow can be represented by an equation of the Carman-Kozeny type for flow through packed beds, Below the flooding point, the following equation is suggested36 and has been shown to agree well with experimental data ... 

The design of a multi-purpose plant for the continuous extraction of liquids with supercritical fluids is presented. To provide flexibility in order to treat different feedstocks, a modular concept was developed based on experience gained in the operation of bench-scale and pilot plants. Four test systems were chosen in order to determine the proper dimensions for the equipment. Based on experimental data, e.g. measurements of flooding points and maximum flows for various column internals, the design pressure and temperature and heat exchange requirements were determined. The plant was built by a German manufacturer and was operated successfully by a Canadian company in Edmonton, Alberta. 

Usually, practical design correlations for and or the characteristic velocity v are directly derived from experimental data. For example, in an Rotating Disc Contactor (RDC), in the operating range of interest, the velocity limit of the dispersed phase at the flooding point is according to Strobel and Salzer [6.30]... 

Based on the theoretical considerations illustrated above and the experimental data found in literature [66], it can be assumed that, due to the constant occurrence of droplets in the packing, the flooding point mechanism in packed columns is defined by the entrainment of droplets. 

The empirical flooding point correlation developed by Billet [15] applies to metal Raschig and Pall rings and reflects the experimental data for the vapour/liquid systems much more accurately, 5(uv,fi) = i 15—20%, than Eckert s correlation [9] does. 

Figure 2-12a. Dependence of the liquid hold-up at the flooding point h p on the phase flow ratio Xq, valid for various systems and packings made of metal, ceramic and plastic for Rep > 2 - experimental data taken by the author in comparison to calculated values based on Eq. (2-47)...

Table Relating to Fig. 2-12 a Experimental hold-up data at the flooding point h ...

Table 2-4. List of experimental data on the flooding point for random 25 mm metal Pall rings, valid for various systems ... 

Figure 2-17a. Grmparison of experimentally determined gas or vapour velocity at the flooding point (uv,Fl)exp and calculated data based on Eq. (2-67), valid for random metal packings of various types, no. of test system as shown in Table 2-2...

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