Sieve plate column

Perforated-plate columns Sieve-plate columns with downcomer Varied-perforation plate... 

Discontinuous rectification is characterised by non-recurring feed and a separation column. To generate a reflux, an overhead condenser is inserted and a cold trap cools the obtained distillate. For analytical-preparative purposes in the laboratory, an apparatus with annulus columns has proved to be successful. This apparatus has a vacuum of up to 0.01 mbar, an output of 1-50 ml/h and low hold-up volume. Larger rectification units have tray columns, sieve plates and packing material with a vacuum of up to 0.1 mbar and outputs of several litres per hour. 

Plaka, T., Ehsani, M. R., and Korchinsky, W. J., Determination of Individual Phase Transfer Units, Nfj and for a 0.6 m Diameter Distillation Column Sieve Plate Methylcyclohexane-Toluene System, Chem. Eng. Res. Des., 316-328 (1989). 

Coward, L. D. G. Column Sieve Plate Gland. British Patent Application 19047/55. 

CJravity-operated extractors a. No mechanical moving parts Spray columns Packed columns Sieve plate columns... 

Pulsed Columns. The efficiency of sieve-plate or packed columns is increased by the appHcation of sinusoidal pulsation to the contents of the column. The weU-distributed turbulence promotes dispersion and mass transfer while tending to reduce axial dispersion in comparison with the unpulsed column. This leads to a substantial reduction in HETS or HTU values. 

The pulsed-plate column is typically fitted with hori2ontal perforated plates or sieve plates which occupy the entire cross section of the column. The total free area of the plate is about 20—25%. The columns ate generally operated at frequencies of 1.5 to 4 H2 with ampHtudes 0.63 to 2.5 cm. The energy dissipated by the pulsations increases both the turbulence and the interfacial areas and greatly improves the mass-transfer efficiency compared to that of an unpulsed column. Pulsed-plate columns in diameters of up to 1.0 m or mote ate widely used in the nuclear industry (139,140). 

L. Burkhart, A. Survey of Simulated Methods for Modeling Pulsed Sieve-Plate Extraction Columns, UCRL-15101, Ames Laboratory, Iowa State University, Ames, Iowa, 1979. 

The term in equation 42 is called a Souders-Brown capacity parameter and is based on the tendency of the upflowing vapor to entrain Hquid with it to the plate above. The term E in equation 43 is called an E-factor. and E to be meaningful the cross-sectional area to which they apply must be specified. The capacity parameter is usually based on the total column cross section minus the area blocked for vapor flow by the downcomer(s). Eor the E-factor, typical operating ranges for sieve plate columns are... 

Minimum allowable capacity of a column is determined by the need for effective dispersion and contacting of the phases. The types of plates differ in their ability to permit Tow flows of gas and liquid. A cross-flow sieve plate can operate at reduced gas flow down to a point where liquid drains through the perforations and gas dispersion is inadequate for good efficiency. Valve plates can be operated at veiy... 

Example 9 Loading/Flooding of a Distillation Plate An available sieve plate column of 2.5-m diameter is being considered for an etbylben-zene/styrene separation. An evaluation of loading at the top plate will be made. Key dimensions of the single-crossflow plate are ... 

Direct Scale-Up of Laboratory Distillation Ljficiency Measurements It has been found by Fair, Null, and Bolles [Ind. Eng. Chem. Process Des. Dev., 22, 53 (1983)] that efficiency measurements in 25- and 50-mm (1- and 2-in-) diameter laboratory Oldersbaw columns closely approach tbe point efficiencies [Eq. (14-129)] measured in large sieve-plate columns. A representative comparison of scales of operation is shown in Fig. 14-37. Note that in order to achieve agreement between efficiencies it is necessaiy to ensure that (1) tbe systems being distilled are tbe same, (2) comparison is made at tbe same relative approach to tbe flood point, (3) operation is at total reflux, and (4) a standard Oldersbaw device (a small perforated-plate column with downcomers) is used in tbe laboratoiy experimentation. Fair et al. made careful comparisons for several systems, utibzing as large-scale information tbe published efficiency studies of Fractionation Research, Inc. 

FIG. 14-37 Overall column efficiency of 25-mm Oldersbaw column compared with point efficiency of 1,22-m-diameter-sieve sieve-plate column of Fractionation Research, Inc, System = cyclohexane-n-heptane, [(Fair, Null, and Bolles, Ind, Eng, Chem, Process Des, Dev, 22, 53 (i.982),]... 

Testing of plates and other devices is carried out by Fractionation Research, Inc. for industrial sponsors. Some of the test data for sieve plates have been published for the cyclohexane//i-heptane and isobu-tane//i-butane systems. Representative data are shown in Fig. 14-43. These are taken from Sakata and Yanagi Jn.stn. Chem. Engis. Symp. See. No. 56, 3.2/21 (1979)] and Yanagi and Sakata [Jnd. Eng. Chem. Proc. Des. Devel, 21, 712 (1982)]. The column diameter was 1.2 m, tray spacing was 600 mm, and weir height was 50 mm. 

FIG. 15-38 Extraction rates for sieve-plate and modified biihhle-plate columns. System benzoic acid-water-toliiene, except where noted. To convert feet to meters, multiply by 0.3048 to convert inches to centimeters, multiply by 2.54. [Alletion, Strom, and Treyhal, Trans. Am. Inst. Cbem. Eng., 39, 361 (1943) Row, Kojfolt, and Withrow, ihid., 37, 559 (1941) Treyhal and Dumoulin, Ind. Eng. Cbem., 34, 709(1942).]... 

Sieve plates are used with 0.41-m (16-inch) tray spacing. Height of column shell ... 

While ethyl chloride is one of the least toxic of all chlorinated hydrocarbons, CE is a toxic pollutant. The off-gas from the reactor is scrubbed with water in two absoiption columns. The first column is intended to recover the majority of unreacted ethanol, hydrogen chloride, and CE. The second scrubber purifies the product fiom traces of unreacted materials and acts as a back-up column in case the first scrubber is out of operation. Each scrubber contains two sieve plates and has an overall column efficiency of 65% (i.e., NTP = 1.3). Following the scrubber, ethyl chloride is finished and sold. The aqueous streams leaving the scrubbers are mixed and recycled to the reactor. A fraction of the CE recycled to the reactor is reduced to ethyl chloride. This side reaction will be called the reduction reaction. The rate of CE depletion in the reactor due to this reaction can be approximated by the following pseudo first order expression ... 

Extractors with mechanical agitation, such as mixer-settlers, Kuhni columns, York-Schiebel columns, etc., should be avoided as much as possible. Up to seven theoretical stages packed extraction columns can be conveniently adopted. Sieve-plate extractors can be used up to 20 stages. When a very efficient extraction has to be carried out with expensive solutes, and for reasons of material stability and requirements of low expensive product inventory, we may have to use centrifugal extractors or hollow-fibre extractors. 

A wide variety of extraction column forms are used in solvent extraction applications and many of these, such as rotary-disc contactors (RDC), Oldshue-Rushton columns, and sieve-plate column extractors, have rather distinct compartments and a geometry, which lends itself to an analysis of column performance in terms of a stagewise model. As the compositions of the phases do not come to equilibrium at any stage, however, the behaviour of the column is therefore basically differential in nature. 

Recovery column diameter 1 m, vessel overall height 20 m, 35 sieve plates, vessel and plates stainless steel, operating pressure 1 bar. 

A plate column diameter 2 m height 25 m, stainless clad vessel, 20 stainless steel sieve plates, operating pressure 5 bar. 

Solvent recovery column plate column, diameter 0.6 m, height 6 m, 10 stainless steel sieve plates, design pressure 2 bar, column material carbon steel. 

Pressure drop. The pressure drop over the plates can be an important design consideration, particularly for vacuum columns. The plate pressure drop will depend on the detailed design of the plate but, in general, sieve plates give the lowest pressure drop, followed by valves, with bubble-caps giving the highest. 

Design the plates for the column specified in Example 11.2. Take the minimum feed rate as 70 per cent of the maximum (maximum feed 10,000 kg/h). Use sieve plates. 

Design a sieve plate column to perform this separation, for a feed rate of 10,000 kg/hour. Treat the feed as a binary mixture of ethanol and water. 

The feed temperature will range from 10 to 25 °C. The column will operate at atmospheric pressure. For a feed of 7500 kg/h, compare the designs for a sieve plate and packed column, for this duty. Use a reflux ratio of 3. Compare the capital and utility cost for the two designs. 

The specification for of a sieve plate column is given below. Make a preliminary mechanical design for the column. You design should include ... 

Prepare a sieve-plate column design for the chlorobenzene distillation and make dimensioned sketches showing details of the plate layout including the weir and the downcomer. 

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