Column collector/distributor

The monoglycerides of the raffinate (the bottom product) is shown in Figure 9 as a function of the superficial velocity of the gas phase at a phase ratio of 19. At an superficial velocity of 10 mm/s the raffinate obtained with different packings is nearly the same except for the Sulzer Packing SMV. At lower superficial velocities the wire mesh packings (Sulzer CY) provide the best yields. The experiments are made at conditions where a falling film disintegrates into drops. Therefore, it seems understandable that the efficiency of the spray column and that of the collector-distributor installations do not much differ. 

Many studies on the flow distribution in random packed beds have been reported in the literature. Mercandelli et al. [8] published a short review of the flow distribution work in random packed trickle bed, which includes the list of various techniques used to determine and quantify the flow distribution. Conventional methods include, for example, collecting liquid at the bottom of the column from different zones while advanced methods include tomographic techniques. Mercandelli et al. [8] used several techniques to quantify liquid distribution in columns of diameters up to 30 cm with three different distributor designs. They used global pressure drop measurements, global residence time distribution (RTD) of the liquid, local heat transfer probes, capacitance tomography and a collector at the bottom of the column. 

The pressure drop per foot of bed depth is given in the statement of the example as 0.6 lb/in2. Thus total pressure drop for the resin bed is [0.6 lb/(in2)(ft)](5 ft) = 3.0 lb/in2 (21 kPa). This excludes the pressure drop due to the liquid distributors and collectors in the column, as well as that due to auxiliary fittings and valves. 

Figure 33 The scheme for a unit with a conical column (1) operating section (2) resin feeding section (3) solution distributor (4) filter, (5) inlet resin pipes (6) feeding resin hopper (7) pump (8) valve (9) rotameter (10) valve (11) probe collectors (12) partition (13) solution feeding filter (14) resin feeding pipe.

We conducted cold flow model experiments in a air-water/glycerin system to investigate a cause of maldistribution in a catalyst bed. The apparatus used was a 30 cm I.D. acrylic column equipped with a liquid distributor at the top and a liquid collector with 33 compartments at the bottom. Bed depth can be varied by combining the pipes. Liquid distribution at a given depth of the bed was estimated by measuring the liquid flow from each compartment of the collector. We examined effects of gas and liquid velocity, liquid viscosity, particle shapes, and ways of catalyst loading on liquid distribution in the bed. An increase in liquid velocity or viscosity slightly improved liquid distribution. However, gas flow rate did not affect liquid distribution. 

Generally, redistributors for large-diameter (> 3-ft) columns are of the orifice or weir type. The orifice type is more popular because it does not require the addition of a liquid collector, which consumes vertical space and increases column cost and complexity. Other pros and cons of orifice and weir redistributors, as well as application guidelines for each type of redistributor, are identical to those described earlier for orifice and weir distributors. The general dos and don ts for distributors and for liquid inlets into distributors also extend to redistributors. Additional guidelines unique for selection, design, and operation of redistributors are presented below. 

Chimney trays (Fig. 4.10a, 6) are used for withdrawing intermediate liquid streams from the column in a packed tower, they are also used as liquid collectors or vapor distributors. Alternative devices used for liquid withdrawal are downcomer trapouts in tray columns, chevron collectors, and some redistributors in packed columns. Compared to these alternative devices, chimney trays have the following advantages ... 

Liquid distributors are often used to correct liquid flow to a more uniform pattern and/or to add more liquid to the reactor. Liquid distributors are also often used to redistribute the liquid phase as well, but a simpler option, shown in Figure 9.9, would be a perforated plate with directional facing. Liquid collectors are used to channel the liquid into the liquid oudet in order to prevent converted/used liquid to stay in the column bottom. The hardest portion of designing a collector is to not interfere with gas distribution, and the available designs are quite wide and diverse. TBRs, on the other hand, tend to use liquid collectors, which are only used for collecting and extracting liquid. 

The multiple phase contact inside the column is promoted by internal mass transfer equipment. Three groups of mass transfer equipment are commonly differentiated, which are separation trays, random packings and structured packings. Besides mass transfer equipment, further column internals are required in rectification to ensure the proper operation of the mass transfer equipment. Such internals may include support and hold-down plates, liquid distributors and redistributors, vapour distributor devices, gas-liquid phase separators and liquid collectors that usually do not participate on mass transfer. 

Main features of a packed distillation column 1. mainways 2. liquid distributor 3. packing 4. liquid collector 5. support grid and 6. vapor from reboiler. 

Figure 8.4 draws attention to the principal internal components of a packed column. The parhcular packing shown is of the structural type displayed in Figure 5.5b. They allow the column diameter, which in distillahon is usually confined to 1 m or less, to exceed that limit many times. Liquid collectors and distributors, which are shown only twice, are usually used every 3 m to coxmteract channeling. This undesirable effect can be particularly severe at low liquid flow rates (vacuum operation).

Both the above mentioned constructions are simple and li ht, which means also cheap, but they are not able to collect and homo nised die whole liquid flow flowing in the column. This purpose is answ i the devices considered below. All of them consist of two main parts collector ai distributor. Because the main types of distributors are considered above, only the respective collectors for the liquid phase will be considered. 

The collector consists of cut cones 1 open at both sides, mounted in the column corpus as presented in the figure. The direction of the gas phase is shown by arrows. The collected liquid leaves the collector by means of pipe 2, connect to the distributor. 

A collector offered in [1] for columns with diameters from 300 to 1200 mm, is presented in Figs. 55 and 56. The design is accomplished by analogy with the liquid distributor RP 2 (Fig. 53), but instead of discharge holes there is a lateral downcomer shaft. The collector permits 100% liquid collection. The... 

The inclined and overlapping lamellas of tihds distributor ensure far-reaching of liquid at small pressure drop. The channels at the lower end of the lamellas, lead the collected liquid into an annular channel which follows the colunan wall. In large columns or with larger liquid loads the lamellas ue also available in a segment version and with transverse central trou for increased liquid distribution. Some typical dhnensions of this collector are given in Table 7. 

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