Column support plates

The separation operation called distillation utihzes vapor and hquid phases at essentially the same temperature and pressure for the coexisting zones. Various lands of devices such as r andom or sti uctui ed packings and plates or tr ays are used to bring the two phases into intimate contact. Trays are stacked one above the other and enclosed in a cyhndrical shell to form a column. Pacldngs are also generally contained in a cyhndrical shell between hold-down and support plates. A typical tray-type distillation column plus major external accessories is shown schematically in Fig. 13-1. 

As indicated above, packed column internals include hqiiid distributors, packing support plates, redistributors (as needed), and holddown plates (to prevent movement of packing under flow conditions). Costs of these internals for columns with random packing are given in Fig. 14-80, based on early 1976 prices, and a Marshall and Swift cost index of 460. 

FIG. 14-80 Cost of internal devices for columns containing dumped packings, a) Holddown plates and support plates, (h) Redistributors, (c) Liquid distributors. [Pikulik and Diaz, Cbem. Eng., 84(21), 106 (Oct. 10, 1977).]... 

Each SynChropak column is tested chromatographically to assure that it has been packed according to specifications. For SynChropak GPC columns, a mixture of a high molecular weight DNA and glycyltyrosine, a dipeptide, is used to evaluate internal volume and efficiency. The mobile phase used for the test is 0.1 M potassium phosphate, pH 7, and the flow rate is 0.5 ml/min for 4.6-mm i.d. columns. Minimum plate count values and operational flow rates are listed in Table 10.4 for 4.6-mm i.d. columns of all supports and the various diameters of the SynChropak GPC 100 columns. 

The typical packed column has one or more beds, each consisting of packing, a support plate, a hold-down support plate, and a liquid distributor. 

Design the column internals plates, distributors, packing supports. 

In vacuum distillation columns, the plate-support rings will act as stiffening rings and strengthen the vessel see Example 13.2. 

Blast loaded structures produce high reaction loads at column supports. This usually requires substantial base plates as well as high capacity anchor bolts. Achieving full anchorage of these bolts is of primary importance and will usually require headed bolts or plates at the embedded end of the bolts to prevent pullout. When anchor bolts are securely anchored into concrete, the failure mechanism is a ductile, tensile failure of the bolt steel. Insufficient edge distance or insufficient spacing between bolts results in a lower anchorage capacity and a brittle failure mode. 

Figure 3.11 — (A) Immobilized peroxidase sensor. Glass-immobilized peroxidase is packed in the flow-cell shown. The plastic support plate fits the top surface of the photomultiplier chamber of the immunometer so as to support the vertically held flow-cell in front of the photomultiplier itself. (B) Flow system for hydrogen peroxide/ethanol determinations. For ethanol determinations, the immobilized alcohol oxidase column is inserted immediately after the injection valve (shown by the arrows). Luminol (62 /zM) and 4-iodophenoI (0.4 M) are dissolved in 200 mM borate buffer (pH 8.9) and pumped at a flow-rate of 0.8 mL/min. Phosphate buffer (10 mM, pH 7.0) is pumped at 1.6 ml/min. (Reproduced from [78] with permission of Elsevier Science Publishers).

In a packed column the liquid comes in at the top, or near the top, and enters the column via a series of nozzles or through a distributor plat. The gas enters below the packing and passes upward. Packing placed in the column is held in place by support plates. 

FIG. 14-57 Beam-type gas-injection support plate for large columns. 

End Effects Analysis of the mass-transfer efficiency of a packed column should take into account that transfer which takes place outside the bed, i.e., at the ends of the packed sections. Inlet gas may very well contact exit liquid below the bottom support plate, and exit gas can contact liquid from some types of distributors (e.g., spray nozzles). The bottom of the column is the more likely place for transfer, and Sil-vey and Keller [Chem. Eng. Prog., 62(1), 68 (1966)] found that the... 

In the Pharmacia approach, the fluid input is split and distributed through six ports on the column end plates.At the entrance of each stream, an anti-jetting device spread the liquid over a fine mesh net. A coarse net between the net and the end plate acts as both a support and a spacer. For the soft Sephadex gels G-50 to G-200, the maximum feasible bed height is 15 cm. Scaleup operations have used as many as six such squat columns in series.The drawbacks of this approach are the cumbersome adsorbent in the column. 

For tray colnmns, liquid flow constrictions are normally found in the tray downcomers. Example causes are lack of adequate froth collapse time, excessive pressure drop for flow under the downcomer baffle, and foreign materials being left in the downcomer by construction people. For packed columns, clogged support plates, broken packings, or growth of fouling deposits can cause liquid flow restrictions. 

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