Versatility of Packed Column over Plate Column
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The document compares plate columns with packed columns for chemical processes, detailing the construction, advantages, and disadvantages of each type. Plate columns are suitable for extensive operations and offer various tray designs for effective gas-liquid contact, while packed columns excel in low-capacity operations, especially for heat-sensitive or corrosive materials. The choice between the two depends on factors such as pressure drop, flexibility, and specific operational needs.
Versatility of Packed Column over Plate Column
- 1. Versatility of Packed Column over Plate Column • Vinit Patil (40) • Manish Pawar (41) • Rehan Husain (47) • Sachin Shinde (55) • Shubham Budhawant (57)
- 2. Plate Column A Plate Column (or Tray Column) is a chemical equipment used to carry out unit operations where it is necessary to transfer mass between a liquid phase and a gas phase. The peculiarity of this gas-liquid contactor is that the gas comes in contact with liquid through different stages; each stage is delimited by two plates (except the stage at the top of the column and the stage at the bottom of the column). Plate towers consist of a vertical column with liquid flowing in the top and out the bottom. The vapor phase enters in the bottom of the column and exits out of the top. Inside of the column are trays or plates. These trays force the liquid to flow back and forth horizontally while the vapor bubbles up through holes in the trays. The purpose of these trays is to increase the amount of contact area between the liquid and vapor phases. Some common applications of plate columns are distillation, gas- liquid absorption and liquid-liquid extraction. In general, plate columns are suitable for both continuous and batch operations.
- 3. Sieve Trays Sieve trays are simply metal plates with holes in them. Vapor passes straight upward through the liquid on the plate. The arrangement, number and size of the holes are design parameters. Advantages 1. Simple construction, 2. Low entrainment, 3. Low maintenance cost 4. Low fouling tendency Disadvantages 1. Less-flexible to varying loads than other two types
- 4. Bubble Cap Trays A bubble cap tray has riser or chimney fitted over each hole, and a cap that covers the riser. The cap is mounted so that there is a space between riser and cap to allow the passage of vapor. Vapor rises through the chimney and is directed downward by the cap, finally discharging through slots in the cap, and finally bubbling through the liquid on the tray. Advantages 1. Moderate capacity 2. Most flexible (high & low vap. & liquid rates) 3. Can provide excellent turndown. Disadvantages 1. High entrainment, 2. High fouling tendency 3. High cost, 4. High pressure drop
- 5. Valve Trays In valve trays, perforations are covered by lift able caps. Vapor flows lifts the caps, thus self creating a flow area for the passage of vapor. The lifting cap directs the vapour to flow horizontally into the liquid, thus providing better mixing than is possible in sieve trays. Advantages: 1. Excellent liquid/vapour contacting. 2. Higher capacity. 3. Higher flexibility than sieve trays. 4. Can handle higher loadings. 5. Low-pressure drop than bubble cap.
- 6. Conditions favoring plate columns: Plate columns can handle wide range of gas and liquid flow rates. Plate efficiency can be predicted more accurately Plate column operation is considerably smooth. Cooling arrangement can be provided in plate column. Plate column provide stage wise contact. When the liquid cause fouling or deposition of solids, even though the tray is blocked up, it is easier to clean it and manholes can be provided over the plate.
- 7. Packed Column Packed columns are more suitable for low capacity operations. Packed columns are particularly useful in the field of vacuum distillation. Here column pressure drop is of paramount importance to minimize the pressure and temperature at the bottom of the column. For separating heat sensitive materials packed columns are useful because the liquid hold up is low. When corrosion is a problem packing may be the only answer. Pressure drop per unit length is less in packed column. Packed column provides continuous contact between the vapor and liquid phases. Packed columns are suitable for handling foaming system. Modern high capacity pickings are available in practically any material. Total weight of packed column is less due to use of low weight and high capacity packing.
- 8. Packing Materials 1. Ceramic 2. Metal 3. Plastic
- 9. Design of Packed Column The design procedure of a packed column consists of the following steps: 1. Select the type and size of packing. 2. Determine the column height required for the specified separation. 3. Determine the column diameter (capacity), to handle the liquid and vapor flow rates. 4. Select and design the column internal features: packing support, liquid distributor and redistributors. Specify separation requirements Select type and size of packing Determine column height(z) Determine column diameter
- 10. Conditions favoring plate columns: Packed towers offer a lower pressure drop. Packed towers are better for corrosive liquids Packed towers are better at handling foaming system small-diameter columns (less than 0.6m) more choices in materials of construction for packings especially in corrosive service (e.g. plastic, ceramic, metal alloys) less liquid entrainment · low liquid hold-up, especially suitable for thermally sensitive material foaming liquids can be handled more readily (less agitation of liquid by the vapour)
- 11. Research Papers