Revamping of Distillation Column Tray

The tray column (or plate column) a particular gas-liquid contactor and it is one the most widely used types of distillation columns. In tray column, the liquid phase flows downward through the column via gravity. A reboiler located at the bottom of the tower separates the stream into a vapor that returns to the column as well as creates a liquid product stream. While the gas phase flows upward. These two phases come in contact in correspondence of holes, valves or bubble caps that fill the area of the plates. This process allows the separation to occur.

Fig. 1 Tray column

The tray essentially acts as a mini column, each accomplishing a fraction of the separation task. Hence, the more trays there are, the better the degree of separation and that overall separation efficiency will depend significantly on the design of the tray. The number of trays and stages in the column is designed for the desired purity and difficulty of the separation process. Height of the column also determines the number of stages.

The Types of Trays

There are five major types of trays: bubble cap tray, sieve tray, dual flow tray, valve tray and baffle tray.

• Bubble cap tray

A bubble cap device consists of a cap and a 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 riser and is directed downward by the cap, finally discharging through slots in the cap, and finally bubbling through the liquid on the tray.

Fig. 2 Bubble cap tray

• Sieve tray

The sieve tray is simply a plate with holes for vapor passage and it is the least expensive tray option. In sieve trays, vapor flowing up through the tower contacts the liquid by passing through small perforations in the tray floor. The arrangement, number and size of the holes are design parameters.

Fig. 3 Sieve tray

• Dual flow tray

The dual flow tray is a high hole area sieve tray without a downcomer. Perforations in the tray allow liquid and gas to flow through. Since no downcomer is used, the cost of the tray is lower than that of a conventional sieve tray. Dual flow tray is suitable in highly fouling services where efficiency and turndown are not concerns.

Fig. 4 Dual flow tray

• Valve tray

The valve tray is typically with the covers provided to the perforations of the sieve tray. The valves will move up or down in response to changing vapor flow rates. At normal flow rate, the valve is roughly in the middle position. At low vapor rates, the disk settles over the perforation and covers it to avoid liquid weeping. The valves should be heavy enough to prevent excessive opening at low vapor flowrates.

Fig. 5 Valve tray

• Baffle tray

Baffle trays are generally designed to give a maximum dispersion of liquid and an optimum contact of liquid and vapor with high capacities. The vapor passes through a curtain of liquid flowing from the tray deck above instead of the normal intimate vapor/liquid contact on the tray deck.

Why Choose Us

As with decades of experience in chemical products and technical service, Alfa Chemistry has become a trustable supplier in petroleum and chemical industry, food and beverage industry, pharmaceutical and bio-technology industry, etc. We can offer revamping of distillation column tray services including equipment improvement and process optimization. Please feel free to contact us for a better solution to your distillation columns.