Gas and liquid contact apparatus – Contact devices – Wet baffle
Reexamination Certificate
1999-12-22
2001-10-09
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Wet baffle
C261S114300, C261S114500
Reexamination Certificate
active
06299146
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improvement of a rectangular downcomer tray in a vapor-liquid contacting tower. More particularly, it relates to an improvement of a novel rectangular downcomer tray having directing components. Directing components are installed in order to improve the distribution of the liquid flow on the tray, uniform the liquid flow and prevent impact weeping of liquid from the present tray to the adjacent tray below. Therefore, the improve tray can raise the separation efficiency of the tray when used in a vapor-liquid contacting tower.
BACKGROUND ART
At present, most trays in domestic and foreign vapor-liquid mass transfer apparatus use arched downcomers, the overflow periphery of which is only the chord length and the arc of the arch does not function. Therefore, they can not offer great liquid capacity and is not suitable to the operation with high liquid-vapor ratios and under pressures. UCC in USA invented an MD tray (Multiple Downeomer Sieve Tray, U.S. Pat. No. 3,410,540) in 60s, which is a sieve tray using rectangular downcomers. All the four sides of the rectangle are overflow periphery and the overflow weir is 2-5 times longer than that of the arched downcomer, suitable to the operation with great liquid capacity and high liquid-vapor ratios. The downeomer is suspended in the vapor phase space and requires no receiving pan, and therefore the bubbling area can be increased by 10-15%. However, because the liquid flow on the MD tray has to turn for 90 degrees; its path is short and its distribution is less uniform, the tray efficiency is somewhat affected. When a tower is expanded and modified with MD trays, replacement of 3 by 4 or 2 by 3 is usually employed (TECHNOLOGY 1988, June 6, Oil & Gas Journal 54). In recent years, UOP Co. in USA has developed ECMD (enhanced Capacity Multiple Downcomer Sieve Tray)for increasing the width of the downeomer and enhancing the liquid treatment capacity, but no improvement is made in liquid flow distribution on the tray, see CHEMICAL ENGINEERING PROGRESS Vol. 66, No. 3.
U.S. Pat. No. 5,382,390 to Resetarits et al., proposes a multiple downcomer tray with notched directing slots. The directing slot is notched at the middle of the bubbling zone among the downcomers and oriented towards the overflow weir of the tray, i.e., the long side of the downcomer. The object of the slot is to push the liquid half way on the liquid flowing path across the tray and decrease the height of the froth and the entrainment of the droplet so as to enhance the vapor throughput. Resetarits thinks that, unlike the normal cross-flow tray, the multiple downcomer tray exhibits no phenomena of sluggish flow and liquid non-uniform residence time; the liquid flow distribution is already uniform. and thus there is no need to improve the liquid flow distribution. Therefore, notching multiple directing slots and determining their position and direction are all for pushing the liquid half way and enhancing the vapor throughout. The research for evaluating the uniformity of the liquid flow distribution by equivalent residence time distribution curves measured with an optical fiber instrument demonstrates that the liquid on the Resetarits' 390 multiple downcomer tray is injected in point form, and then turned for 90 degrees. Therefore, there exists an obvious non-uniform phenomenon (refer to FIG.
5
(
a
)) for the liquid distribution.
The object of the present invention is therefore to notch directing slots and install directing baffles on the liquid receiving zone into which the liquid just enters so as to improve the initial distribution upon entering the tray, allow the liquid flow to turn for 90 degrees smoothly and distribute as uniformly as possible as shown in FIG.
5
(
b
), and thus enhancing the separation efficiency.
SUMMARY OF THE INVENTION
The present invention provides a vapor-liquid contacting tower, which comprises multiple trays having multiple openings and multiple rectangular downcomers, the trays being positioned along the vertical direction and the rectangular downcomer being arranged in parallel and extending downwards from each tray; the angle between the downcomers on the adjacent two trays being 90 degrees. Each downcomer has multiple openings at its bottom, the end of which is located close to and above the adjacent tray below; the liquid flows downwards onto the liquid receiving zone of the adjacent tray below through the bottom openings of the downcomer, then traverses the tray, and arrives at the overflow weir of the downcomer of the tray. The vapor flows upwards through the openings of each tray, bubbles up through the liquid layer and form a bubbling zone, and thereby mass transfer occurs between the vapor and liquid. The improvement lies in that at least a pair of directing slots and at least a pair of directing baffles are installed under the bottom openings of the downcomer of the adjacent tray above and on the receiving zone of the present ray. The directing slot is tilted and heaved up from the tray and located at the center of the liquid receiving zone; the directing baffle is an arched strip fixed on the tray and locates at the outside side of the directing slot and close to the edge of the liquid receiving zone. The directing slot makes the liquid in the receiving zone split to two sides, turn for 90 degrees by the directing baffles, and thereby the liquid flows across the bubbling zone of the tray more uniformly and steadily.
REFERENCES:
patent: 3062517 (1962-11-01), Voetter et al.
patent: 3410540 (1968-11-01), Bruckert
patent: 4174363 (1979-11-01), Bruckert
patent: 4550000 (1985-10-01), Bentham
patent: 5098615 (1992-03-01), Resetarits
patent: 5209875 (1993-05-01), Miller et al.
patent: 5318732 (1994-06-01), Monkelbaan et al.
patent: 5382390 (1995-01-01), Resetarits et al.
patent: 5547617 (1996-08-01), Lee et al.
patent: 5975504 (1999-11-01), Nutter et al.
patent: 1542242-A (1970-04-01), None
Li Ou
Tian Jun
Xu Chongsi
Yao Kejian
Yu Xiaomei
Anderson Kill & Olick P.C.
Bushey C. Scott
China Petro-Chemical Corp.
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