Gas and liquid contact apparatus – Contact devices – Porous mass
Patent
1993-07-27
1995-02-07
Miles, Tim
Gas and liquid contact apparatus
Contact devices
Porous mass
2611141, B01F 304
Patent
active
053873777
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an active liquid distributor containing, packed column. The present invention is particularly useful for mass transfer operations, such as, for example, distillation, absorption stripping and liquid extraction.
It has already been proposed in, for example, U.S. Pat. No. 2,639,130, dated May 19, 1953 "Apparatus For Equalizing Distribution ln packed Columns" P. N. Heere, to provide successive, radially extending vane distributors in a packed column to intercept liquid flowing toward the column wall and to return it to definite predetermined points across the column. This compensates for the action of the upflowing phase, the resistance of the column wall, surface tension and the action of the packing itself, causing the liquid to have a tendency to flow outwardly to the column wall and then down the wall, and thus escaping direct contact with the upwardly flowing gaseous phase.
While the packed columns of Heere are useful,
(1) the distributors contribute little to increasing the gas/liquid contact and mass transfer,
(2) the distributors do not evenly distribute the downward flow of liquid through the packed bed,
(3) the distributors may become flooded and cause maldistribution of the liquid and lower the gas/liquid contacting efficiency of the column.
It has already been proposed in, for example, U.S. Pat. No. 4,504,426, dated Mar. 12, 1985 . "Gas-Liquid Contacting Apparatus", K. T. Chuang et al, to provide perforated, liquid distributing and frothing trays at different levels in a gas-liquid contacting column. Perforated trays generally of this type have been used in upwardly extending, liquid distributing spaces which separate packed beds in a packed column. It has always been considered essential for the perforated trays to be placed in these spaces, which separate packed beds and contribute nothing to the mass transfer between the gas and the liquid, in order to provide unobstructed flow of liquid across the perforated trays to ensure uniform liquid distribution across the perforated trays which is essential for maintaining uniform wetting of the packing.
In a recent paper entitled "Troubleshooting a Packed Vacuum Column", the authors, McMullan et at. presented the results of tests on a packed vacuum column at AlChE Annual Meeting in Chicago on Nov. 11-16, 1990. The authors concluded from the results that the development of uneven liquid distribution in a packed column is inevitable and, for best performance, liquid should be remixed in packing free portions of the column at different levels between the packed beds therein.
It has also been proposed in "Better sieve tray? Add packing" A-B.S.H. Salem et al, Hydrocarbon Processing, May 1988, p. 76-G, and "Performance of Combined Mesh Packing and Sieve Tray in Distillation" to add a shallow bed of packing material on top of sieve trays to increase the efficiency of a sieve tray tower. This development was also investigated by me in Chen et al, "Performance of Combined Mesh Packing and Sieve Tray in Distillation", Cdn. J. of Chem. Eng., Vol 68, June 1990. The systems investigated in these articles did not provide for distribution of liquid onto the underlying packing because the development relied on the use of sieve trays. As is appreciated this type of tray provides solely for transverse flow of liquid across the tray towards its downcomer and thereby provides a transverse distribution of liquid in the packing. As the liquid flows across the tray, vapour bubbles upwardly through the transversely flowing liquid to develop a froth. It is difficult to maintain a level of froth in the packing but for the purposes described in these articles an improvement in performance was noted.
There is a need for a packed column wherein instead of standard perforated trays for supporting packing, or other types of perforated trays in spaces between packed beds, or inactive distributors, i.e. the distributors are inactive by insignificantly contributing to the gas/liquid contact, active distributors are provided, which significantly contribute to t
REFERENCES:
patent: 2639130 (1953-05-01), Heere
patent: 3996317 (1976-12-01), Sarmiento et al.
patent: 4159291 (1979-06-01), Bruckert et al.
patent: 4185075 (1980-01-01), Ellis et al.
patent: 4310475 (1982-01-01), Leva
patent: 4504426 (1985-03-01), Chuang et al.
patent: 4620952 (1986-11-01), Hsieh
patent: 4820456 (1989-04-01), Kiselev
patent: 4956127 (1990-09-01), Binkley et al.
"Performance of Combined Mesh Packing and Sieve Tray in Distillation", G. X. Chen et al, pp. 382-386, Canadian Journal of Chem. Engr., vol. 68, Jun. 1990.
"Better sieve tray? Add packing", S. H. Salem and A. A. Alsaygh, pp. 76-G--76-H, Hydrocarbon Processing, May 1988.
"Troubleshooting A Packed Vacuum Column", B. D. McMullan, pp. 1-13, Aiche Chicago Meeting, Nov. 11-16, 1990.
Miles Tim
The Governors of the University of Alberta
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