Gas and liquid contact apparatus – Contact devices – Rotating gases
Reexamination Certificate
1999-06-22
2001-05-08
Chiesa, Richard L. (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Rotating gases
C096S306000, C261S114100
Reexamination Certificate
active
06227524
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims benefit under 35 U.S.C. 119(a)-(d) of co-pending German patent application No. DE 198 28 884, filed Jun. 22, 1998. German patent application No. DE 198 28 884 is hereby incorporated by reference.
FIELD OF THE INVENTION
The invention concerns a high-speed mass transfer tray utilized in processes to separate liquid-gas (steam) mixtures and for the absorption, rectification, and desorption of mixtures, mainly in such fields as the gas, petroleum, petrochemical, and chemical industry, as well as environmental protection and power technology. The primary range of applications is to be found in processes relating to the treatment of natural gas and processing of hydrocarbons at medium and high pressures on offshore platforms located on continental shelves and on the onshore (mainland).
BACKGROUND OF THE INVENTION
Certain proposed mass transfer tray constructions are equipped with contact and separation elements (CSE) featuring a firmly attached axial swirler at the inlet end and a cyclone separator at the outlet end (Inventor's Certificate USSR, No. 345926, Class B01D 3/20). The supply of the liquid into the contact zone is realized by two rows of annular holes. One is located in the area of the inclined vanes of the axial swirler, and the other is below the swirler. The disadvantage of this type of tray lies in the low level of effectiveness of mass transfer due to undesirable (parasitic) flows in two directions. The first undesirable flow occurs in the free space between the column shell and the CSE, with some part of the liquid flowing from the tray plate directly to the weir without having mass transfer contact with the gas phase. The second undesired flow concerns the backflow of liquid that has already finished the mass transfer process and is now flowing back from the separator to the annular holes, which are intended for supplying liquid for contact with the gas entering the CSE.
Furthermore, a swirler contact element is known (CSE) (inventor's certificate USSR No. 475160, Class B01D 3/30), containing a nozzle with a row of annular holes at its input end and a hollow cyclone separator at its output end. An axial swirler is firmly attached in the perforation zone and contains several inclined vanes. The nozzle features an annular rib at its outer side between the swirler and the separator.
Contrary to the CSE described above, this type of construction allows for a significant increase of the technical-economic performance parameters of the tray. The known CSEs, however, limit the intensity of the mass transfer and, thus, also the effectiveness of the tray.
Another highly effective swirler contact element is known (CSE) (U.S. Pat. No. 4,838,906, U.S. Class 55/238 and European Patent No. 0281628 B1). It contains a short nozzle with a row of annular holes at its input end and a complex axial swirler inside. The firmly attached axial swirler of this CSE has inclined vanes in the upper section and a dense net of short vertical vanes arranged lengthwise to the nozzle axis in the lower section, with the number of straight vanes being at least twice the number of inclined vanes. This cyclone separator may be operated in one or two stages.
Such a construction allows a significant increase of the effectiveness of the mass exchange and the separation of the phases within one single element. However, the mere arrangement of a series of CSEs on a tray does not guarantee the desired high level of mass transfer intensity. Due to the undesired (parasitic) flows on the tray past the CSEs and to the backflow from the separator exit via one deflection ring along the outer wall of the CSE to the annular holes to be once more in contact with the gas, the actual new liquid flow leaves the tray without establishing contact.
Experience collected during practical applications of the CSE in industry shows that not only is an optimal choice of the CSE dimensions and shape a necessity, but also required is an improved organization of the flow of liquids on a tray equipped with CSEs. Here it should be noted that no intensive mixing of the fluid through the gas bubbles occurs on CSE trays, which stands in contrast to bubble cap trays where an intensive thorough mixing of the liquids is performed while they flow from one side of the tray to the other.
SUMMARY OF THE INVENTION
The object of the invention is to design a high-speed tray with CSEs in such a way as to achieve a highly effective mass and heat transfer at high gas velocities by equipping the tray with specially constructed CSEs and tray elements, according to the F factors of 3.5 to 10.5
m
s
kg
m
3
relating to the full cross-section of the tray void with a tray distance of 400 to 600 mm.
The object of the invention finds its solution in the following layout. The mass transfer tray with CSE, the most important element, which consists of an open vertical nozzle resting with its lower end on the tray, and having at least one row of annular holes in the nozzle. A firmly attached axial swirler, with inclined vanes in its upper section and a dense net of short vertical vanes in its lower section arranged lengthwise in the area of the annular holes, is positioned within the vertical nozzle. A cyclone separator is located at the end of the nozzle with deflection rings between the separator and the annular holes. The tray is distinguished by the free cross-section of the CSE for the gas flow, amounting to 0.36 to 0.54 of the pipe cross-section after the swirler, while guaranteeing a maximum performance regarding the gas and liquid throughput and a high level of effectiveness for the mass transfer. In this case, each CSE, between the separator and the perforations, has at least two deflection rings whose diameter is equal to or slightly larger than the outer diameter of the separator, with the weir located at a height of 50 to 300 mm above the lower annular holes.
Such a constructive design of a high-speed contact tray with CSE guarantees a high level of effectiveness for mass transfer at high loads concerning the liquid and gas throughputs due to the larger free cross-section of the CSEs in the swirler zone, and the enlarged phase transfer area. A high level of effectiveness for mass transfer is also due to a preceding atomization of the liquid, which enters the contact element at high speeds, as well as due to the larger height of the liquid weir located above the lower row of annular holes.
In addition, the two deflection rings attached to the outer wall of the nozzle a defined distance from one another, between the cyclone separator and the annular holes, represent a reliable block for undesired backflow to the CSEs of the liquid already used during the mass transfer process.
The outer diameter of the deflection rings has to be at least as large as the diameter of the output end of the cyclone separator. However, in borderline cases, the ring diameter may equal the distance t between the two neighboring CSEs, as long as these components are distributed evenly across the entire tray.
It serves the functionality of the tray to arrange the upper deflection ring in such a way as to locate it below the upper edge of the spillover weir. The lower deflection ring should be distanced from the upper deflection ring by 0.2 to 1.0 times the inner diameter D
i
of the CSE.
Such a constructive design improves the barrier effect. The fresh liquid flow moves in the lower layer on the tray and enters the CSEs through the annular holes. After the mass transfer, the liquid separated in the cyclone separator essentially flows across the tray to the spillover weir as the upper flow layer and then discharges onto the tray below. This type of guidance permits maintaining a high mass transfer level on the tray.
Furthermore, it is also practical to attach vertical barrier baffles, especially on both sides of the liquid input and output sides, which eliminate undesired (parasitic) flows between the column body and the CSEs.
Such a constructive solution ensures the fresh liquid needed for the necess
Hartmann Klaus
Kiselev Victor
Chiesa Richard L.
Gesip mbH
Randall Tipton L.
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