Gas separation: processes – Liquid contacting – Gaseous fluid mixture discharged against or beneath surface...
Reexamination Certificate
1999-04-27
2001-04-03
Smith, Duane S. (Department: 1724)
Gas separation: processes
Liquid contacting
Gaseous fluid mixture discharged against or beneath surface...
C096S338000, C096S339000, C096S350000
Reexamination Certificate
active
06210468
ABSTRACT:
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
This invention is related to a novel apparatus for removing gaseous and particulate contaminants from a gas stream, and more particularly, to a novel gas scrubber and a method of use of the scrubber.
BACKGROUND
It is often necessary or desirable to remove contaminants from a bulk gas stream. Sometimes, process residuals must be eliminated from a carrier gas stream, and, in other applications, foul smelling or potentially hazardous or toxic compounds must be removed from a gas stream in order to satisfy safety and/or environmental concerns with respect to a potential or actual gaseous emission source.
I am aware of various attempts in which an effort has been made to improve the efficiency of a gaseous scrubber. For the most part, the efficiency of gaseous scrubbers which are known to me have one or more of the following shortcomings: (a) they generally require an independent liquid moving device, such as a pump, to effect liquid-gas contact, thus making them undesirable in applications where loss of electrical or other power source may be of concern; and (b) they often do not achieve a high separation efficiency in relatively simple equipment, in order to efficiently remove undesirable components from the exiting gas stream. Thus, the advantages of my simple, multiple-weir scrubber design, which may be utilized without an independent liquid moving device, in order to achieve high efficiency liquid scrubbing of an entering gas stream, are important and self evident.
OBJECTS, ADVANTAGES, AND NOVEL FEATURES
I have now invented, and disclose herein, a novel multiple weir scrubber design for enhancing the efficiency of contaminant removal from a gas stream. My scrubber design is simple, easy to manufacture, and otherwise superior to those designs heretofore used or proposed. In addition, it provides a significant, additional measure of efficiency in certain scrubber applications.
From the foregoing, it will be apparent to the reader that one important and primary object of the present invention resides in the provision of a multiple weir scrubber for improving the efficiency of removal of contaminants from a gas stream, by providing an improved liquid/gas contact flow path.
Other important but more specific objects of the invention reside in the provision of a multiple weir scrubber as described herein which:
can be manufactured in a simple, straightforward manner of materials suitable for the anticipated service;
in conjunction with the preceding object, have the advantage that they can be adapted by installation personnel to quickly fulfill a desired scrubbing requirement;
which utilize as a motive force the differential pressure between the gas inlet and the gas outlet for maintaining the liquid level in various compartments between successive weirs;
which can be manufactured in cylindrical shapes with annular weirs;
which can be manufactured in parallelepiped shapes, with planar weirs;
which in a relatively inexpensive manner, can improve performance, particularly removal efficiency, in scrubber applications.
Other important objects, features, and additional advantages of my invention will become apparent to the reader from the foregoing and from the appended claims and the ensuing detailed description, as the discussion below proceeds in conjunction with examination of the accompanying drawing.
SUMMARY
I have now invented, and disclose herein, a novel multiple weir apparatus useful for removing undesirable contaminants from a flowing gas stream. My scrubber device is designed for use to achieve high efficiency removal of contaminants without the necessity to provide mechanical circulation of the scrubbing liquid. The multiple weir scrubber receives, through an intake passageway, an incoming gas stream from which removal of certain gaseous or particulate components is desirable. The gas stream is received in the scrubber in a first gas chamber at pressure P
1
and turned downwardly into a first pool of scrubbing liquid with liquid level L
1
. The gas stream components which are not absorbed by or reacted with the scrubbing liquid are allowed to escape downstream and upwardly after passing a first underflow weirs UW
1
. The first underflow weir is preferably provided with a plurality of passageways, most preferably V-shaped notches at the lower reaches of the weir, to enhance gas-liquid contact as the gas passes under the first underflow weir UW
1
. The gas stream then traverses a first overflow baffle BO
1
in a second gas chamber at pressure P
2
. At that point, the gas stream is then directed downwardly and into a second pool of scrubbing liquid with liquid level L
2
. The gas stream components which are not absorbed by or reacted with the second pool of scrubbing liquid are allowed to escape downstream and upwardly after passing a second underflow weir UW
2
. The gas stream then traverses a second overflow baffle BO
2
in a third gas chamber at pressure P
3
. The process is repeated as many times as desired, until the gas stream emerges from a final pool of scrubbing liquid at liquid level L
N
and into a final gas chamber at pressure P
N
from which it is discharged through a clean gas outlet.
In a preferred embodiment, the scrubbed gas flow passes exiting the final pool of scrubbing liquid passes through mass transfer packing, and more preferably additionally passes through a final mist eliminator (usually of the wire mesh type) before leaving the scrubber through a gas exit nozzle.
Importantly, energy from the gas pressure and gas movement circulates the scrubbing liquid within the scrubber. Similarly, the gas flow circulates final scrubbing liquid through the mass transfer packing bed. It is an important consequence that no liquid pump is required.
Scrubbing liquid is changed batchwise, as required. Alternately an underflow of scrubbing liquid can circulate counter-currently with respect to the flow of the gas to be scrubbed; it must be appreciated in such cases that a portion of scrubbing liquid flows co-currently with the gas flow over the successive overflow baffles.
Structurally, in a preferred, annular arrangement, the scrubber is supported by a conventional tank support skirt with a lower peripheral support ring. For batchwise applications, a drain line is provided in the lower reaches of the scrubbing liquid containing tank portion to allow removal of waste, contaminated scrubbing liquid, as well as the recharge of fresh scrubbing liquid. Alternately, a parallelepiped shape container may be used to employ my novel scrubber design.
My novel multiple weir scrubber device employs the differential pressure between the inlet and outlet gas flow in order to develop surface area for exposure between the bulk liquid and the bulk gas phases. The gas being scrubbed passes under a set of vee-shaped notches in weirs, and carries some liquid over successive overflow baffles, and carries some liquid into a final mass transfer packing bed. Importantly, the energy from the gas velocity and movement circulates liquid within the scrubber, and through the packed bed. Thus, an independent liquid moving device such as an electric drive pump, is not needed. This is an important advantage in emergency gas scrubber situations, or for gas streams containing combustible gas mixtures.
The novel multiple weir scrubber device described and claimed herein provides a high efficiency, and the unique advantage that no liquid pump is required, compared to conventional scrubbers for similar applications which are known to me. This performance factor is significant in various types of high performance air pollution control applications. There, the thorough liquid/gas mixing and fluid flow design made possible by my unique mult
Goodloe, Jr. R. Reams
Smith Duane S.
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