MULTI-STAGE GAS SCRUBBER

EPURATEUR MULTI-ETAGE DE GAZ

English Abstract

Abstract of the Disclosure
This invention relates to an acid rain eliminator having a very low gas-
phase pressure drop in a spray type multi-stage wet scrubber. It can be
mounted on an existing stack or beside it. Its internal components are an
assembly of vertically spaced cones receiving high velocity mist-like
droplets between the cones and an outer housing. Two orientations of spray
nozzles are used. The natural buoyancy of the hot gases in the stack forces
those gases through the scrubber. No fans or motors are needed.

Claims

The embodiments of the invention in which an exclusive property
or privilege is claimed are defined as follows:
1. A variable stage scrubber for an industrial stack, comprising
an upright cyclinder, an internal assembly of spaced scrubber
cones having a smaller diameter than the inner diameter of the
scrubber providing an annular scrubbing zone there between,
ring header nozzles at the base of each cone and cone cleaner
nozzles at the apex of each cone, wherein each of the header
nozzles and each of the cleaner nozzles are adapted to emit
a high velocity mist-like spray and are positioned to direct
a major portion of said spray directly into said annular
scrubbing zone and against the inner wall of the scrubber.
2. The scrubber of claim 1 including means to selectively supply
scrubbing liquid to said ring header nozzles and said cone
cleaner nozzles.
3. The scrubber of claim 1 further comprising an annular collection
trough: at the base of the scrubber to collect spent scrubbing
liquid and means to transport the liquid from said trough to
a storage means.
4. The scrubber of claim 1 haaving wall sections insertable and
removable for scaling up and down between a single stage scrubber
and a multi-stage scrubber.
5. The scrubber of claim 1 in a side by side mounting with an
industrial stack, having a lower inlet duct to the scrubber and
an upper outlet duct from the scrubber and damper means in
each duct.

Description

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This invention relates to a stack mounted gas scrubber or washing apparatus
or acid rain eliminator for industrial, institutional and major residential
apartment installations.
The stack emission gas that must be eliminated include carbonaceous andinorganic particulates as well as sulfur oxides, carbon oxides, nitrous
oxides, and other undesirable gases. The liquid which is used for scrubbing
the deleterious components is usually water but could include chemical
additives for better gas absorption and, to neutralize their negative impact
in the liquid phase.
The scrubher of the present inventlon uses vertically stacked cones in
combination with controlled water spraying over their conical surfaces and
into an annular space be-tween the cones and an outer containment housing.
The angle of spray may be varied.
Two orientations of spray nozzles are used. Ring header nozzles are used for
gas liquid contacting and to improve the liquid to gas ratio. Cone cleaner
nozzles are used where heavy particulates, produced from the burning of wood
waste are encountered. The size of spray droplets and velocity of the liquid
phase are varied to achieve optimum performance.
The entire annular space between the cones and the outer housing is scrubbed
by high velocity mist~like droplets. After striking the outer housing, the
spray droplets flow by gravity downward to an annular collection trough. The
collected liquid can then be piped to a storage tank for treatment. It may
be necessary to increase the alkaline content of the liquid to offset the
acidic gases encountered in the scrubber.
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The measured performance for the acid rain eliminator is as follows:
Particulate removal efficiency in excess of 75~. Sulfur dioxide, sulfur tri-
oxide, CO, C02, NOx gas emissions reduced by 75X to 90~.
Boiler fuel can be virtually anything burnable. Examples are Bunker oil C,
rubber, hog fuel and other waste materials.
An inverted demister cone is at the top of the multiple cone assembly and
reduces the escape of water droplets to the atmosphere.
It shnuld be noted that multiple cones provide multiple stage scrubbing and
that a single stage scrubber is an embodiment of applicant's invention in a
simpler form.
In summary, the acid rain eliminator is a low energy preformed spray-type
wet scrubber. Based on temperature, velocity of stack gas and the quality of
emissions, the scrubber can be designed for single stage scrubbing or for
multiple stage scrubbing. It can be mounted on an existing stack or beside
it.
The unit is designed for a very low gas-phase pressure drop. Hence, the
natural buoyancy of hot gases rising up the chimney provide the energy
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required to force the flue gas through the scrubber. Equipment such as fans
and motors is not needed. also, hot stack gases minim ke corrosion of the
stack liner.

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In further description of the invention reference is made to the
accompanying drawings wherein,
Figure 1 is a perspective view of a multiple stage
scrubber with the housing broken out,
Figure 2 is a vertical section of a stack mounted
scrubber and,
Figure 3 is a vertical section of a scrubber
mounted beside the stack.
Figure 1 shows a three stage scrubber having vertically stacked co-axial
cones in a cylindrical housing 1. The cones bear designations 2 and a
demister cone is shown at 3. A skirt portion 4 provides an annular
collection trough at the base of the scrubber. A trough drain is shown at 5.
The slow of hot gases upwardly through the scrubber is shown by the arrows.
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Liqu;d spray means that impinge against the cones and into spaces between
cones and into spaces between cones and into the annular space surrounding
the cones is shown in Figure 2.
Ring header nozzles are shown at 6 and are at three levels for a three stage
scrubber. Cone clèaner nozzles 7 are at the apcies of the cones and again at
three levels. The lower cone cleaner shows discharge nozzles at 8. Thus,
spray patterns impinge the desired surfaces and, for certain conditions, may
; overlap. The spent spray droplets fall into the collection trough at the
base of the scrubber. A flanged connection D mounts the scrubber on an
existing stack. Removable ring connectors la permit scaling down the housing
1.

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Figure 3 shows a scrubber mounted in a lower inlet duct 10 leads from the
stack to the base of the scrubber and has a pair of inlet dampers 11. A
return duct 12 from the top of the scrubber to the stack has a single damper
control 13. The inner components of the scrubber are not revealed in this
view since they are the same as in Figure 2.
Further to Figure 3, a liquid storage tank 14 is connected to treatment
units for the removal of particulates and other acidic emissions. These
units are shown collectively at 15. Recycled water and city makeup water are
combined to form the water supply for the nozzles. A pipe head and branch
rùns are shown at 16. heat in the storage tank water may be extracted by
means of a heat exchanger.
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