Gas separation: processes – Liquid contacting – And deflection
Reexamination Certificate
2002-12-16
2004-06-22
Smith, Duane S. (Department: 1724)
Gas separation: processes
Liquid contacting
And deflection
C055SDIG007, C096S275000, C096S323000, C118S326000, C261SDIG003
Reexamination Certificate
active
06752854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a new and useful invention concerning fluid curtain scrubbing of gas borne waste material, a scrubber device, and a method for capture of the gas borne waste materials. The waste material may be a liquid waste entrained in a gas, such as paint entrained in air after spraying the paint onto an article in a spray booth, a particulate waste entrained in a gas, such as dust contained in flue gas, and/or a gaseous waste, such as NO
x
or SO
x
contained in flue gas, by way of example but not limitation. The fluid curtain may be a gas such as air or a liquid such as water or a solvent.
More particularly, the invention relates to a venturi scrubber plate and a waste capture system and method employing the venturi scrubber plate. In one embodiment useful as a waste paint capture system for a paint spraying booth, water flows down a flood sheet positioned downstream of paint spray heads and entrains paint overspray to minimize buildup of paint on the interior of the booth. The water from the flood sheet flows into a trough which additionally receives water from a primary scrubber section. An exhaust fan draws air from the spray booth through the trough and through a throat section leading to the primary scrubber section where a flow of water knocks down remaining waste materials from the air flow before it is exhausted through the exhaust fan. Waste paint capture is improved by positioning a perforated plate over the trough so that the waste paint laden air from the spray booth is sucked through the perforated plate with an advantageous venturi scrubbing effect.
The novel venturi scrubber plate is configured to effectively control air velocity through the plate, preferably in a range of from about 1000 to about 2000 linear feet per minute. This advantageously results in a high turbulence profile for the flow akin to misting or atomization which improves paint capture by up to a factor of three times. Contact with paint detacification chemicals contained in the water is advantageously improved so that paint particle formation is inhibited and dectacification efficiency increased.
2. Description of the Prior Art
Scrubbers are know and work on the general principle of employing a fluid curtain to entrain gases, droplets and/or particles. Passing a stream of airborne material through a water curtain, for example, serves to at least entrain and possibly dissolve (a) gases, such as NO
x
and SO
x
contained in flue gases, (b) droplets, such as waste paint from a spray operation or any entrained liquid in droplet form, and/or (c) particles, such as fly ash contained in flue gas or powder from an electrostatic coating operation such as paint, sugar, salt, or other such commodities.
The scrubber curtain is typically a water curtain, but may be almost any fluid including liquids, such as solvents, for example, alcohols having 1-8 carbon atoms, and gases, such as a curtain of air or inert gas,flowing at a rate chosen to be effective to knock down material to be removed.
Fluid curtains are known in the art as described in, for example, U.S. Pat. Nos. 4,700,615 and 4,946,718 to Stanley Napadow, the disclosures of which are herein incorporated by reference.
U.S. Pat. No. 4,946,718 describes an air curtain protection system for article conveyors of product treatment booths including a paint spraying booth, washer or filter air cleaning system, and baking oven. Product support members extend through a slot provided in a conveyor mechanism housing into the product treatment booth. A blower forces ambient air through a supply nozzle formed by a plenum on one side of the slot and draws air through a suction nozzle formed by a second plenum on the opposite side of the slot to form a high velocity stream or curtain of air across the slot. This reduces the ingress of deleterious heat or atmosphere from the product treatment booth into the conveyor mechanism housing so that a measure of protect is afforded the conveyor and heat is conserved.
A spray booth including both air and water curtains is described in U.S. Pat. No. 4,700,615. Air flows from a plenum provided under a roof assembly of the booth down to the floor and through side plenums and a throat to wash the interior side walls as an air curtain to prevent adherence of paint particles on the side walls. Water curtains are provided within an air cleaning apparatus positioned under the booth floor through which the down flowing air from the spray booth is pulled by a blower. The flowing air is directed through a series of water curtains to an outlet slot where the air velocity is increased and then slowed down in a larger volume separation chamber where water and air are separated. The direction of air and water flow are reversed several times as the air flows serially through the water curtains the concept being to obtain turbulent air/water mixing so that the particles are wetted and brought down by their increased weight. The water and air are discharged into a large precipitation chamber in which the water is collected and the air velocity is reduced substantially before discharge through an air exhaust duct.
An additional waste paint capturing system
10
currently used in an industrial, high volume spray booth is schematically illustrated in cross-section in
FIG. 1
(Prior Art). Articles
1
are transported by a conveyor means
5
through spray booth
10
. Spray heads
15
direct paint
20
onto the articles
1
. An exhaust means
25
removes air
30
and paint overspray
35
from the booth as an air flow
40
to a primary scrubber section
45
which includes a clean water supply means
46
and a water curtain
48
. Within the booth
10
, water
50
flows from a clean water supply means
55
down a flood sheet
60
positioned downstream of paint spray heads
15
and entrains paint overspray
35
to minimize buildup of paint on the interior of booth
10
. The water
50
from the flood sheet
60
flows as a water curtain
65
into a trough
70
which additionally receives water
48
from the primary scrubber section
45
. The exhaust means
25
draws the air flow
40
from the spray booth
10
across the trough
70
, through the water curtain
65
and through a throat section
75
leading to the primary scrubber section
45
where the flow of water
48
wets and knocks down remaining waste paint
35
from the air flow
40
before it is exhausted through exhaust means
25
. The industry standard air velocity across the throat section
75
of the primary scrubber section
45
for effective water wash scrubbing of paint overspray ranges from 1500 to 1750 linear feet per minute. A flow of scrubbed air
80
exits the paint capturing system
10
through the exhaust means
25
.
The effectiveness of such conventional waste capture systems including scrubbers to entrain and remove waste gases, droplets and/or particles leaves much to be desired, however. The costs of downtime and filters required for general maintenance and cleaning of waste capture systems remains excessive, particularly waste paint capture systems where accumulations on booth surfaces is a substantial problem.
Accordingly, it is an object of the present invention to provide a waste material capture system and method having a higher efficiency of waste material capture whether solid, e.g., flue dust or particulates from a powder or electrostatic spray operation such a commodities, for example, sugar and salt, liquid, e.g., paint or other sprayable compositions, or gaseous, e.g., noxious gasses such as NO
x
and/or SO
x
, than that previously known in the prior art.
It is another object of the present invention to provide a waste material capture system and method which permits significantly reduced downtime for cleaning of surfaces, changing of filters, and general maintenance, and thereby significantly reduces operational costs.
It is yet another object of the present invention to provide a waste paint capture system which permits significantly reduced downtime for cleaning of spray booth surfaces, changing
Deitz Michael Shane
Varone Russell
Burdett James R.
Graham Packaging Company L.P.
Haddaway Keith G.
Smith Duane S.
Venable LLP
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