Exhaust gas scrubber and filter assembly

An exhaust treatment system having a water scrubber, a centrifugal water trap for removing water droplets from exhaust flow and a filter for cleaning exhaust gases. The components are housed contiguously so that exhaust piping is not needed between the components. The water trap includes a frustoconical peripheral wall and a plurality of conduits having apertures for directing exhaust obliquely against the wall. The conduit apertures face in the same rotational direction to generate a rotational circulation of exhaust within the trap, which is entirely encircled by an annular filter. The water trap and filter are housed in a portion of the housing that is a low profile flat disc shaped to extend only a limited distance above the scrubber to which it is directly attached.

TECHNICAL FIELD 
This invention relates to exhaust treatment systems for internal combustion 
engines, and more particularly to such systems incorporating water 
scrubbers and particulate filters. 
BACKGROUND OF THE ART 
Reducing the pollutants and high temperatures of internal combustion engine 
exhaust gases and the temperatures of hot surfaces in underground mining 
vehicles is essential to the safety of mine personnel in underground coal 
mines. Diesel engines exhaust hot sulphurous gases, aldehydes, nitrogen 
oxide, unburned hydrocarbons and particulate pollutants. Hot exhaust 
emissions, typically 800.degree.-1000.degree. F., and hot engine surfaces 
can ignite combustible gases and material present in underground mines, 
such as methane and coal dust. 
Water jacketing the engine's exhaust manifold and piping in conjunction 
with the engine's cooling system reduces engine surface temperature 
sufficiently to meet safety requirements. However, the safety hazard and 
pollution problems caused by hot exhaust emissions require water 
scrubbers. Scrubbers either aspirate water into the stream of hot exhaust 
gases or bubble exhaust gases through a water bath to cool them, as shown 
in U.S. Pat. No. 4,300,924 to Coyle, the disclosure of which is 
incorporated herein by reference. Because these scrubbers introduce water 
droplets into the exhaust stream, a water trap is required between the 
scrubber and a downstream filter element to prevent water from entering 
the filter. Water traps typically employ a series of interleaved plates to 
create a labyrinthine path for exhaust gases. Droplets incident on the 
plates adhere to the plates and are drained away. Without such a water 
trap, the filter elements become blocked, degraded and damaged as they 
become wetted by water droplets in the exhaust stream. 
Current exhaust treatment systems use separate water scrubbers, water 
traps, and exhaust filters in series interconnected by exhaust tubing. 
Such an elongated serially connected system has several disadvantages. If 
the system is vertically oriented, it is unsuitable for use in most 
underground mining operations where vertical height is at a premium. The 
necessary horizontal orientation generally requires substantial lengths of 
tubing between the components to span between the engine location and a 
suitable exhaust outlet location, typically at the rear of the vehicle. 
Exhaust tubing must be stainless steel to avoid corrosion. Consequently the 
material cost to construct such an elongated system can be substantial. A 
serially connected system of discrete components is generally cumbersome 
to construct and install as well. 
In addition, the substantial tubing length creates an efficiency-impairing 
exhaust back pressure that wastes fuel and decreases vehicle performance. 
A further disadvantage of serial systems interconnected by substantially 
horizontal tubing lengths is that, even with an effective water trap, 
gaseous water vapor is more likely to condense as it travels further from 
the source. If there is a sufficient temperature gradient between the 
scrubber and the filter, condensation may occur in the cooler tubing near 
the filter. Such condensation may drain into the filter, causing damage, 
impairing filter function and requiring its premature replacement. 
Because of the foregoing problems associated with existing water scrubber 
and water trap-filter systems, there is a need for an effective system, 
especially for underground mining vehicles, that overcomes such problems. 
This, therefore, is the primary objective of the present invention. 
SUMMARY OF THE INVENTION 
Other important objects of the invention are to provide: 
A scrubber and filter system as aforesaid in which the system is contained 
within a compact package that does not protrude above a limited height. 
A system as aforesaid which is integrated into a single unit to limit the 
amount of exhaust tubing required. 
A system as aforesaid which is simple to construct and install. 
A system as aforesaid which creates a limited exhaust back pressure. 
A system as aforesaid which has a limited temperature differential through 
the system so that water reaching the filter remains in a gaseous form. 
According to the illustrated embodiments of the present invention, the 
primary objects are achieved by providing a unitary system having a 
scrubber, a water trap and a filter. The system includes a conventional 
cylindrical scrubber in a cylindrical housing, with a disc-shaped upper 
housing for a water trap and filter attached directly above the scrubber 
housing. The upper housing includes a central exhaust inlet and includes 
an annular water trap surrounding the inlet. In one embodiment the water 
trap comprises a series of annular plates concentrically arranged. The 
annular plates are alternately attached to the top and bottom plates of 
the housing to create a labyrinthine radially outward path for the exhaust 
gases. Drain tubes permit collected water to flow from the water trap. In 
another embodiment, a centrifugal-type water trap is provided. In both 
embodiments, an annular air filter for radial transmission of exhaust 
gases is placed within the housing to circle the water trap. An exhaust 
gas outlet exits the housing at its periphery.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
As shown in FIG. 1, an exhaust treatment system 10 is attached to the body 
12 of a mining vehicle having an upper surface 14. The exhaust treatment 
system 10 has a lower portion 16 including a water scrubber 28, and an 
upper portion 18 including a water trap 22 and air filter 24, as shown in 
FIG. 3. The lower portion 16 is a vertical cylinder, and the upper portion 
18 is a squat, vertical cylinder coaxially aligned with the lower portion 
(as shown in FIG. 2) and attached directly above the lower housing 
portion. The lower scrubber portion 16 does not extend above the vehicle 
body upper surface 14. Thus, the entire system 10 protrudes above the body 
surface by an amount limited to the height of the low profile upper 
portion 18. 
As best shown in FIG. 3, the scrubber 28 has a horizontal flange 30 
attached at its upper end and extending outwardly therefrom. A horizontal, 
generally circular top plate 32 is coextensive with the flange 30 and 
attached thereto to cover the upper end of the scrubber 28. The top plate 
32 is open near its center to define a D-shaped scrubber outlet aperture 
36 offset a limited distance from the center of the scrubber top plate 32 
as shown in FIG. 2. A rubber gasket sheet 34 is coextensive with and rests 
upon the top plate, and defines apertures to correspond to those in the 
top plate. 
The upper portion 18 includes a horizontal base plate 38 on top of and 
connected face-to-face with the scrubber top plate 32, with the gasket 34 
sandwiched therebetween by bolts 39 connecting the periphery of both 
plates to flange 30. Top plate 32 and base plate 38 effectively form a 
common shared wall between the lower housing 16 and the upper housing 18. 
The base plate 38 is generally circular, and is generally coextensive with 
the scrubber top plate 32, except for a protruding peripheral lobe 40 
extending beyond the scrubber top plate 32 at one side. The base plate 38 
further defines a water trap inlet 44 shaped and sized like the scrubber 
outlet aperture 36 and registered therewith. An upper cylindrical wall 46 
is attached at the periphery of the base plate 38 and rises upwardly 
therefrom to a limited height defining the overall height of the upper 
housing 18. An outlet chamber wall 48 rises vertically from the periphery 
of the base plate at the base plate lobe 40 to a height somewhat less than 
the height of the upper cylinder wall 46, with an upper plate 50 
horizontally spanning between the upper edge of the chamber wall 48 and 
the cylindrical wall 46. 
A threaded spindle 52 is attached to the center of the base plate 38 and 
protrudes upwardly therefrom to a height slightly above the upper edge of 
the upper cylindrical wall 46. A flat, circular removable lid 54 has a 
peripheral gasket 56 and is sized to be sealably received within the upper 
cylindrical wall 46 just below the upper edge thereof and well above the 
level of the outlet upper plate 50. The lid 54 defines a central aperture 
60 sized to closely receive the spindle 52. A wing nut 62 threadably 
engages the spindle 52 after the lid has been installed to prevent removal 
of the lid and leakage through the central aperture 60. 
As further shown in FIG. 3, the annular water trap 22 is formed within the 
upper housing portion 18 and includes a series of vertical annular walls 
concentrically arranged within the air filter 24. A first innermost trap 
wall 68 is concentric with the spindle 52 and attached to the base plate 
38 to extend vertically upward therefrom to a height of approximately 
one-third that of the upper cylindrical wall 46. The first trap wall 68 
has a diameter sufficient to entirely encompass the trap outlet 44. A 
second intermediate trap wall 70 is externally concentric with the first 
trap wall 68, and depends downwardly from the removable lid 54 by a 
distance more than half the height of the upper cylindrical wall 46. 
Therefore, there is appreciable overlap between the first trap wall 68 and 
the second trap wall 70. The diameter of the second trap wall 70 exceeds 
that of the first wall 68 by a sufficient amount to define a trap gap 71 
having a limited width where the walls overlap. 
A third trap wall 72 projects upward from the base plate 38 and has a 
diameter slightly greater than the second trap wall 70 so that the third 
wall 72 is positioned concentrically outside thereof and overlapping 
therewith. 
A central chamber 76 is defined in the upper housing 18 within the trap 
walls, above the base plate 38, and below the lid 54. An annular water 
collection channel 78 is defined between the first trap wall 68 and third 
trap wall 72, and above the base plate 38. The base plate 38 defines a 
drain hole 80, as shown in FIG. 2, within the channel 78. The drain hole 
communicates with a drain tube 84, which extends downwardly through lower 
scrubber housing portion 16 and outwardly from the system. The drain tube 
has a substantial diameter of 7/8 inch to facilitate cleaning, but has a 
removable narrow aperture outlet (not shown) to minimize the emission of 
unfiltered exhaust. 
As shown in FIG. 3, an annular chamber 86 is formed within the upper 
housing portion 18 externally of the water trap 22. The annular filter 24 
fits within this chamber 86. The filter 24 has a lower annular gasket 88 
sealed against the base plate 38 and an upper annular gasket 90 sealed 
against the lid 54. Consequently, exhaust gas entering chamber 86 from the 
water trap must pass radially outward through the chamber 86 entirely 
through filter element 24. 
An outlet chamber 94 is defined at one side of the filter by the peripheral 
lobe of the base plate 38, the outlet chamber wall 48 and upper plate 50. 
The base plate lobe 40 defines a circular outlet hole 98 that communicates 
with a downwardly depending outlet tube 102. The outlet tube 102 opens 
into a mixing chamber 104 attached to the vehicle for diluting the emitted 
exhaust gas with ambient air. An optional horizontal outlet 108 in 
communication with the annular chamber 86 may be provided if the vehicle 
configuration dictates. 
As shown in FIGS. 2 and 3, a scrubber exhaust gas temperature sensor 
chamber 110 is attached to the underside of the scrubber top plate 32 and 
encompasses the scrubber outlet aperture. The chamber contains a 
temperature sensor 114 provided by a heat sensing hydraulic valve operably 
connected to a vehicle engine shutdown system (not shown). The chamber 110 
defines a lower aperture 116, through which all exhaust gas flows. The 
exhaust gas subsequently passes over the sensor 114, and through aperture 
36 into the upper portion 18. When the scrubbed exhaust gas exceeds a 
predetermined temperature, preferably no more than about 180.degree. F, 
the sensor causes engine shutdown to prevent overheating and burning of 
the filter 24. 
OPERATION 
The scrubber contained within the lower housing portion 16 operates 
conventionally to cool the engine exhaust with water and remove some 
particulates therefrom. The treated exhaust gases pass upwardly through 
the scrubber outlet aperture 36 and water trap inlet 44 to enter the 
central chamber 76 of the upper housing portion 18, as shown by flow path 
arrows 106. The exhaust gases, which contain suspended water droplets, may 
exit the central chamber 76 only by passing through the water trap. 
To pass through the trap, the gases first flow down through the gap 71 
between the first trap wall 68 and second trap wall 70. As the gases flow 
through the gap 71, the flow velocity necessarily increases, accelerating 
the suspended droplets. The gases then exit the gap downwardly into the 
water collection channel 78, which is more than twice as wide as the gap 
between the first and second trap walls. Accordingly, the velocity of the 
gas diminishes, while the suspended water droplets tend to retain their 
momentum until they impact within the channel. When a droplet contacts any 
surface of the three vertical trap walls, it generally adheres and drains 
downward into the water collection channel 78. 
The gases abruptly reverse direction, proceeding upward between the second 
trap wall 70 and third trap wall 72 with essentially all of the suspended 
water droplets having been collected in the channel 78. The exhaust gases 
are then forced radially outward by the sealed upper end of chamber 86, 
through the filter 24 into the peripheral region between the filter and 
the upper cylindrical wall 46, wherefrom the gases are exhausted through 
the outlet chamber 94 and outlet tube 102. The venturi effect of gases 
exiting the outlet tube 102 draws a stream of fresh air 108 downward into 
the mixing chamber 104 to dilute and cool the exhaust gases. 
The apparatus may be opened for cleaning and filter replacement by 
unscrewing the wing nut 62 and removing the lid 54 to provide access. 
EXAMPLE 
In the preferred embodiment, the system employs an exhaust gas scrubber 
such as shown in U.S. Pat. No. 4,300,924 to Coyle, with the scrubber being 
modified so that the outlet emits exhaust through the horizontal upper 
plate. Accordingly, the water trap and filter portion may be retrofit onto 
an existing scrubber. The upper housing 18 has a diameter of about 25 
inches and rises to a height of about 101/2 inches above the scrubber 
upper surface. The water trap 22 is arranged so that the narrowest gap 71 
between adjacent concentric trap walls is about 3/8 inch, and so that the 
walls vertically overlap by about 1 inch The filter is preferably a paper 
type, model number P5300270, available from Donaldson, Inc., of 
Minneapolis, Minn. Due to the corrosive nature of the exhaust gases and 
fluids, stainless steel is the preferred material throughout the system. 
ALTERNATIVE PREFERRED EMBODIMENT 
FIG. 4 illustrates an alternative exhaust treatment apparatus 120 that has 
a similar function and structure to the apparatus 10 of FIG. 1, except 
that it includes an alternative centrifugal water trap 122. This has been 
found in practice to be an improvement over the first embodiment, because 
the exhaust system back pressure is reduced. 
The water trap 122 includes a frustoconical sidewall 126 that is sealably 
attached at a lower edge 128 to the upper surface of the base plate 38. 
The sidewall 126 is tapered to be downwardly open so that its lower edge 
128 has a larger diameter than its upper edge 130. Consequently, the 
sidewall 126 has an interior surface 134 that faces inwardly and 
downwardly, and an exterior surface 136 that faces outwardly and upwardly. 
In the illustrated embodiment, the interior surface 134 is smooth and has 
a circular cross sectional profile to facilitate circulation within the 
chamber. However, a non-circular profile may be employed as an alternative 
embodiment, and the interior surface 134 may include ridges or other 
protrusions (not shown) to capture water droplets in the circulating flow. 
An annular dam plate 140 is sealably attached at its periphery to the upper 
edge 130 of the sidewall 126. The dam plate 140 defines a circular central 
exit aperture 142. Together, the base plate 38, sidewall 126, and dam 
plate 140 define a water trap chamber 144 that is oriented on a vertical 
axis 146 coincident with the major axes of the scrubber 28 and upper 
cylindrical wall 46. 
As shown in FIG. 5, three elbow-shaped, right angle inlet conduits 148 are 
attached to the base plate 38 in registration with corresponding base 
plate apertures 150 (shown in FIG. 6) to provide means for 1) venting 
exhaust from the scrubber chamber 28 to the water trap chamber 144, 2) 
directing exhaust obliquely against the interior surface 134 of the water 
trap sidewall 12, and 3) circulating gas within the chamber by generating 
a vortex of gas rotating or orbiting about axis 146. Each inlet conduit 
148 has an exit aperture 152 that is circular and oriented in a vertical 
plane. 
As shown in FIG. 4, the water trap 122 preferably includes three inlet 
conduits 148, although alternative embodiments may include one or more 
such conduits, or other means for generating rotation of a fluid within a 
chamber. A duct 154 associated with one of the conduits 148 is attached 
below the base plate 38, such that all of the exhaust passing through the 
conduit must first pass through the duct, in the manner of chamber 110 
shown in FIG. 3. The duct 154 contains a temperature sensor (not shown.) 
The conduits 148 are positioned near the sidewall 126, so that they are 
almost entirely protected from above by the sidewall 126 and dam wall 140. 
The apertures 152 are located entirely beneath the dam wall 140 so that 
emissions from the apertures cannot readily exit the chamber 144 
vertically. The exit apertures 152 all face in the same rotational 
direction. Each conduit's exit aperture 152 is positioned in a plane 
slightly forward of and parallel to a respective vertical plane radiating 
from the axis 146. 
In the illustrated embodiment, the apertures face counterclockwise as 
viewed from above. Instead of facing radially outward from the center of 
the chamber, the conduits each point in a direction offset at an angle 
from the radial direction. Preferably, the conduits point in a direction 
substantially tangent to sidewall, such that the direction of exhaust flow 
passing through or exiting from the conduit is parallel to an imaginary 
line tangent to a portion of the sidewall near or nearest the flow. Thus, 
an exhaust flow 156 exiting each aperture 152 is directed obliquely 
against the interior surface 134. That is, the flow 156 will be deflected 
by the side wall by an angle of less than 90 degrees, and preferably less 
than 45 degrees. 
Accordingly, large water droplets suspended within the exhaust flow 156 
will directly impact on the interior surface 134 and adhere thereto. The 
sustained rotation of gas within the water trap chamber 144 will cause 
such droplets to progress circumferentially about the chamber, and 
downwardly toward the base plate 38 due to the slope of the interior 
surface, the centrifugal effect of such circumferential motion, and 
gravity. Smaller droplets remaining suspended within the exhaust flow 156 
for longer periods may be carried by the vortex of rotating gas within the 
chamber 144 until the effect of centrifugal force draws such droplets to 
contact the interior surface 134. A flow of dewatered gas 158 then exits 
the chamber 144 through the dam plate exit aperture 142. 
The exit aperture 142 is large enough to avoid creating unnecessary back 
pressure in the exhaust system, but is small enough to permit a 
sufficiently wide annulus to create an upper barrier for containing within 
the dewatering chamber 144 the peripheral flow of the vortex. In the 
alternative embodiment, the exit aperture 142 preferably is slightly more 
than one-half the diameter of the dam plate 140, although this dimension 
may be as small as one-quarter of the plate diameter where the filter 24 
is highly sensitive to moisture. The dam plate 140 may be eliminated 
altogether in cases where exhaust moisture is not a substantial concern. 
Means for draining water from the water trap chamber 144 is provided by a 
central drain aperture 162 and a peripheral drain aperture 164 defined in 
the base plate 38. An enclosed drain channel 166 is attached below the 
base plate 38 below the drain apertures 162, 164. The channel 166 empties 
into a drain conduit 168 which communicates with a drain reservoir (not 
shown). The peripheral drain aperture 164 primarily collects fluid 
collecting near the lower edge 128 of the trap sidewall 126; the central 
aperture 162 is positioned at or near the center of the base plate 38 to 
collect water that tends to pile up in the center of the plate at the low 
pressure region created by the inward and upward flow of the dewatered gas 
exiting the chamber. 
The tapered exterior surface 136 of the water trap sidewall 126 provides a 
guide to facilitate the installation of the air filter 24. The outside 
diameter of the sidewall 126 at its lower edge 128 is slightly smaller 
than the interior diameter of the filter 24. Thus, the filter position is 
constrained by the sidewall, but is allowed slight lateral free play so 
that the filter may compress fully downward against gasket 88 to provide a 
seal against the base plate 38. Unlike the embodiment shown in FIG. 3, the 
lid 54 is attached by peripheral over center clamps (not shown), instead 
of by the threaded central spindle. Also, the filter illustrated in FIG. 5 
has a taller aspect ratio and a larger surface area than that shown in 
FIG. 3. This increases filter life and reduces exhaust back pressure, 
although the height and filter chamber design may be varied depending on 
the application. 
Having illustrated and described the principles of the invention by what 
are presently preferred embodiments, it should be apparent to those 
skilled in the art that the illustrated embodiments may be modified 
without departing from such principles. For instance, the means for 
generating circulation within the water trap chamber may be provided by 
structures other than the tangentially directed conduits 148. Orbital air 
flow may be generated by tangentially directed louvers formed in the base 
plate, or by a rotating element such as a turbine within the chamber, 
powered by an external source or by exhaust gas flow. Also, the sidewall 
126 need not be conical with a circular cross section. A polygonal or 
straight-walled chamber boundary may provide the desired circulating flow. 
We claim as our invention not only the illustrated embodiments, but all 
such modifications, variations and equivalents thereof as come within the 
spirit and scope of the following claims.