Apparatus for removing contaminants from a liquid reservoir

An apparatus and method for skimming contaminants from a reservoir of a liquid such as an industrial solvent, including a tubular wand having an end inlet extending into the reservoir, a pressure air line extending along the wand, the air line protruding a side wall of the wand and terminating at a nozzle proximate the inlet, the nozzle being directed into the wand, away from the inlet for producing a vacuum. The wand is adjustably mounted to a base that attaches to the reservoir, and is connected to a vented container for collecting the contaminants that are drawn into the wand. Contaminants can be removed from the surface of the liquid, from proximate the bottom of the reservoir, or from a submerged layer concentrated at an intermediate depth within the reservoir.

BACKGROUND 
The present invention relates to industrial processes, and more 
particularly to apparatus for removing contaminants such as oils from a 
liquid reservoir, extending the life of a batch of process liquid such as 
a solvent. 
In many industrial processes, a liquid such as a solvent is circulated from 
a reservoir to a process location such as a cleaning station, from which 
the liquid is recovered and transported back to the reservoir and reused. 
A problem with such processes is that the liquid gradually gets 
contaminated with foreign material such as oils. When the contamination 
reaches unacceptable levels, the liquid is discarded, and the reservoir is 
refilled. 
The contaminants typically collect in one or more layers within the 
reservoir. For example, in many cases, a film of oil contamination 
accumulates at the top of the liquid in the reservoir. In other cases, a 
layer of liquid or solids collects at the bottom of the reservoir. It is 
also possible for contamination to accumulate in a layer at a boundary 
between different liquid components of the reservoir. 
Thus there is a need for a way to extend the life of the process liquid by 
removing at least a substantial portion of the contaminants from the 
liquid, that is effective with commonly encountered combinations of liquid 
and contaminant, and that is easy and inexpensive to provide and use. 
SUMMARY 
The present invention meets this need by providing a simple apparatus 
utilizing shop air for controllably vacuuming contaminants from a process 
liquid reservoir. The apparatus includes a tubular wand having an end 
inlet, means for mounting the wand with the inlet extending into the 
reservoir, a nozzle mounted in the wand near the inlet and aimed into the 
wand, means for connecting the nozzle to a source of pressure air for 
producing a vacuum at the inlet. The apparatus also includes a vessel for 
the contaminants, and means for fluid connecting the vessel to the wand, 
whereby the contaminants are vacuumed from the reservoir and collected in 
the vessel. The apparatus is particularly simple and inexpensive to 
provide, in that a source of pressure air, known as "shop air" is 
typically available in industrial environments, at a pressure on the order 
of 125 psi. 
The support for the wand can be provided by a base, means for fixably 
mounting the base to the reservoir, and means for fixably locating the 
wand relative to the base. A locating member can extend downwardly from 
the base for engaging a side wall of the reservoir, a clamp member also 
being preferably provided for clamping the locating member against the 
side wall. A pair of the clamp members can be located for clamping 
intersecting portions of the side wall. The wand is preferably adjustably 
mounted to the base by clamped engagement with a trough member that 
rigidly extends from the base. The trough can have its longitudinal axis 
oriented normal to a bottom plate surface of the base for vertically 
orienting the wand. The engagement with the trough member can be against a 
rigid stem portion of the wand. Thus the inlet can be adjustably located 
at a desired elevation within the reservoir at which the contaminants are 
concentrated, for unattended (automatic) removal of the contaminants. For 
example, contaminants such as oil typically float on many solvents. Thus 
when the inlet is adjusted to slightly above the liquid level of the 
reservoir, the floating contaminants can be efficiently vacuumed from the 
surface of the process liquid. Although some of the liquid might be drawn 
into the inlet along with the contaminants, the greater density of the 
process liquid tends to effect a separation of the liquid from the 
contaminants within the wand, at least some of the process liquid falling 
from the inlet back into the reservoir subsequent to such separation. 
The air can be fed to the nozzle through a J-shaped air line or nozzle tube 
that rigidly extends along the stem portion and protrudes a side wall of 
the wand. Also, the nozzle tube preferably extends slightly away from the 
wand near the point of protrusion of the wand side wall, forming a smooth 
reverse curve for efficient conduction of the pressure air to the nozzle 
in a compact arrangement that advantageously permits viewing of the 
contents of the reservoir in the immediate vicinity of the inlet. 
The nozzle can be provided as an end opening of the nozzle tube. Preferably 
the nozzle forms a necked-down end portion of the nozzle tube for 
accelerating the pressurized air as it enters the wand. Preferably the 
nozzle has a nozzle area that is between about 1.5 percent and about 10 
percent of an inside cross-sectional stem area of the wand. More 
preferably, the nozzle area is between about 2.5 percent and about 7 
percent of the stem area. 
Preferably the wand also is equipped with an annular venturi member within 
the stem portion and proximate the nozzle for accelerating an upward 
velocity contaminants entering the wand through the inlet, thereby 
facilitating transfer of the contaminants out of the reservoir. Preferably 
the venturi is located such that the nozzle is within a distance of not 
greater than one inside diameter of the stem portion from the venturi 
member for cooperative interaction between the nozzle and the venturi 
member enhancing the upward velocity of the vacuumed contaminants. The 
venturi member can have a neck area that is from about 25 percent to about 
75 percent of the inside stem area. Preferably the neck area is about 55 
percent of the inside stem area. The vessel is preferably a closed 
container for preventing unwanted atmospheric circulation of the liquid 
and/or solids from the tank, the vessel having inlet means for receiving 
the contaminants, a vessel outlet for exhausting the gas, and trap means 
for retaining the contaminants. The trap means can include a filter 
element from which collected liquid can drip into the container. The trap 
means can include a baffle member partially blocking a path between the 
vessel inlet and outlet. The baffle member can have a tubular, slotted 
portion extending into the container through the inlet, the bottom of the 
tubular portion being closed for preventing forceful downward flow from 
the inlet directly into the contents of the vessel. Preferably the slotted 
openings of the baffle are spaced upwardly from the closed end by at least 
about half an inside diameter of the slotted portion, the openings each 
having a height of about the inside diameter or more.

DESCRIPTION 
The present invention is directed to an apparatus for removing contaminants 
from a reservoir of a liquid such as an industrial solvent, with minimal 
loss of the solvent. With reference to FIGS. 1-7 of the drawings, a 
reservoir or tank 10 having a process or other liquid 11 therein is 
located proximate a source of compressed air, as indicated by the arrow in 
FIG. 1, the air being fed through an air pipe 12. The tank 10 typically 
has a pair of upstanding, intersecting side walls 14, upward extremities 
thereof defining a top surface 15 of the tank 10. The liquid 11 from time 
to time has a quantity of contaminant therein, the contaminant being 
concentrated in one or more contaminant layers 16, one such contaminant 
layer 16 being shown in FIG. 1 as bounded by a top liquid surface 18 of 
the liquid 11. It will be understood that the contaminate layer 16 may be 
submerged at any level (including the bottom) within the tank 10. 
According to the present invention, a skimming apparatus 20 is operative 
for removing contaminants that are concentrated in the layer 16, the 
apparatus having a wand unit 22 for attachment to the tank 10, and a 
collection unit 24 for receiving contaminants from the wand unit 22. The 
wand unit 22 has a base assembly 26 and a wand assembly 28, the wand 
assembly 28 being axially adjustably clamped to the base assembly 26 on a 
vertical wand axis 30. The wand assembly 28 includes a wand tube 32 having 
an end inlet 34, the inlet 34 extending into the reservoir for receiving 
the contaminants, a pressure air line 36 extending along the wand tube 34 
in rigid relation thereto, the air line 36 protruding a side wall of the 
wand tube 32 and terminating at a nozzle opening 38 proximate the inlet 
34, the nozzle opening 38 being proximately concentric with the wand axis 
30 for directing pressure air upwardly into the wand tube 32, away from 
the inlet 34 for producing a vacuum whereby material proximate the wand 
inlet 34 is drawn into the wand tube 32. 
The base assembly 26 includes a base member 40 having an upstanding 
C-shaped member 42 rigidly extending therefrom for receiving the wand 
assembly 28, the C-shaped member 42 having a freely sliding fit upon the 
wand tube 32, a wand thumbscrew 44 threadingly engaging the C-shaped 
member for clamping the wand assembly 28 at a desired elevation relative 
to the tank 10 as further described below. The base member 40 is adapted 
for resting horizontally on the top surface 15 of the tank 10, the 
C-shaped member 42 orienting the wand axis 30 perpendicular to the top 
surface 15. Also, a corner member 46 extends downwardly from the base 
member 40 for registering the base member 40 in fixed lateral relation to 
each of the side walls 14 of the tank 10. Further, the base member 40 is 
formed with a pair of downwardly extending flange portions 48, a clamp 
screw 50 threadingly engaging each of the flange portions 48 for rigidly 
clamping the corner member 46 at the intersection of the side walls 15. 
Thus the wand assembly 28 can be quickly and accurately positioned 
proximate both of the walls 15 with the inlet 34 located at a desired 
elevation relative to the liquid surface 18. 
The upward extremity of the air line 36 is curved downwardly, terminating 
in a wand air fitting 52, an air valve 54 being rigidly connected between 
the air fitting 52 and a conventional quick-disconnect fitting 55. A 
flexible air hose 56, having at least one quick-disconnect coupling 58, 
fluid connects the fitting 55 to the air pipe 12 for controllably 
generating the flow of pressure air from the nozzle opening 38 in response 
to operation of the air valve 54. The wand tube 32 is similarly curved at 
its upward extremity, terminating in a wand outlet fitting 59. A flexible 
transfer hose 60 fluid connects the wand tube 32 to the collection unit 
24, the hose 60 having a first hose fitting 62 for mating with the wand 
outlet fitting 58, and a second hose fitting 64 for connection to the 
collection unit 24. 
As best shown in FIG. 7, the collection unit 24 includes a closed 
collection container 66 having a container inlet 68 and a container outlet 
70, the container inlet 68 being provided with an inlet coupling 72 that 
sealingly threadingly engages the inlet 68 for connecting the second hose 
fitting 64 of the transfer hose 60. The inlet coupling 72 is configured 
for engaging the smaller bung hole of a conventional 55-gallon drum as 
shown in FIGS. 1 and 7, the drum advantageously providing a conveniently 
available large capacity configuration for the collection container 66. 
The conventional larger bung hole of the drum similarly serves as the 
container outlet 70. Contaminants from the tank 10, together with pressure 
air and small amounts of the liquid 11, are carried into the container 66 
through the inlet coupling 66. The collection unit 24 is adapted for 
retaining the contaminants together with whatever quantities of the liquid 
11 that are transferred via the transfer hose 60, but not the pressure 
air. For this purpose, the inlet coupling 72 is provided with a tubular 
baffle member 74 having a plurality of spaced, vertically oriented slots 
76 therein, the baffle member 74 extending into the collection container 
66 with the slots 76 opening inside the container 66, the baffle member 74 
being closed at its bottom extremity by a plug member 78. Thus the stream 
entering the container 66 from the transfer hose 60 is blocked by the plug 
member 76 from forceably splashing into the liquid contents already in the 
container. Instead, the liquid and/or solid components of the stream are 
redirected to the side, falling only under the influence of gravity, while 
the pressure air passes mostly above the liquid, also through the slots 
76, for minimal entrainment of the process liquid 11 and/or the 
contaminants thereof in the pressure air flowing about in the container 
66. 
In the preferred configuration of the collection unit 24 shown in FIG. 7, 
the inlet coupling 72 is a 1" threaded pipe coupling, the baffle member 72 
having an inside diameter d.sub.B of approximately 0.75 inch. The slots 76 
are spaced upwardly from the plug member 78 by a spacing s.sub.B of 
approximately 0.4 inch (at least about half of the inside diameter 
d.sub.B) for effectively redirecting the stream from the transfer hose 60. 
Also, there are a pair of the slots 76, each having a vertical length 
h.sub.B of approximately 4.0 inches and a width w.sub.B of approximately 
0.5 inch. 
As further shown in FIG. 7, the collection unit 24 is provided with an 
exhaust filter assembly 80 for preventing escape of the liquid 11, and/or 
the contaminants thereof, from the container 66. The filter assembly 80 is 
fluid connected to the container 66 by an exhaust coupling 82 that 
sealingly threadingly engages the container outlet 70. An upper extremity 
of the exhaust coupling 82 also sealingly threadingly engages a base ring 
84 of the filter assembly 80, the filter assembly 80 also including a 
vented filter body 86 that is removably sealingly connected to a 
cylindrical engagement surface 88 of the base ring 84. A disc-shaped 
filter element 90 is removably retained within the body 86 by a retainer 
ring 92 such that substantially all of the pressure air entering the 
container inlet 68 must exit only through the filter element 90. 
Preferably, substantially all liquid droplets and/or contaminant particles 
that are carried upwardly through the exhaust coupling 82 are collected by 
the filter element 90, most of the liquid droplets and at least some of 
the contaminant particles collecting as larger drops that fall from the 
filter element 90 and/or the exhaust coupling 82 back into the collection 
container 66. Accordingly, the collection unit 24 is effective for 
permitting escape of the pressure air while retaining in the container 66 
substantially all of the vacuumed contaminant and at least a significant 
portion of the process liquid 11 that is carried therewith from the 
reservoir 10. The exhaust coupling 82 can be a 21/4" threaded pipe 
coupling. 
The couplings 72 and 82, the baffle member 74, and the plug member 78, can 
each be formed of plastic, stainless steel, or aluminum, depending on the 
properties of the process liquid 11, and its contaminants. The base ring 
84 and the filter body 86 can be formed from a suitable plastic, such as 
Teflon.RTM., and the retainer ring 92 can be made from Teflon or stainless 
steel. The filter element 90 itself can be formed of a mesh material, such 
as a commercially available fine-mesh filter element material for swamp 
coolers. 
With further reference to FIGS. 8 and 9, an alternate configuration of the 
collection unit 24 includes a pail 94 having a removable lid 96 sealingly 
affixed thereto, the combination of the pail 94 and the lid 96 functioning 
as the collection container 66. Accordingly, the lid 96 is formed with 
counterparts of the container inlet 68 and the container outlet 70, 
described above. In the configuration of FIGS. 9 and 10, the inlet 
coupling 72 is threadingly advanced downwardly into the container inlet 68 
such that a portion of the coupling 72 protrudes below the lid 96. A 
baffle member 98 is mounted within the pail 94 against the lid 96, the 
baffle member being protruded by the inlet coupling 72 and retained in 
place by a lock nut 100. As shown in FIG. 9, the baffle member 98 extends 
downwardly between the container inlet 68 and the outlet 70 for blocking a 
direct path therebetween within the container 66, the baffle member 98 
also extending beneath the container inlet 68 to proximate a side wall 102 
of the pail 94 for blocking a path directly below the container inlet 68. 
Thus the incoming stream from the transfer hose 60 is blocked from 
directly striking the liquid and/or solid contents of the collection 
container 66, the liquid and/or solid material being further blocked from 
directly migrating to the container outlet. A counterpart of the exhaust 
filter assembly 80 is connected to the container outlet 70 for trapping 
incoming liquids and solids within the collection container 66 as 
described above, the base ring 84 being bonded to the lid 96 by a suitable 
adhesive. When it is desired to empty the pail 94, the filter body 86 can 
be removed from the base ring 84, providing an unobstructed path for the 
contents of the pail 94. 
As further shown in FIG. 6, the wand assembly 28 in a preferred 
configuration includes a venturi member 104 within the wand tube 32, the 
venturi member 104 forming a smooth restriction on the inside of the tube 
32, at a location slightly above the nozzle opening 38. Also, the air line 
36 is rigidly connected along the wand tube by means of a series of tack 
or spot welds 106, the lower portion of the air line 36 smoothly curving 
slightly away from the wand tube 32, the air line 36 also being formed 
with a reverse curve 108, the reverse curvature smoothly continuing within 
the wand tube 32 for alignment of the nozzle opening 38 with the wand axis 
30. The lower extremity of the air line 36 is sealingly connected to the 
protruded wall of the wand tube 32 by a seam weld 110. The wand tube 32 
and the air line 36 are each preferably formed from stainless steel for 
immunity to the process liquid 11 and its contaminants. The transfer hose 
60, and the hose fittings 62 and 64 are preferably formed of Teflon. The 
air valve 54 can be made from brass, and the wand air fitting 52 can be 
made from brass or aluminum, and the quick disconnect fitting 55 can be 
made from aluminum or steel. 
An experimental prototype of the skimming apparatus 20 has been built and 
tested, the wand assembly 28 being configured without the venturi member 
104. The tank 10, was rectangular, having an inside length of 
approximately 41/2 feet, a width of approximately 3 feet, and a depth of 
approximately 21/2 feet, the liquid surface 18 being approximately 1 foot 
below the top surface 15. In the experimental apparatus 20, the wand tube 
32 has an outside diameter D.sub.W of 0.625 inch, an inside diameter 
d.sub.W of 0.5 inch, being formed with a length L of approximately 20 
inches along the wand axis 30 from the end inlet 34 to an upper extremity 
of a straight portion of the wand tube 32. The air line 36 has an outside 
diameter D.sub.A of 0.25 inch, an inside diameter d.sub.A of 0.125 inch, 
the apparatus 20 being tested with the air line 36 fully open, nozzle 
opening 38 having a nozzle inside diameter d.sub.N of 0.125 inch. It has 
been discovered that contaminants such as oil, dust, etc. that collect at 
the liquid surface 18 are most effectively removed from the reservoir 10 
when the end inlet 34 of the wand tube 32 is located a distance .epsilon. 
above the surface 18, the distance .epsilon. being approximately 0.125 
inch. With the apparatus 20 thus configured (without the venturi member 
104, the nozzle opening 38 fully open with the nozzle diameter d.sub.N at 
0.125 inch), and operating from an air pressure of 125 psi at the air pipe 
12 (the air valve 54 being partially open, a flow rate of one gallon total 
of contaminant together with a small quantity of the process liquid 11 
every three minutes was removed from the tank 10. As discussed above, the 
inlet 34 of the wand tube 32 is preferably located proximate a corner 
intersection of adjacent intersecting walls of the tank 10. When the inlet 
34 is so located, a flow of contaminants toward the inlet 34 is observed 
upon the liquid surface 18. As the contaminants are drawn into the 
proximity of the inlet 34, they travel slightly upwardly on a cone-shaped 
portion of the surface 18 that is induced by the vacuum that is developed 
in the wand tube 32. A relatively high-velocity flow of air in the 
restricted annular gap between the wand tube 32 and the surface 18 tends 
to lift and separate the floating contaminants from the process liquid 11. 
An unexpectedly highly efficient sorting process was observed to take 
place under these conditions, such that a very high proportion of the 
material extracted from the tank is from the floating contaminants, to the 
extent that they are present in the tank 10. It is believed that at least 
a portion of the liquid 11 that is lifted from the surface 18 along with 
the contamination tends to fall back into the tank under the influence of 
reduced air current velocities that exist proximate the inlet 34 nearer 
the wand axis 30 from the wand tube 32 itself. It is further believed that 
this process is enhanced by the presence of turbulence and/or vortex air 
currents that are produced within the wand tube 32 between the end opening 
34 and the nozzle opening 38. This effect is only observed with the end 
inlet 34 of the wand tube 32 oriented proximately parallel with the liquid 
surface 18 (the wand axis being vertical), and with the wand tube 32 being 
held in a fixed orientation and elevation slightly above the liquid 
surface 18. 
In further tests with the necked down configuration of the nozzle opening 
38, and with the venturi member 104 in the wand tube 32, it is expected 
that an increased flow rate will be achieved. The venturi member 104 can 
have an inside diameter d.sub.V of between approximately 0.25 inch and 
approximately 0.375 inch, a length l of between approximately 1.0 inch and 
approximately 1.8 inches, the bottom of the venturi member 104 being 
spaced above the nozzle opening 38 by a spacing s of from approximately 
0.25 inch to approximately 0.75 inch. 
Although the present invention has been described in considerable detail 
with reference to certain preferred versions thereof, other versions are 
possible. Therefore, the spirit and scope of the appended claims should 
not necessarily be limited to the description of the preferred versions 
contained herein.