Note: Descriptions are shown in the official language in which they were submitted.
~064473
This invention relates to metering and wetting
systems, for dry powders and is particularly adapted, inter
alia, for wetting polyelectrolytes, or the like, which are
basically coagulation aids used in such processes as waste water
treatment, for example. The polyelectrolyte is actually a
polymer which has recently been introduced as an extremely
- effective means of coagulation. It replaces certain other
chemicals which have been used for many years, such as alum,
for example. The main advantage of polyelectrolytes is that
an extremely small quantity of this polymer will accomplish
what used to take many hundreds of times the quantity of other
chemicals used for coagulation.
` A particular problem occurs in the handling of poly-
electrolyte, which is due to its inherent hygroscopic nature
and the difficulties involved in properly wetting the polymer
and bringing it into solution. Such polymers vary from about 10
to about 50 minutes to "age" after it has been properly wetted,
to transfer into solution. It would appear as through a very
simple method of wetting the polyelectrolyte would be to meter
the polymer directly into a tank and mix it with a mixer. How-
ever, the problem involved with wetting a polyelectrolyte, or
the like, is one created by its extremely hygroscopic nature.
If, for example, one took a handful of polyelectrolyte and
; dumped it into a bucket of water, the outer portion of this
clump would wet instantaneously upon contact with the water,
preventing the center core of the lump from being wetted. The
wetted outer area then becomes a viscous shell and will actually
isolate the still dry encapsulated powder. In fact, it is very
difficult to penetrate the outer wetted shell in an effort to
try and wet the dry powder encapsulated therein. These unwetted
, 1 ~
1064473
part;cles or globules are generally known, in the trade, as
"fish-eyes". Mechanical mixers are also employed, but have
difficulty in breaking down these lumps, particularly within
the allocated period of time required for the aging process or
within allocated process time requirements.
Thus, it is essential that every grain of poly~ -
electrolyte be wetted in order for a metering/wetting polymer ~ -
system to be completely functional.
In addition, once unwetted particles are created and
exist, the fact that they are very difficult to dissolve and
break up is only par~ of the problem. Another serious problem
resides in the extremely adhesive nature of improperly wetted
polymer. The unwetted or partially wetted polyelectrolyte
globules will adhere to practically any surface to which it
comes in contact. Therefore, it is easy to realize that in
transporting a polyelectrolyte solution which contains unwetted
or partially wetted particles, there is a tendency for these
particles to agglomerate and adhere to themselves and to the
inside of the pipes, which creates a serious problem. Thus,
; 20 in operation, if a polyelectrolyte solution containing these
unwetted particles is permitted to pass through pipe lines,
pumps, etc., clogging will undoubtedly result in a very short
period of time, rendering the system useless. On the other
hand, a properly wetted polyelectrolyte solution does not cause
any handling problems per se.
Applicant has discovered a novel combination of
elements combined in such a way as to afford a very economical,
efficient and practical solution of the difficulties and the
- problems above discussed, as will become apparent as the
i 30 description proceeds. Related patents in this art include U.S.
patent No. 3,118,459 issued January 21, 1964 to F.M. Stumpf;
patent No. 3,251,550 issued May 17, 1966 to A. Lippert et al.;
patent No. 1,770,011 issued July 8, 1930; patent No. 3,003,751
~'
.
- : , . . . :
~ .. .. : , ~
iO64473
issued October 10, 1961; patent No.3,351,979 issued Nov. 14,
1967 to J.B. Wilhelmi; patent No.3,386,182 issued June 4, 1968
to A. Lippert; and patent No.2,953,359 issued September 20,1960.
Briefly, my invention contemplates the provision of a
new and improved metering and wetting system characterized by a
volumetric feeder for receiving powdered polyelectrolyte and
supplying metered, conditioned polyelectrolyte to apparatus for
atomizing the polyelectrolyte. The so atomized polyelectrolyte
is passed to a mixing-wetting chamber wherein substantially all
of the atomized particles of polyelectrolyte are wetted and
thence transferred to a mixing tank for aging. After aging the
solution of polyelectrolyte is then ready for use in industry.
In accordance with one aspect of the invention, the
apparatus for atomizing the polyelectrolyte is in the form of a
"tee" which is mounted in a pneumatic conveying line. One branch
of the tee receives the powdered polyelectrolyte from the outlet
of the volumetric feeder and another leg of the tee receives a
controlled quantity of compressed air which intermixes with the
powdered polyelectrolyte in the tee and in the pneumatic line
extending from the third leg of the tee to thereby completely
atomize the polyelectrolyte and convey it to the mixing-wetting
chamber. An air dryer assembly is provided for removing moisture
from the air supplied to the pneumatic system. This air dryer
assembly includes two desiccantchambers each containing asupply
of regenerable beaded desiccant material and a heating element,
and each of the chambers has an opening to the atmosphere. The
system further includes valve means for connecting, in one mode
of operation, the first chamber to the pneumatic system and the
second chamber to a blower, and for connecting in a second mode
of operation the second chamber to the pneumatic system and the
first chamber to the blower. Control means are provided for
,; -.G,
-- 3 --
1064~73
1 controlling the mode of operation of the valve means in preselected
2 timed sequence, whereby when one desiccant chamber is being utilize
the other is being regenerated.
~ According to another aspect of my invention, the mixing-
wetting chamber is conical in shape and vertically mounted with
the so atomized polyelectrolyte entering at the top thereof and
7 a controlled quantity of water entering tangentially through an
inlet disposed at about 90 with respect to the atomized powder
inlet. The top of the wetting chamber is open. The flow of water
is carefully controlled and a selected volume of air is employed
Il to create a positive turbulent wetting action as the water and air
2 combine whereby the atomized polyelectrolyte particles are com-
3 pletely wetted and passed through with the water to a lower outlet
1~ of the mixing-wetting chamber. The mixing-wetting chamber is so
constructed that all internal surfaces are flooded with water
16 to limit any possibility of polymer adhesion and to provide the
optimum percentage of air to water to polymer relationship without
18 flooding, clogging, or improper wetting.
According to another aspect of the invention, there is
~ provided a scrubber assembly mounted on top of the mixing tank,
which is characterized by a cylindrical housing having a blower
2~ mounted on the upper periphery thereof and a plurality of staggered
23 baffle plates mounted on the internal walls. An inlet pipe extends
24 from the middle of the bottom of the housing a short distance
down into the mixing tank. A screen covers the bottom of the inlet
26 pipe and a pair of tangentially oriented water inlet pipes are
27 mounted above the screen to form a water blanket on the screen,
28 thereby providing a negative air draw through the wetting chamber
29 to eliminate dust at this point, assisting in the inward draw of
polymer and water into the mixing tank and preventing polymer dust
31 from adhering to the internal areas of the mixing tank.
106447;3
1 According to stilI another aspect of my invention, the
2 mixing tank which receives the so wetted polyelectrolyte
3 particles from the mixing~wetting chamber is provided with a
4 mechanical mixer for mechanically agitating the polyelectrolyte and
to assist with the complete transfer of same into solution. The
6 foregoing process cycle may operate continuously for as long as
7 required.
8 There has thus been outlined rather broadly the more
9 important features of the invention in order that the detailed
description thereof that follows may be better understood, and in
11 order that the present contribution to the art better appreciated.
12 There are, of course, additional features of the invention that wil L
13 be described more fully hereinafter. Those skilled in the art will
1~ appreciate that the conception on which this disclosure is based
can readily be utilized as the basis for the designing of other
16 structures for carrying out the several purposes of the invention.
17 It is important, therefore, that this disclo~ure be regarded as
lt3 including such equivalent constructions as do not depart from the
19 spirit and scope of the invention.
Several embodiments of the invention have been chosen for
21 purposes of illustration and description, and are shown in the
22 accompanying drawings, forming a part of the specification, wherein
23 Fig. l is a side elevation, partially in section, of a
24 system for metering and wetting polyelectrolyte, constructed ac-
2s cording to the concepts of my invention;
26 Fig. 2 is a plan view of the system of Fig. l;
27 Fig. 3 is an enlarged, medial, vertical, sectional view
28 of a mixing and wetting chamber of the system;
29 Fig. 4 is a greatly enlarged view showing particles of
polyelectrolyte prior to being wetted;
31 Fig. 5 is a view similar to Fig. 4, but showing the
1064473
particles after being wetted;
Fig. 6 is a side elevation, partially in section, of a
system for metering and wetting polyelectrolyte including an air
scrubber9 constructed according to the concepts of my invention;
Fig. 7 is an enlarged sectional view taken along the
line indicated at 7-7 in Fig. 6;
Fig. 8 is an enlarged, medial sectional view of the
lower portion of the air scrubber shown in Fig. 6; and
Fig. 9 is a schematic representation of an air dryer
assembly according to the invention.
In the embodiment of the invention illustrated inFigs.
1 to 5, the system for metering andwetting polyelectrolytes
comprises a volumetric feeder indicated generally at lO,such as
the one described in my U.S. patent 3,186,602 issued June 1,
lS 1965, for example, which includes a bin 12 for receiving
powdered polyelectrolyte or the like to be processed, and which
feeds into a conditioning chamber 14 containing a pair of
concentric augers 16 and 18, Fig. 2, which condition and meter a
predetermined volume of material out through a discharge conduit
20. An electric motor 22 serves to drive the augers through
a variable speed or constant speed drive 24.
The discharge of the volumetric feeder meters the
polymer into a "tee" 26, Fig.2, which is located ina pneumatic
conveying line 28. Either compressed air or a blower unit 30
moves air through the line to atomize the powdered polyelectro-
lyte and convey it to a mixing-wetting chamber 32. A valve 33
serves to control the flow of air, as will be described more
fully hereinafter.
As indicated hereinbefore, the metering and wetting
system ofthepresent invention isparticularlydirected ~ process-
ing polyelectrolyte,which isvery hygroscopic innature and,asa
; consequence,ifthesurfaces ofthe system become wet the atomized
polyelectrolyte will adhere ~ these surfaces. Therefore, it is
- 6 -
:1064473
1 important that the air supplied by the blower unit 30 be substan-
2 tially moisture free. Fig. 9 shows an air dryer assembly according
3 to the invention, which comprises two desiccant chambers 94 and 96
each containing a supply of regenerable beaded desiccant material.
A four-way shuttle valve 98 is included as an integral part of the
6 dryer assembly to direct the air flow through the selected
7 desiccant chamber, as only one chamber is utilized at any given
8 time, while the chamber not in use is having its desiccant material
regenerated. To regenerate the desiccant, the chambers 94 and 96
lo are equipped with heating elements 100 and 102, respectively, which
11 are used to dry the saturated desiccant on a programmable, timed
12 basis. In addition, a small blower 104 is employed to assist in
l3 the drying process.
1~ In operation, the four-way valve 98 is automatically
positioned by an electric actuator 106, which selects the desiccant
16 chamber for use in the system while the other chamber is available
17 for regeneration. For example, in one mode of operation, air is
18 drawn from the atmosphere through a filter 108, through a line
19 110, through the desiccant material in chamber 96, through line 112
through the four-way valve 98, and through a conveying line 114
21 to the blower unit 30. During the period that chamber 96 is being
22 utilized for drying the system air, the desiccant in the second
23 chamber 94 is being regenerated. During the regeneration cycle,
24 air is forced by the blower 104 through pipe 116, the four-way
valve 98, a line 118, over the heater 100 and through the chamber
26 94, through a line 120, and discharges through a filter 122 to the
27 atmosphere.
~ The duration of the regenerative cycle is programmed
29 depending upon the time required to regenerate the particular
desiccant material. When the desiccant in the first chamber 96
31 becomes saturated the four-way valve 98 is switched so that the
~' ' . . , . ' .
~064473
1 assembly changes to its second mode of operation wherein the system
2 air passes se~uentially through the filter 122, the line 120, the
3 chamber 94, the line 118, the four-way valve 98, and through the
4 line 114 to the blower unit 30. At the same time the desiccant
material in the chamber is being regenerated by sequentially pass-
6 ing the air from the small blower 104 through the line 116, the
7 four-way valve 98, the line 112, the chamber 96, over the heater
8 102, and through the line 110 and filter 108 to the atmosphere.
9 As a result, the air dryer assembly removes in excess of ,
ninety-nine percent of the moisture in the air before the air
enters the blower unit 30 and conveying lines, thereby preventing
2 moisture from prematurely contacting the dry polyelectrolyte.
13 As best seen in Figs. 1 and 3, the mixing-wetting chamber
t4 is mounted vertically, and is of conical configuration, with a
water inlet 34 entering tangentially at about 90 with respect to
16 an atomized product nozzle-like inlet 36. As the air carrying the
7 polymer is forced into the mixing-wetting chamber 32 under a few
~ . pounds of pressure, a cyclonic turbulence is created as the air
t9 comes into contact with the flowing water and the tapered portion
of the mixing-wetting portion. This turbulence generates thorough
21 mixing action. Water is supplied through an inlet pipe 38 contain-
22 ing a valve 40, flow meter 42 and a second valve 44 for accurately
23 controlling the flow therethrough. Thus, as seen in Fig. 3,
24 atomized product 46 vertically enters the mixing-wetting chamber
while water 48 enters the chamber horizontally. With this
26 cyclonic mixing-wetting chamber, as indicated at 50, basically
27 each and every particle of the polymer is thoroughly wetted and
28 thence dispensed through an outlet pipe 52 extending a short
29 distance, such as about six inches for example, down into a mixing
or aging tank 54 mounted thereunder. As shown in Fig. 4, the
31 particles of polymer 56 arrive at the mixing-wetting chamber inlet
" . , ' '
1064473
1 as an atomized product 46 and when they leave the chamber each
2 particle of the polymer is thoroughly wetted by the water 48, as
3 shown in Fig. 5. It Will be appreciated that the mixing-wetting
~ chamber 32 is so constructed that all internal surfaces are flooded
with water to eliminate any possibility of polymer adhesion and to
provide the optimum percentage of air to water to polymer rela-
7 tionship without flooding, clogging or improper wetting. The
volume of air is so controlled, by valve 33 that it passes through
without back pressure, thus providing a wetting action whereby
the atomized polyelectrolyte particles are completely wetted in a
11 cyclonic fashion and passed through with the water to the mixing
12 tank 54 therebelow.
13 As best seen in Fig. 1, the mixing tank 54 is provided
14 with a mechanical mixer 57 powered by an electric motor 58. The
purpose of the mixing tank is to provide mechanical assistance
16 through positive mechanical agitation and to provide sufficient
17 time for the aging process, which may take from about ten to about
18 fifty minutes, usually about 15 to about 20 minutes, depending on
19 the particular polyelectrolyte to completely transfer into solution
However, it is important that, as the material enters this mixing
21 or aging tank, the solution is continuously mechanically agitated
22 during this aging period. Once this has been completed, the
23 material may remain in the tank for a numher of hours without any
24 difficulty, such as up to about 48 hours, for example. The mixing
tank is provided with an outlet pipe 60 and an outlet valve 62.
26 A second similar or holding tank 64 may be mounted adjacent to or
27 underneath said mixing tank and is provided for receiving all of
28 the contents of the first mixing tank 54 after the polymer has
29 gone into solution. A pump 66 is utilized to draw the polyelec-
trolyte solution from the second mixing tank 64 and introduce it
31 into the process wherein the polyelectrolyte is being used as a
1064473
1 coagulate. The foregoing process cycle is continuous for as long
2 as required. Since the system operates basically on a batch
3 basis, the solution is normally only prepared on demand, the demand
~ being the amount used in the water purification process. Accord-
ingly, a second or holding tank is emplo~yed so that, after the
6 polyelectrolyte solution is complete, it is automatically dis-
7 charged into the holding tank, once the level in the holding tank
8 is low enough to permit the entire contents of the mixing tank to
9 be dumped. The polyelectrolyte solution is then pumped into the
process from the holding tank. As will be appreciated, the mixing
11 or aging tank is the preparation tank for the solution, and the
12 frequency of this cycle is based on the process usage of the
13 solution, as drawn off from the holding tank. For example, if the~
1~ usage is very small, it may be necessary to prepare only one
solution per day, or perhaps even longer.
16 In order to provide for the complete wetting of all
17 polymers, if a small percentage thereof does happen to escape the
19 initial wetting process, and to further eliminate the escape of
9 loose unwetted particles of polymer into the mixing tank, which
would adhere to the internal surfaces thereof, the system as
21 illustrated in Figs. 6 and 8 is equipped with a scrubber assembly,
22 as indicated generally at 68, which draws the majority of its air
23 supply through the wetting chamber.
24 This scrubber assembly serves multiple purposes; firstly,
it provides a negative air draw through the wetting chamber thereby
26 eliminating dust at this point; secondly, the scrubber aids in the
27 effectiveness of the mixing function in the wetting chamber by
28 providing inward draw of polymer and water; and thirdly, the
~9 scrubber maintains a slight negative draw in the mixing tank thereb Y
eliminating the possibility of unwetted polymer dust blowing about
31 and/or adhering to the internal areas. In operation, the scrubber
1 assembly draws unwetted particles of polymer therethrough which,
2 in turn, results in the complete wetting of any remaining particles
of powder.
The scrubber assembly, as seen in Fig. 6, comprises a
housing 70 having blower suction on the upper periphery thereof,
6 as at 74, and a plurality of staggered baffle plates 76 are mounted
7 on the internal walls. An inlet pipe 78 extends from the bottom
~ of the housing 70 downwardly through a cover 79, and thence a short
9 distance, of the order of about six inches, downwardly into the
mixing tank 54. As seen in Fig. 8, the screen 80, having a mesh
11 size of the order of about l/32 inch, completely covers the bottom
12 of the scrubber inlet pipe 78. Water, under pressure, supplied
13 from any convenient source, enters the scrubber assembly through a
pair of tangentially oriented inlet pipes 82 located a short
distance above the screen 80 with a generally centrifugal motion,
~ as indicated by the arrows 84 in Fig. 7. The screen serves to
f7 form a water blanket 86 thereabove, as best seen in Fig. 8. It is~
18 noted that the pipes 52 and 78 terminate in an upper portion 88
19 above the surface of the solution of polyelectrolyte in the mixing
tank 54.
In operation, the blower 72 draws air and any unwetted
22 polymer contained therein from the wetting chamber, through the
23 pipe 52 and from the upper portion 88 of the mixing tank 54. Thi-s~-
2~ air is drawn up through the water covered screen 80 and any un-
wetted particles of polymer are effectively trapped, wetted, and
26 dropped into the mixing tank. The air is then drawn up through
2~ the cylindrical housing 70 through the baffle arrangement 76,
28 where the moisture contained therein is removed, and then out
29 through the blower 72 and discharged from the outlet 92 into the
atmosphere. Thus, the discharge from the blower is only clean
31 air.
'' - 11 -
'~,"
- . .... ... ,;j,~ . . , ".
10644'73
Tests indicate that when processing certain types of
polyelectrolyte, the quantity of unwetted polymer passing through
3 the wetting chamber may vary up to a maximum of about l.5%. This
percentage is completely dependent upon the mesh or particle size
of the polymer, which is reflected in its ability to atomize. The
6 larger the particle size, the higher the wetting percentage and
the lower the amount of unwetted polymer. The scrubber, however,
8 does provide for lO0~ wetting by trapping and wetting any remainingg polymer material which escapes the initial wetting process. Thus,
the scrubber serves to draw air through the system thereby re-
11 stricting the escape of dust contained therein and preventing
-12 buildup of particles of polymer on the bottom of the cover 79 and13 on the walls of the upper portion 88 of the mixing tank 54.
t4 It will thus be seen that the present invention does
indeed provide an improved metering and wetting system which is
16 superior in simplicity, operability, reliability and efficiency
7 as compared to prior art such devices. The combination of the
8 feeder-atomizing portion, the wetting chamber portion and the
scrubber portion cooperate to provide a complete self-cleaning
and very effective polymer metering and wetting system.
21 Although particular embodiments of the invention are herei22 disclosed for pusposes of explanation, various modification
23 thereof, after study of the specification will be apparent to thos24 skilled in the art to which the invention pertains.
WHAT IS CLAIMED AND DESIRED TO BE SECURED BY LETTERS
26 PATENT IS:
. 27
. .
31
~ .~ . . . .
