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Description  |
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FIELD OF THE INVENTION
The present invention relates to mixing of water soluble additives for
irrigation water. In particular, the present invention provides a venturi
system for introduction of powder additives comprising long linear chain,
high molecular weight, water soluble polymers such as polyacrilamide into
a water stream in combination with low speed contradirectional impellers
for dispersion and mixing of the additive without shearing of long chain
polymers present in the additive.
BACKGROUND OF THE INVENTION
Application of fertilizers, soil additives, and other soil conditioning
products to agricultural fields has become a main stay requirement for
worldwide agricultural operations. Differing materials require various
application methods and many of the additives employed require mixing
prior to application. Such mixed chemicals are often introduced into the
produce fields by incorporation into irrigation water.
Advances in polymer chemistry have led to the evolution of sophisticated
polymers which are now being used agriculturally. The maximum benefit from
the polymers is derived by avoiding mechanical shearing and maintaining
the long chain characteristic of the polymer. In the prior art, the
addition of such additives into irrigation water has employed conventional
mixing techniques, including, hand mixing, standard rotating barrel
mixing, and conventional impeller mixing systems.
These prior art techniques often result in shearing of the long polymer
chains in the additive thereby reducing the efficacy of the additive as it
reaches the soil. The present invention provides an integrated, continuous
flow, mixing system which achieves proper polymer concentrations in the
water by precise metering of powder and flow regulation of water to
prevent congelation, and to allow proper dispersion and hydration of the
dry particles into the irrigation stream. In addition, vigorous yet gentle
agitation is employed to dissolve the additives without adversely altering
their physical properties. System sizing and flow sequencing assures
sufficient time for additives to dissolve thoroughly into solution before
being injected into the irrigation system.
The present invention is amenable to full automation and may be
incorporated in self contained and portable systems.
SUMMARY OF THE INVENTION
The mixing system of the present invention employs a dry product hopper for
introduction of the additive into the system. The additive is metered from
the hopper through a flow regulating device and introduced through a
cyclonic venturi system for combination with irrigation water. A
dispersion tank receives the initial mix of water and additive and
incorporates at least two contradirectional low speed impellers which
vigorously, yet gently, agitate the solution and create counter flow
mixing throughout the dispersion tank.
In various embodiments of the system, a rotating conical disperser located
at the output of the venturis receives the initial water additive solution
for even random dispersal across the solution surface in the dispersion
tank. Additionally, using a progressive cavity pump to transfer solution
from the dispersion tank to a solution aging tank of larger volume, which
also employs counter flow impellers, allows longer term storage of the
mixed solution while avoiding precipitation or congelation of the additive
prior to use.
Multiple dispersion tanks are employed in certain embodiments to allow
mixing of smaller quantities of additive solutions prior to entry into the
solution aging tank. Multiple dispersion tanks allows preparation of an
additive solution in one tank while pumping of solution from the alternate
dispersion tank into the solution aging tank. The present invention
provides continuous flow of irrigation water whole providing adequate
resident time in the aging tank to achieve hydration of the polymer before
being dispersed in irrigation water to the field.
BRIEF DESCRIPTION OF THE DRAWINGS
The details of the invention will be more clearly understood with reference
to the following drawings:
FIG. 1 is a side sectional view of a first embodiment of the system
demonstrating the various elements of the system, including, the additive
hopper, dispersion tank, and solution aging tank, with a horizontal flow
dispersion tank displayed;
FIG. 2a is a sectional end view of the additive hopper and venturi system;
FIG. 2b is a sectional side view of the additive hopper;
FIG. 2c is an exemplary embodiment of an additive flow regulating device
for the exit of the hopper;
FIG. 3a is a top view of an embodiment of the invention as disclosed in
FIG. 1 employing two dispersion tanks and two additive hoppers; FIG. 3b is
a side sectional view demonstrating the various elements of the second
dipersion tank and second additive hopper of FIG. 3a;
FIG. 4 is a detailed sectional view of an exemplary embodiment of the
venturi for use in the present invention;
FIG. 5a is a side sectional view of a second embodiment of the dispersion
tank employing vertical flow orientation of the contradirectional
impellers and incorporating the conical disperser;
FIG. 5b is a top view of an embodiment for the conical disperser; and
FIG. 6 is a side sectional view of a trailer mounted, small scale system
employing the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, FIG. 1 discloses a first embodiment of the
invention which employs a dry additive hopper 10 in which the water
soluble polymer additive is stored and introduced into the system. Twin
cyclonic venturis 12 receive the dry additive from the hopper through
double walled conduits 14 for mixing with water. The paired venturis are
intended to be used one at a time with the second venturi providing backup
for the system in case of clogging of the primary. However, both venturis
may be used in parallel for high demand requirements. Double walled
conduit intermediate the dry additive hopper and the venturis is employed
to collect condensation which may be caused through temperature
differential of the piping in the system due to cold water entering
through the inlet manifold into the venturis. Collection of condensation
by the outer wall of the conduit precludes water contact with the additive
prior to mixing in the cyclonic venturi. Water from the available
irrigation supply is provided through an inline separator/filter for
removing dirt from the irrigation water by pump 16 to piping manifold 18
which introduces water into the cyclonic venturis.
The solution exiting the venturis is received in a dispersion tank 20. The
dispersion tank in the embodiment shown in FIG. 1 incorporates
contradirectional impellers 22 and 24 mounted on a common horizontal shaft
26. Rotation of the shaft by drive motor 28 causes solution within the
dispersion tank to be urged in the direction of arrow 22a by impeller 22
and in the direction of arrow 24a by impeller 24. Use of large paddle, low
velocity impellers allows agitation of the solution in the dispersion tank
without shearing of long chain polymers present in the additive. Those
skilled in the art will recognize that separately shafted counterrotating
impellers driven by common or separate motors may be employed to provide
contradirectional flow required by the present invention. Alternative
embodiments of the invention employ a diagonal mounting of the impeller
shaft or shafts to allow mounting of motors and associated hardware
outside the tank without sealing requirements necessary for extending a
horizontal shaft through the tank wall.
In normal operation, water flow through the venturis into the dispersion
tank begins prior to introduction of water soluble additive from the
hopper. This allows introduction of some water level into the dispersion
tank for initiation of water agitation by the impellers prior to
introduction of the additive. Similarly, water flow continues after
introduction of the additive is complete to flush the venturis and
associated lines. Adjustment of concentration of the water soluble
additive during its introduction to accommodate a proper final
concentration in the dispersion tank is accomplished through metering of
the additive from the hopper through a flow regulating device, as will be
explained in greater detail subsequently.
Once the dispersion tank is full of the proper concentration of additive
and water, the mixture is allowed to remain under agitation by the low
speed contradirectional impellers to assure complete mixing. The additive
mixture is then extracted from the dispersion tank through conduit 30
employing a progressive cavity pump 32 to distribute the additive solution
to a field for application, or as shown in the embodiment of FIG. 1 to
introduce the mixture into a solution aging tank 34 through manifold 35.
The aging tank employs twin contradirectional impellers 36 and 38 mounted
on a common vertical shaft 40 driven by motor 42. As previously described
with regard to the impellers in the dispersion tank, the contradirectional
impellers force the mixture to flow in opposite directions within the
solution aging tank to maintain the mixture in solution thereby precluding
precipitation of the additive. The additive solution is then pumped from
the solution aging tank to an irrigation distribution system in the field
for application. The invention as described is configured as a parallel
branch in the irrigation water flow path which draws water into the
dispersion tank while simultaneously reintroducing mixed solution from the
aging tank in proper concentration into the irrigation stream. Solution
flows simultaneously into and out of the aging tank for a continuous flow
process.
Details of the dry additive hopper of the present system are disclosed in
FIGS. 2a through 2c. As shown in FIG. 2a, the dry additive is introduced
into the top opening 44 of the hopper which employs a lid 46 to preclude
contamination of the dry additive. Internal to the hopper, a sifting
device is employed to deagglomerate the additive. As shown in FIGS. 2a and
2b, a pair of paddle wheels 48 located over the exit ports 50 in the
hopper provide appropriate sifting. In the embodiment shown, the paddle
wheels are driven on a common shaft 52 by an electric motor 54, however,
independent shafts and motors are employed in alternative embodiments.
Metering of the additive from the hopper is accomplished employing a
conventional flow regulating device as shown in FIG. 2c which comprises a
horizontal sliding gate 56 variably occluding orifice 58 in plate 60
mounted in the hopper exit. Those skilled in the art will recognize
alternate flow regulating devices known in the art of dry powder metering
for substitution in the present invention.
FIG. 3a shows an embodiment of the present invention employing dual
dispersion tanks 20 and 21 with dual dry additive hoppers 10 and 11. FIG.
3b shows a side sectional view of the second dipersion tank and second dry
additive hopper with associated components and manifolds wherein the
components previously described with regard to FIG. 1 are identified by
"'" e.g. venturies 12'. Operation of each of the dispersion tanks and
hoppers is as described previously with regard to FIG. 1. Duplication of
the entire process in a second dispersion tank allows one dispersion tank
to be filled and mixed while the other dispersion tank, having completed
the mixing process, is being emptied by pump 32 into the solution aging
tank. Operation in this manner allows the aging tank to maintain a
substantially constant level during initial mixing operations in the
dispersion tanks and enhances the capability of the system to provide
continuous flow to the irrigation system. Mounting of the dual dispersion
tanks, aging tank, and all supporting pumps and power source on a skid
pallet or trailer 62 provides a self contained portable system.
A process controller 64, as seen in FIG. 1, is incorporated to monitor
level sensors 66 in the dispersion tanks and high and low level sensors 68
in the aging tank to automate operation of the mixing process. Control by
the process controller of pumps 16 and 32, manifold valves 31 and 31', as
well as flow regulating device 60 in the hopper outlets, responsive to
fluid levels in the tanks allows complete automation of the system. Those
skilled in the art will recognize the use of appropriate sensors in the
dispersion tanks, including, float or capacitive type sensors.
In operation, the process controller initiates operation by activating pump
16 to provide water to the venturis for mixing of the water soluble
additive. A control signal, activated by a low level indication in the
dispersion tanks provides an exemplary initial start signal. In the dual
dispersion tank system, upon a full indication from the level sensor in
the first dispersion tank, the controller activates pump 32 for transfer
of solution from the dispersion tank into the aging tank 34 with manifold
valve 31 drawing solution from the first dispersion tank. Those skilled in
the art will recognize that addition of a timer to allow adequate
dispersion of the additive in the dispersion tank prior to initiating pump
32 may be employed. The controller selectively operates manifold valving
to allow filling of the second dispersion tank while solution is being
drawn from the first dispersion tank and similarly drawing solution from
the second dispersion tank while refilling the first dispersion tank. This
operation allows a substantially constant flow of solution to the aging
tank which has sufficient volume to provide a constant solution stream at
the desired concentration into the irrigation water. The controller
operates manifold valve 69 to provide initial filling of the solution
aging tank and again, a timer may be employed to assure sufficient
hydration of the solution in the aging tank prior to reintroduction into
the irrigation water. Once in operation, the system disclosed in the
drawings provides a continuous flow of operation, drawing water from the
irrigation supply and returning a proper solution concentration to the
irrigation system for distribution to the field.
The cyclonic flow venturi employed in the embodiments of the invention
shown in the drawings is shown in FIG. 4. The venturi shown is a modified
Penberthy venturi which is commercially available.
As shown in FIG. 4 the venturi employed in the embodiment shown in the
drawings employs sealed air vents at the entry connection 86 which
provides a vacuum in conduit 14 drawing dry additive into the venturi due
to water flow from conduit 18 into the water intake 88. The dry additive
product mixes with the water in the cyclonic body of the venturi 90 and
the solution of water and dispersed dry additive exits the venturi at
orifice 92.
FIG. 5a discloses an alternate embodiment of the dispersion tank 100.
Contradirectional impellers 102 and 104 are mounted vertically on a common
shaft 106 driven by motor 108. Operation of the impellers in this
orientation is as described previously with regard to the solution aging
tank. A conical disburser 110 is also mounted to shaft 106 intermediate
the venturi outlets and the high level water surface. The initial additive
solution exiting the venturis impacts the rotating conical disperser and
is evenly spread across the water surface in the dispersion tank by the
conical disperser. As best seen in FIG. 5, the conical disperser employs
paddle-like spokes 112 which, in the embodiment shown, extend in spaced
curves from the apex of the conical disperser to its rim. A further
refinement of the conical disperser incorporates apertures 114 spaced on
the conical surface to intermediately disperse the additive solution onto
the water surface prior to reaching the periphery of the conical
disperser. Operation of the embodiment of the dispersion tank shown in
FIG. 5a is substantially similar to the description provided with regard
to FIG. 1.
FIG. 6 discloses a trailer mounted limited scale version of the present
invention for easy portability. The embodiment shown in FIG. 6 employs a
single hopper 10 for dry additive, integrally mounted over a single
dispersion tank 20 which incorporates horizontally mounted impellers.
Operation of the system is substantially as described with regard to FIG.
1. The mounting trailer 70 incorporates a self-contained generator 72 for
operation of the water pump 16, impeller motor, and any process controller
employed. Trailer enclosure 74 incorporates shelving 76 for storage of the
dry additive in bag form 78. The totally self-contained system as shown in
FIG. 6, is employable in small-scale operations wherein quantity of
additive supplied to the field or frequency of application preclude the
need for large scale systems such as that disclosed in FIGS. 1 and 3. The
lack of an aging tank in the embodiment shown in FIG. 6 does not allow for
full hydration of the polymer additives, however, adequate dispersion of
the additive in the water is achieved. The system disclosed in FIG. 6 is
particularly applicable to open irrigation systems such as canals and
furrows.
Having now described the invention in detail as required by the patent
statutes, those skilled in the art will recognize substitutions and
modifications to the embodiments of the invention herein. Such
substitution and modifications are within the scope and intent of the
invention as defined in the following claims.
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