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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates, in general, to a mixing system for the
production of materials such as fertilizers, and more particularly to an
automated batch blending system for liquid fertilizer.
Prior art systems for the manufacture of fertilizer have generally been
manually controlled and consist of fluid batch blending devices which
produce 10 to 15 tons of fertilizer per batch, with hourly production
ranging from 30 to 100 tons. Such systems require from 10 to 20 horsepower
per ton to operate, so that the cost for building and operating such a
system, and the production rates which it requires, are so high, that
retail outlets cannot justify their installation and use. As a result,
fertilizer must be made at central locations and transported to the retail
outlets for storage, with consequent increased costs and reduced
efficiency.
SUMMARY OF THE INVENTION
The present invention is directed to a mixing system for the production of
materials such as fertilizers, wherein selected ingredients are added
under controlled conditions to produce the final result. Both liquid and
dry products are mixed in the process, with some of the mixing taking
place in a venturi line and in a product recycling line and other
materials being added directly to a product/mixing holding tank. A control
system automatically regulates control valves in response to measured
conditions and further in accordance with a predetermined sequence by
which specified quantites of material are added to the product in sequence
to produce the final product.
More particularly, the invention includes a weighing and mixing hopper, or
tank, containing a circulating tank eductor for mixing the contents of the
hopper. The hopper is supported by a load beam for weighing the contents
of the hopper and a float sensor is provided to prevent overfilling. An
upper manifold is provided for supplying materials to the mixing hopper,
this manifold receiving water, liquid clay, and aqua, or optionally,
anhydrous ammonia, by way of remotely controllable inlet valves for supply
to the hopper. The manifold also receives product liquid from the
discharge line of a venturi loop leading from a venturi jet where dry
ingredients are added to the product.
A recycling mixing loop is also provided for the hopper, the recycling loop
receiving product liquid from the bottom of the hopper by way of a mixing
pump which supplies the product under pressure to a vertical manifold.
This manifold includes a venturi loop outlet valve for directing product
to the venturi jet, includes an inlet for supplying a phosphate base to
the recycled product, includes an outlet line leading to a storage tank,
and includes an outlet line which leads to the circulating tank eductor in
the hopper to complete the recycling loop. All of these inlet and outlet
lines from the vertical manifold are controlled by remotely operated
valves whereby the material from the mixing hopper can be directed to the
venturi, to storage, or mixed with material such as a phosphate base, and
recycled.
The venturi loop outlet from the vertical manifold leads to a venturi jet
to which is connected a dry hopper for supplying dry ingredients to the
product liquid in the venturi loop. This flow of product liquid creates a
vacuum in the venturi jet which causes dry material to be injected into
the liquid system. The dry hopper is connected to the venturi jet through
a valve which is remotely controlled. A suitable auger, also remotely
controlled, supplies the dry ingredient to the dry hopper as required. The
venturi loop discharge line is connected to the upper manifold, as
previously discussed.
A control panel for the system includes selector switches for regulating
the various valves, pumps, the dry feed auger, and ingredient supplies.
These control switches preferably have three positions, an "off" position,
a "manual" position for manually controlling the respective system
elements, and an "automatic" position which permits control of the
respective system elements by means of a suitable programmable controller
such as a microprocessor located in the control panel. The control panel
preferably also includes a key panel for entry of control data into the
microprocessor, whereby the operator can program the microprocessor to
select the sequence and timing of the various operations so as to control
the composition of the batch. Indicator lamps provide a visual indication
of the operation of each of the system elements, and a suitable readout
panel permits monitoring of the readings obtained from the scale used to
measure the weight of the materials in the mixing hopper, and allows a
comparison of measured and target values. A hold switch may also be
provided on the control panel to permit entry of data into the system
without causing automatic operation of the controlled system elements, and
also permits manual operation of the system.
In operation, the recycling loop for the mixing hopper is opened by opening
the recycle valve, and water is supplied to the mixing hopper by way of
the incoming water line and the upper manifold. The weight of the mixing
hopper is measured by the load scale, is displayed on the control panel
and when that weight reaches a selected target value, the water valve
closes. Thereafter, the valve controlling the supply of liquid clay is
opened and a measured quantity of that material is supplied to the mixing
hopper. This is followed by similar additions of aqua and phosphate base,
with the scale providing measurements of the quantities of materials
added. When these steps have been completed, the mixing pump is turned on
and product from the mixing hopper is blended by circulating the material
through the vertical manifold in the recycle loop and through the
circulating tank eductor. This is done for a predetermined blend time and
thereafter dry induction is initiated as long as the pressure in the
recycle loop is above a certain value.
To carry out dry induction, the venturi loop inlet valve leading to the
venturi loop from the vertical manifold is opened and the recycle valve is
closed. The dry hopper valve is opened and dry ingredients are supplied to
the product flowing through the venturi jet. The flow of liquid from the
mixing hopper through the venturi jet causes dry material to be injected
into the liquid stream, and this mixture is carried through the venturi
discharge to the upper manifold where it is dropped into the
weighing/mixing hopper for mixing and recirculation. When a predetermined
weight of material has been added in this manner, the venturi loop is
closed.
After dry induction, the recycle valve is opened and the mixing pump forces
liquid through the recycle loop and through the recirculating tank eductor
for a predetermined mix time. Thereafter, the recycle valve closes and the
storage valve opens to discharge the blended batch to a storage tank. When
the scale display on the control panel nears zero, indicating that the
mixing hopper is empty, the mixing pump is turned off and the entire
process may be repeated. This process requires three to eight minutes for
completion and produces a maximum batch size of about 2,000 lbs, a size
that is conveniently suited to the needs of retail operators at a
reasonable cost. This allows small volume operators to manufacture liquid
fertilizers on site rather than relying on a central manufacturing point,
thus avoiding high freight and mixing charges.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and additional objects, features and advantages of the
present invention will be apparent to those of skill in the art from a
consideration of the following detailed description of a preferred
embodiment thereof, taken in conjunction with the accompanying drawings in
which:
FIG. 1 is a schematic illustration of the system of the present invention;
and
FIG. 2 is a diagrammatic illustration of the control panel for the system
of FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Turning now to more detailed consideration of the present invention, there
is illustrated in FIG. 1 a batch mixing system 10 for batch blending
products such as liquid fertilizers in accordance with the present
invention. The system incorporates a weighing and mixing hopper 12 which
is generally rectangular, having four inwardly and downwardly sloping side
walls 14, 16, 18 and 20 which slope toward a bottom apex 22 at which is
located an outlet product flow line 24. The hopper 12 is supported by a
circumferential frame 26 and three support legs such as those illustrated
at 28 and 30. Two rear support legs 28 are provided, one at each rear
corner of the generally rectangular hopper, with the legs 28 being mounted
on pivots 32 to permit pivotal motion of the hopper 12. A front edge leg
30 is supported on a suitable scale such as load beam 34. This mounting
arrangement permits the load beam scale to accurately weigh the contents
of the mixing hopper as the material is added to it, so that accurate
batch mixing can be carried out. The load beam is a conventional
electronic load cell, strain gauge, or other conventional weight
measurement device. Mounted within the mixing hopper is a conventional
circulating tank eductor 40, such as that manufactured by Penberthy
Houdaille of Profitstown, Illinois, carried at the lower end of a
recycling flow pipe 42, the eductor outlet being located near the apex 22
of the hopper. Eductor 40 provides agitation and mixing of the product
constituents within the mixing hopper 12 during recycling of product
through a recycling loop generally indicated at 44.
The recycling loop 44 includes the outlet product flow line 24 which leads
from the apex 22 of hopper 12 to the inlet of a high pressure process pump
46 driven by an electric motor 48. The outlet of the pump supplies liquid
product to the lower end of a vertical manifold 50 which, in turn, is
connected at its upper end through a recycle valve 52 to the product
recycling flow pipe 42, completing the recycling loop 44.
Connected near the bottom of the vertical manifold 50 is a venturi loop
inlet valve 54 leading to a venturi loop 55. The valve 54 outlet is
connected by way of product flow line 56 to a venturi jet 58 such as the
"jet pump" manufactured, for example, by Penberthy Houdaille of
Profitstown, Illinois. The jet pump allows dry, fine, soluble ingredients
to be introduced into the liquid product stream from a dry hopper 60 into
which the dry ingredients are fed by means of a dry auger 62. The hopper
60 includes a level sensor 64 which detects the level of material in the
dry hopper and controls the operation of an auger drive motor 66 to
control the flow of dry ingredients into the hopper. The outlet 68 of the
dry hopper is connected by way of a hopper valve 70 to the venturi 58,
this valve being opened to allow a flow of material into the venturi when
liquid is flowing through line 56 and venturi 58. Such a liquid flow
causes the dry material to be injected into the liquid stream and to be
mixed into that stream. The valve 70 closes when the venturi jet is not
operating to prevent liquid from back flowing into the hopper. The output
of the venturi 58 is supplied to a venturi discharge line 72 and is
returned to the weighing and mixing hopper 12 to complete loop 55, as will
be described.
It will be noted that a pressure gauge 74 is provided at the downstream end
of the venturi 58 for permitting an operator to monitor the pressure of
the venturi discharge. This pressure will normally be in the range of zero
to 5 psi.
The vertical manifold in the recycling loop 44 also is connected to a feed
line 80 which incorporates an inlet control valve 82. Feed line 80 is
connected, for example, to a source of phosphate base material in liquid
form which is supplied to the vertical manifold under suitable pressure.
The phosphate material may be supplied from a suitable storage tank by
means of a pump (not shown) or from a similar supply source.
The top end of the vertical manifold 50 is connected through a storage
valve 84 to a discharge line 86 which leads to a storage tank (not shown)
for storage of a completed liquid fertilizer batch. The vertical manifold
includes a high pressure gauge 88 for visual monitoring of the pressure in
the manifold, which may range up to 100 psi, and also includes an
automatic pressure gauge 90 which provides an output signal for use in
monitoring the process pressures during automatic control. This latter
gauge provides an output to the control panel (to be described) for the
system for use in determining control parameters.
Located above the open top of the weighing and mixing hopper 12 is an upper
manifold 100, the lower end of which opens into the mixing hopper 12, as
indicated by the arrow 102. Manifold 100 is connected to discharge flow
line 72 and thus receives the product discharge by the venturi 58, which
product is then dispensed into the hopper 12. Manifold 100 is also
connected to a water line 104 by way of a water control valve 106, is
connected to a liquid clay supply line 108 by way of a clay supply valve
110 and is connected to an incoming aqua (liquid nitrogen) line 112 by way
of control valve 114. Alternatively, the supply line 112 may be connected
to a source of anhydrous ammonia (NH.sub.3) from a separate anhydrous
ammonia venturi loop.
The hopper incorporates a detecting switch 119 at its top for measuring the
product level of the hopper. This switch produces an output signal when
the level exceeds a predetermined valve to close down all of the inputs to
the system so as to prevent overflow.
As illustrated in FIG. 2, a control panel 120 is provided for regulating
the operation of the system of FIG. 1. The control panel incorporates a
plurality of manually operated switches 122 which preferably are three
position switches that can be set to an "off" position, a "manual"
position, or to an "automatic" position, by the system operator. Each
switch is connected so that when it is in the manual position, the switch
activates its corresponding system element and when it is turned off, that
element is also turned off. Thus, if the switch is connected to operate
the motor 48, switching it to manual will turn the motor and pump on, and
switching it to the off position will shut the pump down. The automatic
position of the switch 122 places the operation of that system element
under the control of a programmable controller 124 which may be a
microprocessor and which is located in the control panel and connected to
the switch of the panel by way of cable 126. The microprocessor then
operates the element in accordance with a predetermined program or
sequence to provide the desired fertilizer product. Adjacent each of the
switches 122 is a corresponding indicator lamp 128 which indicates when
the corresponding system element is activated.
The control switches 122 provide automatic-off-manual selective operation
for the water valve 106, the phosphate valve 82, a phosphate pump (not
shown), the aqua valve 114, the clay valve 110, the dry auger feed 66, the
recycle valve 52, the discharge valve 84, the venturi valve 54, the
venturi hopper valve 70, the mixing pump 46 and the optional alarm. A
control switch may also be provided for an optionally available recycling
loop for the anhydrous ammonia supply (not shown) as well as other control
elements that may be desired. Switches may also be provided to control the
input signals from the dry hopper switch 64 and from the automatic
pressure gauge 90 if desired.
The control panel also includes a digital scale readout display 130 which
provides a display of the actual weight of the material in the mixing
hopper 12 to permit the operator to monitor the operation of the system.
The panel also includes an entry keypad 132 by which instructions
concerning the operation of the system are entered into the processor 124
and a keypad display 133 which displays target weights for each stage of
the mixing process. Power switch 134 on panel 120 provides a master power
control for the system, while the auto/hold switch 136 when in the "hold"
position places the system in a hold condition to permit entry of data or
instructions into the processor 124, or to permit manual operation of the
system. Switching the switch 136 to the auto position permits automatic
operation of the batch process.
Processor 124 receives input signals on line 140 from the load beam scale
34 to provide continuous information concerning the weight of the hopper
12. Input line 142 provides a signal from the level sensor 64 on dry
hopper 60, which signal is used to regulate the operation of the auger
drive motor 66. When the system is in operation, the sensor determines
whether the hopper 64 contains the dry ingredient for the mixing process,
and if not, causes the auger 62 to supply such material until the hopper
is full.
Line 144 receives signals from the level switch 119 located at the top of
the mixing hopper 12. This signal is a shutdown signal which occurs when
the hopper 12 is overfull and in response to such a signal the processor
shuts down any inlet lines which might be supplying additional material to
the batch.
Line 146 provides inputs from the pressure gauge 90 and, if desired, from
pressure gauge 74 and similar gauges connected in the input lines 80, 108,
104, or 112 to insure that sufficient liquid pressure is available for the
proper operation of the system. The processor supplies control signals by
way of output line 150 to the drive motor 48 of mixing pump 46 to regulate
the operation of that pump in accordance with the batch process. This
signal is provided in accordance with the program sequence of operation of
the batch process so that the product liquid is cycled through the recycle
loop 44 and through the venturi loop 55 to provide the required mixing of
the constituent elements of the product.
Output line 152 from processor 124 supplies control signals to the several
control valves which regulate the flow of material in the system of FIG.
1. These valves may be any suitable electrically controllable valves which
respond to signals on line 152 for opening and closing. The processor
produces the appropriate signals, for example digital control signals,
together with valve addresses, to select the valves for operation in
accordance with the program sequence established by the system operator.
The output line 154 from microprocessor 124 provides control signals for
the auger motor 66 in response to level signals received from sensor 64 by
way of line 42, as previously discussed. The motor 66 activates the dry
auger 62 to supply material to the hopper 60 as required.
Line 156 from processor 124 provides an alarm signal in response to
selected failures in the system. Thus, for example, an overfill signal
from sensor 119 which results in a shut down of the system may also be
used to activate an alarm by way of line 156.
To operate the system of FIG. 1, the operator first switches the auto/hold
switch 136 to its hold position so as to prevent automatic operation of
the system. The power is then turned on by means of switch 134 and the
scale display 130 comes up and displays the weight of the mixing hopper
12. At the beginning of the cycle, the hopper 12 should be substantially
empty. The scale display should then read zero, and if it does not, then
calibration may be required. Thereafter, if the formula is not
preprogrammed, the operator keypad 132 may be used to enter the desired
formula weights for the batch to be mixed into the processor 124. These
weights are determined by the desired end product and determine the
quantities of water, clay, aqua, phosphate, and any dry ingredients such
as phosphorous. Upon entry of these formula weights, the switch 136 is
turned to the "automatic" position to permit the mixing process to begin.
In the preferred form of the invention, the processor 124 establishes a
sequence of valve openings and pump operation which mixes the ingredients
in the following sequence. First of all, the recycle valve 52 is opened so
that the recycling loop 44 is ready for operation. The water valve 106 is
then opened and water is supplied to the mixing hopper. The weight of the
hopper changes as water is supplied, and this measured weight is displayed
on the scale display 130. The signals from the scale load beams 34 are
supplied to the microprocessor by way of line 140, with the microprocessor
furnishing the display 130 on the control panel. The processor also
monitors the scale weight and when that weight reaches the target scale
weight, which is displayed at 133, as established by the formula, the
water valve 106 closes.
In similar manner, the clay valve 110, the aqua valve 114 and the phosphate
base valve 82 are opened in sequence and liquid under pressure is supplied
through the respective supply lines and through manifold 100 to the hopper
or through manifold 50 and product flow pipe 42 to the mixing hopper 12.
In each case, target weight for the material being added is established,
and when scale 34 indicates that this weight has been reached, the
corresponding valve is closed. These valves are operated sequentially so
that first one valve is opened, its material is supplied to the mixing
hopper, the weight being added to the hopper is monitored, and when the
target weight is reached that valve is shut down and the next valve opened
and the measuring cycle is repeated.
After each of the valves 110, 114, and 80 have been opened and then closed
upon delivery of their respective materials, the microprocessor 124
provides a mixing signal by way of line 150 to the mixing pump 46,
energizing the motor 48 to drive the pump and to circulate the product
from the mixing hopper 12 through the recycling loop 44. The pump draws
liquid product from the bottom of hopper 12 through product flow line 24,
through the pump, upwardly through the vertical manifold 50, through the
open valve 52 and the recycling line 42, through the eductor 40 and back
into the hopper 12. This operation continues for a predetermined blend
time which is sufficient to insure a complete mixing and blending of the
materials added to the hopper.
At the end of the blend time for the liquid product in hopper 12, the dry
ingredient is then added. This accomplished by opening the venturi inlet
valve 54, but this occurs only if the pressure gauge 90 provides a signal
on line 146 indicating that the pressure is above a predetermined level.
If it is not above this level, the flow through the venturi will not
provide a sufficient induction of dry material into the liquid product.
When the venturi valve 54 is opened, the recycle valve 52 is closed to
prevent liquid from bypassing the venturi loop 55. The hopper valve 70 is
then opened and the flow of liquid through the venturi induces dry
ingredient from hopper 60 to flow through the valve 70 and into the
flowing liquid product. This material flows into the venturi discharge
line 72 and is carried to the manifold 100 where it is dropped into the
mixing hopper 12.
During the addition of dry ingredients, the dry auger 62 will be operated
in response to signals on line 154 from the microprocessor whenever the
level switch 64 indicates that the dry ingredient level in the hopper 60
is below a predetermined level. Thus, the dry auger operates to keep the
hopper 60 full to insure addition of the proper quantity of dry ingredient
to the product. The quantity of dry ingredient is measured by the load
beam scale 34, as previously described, with the output from the scale
being supplied to the microprocessor by way of line 140. When the scale
indicates that sufficient dry material has been added to the product; that
is, when the hopper 12 reaches a predetermined weight, the valve 70 is
closed.
Upon completion of the dry induction process in the venturi loop 55, the
recycle valve 52 is reopened and the mixing pump, which continues to
operate, forces liquid around the recycle loop 44 and thus through the
eductor 40. The flow may also continue through the venturi discharge loop
55 for a time to insure that the product in that line is completely
recycled to produce a thorough blending of the product constituents. At
the end of this predetermined mixing time, the storage valve 84 is opened,
the recycle valve 52 is closed, the venturi valve 54 is closed (if it has
not already been closed) and the blended batch is pumped to a storage tank
by way of line 86. The pumping continues until the scale display returns
to zero, indicating that the hopper 12 is empty, at which time the mixing
pump 46 is turned off and the process is complete.
It will be noted that any time the high level shut down switch 119 in the
mixing hopper 12 is activated, the operation of the valves controlling the
incoming ingredients are deactivated and will not function until the
system is reset.
Typical raw materials for the system 10 are as follows:
TABLE I
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DRY MATERIALS
Potash (K.sub.2 O)
62.4% K Fine 71 lbs/ft.sup.3
MAP 10-50-0 Powder 67 lbs/ft.sup.3
MAP 10-52-0 Granular
67 lbs/ft.sup.3
MAP 11-53-0 Granular
67 lbs/ft.sup.3
DAP 18-46-0 Granular
62 lbs/ft.sup.3
Clay (Attadulgite) 50 lbs/ft.sup.3
Powder/Gran.
Limestone Fine 82 lbs ft.sup.3
Urea 45% N 41 lbs/ft.sup.3
WET MATERIAL
Water 8.345 lbs/gal.
Aqua (22-29% total Nitrogen)
8 lbs/gal.
Phosphate Bases
8-24-0 Suspension
11.4 lbs/gal.
10-30-0 Suspension
11.4 lbs/gal.
10-34-0 Clear 11.4 lbs/gal.
Phosphoric Acid
(54% phosphate) 14.25 lbs/gal.
Liquid clay 25% dry wht. 10 lbs/gal.
Urea-ammonium-nitrate
28-0-0 10.67 lbs/gal
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where "MAP" is monoammonium phosphate, and where "DAP" is Dammonium
phosphate.
These materials are mixed in accordance with the formula programmed into
the microprocessor of the present invention.
The following tables illustrate the amounts of materials used for several
fertilizer mixtures produced in accordance with the present invention:
TABLE II
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Formulation:
1.7-5-30 2-6-34 3.3-10-30
0-0-34 0-0-42
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Water 522 lbs 315 lbs 127 lbs
710 lbs
534 lbs
Clay 99 95 78 200 120
8-24-0 417 500 833
Potash 962 1090 962 1090 1346
% Water 40 32 30.5 43 31
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TABLE III
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10-30-0 8-24-0
Formulation
(Using 11-52-0 MAP)
(Using 10-50-0 MAP)
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Water 444 lbs 676 lbs
Clay 100 100
Aqua 302 264
MAP 1154 960
% Water 41 51
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TABLE IV
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Formulation Liquid Lime
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Water 800 lbs
200 Mesh Lime 1200
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In the foregoing formulations, liquid clay is 25% dry and the balance is
water.
To calculate the amounts ofmaterials required in the 8-24-0 formulation of
Table III, for example, the formula is first multiplied by 20, yielding a
160-480-0 formulation. If the MAP formulation is 10-50-0, then the amount
of MAP required is 480/0.50=960 pounds. The Nitrogen is obtained from the
Aqua and the MPA. From 960 pounds of MAP the nitrogen available is
0.10.times.960=96 units of N. The amount required from the Aqua is
160-96=64 units. With 24.2% Aqua being used. 64 units/0.242=264 pounds of
Aqua. The amount of clay is 100 pounds per ton of product, giving the
total of 2,000 pounds of product set out in this example.
To calculate the amounts of material required for the 2-6-34 formulation in
Table II, the formula is first multiplied by 20 to obtain 40-120-680
units. The phosphate source is the 8-24-0, which yields 120/0.24=500 lbs.
The nitrogen from the 8-24-0 is 500.times.0.08=40 units of N. Since 40
units of N are what is required, it is not necessary to add NH.sub.3 to
the product. Potash (62.4%) required is 680/0.624=1090 lbs. The liquid
clay calculation is as follows. 120 lb/ton of liquid clay is needed. There
is 100 lb/ton of liquid clay in the 8-24-0, so this material yields
100/2000.times.500=25 lb of clay. Thus, 120-25=95 lb of liquid clay is
required for each batch.
The system as described above may utilize a mixing hopper of up to about
300 gallons to allow mixing of small batches of products such as liquid
fertilizer. This system provides a simple, easy to use and inexpensive
fertilizer production facility which is suitable for use by retail
outlets, and thus meets a significant need in the industry. Although the
present invention has been disclosed in terms of a preferred embodiment,
it will be apparent that variations and modifications may be made without
departing from the true spirit and scope thereof, as set forth in the
accompanying claims, in which:
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