U.S. patent application number 10/412305 was filed with the patent office on 2003-09-18 for compost granulation method.
This patent application is currently assigned to Agronomic Growth Industries Ltd.. Invention is credited to Phinney, Robin.
Application Number | 20030172699 10/412305 |
Document ID | / |
Family ID | 26830501 |
Filed Date | 2003-09-18 |
United States Patent
Application |
20030172699 |
Kind Code |
A1 |
Phinney, Robin |
September 18, 2003 |
Compost granulation method
Abstract
Method of granulating compost for the formulation of
fertilizers. In one embodiment, the compost is ground to dust and
pan granulated. A variety of ancillary materials may be
incorporated into the compost mix for a wide range of possible
applications. An embodiment is provided where agricultural seeds
may be encapsulated in compost to enhance the quality of seed and
reduce wastage during planting.
Inventors: |
Phinney, Robin; (Calgary,
CA) |
Correspondence
Address: |
OGILVY RENAULT
1981 MCGILL COLLEGE AVENUE
SUITE 1600
MONTREAL
QC
H3A2Y3
CA
|
Assignee: |
Agronomic Growth Industries
Ltd.
Calgary
CA
|
Family ID: |
26830501 |
Appl. No.: |
10/412305 |
Filed: |
April 14, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10412305 |
Apr 14, 2003 |
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09565534 |
May 5, 2000 |
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6582637 |
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60132569 |
May 5, 1999 |
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60132681 |
May 5, 1999 |
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Current U.S.
Class: |
71/64.03 |
Current CPC
Class: |
C05G 5/30 20200201; Y02P
20/145 20151101; C05F 9/04 20130101; Y02A 40/20 20180101; Y02W
30/40 20150501; B01J 2/14 20130101; A01C 1/06 20130101; C05F 9/04
20130101; C05G 1/00 20130101 |
Class at
Publication: |
71/64.03 |
International
Class: |
C05G 005/00 |
Claims
I claim:
1. A method of encapsulating an agronomic seed with compost
material into a granulated pellet, comprising the steps of:
providing a source of dried and pulverized compost material,
pulverized to dust in a size distribution of 90% of less than -150
mesh; providing a source of agronomic seeds; forming a moist
mixture of dry pulverized compost and binder containing moisture,
said mixture containing up to 11% by weight moisture; mixing said
mixture sufficiently to invert the hydrophobicity of said
pulverized compost material, where said pulverized compost material
absorbs said moisture from said binder and forms a flowable
compound; providing a granulation pan; contacting said pan with
said agronomic seeds; contacting said pan with said mixture; and
granulating said mixture about said seeds on said pan by contact of
said mixture with said seeds; and forming pellets of encapsulated
agronomic seeds with compost.
2. The method as set forth in claim 1, wherein said seeds comprise
agricultural crop seeds.
3. The method as set forth in claim 2, wherein said seeds are in a
size distribution of between +35 mesh and -8 mesh.
4. The method as set forth in claim 2, wherein encapsulated seeds
are in a size distribution of between 3 mesh and 12 mesh.
5. The method as set forth in claim 2, wherein at least 30% of
encapsulated seeds contain a single seed.
6. The method as set forth in claim 2, wherein said mixture
includes at least one of sulfur, micronutrients, pH buffers, pH
modifiers, bacteria, ion exchanging clay, molecular sieves,
fertilizer compounds, fertilizer blends, pesticides, fungicides,
minerals or a combination thereof.
7. A method of granulating compost material, comprising the steps
of: providing a source of dried and pulverized compost material,
pulverized to dust in a size distribution of 90% of less than -150
mesh; providing a source of a fertilizer material as a seeding
agent; forming a moist mixture of dry pulverized compost and binder
containing moisture, said mixture containing up to 11% by weight
moisture; mixing said mixture sufficiently to invert the
hydrophobicity of said pulverized compost material, where said
pulverized compost material absorbs said moisture from said binder
and forms a flowable-compound; providing a granulation pan;
contacting said pan with said fertilizer material; contacting said
pan with said mixture; and granulating said mixture about said
fertilizer material on said pan by contact of said mixture with
said seeding agent; and forming pellets of encapsulated fertilizer
material with compost.
8. A granulated compost granule made in accordance with claim
7.
9. A granulated compost granule, comprising: an agronomic seed; and
compost material granulated therearound.
10. A composite compost granule, comprising: a central fertilizer
core; and compost material granulated therearound.
11. A composite granule, comprising: an agronomic seed in a size
distribution of between +35 mesh and -8 mesh; composite material
layered thereon forming a granule having a seed encapsulated
therein in a size distribution of between 6 mesh and 8 mesh.
12. The granule as set forth in claim 11, wherein said seed
comprises an agricultural crop seed.
13. The granule as set forth in claim 11, wherein said seed
comprises an canola seed.
14. The granule as set forth in claim 11, wherein said compost
material comprises animal compost.
15. The granule as set forth in claim 11, wherein said compost
material comprises plant compost.
16. A composite granule, comprising: a homogenous blend of compost
and fertilizer.
17. The granule as set forth in claim 16, wherein said compost is
granulated with seed fertilizer.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application Nos. 60/132,569 filed May 5, 1999 and 60/132,681
filed May 5, 1999.
FIELD OF THE INVENTION
[0002] The present invention relates to granulation of compost
materials and more particularly, the present invention relates to a
method of producing high quality granulated compost and multiple
component compost granules for fertilizer applications.
BACKGROUND OF THE INVENTION
[0003] The granulation art is a mature art and recently significant
advances have been made by Derdall et al., U.S. Pat. No. 5,460,765,
issued Oct. 24, 1995 and subsequently by Phinney in U.S. Pat. No.
6,013,209, issued Jan. 11, 2000.
[0004] With reference to Derdall et al., this disclosure provided
teachings which advanced this art by demonstrating that an ultra
fine powder (-200 mesh) does not cause nucleation of the powder,
but rather results in adhesion of the material to large round
pellets. This process is not unlike the proverbial growth of a
snowball. The technique invented by Derdall et al. clearly provides
excellent process control needed to effectively maximize the
contact of fine particles with binder. As a result, binder
additions of 5% and less are routinely used where the previous art
required approximately double this amount. As is evident, if the
amount of binder can be reduced, the amount of feedstock in the
particle can be increased, which, in turn, provides an improved
pellet or granule.
[0005] The Derdall et al. process established that a large
significant crystal or seed is critical to perform the granule
formulation in one step. Although this is a significant advance in
the art, it does not contemplate granulation of materials directly
on the pan. If a mixture of material which contains the feedstock
to be granulated and moisture is provided in a pre-moistened
mixture, there is effectively no seed or nucleating agent present.
This material is then used directly on the pan containing the
powdered feedstock to facilitate growth of a granule.
[0006] Derdall et al. advanced the granulation art significantly by
demonstrating that powdered material could be granulated, provided
a seed material was used as an initiator to grow the particle.
Prior to the efforts by Applicant, Derdall et al. effectively
taught the state-of-the-art and is an extremely useful process when
seed material can be used to form a granule. Such granules have
obvious cores in the center of the granule.
[0007] In the art, it has been generally recognized that any
particle greater than +150 mesh and -100 mesh causes
over-nucleation on the pan which inevitably leads to the particles
sticking together in agglomerated groups. This led to the
conclusion that in order to make a strong enough pellet a binder
must be present in an amount generally between 4% to 10% in order
to effect proper adhesion of the materials into a consolidated
particle.
[0008] The Derdall et al. reference clearly teaches that there are
stability problems with the process if one uses a seed which
exceeds certain size parameters. In summary, Derdall et al. was the
first to provide a process for granulating powdered material.
[0009] Turning to the Phinney disclosure, an advance over what was
initially demonstrated in Derdall et al., was provided. In the
Phinney patent, it was found that if one were to use a nucleating
agent, which is effectively a powder in the size range of -35 mesh
to 150 mesh, a seed could be grown and composed of the same
material of the final product in a size distribution of
approximately -8 mesh to +4 mesh. The distinction between Derdall
et al. and the Phinney patent resides in the fact that Phinney
recognized that a seed was not initially required to effect
granulation; the seed could be formulated by using an initial
nucleating material in a powder form to first formulate a seed
which could be later grown in further granulation operations. This
resulted in significant advantages in terms of the final product
quality. One of the chief advantages is directed to particle
strength and uniform material accretion about the seed. In view of
the fact that the nucleating material used was effectively
infinitesimally small, the Phinney granules effectively had no core
relative to the particles produced by the Derdall et al. method. In
this manner, the particles produced according to the Phinney
methodology provide particles having a uniformed and uninterrupted
cross-section. Accordingly, a higher feedstock content could be
included in each granule or pellet.
[0010] The Phinney and Derdall et al. references have provided
significant instruction in the granulation art with respect to
materials having fairly high bulk density. In the case of these
references, sulfur has been illustrated as an example that could be
granulated. Sulfur has a fairly high bulk density, approximately of
the order of between 30 and 35 pounds per cubic foot (lbft-.sup.3).
This bulk density presents a particle size of between about 180
mesh and 300 mesh. At this bulk density, there is sufficient mass
to permit the granulation of the product. It has been found that
this is not the case with all materials and problems can arise when
the bulk density drops from the value indicated for sulfur to, for
example, compost. The granulation of compost material presents
unusual complications. Compost material, when pulverized, is
extremely lightweight, hydrophobic and the individual particles
repel one another by electrostatic interaction. The bulk density of
compost is approximately between 20 lbft-.sup.3 to about 25
lbft-.sup.3, which corresponds to a particle size of generally
between about 240 mesh to about 400 mesh. This powder level, taken
together with the properties of compost, the techniques established
in the prior art and particularly, the Derdall et al. and Phinney
references, require modification under certain circumstances to
effect granulation of this valuable agronomic compound.
[0011] The proposition of granulating compost has been proposed in
the prior art as has the concept of coating or otherwise
encapsulating seeds for the protection of the seed until such time
that it is desired for this to germinate.
[0012] Typical of the prior art in this area includes the process
set forth in U.S. Pat. No. 3,905,796, issued September 1975, to
Ghelfi. The disclosure teaches a process for dehydrating manure
based fertilizers where a homogenous and durable pulp is granulated
and dried.
[0013] U.S. Pat. No. 4,082,532, issued to Imhof, Apr. 4, 1978,
discloses a process for manufacturing extruded cattle manure
pellets where the cattle manure is mixed into a pulp and contains a
moisture content between 50 to 55% by weight. The material is
extruded to form strands which are subsequently further broken down
into smaller forms. In this reference and the above-mentioned
reference, there is no discussion as to the use of further
agricultural additives to the compost and very few details
concerning the granulation. It has been discovered in the instant
application that once the compost material has been dried and
pulverized, it is difficult to wet this material in the absence of
a surfactant. The references discussed thus far do not touch on
this issue whatsoever and only provide generic teachings with
respect to the granulation.
[0014] Davis, in U.S. Pat. No. 5,043,007, provides a process for
the production of fertilizer or the fertilizer is binder free
fertilizer. The disclosure provides for a seed material and a
primary and secondary nutrient sources which are put into a blender
under heat until the slurry is formed. The slurry is transferred to
a dryer and the product dried under vacuum and thereafter cooled to
produce a granular or semi-granular fertilizer with a core of a
seed material and a coating of a secondary nutrient crystallized
thereabout.
[0015] In U.S. Pat. No. 5,725,630, issued to Roberts et al., Mar.
10, 1998, a fertilizer plant is set forth as well as a dry granular
fertilizer. The granular fertilizer contains a C1-C6 alkanoic acid
or salt of this compound added on to a dry carrier form of granular
fertilizer. This is a simple coating process and does not provide a
granule having ancillary or auxiliary fertilizer compounds
granulated uniformly therein.
[0016] Turning to additional prior art in the fertilizer/seed
encapsulation field, U.S. Pat. No. 4,779,376, issued to Redenbaugh,
Oct. 25, 1998, discloses an encapsulation method for a botanical
seed where the seed is encapsulated in a water saturated hydrogel
capsule.
[0017] Johnson et al., in U.S. Pat. No. 3,648,409, issued Mar. 14,
1972, discloses a herbicide resistant carrier process for
manufacturing the product. There is disclosed a method and a
herbicide resistant wafer encases a seed and a mixture of water
soluble nutrient binder vermiculite and activated charcoal, which
is subsequently compressed into a desired shape, in this case, a
wafer.
[0018] Other references generally related to seed coating or
encapsulation include U.S. Pat. Nos. 4,759,151, 5,849,320,
3,950,891, 3,905,152, 5,435,821 and 3,651,772.
[0019] The prior art when taken singly or in combination does not
provide specific teaching for the granulation of compost powder
material which may include auxiliary fertilizers, time release
materials, or other suitable additives well known in the
granulation art. Further, the fact that there is no teaching with
respect to the granulation of the compost, it is also submitted
that the art reviewed fails to provide a granulated product having
a seed encapsulated therein while still maintaining desirable
properties such as roundness, particle break strength, rate of
solvation, etc. It would be desirable to have a method as well as a
product directed to enhancing the fertilization of soils where the
fertilizer consists of compost material in a powdered form at the
-150 mesh level or less which may be co-granulated with additional
fertilizer materials such as some of the known fertilizers
discussed hereinafter without the problem of the hydrophobicity of
the compost powder. The present invention satisfies these needs as
well as others.
SUMMARY OF THE INVENTION
[0020] One object of the present invention is to provide an
improved method for granulating compost powder in the absence of a
nucleating material, seeding material, or other initiator. A
further object of one embodiment of the present invention is to
provide a method of encapsulating, by granulation, agricultural
seeds for the purpose of encapsulating the seed.
[0021] One object of the present invention is to provide a method
of granulating compost material, comprising the steps of:
[0022] providing a source of dried pulverized compost material in a
size distribution of 90% of less than -150 mesh;
[0023] forming a moist mixture of dried pulverized compost and
binder containing moisture, the mixture containing up to 11% by
weight moisture in the mixture;
[0024] mixing the mixture sufficiently to invert the hydrophobicity
of the pulverized compost material, where the pulverized compost
material absorbs the moisture from the binder and forms a flowable
compound;
[0025] granulating the mixture into granules on the pan by contact
of the mixture with additional binder material and a surfactant;
and
[0026] forming compost granules in a size distribution of 3 mesh to
12 mesh.
[0027] Advantageously, the compost is sterilized when heated and
pulverized and, therefore, odor and pathogens are not a concern.
This also allows the compost from any source to be used including
animal, plant or combinations of these.
[0028] In view of the hydrophobicity of the powder compost, it has
been found that by providing a free moisture content of up to 11%
by weight on the pan that the process will be viable and produce
granules. In this manner, it is an essential feature of the present
case to include a surfactant to reduce the surface tension of the
compost dust and thus allow granulation to occur directly on the
pan in the absence of any nucleating material or other particle
growth initiators. Suitable surfactants will be appreciated by
those skilled in the art. This process embodiment is effective for
granulating compost in a wide percentage by weight basis.
[0029] The art has established the use of a nucleating agent for
granulating feedstock material under "dry" conditions. This was
established in the Phinney U.S. patent discussed supra. Reference
to this type of condition was also made in the Derdall et al.
patent. In further advances made by Phinney, and particularly those
set forth in PCT Publication, PCT/CA 99/00300, (International
Publication No. WO 99/54029 published on Oct. 28, 1999), it was
established that pan granulation could be effected by simply
providing a wet mixture (a mixture containing moisture, feedstock
and surfactant) and contacting this wet mixture with feedstock
within the pan. This resulted in the formation of granules directly
on the pan in the absence of a nucleating agent or seed. In this
manner, the granulation could be effected by eliminating the step
of formulating a seed.
[0030] As briefly discussed hereinabove, compost presents new
complications for the process designer in view of the properties of
the compost. The bulk density has been mentioned above as well as
the other properties which complicate granulation procedure. In
view of the properties, direct pan granulation such as that
established in the PCT publication is not convenient. Considering
the other existing dry methodology, particularly pre-formulation of
a seed by a nucleation unit operation, this also is unsatisfactory
in view of the properties of the compost. The material is not
conducive to the preparation of a nucleating material in view of
the size distribution of such agents. This is partly due to the
fact that pulverized compost presents the hydrophobicity problem as
well as the electrostatic interaction complication. Simply by these
properties, a material that is inherently self-repulsive and
hydrophobic, cannot effectively be granulated into a pellet as a
nucleating material and most certainly not as a seed with the
ultimate goal of generating a granule acceptable in the
marketplace.
[0031] In the instant case, the full recognition of the compost
properties together with extensive engineering experience have been
combined to overcome the inherent complications with compost
granulation. It is well accepted that the Derdall et al. method as
well as the Phinney method have resulted in significant advances in
the art. Despite this, neither method is particularly well suited
to the granulation of compost, since these references were
primarily concerned with the granulation of higher bulk density
materials having further properties different from compost.
[0032] In the case where it would be desirable to form a granule of
a larger size for a particular use, a multiple phase granulation
process may be followed. Larger granules are applicable in the golf
course fertilizer industry. It is desirable to have larger granules
for time release purposes. As it has been established in the art by
Derdall et al. and Phinney, the material being granulated on the
pan will equilibrate at a certain size distribution, depending on
pan rotation velocity, pan tilt and pan pitch among a host of other
factors. As such, there is a need, under certain circumstances, to
employ a second pan for further material accretion.
[0033] Accordingly, in accordance with a further object of one
embodiment, there is provided a method of granulating compost
material, comprising the steps of:
[0034] providing a source of dried pulverized compost material in a
size distribution of 90% of less than -150 mesh;
[0035] forming a moist mixture of dried pulverized compost and
binder containing moisture, the mixture containing up to 10% by
weight moisture;
[0036] mixing the mixture sufficiently to invert the hydrophobicity
of the pulverized compost material, where the pulverized compost
material absorbs the moisture from the binder and forms a flowable
compound;
[0037] granulating in a first stage the mixture into granules on
the pan by contact of the mixture with additional binder material
and a surfactant, the granules being in a size distribution of
between 3 mesh and 12 mesh and including at least a fraction of
particles in a size distribution of between 8 mesh and 12 mesh;
[0038] granulating the fraction of particles 8 mesh and 12 mesh in
a second stage by contact with the mixture and additional binder;
and
[0039] forming compost granules in a size distribution of between
-3 mesh and +8 mesh.
[0040] In some situations, it is desirable to have a fairly
sizeable granule beyond that which is set forth in the
above-captioned object. From a procedural point of view, the -3
mesh to +8 mesh granules may be further grown to a size
distribution of 1/2" or greater. This can be accomplished by making
use of a drum granulator. Similar unit operations such as binder
addition, surfactants, blending with the binder, would be observed
in the drum to achieve 1/2" granule growth.
[0041] As it will be immediately appreciated to those skilled in
the art, it does not matter the specific order of binder surfactant
being added to the granulating pan, the point here is that the
material on the pan must have an adequate supply of surfactant to
effect granulation together with binder to adhere the compost
mixture. In this manner, the binder surfactant may be mixed and
added to create up to 11% by weight moisture content or these may
be added simultaneously separately. Variations, again, will be
appreciated by those skilled in the art.
[0042] As a further application, the technology set forth herein
fits well with the encapsulation of agricultural seed material and
accordingly, a further object of the present invention according to
a further embodiment is to provide a method of encapsulating an
agronomic seed with compost material into a granulated pellet,
comprising the steps of:
[0043] providing a source of dried and pulverized compost material,
pulverized to dust in a size distribution of 90% of less than -150
mesh;
[0044] providing a source of agronomic seeds;
[0045] forming a moist mixture of dry pulverized compost and binder
containing moisture, the mixture containing up to 11% by weight
moisture;
[0046] mixing the mixture sufficiently to invert the hydrophobicity
of the pulverized compost material, where the pulverized compost
material absorbs the moisture from the binder and forms a flowable
compound;
[0047] providing a granulation pan;
[0048] contacting the pan with the agronomic seeds;
[0049] contacting the pan with the mixture; and
[0050] granulating the mixture about the seeds on the pan by
contact of the mixture with the seeds; and
[0051] forming pellets of encapsulated agronomic seeds with
compost.
[0052] Any seed material could be encapsulated. Examples of
suitable seeds which would particularly benefit from encapsulation
are the light seeds that typically are air dropped including canola
seeds, canary, rape seeds, inter alia. This is problematic since
the seeds, being fairly light are often blown off course relative
to their intended location and this adds significant costs to the
farmer. Further, in many countries "broadcasting" of seeds is now
becoming an unpopular procedure for planting crops. By
encapsulating such seeds, mass is added, the seed is protected and
there is inherent spacing afforded by the granulation material
between seeds when planted. One of the particularly attractive
features of seed encapsulation is that the compost material
effectively acts as a fertilizer for the seed and thus provides a
seed with its own fertilizer. Further, by the provision of adding
further suitable fertilizer materials discussed herein, a most
desirable product results.
[0053] Fertilizer salts cannot be placed too close to the seed. The
osmotic pressure of these salts is too high and the seeds will not
germinate. The 1-1-1-1 in compost is in humates which the plant
readily receives without changing the osmotic pressure.
[0054] Advantageously, the methodology has resulted in greater than
30% of the granules containing a single seed. Further,
encapsulation automatically provides the seed with nutrients and
humates and considering the size of the particle (6 to 8 mesh)
small seeds are not wasted during planting. The coating also
ensures flowability of seeds that would otherwise not flow to
permit greater ease in handling and transportation.
[0055] Typical over seeding costs for Canada could be as high as
50%. With seed costs of $500 per ton, a 50% saving is substantial.
It is well known in farming that the seeds should have uniform
spacing in order to maximize yields. Too many plants too close
together reduces yields significantly. The present invention
eliminates this wastage to provide a cost effective method of
seeding.
[0056] In another application, the agronomic seed may be replaced
by a suitable fertilizer material. Accordingly, a further object of
another embodiment is to provide a method of granulating compost
material, comprising the steps of:
[0057] providing a source of dried and pulverized compost material,
pulverized to dust in a size distribution of 90% of less than -150
mesh;
[0058] providing a source of a fertilizer material as a seeding
agent;
[0059] forming a moist mixture of dry pulverized compost and binder
containing moisture, the mixture containing up to 11% by weight
moisture;
[0060] mixing the mixture sufficiently to invert the hydrophobicity
of the pulverized compost material, where the pulverized compost
material absorbs the moisture from the binder and forms a flowable
compound;
[0061] providing a granulation pan;
[0062] contacting the pan with the fertilizer material;
[0063] contacting the pan with the mixture; and
[0064] granulating the mixture about the fertilizer material on the
pan by contact of the mixture with the seeding agent; and
[0065] forming pellets of encapsulated fertilizer material with
compost.
[0066] A further object of one embodiment of the present invention
is to provide a granulated compost granule, comprising:
[0067] an agronomic seed; and
[0068] compost material granulated therearound.
[0069] An even further object of one embodiment of the present
invention is to provide a composite granule, comprising:
[0070] a homogenous blend of compost and fertilizer.
[0071] A still further object of one embodiment of the present
invention is to provide a composite compost granule,
comprising:
[0072] a central fertilizer core; and
[0073] compost material granulated therearound.
[0074] The advantages ascribable to the products formed in
accordance with the methods are numerous and include the
following:
[0075] a. the product is granulized dry;
[0076] b. particle size can be customized for specific uses;
[0077] c. transportation is greatly simplified relative to
conventional compost;
[0078] d. the granules assist in soil moisture retention by
building up humic content thus improving tolerance against drought
while providing benefit to crop growth;
[0079] e. run-off is prevented together with concomitant nutrient
loss;
[0080] f. soil exchange and buffering capacity are improved;
[0081] g. product is non-toxic and non-burning;
[0082] h. provides sustained long-term benefit to the soil as
opposed to relatively short term benefit of chemical
fertilizers;
[0083] i. provides a source of water insoluble nitrogen that is
released over a long period of time;
[0084] j. provides the opportunity to combine both positive aspects
of organic and inorganic fertilizer synergistic benefit in view of
the co-granulation; and
[0085] k. simplified application which is more precise and less
wasteful relative to broadcasting.
[0086] A still further object of one embodiment of the present
invention is to provide a composite granule, comprising:
[0087] an agronomic seed in a size distribution of between +35 mesh
and -8 mesh;
[0088] composite material layered thereon forming a granule having
a seed encapsulated therein in a size distribution of between 6
mesh and 8 mesh.
[0089] Having thus described the invention, reference will now be
made to the accompanying drawings illustrating preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0090] FIG. 1 is a schematic illustration of one process suitable
for granulating the compost in accordance with one embodiment of
the present invention;
[0091] FIG. 2 is a schematic illustration of an alternative process
useful for granulating the compost according to the present
invention; and
[0092] FIG. 3 is a schematic illustration of a further process
useful for granulating the compost according to the present
invention.
[0093] Similar numerals employed in the text denote similar
elements.
PREFACE
[0094] Mesh referred to herein references Tyler standard screen
scale. NPKS references nitrogen, phosphorous, potassium, sulfur,
well recognized by those skilled in the agricultural engineering
field. Percent content references a percentage by weight basis,
unless otherwise indicated. Pan speed, angle and tilt may be
variable and will depend on the design parameters required of the
formed granules. Specific values are within the purview of one
skilled.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0095] Prior to referring to the details of the invention, it is
important to note that pan granulation of compost material, plant
or animal, has previously not been proposed in view of the fact
that when pulverized the material has an extremely low bulk
density, generally of the order of approximately between 20 and 25
lbft-.sup.3. To compound this, pulverized compost is quite
hydrophobic, inherently resilient due to its fibrous nature and
therefore difficult to compress and also is self-repulsive from an
electrostatic point of view.
[0096] Having such a panacea of inherent complications, the pan
granulation of compost material, particularly considering the bulk
density, is not conducive to the formation of a pellet which will
roll on the pan. Wetting, growth and consolidation of the materials
is not trivial and reference to the prior art does not facilitate
the process. It has been found through experimentation that if the
bulk density of the compost can be increased sufficiently, a pellet
will form and can be grown by accretion of further compost material
or ancillary fertilizer compounds. A successful approach has been
realized by the formation of a mixture having the pulverized
compost material, a suitable surfactant and binder material. The
surfactant contributes by lowering the surface tension of the
compost thus allowing moisture, binder and further compost material
to be mixed. Once mixed, the mixture can be granulated on a pan
with the addition of further binder which may be composed of the
same binder material in the mixture. The addition of further binder
may be in the form of an aerosol application known in the art
[0097] As an example, the granulation may proceed in accordance
with the procedure set forth with respect to FIG. 1.
[0098] Referring now to FIG. 1, shown is an overall schematic
representation of a granulation procedure by which the compost
granules may be formed.
[0099] Reference numeral 10 denotes the introduction of compost
feedstock. The technology set forth herein permits the formation of
most any compost granulated product including blends of various
sulfates, soda ash, sulfur, potash, kaolin, magnesia, potassium
sodium and ammonium chloride, phosphate compounds, blood meals,
inter alia.
[0100] The compost feedstock and binder are introduced into a
pulverizer 12 to pulverize the feedstock such that a product is
produced having a size distribution of 90% less than -150 mesh. A
significant portion is -200 mesh. The pulverizer 12 may be a
classifying pulverizer or air sweep pulverizer or any other
suitable pulverizer known by those skilled in the art. Once
pulverized, the compost stream, generally represented by numeral
14, is introduced into a sealed collection hopper, globally denoted
by numeral 16, which includes a bag house 18 to collect dust.
Collection hopper 16 includes suitable valve 20 for metering dust
into a collection bin 22. Bin 22 communicates with mixer 23 to mix
in binder (approximately 58% solids).
[0101] In the example, a thick lignosulfonate solution was the
binder used. After a short mixing time, the mixture was noted to
develop suitable characteristics for granulating. The dried
pulverized compost, normally hydrophobic, was observed to convert
to a hydrophilic form since the moisture in the binder solution was
"wicked" or transported into the compost and the binder solids
dispersed within the powder mixture. This resulted in a significant
increase in the bulk density to provide a flowable powder.
[0102] From mixer 23, the pre-moistened mixture is fed to feeder
24.
[0103] Moisture and surfactant may be added by suitable means known
to those skilled with delivery denoted by numeral 26. The moisture
content to be observed is up to 11% by weight of the mixture. This
is not to be confused with bound hydrated water. This refers to
free moisture content which is important to facilitate granulation.
Once the correct moisture has been attained, the mixture is passed
to pan granulator 28. In order to form the granules, additional
binder and surfactant material is introduced by, for example,
aerosol. The aerosol is dispensed by a suitable atomiser or wetting
gun 30. The aerosol binder may comprise the same material as
initially pulverized with the compost or alternatively, the binder
may be a different material optionally including an ancillary
fertilizer compound soluble in the binder solution.
[0104] As is known in the art, the pan granulator 28 includes upper
and lower scrapers 34, 36, respectively. The use of the binder
solution at any position from the 12 o'clock through to the 5
o'clock position has been found to be particularly useful. By
making use of the surfactant to reduce the surface tension of the
compost, which is inherently hydrophobic, the bulk density of the
mixture can be increased and thus wetting, growth and consolidation
can be achieved. Suitable surfactants include C.sub.4-C.sub.8
sulfonic acids, sulfonic acids, sodium succinate, inter alia. The
surfactant may be mixed in with the binder or added to the pan.
When the correct free moisture is attained, up to 11% by weight
free moisture, the pan stabilizes at a steady state condition.
[0105] The product formed from pan 28 is typically between 3 mesh
and 12 mesh. The product is discharged and dried with dryer 39.
Dryer 39 may be selected from, for example, Carrier dryers, tray
dryers or roto louver type dryers. The product formed in pan 28 is
additionally transported to dryer 39 via a suitable conveyer,
globally denoted by numeral 41.
[0106] Product exiting dryer 39 via stream 41 is then screened by a
suitable screening arrangement 44 at 3 mesh, 8 mesh and 20 mesh.
The -20 mesh portion is sent to pulverizer 12 for recycling into
the system, the recycling stream being indicated by numeral 46. The
oversize lumps are broken up by a, for example, Fritz mill and are
added to the pan feed or disposed of. The 3 to 12 mesh portion is
the final product and leaves screen 44, as indicated by numeral 48,
as a final finished product.
[0107] Any residual dust which may be present in dryer 39 may be
passed via line 54 for exiting dryer 39 to hopper 56 and the
collected material in hopper 56 either passed onto the bag house 18
via line 58 or passed into the feedstock via line 60. The fines or
dust entering bag house 18 may additionally be passed off onto
ancillary operations, for example, wet scrubbing, as broadly
denoted by numeral 60 in FIG. 1. Other examples will be readily
apparent to those skilled in the art.
[0108] With further reference to pan 28, as is known, the pan may
be adjusted for angle and rotational speed. In addition, it has
been found advantageous to not only change the horizontal
disposition of the pan, but also to laterally tilt the pans to
enhance the efficiency of the granulating process. The specific
angle of tilt and horizontal angle will be dependent upon the
rotational speed and the size of the granule desired to be
produced.
[0109] In respect of a second embodiment of the present invention,
FIG. 2 schematically illustrates a possible circuit.
[0110] In this embodiment, a hopper 32 is included in the circuit
to retain a source of agronomic seeds such as canary seeds, rape
seeds, canola seeds, etc. The seeds may be introduced by a feeder
33 for introduction onto pan 28. In this size distribution, a
product can be formulated when an agronomic seed is encapsulated in
compost. Typically, an industrially useful size distribution for
such products is between 6 mesh and 8 mesh. The final product has
been found to provide extremely useful results in that 30% of the
encapsulated products contain a single seed. This percentage can be
augmented to at least 90% by seed volume increase on the pan. This
is particularly useful to industry in that wastage is minimized and
over seeding is riot a concern in view of the size of the final
product. It is well established in the agricultural art that over
seeding and inconsistent aerial coverage are major problems and
result in excessive costs in the industry. Similar procedures from
those described with respect to FIG. 1 are applicable. As an
alternative, the hopper 32 may contain a fertilizer material such
as ammonium sulfate etc., in a size distribution of between -35
mesh and +150 mesh and thus acts as a nucleating agent. This
augments the granulation procedure to result in the formation of a
composite compost granular having a central core of a fertilizer
material. The compost material, as stated herein, may also contain
a host of different materials.
[0111] Referring now to FIG. 3, shown is a further embodiment of
the present invention.
[0112] In this embodiment, two granulation pans are employed. Pans
28 and 30 cooperate to form a first stage granule and a second
stage larger granule. Mixture, as discussed herein previously, is
introduced to a small pan 30 to form a size distribution of between
3 mesh and 12 mesh with a fraction in a size distribution of
between 8 mesh and 12 mesh. The mixture is fed to pan 30 by feeder
33. The pan 30 includes scraper 38 and 40. The +8 mesh and 12 mesh
particles are passed on to pan 28 and undergo treatment as
established with respect to FIG. 1 until a size distribution of -3
mesh and +8 mesh is achieved. This size distribution may be altered
further, if desired, by passing formed granules from 48 into a drum
granulator 62 for further material accretion up to 0.5 inch
pellets. The accretion in the drum substantially follows the
procedure in the pan as set forth herein. As a further option,
hopper 32 may be used in this circuit process.
[0113] It will also be readily appreciated that any number of pans
can be incorporated into the system to progressively grow or
accrete a granule. To this end, the process is interruptible and
therefore can be custom designed to produce granules having a
variety of layers of material to produce a host of valuable
granules. It will be clear to those skilled in the art that the
process is effective for producing a number of different forms of
fertilizer and has particular utility with respect to the formation
of high grade fertilizer for use on golf courses, etc.
[0114] In terms of the binder, suitable example include neutral
lignosulfonate of potassium or ammonia, starch, sugars, proteins,
water, calcium sulfate, dry glutens, wheat grains, barley grains,
rice grains and calcium phosphate among others. The choice of the
binder will depend on the desired characteristics of the granule
and accordingly, the aforementioned examples are only
exemplary.
[0115] Although embodiments of the invention have been described
above, it is not limited thereto and it will be apparent to those
skilled in the art that numerous modifications form part of the
present invention insofar as they do not depart from the spirit,
nature and scope of the claimed and described invention.
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