U.S. patent application number 11/153287 was filed with the patent office on 2005-11-03 for soil conditioning agglomerates containing calcium.
This patent application is currently assigned to Magic Green Corporation. Invention is credited to Stephen, Roy M., Wommack, Greg.
Application Number | 20050241354 11/153287 |
Document ID | / |
Family ID | 27556971 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241354 |
Kind Code |
A1 |
Wommack, Greg ; et
al. |
November 3, 2005 |
Soil conditioning agglomerates containing calcium
Abstract
Mechanically strong, water-disintegrable agglomerates made from
a particulate calcium source, a water-soluble binder and optionally
containing a primary plant nutrient source and/or micronutrient
source and a process for forming such agglomerates are disclosed.
The agglomerates may be used as a soil liming agent and for
introducing nutrient values into cultivated soil. Also disclosed is
a method for introducing nutrient values into cultivated soil so as
to inhibit leaching of the nutrient values from the soil and
improve utilization of the nutrient values by plants grown in the
soil.
Inventors: |
Wommack, Greg; (Silex,
MO) ; Stephen, Roy M.; (Martinsville, IL) |
Correspondence
Address: |
SENNIGER POWERS LEAVITT AND ROEDEL
ONE METROPOLITAN SQUARE
16TH FLOOR
ST LOUIS
MO
63102
US
|
Assignee: |
Magic Green Corporation
Silex
MO
|
Family ID: |
27556971 |
Appl. No.: |
11/153287 |
Filed: |
June 15, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11153287 |
Jun 15, 2005 |
|
|
|
10147296 |
May 16, 2002 |
|
|
|
6936087 |
|
|
|
|
10147296 |
May 16, 2002 |
|
|
|
09723721 |
Nov 28, 2000 |
|
|
|
6413291 |
|
|
|
|
09723721 |
Nov 28, 2000 |
|
|
|
09300024 |
Apr 27, 1999 |
|
|
|
09723721 |
Nov 28, 2000 |
|
|
|
09067064 |
Apr 27, 1998 |
|
|
|
5997599 |
|
|
|
|
09067064 |
Apr 27, 1998 |
|
|
|
08672226 |
Jul 5, 1996 |
|
|
|
5743934 |
|
|
|
|
08672226 |
Jul 5, 1996 |
|
|
|
08398657 |
Mar 3, 1995 |
|
|
|
09723721 |
|
|
|
|
09067283 |
Apr 27, 1998 |
|
|
|
6287356 |
|
|
|
|
09067283 |
Apr 27, 1998 |
|
|
|
08672226 |
Jul 5, 1996 |
|
|
|
5743934 |
|
|
|
|
08672226 |
Jul 5, 1996 |
|
|
|
08398657 |
Mar 3, 1995 |
|
|
|
60083232 |
Apr 27, 1998 |
|
|
|
Current U.S.
Class: |
71/31 |
Current CPC
Class: |
C05D 3/04 20130101; C05F
11/00 20130101; C05G 5/40 20200201; C05G 5/40 20200201; C05G 1/00
20130101; C05D 3/02 20130101; C05D 3/02 20130101; C05D 3/02
20130101; C05D 3/02 20130101; Y10S 71/903 20130101; C05D 3/00
20130101; C05F 11/00 20130101; C05G 5/12 20200201 |
Class at
Publication: |
071/031 |
International
Class: |
C05C 009/00 |
Claims
1-31. (canceled)
32. An agglomerate for use as a soil conditioner, the agglomerate
being formed by pelletizing a preagglomerate containing a
water-soluble binder selected from the group consisting of
lignosulonates, lignosulfonate salts, polyvinyl alcohol,
polyacrylic acid salts, amylose, methylcellulose,
hydroxyethylcellulose, carboxymethylcellulose,
ethylhydroxyethylcellulose, corn starch, wheat starch, molasses and
mixtures thereof and a particulate calcium source selected from the
group consisting of limestone, dolomitic limestone, gypsum,
hydrated lime and mixtures thereof, the particulate calcium source
having a particle size distribution such that less than about 1% by
weight of the particulate calcium source is +20 mesh, less than
about 10% by weight of the particulate calcium source is -20 +100
mesh and at least about 90% by weight of the particulate calcium
source is -325 mesh Tyler Standard Sieve Series, the agglomerate
comprising at least about 15% by weight of the particulate calcium
source and exhibiting an average green crush strength of at least
about 2 pounds when sized to from -7 to +8 mesh Tyler Standard
Sieve Series.
33. An agglomerate as set forth in claim 32 wherein the particulate
calcium source is selected from the group consisting of limestone,
dolomitic limestone, gypsum and mixtures thereof.
34. An agglomerate as set forth in claim 33 wherein the particulate
calcium source has a particle size distribution such that at least
about 90% by weight of the particulate calcium source is -400 mesh
Tyler Standard Sieve Series.
35. An agglomerate as set forth in claim 34 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 1% by weight (dry basis).
36. An agglomerate as set forth in claim 35 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 2% by weight (dry basis).
37. An agglomerate as set forth in claim 34 wherein the
water-soluble binder is selected from the group consisting of
lignosulfonate, lignosulfonate salts and mixtures thereof.
38. An agglomerate as set forth in claim 37 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 1% by weight (dry basis).
39. An agglomerate as set forth in claim 38 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 2% by weight (dry basis).
40. An agglomerate as set forth in claim 34 wherein the size of the
agglomerate is from -3 to +40 mesh Tyler Standard Sieve Series.
41. An agglomerate as set forth in claim 34 wherein the combined
concentration of CaO and Ca(OH).sub.2 in the particulate calcium
source is at least about 3% by weight.
42. An agglomerate as set forth in claim 34 wherein the magnesium
content of the agglomerate is no greater than about 2.5% by
weight.
43. An agglomerate as set forth in claim 42 wherein the magnesium
content of the agglomerate is no greater than about 1.5% by
weight.
44. An agglomerate as set forth in claim 34 wherein the primary
plant nutrient source functions as the water-soluble binder.
45. A process for forming an agglomerate for use as a soil
conditioning agent, the process comprising: preparing a
preagglomerate containing a water-soluble binder selected from the
group consisting of lignosulonates, lignosulfonate salts, polyvinyl
alcohol, polyacrylic acid salts, amylose, methylcellulose,
hydroxyethylcellulose, carboxymethylcellulose,
ethylhydroxyethylcellulose, corn starch, wheat starch, molasses and
mixtures thereof and a particulate calcium source selected from the
group consisting of limestone, dolomitic limestone, gypsum,
hydrated lime and mixtures thereof, the particulate calcium source
having a particle size distribution such that less than about 1% by
weight of the particulate calcium source is +20 mesh, less than
about 10% by weight of the particulate calcium source is -20 +100
mesh and at least about 90% by weight of the particulate calcium
source is -325 mesh Tyler Standard Sieve Series; and pelletizing
the preagglomerate to form the agglomerate, the proportion of the
particulate calcium source in the preagglomerate being sufficient
such that the agglomerate comprises at least about 15% by weight of
the particulate calcium source.
46. A process as set forth in claim 45 wherein the particulate
calcium source is selected from the group consisting of limestone,
dolomitic limestone, gypsum and mixtures thereof.
47. A process as set forth in claim 46 wherein the particulate
calcium source has a particle size distribution such that at least
about 90% by weight of the particulate calcium source is -400 mesh
Tyler Standard Sieve Series.
48. A process as set forth in claim 47 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 1% by weight (dry basis).
49. A process as set forth in claim 48 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 2% by weight (dry basis).
50. A process as set forth in claim 47 wherein the water-soluble
binder is combined with the other components of the preagglomerate
as an aqueous solution of the binder.
51. A process as set forth in claim 47 wherein the water-soluble
binder is selected from the group consisting of lignosulfonate,
lignosulfonate salts and mixtures thereof.
52. A process as set forth in claim 51 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 1% by weight (dry basis).
53. A process as set forth in claim 52 wherein the amount of
water-soluble binder present in the preagglomerate is at least
about 2% by weight (dry basis).
54. A process as set forth in claim 51 wherein the water-soluble
binder is combined with the other components of the preagglomerate
as an aqueous solution of the binder.
55. A process as set forth in claim 54 wherein the water-soluble
binder comprises a lignosulfonate salt and the aqueous solution of
the binder contains from about 48% to about 60% by weight
solids.
56. A process as set forth in claim 47 wherein the size of the
agglomerate is from -3 to +40 mesh Tyler Standard Sieve Series.
57. A process as set forth in claim 47 wherein the combined
concentration of CaO and Ca(OH).sub.2 in the particulate calcium
source is at least about 3% by weight.
58. A process as set forth in claim 47 wherein the concentration of
magnesium-containing compounds in the preagglomerate is such that
the magnesium content of the agglomerate is no greater than about
2.5% by weight.
59. A process as set forth in claim 58 wherein the concentration of
magnesium-containing compounds in the preagglomerate is such that
the magnesium content of the agglomerate is no greater than about
1.5% by weight.
60. A process as set forth in claim 47 wherein the primary plant
nutrient source functions as the water-soluble binder.
Description
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 60/083,232, filed Apr. 27, 1998, the
disclosure of which is expressly incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to mechanically strong,
water-disintegrable agglomerates containing various particulate
calcium sources for use as a soil conditioner to neutralize soil
acidity and provide a source of nutrient values. The present
invention also relates to processes for forming such agglomerates
as well as to methods of introducing nutrient values into
cultivated soil so as to inhibit leaching of the nutrient values
and improve utilization of the nutrient values by plants grown in
the soil.
[0003] Soil conditioners or liming agents are widely used in
agriculture, lawn care and gardening to reduce soil acidity and
promote plant health. A variety of calcium-containing materials, in
particulate or granulated form, are used as soil liming agents.
Conventional liming agents include: limestone, dolomitic limestone,
lime, slaked or hydrated lime, and gypsum.
[0004] Many industrial processes produce waste solids containing
calcium. For example, the manufacture of cement and lime is
accompanied by the generation of large quantities of dust collected
from the hot gaseous effluents vented from the kiln. Similar
calcium-containing dusts are recovered from the stack gases and ash
residues produced during the burning of manure fuels (i.e., manure
ash). These particulate wastes share two properties that make them
potentially useful for application to cultivated soils: (1)
significant acid neutralization capacity; and (2) high
concentrations of calcium and other important soil nutrients such
as potassium and sulfur. It has been suggested to-use
calcium-containing waste solids such as cement kiln dust to lime
cultivated soil (See T. A. Davis, et al., "Disposal and Utilization
of Waste Kiln Dust From Cement Industry", EPA Report No.
670/2-75-043 (May 1975)) as a way of reclaiming these sizeable
waste streams. However, expanded agricultural utilization of these
waste products has been hindered by problems associated with
storage, handling and application of these finely divided materials
to soils. Raw cement kiln dust exiting the kiln, for example, is
extremely fine, typically consisting of particles having an average
particle size much less than 100 .mu.m, with a large portion of
particles often having a particle size of 10 .mu.m or less. As a
result, the dust is easily carried away by the wind and is
difficult to bulk-blend with other materials in preparing various
fertilizer formulations. Furthermore, modern fertilizer application
equipment for broadcast or row placement of solid fertilizers, is
designed for handling free-flowing, granular or pelletized
materials having an appreciable mean diameter, not dust.
Consequently, numerous problems are encountered when such equipment
is employed for field application of finely-divided dust.
[0005] It would be highly beneficial to develop a process for
granulating or agglomerating cement kiln dust and similar
calcium-containing waste materials capable of consistently
producing a mechanically strong soil conditioning agglomerate that
readily disintegrates when contacted with water. In addition, it
would be advantageous to improve the efficacy of agricultural
liming agents generally and provide agglomerate compositions for
introducing nutrient values into cultivated soil so as to inhibit
leaching of the nutrient values and improve utilization of the
nutrient values by plants grown in the soil.
SUMMARY OF THE INVENTION
[0006] Among the objects of the present invention, therefore, are
the provision of a process for forming an agglomerate comprising
calcium-containing waste materials such as cement kiln dust for use
as a soil conditioning agent; the provision of such a process
capable of producing an agglomerate having sufficient mechanical
strength to withstand the rigors of handling, transport and
application without excessive dusting; the provision of such a
process which produces an agglomerate which disintegrates readily
into particles having substantially the same size as the raw
materials used to form the agglomerate once the agglomerate is
incorporated into soil and exposed to water so that the various
beneficial components of the agglomerate may be rapidly utilized by
plants grown in the soil; and the provision of soil conditioning
agents and agglomerate compositions made from calcium-containing
waste materials as well as from conventional agricultural liming
materials combined with plant nutrient values exhibiting improved
efficacy.
[0007] Briefly, therefore, the present invention is directed to a
process for forming an agglomerate for use as a soil conditioning
agent. The process comprises preparing a preagglomerate containing
a water-soluble binder and a particulate calcium source. The
particulate calcium source has a particle size distribution such
that less than about 1% by weight of the particulate calcium source
is +20 mesh, less than about 10% by weight of the particulate
calcium source is -20 +100 mesh and less than about 25% by weight
of the particulate calcium source is -100 +200 mesh Tyler Standard
Sieve Series. The preagglomerate is pelletized to form the
agglomerate. In accordance with another embodiment, the
preagglomerate additionally contains a primary plant nutrient
source and the particulate calcium source has a particle size
distribution such that at least about 90% by weight of the
particulate calcium source is -250 mesh Tyler Standard Sieve
Series.
[0008] The present invention is further directed to an agglomerate
for use as a soil conditioner and to provide a source of nutrient
values. The agglomerate is formed by pelletizing a preagglomerate
containing a particulate calcium source, a primary plant nutrient
source and a water-soluble binder. The proportions of the
particulate calcium source and the primary plant nutrient source in
the preagglomerate are sufficient such that the agglomerate
comprises about 15% to about 60% by weight of the particulate
calcium source and about 30% to about 80% by weight of the primary
plant nutrient source. The particulate calcium source has a
particle size distribution such that at least about 90% by weight
of the particulate calcium source is -250 mesh Tyler Standard Sieve
Series. The agglomerate having a size ranging from -7 to +8 Tyler
Standard Sieve Series exhibits an average green crush strength of
at least about 2 pounds.
[0009] The present invention is also directed to a method for
introducing nutrient values into cultivated soil so as to inhibit
leaching of the nutrient values from the soil and improve
utilization of the nutrient values by plants grown in the soil. The
method comprises applying to the soil an agglomerate comprising
about 15% to about 60% by weight of a particulate calcium source,
about 30% to about 80% by weight of a primary plant nutrient source
and a water-soluble binder. The particulate calcium source exhibits
a calcium carbonate equivalent value in excess of about 85% and has
a particle size distribution such that at least about 90% by weight
of the particulate calcium source is -250 mesh Tyler Standard Sieve
Series. The agglomerate readily dissolves upon exposure to water to
disintegrate into particles of the particulate calcium source and
primary plant nutrient source.
[0010] Other objects and features of this invention will be in part
apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a flow diagram of one embodiment of the process of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] In accordance with the present invention,
mechanically-strong, water-disintegrable agglomerates produced from
various particulate calcium sources including calcium-containing
waste materials as well as conventional soil liming agents are
provided. The agglomerates are useful as soil conditioners to
neutralize soil acidity and provide a source of nutrient values.
Processes for forming the agglomerates are also provided. The
agglomerate compositions in accordance with the present invention
are useful in introducing nutrient values into cultivated soil in a
manner such that leaching of the nutrient values is inhibited and
utilization of the nutrient values by plants grown in the soil is
improved.
[0013] As used herein, agglomerate means pellets and
irregularly-shaped particles formed by the consolidation of smaller
particles. All mesh sizes herein are in reference to the Tyler
Standard Sieve Series.
[0014] The agglomerates of the present invention are made by
pelletizing a preagglomerate mixture prepared by combining a
water-soluble binder with a particulate calcium source as described
in detail below.
[0015] The particulate calcium source may comprise cement kiln
dust, lime kiln dust, manure ash or other calcium-containing
secondary plant nutrient sources including conventional liming
agents such as limestone, dolomitic limestone, lime, hydrated lime
and gypsum. The particulate calcium source may consist essentially
of any one of the aforementioned calcium-containing materials as
well as mixtures thereof. The gypsum may be derived from natural
sources as well as from byproducts of chemical operations such as
the wet solids and slurries produced in lime scrubbing stack gases
to remove sulfur dioxide. In general, the agglomerates contain at
least about 15% by weight of the particulate calcium source. If
cement kiln dust, lime kiln dust, manure ash or other
calcium-containing waste materials are combined with another
calcium-containing secondary plant nutrient source, it is preferred
that the other calcium sources constitute no more than about 80% by
weight of the particulate calcium source, more preferably from
about 30% to about 70% by weight of the particulate calcium
source.
[0016] In order to achieve the mechanical strength and
disintegration characteristics desired in the agglomerate, the
amount of water-soluble binder present in the preagglomerate is
generally at least about 1% by weight (dry basis). Use of larger
quantities of binder generally yields higher strength agglomerates
which may be desirable in some applications. Preferably, the amount
of binder present in the preagglomerate is at least about 2%, more
preferably, at least about 4% by weight (dry basis). Preferably,
the amount of binder present in the preagglomerate is between about
4% and about 25% by weight (dry basis).
[0017] Suitable water-soluble binders for use in the present
invention include lignosulfonates, lignosulfonate salts (e.g.,
calcium lignosulfonate, ammonium lignosulfonate), water-soluble
fertilizer materials (e.g., potash, ammonium nitrate, urea,
diammonium phosphate), synthetic or naturally occurring polymers
(e.g., polyvinyl alcohol, polyacrylic acid salts, amylose,
methylcellulose, hydroxyethylcellulose, carboxymethylcellulose,
ethylhydroxyethylcellulose, corn starch and wheat starch) and
sugar-based binders such as molasses and those sold by RDE, Inc.,
Crystal Lake, Ill., 60014 under the "BREWEX" and "MOLTECH"
trademarks, as well as mixtures of these various materials. Among
the preferred binders for use in the present invention are the
liquid blends of granulating agents and surfactants sold by Arr-Maz
Products, Winter Haven, Fla. 33880, under the product designations
KGA-300 and KGA-250. An especially preferred binder is the calcium
salt of lignosulfonate such as that sold by LignoTech USA,
Greenwich, Conn. 06830, under the trademark "NORLIG A".
[0018] In addition to the particulate calcium source and
water-soluble binder, the agglomerates may contain appreciable
amounts of various particulate additives. For example, the
agglomerates may comprise a primary plant nutrient source (i.e., a
source of nitrogen, phosphorous and/or potassium), a secondary
plant nutrient source (i.e., a source of magnesium, sulfur, and/or
calcium), and/or a micronutrient source (e.g., a source of iron,
copper, boron, selenium, chromium, vanadium, manganese, zinc and/or
molybdenum). Upon disintegration of the agglomerate, these
additives deliver their benefit to the soil along with the
particulate calcium source. Although the particulate calcium source
may contain appreciable quantities of certain primary plant
nutrients, secondary plant nutrients and/or micronutrients, it
should be understood that primary plant nutrient source, secondary
plant nutrient source and micronutrient source as used herein means
an additive apart from the particulate calcium source intended to
increase the concentration of a desired nutrient or micronutrient
in the agglomerate product.
[0019] For some applications, the agglomerate may contain only a
particulate calcium source and a water-soluble binder, whereas in
other applications the particulate calcium source will account for
from about 15% to about 50% of the weight of the agglomerate. In
those applications where it is desired to introduce nutrient values
into cultivated soil, it is desirable to combine the particulate
calcium source with appreciable quantities of a primary plant
nutrient source of the type typically used in
nitrogen-phosphorus-potassium (N--P--K) fertilizer formulations in
the agglomerate. For example, the agglomerate may contain
conventional sources of nitrogen, phosphorous and potassium such as
ammonium nitrate, ammonium sulfate, alkali metal nitrates, urea,
rock phosphate, ammonium phosphate (e.g.,
(NH.sub.4).sub.2HPO.sub.4, NH.sub.4H.sub.2PO.sub.4.H.sub-
.3PO.sub.4 and NH.sub.4H.sub.2PO.sub.4) bone meal slag, aluminum
phosphate, superphosphate, potash, and potassium salts (e.g.,
chlorides, sulfates and nitrates) and mixtures thereof. The
agglomerate may also contain organic fertilizer ingredients such as
manure and residues from sewage treatment plants. For such
applications, it is preferred that the agglomerate contain from
about 5% to about 40% available nitrogen, more preferably from
about 8% to about 15% available nitrogen, about 10% to about 50%
available phosphoric acid, and/or about 10% to about 50% available
potash. If urea, potash or other N--P--K fertilizer ingredient is
used as a binder, this also has the further beneficial effect of
increasing the primary plant nutrient content of the agglomerate.
Furthermore, if desired, the agglomerates may additionally include
a micronutrient source. Conventional sources of micronutrients may
be used. For example, boron may be added in the form of disodium
octaborate tetrahydrate.
[0020] A preferred agglomerate for use in introducing N--P--K
nutrient values into cultivated soil contains about 30% to about
80% by weight of a primary plant nutrient source and at about 15%
to about 60% by weight of the particulate calcium source, based on
the weight of the agglomerate. A preferred agglomerate for use in
introducing nitrogen into cultivated soils contains about 30% to
about 80% by weight, more preferably about 55% to about 60% by
weight, urea or other source of available nitrogen (e.g., ammonium
nitrate) and at least about 15% to about 60% by weight, more
preferably about 35% to about 45% by weight of the particulate
calcium source, based upon the weight of the agglomerate. In
accordance with another preferred embodiment, an agglomerate for
use in introducing potassium into cultivated soil contains about
30% to about 80% by weight, more preferably about 45% to about 55%
by weight, potassium chloride, potash or other source of potassium
and at least about 15% to about 60% by weight, more preferably
about 45% to about 50% by weight of a calcium source, based upon
the weight of the agglomerate. In these formulations, the N--P--K
fertilizer ingredients function as a binder for the agglomerate as
well as a nutrient source. To improve the mechanical strength,
these preferred agglomerates may further comprise an additional
binder such as one of the lignosulfonate binders disclosed
herein.
[0021] Depending on the selection of materials used in the
particulate calcium source, the particulate calcium source may
contain appreciable quantities of CaO and may further contain other
calcium-containing compounds having the potential to react with
water and form a solid hydrate, such as calcium sulfate
(CaSO.sub.4) and calcium sulfite (CaSO.sub.3), which may be present
in anhydrous or partially-hydrated forms. Other compounds such as
MgO and Na.sub.2SO.sub.4 will also hydrate, but are typically
present in smaller proportions.
[0022] Cement kiln dust, lime kiln dust and manure ash, for
example, may contribute significantly to the concentration of CaO
and other calcium-containing compounds having the potential to be
hydrated present in the particulate calcium source. The composition
of cement kiln dust can vary significantly with the composition of
the raw materials fed to the kiln, the kiln system, the fuel used
to fire the kiln as well as the conditions encountered by the dust
particles in the kiln and in the dust collection apparatus.
Generally, cement kiln dust is comprised of varying amounts of
elements such as Ca, Mg, Si, Al and Fe, trace amounts of heavy
metals and a distribution of alkalies such as K, Na and Li. Most of
these elements are present as carbonates, sulfates, halides,
hydroxides, oxides or silicates. Since the kiln dust has undergone
some degree of calcination, the CaCO.sub.3 content in the dust is
depleted relative to the kiln feed and a significant portion of the
calcium is instead present as CaO. Due to its composition which
includes CaO, raw cement kiln dust exiting the kiln is
highly-reactive toward water and has the potential to hydrate and
harden if exposed to sufficient moisture.
[0023] A representative cement kiln dust composition is set forth
in Table 1 below. However, it should be understood that Table 1 is
intended as merely exemplary and cement kiln dust need not include
all of these constituents in the concentrations listed below nor
are other possible constituents excluded.
1 TABLE 1 Constituent % By Weight CaCO.sub.3 30-60 CaO 5-40
SiO.sub.2 10-20 Al.sub.2O.sub.3 2-6 Fe.sub.2O.sub.3 1-4 MgO 1-4
K.sub.2SO.sub.4 3-9 CaSO.sub.4 2-8 Na.sub.2SO.sub.4 1-3 KCl 1-3 KF
0.1-1 Heavy Metals trace
[0024] Like cement kiln dust, lime kiln dust and manure ash are
finely divided and contain high concentrations of calcium
compounds, including CaO, and are similarly reactive toward water
and have the potential to hydrate and harden when exposed to
moisture. Although similar in composition to cement kiln dust, an
even larger proportion of calcium present in lime kiln dust is in
the form of CaO. Lime kiln dust may contain 50% by weight or more
CaO. Of course, the use of lime in the particulate calcium source
will also increase the CaO content.
[0025] When cement kiln dust, lime kiln dust, manure ash and lime
are contacted with water, CaO and other calcium-containing
compounds present having hydration potential react with the water
and are hydrated. In the case of CaO, the reaction product is
Ca(OH).sub.2, whereas calcium sulfate reacts with water to form
gypsum. The reaction of these components with water is accompanied
by a volumetric expansion or enlargement as they are converted to
their hydrate form. The hydration of CaO to Ca(OH).sub.2 lime is
believed to be accompanied by a particularly significant volumetric
expansion. That is, it is believed that the potential of the
particulate calcium source used in the practice of the present
invention, and ultimately that of the preagglomerate mixture, to
hydrate and expand is predominantly attributable to the presence of
CaO.
[0026] In the practice of the present invention, the preagglomerate
mixture comprising the particulate calcium source and the other
various components of the product is agglomerated using
conventional tumble or growth agglomeration methods which include
contacting the mixture with water in a suitable agglomeration
device. The volumetric expansion which accompanies the hydration of
CaO and other calcium-containing compounds having the potential to
be hydrated present in the preagglomerate may tend to reduce the
mechanical strength of the agglomerates if the concentration of
these compounds in the preagglomerate is excessive. In general, it
has been discovered that if the combined concentration of CaO and
other calcium-containing compounds having the potential to be
hydrated in the preagglomerate exceeds about 10% by weight (dry
basis), the subsequent volumetric expansion of these components can
significantly reduce the mechanical strength of the agglomerates.
Therefore, the combined concentration of CaO and other
calcium-containing compounds having the potential to be hydrated in
the preagglomerate mixture is preferably no greater than about 10%,
more preferably no greater than about 7%, still more preferably no
greater than about 5% and optimally no greater than about 3% by
weight on a dry basis. Controlling the concentration of CaO and
other calcium-containing compounds having the potential to be
hydrated in the preagglomerate mixture in this fashion
advantageously minimizes the extent to which the resulting
agglomerate will swell upon hydration so that an agglomerate
exhibiting sufficient mechanical strength may be produced.
[0027] The concentration of CaO and other calcium-containing
compounds having the potential to be hydrated in the preagglomerate
mixture may be controlled simply by limiting the amount of the
sources of these compounds introduced into the preagglomerate. For
example, if cement kiln dust containing about 30% by weight CaO is
the only source of CaO and other calcium-containing compounds
having the potential to be hydrated in the particulate calcium
source, the amount of cement kiln dust introduced into the
preagglomerate preferably does not exceed about 33% by weight, more
preferably does not exceed about 23% by weight, still more
preferably does not exceed about 17% by weight and optimally does
not exceed about 10% by weight of the preagglomerate mixture. In
addition, limiting the proportion of cement kiln dust, lime kiln
dust and/or manure ash in the preagglomerate may permit the use of
such materials containing relatively high concentrations of heavy
metals (e.g., mercury, lead, arsenic etc.) or other potentially
harmful components. That is, the balance of ingredients in the
preagglomerate serve as a buffer to reduce the concentration of
these components in the agglomerates so as to produce a suitable
liming product that conforms with environmental guidelines.
[0028] Alternatively, the concentration of CaO and other
calcium-containing compounds having the potential to be hydrated in
the preagglomerate mixture is controlled by prehydrating all or a
portion of the components of the particulate calcium source
containing such compounds. For example, upon contacting cement kiln
dust with water, CaO, CaSO.sub.4, CaSO.sub.3 and other components
of the dust having hydration potential react with the water and are
hydrated, thereby reducing the hydration potential of the cement
kiln dust and ultimately of the preagglomerate. Preferably, the
material to be prehydrated is combined with an amount of water less
than the stoichiometric amount necessary to totally hydrate the
components of the material in order to ease subsequent handling of
the hydrated material in the agglomeration process. As the amount
of water combined with the material to be prehydrated approaches or
exceeds the stoichiometric amount needed to totally hydrate the
material, it becomes increasingly difficult to form acceptable
agglomerates because the hydrated material begins to cement
together into progressively larger particles which ultimately
produce agglomerates that do not readily disintegrate when exposed
to water. By combining the material to be prehydrated with an
amount of water less than the stoichiometric amount necessary to
totally hydrate the material, the partially-hydrated material
remains substantially dry and free-flowing and can be easily
combined with the other components of the preagglomerate.
[0029] In those applications where a component of the
preagglomerate mixture is prehydrated, it may be advantageous to
mix the material with wetted, gypsum-containing solids or slurry
produced in lime scrubbing stack gases to remove sulfur dioxide.
Lime scrubber solids typically contain from about 15% to about 30%
by weight water. The water present in the lime scrubber solids
reacts with CaO and other calcium-containing compounds having the
potential to be hydrated in the material to be prehydrated and the
solids further dilute the concentration of CaO and other
calcium-containing compounds having the potential to be hydrated in
the preagglomerate mixture. In addition to providing a convenient
and economical source of prehydration water, including wetted lime
scrubber solids in the preagglomerate mixture is advantageous in
those applications where a sulfur-containing agglomerate is
desired. Moreover, lime scrubber solids may provide a source of
calcium, and gypsum in particular, having a lower concentration of
heavy metals than particulate calcium sources obtained from other
sources and thereby serve as a more effective buffer in reducing
the concentration of heavy metals or other potentially harmful
components in the agglomerate.
[0030] The composition of cement kiln dust, lime kiln dust, manure
ash and other components of the particulate calcium source
containing CaO and other calcium-containing compounds having the
potential to be hydrated, as well as the preagglomerate mixture can
vary substantially. One way of approximating the concentration of
CaO and other calcium-containing compounds having the potential to
be hydrated in cement kiln dust and other materials in the
preagglomerate mixture is to first dry the material to constant
weight at about 100.degree. to about 120.degree. C. The dried
material is then mixed with an amount of water in excess of the
amount needed to totally hydrate the material (e.g., an equivalent
weight of water) and dried again to constant weight at about
100.degree. to about 120.degree. C. The concentration of CaO and
other calcium-containing compounds having the potential to be
hydrated in the material can then be approximated from the
difference between the weight of water added and the weight of the
material after the second drying. This differential represents the
amount of water reacted with CaO and other calcium-containing
compounds having the potential to be hydrated present in the
material to form hydrates and can be used to approximate the
concentration of such compounds in the material and ultimately the
preagglomerate mixture.
[0031] Alternatively, in the absence of a compositional analysis, a
series of agglomeration trials may be used to determine whether the
concentration of CaO and other calcium-containing compounds having
the potential to be hydrated in the preagglomerate mixture needs to
be reduced, either by limiting the amount of the source of these
compounds introduced into the preagglomerate or by prehydrating all
or some of the particulate calcium source and, if prehydration is
employed, the amount of water required to adequately prehydrate the
material. In the case of cement kiln dust, it has been found that
the amount of water necessary to achieve the proper extent of
partial-hydration is usually between about 3% and about 16% by
weight, and more typically between about 4% and about 8% by weight
based on the starting weight of cement kiln dust.
[0032] If components of the preagglomerate mixture are prehydrated,
it is preferred that substantially each particle of the material be
uniformly coated with water to assure greater compositional
uniformity in the prehydrated material. This may be achieved by
using a high energy pin, auger, paddle or ribbon type mixer capable
of intimately mixing the material and water. In order to enhance
the degree of contact between the material to be prehydrated and
the water and provide other beneficial effects, it is preferred to
reduce the particle size of the material, if necessary, by
ballmilling or other suitable means to achieve a particle size
distribution as described below.
[0033] After the material to be prehydrated and water have been
thoroughly mixed, the moistened material is preferably conditioned
by storing it for a time sufficient so that substantially all of
the water is reacted with the material. The moistened material
discharged from the mixer may be stored in a conditioning bin
wherein the hydration reaction between the water and the material
is completed. In general, storage periods (i.e., conditioning
times) from about 1 hour to as much as 24 hours are preferred. The
hydration reaction which occurs upon combining cement kiln dust and
similar materials with water is highly exothermic and its progress
is easily monitored as the moistened material is conditioned by
measuring the temperature rise as the material reacts with the
water. After conditioning, the partially-hydrated material is
substantially dry. Again, since the composition of cement kiln
dust, lime kiln dust, manure ash and other components of the
particulate calcium source may vary considerably, it may be
desirable to conduct a series of trials with a particular material
varying the storage time in order to ensure prehydration is
accomplished as desired.
[0034] Preferably, the particulate calcium source used to prepare
the agglomerate is finely divided. More specifically, it is
preferred that particulate calcium source comprise a mixture of
particles having a size distribution of which less than about 3% by
weight, more preferably, less than about 1% by weight is +20 mesh
and less than about 10% by weight is -20 +100 mesh. More
preferably, less than about 20% by weight of the particles in the
mixture is -100 +150 mesh. Even more preferably, less than about
25% by weight of the particulate calcium source is -100 +200 mesh.
In accordance with even more preferred embodiments of the present
invention, at least about 50% by weight of the particles in the
mixture are -200 mesh. Still more preferably, at least about 75% by
weight of the particles in the mixture are -200 mesh. In a still
more preferred embodiment, at least about 75% by weight of the
particles in the mixture are -200 mesh and at least about 5%, at
least about 25%, or even at least about 50% by weight are -250
mesh. In accordance with a still further preferred embodiment, at
least about 75% by weight of the particles in the mixture are -200
mesh and at least about 5%, at least about 25%, or even at least
about 50% by weight are -325 mesh. In accordance with an especially
preferred embodiment of the present invention, essentially all
(e.g., at least about 90% by weight) of the particles of the
particulate calcium source used to prepare the agglomerate are -100
mesh, preferably -150 mesh, more preferably -200 mesh, even more
preferably -250 mesh, still more preferably -325 mesh and optimally
-400 mesh. By utilizing a finely divided particulate calcium source
in accordance with the preceding description, conversion of the
calcium to plant-usable form (i.e., ionic calcium) once the
agglomerate is incorporated into soil is expedited and optimum
calcium saturation of the treated soil may be more readily
attained. If necessary, ballmilling or other suitable means may be
employed to obtain a desired particle size distribution in the
particulate calcium source.
[0035] In order to provide agglomerates exhibiting a relatively
uniform composition throughout and avoid segregation of the
individual components in the agglomerates, it is preferred that all
of the materials incorporated therein be similarly sized. However,
the particles of the various additives which may be present in the
agglomerates may be somewhat larger than the particles of the
calcium source. Thus, for example, it is preferred that the mixture
of all the various materials incorporated into the agglomerates
have a particle size distribution of which less than about 1% by
weight is +20 mesh and less than about 15% by weight is -20 +100
mesh. More preferably, not more than about 25% by weight of these
particles is -100 +150 mesh. Still more preferably, at least about
20% by weight of the particles in the mixture are -200 mesh. In a
still more preferred embodiment, at least about 50% by weight of
the particles in the mixture are -200 mesh and at least about 5%,
at least about 25%, or even at least about 50% are -325 mesh. As
with the calcium source, it may be necessary to reduce the particle
size of the primary nutrient source and other additives by
ballmilling or other suitable means in order to obtain the desired
particle size distribution.
[0036] The agglomerates of the present invention are prepared by
pelletizing a preagglomerate mixture prepared by combining a
water-soluble binder, the particulate calcium source (some or all
of which may have been prehydrated) and, optionally, the other
ingredients previously mentioned. The materials combined in the
preagglomerate are present in proportions sufficient to provide an
agglomerate of the desired composition. The preagglomerate may
contain a portion of the water required for pelletizing.
[0037] The water-soluble binder may be combined with the other
components of the preagglomerate either as a solid or as an aqueous
solution of the binder. If an aqueous solution of a lignosulfonate
salt is employed, the solution suitably contains from about 48% to
about 60% by weight solids. If a solid binder is used, it is
preferred that a portion of the water necessary for agglomeration
of the preagglomerate (e.g., approximately two-thirds) be added
along with the binder to promote thorough mixing of the binder with
the other components of the preagglomerate. It is preferred that
substantially each particle of the preagglomerate be coated with
binder. This ensures uniformity in both the preagglomerate and in
the final product and may be achieved by using a high energy pin,
auger, paddle or ribbon type mixer capable of intimately mixing the
components of the preagglomerate. Preferably, water and the binder
are introduced at two or more locations into the mixer.
[0038] Although in the preceding description the prehydration of
the particulate calcium source and addition of the binder were
described as two distinct steps, it should be understood that
prehydration of the calcium source and addition of the binder could
take place simultaneously in a single step. For example, the binder
may be added to the particulate calcium source as an aqueous
solution of the binder, the binder solution containing sufficient
water to achieve the appropriate degree of hydration of the calcium
source. In such an operation, the calcium source and binder
solution could be combined in a high energy mixture and then
conditioned for a time sufficient to allow substantially all of the
water to react with the calcium source. A portion of the water
necessary for pelletizing could then be added to the conditioned
material containing the binder along with any additives to form the
preagglomerate. Similarly, the particulate calcium source, a solid
water-soluble binder and an appropriate amount of water could be
mixed intimately in a high energy mixture, conditioned and mixed
with additional water and any additives to form a suitable
preagglomerate.
[0039] The moistened preagglomerate mixture is fed directly to any
suitable agglomeration device as is known in the art and pelletized
to form the agglomerates. Once the agglomerates are formed, the
binder and particulate calcium source form a matrix comprising the
binder disposed within interstices between particles which binds
the agglomerates together. Suitable pelletizing devices include
drum, tub and shallow pan disc pelletizers or any other suitable
tumble or growth agglomeration device. Preferably, a shallow-pan
disc pelletizer is employed as the agglomeration device. Once the
degree of tilt and rotational speed of the pan are determined,
pelletizing of the moistened preagglomerate proceeds as is well
known to those skilled in the art. In addition to these variables,
more water is typically added in the pan to optimize the size and
consistency of the agglomerates produced on the shallow pan disc
pelletizer. The various parameters of the pelletizing step are
controlled as is known in the art so as to produce agglomerates
having a size suitable for broadcast or row placement using
conventional fertilizer application equipment. Typically the
agglomerates should be -3 +40 mesh, more preferably -6 +16
mesh.
[0040] After the agglomerates are discharged from the pelletizer,
they are dried to remove a large portion of the internal water
which is initially present in the newly-formed agglomerates. Active
drying of the agglomerates is preferred to obtain a product having
the desired mechanical strength and disintegration characteristics.
If the agglomerates are not actively dried by heating, the water
present in the freshly pelletized agglomerates may continue to
react with the remaining components of the particulate calcium
source which can still be hydrated and eventually form very hard,
substantially non-disintegrable agglomerates resembling concrete.
Preferably, the newly formed agglomerates are dried to reduce their
moisture content to less than about 1% by weight, more preferably
to less than about 0.5% by weight.
[0041] The agglomerates may be dried in any suitable apparatus. For
example, drying may take place in an oven maintained at a
temperature from about 100.degree. to about 140.degree. C. or a
vibrating fluidized bed dryer or rotary dryer may be employed. In a
continuous process, vibrating fluidized bed or rotary dryers are
preferred since migration of the binder towards the exterior of the
agglomerate is reduced, providing a more uniform product exhibiting
improved mechanical strength. If a vibrating fluidized bed dryer is
used, the dryer is suitably operated with a drying air entrance
temperature of about 315.degree. C. and an exit air temperature of
about 95.degree. C. However, these temperatures may vary
significantly with the residence time of the agglomerates in the
dryer. Preferably, the agglomerates do not exit the dryer at a
temperature in excess of about 65.degree. C. Depending upon the
additives incorporated into the agglomerate, the drying
temperatures noted above may have to be decreased in order to avoid
melting the agglomerate. Furthermore, once drying is complete, it
is preferred to allow the agglomerates to cool before piling in
order to avoid the agglomerates from clumping together.
[0042] Dried agglomerates of the desired size may be separated
using an air induction vibrating screen separator of the type
available from Derrick Corporation, Buffalo, N.Y.
[0043] Once dried, the agglomerates should have sufficient
mechanical strength to withstand normal handling, transportation
and blending without fracturing and without excessive sloughing to
form dust. There are several standardized methods that may be used
for measuring mechanical strength of granular materials. However, a
simple and widely-accepted standard is crush strength. Crush
strength is measured by determining the minimum mass which crushes
an agglomerate of particular size when the mass is placed on the
agglomerate. In the practice of the present invention, the drying
and removal of water from the newly-formed agglomerates is
controlled such that dried agglomerates having a size ranging from
-7 to +8 mesh exhibit an average green crush strength of at least
about 2 pounds (about 0.9 kg), preferably at least about 4 pounds
(about 1.8 kg), more preferably at least about 6 pounds (about 2.7
kg), still more preferably at least about 8 pounds (about 3.6 kg)
and optimally at least about 9 pounds (about 4.1 kg). By green
crush strength it is meant the crush strength of the dried
agglomerates immediately after drying. In our experience, we have
found that in some instances the newly dried agglomerates continue
to increase in hardness as they age. This may be due to residual
moisture present in the dried agglomerates which continues to react
with and hydrate components of the agglomerate, resulting in
further hardening of the agglomerate.
[0044] In order to inhibit dusting of the agglomerated product, a
conventional dust control agent may be employed. For example, a
dust control agent such as that sold by Arr-Maz Products, Winter
Haven, Fla. 33880, under the product designation DUSTROL 30-52 may
be spray applied to the heated agglomerates exiting the dryer.
Other additives may also be spray applied to the finished
agglomerates. For example, if the agglomerate contains a source of
nitrogen, it may be advantageous to apply a coating of a nitrogen
volatilization inhibitor such as that commercially available from
IMC Global, Bannockburn, Ill. 60015, under the trademark
"AGRATAIN". Alternatively, such a nitrogen volatilization inhibitor
could be incorporated into the preagglomerate mixture.
[0045] In certain states of the United States of America, liming
agents such as the agglomerates of the present invention must
comply with local ordinances which establish guidelines for the
disintegration characteristics of such agents when exposed to
water. Generally, liming agents should disintegrate once
incorporated in the soil and exposed to water (e.g., rain) so that
the various beneficial components of the agent can be utilized by
the soil. In addition to substantial mechanical strength, the
agglomerates made in accordance with the present invention
disintegrate rapidly when immersed in water. Once exposed to water,
the water-soluble binder in the agglomerates is readily dissolved,
causing the agglomerates to disintegrate into particles of
substantially the same size as the raw materials used to form the
agglomerates, thereby allowing the agglomerates of the present
invention to serve as an effective liming agent and deliver their
nutrient values to the soil. In a preferred embodiment, the
agglomerates of the present invention will dissolve in less than 10
minutes, more preferably in less than 5 minutes, still more
preferably in less than 3 minutes, still more preferably in less
than 2 minutes, and optimally in less than 1 minute when immersed
in water at about 25.degree. C.
[0046] A process flow diagram is presented in FIG. 1 illustrating
an example of the type of equipment and flow scheme which may be
used in practicing the present invention.
[0047] If prehydration of the particulate calcium source is
employed, the calcium source is loaded into bin 1 and discharged by
feeder 2 at a predetermined rate into a high energy mixer 3 along
with water from pump 4 fed to the mixer at a rate sufficient to
achieve the desired degree of hydration. Suitable high energy
mixing devices include the device shown in U.S. Pat. No. 4,881,887
(Holley) sold by Ferro-Tech, Inc., Wyandotte, Mich. 48192 under the
trademark "FERRO-TECH-TURBULATOR" and those available from Feeco
Corporation, Greenbay, Wis. After sufficient residence time in
mixer 3 to ensure intimate contact between the calcium source and
the water, the hydrated mixture is discharged from mixer 3 into
conditioning bin 5 and stored for a period of time sufficient to
ensure that substantially all of the water has reacted with the
particulate calcium source.
[0048] After conditioning, hydrated material is then discharged at
a predetermined rate from bin 5 by feeder 6 into a second high
energy mixer 7 along with a water-soluble binder, either in a
liquid or a solid form, fed to mixer 7 at a predetermined rate from
storage bin 8. Alternatively, the water-soluble binder could be
combined with the particulate calcium source in mixer 3.
[0049] If prehydration of the particulate calcium source is not
employed, it should be understood that bin 1, feeder 2 high energy
mixer 3 and pump 4 are omitted from the process shown in FIG. 1 and
instead, the particulate calcium source is loaded into bin 5.
[0050] Additional water for pelletizing from pump 9 may be added to
mixer 7 as needed to form the preagglomerate. If a product
comprising the particulate calcium source and binder with no other
additives is desired, then the preagglomerate issues from mixer 7
directly onto a suitable agitated agglomeration device 10 (e.g., a
shallow pan disc pelletizer). Preferably, the preagglomerate is
pelletized using a shallow pan disc pelletizer of the type shown in
U.S. Pat. Nos. 4,726,755 (Holley) and 3,883,281 (Holley) sold by
Ferro-Tech, Inc., Wyandotte, Mich. 48192 under the trademark
"FERRO-TECH".
[0051] If primary plant nutrient source (e.g., potash, urea and
other N--P--K fertilizer components), other secondary plant
nutrient source (e.g., limestone) and/or a micronutrient source
additive are desired in the final agglomerates, these additives may
be fed from bins 11 and 12 directly into mixer 7 along with the
particulate calcium source from feeder 6, binder from storage bin 8
and additional water from pump 9 to form a suitable preagglomerate
which is then fed to agglomeration device 10.
[0052] Agglomerates of the desired size discharged from the
agglomeration device may then be fed directly into a suitable
drying device (not shown) for drying.
[0053] It is known that N--P--K fertilizer ingredients have a
generally acidifying effect on the soils into which they are
incorporated which in turn has detrimental effects on beneficial
microorganisms living in the soil. Furthermore, transfer of
nutrient values from the soil to plants is generally hindered under
acidic conditions. Thus, a problem encountered when introducing a
primary plant nutrient source into soil is that the tendency of the
fertilizer ingredient to lower the pH of the soil is counter
productive to efficient utilization of the nutrient by beneficial
microorganisms and plant life in the soil. As a result, nutrient
values may be under utilized and eventually wasted as they are
leached from the soil by precipitation and irrigation water. This
is both costly and a significant contributor to pollution of
adjacent ground and surface waters.
[0054] The agglomerates in accordance with the present invention
may be employed in a method to introduce nutrient values into
cultivated soil by applying to the soil an agglomerate comprising a
particulate calcium source and a primary plant nutrient source
and/or micronutrient source as previously described. The intimate
mixture of a particulate calcium source and primary plant nutrient
source within the agglomerate counteracts the acidifying effect of
the N--P--K fertilizer component as the agglomerate breaks down in
the soil thereby allowing more rapid transfer of nutrients to plant
life and reducing nutrient loss and pollution due to leaching.
[0055] It has been observed that the beneficial effects of
combining a particulate calcium source with a primary plant
nutrient source in close proximity as in an agglomerate for
application to the soil are further improved by observing certain
criteria. First, the particulate calcium source preferably has a
particle size distribution as previously described. The
finely-divided calcium-containing particles in intimate mixture
with the N--P--K fertilizer component more readily solublized in
the soil and rapidly counteracts acidifying effects so that the
rate of nutrient transfer to the plants is enhanced. Generally, the
finer the particle size distribution of the particulate calcium
source the better. Secondly, the particulate calcium source should
be selected so as to have a relatively high calcium carbonate
equivalent (CCE) value. Preferably, the particulate calcium source
has a calcium carbonate equivalent value in excess of 85%, more
preferably in excess of about 90%, and most preferably in excess of
about 92.5%. Furthermore, it is preferred that the particulate
calcium source contain appreciable quantities of CaO and/or
Ca(OH).sub.2 such that combined concentration of these compounds in
the particulate calcium source is at least about 3% by weight, more
preferably at least about 5% by weight. It is believed that CaO and
Ca(OH).sub.2 exhibit exceptional acid neutralization capacity.
Furthermore, these compounds are more readily converted to
plant-usable ionic calcium than calcium carbonate (CaCO.sub.3),
gypsum (CaSO.sub.4.2H.sub.2O) and other calcium compounds typically
present in soil liming agents and thereby more readily assist in
the transport of nutrient values from the soil to plant life.
[0056] Although an important plant nutrient, excessive
concentrations of magnesium in the soil is not conducive to the
transfer of primary plant nutrients (e.g., phosphates) and
micronutrients from the soil to plant life. Furthermore, the
presence of magnesium in agglomerates containing a particulate
calcium source combined with a primary plant nutrient source and/or
micronutrient source is believed to hinder utilization of the
nutrient values by plant life once the agglomerate disintegrates
after being applied to the soil. Accordingly, the magnesium content
of the agglomerates produced in accordance with the present
invention is preferably no greater than about 2.5% by weight, more
preferably, no greater than about 1.5% by weight and optimally no
greater than about 1.0% by weight. Conventional soil liming agents
often include significant quantities of magnesium compounds. Thus,
special care should be taken to monitor the concentration of
magnesium-containing compounds introduced into the preagglomerate
along with the particulate calcium as well as other components of
the preagglomerate so as to produce an agglomerate having the
desired magnesium content.
[0057] The present invention is illustrated by the following
examples which are merely for the purpose of illustration and are
not to be regarded as limiting the scope of the invention or manner
in which it may be practiced. In the proceeding examples, reference
to weight percentages are based on the starting weight of cement
kiln dust unless otherwise stated.
EXAMPLE 1
[0058] In this example, agglomerates were made from preagglomerate
mixtures containing varying amounts of CaO combined with
CaCO.sub.3, urea and/or potash fines along with an aqueous solution
of NORLIG A brand calcium lignosulfonate (about 54 weight percent
lignosulfonate salt) as a binder. The preagglomerates were formed
by thoroughly mixing CaO with measured quantities of CaCO.sub.3,
urea and/or potash fines. The CaO, CaCO.sub.3, urea and potash
fines each exhibited a particle size of -100 mesh. Once formed, the
preagglomerate was then hand fed to a shallow pan disc pelletizer
and formed into agglomerates. In some trials, the aqueous solution
of lignosulfonate binder was mixed with the other components of the
preagglomerate before being introduced onto the pan, while in other
trials the binder was added to the other materials after they were
introduced onto the pan. It is preferred that the binder be
thoroughly incorporated into the preagglomerate mixture prior to
being introduced into the pan. During pelletizing, approximately 5
to 8 weight percent of additional water (based on the weight of the
preagglomerate including the lignosulfonate binder) was sprayed
onto the agglomerates as they formed in the pan. The agglomerates
were removed from the pan by hand and dried in an oven at
60-85.degree. C. for approximately 30 minutes. After drying, the
resulting agglomerates were screened to produce agglomerates having
a size ranging from approximately -6 to +16 mesh. If possible, the
green crush strength of the dried, screened agglomerates was
determined. Set forth in Table 2 below is the composition of the
preagglomerates and the observed results.
2TABLE 2 Preagglomerate Composition (wt %) Results CaO Potash
CaCO.sub.3 Urea Binder Crush Strength (lb) 95 -- -- -- 5 fell apart
50 -- 45 -- 5 fell apart 25 -- 70 -- 5 fell apart 10 -- 85 -- 5
fell apart 7 -- 88 -- 5 4.3 5 -- 90 -- 5 6.4 3 -- 92 -- 5 9.0 5 --
88 -- 7 7.0 7 -- 86 -- 7 4.2 10 -- 81 -- 9 -2 50 -- -- 45 5 fell
apart 25 -- -- 70 5 fell apart 10 -- -- 85 5 3.0 7 -- -- 88 5 5.8 5
-- -- 90 5 8.2 3 -- -- 92 5 9.6 10 -- -- 83 7 6.0 7 -- -- 86 7 7.1
5 -- -- 88 7 8.1 50 45 -- -- 5 fell apart 25 70 -- -- 5 fell apart
10 85 -- -- 5 3.2 7 88 -- -- 5 5.9 5 90 -- -- 5 8.0 3 92 -- -- 5
9.2 10 83 -- -- 7 5.3 7 86 -- -- 7 6.9 5 88 -- -- 7 8.0 50 22.5 --
22.5 5 fell apart 25 35 -- 35 5 fell apart 10 42.5 -- 42.5 5 3.2 7
44 -- 44 5 6.0 5 45 -- 45 5 7.9 3 46 -- 46 5 8.4
EXAMPLE 2
[0059] Three samples of cement kiln dust taken directly from the
dust collection apparatus of a portland cement plant (Plant A) were
hydrated using varying amounts of water. The three samples were
combined in a high energy mixer with 10, 14 and 16 weight percent
water, respectively and stored in sealed containers for
approximately 24 hours. Each sample of hydrated material was then
mixed with 7 weight percent potash, 5 weight percent of an aqueous
solution of NORLIG A brand calcium lignosulfonate (about 54 weight
percent lignosulfonate salt) and additional water in a high energy
mixer to form a preagglomerate. The preagglomerate was then fed to
a FERRO-TECH brand shallow pan disc pelletizer and formed into
agglomerates. During pelletizing, approximately 5 weight percent of
additional water was added to the forming agglomerates. The
agglomerates had a size ranging from approximately -6 to +16 mesh.
These agglomerates were then oven dried at 120.degree. C. for
approximately 24 hours. The dried agglomerates from all three runs
exhibited a green crush strength of approximately 3 pounds (about
1.4 kg) and disintegrated in a matter of minutes when immersed in
water.
EXAMPLE 3
[0060] Four samples of cement kiln dust were taken directly from
the dust collection apparatus of each of two other portland cement
plants (Plants C and L) and hydrated using varying amounts of
water. The four samples from each plant were combined in a high
energy mixture with 4, 6, 8 and 10 weight percent water,
respectively, and stored in sealed containers for approximately 24
hours. Each of the samples of hydrated material was then mixed with
8 weight percent of an aqueous solution of NORLIG A brand calcium
lignosulfonate (about 54 weight percent lignosulfonate salt) and
additional water in a high energy mixer to produce a
preagglomerate. The preagglomerate was then fed to a FERRO-TECH
brand shallow pan disc pelletizer and formed into agglomerates.
During pelletizing, approximately 2.5 to 5 weight percent of
additional water was added to the forming agglomerates. The
agglomerates had a size ranging from approximately -6 to +16 mesh.
These agglomerates were then oven dried at 120.degree. C. for
approximately 24 hours. The dried agglomerates from all eight runs
exhibited a green crush strength of approximately 1 to 3 pounds
(about 0.5 to 1.4 kg). The crush strength was found to increase as
the amount of water used to partially hydrate the dust was
increased. However, the agglomerates made from the dust hydrated
with 4 weight percent water disintegrated in 1 to 2 minutes when
immersed in water, while the agglomerates made from the dust
hydrated with 10 weight percent water disintegrated in 10 to 20
minutes. The disintegration rate of agglomerates made from the dust
samples hydrated with 6 and 8 weight percent water fell between
these two values.
EXAMPLE 4
[0061] Four samples of cement kiln dust taken directly from the
dust collection apparatus of Plant C were processed exactly as
described in Example 3 except that (1) in addition to the aqueous
solution of NORLIG A brand calcium lignosulfonate, 8 weight percent
of potash was added to the hydrated material; and (2) instead of
approximately 2.5 to 5 weight percent, approximately 10 weight
percent of additional water was added to the forming agglomerates
during pelletizing. Similar results to those in Example 3 were
achieved. The dried agglomerates from all four runs exhibited a
green crush strength of approximately 1 to 3 pounds (about 0.5 to
1.4 kg) which tended to increase as the amount of water used to
partially hydrate the dust was increased. Similarly, the
disintegration rate of the agglomerates decreased as the amount of
water used to partially hydrate the dust was increased.
[0062] The data from Example 3 and the present example demonstrate
the effect of varying the amount of water used to hydrate the dust
on the rate of disintegration of the final agglomerate. Thus, by
varying the amount of water used to hydrate a particular dust, the
disintegration characteristics of the agglomerate may be altered as
desired. Thus, in Example 3 and the present example, if a high rate
of disintegration is desired, then the agglomerates made using 4
weight percent water would be preferred.
[0063] The agglomerates made in the present example were subjected
to a wet sieving test to better examine the disintegration
characteristics of these pellets. The wet sieving test was
conducted by stacking five sieves of differing mesh size such that
the sieve opening decreased progressively from the top sieve to the
bottom sieve. After weighing, a sample of the agglomerates made in
the present example was immersed in water for approximately 48
hours. The moistened material was then deposited on the top sieve
and subjected to a gentle spray of wash water. As the material
disintegrated, it passed through the top sieve along with the wash
water and was deposited onto the next sieve. Wash water was applied
to the top sieve until the water draining through the sieve was
substantially clear. The top sieve was then removed and the washing
process repeated on each subsequent sieve in the stack in the same
fashion as described above. Each of the sieves and any material
remaining on the screens were heated to remove substantially all
the moisture and then weighed. The weight of material (dry) which
did not pass through each sieve was determined by subtracting the
tare weight of each sieve. Summarized in Table 3 below is the
weight percentage of material (based on the starting weight of the
sample of agglomerates) which did not pass through each of the five
sieves in the wet screening test.
3 TABLE 3 Tyler Standard Weight % Sieve Sieve Series Not Passing
Top 9 0 Second 20 0 Third 32 0 Fourth 60 0.8 Bottom 100 7.0
[0064] As noted in Table 3, the agglomerates subjected to the wet
screening test disintegrated such that all of the resulting
particulate matter had a nominal diameter less than 500 .mu.m
(i.e., -32 mesh) and substantially all of the resulting particles
had a nominal diameter less than 150 .mu.m (i.e., -100 mesh).
EXAMPLE 5
[0065] A sample of cement kiln dust taken directly from the dust
collection apparatus of Plant A was processed exactly as described
in Example 2 using 10 weight percent water to hydrate the dust and
using only potash (7 weight percent) as the binder. After oven
drying, the resulting agglomerates having a size ranging from
approximately -6 to +16 mesh exhibited a green crush strength of
approximately 3 pounds (about 1.4 kg) and disintegrated in a matter
of minutes when immersed in water.
EXAMPLE 6
[0066] A sample of cement kiln dust taken directly from the dust
collection apparatus of Plant A was processed exactly as described
in Example 2 using 14 weight percent water to hydrate the dust and
using only 7 weight percent of an aqueous solution of NORLIG A
brand calcium lignosulfonate (about 54 weight percent
lignosulfonate salt) as the binder. A slightly larger amount of the
lignosulfonate salt solution was used than in Example 2 to
compensate for the loss of binding action due to the absence of
potash. After oven drying, the resulting agglomerates having a size
ranging from approximately -6 o +16 mesh exhibited a green crush
strength ranging from approximately 2 to 3 pounds (about 1 to 1.4
kg) and disintegrated in a matter of minutes when immersed in
water.
EXAMPLE 7
[0067] A sample of cement kiln dust taken directly from the dust
collection apparatus of Plant A was processed exactly as described
in Example 2 except that the dust was not hydrated before adding
the binder. After oven drying, the resulting agglomerates having a
size ranging from approximately -6 to +16 mesh exhibited
essentially no crush strength, falling apart by simple vibration or
touch of the hand.
[0068] This example demonstrates the importance of controlling the
concentration of CaO and other calcium-containing compounds having
the potential to be hydrated in the preagglomerate. Unless the
cement kiln dust is sufficiently hydrated before pelletizing or
combined with materials in the preagglomerate to sufficiently
dilute the hydration potential, the components of the
preagglomerate will tend to hydrate excessively during formation of
the agglomerate. Such hydration is accompanied by a volumetric
expansion of the formed agglomerate which renders the agglomerate
weak and undesirable for agricultural uses.
EXAMPLE 8
[0069] A sample of cement kiln dust taken directly from the dust
collection apparatus of Plant C was combined in a high energy
mixture with 14 weight percent water using a residence time of
approximately 1 hour. The hydrated material was then mixed with
both 7 weight percent potash and 5 weight percent of an aqueous
solution of NORLIG A brand calcium lignosulfonate (about 54 weight
percent lignosulfonate salt) in a high energy mixer to form a
preagglomerate. The preagglomerate was then fed to a FERRO-TECH
brand shallow pan disc pelletizer to form agglomerates. During
pelletizing, approximately 2.5 weight percent of additional water
was added to the forming agglomerates. The agglomerates formed had
a size ranging from approximately -6 to +16 mesh. These
agglomerates were then oven dried at 120.degree. C. for
approximately 24 hours. The dried agglomerates exhibited a green
crush strength of from approximately 1 to 2 pounds (about 0.5 to
0.9 kg) and disintegrated in 10 to 20 minutes when immersed in
water.
[0070] It is believed that the somewhat lower crush strength of the
agglomerates produced in this example as compared to Example 2 is a
result of the cement kiln dust containing lower concentrations of
CaO and other components which hydrate upon exposure to water as
compared to the dust used in Example 2. Therefore, the amount of
hydration water should be reduced.
EXAMPLE 9
[0071] A sample of cement kiln dust from Plant C was removed from
an outdoor disposal site where it had been exposed to atmospheric
moisture and rain and was presumably completely hydrated. This
sample was formed into agglomerates without further hydration and
without using a binder. During pelletizing, approximately 5 weight
percent of additional water was added to the forming agglomerates.
The agglomerates formed had a size ranging from approximately -6 to
+16 mesh. These agglomerates were then oven dried at 120.degree. C.
for approximately 24 hours. The dried agglomerates exhibited a
green crush strength of approximately 6 pounds (about 2.7 kg) but
did not disintegrate after several months of immersion in water
and, thus, would not be suitable for agricultural uses.
[0072] This example demonstrates the importance of adding a
water-soluble binder in producing an agglomerate having desirable
disintegration characteristics.
EXAMPLE 10
[0073] A 2.3 kg sample of cement kiln dust taken directly from the
dust collection apparatus of Plant C was ballmilled to a bulk
density of about 863 kg/m.sup.3. The ballmilled dust was hydrated
by combining it with 8 weight percent (0.18 kg) water in a high
energy mixer. After two minutes of mixing, the material was removed
from the mixer and transferred into a sealed container. In order to
simulate bin storage of a large quantity of hydrating cement kiln
dust, the sealed container was placed in an oven maintained at
about 65.degree. C. for a period of about 24 hours. Approximately 1
kg of the hydrated dust was then mixed with about 1 kg of
ballmilled urea and approximately 0.16 kg of an aqueous solution of
NORLIG A brand calcium lignosulfonate (about 54 weight percent
lignosulfonate salt) in a high energy mixer for approximately 18
seconds. This mixture was then fed to a FERRO-TECH brand shallow
pan disc pelletizer and formed into agglomerates. Approximately 7.5
weight percent of water (based on combined weight of hydrated dust
and urea) was added to the mixture in the form of solvent in the
aqueous binder solution and as pelletizing water in the pan. The
formed agglomerates were removed from the pan, allowed to stand at
room temperature for about 24 hours and dried in a portable
fluidized bed dryer at 38.degree. to 50.degree. C. for
approximately 15 minutes. The dried agglomerates were sieved
screened to a size ranging from -6 to +16 mesh. Agglomerates
ranging in size from -7 to +8 mesh exhibited a green crush strength
of about 8 pounds (about 3.6 kg) and a bulk density of about 855
kg/m.sup.3.
[0074] The dried agglomerates were analyzed for both total calcium
and total nitrogen content using comprehensive analysis methods.
Total calcium content was determined by digesting a sample of
pulverized agglomerates in HCl over heat, diluting the resulting
solution and subjecting it to atomic absorption analysis. Total
nitrogen content was determined in accordance with Association of
Official Analytical Chemist (AOAC) Method No. 2.059. The
agglomerates contained 14.85 weight percent calcium and 19.40
weight percent nitrogen. For purposes of comparative liming
capacity, the Ca content of the agglomerates in this example
corresponds to 20.78 weight percent as CaO and 37.11 weight percent
as CaCO.sub.3.
EXAMPLE 11
[0075] A 2.3 kg sample of cement kiln dust taken directly from the
dust collection apparatus of Plant L was ballmilled to a bulk
density of about 679 kg/m.sup.3. The ballmilled dust was hydrated
by combining it with 8 weight percent (0.18 kg) water in a high
energy mixer. After two minutes of mixing, the material was removed
from the mixer and transferred into a sealed container. In order to
simulate bin storage of a large quantity of hydrating cement kiln
dust, the sealed container was placed in an oven maintained at
about 65.degree. C. for a period of about 24 hours. Approximately 1
kg of the hydrated dust was then mixed with about 1 kg of
ballmilled urea and approximately 0.16 kg of an aqueous solution of
NORLIG A brand calcium lignosulfonate (about 54 weight percent
lignosulfonate salt) in a high energy mixer for approximately 18
seconds. This mixture was then fed to a FERRO-TECH brand shallow
pan disc pelletizer and formed into agglomerates. Approximately 9.5
weight percent of water (based on combined weight of hydrated dust
and urea) was added to the mixture in the form of solvent in the
aqueous binder solution and as pelletizing water in the pan. The
formed agglomerates were removed from the pan, allowed to stand at
room temperature for about 24 hours and dried in a portable
fluidized bed dryer at 38.degree. to 50.degree. C. for
approximately 15 minutes. The dried agglomerates were sieved
screened to a size ranging from -6 to +16 mesh. Agglomerates
ranging in size from -7 to +8 mesh exhibited a green crush strength
of about 8 pounds (about 3.6 kg) and a bulk density of about 714
kg/m.sup.3.
[0076] The dried agglomerates were analyzed for both total calcium
and total nitrogen content using the same methods as described in
Example 10. The agglomerates contained 14.19 weight percent calcium
and 19.50 weight percent nitrogen. For purposes of comparative
liming capacity, the Ca content of the agglomerates in this example
corresponds to 19.86 weight percent as CaO and 35.47 weight percent
as CaCO.sub.3.
EXAMPLE 12
[0077] A 2.3 kg sample of cement kiln dust taken directly from the
dust collection apparatus of Plant C was ballmilled to a bulk
density of about 863 kg/m.sup.3. The ballmilled dust was hydrated
by combining it with 8 weight percent (0.18 kg) water in a high
energy mixer. After two minutes of mixing, the material was removed
from the mixer and transferred into a sealed container. In order to
simulate bin storage of a large quantity of hydrating cement kiln
dust, the sealed container was placed in an oven maintained at
about 65.degree. C. for a period of about 24 hours. Approximately
1.5 kg of the hydrated dust was then mixed with about 0.5 kg of
particulate dolomitic limestone, approximately 0.16 kg of an
aqueous solution of NORLIG A brand calcium lignosulfonate (about 54
weight percent lignosulfonate salt) and 75 ml of water in a high
energy mixer for approximately 18 seconds. This mixture was then
fed to a FERRO-TECH brand shallow pan disc pelletizer and formed
into agglomerates. Approximately 18 weight percent of water (based
on combined weight of hydrated dust and dolomitic limestone) was
added to the mixture in the form of solvent in the aqueous binder
solution and as pelletizing water in the pan. After being removed
from the pan, a sample of the agglomerates were dried immediately
in a portable fluidized bed dryer at 38.degree. to 50.degree. C.
for approximately 15 minutes, while the remainder of the
agglomerates were allowed to first stand at room temperature for
about 24 hours and then dried in the portable fluidized bed dryer.
The dried agglomerates were sieved screened to a size ranging from
-6 to +16 mesh. The agglomerates which were allowed to stand 24
hours and having a size ranging from -7 to +8 mesh exhibited a
green crush strength of about 2.4 pounds (about 1.1 kg) and a bulk
density of about 1057 kg/m.sup.3, while similarly sized
agglomerates which were dried immediately in the fluidized bed
dryer exhibited green crush strengths between about 2 and about 3
pounds (between about 1 and about 1.4 kg). If desired, the green
crush strength of the agglomerates could be increased by using a
larger quantity of binder.
EXAMPLE 13
[0078] Urea (2.4 pounds), crushed limestone (0.8 pounds), and
non-prehydrated cement kiln dust (0.8 pounds) were mixed with water
(Test 13-1) or a binder (a solution of lignosulfonate having
approximately 50% solids--Test 13-2) in a Model 12TB34 Batch
Turbulator for 18 seconds to form preagglomerates. The
preagglomerates were hand fed to a Model 024" 2'0" Disc Pelletizer
in which water was being sprayed onto the disc at a 4:30/6:30
positions. The agglomerates were removed by hand and dried at
120.degree. F. to produce screened dry pellets (-6 +16 mesh). The
moisture content and bulk density of the starting materials are
presented below in Table 4:
4 TABLE 4 Raw Data Moisture Bulk Density Urea N/A 636 kg/m.sub.3
Limestone 0% 1330 kg/m.sub.3 Cement Kiln Dust 0% 867 kg/m.sub.3
[0079] The resulting agglomerates were analyzed and found to have
the following characteristics:
[0080] TEST 13-1
[0081] Binder
[0082] (water only)
[0083] Amount of water at Batch Turbulator 50 ml
[0084] Moisture from disc.
[0085] 7%
[0086] Product bulk density
[0087] 764 kg/M.sup.3
[0088] Crush Strength average (-6 +8 mesh) 6 pounds (2.7 kg)
[0089] TEST 13-2
[0090] Binder
[0091] 3% Lignin
[0092] Amount of Water at Batch Turbulator 50 ml
[0093] Moisture from Disc.
[0094] 7%
[0095] Product Bulk Density
[0096] 772 kg/M.sup.3
[0097] Crush Strength Average (-6 +8 mesh) 7 pounds (3.2 kg)
EXAMPLE 14
[0098] The procedure of Example 13 was repeated except that urea
(2.4 pounds) and cement kiln dust (1.6 pounds) were mixed with 50
ml water in the Batch Turbulator for 18 seconds. The results were
as follows:
[0099] Moisture from Disc
[0100] 7%
[0101] Product Bulk Density
[0102] 706 kg/M.sup.3
[0103] Crush Strength Average (-6 +8 mesh) 3 pounds (1.4 kg)
EXAMPLE 15
[0104] In this example, agglomerates were made from preagglomerate
mixtures containing varying amounts of lime kiln dust, manure ash
and potash fines along with KGA-300 liquid wood waste derivative as
a binder. The lime kiln dust and manure ash were analyzed and
determined to contain about 55% and about 7% by weight CaO,
respectively. The lime kiln dust and manure ash exhibited a
particle size distribution such that 90% of the particles were -300
mesh. The potash fines exhibited a particle size distribution such
that 90% of the particles were -150 mesh.
[0105] The preagglomerate mixtures were formed by thoroughly mixing
measured quantities of lime kiln dust, manure ash and potash fines
with the liquid binder. The preagglomerate was hand fed to a
shallow pan disc pelletizer and formed into agglomerates. In some
trials, the liquid wood waste binder was mixed with the other
components of the preagglomerate before being introduced onto the
pan, while in other trials the binder was sprayed onto the other
materials after they were introduced onto the pan. In order to
render the liquid binder better suited for spray application, the
binder was heated to about 80.degree. C. It is preferred that the
binder be thoroughly incorporated into the preagglomerate mixture
prior to being introduced into the pan. During pelletizing,
approximately 5 to 8 weight percent of additional water (based on
the weight of the preagglomerate including the liquid binder) was
sprayed onto the agglomerates as they formed in the pan. The
agglomerates were removed from the pan by hand and dried in an oven
at 60-85.degree. C. for approximately 30 minutes. After drying, the
resulting agglomerates were screened to produce agglomerates having
a size ranging from approximately -6 to +16 mesh. If possible, the
green crush strength of the dried, screened agglomerates was
determined. Set forth in Table 5 below is the composition of the
preagglomerates and the observed results.
5TABLE 5 Preagglomerate Composition (wt %) Lime Kiln Manure Results
Dust Ash Potash Binder Crush strength (lb) 55 -- 45 5 fell apart 25
-- 70 5 fell apart 10 -- 87 3 4.0 10 43.5 43.5 3 5.5 -- 95 -- 5
5.0
EXAMPLE 16
[0106] In this example, agglomerates were made from preagglomerate
mixtures containing varying amounts of a mixture of lime kiln dust
and wetted gypsum combined with potash fines along with KGA-300
liquid wood waste derivative as a binder. The lime kiln dust was
analyzed and determined to contain about 55% by weight CaO. The
lime kiln dust exhibited a particle size distribution such that 90%
of the particles were -300 mesh. The potash fines exhibited a
particle size distribution such that 90% of the particles were -150
mesh. The wetted gypsum was obtained from a lime scrubbing unit
used to remove sulfur dioxide from the gaseous effluent of an
electric power plant and was about 98% pure with a water content of
about 22% by weight.
[0107] The lime kiln dust and wetted gypsum were combined in a
weight proportion of 2 to 3 and mixed thoroughly. The resulting
mixture was then allowed to set for approximately 12 hours,
allowing water present in the wetted gypsum to react with the lime
kiln dust. After conditioning in this fashion, the lime kiln
dust/gypsum mixture appeared essentially dry to the touch. The
preagglomerate mixtures were formed by thoroughly mixing measured
quantities of the conditioned lime kiln dust/gypsum mixture, potash
fines and the liquid binder. The preagglomerate was hand fed to a
shallow pan disc pelletizer and formed into agglomerates. In order
to render the liquid binder better suited for spray application,
the binder was heated to about 80.degree. C. During pelletizing,
approximately 5 to 8 weight percent of additional water (based on
the weight of the preagglomerate including the liquid binder) was
sprayed onto the agglomerates as they formed in the pan. The
agglomerates were removed from the pan by hand and dried in an oven
at 60-85.degree. C. for approximately 30 minutes. After drying, the
resulting agglomerates were screened to produce agglomerates having
a size ranging from approximately -6 to +16 mesh. If possible, the
green crush strength of the dried, screened agglomerates was
determined. Set forth in Table 6 below is the composition of the
preagglomerates and the observed results.
6 TABLE 6 Preagglomerate Composition (wt %) Lime Kiln Dust/ Results
Wetted Gypsum Potash Binder Crush Strength (lb) 50 45 5 3.5 30 65 5
6.0
[0108] In view of the above, it will be seen that the several
objects of the invention are achieved.
[0109] As various changes could be made in the above-described
invention without departing from the scope of the invention, it is
intended that all matter contained in the above description be
interpreted as illustrative and not in a limiting sense.
* * * * *