Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates to grinding blast furnace slag and more parti-
cularly to the use of an additive for improving the efficiency of the grinding
operation as well as improving characteristics of the ground slag product.
Granular blast furnace slag is produced by air and water quenching of
the molten, non-metallic residue remaining after the treatment of metallic ore
in a blast furnace in the production of iron and steel. Grinding of such slag,
followed by exposure to the proper catal~st such as lime, will produce a product
~hich acts as a cementitious material, but only behaves well as such when ground
to a ver~ fine particle size.
The grindlng of an~ solid material to obtain a desired finer particle
size involves the consumption often times of a considerable amount of energy by
the grinding equipment. It is desirable in this grinding therefore to have as
efficient an operation as possible.
It has become custo~ary in grinding products which are used in rela-
tively large volume such as Portland cement to employ chemical "grinding aids".
Such grinding aids are added before or during the grinding operation to assist
in the grinding operation either b~ increasing the rate of production, or by
increasing the fineness of the cement particles at the same rate of production,
without having adverse effects on any of the properties of the ground product.
In scme instances, the presence of the grinding aid in the finished, ground pro-
duct ~ill also cause the ground product to exhibit a re~uced tendency to compact
or to "pack set". The tendenc~ of ground solids to compact or "pack set" is
~hought to be brought about by cleavage of the particles during grinding of
such, ~hich exposes fresh or nascent surPaces ~hlch have high energ~. Reduction
f this tendency to "pack set" or compact is desirable since it facilitates the
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transportation of the ground product.
Many chemicals and combinations thereof have been suggested for use
as grinding aids in the reduction of the particle size of Portland cement
clinker and other hydraulic cement, as well as other "minerals". Some examples
of grinding aids which have been successfully utilized on a commercial scale in
the grinding of Portland cement clinker are phenol, acetic acid, amines and
salts thereof, glycols, and combinations of the foregoing. United States
Patent 3,607,326 to Serafin discloses a grinding aid and pack set inhibitor
for Portland cement and other "minerals" which is an amine salt of an aryl
hydroxy compound, for example, triethanolammonium phenoxide. This patent also
mentions the use of such as useful in the grinding of phosphate rock, iron ore,
bauxite, clay, gypsum, amorphous silica, limestone, beryllium oxide and magnesia.
BRIEF SUMMARY OF THE INVENTION
It has now been discovered that chemical additives of the type dis-
closed in the aforementioned United States Patent 3~607,326 to Serafin are
particularly effective as grinding aids in the grinding of granular blast
furnace slag. The presence of the additives also appear to function to reduce
the tendency of the ground slag product to "pack set".
DETAILED DESCRIPTION OF THE INVENTION
The amine salt additives which have been found particularly effective
as grinding aids and pack set inhibitors for granular blast urnace slag accor-
ding to the invention, are, as aforementioned, described in United States
Patent 3,607,326. As dis~losed in the patent, the salts are produced by the
; reaction of an aryl hydroxy compound such as phenol, with an amine such as
triethanolamine. In preparing the additives one or more aryl hydroxy compounds
are mixed with one or more amines. The starting materials may be pure chemicals
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or mixtures containing differing chemicals or impurities. The methods of pre-
paring the additives are known to the art. Preferably, equimolar parts of the
amine and the aryl hydroxy compounds are employed~ The amine salt additives
according to the invention can be used alone or in combination with other
chemical additives such as other grinding aids to obtain desired results.
The term "aryl" as used herein in describing the aryl hydroxy reac-
tant is intended to refer to phenyl or naphthyl radical. It should be under-
stood that one or more of the hydrogen atoms on the aryl radical may be replaced
by a nitro; halogen, preferably chlorine; alkyl, preferably a l-to-5-carbon
group, more preferably methyl; aryl; preferably of one to three aromatic rings,
amino and alkoxy, preferably a one to five carbon alkoxy group.
The amines employed in the present invention include mono-; di- and
trialkanol amines, or mixtures thereof and morpholine. The alkanol group or
groups in the mono-, di- and trialkanol amines each contain about 1 to 5 carbon
atoms. Illustrative of such alkanolamines are monoethanolamine, diethanolamine,
dipropanolamine, dibutanolamine, triethanolamine, tripropanolamine, etc. as
well as mixtures thereof. Obviously the aforementioned amines employed in the
invention can contain substituent groups which do not deleteriously affect the
reaction of the amine with~the aryl hydroxy compound or the desired effects of
the additive of the invention on blast furnace slag. Exemplary of such non-
deleterious substituted amines are N-methylmorpholine and 4-~2-aminoethoxy)
ethylmorpholine. Trialkanolamines, for example triethanolamine, are especially
preferred for use in forming the additive of the invention.
The term "granular blast furnace slag" as used herein is intended
to refer to the solidified and preliminarily crushed ~preferably -20 mesh,
U. S. Sieve System) mixture of iron ore impurities and fluxing materials re-
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sulting from ~he manufacture of iron and steel in a blast furnace. The chemical
composition of typical blast furnace slags from various parts of the world is
given in Kirk Othmer's Encyclopedia of Chemical Technology, Second Edition, Sup-
plemented ~olume, page ~77 ~1971, John Wiley ~ Sons, Inc.).
G enerally speaking, slags that can be ground in the process of this
invention comprise the ingredients shown in Table I.
TABLE I
Ingredients Weight Percent Preferred
CaO 35-45 about 40
2 3~-40 about 35
A12~3 5~20 about 12
~gO 3-15 about 5
Qthers balance balance
On the same page in the above encyclopedic reference, there is a phase
diagram for the CaO~A1203-SiO2-MgO system ~at least 5% MgO) showing the distinc-
tion between blast furnace slag and other materials of the same general system.
The grinding aids are employed in either dry or liquid form. For con-
venience, the additive is in water solution to permit accurate metering into the
mill stream. In instances where the additive is not very soluble in water, it
can be utilized in liquid form by emulsifying with suitable wetting agent, for
example, sodium dodecyl benezene sulonate. The additive may also contain a
chelating agent ~such as trisodium N-hydroxyethylethylene diamine triacetate hy-
drate ~hereinafter "NEDTA") in order to chelate the cations commonly found in
hard water and thereby prev~nt precipitation of the product. The addition of
the additive of the invention to the slag is accomplished either prior to the
grinding operation, or the additive is introduced into the grinding mill during
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the grinding thereof. If the additive is employed merely for the reduction ofpack set or for fluidizing purposes, it is added at any convenient point in the
processing.
The additive is employed effectively over a relatively wide range.
The preerred range is about 0.001 to 1 percent based on the weight of the slag,
i.e. the weight of additive solids based on the weight of the slag solids ~here-
in referred to as solids on solids). In a particularly preferred embodiment,
the amount of additive employed is about 0.004 to 0.04 percent. Higher levels
are employed if grinding to a relatively high surface area is desired, and the
amount of additive is limited solely by the desired surace area and the degree
qf fluidi~y desired.
The term "pack set" as used herein is intended to refer to the agglo-
meration or adhesion of particles by, for example, storing or transporting in
bulk. Adhesion results from surface forces, the majority of which are believed
to be created during the grinding of the slag. "Pack set index" is a relative
term which indicates numerically how prone a particular material is to start
1O~ing after it is stored or transported in bulk. "Pack set index ratio" is
the relative pack set index of an untreated sample compared to a sample treated
with additives. This ratio is used to permit comparisons to be made between
diferent samples.
Pack set index is determined in the following manner:
One hundred grams of the slag is placed in a 250 milliliter Erhlen-
meyer flask set on top of a variable vibrator. The flask containing the slag
is vibrated 15 seconds after which it is removed from the vibrator and set into
a jig with the axis of the flask lying horizontally. The flask is then rotated
around its axis until the slag which is compacted in the bottom of the flask
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collapses~ Such rotation is accomplished by twisting the flask at 180 angles
at approximately 100 twists per minute. The number of 180 twists required for
the slag sample to collapse establishes the pack set index. Thus the greater
the energy required to break up the bed, the higher will be the pack set index.
The invention is illustrated further by the following non-limiting
Examples.
EXAMPLE I
An additi~e composition according to the invention is prepared con-
taining the following components:
Components Percent By Weight
Phenol 31
Triethanolamine 49
Water 19.5
Chelating agent ~"NEDTA") 0.25
Dye 0.25
The composition shown above is prepared using the following steps:
Steps
1. Combine phenol and 38~ of the total required amount of triethanol-
amlne; mlx.
2. Add remainder of triethanolamine to step 1 material; mix.
3. Mix water, chelating agent and dye in a separate container.
4. Combine step 2 material with step 3 material.
EXAMPLE II
Several chemical products were tested for usefulness as grinding aids
in the grinding of blast furnace slag. The chemical products were products pre-
viously sold ~nd used commercially as grinding aids and pack set inhibitors in
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the grinding of Portland cement clinker. In one study, the results of which are
reported in Table IIbelow, replicate grinds were performed using 3500 grams of
granular blast furnace slag ~-20 mesh) in a laboratory batch mill. The grinds
were performed for approximately 20,000 revolutions at 220 Fahrenheit using as
grinding aids ~i) an additive composition produced as in Example I; ~ a gly-
col based product; and ~iii) combinations of ~i) and ~ Grinds were also
made using no grinding aid at all, the latter serving as a control blank. The
results are shown in Table II.
TABLE II
Blaine Surface Area
GrindingAddition Per2Mill Revolution %Improvement
Aid Ràte ~cm /gm/rev) Average Over ~lank
.
Run ~1 Run #2
N~ne - 00235~ 0.2395 002377
Commercial~glycoll) 0.02 002451 0.2469 0.2460 3O5
Example I 0.02 0.2557 0.2528 0.2542 7.0
Commercial(glycoll) 0.02 0.2479 0.2489 0.2484 4.5
~Example, 1:1
Example I 0.04 0O2719 0O2692 0.2705 13.8
Commercial(glycoll) 0.04 0.2660 0.2644 0.2652 11.6
~Example, 1:1
(1) A proprietary mixture containing approximately 90 percent diethy-
lene glycol by weight of total solidsO
Ex Q le III
In another grinding study, replicate grinds of blast furnace slag
were made as in Example II except that the test samples were ground for approx-
imately 11,000 revolutions of the batch mill. The products tested for effec-
tiveness as grindin~ aids included a composition of the invention tmade as in
Example I), the glycol-based commercial grinding aid of Example II, and another
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commercial product based on an acetate salt, also used previously as a grinding
aid for Portland cement. The results are shown in Table III.
TABLE IIT
Blaine Surface
Area Per Mill
Grinding Addition Rate Rev~lution % Improvement
Aid ~% solids on solids) (cm /gm!rev) _ Over Blank
None - 0.3087
Commercial ~acetatel) 0O02 0.3172 2.7
Commercial tglycol) O.02 0.3183 3.1
Example I 0.02 0.3246 5.1
Commercial ~acetatel) 0.04 0.3302 7.0
Commercial ~glycol) 0.04 0.3294 6.7
Example I 0.04 0.3388 9.8
~ 1) A proprietary comme~cial product containing about 60 percent by
weight of an acetate salt based on the total solids present.
Example I~
A test was conducted to determine the effectiveness of the grinding
aid of the invention (Example I) as a pack set inhibitor for ground blast fur-
nace slag. The test was conducted in the manner described above. The results
10, sho~n in Table IV below indicate that the slag grinding aid of the invention
also acts to reduce the tendency of the ground slag to "pack set".
TA~E' IV
~fect Of Additive Qf The Invention On "Pack Set Index
_ _A ._ _ _ _ _ .~ ~ = = ' _ .. _ . ~ _
Pack Set Inhibitor Addition Rate Pack Set Index
%solids on solids)
None - 6
Example I O.02 2
Example I 0.04 0
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As is evidenced by the above Examples, a highly effective grinding aid
or ground blast furnace slag has been found. The additive also acts as a pack-
set inhibitor of the ground product. The grinding aid of the invention was un-
expectedly shown to be more effective as a grinding aid for the slag than pro-
ducts based upon glycols and acetate salts> which like the additive of the in-
vention have been previously utilized as grinding aids for Portland cement,
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