Synthetic silicate pellet compositions

Details Synthetic silicate pellet compositions Synthetic silicate pellet compositions

1999-10-12

2001-04-03

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C501S029000

Reexamination Certificate

active

06211103

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to glass-making, and, more particularly, to a method of making a synthetic calcium/magnesium silicate pellet having varied properties, such synthetic silicate pellets themselves, and to the using of such synthetic silicate pellets in glass-making systems.
BACKGROUND
In general, glass-making involves the combination of precursive materials for melting and reacting together to form a desired glass composition. The volume and use of glass is such that natural resources are traditionally favored with a cost-optimal amount of beneficiation of such materials for glass-production purposes.
Some of the historical glass-making schemes involved the combining of sand (as a silica source), lime (as a calcium source) and soda ash (as a sodium source) along with other materials and processing to form the ubiquitous glass products. Such processes traditionally suffered from, and continue to suffer from, production limitations. Among the more critical limitations are batch-free time (the time required to completely dissolve the combined materials) and the fining time (the time to remove gases from the melt which form undesired bubbles in the melt and resulting glass). Other limitations involve the handling problems associated with the precursive materials, such as crumbling, dusting, clumping, sintering deficiencies and the like.
Progress has been made in the glass-making processes by the use of specially processed or beneficiated materials intended for use as glass precursive materials. In particular, a class of synthetic silicates have been developed encompassing various forms of synthetic calcium silicates, magnesium silicates and/or calcium magnesium silicates. Exemplary of such materials are SYNSIL™ synthetic silicates. While such synthetic silicates can provide beneficial results, there continues to be a need for enhanced precursive materials for the glass-making technologies.
SUMMARY
An object of the present invention is to provide a synthetic silicate as a precursive glass-making material in a composition and form which reduces handling problems in the glass-making process.
Another object of the present invention is to provide a synthetic silicate as a precursive glass-making material in a composition and form which enhances the melting process in the glass-making process.
These and other objectives are achieved by providing a synthetic silicate composition comprised of a calcium/magnesium silicate material of controlled formulation, an alumina silicate binder, a catalyst and silica fines. The binder and catalyst are alternatively present, providing respectively preferred advantages of enhanced compression strengths and enhanced sintering characteristics and yields of such synthetic silicates.
DETAILED DESCRIPTION OF INVENTION
An embodiment of the present invention is a novel composition comprising (i) a silicate material having an empirical formula of Ca
x
Mg
y
Si
z
O
(x+y+2z)
, wherein the values of x, y, and z are such that at least one of x and y are not zero and the values are such that the novel composition is suitable as a glass precursor material; (ii) an alumina silicate binder in an amount effective to impart a compression strength sufficient to enable a pellet formed from the novel composition to be handled at ambient temperature and sintered without substantial structured damage to said pellet; and (iii) silica fines in an amount such that the composition is suitable as a glass precursor material. This composition has use as precursive material in the glass-making process. Other additives or elements of composition may be added with regard to the particular specific glass being produced. The manufacturer of such glass will make the adjustments to the variables of the elements of the composition so as to be suitable for his intended end glass product. pounds of water. This solution is added to the blender at a rate of 1.1 pounds per minute until hydration is complete. After the completion of water addition continue to mix for two (2) minutes. This material is then formed into one half inch in diameter pellets and air-dried for twenty-four (24) hours.
Six Percent Calcium Aluminate and Fume Silica Binder
Forty-seven (47) pounds of pebble lime, forty-seven pounds of sand, and six (6) pounds of fume silica are placed in a ribbon blender. Two (2) pounds of sodium hydroxide is dissolved in twenty-three (23) pounds of water. This solution is added to the lime, sand, and silica mixture at 1.1 pounds per minute until hydration is complete. After completion of water addition, six (6) pounds of Secar 71 cement is added to the blender and blending is continued for two (2) minutes. This material is the formed into one half inch in diameter pellets and air-dried for twenty-four (24) hours.
Twenty-one representative pellets are selected from each of the formulations above. Individual pellets are placed on the tester and evaluated as outlined above. An average of the results is given in TABLE 1.
TABLE 1
Compression Strength Test (pounds)
Ambient
Temperature
Temp.
500° C.
600° C.
700° C.
800° C.
900° C.
1000° C.
1100° C.
Control
34.3
56.4
34
17.1
12
3
1
N/A
6% Secar 71
61.7
71.6
31.8
18.0
20.0
17.6
25.4
18.8
EXAMPLE 2
An attrition test, as described above, is done on the pellets produced through the processes described in Example 1. An attrition test is done as described above, to determine the amount of fines produced by the dynamic motion of a rotary kiln. In this test the mixture with no binder is compared with the mixture in which six (6) percent of Secar 71 cement is added.
One embodiment of the present composition invention is a silicate material having an empirical formula of Ca
x
Mg
y
Si
z
O
(x+y+2z)
. The values chosen for such empirical formula are such that the composition is suitable as glass precursor material as discussed above. Either x or y may be zero, but both x and y are not zero. Accordingly, the silicate material may be of a nature as to be a wollastonite-type (Ca
X
Si
1
O
3
) material or a diopside-type (Ca
X
Mg
Y
Si
2
O
6
) material or an enstatite-type (Mg
Y
Si
1
O
3
) material and the like. What is meant by “type” material is exemplified as follows: a wollastonite-type material may in fact be natural or synthetic wollastonite (Ca
1
Si
1
O
3
) or a compound whose elemental proportions approximates such formula. Similarly, a diopside-type material may be a natural or synthetic diopside (Ca
1
Mg
1
Si
2
O
6
) or a compound with similar elemental proportions. For instance, the proportions of calcium to magnesium need not necessarily be one to one. In a preferred embodiment of the present invention a preferred ratio of calcium to magnesium is about one-half to about ten, more preferably about one to about two. A particularly more preferred range is a proportion of calcium to magnesium between the values of about 1.4 to about 1.7. Similarly, an enstatite-type material may be a synthetic or natural enstatite (Mg
1
Si
1
O
3
) or a compound with similar elemental proportions. For instance, an enstatite-type material may not strictly have a one to one proportion between the magnesium and silica in the compound. Accordingly the present invention involves compounds with a general empirical formula of Ca
x
Mg
y
Si
z
O
(x+y+2z)
, whose relative proportions may duplicate the natural wollastonite, diopside, or enstatite material or be approximations. In all instances for the present invention, however, at least a significant amount of calcium or magnesium should be present in the silicate material. Other non-listed elements may be present in non-effective amounts in the compounds as trace or contaminant materials as long as such does not significantly alter the benefits of the present inventive compositions in the intended glass formation products. Throughout the specification it will also be appreciated by those in the art that the empirical values for the oxygen content may not strictly be x+y+2z, but will be sufficiently approximate to such so that the composition is able to perform a

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