Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-07-19
2002-11-12
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S819000, C106S823000, C106S600000, C106S606000, C106S632000, C106S638000, C106S713000, C106S802000
Reexamination Certificate
active
06478870
ABSTRACT:
BACKGROUND OF INVENTION
The present invention is a process for preparing a flowable slurry comprising mixing an alkaline material selected from the group consisting of chlorosilicon manufacturing byproducts, direct process residue gels, cement kiln dust and mixtures thereof, optionally clay, about 25 to 70 wt. % water and a process aid selected from the group consisting of sucrose, raffinose, lignin, methylglucopyranoside, lactose, fructose, sodium polyphosphate, trehalose and mixtures thereof to form the flowable slurry. The process is especially useful as an economical and an environmentally sound method for recycling alkaline raw materials for cement manufacture.
The preparation of portland cement is well known in the art. Portland cement is a hydraulic cement characterized by the ability to set and harden in water. Generally, portland cement is manufactured by mixing suitable raw materials with water, burning at suitable temperatures to effect clinker formation, and grinding the resulting clinkers to the fineness required for hardening by reaction with water. The burning operation generates a fine alkaline particulate byproduct called cement kiln dust that is difficult to recycle. Cement kiln dust typically comprises about 1-3 wt. % or more of the above product from the cement production operation.
The portland cement resulting from the above process consists mainly of tricalcium silicate and dicalcium silicate. These two materials are primarily derived from two raw materials: one rich in calcium such as limestone, chalk, marl, oyster or clam shells; and the other rich in silica such as clay, shale, sand or quartz.
Bunce, et. al in U.S. Pat. No.5,374,310 teach the use of a silicon containing product resulting from the hydrolysis of chlorosilicon by-product as materials for cement production. However, when such materials are added to a clay slurry for use in cement manufacture, a thick, non-flowable paste forms which prevents further downstream processing, especially when small amounts of water are used.
It would also be useful to use other alkaline materials such as other chlorosilicon manufacturing byproducts and cement kiln dust in the manufacture of cement. Unfortunately, these materials, too, suffer from the disadvantage that they form thick pastes that are difficult to manage unless large amounts of water are used.
The present inventors have now discovered that flowable slurries of such alkaline materials can be maintained by mixing them with certain process aids selected from the group consisting of sucrose, raffinose, lignin, methylglucopyranoside, lactose, fructose, sodium polyphosphate, trehalose and mixtures thereof.
SUMMARY OF INVENTION
The present invention is a process for preparing a flowable slurry comprising mixing:
25-70 wt. % water;
an alkaline material selected from the group consisting of chlorosilicon manufacturing byproducts, direct process residue gels, cement kiln dust and mixtures thereof;
optionally, clay; and
a process aid selected from the group consisting of sucrose, raffinose, lignin, methylglucopyranoside, lactose, fructose, sodium polyphosphate, trehalose and mixtures thereof
to form a flowable slurry.
DETAILED DESCRIPTION OF INVENTION
The present invention is a process for preparing a flowable slurry comprising an alkaline material, a process aid, optionally clay and water. The process aid inhibits the formation of thick pastes that result when the alkaline material and, optionally, clay are mixed with water.
The alkaline materials useful herein comprise chlorosilicon manufacturing byproducts, direct process residue gels, cement kiln dust, and mixtures thereof.
The “chlorosilicon manufacturing by-products” result from manufacturing operations in which chlorosilicons are produced. Typical of chlorosilicon manufacturing operations are the reaction of silicon metal with methyl chloride to form methyl chlorosilanes and the reaction of silicon metal with hydrogen chloride to produce chlorosilanes. Unfortunately, these operations produce a number of undesirable by-products and waste streams that require disposal.
These by-products and waste streams are often acidic and, thus, are often neutralized prior to use. An example of one such neutralization method is described in U.S. Pat. No. 5,000,934, in which a spent bed resulting from the reaction of halides with silicon metal is neutralized with a strong base and elevated temperature. This reference is incorporated herein by reference. The metal salts that are generated by processes such as this or other by-product disposal processes, as well as any other incidental metal salts generated by chlorosilicon production processes which will be known to those with ordinary skill are generally captured to avoid discharge to the environment and can be used in the process of the present invention.
A specific example of a by-product useful in the process of the present invention comprises that generated by the metal hydroxide precipitation during the purification of wastewater from chlorosilicon manufacturing.
The by-products resulting from these processes may comprise metal oxides, such as CaO, SiO
2
, Al
2
O
3
, Fe
2
O
3
, MgO, K
2
O, Na
2
O, SO
3
, TiO
2
, P
2
O
5
, SrO, Bao, and Mn
3
O
4
. While the actual composition is not critical to the invention, typical chemical compositions of the by-product from the example of the previous paragraph may comprise 0 to 30 wt. % CaO, 0 to 35 wt. % SiO
2
, 0 to 5 wt. % Al
2
O
3
, 0 to 4 wt. % Fe
2
O
3
, 0 to 8 wt. % MgO, 0 to 1 wt. % K
2
O, 0 to 0.5 wt. % Na
2
O, 0 to 1 wt. % SO
3
, 0 to 1 wt. % TiO
2
, 0 to 0.1 wt. % P
2
O
5
, 0 to 0.1 wt. % SrO, 0 to 0.1 wt. % BaO, 0 to 0.5 wt. % Mn
3
O
4
and 0 to 30 wt. % water.
Another alkaline material useful in the present invention is direct process residue gel. Examples of this material are described in U.S. Pat. Nos. 4,408,030 and 5,374,310, which are incorporated herein by reference. These references describe the formation of gels from the by-products of the reaction of silicon metal with methyl chloride to produce chlorosilanes (the ‘direct process’). The gels are formed by the hydrolysis of a variety of these chlorosilion by-products including, for example, silanes, disilanes, disiloxanes, silane oligomers, siloxane oligomers, silphenylenes and silalkylenes. This hydrolysis occurs in an aqueous medium as described in the above patents, which may comprise additives such as HCl and/or CaCl
2
.
A typical composition of this gel comprises water, CaCl
2
, and the hydrolyzed products of the hydrolysis.
Also useful as alkaline materials in the present invention are other calcium rich materials, such as, cement kiln dust which, as described above, is a by-product generated during Portland cement manufacturing operations. Generally, Portland cements are manufactured by mixing suitable raw materials with water, burning at suitable temperatures to effect clinker formation, and grinding the resulting clinkers to the fineness required for hardening by reaction with water. The burning operation generates the fine alkaline particulate, cement kiln dust. While the actual composition is not critical to the invention, typical chemical compositions for cement kiln dust are in the range of about 15 to 55 wt. % CaO, 10 to 35 wt. % SiO
2
, 2 to 10 wt. % Al
2
O
3
, 1 to 6 wt. % Fe
2
O
3
, 1 to 11 wt. % MgO, 0.2 to 2 wt. % K
2
O, 0.05 to 1.0 wt. % Na
2
O, and 0.1 to 2 wt. % SO
3
.
The alkaline materials are typically added to the slurry of the present invention in amounts up to about 40 wt. % based on the total weight of the slurry when clay is present, and up to about 65% when clay is not part of the slurry. Often, the alkaline materials are used in amounts up to about 30 wt. % or, alternatively, about 1 to 30 wt. %, based on the total weight of the slurry when clay is included, and up to about 60 wt. % or, alternatively, 0.1 to 60 wt. %, when clay is not part of the slurry. Obviously, smaller amounts are also within the scope of the invention.
The process aids used in the present invention are selected from the group consisting of sucrose, ra
De Cesare Jim L.
Dow Corning Corporation
Gobrogge Rogerr E.
Warren Jennifer S.
Wood Elizabeth D.
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