JPS58167731A - Heat-retaining agent for molten metal - Google Patents

Abstract

PURPOSE:To obtain the inexpensive heat-retaining agent for molten metal having an effective heat-retaining property, by saturating the mixture of a sugar liquid and milky lime with carbon dioxide gas, and using the resulting by-produced calcium carbonate as a material. CONSTITUTION:By-produced calcium carbonate is prepared by the carbonic acid-saturating method to saturate the mixture of a sugar liquid and milky lime with carbon dioxide gas and to remove impurities from the sugar liquid. This calcium carbonate is mixed with diatom, pearlite or the like as a filtering assistant, and the cake of calcium carbonate is separated from the refined sugar liquid. This by-produced calcium carbonate having small apparent specific gravity is inexpensive and useful as a heat-retaining agent. In order to make good use of said property, about 10-70wt% another heat-retaining agent such as pearlite, diatom or vermiculite is pref. added as an additional component to the calcium carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat insulating material for molten metal during metal scouring or casting.

Traditionally, rice husks, burnt materials, etc. have been used as this type of heat insulating material, but these have the operational problem of emitting a large amount of dust when they are used, and because they are seasonal materials, their supply is not constant throughout the year. Recently, heat insulating materials formed from 5in2 of nacre, obsidian, perlite, diatomaceous earth, etc. as main components have been used. As a heat insulating material for molten metal, it is preferable to use a material that does not melt even at the melting temperature of the metal and retains heat 1 for a long time, but materials whose main component is 5in2 are Since the specific gravity increases and the layer height decreases, it is necessary to use a larger amount of heat insulating material in order to maintain a constant heat retaining effect. To solve this problem, a heat insulating material containing magnesium oxide or calcium oxide, which has a higher melting point and has been conventionally used as a fireproof material, may be considered. However, these basic oxides usually have a C apparent specific gravity more than twice that of pearlite, etc., and when used alone, they do not have the advantage of replacing pearlite, etc. in terms of heat retention effect. There wasn't. By blending pumice with these basic oxides, 1) Ill.

There is an invention (Japanese Unexamined Patent Publication No. 56-128661) that attempts to improve both high temperature resistance and heat retention by reducing the weight of the basic oxide, but this invention does not reduce the apparent specific gravity of the basic oxide itself. It only reduces the apparent ratio Φ as a mixture, so if you want to take advantage of the high temperature resistance characteristics of basic oxides, you should use a considerable amount of basic oxides. Unfortunately, this type of heat insulating material, which requires low cost, has problems.

As a result of intensive research aimed at developing a heat insulating material with low cost and effective heat retention properties, the present inventors found that byproducts produced by the carbonation filling method used in the sugar industry to remove impurities from sugar solution. It was discovered that raw calcium carbonate has properties preferable as a raw material for a heat insulating material for molten metal, and the present invention was achieved.

That is, the heat insulating material of the present invention is made from calcium carbonate, a by-product produced by a carbonation method in which a mixture of infusion solution and milk of lime is filled with carbon dioxide gas to remove impurities from the sugar solution. It is a feature.

The carbonation method is a method commonly used in the sugar manufacturing process to remove impurities from the sugar solution, in which milk of lime is mixed with the sugar solution and carbon dioxide is added to it in a carbonation tank. It fills up the gas.

A filter aid is added to the saturated mixture to filter out the produced calcium carbonate, and the mixture is separated into a refined sugar solution and a calcium carbonate cake by a filter.

The filter aid is used to facilitate the separation of purified infusion fluid and calcium carbonate, and typically includes diatomaceous earth and perlite, which are used alone or in combination. Table 1 shows the properties of the by-product light calcium carbonate obtained by this method. Table 1 shows an example of using perlite as a filter aid, and also shows the properties of so-called heavy calcium carbonate obtained by crushing limestone as a comparative example.

(Note 2) O/cc starch glue 2% vertically 5mm length 20111 when filled with pellets with moisture content 1.2% vertically.

The reason why the present inventors used calcium carbonate as a raw material as a heat insulating material for molten metal is not only because of the high temperature resistance of calcium oxide, which is a decomposition product of calcium carbonate, but also because of the characteristics of carbon dioxide, another decomposition product. This is because we focused on In other words, carbon dioxide has a lower thermal conductivity than air, and has a higher heat retention capacity. In order to make full use of this property, it is desirable that carbon dioxide be retained in the voids of the heat insulating material, and for this reason, it is also desirable that the apparent specific gravity be small. In this respect, the by-product calcium carbonate produced by the carbonation saturation method has a relatively small apparent specific gravity and is inexpensive, so it is preferable as a heat insulating material. Furthermore, in order to take advantage of this characteristic, heat insulating materials that have been conventionally used such as perlite, perlite, diatomaceous earth, verminyquirite, obsidian, rice husks, straw ash, burning materials, paper sludge incineration ash, and waste activated carbon are added. 10 to 1 to calcium carbonate as an agent.
It is desirable to further reduce the overall apparent specific gravity by adding 0%.

Next, an example of the method for producing the heat insulating material for molten metal of the present invention will be described in detail.

The by-product calcium carbonate produced by the above-mentioned carbonate filling method is dried in a multi-machine to reduce the water content to about 15% by weight to make it suitable for mixing and molding. Next, additives are added to reduce the apparent specific gravity, and the water content is adjusted to 20 to 30% by weight, which is suitable for molding, while thoroughly mixed with a mixer. After thoroughly mixing the mixture with glue (glue, molasses, bentonite, etc.), it is molded into pellets using an extrusion molding machine.
Dry in a dryer to a moisture content of 3% by weight or less.

Since the present invention is characterized by using by-product calcium carbonate produced by the carbonation saturation method as a raw material, it is within the scope of the present invention to add other additives as long as this property is retained. Moreover, the manufactured hFA is not particularly limited.

The heat insulating material according to the present invention has the following effects.

(a) Calcium carbonate, a raw material component, does not decompose when used as a heat insulator. Ca CO3- + Ca O + CO2: Decomposition temperature 8
25℃>, calcium oxide 417% 8m (M point 257
2°C), the apparent specific gravity does not increase in the usage state, and the carbon oxide gas has a higher apparent specific gravity than air (b) The by-product calcium carbonate used in the present invention has a higher apparent specific gravity than ground calcium carbonate. is small, that is, the porosity is large,
Not only is it advantageous in terms of heat retention, but the carbon dioxide gas generated during use replaces the air in the voids, and since carbon dioxide is stronger than air, it is retained in the voids without escaping, resulting in an even greater heat retention effect. play.

(c) The decomposition reaction progresses gradually even at temperatures above 1000°C, so during use, carbon dioxide gas is generated from the lower part of the heat insulating material layer that comes into contact with the molten metal, and gradually moves to the F section, so it is difficult to keep the heat insulated. The effect lasts for a long time.

(d) It is easy to mold, and when made into granules, it is easy to handle and there are no operational problems such as dust scattering.

(e) If the apparent specific gravity is further reduced by adding the conventional heat insulating material, the heat retaining effect based on the small apparent specific gravity of machining and the heat retaining effect based on the generated carbon dioxide gas will be synergistic. This greatly increases the heat retention effect.

Examples of the present invention are shown below.

Since the carbonation saturation method is a common method in the sugar manufacturing industry, the process up to the production of by-product calcium carbonate will be briefly described. First, a certain proportion of washed molasses is added to raw sugar and mixed in a mingler and mixer, and then passed through a washing sugar separator to remove impurities attached to the crystal surface of the raw sugar and wash the sugar.

This washed sugar is dissolved in Merck to form a sugar solution with a predetermined concentration and temperature, milk of lime is added, and the solution is filled with carbon dioxide gas in a carbonation tank. Approximately 10% of the calcium carbonate produced
Perlite corresponding to - is added as a filter aid.

This is filtered to separate it from the refined sugar solution, dehydrated, and then
Obtain I-based calcium carbonate. The composition of this by-product calcium carbonate is as follows.

Ca CO345i 1% by weight Perlite 5 Sugar and impurities 4 Moisture Additives and/or thickeners to reduce the apparent specific gravity in the ratio shown in Table 2 to the by-product calcium carbonate in 4 as described above. According to the manufacturing method described above, a pellet-shaped heat insulating material (diameter 5alI11 length 3-25mm) having a moisture content of 3% by weight or less was manufactured. As additives for reducing the apparent specific gravity, used perlite and paper sludge incineration ash were used as filter aids.

The former originates from the liquor industry and its composition is as follows.

Perlite 433 Organic substances and impurities 5 Moisture 52 The latter is generated from the paper industry and its composition is as follows.

S i O2611 Juumaru F e20. 2 AI, 0. 22 Ca0 8 Others 5 Moisture 2 Table 2 Raw materials and chemical composition of heat insulating material [Φ% 1 When 250 kQ of the sample with the composition shown in Table 2 is added to molten steel 150 [in a ladle at a steel factory] The heat retention effect is shown in Table 3. The thickness of the heat insulating material cast covering the molten steel was approximately 10 cm, and no powder was generated during charging. Table 3 shows the temperature change of the molten steel after adding the heat insulating material.

The experimental results shown in Section 1 show that the rate of temperature drop after time has passed is smaller than the initial temperature drop, which indicates that disease pathogen dioxide is generated from the insulation material of the present invention, which increases the heat retention effect. It shows that

As mentioned above, the heat insulating material of the present invention exhibits an extremely effective heat insulating effect during metal scouring and casting, and is also economical and stable since it effectively utilizes industrial waste. It is of great benefit to the industrial world because it not only enables supply, but also contributes to resource conservation and environmental conservation.

Claims (1)

[Scope of Claims] (1) It is characterized by using as a raw material calcium carbonate, a by-product produced by a carbonation method in which a mixture of an infusion solution and milk of lime is filled with carbon dioxide gas to remove impurities in the infusion solution. A heat insulating material for molten metal. (2) The heat insulating material for molten metal according to claim (1), wherein an additive is added to the by-product calcium carbonate to reduce the apparent specific gravity. (3) The heat insulating material for molten metal according to claim (1), which is obtained by adding a filter aid to the by-product calcium carbonate, separating it from the purified infusion, drying, and molding. (4) The heat insulation for molten metal according to claim (3), wherein an additive for reducing the apparent specific gravity is added to the by-product calcium carbonate and filter aid after separation from the purified infusion solution. Material. (5) The heat insulating material for molten metal according to claim (3) or (4), wherein the filter aid is perlite and/or diatomaceous earth. (6) Claims in which the additive is any one of perlite, pearlite, diatomaceous earth, verminyquirite, obsidian, wood chips, rice husks, straw ash, burning material, papermaking sludge incineration ash, waste activated carbon, or a mixture thereof. The heat insulating material for molten metal according to item (2) or item (4).