KR920010352B1 - Process for the preparation of aluminus cements - Google Patents

Abstract

The high grade alumina cement having 20,000-30,000 cm2/g of the specific cross section is manufactured by (a) firstly heating at 1,100-1,400 deg.C the homogeneous mixture having the molar ratio of aluminum oxide to calcium oxide, 2:1, (b) hydrating the primary fired body at 20-50 deg.C for 10 hrs. to make the hardened body, (c) obtaining the secondary clinker according to the secondary heating of the hardened body at the same temperature range, (d) pulverizing the clinker or alumina-added clinker containing 80- 90 % alumina to the total.

Description

Manufacturing method of high quality alumina cement

1 is a schematic manufacturing process diagram of a high quality alumina cement according to the present invention.

In the present invention, in preparing the alumina cement, the calcium oxide raw material and the aluminum oxide raw material are uniformly mixed to hydrate the first calcined and cooled between 1100-1400 ° C., and then the secondary calcined and cooled at the same temperature range to increase the alumina content. The present invention relates to a method for producing high quality alumina cement having a high hydration reaction at 80-90 ° C.

Conventionally, in order to manufacture cement having an alumina content of 70% or more, the raw material mixture is sintered by a single heat treatment (1500-1600 ° C.) and then pulverized as it is or mixed with alumina, where the total alumina content of the cement is 82%. Did not go beyond. In addition, the main mineral phases of the resulting cement were CaO.Al ₂ O ₃ and α-alumina, and other small amounts of CaO.2Al ₂ O ₃ or 12CaO.7Al ₂ O ₃ were present.

In order to make cement with an alumina content of 82% or more by the conventional manufacturing method as described above, 1) When the alumina content of the raw material mixture is fired at a higher rate than before, there is too much alumina remaining in the clinker or firing at a high temperature. In addition, CaO.2Al ₂ O _{3 is} mainly a clunker with weak hydration reactivity, and 2) when the alumina content mixed in the grinder grinding is higher than before, the hydration strength of the cement produced is weakened. Likewise, cement with high alumina content and high hydration strength could not be produced.

Accordingly, an object of the present invention is to activate the hydration reactivity of the clinker because the alumina content of the clinker containing CaO.2Al ₁ O ₃ as the main mineral reaches 78.4% in the method of (1), (2), This is to obtain high quality alumina cement having higher alumina content (80-90%) than conventional alumina cement by pulverizing the clinker itself or adding alumina at the time of the clinker grinding.

A schematic configuration of the process for producing high quality alumina cement in the present invention is shown in FIG.

First, when the mixture of potassium oxide and aluminum oxide is mixed so that the molar ratio of aluminum oxide to calcium oxide is 2: 1, the mixture is heated and sintered at a temperature above the level where free calcium oxide remains (1100-1400 ° C.). Firing clinker is obtained. In this case, the raw materials are chemical limes (CaO, CaCO ₃ , Ca (OH) ₂ ), high-grade limestone, chemical alumina or aluminum hydroxide, high-quality white bauxite, and the like.

A characteristic of the primary calcined clinker is that it is easy to grind into a multi-mineral phase composed of calcium aluminates and unreacted alumina mainly based on CaO.Al ₂ O ₃ . In addition, the pulverized product of the primary clinker has a certain degree of hydration, so that when it is reacted with water, the strength is not large. A cured product of size can be obtained. This cured body consists of a dense structure of gibbsite, calcium hydrate aluminate, small amount of calcium hydrate aluminate and alumina.

In the next process, the cured product obtained above is heated (1100-1400 ° C.) and thermally decomposed. When the temperature is about 400-500 ° C., most of the crystal water is blown away and a decomposition product having the following characteristics is produced. That is, in order to relieve the stress generated at the interface between the hydrate and the decomposition product due to the severe volume change due to the discharge of the crystallized water, the decomposition product is cracked finely and uniformly so that the specific surface area is greatly increased while there are many crystal defects and strains. The state has excess physical energy.

Therefore, if the cured product is continuously heated, 12CaO.7Al ₂ O ₃ , which is a decomposition product, highly reactive amorphous alumina, calcium hydroxide aluminate and alumina that existed in the cured product are easily reacted between components, and at a relatively low temperature, CaO.2Al the ₂ O ₃ is formed as a clean growing state gwangmulsang. At this time, the surface area of the material and the crystal imperfections decrease rapidly in proportion to the firing temperature due to the formation of secondary particles and the crystallization. Therefore, the heating is stopped at a point where CaO.2Al ₂ O ₃ , the main mineral of the clinker, is produced. Allow to cool to get the final clinker.

The characteristic of the clinker produced by the above method is the mineral composition in which CaO.2Al ₂ O ₃ is the main mineral phase and a small amount of CaO.2Al ₂ O ₃ and α-alumina are present. Compared to the conventional clinker, the surface area of the powder is much larger and the crystallinity is lower because the particles of the powder have a microstructure in which hydrates and pyrolysis products remain in the intermediate stage of manufacture. .

Therefore, the hydration characteristics of the alumina cement made by pulverization are short induction period and large hydration reactivity because the initial dissolution rate is high when mixing with water and the particles are hardly covered with the initial hydrate.

In the manufacturing method of the present invention, not only can be fired at a much lower temperature than the conventional one, but also raises the alumina component of the clinker itself by up to 80% to increase the fire resistance. And the strength is also greatly improved. In addition, since the produced clinker is a porous active clinker, the grinding properties are also excellent.

When alumina is added and ground to a clinker having such characteristics, high quality alumina cement having a total alumina content of 90% in cement is obtained.

Hereinafter, in preparing a high quality alumina cement according to the present invention, it will be described through examples.

EXAMPLE

Limestone pulverized to less than 15% of 88㎛ standard residue (CaO: 57.70%, SiO ₂ : 1.88%, Al ₂ O ₃ : 0.81%, Fe ₂ O ₃ : 0.23%, MgO: 0.46%, Ig.loss: 43.02% ) And chemical alumina are mixed so that the molar ratio of CaO: Al ₂ O ₃ is 1: 2, and heated at 1250 ° C. to produce a primary calcined cleaner.

The primary clinker was pulverized with less than 15% of 88㎛ sieve residue, and kneaded by adding water to make water: solid = 1: 2, and then granulated to 15-20mm in diameter, Time left hydrated. Heating this at 1100 ° C. produces an active clinker of secondary firing.

In the final cement production, the amount of alumina incorporation is Al ₂ O ₃ -80% cement and Al ₂ O ₃ -90% cement depending on the product.

TABLE 1

Table 1 is a major performance comparison table of the prior art and the invention of the alumina cement, showing the excellent hydration reaction and strength of the invention cement.

Claims (2)

The primary firing is performed by heating and baking a uniform mixture obtained by combining an aluminum oxide raw material and a calcium oxide raw material such that the molar ratio of Al ₂ O ₃ : CaO is 2: 1 at a temperature of 1100 ° C. to 1400 ° C. After cooling the water to obtain a cured product by performing a hydration reaction, after performing the secondary firing by firing the cured body in the same temperature range as the primary firing temperature to the secondary firing, the secondary clean produced by the secondary firing Or grinding the beaker as it is, or adding and pulverizing the alumina so that the total alumina content is 80 to 90%. The method according to claim 1, wherein the primary clinker produced by primary firing is left for 10 hours in a humidity of 20 ° to 50 ° C. for hydration reaction, and then the hardened body is calcined to obtain a highly active CaO.2Al ₂ O ₃ component. A method for producing high quality alumina cement, characterized in that the clinker can be easily synthesized and the specific surface area is increased to 20,000 to 30,000 cm 2 / g.

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