JPS5823339B2 - Sekidayori Kozoyoujinkokotsuzaio Seizousurhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing artificial aggregate that can be used for structural purposes.

Recently, with the expansion of concrete construction work, the amount of aggregate used has increased, and the supply of river gravel, which has a suitable shape, strength, and other properties as aggregate, can meet the demand and destroy rocks. In this situation, crushed stone, which has properties inferior to river gravel, is also used.

The present inventors completed the present invention as a result of various studies aimed at obtaining an artificial aggregate that has properties comparable to those of river gravel as a structural aggregate.

In other words, the present invention utilizes red mud, which is discharged in large quantities during the manufacturing process of alumina used in aluminum smelting, and which has been discarded without any proper use, or rather with difficulty in disposing of it. By granulating particles of arbitrary size into a spherical shape and firing them, it becomes comparable to river gravel.
Rather, they succeeded in producing structural aggregate with excellent properties.

That is, in the present invention, after drying red mud granules in the shape of spheres of arbitrary particle size with a moisture content of 3% or more, the inlet temperature is set to 60°C.
Pour into a firing furnace maintained at 0°C to 800°C and heat to 1100 to 1
This is a method for producing structural aggregate that is fired at 300°C and slowly cooled to form sintered grains with properties comparable to river gravel.

The red mud used in the present invention is waste discharged in the alumina production process known as the Bayer process, and is produced when bauxite, an alumina raw material, is heat-treated with an alkaline solution to elute the alumina content. It is a reddish-brown, viscous, fine-grained mud with a high water content, containing iron oxide, alumina, silicic acid, alkali, etc., which are separated and discharged as an alkali-insoluble residue.

However, although various studies have been conducted and numerous proposals have been made in order to find suitable uses for these materials, there is no satisfactory use for them, and the current situation is that they are disposed of in the ocean or in dumping ponds.

The present invention will be explained.

First, we use any type of dryer to prevent the granulated particles from collapsing not only when the spherical red mud particles are put into the kiln but also when they are rapidly heated in the kiln. and dry to a moisture content of 3% or less.

Next, the dried red mud grains are put into a firing furnace whose inlet temperature is maintained at 600 to 800°C and fired.

In this case, maintaining the inlet temperature of the kiln at around 600 to 800°C means that the red mud grains can pass through the heated atmosphere zone in this temperature range in a state containing about 3% or less of water. This is necessary in order to obtain a sufficiently sintered and high-strength product in which the grains do not collapse and maintain their spherical shape.

The firing temperature in the firing furnace needs to be maintained at 1100 to 1300°C.

This is because if the temperature is lower than 1100℃, sintering will be insufficient and a sufficient temperature cannot be obtained, and if the temperature exceeds 1300℃, the red mud grains will begin to soften and melt, and the grains will fuse together, forming a spherical shape. This is because it becomes impossible to maintain the quality of the product, and a good product cannot be obtained.
It is preferable to bake at around 1200°C.

Next, the fired red mud sintered grains are slowly cooled.

The product sintered grains thus obtained are sintered and have a slightly smaller diameter than the dry grains, but maintain a spherical shape.

As a result of testing the red mud sintered grains according to the JISA Allo-1951 method, the specific gravity was 2.5 to 2.9, the water absorption rate was 1.3% to 1.8%, and the degree of single grain pressure enhancement was also measured. The results were 251 to 259 Ky/CIrL2, and it was found that the properties were comparable to those of river gravel.

In addition, a concrete test was conducted using the product of the present invention as an aggregate, and the compressive strength, bending strength, tensile strength, etc. were determined according to the JIS test method. Kf/cm2
．． 31 to 2/crrL2 theater, using river gravel tar
, the results obtained by the same method at the same time are 27, respectively.
4 Kp/crrL2.44 to 1i'/cIrL",
It was shown that the sintered particles of the present invention can be used satisfactorily as an aggregate for concrete structures.

Aggregates with such excellent properties can be obtained from red mud because when red mud is heated, bound water begins to dissociate around 200°C, and the process rapidly progresses between 300 and 400°C.
At 00℃, most of the bound water is released, and at the same time sodalite (3Na2O・3At2), which is a mineral contained in red mud, is released.
03-5 S 1O2-nl-I20) is converted to anhydrous nepheline (Na 2O-A40s .2 S 102).

By 1200℃, the bound water in red mud has completely disappeared and quartz (
S102) and anatase (T i 02 ) disappear, colored titanite (F e2 o3・T t 02 ) is generated, and a part of hematite (F e203 ) is reduced, and 1
At 200-1300°C, nepheline is converted into carnegiete (Na2O'At203'2SI0), respectively.
2) D. The colored titanite begins to disappear, and T A02 becomes a solid solution in hematite.

During this time, sintering progresses at around 1200°C, and after cooling, it becomes a strong artificial mineral in which fine crystals such as nepheline and hematite are combined. By using the method of the present invention, these reactions, This is thought to be due to the fact that changes in mineral composition, bonding of microcrystals, etc. occur extremely smoothly, quickly, and sufficiently.

In this way, the present invention is capable of drying red mud granules granulated into spheres to a moisture content of 3% or less, and then adjusting the inlet temperature to 600°C to 8°C.
Concrete is passed through the heated atmosphere of a kiln maintained at 00°C, then fired and slowly cooled, resulting in concrete of any grain size that maintains its spherical shape and has properties comparable to river gravel. This is an important invention that allows structural aggregates to be produced using red mud, which has traditionally been discarded and difficult to dispose of, as a raw material.

Next, an example will be described.

Example: A red mud cake discharged from a Bayer process alumina factory and having the composition shown in the table below, and a dried red mud powder (
H2O2, 4%) was mixed at a ratio of 6 parts to 10 parts, water was added to adjust the moisture content to 14.5%, and the tilt angle was 53° and the number of rotations was 2.
21 in a 1 mφ dish-type granulator set at 2 r, p, m.
0K? /Hr, and granulated while sprinkling water to make the water content of red mud 21.3%.
~15 75%, 5~107A7A23%, 5~2.5
Almost spherical red mud particles with a particle size and particle size distribution of 2% In1K were obtained.

Next, the red mud grains were supplied to a three-stage band dryer with a band width of 5QQim at a rate of 150 kg/Hr, and dried for 22 hours.
It was dried at 0° C. for a residence time of 40 minutes to obtain dried red mud particles with a water content of 1%.

These dried red mud grains have a diameter of 1m, a length of 6m, and a rotation speed of 0.5.
r, plm, and fed at a rate of 135 Ky/Hr to a rotary kiln whose inlet temperature was maintained at 780°C.
It was fired at 00°C for a residence time of 25 hours.

The sintered red mud grains were slowly cooled to 500° C. in 1 hour using a vertical cooler with an effective internal volume of about 0.04 m 3 , and then taken out and left to cool to form a product.

; The sintered grains obtained by the present invention have a diameter of 10 to 15 mm48
%, 5-10m1rL47%, 5-25mm4%, 25
The particles had a spherical shape with a particle size distribution of 1% smaller than the average particle diameter, and although the particle size had become slightly smaller due to sintering during firing, the particles were not broken or fused.

In addition, this sintered grain was tested in JIS A 1110-195
The specific gravity and water absorption amount were measured according to 1, the stability test was performed according to JIS A 1122-1954, and the weight loss at abrasion was measured according to JIS A 1121-1951.

Furthermore, single grain crushing strength was also determined.

The results are shown in the table below along with the results of a similar test on river gravel.

The results show that the sintered grains according to the present invention have properties comparable to river gravel, such as almost no internal crack defects and high strength.

Subsequently, various concrete tests were conducted using the sintered particles according to the present invention as coarse aggregate.

Among them, W/C 65% using river sand as fine aggregate;
The results of various strength tests prepared under the conditions of Slump 18crIL are shown below.

In other words, JISA. 11132-1963, the strength test sample book was prepared and cured, and the compressive strength test was conducted in accordance with JISA1108-1963, and the bending strength test was conducted in accordance with JISA1108-1963.
IS A1106-1964. JIS tensile strength test
Measured based on A1113-1964.

These results are shown in the table below, along with the results of measurements made at the same time using river gravel.

These results also indicate that the sintered grains according to the present invention exhibit slightly higher values than river gravel, have properties that are comparable to river gravel, and can be fully used as aggregate for concrete structures. It is clear.

Claims (1)

[Claims] 1. Red mud granules of arbitrary particle size are granulated into spherical shapes with 3% water content.
After drying as follows, the particles are put into a sintering furnace whose inlet temperature is maintained at 600°C to 800°C and fired at 1100°C to 1300°C to form sintered grains having characteristics equivalent to river gravel. A method of producing artificial aggregate for concrete IJ-to structure from red mud.