JPS58186430A - Granulating method of red mud - Google Patents

Abstract

PURPOSE:To obtain a red mud granule which has no adhesive strength and is rigid by granulating hydrous red mud cake while adding >=1 kind coal factory dust, coal ash, coke ash, soot or dry red mud thereto on the verge of ending of the granulation. CONSTITUTION:The red mud slurry discharged from an alumina production stage is filtered to 9.3wt% stuck moisture with a press filter, whereby red mud cake is obtained. The red mud cake is put in a tray type granulator having 2.8m inside diameter and 0.55m depth, and the granulator is operated at 9rpm and 43 deg. angle of inclination. The red mud cake is thus granulated while 3wt% lime factory dust basing on the weight of the supplied red mud is added thereto. The lime factory dust to be added in this stage is mixed with the red mud at around the time when the red mud is removed from the granulator after granulation. The red mud which is difficult to handle is granulated to the rigid grnules having no adhesive strength by the above-mentioned method and the granules are handled easily when the granules are to be utilized in various applications thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for granulating red mud, preferably for ease of subsequent handling.

Red mud, that is, the residual liquid obtained by alkali extraction of alumina from bauxite in the alumina production process by the so-called Bayer method, usually has a FetO content of 130 to 501%, A/! ,
0゜15-25 double lid 9, Stow 8-IF1kjlN
%'I'i0t 5-10 weight S1Nm, 03-101
The composition is kX, Ig, Losg8-12gS, and its constituent particles are very fine.

Traditionally, this red mud was dumped into the ocean as industrial waste.

It used to be disposed of in landfills, etc., but it is used as a source of iron during cement production.
Many uses have been found for it, such as artificial aggregates, raw materials for refractories such as bricks, catalyst carriers, and soil conditioners.

However, since the alumina is discharged as a slurry containing a large amount of moisture during the alumina porcelain production process, the moisture must be removed and the alumina must be made into a form that is easy to handle when used for any purpose.

For this purpose, dehydration and drying are usually performed, but the particles that make up red mud are very fine, so it is difficult to dehydrate, and it gets stuck in storage hoppers and belt conveyor transition areas, making it difficult to handle. When the moisture on the surface evaporates, dust is generated and the work environment is worsened.

That is, dehydrated red mud cake has the trade-off drawbacks of adhesion and dust generation.

Examples of methods for treating red mud with such strong properties include a method of granulating it while applying heat from the outside, as shown in JP-A No. 1852-3596, and a method of granulating it while applying heat from the outside, as shown in JP-A No. 48-45494. A method has been proposed in which red mud, which has been thoroughly dehydrated and turned into pellets, is dehydrated by adding expensive chemicals, but both of these methods are time-consuming and are not economical. .

The present invention relates to a method for making the above-mentioned red mud into a form that is easy to handle, and its gist is that when granulating water-containing red mud cake using a granulator, lime factory dust, coal ash, coke ash, etc. , granulation while adding one or more kinds of cheap and easily available powders such as smoke soot or dried red mud.

Examples of the method of the present invention will be described below.

<Example> The red mud slurry discharged from the alumina production process was filtered with a press filter to remove 29.51L of adhering moisture, and
A red mud cake consisting of particles having a camphor particle size distribution as shown in Table 1 was obtained.

#i1 red mud cake with inner diameter 2.811mm. A dish-type granulator with a depth of α55 was operated continuously at 9 rpm and an inclination angle of 45°, and 3% by weight of lime factory dust was added to the amount of red mud supplied for granulation. The lime factory dust added in this case was added so as to be mixed with the red mud just before it was granulated and removed from the granulator.

Next, 300f of the granules granulated in this manner were put into a measuring cylinder f with a blind stopper, and after being rolled 50a, -α8
The ratio of 4■ is taken as the abrasion dust rate, and after repeating 5 times the operation of putting 300f of granules in a basin and tilting the basin from a height of 211 to let the granules fall -084 ■
The proportion of dust was determined and this was taken as the falling dust rate.

Table 2 shows the abrasion dust rate and falling dust rate of the red mud cake obtained in the same manner as the abrasion dust rate and falling dust rate of the red mud cake before granulation. (The numbers in the figure indicate the size, and the units are simple).The sample was placed in a hopper as shown in the figure, and an extraction test was conducted using a belt feeder. I couldn't see it.

As is clear from the above examples, in the present invention, the red mud slurry containing a large amount of water is kept in a red mud cake having a water content (25 to 35 weight 9) that can be easily produced industrially, and the water content is reduced to less than that. In order to reduce the granulation, the above-mentioned granular material such as lime factory dust can be added just before the completion of granulation, without taking steps such as increasing the amount of heat or adding dehydrating agents. The granulation used in the present invention is not limited to transfer granulation, and may be vibration granulation.

The reason why the powder such as lime factory dust added in the present invention is added just before the end of granulation is that the moisture content of the present invention is considerably higher than the moisture content of 18 to 20 times S, which is usually suitable for granulation of only red mud. Since a large amount of red mud cake is used, even if these powders are added from the early stage of granulation, they will only be consumed regardless of granulation and hardening, and a large amount of powder and granules will be required. This is because if the powder is added at the stage when the growth is almost completed, a strong shell can be efficiently formed on the surface of the granules even with a small amount of addition.

As described above, according to the present invention, red mud, which is difficult to handle in IC, can be made into non-adhesive and strong granules, which makes it easier to handle when used for various purposes afterwards.

[Brief explanation of the drawing]

The drawing is a schematic explanatory diagram of a hopper used to observe the adhesion of granulated red mud according to the present invention.

Claims (1)

[Claims] l When granulating the water-containing red mud cake using a granulator, one or more types of powder such as lime factory dust, coal dust, coke ash, smoke soot, or dried red mud are added just before the granulation is completed. A method for granulating red mud, which is characterized by granulation.