JPH0310026A - Clayey Ni ore briquetting method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a briquetting method for clayey NiK stone, particularly in the briquetting process when producing ferronickel by smelting Ni oxide ore, etc. This paper proposes a new technology for adjusting the briquette raw material supplied to a briquette machine (hereinafter referred to as a "briquette machine") by focusing on clay bones and moisture.

[Conventional technology]

Generally, Ni (ferronickel) used in the production of austenitic stainless steel is produced by smelting Ni silicate ore such as garnilite. Since this Ni oxide ore is a viscous wet ore and contains a large amount of water, it is usually smelted as follows.

In other words, in the method called the all-wet method, first, a large amount of water is added to each of the main raw materials and auxiliary raw materials such as ore, carbonaceous material, and limestone, and each is wet-pulverized into a slurry form, and then these raw materials are The mixed material is dehydrated and formed into pellets or the like. Thereafter, this pellet is charged into, for example, a grate type rotary kiln, and is dried, preheated, and fired to reduce metals such as Ni and grow as a rufupe, and then discharged as a talin powder. Through subsequent processing, this talincar is made into a ferroalloy such as ferronickel.

However, with this method, a large amount of water is added to the main raw material and auxiliary raw materials, and the water is removed in the form of a slurry using a drum filter, etc., so dehydration is not sufficient, and furthermore, each raw material is mixed in a slurry state. Because of this, it is difficult to uniformly mix raw materials, and in particular, it is extremely difficult to uniformly disperse and mix large amounts of carbonaceous materials with large differences in specific gravity.

In order to overcome this drawback, the present applicant has
Previously, in Japanese Patent Application Laid-Open No. 62-23944, Ni oxide ore, which is the main raw material, is divided into two parts depending on the quality of dehydration. One of the ores, that is, the ore with poor dehydration properties, is pulverized through a dry pulverization process, and the other is We proposed a method in which a mixed raw material is prepared by pulverizing ore, that is, ore with good dewatering properties, through a wet pulverization process.

The technology related to this prior proposal will be explained below.

The dry crushing process is a process of crushing ore in a dry state, and it can be configured in any way as long as the ore can be crushed into a diameter of about 211mm, but usually, as shown in FIG. , a cyclone 2 and a bag filter 3 are connected to each other, and dry air is sent from a hot blast furnace 4 to the attritor 1. Therefore, a part of the ore usually contains about 25 to 40% water and has a diameter of about -300 W, but it is ground in a dry state in a grinder such as a ball mill, and the particle size is adjusted to about -2 Tsuru. It is dried to a moisture content of less than 10%.

On the other hand, the wet crushing process is a process of processing ore into a slurry with good dewatering properties, and usually consists of a wet tube mill 5, a plurality of slurry tanks 6, and a drum as shown in FIG. Connect the filter 7. In other words, ore with good dehydration properties (usually contains 20 to 30% water and has a particle size of about 1,300 fins) is milled with water in a wet tube mill 5, with a water content of about 50%. This slurry is temporarily stocked in a slurry tank 6, and then sequentially dehydrated in a drum filter 7 to a moisture content of about 28 to 35% and made into a cake.

Next, each raw material adjusted to a particle size of about -2 m is mixed and kneaded in appropriate amounts in a mixing and kneading step.

The moisture content of each raw material at this time is 10 to 20% due to the crushing strength of the briquettes, drying in the post-process, and saving of thermal energy for preheating.
%, preferably 15 to 20%.

In other words, a certain amount of moisture is required to increase the strength of the briquettes and other briquettes in the subsequent dough-making process.On the other hand, if this moisture content is too large, the dough-making properties will be impaired and the preheating process will be too high. Drying requires a large amount of thermal energy,
Sufficient drying may not be possible due to the exhaust gas during reduction firing, and from this point of view the upper limit is about 20%.

[Problem to be solved by the invention]

Conventionally, the moisture content of mixed raw materials has been qualitatively adjusted mainly based on the moldability of the briquettes, but when focusing on the mixing characteristics of the raw materials and the strength of the briquettes, it has become clear that the simple moisture adjustment described above is not enough. It turned out that.

FIG. 2 shows the relationship between moisture content and crushing strength of various brands of ore. As can be seen from this figure, it is clear that all raw materials have the same tendency, in that the lower the moisture content, the stronger the compressive strength.

However, it has been found that depending on the type (brand) of the raw material, there are significant differences in the desirable range of suitable moisture content for achieving the desired briquette strength, and moisture control has been difficult in practice.

The purpose of the present invention is to propose a technique that can overcome the drawbacks of the prior art in that a desired briquette cannot be produced because a mixed raw material suitable for obtaining the desired briquette strength cannot be adjusted. be.

[Means to solve the problem]

In view of the above-mentioned state of the art, in the present invention, as a method with stable crushing strength and excellent formability (briquette formation), clayey Ni ore is processed dry or wet depending on the dewaterability. In the method, the powder is mixed and adjusted in an appropriate amount to have the moisture content necessary to obtain the desired briquette strength, and the mixed raw material with the moisture content adjusted in this way is made into briquettes using a briquette machine. The water content of the mixed raw material supplied to the machine is adjusted according to the average clay content of the ore to be mixed, and the mixed raw material is sufficiently kneaded and cured to homogenize it before making the dough. We propose a method for briquetting clayey Ni ore.

In the above briquette method, the water content of the mixed main raw materials to be controlled increases as the clay content increases, but the preferred clay content is 50% or more when various ores are mixed.

[For production]

In general, the bonding strength of briquettes is the chemical bonding force when a binder is used, and the bonding force due to melting when firing or hot briquettes are used.

On the other hand, when molding is performed simply by applying pressure at room temperature as in the present invention, the bonding force is increased by increasing the physicochemical bonding force, that is, the attractive force between particles by shortening the distance between particles by applying pressure. obtain. For such physicochemical bonding strength, moisture is an important factor as well as raw material particle size and compression force, but according to the findings of the present inventors,
In the case of ores, primarily clayey Ni ores such as garnilite (siliceous nickelite), it has been found that the clay content of the ore is particularly important. Note that the clay content of the ore is a value determined based on the clay content testing method for foundry sand of JIS A 1204 or JTS Z 2601.

This is because, as can be seen from Figure 3, the influence of moisture on briquette strength varies greatly depending on the brand of ore, and the same level of moisture, for example 17%, cannot always be said to be appropriate. In other words, the thio shown in the same figure cannot be molded,
On the other hand, when comparing Nakechi, Bomara, and Riotsuba, which can be molded, the latter has a higher crushing strength, and the appropriate value changes for each. Therefore, in order to obtain the final target briquette strength, it is found that the briquette raw material must be adjusted with other parameters other than or in addition to the moisture content.

Therefore, we investigated the relationship between the clay content and suitable moisture content of the ore, using the briquette strength as the crushing strength, and considered quantifying the suitable moisture content.

For the experiment, we selected four types of ores - thio, nakechi, bomala, and riotuba, with chemical compositions as shown in Table 1 below, which we had obtained, and mixed them with -2 fl of carbonaceous material 1 limestone and dust. A predetermined amount of water is added to prepare various briquette moisture samples ranging from 15% to 23%, and the wet samples are -
After straining through a 2.40 degree sieve, while adding a blending operation,
After curing for 3 days, it was heated to 40mm while applying a load of 3L.
It was formed into a briquette of 20mm x 20mm. This was subjected to a crushing strength test.

The results of the crushing strength test are already shown in Figure 2. The crushing strength could only be measured up to 30 kg due to the scale, but although scale over was observed for the Pomalaite and Riotubaite on the low moisture side, the strength of all brands tended to decrease as the moisture content increased. In particular, low-clay briquettes have low overall strength, and water oozes out during briquette formation from the considerably low moisture side (indicated by the X mark in the figure). It turned out to be a weak briquette.

From the above results, it was found that the presence of water in the raw material has a large effect on the crushing strength of briquettes. That is, when free water appears between raw material particles, the briquette strength decreases significantly. This is thought to be because the presence of free water makes it easier for the briquette constituent particles to move using water as a lubricant.

The present inventors have found that such free water is more likely to appear depending on the type of ore, while others are less likely to appear, and that this is related to the clay content of the ore. In other words, the results of pulverizing the sample ore to 1100 mesh and examining the presence of clay content and free water are shown in Figure 3. In order to increase the briquette strength, at least more than the solid line in the figure is required. It is clear from the following that the moisture content of raw materials should be suppressed. This means that, for example, if 18% is selected as the briquette moisture content, it is necessary to ensure that the clay content of the 1,100-mesh standard sample of raw material ore is approximately 55% or more.

In addition, for the low moisture samples (<14%) of various ores, it was observed that the raw materials were caught in the mold during briquette molding.

Furthermore, even if the clay content of the ore becomes too large, the raw material tends to stick to the mold, so the upper limit is thought to be about 80%.

As explained above, the relationship between clay content and moisture to obtain the target briquette strength is as shown in Figure 3, and if the appropriate moisture content of the raw material is determined within the range surrounded by the solid line in this figure, Desirable briquettes are possible.

Next, in the present invention, it is necessary to knead and cure the mixed raw materials supplied to the briquette machine to make them homogeneous. This is because, in the case of the present invention, raw materials are processed using a semi-dry method, including wet processing and dry processing, depending on the dehydration properties of the ore, so the moisture content of the mixed raw materials to be mixed is significantly different. This is because uniform mixing is difficult in a short time.

In order to solve this problem, the present invention attempts to homogenize the mixed raw materials by sufficiently kneading and curing them by increasing the mixing time or by increasing the load of the rod mill.

That is, in the mixing and kneading process, as mentioned above, a large amount of carbonaceous material is blended in addition to the main raw materials, and the moisture content is adjusted as described above, but on top of that, these mixed raw materials need to be uniformly dispersed. There is. That is, after kneading the raw materials, the diameter is 20~
The briquettes are made into raw or almond-shaped briquettes of about 30 fl, but if moisture and interior materials are unevenly present at this time, the strength of the briquettes decreases. Therefore, it is necessary to perform further kneading than in the conventional example. From this point of view, in the method of the present invention, as shown in FIG. 1, a mixer 10 such as a pug mill and a kneader 11 such as a rod mill are connected in series. If the raw materials are mixed in advance in the mixer 10 such as a pug mill and then slightly crushed and kneaded in the kneader 11 such as a rod mill, the particles in each raw material that have already been crushed will be crushed by the kneader 11 such as a rod mill. The particles are further refined by crushing, and the mixture is stirred and kneaded uniformly, so that water and carbonaceous materials are uniformly dispersed, and the granulation properties are improved.

Note that the uniformly kneaded mixed wire material is temporarily stocked in the raw material yard 12 and sent to the next making process as required.

〔Example〕

5 to 15 wt% of carbonaceous material is added as an auxiliary raw material to the main raw material obtained by mixing each of the ores shown in Table 1 in the proportions shown in Table 2.
Limestone powder 6-10Alt%, other return dust l
A briquette feedstock containing O~20-L% was prepared.

This briquette raw material is processed using a briquette machine (capacity 27t/l1).
r), gate opening 50-1501m, roll clearance 1-41m, roll pressure 80-150 Kg/
cm" and roll rotation speed of 10 to 15 rpm.

The results are shown in Table 3.

Table 3 As can be seen from the results, briquettes with satisfactory strength were obtained at a high yield.

〔Effect of the invention〕

As explained above, according to the present invention, the briquette strength can always be controlled above a certain level, the molding yield can be improved, and in particular, the unmoldability and powdering can be significantly reduced, so that the kiln operation can be improved. becomes stable.

[Brief explanation of drawings]

Figure 1 is a flow sheet for carrying out the method of the present invention, Figure 2 is a graph showing the relationship between the moisture content of briquette raw materials and crushing strength, and Figure 3 is a graph showing the relationship between moisture content and crushing strength of briquette raw materials. It is a graph showing the relationship between clay powder and briquette strength. l... Attritor, 2... Cyclone, 3... Bag filter, 4... Hot stove, 5... Wet tube mill, 6... Slurry tank, 7... Drum filter,
8...Rod mill, 3', 9...Storage tank, lO・
...Mixer, 11...Kneading machine, 12...Raw material yard, 13...Grade, 13'...Dumpling machine, 14
...Ore discharge chute, 15...Rotary kiln, 1
6...Burna.

Claims (1)

[Claims] 1. Clay N treated dry or wet depending on dehydration properties
In a method of mixing ore powder in an appropriate amount at a time to have the moisture content necessary to obtain the desired briquette strength, and forming the mixed raw material with the moisture content adjusted in this way using a briquette machine, The moisture content of the mixed raw material supplied to the briquetting machine is adjusted according to the average clay content of the ore to be mixed, and the mixed raw material is kneaded and cured to homogenize it before briquetting. Characteristic briquette method for clayey Ni ore.