JP2790026B2 - Method for producing calcined agglomerate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a calcined agglomerate suitable for blending a large amount of iron ore containing high crystal water as fine iron ore.

[0002]

2. Description of the Related Art As a raw material for a blast furnace or a raw material for direct reduction ironmaking, calcined agglomerate obtained by pelletizing and firing fine iron ore is used. A method for producing calcined agglomerate is disclosed in JP-A-63-14 / 1988.
No. 9336. Hereinafter, this manufacturing method will be described.

[0003] Fine iron ore having a particle size of 8 mm or less is mixed with a medium solvent such as quick lime, limestone, bentonite or the like so that the basicity (CaO / SiO ₂ ) in the calcined agglomerate becomes 1.0 to 2.5. Add and mix with a first drum mixer while adding water.
The resulting mixture is fed to a disc pelletizer, water is added and granulated to form raw pellets having a particle size of 3 to 13 mm. At this time, the moisture content of the raw pellets was 7.8 to 8.5%.
Adjust the amount of water added so that

Next, the raw pellets are supplied to a drum mixer, and coke breeze having a particle ratio of 38 to 43 wt% of a particle size of 1 mm or more (hereinafter referred to as a +1 mm particle size) of 2.5 to 4.0 wt%.
% To cover the surface of the raw pellets with coke breeze. The raw pellets coated with coke breeze are charged into an endless moving great firing furnace. In the raw pellet layer loaded on the grate, first, exhaust gas at 150 to 350 ° C. is sucked downward through the raw pellet layer in the drying zone, and the raw pellets are dried. Thereafter, a high temperature combustion flame is sprayed on the upper surface of the raw pellet layer in the ignition furnace to ignite the coated coke. Next, the burning zone of the coated powder coke advances from the upper surface to the lower surface of the raw pellet layer by downward suction of the outside air, and the raw pellets are fired by the high temperature combustion exhaust gas generated in the combustion zone.

At this time, the slag components of the solvent and the iron ore are melted and solidified to form a block in which the fired pellets are combined. This block is discharged from the ore discharge section of the endless moving great type kiln. The ejected block is
Crushed and sized by crusher and screen,
It becomes a calcined agglomerate of a size suitable for charging the blast furnace. The calcined agglomerate produced in this manner has excellent reducing properties, does not flow unevenly to the center when charged into a blast furnace, and has excellent air permeability.

[0006]

However, in the conventional production method, a high crystal water content iron ore such as limonite iron ore (F ₂ O ₃ .mH ₂ O) or the like is blended as an iron ore raw material in an amount of 40 wt% or more. When producing calcined ore, there were the following problems.

(1) Since the iron ore containing high crystal water has a high saturated moisture value, when a drum mixer and a disc pelletizer are subjected to the same water addition as a conventional hematite or magnetite-based ore, granulation properties are high. Is poor, and the air permeability deteriorates during firing. Therefore, the yield of the calcined agglomerate decreases, and the quality, particularly, the cold strength, decreases.

(2) When a calcined agglomerate is produced by mixing 40% by weight or more of iron ore containing high crystal water, as in the conventional case, +
When coke breeze having a 1 mm particle size of 38 to 42% is used, heat shortage occurs in the upper layer of the raw pellet layer and overmelting occurs due to excessive heat in the middle layer and the lower layer, resulting in poor air permeability. Therefore, the yield of calcined agglomerate decreases, and the cold strength and the reducibility deteriorate.

[0009]

The present invention solves the above problems by the following method. 40 iron ore containing high crystal water
% Or more, the amount of water added in the disc pelletizer is increased in accordance with the increasing ratio of the iron ore containing high crystal water content, and at the same time, the coated powder coke is changed to a coke powder having a particle size of 1 mm or more and a particle ratio of 30% or less. .

[0010] The amount of added water in the disc pelletizer varies depending on the brand of the high crystal water content iron ore used, but generally, the amount of the high crystal water content iron ore is 10 wt%.
For every increase, the proportion of iron ore containing high crystal water is 20%
10 times the amount of water added by the disc pelletizer in the following cases
~ 15%.

[0011]

Among the above problems, the present inventors conducted the following investigation using actual equipment on the effect of an increase in the mixing ratio of iron ore containing high crystal water on the granulation properties of raw pellets. went. FIG. 1 is a diagram showing the granulation and coke breeze coating steps of the actual machine in which this investigation was conducted.

In the figure, quicklime (B
L), blending powder (B) as fine iron ore, limestone (L), and returned ore (R) are cut out from the mixing tank 1 by a predetermined amount. The cut-out raw materials are mixed by the first drum mixer 2 while adding water. Thereafter, the mixture is supplied to the disc pelletizer 3, granulated while adding water, and formed into raw pellets. Next, the raw pellets are supplied to the second drum mixer 5 together with the coke breeze cut out from the coke breeze tank 4, and the surface thereof is coated with the coke breeze. The raw pellets coated with coke breeze are conveyed to an endless moving great firing furnace. In addition, the iron ore containing high crystal water is blended with the blending powder at a predetermined ratio.

(Investigation 1): First, the granulation properties of the raw pellets when the mixing ratio of the iron ore containing high crystallization water was small were investigated under the following conditions. The compounding amount of the iron ore containing high crystal water in the fine iron ore raw material was set to 20% by weight. The production amount of the raw pellets in this case was 1170 ton / hr. The water content of the raw material was 5.4%, and water was added so that the water content of the raw pellets was 8%. At this time, about 2/3 of the added water amount, 20 tons, was added to the first drum mixer 2. ,
The remaining 1/3 of 10 ton was added by a disc pelletizer 3. The distribution of the added water is the same as the conventional method. In this case, the -3 mm particle size ratio of the raw pellets after granulation is 38%.
Met.

(Survey 2): Next, the granulation properties of the raw pellets when a large amount of iron ore containing high crystal water was blended were examined under the following conditions. Raw pellets were produced using a raw material in which the content of the high crystal water-containing iron ore in the raw material of fine iron ore was 40 wt%. The raw pellet production was the same as in Study 1, and the raw material carried in at this time was 5.6%,
Water was added with the drum mixer 2 and the disc pelletizer so that the moisture value of the raw pellets was 8.2%, and the distribution and the amount of the added water were the same as those in Study 1. in this case,
The -3 mm particle size ratio of the raw pellets after granulation was 45 wt%.

(Survey 3): From the results of Study 2, when a large amount of iron ore containing high crystallization water is blended, if the moisture value of the raw pellets and the distribution of added water are made the same as in the conventional method, granulation of the raw pellets It was confirmed that the property deteriorated. Therefore, focusing on the fact that the iron ore containing high crystal water has a high saturated moisture value, a granulation test was performed under the following conditions in which the moisture value of the raw pellets and the amount of water added by a disk pelletizer were increased. In addition, the reason for increasing the amount of added water only by the disc pelletizer is that if the amount of added water in the first drum mixer for the purpose of mixing the raw materials is increased, granulation of the raw materials proceeds, and uniform mixing is hindered. This is to prevent the hydration reaction of quicklime from proceeding excessively and to avoid increasing the amount of raw material adhering to the wall of the drum mixer.

Raw pellets were manufactured using a raw material in which the amount of the iron ore containing high crystal water contained in the raw material of fine iron ore was 45 wt%. The production amount of the raw pellets was 1170 ton / hr, and the water content of the raw material was 5.6%. In Study 3, the amount of added water in the disc pelletizer was 10 ton / hr, the same as in Studies 1 and 2, and the amount of added water in the disc pelletizer was increased by 35% to 13.5 ton. As a result, the moisture value of the raw pellets was 8.5%. In this case, the -3 mm particle size ratio of the raw pellets after granulation is 39%.
Met. This value is almost the same as that in the investigation 1. Even if a large amount of iron ore containing high crystal water is blended in a large amount, the granulation property is improved by increasing the amount of added water with a disk pelletizer according to the increase in the blending amount. It was confirmed that.

In other words, when the high crystal water content iron ore is blended by 40% or more, the raw pellets after granulation increase by -3 mm%, but in such a case, the mixing ratio of the high crystal water content iron ore increases. By increasing the amount of water added to the disc pelletizer accordingly, the increase in raw pellets after granulation—3 mm% is suppressed.

Next, when 40% or more of the iron ore containing high crystal water is blended, the conventional coated powder coke (+1 mm particle size is 38%) is used.
(~ 42% coke breeze), the following investigation was conducted to investigate the cause of heat shortage in the upper layer of the raw pellet layer of the firing furnace and excess heat in the middle and lower layers.

(Survey 4): Raw pellets were produced by using the same raw materials and water addition conditions as in Survey 3, and the raw pellets coated with coke breeze having a particle size of +1 mm and 42% were charged into a firing furnace. Then, the distribution of the total carbon amount (T-C%) in the height direction of the raw pellet layer was examined. FIG.
This shows the total carbon amount distribution (hereinafter, abbreviated as carbon amount distribution) in this case. The figures are top, middle,
A substantially uniform total carbon distribution is shown in the lower layer. Due to this uniform distribution of carbon content, especially when firing raw pellets containing a large amount of high crystal water-containing iron ore that requires a large amount of firing heat, insufficient heat occurs in the upper layer of the raw pellet layer, Was found to produce excess heat.

From the results of Investigation 4, it was found that to solve the above problem, coke breeze should be segregated so that the amount of carbon is large in the upper layer and smaller in the lower layer. The segregated coke breeze is coke breeze remaining without being coated with the raw pellets. Then, the coke amount distribution of the raw pellet layer coated with less coke powder +1 mm% than the conventional coke powder was investigated.

(Survey 5) The distribution of the amount of carbon in the height direction of the raw pellet layer was examined under the same conditions as in Study 4 except that the +1 mm particle size was 28%. FIG. 2 shows the carbon amount distribution in this case. The figure shows that the amount of carbon is large in the upper layer and decreases as it goes down to the lower layer. This is a preferable distribution which solves the above-mentioned problem when a large amount of iron ore containing high crystal water is blended.

That is, when a large amount of iron ore containing high crystal water is blended in a large amount, the +1 mm particle size of the coated powder coke is set to 28% or less, whereby heat is insufficient in the upper layer of the raw pellet layer,
The problem of excessive heat in the middle and lower layers can be solved.

[0023]

Embodiments of the present invention will be described below. The production amount of the raw pellets was 1170 ton / hr, and the compounding amount of the iron ore containing high crystal water in the raw material of fine iron ore was 45 wt%. The carried-in moisture of the raw material was 5.6%. The amount of water to be added in the first drum mixer 2 is set to 20 tons, which is the same as the conventional one, and the amount of water to be added in the disc pelletizer is increased by 35% compared to the conventional one.
3.5 tons. As a result, the moisture value of the raw pellets was 8.5%. To the raw pellets thus produced,
+1 mm coated with coke breeze having a particle size of 28%, and charged into an endless moving great-type calcination furnace to produce a calcination agglomerate. At this time, the air permeability (JPU) of the raw pellet layer on the firing furnace, the pot yield of the fired agglomerate and the tumbler strength (cold strength)
Is shown in FIG.

FIG. 4 shows, for comparison, the mixing ratio of the iron ore containing high crystallization water in the fine iron ore raw material, the water value of the raw pellets, and the distribution of the added water amount were the same as those of the above embodiment of the present invention. The specifications when a calcined agglomerate was produced using +1 mm particle size coke having a particle size of 42% as the coated coke are shown as comparative examples. FIG. 4 shows that the air permeability of the raw pellet layer according to the present invention, the pot yield of the calcined agglomerate and the tumbler strength are superior to those of the comparative example.

[0025]

According to the present invention, it is possible to mix a large amount of iron ore containing high crystallization water in a large amount of 40% or more as a raw material of fine iron ore, and it is possible to improve the quality and production yield of calcined agglomerate. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a granulation step of an actual machine subjected to a survey according to the present invention.

FIG. 2 is a graph showing a carbon content distribution of a raw pellet layer when coated with coke breeze having a particle size of +1 mm and 28%.

FIG. 3 is a graph showing a carbon content distribution of a raw pellet layer when a +1 mm particle size is covered with 42% coke breeze.

FIG. 4 is a graph showing production data at the time of producing a calcined agglomerate according to the present invention and a comparative example.

[Explanation of symbols]

 2 First drum mixer 3 Disk pelletizer 5 Second drum mixer

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hidetoshi Noda 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Riki Takai 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) C22B 1/16

Claims (1)

(57) [Claims] 1. A mixture of a fine iron ore and a medium solvent added thereto, and the mixture is granulated to form raw pellets. The obtained raw pellets are coated with coke breeze and charged into an endless moving grate type firing furnace. In a method for producing a calcined agglomerate by calcining to produce a calcined agglomerate, when a high crystal water-containing iron ore is blended in an amount of 40% or more, addition in a disk pelletizer according to an increasing ratio of the high crystal water-containing iron ore With increasing water volume,
A method for producing a calcined agglomerate, wherein coke breeze having a particle size of 1 mm or more and a particle ratio of 30% or less is used as a coated coke of raw pellets.