JPS61253330A - Manufacture of uncalcined briquetted ore - Google Patents

Abstract

PURPOSE:To manufacture the titled ore with a low cost by using a large quantity of coarse grain ore, by compacting materials such as iron ore, cement, cokes, lime stone, water, immediately bringing the green compact into contact with gaseous carbonic acid, then drying and curing it to a prescribed hardness. CONSTITUTION:A material 2 composed of mixture of iron ore fines, cement, cokes fines, lime store fines and water, etc. is supplied to a compacting roll 3 from a hopper 1 to compact it. In this case, water saturation ratio is adjusted desirably, to 0.15-0.9. A green compact 4 obtd. thereby is exposed to gas contg. >=5vol% CO2 at a gaseous CO2 curing part 5 immediately after compacting, to cover the surface with CaCO3 and harden it. Thereafter, the compact 4 is carried to a yard 7 by a conveyer 6, and uncalcined briquetted ore having strength required for charging into blast furnace is obtd. by drying and curing, etc. for 10 day. As the other aging method, gaseous carbonic acid treatment by waste gas contg. it and drying treatment, or blasting treatment, etc., of vapor or hot wind of the compact, by packed tower, etc., are effective.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing uncalcined agglomerate ore.

(Conventional technology, problems) Sintered ore, fired pellets, etc. are used as raw materials for blast furnaces, and they have a certain track record, but they are not necessarily advantageous in terms of the energy used.Recent trends include these. Cold pellets using a binder such as cement are attracting attention as an alternative to cold pellets.However, these cold pellets also have their own drawbacks, the biggest being the high cost of electricity for crushing the raw material ore. These disadvantages include the round shape of the finished product, the long time required for cement curing, and mutual adhesion during the curing process.Due to these drawbacks, this cold pellet has not been put into practical use except for a few. The present inventors believe that in order to compensate for these drawbacks of cold pellets, it is necessary to develop a molding method using coarse-grained ore instead of granulation.However, The ore lump A produced by the molding method using this coarse ore T-pace has a low molded product strength immediately after molding (hereinafter referred to as molded product green strength), similar to granulation, and is powdered during the subsequent transportation process. , it has the fatal drawback of collapsing.

In this way, when trying to compensate for the drawbacks of pellets and considering other molding methods, other drawbacks arise.

In order to compensate for these shortcomings, the present inventors conducted various studies and found the following solution. The details are described below.

(Means for Solving the Problem 2) The present invention involves compression molding a mixture of iron ore powder, cement, coke powder, pentate powder, water, etc. with a roll, and then immediately carbonating the molded product. 5 Vat for gas.

A method for producing non-calcined agglomerate ore, which comprises coating the surface of the molded product with calcium carbonate and curing it by exposing it to a gas containing at least and iron ore powder, cement, coke powder,
A mixture of limestone powder and water? Immediately after molding, the molded product, which has been compressed and molded using rolls and whose moisture saturation is adjusted to 0.15 to 0.9, is treated with a gas containing 5Vot, % or more of carbon dioxide gas, to coat the surface of the molded product with calcium carbonate. This is a method for producing non-calcined agglomerates, which is characterized by coating and hardening the agglomerate with a powder, followed by drying and curing to the strength required for charging into a blast furnace. After hardening, the rolled product is cured in a yard for about 10 days, then treated with carbon dioxide gas and dried using exhaust gas containing carbon dioxide in a packed tower, etc., and then cured again by blowing steam or hot air into it in a packed tower, etc. , drying, etc.

In addition, Appearance is specific gravity It is.

The present inventors have discovered that carbon dioxide treatment is effective as a means of improving the raw strength of molded products. It is a known fact that treating a cement compound with carbon dioxide gas improves its strength development rate.

The present inventors have discovered that under certain conditions, the rate of strength development becomes extremely high. This is shown in FIG. 1, and it can be seen that by treating the cement mixture with carbon dioxide gas, the strength normally obtained by curing for 1 to 3 days can be obtained in about 5 to 15 minutes. Furthermore, by this carbon dioxide treatment, the reaction of the binder such as cement on the surface is completed, and it is possible to prevent the molded products from adhering to each other during the subsequent curing period.

However, it is not always possible to obtain the above-mentioned strength by this carbon dioxide treatment, and in order to promote the development of the strength, it is necessary to consider the molding conditions.

In order for the cement mixture to develop strength through carbon dioxide treatment, the following reaction must occur between cement, carbon dioxide, and water.

30aO@8i02 +H10→0a(OH)1 +
a・OaO@5i02 @H! 0 -
'・・・・・・(1) 20aOa 8i02 + H2O
+0a(OH)2-1- n aOaO・5iO8・H
2O... (2) Ota (OH) 2+00 snow →0
aO03+H20°°−−゛−(3) Above (1), (2
) is the normal cement water use reaction, and (3)
is the carbonation reaction of 0a(OH)z. Therefore (1)
, The reaction rate of (2) is low, so a certain amount of curing period is required to obtain the required strength, but the effect of carbon dioxide treatment here is as follows from equation (3): 1
), 0a(OH)1 produced in the reaction of (2) is 0
Because it is discharged outside the system as aO03, (1), (
It can be mentioned that the reaction 2) is promoted accordingly. Therefore, in order for strength to develop due to the promotion of reactions (1) and (2), reaction (3) occurs, and for that purpose, carbon dioxide gas dissolves in water and 00. -2, and reactions (1), (2), and (3) also need to occur inside the molded product. That is, it is necessary for carbon dioxide gas to diffuse into the interior of the sample, and for this purpose, it is necessary to control the water saturation level of the pores of the molded product. In other words, when the water saturation degree of the pores is 1.0, it means that all the pores of the molded product are filled with water, and in that case, the reaction between Oa(OH)* and carbon dioxide gas (3 ) will only occur on the sample surface. This is because the generated 0a003 covers the sample surface and inhibits the carbon dioxide gas from diffusing into the sample. Furthermore, the fact that the moisture saturation degree of the pores is 0 means that there is no moisture in the pores at all, and the reaction (3) will not occur at all.

Therefore, in order for carbon dioxide to diffuse into the sample, it is necessary to control the moisture saturation in the pores of the molded product as described above to between 0.15 and 0.9, and the best moisture saturation in the pores is O
12 - Also, the hydration reaction rate of 20aO*8i01 in (2) is 3C
2010.810. in cement is very low compared to that of aO.8i01. is said to be ineffective for early strength development. However, according to the above-mentioned nine ideas of the present inventors, under carbon dioxide treatment, 20aO・8i02
However, it can be said that early strength development is fully possible. Therefore, 20aO@8i0s alone can act as a binder under carbon dioxide treatment. Similar thing is 0aOe310
3 can be used as a binder as well as 20aO/5i02. The same can be said for steelmaking slag. In other words, it can be said that carbon dioxide treatment immediately after molding can sufficiently compensate for the disadvantages of molding methods using coarse ore as a base (low strength of molded material, powdering and disintegration during transportation process). .

Another advantage of this conveyor surface curing method is that since the hydration reaction has already been completed on the surface of the molded product, it is possible to prevent the molded products from adhering to each other during the edge process and yard curing period.

The carbon dioxide concentration necessary for early strength development is 5% or more, and the concentration of normal exhaust gas is sufficient.

This carbon dioxide treatment immediately after molding prevents pulverization and
Although collapse can be prevented, the strength is low as a raw material for blast furnaces, and secondary treatment (secondary curing) is required. This secondary regimen includes the following:

[I] Yard curing f:: In order to develop the strength of molded products treated with carbon dioxide immediately after molding, they are piled up in a yard and left/temporarily stored for about 10 days [■] Steam curing method: Treated with carbon dioxide gas immediately after molding In order to develop the strength of the molded product, the molded product is placed in a packed tower, etc., and steam-cured or hot air-cured (III).
Exhaust gas curing method: In order to develop the strength of the formed product that has been treated with carbon dioxide immediately after molding, the molded product is placed in a packed tower, etc., and is treated with carbon dioxide and dried using exhaust gas containing carbon dioxide.In addition, slaked lime% In the case of a binder that replaces cement, such as 20aO"8 ion, methods [I) and (n) are inappropriate, and only the method (TfD) can be adopted.

Based on the above, a molding method based on coarse-grained ore, that is, a molding method that replaces granulation, can be achieved by adopting the process shown in FIG.

From the above, the drawbacks of cold pellets can be sufficiently compensated for, and it is therefore possible to produce low-cost non-calcined agglomerate ore by using a large amount of coarse-grained ore (reducing the cost per crushing).

(Implementation row) ■Experiment on improving molding yield and green strength of molded products by carbon dioxide treatment (1) After thoroughly kneading a mixture of cement: ore: coke powder = 5:95:5 while adding an appropriate amount of water. , 400 yang/-
Press molded at a molding pressure of (molding dimensions: 20wψX 2
0ws). This molded product was treated with carbon dioxide gas under the following conditions.

[Carbon dioxide treatment conditions]

Carbon dioxide concentration = 100%, carbon dioxide amount = 1 t/min, treatment temperature = ~20°C, carbon dioxide treatment time = 3 to 180 minutes The relationship between the crushing strength after treatment and the carbon dioxide treatment time is shown in Figure 1. . From the results in the figure, it can be seen that a crushing strength of 100 kg/cIIi was developed even when the carbon dioxide gas treatment time was about 5 minutes. This crushing strength of 10019/d corresponds to the crushing strength of the above-mentioned press molded product which was not treated with carbon dioxide after curing at 40°C for 24 hours. Therefore, it can be said that the strength development of the press-molded product was promoted by the carbon dioxide treatment as described above.

Experiment (2) After thoroughly kneading a mixture of cement: ore: coke powder = 5:95:5 while adding an appropriate amount of water,
Press molded with a molding pressure of m (molding dimensions: 100mX
1100m x 100゜This molded product is 20m x 20
After crushing to about tm, it was treated with carbon dioxide gas under the following conditions.

[Carbon dioxide treatment conditions]

Carbon dioxide concentration = too, carbon dioxide amount = 1 t/min.

Treatment temperature = ~20℃, carbon dioxide treatment time 5 minutes
~ 30 minutes processing amount = tkf [Measurement of strength of molded product treated with carbon dioxide] 1 kq of molded product treated with carbon dioxide gas is dropped twice onto an iron plate from a height of 2 meters, and the proportion of the molded product is Shutter strength. The relationship between the shutter strength and the carbon dioxide treatment time is shown in FIG.

From the results shown in the figure, it can be seen that the shutter strength of the molded product is significantly improved by carbonate scum treatment. Therefore, as mentioned above, it can be said that such carbon dioxide gas treatment can sufficiently compensate for the drawback of the roll forming method that the green strength immediately after forming is low.

Experiment (3) After thoroughly kneading a mixture of cement: ore: coke powder = 5:95:5 while adding an appropriate amount of water, 400 kf/
Press molded at - molding pressure (molding size: 100ww
X 100wX 10wm I, this molded product ~20
After crushing into pieces of about m x 20 m, they were treated with carbon dioxide gas under the following conditions.

[Carbon dioxide treatment conditions]

Carbon dioxide concentration = 3-100%, carbon dioxide amount = 20-30
t/min, treatment temperature = ~2oC, carbon dioxide treatment time = 10
For a minute, carbonated acid treated acid = 1 gin [Measurement of strength of carbonated molded product] Carbonated molded product ~ 1 kg is dropped twice from a height of 2 meters onto a steel plate, and the 5% strength is measured. It was taken as the shutter strength of the molded product. The shutter strength is the carbon dioxide amount, carbon dioxide processing time, carbon dioxide scum f1
Figure 3 (assumes carbon dioxide concentration = 100% and shows the relationship between carbon dioxide amount and shutter strength) and Figure 4 (assumes carbon dioxide concentration = 20t/min and shows the relationship between carbon dioxide gas amount and shutter strength) ] shows the relationship between density and shutter strength.

It can be seen that a carbon dioxide concentration of 5% or more is sufficient to ensure a shutter strength of 90% or more with a carbon dioxide treatment time of 5 minutes. However, as the carbon dioxide concentration decreases, it is necessary to increase the amount of gas (here, the value of shutter strength of 90% or more is the same as in experiment (1), when the press molding is not treated with carbon dioxide gas at 40℃ x 24 hours. Since Ab, which corresponds to the shutter strength after curing, is greater than Ab, it is possible to manufacture a sufficiently strong molded product by using the roll molding method in combination with the carbon dioxide gas treatment method.A flow diagram thereof is shown in FIG.

■Experiment on molding conditions suitable for carbon dioxide treatment (4) After thoroughly kneading a mixture of cement, two ore and two powder coke = 5:95:5 with water added so that the moisture content is as follows, 400ke/- Press molding was carried out using molding pressure (molding dimensions: 20+o+ψX 20 m).

This molded product was treated with carbon dioxide gas under the following conditions. (moisture:
4%, 5%, 6chi, 7chi, 8%] [Carbon dioxide treatment conditions] Carbon dioxide concentration 1 = too%, 20%, carbon dioxide amount = 1t/
min, treatment temperature = ~20 tl:, carbon dioxide treatment time = 10
FIG. 6 shows the relationship between the crushing strength after the minute treatment and the carbon dioxide gas treatment time. From the results shown in the figure, it can be seen that the strength development due to carbon dioxide gas treatment has a very close relationship with the molding moisture.

From the measurement results of the porosity of this molded product (after drying), the water saturation degree of the pores of the molded product was calculated. This is shown in Figure 7. It can be seen that almost no strength development occurs when the water saturation is more than 0.9 or less than Fio, ts. It can also be said that this value hardly changes depending on the level of carbon dioxide concentration.

■Strength development experiment by carbon dioxide treatment of 20a0, 8i02, etc. (5) A blend of binder: ore: coke powder = 5:95:5 was treated in the same manner as in experiment (1) and press-molded. It was also treated with carbon dioxide gas under the same conditions as in Experiment (1), and its crushing strength was measured. The following binders were used.

(a) β -20aO@5i01. (
b) γ-20aO・8 iol, (c)
OaO・5tos (wollastonite), ni) converter slag These binders, except for γ-20aO・8i01, are ground to a plain index of ~3500 cd/9.

The results are shown in FIG. It can be seen that the strength of each binder is developed.

■Experiment to investigate curing after curing of containers and containers (6) The press moldings treated with carbon dioxide gas in experiment (1) were cured for 1, 3, 7, and 10 days in a constant temperature and humidity chamber at 40°C. did. For comparison, the strength development status of press-formed products that were not treated with carbon dioxide gas was also investigated.

The results are shown in FIG. The developed strength increases during the curing period regardless of the presence or absence of carbon dioxide gas treatment, and it can be said that even if a treatment such as the conveyor curing proposed in the present invention is performed, the strength development of cement will not be hindered.

Therefore, by combining roll forming, conveyor curing, and ten-atmosphere curing, it becomes possible to produce uncalcined agglomerate ore by the roll forming method.

Experiment (7) The press molded product treated with carbon dioxide gas in Experiment (1) was heated to 70°C
Steam curing was performed for 1 to 5 hours. The results are shown in FIG. For comparison, we also investigated the strength development status of press moldings that were not treated with carbon dioxide.6Even if a treatment such as the conveyor curing proposed in the present invention is applied, the strength development of cement due to steam curing is hindered. I can say that there is no such thing.

Therefore, (effects of the invention) As explained above, according to the present invention, the drawbacks of cold pellets can be fully compensated for, and it is possible to manufacture non-calcined agglomerates at low cost by using a large amount of coarse-grained ore. becomes.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams showing the state of strength development due to carbon dioxide curing, Figure 5 is a flow diagram illustrating the production of uncalcined agglomerate by a combination of roll forming method and carbon dioxide treatment method, Figures 6 and 7 are diagrams showing the strength development status due to carbon dioxide gas treatment. Figure 8 is a diagram showing the strength development status and binder during carbon dioxide gas treatment. Figure 9 is a diagram showing the change in strength over time of the carbon dioxide treated product. FIG. 10 is a diagram showing the strength development due to steam curing of the carbon dioxide treated material. 1... hopper, 2... ffi feed, 3... molding roll, 4... molded product, 5... CO gas curing section,
6...conveyor, 7...yard. Agent Patent attorney Masamitsu Aki Sawa and 2 others to 2D37 #5060'r θ090 too
1517 tm intervention curing FR period 1 ＞
a- is -￥N, Heset＼＼-Cracked Nayada× Illusion 5

Claims (8)

[Claims] (1) A molded product made by compression molding a mixture of iron ore powder, cement, coke powder, limestone powder, water, etc. with a roll is treated by exposing it to a gas containing 5 vol, % or more of carbon dioxide gas immediately after molding to treat the surface of the molded product. A method for producing uncalcined agglomerated ore, which comprises coating and curing with calcium carbonate, followed by drying and curing to the strength required for charging into a blast furnace. (2) The method for producing uncalcined agglomerate ore according to claim 1, wherein the hardened roll-formed product is cured in a yard for about 10 days. (3) The method for producing non-calcined agglomerate ore according to claim 1, wherein the hardened roll-formed product is treated with carbon dioxide gas and dried again with exhaust gas containing carbon dioxide gas in a packed tower or the like. (4) The method for producing uncalcined agglomerate ore according to claim 1, wherein the hardened roll-formed product is cured again by blowing steam or hot air in a packed tower or the like, and then dried. (5) A mixture of iron ore powder, cement, coke powder, limestone powder, water, etc. is compression molded using rolls, and the molded product whose water saturation degree is adjusted to 0.15 to 0.9 is heated using carbon dioxide immediately after molding. 5Vol. A method for producing unfired agglomerate ore, which comprises coating the surface of the molded product with calcium carbonate and curing it by exposing it to a gas containing % or more, and then drying and curing it to the strength required for charging into a blast furnace. (6) The method for producing uncalcined agglomerate ore according to claim 5, wherein the hardened roll-formed product is cured in a yard for about 10 days. (7) The method for producing a non-calcined agglomerated ore according to claim 5, wherein the hardened roll-formed product is treated with carbon dioxide gas and dried again with exhaust gas containing carbon dioxide gas in a packed tower or the like. (8) The method for producing uncalcined agglomerate ore according to claim 5, wherein the hardened roll-formed product is cured again by blowing steam or hot air in a packed tower or the like, and then dried.