JPS62177132A - Manufacture of unfired briquetted ore - Google Patents

Abstract

PURPOSE:To manufacture unfired briquetted ore having strength necessary for charging into a blast furnace in a short time by adding powdery dicalcium silicate to powder as starting material, kneading and compression-molding them, regulating the water content in the resulting molded bodies and bringing the molded bodies into contact with gaseous CO2. CONSTITUTION:Powdery dicalcium silicate as a binder is added to iron ore-base powder as starting material for a blast furnace. They are kneaded and compression-molded with a roll to form molded bodies such as flakes and the water content in the molded bodies is regulated to 0.1-4.5wt% by drying or other method. The molded bodies are then hardened by carbonation curing in an atmosphere contg. >=5vol% gaseous CO2. By this method, the curing time can be shortened and unfired briquetted ore having improved strength after curing is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing uncalcined agglomerated ore.

(Prior art) Iron-making raw materials containing iron need to be agglomerated depending on their purpose, and the agglomeration methods include (1) sintering method (2)
) Baked pellet method and fired briquette method (3) Non-fired agglomeration method (cold pellets, briquettes, roll molded products)
and so on.

Regarding (1) and (2) above, since it is necessary to sinter the product in order to add strength to the product, not only large-scale equipment and energy are used, but also sulfur oxides generated during the sintering process, The problem is that nitrogen oxides, dust, etc. are emitted, causing pollution.

Regarding (3) above, it has been rapidly developed in recent years to solve all of the problems in (1) and (2) above.
It takes a long time (usually 7 to 10 days) to develop strength.

In addition to requiring large-scale curing equipment, curing time is long (
However, it does have disadvantages such as reduced productivity due to

In order to solve all of these drawbacks, for example, Japanese Patent Application Laid-Open No. 48-2
As described in Japanese Patent No. 3613, in order to improve the strength of the granulated material, there is a method of exposing the granulated material to an air flow containing carbon dioxide gas for several days to ensure a crushing strength of ff 20 k1 or more per 1 pellet. Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 57-92143, pellets using powdered dicalcium silicate (represented by 2CaO-8IO□) as a binder are used.
(It is disclosed that curing is performed in an H, CO2 gas atmosphere.

(Problems to be Solved by the Invention) In order to improve the strength of molded products conventionally formed by the non-fired agglomeration method and shorten the time for strength development, the type of binder, the amount of binder added, and the amount of binder used in the carbonation curing method have been developed. Various addition methods and curing methods (curing time, carbon dioxide concentration, carbon dioxide amount) have been studied, but if the moisture content of the molded product, the type of raw material for the molded product, or the particle size of the molded product changes during curing, The curing effect changes significantly, and it may not be possible to obtain the desired strength during actual operation, resulting in the generation of fine powder, an increase in the use of binder more than necessary, or an extension of curing time, resulting in an increase in manufacturing costs and production volume. This caused major problems such as a decline in production and fluctuations in production.

In view of the above-mentioned circumstances, the present invention provides a method for continuously obtaining uncalcined agglomerated ore with the strength necessary for charging into a blast furnace in a short period of time.

(Means and effects for solving all the problems) The present invention provides 2 CaO/SiO□, a powder whose hardening reaction is extremely rapid, by forming carbonate and hydrate as a binder in a powder mainly composed of iron ore. and water if necessary. After mixing, the flaky molded product is compressed using a roll molding machine and dried, etc. until the moisture content of the molded product is 0.
By maintaining the concentration at 1 to 4.5 wt% and carrying out carbonation curing treatment with a gas containing 1% or more of carbon dioxide 5Vo,
The use of non-calcined agglomerate ore makes it possible to produce molded products with consistently high strength after curing in a short time even when the special water content, raw material type, and raw material particle size change. This is the manufacturing method.

The present invention will be explained in detail below.

The figure shows powdered 2CaO・S as a binder in experiments.
Add iO□ and use a roll forming machine to produce 600 kP/c
This figure shows the influence of the moisture content of the molded product during curing and the curing time on the strength after curing when a molded product molded with a compression force of m2 is carbonated and cured.

From this, when powdered 2CaO-8102 is added as a binder and the molded product is fully carbonated and cured using a roll molding machine, what is the strength after carbonation and curing? In order to improve
It has been found that there is an appropriate moisture range for the moisture content of the molded product to be cured during carbonation curing, and this appropriate moisture range is such that the moisture content of the cured molded product is 4.5 wt % or less.

Conventionally, 2CaO-8iO2 powder was considered unsuitable as a curing agent due to its slow water utilization reaction rate, but CO2
In a gas atmosphere, the water utilization reaction is promoted, producing calcium silicate hydrate and CaCo3Kl, which are effective for hardening.In other words, the discovery of strength through carbonation of 2CaO-8iO2 is thought to proceed through the following reaction. It will be done.

Co2+ I(20→H2CO3...(1)H2Co
3+2 CaO@S io□−+ CaCO3+ Ca
O-S 102-H20...(2) From the above reaction formula, in order to develop strength through carbonation effectively and quickly, (a) Moisture? Since the reaction occurs through the reaction, moisture is essential, but it is also necessary that moisture and ``ingu'' exist at the contact points of the powder particles, which require strength. (b) In order to advantageously allow carbon dioxide to penetrate into the molded product,
It is necessary to secure pores as a path for carbon dioxide gas.

Therefore, when molding into pellets using a pelletizer, for example, adding all of the 8 to 10 wt% required to make the molded product have a total low moisture content is important because moisture and binder are added to the contact points of powder particles due to capillary action. This results in the effect of preferentially allowing carbon dioxide to exist, and the effect of ensuring all routes for carbon dioxide gas.

Is roll compression molding the most effective way to achieve this effect? It is something that can be demonstrated. In other words, (1) the added moisture oozes out of the system of the molded product (C) during molding, thereby promoting the above-mentioned effects; (1) molding moisture can be reduced; (2) the binder can be reduced compared to all pellets; (2) ore grain size coarser than all pellets; Since it can be made into granules, the power cost for crushing can be completely reduced. ■ The strength of the molded product is fast, so it can be produced continuously. ■ Since it can be molded into flakes, the angle of repose can prevent uneven distribution in the blast furnace.

Moisture of the molded product in the present invention (5.0.1 to 4.5wt
%, the amount of water added during kneading may be within this range, but in this case a strong compressive force is required.
Since power costs and the like increase, it is preferable to reduce moisture content by drying after molding.

The moisture retention range of the molded product is as explained in the experimental diagram above (the maximum is 4.5 wt%, and the minimum is 0.1 wt% when the moisture content is almost zero, the carbonation reaction of the binder hardly progresses). % or more, but the most preferable appropriate range is 0.5 to 4.0 wt%.

The carbon dioxide concentration needs to be 5Vo1% or more from the carbonation reaction, and even if exhaust gas from a hot blast oven or coke oven, etc., which contains a large amount of CO2, is used as the CO2 gas, sufficient effects can be achieved. be.

Further, the 2CaO-8iO□ used in the present invention may be a converter slag containing a large amount of 2CaO-8iO□ or an electric furnace slag all around the slag, or, for example, by adding all the limestone and silica stone,
It may be manufactured by adjusting the composition to 2CaO-8iO2 and firing it in a cement kiln.

(Example) 2CaO-8I02 was added as a binder to each limestone raw material.
(Electric furnace slag containing a large amount in 2CaO”5i02,
Alternatively, converter slag was used. ), add water and gold necessary for molding, and knead thoroughly to obtain a molding force of 500 to 80.
Roll forming the agglomerate at 0 kJ/cFn2 to make the entire flake-like agglomerate ore, set up a curing chamber, keep the agglomerate dry and dry so that the moisture content of the agglomerate falls within the range of the present invention, and cure and harden in a CO□ gas atmosphere. Ta.

These manufacturing conditions and results were used as a comparative example by adding all the cement as a binder to conventional various ore raw materials.
Adding the water necessary for molding, the total molding force is 500 to 80
A flaky agglomerate was formed by roll forming at 0 kt/crn2, and Table 1 shows the results of curing and hardening this in a CO2 gas atmosphere.

As can be seen from the table above, in this example, even if the type of drinking raw material or the particle size of the raw material changes, the effect is not that great.
Moreover, the curing time was shortened and the strength after curing was greatly improved compared to the conventional method.

(Effects of the Invention) As described above, according to the present invention, it is possible to greatly shorten the carbonation curing time and greatly improve the carbonation curing time.
Furthermore, in the conventional method, it has become possible to reduce the amount of binder used in order to shorten the curing time and ensure the strength of the curing waves.

Furthermore, even if the type of raw material used or the particle size of the raw material changes, it is possible to always carry out optimal carbonation curing, which has the excellent effect of dramatically improving the overall carbonation curing method.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the moisture content of molded products and shutter strength during CO2 curing in experiments.

Claims (1)

[Claims] Powdered dicalcium silicate (2CaO・SiO_
2) was added and kneaded, the moisture content of the molded product was adjusted to 0.1 to 4.5 wt% by roll compression molding, and the carbon dioxide was
A method for producing uncalcined agglomerate ore, which comprises hardening the ore by contacting it with a gas containing vol% or more.