JPS62177133A - Method for cold bonding granular material - Google Patents

Abstract

PURPOSE:To manufacture molded bodies having high strength after curing in a short time by bringing kneaded and molded bodies into contact with gaseous CO2 and keeping the water content in the molded bodies at a value corresponding to the water content in the molded bodies in a period in which the molded bodies are dried at a reduction of volume during the contact. CONSTITUTION:A binder such as Portland cement is added to a granular material such as fine iron ore and they are kneaded and molded. The resulting molded bodies are hardened by carbonation curing in an atmosphere contg. 5vol% gaseous CO2. During this time, the water content in the molded bodies is kept at a value corresponding to the water content in the molded bodies in a period in which the molded bodies are dried at a reduction of volume. The period in which the molded bodies are dried at a reduction of volume is recognized by a change in the dew point of exhaust gas for drying or the water content. By this cold bonding method, the carbonation curing period can be shortened and molded bodies having high strength after curing are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for cold bonding ores, coal, coke, dust, etc.

(Prior Art) There are many fields in which it is necessary to turn particulate materials into solid lumps. For example, in the steel industry, particulate iron ore, which is a raw material for blast furnaces, particulate iron ore, particulate coke, It also includes granular coal, which is a raw material for coke ovens, and generated dust, which takes into consideration the effective use of valuable metals and fuel.

In recent years, as a method for processing such particulate materials, cold bonding methods have been rapidly developed from the viewpoint of reducing the energy required for processing and making it non-polluting. A binder is added to the particulate material in order to form it into a granular material, add strength to withstand the process of use, reduce powdering rate, and fully increase the utility value. Although all treatments are carried out, it takes a long time (usually 7 to 10 days) to develop strength, and large-scale curing equipment is required.
It has drawbacks such as a decrease in productivity due to the long curing time.

In order to solve these drawbacks, for example, Japanese Patent Application Laid-Open No. 48-2
As stated in Publication No. 3613, in order to completely improve the strength of granulated pellets in a method for manufacturing raw material pellets for steelmaking,
2 per pellet after several days of exposure to a carbon dioxide-containing air stream.
There is a method to ensure crushing strength of 0 kp or more.

(Problems to be Solved by the Invention) In order to improve the strength of molded products and shorten the time for developing strength, in the conventional cold bonding method for particulate materials, carbonation curing is fully adopted, and binder The type of binder, the amount of binder added, the method of adding binder, and the curing method (curing time, carbon dioxide concentration, amount of carbon dioxide, moisture content of molded product during curing) have all been investigated. If the diameter, binder type, or moisture content of the molded product changes during curing, the curing effect will change significantly, and it may not be possible to obtain the desired strength during actual operation, resulting in the generation of fine powder or excessive This has led to major problems such as the use of binders and extended curing times, increased manufacturing costs, decreased production, and fluctuations in production.

The present invention has been made in order to advantageously solve the above-mentioned difficulties, and uses binders that are entirely carbonate-forming as binders, such as cement, cement clinker, dicalcium silicate (2CaO-8i02), wollastonite ( CaO-810□), blast furnace slag, converter slag, electric furnace slag, and slaked lime were added to the molded product by the non-calcined agglomeration method.When the molded product was completely carbonated and cured, the water content of the molded product was removed. By maintaining the lapse rate at a value corresponding to the moisture content during the drying period and carrying out carbonation curing, the optimum carbonation curing is always carried out.

(Means and effects for solving all the problems) The present invention provides cement,
Cement clinker, Gui Calcium Silica) (2
CaO8i02), wollastonite (CaO-810
2) After mixing a binder that hardens by forming carbonates such as blast furnace slag, converter slag, electric furnace slag, and slaked lime, and adding a predetermined amount of water if necessary, In a method in which a molded product formed by a fired agglomeration method is carbonated and cured by injecting a gas containing at least 1% of total carbon dioxide gas, the moisture content of the molded product, the moisture content of the molded product during the lapse rate drying period, By maintaining the value equivalent to , and performing carbonation curing treatment, high strength after curing can be maintained even if the raw material type, particle size, binder type, or moisture content of the molded material changes during curing. This is a cold bonding method for particulate materials that makes it possible to manufacture molded articles having the following properties in a short time.

The present invention will be explained in detail below.

Figure 1 shows the influence of the moisture content of the molded product during curing and the curing time on the strength after curing, when carbonating and curing pellets molded by adding Portland cement) 1 as a binder and thoroughly beletizing iron ore. It is something that

From this, it can be seen that during carbonation curing, there is an appropriate moisture range for the molded material to be cured, and this appropriate moisture range is a value in which the moisture content of the molded material to be cured corresponds to the moisture content during the lapse rate drying period of the molded material. It turns out that there is something.

Conventionally, it is thought that the strength of molded products of cement binders develops through the progress of the hydration reaction of cement, and the strength development speed is extremely slow, and it takes a long time of 7 to 10 days to reach the specified strength. It takes. On the other hand, during carbonation curing, the hydration reaction is promoted, and calcium silicate hydrate and CaCO5'! It is thought that i' is produced and the reaction proceeds as follows.

3CaO1ISiO2+H20→Ca(OH)2+Ca
O・5L02・H2O...(1) 2CaO・SiO□+H20→Ca(OH)2+Cao
-8I02.H2°...(2) That is, the reaction formulas (1) and (2) above are normal cement hydration reactions, and the reaction rate is slow. On the other hand, in the reaction (3) above, Ca(OH)2 produced in the reactions (1) and (2) above becomes CaCO3 due to carbon dioxide gas dissolved in water, but Ca(OH) 2 is discharged outside the system as CaCO3, so the above (1)
This is a complex reaction in which the reaction (2) is promoted and the production of CaCO3 necessary for developing strength is also promoted.

Although the reaction in cement has been shown above, the reaction is similar in cement clinker-1 blast furnace slag and slaked lime. Therefore, in order to effectively (and quickly) develop strength through carbonation, the following points are important. Namely, water is indispensable because the reaction occurs through al moisture, but the most important Moisture and a binder must be present at the contact point of the powder or granule particles where carbonation is required. For this purpose, pores are secured as carbon dioxide gas paths.

Therefore, by reducing the moisture content of the molded product during carbonation curing to a low level corresponding to the moisture content during the drying period of the molded product, moisture and binder are preferentially transferred to the contact points of powder particles due to capillary action. This means that the effect of making all the carbon dioxide gas exist and the effect of securing all the routes for carbon dioxide gas will be fully exerted.

The lapse rate drying period is a technical term generally used in drying theory such as chemical engineering, and is indicated by the region (■) in the relationship curve between dry matter moisture and drying rate in FIG. In the case of particulate materials, moisture within the lapse rate drying period is considered to exist at the contact points of each particle, but the lapse rate drying period varies widely depending on each material.

Therefore, if the raw material type or particle size of the molded product changes, the lapse rate drying period will naturally change, so the inventors detected the lapse rate and drying period from changes in the dew point or moisture content of the exhausted drying flue gas. I thought about doing it.

In other words, as shown in Fig. 2, during the constant rate drying period (region H), the drying rate is constant, so the dew point or moisture content of the drying exhaust gas remains constant;
(2), the drying speed decreases, so the dew point or moisture content of the drying exhaust gas does not remain at a constant value, and as the drying speed decreases, the value decreases ( It is possible to detect the lapse rate drying period.

Figure 3 shows the strength development of a molded product made by adding early-strength cementola as a binder and molding iron ore using a roll forming machine, and then fully carbonating and curing it. However, the non-fired agglomeration method has changed. However, it is possible to improve the strength after curing by maintaining the powder extinction rate of the molded product at a value corresponding to the moisture content during the drying period and performing carbonation curing.

Figure 4 also shows dicalcium silicone 14 as a binder.
-Additionally, the molded product formed using a coal full roll molding machine,
This is a diagram illustrating the development of strength after carbonation curing.

When calcium silicate is used as a binder, the carbonation reaction is slightly different from that of cement, and is thought to proceed as follows.

CO2+H2O-+H2CO3...(4)H2Co3
+2CaO-8IO, -+CaCO3+CaO-81
02-H20...(5) However, in the case of dicalcium silicate, as in the case of cement, in order for the carbonation reaction to be carried out sufficiently, it is necessary to conduct the reaction in a state where the moisture content is high, and the molded product It is necessary to take all aspects of the infiltration of carbon dioxide gas into consideration, and carbonation curing during the lapse rate drying period is the most effective. The same can be said of wollastonite, converter slag, and electric furnace slag.

In addition, the carbon dioxide concentration needs to be 5VoA- or more due to the carbonation reaction, and even if exhaust gas from a hot air stove or coke oven containing a large amount of CO2 is used as the CO2 gas,
It can be fully effective.

Therefore, carbonate is completely formed by carbonation reaction through water,
For binders that develop strength, even when the raw material type, particle size, type of binder, and non-fired agglomeration method change, the moisture content of the molded product during carbonation curing can be reduced to zero (except for zero moisture).
By maintaining the lapse rate of the molded product at a value corresponding to the moisture content during the drying period and performing carbonation curing, optimal carbonation curing can be performed at all times, and all molded products with high strength can be produced quickly.

(Example) Next, the present invention? The non-fired agglomeration method was applied to various agglomerated molded products, carbonation curing was performed, and the operational results are shown in Table 1 along with all conventional operational results.

As is clear from the results in this table, a binder that hardens due to the formation of carbonate is used as a binder, and the moisture content of the molded material during carbonation curing and the drying period at which the molded material loses its moisture content are reduced to zero. By maintaining the moisture content at a value equivalent to 100% and performing carbonation curing treatment, even if the raw material type, particle size, binder type, or non-fired agglomeration method changes, it will not be affected at all. It is possible to always carry out optimal carbonation curing, and it is possible to greatly shorten the curing time and greatly improve the strength of the molded product after curing, allowing for rapid production of all molded products with high strength.

It has also become possible to reduce the amount of binder used in the conventional method to shorten the curing time and ensure the strength of the molded product after curing.

(Effects of the Invention) As described above, according to the present invention, it is possible to significantly shorten the carbonation curing time and greatly improve the post-carbonation strength.
Moldings with high strength can always be produced quickly. Furthermore, in the conventional method, it is possible to reduce the amount of binder used to shorten curing time and ensure strength after curing, and it has become possible to significantly reduce manufacturing costs.

The present invention constantly presents the optimal carbonation curing method even if the raw material type, raw material particle size, binder type, and non-fired agglomeration method change, and it dramatically improves the carbonation curing method. It is something that makes you

[Brief explanation of drawings]

FIGS. 1, 3, and 4 are graphs showing the relationship between the drying state and pellet strength of the present invention in experiments, and FIG. 2 is a drying theory graph for explaining the present invention.

Claims (1)

[Claims] 1. A binder is added to particulate material and kneaded, and the moisture content of the molded product is maintained at a value corresponding to the moisture content during the drying period while carbon dioxide gas is 5 vol% or more. A method for cold bonding particulate materials, characterized by bringing them into contact with a containing gas and curing them. 2. The method for cold bonding particulate materials according to claim 1, wherein the lapse rate drying period of the molded product is detected from a change in the dew point or moisture content of the drying exhaust gas.