KR890003136B1 - Hardening method of iron oxide mine - Google Patents

Abstract

A method for hardening the iron oxide pellets comprises; adding a binder to raw materials including unfired iron ore and dust mainly containing oxides of iron; forming green pellets by removing 10-15 vol.% moisture of mixture in the disc-type pelletizer; first hardening green pellets for 6 hours in the closed container preheated to 20-100 deg.C; and second hardening geen pellets for 3 hours in the closed container containing the saturated steam of 60-100 deg.C.

Description

Hardening method of iron oxide compacted light

1 is a change in the compressive strength according to the curing temperature during the first curing.

2 is the change in compressive strength with temperature during secondary curing.

3 is a change in the shape of the pellet according to the curing temperature after the first curing.

4 is a change in the compressive strength according to the drying temperature during the drying treatment.

The present invention relates to a method for curing non-baked compacted light using iron oxide particles as a pretreatment method for a metallurgical raw material. Conventionally, sintered or fired pellets have been used as blast furnace charges, but environmental pollution due to dust and exhaust gas has become a problem during the firing process of compacted ore.

A common recipe for this is iron oxide particles. The magnetic binder and water were mixed, granulated into spherical pellets, and cured by a predetermined method.

As a curing method, there is an air curing method in which non-fired pellets are left in the air under normal temperature and pressure. According to this method, there is an advantage that no separate equipment or device is required for curing the pellet, but it takes a long time until the pellet shows the final strength value up to 28 days. In order to improve this problem, the following method has been proposed. 1. Japanese Patent Publication No. 83-36054: After pelleting, the pellets are left to stand at room temperature for 3 days and then cured with saturated steam at 100 ° C. for 3 hours and then cured yards secondly. 2: Japanese Patent Publication 80-12169: Method of curing the yards secondly after the first curing in a sealed container. 3: Japanese Patent 80-32769: Method of curing at 160-230 ° C., 10-70 atm, and 1-20 hours in a water vapor pressure and temperature control device (Auto Clave), but in the case of paragraph 1, the yard due to the prolonged treatment period There is a problem in securing and because the proper conditions are not specified in paragraph 2, the problem of differentiation of pellets according to curing temperature is not solved.

Accordingly, the present invention limits the curing temperature of the raw pellets under atmospheric pressure during the production of non-fired pellets, thereby reducing the total curing time by omitting the raw pellets, and preventing the deformation of the pellets while reaching the appropriate strength. For the purpose of

In other words, as a result of a series of experiments on curing treatment, the raw pellets discharged from the pelletizer were first stored in the sealed container based on the phenomenon that cracks, differentiation, and strength of pellets were changed depending on the curing temperature during curing of non-plastic pellets. After curing at the maximum temperature to the extent that the pellets do not differentiate from, characterized in that the secondary curing by hot steam and the drying treatment by heating air.

Hereinafter, a method according to the present invention will be described in detail with reference to Examples. It was mix | blended as iron ore and the dust generate | occur | produced in steel mill as raw materials as shown in Table 1.

TABLE 1

This blended raw material was charged into a disk-type pelletizer and combined into fresh pellets while watering 10-15% of water. When the diameter of the raw pellet grows to 10-15mm, it is discharged from the pelletizer and the first curing for 6 hours at the temperature of 20-100 ℃ in a sealed container, and then 60-100 ℃ in a separate sealed container. Secondary curing was performed with saturated steam for 3 hours. The curing results of each stage are shown in FIGS. 1 and 2, respectively.

1 shows the compressive strength of the pellets at each curing temperature. The curing strength increases as the curing temperature increases up to 70 ℃, but at the curing temperature above 70 ℃, the strength of the pellet decreases due to cracking or differentiation of the pellet. Couldn't keep up

As can be seen in FIG. 3 showing the shape of the pellets cured at 70 ° C. and 80 ° C., the pellets cured at 80 ° C. were cracked to the surface or the inside, and some of the outer parts were erupted and detached. In the case of curing at 100 ° C, the pellets were all differentiated and the strength could not be measured. Therefore, it was found that the primary curing temperature was in the range of 60-70 ° C, considering the pellet's self-maintenance. 2 shows the compressive strength of 60-100 ° C. saturated steam secondary cured pellets in a sealed container, which was cured at 60 ° C. and 70 ° C., which was effective as the primary curing temperature.

As a result, the pellets tended to increase the compressive strength after curing as the curing time increased up to 100 ° C. In other words, the cracks and differentiation of the pellets did not appear as in the case of the primary curing. As described above, the pellets subjected to the two-step curing treatment were dried by heating air to remove moisture and increase strength. The primary and secondary cured pellets were dried by heating air for 2 hours in the temperature range of 100-300 ° C. and the compressive strength thereof was shown in FIG. 4, whereby the drying temperature was increased to 250 ° C. The strength increase effect was obvious, but the strength slightly decreased at higher temperatures. Therefore, considering the efficient use of energy and strength properties as a conventional blast furnace charge, it can be seen that the drying temperature is in the range of 200-250 ° C.

The following describes the effect of curing conditions on the pellet strength at each stage.

Dividing the curing temperature into two stages of low temperature and high temperature is that when the raw pellets assembled by water addition at room temperature are discharged from the pelletizer and cured at high temperature, the air in the pellet pores expands and is released to the surface to crack. To severe eruptions.

That is, if the primary curing is at a temperature at which the pellets do not cause cracking or differentiation, even if the secondary curing is performed at high temperature, the pellets are sufficiently cured and the temperature of the pellets is raised so that cracking or differentiation does not occur. Curing in a sealed container or with saturated steam is to protect the water from loss in the pellets because water is absolutely required for solid phase bonding of a hydraulic binder such as cement. Heating the pellets has the effect of promoting hardening by encouraging exothermic reactions when the cement hardens.

The drying treatment removes the water in the pellets from cement and hydrates and removes the excess free moisture. The strength of the pellets is increased by the dehydration of cement hydrates. . Thus curing the pellets to which the cement is added in accordance with the present invention as described above has an effect that the pellets can be produced in a short time within 12 hours of high-strength non-fired, which does not cause cracking or differentiation.

Claims (1)

The non-fired iron ore with cement and the iron oxide agglomerated mineral of dust generated in the steel mill are dried immediately after the first and second curing treatments, and the first curing conditions are heated to 60-70 ℃ in an airtight container. Curing method of iron oxide compacted light characterized by curing.

Images