JPH0471023B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing ferronic slag for concrete aggregate. [Prior Art] It is known that a large amount of slag (ferronite slag) is produced when crude ferronite is industrially produced from silica nickelite such as garillite ore. The industrial method for producing Ferronitskel is generally an electric furnace method in which carbonaceous materials such as coke and anthracite are added as a reducing agent to calcined ore and smelted in an electric furnace;
The blast furnace method, in which ore processed into nodules, a solvent such as limestone, and carbonaceous materials are mixed and smelted in a blast furnace; and the rotary kiln method, in which the ore, solvent, and carbonaceous materials are crushed and mixed, and then smelted in a rotary kiln are used. The solution slag produced by these manufacturing methods is processed by a method of crushing it in a water tank or with high-pressure water and granulating it by rapid cooling (granulated slag), and the slag obtained by the electric furnace method is treated as a layer on the roadbed. There are also methods for cooling the solution slag while pouring water into it (drying), and cooling and granulating it by injecting a large amount of air while the solution slag is falling (air-crushed slag). By the way, the typical composition of silica nickelite used as a raw material is 2-3% Ni, 8-20% Fe.
%, MgO 20-30% and SiO ₂ 30-50%, and the content of metal components such as Ni and Fe is low, so the Ni grade is low.
A large amount of slag is generated when producing 20 to 25% ferronitskel, and the amount of slag generated in Japan reaches around 1.5 million tons per year. Ferronic slag, which is generated in large quantities, is partially used as an MgO source and as a solvent in iron smelting.
It is also used as a raw material for silicon fertilizer, etc.
Most of the waste has been used for landfill or simply for disposal. However, the current situation is that the amount of ferronitkel slag generated is so large that it is difficult to secure land and space for reclamation and deposition, resulting in an increase in processing costs that cannot be ignored. Therefore, there has been a desire to develop new uses for the effective use of resources, and recently, the use as fine aggregate for concrete has attracted attention as such a new use. In other words, in the civil engineering and construction industry, as the natural river sand that has traditionally been used as fine aggregate for concrete runs out, sea sand is being substituted, but there are problems such as residual salt in the sand corroding reinforcing bars. , there was a need for a stable supply of high-quality fine aggregate, but most of the ferronitkel slags mentioned above are suitable as fine aggregates by adjusting the particle size, and there are no problems in terms of workability, concrete strength, etc. I found out. [Problems to be solved by the invention] However, the slag produced by the electric furnace method and granulated (hereinafter referred to as "granulated electric furnace slag")
Although it is produced in the largest amount, depending on the conditions of use, it can cause a so-called alkaline aggregate reaction that reacts with the alkali in cement, causing abnormal expansion and cracks in concrete. It turned out to be. According to research conducted by the present inventors, the reason why electric furnace granulated slag is susceptible to alkaline aggregate reactions is that its mineral composition is high in forsterite (2MgO・SiO ₂ ) that crystallizes due to rapid cooling and silica content. This is because the glass with high silica content easily reacts with the alkali in cement.On the other hand, other ferronite slags have enstatite (MgO・SiO ₂ ) as their main component. It was found that the alkaline aggregate reaction did not occur because the glass content was extremely low. The reason why the electric furnace granulated slag contains a large amount of glass with a high silica content is thought to be the result of rapidly cooling the solution slag at 1500 to 1600°C generated by the electric furnace method during granulation, as described above. Therefore, in order to suppress the formation of glass with a high silica content, it is necessary to change the slag composition by adding limestone etc. during electric furnace smelting, or to stop slag granulation and dry slag. Alternatively, a possible countermeasure is to gradually cool the material by air crushing. However, the former method has the problem that additives increase the cost of auxiliary raw materials, melting energy costs, etc. and complicate the work, while the latter method requires a large area and long processing time, and Since the high-temperature slag above is collected while being crushed with a bulldozer, there are problems in that the environment is degraded and the number of man-hours increases, which also makes the work more complicated. Furthermore, these methods include
In order to use the obtained slag as a fine aggregate, there is a drawback that operations for adjusting particle size such as crushing and sieving require greater costs. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing ferronic slag suitable as concrete aggregate without causing an alkaline aggregate reaction from granulated electric furnace slag. [Means for Solving the Problems] That is, the present invention solves the problems of the prior art by crushing molten ferronic slag produced in the ferronic slag production process using an electric furnace method. The present invention provides a method for producing ferro-nickel slag for use in concrete aggregate, which comprises heating and holding the obtained granular ferro-nickel slag at 1000° C. or higher and then cooling it. In the production method of the present invention, the required heating time depends on the heating temperature, and generally the higher the temperature, the shorter the heating time can achieve the desired effect. For example, heating for about 2 hours or more is preferable at about 1000 to 1100°C, but heating for about 1 hour or more is sufficient at about 1200°C. For temperatures in the range of 1100-1200°C, the minimum required time is in the range of 1-2 hours.
The required heating time at a temperature of 1000℃ or higher is
As shown in Examples below, those skilled in the art can easily understand this through simple experiments. The atmosphere for heating is not particularly limited, and air is sufficient. Further, the heating furnace used for heating is not particularly limited, and examples thereof include a rotary kiln, a Hereschoff furnace, a tunnel kiln, and the like, and a normal heating furnace can be used. Note that it is economical to use various types of waste heat generated in the ferronic slag smelting process as an auxiliary heat source. Further, in the method of the present invention, the method of cooling after heating is not particularly limited, and slow cooling or rapid cooling may be used. Rapid cooling allows production to be completed in a short time. [Function] By the heat treatment in the method of the present invention, forsterite and glass with a high silica content in the granulated electric furnace slag are converted to enstatite. [Example] Hereinafter, the present invention will be specifically explained with reference to Examples. (1) Sample slags A to E shown in Table 1 are the slags generated when producing crude ferronickel by the blast furnace method, rotary kiln method, or electric furnace method, respectively, and are processed by water pulverization, dry slag, or wind pulverization. The same table shows the chemical composition, mineral composition determined by X-ray analysis and microscopic observation, and potential alkali content when used as concrete aggregate according to the method specified in ASTM C-289. The results of a reactivity test (alkaline aggregate reaction test) are shown. Furthermore, Figure 2 is a graph showing the relationship between the amount of dissolved silica (SC) and the amount of alkali concentration reduction in each sample slag obtained in this alkali aggregate reaction test. Sample points that fall to the left indicate that the reactivity with alkali is potentially harmful, while sample points that fall to the left are harmless. Among the sample slags A to E, only C, which is granulated electric furnace slag, is in the harmful range, indicating that it is problematic as a concrete aggregate. (2) 2 kg of the same slag as sample slag C in Table 1 was placed in an alumina pot without changing the particle size, and the silicate unit was heated to a predetermined temperature for each experiment number as shown in Table 2. The samples were charged into an electric furnace and maintained at the above temperature for the time shown in the table. Thereafter, the slag was taken out of the furnace and allowed to cool at room temperature. The slag after cooling was subjected to an alkali aggregate reaction test according to the method of ASTM-C289 described above, and the amount of alkali concentration reduction (RC) and the amount of dissolved silica (SC) were measured. The results are shown in Table 2 and Figure 1.
The results of Experiment No. 5 are also shown in Table 1 for comparison. Experiment No. 1 is Sample C itself without heat treatment, and experiments marked with * in Table 2
No. indicates a comparative example. The above results show that it is possible to move the potential alkali reactivity of slag to a harmless range by heat treatment at a temperature of 1000°C or higher.
Experiments No. 3, 4, 6, and 7 show that even at heating temperatures of 1000°C or higher, sufficient effects cannot be obtained if the heating time is too short, and the required heating time varies depending on each temperature. It shows that it can be easily found.

【table】

〔Effect of the invention〕

The ferronitkel slag obtained by the production method of the present invention overcomes the latent reactivity with alkali that granulated electric furnace slag originally has, and does not cause an alkali aggregate reaction when used as concrete aggregate. It's something that doesn't exist. Therefore, the industrial significance of the present invention is extremely great, as it opens up a way to safely and effectively utilize granulated electric furnace slag, and also enables a stable supply of concrete aggregate, which is in short supply.

[Brief explanation of drawings]

FIG. 1 shows the results of the alkali aggregate reaction test conducted in the examples, and FIG. 2 shows the results of the alkali aggregate reaction test of various slags.

Claims (1)

[Claims] 1. A concrete aggregate concrete slag made by heating and holding granular ferronic slag at 1000°C or higher and then cooling it, which is obtained by crushing molten ferronic slag produced in the ferronic slag manufacturing process using the electric furnace method. The manufacturing method of Eronitskel slag.