JPH0132196B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention recovers useful iron from coal ash and converter slag, both of which are industrial waste, and
The present invention relates to a method for producing a silicate fertilizer containing silicic acid, magnesium, and phosphoric acid in a form effective as a fertilizer. As the supply-demand relationship for oil becomes increasingly tense and prices rise, coal is once again being used. However, after coal burns, a large amount of residual ash is generated, and the amount varies depending on the type of coal, but
It typically weighs as much as 15-20% of the original coal weight. Therefore, what should be done about its disposal?
Another issue is becoming important. On the other hand, converter slag produced during steelmaking operations is also an industrial waste that has no other use, and it is difficult to dispose of it. In addition to silicic acid, alumina, calcium oxide, and iron oxide, coal ash contains various components such as some unburned carbon and a trace amount of boron. Recently, in order to suppress the _NO
It also extends to In addition to large amounts of calcium oxide, converter slag also contains silicic acid, iron oxide, phosphoric acid,
Contains magnesium oxide. The present inventors intended to reuse useful components in these wastes, and as a result of collaborative research,
By using unburned carbon in coal ash, a considerable proportion of iron oxide in ash and slag can be reduced to metallic iron, and by making the whole glassy, magnesium and phosphoric acid are The present inventors have discovered that it is possible to obtain a silicic acid material that exists in the form of boron and contains an appropriate amount of boron, leading to the present invention. The method of producing silicate fertilizer from industrial waste according to the present invention involves mixing and melting coal ash and converter slag, and using the ash contained in the ash to absorb at least one part of the iron oxide in the ash and slag. A vitreous material containing silicic acid, magnesium and phosphoric acid in a form useful as fertilizer is obtained by reducing the fraction to metallic iron and cooling the melt with water, from which the metallic iron is separated and recovered. consists of doing. The blending ratio of coal ash and converter slag is determined in accordance with the ratio of useful components contained in each and the characteristics of the product to be obtained. In practice, the ratio of the amounts of the two generated as waste to be treated may be an important factor. In general,
It is preferable to select from the range of 8:2 to 2:8 in terms of weight ratio, preferably 6:4 to 4:6. Particularly in the case of this preferable weight ratio, the viscosity of the melt is low and the melt can be melted at a relatively low temperature. It is advantageous to be able to tap. The mixture is generally melted at a temperature of 1,300 DEG to 1,600 DEG C., although it depends on the blending ratio of the raw materials as described above. As a device for this purpose, an arc furnace is suitable because it can easily obtain high temperatures. Since converter slag is obtained in a molten state at the end of the steelmaking process, it is a good idea to utilize the sensible and latent heat it possesses. It is practical for the present invention to transfer the coal into the above-mentioned arc furnace, raise the temperature there using some electric power, and carry out the reaction with the coal ash. Mixing of slag and coal ash can be done either by adding coal ash to the molten slag flow during the above transfer and stirring it as it flows down, or by charging coal ash into the arc furnace in advance and pouring the molten slag onto it. It is recommended to create a stirring effect by injecting . The combined melting of coal ash and converter slag reduces the iron oxide to metallic iron by at least 50%, and in preferred operations, 60-70% or more. When water-cooling the molten material,
This iron becomes granular and is almost completely separated from the glass material, so it can be easily recovered by methods such as magnetic separation. Of course, this recovered iron can be reused as a raw material for steelmaking. The water-cooled pulverization of the melt may be carried out, for example, in accordance with established techniques for pulverization of blast furnace slag. The vitreous material obtained by separating metallic iron particles has particles the size of river sand and can be applied as is as a silicate fertilizer, although this varies somewhat depending on the granulation conditions. As is well known, silicic acid fertilizer, commonly known as silicic acid fertilizer, is one of the important ordinary fertilizers. When viewed as a calcic fertilizer, the one according to the present invention has a well-balanced ratio of CaO and SiO ₂ in converter slag, where the latter is insufficient, but SiO ₂ from coal ash makes up for this deficiency. Become something. Additionally, magnesium and phosphoric acid in the converter slag (some of which is also added from the ash) are effective in their soluble form, and trace components such as boron in the coal ash can be utilized. This silicate fertilizer is also useful as a soil improvement material. In this manner, the present invention not only produces useful silicate fertilizer from industrial waste that is difficult to process, but also recovers metallic iron to realize more efficient use of resources. Example Fly ash, which is coal ash discharged from a thermal power plant, and converter slag generated during the manufacturing of ordinary steel, having the following composition (wt%), were used as raw materials.

[Table] * Atomic absorption method 〓

Measured by 〓

** Vanadomolybdic acid method〓
The above raw materials were mixed in various proportions and melted using a high frequency furnace, and the melt was poured into water and rapidly cooled. (1) 600g of coal ash and 175g of converter slag (77:23) were mixed and melted at 1585℃. The melt was viscous and had low fluidity. By water grinding, 560 g of a sandy product was obtained. Its components and eluate are as follows.

[Table] (2) 480 g of coal ash and 320 g of converter slag (6:4) were mixed and melted at a temperature of 1450°C, but the molten material had a low viscosity and could be tapped even at 1300°C. Since spherical metallic iron was found mixed in the sandy material obtained by water pulverization, it was sorted by magnetic force. The products obtained were 705 g of glassy material and 32 g of metallic iron. The composition of the glassy material and the eluted content are shown below.

[Table] (3) 320g of coal ash and 480g of converter slag (4:6) were mixed and heated to 1450℃. In this case as well, the melt had a low viscosity and was mobile even at 1300°C. A considerable amount of metallic iron particles was found in the granulated product, amounting to 32 g, and 670 g of glassy material produced.

[Table] (4) 120 g of coal ash and 480 g of converter slag (2:8) were mixed and melted. The viscosity of the melt was somewhat high and tapping was carried out at 1450°C. 510 g of sandy glassy material and 42 g of granular metallic iron were obtained.

【table】

Claims (1)

[Claims] 1. Coal ash and converter slag are mixed and melted, at least a portion of the iron oxide in the ash and slag is reduced to metallic iron from the carbon content in the ash, and the molten product is A vitreous material containing silicic acid, magnesium and phosphoric acid in a form useful as a fertilizer is obtained in a crushed state by cooling with water, from which metallic iron is separated and recovered. A method of producing fertilizer. 2 Coal ash and converter slag in a weight ratio of 8:2~
2. A method for producing a silicic acid fertilizer according to claim 1, comprising mixing and melting in a ratio of 2:8, preferably 6:4 to 4:6. 3. A method for producing a silicate fertilizer according to claim 1, which comprises transferring converter slag obtained in a molten state from the steelmaking process to an arc furnace and melting it together with coal ash there.