JPS62256765A - Mixed sintered body comprising silicon carbide and coke - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a carbonized coke that can be used as a silicon source and fuel in the production of cast iron in cupolas and in the production of foundry pig iron containing high-silicon pig iron. The present invention relates to a silicon sintered body (hereinafter simply referred to as a sintered body) and a method for manufacturing the same.

(Prior art) Normally, in the production method of cast iron for cupolas, in addition to base metals such as foundry pig iron, steel scrap, and waste iron, raw materials containing metal base materials such as silicon and iron are mixed into foundry coke. The foundry coke is then charged into a cupola, and the foundry coke is combusted by the air sent into the furnace, heating the inside of the furnace to a high temperature and melting the base metals. In addition, the method for producing foundry pig iron containing high-silicon pig iron involves charging iron ore, coke, silicic acid compounds, etc. into a blast furnace, and blowing air into the furnace to burn the coke and maintain a high temperature and strongly reducing atmosphere inside the furnace. It is produced by reducing and dissolving iron ore and silicic acid compounds. Therefore, the coke used in these manufacturing methods is made from raw coal, petroleum coke, and pitch, which are pulverized and blended in a coke oven at a temperature at or above the pyrolysis temperature, i.e., 950 - 00°C, with air shut off. and about 1
It is a solid cytoplasmic carbonization residue produced by heating for about 7 to 24 hours, and its main component is carbon. However, when producing castings for cupolas and using raw metals such as steel scraps with low silicon content, it is necessary to replenish the shortage of the required Si value to be included in the molten cast iron. Therefore, silicon iron, high-silicon pig iron, metallurgical silicon carbide briquettes, etc. are usually added and charged.
In order to obtain a molten metal of 5 iron, it is essential that the contents of carbon and silicon have predetermined values. The silicon iron and high-silicon pig iron supplied to compensate for the above Si value deficiency have different melting points from the ingots charged into the cupola furnace at the same time, so their melting times do not match, and the ingots are Because the rate of descent in the furnace is not constant, the Si content in the molten metal varies,
In addition, silicon carbide briquettes for metallurgy use cement as a binder and will disintegrate and scatter at a temperature lower than the melting temperature of the base metals, so a certain amount of silicon carbide will be in the molten metal commensurate with the amount of melted base metals. It is undesirable that the 31 content be dissolved in the 31 content, and in this case, variations in the 31 content cannot be avoided. In addition, coke is used as a reducing agent, a fuel source, and a carbon filler.
Coke has a large amount of sensible heat when it burns and becomes CO□ or CO gas and radiates out of the furnace. For example, when compared with the combustion reaction of Si in silicon carbide, there is almost no difference in the heat of formation of the oxidation reaction per unit weight between C and SL, but the amount of oxygen required for combustion is greater for C than for Sj. Because it is large (
Si:C=28: 12) C requires a larger amount of air to be blown into the furnace than Si, and therefore has the disadvantage that the thermal efficiency of the furnace cannot be said to be good. Furthermore, the carbon in the coke in the cupola furnace reacts with the oxygen in the blown air, resulting in ○, + C = CO2 + 97.8Kca.
It becomes CC2 gas like l/Mat. The metal is heated and melted by this heat generation, and the coke held at a certain height in the cupola furnace (called bed coke) is 1
It is estimated that the temperature will rise to 700-1800°C. At such high temperatures, some CO2 gas comes into contact with the heated bed: CO2+C=2GO-37°4
It causes an endothermic reaction such as Kcal/Mol and turns into CO gas, lowering the temperature inside the furnace. In this way, part of the combustion heat of coke is absorbed, so a decrease in thermal efficiency is unavoidable.

(M. Problems to be Solved) The present inventors have improved the above-mentioned drawbacks, and the silicon replenishment source and fuel source when producing cast iron in a cupola furnace and when producing pig iron for foundry including high silicon pig iron. As a result of various studies on raw materials that can be used as a material, the present invention was completed.The purpose of the present invention is to provide an insert material that is useful as silicon replenishment and fuel for use in the production of cast iron and foundry pig iron. There is something to do.

(Means for Solving the Problems) The present invention is a mixed sintered body consisting of a carbon raw material for coke production and silicon carbide, wherein the charcoal for coke production and the materials No. 11 are coal, petroleum coke, and pitch; As mentioned above, any of these raw materials obtained by carbonization under a strongly reducing atmosphere can be used in the present invention. On the other hand, silicon carbide is generally produced by combining raw materials silica sand and petroleum coke in a batch-type electric resistance furnace. It is made by charging and heating to a temperature of 1600°C to 2500°C. Silicon carbide forms β crystals at low temperatures and 1 crystals at high temperatures.
However, the silicon carbide used in the present invention can be used in either one or no silicon carbide, and can also be used to produce silicon carbide-containing substances or silicon carbide produced in the hearth of a furnace for producing silicon iron or metal silicon. It is also possible to use heating elements, furnace materials, ceramic scraps, etc.6. However, the method for producing the sintered body of the present invention is similar to that for coke production.
Coke coking coal etc. and silicon carbide are charged into a coke oven, air is shut off, and the temperature is around 950 to 1100℃.
The silicon carbide was heated and sintered for 24 hours, and the silicon carbide did not melt in the coke oven or undergo chemical reactions with other substances to change its quality, and the silicon carbide and carbon were uniformly dispersed. It becomes a sintered body in this state.

The amount of silicon carbide added can be arbitrarily changed depending on the intended use of the sintered body. That is, as mentioned above, the sintered body of the present invention may be used as a silicon source in the production of cast iron or as a substitute for foundry coke, and the sintered body of the present invention always exhibits both functions. However, if the former is used mainly, the silicon carbide content in the sintered body is 50
% or more, and the particle size of silicon carbide is 100μ
If the latter is the main type, the silicon carbide content should be as low as about 15%, and the particle size should preferably be in the form of a fine powder of about 100 μm or less. The sintered body of the present invention may be used alone or in combination with other silicon raw materials and coke.

To explain how to use the sintered body of the present invention and the inside of the furnace due to the presence of the sintered body, the sintered body of the present invention is placed on top of bed coke charged in advance in a cupola furnace as fuel coke, pig iron, and steel scrap. When the coke is combusted by blowing air through the tuyeres installed at the bottom of the furnace body, the coke is combusted by filling the base metals such as return material, waste pig iron, and slag-making lime or limestone in a layer at a certain ratio. The melted base metal becomes droplets and drips into the sump while passing through the gaps in the bed coke, and the droplets come into contact with silicon carbide exposed on the surface of the sintered body. However, since the dissolution rate of silicon carbide into molten metal is several times faster than that of carbon (graphite), droplets that come into contact with silicon carbide quickly dissolve and absorb fine particles of silicon carbide. Then, the droplets absorb silicon carbide and have a silicon and carbon content of γich. When they descend further and pass through the oxygen-rich high-temperature part at the tip of the tuyere, silicon and carbon are oxidized more preferentially than iron. Therefore, the production of iron oxide in the molten metal, that is, the oxidation reaction of the target cast iron can be suppressed. In addition, as mentioned above, sintered bodies act as a fuel in the same way as coke, but the oxidation product of silicon in sintered bodies is solid silicon oxide, so gaseous carbon monoxide and Unlike carbon dioxide, it does not dissipate into the atmosphere with sensible heat, and the amount of oxygen required per unit weight is smaller than that of coke, so air-based agents can be used with a significantly higher fx'6 concentration, thus eliminating unnecessary nitrogen. The thermal efficiency of the furnace is increased because the amount of feed is reduced. As a result, the temperature inside the furnace can be raised, which makes it possible to produce high-temperature molten metal and slag with good fluidity. By increasing the amount of iron, a highly reactive basic slag is created, which reduces oxides and sulfur in the bath water, resulting in the production of high-quality cast iron. Furthermore, since the sintered body of the present invention uniformly contains silicon carbide, the amount of carbon exposed on the surface of the sintered body is clearly less than that of coke, and therefore the CO gas generated by the above-mentioned reduction reaction is reduced. The amount is reduced by the amount of exposed carbon, which has the advantage of reducing black loss.

In addition, in actual operation, just before the tuyere, the Sun adhering to the surface of the burned sintered body was removed from the C injected from the tuyere.
It is effective to combine with aO fine powder and CaO introduced from the charging port to generate low-melting 5in2.CaO and remove it in advance in order to promote the combustion reaction of silicon carbide. In addition, the generation of 5in2・CaO is caused by free Sin in the slab,
As the activity decreases, SiO□12C decreases.
By suppressing the progress of the endothermic reaction of = Si + 2CO, it is possible to prevent black spots and an increase in CO gas.

The present invention will be explained below with reference to Examples.

(Example) 4 ton/h, acidic, dehumidifying, water-cooled cupola furnace used 1, fixed carbon of the present invention 7362%, silicon carbide 15.1%
The sintered body was blended with materials such as pig iron and steel scrap, and for comparison, conventional foundry coke was used instead of the sintered body, and the operation was carried out with all other formulations being the same. - Table 1 shows the results of comparing the average operating values between the two.

Table 1 (Effects) As described above, the present invention uses a mixed sintered body consisting of silicon carbide and coke when producing cast iron and foundry pig iron in a cupola furnace. This produces effects such as being able to obtain a stable molten Si and increasing the thermal efficiency of the furnace.

Claims (1)

[Scope of Claims] 1. Mixed sintered body for producing pig iron and cast iron made of silicon carbide and coke 2. Silicon carbide and coke are mixed with 950-1
A method for producing a mixed sintered body for producing pig iron and cast iron, characterized by sintering at a temperature around 100°C.