JPH08926B2 - Mixed sintered body composed of silicon carbide and coke - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coke-carbonization that can be used as a silicon source and a fuel when producing cast iron in a cupola furnace and when producing pig iron for casting 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 method for producing cast iron in a cupola furnace, in addition to pig iron for casting, steel scrap, and bare metal such as pig iron, a raw material containing a metal element such as silicon and metal is used together with coke for casting. It is charged into a cupola furnace, the coke for casting is burned by the air sent into the furnace, and the inside of the furnace is heated to a high temperature to melt the ingots. Further, the method for producing pig iron for castings containing high silicon pig iron is to charge iron ore, coke, silicic acid compound, etc. into a blast furnace and send air into the furnace to burn the coke and keep the furnace at a high temperature and strongly reducing atmosphere. It is produced by reducing and dissolving iron ore and silicic acid compounds. Therefore, the coke used in these production methods is pulverized and blended with raw material coal / petroleum coke and pitch as raw materials, and cuts off air at a high temperature of pyrolysis temperature or higher in a coke oven, i.e., 950 to 1100 ° C. A solid cytoplasmic distillation residue produced by heating for about 17 to 24 hours,
Its main component is carbon. However, when producing castings in a cupola furnace, when using metal ingots with a low silicon content such as steel scrap, the shortfall of the required Si value to be contained in the cast iron molten metal must be supplemented. Therefore, silicon iron, high silicon pig iron, silicon carbide briquette for metallurgy, etc. are usually added and charged, and the contents of carbon and silicon must have predetermined values in order to obtain a good quality cast iron melt. Is essential. The silicon iron and high-silicon pig iron replenished as the above-mentioned shortage of the Si value have different melting points from the ingots charged in the cupola furnace at the same time, so the melting timing does not match,
Since the speed at which the metal ingots descend in the furnace is not constant, the Si content in the molten metal varies, and the silicon carbide briquette for metallurgy uses cement as a binder, and the temperature at which metal ingots melt Since it disintegrates and disperses at low temperature, it is not hoped that a certain amount of silicon carbide corresponding to the amount of metal ingot will dissolve in the molten metal, and in this case also avoid variations in the Si content. I can't. In addition, coke is used as a fuel source as well as a carbon source, as well as a reducing agent, but when coke burns into CO ₂ or CO gas and is released outside the furnace, a large amount of Have a fever 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 between C and Si per unit weight, but the amount of oxygen used for combustion is C compared to Si. Since it is large (Si: C = 28: 12), C requires a larger amount of air to be blown into the furnace than Si, and therefore the thermal efficiency of the furnace is not good. Furthermore, the carbon in the coke in the cupola furnace reacts with the oxygen in the blown air and reacts with C such as O _Z + C = CO _Z + 97.8Kcal / Mol.
It becomes O _Z gas. The heat generated melts the metal,
It is estimated that the coke (called bed coke) held up to a certain height in the cupola furnace rises to 1700-1800 ℃. Under such a high temperature, some CO ₂ gas comes into contact with the heated bed coke and CO _Z + C = 2CO−3.
An endothermic reaction such as 7.4 Kcal / Mol occurs to change to CO gas and lower the temperature inside the furnace. In this way, a part of the combustion heat of the coke is absorbed, so that a decrease in thermal efficiency cannot be avoided.

(Problems to be solved) The present inventors have improved the above-mentioned drawbacks and used as a silicon supplement source and a fuel source when producing cast iron in a cupola furnace and when producing pig iron for casting containing high silicon pig iron. As a result of various studies on possible raw materials, the present invention has been completed, and an object of the present invention is to provide an insertion material useful as a silicon supplement and a fuel used when producing cast iron and pig iron for casting.

(Means for Solving Problems) The present invention is a powdery granular mixed sintered body composed of a carbon raw material for coke production and silicon carbide, wherein the carbon raw material for coke production is coal, petroleum coke and pitch. As described above, these raw materials are dry-distilled in a strongly reducing atmosphere, and any raw material can be used in the present invention.On the other hand, silicon carbide is generally used as a raw material for a batch type electric resistance furnace with silica sand. It is made by charging petroleum coke and heating it to a temperature of 1600 ℃ to 2500 ℃. Silicon carbide forms β crystals at low temperatures and α at high temperatures
However, the silicon carbide used in the present invention is α
Not only crystal and β crystal can be used, but also silicon carbide-containing substances generated in the hearth of a furnace that manufactures silicon iron and metallic silicon, heating elements containing silicon carbide, furnace materials, and scrap ceramics are also used. it can.

However, the method for producing the sintered body of the present invention is similar to the method for producing coke, in which coke raw material carbon and the like and silicon carbide are charged into a coke oven and air is shut off.
Sintered by heating at a temperature of around 950 to 1100 ° C for about 17 to 24 hours. Silicon carbide may be melted in a coke oven or may undergo a chemical reaction with other substances to be altered. Instead, silicon carbide and carbon become a sintered body in a state of being uniformly dispersed.

The amount of silicon carbide added can be arbitrarily changed depending on the purpose of use of the sintered body. That is, as described above, the sintered body of the present invention may be used as a silicon source in the production of cast iron or may be used as a substitute for coke for casting, and the sintered body of the present invention always exhibits both functions. In Although,
When the former is mainly used, the content of silicon carbide in the sintered body is 50
% Or more, and the particle size of silicon carbide is coarse particles of 100 μ or more, and when the latter is mainly used, the silicon carbide content is a low rate composition of about 15%. Granularity is also 10
A fine powder having a size of 0 μ or less is preferable. The sintered body of the present invention may be used alone or in combination with other silicon carbide and coke.

Explaining the usage of 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 a bed coke previously charged in a cupola furnace, the fuel coke, pig iron, and steel scrap. When the coke is burned by sending air from the tuyere provided at the bottom of the furnace body, the coke is directly above the coke when the coke is burned by packing the return material, the metal such as the dead pig iron, and the lime or limestone for slag The ingots melted in step 1 become droplets and drop into the molten metal pool while passing through the gap of the bed coke, but the droplets contact the silicon carbide exposed on the surface of the sintered body. However, since the dissolution rate of silicon carbide in the molten metal is several times faster than that of carbon (graphite), the droplets in contact with silicon carbide quickly dissolve and absorb the fine particles of silicon carbide. Then, when the droplets that absorb silicon carbide and the content of silicon and carbon becomes γich further drop and pass through the high temperature portion of the tuyere with excess oxygen, silicon and carbon are oxidized preferentially over iron. Therefore, the generation of iron oxide in the molten metal, that is, the oxidation reaction of the target cast iron can be suppressed. Further, as described above, the sintered body acts as a fuel like coke, but since the oxidation product of silicon in the sintered body is solid silicon oxide, gaseous carbon monoxide or Unlike carbon dioxide, it does not dissipate into the atmosphere with sensible heat, and the required oxygen amount per unit weight is smaller than that of coke, so air consumption can be significantly reduced, and therefore unnecessary nitrogen is introduced. The thermal efficiency of the furnace is increased because the quantity is reduced. As a result, the temperature inside the furnace can be increased, which makes it possible to generate high-temperature molten metal or slag with good fluidity, and therefore, it is possible to mix high-quality steel scrap with a low impurity content at a high rate. By increasing the amount of lime, a highly reactive basic slag is produced, and oxides and sulfur in the bath water are reduced, resulting in high quality cast iron. Further, since silicon carbide is uniformly contained in the sintered body of the present invention, the amount of carbon exposed on the surface of the sintered body is clearly smaller than that of coke, so that the amount of CO gas generated by the above-mentioned reduction reaction is small. Since the amount of exposed carbon is reduced, there is an advantage of reducing heat loss.

In actual operation, just before the tuyere, CaO was blown from the tuyere with SiOz adhering to the surface of the burned sintered body.
Low melting SiO combined with fine powder and CaO charged from the charging port
Generating z · CaO and separating and removing it is effective in promoting the combustion reaction of silicon carbide. In addition, since the generation of SiOz · CaO reduces the free SiOz in the slag and lowers the SiOz activity, the progress of the endothermic reaction of SiOz + 2C = Si + 2CO can be suppressed, and heat loss and CO gas increase can be prevented.

 Hereinafter, the present invention will be described with reference to examples.

(Example) 4ton / h, acidity, dehumidification, water-cooled cupola furnace was used 1. Solid carbon 73.2% and silicon carbide 15.1% sintered body of the present invention was blended with materials such as pig iron scraps, and as a comparison. The coke for casting, which has been used conventionally, was used instead of the sintered body, and the other components were all operated in the same manner. Table 1 shows the results of averaging the operating values for one month and comparing them.

(Effect) As described above, according to the present invention, by using the powdery granular mixed sintered body made of silicon carbide and coke when producing cast iron in the cupola furnace and producing pig iron for casting, The effect is that a stable molten metal of the component Si can be obtained and the thermal efficiency of the furnace can be increased.

Claims (2)

[Claims] 1. A powder-granular mixed sintered body for producing pig iron and cast iron, which comprises silicon carbide and coke. 2. Air is cut off between silicon carbide and coke.
A method for producing a powdery or granular mixed sintered body for producing pig iron and cast iron, which comprises sintering at a temperature of around 0 to 1100 ° C.