JPS6342684B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a slag foaming control method that can be suitably implemented to suppress slag foaming in a metal refining furnace such as a steelworks. [Prior art] Hot metal tapped from a blast furnace is often subjected to desiliconization treatment in a hot metal pot or torpedo car, but the reaction at that time generates a large amount of CO gas.
The slag deposited in the upper layer is foamed. When this bubbling becomes large, slag overflows from the hot metal ladle, etc., making it impossible to inject any more hot metal, and transport efficiency may decrease. The causes of this slag bubbling phenomenon are (1) viscosity, especially at the surface of the slag, (2) surface tension of the slag, (3) presence of suspended solid particles, and (4) oxidation of suspended carbon-saturated iron particles. These factors are explained below. ●Slag viscosity The relationship between the temperature and viscosity of molten slag is that when the slag temperature is 1500℃ or higher, the viscosity hardly changes;
When the temperature drops below 1500°C, the temperature rises rapidly, and in extreme cases, when the temperature drops by 170°C, the viscosity increases by about 8 times. In particular, since the slag in the foam-like surface layer does not undergo convection, the temperature drop is more significant than in the interior of the slag, which is considered to be a factor in increasing the viscosity and increasing foaming. ●Surface tension of slag Some of the SiO ₂ present in slag is a surface active substance such as SiO ₄ ⁴ and is adsorbed to the surface layer, and Fe ₂ O ₃ , P ₂ O ₅ , etc. contained in slag are is also a surface active substance and is adsorbed on the surface layer along with SiO ₄ ⁴ and the like. Surface tension plays a large role in the stability of slag foam, and the presence of these surface-active substances lowers the surface tension and makes the foam more difficult to break. In the case of slag, unlike the case of general aqueous solutions, it is known that the higher the temperature, the greater the surface tension, and furthermore, the higher the temperature, the shorter the life of the foam. ●Presence of suspended solid particles There are suspended solid particles such as unreacted CaO in the slag, but these exist in the foam layer.
This prevents the sedimentation and separation of the slag in the foam layer, making the foam layer difficult to destroy. ● Oxidation of suspended fine particles of carbon-saturated iron There are fine particles of carbon-saturated iron in the slag, and in the slag layer with a high oxygen potential, the carbon content oxidizes to CO gas, but suspended carbon-saturated iron particles It is thought that gas generation occurs rapidly because the particles are small. The slag bubbling phenomenon referred to here is a combination of the above-mentioned bubbling factors (1) to (4), and the bubbling phenomenon occurs rapidly, resulting in the foam layer overflowing to the outside of the system. It refers to a phenomenon. That is, there is a significant increase in slag viscosity due to a decrease in temperature, a decrease in surface tension due to the presence of surface viscous substances, and an increase in internal gas pressure due to the rapid generation of CO gas due to the oxidation of carbon in carbon-saturated iron. It can be thought that these equilibriums are instantaneously broken, and the gas suddenly protrudes to the outside, causing slag foam to overflow. To prevent this slag foaming phenomenon, measures have been taken to date, such as adjusting operating conditions, destroying the foam layer by blowing gas, thermally destroying it with a burner, and increasing the slag surface temperature by adding pulp waste. However, a satisfactory solution has not yet been reached. Here, the present inventors previously applied for a patent application filed in 1983-
No. 274493 (Japanese Unexamined Patent Publication No. 136512/1983) proposed an anti-foaming agent in which metal aluminum powder and carbonaceous powder were mixed with a binder. That is, when this inhibitor is applied to the slag surface, the heat of combustion of the carbonaceous material and the heat of reaction between the iron oxide in the aluminum slag lowers the viscosity of the slag surface, thereby reducing bubbling. However, one problem with this inhibitor was that it should have a sustained effect. [Object of the Invention] An object of the present invention is to provide a method for controlling slag foaming that can solve the above-mentioned problems and can extremely effectively prevent slag foaming and maintain the effect. There is a particular thing. [Summary of the invention] The gist of the present invention for achieving the above object is as follows:
In order to suppress the bubbling phenomenon of slag that occurs in metal smelting furnaces, a first material is a mixture of a light metal powder with a specific gravity of 5 or less and a carbonaceous powder, and a second material is a mixture of a carbonaceous powder and a calcium chloride powder. This is a method for controlling bubbling of slag, which is characterized by sequentially injecting the substances No. 2 and 2 onto the slag surface. [Embodiments of the Invention] In the method according to the present invention, a slag is produced using a first substance that is a mixture of a light metal powder and a carbonaceous substance powder, and a second substance that is a mixture of a carbonaceous substance powder and a calcium chloride powder. This suppresses foaming. Here, the first substance plays a leading role in preventing slag foaming, and the second substance plays a role in sustaining the effect. That is, when the first substance is added to the slag surface, it reduces the viscosity of the slag surface by transmitting the heat of combustion of the carbonaceous material and the heat of reaction between the light metal iron oxide in the slag to the slag surface. act. In addition, in the second substance that is subsequently added, calcium chloride melts with the CaO in the slag along with the combustion heat of the carbonaceous substance, producing a low melting point substance that reduces the gas pressure inside the slag and prevents the foaming of the slag. do. Metals with a specific gravity of 5 or less can be used as light metal powders, such as aluminum, magnesium, silicon,
Titanium, etc. and alloys containing these can also be used.
Figure 1 shows the relationship between specific gravity, free energy of oxide formation, and heat of formation for each metal.
In the figure, the ○ mark is the free energy at 1000℃, and the △ mark is the heat of formation at room temperature. Therefore, from this Figure 1, metals that are more reactive with oxygen than iron oxide, that is, metals whose free energy is smaller than that of iron oxide and whose heat of formation is smaller than iron oxide, include manganese, aluminum, silicon, Mention may be made of light metals such as beryllium, magnesium, calcium and titanium. However, considering actual economic effects and ease of handling, aluminum, magnesium, silicon, and titanium are preferable as the metals to be added, and aluminum ash is the most desirable as it is economically available. . Examples of the carbonaceous material include coke, coal, tar, etc., and so-called coke breeze is most suitable in terms of handling and economy. Calcium chloride used at the same time includes anhydrous salts and dihydrate salts, but dihydrate salts are economically effective. This is because when poured onto the slag surface, the volume expands approximately 1000 times when the crystal water, etc. contained therein evaporates, and is expected to mechanically destroy the slag foam. Note that the particle size of each powder of carbonaceous material, light metal, and calcium chloride is preferably 5 mm or less in terms of reactivity with slag. When adding the first substance to the slag surface, the light metal added together with the carbonaceous substance causes a so-called thermite reaction with iron oxide in the slag, similar to the case of aluminum, and the heat of reaction is as shown in the table below. . Al Mg Si Ti 3897 3354 3235 2054 (Kcal/Kg) As is clear from these values, there is no large difference in the heat of reaction of each light metal with iron oxide. Therefore, from an economic standpoint, aluminum is the most suitable light metal. Next, a case where coke is used as the carbonaceous material of the first substance and aluminum or aluminum ash is used as the light metal will be described in detail. When the first substance consisting of coke and aluminum is poured onto the slag surface, C + O ₂ = CO ₂ ...... (1) 2Al + 3FeO = Al ₂ O ₃ ...... (2), and the reaction heat in equation (1) is 7837 Kcal. /Kg, the reaction heat in equation (2) is 3897Kcal/Kg, and the generated heat is transferred to the slag surface. This heat reduces the viscosity of the slag surface. Therefore, the blending ratio of the carbonaceous material and the light metal powder has an important meaning in carrying out the above-mentioned reaction. That is, if the light metal powder is less than 5% relative to 100% carbonaceous material, no heat of reaction with iron oxide can be expected, and if it is more than 80%, the total amount of heat will be insufficient. Next, by introducing the second substance onto the slag surface, the calcium chloride (CaCl ₂ ) contained in the second substance is released together with the combustion heat of the carbonaceous substance contained.
releases water and becomes steam, but the volume increases by approximately 1000 times and mechanically destroys the foaming of the slag. Calcium chloride then fuses with calcium oxide (CaO) in the slag to produce a low melting point substance, so
The surface of the slag softens, lowering the internal gas pressure, and suppressing foaming of the slag. Figure 2 shows a phase diagram of the CaCl ₂ -CaO system.
At °C _CaCl2 dissolves 20% CaO. If there is more CaO than that, CaO will form primary crystals in the melt.
is precipitated, but since the purpose is to prevent bubbling by lowering the internal gas pressure, a solid phase may be present. Calcium chloride used in the second substance is
As already mentioned, a dihydrate salt is preferable, and the addition ratio is determined from the thermal equilibrium. In other words, when a second substance is introduced onto _the slag surface, CaCl ₂ 2H 2 O decomposes due to the reaction CaCl ₂ 2H ₂ O = CaCl ₂ + 2H ₂ O, producing 2 moles of H ₂ along with CaCl ₂ . do. Therefore, the blending ratio of calcium chloride in the second substance is determined from the balance between the heat of combustion of the carbonaceous material, the sensible heat of _CaCl2 , and the sensible heat of vaporization of the generated water. In other words, the amount of heat required to heat the slag from 25℃ to 1400℃ for CaCl ₂ is 0.76Kg.
353Kcal/Kg, _H2O : 1388Kcal/about 0.24Kg
Kg, the sensible heat of calcium chloride is 601 Kcal/Kg. Therefore, for example, if the carbonaceous material is coke, its calorific value is 6500 Kcal/Kg, and the relationship between the blending ratio of coke and calcium chloride and the calorific value of the second substance can be shown in the following table.

[Table] As is clear from this table, as the blending ratio of calcium chloride increases, the calorific value of the second substance decreases, but in order to make the total calorific value of the second substance 4500Kcal/Kg, It is appropriate that the weight ratio of calcium chloride to 100% coke is 1 to 25%. In addition, when we implemented the above-mentioned slag foaming control method in the desiliconization treatment process of hot metal and observed the state of the slag level using a level meter, the slag level decreased as shown in Figure 3, and the slag foaming was ensured. It was confirmed that this was suppressed. [Effects of the Invention] As explained above, the slag foaming control method according to the present invention partially controls the slag temperature by sequentially introducing the first substance and the second substance into the slag in the upper layer of hot metal. It increases the viscosity of the slag and lowers its viscosity, making it easier for the foam to be destroyed and the gas inside to escape from this part, and the effect is sustained, so the foaming of the slag can be effectively reduced.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the free energy of oxide formation and heat of formation with respect to the specific gravity of each metal, Figure 2 is a phase diagram of CaCl ₂ -CaO, and Figure 3 is a graph of measured slag level values. .

Claims (1)

[Claims] 1. In order to suppress the bubbling phenomenon of slag that occurs in a metal smelting furnace, a first substance that is a mixture of a light metal powder with a specific gravity of 5 or less and a carbonaceous powder, and a carbonaceous powder and chloride The second mixture with calcium powder
A method for controlling bubbling of slag, characterized by sequentially injecting the following substances onto the slag surface. 2. The method for controlling foaming of slag according to claim 1, wherein the carbonaceous material used in the first material and the second material is coke, coal, or tar. 3. Calcium chloride used in the second substance is an anhydrous salt or a dihydrate salt. Claim 1
The method for controlling foaming of slag described in Section. 4 The blending ratio of the light metal powder in the first substance is:
Weight ratio of 5 to 80 parts of light metals per 100 parts of carbonaceous material
A method for controlling foaming of slag according to claim 1. 5 The blending ratio of the carbonaceous material and calcium chloride used in the second substance is the weight ratio of the carbonaceous material to the calcium chloride.
The method for controlling foaming of slag according to claim 1, wherein the amount of calcium chloride is 1 to 25 parts per 100 parts. 6. The method for controlling foaming of slag according to claim 1, wherein the particle size of each powder of the carbonaceous material, light metal, and calcium chloride is 5 mm or less.