JPH10122753A - Combustion control method of melting furnace, and rotary melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion control method and a rotary melting furnace in which the heat efficiency is improved by making effective use of the chemical reaction between the combustion gas in the melting furnace and the raw material to be melted to reduce the melting time. SOLUTION: In a combustion control method of a melting furnace in with the raw material 8 to be melted comprising the iron source raw material and the composition regulating material is charged and burned with the fuel 32 and oxygen 33 to achieve the heating and melting, the in-furnace gas composition is directly detected, or the chemical reaction model to obtain the relationship of the chemical reaction of the in-furnace combustion gas with the raw material 8 to be melted in advance is prepared, and in the actual melting, the temperature of the raw material 8 to be melted is estimated on the basis of the chemical reaction model from the detected value of the discharged gas, and at least one of the feed quantity of the fuel 32 and oxygen 33 is determined so that the in-furnace reaction is the exothermic reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting furnace, and more particularly, to a rotary melting furnace in which oxygen and fuel are burned in a furnace, and the heat of combustion heats and melts a raw material charged in the furnace. A combustion control method and a rotary melting furnace.

[0002]

2. Description of the Related Art One of melting furnaces is a rotary melting furnace. It is mainly composed of a cylindrical furnace main body, a furnace body driving device, and a burner which are placed horizontally and rotate around the central axis, and the charged raw material rotates with the flame generated by the burner and the heat stored by the flame. It is heated and melted by heat transfer from the refractory wall. In recent years, as a burner fuel, a fuel in which pure oxygen is used in combination with a fluid fuel such as propane is becoming widespread in terms of improving energy efficiency, reducing exhaust gas, and expanding the range of use of raw materials. The combustion adjustment of the burner in the rotary melting furnace is performed by adjusting the opening of a fuel or oxygen valve connected to the burner. For example, in the case of melting for cast iron, the valve opening of each of the fuel and oxygen is adjusted so that the flow rates obtained empirically through the operation are adjusted based on the mixing ratio of the iron raw material and the auxiliary material among the molten raw materials to be charged. The flow rates of fuel and oxygen may be constant throughout the entire dissolution process or may be varied, but are varied in several steps, and are only stepwise changed to a predetermined state. . Here, the auxiliary material refers to a material charged together with the iron raw material in order to adjust the components of the molten metal and the atmosphere in the furnace.

[0003]

FIG. 5 shows the weights of Fe, C, Si and Mn components contained in the entire iron raw material and auxiliary materials charged in the rotary melting furnace in the case of melting cast iron, and the completion of melting. Examples of these components left behind in the melt as well as the weight lost are shown. In particular, the loss ratio of C is large, and a weight almost equivalent to the total amount of the carburized material in the added auxiliary material is consumed as a result of reacting with the fuel and oxygen. Although the related chemical reaction will be described later, the consumed amount is discharged as CO or CO ₂ , and the degree of the endothermic reaction and the exothermic reaction at this time greatly affects the dissolution efficiency. Therefore, in order to enhance the dissolution efficiency, it is important to supply a fuel or oxygen flow rate to the burner so that the reaction of the carburized material promotes an exothermic reaction. However, the reaction mode and the reaction rate vary greatly depending on the temperature and the composition of the atmosphere gas in the furnace. An object of the present invention is to provide a combustion control method for maintaining a high combustion efficiency in accordance with a combustion state in a melting furnace, and a rotary melting furnace using the same.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a combustion control method for a melting furnace, in which a raw material is charged and a fuel and oxygen are burned to melt by heating. Determining a supply flow rate of at least one of fuel and oxygen based on the flow rate and at least the CO gas concentration of CO and H ₂ gas in the furnace so that the reaction in the furnace becomes an exothermic reaction. I have. In a high-temperature state in which CO and H ₂ are generated, there is a relationship that the gas concentration of CO is higher than the gas concentration of H _2. However, the supply flow rate of at least one of fuel and oxygen is preferably determined based on the concentrations of both CO and H ₂ gas so that the reaction in the furnace becomes an exothermic reaction. Further, the combustion control method for a melting furnace of the present invention is a combustion control method for a melting furnace in which a melting raw material is charged and fuel and oxygen are burned to heat and melt, wherein CO, H ₂ , and O ₂ gas in the furnace are , when CO or concentration of H ₂ is equal to or higher than a set value, the fuel so that the supply flow rate of fuel and oxygen, the reaction in the furnace on the basis of at least CO gas concentration of CO and H ₂ gas is an exothermic reaction Or, determine the supply flow rate of at least one of oxygen, and if it is less than the set value, compare whether the O ₂ concentration is equal to or more than the set value. The amount of unreacted O ₂ is calculated from the concentration of O ₂ in
_{(2) The} method is characterized in that the supply flow rate of at least one of fuel and oxygen is determined so as to decrease the concentration. Note in the above, first a determination is CO or concentration of H _2, although said to perform the process of determination of the O ₂ concentration when CO or concentration of H ₂ was below the determination reference value, the gas concentration meter If the response characteristics differ depending on the type of gas and the O ₂ concentration detection is faster, the O ₂ concentration determination may be performed first.

Further, the method for controlling combustion of a melting furnace according to the present invention finds the relationship between the combustion gas in the furnace and the chemical reaction of the melting raw material in the melting furnace in which the raw material is charged and the fuel and oxygen are burned and heated and melted. A chemical reaction model is created in advance, and the temperature of the dissolved raw material and the composition of the gas in the furnace are calculated based on the composition of the detected exhaust gas based on the chemical reaction model, so that the fuel in the furnace becomes an exothermic reaction. Alternatively, at least one of the supply flow rates of oxygen is determined. In addition,
It is preferable to detect the CO and CO ₂ concentrations of the exhaust gas and calculate the temperature of the dissolved raw material and the composition of the gas in the furnace from the ratio based on a chemical reaction model. Further, the combustion control method for a melting furnace according to the present invention is a combustion control method for a melting furnace in which a melting raw material is charged and fuel and oxygen are burned and heated and melted, wherein a relationship between a combustion gas in the furnace and a chemical reaction of the melting raw material is determined. The chemical reaction model to be obtained is created in advance, and the concentrations of CO, CO ₂ , and O ₂ in the exhaust gas are detected. When the CO concentration is equal to or higher than the set value, the chemical reaction model is also obtained from the ratio of the CO and CO ₂ concentrations. In addition, the temperature of the dissolved raw materials and the composition of the gas in the furnace are calculated so that the reaction in the furnace becomes an exothermic reaction.If the reaction is less than the set value, the O ₂ concentration is compared with the set value, and if it is higher than the set value, Calculates the amount of unreacted O ₂ from the supply flow rates of fuel and oxygen and the concentration of CO ₂ and O _{2 in} the exhaust gas, and calculates the amount of fuel or oxygen based on the supply flow rates of fuel and oxygen so that the O ₂ concentration decreases. Determining the supply amount of at least one of That. In the above description, it is described that the determination of the CO concentration is performed first, and the process of determining the O ₂ concentration is performed when the CO concentration is lower than the determination reference value. For example, when the O ₂ concentration detection is earlier, the O ₂ concentration determination may be performed first.

Further, according to the present invention, there is provided a combustion control method for a melting furnace, in which a supply process of fuel and oxygen from the start of melting determined by any one of the combustion control methods of the present invention is stored in a storage device. Is characterized in that the stored fuel and oxygen supply process is regenerated to supply fuel or oxygen. Further, it is preferable that the above-mentioned dissolved raw material is an auxiliary raw material containing an iron raw material and at least a carburizing material. Further, the rotary melting furnace of the present invention is a rotary melting furnace in which a melting raw material is charged and fuel and oxygen are burned to be heated and melted. In the rotary melting furnace, a gas concentration meter for detecting the concentration of gas generated in the furnace is provided. A flow rate control valve for controlling the flow rate of fuel and oxygen, a flow rate control valve regulator for inputting a signal of the detector and outputting an opening control command to the flow rate control valve, An arithmetic and control unit is provided which inputs a detected value, performs an arithmetic processing on a supply flow rate command value of at least one of fuel and oxygen, and outputs it to the flow control valve regulator. It is preferable that the arithmetic and control unit outputs a supply flow rate command value of at least one of fuel and oxygen to the flow rate control valve regulator, stores an output process, and reproduces the output process in the subsequent dissolution.

[0007]

Embodiments of the present invention will be described below with reference to a case where cast iron is melted in a rotary melting furnace. (Embodiment 1) FIG. 1 shows a cross section of a rotary melting furnace and a combustion control system of a gas burner. A furnace body 5 having a cylindrical body 1 and conical parts 2 and 3 connected to both ends thereof and rotating around a central axis, and a molten fuel charged in the furnace body 5 is supplied with a fluid fuel by oxygen. Burner 6 to burn and melt
And a chimney-shaped exhaust passage 7 for allowing combustion exhaust gas to escape to the outside, and a charging machine (not shown) for charging the raw material 8 and the like into the furnace body 5. In this description, propane gas and oxygen are used as burner fuels, but methane gas, butane gas, or kerosene may be used instead of propane gas.

An opening 9 at one end of the furnace body 5 serves as a burner mounting port, and an opening 10 at the other end of the furnace body 5 serves as a charging port for the melting raw material 8 and an exhaust gas outlet. Reference numeral 11 denotes a tap hole provided in the conical portion 3 of the furnace body 5, which is closed except when tapping. A detector 40 for detecting the gas concentrations of CO, H ₂ , and O ₂ in the furnace is attached to the other end opening 10 side, and connected to a converter 42 via a signal line 41. The converter 42 constitutes a gas concentration meter in combination with the detection unit 40, and converts a signal detected by the detection unit 40 into a gas concentration value and outputs the gas to the outside.

Here, the burner 6 has a structure having a fuel injection port in the center and an oxygen supply port on the outer periphery. A fuel and oxygen supply system is connected upstream of the burner 6, and an oxygen flow control valve 30 of the oxygen supply system and a fuel flow control valve 31 of the fuel supply system are connected to each other. An oxygen supply source 32 is connected upstream of the oxygen flow control valve 30, and a fuel supply source 33 is connected upstream of the fuel flow control valve 31.

The oxygen flow control valve 30 and the fuel flow control valve 31 have flow control valve regulators 34 and 35, respectively.
Are connected, and each flow control valve regulator 34, 35
Are flow rate instruction signal lines 36 and 37 from the arithmetic and control unit 20.
Is connected. The arithmetic and control unit 20 is connected to a converter 42 of the gas concentration meter by a signal line 43, and based on the detected gas concentration, a command for an oxygen flow rate and a fuel flow rate to be supplied to the rotary melting furnace by a method described later. Calculate and output the value. The flow control valve regulators 34 and 35 respond to the flow command value from the arithmetic and control unit 20 with the oxygen pipe 40 and the fuel gas pipe 4.
The actual flow value from each of the flow detectors 38 and 39 provided in 1 is fed back to control the opening of the oxygen flow control valve 30 and the fuel flow control valve 31. Then, by controlling the opening degree, the flow rate of oxygen and the flow rate of fuel gas supplied to the burner 6 are controlled with high accuracy, and the calorific value and the composition of combustion gas to the burner in the furnace are controlled.

Next, a melting step for obtaining a molten metal for cast iron using the above-mentioned rotary melting furnace and a reaction of combustion gas in the rotary melting furnace will be described. First, the dissolving step will be described.
First, a predetermined amount of iron raw materials such as cast iron and steel chips and auxiliary materials are charged into the furnace body 5 through the opening 10. After attaching the chimney-shaped exhaust passage 7 to the opening 10, the burner 6 is set to the opening 9 at one end of the furnace body 5, ignited, and melting is started. The iron raw material is dissolved by being heated mainly by radiant heat and conduction heat from the refractory material 12 heated by the burner flame, radiant heat from the burner flame, and the like. The setting of the burner at the start of melting is a reference fuel gas flow rate determined according to the furnace and an oxygen flow rate for completely burning the reference fuel gas flow rate.

Next, the reaction of the combustion gas related to melting in the rotary melting furnace will be described. If the fuel is propane gas,
When the mixing ratio is 1.0, that is, in the case of complete combustion, the reaction between fuel and oxygen is represented by the following equation (1).

[Formula 1] C ₃ H ₈ + 5O ₂ → 3CO ₂ + 4H ₂ O + [+ Q1] Here, [] indicates the heat of reaction, + indicates an exothermic reaction, and − indicates an endothermic reaction. In the case of a rotary melting furnace, as the temperature of the melting raw material increases, the rightward direction of the reversible reaction represented by Formulas 2 and 3 between the carburizing material, one of the auxiliary materials, and the combustion gas, that is, CO ₂ and steam, is increased. The reaction becomes active.

## EQU2 ## C + CO ₂ {2CO + [− Q2] ”is used as a symbol representing a reversible reaction. The same applies hereinafter.

## EQU3 ## C + H ₂ O 方向 CO + H ₂ + [− Q3] The reaction to the right in Equations 2 and 3 is an endothermic reaction. That is, since heat is taken from the surroundings, the heat efficiency is reduced.

Here, when the mixing ratio of the burner fuel is insufficient for oxygen of 1.0 or less, some of the propane gas becomes unreacted, so that the total calorific value generated by burning the fuel decreases. As a result, the combustion gas and the carburizing agent cause endothermic reactions of Formulas 2 and 3, which further lowers the thermal efficiency and prolongs the melting time. On the other hand, if the mixing ratio is 1.0 or more, the excess oxygen remaining in the combustion reaction with the fuel at the same time as the reactions of Equations 2 and 3 will flow into the furnace, and this oxygen reaches the carburizing material. Then, an exothermic reaction to the right of the reaction shown in Expression 4 occurs.

[Formula 4] 2C + O ₂ ⇔2CO + [+ Q4] Furthermore, in the furnace in a high temperature state, C generated in Formulas 2 to 4 is obtained.
An exothermic reaction occurs between O, H ₂ and surplus oxygen in the right direction of the reaction of Formulas 5 and 6.

## EQU5 ## 2CO + O ₂ ⇔2CO ₂ + [+ Q5]

[6] _{2H 2 + O 2 ⇔2H 2 O} + [+ Q6] heat Q5 to CO by the number 5 occurs when reacts with O ₂ vary in CO ₂ is the same molar volume with number 2 reaction C
It is larger than the heat quantity Q2 absorbed when O is generated. Further, the amount of heat Q6 generated when H ₂ changes to steam in Equation 6 is larger than the amount of heat Q3 absorbed when H ₂ having the same molar volume is generated by the reaction of Equation 3. Therefore, when the mixture ratio of the fuel gas and the oxygen gas is set to be larger than 1.0, the exothermic reaction of Formula 4 is promoted in the vicinity of the carburized material, and the reaction of Formula 2 to Formula 4 is performed in the gas region far from the carburized material. CO and H ₂ generated by the above react with O _2, and the exothermic reactions of Formulas 5 and 6 occur.

The direction and speed of the reaction of Formulas 2 to 6 are affected by the temperature of the dissolved raw material, the temperature of the gas, and the gas partial pressure, as described later. On the other hand, supplying excessive oxygen from the burner 6 to the reactions of Equations 5 and 6 consumes heat for heating the wastefully discharged oxygen. Also the thermal efficiency decreases. Further, since an excessive oxidation reaction of the dissolved raw material occurs, the yield of the dissolved raw material is reduced.

In order to increase the combustion efficiency, it is necessary to supply optimal amounts of fuel and oxygen that can effectively utilize the exothermic reaction of Formulas 4 to 6 in accordance with the reaction characteristics in the furnace that change with temperature and gas composition. is there. The oxygen flow rate required to cause the chemical reaction of Formulas 5 and 6 with respect to CO and H ₂ gas generated in the furnace depends on the supply flow rates of propane gas and oxygen at that time, and CO and H in the furnace. _It can be obtained by knowing the gas concentration of ₂ . As described above, when CO and H ₂ are generated in the furnace gas due to the reaction between the combustion gas and the carburizing material, the CO concentration and the H ₂ concentration are detected and necessary for the exothermic reactions of Formulas 5 and 6. Determine the increase flow rate of oxygen, but if the carburized material disappears or the oxygen supply flow rate becomes excessive and unreacted oxygen remains, determine the decrease flow rate of oxygen and always optimize the burner. Supplying fuel and oxygen. The concept is described below.

In the state where all the oxygen has reacted and no unreacted oxygen exists, if the supply flow rate of the propane gas and the supply flow rate of the oxygen gas are respectively g and w mol / s, the total gas flow rate flowing in the furnace V mol / s s is stoichiometrically approximately represented by equation (7).

V = 7 · g + w−5 · g The corrected increase amount Δw of the oxygen gas into the burner is calculated based on the CO gas concentration [CO] and the H ₂ gas concentration [H ₂ ] in the furnace gas. It can be obtained by Expression 8.

Equation 8] Δw = 0.5 ([CO] + [H 2]) · V Accordingly, the current of the oxygen gas supply flow rate, the value obtained by adding the correction increment calculated by the number 8, the oxygen flow control Valve 3
The opening degree of 0 may be controlled. In a high-temperature state in which CO and H ₂ are generated by the reactions of Equations 2 and 3 in a rotary furnace for cast iron, the CO gas concentration is higher than the H ₂ gas concentration. For this reason, C having a relatively large concentration
Even when the oxygen supply flow rate is increased by calculating Equation 8 using the concentration of only O, the effect of the exothermic reaction can be obtained. At this time, the term of the H ₂ gas concentration may be set to zero.

Further, dissolution middle pressure results loss of carbonaceous material reaction or too large mixing ratio of fuel gas and oxygen gas eliminates the CO, oxygen in a state where excess O ₂ is adapted to be discharged A method for reducing the supply flow rate will be described.
Propane gas supply flow rate, reaction amount of carburizing material, unreacted O ₂
Assuming that the flow rates are g, u, and v mol / s, the reaction in the furnace in an excess oxygen state is stoichiometrically represented by the relationship of Formulas 9 to 11.

(Equation 9)

(Equation 10)

[Equation 11] Oxygen flow rate (u + v) mol that does not react with propane gas
/ s is expressed by Equation 12 using the mixing amount λ of the propane gas supply amount g and the burner fuel.

Equation 12] ratio of u + v = 5g (λ- 1.0) occupying the furnace gas O ₂ [O _2] is a number 13 on the relationship number 9 number 12.

[O ₂ ] = v / (7g + u + v) = v / ｛7
g + 5 g (λ−1.0)｝ The unreacted O ₂ amount vmol / s can be obtained by Expression 14 based on the known burner fuel supply amount and the detected O ₂ concentration value in the exhaust gas.

V = g (2 + 5λ) [O ₂ ]

Next, in an actual melting operation, a method of correcting and adjusting the oxygen gas supply flow rate based on the CO, H ₂ , and O ₂ concentrations of the furnace gas detected by the gas concentration meter to control combustion. Will be described with reference to the flowchart of FIG. First, at the start, the reference flow rate of the fuel gas of the burner, which is determined based on the amounts of the iron raw material and the carburizing material charged, and the determination reference values p1 and p2 of the CO concentration and the O ₂ concentration are sent to the arithmetic and control unit 20. Input and memorize. When the automatic combustion control is started, the arithmetic and control unit 20 calculates the reference fuel flow rate value input before the start and the flow rate value of the oxygen having a mixing ratio of 1.0 with respect to the fuel by the fuel flow rate control valve regulator 3.
5 and output to the oxygen flow control valve regulator 34 (step 101). Then, time counting is performed for a time corresponding to the control cycle Tc (step 102). Next, C in the gas in the furnace is measured using a gas concentration meter including the detection unit 40 and the converter 42.
The concentrations of O, H ₂ , and O ₂ are measured (step 103), and it is first determined whether CO is present at or above the determination reference value p1.
(Step 104).

When CO is detected equal to or greater than the determination reference value p1, the following processing is performed. CO and H measured in the previous step
_Using the gas concentration of ₂ and the supply flow rates of fuel and oxygen to the burner, calculate the oxygen flow rate required for the reactions of Equations 5 and 6, that is, the increase flow rate relative to the current oxygen supply rate (Step 105). The output value to the flow control valve adjuster 34 is corrected (step 106).

On the other hand, at step 104, the judgment reference value p1
If the above CO concentration is not detected, unreacted O ₂
It is determined whether or not is greater than or equal to the determination reference value p2 (step 107). When the O ₂ concentration is detected to be equal to or greater than the determination reference value p2, the excess oxygen flow rate is calculated in Equations 9 to 14 using the O ₂ concentration and the flow rates of the fuel and oxygen supplied to the burner.
(Step 108), the output value to the oxygen flow control valve regulator 34 is corrected (Step 106). On the other hand, Step 1
O ₂ concentration if not detected criterion value p2 higher, to maintain the supply flow rate of the present fuel and oxygen at 07. Then, the process returns to the time count process which is the control cycle.

The control cycle Tc is set to, for example, Tc = 1 min in accordance with the target melting furnace. The oxygen flow rate from the oxygen flow rate control valve 30 is given to the oxygen flow rate control valve regulator 34 by the arithmetic and control unit 20. The time is reached when the flow rate value is reached and the state of the furnace gas reaches a steady state reflecting the operation result. Further, the reference values p1 for determining the CO concentration and the O ₂ concentration,
p2 is, for example, 1% or 2%, and is set to a value in consideration of a value that can be stably detected by the gas concentration meter. Further, although the concentration is lower than that of CO, the determination in step 104 is H ₂
The concentration may be performed.

The processing described in the flowchart of FIG.
The process is repeated until the temperature of the melting raw material reaches a temperature at which iron can be melted and the hot water can be discharged, for example, 1520 ° C. Next, a part of the molten metal is taken out and subjected to component analysis, and component adjustment is performed as necessary. If the temperature and components are satisfied, the burner 6
Is stopped, and the tap hole 11 is opened to discharge the tap water.

(Embodiment 2) In Embodiment 1 described above,
The method of detecting the concentration of the gas generated in the furnace and determining the supply flow rate of at least one of the fuel and oxygen based on the detected gas concentration has been described. A method of detecting the concentration of exhaust gas, calculating the composition of gas generated in the furnace based on a chemical reaction model created in advance, and determining the supply flow rate of at least one of fuel and oxygen based on this Will be described. FIG. 3 shows a rotary melting furnace and a combustion control system according to the present embodiment. A gas sampling pipe 16 is attached to the outlet of the exhaust gas outlet 10 and connected to a gas concentration meter 19 for CO, CO ₂ and O ₂ via a pipe 17. The gas concentration meter 19 cools and dehumidifies moisture from the exhaust gas taken in from the gas sampling pipe 16 and measures the concentration of each gas in a dry state. The arithmetic and control unit 20 has a built-in chemical reaction model, which will be described later, and is connected to the above-mentioned gas concentration meter 19 via a signal line 18. Based on the chemical reaction model and the detected gas concentration, the oxygen supplied to the rotary melting furnace is controlled. Calculate the flow rate and fuel flow rate. Other configurations are the same as those of the first embodiment, and are denoted by the same symbols.

Since the concentration of CO ₂ and CO in the atmosphere is low,
Even if the exhaust gas entering the gas sampling pipe 16 is diluted with the atmosphere or the water vapor is removed from the entire sampling gas, the ratio hardly changes. Therefore, in the second embodiment, the reaction between the carburizing material and the combustion gas starts, and in a state where O ₂ is insufficient and CO is detected, the CO concentration in the exhaust gas and the CO ₂
Calculate and correct the required oxygen supply flow rate by detecting the concentration and calculating the ratio, and calculating the raw material temperature in the furnace and the total composition of the true gas in the furnace at the same ratio from the chemical reaction model described later. And output the correction. Also, if the carburized material disappears or the mixing ratio of fuel gas and oxygen gas becomes too large, CO
When the excess O ₂ has been detected and the excess O ₂ has been detected, the excess oxygen supply flow rate is calculated and corrected from the detected values of the O ₂ and CO ₂ concentrations in the exhaust gas, taking into account the mixing of air into the sample gas. Output. Hereinafter, a chemical reaction model, a method of detecting a CO concentration and a CO ₂ concentration in an exhaust gas, a chemical reaction model, and an exhaust gas, and using the ratio to determine an oxygen flow rate necessary for an exothermic reaction of Formulas 5 and 6, and an oxygen excess A method for reducing the oxygen supply flow rate by using the detected values of CO ₂ and O ₂ sometimes will be specifically described.

First, a chemical reaction model will be described. The chemical reaction model is a mathematical expression of a stoichiometric relationship of related substances with respect to a chemical reaction occurring between a combustion gas and a dissolved raw material in a furnace. The chemical reaction of interest is basically
Although the reaction progress rate of each chemical reaction is limited by each chemical reaction rate and mass transfer rate, the chemical reaction of the entire furnace in the individual furnace is based on the individual chemical reaction. Cannot simply be done. However, in the rotary melting furnace described in this description, the combustion gas generated by burning the fuel in the burner is always flowing from the burner side to the outlet, and is constantly stirred even if it reacts with the carbonized material in the furnace. Fluctuations in the gas components in the furnace are extremely gentle because they flow out after mixing under the bath. For this reason, the atmosphere in the furnace is regarded as a period of transition to the chemical thermodynamic equilibrium state, and the temperature rise and melting process is a phenomenon that is much longer than the chemical reaction rate. Since the change in the components is related as a function of the temperature of the molten material, the chemical reaction of the combustion gas and the carburized material in the entire furnace is approximately formulated using chemical thermodynamic equilibrium theory. The original chemical thermodynamic equilibrium theory gives the final equilibrium state of the reaction of related substances at a certain temperature and does not specify the progress rate of the reaction, but it burns from the burner and flows through the furnace. Determines the stoichiometric relationship of related substances in the transient stage when the reaction reaches an equilibrium state by specifying the ratio of gas reacting with dissolved raw materials to the total amount of flowing combustion gas (hereinafter referred to as reaction rate) it can. The reaction rate can be identified by measuring the actual reaction state of the melting furnace. In other words, the chemical reaction model means that fuel gas and oxygen gas are burned by a burner in a rotary melting furnace, and the composition of CO ₂ , H ₂ O, and O ₂ according to the flow rate of each gas is converted to one end of the furnace. Dissolves the relationship between how much of the whole reacts with the dissolved raw material, especially the carburized material, while flowing out from the opposite side after flowing in from the opposite side, and finally changes to the state of the gas composition. It is expressed as a function of the temperature of the raw materials to be compatible with the intended rotary melting furnace and the blending conditions of the melting raw materials used.

Next, a method of obtaining the gas composition in the furnace using a chemical reaction model will be described. In the chemical reaction model, the inside of the furnace is considered as two layers, a gas layer and a raw material layer. In the case of a rotary melting furnace, the bottom side area obtained by multiplying the reactor volume by the reaction rate is regarded as the raw material layer, and the rest is regarded as the gas layer. I think it will be. Specifically, the following processing is performed. The gas in the layer and the temperature tg1 of the raw material are given. O ₂ , H ₂ O, and O ₂ in the furnace when the flow rate of fuel and the combustion gas of oxygen supplied to the burner enter the furnace and are uniformly mixed.
The CO ₂ , CO, and H ₂ gas amounts and mole fractions are determined. A constant ratio α (reaction rate) is transferred from the combustion gas in the entire furnace to the raw material layer, and a chemical thermodynamic equilibrium state of the chemical reaction between the gas and the carburized material at the temperature tg1 is obtained. The reaction gas that has reached the above-mentioned chemical thermodynamic equilibrium state is returned to the gas layer, and the intermediate mole number of each gas when uniformly mixed with the unreacted gas is determined. A chemical thermodynamic equilibrium state of a chemical reaction of the composition gas at the temperature tg1 is determined. By the above processing, the composition of the furnace gas according to the furnace temperature tg1 and the supply flow rate and the reaction rate of the fuel and oxygen to the combustion burner is obtained.

Next, chemical thermodynamic equilibrium, which is a basic idea of a chemical reaction model, will be described. First, the reaction model of the raw material layer (described above) will be described. From the chemical thermodynamic equilibrium theory, the independent reaction equation required to determine the gas partial pressure of the gas components related to the in-furnace reaction of Equations 2 to 6 is given by Equation 15
From Equation 17 can be summarized into three. It is needless to say that the combination is not limited to the combination of the following three formulas as long as the combination can provide an independent relationship between the related gas components.

[Equation 15] C + CO ₂ ⇔2CO

[Formula 16] C + O ₂ ⇔CO ₂

H ₂ + / · O ₂ ⇔H ₂ O The equilibrium constants of the respective reactions of Equations (15), (16) and (17) are represented by K1 and K, respectively.
2, K3, and target gases CO ₂ , H ₂ O, O ₂ , CO, H ₂
Is expressed by Pco ₂ , Ph ₂ o, Po ₂ , Pco, Ph ₂ , the relational expressions of Expressions 18 to 20 are established from the van Hoff-Hoff isotherm and the standard free energy change.

K1 = (Pco) ² / Pco ₂ = exp {− (170710−174.5T) / RT}

K2 = Pco ₂ / Po ₂ = exp {− (− 394577−1.13T) / RT}

Equation 20] ^{_{K3 = (Ph 2 o) 2}} / ((Ph 2) 2 · Po 2) = exp {- (- 492698 + 109.84T) / RT} where R is the gas constant, T is the absolute temperature. That is, once the temperature is determined, the equilibrium constant at that temperature is determined.

Pco ₂ , Ph ₂ o, Po ₂ , Pco, Ph ₂ are determined by the following method from the condition that the total pressure in the furnace is 1 atm and the initial condition of the supply flow rate of the fuel gas. CO ₂ , H ₂ O, O ₂ ,
The mole numbers of CO, H ₂ gases in the furnace are A, B, C,
The ratio (reaction rate) represented by D and E and regarded as moving to the raw material layer of the gas in the furnace in the chemical reaction model is defined as α. Then, the numbers of moles of CO ₂ , H ₂ O, O ₂ , CO, and H ₂ before the reaction are represented by a (= α · A), b (= α · B), c (= α · C), and d, respectively.
(= Α · D) and e (= α · E), and Equation 15, Equation 16, and Equation 1
When the reaction direction and the reaction amount (number of moles) of 7 are determined as in Equations 21, 22, and 23, the relationship between the partial pressure of each gas after the reaction and the number of moles is as shown in Equations 24 to 28.

## EQU21 ## C + CO ₂ → 2CO: x mole

## EQU22 ## C + O ₂ ← CO ₂ : y mol

H ₂ + 1/2 · O ₂ ← H ₂ O: z mol

## EQU24 ## Pco ₂ = (a-xy) / (a + b + c + d + e)
+ 1 / 2.z + x)

## EQU25 ## Ph ₂ o = (b−z) / (a + b + c + d + e + 1/2 · z + x)

## EQU26 ## Po ₂ = (c + y + 1 / 2.z) / (a + b + c + d)
+ E + 1 / 2.z + x)

## EQU27 ## Pco = (d + 2x) / (a + b + c + d + e + 1)
/ 2z + x)

[Expression 28] Ph ₂ = (e + z) / (a + b + c + d + e + 1/2 · z + x) By substituting Expressions 24 to 28 into Expressions 18 to 20, the relationship of Expressions 29 to 31 is obtained.

K1 = (d + 2x) ² / {(a + b + c + d + e)
+ 1 / 2.z + x) (a-xy)}

K2 = (a-xy) / (c + y + 1 / 2.z)

K3 = (b−z) ² (a + b + c + 1/2 · z + x)
/ {(E + z) ² (c + y + 1/2 · z)} If the temperature is determined, K1, K2, and K3 are uniquely determined from Expressions 18 to 20. Therefore, a solution can be obtained from three relational expressions for three variables x, y, and z, and the number of moles of CO ₂ , H ₂ O, O ₂ , CO, and H _{2 in} the equilibrium state can be determined. The pressure relationship is determined.

Next, a reaction model in the gas layer (described above) will be described. The target reaction formulas are Equations 5 and 6.
When the equilibrium constants of the respective reactions of Equations 5 and 6 are represented by K4 and K5, the following relational expression is established as in the case of the raw material layer.

K4 = Pco ₂ / (Pco · (Po ₂ ) ^1/2 ) = exp {− (− 282420 + 86.82T) / RT}

K5 = Ph ₂ o / (Ph ₂ · (Po ₂ ) ^1/2 ) = exp {− (− 239530 + 18.74TlogT−9.247T) / RT} P
co ₂ , Ph ₂ o, Po ₂ , Pco, and Ph ₂ are determined by the following method from the condition that the total pressure in the furnace is 1 atm and the initial condition of the supply flow rate of the fuel gas. The number of moles of CO ₂ , H ₂ O, O ₂ , CO and H ₂ before the reaction is a1 (= (1−α) · A + (a−x−y)),
b1 (= (1-α) · B + (b−z)), c1 (= (1-α) · C
+ (C + y + 1/2 · z)), d1 (= (1−α) · D + (d + 2
X)), e1 (= (1−α) · E + (e + z)).
When the reaction direction and the reaction amount (molar number) in Equation 6 are determined as in Equations 34 and 35, the relationship between the partial pressure of each gas after the reaction and the number of moles is as shown in Equations 36 to 40.

[Formula 34] CO + 1/2 · O ₂ → CO ₂ : x1 mol

H ₂ O + 1/2 · O ₂ → CO ₂ : y1 mol

[Expression 36] Pco ₂ = (a1 + x1) / A

[Formula 37] Pco = (b1−x1) / A

[Equation 38] Ph ₂ o = (c1 + y1) / A

[Formula 39] Ph ₂ = (d1-y1) / A

Po ₂ = (e 1 −x 1/2 −y 1/2) / A where A is the total number of moles of the gas in the furnace after the reaction in the equations 36 to 40, and is the equation 41.

A = a1 + b1 + c1 + d1 + e1- (x1 + y1) / 2 By substituting Equations 36 to 40 into Equations 32 and 33, the relation of Equations 42 and 43 is obtained.

K4 = {(a1 + x1) / A} / [{(b1−x1) / A}
・ {(E1-x1 / 2-y1 / 2) / A} ^1/2 ]

K5 = {(c1 + y1) / A} / [{(d1-y1) / A}
[{(E1-x1 / 2-y1 / 2) / A} ^1/2 ] If the temperature is determined, K4 and K5 are uniquely determined from Equations 32 and 33. From the above, a solution is obtained because there are two relational expressions for two variables x1 and y1, and the final CO in the furnace is obtained.
₂ , the number of moles of H ₂ O, O ₂ , CO and H ₂ and the partial pressure are determined. Since the furnace pressure has a total pressure of 1 atm, the partial pressure is equal to the gas concentration.

The reaction rate α of the chemical reaction model for determining the gas amount of the raw material layer with respect to the entire gas in the furnace is to measure the CO and CO ₂ gas concentrations and the temperature change of the raw materials in the model operation of the actual furnace. Can be identified. To the fuel gas supply conditions of the actual furnace model operation, the as chemical reactions fluctuation parameter response rates model, determined by calculating the relationship between the raw material temperature and gas concentration of CO and CO ₂ that the water vapor partial removal, the actual measured value The reaction rate closest to the change is defined as the reaction rate under the fuel gas supply conditions. As a result of performing model melting for the raw material of the actual rotary melting furnace with respect to the mixing ratio of different fuels, if the relationship between the temperature of the raw material, the charged amount of the carburizing material, and the reaction rate is as shown in FIG. It was found that the reaction inside the installed rotary melting furnace could be modeled. Once a chemical reaction model can be created, even if the supply process of fuel and oxygen changes, it becomes possible to calculate the gas composition in the furnace corresponding to the temperature of the dissolved raw material.

Next, CO and CO are calculated based on the chemical reaction model.
A method of determining the oxygen flow rate required for the exothermic reactions of Equations 5 and 6 using the concentration ratio of ₂ will be described. FIG. 7 shows a case where the mixing ratio of propane gas to oxygen is 1.0, and the CO gas concentration [CO] obtained based on the chemical reaction model using the reaction rate identified from the actual dissolution experiment results. The relationship between the ratio of the CO ₂ gas concentration [CO ₂ ] and the raw material temperature is shown. [CO]
The / [CO ₂ ] ratio increases from 0 with increasing raw material temperature. That is, when the mixing ratio is 1.0, CO is not present at first, and the temperature of the raw material rises, and the reaction between the combustion gas and the carburizing material becomes active, and increases with the temperature rise. . Even if the mixing ratio of oxygen is excessive with respect to propane gas, the value is different, but there is no difference in the upward slope, and there is a 1: 1 correspondence between the raw material temperature and the [CO] / [CO ₂ ] ratio. Therefore, [CO] / [C
If the O ₂ ] ratio is determined, the temperature of the raw material in the furnace can be estimated, and the molar volume, partial pressure, and gas concentration of CO gas and H ₂ gas in the furnace can be determined from the chemical reaction model. That is, the amount of oxygen necessary for the reactions of Equations 5 and 6 is obtained.

[0032] Next, dissolution middle carburization material eliminates CO to the mixing ratio becomes too large results disappearance, or fuel gas and oxygen gas in the reaction, oxygen in the state of excess O ₂ is adapted to be discharged The method of reducing the supply will be described. Assuming that the supply flow rate of propane gas, the reaction amount of the carburizing material, and the unreacted O ₂ flow rate are g, u, and v mol / s, respectively, the reaction in the furnace is stoichiometrically in the case of excess O ₂ when １１ 11

Assuming that the mixing ratio of air into the gas sampling tube is β,
Then, the mixing ratio β is the dry gas CO _TwoConcentration [CO_Two] And O
_TwoConcentration [O_Two] From Expression 44.

Β = [1-([CO ₂ ] + [O ₂ ])] /
[0.79- {1 - ([CO 2] + [O 2])}] From this, unreacted O ₂ amount v moles in consideration of the contamination of the air mixing ratio β and O ₂ concentration in the air [O ₂ ] from Equation 45.

V = g (5λ-2) (1 + β) ｛[O ₂ ] −
0.21β / (1 + β)｝ Therefore, if the oxygen amount calculated in Equation 45 is reduced from the burner fuel, excess oxygen can be eliminated.

Next, in the actual melting operation, based on the CO, CO ₂ , and O ₂ concentrations of the exhaust gas detected by the gas concentration meter 19, the supply amount of oxygen gas is corrected using a built-in chemical reaction model. FIG. 4 shows a method of adjusting and controlling combustion.
This will be described with reference to the flowchart of FIG. First, at the start, a reference flow rate of the burner fuel gas determined from the amounts of the iron raw material and the carburized material charged, and the amounts of the raw materials, and a determination standard of the CO concentration and the O ₂ concentration are given to the arithmetic and control unit 20. The values p1 and p2 are input and stored. When the automatic combustion control is started, the arithmetic and control unit 20 calculates the reference fuel flow rate value input before the start and the flow rate value of the oxygen having a mixing ratio of 1.0 with respect to the fuel by the fuel flow rate control valve regulator 3.
5 and output to the oxygen flow control valve regulator 34 (step 201). Then, a time is counted for a time corresponding to the control cycle Tc (step 202). Next, gas concentration meter 1
9 to measure the concentration of CO, CO ₂ and O _{2 in} the exhaust gas
(Step 203) First, it is determined whether or not CO is present at or above the determination reference value p1 (Step 204).

When CO is detected equal to or more than the determination reference value p1, the following processing is performed. First, the concentration ratio between CO concentration and CO ₂ [C
O] / [CO ₂ ] = r is calculated (step 205). Then, based on the built-in chemical reaction model, after determining the reaction rate α to be applied from the current mixing ratio of fuel and oxygen supply flow rate,
A raw material temperature tr at which the ratio of the CO concentration to the CO ₂ concentration is r is obtained, and the gas concentrations of CO and H _{2 including} H ₂ O in the furnace at that time are calculated (step 206). Then, using the gas concentrations of CO and H ₂ calculated in the previous step and the supply flow rates of fuel and oxygen to the burner, the oxygen flow rate required for the reactions of Equations 5 and 6, ie, the current oxygen supply rate, The increase flow rate is calculated (step 207), and the output value to the oxygen flow control valve regulator 34 is corrected (step 208).

On the other hand, at step 204, the judgment reference value p1
If the above CO concentration is not detected, unreacted O ₂
It is determined whether or not is greater than or equal to the determination reference value p2 (step 209). If O ₂ is detected at or above the determination reference value p ₂ , the excess oxygen flow rate is calculated in Equations 44 to 45 using the O ₂ concentration and the supply flow rates of fuel and oxygen to the burner.
(Step 210), the output value to the oxygen flow control valve regulator 34 is corrected (Step 208). On the other hand, step 2
If the O ₂ concentration is not detected criterion value p2 higher at 09, maintaining the supply amount of the current fuel and oxygen. Then, the process returns to the time count process which is the control cycle.

The control cycle Tc, the reference values p1 and p2 for the CO concentration and the O ₂ concentration are the same as in the first embodiment, the response of the fuel and oxygen flow control valve system, the stable detection of the gas concentration meter, or Use a value that takes into account the effects of air mixing into the gas sampling pipe. The process described in the flowchart of FIG. 4 is repeated until the temperature of the dissolving raw material reaches a temperature at which iron can be melted and discharged, and component adjustment is performed as necessary.
When the temperature and components are satisfied, the burner 6 is stopped, the tap 11 is opened, and the tap water is discharged. By applying the chemical reaction model as described above, detecting the concentration of CO and CO ₂ in the exhaust gas and controlling the supply flow rate of oxygen to the combustion burner, the maximum thermal efficiency can be adjusted according to the chemical reaction state in the furnace. The resulting burner combustion control can be realized. In the above description, thermodynamic equilibrium was applied to the chemical reaction model, but as reported for char or coke, a model consisting of the overall reaction rate of the chemical reaction resistance and the diffusion resistance in the fluid film was used. May be.

In the first and second embodiments, the controlled oxygen is supplied to the burner. However, an auxiliary oxygen supply path may be provided separately. In addition, the maximum supply amount of oxygen to the burner is limited, and if CO remains even when the oxygen supply amount is set to the maximum value, the flow rate of the fuel may be reduced. Further, the fuel may be increased or decreased while the oxygen flow rate is kept constant. In any case, if the relationship between fuel and oxygen of the formula 1 is used, the method can be easily implemented by the method described in the present invention. Also,
In the first and second embodiments, the determination of the CO concentration is performed first, and the process of determining the O ₂ concentration is performed when the CO concentration is lower than the determination reference value. However, depending on the type of gas, if the O ₂ concentration detection is faster, the O ₂ concentration determination may be performed first.

Further, in the case where the dissolution in which the mixing of the dissolving raw materials to be charged is the same is repeated, the dissolution is first performed by the combustion control method using the gas concentration detection described in the first or second embodiment, and at the same time, The process of supplying fuel and oxygen to the combustion burner at that time is stored in the memory of the arithmetic and control unit 20, and the subsequent dissolution is performed using the stored data of the process of supplying fuel and oxygen having the same blending of the dissolved raw materials. May be sequentially read out as the dissolution time elapses, and a method of controlling the flow rates of fuel and oxygen may be used. According to this method, since it is not necessary to measure the gas concentration at all times, heat resistance is required to reduce the heat loss of the gas sampling tube, which is expensive, and the maintenance and inspection of the dust filter and the reference gas of the gas concentration meter. Work can be reduced.

[0040]

In the melting furnace according to the present invention, the concentrations of CO and H _{2 in} the furnace gas are detected to determine the supply flow rates of fuel and oxygen required for the oxidative exothermic reaction. When oxygen is excessive, the concentrations of CO ₂ and O ₂ are detected to suppress excess oxygen. As a result, since the exothermic reaction in the furnace is always performed at the maximum efficiency, the overall thermal efficiency can be increased, so that the melting time is shortened, the raw material is prevented from being excessively oxidized, and the yield is improved. Even in melting furnaces where it is difficult to directly measure the temperature of the gas components inside the furnace and the melting raw materials, by creating a chemical reaction model of the combustion gas and the melting raw materials in advance, water vapor condenses after sampling. ,
From the detected concentration values of CO, CO ₂ and O ₂ in the exhaust gas after dehumidification, it is possible to estimate the gas composition including the water vapor inside the furnace, and to determine the fuel and oxygen supply flow rates to the burner to achieve the maximum thermal efficiency. Can be determined. In addition, when the melting conditions are the same, it is possible to regenerate and melt the flow pattern of the fuel and oxygen supply to the burner in the combustion control melting performed by the gas concentration detection performed earlier. Operation, and stabilization of the molten metal component and the raw material yield can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a melting furnace for cast iron and a system diagram of a combustion control device for explaining a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a combustion control method according to the first embodiment of the present invention;

FIG. 3 is a schematic diagram of a melting furnace for cast iron and a system diagram of a combustion control device for explaining Embodiment 2 of the present invention.

FIG. 4 is a flowchart illustrating a combustion control method according to a second embodiment of the present invention;

FIG. 5 shows examples of weights of charged components, molten metal components, and lost components in the rotary melting furnace according to the present invention.

FIG. 6 shows the relationship between the mixing ratio of fuel and the reaction rate in the rotary melting furnace of the present invention.

FIG. 7: Raw material temperature and (C) in the rotary melting furnace of the present invention.
Example of the relationship of O gas concentration / (CO ₂ gas concentration)

[Explanation of symbols]

 5 Melting furnace body 6 Burner 19 Gas concentration meter 20 Arithmetic controller 30 Flow control valve for oxygen 31 Flow control valve for fuel 34 Oxygen flow control valve adjuster 35 Fuel flow control valve adjuster 38 Oxygen flow detector 39 ... Fuel flow detector 40 ... Detector of gas concentration meter 42 ... Transformer of gas concentration meter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Sato 2nd Daifuku, Kuwana-shi, Mie Hitachi Metals Co., Ltd. Kuwana Plant (72) Inventor Kohei Imanishi 35 Nagahama-cho, Kanda-cho, Kyoto-gun, Fukuoka Prefecture Hitachi Metals, Ltd. Kyushu factory

Claims (9)

[Claims] In a combustion control method for a melting furnace, in which a raw material is charged and fuel and oxygen are burned to heat and melt, a supply flow rate of fuel and oxygen, and at least CO ₂ of CO and H ₂ gas in the furnace. A combustion control method for a melting furnace, comprising: determining a supply flow rate of at least one of fuel and oxygen based on a gas concentration so that a reaction in the furnace becomes an exothermic reaction. 2. A combustion control method for a melting furnace in which a melting raw material is charged and a fuel and oxygen are burned and heated and melted, wherein CO or H ₂ concentration of CO, H ₂ and O ₂ gas in the furnace is reduced. If the set value is exceeded, the supply flow rates of fuel and oxygen and CO
Is at least CO gas concentration and based on furnace of reaction is determined at least one of the supply flow rate of fuel or oxygen so that the exothermic reaction and O ₂ concentration is less than the set value of the H ₂ gas Compare with the set value or not, and if it is not less than the set value, calculate the amount of unreacted O ₂ from the supply flow rate of fuel and oxygen and the concentration of O _{2 in} the furnace gas so that the O ₂ concentration decreases. Determining a supply flow rate of at least one of fuel and oxygen. 3. A combustion control method for a melting furnace in which a molten raw material is charged and a fuel and oxygen are burned and heated and melted, and a chemical reaction model for obtaining a relationship between a combustion gas in the furnace and a chemical reaction between the molten raw material is created in advance. Then, the temperature of the dissolved raw material and the composition of the furnace gas are calculated based on the chemical reaction model from the detected composition of the exhaust gas, and the reaction in the furnace becomes an exothermic reaction based on the supply flow rates of the fuel and oxygen. Thus, a method for controlling combustion in a melting furnace, comprising determining the supply flow rate of at least one of fuel and oxygen. 4. Detecting CO and CO ₂ concentration of exhaust gas,
4. The combustion control method for a melting furnace according to claim 3, wherein the temperature of the melting raw material and the composition of the gas in the furnace are calculated from the ratio based on a chemical reaction model. 5. In a combustion control method for a melting furnace in which a melted raw material is charged and fuel and oxygen are burned and heated and melted, a chemical reaction model for obtaining a relationship between a combustion gas in the furnace and a chemical reaction between the melted raw material is created in advance. Then, the concentrations of CO, CO ₂ , and O ₂ in the exhaust gas are detected, and when the CO concentration is equal to or higher than the set value, the temperature of the dissolved raw material is determined based on the chemical reaction model from the ratio of CO and CO ₂ concentrations. as to calculate the composition of the in-furnace gas reaction in the furnace is an exothermic reaction, and if less than the set value is compared with a set value of O ₂ concentration, the supply flow rate of fuel and oxygen in the case of more than the set value And calculating the amount of unreacted O ₂ from the concentrations of CO ₂ and O _{2 in} the exhaust gas and reducing the supply amount of fuel or oxygen based on the supply flow rates of fuel and oxygen so that the O ₂ concentration decreases. A method for controlling combustion in a melting furnace, comprising: 6. A series of fuel and oxygen supply steps from the start of melting are stored in a storage device, and in the subsequent melting, the stored fuel and oxygen supply steps are regenerated to supply fuel or oxygen. The combustion control method for a melting furnace according to any one of claims 1 to 5, characterized in that: 7. The combustion control method for a melting furnace according to claim 1, wherein the melting raw material is an auxiliary material containing an iron raw material and at least a carburizing material. 8. In a rotary melting furnace for heating and melting fuel and oxygen by charging melted raw materials, a gas concentration meter for detecting the concentration of gas generated in the furnace, and detecting the flow rates of the fuel and oxygen. Detector, a flow control valve for controlling the flow rates of fuel and oxygen, a flow control valve regulator for inputting a signal of the detector and outputting an opening control command to the flow control valve, and inputting a detection value of the gas concentration meter. A rotary melting furnace, comprising: an arithmetic and control unit for arithmetically processing a supply flow rate command value of at least one of fuel and oxygen and outputting the command value to the flow rate control valve regulator. 9. The arithmetic and control unit outputs a supply flow command value of at least one of fuel and oxygen to the flow control valve regulator, stores an output process, and reproduces the output process in the subsequent dissolution. 9. The method according to claim 8, wherein
The rotary melting furnace described.