JP2897363B2 - Hot metal production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of manufacturing pig iron using a cylindrical furnace and scrap and iron ore as an iron source, by controlling a blow-off time and an amount of coke charged next time. And a method for economically and stably producing hot metal whose temperature and components are stable.

(Prior art) At present, most of pig iron is manufactured by a blast furnace. The blast furnace iron making method itself has been continuously improved over the years, and has become extremely excellent as a technology for mass production of iron pig. However, the blast furnace iron making method uses sintered ore as an iron source and high-grade coke as a fuel (reducing material), and there are limitations on the raw fuel that can be used. In addition, blast furnaces in recent years have become enormous, and since they cannot be easily stopped and restarted after they have been fired, they lack flexibility in responding to changes in steel material demand.

In order to solve the problems of the conventional blast furnace iron making method as described above, the present applicant uses a cylindrical furnace similar to a converter for steelmaking and uses a new iron making method using ore and scrap as an iron source. And filed a patent application earlier (Japanese Unexamined Patent Publication No. 1-290711).
issue).

In the above pig iron manufacturing method, a cylindrical furnace 1 of a converter type as shown in FIG. 1 is used. As shown in the drawing, the cylindrical furnace 1 has an opening 2 for discharging gas inside the furnace and charging raw materials at an upper part of the furnace, a primary tuyere 3 for blowing a supporting gas and a fuel as needed at a lower part of the furnace wall, Secondary tuyere 4, injecting a supporting gas into the upper furnace wall,
A tap hole 5 for discharging hot metal and slag 8 is provided at the furnace bottom.

In order to produce hot metal using the cylindrical furnace 1, first, a coke packed bed 7 is provided at a lower part in the furnace, and a scrap 6-1 is placed thereon.
And a filling layer 6 of iron ore 6-2. Then, a combustion supporting gas and, if necessary, fuel are blown into the lower coke layer 7 from the primary tuyere 3 to cause a reaction of the following formula (1), and the heat of the reaction keeps the coke layer 7 at a high temperature.

C + 1 / 2O ₂ → CO + 29,400 kcal / kmol · C (1) The CO generated by the above equation (1) is used as a combustible gas blown from the secondary tuyere 4 at the packed layer 6 of scrap and iron ore. The reaction (secondary combustion) of the following equation (2) occurs. The heat of reaction is used to heat and melt the scrap and iron ore.

CO + 1 / 2O ₂ → CO ₂ +67,590 kcal / kmol · CO (2) The iron ore (molten iron oxide) melted by this reaction is dropped on the lower coke layer 7 and the high temperature coke and the following formula (3) Reacts immediately after reaction.

Fe ₂ O ₃ + 3C → 2Fe + 3CO −108,090 kcal / kmol · Fe ₂ O ₃ … (3) In the reaction of the above formula (3), there is no CO ₂ nearby, so the reaction of the formula (3) is inhibited by CO ₂ It will not be done. The CO generated in the equations (1) and (3) is subjected to secondary combustion in the packed bed 6 of scrap and iron ore, so that it is effectively used for heating and melting them to achieve high fuel efficiency. .

As described above, according to the method for producing hot metal proposed earlier by the present applicant, hot metal can be produced from scrap and iron ore with high efficiency in a converter type cylindrical furnace. Normally, in the operation of this hot metal production method, the control of the blow-off time or the amount of coke charged next time is performed by measuring the packed bed height in the furnace using a sounding device. For this reason, a situation occurs in which the determination of the completion of dissolution is delayed or an appropriate amount of coke is not charged.

In actual operation, operation of the ratio of scrap and iron ore in terms of iron equivalent charge (hereinafter referred to as SR ratio), the amount of injected combustion supporting gas and fuel during melting or for each charge, or the amount of coke charged In some cases, the conditions may be changed. The time series changes in the amount of hot metal produced in the furnace during the melting process (hot metal production) and the bed coke consumption in the furnace are accurately grasped, and blowing is stopped at the same time as melting is completed. In order to predict the inner bed coke height and furnace heat and stabilize the furnace condition, hot metal temperature and components, it is important to control the amount of coke charged in the next charge.

Japanese Patent Application Laid-Open No. 1-195232 discloses a method for detecting the completion timing of melting of a cold material containing iron. In this method, the low frequency component vibration force and the full frequency component vibration force of the furnace body vibration of the converter are measured, the ratio of these two vibration forces is calculated, and melting is performed when the ratio reaches a preset value. Is determined to be completed. To implement this method, it is necessary to install the measurement sensor directly on the furnace auxiliary equipment, but it is easy to select the measurement sensor setting position that can accurately measure the sensitive frequency and frequency in the furnace body and the furnace. It seems not. Also,
In this method, the whole swing of the molten iron liquid level in the furnace before and after the melting of the iron-containing cold material charged in the converter where the seed water is present is a key point of the determination method. However, in the method for producing hot metal proposed by the present applicants earlier, a bed of coke bed exists at the bottom of the furnace and is continuously stored in the bed. It is difficult to apply the judgment method based on the whole swing.

Further, as an example of a method for predicting furnace heat reduction in a conventional blast furnace method, there is a method disclosed in Japanese Patent Application Laid-Open No. 63-297517. In this method, the temperature difference of the inner wall of the blast furnace is measured, the solution loss carbon amount and the N
The measured temperature of the blast furnace is accurately measured by comparing the measured values of the concentrations with the set values that change every moment to predict the temperature drop of the blast furnace. JP-A-62-2975
The furnace heat drop prediction method disclosed in Japanese Patent Publication No. 17 is useful as a method for preventing furnace heat drop except that the criteria for judging furnace heat low are complicated. However, the total amount of coke consumed in the furnace (solution loss, Therefore, the amount of coke used is not directly determined, and the amount of coke used is not controlled to reduce the amount.

(Problem to be Solved by the Invention) The present invention has been made for the purpose of solving the above-mentioned problem in a method of producing hot metal using a scrap furnace and iron ore as an iron source using a cylindrical furnace, An object of the present invention is to provide a method for economically producing hot metal having a stable temperature and composition under favorable conditions by controlling the timing and the amount of coke charged next time.

(Means for Solving the Problems) In the actual operation of the cylindrical furnace described above, the present inventors
(A) If the blowing is stopped at the same time as the completion of melting of the charged iron source, useless blowing can be prevented, so that the consumption of the supporting gas, fuel and coke can be reduced. (B) The amount of bed coke in the furnace at the start of melting. It was found that controlling the coke charging rate so that the temperature became constant for each charge can prevent the furnace heat from decreasing, stabilizing the furnace conditions, hot metal temperature and components, and reducing coke consumption. Therefore, a specific method for determining the timing of the above-mentioned blowing stop and the amount of coke charged most appropriately was studied, and the present invention described below was completed.

The gist of the present invention is that, in the above-described method for producing hot metal using a cylindrical furnace, during operation, material adjustment and heat adjustment in the furnace are performed at predetermined timings, and the production amount of hot metal in the furnace and the bed coke in the furnace are determined in time series. Calculating the consumption amount, predicting the melting completion time and the excess / deficiency amount of the bed coke in the furnace from the calculated value, and controlling the blowing stop time and the next charging coke amount based on the prediction. Hot metal production method ”.

In the method of the present invention, the ore to be used may be ordinary iron ore, ore containing a large amount of Mn, Cr, Mo, Ni or the like, or an oxide thereof. In addition, auxiliary raw materials such as quartzite, limestone, serpentine, and fluorite can be charged together with these ores and coke. It is also possible to use a high alloy scrap such as stainless steel scrap as a scrap, and to reuse useful elements therein.

Iron ore can be blown not only from the upper opening of the furnace, but also from the primary and / or secondary tuyeres.

The supporting gas blown from the primary and secondary tuyeres is O ₂
It is a contained gas. From the primary tuyere, pulverized coal fuel and / or hydrocarbon-based fuel for auxiliary combustion can also be blown together with the supporting gas.

(Operation) FIG. 2 is a block diagram showing the main points of the method of the present invention, and FIG.
The figure is a schematic diagram showing an example of a cylindrical furnace melting apparatus used for carrying out the method of the present invention and various measuring instruments attached thereto. Hereinafter, the method of the present invention will be specifically described with reference to these drawings.

In the method of the present invention, material and thermal settlement are performed. For this purpose, as shown in FIG.
It is necessary to obtain blast information, waste gas information and furnace body heat radiation information. These pieces of information are collected using various auxiliary equipments shown in FIG.

Charge information: As charge information, the amounts of ore, coke, and auxiliary materials charged are measured by a weighing bin 18 and the amount of scrap is measured by a weighing device 19, and data is sampled each time charging is performed.
Ore, coke and adjuncts are charged belt conveyor 10
The scrap is charged into the furnace through the raw material charging port 9 through the opening, and the hood 12 is opened and the scrap is charged into the furnace using the chute 11.

Ventilation information: Ventilation information is obtained from the primary tuyere 3 at the primary combustible gas flowmeter and pressure gauge 20 and the solid fuel weighing bin 22, and at the secondary tuyere 4 at the secondary combustible gas flowmeter and pressure gauge 21. It is measured and data sampled.

Waste gas information: The opening 2 of the cylindrical furnace 1 is isolated from the atmosphere by a hood 12, and the waste gas during operation is a waste gas riser 13 and a waste gas descender 1.
4. The air is exhausted to the atmosphere via the primary dust collector 15, the secondary dust collector 16, and the exhaust fan 17. For waste gas information, see the waste gas thermometer 23,
Waste gas pressure gauge 24, waste gas flow meter 25 and waste gas analyzer 26
Is measured and data sampled. Waste gas components
CO, CO ₂ , O ₂ , H ₂ and N ₂ are analyzed.

Furnace body heat radiation information: The furnace body heat radiation information is obtained by measuring the refractory temperature at each position of the furnace body refractory using a refractory thermometer 27 dispersed and embedded in the furnace body refractory of the cylindrical furnace 1. .

The above information (1) is continuously collected during the operation, usually at intervals of about 10 from the start to the end of the operation.

The hot metal weighing device 28 and the hot metal thermometer 29 are used when actually measuring the hot metal output and the hot metal temperature.For example, when comparing the calculated predicted value with the actually measured value for a test, the hot metal component and the hot metal component are measured. Is sampled each time.

The sounding device 30 measures the height of the charged bed, and when the method of the present invention is not performed, the raw material charge is controlled by measuring the bed height during operation. In the inventive method, it is only an auxiliary use.

A description will be given of a method of performing material accounting and thermal accounting based on the information collected as described above, and controlling the timing of stopping air blowing and the amount of coke charged next time.

The above-mentioned operation measurement data is sampled at predetermined timings, and after data processing, a time-series data file is created. The created time-series data file is input to the mass balance model built into the computer, and the material is calculated sequentially.The cylinder type is calculated from the amount of coke and fuel consumed by combustion with the supporting gas and the flow rate of each exhaust gas component. Various reactions in the furnace, that is, (1),
The amounts of the reactions (2), (3) and the solution loss reaction shown in the following equation (4) are sequentially and accurately quantified.

C + CO ₂ → 2CO−38200 kcal / kmol · C (4) Heat input and output of cylindrical furnace such as reaction heat based on the reaction amount of various reactions in the furnace, heat dissipated by furnace refractories, and sensible heat carried away by waste gas Is calculated using a heat balance model, and the amount of hot metal produced from the difference between heat input and heat output is calculated sequentially, so the amount of hot metal generated in the furnace and the amount of coke consumed by carburizing into the hot metal are calculated in time series. can do.

The in-furnace hot metal production calculated by the model is displayed on the CRT screen together with the actually measured iron output at each predetermined timing. In this way, the amount of hot metal produced in the furnace in a time series is calculated and displayed online during operation, and operating conditions such as the SR ratio, the amount of injected gas and fuel during melting or for each charge, and the amount of coke charged change. Even in this case, it is possible to accurately predict the hot metal production in the furnace. Further, since the melting completion time is predicted, it is possible to control the blowing stop time. As a result, it is possible to avoid useless blowing at the end of melting, so that it is possible to reduce the amount of support gas fuel and coke used.

In addition, the total amount of coke consumed in the furnace consumed for combustion, solution loss, and carburization of molten iron calculated by the model is calculated for each charge. Predict the amount,
The furnace heat control is performed by controlling the amount of coke charged next time. These predicted values and control values are sequentially displayed on the CRT screen together with the measured tapping temperature. In this way, during operation, the amount of bed coke is accurately predicted online and the amount of coke charged in the furnace is controlled the next time, and the amount of bed coke in the furnace at each charge is kept constant. It is possible to stabilize the furnace condition, hot metal temperature and components, and reduce coke consumption.

Next, the prediction accuracy of the amount of hot metal produced in the furnace by the method of the present invention will be described.

FIG. 4 is a diagram showing a comparison between the final hot metal production for each charge calculated by the method of the present invention and the actually measured hot metal output.

As shown in the figure, the values calculated by the method of the present invention and the measured values are in good agreement, and the error is as small as 3% on average. From these results, it is clear that the method of the present invention can sufficiently determine the dissolution.

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

(Examples 1 and 2) The apparatus used was the apparatus shown in FIG. 3 described above. The furnace size of the cylindrical furnace was 1.5 m in diameter, the height from the furnace bottom to the furnace opening was 3.6 m, and the internal volume was 6 m. ³ The primary tuyere starts from the hearth
A total of eight secondary tuyeres were installed at a height of 0.8 m and four secondary tuyeres at a height of 1.2 m from the furnace bottom, each with four 90 ° intervals on the side wall. A tap hole is provided in the lower part of the furnace wall.

The raw material is a square body with a side of almost 0.45 m and a bulk specific gravity of 3.5 ton / m
The scrap ( ³ ) (iron purity: 99%) and iron ore having the chemical composition shown in Table 1 were used, and the coke and pulverized coal shown in Table 2 were used as fuel.

The operating conditions were as follows: coke was charged up to the level including the primary tuyere, and scrap and iron ore (SR ratio 100% or 7
5%). And the primary tuyeres blowing the pulverized coal of 1000Nm ³ / h of oxygen and 1,400kg / h from, was blown into the 600Nm ³ / h of oxygen, respectively from the secondary tuyeres.

Example 1 and Example 2 in Table 3 have different SR ratios.
In the operation example in the case of 100% and 75% iron source blending, the operation was performed by predicting the amount of hot metal produced in the furnace in time series.

Comparative Example 1 and Comparative Example 2 in Table 3 are operation examples in which the SR ratio was 100% and 75%, respectively. .

The results of the operation are shown in Table 3. As is clear from Table 3, the fuel consumption (coke consumption + pulverized coal consumption) in Example 1 was 36 kg / t (36 k / ton of hot metal) compared to Comparative Example 1.
g), Example 2 is 29 kg / t lower than Comparative Example 2.
The amount of oxygen used in the example is also 16 to 26 Nm ³ / t less than that in the comparative example.
Although the melting time was also reduced by 11 to 19%, there was no difference in the tapping amount, and it is clear that the prediction of the completion of melting according to the present invention was appropriate.

(Example 3) In Example 3, the amount of bed coke was predicted using the method of the present invention, and the operation was performed by controlling the amount of coke charged next time.

The basic conditions of the third embodiment are the same as those of the first or second embodiment. The bed coke excess / deficiency is determined by comparing the initial bed coke height (amount) with the increase / decrease of bed coke calculated by the following equation (5).

Increase / decrease in bed coke = [coke charge / charge] − [consumed coke / charge] (5) In the equation (5), [consumed coke / charge] includes the amount of hot metal carburized.

As Comparative Example 3, the filling bed height in the furnace was measured with a sounding device during melting under the same basic conditions as in Example 3, and the coke amount charged next time was set to the coke amount / charge previously set in accordance with the time series transition. Coordinating operations were also performed.

FIG. 5 is a diagram showing the amount of coke used, the temperature of the hot metal and the C concentration in the hot metal for each charge, comparing the example with the comparative example.

As shown in the figure, in Example 3, the hot metal temperature was maintained at approximately 1450 ° C., and the [C] concentration in the hot metal was maintained substantially at an average value of approximately 4.5% by weight, and the hot metal temperature and the composition were stabilized as compared with Comparative Example 3. did. In addition, the average value of the coke consumption for each charge was 136 kg / ton in Example 3, which was 14 kg / ton reduced from 150 kg / ton in Comparative Example 3.

(Effect of the Invention) The method for producing hot metal of the present invention uses a much smaller and simpler cylindrical furnace as compared with a blast furnace, and uses iron ore and scrap together with ore as a source of iron to flexibly fly iron. Is a way that can be done. In addition, since the amount of hot metal production in the furnace can be calculated in time series in response to changes in operating conditions, it is possible to accurately predict when to stop blowing air, thereby improving productivity and reducing the amount of combustible gas, fuel and coke used in production. Costs can be reduced.

In addition, since the amount of bed coke in the furnace can be predicted, it is possible to control the amount of coke charged in the next time, prevent the furnace heat from decreasing, stabilize the furnace condition and hot metal temperature, components, and reduce the amount of coke used. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a cylindrical furnace used for carrying out the method of the present invention and the state of the interior of the furnace, FIG. 2 is a block diagram illustrating the gist of the present invention, and FIG. FIG. 4 is a schematic cross-sectional view showing an example of a cylindrical furnace melting apparatus used for carrying out the method and various measuring instruments attached thereto. FIG. 4 shows the amount of hot metal production (calculated value) for each charge calculated by the method of the present invention; FIG. 5 is a diagram showing the measured amount of hot metal in comparison, FIG. 5 is a diagram showing the amount of coke used for each charge, the hot metal temperature and the C concentration in the hot metal in comparison with the examples and comparative examples.

Claims (1)

(57) [Claims] 1. A cylindrical furnace having an opening for discharging gas in the furnace and charging a raw material at an upper part thereof, a primary tuyere at a furnace bottom part and / or a lower side wall, and a secondary tuyere at an upper side wall thereof, A packed layer of coke is formed from the bottom of the furnace to a level including the primary tuyere, and a packed layer of scrap and iron ore is formed thereon to a level including the secondary tuyere. In the method of manufacturing hot metal in which the supporting gas is blown from the next tuyere, during the operation, material accounting and thermal accounting in the furnace are performed at predetermined timings to calculate the hot metal production and furnace coke consumption in time series. And a method for controlling the blow-off time and the amount of coke charged next time by predicting the melting completion time and the excess / deficiency of bed coke in the furnace from the calculated values.