JPH01195217A - Operation of melting and reducing furnace - Google Patents

Abstract

PURPOSE:To appropriately control the operation of a melting and reducing furnace by integrating the calculated values of every instantaneous oxygen amt. accumulated in the furnace to obtain the amt. of the metal oxide remaining in the furnace and its rate of change, and detecting the progress of the reduction reaction. CONSTITUTION:The flow rate of oxygen supplied into the furnace from an oxygen lance 2 and a bottom-blowing tuyere 3, the flow rate of generated gas by a generated gas flowmeter 9, the supply rates of prereduced ore, coal, and auxiliary material by weighers 4a, 5a, and 6a, the content of O2 in the generated gas by a gas analyzer 8, etc., are inputted to a process computer 11. Every instantaneous oxygen amt. accumulated in the furnace is integrated from the difference between the sum of oxygen supplied into the furnace and the sum of oxygen discharged from the furnace to compute the amt. of the metal oxide remaining in the furnace and its rate of change. The progress of the reaction is detected based on the computed results, and the furnace is stably and efficiently controlled. The supply rates of oxygen and carbonaceous material, the height of the lance 2, and the agitating force for a metal bath 12 and molten slag 13 are independently or integrally controlled based on the obtained metal oxide amt. and its rate of change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an operation method for efficiently and stably operating metal melting reduction.

[Conventional technology]

In a smelting reduction furnace, coal is burned in the form of lumps or while blowing oxygen gas into the furnace, and the molten slag and molten metal in the furnace are stirred to reduce the ore thrown in to obtain molten metal. It is necessary to constantly detect during operation whether the reduction reaction in the furnace is progressing as per the operational target, whether the material/heat balance is as planned, and to control these status values normally. For this purpose, it is particularly important to understand and properly control the components of the molten slag in the furnace, the temperature of the metal bath, etc.

As a conventional technique for performing such control, for example, there is a method for operating a smelting-reduction system disclosed in Japanese Patent Application Laid-Open No. 60-218407. It is intended only to provide a control method.

[Problem to be solved by the invention]

In smelting reduction, generally all of the oxidized metal in the ore added to the furnace is not necessarily reduced immediately and becomes molten metal, but a portion is mainly dissolved in the slag and exists as an oxidized metal component. The metal oxide concentration in this slag eventually reaches a concentration at which the rate at which the reducing agent in the furnace reacts with the metal oxide is in equilibrium with the ore supply rate. While repeating various tests, the inventors found that this equilibrium concentration differs depending on the stirring conditions of the metal bath and molten slag in the furnace, the carbon concentration in the metal bath, the amount of carbonaceous material in the molten slag, the oxygen supply condition, etc. I found out that.

In other words, the metal oxide concentration in the slag is not always constant;
It changes in response to changes in the situation inside the furnace. moreover,
Since the actual reduction reaction rate is different from the ore input rate,
It was also discovered that thermally stable operations cannot be achieved by simply determining the heat balance such as reaction heat based on the ore input rate. In addition, it is not uncommon for unreduced metal oxides to rapidly accumulate in the slag depending on changes in the conditions inside the furnace, and it is possible to continuously and instantly detect that the reaction inside the furnace is progressing properly. It was technically difficult to do so.

By the way, in the technique disclosed in the above-mentioned publication, the reduction rate in the furnace and the composition of the generated gas are measured to control the supply state of the pre-reduced ore, coal and oxygen. However, this method cannot measure the composition of the slag, especially the concentration (and total amount) of metal oxides in the slag.
It is difficult to judge whether the reduction reaction rate is progressing as intended or whether abnormal reactions will occur due to excessive concentration of metal oxide in the slag. It was difficult to properly control the speed.

In addition, in general conventional technology including the above technology, in order to determine whether the reduction reaction in the furnace is appropriate, it is necessary to collect molten slag from the furnace and analyze it. Methods have been used to measure metal oxide concentrations. However, in this measurement method, samples are collected intermittently, and analysis of the slag sample requires a long time of more than ten minutes, so the situation inside the furnace changes in a short period of time. In a furnace, it has been impossible to perform precise control that responds immediately to the actual reaction.

The present invention was developed in view of the above-mentioned problems, and is capable of continuously and instantaneously detecting changes in the reaction inside the furnace and keeping the reduction reaction and heat balance inside the furnace proceeding appropriately and stably. Provides operating methods that allow

[Means to solve the problem]

The present invention continuously measures the total amount of oxygen supplied into the furnace and the total amount of oxygen discharged from the furnace, and calculates the amount of oxygen accumulated in the furnace at that point from the difference between the two totals. This is a method of operating a smelting reduction furnace characterized by detecting the progress of the reaction by calculating and integrating the calculated values to determine the amount of oxidized metal remaining in the furnace and its rate of change. Continuously measure the total amount of oxygen supplied and the total amount of oxygen discharged from the furnace, calculate the amount of oxygen accumulated in the furnace at that point from the difference between the two totals, and calculate the calculated value. The amount of oxidized metal remaining in the furnace and the rate of change thereof are calculated by integrating the amount of oxidized metal remaining in the furnace.The oxygen supply rate and lance height, the carbon material supply rate, and the stirring power of the metal bath and molten slag can be adjusted individually or in combination. This is a method of operating a smelting reduction furnace characterized by control.

(for production) The present invention will be explained in detail below along with its operation.

In the present invention, in order to detect and understand the progress of the reaction in the furnace and the heat balance, etc., the oxygen balance in the melting reduction furnace is measured at every moment, and based on this, the oxygen balance in the furnace is measured. Mainly, calculate and understand the amount of metal oxide remaining in the slag and the concentration of metal oxide in the slag, and control operations appropriately.

First, to explain the reaction situation in a smelting reduction furnace, as mentioned earlier, all of the gaseous oxygen supplied into the furnace and the oxygen in the ore immediately react and are discharged outside the furnace as generated gas. As a result of various tests, we have found several relationships, such as that the oxygen remaining in the furnace is not necessarily a metal oxide, and that most of the oxygen remaining in the furnace exists as metal oxides.

In other words, he invented the ability to determine the amount of oxidized metal that remains unreduced in the furnace by determining the residual oxygen calculated from the measured values of oxygen supplied into the furnace and oxygen discharged. . Further, the value of the metal oxide concentration in the slag is calculated and obtained from the total amount of metal oxide and the amount of impurities such as 5102, CaO, etc. accumulated in the furnace from raw materials such as ores and carbonaceous materials incorporated into the slag. Furthermore, the actual reduction reaction rate in the furnace can be determined from the relationship between the change in the amount of oxidized metal in the furnace and the ore input speed, so the actual reduction reaction heat etc. can be accurately calculated at a given moment. The inventors of the present invention have made it possible to achieve this goal.

Here, an example of the configuration of smelting reduction for determining the amount of metal oxide remaining in the furnace and the concentration in the slag in the present invention will be described.

FIG. 1 is a block connection diagram showing an example of melt reduction control for carrying out the present invention. 1 is a furnace body, 2 is an oxygen supply lance, and a flow meter 28 is attached to the base. 3 is a bottom blowing tuyere, and a flow meter 3a is similarly attached thereto.

A preliminary reduced ore (ore) supply device 4, a coal supply device 5, and an auxiliary raw material supply device 6 are provided on the furnace, and are equipped with measuring instruments 4a and 5, respectively.
a.

The raw material is supplied into the furnace from the chute via 6a. The exhaust duct installed on the furnace is connected to an induction fan 10 via a generated gas cooler 14 and a sifter 7, and a generated gas component analyzer 8 and a generated gas flow meter 9 are installed in the middle of the exhaust duct. Note that 12 is molten iron and 13 is molten slag.

Here, the supplied oxygen flow rate is measured by the flowmeters 2a and 3a, and the meter 4
a, 5a, and 6a indicate the preliminary reduction ore supply rate, coal supply rate, and auxiliary raw material supply rate; the generated gas flow rate meter 9 indicates the generated gas flow rate;
The gas component analyzer 8 analyzes the generated gas. Go, CO2
, ) 121820 are measured and input into the process computer 11.

The process computer 11 performs the following calculations.

Change in amount of residual oxygen per unit time = (Supplied oxygen flow rate) + (pre-reduced ore supply rate) x (active oxygen ratio of pre-reduced ore) 100% source material supply rate) x (active oxygen ratio of auxiliary raw material) - (generated Gas flow rate) × (oxygen content ratio) ・・・・・・・・・(l
)Contained oxygen ratio-((h+1/2 CO+CO2-1-
1/2820) (a+oJ2) ”””””(2)≠
(Change in amount of residual oxygen per unit time) x (number of equivalents) x (metal atomic weight) ------- (4) Oxidized metal concentration in slag = (amount of residual metal oxide) / (amount of generated slag)... (6) Based on the above calculation results, an operating method for stably and efficiently controlling the melting reduction furnace will be described below.

First of all, we calculate the reduction reaction rate from the rate of change in the amount of residual oxidized metal in the furnace (and the oxidized metal concentration in slag), and calculate the amount of heat absorbed in the reduction reaction, the sensible heat of the molten metal, slag, generated gas, etc. The method calculates the amount of heat consumed in the furnace from the amount of heat available in the furnace, etc., and controls the supply rate and state of the carbon material and oxygen, which are heat sources, so that the temperature of the metal bath falls within the target range. To give a concrete example of what is controlled, the combustion rate of the carbonaceous material and the Change the secondary combustion rate, etc.

Secondly, it is important to prevent abnormal reactions that occur due to excessive metal oxide concentration in slag, such as slag bumping from the furnace mouth due to excessive slag foaming, and to maintain a stable state. important for proper operations. Therefore, based on the calculation results, the stirring power of the metal bath and molten slag, the supply rate of carbonaceous material, etc. are adjusted so that the metal oxide concentration in the slag is within the range below the upper limit of the metal oxide concentration in the slag, which is a stable operation condition. The amount of carbon remaining in the furnace is controlled by changing the amount of carbon, and the oxygen supply rate is also controlled. Here, the stirring force of the metal bath and molten slag is controlled mainly by adjusting the flow rate of the bottom blowing gas.

These controls are based on the calculation result of the amount of residual metal oxide in the furnace by the process computer 11, and the process computer issues control commands to the measuring instruments 4a and 5a.
The flow rate regulator 2 controls the supply rate of ore and carbonaceous materials.
a and 3a to control the oxygen supply rate and the stirring state of the metal bath and molten slag, and roughly move the lance 2 up and down to control the secondary combustion.

(Example) An example in which the present invention is applied to melting and reduction of iron will be described below.

The results of operations aimed at the conditions described below are as follows:
It is shown in FIG. 2 (Example) and FIG. 3 (Comparative Example). Here, the results of measuring the iron concentration in the slag (the sum of the concentrations of Fe3+ and Fe'' in the slag), hot metal temperature, and slag height are plotted as indicators of the control accuracy of the operating conditions.

(Conditions) (a) Smelting reduction furnace capacity □ 30 T/H (b) Smelting reduction control □ 100 tons (8) Hot metal temperature □ 1500℃ (d) Molten iron composition □C4,8%SiO,02%M
n O, 22% S O, 09% P O, 07% (e)
Components in slag □ Basicity 1.35 Mg07% 12038% As can be seen from the comparison between Figures 2 and 3, according to the operating method to which the present invention is applied, both the hot metal temperature and the iron concentration in the slag are stable. The reaction and heat balance could be controlled stably from beginning to end, and there was no bumping of slag from the furnace mouth due to abnormal slag foaming during operation. However, in the operation of the comparative example where proper reaction and heat balance control could not be carried out, the reduction reaction was delayed and the iron concentration in the slag increased, and the heat balance could not be maintained and the hot metal temperature decreased. It's stored away. Furthermore, due to the increase in the iron concentration in the slag, that is, the iron oxide concentration, the iron oxide in the slag reacts with the carbonic acid or carbonaceous material in the granulated iron, causing abnormal slag foaming, and the slag is removed from the furnace mouth. It was not possible to maintain stable operating conditions as the water was gushing out.

Further, a comparison of the productivity, the unit consumption of coal for the heat source, and the unit consumption of the refractory material of the furnace after long-term operation according to the present invention and the conventional method is shown below.

〔Effect of the invention〕

As explained above, according to the operating method according to the present invention, changes in reactions and heat balance in the furnace are continuously and instantaneously detected, and the concentration of oxidized metal in the slag and the metal Since the bath temperature can be controlled within the target range, changes such as abnormal phenomena in the reaction can be dealt with in advance, the melting reduction reaction rate is stabilized and operability is improved, and the bath temperature can be lowered. No reaction delay occurs. Furthermore, since the heat balance is stable and unnecessary high-temperature operations are no longer required, the consumption of carbonaceous materials as a heat source is reduced, and wear and tear on refractories due to high-temperature molten metal and molten slag can be prevented. Manufacturing costs can also be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing an example of melt reduction control for carrying out the present invention, and FIGS. 2 and 3 are graphs of an example and a comparative example showing operating conditions. DESCRIPTION OF SYMBOLS 1... Furnace body, 2... Oxidation lance, 3... Bottom blowing tuyere, 2a, 3a... Flow meter, 4... Preliminary reduced ore supply device, 5... Coal Supply device, 6...auxiliary raw material supply device, 4a. 5a, 6a... Measuring instrument, 8... Generated gas component analyzer, 9... Generated gas flow meter, 11... Process computer. Agent Patent Attorney Masaaki Akizawa Mitsunobu 7i'1 Figure

Claims (1)

[Claims] 1. Continuously measure the total amount of oxygen supplied into the furnace and the total amount of oxygen discharged from the furnace, and calculate the amount of oxygen accumulated in the furnace at that point based on the difference between the two totals. 1. A method for operating a smelting-reduction furnace, characterized in that the progress of a reaction is detected by calculating the amount of oxygen remaining in the furnace and calculating the amount of oxidized metal remaining in the furnace and the rate of change thereof by integrating the calculated values. 2. Continuously measure the total amount of oxygen supplied into the furnace and the total amount of oxygen discharged from the furnace, and calculate the amount of oxygen accumulated in the furnace at that point from the difference between the two totals. , the amount of oxidized metal remaining in the furnace and its rate of change are determined by integrating the calculated values, and then the oxygen supply rate and lance height, the carbon material supply rate, and the stirring power of the metal bath and molten slag are determined. A method of operating a melting reduction furnace characterized by controlling it alone or in combination.