JPH03173711A - Method and apparatus for regulating gas flow for pre-reduction in smelting reduction equipment providing pre-reduction furnace - Google Patents

Abstract

PURPOSE:To keep ore under suitable fluidized condition and to enable suitable pre- reduction by varying gas pressure for introducing into a pre-reduction furnace and regulating the actual flow rate. CONSTITUTION:A flow detector 18 outputs gas flow rate passing through a duct 11 to a computing control unit 20. The computing control unit 20 calculates the suitable pressure, which is outputted to a comparison adjusting device 21 and also opening degree regulating signal decided with calculation is transmitted to a damper 17 to regulate the opening degree. The pressure at the inlet of the pre-reduction furnace 2 is detected with a pressure detector 19 and this is outputted to the comparison adjusting device 21. The comparison adjusting device 21 compares this pressure signal and the pressure signal from the computing control unit 20 and the opening degree regulating signal is transmitted to the damper 16 so that the actual pressure approaches the suitable pressure to regulate the opening degree. By this method, for the variations of gas pressure and flow rate generated in the smelting reduction furnace, the fluidity in pre-reduction furnace 2 is kept under the suitable condition, thereby smooth operation of the furnace is made possible.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applicable to a smelting and reduction equipment for iron ore, etc. equipped with a fluidized bed type pre-reduction furnace, when gas generated from the smelting reduction furnace is introduced into the pre-reduction furnace. The present invention relates to a method for adjusting gas flow and an apparatus suitable for carrying out the method.

[Conventional technology]

The iron bath smelting reduction method is attracting attention as an alternative pig iron production technology to the blast furnace method.

In this smelting reduction method, in order to increase energy efficiency, preliminary reduction of ore is performed using reducing gas generated from a smelting reduction furnace. As a preliminary flijs furnace for this,
A fluidized bed type reduction furnace is often used because it allows the raw iron powder to be used as it is and because heat exchange and reaction are fast.

In the conventional method using such a fluidized bed pre-reduction furnace, the gas generated in the melting reduction furnace is directly introduced into the pre-reduction furnace. In terms of energy efficiency, it is advantageous to use the entire amount of gas generated in the smelting reduction furnace for preliminary reduction, and it is sufficient and appropriate to set the shape and dimensions of the preliminary reduction furnace in consideration of the flow rate of generated gas. This method is based on the idea that preliminary reduction can be carried out, and such a method is disclosed in, for example, Japanese Patent Application Laid-open Nos. 58-210110, 62-23915, and 62-60805. ing.

[Problem to be solved by the invention]

In a fluidized bed pre-reduction furnace, in order to fluidize the charged granular ore in an appropriate state, the gas flow rate (actual flow rate or flow rate) introduced into the furnace must be adjusted according to the shape and dimensions of the furnace body. It needs to be within an appropriate range. In other words, if the gas flow rate is low, the ore will not fluidize properly;
If the amount is too high, the amount of ore scattered outside the furnace together with the exhaust gas will increase, and in either case, a uniform and sufficient preliminary reduction reaction cannot be expected. Troubles are likely to occur with the setting values.

However, in the operation of smelting reduction furnaces, which have been studied for practical use in recent years, the generated gas, that is, the gas introduced into the preliminary reduction furnace, tends to fluctuate greatly in both pressure and flow rate due to the following reasons. It has no choice but to take this form. That is, this is due to the following reasons.

i) The smelting reduction method has the great advantage of being able to flexibly adjust the production volume, and operating conditions such as the amount of raw material charged, the amount of oxygen blown, and the temperature inside the furnace change significantly depending on the production volume.

■) The higher the gas pressure in the smelting reduction furnace, the higher the gas density, which can promote the reduction reaction, and also has the advantage of making the equipment more compact. It is advantageous to operate under the above conditions.

■) In order to improve economic efficiency, various raw materials (for example,
It is necessary to use various types of coal, etc., which have different volatile contents and therefore generate different amounts of gas.

In operations where the amount of gas generated fluctuates greatly in this way, the conventional method of directly introducing the gas generated in the smelting reduction furnace into the pre-reduction furnace cannot fluidize the ore properly, and therefore it is difficult to fluidize the ore properly. We cannot expect a preliminary return.

To solve this problem, we have designed equipment based on a relatively large amount of gas, and if the amount of gas required for fluidization is insufficient during actual operation, some of the exhaust gas from the pre-reduction furnace will be A method is being considered in which the gas is recirculated and added to the generated gas from the smelting reduction furnace, and then introduced into the preliminary reduction furnace.

However, with this method, it is necessary to increase the pressure of the gas in order to recirculate the gas whose pressure has decreased after being discharged from the pre-reduction furnace, and for this purpose, the gas is cooled and dusted at the pressure boosting compressor and the compressor input side. A heating device is required to raise the temperature of the gas again after passing through these devices, resulting in a large amount of equipment cost and operating cost.

The present invention was made in view of such conventional problems,
Even if the pressure and flow rate of the generated gas fluctuates significantly depending on the operating conditions of the smelting reduction furnace, the ore can be maintained in an appropriate fluidized state in the fluidized bed pre-reduction furnace, and this can be achieved economically. The purpose of the present invention is to provide a method for adjusting the flow rate of a prereducing gas and an apparatus suitable for carrying out the method.

[Means to solve the problem]

The method for adjusting the flow rate of pre-reducing gas according to the present invention to achieve such an objective is to Its feature is that the actual flow rate is adjusted by changing the pressure of the gas introduced into the preliminary reduction furnace so as to fluidize it appropriately.

Moreover, the apparatus according to the present invention for carrying out such a method includes a reducing gas flow path from the smelting reduction furnace to the preliminary reduction furnace,
Its feature is that an opening adjustment valve is provided in each of the exhaust gas passages from the preliminary reduction furnace.

[For production]

The present invention utilizes the principle that the volume of a compressible fluid changes by changing its pressure. In other words, by changing the pressure of the gas generated in the smelting reduction furnace using the method of the present invention, the volume of the gas increases or decreases, and the actual flow rate of the gas is adjusted before being introduced into the pre-reduction furnace (hereinafter, description regarding the gas flow rate) In the above, when simply written as "flow rate", it means the flow rate 1, for example, Nrn'/hr in a standard state, whereas the flow rate under the actual pressure and temperature of the gas is called the "actual flow rate"). Such changes in gas pressure are performed depending on the amount and pressure of gas generated from the melting reduction furnace. For example, when the amount of gas generated in the smelting reduction furnace is insufficient to fluidize the ore in the pre-reduction furnace.

By lowering the pressure, the actual flow rate is increased and the ore is properly fluidized. Conversely, when the amount of gas generated is too large, the pressure is increased and the actual flow rate is reduced to remove the ore from the pre-reducing furnace. The scattering of ore can be suppressed.

Further, according to the apparatus of the present invention, by adjusting the opening degree of the opening degree adjusting valve provided in each gas flow path, the pressure of the gas generated in the smelting reduction and furnace can be changed according to the above adjustment method. The flow rate can be adjusted and introduced into the preliminary reduction furnace.

For example, if you reduce the opening of the regulating valve in the reducing gas flow path and increase the opening of the regulating valve in the exhaust gas flow path, the pressure of the gas introduced into the preliminary reduction furnace will decrease; If you do the opposite, the gas pressure will increase. As described above, according to the device of the present invention, the above-mentioned gas flow rate adjustment can be performed only by operating the opening adjustment valve.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which 1 is a smelting reduction furnace, 2 is a fluidized bed pre-reduction furnace, and 3 is a reducing gas flow for introducing gas generated from the smelting reduction furnace into the pre-reduction furnace. 4 is an exhaust gas flow path from the preliminary reduction furnace, and 6 and 7 are cyclones provided in each of the gas flow paths. The reducing gas flow path 3 is connected to the ducts 8 and 9 on the upstream and downstream sides of the cyclone 6, and the exhaust gas flow path 4 is connected to the cyclone 7.
ducts 10.11 on the upstream and downstream sides of the duct 10.11, respectively.

In such a smelting reduction facility, iron ore is first charged into a pre-reduction furnace 2, preheated and pre-reduced in a solid state, and then
It is charged into the melting reduction furnace 1 and melted and reduced.

The fluidized bed pre-reduction furnace 2 is supplied with gas generated from the smelting reduction furnace through a reducing gas passage 3. That is, the generated gas of the smelting reduction furnace containing CO as a main component is led to the cyclone 6 through the duct 8 constituting the reducing gas flow path 3 to remove dust, and then introduced into the lower part of the pre-reduction furnace 2 through the duct 9. Ru. In the preliminary reduction furnace 2, a dispersion plate 12 having a large number of through holes is used.
Powder-like ore is charged onto the rectifying plate and the gas is flowed from below the dispersion plate 12 to fluidize the ore and form a fluidized bed 5. The ore is stirred in the flow R5, reacts with the reducing gas, is pre-reduced and preheated, and is discharged from the discharge port 13 as a pre-reduced ore. On the other hand, the gas discharged from the pre-reduction furnace 2 is guided to the cyclone 7 through a duct 10 constituting the exhaust gas flow path 4, and after collecting the fine ore particles scattered from inside the furnace, the gas is passed through the duct 11. The gas is sent to a gas processing facility (not shown).

In this embodiment, the pre-reduced ore discharged from the discharge port 13 is poured into the melting reduction furnace 1 through the transfer pipe 14 and charged (charging by gravity fall), and the fine powder collected by the cyclone 7 The pre-reduced ore is gas-transferred to the smelting reduction furnace 1 through a transfer pipe 15 and charged by so-called injection. That is, the pre-reduced ore is classified into medium/coarse particles and fine particles, and each is charged into the smelting reduction furnace 1 through separate routes.

In the melting reduction equipment as described above, a damper 16 serving as an opening adjustment valve is installed in the middle of the duct 9 constituting the reducing gas flow path 3.
A similar damper 17 is also provided in the middle of the duct 11 constituting the exhaust gas flow path 4.

In order to control the opening degrees of these dampers 16 and 17, a gas flow rate detector 18 is provided in the duct 11, and a pressure detector 19 is provided at the gas inlet in the preliminary reduction furnace 2. Each damper 1 is
An arithmetic controller 20 and a comparison adjuster 21 are provided for controlling 6 and 17. The dampers 16, 17 and each instrumentation means described above adjust the flow of the introduced gas in order to properly fluidize the ore in the preliminary reduction furnace 2. Its effect will be described later.

In order to fluidize the granular ore in the preliminary reduction furnace 2, the actual flow rate of the gas introduced needs to be appropriate as described above. FIG. 2 shows an investigation of the relationship between gas flow rate and gas pressure capable of fluidizing ore to an appropriate state using a preliminary reduction furnace 2 and a test fluidized bed furnace (not shown).

The figure shows the flow rate of gas introduced into the fluidized bed furnace (including the preliminary reduction furnace 2; the same applies hereinafter) (the flow rate when the gas volume is converted to the standard state, for example, the flow rate in units of Nm3/h). The horizontal axis represents the relative value (%) to the reference value (design value) for the gas, and the vertical axis represents the pressure at the inlet of the fluidized bed furnace (hereinafter referred to as inlet pressure, unit: kg/cm"G). It is centered on this.

In Figure 2, the solid line A indicates the minimum required gas flow rate to fluidize the ore in relation to its inlet pressure.
Appropriate fluidization of the ore cannot be obtained under the conditions (gas flow rate and inlet pressure) in the region to the left of the solid line A when facing the paper.As can be seen from the figure, as the gas pressure increases, the gas The actual flow rate decreases because the volume of
(flow rate under standard conditions) increases.

In contrast, Fig. 2 shows that even if the gas flow rate decreases and the ore no longer fluidizes properly, if the inlet pressure is changed to satisfy the conditions in the region to the right of solid line A, the amount will be reduced. This shows that appropriate fluidization can be achieved again even with a high flow rate of gas. For example, inlet pressure crab 2, Okg/
cm"G, flow rate: If the flow rate is reduced to 60% when 100% gas is introduced, the ore will not be fluidized properly if the pressure remains at 2.0kg/C2S"G. This is 0.8 kg/a
If you change to m ” G, the state will be in the right side area of the solid line A, and proper fluidization will occur again.This means that even if the gas flow rate in the standard state is the same 60%, the pressure must be lowered. This is because the actual flow rate increases (approximately 3.0/1.8 times (absolute direct ratio) as the inlet pressure changes).

On the other hand, if the flow rate of gas introduced into the fluidized calendar furnace is too high, there is a problem that a large amount of ore will be scattered outside the furnace together with the gas, so we also investigated the conditions that limit this.

In the above embodiment, the pre-reduced ore in the form of fine particles scattered from the pre-reduction furnace 2 is collected by the cyclone 7 and handled separately from medium and coarse particles, but the fine particles scattered outside the furnace are handled separately. Among them, those with a relatively coarse particle size have not been sufficiently pre-reduced.

In addition, since clogging and abrasion of the cyclone 7 and the transfer pipe 15 occur, it is necessary to limit the scattered ore to those having a minute particle size. The inventors of the present invention have taken this point into consideration and have found that the solid line in FIG. 2 can be defined as a condition for limiting the particle size of the ore scattered with the gas from the fluidized bed furnace to, for example, 0.5 mm or less. The solid line port indicates the gas flow rate that satisfies the condition in relation to the inlet pressure, and under the conditions on the right side of the solid line port, ore with a particle size exceeding 0.5 m will be scattered. Although not shown, for example, the above particle size is 1.

The boundary line to limit the grain size to O- or below is set slightly to the right of the solid line port, and under conditions in the area far to the right of the solid line port, most of the ore of all grain sizes will be scattered from the fluidized bed furnace. This was also confirmed.

Therefore, in the preliminary reduction furnace 2, ore having a particle size exceeding 0.5 am is fluidized to an appropriate state, and
In order to scatter and classify only ores with a particle size smaller than that with the gas, it is necessary to maintain the inlet gas condition during operation in the area between the solid line A and the solid line port in Figure 2 (shaded area). . In other words, by keeping the inlet gas condition in the above range, proper fluidization and proper classification in the preliminary reduction furnace can be maintained, and by changing the gas pressure as described above, the melting reduction furnace 1 This means that the fluctuations in gas pressure and flow rate that occur can be adequately coped with. Furthermore, since there is a certain relationship between the inlet gas pressure of the pre-reducing furnace and the gas pressure inside the furnace, it is also possible to measure and change/adjust the in-furnace gas pressure instead of the pre-reducing furnace inlet gas pressure. , the same effect as described above can be obtained.

The specific method will be explained below based on FIG.

In the equipment shown in FIG. 1, the opening degrees of the damper 16 and the damper 17 are adjusted in the following manner to control the flow of the preliminary reduction gas. The flow rate detector 18 has a correction function based on temperature and pressure, and outputs the flow rate of gas passing through the duct 11 to the arithmetic controller 20 as a value in a standard state. The arithmetic controller 20 is preset with an appropriate gas inlet pressure/car flow rate relationship (for example, the shaded area in FIG. 2), and based on this relationship, the flow rate value input from the flow rate detector 18 is determined. Calculate the appropriate pressure at
Send a call to 7. The opening degree of the damper 17 is adjusted by a drive means (not shown) based on a signal thereof. On the other hand, the pressure at the inlet of the preliminary reduction furnace 2 is detected by the pressure detector 19 and output to the comparison regulator 21 . The comparison regulator 21 compares this pressure (actual pressure) signal with the pressure (proper pressure) signal input from the arithmetic controller 2o, and sends an opening adjustment signal to the damper 16 so that the actual pressure approaches the proper pressure. Based on this signal, the opening degree of the damper 16 is adjusted by a drive means (not shown). In this way, the instrumentation means is the damper 16
, 17, cascade control is performed to determine the inlet pressure of the preliminary reduction furnace 2 according to the gas flow rate.

To explain a more specific example of such control, for example, the generated gas pressure crab 2 of the melting reduction furnace 1. Okg/cm2G
, the inlet pressure of the preliminary reduction furnace 2 2, 0 kg/c
When the generated gas flow rate decreases from 100% to 60% during operation under the condition of m'G, the dampers 16, 17 and the instrumentation operate as follows. That is, the flow rate detector 18
detects the gas flow rate (60%), the arithmetic controller 20 sets the appropriate pressure (for example, 0, 8 kg) based on this detected value.
/ cm ”G) and compares and compares this signal with the adjuster 21
At the same time, a signal to increase the opening degree is sent to the damper 17. The comparison regulator 21 compares the pressure (2,0 kg/(!l''G)) detected by the pressure detector 19 with the appropriate pressure signal, and sends a signal in the opening range to the damper 16.

By adjusting the opening degrees of the dampers 16 and 17 in this manner, the inlet pressure and flow rate of the gas enter the region between the solid line 490 in FIG. 2, and the ore is properly fluidized in the preliminary reduction furnace 2. It becomes like this.

In reality, such control is performed continuously based on changes in the gas flow rate, so that an appropriate fluidized state can always be maintained.

For example, the inlet gas pressure of the preliminary reduction furnace 2 is 0°8 k.
g/cn" When the flow rate increases from 100% to 160% during operation at G, the opening of the damper 16 is increased by the control described above, the damper 17 is adjusted in the direction of the opening range, and the gas inlet is The pressure is increased to, for example, 2 kg/an''G. The condition of 2kg/cs"0 160% is included in the shaded area in Figure 2, and the ore is appropriately fluidized in the pre-reduction furnace 2, and the scattering of the pre-reduced ore with a particle size exceeding 0.5 m is prevented. be done.

In addition, due to the pressure fluctuation of the gas generated in the melting reduction furnace 1,
Even in the case where the gas flow rate is constant and only the inlet pressure of the pre-reducing furnace 2 changes, similar control can maintain the gas state in a region where proper flow can be obtained.

In this way, by performing the above-described control using the apparatus shown in FIG. 1, the pressure and flow rate of the gas generated in the melting reduction furnace 1 can be controlled over a wide range of fluctuations.

The pre-reduction furnace 2 can be operated while maintaining fluidization in an appropriate state at all times.

In the embodiments described above, for example, instead of using the gas flow rate detector 18, the amount of generated gas may be estimated based on the amount of various raw materials charged into the smelting reduction furnace 1 and the amount of blown gas. good. The flow rate of gas generated in a smelting reduction furnace can be calculated fairly accurately from the amounts of charged raw materials and blown gas.

Further, by providing an exhaust gas cooler and a dust remover on the upstream side of the flow rate detector 18 in the duct 11.

The accuracy and life of the detector 18 can be improved. Furthermore, a duct 8 or 9 between the melting reduction furnace 1 and the damper 16
By extracting a portion of the reducing gas from the reactor and sending it out of the system via the control valve, it becomes possible to arbitrarily reduce the reducing gas flow rate entering the preliminary reduction furnace 2, further improving operational flexibility. can be done.

In addition, the opening adjustment valves provided in the reducing gas flow path 3 and the exhaust gas flow path 4 are not limited to the butterfly valve type damper as in this embodiment, but also various types of opening adjustment valves including gate type valves. It is possible to use a valve. Further, the opening adjustment valve may be composed of a plurality of valves.

In addition, in controlling the gas flow rate as described above, the operating state of the pre-reducing furnace 2 can be properly controlled by so-called planting control, which always keeps the inlet pressure of the pre-reducing furnace 2 constant regardless of the gas pressure generated in the smelting-reducing furnace 1. In this case, if the inlet pressure is kept as high as possible, the density of the gas can be increased and the preliminary reduction efficiency can be improved.

It goes without saying that the method and apparatus of the present invention as described above are not limited to smelting reduction for iron manufacturing, but can also be applied to smelting reduction of other metals.

〔Effect of the invention〕

As described above, according to the method and apparatus of the present invention, even if the pressure and flow rate of the generated gas fluctuate significantly depending on the operating state of the smelting reduction furnace, the ore can be properly fluidized in the fluidized bed pre-reduction furnace. The ore can be kept in a state of oxidation, and the ore can be properly reduced in advance. In this way, appropriate preliminary reduction can be performed regardless of the amount of gas generated or pressure in the smelting reduction furnace, so it is possible to flexibly adjust production volume and change operating conditions, which are the original characteristics of smelting reduction. It can be done arbitrarily. In addition, such an effect can be achieved by simply providing an opening adjustment valve in the gas flow path and adjusting the opening adjustment valve therebetween, which has the advantage of reducing the burden on equipment and operating costs.

[Brief explanation of the drawing]

FIG. 1 is an overall explanatory diagram showing one embodiment of the present invention. FIG. 2 shows the gas flow rate and gas pressure conditions for properly fluidizing ore in a fluidized bed furnace. In the figure, 1 is a melting reduction furnace, and 2 is a preliminary reduction furnace. 3 is a reducing gas flow path, 4 is an exhaust gas flow path, and 16.17 is a damper. Figure 1 Figure 2 Gas flow rate (%)

Claims (1)

[Claims] 1. In an operation method in which ore is pre-reduced in a fluidized bed pre-reduction furnace and then melted and reduced in a smelting reduction furnace, the gas generated in the smelting reduction furnace is used as a pre-reduction gas to be sent to the pre-reduction furnace. When introducing the ore, the actual flow rate is adjusted by changing the pressure of the gas introduced into the pre-reducing furnace or the gas pressure in the pre-reducing furnace so that the ore is appropriately fluidized in the pre-reducing furnace. A method for adjusting the flow of preliminary reduction gas in a smelting reduction facility equipped with a reduction furnace. 2. In a device for adjusting the flow of gas for preliminary reduction in equipment in which ore is pre-reduced in a fluidized bed pre-reduction furnace in which the gas generated in the smelting-reduction furnace is introduced as a preliminary-reduction gas, and then melted and reduced in a smelting-reduction furnace. , a smelting reduction equipment equipped with a pre-reduction furnace, characterized in that opening adjustment valves are provided in each of the reducing gas flow path from the smelting reduction furnace to the pre-reduction furnace and the exhaust gas flow path from the pre-reduction furnace. A device for adjusting the gas flow for pre-reduction in.