JP6102348B2 - Recovery method of converter exhaust gas - Google Patents

Description

  The present invention relates to a converter exhaust gas recovery method for collecting exhaust gas generated in a converter and recovering it in an unburned state.

The exhaust gas generated during converter refining is a gas containing carbon monoxide at a high concentration. As a method for treating the converter exhaust gas, there are a combustion method in which carbon monoxide in the exhaust gas is burned at the top of the converter furnace, and heat is recovered as steam, and a non-combustion method in which carbon monoxide is recovered without burning. However, the non-combustion method is the mainstream.
However, when exhaust gas is recovered by the non-combustion method, the exhaust gas is flammable (hereinafter also referred to as flammable gas), and therefore there is a risk of explosion when the oxygen concentration reaches a certain value.
Therefore, for example, in Patent Document 1, an inert gas layer (a layer mainly composed of CO ₂ , H ₂ O, and N ₂ ) necessary for eliminating exhaust gas in the flue at the end of exhaust gas recovery is not excessive or insufficient. An exhaust gas recovery method is disclosed that improves the recovery rate of the combustible gas produced and eliminates the risk of explosion due to the oxygen concentration in the recovered gas exceeding a certain value.

Japanese Patent Publication No. 63-5449

However, the conventional method still has the following problems to be solved.
The above method, before the blowing end of the converter, all of the combustible gas in the flue to replace with inert gas, and setting the air intake flow quantity. However, in order to ensure safety, it is not necessary to completely replace the inside of the flue with an inert gas before the end of blowing, and in this way, when replacing with an inert gas completely, combustible gas due to combustion loss. The amount of recovered is reduced.
In the method described above, the carbon concentration was measured by inserting a sub-lance into the molten steel by decarburization rate that the measured value based, is performed for calculating the air intake flow rate from the outside. However, in the measurement of carbon concentration using a sub-lance, because variations in the measured value increases, the calculation accuracy of the air inlet stream volume decreases.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a converter exhaust gas recovery method that improves the recovery efficiency of combustible gas generated in a converter.

The gist of the present invention made to solve the above problems is as follows.
(1) The exhaust gas generated by the blowing of the converter is collected in a gas holder through the flue in an unburned state, and the exhaust gas is sucked into the flue by inhaling air at the end of the blowing of the converter. In a method for recovering converter exhaust gas that is burned and generates an inert gas in the flue,
At the end of blowing of the converter, the CO concentration of the exhaust gas in the region where the exhaust gas in the flue is recovered and diffused is set to the flue stack so that the CO concentration by the gas holder set in advance becomes the lower limit CO concentration of recovery. recovery process of the converter exhaust gas and adjusting the inlet stream amount and the intake timing of air.

(2) inlet stream of air into the flue from the flow rate and the CO concentration of the exhaust gas to calculate the CO flow amount of the exhaust gas, the air flow amount required to produce the inert gas from the CO flow amount The converter exhaust gas recovery method according to (1), characterized in that it is calculated.

(3) The timing of starting the intake of air into the flue is defined as the time required from the start of air intake to the end of blowing of the converter, and the CO concentration of exhaust gas in the region from the start of air intake to the recovery lower limit CO. The converter exhaust gas recovery method according to (1) or (2) , wherein a difference from a time required to reach a concentration is set to “0” .

According to the converter exhaust gas recovery method of the present invention, the smoke concentration is reduced so that the CO concentration of the exhaust gas in the region where the exhaust gas recovery and emission are switched at the end of the blowing of the converter becomes the recovery lower limit CO concentration of the gas holder. since adjusting the intake flow amount and the intake timing of air to the canal while suppressing to a minimum the combustible gas can not remain recovered flue at blowing end, Minimizes combustion loss of the combustible gas Therefore, recovery efficiency can be improved.

It is explanatory drawing of the waste gas recovery equipment to which the recovery method of the converter exhaust gas which concerns on one embodiment of this invention is applied. (A)-(C) is explanatory drawing which shows the gas composition in a flue at the time of completion | finish of blowing of a converter, respectively, (D)-(F) is the installation position of each switching valve of (A)-(C), respectively. It is a graph which shows transition of CO density | concentration and flow volume of exhaust gas in.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, a converter exhaust gas recovery facility to which a converter exhaust gas recovery method according to an embodiment of the present invention is applied will be described, and then a converter exhaust gas recovery method according to an embodiment of the present invention will be described.

As shown in FIG. 1, a converter exhaust gas recovery facility (hereinafter also simply referred to as a recovery facility) 10 emits exhaust gas (ie, combustible gas) generated by blowing the converter 11 in an unburned state. This is a facility for collecting in a gas holder (hereinafter also simply referred to as a holder) 13 through a road (duct) 12.
In this flue 12, from the converter 11 side (upstream side) to the holder 13 side (downstream side), a hood 14, a radiation unit 15, a dust collector 16, an induction fan (attraction fan) 17, a switching valve 18, and The recovery valve 19 is sequentially provided.

The above-described hood 14 is disposed above the converter 11 so as to cover the furnace port 20 of the converter 11 and collects exhaust gas generated in the converter 11.
The radiating unit 15 cools the exhaust gas flowing into the flue 12.
A CO concentration analyzer 21 is provided at the top of the radiating section 15 (upstream of the flue 12), and the CO concentration (carbon monoxide concentration) in the exhaust gas can be sequentially analyzed by taking a part of the exhaust gas. It has a configuration. The CO concentration analyzer 21 is not particularly limited as long as it is configured to analyze the CO concentration, and the CO concentration analysis interval may be a time that does not hinder the operation of the recovery facility 10. That's fine.

The dust collector 16 collects exhaust gas, and a damper (not shown) is provided at the throttle portion. The number of dust collectors 16 is two here, but may be one, or a plurality of three or more.
The induction fan 17 has a function of sucking the exhaust gas generated from the converter 11.
The switching valve 18 is, for example, a three-way valve, and can switch the flow path of the exhaust gas to the direction of the holder 13 (recovery) or the direction of the chimney 22 (dispersion).
The recovery valve 19 blocks the exhaust gas flow path toward the holder 13.
The flue 12 is also provided with a flow meter (not shown) for measuring the flow rate of the exhaust gas in the flue 12 and an oxygen concentration meter (not shown) for measuring the oxygen concentration in the exhaust gas.

The operations of the dust collector 16, the induction fan 17, the switching valve 18, and the recovery valve 19 can be controlled by a control device (not shown). The control device also manages the measured values of the CO concentration analyzer 21, the exhaust gas flow meter, and the oxygen concentration meter. Based on these measured values, the dust collector 16, the induction fan 17, the switching valve 18, and Each operation of the recovery valve 19 can be controlled.
In particular, the switching control of the switching valve 18 is performed so that the flow path is directed from the gas holder 13 toward the chimney 22 under the following conditions.
-When blowing of the converter 11 is completed-When the CO concentration of the exhaust gas in the flue 12 falls below a preset concentration-The oxygen concentration of the exhaust gas in the flue 12 rises above a preset concentration Case

In the use of the converter exhaust gas recovery facility 10 shown above, the exhaust gas (that is, combustible gas) generated from the converter 11 is sucked by the induction fan 17 and enters the flue 12 through the hood 14. Lead. The flow rate of the exhaust gas flowing in the flue 12 is adjusted by changing the opening of the damper provided in each dust collector 16 without changing the suction force of the induction fan 17 (under the condition that the suction force is constant). it can.
The exhaust gas introduced into the flue 12 is cooled by the radiating unit 15 and further removed by the dust collector 16, and then passes through the induction fan 17.

Here, when the converter 11 is being blown (acid delivery) and combustible gas is generated, the control unit switches the flow path so as to face the gas holder 13 as described above. The valve 18 is controlled, and the recovery valve 19 is controlled to be opened, and the exhaust gas is recovered in the gas holder 13 through the flue 12 in an unburned state.
On the other hand, when the blowing of the converter 11 is completed, the control device controls the switching valve 18 so that the flow path is directed toward the chimney 22, and the exhaust gas is sent to the chimney 22. The combustible exhaust gas in the flue 12 is diffused from the chimney 22.

Subsequently, a converter exhaust gas recovery method according to an embodiment of the present invention will be described with reference to the converter exhaust gas recovery facility 10 described above.
When exhaust gas is recovered by a non-combustion method, an inert gas layer is formed by burning a combustible gas with air at the end of blowing. As shown in FIG. 2 (A), when combustion of the combustible gas is caused until the inside of the flue 12 is completely replaced with the inert gas by the end of blowing of the converter 11, the amount of recovered combustible gas Decreases.
In particular, the length of the flue 12 from the hood 14 to the switching valve 18 is generally as long as, for example, about 30 to 100 m (here, 50 m), and all of the combustible gas in the flue 12 is It is uneconomical to burn it with air drawn into the flue 12 from the hood 14 into an inert gas.

Accordingly, the present inventors have found, after intensive studies, the blow end of the converter 11, to suck the air into the flue 12 is burned exhaust gas, the inert gas flue 12 (CO ₂ ) In order to increase the recovery efficiency of the combustible gas in the flue 12, at the position of the region R where the exhaust gas in the flue 12 is recovered and switched at the end of blowing, It was conceived that it was necessary to satisfy that the CO concentration was the lower limit CO concentration for recovery. The CO concentration at the position of the region R is estimated based on the measured value of the CO concentration analyzer 21 provided on the upstream side of the region R described above. The recovery efficiency is “recovered amount × calorie correction (CO concentration, H ₂ concentration)”.

The situation in the flue 12 satisfying the above is illustrated in FIG.
Specifically, at the end of blowing of the converter 11, the exhaust gas that can be recovered by the gas holder 13 is not in the flue 12 upstream (converter 11) side (minimum) from the switching valve 18, and is combustible gas. This is a situation where the combustion loss of the gas is minimized.
In this case, in the flue 12 on the downstream side (gas holder 13) side from the position where the switching valve 18 is installed, exhaust gas (combustible gas) having a concentration lower than the recovery lower limit CO concentration by the gas holder set in advance exists. On the other hand, in the flue 12 on the upstream side from the installation position of the switching valve 18 described above, although there is a certain amount of CO concentration, there is exhaust gas (gas that cannot be recovered) below the above-described recovery lower limit CO concentration. Further, an inert gas exists on the upstream side.

On the other hand, FIG. 2 (A) shows a situation in which the amount of combustible gas recovered is reduced due to combustion loss because all the combustible gas in the flue 12 is replaced with inert gas at the end of blowing of the converter 11. (See Patent Document 1 described above). This is because, as shown in FIG. 2 (D), the blow end of the converter 11, the air flow amount to be sucked from the hood 14 to the flue 12 (exhaust gas flow rate) is excessive, yet the intake time of air early By past.
FIG. 2 (C) shows a situation in which a large amount of combustible gas that can be recovered by the gas holder 13 exists in the flue 12 at the end of blowing of the converter 11 and a recovery loss of the combustible gas occurs. . This is because, as shown in FIG. 2 (F), the intake timing of the air to be sucked into the flue 12 from the hood 14 is too late. For this reason, exhaust gas (combustible gas) having a concentration equal to or higher than the recovery lower limit CO concentration also exists in the flue 12 on the upstream side of the installation position of the switching valve 18 described above.

From the above, it is necessary to operate the converter exhaust gas recovery facility 10 as shown in FIG. 2E so that the situation of FIG. That is, at the end of blowing of the converter 11, the CO concentration of the exhaust gas in the region R where the exhaust gas in the flue 12 is recovered and switched is set to the recovery lower limit CO concentration by the gas holder 13 set in advance. it is necessary to adjust the suction start timing and the intake flow rate of air into the flue 12.
Here, the above-described lower limit of recovery CO concentration is a concentration that can be variously changed according to the purpose of use of the combustible gas. (CO concentration) can be used. In addition, although the upper limit of this range is not prescribed | regulated in particular, if the CO density | concentration of the combustible gas at the time of blowing is considered, it will be about 40 mass%, for example.
In addition, the above-described region R is preferably an installation position of the switching valve 18, but may be, for example, a range of about 5 m on the upstream side and the downstream side across the switching valve 18.

In optimizing the timing of starting the suction of air into the flue 12 (suction start timing), the time T1 required from the start of air suction to the end of blowing of the converter 11 and the region R from the start of air suction It is preferable to set the time T1 so that the difference from the time T2 required for the exhaust gas CO concentration to reach the recovery lower limit CO concentration becomes “0”.
For this reason, when the converter 11 is operated, the time T1 is adjusted, and the feedback control for operating the converter 11 of the next charge at the timing when the difference between the time T1 and the time T2 becomes “0” (for example, 30 By performing (about 40 charges), an appropriate time T1 can be obtained.

  In setting the above time T1, it is premised that the generation rates of the CO gas generated in the converter 11 are equal. This is because when the generation rate of CO gas changes, the state of decrease in CO concentration due to inhaled air changes. Since the CO gas generation rate varies depending on the oxygen blowing rate and the carbon concentration in the molten steel at the end of blowing, the results of changing these are stored as a table in the control device, and the time T1 is changed. Although it is good to use, for example, the result of the oxygen blowing rate (a certain blowing rate) obtained in advance or the result of the carbon concentration (a certain carbon concentration) in the molten steel at the end of the blowing obtained in advance is corrected. Can also be used.

Further, the intake flow amount of air into the the flue 12, the air flow amount necessary for the flow rate and the CO concentration of the exhaust gas to calculate the CO flow amount of the exhaust gas, generates an inert gas from the CO flow amount Can be calculated. This will be specifically described below.
First, the CO concentration in the exhaust gas obtained in CO concentration analyzer 21, and a flow rate of the exhaust gas obtained by the flow meter, to calculate a CO flow amount in the exhaust gas.
Then, to calculate the intake flow amount of air (oxygen) required for the calculated CO flow amount CO 2 _(inert gas).
Then, the intake flow amount of the calculated air from the sum of the flow rate of the exhaust gas obtained by the flow meter, to calculate the exhaust gas flow rate required.
The series of operations described above are executed by a program executed in the control device, but the required exhaust gas flow rate fg _(*) can also be calculated by the following equation, for example.

fg _(*) = (1 + 79/42 × λ) × fg ₍₀₎ + f _{N2 (P)} + f _{N2 (OB)}
λ: Furnace port burning rate (λ is set for inert control)
_{λ = (f CO2 -f CO2 (} 0)) / (f CO + f CO2 -f CO2 (0))
f _CO: CO gas stream of flue gas (= fg × _{X CO)}
f _CO2: CO ₂ gas stream of flue gas (= fg × _{X CO2)}
f _{O2: O 2} Gas flow amount in the exhaust gas (= fg × _{X O2)}
f _{CO2 (0):} the furnace generating CO ₂ gas flow amount _{(= f CO2 -2 × (21} /79 × f N2 -f O2))
fg _(0): the furnace gas generated total flow rate _{(= fg-f N2 -f N2} (P) -f N2 (OB))
fg: exhaust gas flow amount _{f N2: N 2} gas flow amount in the exhaust gas _{(= fg × X N2 -f N2} (OB) -f N2 (P))
f _{N2 (OB):} bottom blown et stream of _{N 2} amount _{<br/> f N2 (P): N} 2 flow rate from the purge <br/> X _{N2: N 2} concentration ₍₌ 1-X _{CO -X CO2} -X _O2 -X _H2)
X gas: Concentration of each gas

Based on the obtained result, the opening degree of the damper is adjusted, and a necessary exhaust gas flow rate is caused to flow into the flue 12.
As a result, the converter exhaust gas recovery facility 10 can be operated as shown in FIG. 2 (E), and as a result, the gas composition in the flue 12 can be brought into the situation shown in FIG. 2 (B). .
Therefore, by using the converter exhaust gas recovery method of the present invention, the recovery efficiency of the combustible gas generated in the converter can be improved.

  As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, the case where the recovery method of the converter exhaust gas of the present invention is configured by combining a part or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.

10: Converter exhaust gas recovery equipment, 11: Converter, 12: Flue, 13: Gas holder, 14: Hood, 15: Radiation part, 16: Dust collector, 17: Induction fan, 18: Switching valve, 19: Recovery Valve, 20: Furnace, 21: CO concentration analyzer, 22: Chimney

Claims (3)

The exhaust gas generated by blowing the converter is collected in a gas holder through the flue in an unburned state, and at the end of the blowing of the converter, air is sucked into the flue to burn the exhaust gas, In the recovery method of the converter exhaust gas for generating an inert gas in the flue,
At the end of blowing of the converter, the CO concentration of the exhaust gas in the region where the exhaust gas in the flue is recovered and diffused is set to the flue stack so that the CO concentration by the gas holder set in advance becomes the lower limit CO concentration of recovery. recovery process of the converter exhaust gas, characterized in that the suction start timing of the air adjusting an intake flow quantity. In the recovery process of the converter exhaust gas according to claim 1, the intake flow amount of air into the flue from the flow rate and the CO concentration of the exhaust gas to calculate the CO flow amount of the exhaust gas, the inert gas from the CO flow amount recovery process of the converter exhaust gases and obtaining by calculating the air flow amount required to produce. 3. The converter exhaust gas recovery method according to claim 1, wherein the timing of starting the suction of air into the flue is determined from the time required from the start of suction of air to the end of blowing of the converter, and the start of suction of air. A converter exhaust gas recovery method, wherein the difference between the time required for the CO concentration of the exhaust gas in the region to reach the recovery lower limit CO concentration is set to "0" .

Images