JPH0310875B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for treating exhaust gas generated from a hot metal pretreatment vessel, and more specifically, to a method for treating exhaust gas generated from a hot metal pretreatment vessel. Maintains the proper gas pressure within the exhaust gas, thereby reducing the
This relates to a method for completely combusting CO gas and recovering valuable components sufficiently.

[Prior Art] Hot metal tapped from a blast furnace is generally received in a ladle, pig iron mixing car, etc. before being charged into a converter, and various preliminary treatments are performed using these as processing vessels. In other words, the preliminary treatment involves adding molten metal in the treatment container to
This is carried out by introducing a dephosphorization and desulfurization agent containing an alkali metal compound as a main component or by blowing in a carrier gas, and the hot metal is subjected to dephosphorization and desulfurization treatment.
By the way, among the scouring agents used in the pretreatment of hot metal, a particularly common alkali metal compound (mainly sodium carbonate, commonly known as soda ash) is mostly emitted as CO ₂ during scouring, but a considerable amount is is emitted as sodium gas or sodium carbonate dust. Therefore, if the exhaust gas generated from the hot metal pretreatment vessel is released to the outside of the system as it is, it will cause environmental pollution. In addition, the above exhaust gas contains a large amount of CO gas, which is a flammable gas, and this exhaust gas also has a large amount of sensible heat, so the effective use of these gases is attracting attention.
Various strategies are being developed. The present applicant has previously proposed a system for recovering dust and valuable components contained in exhaust gas, paying attention to both environmental protection measures and economic efficiency.

FIG. 3 is a conceptual diagram showing the system, in which the exhaust gas generated from the processing container 1 is transferred to the splash cover 29.
After being mixed with the primary air A sucked through the opening of the duct 8, 8a, 8b by the suction blower 6,
The inside is sucked in the direction of arrow B. In this suction process, the exhaust gas is first mixed with secondary air sucked in through the opening 15 provided in the duct 8, and the CO gas contained in the exhaust gas is completely combusted.
Next, the combustion exhaust gas, which has reached a high temperature of 1300℃ or more,
When passing through a flow path provided with a water-cooled wall 2 on the inner surface of the duct, radiant heat is removed (that is, heat is recovered by the water-cooled wall 2), and the temperature drops to 900 to 1200°C. Since the combustion exhaust gas temperature is lower than the dust melting temperature due to the above-mentioned temperature drop, the molten dust is solidified, and the phenomenon of dust adhesion to the subsequent wall of the heat recovery device 3 is avoided. The cooled combustion exhaust gas is cooled while passing through a heat recovery device 3 formed by intersecting and arranging water pipes, for example, and sensible heat is recovered. Heat recovery device 3
The exhaust gas that has passed through reaches the duct 8a, and the opening 1
After being cooled by being supplied with air from 6, it flows into an electrostatic precipitator 5 to remove dust. Note that when the exhaust gas temperature is high, water of about 5% by volume or more may be required to maintain the charged state of the dust, so steam or water is introduced from the opening 16 as necessary. The dust captured by the electrostatic precipitator 5 is collected in a dust recovery device 7, and is reused as a processing agent via a recovery path 9. The other duct 8b
The combustion exhaust gas that has entered is drawn into the suction blower 6 and dissipated into the atmosphere 10. In the above exhaust gas treatment system, a temperature sensor T is inserted into the water cooling wall 2 of the duct 8, a pressure sensor P is inserted into the duct 8b, and an air introduction path 15 is inserted into the opening 15.
Dampers 13 and 14 are arranged in the a and duct 8b, and the detection data from the temperature detector T and pressure detector P is input to the control unit 11, and the control unit 11 issues commands to the damper controllers 12 and 12a. By adjusting the opening degrees of the dampers 13 and 14, the pressure inside the exhaust gas treatment system, that is, the ducts 8, 8a, and 8b is controlled.

[Problems to be Solved by the Invention] However, in the above exhaust gas treatment method, the basics of pressure control and temperature control vary depending on the type of pretreatment (dephosphorization, desulfurization, or desiliconization), the amount of pretreatment, and the pretreatment time. The disadvantage is that it is necessary to change the target setting value each time, and the operation is complicated. In addition, since the temperature control and pressure control are simple, they have poor ability to follow pressure fluctuations within the processing system, and the amount of intake air cannot be properly adjusted.
It was not possible to completely burn the CO gas.
In particular, since the pressure on the inlet side of the suction blower 6 is controlled, the pressure on the inlet side of the heat recovery device cannot be said to be properly controlled. Combustion exhaust gas may flow backward through the introduction passage 15a and the like and be ejected, and since combustion air is not introduced into the duct 8, unburned gas remains and is not effectively utilized.
It may be discharged to the outside of the system via 8b. On the other hand, if the above pressure becomes significantly negative, excessive low-temperature air flows into the duct 8, which lowers the combustion exhaust gas temperature and deteriorates the heat recovery efficiency in the heat recovery device 3, making it impossible to recover waste heat sufficiently. become unable.

The present invention has been made with attention to these circumstances, and is a method for achieving complete combustion of CO gas by performing a treatment method that can completely burn CO gas in exhaust gas, particularly a pressure control method. By providing this, it is possible to prevent the outflow of unburned gas and explosive combustion of the outflowed unburned gas, avoid backsulfur emission of exhaust gas, and perform efficient heat recovery. .

[Means for Solving the Problems] The method of the present invention, which achieves the above object, involves mixing air with exhaust gas generated from a hot metal pretreatment vessel and combusting the mixture, and then cooling the combustion exhaust gas with a heat recovery device. Then, when the flue gas is removed from the duct in the dust collector and discharged to the outside of the system, the pressure of the flue gas at the inlet of the heat recovery equipment and the concentration of CO and O ₂ in the flue gas at the exit of the heat recovery equipment are measured. The gist is that the amount of combustion air supplied to the exhaust gas treatment system is adjusted based on the detected data.

[Function] In the present invention, the pressure on the heat recovery device inlet side (CO gas combustion area) and the CO concentration and O ₂ concentration on the heat recovery device outlet side (combustion exhaust gas outflow area) are detected, and not only the pressure detection data but also the pressure detection data are detected. By using each information of CO concentration detection data and O ₂ concentration detection data as control data, pressure control of the exhaust gas treatment system is performed with high precision. In other words, since the pressure in the combustion region is directly detected and the pressure is controlled, the pressure in the combustion region can be accurately controlled to an appropriate negative pressure, and the amount of combustion air introduced into the combustion region can be maintained appropriately. Therefore, complete combustion of CO gas can be achieved. On the other hand, by detecting the CO concentration and O ₂ concentration in the combustion exhaust gas in the combustion exhaust gas outflow region, it is possible to know whether the CO gas combustion state in the combustion region is appropriate. In other words, if the CO concentration is high, it can be determined that the CO gas has not been completely combusted, so the amount of air introduced for combustion can be adjusted to increase.On the other hand, if the O ₂ concentration is high, the O ₂ has not been sufficiently consumed in the combustion area. In other words, it can be seen that the amount of combustion air introduced is excessive, so the amount of air introduced can be adjusted to reduce the amount of air introduced.
(If the amount of combustion air introduced is excessive, the combustion exhaust gas temperature will drop and the heat recovery efficiency in the heat recovery device will deteriorate.) By doing so, it is possible to achieve complete combustion of CO gas and improve heat recovery efficiency. can.

As described above, in the present invention, in addition to control using pressure detection data, correction control is performed using CO concentration detection data and O ₂ concentration detection data, so the pressure in the exhaust gas treatment system can be controlled more accurately, and CO gas Effects such as complete combustion and improved heat recovery efficiency can be obtained.

[Example] FIG. 1 is a conceptual diagram showing an embodiment of the method of the present invention,
FIG. 2 is a schematic explanatory diagram showing the detailed structure of the control section in FIG. 1. Exhaust gas generated from the processing container (pig-mixing car) 1 is sucked into the suction blower and passes through the ducts 8, 8a, and 8b in sequence. and is emitted from the dispersion tower 17 to the atmosphere 10. That is, first, the CO gas in the exhaust gas is mixed with the primary air A sucked through the opening of the splash cover 29 and the secondary air B sucked through the opening 15 of the duct 8 and combusted, resulting in the generated combustion exhaust gas. is cooled in the heat recovery device 3, and the heat retained in the combustion exhaust gas is recovered. Next, the combustion exhaust gas reaches the duct 8a and is mixed with the tertiary air C from the opening 16, where the exhaust gas temperature further drops (below 350°C), and after the dust is removed by the electrostatic precipitator 5, the cleaned exhaust gas is is discharged into the atmosphere 10 via a suction blower 6. In this process, the pressure in the duct 8 on the inlet side of the heat recovery device 3 is detected by the pressure detector P, and the CO concentration and O ₂ concentration in the combustion exhaust gas are detected in the duct 8a on the outlet side of the heat recovery device 3. It is detected by detectors 28 and 28a. Note that 12 is a controller that adjusts the opening degree of the damper 13 attached to the secondary air introduction path 15a;
a indicates the opening controller of the damper 14 installed in the duct 8b, and a damper 18 is installed in the tertiary air introduction path 16a, and its opening is controlled by the tertiary air conditioner 30. has been done.

On the other hand, the controller 11 is configured as shown in FIG. 2. First, the basic setting signal from the opening setting device 26 is inputted to the addition calculator 24a, and then the basic setting signal from the opening setting device 26 is inputted to the addition calculator 24a. The corrected correction data is input to the secondary air controller 12, thereby adjusting the opening degree of the damper 13 of the secondary air introduction path 15a. On the other hand, the basic signal emitted from the pressure pattern setter 23 is input to the addition calculator 24b, and the detection data from the O ₂ detector 28 is inputted to the addition calculator 24b via the O ₂ concentration regulator 21.
The basic signal is corrected. The corrected signal is then input as a set value to the pressure regulator 25, and the pressure regulator 25 outputs a control signal so that the detection data from the pressure detector P matches this set value. Furthermore, the control signal input from the pressure regulator 25 to the addition calculator 24c is corrected by the data signal from the tertiary air regulator 30.
That is, the control signal from the pressure regulator 25 is corrected by inputting the data signal obtained by processing data corresponding to the output signal of the tertiary air regulator 30 in the differential calculator 22 to the addition calculator 24c. . The control signal corrected in this way is input to the downper controller 12a, and the damper 14 interposed in the duct 8b
The opening degree is adjusted. In the above, the secondary air amount control based on CO detection data is configured to increase the secondary air amount when the CO concentration increases. The above control is preferably adjusted so that the CO concentration in the exhaust gas is 1% or less. On the other hand, intake air volume control using O ₂ detection data lowers the pressure set value and increases the intake air volume when the O ₂ concentration becomes low.
It is configured to increase the O ₂ concentration, and conversely, when the O ₂ concentration in the exhaust gas becomes high, it is configured to increase the pressure setting value and reduce the amount of intake air to return the O ₂ concentration to normal.

Further, in the embodiment described above, if some abnormality occurs during control and the CO concentration or O ₂ concentration suddenly increases, the upper limit values are detected by the upper limit value detectors 20 and 21, the relay 19 is activated, and the switch of the concentration control circuit is activated. S
A mechanism is built in to interrupt O 2 concentration control by opening the O ₂ concentration control. As a result, the pressure set value is switched to control based on pressure detection, and pressure control is quickly stabilized. It is preferable to adjust the pressure so that the pressure at the inlet (duct 8) is maintained at -3 to _-10 mmH2O.

[Effects of the Invention] The present invention is configured as described above, and can obtain the effects summarized below.

(1) Pressure detection data, CO concentration detection data, and
Since the amount of air introduced into the exhaust gas treatment system is adjusted based on the O ₂ concentration detection data, the pressure of the gas in the system can be controlled with high precision, ensuring complete combustion of the CO gas contained in the hot metal pretreatment exhaust gas. be able to.

(2) Therefore, unburned gas is not discharged outside the system.

(3) Since the gas pressure in the exhaust gas treatment system does not become positive, it is possible to prevent exhaust gas from blowing out from the primary air or secondary air introduction point.

(4) Since the inside of the exhaust gas treatment system does not become significantly negative pressure, it is possible to prevent the exhaust gas temperature from decreasing on the inlet side of the heat recovery device and maintain high heat recovery efficiency.

(5) Since gas pressure control with high precision and excellent followability is achieved, the type of pretreatment, processing amount,
Even if there is a difference in processing time, etc., there is no need to change the standard pressure setting value, and no complicated setting operation is required.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing an embodiment of the present invention, Figure 2 is a conceptual diagram showing an embodiment of the present invention.
The figure is a detailed explanatory diagram of the control section in FIG. 1, and FIG. 3 is a conceptual diagram showing a conventional exhaust gas treatment method. DESCRIPTION OF SYMBOLS 1... Processing container, 3... Heat recovery device, 5... Electric precipitator, 6... Suction blower, 7... Dust recovery device, 8, 8a, 8b... Duct, 11... Control unit, 12 , 12a...damper controller, 13,1
4, 18... Damper, 15a... Secondary air introduction path, 16a... Tertiary air introduction path, 19... Relay, 23... Pressure pattern setter, 24a, 24
b, 24c... Addition calculator, 25... Pressure regulator, 26... Opening degree setting device, 28... O ₂ concentration detector, 28a... CO concentration detector, 29... Splash cover, P... ...Pressure detector.

Claims (1)

[Claims] 1 After mixing air with the exhaust gas generated from the hot metal pretreatment container and combusting it, the combustion exhaust gas is cooled by a heat recovery device, and then the dust in the combustion exhaust gas is removed by a dust collector and sent out of the system. When discharging,
The combustion exhaust gas pressure at the inlet of the heat recovery equipment and the CO concentration and O ₂ concentration in the combustion exhaust gas at the exit of the heat recovery equipment are detected, and the amount of combustion air to be fed to the exhaust gas treatment system is determined based on these detected data. An exhaust gas treatment method characterized by adjusting.