JPH0757894B2 - Cleaning method of main exhaust gas of sintering machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cleaning method using a bag filter for main exhaust gas of a sintering machine for pretreating powdered ore.

[Conventional technology]

Generally, a sintering machine for pretreatment of powdered ore has a wind box of the sintering machine 1 connected to a main duct 20 as shown in FIG.
By sucking exhaust gas from each air box through the sintering machine 1 after ignition in the ignition furnace 9 by the main exhauster 4 provided in this main duct 20, raw material ore containing water on the sintering machine is obtained. Bake. This exhaust gas has properties as shown in Tables 1 to 3 as an example, though it varies depending on properties of raw materials, operating conditions, equipment conditions and the like.

In the past, dust was removed by a dry cyclone 19 provided in front of the main exhauster 4, and then was emitted from the chimney 6 via the silencer 5 and the dry electrostatic precipitator 10, but to further reduce the dust content in the emitted gas. A gas cleaning device such as a dry type electrostatic precipitator has been installed or added as an alternative. In recent years, regulations on the emission of harmful gases such as sulfur oxides and nitrogen oxides from stacks have become stricter, and gas treatment devices such as desulfurization devices and denitration devices have been installed or expanded in this main exhaust line ( JP-A-1-68429).

[Problems to be Solved by the Invention]

Over the past few years, in addition to the above harmful gas regulations, residents around the steelworks have been increasingly demanding improvements in the living environment such as preventing soiling of laundry and pollution of agricultural products. The suppression of quantity has come to be screamed strongly. However, conventional dry cyclones, dry electrostatic precipitators, etc. have limitations on sintering exhaust gas,
It has become difficult to say that the amount of dust fall is sufficiently suppressed. What is considered here is to introduce a bag filter that is relatively inexpensive in equipment, has extremely good dust collection performance, and can reduce the amount of dust discharged from the chimney.

However, the main exhaust gas of the sintering machine has the following problems in using the bag filter, and so far, the main exhaust line of this sintering machine has not used the bag filter.

(1) When the sintering machine is started up, the exhaust gas temperature is low, and the moisture introduced from the sintering raw material condenses in the gas flow stagnation area of the main duct, gas purifier, etc. It binds to and combines with corrosive components such as dust and sulfur oxides, and adheres to components such as main ducts and gas purifiers, or corrodes those components. Therefore, when a bag filter is used, there is a possibility that pressure loss will increase due to clogging of the filter cloth, and that the filter cloth and the filter cloth fitting will be corroded and deteriorated.

(2) On the other hand, the exhaust gas temperature may reach an abnormally high temperature of 200 ° C or more even when the sintering machine is suddenly stopped or during general operation. Combustible substances coming from the sintering raw material, grease for sealing the sintering machine There is also a risk of burning. Therefore, in the case of a bag filter, there is a possibility that the filter cloth may be ignited by the high exhaust gas temperature and the burning of combustibles, resulting in burning.

The present invention provides a cleaning method with a high gas cleanliness by using a bag filter in the main exhaust line by solving the problems in using the bag filter in the case of using the bag filter in the main exhaust line of the sintering machine. To do.

[Means for Solving the Problems]

The present invention is a method for cleaning a main exhaust gas of a sintering machine, which uses a bag filter as a gas cleaning device in a main exhaust gas cleaning line of the sintering machine, when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine. In this case, the dew condensation on the bag filter filter cloth is prevented to prevent the filter cloth from being clogged and prevent the bag filter filter cloth from being burned due to an abnormal temperature rise such as when the sintering machine is stopped. If necessary, the main exhaust gas line consists of two lines, a bag filter use line and a dry electrostatic precipitator use line, and used properly. Furthermore, in the main exhaust gas cleaning line of the sintering machine, desulfurization is performed simultaneously with gas cleaning. Exhaust heat recovery.

[Work]

Condensation often occurs in the gas flow stagnation area of the main duct and bag filter, which is about 30 to 60 minutes after the start of operation of the sintering machine where the temperature of the main exhaust gas is low. Therefore, dew condensation can be prevented by making the temperature of the main exhaust gas equal to or higher than the steam saturation temperature at this time.

At this time, the following means are available to raise the main exhaust gas temperature to the steam saturation temperature or higher.

(1) A high temperature combustion gas is blown from a heating furnace separately provided in the main duct upstream of the bag filter, and this is mixed with the main exhaust gas of the sintering machine to raise the temperature.

(2) Steam trace the bag filter body and the main duct in front of the bag filter.

(3) Before starting the operation of the sintering machine, burn the fuel gas (such as coke oven gas) in the sintering ignition furnace, suck it in with the main exhaust fan through the main duct, and preheat the main duct and bag filter. Started operation of the sintering machine.

(4) A plurality of burners are fixedly installed in the main duct upstream of the bag filter to generate combustion flames, and the combustion flames raise the temperature of the exhaust gas in the main ducts.

Also, when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine,
The following are means for not using a gas cleaning line with a bag filter.

(5) The main exhaust line of the sintering machine is divided into two lines, a high sulfur oxide concentration line (a line for installing a dry electrostatic precipitator and a wet desulfurizer) and a low sulfur oxide concentration line (a line for installing a bag filter). During the period when the main exhaust gas temperature is low at the beginning of the operation of the sintering machine, only the sulfur oxide high concentration line is operated, and both lines are removed after the main exhaust gas temperature rises and there is no concern about clogging of bag filters and filter cloths. Get up and running.

(6) A bag filter and a dry electrostatic precipitator are installed in parallel in the sintering main exhaust line, and when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine, the dry electrostatic precipitator line is activated and the main exhaust gas temperature rises. Switch to the bag filter line with.

Other methods for preventing condensation on the bag filter and methods for adding desulfurization and heat recovery functions are as follows.

(7) A powder supply device is installed in the main duct of the vulcanization of the bag filter, and the powder is supplied from the powder supply device to the bag filter before starting the operation of the sintering machine. A filtration layer is formed (a so-called precoat method).

The powder for precoating is preferably slaked lime powder, powder coke, sintering environment dust collection dust or the like, which has a high hygroscopic effect. In particular, slaked lime powder can be expected to have a desulfurizing effect if it is constantly used during the sintering operation.
However, the availability of collected dust here is reduced, so
The following measures are available to improve the desulfurization effect as well as the duct availability.

(8) The main sintering exhaust line is divided into a sulfur oxide high-concentration line and a sulfur oxide low-concentration line, each provided with a bag filter, and the sulfur oxide high-concentration line is equipped with a gas heating furnace, a boiler, and A powder supply device is provided, and a gas heating furnace is used as a measure to prevent condensation of exhaust gas at the beginning of the operation of the sintering machine. During normal operation, heat is recovered by a boiler and desulfurized with slaked lime powder supplied from the powder supply device.

In this case, the bag filter dust on the high concentration line of sulfur oxide contains the reaction product of sulfur oxide and slaked lime, so it is not available and is discarded.The bag filter duct on the low concentration line of sulfur oxide is reused. I can. On the other hand, there are the following means for preventing the temperature rise of the exhaust gas, that is, for preventing the filter cloth from being burnt out of the bag filter.

(9) When the sintering machine is stopped, it works in conjunction with the sintering machine to reduce the opening of the damper in front of the main exhauster.

(10) When operating the sintering machine, control the exhaust gas temperature before the bag filter. For example, if the temperature exceeds a certain upper limit temperature, cool air (normal temperature air) is introduced from the end of the main duct to maintain the exhaust gas temperature below the certain upper limit temperature. To do.

(11) Always control the exhaust gas temperature before the bag filter during the sintering operation, reduce the amount of combustible material (carbonaceous material) in the sintering raw material at 140 ° C to 160 ° C, and burn it at 160 ° C or higher. Stop the binding and reduce the opening of the damper in front of the main exhaust fan.

In carrying out the above (1) to (11), by adopting one or more of each measure, it is possible to apply a bag filter to the filter cloth when the bag filter is used in the main exhaust gas cleaning line of the sintering machine. It is possible to prevent deterioration of the gas cleaning property due to clogging, prevent burning of the bag filter filter cloth, extend the life of the bag filter, and also perform desulfurization, heat recovery, etc. advantageously.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart of an example of preventing dew condensation in a main duct and a bag filter by mixing high temperature combustion gas from a separately provided gas combustion furnace into sintering exhaust gas and raising its temperature.

In this example, the air box of the sintering machine 1 is connected to the main duct 20, and the main exhaust fan 4 after the bag filter 2 provided in the main duct 20 ignites the sintering machine 1 in the ignition furnace 9.
A gas heating furnace 7 is provided near the main duct 20 in front of the bag filter 2 in the sintering main exhaust line that sucks the exhaust gas from each wind box through the air conditioner, and when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine, For example, blast furnace gas is combusted in the gas heating furnace 7, and this high temperature combustion gas is pressurized and blown into the main duct 20 on the vulcanization side of the bag filter 2 and mixed with the main exhaust gas, so that there is no fear of dew condensation. Raise to temperature. In this case, in consideration of the changes in the water content, flow rate, and temperature of the main exhaust gas at this time, the conditions for blowing the high-temperature combustion gas from the gas heating furnace 7 are set so that the temperature introduced into the bag filter becomes the condensation temperature or higher. To do.

Note that, for example, a high temperature gas may be introduced from another system without providing a heating furnace.

FIG. 2 shows that the fuel gas is burned in the sinter ignition furnace prior to the start of the sintering operation, and the combustion gas causes the main duct,
It is a flowchart of the example which preheats a bag filter and prevents dew condensation. In this example, fuel gas is burned in the ignition furnace 9 to start the operation of the sintering machine 1, and is sucked by the main exhauster 4 via the main duct 20, and the main duct 20 and the bag filter 2 are sucked.
By preheating until the surface temperature of the product reaches, for example, 120 to 160 ° C, the sintering operation is started to prevent dew condensation even when the main exhaust gas with a low temperature in the initial operation is introduced into the back filter. . This preheating condition can be easily set in advance. FIG. 3 is a flow chart of an example in which the main exhaust gas cleaning line of the sintering machine is composed of two lines and these two lines are used properly to prevent dew condensation on the bag filter. In this example, the main exhaust line of the sintering machine is a sulfur oxide high concentration line (the exhaust gas suction line from the exhaust expansion side has the dry electrostatic precipitator 10 and the wet desulfurization device 11) and the sulfur oxide low concentration line (supply The exhaust gas suction line from the expansion side is divided into two lines (having a bag filter 2), and when the temperature of the main exhaust gas is low at the beginning of the sintering machine operation, gas purification is performed only with the sulfur oxide high-concentration line. When the gas temperature rises and the concern about dew condensation is resolved, the gas cleaning with the sulfur oxide low-concentration line using the bag filter will be started, and the gas cleaning will be performed on both lines. In this case, the timing for starting the gas cleaning of the sulfur oxide low-concentration line may be set in advance according to the operating conditions, or the temperature of the main exhaust gas may be measured and the main exhaust gas may reach a predetermined temperature or higher. It may be the time when it is confirmed.

Since the main exhaust gas of the sulfur oxide low concentration line has a higher temperature than the exhaust gas of the sulfur oxide low concentration line, an exhaust gas thermometer 21 and a damper 12 are provided in front of the dry electrostatic precipitator 10 and the sulfur oxide low concentration line is also provided. An exhaust gas thermometer 22 and a damper 13 are installed in front of the bag filter 2 of No. 1, and a bumper 1 is provided with a temperature control device 23 so as to always maintain the temperature above the steam condensation start temperature.
2. The opening of the damper 13 may be automatically adjusted. That is, when the temperature of the main exhaust gas in the low sulfur oxide concentration line is low, the main exhaust gas with a high temperature in the high sulfur oxide concentration line is mixed with the main exhaust gas in the low sulfur oxide concentration line to reduce the low sulfur oxide concentration. The main exhaust gas of the line can be increased and its temperature can be raised to some extent.

FIG. 4 is a flow chart of an example in which the bag filter 2 and the dry electrostatic precipitator 10 are provided in parallel in the cleaning line of the main clean gas of the sintering machine and are switched and used. In this example, the line having the dry electrostatic precipitator 10 and the line having the bag filter 2 are parallel lines, and gas cleaning is performed by the dry electrostatic precipitator 10 line when the exhaust gas temperature is low at the beginning of the operation of the sintering machine. When the exhaust gas temperature rises, switch to gas cleaning in the bag filter 2 line. The timing of this switch is
A timer may be set in advance according to the operating conditions, or the main exhaust gas temperature may be measured and switched when the temperature reaches a predetermined temperature.

FIG. 5 is a flow chart of an example of reducing the influence of dew condensation by preventing the filter cloth from leaking from the bag filter in the main exhaust gas cleaning line of the sintering machine. In this example, a powder supply device 16 is provided near the main duct 20 of the bag filter 2 and the main air blower blows powder into the main duct 20 from the powder supply device 16 before starting the sintering machine. As shown in FIG. 9, the filter cloth of the bag filter 2 is sucked by
A primary filtration layer 25 is formed on the surface of 24. Here, as the powder, a calcium-based powder such as inexpensive slaked lime that is hygroscopic and desulfurizing is mainly used.

FIG. 6 is a flow chart of an example in which the cleaning lines for the main exhaust gas of the sintering machine shown in FIGS. In this example, the main exhaust line of the sintering machine is divided into a sulfur oxide high-concentration line and a sulfur oxide high-concentration line, each provided with a bag filter 2, and the sulfur oxide high-concentration line has a gas heating furnace. 7, Boiler 26, Powder supply device 16 is installed, and gas heating furnace 7 is used as a measure to prevent condensation of exhaust gas at the beginning of the operation of the sintering machine. During normal operation, heat is recovered by the boiler 26, and from the powder supply device 16 It has functions other than cleaning the main exhaust gas, such as desulfurization with the supplied slaked lime powder. On the other hand, in the sulfur oxide low-concentration line, only the main exhaust gas is cleaned during normal operation.

FIG. 7 is a flow chart of an example of preventing burnout of the bag filter when the exhaust gas temperature abnormally rises in the main exhaust gas cleaning line when the sintering machine is stopped. In this example, when the sintering machine is stopped, the damper 3 in front of the main exhauster 4 is controlled in conjunction with the stop signal of the drive motor 17 of the sintering machine 1 to reduce the opening degree of the main exhaust machine 4, The suction of the main exhaust gas by the air blower 4 is stopped to prevent the main exhaust gas from rising abnormally, and the filter cloth of the bag filter 2 is prevented from burning.

FIG. 8 is a flow chart of an example of preventing burning of the bag filter when the temperature of the main exhaust gas in the main exhaust gas cleaning line during normal sintering operation rises. In this example, the exhaust gas temperature in front of the bag filter 2 is constantly controlled. For example, if the exhaust gas temperature exceeds a certain upper limit temperature, the cool air at the end of the main duct 20 under the sintering machine is adjusted according to the flow rate of the exhaust gas and its temperature. (Room temperature air) A required amount of cold air for controlling the temperature below the upper limit temperature is introduced into the main duct 20 from the introduction device 18 to maintain the exhaust gas temperature below the upper limit temperature.

〔The invention's effect〕

In the present invention, it is possible to prevent dew condensation of water in the main exhaust gas when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine, and when the sintering machine is stopped or during the normal operation of the main exhaust gas. It is possible to prevent an abnormal rise in the gas temperature, without clogging of the filter cloth of the bag filter, corrosion or deterioration of the filter cloth or the metal fittings of the filter cloth, burnout or deterioration of the filter cloth, and equipment cost and running cost. However, it is cheap and the performance of reducing the amount of discharged dust can be maintained at a high level.

[Brief description of drawings]

1 to 6 are flow charts for preventing dew condensation at the time of starting the sintering machine of the present invention, and FIGS. 7 to 8 are flow charts for preventing exhaust gas temperature rise at the time of stopping the sintering machine of the present invention or during normal times. FIG. 9 is a diagram showing the precoating condition of the filter cloth inside the bag filter, and FIG. 10 is a diagram showing an example of the flow of the conventional sintering main exhaust line. 1: Sintering machine 2: Bag filter 3: Damper 4: Main air exhauster 5: Muffler 6: Chimney 7: Gas heating furnace 8: Sintering machine charging device 9: Ignition furnace 10: Dry electrostatic precipitator 11: Wet desulfurization Equipment 12, 13: Damper 14: Booster front damper 15: Booster 16: Powder supply device 17: Drive motor 18: Cold air introduction device 19: Dry cyclone 20: Main duct 21, 22: Exhaust gas thermometer 23: Temperature control Device 24: Filter cloth 25: Primary filtration layer 26: Boiler

Claims (15)

[Claims] 1. A main exhaust gas cleaning line of a sintering machine which uses a bag filter as a gas cleaning device between the sintering machine and a chimney, and when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine. A method for cleaning main exhaust gas of a sintering machine, which comprises raising the filter cloth temperature of a bag filter to a temperature above the condensation temperature to prevent condensation on the filter cloth and preventing clogging of the filter cloth. 2. The method according to claim 1, wherein a blowing device is provided around the main duct upstream of the bag filter, and high temperature combustion gas is blown into the main duct from the blowing device to mix it with the main exhaust gas. A method for cleaning main exhaust gas of a sintering machine, which comprises raising the temperature of gas to raise the temperature of a filter cloth of a bag filter to a temperature above dew condensation temperature. 3. The method according to claim 1, wherein the fuel gas is combusted in a sintering ignition furnace before the operation of the sintering machine is started, and the combustion gas is sucked by a main exhaust fan through a main duct, and a bag filter is used. A method for cleaning main exhaust gas of a sintering machine, which comprises starting the sintering machine after preheating the filter cloth temperature to above the condensation temperature. 4. The method according to claim 1, wherein a plurality of burners are fixedly installed in a main duct upstream of the bag filter, combustion flames are generated by the burners, and the combustion flames generate the combustion flames.
A method for cleaning main exhaust gas of a sintering machine, which comprises raising the temperature of main exhaust gas passing through the main duct to a temperature above dew condensation temperature. 5. A main exhaust gas cleaning line of a sintering machine, a dry oxide precipitator and a high-concentration sulfur oxide line equipped with a wet desulfurization device, and a low-concentration sulfur oxide line equipped with a bag filter. It is characterized in that when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine, the gas is cleaned with the sulfur oxide high concentration line, and after the temperature of the main exhaust gas rises, the gas is cleaned with both lines. Cleaning method of main exhaust gas of sintering machine. 6. A bag filter line and a dry electrostatic precipitator line are arranged in parallel in the main exhaust gas cleaning line of the sintering machine, and the dry electrostatic precipitator line is used when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine. A method for cleaning main exhaust gas of a sintering machine, which comprises performing gas cleaning and switching to a bag filter line when the temperature of the main exhaust gas rises to perform gas cleaning. 7. A main exhaust gas cleaning line of a sintering machine is divided into a sulfur oxide high-concentration line and a sulfur oxide low-concentration line. A gas heating device and a boiler are installed on the side, and when the temperature of the main exhaust gas is low at the beginning of the operation of the sintering machine, the high temperature combustion gas from the gas heating device heats and heats the main exhaust gas in the main duct to filter it. A method for cleaning the main exhaust gas of a sintering machine, which is characterized by preventing condensation on the cloth to prevent clogging of the filter cloth and recovering heat with a boiler during normal operation. 8. A main exhaust gas cleaning line of a sintering machine, which uses a bag filter as a gas cleaning device between the sintering machine and the chimney, and the temperature of the main exhaust gas rises abnormally due to the stop of the sintering machine or the like. A method for cleaning the main exhaust gas of a sintering machine, which is characterized by suppressing the temperature rise in the bag filter to prevent the filter cloth from being burnt out. 9. The method according to claim 8, wherein when the sintering machine is stopped, the opening of the damper in front of the main exhauster of the sintering machine is reduced to suppress the temperature rise in the bag filter. Cleaning method of main exhaust gas of sintering machine. 10. The method according to claim 8, wherein the temperature of the main exhaust gas of the sintering machine upstream of the bag filter is measured, and when the temperature is in the bag filter cloth burning temperature range, the main duct upstream of the bag filter. A method for cleaning main exhaust gas of a sintering machine, characterized in that cool air is blown into the bag filter to suppress temperature rise in a bag filter. 11. The method according to claim 8, wherein the temperature of the main exhaust gas of the sintering machine upstream of the bag filter is measured, and when the temperature is 140 to 160 ° C., the amount of combustible material in the sintering raw material. Of the sintering machine, the sintering machine is stopped when the temperature is 160 ° C or higher, and the damper opening in front of the main exhaust machine of the sintering machine is reduced to suppress the temperature rise in the bag filter. How to clean the main exhaust gas. 12. The main exhaust gas cleaning line of the sintering machine is divided into a gas cleaning line using a bag filter and a gas cleaning line using a dry electrostatic precipitator, and the gas cleaning line using a dry electrostatic precipitator is used when the sintering machine is stopped and at the beginning of operation. The main exhaust gas is cleaned, and during normal operation, the main exhaust gas is cleaned with a bag filter gas cleaning line to prevent clogging of the bag filter cloth due to condensation and burning of the bag filter cloth due to temperature rise. A method for cleaning the main exhaust gas of a sintering machine. 13. The method according to any one of claims 1 to 12, wherein a desulfurizing agent is injected into the main exhaust gas upstream of the bag filter in the main exhaust gas cleaning line of the sintering machine using the bag filter. A method for cleaning the main exhaust gas of a sintering machine, which also desulfurizes the exhaust gas. 14. The method according to claim 13, wherein a desulfurizing agent is first injected into the main duct on the upstream side of the bag filter in the main exhaust gas cleaning line by the bag filter to inject the desulfurizing agent into the bag filter cloth. A method for cleaning main exhaust gas of a sintering machine, which comprises forming a primary filtration layer. 15. The method according to any one of claims 1 to 6 and 8 to 14, wherein a heat recovery boiler is provided on the vulcanization side of the bag filter to recover heat of the main exhaust gas introduced into the bag filter. A method for cleaning the main exhaust gas of a sintering machine, which is characterized by