KR102348070B1 - Hot blast stove recirculation facility and operating method thereof - Google Patents

Abstract

The present invention provides a combustion chamber for generating high-temperature combustion exhaust gas by burning air supplied from an air supply pipe and fuel gas supplied from a fuel supply pipe, storing heat of the high-temperature combustion exhaust gas in communication with the combustion chamber, and heating the cold wind introduced during blowing, The heat storage chamber transported to the combustion chamber, the mixed cooling chamber supplied to the blast furnace by controlling the temperature of the heated air supplied from the combustion chamber through introduction of a part or additional cold air of the cold air, and the exhaust gas discharged from the lower part of the heat storage chamber as a stack It relates to a hot stove exhaust gas recirculation facility having a hot stove having an exhaust gas pipe provided with a heat exchanger on the path and an exhaust gas recirculation pipe for recirculating the exhaust gas of the exhaust gas pipe. According to the present invention, a recirculation method is introduced in which the excess combustion air flowing into the combustion chamber is replaced with the exhaust gas, that is, the excess combustion air is replaced with the exhaust gas to a level capable of lowering the combustion flame temperature with the existing excess combustion air. By doing so, it is possible to recirculate the heat energy into the hot stove to increase combustion and thermal efficiency. In addition, it is possible to protect the equipment from damage to the hot stove facility due to high temperature, and at the same time, in place _{of O 2 in the existing excess air, CO 2} , H ₂ O, etc. in the exhaust gas are introduced, and NOx in the exhaust gas is also recirculated, so NOx emission can be reduced can be lowered

Description

HOT BLAST STOVE RECIRCULATION FACILITY AND OPERATING METHOD THEREOF

The present invention relates to a hot stove recirculation facility and operation method, and more particularly, to a hot stove recirculation facility capable of increasing thermal efficiency by recirculating exhaust gas and an operating method thereof.

Typically, the blast-furnace process includes a hot stove facility that supplies hot air of about 1,100˚C or more into the blast furnace through a tuyere at the bottom of the blast furnace. Blast furnace processes, including blast furnaces and hot stoves, are the largest energy consumers in integrated iron and steel works. In addition, the energy consumed in steelmaking is a dominant factor in determining the carbon consumption of an integrated steelmaking process and thus the emission of carbon dioxide. Therefore, increasing the thermal efficiency of the blast furnace hot stove is a major issue.

The operation of a hot stove consists of a combustion (heat storage) process and a blowing (hot air) process. Among them, in the combustion process, mixed gas and air are usually burned in the combustion chamber of the hot stove to generate high-temperature combustion exhaust gas, the heat storage material goes to the heat storage chamber of the stove, and the medium temperature combustion exhaust gas is discharged to the lower part of the heat storage chamber to generate flue gas. It consists of a process of being discharged to a stack through a valve and a heat recovery heat exchanger. In the blowing process, after passing through the heat storage chamber and the combustion chamber where the cold air is stored at a high temperature, a part of the cold air is directly introduced and mixed in the mixed cooling chamber in consideration of the exit temperature of the hot air, and then provided to the blast furnace.

In the case of a blast furnace in order to continuously generate hot air in the above process, hot stove facilities No. 1 to No. 4 are usually equipped, and among these, when hot stove Nos. 1 and 2 is a combustion process, the remaining hot stove is a blowing process carry out On the other hand, the hot stove is operated in such a way that No. 1 to No. 4 are sequentially burned, No. 1 stops after No. 1 and No. 2 burns, No. 2 and No. 3 burn, No. 2 stops, No. 3, No. 4 burns. As such, when switching from the second combustion to the first combustion, the combustion operation of the preceding hot stove (eg, No. 1) is stopped and the blowing operation is started.

On the other hand, in general, a mixed gas of BFG (Blast Furnace Gas) and COG (Coke Oven Gas) is used as the hot stove fuel. BFG is the top gas leaving the blast furnace. The main component of BFG is N ₂ (about 45 to 60%), and about 20 to 30% of CO and CO ₂ and 1 to 5% H ₂ and H ₂ O are included. has been The hot stove fuel gas is composed of low-grade fuel with a relatively low heating value, and in order to ensure the high-temperature hot air temperature for the blast furnace, BFG is mixed with a high calorific value gas such as COG or natural gas. it is common to do

In general, the temperature of the dome and the temperature of the exhaust gas are managed during the combustion (heat storage) process for the hot stove facility and the hot air management. The dome temperature is determined by the temperature of the incoming combustion gas, and the dome temperature must be controlled to an appropriate temperature in consideration of the protection of the hot stove facility and thermal efficiency. For dome temperature control, it is common to control the amount of cold air entering the combustion chamber during combustion, and to control the flow rate of mixed gas (BFG+COG) for flue gas temperature control. If the dome temperature is higher than the control temperature, excess air is introduced to lower the combustion flame temperature, thereby controlling the dome temperature to be lower than the control temperature. However, this control method has a problem in that excessive air input inevitably occurs, and in the mixing of fuel gas and combustion air in the combustion chamber, due to problems such as low calorific value of fuel gas, compared to LNG combustion burners By injecting combustion air excessively, there are many cases in which combustion efficiency is increased to reduce the generation of unburned CO and the like.

In addition, the supply of high-temperature hot air to the blast furnace is an important factor for increasing the energy efficiency of the blast furnace process, so to ensure the high-temperature hot air temperature, excessive heat storage in the heat storage chamber occurs, which causes heat loss to the exhaust gas. In other words, if the dome temperature control and the flue gas temperature control of the hot stove are not properly performed, the overheated state occurs, causing unnecessary heat loss and lowering the heat utilization efficiency. will cause significant disruption.

On the other hand, in the hot stove as described above, a large amount of exhaust gas is generated by the combustion of a large amount of gas fuel and combustion air, _{and the hot air exhaust gas containing environmental pollutants such as SOx, NOx, CO 2} gas and dust contained therein is produced in large amount. is emitted Recently, as various environmental regulations become stricter, there is a need for a technology to economically treat environmental pollutants emitted from hot stoves.

Therefore, during the combustion (heat storage) period, to increase the dome temperature control and fuel-combustion air mixing degree, heat loss due to the exhaust of a large amount of exhaust gas due to the input of excess air, high temperature heat generation due to excess heat storage to ensure the high-temperature hot air temperature Problems such as heat loss and reduction of emissions of environmental pollutants such as a large amount of NOx contained in a large amount of exhaust gas are issues that need to be resolved. That is, in terms of heat utilization efficiency and environmental pollution prevention of the hot stove, it is the main issue of the hot stove to reduce heat loss due to a large amount of/high temperature exhaust gas and the emission of a large amount of NOx contained in the exhaust gas.

In order to solve the above problems, it is known to preheat fuel and air supplied to a hot stove burner using a heat recovery unit. However, the method has problems such as limitations in flue gas temperature, high investment cost of heat recovery equipment, and difficulties in management due to the complexity of the preheating process. , there is still a large amount of heat loss.

The exhaust gas recirculation technology of combustion facilities applied to automobile engines and power plants, which can be considered in other ways, does not operate the heat storage-hot air cycle performed in the blast furnace hot stove, and it is difficult to apply because there are significant differences in operating conditions and methods such as excessive air input. do. In particular, the known exhaust gas recirculation technology is focused on reducing NOx by lowering the combustion flame temperature through circulation of the combustion exhaust gas. . On the other hand, as described above, the exhaust gas recirculation technology being developed at the Swerea research institute in order to solve the problem that the thermal storage state is lowered due to the lowering of the combustion flame temperature is a method of adding _{Enriched-O 2 to the combustion air at the same time as the exhaust gas recirculation.} However, this is not economical and overall energy efficiency is poor due to the manufacturing cost of _{Enriched-O 2} , and it is sufficient to accelerate thermal NOx generation or damage the refractory material of the hot stove due to the rise _{in the local O 2 concentration in the combustion section.} There is a problem in that a flame having a high peak temperature is generated.

That is, in the operation of the hot stove, during the combustion (heat storage) period, heat loss due to excessive air input to increase the dome temperature control and fuel-combustion air mixing degree, heat loss for a large amount of exhaust gas, and excess heat storage to ensure the high temperature of the hot air It is a facing problem that needs to solve problems such as heat loss due to high-temperature heat generation by high-temperature heat generation, and reduction of the emission of environmental pollutants such as a large amount of NOx contained in a large amount of exhaust gas.

The present invention is to solve the above problems, and to provide a hot stove flue gas recirculation facility and operation method capable of increasing thermal efficiency.

According to one aspect of the present invention, a combustion chamber for generating high-temperature combustion exhaust gas by burning air supplied from an air supply pipe and fuel gas supplied from a fuel supply pipe, and communicating with the combustion chamber to store heat of the high-temperature combustion exhaust gas and to be introduced when blowing A heat storage chamber that heats cold air and transfers it to the combustion chamber, a mixed cooling chamber that controls the temperature of the heated air supplied from the combustion chamber through introduction of a part or additional cold air of the cold air and supplies it to the blast furnace, and discharges from the lower part of the heat storage chamber A hot stove exhaust gas recirculation facility is provided that transports the exhaust gas to be used to a stack and includes a hot stove having an exhaust gas pipe provided with a heat exchanger on a path, and an exhaust gas recirculation pipe that recirculates the exhaust gas of the exhaust gas pipe.

The hot stove and the exhaust gas recirculation pipe may consist of a plurality.

The exhaust gas recirculation pipe may be branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the air supply pipe.

The exhaust gas recirculation pipe may be branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the fuel supply pipe.

The exhaust gas recirculation pipe is an individual exhaust gas pipe of a plurality of hot stoves merged to withdraw one or more from the rear end of the heat exchanger installed in one exhaust gas pipe and introduced it into an air supply pipe of an individual hot stove combustion chamber, or a plurality of hot stoves The exhaust gas may be introduced into the air supply pipe before branching into the air supply pipe of the individual combustion chamber that is introduced into the configured hot stove facility.

The exhaust gas recirculation pipe may be branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the combustion chamber.

The exhaust gas recirculation pipe may be branched from the front or rear end of the heat exchanger to introduce the flue gas into the lower part of the flame generated in the combustion chamber.

The exhaust gas recirculation pipe may be combined with the individual exhaust gas pipes of a plurality of hot stoves to withdraw one or more from the front end or the rear end of the heat exchanger installed in one exhaust gas pipe to introduce the exhaust gas into the individual hot stove combustion chamber.

The exhaust gas recirculation pipe may be branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the communication part between the combustion chamber and the heat storage chamber.

In the exhaust gas recirculation pipe, individual exhaust gas pipes of a plurality of hot stoves are merged to withdraw one or more from the front or rear end of the heat exchanger installed in one exhaust gas pipe, and the exhaust gas is introduced into the communication part between the combustion chamber and the heat storage chamber of the individual hot stove. can do.

The exhaust gas recirculation pipe may be branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the mixed cooling chamber.

The exhaust gas recirculation pipe may branch from the front end or rear end of the heat exchanger to introduce the exhaust gas of the hot stove being blown into the mixed cooling chamber of the hot stove being blown.

In the exhaust gas recirculation pipe, individual exhaust gas pipes of a plurality of hot stoves are merged to withdraw one or more from the front end or rear end of the heat exchanger installed in one exhaust gas pipe, and the exhaust gas may be introduced into the mixed cooling chamber of the individual hot stove.

The exhaust gas recirculation pipe may include an exhaust gas flow rate control valve.

The exhaust gas recirculation pipe may include a dilution air inlet pipe for introducing the dilution air and a dilution air inlet control valve for controlling the dilution air flow rate.

The exhaust gas recirculation pipe may include a shut-off valve for controlling the reverse flow of combustion air, fuel, and hot air.

The air inlet pipe for dilution of the exhaust gas recirculation pipe may include one or more selected from a filter, a thermometer, a pressure gauge, a flow meter, a blower, and a shut-off valve for controlling the reverse flow.

The exhaust gas recirculation pipe may include one or more selected from a filter, a blower, a thermometer, a pressure gauge, and a flowmeter.

The air supply pipe may include a mixing chamber for mixing the recirculated exhaust gas and air or fuel.

The air supply pipe and the fuel supply pipe may include a flow control valve.

According to another aspect of the present invention, as a method of operating a hot stove flue gas recirculation facility, there is provided a hot stove operating method having an exhaust gas recirculation ratio of 2 to 30% according to the following formula.

Exhaust gas recirculation ratio = (recirculation exhaust gas amount/(total exhaust gas generation amount)x100

The amount of combustion air may be reduced by 50 to 200% compared to the amount of recirculation exhaust gas.

The recirculation of the exhaust gas may be performed when the oxygen concentration in the exhaust gas is 1.5 vol% or more, or when the theoretical air ratio between fuel and combustion air is 1.15 times or more.

In order to adjust the control hot air temperature in real time, the exhaust gas recirculation ratio according to the following formula may be 0 to 100%.

Exhaust gas recirculation ratio = (recirculation exhaust gas amount/(total exhaust gas generation amount)x100

According to the present invention, a recirculation method is introduced in which the excess combustion air flowing into the combustion chamber is replaced with the exhaust gas, that is, the excess combustion air is replaced with the exhaust gas to a level capable of lowering the combustion flame temperature with the existing excess combustion air. By doing so, it is possible to recirculate the heat energy into the hot stove to increase combustion and thermal efficiency.

In addition, it is possible to protect the equipment from damage to the hot stove facility due to high temperature, and at the same time, in place _{of O 2 in the existing excess air, CO 2} , H ₂ O, etc. in the exhaust gas are introduced, and NOx in the exhaust gas is also recirculated, so NOx emission can be reduced can be lowered

1 schematically shows a hot stove flue gas recirculation apparatus according to a first embodiment of the present invention.
Figure 2 schematically shows a hot stove flue gas recirculation device according to a second embodiment of the present invention.
Figure 3 schematically shows a hot stove flue gas recirculation device according to a third embodiment of the present invention.
Figure 4 schematically shows a hot stove flue gas recirculation device according to a fourth embodiment of the present invention.
Figure 5 schematically shows a hot stove flue gas recirculation device according to a fifth embodiment of the present invention.
6 schematically shows a hot stove exhaust gas recirculation device according to a sixth embodiment of the present invention.
7 is a conceptual diagram schematically illustrating the operation standard of a combustion (heat storage) process of a conventional hot stove.
8 shows the relationship between excess air and combustion flame temperature.
9 shows the correlation between temperature and thermodynamic nitrogen oxide (NOx) concentration when the oxygen concentration in the exhaust gas by excess air combustion is 5% by volume and when the oxygen concentration is 3% by volume through exhaust gas recirculation.
10 shows the correlation between excess air and nitrogen oxide (NOx) concentration.
11 is a process flow chart comparing the excess air combustion process (a) and the combustion process (b) in which the exhaust gas recirculation process is introduced to lower the oxygen concentration in the exhaust gas, and the energy and NOx savings/loss pointers of the two combustion processes. will be.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a hot blast furnace flue gas recirculation device, and FIGS. 1 to 6 schematically show the hot blast furnace flue gas recirculation device and a method of recirculating the hot blast furnace exhaust gas using the same according to the present invention. Hereinafter, the present invention will be described in more detail with reference to FIGS. 1 to 6 .

According to one aspect of the present invention, a combustion chamber for generating high-temperature combustion exhaust gas by burning air supplied from an air supply pipe and fuel gas supplied from a fuel supply pipe, and communicating with the combustion chamber to store heat of the high-temperature combustion exhaust gas and to be introduced when blowing A heat storage chamber that heats cold air and transfers it to the combustion chamber, a mixed cooling chamber that controls the temperature of the heated air supplied from the combustion chamber through introduction of a part or additional cold air of the cold air and supplies it to the blast furnace, and discharges from the lower part of the heat storage chamber A hot stove exhaust gas recirculation facility is provided that transports the exhaust gas to be used to a stack and includes a hot stove having an exhaust gas pipe provided with a heat exchanger on a path, and an exhaust gas recirculation pipe that recirculates the exhaust gas of the exhaust gas pipe.

In the combustion chamber, a hot air is ultimately generated from heat energy obtained through combustion of the fuel gas supplied from the fuel supply pipe and the air supplied from the air supply pipe by a burner or the like, and the hot air is mixed with the air supplied from the blower in the mixed cooling chamber, After adjusting the temperature, it is fed to the blast furnace. On the other hand, the high-heat gas generated during combustion passes through the heat storage chamber, heats the heat storage smoke in the heat storage chamber, is transferred to the stack through the exhaust gas pipe, and is discharged. has been In addition, cold air may be introduced into the heat storage chamber through a blower.

In the present invention, it is branched from the exhaust gas pipe, and an exhaust gas recirculation pipe for recirculating the exhaust gas of the exhaust gas pipe is provided. It is preferable that the exhaust gas recirculation pipe is provided with an exhaust gas flow control valve for controlling the amount of circulating exhaust gas. In addition, it is more preferable that the exhaust gas circulation pipe is provided with an air inlet pipe for dilution and an air inflow control valve for dilution capable of controlling the inflow amount of the dilution air in order to control the temperature and oxygen concentration of the circulating exhaust gas, It is preferable that the air inlet control valve be configured to control the air flow rate more precisely than the air flow rate controlled by the air supply pipe. In this way, through the control of the exhaust gas flow control valve and the dilution air inlet control valve, the amount of circulated exhaust gas and air supplied from the outside to the exhaust gas pipe is controlled, and further, the required amount of circulating exhaust gas, temperature and oxygen concentration are controlled. can do.

Furthermore, the exhaust gas recirculation pipe may further include one or more selected from a filter for filtering impurities in the exhaust gas, a thermometer, a pressure gauge, a flow meter, and a blower for smooth flow of the fluid, and the dilution air inlet pipe includes exhaust gas, At least one selected from a shut-off valve for controlling the backflow of combustion air and fuel, a filter for filtering impurities, a thermometer, a pressure gauge, a flow meter, and a blower for smooth flow of the fluid may be further provided. If necessary, a facility capable of removing SOx, excess moisture, dust, etc. in the exhaust gas may be provided in the exhaust gas recirculation pipe.

The hot stove may be formed in plurality. For example, the hot stove may consist of four, and when two of the hot stoves perform a combustion process, the remaining hot stoves may perform a blowing process. As described above, for individual control of a conventional hot stove facility composed of two or more hot stoves, it is preferable to provide the exhaust gas recirculation pipe, air supply pipe, fuel supply pipe, and exhaust gas pipe in individual hot stoves.

On the other hand, the air supply pipe for supplying combustion air to the combustion chamber and the fuel supply pipe for supplying fuel gas to the combustion chamber may be provided with a flow rate control valve for controlling the amount of air and fuel supplied. In addition, as will be described later, when the recirculated exhaust gas is connected to the air supply pipe and introduced, a mixing chamber for mixing the exhaust gas and air may be further provided.

On the other hand, FIG. 1 schematically shows a hot stove exhaust gas recirculation facility according to an embodiment of the present invention. According to the present invention, the exhaust gas recirculation pipe is branched from the rear end of the heat exchanger installed in the path of the exhaust gas pipe, and the air supply pipe flue gas can be introduced. The exhaust gas recirculation pipe may be connected to an air supply pipe of an individual hot stove combustion chamber by drawing out at least one exhaust gas pipe from the rear end of the heat exchanger installed in one exhaust gas pipe by merging two or more individual exhaust gas pipes of the hot stove. It may be connected to the air supply pipe before branching to the air supply pipe of the individual combustion chamber that is introduced into the hot stove facility composed of a furnace. That is, by replacing the excess combustion air introduced into the combustion chamber and inputting the exhaust gas, heat energy is recirculated into the hot stove to increase combustion and thermal efficiency, and damage to the hot stove facility due to high temperature can be protected. _{In addition, CO 2} and H ₂ O in the exhaust gas are introduced instead of O2 included in the existing excess combustion air, and NOx in the exhaust gas is recirculated, thereby reducing NOx emission.

Figure 2 schematically shows a hot stove flue gas recirculation facility according to an embodiment of the present invention. According to another embodiment of the present invention, the flue gas recirculation pipe is branched from the front end of the heat exchanger installed in the path of the flue gas pipe, The exhaust gas can be introduced through the air supply pipe. That is, the exhaust gas recirculation pipe may be connected to an air supply pipe of an individual hot stove combustion chamber by drawing at least one exhaust gas recirculation pipe from the front end of the heat exchanger installed in one exhaust gas pipe by combining two or more individual exhaust gas pipes of the hot stove. It may be connected to the air supply pipe before branching to the air supply pipe of the individual combustion chamber that is introduced into the hot stove facility composed of the hot stove. The same effect can be expected when branching from the rear end of the heat exchanger described above, and further, when branching from the front end of the heat exchanger, the temperature of the circulated exhaust gas is higher, so the advantage of further improving the heat utilization rate is have.

In addition, according to an embodiment of the present invention, the exhaust gas recirculation pipe may branch from the front or rear end of the heat exchanger to introduce the exhaust gas into the fuel supply pipe. That is, in the exhaust gas recirculation pipe, two or more individual exhaust gas pipes of the hot stove are merged, and one or more of the heat exchangers installed in one exhaust gas pipe are drawn out from the front end or the rear end, and may be connected to the fuel supply pipe of the individual hot stove combustion chamber, It may be connected to the fuel supply pipe before branching to the fuel supply pipe of the individual combustion chamber that is introduced into the hot stove facility composed of a plurality of hot stoves. The same effect can be expected as in the case of branching from the front or rear end of the heat exchanger described above, and further, when the exhaust gas is introduced into the fuel supply pipe, the combustion efficiency is improved by increasing the temperature of the fuel and mixing it with the fuel in advance. There are advantages that can be

In addition, as described above, the exhaust gas recirculation pipe, the air supply pipe and the fuel supply pipe may consist of a plurality, and the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the air supply pipe and the fuel supply pipe, respectively. Also, it is preferable to provide the exhaust gas recirculation pipe, the air supply pipe and the fuel supply pipe in the individual hot stove for combustion control of the individual hot stove in a conventional hot stove facility composed of a plurality of hot stoves.

3 schematically shows a hot stove flue gas recirculation facility according to an embodiment of the present invention. According to another embodiment of the present invention, the flue gas recirculation pipe is branched from the front end or rear end of the heat exchanger to a combustion chamber, More preferably, the flue gas may be introduced into the lower portion of the flame generated in the combustion chamber, more preferably in the middle of the combustion chamber. That is, in the exhaust gas recirculation pipe, two or more individual flue gas pipes of the hot stove are merged, one or more may be drawn out from the front or rear end of the heat exchanger installed in one flue gas pipe, and may be connected to the individual hot stove combustion chamber. The same effect can be expected as in the case of branching at the front or rear end of the heat exchanger described above, and furthermore, the temperature of the combustion exhaust gas is lowered by mixing with the combustion exhaust gas burned in the main combustion part of the combustion chamber, and the unburned components are remixed for secondary combustion It can induce , and the combustion flame inside the combustion chamber can reduce the damage to the combustion chamber refractories.

4 schematically shows a hot stove flue gas recirculation facility according to an embodiment of the present invention. According to another embodiment of the present invention, the flue gas recirculation pipe is branched from the front or rear end of the heat exchanger to form a combustion chamber and a heat storage chamber. The flue gas can be introduced through the communication part. That is, in the exhaust gas recirculation pipe, two or more individual exhaust gas pipes of the hot stove are merged, and at least one is drawn out from the front or rear end of the heat exchanger installed in one exhaust gas pipe, and connected to the communication part between the combustion chamber and the heat storage chamber of the individual hot stove. You may. The same effect can be expected as in the case of branching at the front or rear end of the heat exchanger described above, and further, by introducing the exhaust gas into the communication part of the combustion chamber and the heat storage chamber, it is mixed with the combustion exhaust gas burned in the main combustion part of the combustion chamber to produce the combustion exhaust gas. By lowering the temperature and introducing the flue gas near the dome temperature, it has the advantage of more actively controlling the dome temperature.

5 schematically shows a hot stove flue gas recirculation facility according to an embodiment of the present invention. According to another embodiment of the present invention, the flue gas recirculation pipe is branched from the front end or rear end of the heat exchanger to the exhaust gas mixture into the cooling chamber. can be inserted. That is, in the exhaust gas recirculation pipe, two or more individual exhaust gas pipes of the hot stove are merged, and one or more of the heat exchangers installed in one exhaust gas pipe are drawn out from the front end or the rear end, and may be connected to the mixed cooling chamber of the individual hot stove. . The same effect can be expected as in the case of branching from the front or rear end of the heat exchanger described above, and further, by introducing the exhaust gas into the mixed cooling chamber of the hot air furnace during combustion, the combustion heat energy coming into the mixed cooling chamber can be induced into the dome and the heat storage chamber. It has the advantage of efficiently using thermal energy.

In addition, as described above, since the exhaust gas recirculation pipe may be provided in plurality, in one hot stove, the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to the combustion chamber, the combustion chamber and the heat storage chamber communicating part, and the mixed cooling chamber, respectively. By connecting one or more and introducing the exhaust gas, flexibility in operation of the hot stove can be secured. This also applies to the case of a plurality of hot stoves, and accordingly, various combinations of exhaust gas recirculation can be made as needed in each hot stove.

6 is a schematic view of a hot stove exhaust gas recirculation apparatus according to an embodiment of the present invention. According to another embodiment of the present invention, the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger. The exhaust gas of the hot stove that is burning can be introduced into the mixed cooling chamber. That is, in the exhaust gas recirculation pipe, two or more individual exhaust gas pipes of the hot stove are merged, and one or more of the heat exchangers installed in one exhaust gas pipe are drawn out from the front end or the rear end to be connected to the mixed cooling chamber of the individual hot stove, and , the exhaust gas may be introduced into the mixed cooling chamber of the hot stove being blown. When the exhaust gas is introduced into the mixed cooling chamber of the hot stove being blown, it is possible to control the hot air temperature by mixing it with the hot air, thereby improving the heat utilization rate, and as described above, the exhaust gas supplied from the front or rear end of the heat exchanger. Since the temperature may be different, there is an advantage that the control of the hot air temperature is easier accordingly. At this time, in order to prevent the backflow of hot air from the mixed cooling chamber, it is preferable that the exhaust gas recirculation pipe is provided with a shut-off valve.

On the other hand, according to another aspect of the present invention, as the operating method of the above-described hot stove exhaust gas recirculation facility, there is provided a hot stove facility operating method in which the exhaust gas recirculation ratio according to the following formula is 5 to 30%.

Exhaust gas recirculation ratio = (recirculation exhaust gas amount/(total exhaust gas generation amount)x100

In addition, there is provided a hot blast furnace flue gas recirculation facility operating method having an exhaust gas recirculation ratio of 0 to 100% according to the following equation in order to adjust the control hot air temperature in real time.

Exhaust gas recirculation ratio = (recirculation exhaust gas amount/(total exhaust gas generation amount)x100

7 is a conceptual diagram schematically showing the operation standards of the combustion (heat storage) process of a conventional hot stove, and FIG. 8 is a diagram illustrating the relationship between excess air and combustion flame temperature. As shown in FIG. 7, the specific combustion (heat storage) process operation standard in the present invention is different from the existing operating method of introducing excess combustion air, as shown in FIG. 8, the level at which the combustion flame temperature can be lowered with the excess combustion air By introducing the recirculated exhaust gas instead of the excess combustion air into the furnace, heat energy is recirculated into the hot stove to increase combustion and thermal efficiency, and damage to the hot stove facility due to high temperature can be protected.

In FIG. 8, the gas fuel used for calculating the flame temperature was methane 2.3%, ethylene 0.2%, hydrogen 6.6%, carbon monoxide 22.3%, carbon dioxide 17.7%, water ( Water) 4.8% and nitrogen (Nitrogen) 46.1% composition were used, and the exhaust gas circulation rate (exhaust gas recirculation ratio = (recycle exhaust gas amount / (total exhaust gas generation amount) x 100) considering the combustion flame temperature is preferably 2 to 30%.

When the exhaust gas circulation rate according to the above formula is less than 2%, the heat recovery effect is insignificant, whereas when the exhaust gas circulation rate exceeds 30%, the combustion flame temperature is lower than that of the general heat storage process, and efficient heat storage cannot be achieved. Have. However, if the dome temperature management upper limit is continuously exceeded, it is possible to temporarily circulate the exhaust gas by setting the exhaust gas circulation rate to 30% or more, but it is more preferable that it is 30% or less for efficient heat storage.

On the other hand, the exhaust gas recirculation period is preferably performed when the oxygen concentration in the exhaust gas is 1.5 vol% or more, or the theoretical air ratio of fuel and combustion air is 1.15 times or more. When the oxygen concentration in the exhaust gas is less than 1.5% by volume, or the theoretical air ratio of fuel and combustion air is less than 1.15 times, a large amount of incomplete combustion occurs and a large amount of unburned CO is generated, which has a problem of lowering combustion efficiency. It is preferable that the oxygen concentration in the exhaust gas exhibiting effective fuel saving efficiency is 1.5 vol% or more and less than 3.5 vol%.

As described above, in the present invention _{, CO 2} and H ₂ O in the exhaust gas are introduced instead _{of O 2} contained in the existing excess combustion air, and NOx in the exhaust gas is recirculated, thereby reducing NOx emission. 9 shows the correlation between the temperature and the thermodynamic nitrogen oxide (NOx) concentration in the case where the oxygen concentration in the exhaust gas by excess air combustion is 5% by volume and when the oxygen concentration is 3% by volume through exhaust gas recirculation. . Referring to FIG. 9 , when the oxygen concentration during combustion was 3% by volume compared to 5% by volume, it was evaluated that the thermodynamic NOx generation concentration was approximately 23% lower at all temperatures.

On the other hand, FIG. 10 shows a correlation between excess air and nitrogen oxide (NOx) concentration. Referring to FIG. 10, in the case of NOx generation concentration according to an increase in oxygen concentration due to input of excess air, the NOx peak concentration is In addition, it can be seen that below the NOx peak, the oxygen concentration in the exhaust gas increases continuously. The excess oxygen concentration at which the NOx peak concentration occurs varies depending on the facility, the temperature in the combustion chamber, and the operating method, but in the case of a hot stove, it occurs around 5%. It can be seen that the amount of oxide generated is reduced.

On the other hand, in order to confirm the effect of increasing the heat use efficiency of the hot stove according to the present invention, the energy saving effect was calculated for a large hot ^{stove with a capacity of 6000 m 3 and shown in Table 1.}

11 is a process flow chart comparing the excess air combustion process (a) and the combustion process (b) in which the exhaust gas recirculation process is introduced to lower the oxygen concentration in the exhaust gas, and energy and NOX of the two combustion processes. will be. When the economic feasibility is evaluated with reference to this, the results shown in Tables 1 to 3 can be obtained.

Item history CASE1 CASE2 CASE3 CASE4 Reduced array loss
(array recovery)
(One) Exhaust gas circulation (Nm ³ /h) 47.109 47.109 22,000 51,819 Recovered Calorie (Mcal/h) 3,648 2,819 1,703 4,924 Gain (KRW billion/year) 12.14 9.38 5.67 16.39 excess air
Reduction of transport power (2) Reduced air volume (Nm ³ /h) 47,109 47,109 25,000 58,886 Air Fan Energy (MW) 0.22 0.22 0.12 0.27 Gain (KRW billion/year) 1.78 1.78 0.95 2.23 NOx emission reduction (3) Average NOx reduction (ppm) 12 12 - 20 NOx reduction (kg/year) 92.3 92.3 42.0 125.8 Gain (KRW billion/year) 1.97 1.97 0.89 2.68 flue gas circulation
power loss
(4) Exhaust gas circulation (Nm ³ /h) -41,456 -41,456 -22,000 -51,819 Circulating Fan Energy (MW)* -0.31 -0.28 -0.17 -0.43 Loss cost (KRW 100 million/year) -2.55 -2.29 -1.36 -3.52 fuel loss
(5) Max. CO emission concentration (ppm) - - - 12,000 Max. CO emission rate (%) - - - 5 Recovered heat (Mcal/h) - - - 754 Gain (KRW billion/year) - - - 2.51 total gain Net profit (KRW 100 million/year) 13.34 10.84 6.16 20.30

Common Calculation Criteria Fuel flow (Nm ³ /h) 180,000 Blower efficiency (%) 70 Step-up (mmAq) 1,200 Hot stove operation rate (%) 95 Electricity unit price (KRW/kw) 98 Average exhaust gas temperature (℃) 220 Exhaust gas specific heat (kcal/Nm ³ ) 0.352 NOx reduction (KRW/kg) 2,130

By CASE CASE Based on O _{2 concentration} return exhaust temperature #One 5%→3% 220 ℃ #2 5%→3% 170 ℃ #3 5%→3% 170 ℃ #4 5%→2.5% 270 ℃

Referring to Tables 1 to 3, the amount of heat recovered is ~2% of the fuel of the hot stove. Considering that the annual fuel cost of the stove used in this calculation is 100 billion won, fuel savings of 2 billion and about 180,000 tons of CO _{2 are} reduced This is possible, and it was evaluated that NOx can also be reduced by more than 10%. As described above, according to the present invention, it can be confirmed that it is possible to increase the heat use efficiency of the hot stove and to _{prevent environmental pollution such as CO 2 / NOx.}

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible within the scope without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

10: Cold blast mixing valve
20: Cold blast mixing control valve
30: Cold blast valve
35: Cold blast control valve
40: pressure equalizing valve (Pressure equalizing valve)
50: pressure equalizing control valve (Pressure equalizing control valve)
80: Hot blast valve
90: Combustion Air valve for burner
95: Combustion Air control valve for burner
110: gas valve (Gas valve for burner)
140: chimney valve (Chimney valve)
170: pressure relief valve (Pressure relief Valve)
180: pressure relief control valve (Pressure relief control Valve)
200: gas shutoff valve
210: burner flow control valve
250, 260, 270: heat exchanger
310: exhaust gas recirculation pipe flow control valve
320: exhaust gas recirculation pipe air inlet control valve
330: filter
340: blower
350: flow meter
360: mixing mixer
380: shut-off valve
400: stack
500: heat storage chamber
600: combustion chamber
700: mixed cold room
800: flue gas pipe
900: exhaust gas recirculation pipe

Claims (24)

A combustion chamber that burns air supplied from the air supply pipe and fuel gas supplied from the fuel supply pipe to generate high-temperature combustion exhaust gas;
a heat storage chamber communicating with the combustion chamber to store heat of the high-temperature combustion exhaust gas, heating the cold wind introduced during blowing, and transferring it to the combustion chamber;
A mixed cooling chamber for supplying a blast furnace by controlling the temperature of the heated air supplied from the combustion chamber through introduction of a part or additional cold air of the cold air;
a hot stove having an exhaust gas pipe that transports the exhaust gas discharged from the lower portion of the heat storage chamber to a stack and is provided with a heat exchanger on the path; and
and an exhaust gas recirculation pipe for recirculating the exhaust gas of the exhaust gas pipe,
The exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the exhaust gas into at least one of an air supply pipe and a fuel supply pipe, a hot stove exhaust gas recirculation facility.
According to claim 1,
The hot stove and the exhaust gas recirculation pipe will consist of a plurality of, the hot stove exhaust gas recirculation facility.
delete delete 3. The method of claim 2,
The exhaust gas recirculation pipe is an individual exhaust gas pipe of a plurality of hot stoves merged to withdraw one or more from the rear end of the heat exchanger installed in one exhaust gas pipe and introduced it into an air supply pipe of an individual hot stove combustion chamber, or a plurality of hot stoves A hot stove flue gas recirculation facility that introduces the exhaust gas into the air supply pipe before branching into the air supply pipe of the individual combustion chamber that is introduced into the configured hot stove facility.
According to claim 1,
In addition, the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the combustion chamber, the hot stove flue gas recirculation facility.
According to claim 1,
In addition, the flue gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the flue gas into the lower part of the flame generated in the combustion chamber, the hot stove flue gas recirculation facility.
3. The method of claim 2,
In the exhaust gas recirculation pipe, individual exhaust gas pipes of a plurality of hot stoves are merged to withdraw one or more from the front end or rear end of the heat exchanger installed in one exhaust gas pipe, and the exhaust gas is introduced into the individual hot stove combustion chamber. flue gas recirculation plant.
According to claim 1,
In addition, the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the communication part between the combustion chamber and the heat storage chamber, the hot stove exhaust gas recirculation facility.
3. The method of claim 2,
In the exhaust gas recirculation pipe, individual exhaust gas pipes of a plurality of hot stoves are merged to withdraw one or more from the front end or rear end of the heat exchanger installed in one exhaust gas pipe, and the exhaust gas is introduced into the communication part between the combustion chamber and the heat storage chamber of the individual hot stove. What is done is a hot stove flue gas recirculation facility.
According to claim 1,
In addition, the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the exhaust gas into the mixed cooling chamber, the hot stove exhaust gas recirculation facility.
According to claim 1,
In addition, the exhaust gas recirculation pipe is branched from the front or rear end of the heat exchanger to introduce the exhaust gas of the hot stove being burned into the mixed cooling chamber of the hot stove being blown, the hot stove exhaust gas recirculation facility.
3. The method of claim 2,
In the exhaust gas recirculation pipe, individual exhaust gas pipes of a plurality of hot stoves are merged to withdraw one or more from the front end or rear end of the heat exchanger installed in one exhaust gas pipe, and the exhaust gas is introduced into the mixed cooling chamber of the individual hot stove, Furnace flue gas recirculation facility.
According to claim 1,
The exhaust gas recirculation pipe will be provided with an exhaust gas flow control valve, a hot stove exhaust gas recirculation facility.
According to claim 1,
The exhaust gas recirculation pipe will include a dilution air inlet pipe for introducing the dilution air and a dilution air inflow control valve for controlling the dilution air flow rate, the hot stove exhaust gas recirculation facility.
According to claim 1,
The flue gas recirculation pipe will be provided with a shut-off valve for controlling the reverse flow of combustion air, fuel, and hot air, the hot stove flue gas recirculation facility.
16. The method of claim 15,
The dilution air inlet pipe of the exhaust gas recirculation pipe will include at least one selected from a filter, a thermometer, a pressure gauge, a flow meter, a blower, and a shut-off valve for controlling the backflow, the hot stove exhaust gas recirculation facility.
According to claim 1,
The exhaust gas recirculation pipe is to have one or more selected from a filter, a blower, a thermometer, a pressure gauge and a flowmeter (flowmeter), the hot stove exhaust gas recirculation facility.
According to claim 1,
The air supply pipe will have a mixing chamber for mixing the recirculated exhaust and air or fuel, the hot stove flue gas recirculation facility.
According to claim 1,
The air supply pipe and the fuel supply pipe will have a flow control valve, the hot stove flue gas recirculation facility.
A method of operating a hot stove flue gas recirculation facility according to any one of claims 1, 2 and 5 to 20, comprising:
A method of operating a hot stove flue gas recirculation facility having an exhaust gas recirculation ratio of 2 to 30% according to the following formula.
Exhaust gas recirculation ratio = (recirculation exhaust gas amount/(total exhaust gas generation amount)x100
22. The method of claim 21,
The combustion air amount is reduced by 50 to 200% compared to the recirculation exhaust gas amount, the hot stove flue gas recirculation facility operating method.
22. The method of claim 21,
The recirculation of the exhaust gas is performed when the oxygen concentration in the exhaust gas is 1.5% by volume or more, or the theoretical air ratio of fuel and combustion air is 1.15 times or more, the hot stove exhaust gas recirculation facility operating method.
A method of operating a hot stove flue gas recirculation facility according to any one of claims 1, 2 and 5 to 20, comprising:
In order to adjust the control hot air temperature in real time, the exhaust gas recirculation ratio according to the following formula is 0 to 100%.
Exhaust gas recirculation ratio = (recirculation exhaust gas amount/(total exhaust gas generation amount)x100

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