JP7229796B2 - BFG burner device, boiler provided with same, and method of operating BFG burner device - Google Patents

Description

The present disclosure relates to a BFG burner apparatus, a boiler having the same, and a method of operating a BFG burner apparatus.

A large-sized boiler such as a coal-fired boiler has a hollow, vertically installed furnace, and a plurality of combustion burners are arranged on the furnace wall along the circumferential direction of the furnace. In the coal-fired boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is arranged in the flue. Then, the combustion burner injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame and generate combustion gas that flows into the flue. A heat exchanger is installed in a region where the combustion gas flows, and superheated steam is generated by heating water or steam flowing inside the heat transfer tubes constituting the heat exchanger.

In recent years, from the viewpoint of effective utilization of energy resources, the gas generated in the steelmaking process and obtained as a by-product gas from the blast furnace (blast furnace gas: BFG (Blast Furnace Gas)) has also come to be used as fuel in boilers. (For example, Patent Document 1). However, BFG has a low calorific value (low calorie) and poor combustibility, and there are time fluctuations in the flow rate and composition. Co-firing using a burner (for example, a coal burner) that burns a carbon-containing solid fuel such as a carbon-containing solid fuel is common.

Japanese Patent No. 6051952

Here, referring to FIGS. 4A, 4B, and 5, problems that occur when coal and BFG are co-fired in a boiler furnace will be described. FIG. 4A is an air system diagram of a BFG burner and a coal burner as a reference example, and FIG. 4B is a front view of the BFG burner and a coal burner as a reference example viewed from the furnace side.

As shown in FIGS. 4A and 4B, a boiler 110 for co-firing coal and BFG is provided on a furnace wall constituting a furnace 111, and coal burners 121, 122, 123, and 124 are provided on the upper stage thereof, for example, in four stages. and BFG burners 161, 162, and 163 provided in, for example, three stages in the lower stage. A windbox 136 is provided at the mounting position of each coal burner 121, 122, 123, 124, and a windbox 168 is provided at the mounting position of each BFG burner 161, 162, 163, respectively. Each BFG burner 161, 162, 163 is connected via a wind box damper (not shown) provided in each BFG burner 161, 162, 163, respectively, and then connected to the upstream air duct 137 via a damper 164. Connected. Similarly, each coal burner 121, 122, 123, 124 is also connected to a damper 165 via a wind box damper (not shown) provided in each coal burner 121, 122, 123, 124. It is connected to the upstream air duct 137 via. With such a configuration, air is distributed and supplied from the air duct 137 to the coal burners 121, 122, 123, 124 and the BFG burners 161, 162, 163, respectively. The temperature of the supplied air is, for example, about 300° C. to 350° C. during normal operation.

As shown in FIG. 4B , the coal burner 121 includes a fuel nozzle 191 that ejects fuel such as pulverized coal together with primary air for transportation (transportation gas), and is provided around the fuel nozzle 191 . (The other coal burners 122, 123, 124 also have the same structure). On the other hand, the BFG burner 161 has a lattice-shaped burner nozzle in order to improve the combustibility of BFG. (The other BFG burners 162 and 163 have the same structure).

A boiler for co-firing pulverized coal and BFG is configured to cover a 100% load in the case of coal-only firing. BFG is a by-product gas generated in the iron-making process, and since the flow rate and composition fluctuate, the BFG is operated by switching the number of burners used, for example, with a maximum load of 50% of the boiler load. Specifically, when the flow rate of BFG decreases, the number of BFG burners 161, 162, and 163 to be used is reduced according to the flow rate of BFG, and the corresponding load is compensated for by the coal burners 121, 122, 123, and 124. drive like On the other hand, when the flow rate of BFG increases, for example, the number of coal burners 121, 122, 123 and 124 is reduced and some of them are stopped.

When co-firing coal pulverized coal and BFG, the ratio of the amount of combustion oxygen supplied to the entire boiler is kept constant corresponding to the amount of fuel supplied to the entire boiler. Specifically, combustion air (oxidizing gas) The supply amount of is constant at a predetermined amount. However, since BFG is a gaseous fuel, it is more combustible than pulverized coal, and consumes oxygen quickly inside the furnace. By depriving the oxygen necessary for the process, the unburned portion of the pulverized coal increases. Therefore, the amount of combustion air to be supplied to the BFG burners 161, 162, 163 is set to be smaller than that in the case of mono-combustion of BFG.

In this case, when co-firing all the coal burners 121, 122, 123, 124 and all the BFG burners 161, 162, 163, the amount of air required for the single-firing state of each burner with respect to the total amount of air supplied to the boiler is to co-firing state, change as follows: Specifically, with respect to the total amount of air supply to the boiler, for example, when all the coal burners 121, 122, 123, and 124 are singly burned in a single combustion state, the combustion air supply amount is 70%, and all the BFG burners 161 , 162 and 163 are burned singly in a single combustion state, and the combustion air supply rate is 30% as a standard condition. The amount of combustion air supplied to the coal burners 121, 122, 123, and 124 is increased from the required amount for coal-only combustion (eg, increased from 70% to 80-85%). Then, the amount of combustion air supplied to the BFG burners 161, 162, 163 is reduced (for example, 30% is reduced to 15 to 20%) to reduce the required amount for BFG burning, so that the combustion of pulverized coal and BFG is reduced. Gender differences can be compensated for.

In this case, the following new problem may arise. This problem will be explained in more detail with reference to FIG. FIG. 5 is a schematic side cross-sectional view of a BFG burner as a reference example, and the inside of the tip portion 170, which is the inside of the furnace of the BFG burner 161, is alternately formed with BFG flow paths and combustion air flow paths. , BFG jetted into the furnace and combustion air are mixed and combusted. In FIG. 5, solid line arrows indicate the flow of BFG, broken line arrows indicate the flow of combustion air, and dotted line arrows indicate the flow of unburned gas. Further, in FIG. 5, the right side of the paper indicates the outside of the furnace, and the left side of the paper indicates the inside of the furnace.

As shown in FIG. 5, the BFG burner 161 has a BFG nozzle 166 forming a BFG flow path on the outside of the furnace. A wind box 168 is connected which forms a flow path for the . The BFG burner 161 also includes a tip portion 170 whose interior is partitioned by a partition portion 169 so that, for example, two stages in the vertical direction and six rows in the width direction are formed inside the furnace. Between each channel defined inside the tip portion 170 and the BFG nozzle 166 and the wind box 168, each channel defined inside the tip portion 170 has a BFG channel and a combustion air channel. are formed alternately in the vertical direction and in the width direction. The connecting portion between the tip portion 170, the connecting portion 171 and the wind box 168, the connecting portion between the connecting portion 171 and the BFG nozzle 166, and the connecting portion between the partition portion 169 and the connecting portion 171 are connected by welding or the like ( welded structural parts, etc.).

In FIG. 5, for example, the BFG burner 161 on the upper side of the page is in operation, and the BFG burner 162 on the lower side is stopping the supply of BFG. In the lower BFG burners 162 that are stopped, although the corresponding windbox dampers are closed, a small amount of combustion air leaks through the flow path formed between the BFG nozzle 166 and the windbox 168. ing.

When the amount of combustion air supplied to the BFG burner 161 is reduced, the flow velocity of the combustion air decreases, so unburned gas NG may be likely to be generated during BFG combustion (for example, the combustion air flow velocity On the other hand, when co-firing, the flow velocity is reduced from 65% to 50% by reducing the amount of combustion air). At this time, the ash generated by the coal burners 121, 122, 123, and 124 during the combustion of pulverized coal tends to flow into the BFG burner 162 on the vertically lower side. If there is a BFG burner (BFG burner 162 in FIG. 5) whose supply of BFG is stopped, the ash that has flowed accumulates at the tip portion 170 of the BFG burner 162 that is stopped, and the tip portion of the BFG burner 162 is blocked. It may get lost.

In addition, since there is a BFG burner (BFG burner 162 in FIG. 5) whose supply of BFG is stopped, part of the unburned gas NG of BFG flows into the inside of the stopped BFG burner 162 and wind box 168. may be lost. Then, a small amount of combustion air that flows into the wind box 168 of the BFG burner 162 that is stopped may react with the unburned gas NG that has flowed into the BFG burner 162 and the wind box 168 and burn ( Combustion B) in FIG. This can cause the BFG burner 162 and windbox 168 to heat up unevenly and damage the BFG burner system comprising the BFG burner 162 and windbox 168 . In particular, cracks are likely to occur in the shape change portion, which is the welded structure portion in the BFG burner 162, and the temperature of this portion rises locally, and the BFG reacts with the combustion air during operation of the BFG burner 162. Furthermore, there is a possibility that cracks will expand, and in this case, there is a problem that the service life of the BFG burner device is shortened.

The present disclosure has been made in view of such circumstances, and the unburned gas of the BFG that has flowed into the BFG burner and the wind box during which the supply of BFG is stopped is burned inside, and the BFG burner device is It is an object of the present invention to provide a BFG burner device and a method of operating the BFG burner device that can prevent damage.

In order to solve the above problems, the present disclosure employs the following means.
The BFG burner device of the present disclosure includes a BFG burner provided on a wall surface of a furnace for burning blast furnace gas in the furnace, and a wind box connected in communication with the BFG burner to supply oxidizing gas to the BFG burner. a gas introduction line connected to the wind box for introducing non-combustible gas into the wind box; and flowing the non-combustible gas to the gas introduction line when the supply of the blast furnace gas to the BFG burner is stopped and a gas supply control unit.

In the BFG burner device of the present disclosure, a gas introduction line for introducing noncombustible gas is connected to the wind box of the BFG burner, and the gas supply control unit controls the gas supply when the supply of BFG to the BFG burner is stopped. A non-combustible gas is flowed through the introduction line. As a result, unburned gas is blown out from the tip of the inside of the furnace of the BFG burner whose supply of BFG is stopped, so that unburned BFG (blast furnace gas) gas flows into the inside of the stopped BFG burner and wind box. can be prevented. Therefore, the unburned gas of BFG flowing into the inside of the BFG burner and the wind box burns with the oxidizing gas inside, and the temperature of the BFG burner and the wind box rises unevenly, and the BFG burner device is damaged. can be prevented. As a result, repair work due to damage to the BFG burner device and maintenance work for the BFG burner device can be suppressed. In addition, since it is possible to prevent cracks from occurring in the welded structure portion in the BFG burner device, the BFG reacts with the oxidizing gas during operation of the BFG burner, causing a local temperature rise and causing the above cracks. can be prevented from expanding, the life of the BFG burner device can be extended. Also, the gas supply control unit for introducing the non-combustible gas into the wind box of the BFG burner is composed of, for example, a damper and a control device that controls the damper, and can adjust the flow rate of the non-combustible gas introduced into the wind box.

In the above BFG burner device, the wind box is provided with a thermometer for measuring the temperature of the wind box, and the flow rate of the incombustible gas introduced into the wind box is determined by the measured value of the thermometer. Adjusted to be below the set value.

If the flow rate of non-combustible gas introduced into the wind box is adjusted so that the reading of the thermometer installed in the wind box is below a predetermined set value, the temperature inside the wind box is maintained below the set value. be able to. This makes it possible to more reliably prevent damage to the BFG burner device. Further, the predetermined set value may be set so as to be the endurable temperature (for example, 400° C. or less) of the constituent members (for example, carbon steel or low alloy steel) that constitute the wind box of the BFG burner, for example.

In the above BFG burner device, it is preferable that the BFG burner is provided on the wall surface of the furnace and arranged in the vicinity of the vertically lower side of the main fuel burner that burns the carbon-containing solid fuel.

The BFG burner apparatus of the present disclosure is configured such that gas is blown out from the tip portion inside the furnace of the BFG burner during which the supply of BFG is stopped. Therefore, when the BFG burner is arranged in the vicinity of the vertically lower side of the main fuel burner that burns carbon-containing solid fuel (for example, pulverized coal) (for example, vertically below the coal burner that burns pulverized coal), the carbon-containing solid fuel Even if the ash generated during fuel combustion flows toward the BFG burner, it is possible to prevent the flowing ash from accumulating at the tip of the stopped BFG burner. That is, clogging (ash clogging) of the tip of the BFG burner with ash can be prevented.

In the BFG burner apparatus of the present disclosure, the non-combustible gas is preferably gas recycle gas or steam derived from exhaust gas produced by combustion of the blast furnace gas and/or carbon-containing solid fuel.

Examples of the non-combustible gas flowing through the gas introduction line include GR (gas recirculation) gas derived from exhaust gas generated by combustion of fuel in the furnace, and steam. GR gas can adjust the oxygen concentration of the oxidizing gas supplied to the furnace. It is designed to be introduced near the bottom of the Even if part of the GR gas introduced into the furnace is introduced into the wind box, the total amount of GR gas introduced into the furnace does not change. It is possible to reduce the influence on the combustion performance inside. Steam can be used as the non-combustible gas in a boiler that is not adapted to introduce GR gas. When steam is introduced into the wind box, it is possible to reduce costs by adopting a configuration in which steam for internal use is used, which eliminates the need for major modification of the boiler equipment.

The boiler of the present disclosure comprises the BFG burner apparatus described above.

Since the boiler of the present disclosure includes the above-described BFG burner device, the unburned BFG gas that has flowed into the BFG burner and the wind box is burned inside, and the BFG burner device is prevented from being damaged. be able to. As a result, the life of the BFG burner device can be extended. Therefore, it becomes a highly economical boiler.

A method of operating a BFG burner apparatus of the present disclosure includes a BFG burner provided on a wall surface of a furnace and configured to burn blast furnace gas in the furnace, and a BFG burner connected in communication with the BFG burner to supply oxidizing gas to the BFG burner. and a gas introduction line connected to the wind box for introducing non-combustible gas into the wind box, wherein the supply of the blast furnace gas to the BFG burner is stopped. a gas introduction step of introducing the non-combustible gas into the gas introduction line when the gas introduction line is closed.

A method of operating a BFG burner apparatus of the present disclosure includes a gas introduction step of introducing non-combustible gas into a gas introduction line connected to a wind box when the supply of BFG to the BFG burner is stopped. As a result, unburned gas is blown out from the tip of the inside of the furnace of the BFG burner whose supply of BFG is stopped, so that unburned BFG (blast furnace gas) gas flows into the inside of the stopped BFG burner and wind box. can be prevented. Therefore, the unburned gas of BFG flowing into the inside of the BFG burner and the wind box burns with the oxidizing gas inside, and the temperature of the BFG burner and the wind box rises unevenly, and the BFG burner device is damaged. can be prevented. As a result, repair work due to damage to the BFG burner device and maintenance work for the BFG burner device can be suppressed. In addition, since it is possible to prevent cracks from occurring in the welded structure portion in the BFG burner device, the BFG reacts with the oxidizing gas during operation of the BFG burner, causing a local temperature rise and causing the above cracks. can be prevented from expanding, the life of the BFG burner device can be extended. Also, the gas introduction step can be performed by a gas supply control unit, which is composed of, for example, a damper and a control device for controlling the damper, and can adjust the flow rate of the incombustible gas introduced into the wind box.

According to the BFG burner device and the operation method of the BFG burner device of the present disclosure, it is possible to suppress the clogging of the BFG burner by the pulverized coal ash while the BFG supply is stopped, and the dust that has flowed into the stopped BFG burner and the wind box. It is possible to prevent the combustion gas from burning inside and damaging the BFG burner device.

1 is a schematic configuration diagram representing a co-firing boiler according to an embodiment of the present disclosure; FIG. FIG. 2 is an air system diagram of a BFG burner and a coal burner in the boiler of FIG. 1; It is the front view seen from the furnace side of the BFG burner and the coal burner in the boiler of FIG. 2 is a schematic side sectional view of a BFG burner apparatus in the boiler of FIG. 1; FIG. It is an air system diagram of a BFG burner and a coal burner as a reference example. It is the front view seen from the furnace side of a BFG burner and a coal burner as a reference example. It is a schematic sectional side view of a BFG burner as a reference example.

Preferred embodiments according to the present disclosure will be described below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, the present disclosure also includes a combination of each embodiment. Also, in this specification, GR (gas recirculation) is an abbreviation for Gas Recirculation.

〔boiler〕
FIG. 1 is a schematic configuration diagram showing the co-firing boiler of the present embodiment.

The boiler of the present embodiment uses pulverized coal obtained by pulverizing coal as pulverized fuel (carbon-containing solid fuel), burns this pulverized coal with a coal burner (main fuel burner), and generates BFG (blast furnace gas) generated in a blast furnace. is burned with a BFG burner (co-firing). The boiler of the present embodiment is a mixed combustion boiler capable of recovering the heat generated by the combustion of these components and exchanging heat with feed water or steam to generate superheated steam. In the following description, "up" and "up" indicate the upper side in the vertical direction, and "down" and "lower side" indicate the lower side in the vertical direction.

In this embodiment, as shown in FIG. 1, the mixed combustion boiler 10 has a furnace 11, a combustion device 12, and a flue 13. As shown in FIG. The furnace 11 has, for example, a hollow square shape and is installed along the vertical direction. A furnace wall (heat transfer tube) constituting the furnace 11 is composed of a plurality of evaporating tubes and fins connecting them, and suppresses temperature rise of the furnace wall by exchanging heat with feed water and steam.

The combustion device 12 is provided on the lower side of the furnace wall that constitutes the furnace 11 . In this embodiment, the combustion device 12 includes multiple coal burners (eg, 21, 22, 23, 24) and multiple BFG burners (eg, 61, 62, 63) mounted to the furnace wall. For example, the coal burners 21 , 22 , 23 , 24 and the BFG burners 61 , 62 , 63 are arranged in a plurality of stages along the vertical direction as one set arranged at equal intervals along the circumferential direction. In this embodiment, four stages (four per stage) of coal burners and three stages (four per stage) of BFG burners are provided. However, the shape of the furnace, the number of coal burners and BFG burners in one stage, and the number of stages are not limited to this embodiment.

Each coal burner 21,22,23,24 is connected to pulverizers (mills) 31,32,33,34 via pulverized coal supply pipes 26,27,28,29. Although not shown, the crushers 31, 32, 33, and 34 have, for example, a housing in which a rotary table is rotatably supported, and a plurality of rollers above the rotary table are rotatable in conjunction with the rotation of the rotary table. It is supported by When the coal is fed between a plurality of rollers and the rotary table, it is pulverized to a predetermined pulverized coal size and transported to a classifier (not shown) by a carrier gas (primary air, oxidizing gas). The classified pulverized coal can be supplied to coal burners 21 , 22 , 23 and 24 from pulverized coal supply pipes 26 , 27 , 28 and 29 .

Each BFG burner 61 , 62 , 63 is connected to a BFG (blast furnace gas) supply tank 35 via a BFG (blast furnace gas) supply pipe 30 . The BFG supply tank 35 supplies BFG to the BFG burners 61 , 62 , 63 .

Further, the furnace 11 is provided with wind boxes 36 at the mounting positions of the coal burners 21, 22, 23 and 24, and wind boxes 68 at the mounting positions of the BFG burners 61, 62 and 63, respectively. One end of an air duct 37 is connected to the wind boxes 36 and 68 . Air duct 37 is provided with blower 38 at the other end.

Further, the furnace 11 is provided with additional air nozzles 39 above the mounting positions of the coal burners 21, 22, 23, 24. As shown in FIG. An end of a branch air duct 40 branched from the air duct 37 is connected to the additional air nozzle 39 . Therefore, the combustion air (fuel gas combustion air/secondary air, oxidizing gas) sent by the blower 38 is supplied from the air duct 37 to the wind boxes 36, 68, and the coal burners 21, 22 are supplied from the wind box 36 to the respective coal burners 21, 22. , 23, 24 and from windbox 68 to each BFG burner 61, 62, 63 respectively. Further, additional combustion air (additional air) sent by the blower 38 can be supplied to the additional air nozzle 39 from the branch air duct 40 .

The flue 13 is connected to the upper part of the furnace 11 in the vertical direction. The flue 13 is provided with, for example, superheaters 41, 42, 43, reheaters 44, 45, an evaporator 46, and an economizer 47 as heat exchangers for recovering the heat of the combustion gas. Heat exchange is performed between the combustion gas generated by the combustion in 11 and the water or steam flowing through each heat exchanger. Note that FIG. 1 does not accurately show the positions of the heat exchangers (superheaters 41, 42, 43, reheaters 44, 45, evaporator 46, economizer 47) in the flue 13. .

A gas duct 48 is connected to the downstream side of the flue 13 through which the combustion gas that has undergone heat exchange is discharged. An air heater (air preheater) 49 is provided between the gas duct 48 and the air duct 37, and heat exchange is performed between the air flowing through the air duct 37 and the combustion gas flowing through the gas duct 48. , 23, 24 and the BFG burners 61, 62, 63 can be heated.

The boiler 10 has a gas recirculation duct 72 and a blower 73 . The gas recirculation duct 72 is connected at one end to the flue 13 downstream of the evaporator 46 and at the other end to the bottom of the furnace 11 . The blower 73 is connected to the gas recirculation duct 72 , pressurizes part of the exhaust gas (GR gas: gas recirculation gas) flowing through the flue 13 , and supplies it to the furnace 11 . The boiler 10 can adjust the oxygen concentration of the air supplied to the furnace 11 by supplying part of the exhaust gas into the furnace 11 with the gas recirculation duct 72 and the blower 73 . Thereby, the amount of combustion gas in the furnace 11 is adjusted. When the temperature of combustion gas generated by combustion in the furnace 11 is approximately 1,200°C, the temperature of GR gas is approximately 350°C to 500°C, for example.

The downstream side of the blower 73 in the gas recirculation duct 72 is branched and connected to the wind box 68 (gas introduction line 74). The boiler 10 is configured such that the GR gas can be introduced from the gas recirculation duct 72 to the wind box 68 via the gas introduction line 74 .

A denitration catalyst 50 is provided in the flue 13 upstream of the air heater 49 . The denitrification catalyst 50 supplies a reducing agent such as ammonia or urea water, which has an action of reducing nitrogen oxides, into the flue 13, and causes the reaction between the nitrogen oxides and the reducing agent in the combustion gas to which the reducing agent is supplied. By promoting it, nitrogen oxides in the combustion gas are removed and reduced. A gas duct 48 connected to the flue 13 is provided with a dust processing device (electrostatic precipitator, desulfurization device) 51, an induced draft fan 52, etc. at a position downstream of the air heater 49, and a chimney 53 at the downstream end. ing.

On the other hand, when the pulverizers 31, 32, 33, and 34 are driven, the pulverized coal fuel is fed to the coal burners 21, 22, 23, 23, 23, 23 through the pulverized coal supply pipes 26, 27, 28, 29 together with the carrier gas. 24. Also, heated combustion air (oxidizing gas) is supplied from the air duct 37 to the coal burners 21 , 22 , 23 , 24 via the wind box 36 . Then, the coal burners 21, 22, 23, 24 blow into the furnace 11 a pulverized fuel mixture in which pulverized coal and a carrier gas (primary air, oxidizing gas) are mixed, and also blow combustion air into the furnace 11, A flame can be formed by igniting at this time. At this time, BFG and combustion air are supplied to the BFG burners 61, 62, and 63, and the BFG is burned, thereby co-firing coal and BFG. As a result, a flame is generated in the lower part of the furnace 11, and the combustion gas rises inside the furnace 11 and is discharged into the flue 13. Air is used as the oxidizing gas in this embodiment. It may have a higher or lower oxygen ratio than air, and can be used by optimizing the fuel flow rate.

After that, the combustion gas undergoes heat exchange in superheaters 41, 42, 43, reheaters 44, 45, evaporator 46, and economizer 47 arranged in flue 13, and then nitrogen oxides are converted by denitration catalyst 50. After being reduced and removed, the particulate matter is removed by the dust treatment device 51 and the sulfur content is removed, it is discharged into the atmosphere from the chimney 53 .

Next, the BFG burner device of this embodiment will be described more specifically with reference to FIGS. 2A and 2B.
2A is an air system diagram of a BFG burner and a coal burner in the boiler of FIG. 1. FIG. 2B is a front view of the BFG burner and the coal burner in the boiler of FIG. 1 as viewed from the furnace side; FIG.

As shown in FIGS. 2A and 2B, the boiler 10 includes coal burners 21, 22, 23, and 24, which are provided in, for example, four stages on the upper stage of the furnace wall that constitutes the furnace 11, and, for example, three stages, which are provided on the lower stage. and BFG burners 61 , 62 , 63 . Each BFG burner 61, 62, 63 is connected via a wind box damper (not shown) provided in each BFG burner 61, 62, 63, respectively, and then connected to the upstream air duct 37 via a damper 64. Connected. Similarly, the coal burners 21, 22, 23, and 24 are also connected to the damper 65 through wind box dampers (not shown) provided in each of the coal burners 21, 22, 23, and 24. is connected to the upstream air duct 37 . With such a configuration, air is distributed and supplied from the air duct 37 to the coal burners 21, 22, 23, 24 and the BFG burners 61, 62, 63, respectively. The temperature of the supplied air is, for example, about 300°C to 350°C.

Gas introduction lines 74 for non-combustible gas are connected to each of the BFG burners 61, 62, 63 and the damper 64 downstream of the connecting point (three locations in total). These gas introduction lines 74 are connected to each other on the upstream side via dampers 75, and then connected to a gas recirculation duct 72 (not shown in FIG. 2A) positioned further upstream. In such a configuration, by adjusting the opening degree of each damper 75, the flow rate of GR gas flowing to each BFG burner 61, 62, 63 can be individually adjusted. The opening of each damper 75 is adjusted by a gas supply controller 76 . When the gas supply control device 76 detects a stopped BFG burner (for example, 63), it opens the corresponding damper 75 and supplies the GR gas to the BFG burner 63 through the gas introduction line 74 to which the BFG supply is stopped. control the flow of The gas supply controller 77 of this embodiment is composed of a damper 75 and a gas supply controller 76 .

The gas supply control device 76 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads out this program to a RAM or the like, and executes information processing and arithmetic processing. As a result, various functions are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

The BFG burner device 81 of this embodiment is composed of the BFG burners 61, 62, 63, the wind box 68 (not shown in FIG. 2B), the gas introduction line 74, and the gas supply controller 77 described above.

As shown in FIG. 2B, the coal burner 21 includes a fuel nozzle 91 that ejects fuel together with primary air for transportation into the furnace, and is provided around the fuel nozzle 91, and secondary air ( (the other coal burners 22, 23, 24 also have a similar structure). On the other hand, in the BFG burner 61, the burner nozzle has a lattice shape in order to improve the combustibility of BFG, and the BFG flow path and the combustion air flow path are alternately formed, and the BFG jetted into the furnace and the combustion (The other BFG burners 62 and 63 have the same structure).

Next, referring to FIG. 3, the gas introduction control to the wind box in the BFG burner device of this embodiment will be described more specifically. 3 is a schematic side sectional view of a BFG burner apparatus in the boiler of FIG. 1; FIG. In FIG. 3, the right side of the paper indicates the outside of the furnace, and the left side of the paper indicates the inside of the furnace.

As shown in FIG. 3, the BFG burner 61 has a BFG nozzle 66 forming a BFG flow path on the outside of the furnace. A wind box 68 is connected which forms a flow path for the . The BFG burner 61 also includes a tip portion 70 whose interior is partitioned by partitions 69 so that, for example, two stages in the vertical direction and six rows in the width direction are formed inside the furnace. Between each channel defined inside the tip portion 70 and the BFG nozzle 66 and wind box 68, each channel defined inside the tip portion 70 has a BFG channel and a combustion air channel. are formed alternately in the vertical direction and in the width direction. The connecting portion between the tip portion 70, the connecting portion 71, and the wind box 68, the connecting portion between the connecting portion 71 and the BFG nozzle 66, and the connecting portion between the partition portion 69 and the connecting portion 71 are connected by welding or the like ( welded structural parts, etc.). Note that the BFG burner 61 shown in FIG. 3 is in the process of stopping the supply of BFG. Further, the number of stages and the number of rows of the tip portion 70 partitioned by the partitioning portion 69 are not limited to this.

Examples of materials for the wind box 68 include carbon steel and low alloy steel. Examples of the material of the BFG burner 61 (specifically, the BFG nozzle 66, the partition portion 69, the tip portion 70, and the connection portion 71) include stainless steel.

In the BFG burner device 81 shown in FIG. 3, a plurality of thermometers 78 are provided for measuring the temperature of the portion surrounded by the dashed circle in FIG. are omitted and only representative examples are shown). The output of thermometer 78 is configured to be sent to gas supply controller 76 . The gas supply control device 76 detects the stoppage of the BFG supply of the BFG burner 61 and then controls the opening/closing and the degree of opening of each damper 75 based on the output of these thermometers 78 . At this time, the flow rate of the GR gas introduced into the wind box 68 is adjusted so that the measured value of the thermometer 78 is equal to or less than a predetermined set value. In the boiler 10 according to the present embodiment, based on the durability of the material of the wind box 68, the predetermined measured value of the thermometer 78 (especially the thermometer 78 provided in the wind box 68) is 400° C. or less. The flow rate of the GR gas introduced into the wind box 68 may be adjusted so that Note that the above set values may be appropriately determined depending on the structure in addition to the material of the wind box 68 and the BFG burner 61 .

[Method of operating BFG burner device]
Next, an example of a method of operating the BFG burner apparatus of the present disclosure will be described.
A method of operating a BFG burner apparatus of the present disclosure is a method of operating a BFG burner apparatus for performing a gas introducing step in the above-described BFG burner apparatus. In the gas introduction step, non-combustible gas is introduced into the gas introduction line while the supply of BFG to the BFG burner is stopped.

In addition, below, in the boiler 10 shown in FIG. 1, although the case where the operating method of the BFG burner apparatus of this disclosure is applied is demonstrated as an example, it is not limited to this.

(Gas introduction process)
In the gas introduction step, the GR gas is introduced into the gas introduction line 74 while the supply of BFG to the BFG burner 61 is stopped. Specifically, the damper 75 corresponding to the BFG burner 61 being stopped is opened to introduce the GR gas into the wind box 68 of the BFG burner 61 . The flow rate of the GR gas introduced into the wind box 68 is adjusted, for example, so that the measured value of the thermometer 78 provided in the BFG burner device 81 is less than or equal to a predetermined set value.

The above-described gas introduction step is performed by a gas supply control unit 77 that includes, for example, a damper 75 that adjusts the flow rate of noncombustible gas introduced into the wind box 68 and a control device (gas supply control device 76) that controls the damper 75. can also

In addition, when stopping the supply of BFG to the BFG burners 61, 62, 63, for example, when the flow rate of BFG decreases, the BFG burners 61, 62, 63 used for burning BFG according to the flow rate of BFG Reduce the number of trains and operate to compensate for the corresponding load. Specifically, when the BFG flow rate decreases, for example, the BFG burners 63 are stopped in order from the lowest stage. Conversely, when increasing the supply of BFG to the BFG burners 61, 62, 63 and igniting the BFG burners 61, 62, 63, for example, the BFG burners 61 in the uppermost stage are ignited in order. On the other hand, when the BFG flow rate increases, the coal burners 21, 22, 23, and 24, for example, stop supplying pulverized coal in order from the coal burner 21 in the uppermost stage.

In the above-described embodiment, the GR gas is used as the incombustible gas introduced into the wind box 68, but the present invention is not limited to this. For example, steam may be used as the non-combustible gas introduced into the wind box 68 . When steam is introduced into the wind box 68, it may be configured to use steam for internal use. The use of in-house steam eliminates the need for extensive remodeling of the equipment of the boiler 10, thereby reducing costs. Also, the temperature of the steam to be introduced can be, for example, about 300°C to 350°C.

With the configuration described above, according to this embodiment, the following effects are obtained.
In the BFG burner device 81 of the present embodiment, a gas introduction line 74 for introducing noncombustible gas is connected to the wind box 68 of the BFG burner 61, and the gas supply control unit 77 controls the supply of BFG to the BFG burner 61. A non-combustible gas is flowed through the gas introduction line 74 while the engine is stopped. As a result, unburned gas is blown out from the furnace inner tip portion 70 of the BFG burner 61 whose supply of BFG is stopped, so that the unburned gas of BFG flows into the inside of the stopped BFG burner 61 and the wind box 68. can be prevented. Therefore, the unburned gas of BFG flowing into the inside of the BFG burner 61 and the wind box 68 is combusted with the oxidizing gas (combustion air) inside, and the temperature of the BFG burner 61 and the wind box 68 rises unevenly. , the BFG burner device 81 can be prevented from being damaged. As a result, repair work due to damage to the BFG burner device 81 and maintenance work for the BFG burner device 81 can be suppressed. In addition, since it is possible to prevent cracks from occurring in the welded structure portion in the BFG burner device 81, the BFG reacts with the combustion air during operation of the BFG burner 61, causing a local temperature rise and causing the above Since it is possible to prevent the cracks from expanding, the life of the BFG burner device 81 can be extended. A gas supply control unit 77 that introduces nonflammable gas into the wind box 68 of the BFG burner 61 is composed of, for example, a damper 75 and a control device (gas supply control device 76) that controls the damper 75. The gas introduction flow rate can be adjusted.

If the flow rate of the non-combustible gas introduced into the wind box 68 is adjusted so that the measured value of the thermometer 78 provided in the wind box 68 is below a predetermined set value, the temperature inside the wind box 68 is reduced to the set value. can be maintained below. As a result, damage to the BFG burner device 81 can be more reliably prevented. Further, the predetermined set value may be set so as to be the endurable temperature (for example, 400° C. or less) of the constituent members (for example, carbon steel or low alloy steel) that constitute the wind box 68 of the BFG burner 61, for example.

The BFG burner device 81 of the present embodiment is configured such that gas is blown out from the furnace inner tip portion 70 of the BFG burner 61 while the supply of BFG is stopped. Therefore, the BFG burner 61 is placed in the vicinity of the vertically lower side of the main fuel burners (coal burners 21, 22, 23, 24) burning carbon-containing solid fuel (for example, pulverized coal) (for example, the coal burners 21, 21 for 22, 23, 24), even if the ash generated during the combustion of the carbon-containing solid fuel flows to the BFG burner 61 side, the flowing ash is at the tip of the stopped BFG burner 61 70 can be prevented from being accumulated. That is, clogging (ash clogging) of the tip portion 70 of the BFG burner 61 by ash can be prevented.

Examples of the incombustible gas flowing through the gas introduction line 74 include GR gas derived from exhaust gas generated by combustion of fuel in the furnace 11 and steam. The GR gas can adjust the oxygen concentration of the combustion air (oxidizing gas) supplied to the furnace 11. For example, exhaust gas extracted from the inlet of the economizer 47 of the mixed combustion boiler 10 is pressurized by the blower 73 and It is put into the furnace 11 and is designed to be introduced near the bottom of the furnace 11 . Even if part of the GR gas introduced into the furnace 11 is introduced into the wind box 68, the total amount of GR gas introduced into the furnace 11 does not change. However, the influence on the combustion performance in the furnace 11 can be reduced. Steam can be used as the non-combustible gas in a boiler that is not adapted to introduce GR gas. When steam is introduced into the wind box 68, by adopting a configuration in which steam for internal use is used, the co-combustion boiler 10 does not need to be extensively modified, so the cost can be reduced.

Since the mixed combustion boiler 10 of the present embodiment includes the BFG burner device 81 described above, the unburned BFG gas that has flowed into the BFG burner 61 and the wind box 68 is burned inside, and the BFG burner device 81 can be prevented from being damaged. As a result, the life of the BFG burner device 81 can be extended. Therefore, the co-firing boiler 10 is highly economical.

The operating method of the BFG burner device 81 of the present embodiment includes a gas introducing step of introducing non-combustible gas into the gas introducing line 74 connected to the wind box 68 when the supply of BFG to the BFG burner 61 is stopped. have. As a result, unburned gas is blown out from the furnace inner tip portion 70 of the BFG burner 61 whose supply of BFG is stopped, so that the unburned gas of BFG flows into the inside of the stopped BFG burner 61 and the wind box 68. can be prevented. Therefore, the unburned gas of BFG flowing into the inside of the BFG burner 61 and the wind box 68 is combusted with the combustion air inside, the temperature of the BFG burner 61 and the wind box 68 rises unevenly, and the BFG burner device 81 can be prevented from being damaged. As a result, repair work due to damage to the BFG burner device 81 and maintenance work for the BFG burner device 81 can be suppressed. In addition, since it is possible to prevent cracks from occurring in the welded structure portion in the BFG burner device 81, the BFG reacts with the combustion air during operation of the BFG burner 61, causing a local temperature rise and causing the above Since it is possible to prevent the cracks from expanding, the life of the BFG burner device 81 can be extended.

Further, in the above-described embodiment, the case where the BFG burner has three stages has been described as an example, but the number of stages of the BFG burner is not limited to this. The number of stages of the BFG burner may be one, two, or four or more. Also, the installation position of the BFG burner is not limited to below the coal burner as in the above embodiment. Specifically, the BFG burner may be installed above the coal burner. In this case, since the ash generated when the carbon-containing solid fuel is burned in the coal burner does not flow to the BFG burner side, it is possible to prevent the flowing ash from accumulating at the tip of the stopped BFG burner. can be prevented.

Further, in the above-described embodiment, the boiler of the present disclosure is a mixed combustion boiler, but the boiler may use biomass, petroleum coke, petroleum residue, or the like as the solid fuel. In addition, the fuel is not limited to solid fuel, and can be used for oil-fired boilers such as heavy oil.

10 Co-firing boiler (boiler)
11 Furnace 12 Combustion device 13 Flue 21, 22, 23, 24 Coal burner (main fuel burner)
26, 27, 28, 29 pulverized coal supply pipe 30 BFG (blast furnace gas) supply pipe 31, 32, 33, 34 pulverizer 35 BFG (blast furnace gas) supply tank 36, 68 wind box 37 air duct 38 blower 39 additional air nozzle 40 branch air ducts 41, 42, 43 superheater (heat exchanger)
44, 45 reheater (heat exchanger)
46 evaporator (heat exchanger)
47 Economizer (Heat Exchanger)
48 gas duct 49 air heater 50 denitrification catalyst 51 dust treatment device (electrostatic precipitator, desulfurization device)
52 induced draft fan 53 chimney 61, 62, 63 BFG burner 64, 65 damper 66 BFG nozzle 69 partition 70 tip 71 connection 72 gas recirculation duct 73 blower 74 gas introduction line 75 damper 76 gas supply controller 77 gas supply control Part 78 Thermometer 81 BFG burner device 91 Fuel nozzle 92 Secondary air nozzle B Combustion NG Unburned gas

Claims (5)

A BFG burner provided on the wall surface of the furnace and burning blast furnace gas in the furnace;
a windbox connected in communication with the BFG burner and supplying an oxidizing gas to the BFG burner;
a gas introduction line connected to the wind box for introducing non-combustible gas into the wind box;
a gas supply control unit for flowing the non-combustible gas into the gas introduction line when the supply of the blast furnace gas to the BFG burner is stopped;
with
The windbox is provided with a thermometer for measuring the temperature of the windbox,
A BFG burner apparatus in which a flow rate of the incombustible gas introduced into the wind box is adjusted so that the measured value of the thermometer is equal to or less than a predetermined set value. 2. The BFG burner apparatus according to claim 1 , wherein said BFG burner is provided on a wall surface of said furnace and arranged near a vertically lower side of a main fuel burner for burning a carbon-containing solid fuel. 2. The BFG burner apparatus according to claim 1 , wherein said non-combustible gas is gas recirculated gas or steam derived from exhaust gas produced by combustion of said blast furnace gas and/or carbon-containing solid fuel. A boiler comprising the BFG burner device according to any one of claims 1 to 3 . A BFG burner provided on the wall surface of the furnace and burning blast furnace gas in the furnace, a wind box connected in communication with the BFG burner and supplying oxidizing gas to the BFG burner, and a wind box connected to the wind box , a method for operating a BFG burner device comprising a gas introduction line for introducing noncombustible gas into the wind box , and a thermometer provided in the wind box for measuring the temperature of the wind box,
A gas introduction step of introducing the non-combustible gas into the gas introduction line when the supply of the blast furnace gas to the BFG burner is stopped ;
A method of operating a BFG burner device, wherein in the gas introduction step, the flow rate of the non-combustible gas introduced into the wind box is adjusted so that the measured value of the thermometer is equal to or less than a predetermined set value.

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