CN111520704B

CN111520704B - BFG burner device, operation method thereof and boiler having the same

Info

Publication number: CN111520704B
Application number: CN202010074349.5A
Authority: CN
Inventors: 金子琢磨; 三村匠; 林和也
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2019-02-01
Filing date: 2020-01-22
Publication date: 2022-09-13
Anticipated expiration: 2040-01-22
Also published as: JP7229796B2; CN111520704A; JP2020125859A

Abstract

Provided are a BFG burner device, a method for operating the same, and a boiler equipped with the same, wherein the BFG burner device can be prevented from being damaged by the combustion of the unburned gas of BFG flowing into the inside of a BFG burner and a wind box during the supply stoppage of BFG. The BFG burner device is provided with: BFG burners (61, 62, 63) provided on the wall surface of the furnace (11) and configured to burn blast furnace gas in the furnace (11); a wind box (68) which communicates with the BFG burners (61, 62, 63) and is connected to the BFG burners (61, 62, 63) to supply oxidizing gas to the BFG burners (61, 62, 63); a gas introduction line (74) that is connected to the wind box (68) and introduces a noncombustible gas into the wind box (68); and a gas supply control unit that causes a noncombustible gas to flow through the gas introduction line (74) when the supply of blast furnace gas to the BFG burners (61, 62, 63) is stopped.

Description

BFG burner device, operation method thereof and boiler provided with BFG burner device

Technical Field

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

Background

A large boiler such as a coal-fired boiler has a furnace vertically disposed in a hollow shape, and a plurality of burners are arranged on a wall of the furnace in a circumferential direction of the furnace. The coal-fired boiler is connected to a flue above the furnace in the vertical direction, and a heat exchanger for generating steam is disposed in the flue. The burner injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame, generates combustion gas, and flows the combustion gas into the flue. A heat exchanger is provided in a region where the combustion gas flows, and water or steam flowing in a heat transfer pipe constituting the heat exchanger is heated to generate superheated steam.

In recent years, from the viewpoint of effective utilization of energy resources, a gas (blast Furnace gas) generated in the iron making process and obtained as a by-product gas from a blast Furnace is also used as a fuel in a boiler (for example, patent document 1). However, BFG has a low calorific value (low calorie), is poor in combustibility, and has a time-varying flow rate and composition, and therefore, in addition to a burner (BFG burner) for burning BFG, a burner (e.g., coal burner) for burning another fuel (e.g., a carbonaceous solid fuel such as coal) is generally used for co-combustion.

[ Prior Art document ]

[ patent document ]

[ patent document 1 ] Japanese patent No. 6051952

Disclosure of Invention

[ SUMMARY OF THE INVENTION ]

[ problem to be solved by the invention ]

Fig. 4A, 4B, and 5 are shown, and problems occurring when coal and BFG are co-fired in a furnace of a boiler 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 the coal burner as a reference example, as viewed from a furnace side.

As shown in fig. 4A and 4B, a boiler 110 for co-combustion of coal and BFG is provided on a furnace wall constituting a furnace 111, and includes, for example, 4 stages of

coal burners

121, 122, 123, and 124 provided in an upper stage and 3 stages of

BFG burners

161, 162, and 163 provided in a lower stage. The wind box 136 is provided at the installation position of each of the

coal burners

121, 122, 123, 124, and the wind box 168 is provided at the installation position of each of the BFG

burners

161, 162, 163. The BFG

burners

161, 162, and 163 are connected to the upstream air passage 137 via windbox dampers (not shown) provided in the BFG

burners

161, 162, and 163, respectively, and then connected to the upstream air passage 137 via dampers 164. Similarly, the

coal burners

121, 122, 123, and 124 are also connected to a damper 165 via a bellows damper (not shown) provided in each of the

coal burners

121, 122, 123, and 124, and are also connected to the upstream air passage 137 via the damper 165. With this configuration, air is distributed and supplied from the air passage 137 to the

coal burners

121, 122, 123, and 124 and the

BFG burners

161, 162, and 163, respectively. The temperature of the supplied air is, for example, about 300 to 350 ℃ in normal operation.

As shown in fig. 4B, the coal burner 121 has a structure including a fuel nozzle 191 for ejecting fuel such as pulverized coal together with primary air for conveyance (conveyance gas), and a secondary air nozzle 192 provided around the fuel nozzle 191 to form a flow path for secondary air (combustion air) on the outer peripheral side of the fuel nozzle 191 (the

other coal burners

122, 123, 124 have the same structure). On the other hand, in order to improve the combustibility of the BFG, the burner nozzles of the BFG burner 161 are formed in a lattice shape, and the BFG flow paths and the combustion air flow paths are alternately formed, so that the BFG ejected into the furnace is mixed with the combustion air and combusted (the same applies to the other BFG burners 162 and 163).

In a boiler in which pulverized coal of coal and BFG are mixed-fired, a structure capable of providing 100% load in the case of coal-only firing is provided. The BFG is a by-product gas generated in the iron making process, and since the flow rate and composition vary, the BFG is operated by switching the number of burners used as, for example, the maximum load of 50% of the boiler load. Specifically, when the flow rate of the BFG is decreased, the number of

BFG burners

161, 162, 163 used according to the flow rate of the BFG is decreased, and the

coal burners

121, 122, 123, 124 are operated so as to compensate for the load of the portion. On the other hand, when the flow rate of BFG increases, the number of

coal burners

121, 122, 123, 124 is reduced, for example, and operation is partially stopped.

When pulverized coal of coal and BFG are mixed and burned, the supply rate of oxygen for combustion to the entire boiler is made constant in accordance with the fuel supply to the entire boiler, specifically, the supply rate of combustion air (oxidizing gas) is made constant at a predetermined amount. However, BFG is a gas fuel, and therefore has better combustibility than pulverized coal, and consumes oxygen rapidly in the furnace interior, and the unburned components of pulverized coal increase by depriving oxygen necessary for the combustion of pulverized coal downstream of the

BFG burners

161, 162, 163. Therefore, the amount of combustion air supplied to the

BFG burners

161, 162, 163 is set to be smaller than that in the case of exclusively BFG combustion.

In this case, when the mixed combustion is performed in all the

coal burners

121, 122, 123, 124 and all the

BFG burners

161, 162, 163, the total amount of air supplied to the boiler is changed as follows, for example, in order to change the air amount necessary for the dedicated combustion state of each burner to the mixed combustion state. Specifically, for example, the standard conditions are taken such that the supply amount of combustion air for the single-body combustion in the dedicated combustion state is 70% for all the

coal burners

121, 122, 123, 124, and the supply amount of combustion air for the single-body combustion in the dedicated combustion state is 30% for all the

BFG burners

161, 162, 163, with respect to the entire supply amount of air to the boiler. The amount of air for combustion supplied to the

coal burners

121, 122, 123, 124 is increased from the amount necessary for exclusive combustion of coal (for example, 70% is increased to 80 to 85%). Further, the difference in combustibility between the pulverized coal and the BFG can be corrected by reducing the amount of combustion air supplied to the

BFG burners

161, 162, 163 by an amount necessary for BFG-only combustion (for example, by reducing 30% to 15 to 20%).

In this case, the following new problems may occur. This problem will be described in more detail with reference to fig. 5. Fig. 5 is a schematic side sectional view of a BFG burner as a reference example, and the inside of the BFG burner 161, that is, the inside of the tip portion 170, has a structure in which a flow path of BFG and a flow path of combustion air are alternately formed and the BFG ejected into the furnace is mixed with the combustion air and burned. In fig. 5, solid arrows indicate BFG flow, dashed arrows indicate combustion air flow, and dotted arrows indicate unburned gas flow. In fig. 5, the right direction of the drawing shows the outside of the furnace, and the left direction of the drawing shows the inside of the furnace.

As shown in fig. 5, the BFG burner 161 includes BFG nozzles 166 forming a BFG flow path outside the furnace, and a windbox 168 forming a combustion air flow path is connected to the outer periphery of the BFG nozzles 166 in the vertical direction of the BFG nozzles 166. The BFG burner 161 includes a tip portion 170 having 2 stages formed in the vertical direction and 6 rows of flow paths formed in the width direction, for example, on the furnace inner side and partitioned by a partition portion 169. The respective flow paths defined inside the tip portion 170 are connected to the BFG nozzle 166 and the wind box 168 by a connecting portion 171 so that a flow path of BFG and a flow path of combustion air are alternately formed in the vertical direction and the width direction of the respective flow paths defined inside the tip portion 170. The connection portion between the tip portion 170 and the connection portion 171 and the bellows 168, the connection portion between the connection portion 171 and the BFG nozzle 166, and the connection portion between the partition portion 169 and the connection portion 171 are connected by welding or the like (forming a welded structure portion or the like).

In fig. 5, for example, the BFG burner 161 on the upper side of the drawing is in operation, and the BFG burner 162 on the lower side is in the supply stop of BFG. In the lower BFG burner 162 that is stopped, the corresponding windbox damper is closed, but a slight amount of combustion air leaks and flows into the flow path formed between the BFG nozzle 166 and the windbox 168.

When the combustion air supply amount to the BFG burner 161 is reduced, the flow rate of the combustion air is reduced, and therefore, the unburned gas NG is likely to be generated during combustion of BFG (for example, the flow rate is reduced from 65% to 50% by reducing the combustion air amount during co-combustion with respect to the combustion air flow rate during BFG-only combustion). At this time, ash content during the combustion of the pulverized coal tends to flow into the BFG burner 162 located vertically below the

coal burners

121, 122, 123, and 124. When the BFG burner (in fig. 5, the BFG burner 162) whose BFG supply is stopped is present, the ash flowing in accumulates at the front end 170 of the stopped BFG burner 162, and the front end of the BFG burner 162 may be blocked.

Further, since the BFG burner (the BFG burner 162 in fig. 5) whose BFG supply is stopped exists, part of the unburned gas NG of the BFG may flow into the inside of the stopped BFG burner 162 and the wind box 168. Then, a slight amount of combustion air flowing into the wind box 168 of the stopped BFG burner 162 may react with the unburned gas NG flowing into the BFG burner 162 and the wind box 168 to be combusted (combustion B in fig. 5). This causes uneven temperature rise in the BFG burner 162 and the wind box 168, which may damage the BFG burner apparatus including the BFG burner 162 and the wind box 168. In particular, cracks are likely to occur in the welded structure portion, i.e., the shape-changed portion, in the BFG burner 162, and the temperature of the portion is locally increased, so that the BFG reacts with combustion air during operation of the BFG burner 162 and the cracks may be further enlarged, which may cause a problem of a reduction in the life of the BFG burner apparatus.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a BFG burner apparatus and an operation method of the BFG burner apparatus, which can prevent damage to the BFG burner apparatus due to internal combustion of unburned gas of BFG flowing into the inside of a BFG burner and a windbox during which supply of BFG is stopped.

[ MEANS FOR solving PROBLEMS ] A method for solving the problems

In order to solve the above problem, the present disclosure adopts the following aspects.

The disclosed BFG burner device is provided with: the BFG burner is arranged on the wall surface of the furnace, so that blast furnace gas is combusted in the furnace; a wind box connected to the BFG burner and communicating with the BFG burner, for supplying an oxidizing gas to the BFG burner; a gas introduction line connected to the wind box, for introducing a noncombustible gas into the wind box; and a gas supply control unit that causes the noncombustible gas to flow through the gas introduction line when the supply of the blast furnace gas to the BFG burner is stopped.

In the BFG burner apparatus of the present disclosure, a gas introduction line for introducing a noncombustible gas is connected to a wind box of the BFG burner, and the gas supply control unit causes the noncombustible gas to flow through the gas introduction line when the supply of BFG to the BFG burner is stopped. This blows out the incombustible gas from the furnace-interior tip portion of the BFG burner whose BFG supply is stopped, and therefore prevents the inflow of the unburned gas of BFG (blast furnace gas) into the stopped BFG burner and the windbox. Therefore, the unburned gas of the BFG flowing into the inside of the BFG burner and the windbox can be prevented from being burned with the oxidizing gas inside and from being unevenly heated in the BFG burner and the windbox, thereby preventing the BFG burner apparatus from being damaged. This can suppress the occurrence of repair work due to damage to the BFG burner apparatus or inspection work for the BFG burner apparatus. In addition, since cracks can be prevented from occurring in the welded structure portion in the BFG burner apparatus, the BFG burner apparatus can be prevented from being elongated because of local temperature increase due to reaction between the BFG and the oxidizing gas during operation of the BFG burner, and thus the life of the BFG burner apparatus can be prolonged. The gas supply control unit for introducing the noncombustible gas into the windbox of the BFG burner is constituted by, for example, a damper and a control device for controlling the damper, and can adjust the introduction flow rate of the noncombustible gas into the windbox.

In the BFG burner apparatus, it is preferable that a thermometer for measuring a temperature of the windbox is provided in the windbox, and an introduction flow rate of the noncombustible gas into the windbox is adjusted so that a measured value of the thermometer becomes a predetermined set value or less.

The temperature in the windbox can be maintained at or below a set value if the flow rate of introduction of the noncombustible gas into the windbox is adjusted so that a measured value of a thermometer provided in the windbox becomes equal to or less than a predetermined set value. This can more reliably prevent damage to the BFG burner apparatus. The predetermined set value may be set to, for example, a durable temperature (e.g., 400 ℃ or lower) of a component (e.g., carbon steel or low alloy steel) constituting a windbox of the BFG burner.

In the BFG burner apparatus, it is preferable that the BFG burner is disposed on a wall surface of the furnace in the vicinity of a vertically lower side of a main fuel burner for burning a carbonaceous solid fuel.

In the BFG burner apparatus of the present disclosure, the gas is blown out from the furnace-inside tip portion of the BFG burner in which the BFG supply is stopped. Therefore, in the case where the BFG burner is disposed in the vicinity of the vertically lower side of the main fuel burner that burns the carbonaceous solid fuel (for example, pulverized coal) (for example, vertically lower side of the coal burner that burns pulverized coal), even if the ash generated at the time of combustion of the carbonaceous solid fuel flows toward the BFG burner, the ash that has flowed in can be prevented from accumulating at the tip end portion of the BFG burner that is being stopped. That is, the clogging of the front end portion of the BFG burner (ash clogging) due to ash can be prevented.

In the BFG burner apparatus of the present disclosure, preferably, the noncombustible gas is a gas recirculation gas or steam from an exhaust gas generated by combustion of the blast furnace gas and/or the carbonaceous solid fuel.

Examples of the non-combustible gas flowing through the gas introduction line include GR (gas recirculation) gas and steam, which are exhaust gas generated by combustion of fuel in a furnace. The GR gas is a gas capable of adjusting the oxygen concentration of the oxidizing gas supplied to the furnace, and is, for example, a gas in which exhaust gas extracted from an inlet of a economizer of a boiler is pressurized by a blower and is introduced into the furnace again, and is introduced into the vicinity of the bottom of the furnace. Even if a part of the GR gas fed into the furnace is introduced into the wind box, the total amount of the GR gas introduced into the furnace does not change, and therefore, even if the gas introduction line as described above is connected to the wind box, the influence on the combustion performance in the furnace can be reduced. In the boiler in which GR gas is not introduced, steam can be used as a non-combustible gas. When the steam is introduced into the wind box, the steam for use in the station is used, and thus, the boiler facility does not need to be significantly modified, and thus, the cost can be reduced.

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

In the boiler according to the present disclosure, since the BFG burner apparatus is provided, the unburned gas of BFG flowing into the BFG burner and the wind box can be prevented from being burned inside and damaging the BFG burner apparatus. This makes it possible to extend the life of the BFG burner apparatus. Therefore, the boiler is economically advantageous.

In the operation method of the BFG burner apparatus of the present disclosure, the BFG burner apparatus includes: the BFG burner is arranged on the wall surface of the furnace, so that blast furnace gas is combusted in the furnace; a wind box connected to the BFG burner and communicating with the BFG burner, for supplying an oxidizing gas to the BFG burner; and a gas introduction line connected to the windbox and introducing a noncombustible gas into the windbox, wherein the operation method of the BFG burner apparatus includes a gas introduction step of introducing the noncombustible gas into the gas introduction line when supply of the blast furnace gas to the BFG burner is stopped.

The operation method of the BFG burner apparatus of the present disclosure includes a gas introduction step of introducing a noncombustible gas into a gas introduction line connected to a windbox when the supply of BFG to the BFG burner is stopped. This blows out the incombustible gas from the furnace-interior tip portion of the BFG burner whose BFG supply is stopped, and therefore prevents the inflow of the unburned gas of BFG (blast furnace gas) into the stopped BFG burner and the windbox. Therefore, the unburned gas of the BFG flowing into the inside of the BFG burner and the windbox can be prevented from being burned with the oxidizing gas inside, and the BFG burner and the windbox are prevented from being unevenly heated, thereby damaging the BFG burner apparatus. This can suppress the occurrence of repair work due to damage to the BFG burner apparatus or repair work for the BFG burner apparatus. Furthermore, since cracks can be prevented from occurring in the welded structure portion in the BFG burner apparatus, the BFG burner apparatus can be prevented from having a long life because the BFG reacts with the oxidizing gas and the temperature thereof locally increases during operation of the BFG burner, thereby preventing the cracks from being enlarged. The gas introduction step may be performed by a gas supply control unit configured by, for example, a damper or a control device for controlling the damper, and capable of adjusting the introduction flow rate of the noncombustible gas into the wind box.

[ Effect of the invention ]

According to the BFG burner apparatus and the operation method of the BFG burner apparatus of the present disclosure, it is possible to suppress the blockage of the BFG burner due to the fine coal ash during the stoppage of the BFG supply, and it is possible to prevent the damage of the BFG burner apparatus due to the combustion of the unburned gas flowing into the inside of the stopped BFG burner and wind box.

Drawings

Fig. 1 is a schematic configuration diagram illustrating a multi-fuel boiler according to an embodiment of the present disclosure.

Fig. 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, viewed from the furnace side.

Fig. 3 is a diagrammatic side sectional view of a BFG burner apparatus in the boiler of fig. 1.

Fig. 4A is an air system diagram of a BFG burner and a coal burner as a reference example.

Fig. 4B is a front view of the BFG burner and the coal burner as a reference example, as viewed from the furnace side.

Fig. 5 is a schematic side sectional view of a BFG burner as a reference example.

[ notation ] to show

10 multifuel combustion 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

30BFG (blast furnace gas) supply pipe

31. 32, 33, 34 pulverizer

35BFG (blast furnace gas) supply tank

36. 68 bellows

37 air channel

38 blower

39 supply air nozzle

40 branch air channel

41. 42, 43 superheater (Heat exchanger)

44. 45 reheater (Heat exchanger)

46 evaporator (Heat exchanger)

47 coal economizer (Heat exchanger)

48 gas channel

49 air heater

50 denitration catalyst

51 coal dust treatment device (electric dust collector, desulphurization device)

52 induction blower

53 chimney

61. 62, 63BFG burner

64. 65 air door

66BFG nozzle

69 division part

70 front end portion

71 connecting part

72 gas recirculation passage

73 blower

74 gas introduction line

75 air door

76 gas supply control device

77 gas supply control part

78 thermometer

81BFG burner device

91 fuel injection nozzle

92 secondary air nozzle

B combustion

Unburned gas of NG

Detailed Description

Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments, and when there are a plurality of embodiments, the present disclosure also includes a configuration in which the respective embodiments are combined. In the present specification, GR (Gas Recirculation) is an abbreviation for Gas Recirculation.

[ boiler ]

Fig. 1 is a schematic configuration diagram showing a multi-firing boiler according to the present embodiment.

The boiler of the present embodiment uses pulverized coal obtained by pulverizing coal as a fine powder fuel (carbon-containing solid fuel), and the pulverized coal is combusted by a coal burner (main fuel burner) and BFG (blast furnace gas) generated in a blast furnace is combusted (co-combustion) by a BFG burner. The boiler of the present embodiment is a combined combustion boiler that recovers heat generated by the above-described combustion and exchanges heat with feed water or steam to generate superheated steam. In the following description, upper or upper means an upper side in the vertical direction, and lower or lower means a lower side in the vertical direction.

In the present embodiment, as shown in fig. 1, a multi-fuel fired boiler 10 includes a furnace 11, a combustion device 12, and a flue 13. The furnace 11 is provided in a vertical direction in a hollow shape of a rectangular cylinder, for example. The furnace wall (heat transfer pipe) constituting the furnace 11 is composed of a plurality of evaporation pipes and fins connecting these, and suppresses temperature rise of the furnace wall by heat exchange with feed water or steam.

The combustion apparatus 12 is provided on a lower portion side of a furnace wall constituting the furnace 11. In the present embodiment, the combustion apparatus 12 includes a plurality of coal burners (e.g., 21, 22, 23, and 24) and a plurality of BFG burners (e.g., 61, 62, and 63) attached to the furnace wall. For example, the

coal burners

21, 22, 23, and 24 and the

BFG burners

61, 62, and 63 are arranged in 1 group at equal intervals in the circumferential direction, and a plurality of stages are arranged in the vertical direction. In the present embodiment, the coal burner is provided with 4 stages (4/stage), and the BFG burner is provided with 3 stages (4/stage). 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.

The

coal burners

21, 22, 23, and 24 are connected to pulverizers (mills) 31, 32, 33, and 34 via pulverized

coal supply pipes

26, 27, 28, and 29. Although not shown, the

grinders

31, 32, 33, and 34 are configured such that, for example, a rotary table is supported in a housing so as to be rotatable, and a plurality of rollers are supported above the rotary table so as to be rotatable in conjunction with the rotation of the rotary table. When coal is charged between the plurality of rollers and the rotating table, the coal is pulverized into a predetermined size of pulverized coal, and the pulverized coal after classification can be supplied to the

coal burners

21, 22, 23, and 24 by conveying gas (primary air, oxidizing gas) to a classifier (not shown) and conveying the pulverized coal from the pulverized

coal supply pipes

26, 27, 28, and 29.

The BFG burners 61, 62, and 63 are connected to a BFG (blast furnace gas) supply tank 35 via a BFG supply pipe 30.

BFG burners

61, 62, 63 are supplied with BFG through BFG supply tank 35.

In the furnace 11, a windbox 36 is provided at the installation position of each

coal burner

21, 22, 23, 24, and a windbox 68 is provided at the installation position of each

BFG burner

61, 62, 63. One end of the air duct 37 is connected to the

bellows

36, 68. The air passage 37 is provided with a blower 38 at the other end.

The furnace 11 is provided with a supply air nozzle 39 above the installation position of each of the

coal burners

21, 22, 23, and 24. An end of a branch air passage 40 branched from the air passage 37 is connected to the supply air nozzle 39. Therefore, the combustion air (fuel gas combustion air/secondary air, oxidizing gas) sent by the blower 38 can be supplied from the air passage 37 to the

windboxes

36, 68, from the windbox 36 to the

coal burners

21, 22, 23, 24, and from the windbox 68 to the

BFG burners

61, 62, 63, respectively. The additional air for combustion (make-up air) sent by the blower 38 can be supplied from the branch air duct 40 to the make-up air nozzle 39.

The flue 13 is connected to the upper portion of the furnace 11 in the vertical direction. The flue 13 is provided with, for example,

superheaters

41, 42, and 43, reheaters 44 and 45, an evaporator 46, and a economizer 47 as heat exchangers for recovering heat of the combustion gas, and performs heat exchange between the combustion gas generated by combustion in the furnace 11 and the feed water and steam flowing through the heat exchangers. In fig. 1, the positions of the heat exchangers (

superheaters

41, 42, and 43, reheaters 44 and 45, evaporator 46, and economizer 47) in the flue 13 are not accurately shown.

The flue 13 is connected at its downstream side with a gas passage 48 through which the combustion gas after heat exchange is discharged. The gas duct 48 is provided with an air heater (air preheater) 49 between the air duct 37 and the air duct 48, and the air flowing through the air duct 37 and the combustion gas flowing through the gas duct 48 can exchange heat therebetween to raise the temperature of the combustion air supplied to the

coal burners

21, 22, 23, 24 and the

BFG burners

61, 62, 63.

The boiler 10 has a gas recirculation passage 72, a blower 73. The gas recirculation passage 72 has one end connected to the downstream side of the evaporator 46 of the flue 13 and the other end connected to the bottom of the furnace 11. The blower 73 is connected to the gas recirculation passage 72, and a part of the exhaust gas flowing through the flue 13 (GR gas: gas recirculation gas) is pressurized by the blower 73 and supplied to the furnace 11. The boiler 10 can adjust the oxygen concentration of the air supplied to the furnace 11 by supplying a part of the exhaust gas into the furnace 11 by the gas recirculation passage 72 and the blower 73. Thereby, the amount of combustion gas in the furnace 11 is adjusted. In the case where the temperature of the combustion gas generated by the combustion in the furnace 11 is about 1200 ℃, the temperature of the GR gas is, for example, about 350 ℃ to 500 ℃.

The gas recirculation passage 72 branches off on the downstream side of the blower 73 and is connected to the wind box 68 (gas introduction line 74). In the boiler 10, the GR gas can be introduced from the gas recirculation passage 72 to the wind box 68 through the gas introduction line 74.

Further, the flue 13 is provided with a denitration catalyst 50 at a position on the upstream side of the air heater 49. The denitration catalyst 50 supplies a reducing agent having a function of reducing nitrogen oxides such as ammonia and urea water into the flue 13, and accelerates a reaction between the nitrogen oxides and the reducing agent by the combustion gas to which the reducing agent is supplied, thereby removing and reducing the nitrogen oxides in the combustion gas. The gas duct 48 connected to the flue 13 is provided with a dust treatment device (electric dust collector, desulfurizer) 51, an induced draft fan 52, and the like at a position downstream of the air heater 49, and a chimney 53 at a downstream end.

On the other hand, when the

pulverizers

31, 32, 33, and 34 are driven, the pulverized coal fuel is supplied to the

coal burners

21, 22, 23, and 24 through the pulverized

coal supply pipes

26, 27, 28, and 29 together with the transportation gas. Then, the heated combustion air (oxidizing gas) is supplied from the air passage 37 to the

coal burners

21, 22, 23, and 24 through the wind box 36. Then, the

coal burners

21, 22, 23, and 24 can form flames by igniting the pulverized coal and the pulverized coal mixed gas mixed with the transport gas (primary air, oxidizing gas) and the combustion air into the furnace 11. At this time, BFG and combustion air are supplied to the

BFG burners

61, 62, 63, and the combustion of BFG causes the mixed combustion of coal and BFG. As a result, flames are generated in the lower portion of the furnace 11, and the combustion gas rises in the furnace 11 and is discharged to the flue 13. In the present embodiment, air is used as the oxidizing gas. The gas having a higher oxygen ratio than air or conversely a lower oxygen ratio than air may be used by rationalizing the fuel flow rate.

The combustion gas is subjected to heat exchange by the

superheaters

41, 42, and 43, reheaters 44 and 45, evaporator 46, and economizer 47 disposed in the flue 13, and thereafter, nitrogen oxides are reduced and removed by the denitration catalyst 50, particulate matter is removed by the coal dust treatment device 51, and sulfur components are removed, and thereafter, the combustion gas is discharged to the atmosphere from the stack 53.

Next, fig. 2A and 2B are shown to more specifically describe the BFG burner apparatus of the present embodiment.

Fig. 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, viewed from the furnace side.

As shown in fig. 2A and 2B, the boiler 10 includes, for example, 4 stages of

coal burners

21, 22, 23, and 24 provided in an upper section of a furnace wall constituting the furnace 11, and, for example, 3 stages of

BFG burners

61, 62, and 63 provided in a lower section. The BFG burners 61, 62, and 63 are connected to the upstream air passage 37 via a windbox damper (not shown) provided in each of the

BFG burners

61, 62, and 63, and then via a damper 64. Similarly, the

coal burners

21, 22, 23, and 24 are also connected to the damper 65 via a bellows damper (not shown) provided in each of the

coal burners

21, 22, 23, and 24, and are also connected to the upstream air passage 37 via the damper 65. With this configuration, air is distributed and supplied from the air duct 37 to the

coal burners

21, 22, 23, and 24 and the

BFG burners

61, 62, and 63, respectively. The temperature of the supplied air is, for example, about 300 to 350 ℃.

Gas introduction lines 74 for inert gas (3 total points) are connected to the downstream side of the connection points between the

BFG burners

61, 62, 63 and the damper 64. The gas introduction lines 74 are connected to each other on the upstream side via dampers 75, and then further connected to the gas recirculation passage 72, not shown in fig. 2A, on the upstream side. In such a configuration, the flow rate of the GR gas flowing to each of the

BFG burners

61, 62, 63 can be individually adjusted by adjusting the opening degree of each damper 75. The opening degree of each damper 75 is adjusted by the gas supply control device 76. When a stopped BFG burner (e.g., 63) is detected, the gas supply control device 76 opens the corresponding damper 75 to control the GR gas to flow to the BFG burner 63 whose BFG supply is stopped via the gas introduction line 74. The gas supply control unit 77 of the present embodiment is composed of a damper 75 and a gas supply control device 76.

The gas supply control device 76 is constituted by, 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 as an example, and the CPU reads out the program to a RAM or the like and executes processing and arithmetic processing of information, thereby realizing various functions. The program may be installed in advance in a ROM or another storage medium, provided in a state stored in a computer-readable storage medium, distributed via wired or wireless communication means, or the like. The storage medium that can be read by the computer is a magnetic disk, an optical magnetic disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

The BFG burners 61, 62, 63, the wind box 68 (not shown in fig. 2B), the gas introduction line 74, and the gas supply control unit 77 described above constitute the BFG burner apparatus 81 of the present embodiment.

As shown in fig. 2B, the coal burner 21 has a structure including a fuel nozzle 91 for ejecting fuel into the furnace together with primary air for transportation, and a secondary air nozzle 92 provided around the fuel nozzle 91 and forming a flow path for secondary air (combustion air) on the outer peripheral side of the fuel nozzle 91 (the

other coal burners

22, 23, and 24 have the same structure). On the other hand, in order to improve the combustibility of BFG, the burner nozzles of the BFG burner 61 are lattice-shaped, and the BFG flow paths and the combustion air flow paths are alternately formed, so that the BFG injected into the furnace is mixed with the combustion air and combusted (the

other BFG burners

62 and 63 have the same structure).

Next, referring to fig. 3, the gas introduction control into the windbox of the BFG burner apparatus according to the present embodiment will be described in more detail. Fig. 3 is a diagrammatic side sectional view of a BFG burner apparatus in the boiler of fig. 1. In fig. 3, the right direction of the drawing shows the outside of the furnace, and the left direction of the drawing shows the inside of the furnace.

As shown in fig. 3, the BFG burner 61 includes BFG nozzles 66 forming a BFG flow path on the outside of the furnace, and a windbox 68 forming a combustion air flow path is connected to the outer periphery of the BFG nozzles 66 in the vertical direction of the BFG nozzles 66. The BFG burner 61 includes a tip portion 70 whose interior is divided by a dividing portion 69 so as to form 2 stages in the vertical direction and 6 rows of flow paths in the width direction, for example, in the furnace interior. The respective flow paths defined inside the tip portion 70 are connected to the BFG nozzle 66 and the wind box 68 by the connection portion 71 so that the BFG flow path and the combustion air flow path are alternately formed in the vertical direction and the width direction in the respective flow paths defined inside the tip portion 70. The connection portion between the tip portion 70 and the connection portion 71 and the bellows 68, the connection portion between the connection portion 71 and the BFG nozzle 66, and the connection portion between the partition portion 69 and the connection portion 71 are connected by welding or the like (forming a welded structure portion or the like). The BFG burner 61 shown in fig. 3 stops supplying BFG. The number of segments and the number of columns into which the tip portion 70 is divided by the dividing portion 69 are not limited to these.

Examples of the material of the bellows 68 include carbon steel and low alloy steel. The BFG burner 61 (specifically, the BFG nozzle 66, the dividing section 69, the tip section 70, and the connecting section 71) is made of, for example, stainless steel.

In the BFG burner apparatus 81 shown in fig. 3, a plurality of thermometers 78 for measuring the temperature of a portion surrounded by a dotted circle in fig. 3 are provided (only a representative example of the thermometers 78 is shown in fig. 3 with a part of the thermometers 78 omitted). The output of the thermometer 78 is sent to the gas supply control device 76. The gas supply control device 76 detects the stoppage of the BFG supply to the BFG burner 61, and controls the opening and closing and the degree of opening of each damper 75 based on the output of the thermometer 78. At this time, the introduction flow rate of the GR gas into the bellows 68 is adjusted so that the measurement value of the thermometer 78 becomes equal to or less than a predetermined set value. In the boiler 10 of the present embodiment, the flow rate of the GR gas introduced into the wind box 68 may be adjusted so that a predetermined measurement value of the thermometer 78 (particularly, the thermometer 78 provided in the wind box 68) becomes 400 ℃. The set values described above may be determined appropriately according to the structure, in addition to the materials of the windbox 68 and the BFG burner 61.

[ operating method of BFG burner device ]

Next, an example of an operation method of the BFG burner apparatus of the present disclosure will be described.

The operation method of the BFG burner apparatus of the present disclosure is an operation method of a BFG burner apparatus in which the gas introduction step is performed in the above-described BFG burner apparatus. In the gas introduction step, the noncombustible gas is introduced into the gas introduction line when the supply of BFG to the BFG burner is stopped.

In the following description, an example is given in which the operation method of the BFG burner apparatus according to the present disclosure is applied to the boiler 10 shown in fig. 1, but the operation method is not limited to this.

(gas introduction step)

In the gas introduction step, when the supply of BFG to the BFG burner 61 is stopped, GR gas is introduced into the gas introduction line 74. Specifically, for the stopped BFG burner 61, the damper 75 corresponding to the BFG burner 61 is opened, and GR gas is introduced into the windbox 68 of the BFG burner 61. The introduction flow rate of the GR gas into the bellows 68 is adjusted so that, for example, a measurement value of the thermometer 78 provided in the BFG burner apparatus 81 becomes equal to or less than a predetermined set value.

The gas introduction step can be performed by, for example, a gas supply control unit 77, and the gas supply control unit 77 is constituted by a damper 75 that adjusts the introduction flow rate of the noncombustible gas into the windbox 68, and a control device (gas supply control device 76) that controls the damper 75.

When the supply of BFG to the

BFG burners

61, 62, 63 is stopped, for example, when the flow rate of BFG is decreased, the number of

BFG burners

61, 62, 63 used for the combustion of BFG is decreased according to the flow rate of BFG, and the operation is performed so as to compensate for the load of the part. Specifically, when the flow rate of the BFG decreases, the BFG burners 63 in the lowest stage are stopped in order, for example. Conversely, when the

BFG burners

61, 62, and 63 are ignited by increasing the BFG supply to the

BFG burners

61, 62, and 63, the ignition is performed sequentially from the uppermost BFG burner 61, for example. On the other hand, when the flow rate of BFG increases, the

coal burners

21, 22, 23, and 24 stop the supply of pulverized coal in order from the uppermost coal burner 21, for example.

In the above-described embodiment, the GR gas is used as an example of the noncombustible gas introduced into the wind box 68, but the present invention is not limited thereto. For example, steam may be used as the noncombustible gas introduced into the wind box 68. When the steam is introduced into the wind box 68, the steam for use in the station may be used. By using the internal steam, a significant modification of the equipment of the boiler 10 is not required, and therefore, low cost can be achieved. The temperature of the introduced steam may be, for example, about 300 to 350 ℃.

With the above-described configuration, the present embodiment provides the following operational advantages.

In the BFG burner apparatus 81 of the present embodiment, a gas introduction line 74 for introducing a noncombustible gas is connected to the windbox 68 of the BFG burner 61, and the gas supply control unit 77 causes the noncombustible gas to flow through the gas introduction line 74 when the supply of BFG to the BFG burner 61 is stopped. Accordingly, since the incombustible gas is blown out from the furnace-interior front end portion 70 of the BFG burner 61 in which the supply of BFG is stopped, the inflow of the incombustible gas of BFG into the inside of the stopped BFG burner 61 and windbox 68 can be prevented. Therefore, the unburned gas of the BFG flowing into the inside of the BFG burner 61 and the windbox 68 is burned with the oxidizing gas (combustion air) inside, and the BFG burner 61 and the windbox 68 are prevented from being unevenly heated, and the BFG burner apparatus 81 is prevented from being damaged. This can suppress the occurrence of repair work due to damage to the BFG burner apparatus 81 or inspection work of the BFG burner apparatus 81. Furthermore, cracks can be prevented from occurring in the welded structure portion in the BFG burner apparatus 81, and therefore, it is possible to prevent the BFG from reacting with the combustion air and locally increasing the temperature during operation of the BFG burner 61, and to prevent the cracks from expanding, so that the BFG burner apparatus 81 can have a long life. The gas supply control unit 77 for introducing the noncombustible gas into the windbox 68 of the BFG burner 61 is constituted by, for example, a damper 75 and a control device (gas supply control device 76) for controlling the damper 75, and can adjust the introduction flow rate of the noncombustible gas into the windbox 68.

If the introduction flow rate of the noncombustible gas into the windbox 68 is adjusted so that the measurement value of the thermometer 78 provided in the windbox 68 becomes equal to or less than a predetermined set value, the temperature in the windbox 68 can be maintained at or below the set value. This can more reliably prevent damage to the BFG burner apparatus 81. The predetermined set value may be set to, for example, a durable temperature (e.g., 400 ℃ or lower) of a component (e.g., carbon steel or low alloy steel) constituting the wind box 68 of the BFG burner 61.

The BFG burner apparatus 81 of the present embodiment is configured to blow gas from the furnace-inside tip portion 70 of the BFG burner 61 during which the BFG supply is stopped. Therefore, in the case where the BFG burner 61 is disposed in the vicinity of the vertical lower side of the main fuel burners (

coal burners

21, 22, 23, 24) that burn the carbonaceous solid fuel (for example, pulverized coal) (for example, below the

coal burners

21, 22, 23, 24 that burn pulverized coal), even if the ash generated during the combustion of the carbonaceous solid fuel flows toward the BFG burner 61, the flowing ash can be prevented from accumulating at the tip end portion 70 of the BFG burner 61 that is in a stop state. That is, the clogging (ash clogging) of the tip portion 70 of the BFG burner 61 due to ash can be prevented.

Examples of the noncombustible gas flowing through the gas introduction line 74 include GR gas and steam derived from an exhaust gas generated by combustion of fuel in the furnace 11. The GR gas is a gas capable of adjusting the oxygen concentration of the combustion air (oxidizing gas) supplied to the furnace 11, and is, for example, a gas in which the exhaust gas extracted from the inlet of the economizer 47 of the multi-fuel fired boiler 10 is pressurized by the blower 73 and is again introduced into the furnace 11, and is introduced into the vicinity of the bottom of the furnace 11. Even if a part of the GR gas fed into the furnace 11 is introduced into the wind box 68, the total amount of the GR gas introduced into the furnace 11 does not change, and therefore, even if the gas introduction line 74 as described above is connected to the wind box 68, the influence on the combustion performance in the furnace 11 can be reduced. In the boiler in which GR gas is not introduced, steam can be used as a non-combustible gas. When the steam is introduced into the wind box 68, the in-station steam is used, and thus a significant modification of the plant of the multi-fuel fired boiler 10 is not necessary, and therefore, low cost can be achieved.

In the mixed combustion boiler 10 according to the present embodiment, since the BFG burner apparatus 81 described above is provided, the unburned gas of BFG that flows into the inside of the BFG burner 61 and the wind box 68 can be prevented from being burned inside and damaging the BFG burner apparatus 81. This makes it possible to extend the life of the BFG burner apparatus 81. Therefore, the hybrid combustion boiler 10 is economically advantageous.

The operation method of the BFG burner apparatus 81 of the present embodiment includes a gas introduction step of introducing a noncombustible gas into the gas introduction line 74 connected to the windbox 68 when the supply of BFG to the BFG burner 61 is stopped. This causes the incombustible gas to be blown out from the furnace-interior front end portion 70 of the BFG burner 61 during which the supply of BFG is stopped, and therefore, the inflow of the unburned gas of BFG into the stopped BFG burner 61 and the windbox 68 can be prevented. Therefore, the unburned gas of BFG that flows into the BFG burner 61 and the windbox 68 can be prevented from being burned with the combustion air inside, and the BFG burner 61 and the windbox 68 are prevented from being damaged due to uneven temperature rise. This can suppress the occurrence of repair work due to damage to the BFG burner apparatus 81 and inspection work for the BFG burner apparatus 81. Furthermore, since cracks can be prevented from occurring in the welded structure portion in the BFG burner apparatus 81, the BFG can be prevented from reacting with the combustion air during operation of the BFG burner 61 to locally increase the temperature, and the cracks can be prevented from growing, so that the BFG burner apparatus 81 can be made long-lived.

In the above-described embodiment, the case where the BFG burner is 3 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 combustor can be 1 stage or 2 stages, and can also be more than 4 stages. The location of the BFG burner is not limited to the lower side of the coal burner as in the above-described embodiment. Specifically, a BFG burner may be disposed above the coal burner. In this case, since the ash generated during combustion of the carbonaceous solid fuel in the coal burner does not flow toward the BFG burner, the ash flowing in can be prevented from accumulating at the tip of the BFG burner that is stopped.

In the above-described embodiment, the boiler of the present disclosure is a mixed-combustion boiler, but a boiler using biomass, petroleum coke, petroleum residue, or the like as a solid fuel may be used. The fuel is not limited to solid fuel, and may be used in an oil burning boiler such as heavy oil.

Claims

1. A BFG burner apparatus, comprising:

the BFG burner is arranged on the wall surface of the furnace, so that blast furnace gas is combusted in the furnace;

a wind box connected to the BFG burner and communicating with the BFG burner, for supplying an oxidizing gas to the BFG burner;

a gas introduction line connected to the wind box, for introducing a noncombustible gas into the wind box; and

a gas supply control unit that causes the noncombustible gas to flow into the gas introduction line when supply of the blast furnace gas to the BFG burner is stopped,

the noncombustible gas is a gas recirculation gas or steam derived from an exhaust gas generated by combustion of the blast furnace gas and/or the carbon-containing solid fuel.

2. The BFG burner apparatus as recited in claim 1,

a thermometer for measuring the temperature of the air box is arranged on the air box,

the flow rate of the noncombustible gas introduced into the windbox is adjusted so that a measured value of the thermometer becomes equal to or less than a predetermined set value.

3. The BFG burner apparatus as recited in claim 1 or 2,

the BFG burner is disposed on a wall surface of the furnace in the vicinity of a vertically lower side of a main fuel burner for burning a carbonaceous solid fuel.

4. A boiler comprising the BFG burner device according to any one of claims 1 to 3.

5. A method of operating a BFG burner apparatus, wherein,

the BFG burner device is provided with:

a wind box connected to the BFG burner and configured to supply an oxidizing gas to the BFG burner; and

a gas introduction line connected to the wind box to introduce a noncombustible gas into the wind box,

the operation method of the BFG burner apparatus includes a gas introduction step of introducing the noncombustible gas into the gas introduction line when the supply of the blast furnace gas to the BFG burner is stopped,

the noncombustible gas is a gas recirculation gas or steam derived from an exhaust gas generated by combustion of the blast furnace gas and/or the carbonaceous solid fuel.