JP2014025697A - Boiler and method of designing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have a non-ignition state to further improve safety by preventing push-in of combustion air into a furnace from a blower, when an unburned fuel is accumulated in the furnace by a prescribed amount or more.SOLUTION: A clearance gap excluding its lower end portion, between inner water tubes 5, 5 configuring an inner water tube array 7 is closed by an inner vertical fin 9. A clearance gap excluding its upper end portion, between outer water tubes 6, 6 configuring an outer water tube array 8 is closed by an outer vertical fin 11. An upward flow channel 29 is formed between the inner water tube array 7 and the outer water tube array 8 between the lower end portion of the inner vertical fin 9 and the upper end portion of the outer vertical fin 11. The selection of the blower 26, the determination of a frequency in invertor-controlling the blower 26, and the determination of the height h of the upward flow channel 29 are performed so that a relational expression of γ×g×h>P1 is satisfied, when a density of fuel is γ, a gravitational acceleration is g, a height of the upward flow channel 29 is h, and a maximum discharge pressure of the blower 26 is P1.

Description

  The present invention relates to various boilers including a steam boiler, a hot water boiler and a heat medium boiler, and a design method thereof. In particular, the present invention relates to a boiler for burning liquid fuel and a design method thereof.

  Conventionally, as disclosed in Patent Document 1 below, the inner water tube row (7) and the outer water tube row (8) are provided in a concentric cylindrical shape, and the inner water tube row (7) leaves a setting region at the lower end. The inner vertical fins (9) are provided so as to close the gaps between the adjacent inner water pipes (5, 5), while the outer water pipe row (8) is adjacent to the set area of the upper end portion. There is known a boiler (1) provided with an outer vertical fin (11) so as to close a gap between outer water pipes (6, 6).

  In this type of boiler (1), the combustion gas produced by the burner (17) passes through the gap (10) at the lower end of the inner water tube row (7), and the inner water tube row (7) and the outer water tube row (8). Is led upward through the gap (12) at the upper end of the outer water pipe row (8). Thereafter, the exhaust gas is discharged to the outside through the flue (14) connected to the can cover (13).

JP 2008-267713 A

  In the case of a burner that burns liquid fuel such as kerosene, light oil, or heavy oil, unburned fuel may accumulate in the lower part of the furnace due to disturbance of the air-fuel ratio. The unburned fuel is pushed out along the flow path of the combustion gas due to the pressure in the furnace, and may leak out of the furnace from the connection between the can cover and the flue (or economizer).

  The problem to be solved by the present invention is to further improve the safety as non-ignition by preventing the blower from pushing the combustion air into the furnace when a predetermined amount of unburned fuel is accumulated in the furnace. This is the issue.

  The present invention has been made to solve the above problems, and the invention according to claim 1 is a boiler for burning liquid fuel, and is arranged in a cylindrical shape between an upper header and a lower header. A plurality of heat transfer tubes constituting a heat transfer tube row, and a cylindrical can cover provided between the upper header and the lower header so as to surround the heat transfer tube row, combustion gas, The burner is discharged to the outside of the can body cover through an upward flow path between the inner and outer heat transfer tube arrays or an upward flow path between the heat transfer tube arrays and the can body cover, and reaches a predetermined height in the upward flow path. When the unburned fuel from the fuel is accumulated at the bottom of the furnace, the combustion air is prevented from being pushed into the furnace by the blower, so that the operation is stopped due to non-ignition.

  According to the first aspect of the present invention, when unburned fuel is accumulated in the furnace for a predetermined amount or more, it becomes impossible to push the combustion air into the furnace by the blower. Can be increased.

  According to a second aspect of the present invention, an inner heat transfer tube row and an outer heat transfer tube row are arranged concentrically between the upper header and the lower header, and the inner heat transfer tube row A plurality of inner heat transfer tubes are arranged in a cylindrical shape, and a gap between adjacent inner heat transfer tubes is closed by an inner vertical fin leaving a lower end portion, and the outer heat transfer tube row is formed by a plurality of outer heat transfer tube rows. The heat transfer tubes are arranged in a cylindrical shape, and a gap between the adjacent outer heat transfer tubes is configured to be closed with an outer vertical fin leaving an upper end portion, and the upward flow path is formed with a lower end portion of the inner vertical fin 2. The boiler according to claim 1, wherein the boiler is configured between the inner heat transfer tube row and the outer heat transfer tube row between an upper end portion of the outer vertical fins.

  According to invention of Claim 2, an upward flow path is comprised between an inner side heat exchanger tube row | line | column and an outer side heat exchanger tube row | line | column between the lower end part of an inner side vertical fin, and the upper end part of an outer side vertical fin. . Thereby, formation of an upward flow path and its height setting can be performed with a simple configuration.

  Invention of Claim 3 is the boiler design method of Claim 1 or Claim 2, Comprising: The density of fuel is (gamma), the acceleration of gravity is g, the height of the said upward flow path is h, When the maximum discharge pressure is P1, the selection of the blower, the setting of the frequency when the blower is inverter-controlled so as to satisfy the relational expression of γ × g × h> P1, the setting of the maximum discharge pressure during the operation of the blower, Or it is the design method of the boiler characterized by setting the height h of the said upward flow path.

  According to the invention described in claim 3, among the selection of the blower, the setting of the frequency when the blower is inverter-controlled, the setting of the maximum discharge pressure during the operation of the blower, and the setting of the height h of the upward flow path, By adjusting any one or more, even if the blower is operated at the maximum discharge pressure, the unburned fuel cannot be pushed up to the upper end of the upward flow path. Thereby, when unburned fuel accumulates more than predetermined in the furnace, it becomes impossible to push the combustion air into the furnace by the blower, so that safety can be further improved by non-ignition. In addition, fuel leakage outside the furnace can be reliably prevented.

  Invention of Claim 4 is the boiler design method of Claim 1 or Claim 2, Comprising: The density of a fuel is (gamma), the acceleration of gravity is g, the height of the said upward flow path is h, When the maximum discharge pressure during operation is P2, the selection of the blower, the setting of the frequency when the blower is controlled by the inverter, and the maximum discharge pressure during operation of the blower so as to satisfy the relational expression γ × g × h> P2 Or a setting method of the height h of the upward flow path.

  According to the invention described in claim 4, among the selection of the blower, the setting of the frequency when the blower is inverter-controlled, the setting of the maximum discharge pressure during the operation of the blower, and the setting of the height h of the upward flow path, By adjusting any one or more, unburned fuel cannot be pushed up to the upper end of the upward flow path even when the discharge pressure of the blower becomes maximum during operation of the boiler. Thereby, when unburned fuel accumulates more than predetermined in the furnace, it becomes impossible to push the combustion air into the furnace by the blower, so that safety can be further improved by non-ignition. In addition, fuel leakage outside the furnace can be reliably prevented.

  According to the present invention, when unburned fuel is accumulated in the furnace for a predetermined amount or more, the combustion air is prevented from being pushed into the furnace by the blower, so that non-ignition occurs and safety is further improved. it can.

It is a schematic longitudinal cross-sectional view which shows one Example of the boiler of this invention. It is a schematic longitudinal cross-sectional view which shows the state which the unburned fuel collected in the boiler of FIG. It is a figure which shows an example of the performance curve of the air blower of the boiler of FIG.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view showing an embodiment of the boiler of the present invention. The boiler 1 of this embodiment is a multi-tube once-through boiler provided with a cylindrical can body 2. The can body 2 is configured by connecting the upper header 3 and the lower header 4 with a large number of water tubes (heat transfer tubes) 5 and 6 arranged in a cylindrical shape.

  The upper header 3 and the lower header 4 are vertically spaced apart from each other in parallel, and each has a hollow annular shape. Further, the upper header 3 and the lower header 4 are respectively arranged horizontally and on the same axis.

  Each of the water pipes 5 and 6 is arranged vertically and has an upper end connected to the upper header 3 and a lower end connected to the lower header 4. The water pipes 5 and 6 are sequentially arranged in the circumferential direction of the upper header 3 and the lower header 4 to form cylindrical water pipe rows 7 and 8. In the present embodiment, the inner water tube row 7 and the outer water tube row 8 are provided in a concentric cylindrical shape. The inner water tube row 7 is composed of inner water tubes 5, 5,... Arranged in a cylindrical shape. On the other hand, the outer water tube row 8 is configured by outer water tubes 6, 6,... Arranged in a cylindrical shape so as to surround the inner water tube row 7.

  Inner vertical fins 9 are provided in the inner water tube row 7 so as to close the gap between the adjacent inner water tubes 5 and 5, leaving a setting region at the lower end. That is, the gap between the inner water pipes 5 and 5 is closed by the inner vertical fin 9 leaving the setting region at the lower end. The inner water tube row 7 is provided with a gap between the adjacent inner water tubes 5 and 5 at the lower end where the inner vertical fin 9 is not provided. The gap is a communication portion (referred to as an inner row communication portion) 10 for communicating the inner side and the outer side of the inner water tube row 7.

  The outer vertical fin 11 is provided in the outer water pipe row 8 so as to close a gap between the adjacent outer water pipes 6 and 6 while leaving a setting region at the upper end. That is, the gap between the outer water pipes 6 and 6 is closed by the outer vertical fin 11 while leaving the set area at the upper end. The outer water pipe row 8 has a gap between the adjacent outer water pipes 6 and 6 at the upper end where the outer vertical fin 11 is not provided. The gap is a communication portion (referred to as an outer row communication portion) 12 for communicating the inner side and the outer side of the outer water tube row 8.

  Each inner water pipe 5 and each outer water pipe 6 may be provided with protrusions on the peripheral side as desired to increase the heat transfer area. For example, each inner water pipe 5 is provided with horizontal fins or studs on the surface constituting the outer peripheral surface of the cylindrical inner water pipe row 7, or each outer water pipe 6 is provided with the inner circumference of the cylindrical outer water pipe row 8. You may provide a horizontal fin and a stud in the surface which comprises a surface. In addition, when providing a horizontal fin in each inner water pipe 5 and / or each outer water pipe 6, the horizontal fin may be installed in a horizontal state or inclined upward as it goes to one circumferential direction of the can body 2. May be.

  A cylindrical can cover 13 is further provided between the upper header 3 and the lower header 4 so as to surround the outer water tube row 8. In the illustrated example, the can cover 13 includes an inner cylinder 14 and an outer cylinder 15 having a larger diameter. The inner cylinder 14 has a lower end portion fixed to the lower header 4 and an upper end portion disposed at a height corresponding to the lower end portion of the outer row communication portion 12. On the other hand, the outer cylinder 15 has an upper end fixed to the upper header 3 and a lower end disposed at a height corresponding to the midway in the vertical direction of the inner cylinder 14. In this way, in the can body cover 13, the lower end portion of the inner cylinder 14 is sealed with the gap between the lower header 4 and the upper end portion of the outer cylinder 15 is sealed with the gap with the upper header 3. Further, a gap between the inner cylinder 14 and the outer cylinder 15 is sealed at the lower end portion of the outer cylinder 15. Further, the cylindrical gap between the inner cylinder 14 of the can body cover 13 and the outer water tube row 8 is filled with a heat insulating material 16.

  A flue 17 is connected to the outer cylinder 15 of the can cover 13 in a part in the circumferential direction. Further, the boiler 1 is provided with a cylindrical casing 18 so as to surround the can body cover 13. The flue 17 is led out of the can body 2 through the casing 18.

  Refractory materials 19 and 19 are provided on the lower surface of the upper header 3 and the upper surface of the lower header 4 so as to cover the connecting portions between the headers 3 and 4 and the water tubes 5 and 6. At this time, the refractory material 19 on the lower header 4 side is provided so as to block the central portion of the lower header 4. In the center of the refractory material 19 on the lower header 4 side, an inverted frustoconical recess 20 is formed.

  By the way, in the example of illustration, each inner side water pipe 5 has the small diameter part 21 in the position corresponding to the inner row communication part 10. FIG. This is to reduce the pressure loss when the combustion gas enters the combustion gas flow path 22 between the inner and outer water pipe rows 7 and 8 via the inner row communication portion 10. On the other hand, in the illustrated example, each outer water pipe 6 does not have a small diameter part at a position corresponding to the outer row communication part 12, but may have a small diameter part like each inner water pipe 5.

  A burner 23 is provided at the center of the upper header 3 downward. The burner 23 is supplied with liquid fuel (for example, A heavy oil) and combustion air. Specifically, liquid fuel is sprayed from the burner 23 through the fuel pump 24 and the fuel valve 25 into the can body 2, and combustion air is discharged from the blower 26 through the wind box 27. Therefore, if the fuel to be sprayed is ignited by an ignition device (not shown), the fuel can be burned in the can body 2. At this time, the inside of the inner water tube row 7 functions as a combustion chamber 28. The amount of combustion can be adjusted by changing the flow rates of fuel and combustion air. At that time, the flow rate of the combustion air may be controlled by an inverter of a motor (not shown) of the blower 26, or alternatively or in addition to a damper ( The degree of opening may be adjusted.

  Combustion gas resulting from combustion of fuel 28 in the combustion chamber is led to the combustion gas flow path 22 between the inner water tube row 7 and the outer water tube row 8 via the inner row communication portion 10. Then, the combustion gas is led out to the can body cover 13 via the outer row communication portion 12. Then, it is discharged to the outside as exhaust gas through the flue 17 connected to the can cover 13. During this time, the combustion gas exchanges heat with the water in the water pipes 5 and 6, and the water in the water pipes 5 and 6 is heated. Thereby, steam can be taken out from the upper header 3, and the steam is sent to a steam use facility (not shown) via a steam separator (not shown). By the way, an economizer may be installed in the flue 17.

  Of the combustion gas flow path 22 between the inner water pipe row 7 and the outer water pipe row 8, the region from the lower end portion of the inner vertical fin 9 to the upper end portion of the outer vertical fin 11 is referred to as an upward flow passage 29. To do. That is, the upward flow path 29 refers to a region indicated by the height h in FIG.

  FIG. 2 shows a state in which the unburned fuel 30 is accumulated in the furnace due to the disturbance of the air-fuel ratio during operation of the boiler 1 of the present embodiment. The unburned fuel 30 accumulates at the bottom of the combustion chamber 28. However, as the amount increases, the unburned fuel 30 accumulates so as to advance upward in the upward flow path 29 due to the furnace pressure. However, the boiler 1 of the present embodiment is configured so that the unburned fuel 30 is not pushed out of the can body 2 beyond the upward flow path 29 even if such a situation occurs.

  That is, even when the unburned fuel 30 from the burner 23 accumulates at the bottom of the furnace, the operation is performed at the furnace pressure at which the unburned fuel 30 cannot be pushed out beyond the upward flow path 29. For example, in the boiler 1 of this embodiment, when the fuel density is γ, the gravitational acceleration is g, the height of the upward flow path 29 is h, and the maximum discharge pressure on the performance of the blower 26 is P1, γ × g × It is configured to satisfy the relational expression h> P1. Alternatively, in the boiler 1 of this embodiment, when the fuel density is γ, the acceleration of gravity is g, the height of the upward flow path 29 is h, and the maximum discharge pressure during operation of the blower 26 is P2, γ × g × It is configured to satisfy the relational expression h> P2. In any case, the blower 26 may be selected, the frequency when the blower 26 is inverter-controlled, or the height h of the upward flow path 29 may be determined so as to satisfy the relational expression. .

For example, when A heavy oil (density 0.86 g / cm ³ ) is used as the fuel and the height h of the upward flow path 29 is 935 mm, 0.86 × 9.8 × 935 = 7808 Pa, so It is sufficient to operate at a discharge pressure of less than 7880 Pa.

  In such a configuration, even if unburned fuel accumulates in the furnace, the fuel cannot be pushed up to the upper end of the upward flow path 29 at the height h due to the pressure in the furnace. Thereby, the outflow of fuel to the outside of the furnace can be prevented. Moreover, since the pushing of the combustion air into the furnace by the blower 26 is prevented, safety can be improved by stopping the operation of the boiler 1 by causing non-ignition.

  FIG. 3 is a diagram illustrating an example of a performance curve of the blower 26, in which the horizontal axis indicates the air volume and the vertical axis indicates the static pressure. Since the maximum discharge pressure P1 of the blower 26 can be found from such a performance curve, the blower 26 is selected or the height h of the upward flow path 29 can be determined so as to satisfy the above-described relational expression γ × g × h> P1. That's fine.

  When the blower 26 is operated at a pressure lower than the maximum discharge pressure P1, the blower 26 is selected so as to satisfy the above-described relational expression γ × g × h> P2 with the maximum discharge pressure P2 during operation, The maximum discharge pressure P2 may be determined or the height h of the upward flow path 29 may be determined.

  Similarly, when the blower 26 is controlled by an inverter, for example, when operating with a performance curve indicated by a broken line in FIG. 3, the maximum discharge pressure P1 ′ is used to satisfy the relational expression γ × g × h> P1 ′. When the operation is performed at a pressure lower than the maximum discharge pressure P1 ′, the maximum discharge pressure P2 ′ during operation may be used to satisfy the relational expression γ × g × h> P2 ′. At that time, the height h of the upward flow path 29 is determined first, and the frequency (broken line in FIG. 3) for inverter control of the blower 26 is set, and the range in the performance curve to be operated is designed. Just do it.

  The boiler 1 of this invention is not restricted to the structure of the said Example, It can change suitably. In particular, there is an upward flow path 29 at any location, and the blower 26 cannot push up the liquid fuel to the upper end of the upward flow path 29 due to the relationship between the height of the upward flow path 29 and the pressure in the furnace. If it exists, the structure of the boiler 1 can be changed suitably. For example, the outer water pipe row 8 may be omitted, and the upward flow path 29 may be formed between the inner water pipe row 7 and the can body cover 13. In that case, the upward flow path 29 extends from the lower end of the inner vertical fin 9 to the upper end of the inner cylinder 14 (or the lower end of the opening from the can body cover 13 to the flue 17 when the can body cover 13 is simply cylindrical). Up to.

  Moreover, it can apply also to a heat-medium boiler other than a steam boiler and a hot water boiler, for example. In this case, in the said Example, a water tube can be paraphrased as a heat exchanger tube, and a water tube row | line | column can be paraphrased.

1 boiler 2 can body 3 upper header 4 lower header 5 inner water tube (inner heat transfer tube)
6 Outside water pipe (outside heat transfer pipe)
7 Inner water tube row (inner heat transfer tube row)
8 Outside water tube row (outside heat transfer tube row)
9 Inner vertical fin 11 Outer vertical fin 13 Can body cover 22 Combustion gas flow path 23 Burner 26 Blower 29 Upward flow path 30 Unburned fuel

Claims (4)

In boilers that burn liquid fuel,
A plurality of heat transfer tubes arranged in a cylindrical shape between the upper header and the lower header to form a heat transfer tube array;
A cylindrical can cover provided between the upper header and the lower header so as to surround the heat transfer tube row,
Combustion gas is discharged out of the can body cover through an upward flow path between the inner and outer heat transfer tube rows, or an upward flow channel between the heat transfer tube rows and the can body cover,
When unburned fuel from the burner accumulates at the bottom of the furnace up to a predetermined height in the upward flow path, the operation is stopped by making the combustion air into the furnace blocked by the blower, resulting in non-ignition. A boiler characterized by Between the upper header and the lower header, an inner heat transfer tube row and an outer heat transfer tube row are arranged in a concentric cylindrical shape,
The inner heat transfer tube row is configured such that a plurality of inner heat transfer tubes are arranged in a cylindrical shape, and a gap between the adjacent inner heat transfer tubes is closed with an inner vertical fin leaving a lower end portion,
The outer heat transfer tube array is configured such that a plurality of outer heat transfer tubes are arranged in a cylindrical shape, and a gap between adjacent outer heat transfer tubes is closed with an outer vertical fin leaving an upper end portion,
The upward flow path is configured between the inner heat transfer tube row and the outer heat transfer tube row between a lower end portion of the inner vertical fin and an upper end portion of the outer vertical fin. Item 4. The boiler according to item 1. A boiler design method according to claim 1 or claim 2, wherein
Select the blower so that the relation of γ × g × h> P1 is satisfied, where γ is the fuel density, g is the acceleration of gravity, h is the height of the upward flow path, and P1 is the maximum discharge pressure of the blower. A boiler design method comprising: setting a frequency when the blower is inverter-controlled, setting a maximum discharge pressure during operation of the blower, or setting a height h of the upward flow path. A boiler design method according to claim 1 or claim 2, wherein
When the fuel density is γ, the gravitational acceleration is g, the height of the upward flow path is h, and the maximum discharge pressure during operation of the blower is P2, so that the relational expression of γ × g × h> P2 is satisfied. A boiler design method comprising: selecting a blower, setting a frequency when the blower is inverter-controlled, setting a maximum discharge pressure during operation of the blower, or setting a height h of the upward flow path.

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