JPH0814362B2 - Boiler system with combustion gas recirculation mechanism - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler system having a combustion gas recirculation mechanism for improving combustion performance and reducing harmful combustion exhaust gas production.

[0002]

2. Description of the Related Art In recent years, due to environmental pollution and the like, further reduction of harmful combustion exhaust gas, particularly NOx and CO, has been required in boilers. Various measures for reducing such harmful combustion exhaust have been proposed. Among them, by reducing the NOx (particularly thermal NOx) by recirculating the combustion gas and controlling the combustion temperature to a low level. There is a plan. Specific examples of such an exhaust gas recirculation method include a method in which the combustion gas recirculates by the combustion burner itself, an exhaust gas recirculation path provided outside the can body, and the like.

[0003]

By the way, the above-mentioned combustion gas recirculation system has not been widely spread because it has the following problems, respectively.

First, in the case where a combustion gas recirculation mechanism is incorporated in the combustion burner itself, the structure of the combustion burner itself becomes complicated, and it is difficult to adjust the combustion gas generation amount of the combustion burner and the combustion gas circulation amount. .

Next, a boiler can body equipped with a combustion gas recirculation mechanism requires a new duct for exhaust gas recirculation outside the can body, which increases the size of the boiler system itself. Invite. This problem has become an important issue especially in the simple class and small class in which the amount of evaporation is small. Further, when the duct for exhaust gas recirculation is provided outside the can as described above, the amount of heat released from the combustion gas flowing inside the can is not negligible, which is an obstacle to improvement of thermal efficiency. Therefore, a technical problem to be solved by the present invention is to provide a boiler system in which combustion gas is recirculated with a simple structure to reduce harmful combustion exhaust gas.

[0006]

The present invention has been made to solve the above problems, and more specifically,
A plurality of heat transfer tubes are arranged between a pair of heat transfer tube walls that are parallel to each other, a combustion burner is arranged in one opening of the heat transfer tube wall, and a combustion exhaust gas outlet is formed in the other opening. , The combustion gas is configured to flow in parallel between the heat transfer tube walls,
The first feature is that a partition wall for partitioning the combustion gas flow into a main flow path and a reflux path is provided on the upstream side of the combustion gas flow on the heat transfer tube wall, and the combustion gas is further provided on the downstream side of the partition wall. The second characteristic is that the retention space portion of the above is formed.

[0007]

1 and 2 show an embodiment of a boiler system equipped with a combustion gas recirculation mechanism according to the present invention. In the drawing, (10) is a large number of heat transfer tubes (11) (11) ...
, (20) (20) ... are a plurality of heat transfer tubes arranged between the heat transfer tube walls (10) (10), (40)
Is a combustion burner arranged at one side opening between the heat transfer tube walls (10) and (10), and (C) is formed at the other side opening between the heat transfer tube walls (10) and (10). The combustion exhaust gas outlet is shown. The heat transfer tube wall
(10) The heat transfer tubes (11), (11), and the heat transfer tube wall (10) constituting the (10)
The upper and lower ends of the heat transfer pipes (20) (20) disposed between (10) are connected to an upper header and a lower header (not shown), respectively.

In this embodiment, the heat transfer tube wall (10) has a plurality of heat transfer tubes (11) arranged in tandem at appropriate intervals to form a gap between the heat transfer tubes (11) (11). These heat transfer tubes (11)
(11) Flat plate fin-shaped member extending along the axial direction of
(12) (12)… The structure closed by these heat transfer tube walls (1
0) and (10) are arranged at appropriate intervals so as to be substantially parallel to each other.

The plurality of heat transfer tubes (20) (20) ... Arranged between the heat transfer tube walls (10) (10) are arranged in an appropriate arrangement, for example, in a two-row vertical arrangement. Heat transfer tube wall (10)
The heat transfer tubes in adjacent rows, including the heat transfer tubes (11), (11), etc. in (10), are arranged in a staggered pattern. Also, each heat transfer tube (11) (11)
…, (20) (20)… The mutual spacing is preferably set to be approximately equal to or less than the diameter of each heat transfer tube (11) (20), and these gaps are all the same. May be different from each other as long as they are within the above conditions.

Of the heat transfer tubes between the heat transfer tube walls (10) and (10), the heat transfer tube (20) located in front of the combustion burner (40) and downstream from the heat transfer tube (20) in the combustion gas flow direction. In the gap between the heat transfer tubes (20) that are adjacent to each other, these heat transfer tubes (20) (20)
Vertical fin-like members (F) (F) are arranged along the axial direction of ... to close the gaps between the heat transfer tubes (20) (20) ... and to partition walls along the flow direction of the combustion gas ( 30) has been formed. This partition wall (30) allows the main flow path (A) of the combustion gas to flow between the partition walls (30) and (30).
The heat transfer tube wall and the partition wall (30) are partitioned as a recirculation path (B) for the recirculated gas.

The combustion burner (40) is, for example, a surface combustion burner, and a gap between the combustion burner (40) and the heat transfer tube (20) located immediately before the combustion burner (40) is a predetermined distance, for example, the heat transfer tube (20). It is set to be equal to or less than about 3 times the diameter of the heat transfer tube wall (10), (10), the heat transfer tube (11) (11) ... The adjacent heat transfer tubes are also set with the above distance as a reference.

In the above-mentioned structure, the combustion flame from the combustion burner (40) is transferred to the heat transfer tubes (11) (11) ..., (20) (20). Heat pipe wall (10)
The gas flows through the space (10) toward the combustion exhaust gas outlet (C), and during that time, heat is transferred to the heat transfer tubes (11) (11) ..., (20) (20). Since the gap between the burner (40) and the immediately preceding heat transfer tube (20) and each heat transfer tube (11) (10) ..., (20) (20) ... is set as narrow as described above, combustion flame and combustion gas It flows toward the combustion exhaust gas outlet (C) while maintaining a high flow velocity, and an extremely high contact heat transfer coefficient can be obtained.

In such a distribution process of combustion gas,
The main flow of the combustion gas from the combustion burner (40) flows between the partition walls (30) (30), but at this time, the combustion burner (40) and the partition wall (30)
This main flow causes a pressure drop between the partition walls (30) and (30), so that part of the combustion gas that has passed between the partition walls (30) and (30) is between the partition wall (30) and the heat transfer tube wall (10). It circulates in the vicinity of the combustion burner (40) through the reflux path (B). Therefore, an increase in the reaction temperature of the combustion flame is suppressed, and an unnecessary temperature increase is prevented, so that the generation of thermal NOx is suppressed.

The combustion gas that has passed between the partition walls (30) (30) is retained on the downstream side for a relatively long period of time, whereby the oxidation reaction is promoted and CO is particularly prevented from being generated.

FIGS. 3 and 4 show another embodiment of the present invention. The fundamental difference from the above embodiment is that the heat transfer tube wall is
(10) The heat transfer tubes (20) (20) arranged between (10) are applied to a can body in three rows. The features of this embodiment are:
First, the partition walls (30) (30) are formed by closely arranging the heat transfer tubes (20) (20), and further, the combustion gas retention space is formed on the downstream side of the partition walls (30) (30). That is, (D) is formed.
In particular, the heat transfer tube gap around this retention space (D) is formed with a relatively wide gap and a small pressure loss.
In addition, it is preferable that the combustion gas from the upstream side flow in and the combustion gas flow out so as to expand to the downstream side.

In this embodiment, in addition to the same effect by recirculation of the combustion gas as in the above embodiment, the retention space (D) extends the time for which the combustion gas is retained in the can, and in particular, the unburned material The harmful exhaust emissions can be reduced by inducing the oxidation reaction of.

In the embodiment shown in FIGS. 3 and 4, the heat transfer tubes (20) (20) ... Arranged between the heat transfer tube walls (10) (10) are arranged in odd rows (3 rows). The retention space portion (D) is provided not only for such a can body, but also for the can body as shown in FIGS.
(10) It can also be applied to a case where a plurality of rows of heat transfer tubes (20) (20) ... Are arranged between (10).

In each of the above embodiments, each heat transfer tube wall (10) is provided with a plurality of heat transfer tubes (11) (11) ... Although the gaps 11), 11) are closed by the flat fin member 12, the structure of the heat transfer tube wall in the present invention allows the gaps between the heat transfer tubes 11 to be appropriately arranged. Each heat transfer tube, even if it is made of refractory
(11) may be closely arranged, and
The number of rows of heat transfer tubes arranged between the walls of the heat transfer tubes is not limited to that in the above embodiment.

[0019]

As described above, according to the present invention, for example, a long mixing section and a complicated structure, which are required in the related art, are not required, and the structure of the boiler system is simplified, downsized, and a unit installation space is provided. The heat recovery efficiency per hit can be improved.

Further, in the boiler system according to the present invention, since the combustion gas is recirculated in the can, the extra amount from the combustion gas is provided as compared with the conventional one having an independent combustion gas recirculation flow path. There is no significant heat dissipation, and it is possible to prevent a decrease in thermal efficiency.

Also, since the combustion gas is recirculated in the furnace to be supplied to the combustion burner (40) side, the unburned portion contained in the flame from the combustion burner (40) is heated and mixed. Is promoted to obtain a uniform combustion flame, and at this time, the combustion gas is supplied into the combustion flame, so that the temperature rise of the combustion flame is suppressed and harmful exhaust gas, especially thermal NOx Generation can be suppressed.

In addition, since the heat transfer tubes of the can itself are arranged in the flow direction of the combustion gas as described above, the oxidization reaction of the unburned component is carried out during this period due to the retention of the combustion gas, especially the reduction of CO. Can be achieved.

[Brief description of drawings]

FIG. 1 is a plan view illustrating a schematic structure of a can body according to an embodiment of the present invention.

FIG. 2 is an enlarged view for explaining the operation in the embodiment of FIG.

FIG. 3 is a plan view illustrating the schematic structure of a can body according to another embodiment of the present invention.

FIG. 4 is an enlarged view for explaining the operation in the embodiment of FIG.

[Explanation of symbols]

 (10)… Heat transfer tube wall (11)… Heat transfer tube (12)… Fin-shaped member (20)… Heat transfer tube (30)… Differential wall (40)… Combustion burner (A)… Main flow path (B)… Recirculation path (C)… Combustion exhaust gas outlet (D)… Staying space (F)… Fin-shaped member

Claims (4)

[Claims] 1. A pair of heat transfer tube walls (10) (1) which are parallel to each other.
A plurality of heat transfer tubes (20) (20) are arranged between (0), a combustion burner (40) is arranged at one opening of the heat transfer tube walls (10) (10), and the other side opening is formed. Combustion exhaust gas outlet (C) is formed on the heat transfer pipe wall (10), so that the combustion gas flows in parallel between the heat transfer pipe walls (10) and (10). A boiler system having a combustion gas recirculation mechanism, characterized in that a partition wall (30) for partitioning a combustion gas flow into a main flow path (A) and a return flow path (B) is provided on the upstream side of the flow. 2. A pair of heat transfer tube walls (10) (1) which are parallel to each other.
A plurality of heat transfer tubes (20) (20) are arranged between (0), a combustion burner (40) is arranged at one opening of the heat transfer tube walls (10) (10), and the other side opening is formed. Combustion exhaust gas outlet (C) is formed on the heat transfer pipe wall (10), so that the combustion gas flows in parallel between the heat transfer pipe walls (10) and (10). A partition that divides the combustion gas flow into a main flow path (A) and a return flow path (B) on the upstream side of the flow.
A boiler system equipped with a combustion gas recirculation mechanism, characterized in that a combustion gas retention space (D) is formed on the downstream side of the partition wall (30) with the provision of (30). 3. The main flow path (A) and the return flow path for the combustion gas
The partition wall (30) that is divided into (B) and (B) is closed by a vertical fin spacer (F) that fills the gap between the heat transfer tubes (20) (20) ... along the axial direction of the heat transfer tubes (20) (20). 3. A boiler system having a combustion gas recirculation mechanism according to claim 1, wherein the boiler system is formed by 4. The main flow path (A) and the return flow path for the combustion gas
3. The combustion gas recirculation mechanism according to claim 1 or 2, wherein the partition wall (30) partitioned into (B) is formed by heat transfer tubes (20) (20) ... Boiler system.