JP3857792B2 - Exhaust gas refire boiler for cogeneration - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas refire boiler for cogeneration that uses exhaust gas from a gas turbine or gas engine generator as a heat source.
[0002]
[Prior art]
Generally, in a cogeneration system, an exhaust gas reburning burner is provided in order to further heat and use high-temperature exhaust gas from a turbine or an engine. FIG. 4 shows an example of this, and the hole 11 for introducing the exhaust from the turbine into the combustion chamber 2 of the normal boiler is provided at a position away from the place where the exhaust reburner 4 is mounted. However, in a small cogeneration system, as shown in FIG. 5, an attempt has been made to use the burner mounting hole 3 as an exhaust introduction hole. That is, in the figure, the cylinder portion of the burner 4 has a double structure of the inner and outer cylinders 9 and 10, and exhaust gas is introduced into the combustion chamber 2 through the outer cylinder 10. In this way, since a general-purpose boiler can be used, it is advantageous in terms of cost, and by appropriately cooling the flame by exhaust, it is possible to prevent the occurrence of a local high temperature region in the flame and to reduce NOx. There is an advantage that the generation amount of can be suppressed.
[0003]
[Problems to be solved by the invention]
However, the configuration of FIG. 5 poses no problem when the burner 4 is always fully operated, but when the burner is turned down in accordance with the load of the boiler and the combustion amount is adjusted, the combustion is performed so as to surround the flame. The flow rate or flow velocity of the exhaust gas fed into the chamber 2 becomes relatively large with respect to the flame ejection speed, and therefore, there is a problem that the flame is excessively cooled by the exhaust gas and incomplete combustion is likely to occur. . A curve B in the graph of FIG. 3B shows a state in which the exhaust reburn burner 4 is turned down. When the combustion amount is reduced to 75% or less, the CO gas rapidly increases. Therefore, the present invention eliminates such problems, and even when the exhaust is introduced using the burner mounting hole 3, the exhaust gas reburning boiler can increase the turndown ratio of the burner 4. The object is to provide a structure.
[0004]
[Means for Solving the Problems]
As shown in FIG. 1, the cogeneration exhaust reburning boiler according to the present invention is for holding a burner attached to the inner peripheral surface of the burner mounting hole 3 and the burner mounting hole 3 formed in the wall of the combustion chamber 2 of the exhaust reburning boiler 1 . some gap 5 between the cylindrical portion 7a of the adapter 7 is provided, along with by inserting the burner tube section to the cylindrical portion 7a of the adapter 7, to supply the exhaust through the gap 5 into the combustion chamber 2, the adapter A flange-shaped or cone-shaped guide member 6 is provided on the outer periphery of the cylindrical portion 7a of the cylinder 7 , and the guide member 6 is directed obliquely outward so as to separate the direction of exhaust emission from the flame. According to this, the exhaust gas generated from the flame stagnate between the flame root and the exhaust flow, so that the engine exhaust does not contact the flame root, and therefore when the burner combustion amount is reduced. Even in the flame Since the components are not cooled by the exhaust flow, it is possible to prevent the generation of CO due to incomplete combustion, and this exhaust flow is pulled back inward because the pressure on the inner side decreases in the front, and eventually the tip of the flame This is in contact with the portion, which prevents an excessive increase in the flame temperature and suppresses the generation of NOx .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A shows the overall structure of an embodiment of a cogeneration exhaust gas refired boiler according to the present invention, and FIG. 1B shows the main part thereof. The exhaust reburning burner 4 is mounted in a burner mounting hole 3 formed in the wall 2a of the combustion chamber 2 of the exhaust reburning boiler 1 with a slight gap 5 between the inner peripheral surface of the hole 3 and Exhaust gas from the gas turbine or the gas engine is supplied into the combustion chamber 2 through the gap 5. Reference numeral 7 denotes a cylindrical adapter for holding the burner 4 in the burner mounting hole 3. A connection port 8 for connecting an exhaust duct is provided on the outer peripheral surface of the adapter, and the exhaust gas supplied into the adapter 7 is The burner mounting hole 3 is jetted into the combustion chamber 2 through a gap 5 between the inner peripheral surface of the burner mounting hole 3 and the cylindrical portion of the burner 4. At this time, it is provided on the outer periphery of the burner cylindrical portion. The flange-shaped or cone-shaped guide member 6 is directed obliquely outward so that the direction in which the exhaust is ejected is separated from the flame. In this way, the exhaust flow that is ejected while spreading outward acts to reduce the atmospheric pressure inside it, so that it is attracted to the inside again in front and comes into contact with the flame. Suppresses the occurrence. At that time, however, the flame is almost completely combusted and does not cause incomplete combustion in contact with the exhaust. Eventually, the guide member 6 prevents the generation of CO gas while maintaining the low NOx effect by slightly delaying the contact timing between the exhaust gas and the flame. Further, when the burner 4 is turned down according to the load of the boiler 2 and the flame becomes small, in the conventional example of FIG. 6, the flow rate and flow velocity of the exhaust gas become relatively large, so the flame is overcooled by the exhaust gas. However, according to the present invention, exhaust does not come into contact with the flame that has been turned down, so there is no possibility of causing incomplete combustion.
[0006]
In the embodiment of FIG. 2 , an adapter 7 for holding the burner 4 in the burner mounting hole 3 is used, and the above-described guide member 6 is provided on the outer peripheral surface of the cylindrical portion 7a. In this case, the exhaust gas enters from the duct connection port 8 provided in the outer cylinder of the adapter 7 and passes through the gap 5 between the adapter cylindrical portion 7a and the inner peripheral surface of the burner mounting hole 3. As in the case of No. 2, the guide member 6 on the outer periphery of the adapter cylindrical portion 7a is deflected obliquely outward, so that it does not come into contact with the unburned portion of the flame or a small squeezed flame, thereby preventing the generation of CO. Is done.
[0007]
Further, as in the conventional example of FIG. 6, the outer periphery of the inner cylinder 9 is also provided when the cylinder portion of the burner 4 has a double structure of the inner cylinder 9 and the outer cylinder 10 and exhaust gas is supplied through the outer cylinder 10. By providing the flange-shaped or cone-shaped guide member 7 as shown in FIGS. 1 to 2 and directing the direction of exhaust emission obliquely outward, the same effect as in FIGS. Can be made.
[0008]
3A and 3B show the effect of reducing NOx and CO according to the present invention, and FIG. 3A shows the NOx generation amount according to the embodiment of FIG. 1 compared with the conventional example of FIG. The horizontal axis is the turndown rate. FIG. 5B is a comparison of the amount of CO gas generated by the embodiment of FIG. 1 with that of the conventional example of FIG. 5. According to the present invention, almost no CO is generated even when the turndown ratio is 10: 1. It has been shown.
[0009]
【The invention's effect】
According to the present invention, as described above, by sharing the exhaust introduction port 12 of the cogeneration exhaust reburning boiler with the burner mounting hole 3, the cost of the boiler can be reduced, and the burner holding adapter attached to the burner mounting hole can be reduced . A slight gap is provided between the cylindrical portion and the inner peripheral surface of the burner mounting hole, the burner cylinder portion is inserted into the cylindrical portion of the adapter, the exhaust gas is supplied into the combustion chamber through the gap, and the adapter A flange-shaped or cone-shaped guide member is provided on the outer peripheral surface of the cylindrical portion of the cylinder, and the discharge direction of the exhaust gas is directed diagonally outward so as to be separated from the flame of the burner by the guide member. The exhaust direction of the exhaust gas sent to is directed diagonally outward, and the exhaust does not contact the flame at the base of the flame, and the exhaust is appropriately mixed with the flame at the tip of the flame and the amount of NOx generated In this way, not only during full combustion but also during turn-down, incomplete combustion due to contact between exhaust and unburned components of the flame is prevented, CO generation is reduced, and combustion is unstable. Therefore, a simple straight flame burner can be used and a general-purpose boiler can be used without using a burner with a complicated structure such as a split flame type or an exhaust gas recirculation type. Thus, there is an advantage that the NOx reduction of the cogeneration exhaust gas reburning boiler can be performed.
[Brief description of the drawings]
FIG. 1A is a schematic cross-sectional view of an embodiment of the present invention, and FIG.
FIG. 2A is a front view of an essential part of another embodiment of the present invention, and FIG. 2B is a bottom view showing a cross-section with a part cut away.
FIG. 3 is a graph showing the NOx reduction effect according to the present invention, and (b) is a graph showing the CO reduction effect due to the above.
FIG. 4 is a longitudinal sectional view of a conventional example.
FIG. 5 is a longitudinal sectional view of another conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exhaust reheating boiler 2 Combustion chamber 3 Burner mounting hole 4 Exhaust reburning burner 5 Gap 6 Guide member 7 Adapter 8 Exhaust duct connection port 9 Inner cylinder 10 Outer cylinder 11 Exhaust inlet

Claims (1)

In an exhaust gas reheating boiler that uses exhaust gas from a gas engine or gas turbine by reheating with a burner, it is between the cylindrical portion of the burner holding adapter attached to the burner mounting hole of the boiler combustion chamber and the inner peripheral surface of the burner mounting hole. A slight gap is provided, a burner cylinder part is inserted into the cylindrical part of the adapter, the exhaust gas is supplied into the combustion chamber through the gap, and a flange-shaped or cone-shaped guide is provided on the outer peripheral surface of the cylindrical part of the adapter. An exhaust gas refired boiler for cogeneration, characterized in that a member is provided and the exhaust direction of the exhaust gas is directed obliquely outward so as to be separated from the flame of the burner by the guide member.

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