JPH05676Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Industrial application field] The invention has a simple structure that is installed in a duct between the boiler outlet and the denitrifier inlet for commercial use, and has excellent gas mixing performance at low loads. This invention relates to a gas mixing device with low pressure loss during high loads.

[Conventional technology]

Commercial boilers are equipped with denitrifiers to remove nitrogen oxides (NOx) from exhaust gas. Ceramic catalysts are generally installed in layers inside the denitrifier, but the activity of these catalysts drops significantly below a certain temperature, so when the boiler operating load is low, some of the gas in the boiler flue is It is necessary to bleed the gas (bypass) and mix it with the outlet gas to increase the temperature, and a device for this purpose, ie a gas mixing device, is used.

FIGS. 2 and 3 are explanatory diagrams of a conventional gas mixing device.

In Figure 2, figure b is an enlarged view of part A of figure a, and figure c is an enlarged view of part A of figure a.
The figure is a view taken along the line CC in figure b, and the figure d is a view taken along the line D-D in figure c. In FIG. 2, a bypass duct 2 for extracting air is provided at the rear wall of the boiler rear flue duct 1 between the reheater 5 and the economizer 6.
This is an example in which a lattice mixer 7 is installed in the lower part of the bypass duct 2 in the middle of the boiler outlet duct 3. Figures b, c, and d in Figure 2 show the grid mixer 7.
This is a diagram illustrating the details of a vertical member 8 having an airfoil-shaped cross section.
and the horizontal member 9 are combined in a grid pattern, and the exhaust gas flowing down through the vertical member 8 is arranged vertically and flows into the horizontal member 9 through the notch hole 15 and is discharged from the opening 16 at the rear end of the horizontal member 9. Ru.

On the other hand, the low-temperature gas that has passed through the economizer 6 flows through the gaps in the grid-like mixer 7. These two gases flow into the denitrification device 4 while mixing with each other in the downstream region of the grid-like mixer 7. Note that 11 in the figure indicates a bypass damper. Further, FIG. 3 is an explanatory diagram of a conventional mixer having a curved duct, and parts having the same reference numerals as those in FIG. 2 indicate the same parts as shown in FIG. 2. Third
The figure shows a long curved duct 1 in which the exhaust gas is diverted 180 degrees to the boiler outlet duct 3 between the economizer 6 and the denitrifier 4.
This is a mixer having a structure in which 2 is provided, and the gas is mixed with the bypass gas by the secondary flow generated in the curved duct 12.

[Problem that the invention attempts to solve]

Although the lattice mixer shown in Figure 2 above has excellent mixing performance, it has a complicated structure and the mixer itself has a large resistance to the flow of exhaust gas. There are disadvantages such as large pressure loss (often). Further, the mixer having the curved duct shown in FIG. 3 requires a long duct that can be turned by 180 degrees, and has the disadvantage that pressure loss becomes large at high loads when no bypass is required.

As mentioned above, conventional gas mixers have problems such as having a complicated structure or requiring a long duct, and in addition, the pressure loss is excessive at high loads that do not require a gas bypass. There were problems such as the need to increase the amount of water.

The present invention was devised in view of the current situation, and it is an object of the present invention to provide a gas mixing device that has a simple structure, does not require a long duct, has excellent gas mixing performance at low loads, and has low pressure loss under high loads. The purpose is to

[Means for solving problems]

The present invention includes a protrusion protruding from the exhaust gas duct between the economizer and the denitrifier, a bypass passage having one end communicating with the duct upstream of the economizer and the other end communicating with the protrusion, and The duct is characterized by being equipped with a damper installed near the protrusion in the duct so as to be openable and closable and to block the duct when the damper is closed and to turn the flow of the exhaust gas along the inner wall of the protrusion. This paper proposes a gas mixing device that

[Effect]

In the gas mixing device with the above configuration, when a gas bypass is not required and therefore gas mixing is not required at high load, the damper is fully opened and the exhaust gas is introduced from the economizer to the denitrification device with minimum pressure loss, On the other hand, when a gas bypass is required and high-temperature bypass gas and low-temperature exhaust gas downstream of the economizer are required to be mixed, the damper is fully closed and the exhaust gas downstream of the economizer is turned around along the inner wall of the protrusion. The rotation effectively mixes the bypass gas introduced into the protrusion from upstream of the economizer via the bypass path, so that a mixing effect similar to that of a conventional mixer having a curved duct can be obtained.

In this way, the structure is simple, no long bent ducts are required, the pressure loss is small at high loads, and the gas mixing effect is large at low loads.

〔Example〕

A gas mixing device according to an embodiment of the present invention will be described with reference to Fig. 1. In Fig. 1, the parts with the same reference numerals as in Fig. 2 indicate parts having the same functions as in Fig. 2, and Figs. b and c are enlarged views of part A in Fig. a for explaining its operation.
Reference numeral 13 denotes a protrusion protruding upward from the upper part of the boiler outlet duct 3, which is a duct between the economizer 6 and the denitrifier 4. Reference numeral 14 denotes a bypass passage 10, one end of which is connected to a duct upstream of the economizer 6 and the other end of which is connected to the protrusion 13. The bypass passage 10 is made up of a number of square plate-shaped dampers arranged horizontally on the lower part of a surface perpendicular to the exhaust gas flow near the protrusion 13 of the boiler outlet duct 3, and is axially attached to the side wall of the boiler outlet duct 3 so that the ends of the square plates of adjacent dampers overlap each other when closed.

In a mixing device with such a configuration, when the load is high and gas bypass is not required, the damper 10 is fully opened to guide the exhaust gas from the economizer 6 to the denitrifier 4, as shown in Figure b, while when the load is low, the damper 10 is fully opened as shown in Figure b. When a gas bypass is required, the damper 10 is fully closed as shown in Fig. c, and the exhaust gas downstream of the economizer 6 is rotated along the inner wall of the protrusion 13 to reduce the amount of carbon introduced via the bypass path 14. After being mixed with the high-temperature bypass gas upstream of the vessel 6, it is supplied to the denitrification unit 4.

As described above, the gas mixing device of this embodiment has a simple structure and does not require a long duct, so there is little resistance to the flow of exhaust gas, and therefore, pressure loss during high loads is small. Furthermore, at low loads, the mixing effect of the exhaust gas rotation causes the exhaust gas to be mixed with the bypass gas, resulting in a large mixing effect.

[Effect of idea]

The gas mixing device of the present invention has a simple structure, does not require a long duct, has excellent gas mixing performance at low loads, and has the unique effects of low pressure loss at high loads.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a mixing device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a conventional lattice mixer, and FIG.
The figure is an explanatory diagram of a conventional mixer having a curved duct. 1... Boiler rear flue duct, 2... Bypass duct, 3... Boiler outlet duct, 4... Denitrifier, 5... Reheater, 6... Energy saver, 7... Grid mixer , 8... Vertical member, 9... Horizontal member, 10...
Damper, 11... Bypass damper, 12... Bent duct, 13... Protrusion, 14... Bypass path,
15... Notch hole, 16... Opening.

Claims (1)

[Scope of utility model registration request] a protrusion protruding from the exhaust gas duct between the economizer and the denitrifier; a bypass passage whose one end communicates with the duct upstream of the economizer and the other end communicates with the protrusion; a damper installed near the protrusion so as to be openable and closable and to block the duct when the damper is closed and to turn the flow of the exhaust gas along the inner wall of the protrusion; Mixing equipment.