JPS60216103A - Guide structure of combustion gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a structure for guiding a combustion gas flow inside a combustion chamber of a boiler or the like. The present invention relates to an effective combustion gas guide structure for preventing combustion.

[Background of the invention]

First, a structure for guiding combustion gas inside a combustion chamber of a conventional boiler or the like will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of a schematic structure inside a combustion chamber and a flow state of combustion gas in a conventional water tube boiler or the like. As is clear from the figure, a superheater or reheater having an inlet header 2 and an outlet header 3 is installed inside the combustion chamber of the boiler surrounded by the boiler water-cooled wall tubes 1, and is connected to three types of heat exchanger tube groups 4, 5. and 6.

The flow of combustion gas to heat exchanger tube group 6 is substantially uniform and perpendicular to the heat exchanger tubes; In particular, heat exchanger tube group 5 is installed immediately after the combustion gas flow changes direction from upward flow to downward flow (section A in Figure 1), so in heat exchanger tube group 5 i), combustion gas The flow of the combustion gas is greatly biased, resulting in a section where almost no combustion gas flows, a so-called separation section of the combustion gas flow (section B in Fig. 1). The heat transfer tubes in this separated area do not effectively contribute to heat transfer, and in the uneven flow area where the combustion gas is significantly skewed, the combustion gas no longer flows perpendicularly to the heat transfer tube, reducing heat transfer efficiency. It turns out. Furthermore, when a separation phenomenon occurs in the combustion gas flow, it becomes a hydrodynamic loss, leading to an increase in pressure loss (draft loss) in the combustion gas system. This results in a load.

In order to prevent the uneven flow and separation phenomenon of combustion gas in the boiler mentioned above, it is possible to install a member such as a combustion gas guide plate, but this combustion gas guide member is installed at a temperature of approximately 900°C in the boiler combustion chamber. Because the temperature is ~700°C, high-temperature oxidation is severe and sulfur oxides (SOX) or nitrogen oxides (
This resulted in high-temperature corrosion due to vanadium, sodium, etc. contained in the combustion ash, and the lifespan of the combustion gas guide member was extremely short, at most one year.

In addition, because the heat transfer efficiency decreases due to the uneven flow and separation phenomenon of combustion gas, it is necessary to use a heat transfer tube group whose heat transfer area is increased by the amount of the decrease in heat transfer efficiency, in order to obtain the specified steam temperature. The disadvantage was that it could not be done.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional structure, permanently prevent uneven flow and separation of combustion gas flow in the high-temperature combustion region of a boiler combustion chamber, and improve the heat exchange efficiency of a group of heat transfer tubes. The object of the present invention is to provide a new and effective combustion gas guiding structure for reducing draft loss (ventilation resistance) of combustion gas.

[Summary of the invention]

In short, the present invention provides a combustion gas guide member made of a refractory material such as metal or ceramics in a heat exchanger tube of a boiler in a low temperature section in order to prevent drift and separation of combustion gas in a high temperature combustion region of a combustion chamber of a boiler or the like. established,
The combustion gas guide member is cooled by utilizing the cooling effect of the boiler heat transfer tube to prevent the guide member from being oxidized or corroded by the high temperature and corrosive combustion gas. This is an effective guide structure for combustion gas in permanent boilers with a long life.

The shape of the guide member attached to the heat exchanger tube in the low-temperature part of the boiler may be plate-shaped, angled or channel-shaped, and in short, the gas guide structure must be such that the high-temperature combustion gas flow does not cause drift or separation phenomenon. The material may be a heat-resistant material such as a metal or ceramic having appropriate heat resistance, corrosion resistance, and strength.

Since the combustion gas guide structure according to the present invention can effectively prevent combustion gas drift and separation, the combustion gas flows perpendicularly to the heat exchanger tube group, and as a result, the heat exchange efficiency in the heat exchanger tube group is improved. , and the draft loss of the combustion gas can be reduced, which has the effect of reducing the heat transfer area of the heat transfer tube group and the load on the blower.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Note that in the figures, parts with the same reference numerals indicate the same components. FIG. 2 is a sectional view schematically showing the internal structure of the boiler combustion chamber according to the present invention. As shown in the figure, a superheater or reheater having an inlet header 2 and an outlet header 3 is installed inside the combustion chamber of the boiler surrounded by boiler water-cooled wall tubes 1.
It is composed of heat exchanger tube groups 4, 5 and 6 of different types.

As shown in Figure 3, in the part where the combustion gas flow changes direction from upward flow to downward flow (section C in Figure 2), a metal relate with a fin structure is welded to the boiler heat exchanger tube, and its surface is Low temperature coated with castable refractory (approximately 3
The steam heat transfer tubes (50° C. to 500° C.) are arranged in a structure to guide the combustion gas so as not to cause drift or separation in the combustion gas flow. The combustion gas temperature at part 0 in Figure 2, where the direction of the combustion gas flow changes from an upward flow to a downward flow, is approximately 900°C to 700°C. In the case of a combustion gas guide structure with welded plates, the temperature of the metal plate of the fin structure is approximately 500℃, which means that high-temperature oxidation and high-temperature corrosion hardly occur, resulting in a long life as a combustion gas guide structure in high-temperature areas. , 4 for permanent use.

However, in the combustion gas guide structure in which a metal plate is attached to the steam heat transfer tube described above, the temperature of the surrounding combustion gas is 700°C.
℃, and if the temperature of the cooling steam is 500℃,
The temperature of the metal plate of the heat exchanger tube is approximately 700°C. In this case 9 In a normal oil-fired or coal-fired boiler, highly corrosive gas (SO or NO) is contained in the combustion gas.
X) and ash (vanadium or sodium compounds) when the temperature of the metal plate is about 700°C.

Severe high-temperature corrosion occurs with a corrosion thinning rate of approximately 2mm/10'h (on one side of the metal plate).1For example, even if a metal plate with an inner thickness of 4WI+ is used as a guide plate, it will wear out in about a year. It turns out.

On the other hand, in the case of the combustion gas guide structure cooled by the low-temperature steam heat transfer tube of the present invention, the temperature of the metal plate is approximately 500°C or less, which is an area where high-temperature corrosion hardly occurs, and the gas guide structure is permanent. becomes.

Next, other embodiments of the present invention will be described. Figure 4 shows
An example is shown in which a combustion gas guide plate is fixed to a heat exchanger tube of a boiler using U-shaped bolts and nuts. In addition, Figure 5 shows a so-called membrane wall (membrane wall), such as a boiler water cooling wall, by welding a fin-shaped metal plate to the heat exchanger tube of a boiler.
This type has the highest cooling efficiency and is effective in areas where the combustion gas temperature is higher.

〔Effect of the invention〕

As explained in detail above, in the combustion gas guide structure of a boiler or the like according to the present invention, the metal member, which is the gas guide plate attached to the boiler heat transfer tube, is cooled by low-temperature steam. Corrosion can be prevented, and the gas guide structure of the present invention can be used permanently, whereas the conventional structure has a lifespan of about one year.

Also, the material of the metal member used as the gas guide plate.

It is economical to be able to change from conventionally used heat-resistant steel or stainless steel to lower grade steel, such as low alloy steel or carbon steel.

Furthermore, according to the combustion gas guide structure according to the present invention, the linear flow and separation phenomenon of combustion gas can be permanently prevented, and the combustion gas flow flows perpendicularly to the boiler heat exchanger tube group, so that the heat exchange efficiency of the heat exchanger tube group is improved. Improve.

It is sufficient to use a heat transfer tube group whose heat transfer area is reduced by about lθ to 25% compared to the heat transfer area of the heat transfer tube group in the portion where the uneven flow and separation phenomenon of the combustion gas flow occurs in the conventional structure.

Furthermore, since the heat transfer characteristics in the heat transfer tube group almost match the design values and the characteristics during actual operation, the reliability of the calculated steam temperature characteristics becomes extremely high. Furthermore, since drifting and separation of the combustion gas can be prevented, ventilation resistance is reduced, and the load on the blower can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic structure inside a conventional boiler combustion chamber, FIG. 2 is a sectional view showing a schematic structure inside a boiler combustion chamber according to the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 3 is a sectional view showing a combustion gas guide structure. FIGS. 4 and 5 are cross-sectional views showing combustion gas guide structures according to other embodiments of the present invention. 1... Boiler water cooling wall tube 2... Inlet header 3...
Outlet pipe header 4,5.6... Heat exchanger tube group 7... Heat exchanger tube with guide plate 8... Boiler heat exchanger tube 9... Fin 10
... Castable refractory 11 ... U-shaped bolt 1
2...Natsuto 13...Guidance board 14...Membrane wall structure representative patent attorney Junnosuke Nakamura 1 figure A IF5 figure 3 and 1 figure 4 figure 5 figure only

Claims (1)

[Claims] 1. In a boiler combustion chamber composed of a plurality of heat exchanger tube groups, a combustion gas guide member is provided in a boiler heat exchanger tube in a low temperature section in a high temperature combustion region where the combustion gas flow changes direction. A combustion gas guide structure characterized in that a cooling type gas guide member is disposed in the high temperature combustion region, and the cooling type gas guide member prevents drifting and separation of high temperature combustion gas. 2. A patent in which the cooling type gas guide member is characterized in that a plate, angle or channel-shaped metal is welded to the heat exchanger tube as a fin, and one or both surfaces in contact with high temperature combustion gas are covered with a refractory material. A combustion gas guide structure according to claim 1. 3. The combustion gas guide structure according to claim 1 or 2, wherein the cooling type gas guide member is fixed to a plate, angle or channel-shaped metal with bolts and nuts. 4. The cooling type gas guide member is characterized in that it has a membrane structure by welding metal plates, angles or channels as fins to the heat transfer tube, or Combustion gas guide structure according to item 2.