JP2000304239A - Boiler device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler device to form a heat transfer part in a compact manner, a eliminate a limit of a gas temperature at a furnace outlet, and form a whole in a compact manner. SOLUTION: This boiler device comprises a mill 1 to effect milling of coal, a primary air piping 2 to cause conveyance of milled coal (pulverized coal) by air and feed the milled coal as a flow of pulverized coal to the wake side; a burner 3 to cause combustion of a flow of pulverized coal from the primary air piping 2 together with combustion air through a combustion air piping 30; a furnace 4 in which burners 3 are arranged; a furnace heat transfer wall 31 to absorb heat from combustion gas generated by combustion in the furnace 4 and generate steam; a heat transfer pipe 5 situated in a gas flow passage connected to the furnace 4; an environment device 6, such as a desulfurizing device, to treat exhaust gas from a boiler outlet lowered in temperature through heat absorption of the heat transfer pipe 5; and a chimney 7 to discharge exhaust gas, brought into a harmless state, to the atmosphere by environment device 6. In a so formed boiler device, a high temperature dust collecting device 11 is situated in an upstream side from a rear heat transfer pipe 5 part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler apparatus such as a power generation boiler using a fuel such as coal, which generates a large amount of ash by burning, and more particularly to a boiler apparatus having a compact furnace and heat transfer unit.

[0002]

2. Description of the Related Art In a coal-fired boiler or the like using coal as a fuel, a large amount of ash is generated by combustion.

FIG. 6 shows the structure of a conventional coal-fired boiler (boiler apparatus).

A coal-fired boiler includes a mill 1 for pulverizing coal as a fuel, and a primary air pipe 2 for conveying pulverized coal (hereinafter referred to as pulverized coal) to the air and supplying it as a pulverized coal stream to a downstream side. A burner 3 for burning the pulverized coal stream from the primary air pipe 2 together with the combustion air from the combustion air pipe 30, a furnace 4 provided with the burner 3, and combustion in the furnace 4. A furnace heat transfer wall 31 for absorbing heat from the generated combustion gas to generate steam, and a heat transfer tube 5 provided in a gas passage connected to the furnace 4 provided with the furnace heat transfer wall 31; An environmental device 6 such as a desulfurization device for processing exhaust gas from the boiler outlet, which has been cooled to a low temperature by heat absorption of the heat transfer tube 5, and a chimney 7 for releasing exhaust gas detoxified by the environmental device 6 to the atmosphere. I have. Further, it comprises a steam turbine and a generator 8 for converting steam energy generated in the boiler device into electric energy.
Here, in a coal-fired boiler, ash generated by combustion of coal poses a problem. Generally, ash is present in coal at about 10% of the coal weight. In other words, a boiler for power generation of 1000MW class consumes 300t / h of coal and 30t / h
The ash has been generated. This ash is a fine powder having a particle size of several tens of microns or less, and its melting temperature (hereinafter referred to as a melting point) is about 1400 ° C. or more, although it differs depending on the type of coal. Normally, this ash is generated in the furnace heat transfer wall 31 or in the suspended heat transfer section 5-1 provided from the upper part of the furnace to the gas flow path immediately after the furnace outlet, since the gas temperature is high and is higher than the melting point of the ash. Is melted and adheres to the heat transfer portion, but is cooled and solidified because the fluid to be heated flows in the heat transfer portion.
What has further solidified will grow. Of these, those that became heavier and peeled off and fell were collected from the lower part of the furnace. In the rear heat transfer section 32, which is the latter half of the gas flow path, the gas temperature is relatively low and is lower than the melting point of the ash, so that the ash does not melt and adheres to the heat transfer section. The ash that has adhered and accumulated is removed by an ash removing device (soot blower) 9, dropped, and collected by a hopper 10 below.

[0005]

The coal-fired boiler has the following three problems due to the presence of such ash.

The first problem is that the ash adheres to the heat transfer tubes constituting the suspended heat transfer section 5-1, the horizontal heat transfer section 5-2, the rear heat transfer section 32, and the like, thereby deteriorating the heat transfer performance. That is. In order to remove the ash attached to the heat transfer tubes, a steam spray device (ash removal device) called a soot blower is operated regularly, but the ash cannot be completely removed. The number of heat transfer tubes (heat transfer area) is set on the assumption that they adhere to some extent. For this reason, a coal-fired boiler requires a larger heat transfer surface than other gas-fired and oil-fired boilers.

The second problem is that the ash collides with the heat transfer tube and causes erosion on the surface of the heat transfer tube, so that the flow velocity through the heat transfer section is limited. In general, increasing the flow velocity promotes heat transfer and allows the heat transfer surface to be designed smaller. However, when the flow velocity is high, especially at 20 m / s or more, the erosion becomes large (the size of the erosion is proportional to the 3.5th power of the flow velocity). / s is designed to be slow. Therefore, a large heat transfer surface is required, and a large duct is required as compared with a gas-fired or oil-fired boiler in which ash is not a problem.

Third, if the molten ash adheres to the heat transfer tube such as the suspended heat transfer section 5-1 and the like, it becomes difficult to remove the ash. Therefore, the gas temperature at the furnace outlet is controlled to be 1400 ° C. or less. I have. The ash melts above the melting temperature (usually about 1400 ° C) and has a strong adhesive force. If the ash adheres to the heat transfer tube above this temperature, the molten ash has a large adhesive force and is easily removed. You can't do that. In addition, a large lump is formed around the location where the molten ash adheres, thereby covering the heat transfer surface. Therefore, the gas temperature at the furnace outlet is designed to be 1400 ° C or less (actually changed according to the type of coal used). Specifically, by increasing the size of the furnace (by increasing the distance from the burner), the amount of heat absorbed by the heat transfer walls 31 in the furnace is increased, and the gas temperature at the furnace outlet is kept low. Therefore, there is a problem that the furnace becomes large.

An object of the present invention is to remove ash generated by combustion in a furnace immediately before a heat transfer tube, thereby solving problems such as erosion of a heat transfer portion and a decrease in heat transfer amount, and making the heat transfer portion compact. It is another object of the present invention to provide a boiler apparatus that eliminates the restriction on the gas temperature at the furnace outlet and makes the whole compact.

[0010]

The object of the present invention is to provide a boiler apparatus using a fuel that generates a large amount of ash by combustion, by a first means in which a high-temperature dust collector is installed between a combustion section and a steam generator. Achieved.

[0011] The above object is achieved by a second means in which a plurality of revolving dust collectors are installed as the high-temperature dust collector in the first means.

The above object is achieved by a third means in which a plurality of collision-type dust collectors are provided as the high-temperature dust collector in the first means.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is an explanatory view showing an embodiment of the present invention.
2 is an explanatory diagram showing a high-temperature dust collector for carrying out the present invention, FIG. 3 is an explanatory diagram showing the relationship between the amount of ash attached to the heat transfer tube and heat transfer characteristics, and FIG. 4 is a diagram showing the relationship between furnace height and gas temperature. It is explanatory drawing which shows a relationship.

As shown in FIG. 1, the coal-fired boiler includes a mill 1 for pulverizing coal as a fuel, and a pulverized coal (hereinafter referred to as pulverized coal) which is conveyed to air to form a pulverized coal stream on the downstream side. A primary air pipe 2 to be supplied, a burner 3 for burning the pulverized coal stream from the primary air pipe 2 together with combustion air from a combustion air pipe 30, a furnace 4 provided with the burner 3, Furnace heat transfer wall 31 for absorbing heat from combustion gas generated by combustion in furnace 4 to generate steam.
And a heat transfer tube 5 provided in a gas flow path connected to the furnace 4 having the furnace heat transfer wall 31 provided therein, and desulfurization for processing exhaust gas from a boiler outlet which has been cooled to a low temperature by heat absorption of the heat transfer tube 5. It comprises an environmental device 6 such as a device, and a chimney 7 for discharging exhaust gas detoxified by the environmental device 6 to the atmosphere. Further, it comprises a steam turbine and a generator 8 for converting steam energy generated in the boiler device into electric energy.

In such a boiler, in the embodiment of the present invention, the high-temperature dust collector 11 is installed upstream of the rear heat transfer tube 5 (downstream of the furnace outlet). The high-temperature dust collector 11 employs a structure in which a rotary (cyclone-type) dust collector 12 as shown in FIG. 2 is attached, for example.
FIG. 2 shows a case where two revolving dust collectors are attached for the sake of simplicity.

In FIG. 2, reference numeral 12 denotes a rotary dust collector, 13
Is a partition for partitioning a gas flow path, and 14 is a rotary dust collector 1
2, inlet 15 to swirl vanes, 16 to exhaust gas outlet,
Reference numeral 17 denotes an outlet provided at the center of the inlet 14.

As shown in FIG. 2, the high-temperature dust collecting device 11
High-temperature exhaust gas flows together with the ash from the left side (furnace side), and all of the exhaust gas enters each of the rotary dust collectors 12 through the plurality of inlets 14 of the partition wall 13 installed diagonally.

The swirl vanes 15 are attached to the inflow port 14 of the swirl type dust collector 12, and the discharged exhaust gas forms a swirl flow. Then, due to the centrifugal force generated by the swirling flow, the ash particles in the exhaust gas are collected outside the swirling dust collector 12 (the inner wall side of the cylindrical portion of the swirling dust collector 12) and fall downward. On the other hand, the exhaust gas that has been dedusted is supplied to the rotary dust collector
The exhaust gas is discharged from an exhaust gas outlet 16 at the center of 2, exits from a plurality of outlets 17 from below to above a diagonally installed partition wall, and is sent to the rear heat transfer tube 5.
The ash particles contained in the exhaust gas are almost collected by such a swirl type dust collector 12. The performance of the revolving dust collector 12 is capable of collecting particles of about 10 μm or more. Therefore, about 10% of the ash particles leak to the rear heat transfer tube 5 side without being collected by the revolving dust collector 12. In particular, particles having a size of 100 μm or more, which are the main cause of erosion of the heat transfer tube, can be completely collected, so that the effects of erosion can be reduced to the level of heavy oil fired boilers.

In the present embodiment, the gas flow rate passing through the rear heat transfer tube 5 can be set to 20 m / s, which is twice as large as that of the conventional coal-fired boiler. By doubling the gas flow rate in this way, the heat transfer coefficient of the heat transfer tube is increased by about 1.5 times, so that the heat transfer area can be reduced to 66%.

Further, the amount of ash to the rear heat transfer tube 5 side is
With 10%, there is almost no ash adhering to the heat transfer surface, and it is possible to design with a larger heat transfer amount than before. FIG. 3 shows the relationship between the amount of ash adhering to the heat transfer tube and the heat transfer coefficient. The present embodiment (“the present invention” shown in FIG. In (), it can be seen that the amount of heat transfer increased by about 30% due to the decrease in the amount of ash attached. In FIG. 3, the vertical axis represents the heat transfer coefficient, and the horizontal axis represents the ash adhesion amount.

In addition, since the amount of ash that goes to the rear heat transfer tube is reduced, it is possible to prevent a decrease in heat transfer efficiency due to the attachment of ash, and to further reduce the heat transfer area. Also,
Repair equipment to remove ash is not required or can be reduced.

From the above, the size of the rear heat transfer section is
The size is about 50% (0.66 × 1 / 1.3) (area ratio) compared to the conventional one.

In the conventional furnace, the gas temperature at the furnace outlet is set to 1400 ° C. or less in order to prevent the molten ash from adhering to the rear heat transfer tube 5, but the molten ash is discharged from the furnace outlet. Even if this occurs, the gas is collected by the high-temperature dust collector 11 and does not go to the rear heat transfer tube 5, so that the gas temperature at the furnace outlet can be set high. In the present embodiment, the furnace outlet gas temperature is designed to be 1600 ° C. in consideration of the influence of the heat load on the furnace heat transfer wall 31 of the furnace 4 and the like. FIG. 4 shows the relationship between the furnace height and the gas temperature. By allowing the gas temperature at the furnace outlet to 1600 ° C., the height of the furnace 4 can be set to be about 5 m lower than the conventional one. In FIG. 4, the vertical axis represents the furnace height, and the horizontal axis represents the gas temperature.

In this embodiment, the high-temperature dust collector 11
A heat exchanger 18 (see FIG. 1) for recovering the heat of the high-temperature ash is set in the wake of the high-speed ash, and high-efficiency operation is performed. Also, depending on the type of coal used, heavy metals may be mixed in the ash generated by the conventional coal-fired boiler. In this case, there is a problem that this ash cannot be reused as a cement material or the like, but the ash collected by the high-temperature dust collector 11 of the present invention does not contain heavy metals. This is because heavy metal components exist in the gas phase at high temperatures (above about 1000 ° C), so the ash collected in a higher temperature environment is extremely clean and can be reused in cement materials, etc. There are advantages.

In this embodiment, the rotary dust collector 1
Two parts were made of ceramics to provide heat resistance, and 13 parts of the partition walls installed diagonally were water walls. Swivel dust collector 1
The inside of 2 is kept above the melting temperature of the ash, so there is no ash adhesion.

Next, another embodiment of the present invention will be described with reference to FIG.

FIGS. 5A and 5B are explanatory views showing another embodiment of the high-temperature dust collector, in which FIG. 5A is a view from above and FIG. 5B is a view from the side.

FIGS. 5A and 5B show an example in which a collision plate type dust collector 20 is employed as a high temperature dust collector. Collision plate type dust collector 2
0 denotes a plurality of U-shaped collision plates 21 in the flow path of the exhaust gas of the furnace.
Are arranged in a staggered arrangement as shown in FIG. 5 (a). As a result, the ash particles suspended in the exhaust gas collide with the concave groove side of the U-shaped collision plate 21 and lose their flow velocity, and fall downward and are collected as shown in FIG. 5B.

In the other embodiment, the collection rate is not high as compared with the rotary dust collector, but the structure is simple,
The effect is that large particles that cause erosion can be collected. In addition, there is also an effect that the pressure loss in the flow path can be smaller than that of the rotary dust collector.

The U-shaped collision plate 21 may be made of ceramic or water-cooled. When ash is attached, an attached ash removing device such as a soot blower may be installed in addition to the configuration shown in FIG.

[0032]

According to the first aspect of the present invention, the ash in the exhaust gas can be removed upstream of the rear heat transfer tube.
The flow velocity of the rear heat transfer tube can be increased, and the heat transfer area can be reduced. Further, since the molten ash does not go to the rear heat transfer tube, the temperature of the gas at the furnace outlet can be set high, and the whole can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing a high-temperature dust collector for carrying out the present invention.

FIG. 3 is an explanatory diagram showing a relationship between an amount of ash attached to a heat transfer tube and heat transfer characteristics.

FIG. 4 is an explanatory diagram showing the relationship between furnace height and gas temperature.

FIGS. 5A and 5B are explanatory diagrams showing another embodiment of the present invention.

FIG. 6 is an explanatory view showing a conventional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mill 2 Primary air piping 3 Burner 4 Furnace 5 Heat transfer tube 11 High-temperature dust collector 12 Rotary dust collector 13 Partition wall 14 Inlet 15 Swirl vane 16 Exhaust gas outlet 17 Outlet 20 Collision plate type dust collector 21 Collision plate

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hidehisa Yoshimaria 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside Kure Research Laboratories Co., Ltd. (72) Inventor Takahiro Marumoto 3-36 Takara-cho Kure City, Hiroshima Prefecture Babkotsuk Hitachi F-term in Kure Laboratory Co., Ltd. (reference) 3K070 DA07 DA27 DA29

Claims (3)

[Claims] 1. A boiler apparatus using a fuel that generates a large amount of ash by combustion, wherein a high-temperature dust collector is installed between a combustion section and a steam generator. 2. The boiler apparatus according to claim 1, wherein a plurality of revolving dust collectors are installed as the high-temperature dust collector. 3. The boiler device according to claim 1, wherein a plurality of collision type dust collectors are installed as said high temperature dust collector.