JP2001304501A - Oil/gas combustion switching type boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil/gas combustion switching type boiler which can burn oil or gas as occasion demands with proper switching without the change or the like of a furnace structure while avoiding lowering of plant efficiency or increase of costs. SOLUTION: A heating tube used as a secondary superheater at the time of burning oil is employed as an evaporator 6' when a gas is burnt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil / gas combustion switching boiler.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a boiler. In FIG. 3, reference numeral 1 denotes a boiler main body, 2 denotes a furnace of the boiler main body 1, and 3 denotes a rear heat transfer section formed downstream of the furnace 2. Reference numeral 4 denotes a burner for injecting fuel into the furnace 2 for combustion, 5 denotes a primary superheater, 6 denotes a secondary superheater, 7 denotes a final superheater, 8 denotes a reheater, 9 denotes a economizer, and 10 denotes steam. It is a drum, and generates fuel gas by injecting fuel from the burner 4 into the furnace 2 of the boiler body 1 and burns the fuel. The generated combustion gas is circulated from the furnace 2 to the rear heat transfer unit 3. The heat is exchanged with the secondary superheater 6, the final superheater 7, the reheater 8, the primary superheater 5, and the economizer 9, and the exhaust gas after the heat exchange is subjected to flue gas such as denitration and desulfurization provided on the downstream side. After removing nitrogen oxides, sulfur oxides, and the like by a processing device (not shown), they are released to the atmosphere.

On the other hand, the boiler feedwater is preheated by a economizer 9 and enters a steam drum 10, from which the downfall of the downcomer pipe 11 and the downcomer pipe constituting the rear wall of the rear heat transfer section 3 is performed. , Enters the furnace wall pipe of the furnace 2 from the lower pipe side, rises while receiving heat, returns to the steam drum 10 via the brackish water mixing line 12 in a brackish water mixed state, where the brackish water is separated,
Only steam is sent to the primary superheater 5 via the main steam line 13, from the primary superheater 5 to the secondary superheater 6 via the primary superheated steam line 14, and from the secondary superheater 6 The superheated steam is sent to the final superheater 7 through the superheated steam line 15, becomes superheated steam of a predetermined temperature, and is guided to a high-pressure turbine (not shown) through the final superheated steam line 16. The high-pressure turbine is driven to generate electric power. At the same time, the steam after driving the high-pressure turbine is led to a reheater 8,
After being reheated, the steam is introduced into a medium / low pressure turbine (not shown), the medium / low pressure turbine is driven to generate power, and the steam after driving the medium / low pressure turbine is not shown. It is led to the condenser and returned to the boiler feedwater.The boiler feedwater passes through a condensate desalination device, a low-pressure feedwater heater and a deaerator (not shown), and a high-pressure feedwater heater through a feedwater pump. And sent to the economizer 9 and circulated.

[0004] The secondary superheater 6 is formed by a hanger tube for supporting the final superheater 7 and the reheater 8.

[0005]

In the above-mentioned boiler, however, oil such as heavy oil or gas such as natural gas as a fuel may be appropriately switched and burned according to the price at that time. A request may be made to do so.

Generally, the form of heat transfer in the boiler main body 1 is radiant heat collection in the furnace 2 and contact heat collection in the rear heat transfer section 3, but the ratio of carbon to hydrogen in oil and gas is (So-called C / H ratio), the oil has a large radiant heat and the contact heat is small, whereas the gas has a small radiant heat. , The contact heat collection becomes large.

In a recent boiler, a part of the exhaust gas discharged from the boiler main body 1 is returned to the furnace 2 to lower the flame temperature to reduce the radiated heat collection and increase the gas flow rate flowing through the rear heat transfer section 3. Controlling the outlet steam temperature of the reheater 8 is performed by performing so-called exhaust gas recirculation to increase the contact heat collection. In the case of a boiler designed based on oil, the exhaust gas recirculation is performed. The flow rate is
The load becomes maximum when the load is about 70%,
Normally, the load is minimized at a load of 00 [%]. However, when gas is burned in such a boiler, the exhaust gas recirculation flow rate during gas combustion becomes relatively lower than that during oil combustion. , High load zone (for example, about 80
(% Load), the exhaust gas recirculation flow rate becomes zero, and the outlet steam temperature of the reheater 8 becomes too high, so that it becomes necessary to spray water on the inlet side of the reheater 8,
There was a disadvantage that the plant efficiency was reduced.

Further, since the contact heat collection becomes large during the combustion of the gas, the amount of water sprayed in the middle of the secondary superheated steam line 15 on the exit side of the secondary superheater 6 is controlled in order to control the superheated steam temperature. In this case, the amount of superheated steam introduced from the final superheater 7 to the high-pressure turbine via the final superheated steam line 16 is determined according to the load.
The amount of the spray increases, the steam flow rate flowing through the heat transfer surface of the secondary superheater 6 decreases, the metal temperature increases, and a pipe made of an expensive material having high heat resistance is connected to the secondary superheater 6. There was also a problem that it had to be used, leading to an increase in cost.

On the other hand, by increasing the number of stages of the burners 4 provided in the furnace 2 and arranging a burner for oil on the upper side and a burner for gas on the lower side, when burning gas,
Apparently, the furnace 2 was made larger than the oil
In this case, it is not necessary to spray the inlet of the reheater 8 as described above, but this leads to an increase in the equipment cost of the furnace 2 and There was a disadvantage that the lower part of the furnace 2 was wasted when oil was burned.

The present invention has been made in view of the above-mentioned circumstances, and it has been found that oil and gas can be appropriately switched and burned as necessary, while avoiding a decrease in plant efficiency and an increase in cost, without changing the structure of the furnace. It is an object of the present invention to provide an oil / gas combustion switching type boiler capable of reducing the temperature.

[0011]

The present invention is characterized in that a heat transfer tube used as a secondary superheater during oil combustion is used as an evaporator during gas combustion. It's a boiler.

According to the above means, the following effects can be obtained.

[0013] In the case of gas, the radiant heat collection is relatively small and the contact heat collection is relatively large as compared with the case of oil, but as described above, a heat transfer tube used as a secondary superheater during oil combustion is used. When used as an evaporator during gas combustion, it is possible to compensate for the decrease in radiant heat collection with the heat transfer surface of the evaporator, and to cope with the increase in contact heat collection by eliminating the secondary superheater. It is possible to prevent the steam temperature at the outlet of the reheater from rising too high.Therefore, there is no need to spray water on the inlet side of the reheater, so that the plant efficiency does not decrease and the temperature of the superheated steam is controlled. The amount of water sprayed on the furnace does not increase, the rise in metal temperature of the superheater can be avoided, and the need for expensive heat-resistant pipes is eliminated. Increased number of stages Because the do not have to, not increase also the equipment cost of the furnace, it is not even like that the lower part of the furnace is wasted when oil combustion.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an example of an embodiment of the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIG. 3 represent the same components, and the basic configuration is shown in FIG. It is the same as the conventional one shown here, but the feature of this illustrated example is that
As shown in FIG. 1, a heat transfer tube used as a secondary superheater 6 during oil combustion is configured to be used as an evaporator 6 ′ during gas combustion.

In the illustrated example, the primary superheated steam line 14 hangs down from the bottom of the steam drum 10 and is connected to the middle thereof.
A precipitation line 17 for guiding a portion of the water in the steam drum 10 to the secondary superheater 6 during gas combustion and using the secondary superheater 6 as an evaporator 6 ′, and a rain line 17 provided in the middle of the rain line 17. A switching valve 18 that is closed during oil combustion and opened during gas combustion, and is provided in the middle of the primary superheated steam line 14 upstream of the connection of the precipitation line 17 and is opened during oil combustion and closed during gas combustion. Switching valve 19
An evaporator line 20 for branching from the middle of the secondary superheated steam line 15 and connected to the steam drum 10 for guiding steam in a brackish water mixed state heated by the evaporator 6 ′ during gas combustion to the steam drum 10; A switching valve 21 provided in the middle of the evaporator line 20 and closed during oil combustion and opened during gas combustion, and provided in the middle of the secondary superheated steam line 15 downstream from the branch point of the evaporator line 20; Switching valve 22 opened during oil combustion and closed during gas combustion
Is branched from the middle of the primary superheated steam line 14 on the upstream side of the switching valve 19 and connected to the middle of the secondary superheated steam line 15 on the downstream side of the switching valve 22, and is heated by the primary superheater 5 during gas combustion. A bypass line 23 for guiding the superheated steam to the final superheater 7 and a switching valve 24 provided in the middle of the bypass line 23 and closed during oil combustion and opened during gas combustion are provided.
The heat transfer tube used as the secondary superheater 6 at the time of oil combustion is used as the evaporator 6 'at the time of gas combustion by opening / closing operations of 8, 19, 21, 22, 24.

Next, the operation of the illustrated example will be described.

At the time of oil combustion, as shown in FIG. 1, the switching valve 18 is closed, the switching valve 19 is open, the switching valve 21 is closed, the switching valve 22 is open, and the switching valve 24 is closed. As in the case of the conventional example shown in FIG.
Preheated into the steam drum 10 and the steam drum 10
Down from the downcomer constituting the rear wall of the downcomer mother pipe 11 and the rear heat transfer section 3, enter the furnace wall pipe of the furnace 2 from the lower pipe side,
It rises while receiving heat, returns to the steam drum 10 via the brackish water mixing line 12 in a brackish water mixing state, where the brackish water separation is performed, and only the steam is sent to the primary superheater 5 via the main steam line 13, It is sent from the primary superheater 5 to the secondary superheater 6 via the primary superheated steam line 14, and is sent from the secondary superheater 6 to the final superheater 7 via the secondary superheated steam line 15 and has a predetermined temperature. Superheated steam and final superheated steam line 1
6, the high-pressure turbine is driven to generate electric power by driving the high-pressure turbine, and the steam after driving the high-pressure turbine is guided to a reheater 8, and the reheater 8 After being reheated, the steam is introduced into a medium / low pressure turbine (not shown), the medium / low pressure turbine is driven to generate power, and the steam after driving the medium / low pressure turbine is not shown. It is led to the condenser and returned to the boiler feedwater.The boiler feedwater passes through a condensate desalination device, a low-pressure feedwater heater and a deaerator (not shown), and a high-pressure feedwater heater through a feedwater pump. And sent to the economizer 9 and circulated.

On the other hand, at the time of gas combustion, as shown in FIG. 2, the switching valve 18 is opened, the switching valve 19 is closed, the switching valve 21 is opened, the switching valve 22 is closed, and the switching valve 24 is opened. The water supply is preheated in a economizer 9 and the steam drum 1
0, from the steam drum 10, descend the downcomer tube 11 and the downcomer tube constituting the rear wall of the rear heat transfer section 3, enter the furnace wall tube of the furnace 2 from the lower pipe side, and rise while receiving heat. , A steam drum 1 through a brackish water mixing line 12 in a brackish water mixing state
0, and at the same time, a part of the water preheated by the economizer 9 and entering the steam drum 10 descends down the precipitation line 17 and is led to the evaporator 6 ′, where the evaporator 6 ′ It rises while receiving heat, returns to the steam drum 10 via the evaporator line 20 in a state of brackish water mixing, where steam separation is performed, and only steam is passed through the main steam line 13 to the primary superheater 5.
From the primary superheater 5 to the primary superheated steam line 14
And to the final superheater 7 via the bypass line 23,
It becomes superheated steam of a predetermined temperature and is guided to a high-pressure turbine (not shown) through a final superheated steam line 16, and the high-pressure turbine is driven to generate electric power. After being guided to the heater 8 and reheated by the reheater 8, it is introduced into a medium / low pressure turbine (not shown), and the medium / low pressure turbine is driven to generate electric power. Is driven to a condenser (not shown) and returned to the boiler feedwater.The boiler feedwater includes a condensate desalination device (not shown), a low-pressure feedwater heater, and a deaerator. Then, the water is pumped to the economizer 9 by the feed water pump via the high pressure feed water heater and circulated.

In the case of gas, the radiation heat is relatively small and the contact heat is relatively large as compared with the case of oil. However, as described above, the heat transfer tube used as the secondary superheater 6 during oil combustion is used. When used as the evaporator 6 'during gas combustion, the heat transfer surface of the evaporator 6' makes it possible to compensate for the reduced radiated heat collection,
In addition, it is possible to cope with the increase in the contact heat collection by eliminating the secondary superheater 6, and it is possible to prevent the outlet steam temperature of the reheater 8 from becoming too high. No need to spray, the plant efficiency does not decrease, the amount of water to spray to control the superheated steam temperature does not increase, the rise in metal temperature of the superheater is avoided, and high heat resistance and expensive It is not necessary to use a tube made of a material, and it is possible to avoid cost increase.
It is not necessary to increase the number of stages of the burners 4 provided in the furnace, so that the equipment cost of the furnace 2 does not increase, and the furnace 2
There is no such thing as wasting the bottom of the.

In this manner, oil and gas can be appropriately switched and burned as required, while avoiding a decrease in plant efficiency and an increase in cost and without changing the structure of the furnace 2 or the like.

It should be noted that the oil / gas combustion switching boiler of the present invention is not limited to the above-described illustrated example, and various changes can be made without departing from the gist of the present invention. .

[0023]

As described above, according to the oil / gas combustion switching type boiler of the present invention, the oil and gas combustion switching type boiler can be used without changing the furnace structure while avoiding a decrease in plant efficiency and cost. An excellent effect that the gas can be appropriately switched and burned as required can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram at the time of oil combustion in an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram at the time of gas combustion in an example of an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler main body 2 Furnace 3 Rear heat transfer part 4 Burner 5 Primary superheater 6 Secondary superheater 6 'Evaporator 7 Final superheater 8 Reheater 9 Energy saving device 10 Steam drum 14 Primary superheated steam line 15 Secondary superheated steam Line 17 Precipitation line 18 Switching valve 19 Switching valve 20 Evaporator line 21 Switching valve 22 Switching valve 23 Bypass line 24 Switching valve

Claims (1)

[Claims] 1. An oil / gas combustion switching type boiler, wherein a heat transfer tube used as a secondary superheater during oil combustion is used as an evaporator during gas combustion.