JPH05172308A - Reducing method for n2o of fluidized bed boiler - Google Patents

Abstract

PURPOSE:To reduce NOx of a fluidized bed boiler by providing O2 separation equipment on the way of the extension of an air duct and separating O2 from the air introduced into a firing furnace to send the same into the firing furnace. CONSTITUTION:O2 separation equipment 14 for separating O2 in air to send the same into a firing furnace 1 and removing N2 from air is provided on the way of the extension of an air duct 4 and the leading end of a gas circulating duct 12 circulating a part of exhaust gas into the firing furnace 1 is connected to the air duct 4 between the O2 separation equipment 14 and the firing furnace 1. Further, SO2/CO2 liquefying equipment 15 cooling exhaust gas under pressure to liquefy SO2 and CO2 to separate them from the exhaust gas is provided on the way of the extension of a flue 10 and a combustion chamber 18 equipped with a fuel burner 17 for reheating exhaust gas is provided on the downstream side of said equipment 15. By this constitution, the generation of thermal NOx wherein N2 and O2 in air are bonded at high temp. is suppressed and the amount of exhaust gas can be reduced and, therefore, the combustion chamber 18 low in exhaust gas treatment capacity and reduced in the consumption of fuel can be adapted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing N ₂ O in a fluidized bed boiler useful for pollution prevention.

[0002]

2. Description of the Related Art FIG. 4 is a side view schematically showing an example of a conventional fluidized bed boiler. Reference numeral 1 is a furnace, and an air dispersion plate 2 having a large number of small air holes is provided in the lower portion of the furnace 1, and inert particles (such as silica sand or limestone) serving as a fluid medium 3 are deposited on the air dispersion plate 2. Let In addition, 4 indicates the air supplied by a pushing fan (not shown) to the furnace 1
It is a wind path leading to the bottom of.

Further, 5 is a rear heat transfer section, which has a heat exchange section 8 formed by a superheater 6, a economizer 7, etc., and a flue 10 leading to a chimney 9 below the heat exchange section 8. And the exhaust gas recirculation route 11 and the exhaust gas recirculation route 1
Reference numeral 1 is formed of a gas recirculation duct 12 and a gas recirculation fan 13, and is connected to the furnace 1 via the air passage 4.
The arrow a indicates the flow direction of the exhaust gas.

When the fluidized medium 3 on the air dispersion plate 2 is heated to a temperature higher than the ignition temperature of coal, and pulverized coal and high-temperature primary air are fed into the furnace 1 from the air passage 4, the fluidized medium 3 vigorously moves to generate air. And pulverized coal are mixed and become a continuous combustion state. Thus, the exhaust gas flowing from the furnace 1 into the rear heat transfer section 5 heats the saturated steam in the superheater 6 when passing through the rear heat transfer section 5, and preheats the feed water in the economizer 7. Part of the exhaust gas, which has undergone heat exchange in the exchange section 8 and whose residual heat has been recovered, is sucked by the gas recirculation fan 13, circulated through the gas recirculation duct 12 and the air passage 4 into the furnace 1, and the remaining exhaust gas is It is discharged from the chimney 9 to the outside through the flue 10.

Since the fluidized-bed boiler described above has a low combustion temperature, it absorbs infrared rays emitted from the ground surface and returns the heat escaping to outer space to the ground surface to raise the temperature, so that N ₂ O has a high greenhouse effect. Often occurs.

[0006] Thus, by reheating the flue gas, dinitrogen monoxide (hereinafter referred to as N ₂ O) and how to convert the nitrogen (hereinafter referred to as N _2), the N ₂ O using a very expensive catalyst A method of processing has been proposed.

[0007]

However, the above-mentioned method of reheating exhaust gas requires a large amount of fuel to raise the temperature of a large amount of exhaust gas to 800 ° C. to 1200 ° C., which is uneconomical. Further, the above-mentioned method of treating exhaust gas with a catalyst requires a large amount of catalyst to be provided for treating a large amount of exhaust gas, and thus has a problem of a large economical burden.

In view of the above-mentioned circumstances, the present invention separates and removes nitrogen (hereinafter referred to as N ₂ ) from the air before it is fed into the furnace, and further, sulfurous acid gas (hereinafter referred to as SO ₂ ) from the exhaust gas.
As a (hereinafter referred to as CO ₂₎ carbon dioxide and liquefied removed, after reducing the amount of exhaust gas to a few percent, to provide a N ₂ O reduction method of the fluidized bed boiler can process N ₂ 0 It was done as a purpose.

[0009]

In order to achieve the above object, a method for reducing N ₂ O in a fluidized bed boiler according to the first invention is a fluidized bed boiler including a furnace having a fluidized bed and a rear heat transfer section. In the above, the O ₂ separation equipment separates O ₂ from the air into the furnace, and recirculates part of the exhaust gas flowing through the flue connected to the outlet side of the rear heat transfer section to the furnace, leaving the rest. SO ₂ and CO ₂ are liquefied and separated from the exhaust gas by pressurizing and cooling the exhaust gas of the exhaust gas with an SO ₂ / CO ₂ liquefaction equipment provided in the middle of the extension of the flue, and the downstream side of the SO ₂ / CO ₂ liquefaction equipment. The exhaust gas separated from the SO ₂ and CO ₂ flowing in the exhaust gas is reheated by the fuel burner to change N ₂ O in the exhaust gas to N _{2 and the} like, and then exhausted to the outside. N ₂ O reduction method of the fluidized bed boiler comprises a furnace and the heat recovery unit with a fluidized bed In a fluidized bed boiler, to separate the O ₂ in the air by O ₂ separation equipment and fed to the furnace, also recirculate part of the exhaust gas flowing in the flue connected to the outlet side of the heat recovery unit to the furnace is allowed, liquefied separates the SO ₂ and CO ₂ remaining exhaust gas from the exhaust gas by pressurized cooling by SO ₂ / CO ₂ liquefaction plant provided in extension設途flue, the SO ₂ / C
The exhaust gas separated from SO ₂ and CO ₂ flowing on the downstream side of the O ₂ liquefaction facility is passed through a catalyst to change N ₂ O in the exhaust gas to N ₂ and then discharged to the outside.

[0010]

Therefore, according to the first aspect of the invention, the air supplied to the O ₂ separation facility through the air passage is treated by the O ₂ separation facility to separate O ₂ from the air, and the other is released to the atmosphere. This removes N ₂ and feeds the O ₂ into the furnace. Further, by pressurized cooling the exhaust gas flowing in the stack direction through the flue in SO ₂ / CO ₂ liquefaction plant provided in extension設途flue separates the SO ₂ and CO ₂ from the exhaust gas. As a result, the exhaust gas, which has been reduced in quantity, is heated by the combustion chamber and the N ₂ in the exhaust gas is increased.
After reducing O, the exhaust gas is discharged to the outside.

[0011] In the second invention, likewise the O ₂ to the first invention is fed to the furnace, separating the SO ₂ and CO ₂ from the exhaust gas in SO ₂ / CO ₂ liquefaction plant. As a result, N ₂ O contained in the exhaust gas, which has been reduced in quantity, is treated with a catalyst and then discharged to the outside.

[0012]

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

FIG. 1 shows the N ₂ O of the fluidized bed boiler of the first invention.
FIG. 2 is a side view showing an outline of the reduction method, and FIG. 2 is a vapor pressure curve diagram of liquefied gas related to the N ₂ O reduction method of the fluidized bed boiler of FIG.

The basic structure is substantially the same as that of the conventional fluidized bed boiler shown in FIG. 4, and the same parts as those shown in FIG. 4 are designated by the same reference numerals.

[0015] During extension設途wind path 4 of this embodiment, the O ₂ in the air is separated and to fed the O ₂ to the furnace 1, and O ₂ separation facility 14 is provided, the The tip of a gas recirculation duct 12 that circulates a part of the exhaust gas into the furnace 1 is connected to the air passage 4 between the O ₂ separation facility 14 and the furnace 1.

During the extension of the flue 10, in order to separate SO ₂ and CO ₂ in the exhaust gas, the exhaust gas is pressurized and cooled to liquefy SO ₂ and CO ₂ and separate it from the exhaust gas. Possible S
An O ₂ / CO ₂ liquefaction facility 15 is provided, and a combustion chamber 18 equipped with a fuel burner 17 for reheating exhaust gas is provided downstream of the SO ₂ / CO ₂ liquefaction facility 15.

Since the configuration other than the above is the same as that of the conventional fluidized bed boiler shown in FIG. 4, its description is omitted.

Next, the operation will be described. The air supplied to the O ₂ separation equipment 14 via the air passage 4 is supplied to the O ₂ separation equipment 1
O ₂ is separated from the air by treatment with 4 and N ₂ is removed by releasing the other into the atmosphere, and the O ₂ is fed into the furnace 1.

The exhaust gas flowing toward the chimney 9 through the flue 10 is provided with SO ₂ / CO ₂ which is provided during the extension of the flue 10.
By the liquefaction facility 15, pressure cooling (for example, a pressure of 2 Kg / cm ^{2) is} applied so that the pressure and temperature conditions shown in FIG.
Below, SO ₂ liquefies at 280 ° K and CO ₂ at 205 ° K.
Liquefies), so that SO ₂ and C
Separated from O ₂ . As a result, the exhaust gas is quantitatively reduced to several percent. The fuel burner 17 in the combustion chamber 18 is ignited and burned to reheat the reduced exhaust gas, and N ₂ O in the exhaust gas is converted to N ₂
By reducing the amount of N ₂ O, etc.

According to the, the O ₂ separation equipment 14 provided in the air duct 4 extending設途, as by separating the O ₂ from the air to fed into the furnace 1 may fed the O ₂ to the furnace 1 Having formed, thermal NO to N ₂ in the air is bonded with O ₂ and high temperature
Generation of _x is suppressed, and the amount of exhaust gas can be reduced to about 1/5. Further, since the SO ₂ / CO ₂ liquefaction facility 15 is provided in the middle of the extension of the flue 10 so that SO ₂ and CO ₂ in the exhaust gas can be liquefied and separated, the exhaust gas amount can be further reduced and the conventional boiler can be used. Since it is only necessary to treat the exhaust gas reduced to a few% of the exhaust gas amount, it is possible to apply the combustion chamber 18 having a low exhaust gas treatment capacity and a low fuel consumption amount, which is economically advantageous.

FIG. 3 shows the N ₂ O of the fluidized bed boiler of the second invention.
It is a side view showing the outline of the reduction method. The basic configuration is shown in Figure 1.
The method is substantially the same as the method for reducing N ₂ O of the fluidized bed boiler of the first invention shown in FIG. 1, and the same parts as those shown in FIG.

A catalyst 16 capable of treating N ₂ O is provided downstream of the SO ₂ / CO ₂ liquefaction facility 15 of the _second embodiment of the invention.

The configuration other than the above is the same as that of the method for reducing N ₂ O of the fluidized bed boiler of the first invention shown in FIG. 1, and therefore its explanation is omitted.

Next, the operation will be described. The air supplied to the O ₂ separation equipment 14 via the air passage 4 is supplied to the O ₂ separation equipment 1
O ₂ is separated from the air by treatment with 4 and N ₂ is removed by releasing the other into the atmosphere, and the O ₂ is fed into the furnace 1.

The exhaust gas flowing toward the chimney 9 through the flue 10 is replaced with SO ₂ / CO ₂ provided in the middle of the extension of the flue 10.
By the liquefaction facility 15, pressure cooling (for example, a pressure of 2 Kg / cm ^{2) is} applied so that the pressure and temperature conditions shown in FIG.
Below, SO ₂ liquefies at 280 ° K and CO ₂ at 205 ° K.
Liquefies), so that SO ₂ and C
Separated from O ₂ . As a result, the exhaust gas is quantitatively reduced to several percent. By treating the reduced exhaust gas with the catalyst 16, N ₂ O in the exhaust gas is reduced.

According to the, the O ₂ separation equipment 14 provided in the air duct 4 extending設途, as by separating the O ₂ from the air to fed into the furnace 1 may fed the O ₂ to the furnace 1 Having formed, thermal NO to N ₂ in the air is bonded with O ₂ and high temperature
Generation of _x is suppressed, and the amount of exhaust gas can be reduced to about 1/5. Further, since the SO ₂ / CO ₂ liquefaction facility 15 is provided in the middle of the extension of the flue 10 so that the SO ₂ and CO ₂ in the exhaust gas can be liquefied and separated, the exhaust gas amount can be further reduced and the conventional boiler can be used. Since it is only necessary to treat the exhaust gas reduced to a few percent of the exhaust gas amount, it is possible to apply the catalyst 16 having a low exhaust gas treatment capacity and a small amount, which is economically advantageous.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0028]

According to the method for reducing N ₂ O of the fluidized bed boiler of the present invention, various excellent effects as described below can be obtained.

I) An O ₂ separation facility is provided in the middle of the extension of the air duct,
Since O ₂ was separated from the air fed into the furnace and the O ₂ was formed so as to be fed into the furnace, the generation of thermal NO _x , which combines N _{2 in} the air with O ₂ at a high temperature, is generated. It can be suppressed, and the amount of exhaust gas can be reduced to about 1/5.

II) Furthermore, SO ₂ / C is added during the extension of the flue.
Since the O ₂ liquefaction facility is provided so that SO ₂ and CO _{2 in} the exhaust gas can be liquefied and separated, the amount of the exhaust gas can be reduced to several percent. Therefore, in the first invention, the fuel burner is reheated to reheat the exhaust gas. As a result, the amount of fuel consumed is small, and the second invention requires only a small amount of catalyst to be provided according to the amount of exhaust gas that must be treated, and both are economically useful.

[Brief description of drawings]

FIG. 1 is a side view showing an outline of a method for reducing N ₂ O of a fluidized bed boiler of a first invention.

FIG. 2 is a vapor pressure curve diagram of a liquefied gas related to the N ₂ O reduction method of the fluidized bed boiler of FIG.

FIG. 3 is a side view showing an outline of a method for reducing N ₂ O in a fluidized bed boiler of the second invention.

FIG. 4 is a side view schematically showing an example of a conventional fluidized bed boiler.

[Explanation of symbols]

1 Furnace 4 Airway 5 Rear Heat Transfer Section 9 Chimney 10 Flue 12 Gas Recirculation Duct 13 Gas Recirculation Fan 14 O ₂ Separation Equipment 15 SO ₂ / CO ₂ Liquefaction Equipment 16 Catalyst 17 Fuel Burner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoshi Kimura 3-2-16 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Co., Ltd. Toyosu General Office

Claims (2)

[Claims] 1. A fluidized bed boiler comprising a furnace and the heat recovery unit with a fluidized bed, separating the O ₂ in the air fed to the furnace by O ₂ separation equipment, also in the heat recovery area Part of the exhaust gas flowing through the flue connected to the outlet side is recirculated to the furnace, and the remaining exhaust gas is SO ₂ /
CO ₂ liquefaction plant by liquefying separation of SO ₂ and CO ₂ from the exhaust gas by cooling under pressure, the fuel exhaust gas, which is separated and SO ₂ and CO ₂ flowing through the downstream side of the SO ₂ / CO ₂ liquefaction plant A method for reducing N ₂ O in a fluidized bed boiler, which comprises reheating with a burner to convert N ₂ O in exhaust gas into N _{2 and the} like, and then discharging the N ₂ O to the outside. 2. A fluidized bed boiler comprising a furnace and the heat recovery unit with a fluidized bed, separating the O ₂ in the air fed to the furnace by O ₂ separation equipment, also in the heat recovery area Part of the exhaust gas flowing through the flue connected to the outlet side is recirculated to the furnace, and the remaining exhaust gas is SO ₂ /
The SO ₂ and CO ₂ liquefied separated from the exhaust gas by pressurized cooling by CO ₂ liquefaction plant, the catalyst the SO ₂ / CO ₂ liquefaction plant flue gas are separated and SO ₂ and CO ₂ flowing through the downstream side of A method for reducing N ₂ O in a fluidized bed boiler, which comprises converting N ₂ O in the exhaust gas to N ₂ etc. through exhaust gas and then discharging it to the outside.