JP2001235101A - High-temperature high-pressure circulating fluidized bed boiler using refuse as fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circulating fluidized boiler which uses refuse as fuel, can generate high-temperature high-pressure steam of >=60 kg/cm2, and can be manufactured inexpensively and the power generating efficiency of which can be improved move without using a special corrosion resistant material or employing a corrosion inhibiling execution method. SOLUTION: This circulating fluidized bed boiler is provided with a combustion chamber section A, a cyclone section B, and a back path section C, generates high-pressure steam of >=60 kg/cm2, and uses refuse as fuel. In the boiler, the whole or partial enclosure of the combustion chamber section A is formed of a membrane wall 1 and the internal surface of the wall 1 is covered with a highly heat-conductive internal insulation. In the loop seal section B2 of the cyclone section B, in addition, either one or both of a steam superheater 21 and a saturated water pipe 21 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating fluidized-bed boiler using municipal solid waste, industrial waste, RDF, sludge, etc. (hereinafter referred to as waste) as a fuel. The present invention relates to a high-temperature and high-pressure circulating fluidized-bed boiler capable of obtaining high-temperature and high-pressure steam of 60 kg / cm ² or more without causing a significant increase in production cost due to adoption of a corrosion prevention method.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional circulating fluidized-bed boiler capable of generating steam at 400 ° and 40 kg / cm ² using waste (RDF) as fuel.
The circulating fluidized bed boiler includes a combustion chamber section A, a cyclone section B, a back pass section C, and the like.

The combustion chamber section A of the circulating fluidized bed boiler has a fluidized combustion section A ₁ and a heat absorption section A _{2. The} outer periphery of the combustion chamber section A is airtight between adjacent water pipes via a fin plate. It is constituted by a so-called membrane wall 1 which is connected in a shape. Furthermore, the flow in the combustion chamber portion A ₁ of the membrane wall 1 and an inner surface of the membrane wall 1 of the heat absorbing portion A ₂ upper unit and furnace material 2 is disposed, the boiler tube (not shown for forming the membrane wall 1 ) And a fin plate (not shown) for connecting and sealing between the boiler tubes are protected. In FIG. 3, the entire outer periphery of the combustion chamber portion A is formed by the membrane wall 1, but the heat absorbing portion A ₂ alone may be used as the membrane wall 1.

[0004] The cyclone section B is composed of a cyclone body B _1.
And includes a loop seal portion B _2, the loop seal portion B _2, the fluidized bed is formed by supplying a fluidized air a _3. Further, the body portion and the like of the cyclone body B ₁ represents is formed by the water tube group, the heat absorption of the combustion gas G is achieved. FIG. 3 shows an example in which a steam of 400 ° C. and 40 kg / cm ² is generated.
In the example where the temperature is high near 00 ° C., the loop seal portion B
₂ is provided with a heating tube (not shown).

The back path section C includes a radiation cooling section C ₁ , a partition wall C _{2, a} gas path section C _{3, and the} like. The outer periphery of the back path section C and the partition wall C ₂ are constituted by the membrane wall 1. I have.

In FIG. 3, F represents fuel (RDF),
a ₁ is primary air, a ₂ is secondary air, G is combustion gas, S is a fluid medium (sand), 3 is a fuel supply port, 4 is a fluid nozzle, 5
Is a bottom drain, 6 is a fluid medium outlet, 7 is a fluid medium return port, 8 is a steam drum, 9 to 11 are headers, and 12 is 1
Secondary superheater, 13 is a secondary superheater, 14 is a bank tube,
15 is an economizer, 16 is a flue, and 16a is an exhaust gas outlet.

[0007] Fuel F is fluidized bed combustion through the fuel supply port 3.
Part A₁Is supplied to the bottom of
Next air a₁Into the so-called thick layer formed in the
A _TwoBurns violently by the supply of. Combustion gas G and dance
The rising fluid medium S, etc._TwoUpper fluid medium guide
It is led out of the outlet 6 to the cyclone section B, where the combustion gas
G and the fluid medium S. Collected fluid medium S
Is the loop seal part B_TwoThrough the fluid medium return port 7
Dynamic combustion section A₁Returned to

The heat absorption from the combustion gas G is
Membrane wall 1, each membrane wall 1 of the back path section C,
Water tube group in cyclone section B, gas path section C_ThreeEach provided in
Superheaters 12, 13 ・ Bank tube 14 ・ Economizer
15 mag. Also discharged from the exhaust gas outlet 16a
Combustion exhaust gas G of about 150 ° to 200 ° C ₀′ Is waste gas
Chimney through a wastewater treatment device and an induction ventilator (not shown)
Released more into the atmosphere.

Incidentally, a large amount of vinyl chloride or sodium chloride (Na) is usually contained in the waste forming the fuel F.
Cl) and the like. As a result, the combustion gas G generated by the combustion has an HCl concentration of 500 to 20 inevitably.
The concentration is as high as about 00 ppm. On the other hand, as is well known, a metal material constituting a boiler exposed to a high-temperature combustion gas having a temperature of about 700 ° C. or more has a metal material temperature of about 330 ° C.
When the temperature exceeds ℃, high-temperature corrosion occurs due to HCl and salts in the dust and the like, and the life of the boiler is not maintained for one year.

That is, according to the corrosion characteristics of the generally used HCl-containing combustion gas, the metal temperature is 150 ° to 3 °.
At 30 ° C., the degree of corrosion becomes relatively low. As a result, for example, in the case of a steam superheater, if the steam temperature is 300 ° C. or lower, the wall temperature of the superheater tube becomes approximately 330 ° C. or lower, and even if a carbon steel superheater is used, severe HCl corrosion occurs. Can be avoided and the life is not significantly shortened. Therefore, in a conventional boiler using waste as a fuel, it is customary to limit the steam temperature to about 300 ° C. or less, and as a result, it is possible to obtain a power generation efficiency of about 10 to 15%. Has become. At present, in a boiler in a municipal solid waste incinerator, 40 kg / cm ² ×
The steam condition at 400 ° C. is the best, and SUS material is used for the superheater tube.

On the other hand, in the circulating fluidized bed boiler shown in FIG.
Cyclone body B₁And fluidized combustion section A ₁Fluid medium between
For the purpose of circulating the seal and the fluid medium in the circulation path of S
Loop seal B composed of fluidized bed_TwoAre formed.
Therefore, this loop seal portion B_TwoHeat exchanger inside
High-temperature steam of 400 ° C or more
Can be obtained. Because the loop seal part B_TwoInside
Has almost no combustion gas G and the HCl concentration is almost zero.
There is almost no dust on the pipe wall
This is because hot corrosion does not occur.

However, in the circulating fluidized bed boiler, the combustion gas G and the fluid medium S are formed on the membrane wall 1 forming the combustion chamber A.
Are brought into direct contact with each other to absorb heat, thereby preventing the temperature of the combustion chamber A from excessively rising. However, the steam conditions 100kg / cm ² · 500
If set ° C. to and in the general specifications of this type of circulating fluidized bed boiler, the boiler water temperature becomes about 320 ° C., as a result, the membrane wall constituting a heat absorbing portion A ₂ of the combustion chamber portion A The water tube temperature of No. 1 is 330 ° C. or higher. In addition, the temperature of the intermediate portion of the fin plate constituting the membrane wall 1 will be higher than the temperature of the water pipe. as a result,
In a commonly used carbon steel, the occurrence of the high-temperature corrosion on the membrane wall 1 becomes unavoidable, and furthermore, abrasion of the fluid medium is added, so that some special corrosion occurs on the membrane wall 1 forming the combustion chamber portion A. Wear prevention measures are required.

[0013] Regarding corrosion, the same applies to the membrane wall 1 forming the back pass portion C. For example, in the general specifications of this type circulating fluidized bed boiler is set to be the temperature of the combustion gas G flowing into the back path portion C to the gas path portion C ₃ to about 650 ° C. or less. Therefore, the radiation cooling unit C ₁ and the partition wall C ₂ provided consisting of the membrane wall 1 to the upstream side of the gas path portion C _3, so as to absorb the heat of the combustion gas G. This is because, even at the same steam temperature, the lower temperature of the combustion gas G is better than the steam superheater 12.1.
It is known from experience that the life of No. 3 is prolonged and the frequency of occurrence of troubles due to high-temperature corrosion is reduced.
However, when the steam condition is set to 100 kg / cm ² · 500 ° C., the radiation cooling portion C ₁ and the like of the back pass portion C are formed as in the case of the membrane wall 1 in the heat absorbing portion A _2. High-temperature corrosion occurs on the membrane wall 1, and a general carbon steel material cannot be used as it is.

As a result, in the conventional circulating fluidized bed boiler shown in FIG. 3, the steam pressure is limited to about 60 kg / cm ² , and it is impossible to further increase the temperature and pressure. . If the steam pressure is about 60 kg / cm ² or less, the temperature of the still water is about 285 ° C., and therefore the temperature of the fin never exceeds 320 ° C. As a result, 700 ° C
This is because remarkable high-temperature corrosion does not occur even in the high-temperature combustion gas G described above.

In the conventional circulating fluidized-bed boiler shown in FIG. 3, the membrane wall 1 is made of a special corrosion-resistant steel, or a protective film formed by thermal spraying is used.
The steam condition can be set to 60 kg / cm ² · 400 ° C. or higher. However, in this case, there is a problem that a long life cannot be obtained even though the manufacturing cost of the boiler is greatly increased. In particular, there is a problem that the life cannot be predicted in a combustion chamber in which corrosion and wear progress.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional circulating fluidized-bed boiler, that is, when the steam pressure is set to about 60 kg / cm ² or more, the boiler can water temperature is reduced. At about 285 ° C. or higher, high-temperature corrosion of the membrane wall 1 forming the heat absorbing portion A ₂ of the combustion chamber portion A and the membrane wall 1 forming the back pass portion C becomes unavoidable. As a result, the power generation efficiency due to the high temperature and high pressure of steam If the steam cannot be significantly improved, and if high-temperature, high-pressure steam is applied by using corrosion-resistant materials or special methods to prevent corrosion, not only will the boiler production costs rise, but also the service life will increase. steam but is intended to St. resolve extremely short that such problems, the inside surface of the membrane wall 1 to form the combustion chamber a is covered with a thin protective furnace material having high thermal conductivity, in the loop seal portion B ₂ Superheater or saturation Such as by installing a heat exchanger such as a tube, or use a special corrosion resistance steel, without performing special protective measures thermal spraying the membrane wall 1
An object of the present invention is to provide a high-temperature and high-pressure circulating fluidized-bed boiler using waste as a fuel, which can produce high-temperature and high-pressure steam of about 00 kg / cm ² · 500 ° C.

[0017]

According to the first aspect of the present invention, there is provided a high-temperature high-pressure high-pressure fuel comprising a combustion chamber section A, a cyclone section B, and a back path section C, and having a steam pressure of 60 kg / cm ² or more. In the circulating fluidized-bed boiler, the whole or a part of the outer periphery of the combustion chamber portion A is formed by the membrane wall 1 and the inner surface thereof is covered with a highly heat-conductive furnace material, and the loop seal of the cyclone portion B is formed. it is obtained by a configuration in which either one or both of the steam superheater 21 and the saturated water pipe 21 in part B _2.

According to a second aspect of the present invention, in the first aspect of the present invention, a recirculation exhaust gas supply port 19 is provided in the combustion chamber section A, and the exhaust gas treatment equipment is installed downstream of the exhaust gas outlet 27 of the back path section C. the recirculated exhaust gas G ₀ which branches from the outlet duct by supplying to the recirculated exhaust gas supply port 19, reduces the need endotherm in the combustion chamber, preventing an increase in the size of the combustion chamber,
The combustion temperature of the combustion chamber C is adjusted.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the inner surface of the membrane wall 1 of the combustion chamber is thinned to a thickness of 60 mm or less using a furnace material having good heat conductivity such as silicon carbide. It is constructed as a layer to protect the membrane wall surface and secure heat absorption in the combustion chamber.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the back path portion C is used as a back path portion C of a furnace construction structure and the inside of the back path portion C is provided. An economizer is arranged before and after the steam superheater.

According to a fifth aspect of the present invention, in the first, second or third aspect of the present invention, the back path portion C is formed by forming an outer enclosure with the membrane wall 1 and forming an inner surface thereof with a high heat transfer property. a radiative cooling section C ₁ of the structure covered with furnace material, formed from the gas path portion C ₃ Metropolitan of furnace structure which communicates with the radiation cooling unit C _1, economizer before and after the steam superheater in the gas path portion C ₃ Is arranged.

According to a sixth aspect of the present invention, in the first, second, third, fourth or fifth aspect of the present invention, the superheater is heated by the primary steam superheater 12 and the secondary steam superheater 13. after it was allowed to decrease in desuperheater 26 the steam is obtained by the arrangement of overheating by tertiary steam superheater 21 provided in the loop seal portion B _2.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG. 2 is a block diagram showing a second embodiment of the present invention. In FIGS. 1 and 2,
The same members as those of the conventional circulating fluidized bed boiler shown in FIG. 3 are denoted by the same reference numerals.

In FIGS. 1 and 2, A is a combustion chamber, B is
Is a cyclone section, C is a back pass section, and the second section in FIG.
In the embodiment, the configuration of the back path unit C is slightly different from that of the first embodiment of FIG.

[0025] The combustion chamber A is configured from the fluidized combustion section A ₁ and the heat absorbing portion A _2, and is formed into a box shape (or cylindrical). The outer enclosure of the combustion chamber portion A is formed by a so-called membrane wall 1 having a structure in which water pipes are connected in a gastight manner by welding with a fin plate.

Further, the inner surface of the membrane wall 1 to form the heat absorbing portion A ₂ is a furnace material 2a of a relatively thin, highly thermally conductive having a thickness of about 20 to 50 mm (e.g., silicon carbide SiC, etc.) its entire surface covered Have been done. That is, the thin furnace material 2a
Is provided by a so-called stud construction method in which a number of short studs are planted on the inner surface of the membrane wall 1 and a furnace material is applied thereto and fixed.
To prevent hot gas corrosion caused by HCl or the like due to the direct contact of the combustion gas G with the inner surface of the substrate.

Further, the inner surface of the fluidized combustion part A ₁ (the bottom part of the combustion chamber part A) is worn by the fluidized medium S flowing down along the wall surface and maintains the temperature of the fluidized bed (at a temperature of at least 850 ° C. From the viewpoint of (for more than one second), the entire surface is covered with a furnace material 2b composed of a relatively thick precaster block or caster.

[0028] Note that at 1, although the entire outer enclosure of the combustion chamber portion A constituted by the membrane walls 1, only a portion of the heat absorbing portion A ₂ which has been subjected to so-called stud construction with the membrane walls 1, Those who fluidized combustion section a ₁ without the water pipe circumference, it is also possible to adopt a configuration which is disposed a furnace material on an inner surface side of the conventional iron plate circumference. The combustion chamber section A has a fuel supply port 3, a flow nozzle 4, a bottom drain discharge port 5, a fluid medium outlet port 6, a fluid medium return port 7, a steam drum 8, a header 9a, 9
b, 9c, primary air supply port 17, secondary air supply port 18,
Recirculated exhaust gas supply ports 19a and 19b are provided respectively.

[0029] at the recirculating exhaust gas supply port 19a · 19b are respectively provided on the lower portion of the lower portion and the heat absorbing portion A ₂ fluidized combustion section A _1, on the downstream side for example exhaust gas treatment system outlet of the back path portion C The amount of the combustion exhaust gas G ₀ ′ which has been branched and suctioned is appropriately supplied to the furnace as the recirculated exhaust gas G ₀ , so that the temperature of the combustion gas G flowing out from the upper portion of the heat absorbing portion A ₂ is reduced by about 90 °.
The temperature is adjusted to 0 ° C or less. That is, when the heat of the combustion gas G is absorbed through the furnace material 2a provided by the stud construction, the heat absorbing property is slightly reduced due to the heat conduction resistance of the furnace material 2b. Therefore, in order to maintain the combustion temperature at about 900 ° C., the height of the combustion chamber A must be increased to increase the heat transfer surface, and in order to prevent the elongation of the height, the recirculated exhaust gas having a temperature of about 180 ° C. G ₀ is supplied into the combustion chamber A. In FIG. 1, the exhaust gas is recirculated in an amount of about 5 to 30% during the steady operation of the boiler as described later.

The cyclone section B is a cyclone body B ₁
It is formed from the loop seal portion B ₂ Prefecture and. Further, the outer wall of the cyclone body B ₁ represents the example of FIG. 1 is formed with the same structure and the membrane wall, the inner surface of the high thermal conductivity of the furnace material having a heat resistance and abrasion resistance (e.g., S
Although the coating is protected by iC or the like, the coating may be partially formed into a membrane structure or a structure in which a furnace material is provided on the inner surface side of a normal steel plate enclosure. Moreover, the the loop seal portion B _2, the are from the bottom is supplied flow air a _3, whereby the fluid medium S in the loop seal portion B ₂ forms a so-called fluidized bed.

[0031] Inside of the loop seal portion B _2, is provided with a heat exchanger such as a saturated water pipe 20 and the tertiary steam superheater 21, the heat of the fluidized medium S In the loop seal portion B ₂ by absorbing, or lower the stature of the combustion chamber a, or so as to reduce the amount of low-temperature recirculated exhaust gas G _0. Either one or both of the tertiary steam superheater 21 and the saturated water pipe 20 are provided depending on heat balance.

The back path portion C is formed in a tubular shape by a so-called furnace construction structure, and since the outer enclosure is not a membrane wall structure, there is no need to take measures against high-temperature corrosion such as thermal spraying or using a high-grade material having corrosion resistance. . In the backpass part C,
Secondary economizer 2 in order from the inlet side of high-temperature combustion gas G
2, first bank tube 23, primary steam superheater 12, 2
A secondary steam superheater 13, a second bank tube 24, and a primary economizer 25 are provided, respectively, and the heat of the combustion gas G is sequentially absorbed by contact heat transfer or the like.

That is, the boiler feed water W ₀ is supplied to the steam drum 8 through the primary economizer 25 and the secondary economizer 22. The steam generated from the steam drum 8 is supplied to the primary steam superheater 12, the secondary steam superheater 13, the desuperheaters 26, 3
About 100 kg / cm ² · 50 through the secondary steam superheater 21
The high-temperature high-pressure steam St at 0 ° C. is supplied to a steam turbine (not shown). The desuperheater 26 is a tertiary steam superheater 2
The temperature of the superheated steam from the secondary steam superheater 13 is adjusted so that the outlet steam temperature of No. 1 becomes the planned temperature.

The secondary economizer 22 reduces the temperature of the high-temperature combustion gas G at about 800 ° C. to about 650 ° C. or less. Boiler feed water W at the exit of the secondary economizer 22
_Since the temperature of ₀ is about 300 ° C, the secondary economizer 2
The tube wall temperature of the heat exchange tube 2 is kept at about 320 ° C. or lower, and therefore, even in the high temperature combustion gas G at 800 ° C., remarkable high temperature corrosion does not occur.

The first bank tube (boiler evaporation tube)
The 23 and the second bank tubes 24 are provided to balance the heat absorption, thereby compensating for the shortage of the heat absorption required for the saturated steam, and preventing the so-called evaporation eco in the economizer. The first bank tube 23 is made of carbon steel provided with a thermal spray protective layer, and the second bank tube 24 is made of stainless steel, but any type may be used. Of course. Further, carbon steel may be used as an easily replaceable structure. The method of providing a thermal spray protective layer on carbon steel is easier to construct than a conventional method of providing a thermal spray protective layer on the membrane wall, has no fins, has a longer life, and reduces repair costs and corrosion countermeasure costs. Becomes possible. In addition, whether or not to install the two bank tubes 23 and 24 is determined by the calorific value of the waste fuel F to be burned, and in the case of the fuel F with a small calorific value, such installation is omitted.

The primary steam superheater 12 and the secondary steam superheater 13 are the same as those used in the conventional boiler, and the combustion gas G at about 620 ° C. is used for the secondary steam superheater. The temperature at the outlet 13 is about 500 ° C. The heat exchange tube of the secondary economizer 25 is made of carbon steel,
The boiler feed water W _{O at} about 200 ° C is heated to about 300 ° C.

FIG. 2 shows a second embodiment of the present invention, in which only the back path section C is different from the case of the first embodiment of FIG. That is, in the second embodiment, the back pass portion C is formed by the radiant cooling portion C ₁ and the gas pass portion C ₃ , and in the radiant cooling portion C ₁ from about 800 ° C. to about 6 ° C.
50 ° to 700 ° C. to cool the combustion gas flows into the gas path portion C _3. Therefore, the bank tube 23 at the inlet of the superheater in the gas flow direction in FIG. 1 is not required, and the exhaust gas temperature is reduced to about 620 ° C. only by the secondary economizer.

The radiant cooling part C ₁ has an entire outer wall formed by a membrane wall 1, and an inner surface of the membrane wall 1 is formed by a thin heat-resistant and high-heat-conducting furnace material 2 a (for example, SiC). It is covered to prevent direct contact of the combustion gas G having a high HCl concentration, thereby suppressing the occurrence of corrosion.

The gas path section C ₃ is formed in a tubular shape by a so-called furnace construction, and a secondary economizer 22, a primary steam superheater 12, a secondary steam superheater 13, and a bank tube 14 are arranged inside the gas path section C _3. Has been established. Reference numeral 25 denotes a secondary economizer, which is provided in the exhaust gas flue 16. Reference numeral 28 denotes a dust discharge conveyor.

In the second embodiment shown in FIG. 2, the temperature of the combustion gas G is reduced to 65 by the heat absorption in the radiation cooling section C _1.
0 ° to 700 ° C., and then the secondary economizer 22
By reducing the temperature to about 620 ° C.
The bank tube is omitted. Note that the secondary economizer 22 is made of carbon steel for the same reason as in the first embodiment, but the combustion gas temperature at the inlet side is 6 mm.
Since the temperature is further reduced to 50 ° to 700 ° C., occurrence of high-temperature corrosion due to HCl or the like is further reduced.

Next, the operation of the circulating fluidized-bed boiler according to the present invention when generating high-temperature and high-pressure steam at about 500 ° C. and about 100 kg / cm ² will be described. Referring to FIG. 1, R having a low calorific value of 3700 kcal / kg as a fuel
DF fuel F is supplied at a rate of 100 tons / day to perform so-called fluidized bed combustion (total heat input: 15.42 million kcal /
h). The outer dimensions of the combustion chamber A are about 3000 mmW x
3000 mmL x 20,000 mmH (height),
The external dimensions of the back path section C are about 3800 mmW x 3
It is 800 mmL x 20,000 mmH (height).

[0042] The combustion of the RDF fuel allows the boiler to operate normally.
The combustion gas temperature in the combustion chamber A during the rotation is about 870 °
~ 900 ° C and about 880 ° C from the fluid medium outlet 6
Combustion gas G (about 43,000 Nm^Three/ H ・ Exhaust gas recirculation
The mixture of the fluid medium (sand) S with the cyclone
It is derived to the unit B. In addition, 1 during steady operation of the boiler
Next air a₁Is about 20,000Nm ^Three/ H (temperature
About 30 ° C) and secondary air a_TwoSupply amount of 12,0
00Nm^Three/ H (temperature about 30 ° C) and recirculated exhaust gas
Sus G₀Supply amount of 72,000Nm ^Three/ H (recirculation rate 2
0% and a temperature of about 180 ° C.).

The fluid medium S separated in the cyclone section B is cooled down by about 50 to 100 ° C. in the cyclone body B ₁ ,
It falls to the loop seal portion B _2. Further, the sand S that has fallen into the loop seal portion B ₂ is now flowing is fluidized by supplying air a _3, saturated water pipe 20 between them and tertiary steam superheater 2
After being cooled by 1, it returned from the fluidized medium return port 7 to the fluidized combustion unit A _2.

The combustion gas G cooled to about 800 ° C. in the cyclone section B is introduced into the back pass section C, where it is cooled to about 620 ° C. by the secondary economizer 22 and the first bank tube 23. Then, it is cooled to about 500 ° C. by the primary steam superheater 12 and the secondary steam superheater 13. Thereafter, the flue gas G ₀ ′ is separated by the second bank tube 24 and the primary economizer 25 from about 230 ° to 25 °.
After being cooled to 0 ° C., the waste gas is sent from an exhaust gas outlet 27 to a waste gas treatment device (not shown), purified, and then discharged to the atmosphere via an induction ventilator and a chimney (not shown).

Boiler feed water W ₀ is about 140 ° C. to 150 ° C.
Is supplied to the primary economizer 25, and 200 ° to 220 °.
C. and then into the secondary economizer 22 where it is heated to about 290-300.degree.
Supplied to The saturated steam from the steam drum 8 is
The primary steam superheater 12 and the secondary steam superheater 13 are superheated to about 400 ° C. Thereafter, the temperature is adjusted by the desuperheater 26, and then introduced into the tertiary steam superheater 21, where it is superheated to about 500 ° C. to obtain about 100 kg / cm.
High temperature and high pressure steam St of ² · 500 ° C. and supplied to a steam turbine (not shown).

[0046]

According to the present invention, the inner surface of the membrane wall 1 forming the combustion chamber portion A is protected by a relatively thin layered furnace material having good heat conductivity. As a result, by setting the steam condition to a high pressure and a high temperature of about 100 kg / cm ² · 500 ° C., even if the boiler can water temperature becomes a high temperature of about 310 ° to 320 ° C., the combustion gas having a high HCl concentration remains on the membrane wall 1. Intense high-temperature corrosion due to the synergistic action of G and dust does not occur, and the useful life of the membrane wall 1 can be greatly extended.

Further, by forming a protective layer on the inner surface of the membrane wall 1, the heat absorption of the membrane wall 1 is slightly reduced. As a result, the temperature of the combustion chamber A tends to increase. However, since you are configured to absorb heat of the loop seal portion B ₂ in a saturated water pipe 20 and the tertiary steam superheater 21 is provided fluid medium S in the cyclone part B, the temperature of the combustion chamber portion A is about 850 ° ~ The temperature is maintained at 900 ° C., and the combustion chamber can be prevented from being enlarged.

In the present invention, a surplus heat amount when the calorific value of the waste fuel F is high due to recirculation of exhaust gas is taken out to reduce the amount of heat absorbed in the combustion chamber A. Therefore, by adjusting the amount of the recirculated exhaust gas G ₀ , the temperature in the combustion chamber A can be maintained at 850 to 900 ° C., and the combustion chamber A can be effectively prevented from being extremely large.

By performing exhaust gas recirculation,
Even when the boiler load is 50% or less, the temperature in the combustion chamber A is kept at 850 ° C. or more for 2 seconds or more by reducing the exhaust gas recirculation amount without operating the auxiliary combustion equipment. Can be maintained, and compliance with the guidelines for dioxin reduction can be achieved even at low loads.

In the present invention, the secondary economizer 22 is provided in the high temperature combustion gas G at about 800 ° C., and the temperature of the combustion gas G is cooled to 620 ° to 650 ° C. As a result, the primary steam superheater 12 and the secondary steam superheater 1
The high temperature corrosion generated in carbon steel 3 is relatively small even with carbon steel, and the boiler life can be greatly extended. Further, the temperature of the secondary economizer 22 boiler feedwater W ₀ of the exit is about 290 ° to 300 ° C., as a result, the tube wall temperature is about 3
It is kept below 20 ° C. Therefore, even if the secondary economizer 22 is installed in the high-temperature combustion gas G at about 800 ° C., severe high-temperature corrosion does not occur, and a long-life operation is possible.

In the present invention, the inner surface of the membrane wall 1 of the radiant cooling section C _{1 in} the combustion chamber section A and the back pass section is
A so-called stud method is used to cover with a relatively thin layer of high heat conductive furnace material. As a result, the protective layer of the membrane wall 1 can be formed relatively inexpensively and efficiently, and the heat absorption performance can be reduced only slightly. As a result, the protection layer can be formed more economically than in the case of protection using a conventional caster or the like, and the size of the combustion chamber portion A can be effectively suppressed. The present invention has excellent practical utility as described above.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a circulating fluidized-bed boiler according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of a circulating fluidized-bed boiler according to the present invention.

FIG. 3 is a block diagram showing an outline of a conventional circulating fluidized-bed boiler using waste as fuel.

[Explanation of symbols]

a ₁ is the primary air, a ₂ the secondary air, a ₃ fluidized air, F
Is RDF fuel, G is combustion gas, S is fluid medium (sand), G
₀ is recirculated exhaust gas, W ₀ is boiler feed water, St is high-temperature and high-pressure steam, A is a combustion chamber, A ₁ is a fluidized combustion section, A ₂ is a heat absorbing section, B is a cyclone section, B ₁ is a cyclone body, B ₂ Is a loop seal portion, C is a back pass portion, C ₁ is a radiation cooling portion, C ₂ is a partition wall, C ₃ is a gas pass portion, 1 is a membrane wall, 2 is a furnace material, 3 is a fuel supply port, 4 is a flow nozzle. 5 is a bottle drain outlet, 6 is a fluid medium outlet, 7 is a fluid medium return port, 8 is an upper steam drum, 9 to 11 are headers, 12 is a primary steam superheater, and 13 is a secondary steam superheater. , 1
4 is a bank tube, 15 is an economizer, 16 is a flue, 16a is an exhaust gas outlet, 17 is a primary air supply port, 18
Is a secondary air supply port, 19 is a recirculation exhaust gas supply port, 20 is a saturated water pipe, 21 is a tertiary steam superheater, 22 is a secondary economizer, 23 is a first bank tube, 24 is a second bank tube, and 25 is Primary economizer, 26 is a cooler, 27
Is an exhaust gas outlet at the back path, and 28 is a dust discharge conveyor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Saiga 2-2-233 Kinrakuji-cho, Amagasaki-shi, Hyogo Inside of Takuma Co., Ltd. (72) Inventor Kazuo Taniguchi 2-2-233, Kinraku-cho, Amagasaki-shi, Hyogo Takuma Corporation

Claims (6)

[Claims] 1. A high-temperature and high-pressure circulating fluidized-bed boiler provided with a combustion chamber, a cyclone, and a backpass and having a fuel pressure of 60 kg / cm ² or more as a fuel and having a high vapor pressure, outside the combustion chamber. All or part of the enclosure is formed by a membrane wall and the inner surface thereof is covered with a highly heat-conductive furnace material, and one or both of a steam superheater and a saturated water pipe are provided in a loop seal section below the cyclone section. A high-temperature and high-pressure circulating fluidized-bed boiler using waste as fuel, wherein the boiler is configured to be provided. 2. A recirculation exhaust gas supply port is provided in a combustion chamber portion,
The waste according to claim 1, wherein the combustion temperature of the combustion chamber is adjusted by supplying recirculated exhaust gas branched at an exhaust gas treatment facility outlet downstream of a back path section to the recirculated exhaust gas supply port. A high-temperature, high-pressure circulating fluidized-bed boiler that uses fuel. 3. The fuel according to claim 1, wherein the inner surface of the membrane wall of the combustion chamber is covered with a thin layered furnace material made of silicon carbide formed by a stud method. High temperature and high pressure circulating fluidized bed boiler. 4. A backpass portion having a furnace construction structure, wherein an economizer is provided before and after a steam superheater in the backpass portion. A high-temperature, high-pressure circulating fluidized-bed boiler using the waste described in 1 above as a fuel. 5. A radiant cooling portion having a back path portion in which an outer enclosure is formed by a membrane wall and an inner surface thereof is covered with a furnace material having high heat conductivity, and a furnace construction structure communicating with the radiant cooling portion. 4. A high-temperature and high-pressure circulating fluidized bed using waste as a fuel according to claim 1, wherein the gas path is formed from a gas path, and an economizer is disposed before and after the steam superheater in the gas path. boiler. 6. A structure in which the steam superheated by the primary steam superheater and the secondary steam superheater is cooled by a desuperheater and then superheated by a tertiary steam superheater provided in the loop seal portion. A high-temperature and high-pressure circulating fluidized-bed boiler using waste as a fuel according to any one of claims 1, 2, 3, 4, and 5.