JPH035846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for granulating and supplying a desulfurizing agent such as limestone or dolomite and collected fly ash to a fluidized bed in a fluidized bed boiler.

BACKGROUND ART In a fluidized bed boiler that performs in-furnace desulfurization, limestone, dolomite, etc. (hereinafter simply referred to as limestone) may be used as a desulfurization agent. In a fluidized bed boiler that performs in-furnace desulfurization, the amount of limestone supplied is determined by the limit on the SO ₂ concentration in the exhaust gas and the fuel.

Conventionally, in a fluidized bed boiler, the exhaust gas from the fluidized bed boiler 1 is passed through a cyclone 2 as shown in FIG.
The exhaust gas from the cyclone 2 is introduced into a dust collector 3 such as an electrostatic precipitator, a bag filter, or a sand filter dust collector for secondary dust collection, and then is passed through a chimney 4. A once-through method is generally used. However, this once-through method has poor combustion efficiency and requires a large amount of limestone, so in order to improve combustion efficiency and reduce fresh limestone, the fly ash collected by cyclone 2 is converted into powder as shown in Figure 6. The ash recycling method is adopted in which the ash is circulated and supplied to the fluidized bed as it is, but since the particle size is small and the residence time in the sulfur bed and freeboard is short when it is in powder form, it is possible to significantly improve combustion efficiency and Reduction of fresh limestone requires a large amount of ash recycling. Additionally, in order to burn the unburned carbon in the timer-collected ash, an unburnt carbon combustion fluidized bed furnace (CBC) is installed downstream of the cyclone 2.

Problems to be Solved by the Invention Regarding desulfurization performance in a fixed bed, the smaller the limestone particle size, the higher the desulfurization performance, but in a fluidized bed, if the particle size is reduced, particles below a certain size will scatter. . In a fluidized bed boiler, increasing the residence time of the desulfurizing agent in the fluidized bed increases the desulfurization performance, and also in order to maintain the height of the fluidized bed, reducing the limestone particle size requires a large amount of limestone. For this reason, in fluidized bed boilers, crushed limestone is often used after being cut down to a particle size of 1 to 3 mm. However, there is a problem in that the price of undercut limestone is significantly higher than that of uncut limestone.

On the other hand, fly ash contains CaO, CaCO ₃ , CaSO ₄ ,
It contains SiO ₂ , Al ₂ O ₃ , chia, etc.
It is known that when water is added to fly ash, the following reaction occurs and it hardens.

3caO・3Al ₂ O ₃・CaSO ₄ +6CaO＋8CaSO ₄ +96H ₂ O→3(3CaO
・Al ₂ O ₃・3CaOSO ₄・32H ₂ O) The present invention was made in view of the above points, and involves mixing collected fly ash with limestone, granulating it, and supplying the granulated material to a fluidized bed. The object of the present invention is to provide a method for supplying a desulfurizing agent and fly ash granulation to a fluidized bed boiler, thereby making it possible to reduce fresh limestone and improve combustion efficiency.

Means and Effects for Solving the Problems The method of the present invention will be explained using the numbers shown in FIGS. 1 to 4. The method of the first invention is a method in which exhaust gas from a fluidized bed boiler 1 is introduced into a cyclone 2 for primary dust collection, and exhaust gas from the cyclone 2 is introduced into a dust collector 3 for secondary dust collection. Fly ash consisting of the cyclone 2 and the dust collector 3, or the fine desulfurizing agent and unburned carbon extracted from the cyclone 2, is introduced into the granulating device 5, and granulated by adding the desulfurizing agent in powder form and water. After that, the method of the second invention is characterized by supplying the granulated material to the fluidized bed boiler 1. Fly ash made of carbon or the like is introduced into the granulator 5, while the granular desulfurizing agent is classified in advance into a powdery desulfurizing agent and a granular desulfurizing agent, and the granular desulfurizing agent is directly supplied to the fluidized bed boiler 1.
It is characterized in that the powdered desulfurization agent is added to the granulator 5 together with water and granulated with the fly ash, and then the granulated material is supplied to the fluidized bed boiler 1.

Further, in the method of the third invention, the exhaust gas from the main combustion fluidized bed boiler 8 is introduced into the cyclone 2 for primary dust collection, and the exhaust gas from the cyclone 2 is introduced into the dust collector 3 for secondary dust collection. , a part or all of the fly ash extracted from the cyclone 2 is introduced into an unburned carbon burning fluidized bed furnace 9, and the exhaust gas from the unburned carbon burning fluidized bed furnace 9 is passed through the cyclone for an unburned carbon burning fluidized bed furnace. 10, the cyclone 2, the dust collector 3 and the cyclone 10 for an unburned carbon-burning fluidized bed furnace; Introducing fly ash consisting of fine powder desulfurization agent, unburned carbon, etc. extracted from the cyclone 10 and cyclone 2 for carbon-burning fluidized bed furnaces or the cyclone 10 for unburned carbon-burning fluidized bed furnaces into the granulator 5,
The method of the fourth invention is characterized in that after granulating by adding a powdery desulfurizing agent and water, the granulated material is supplied to the main combustion fluidized bed boiler 8. Cyclone 10 for unburnt carbon combustion fluidized bed furnace, or dust collector 3 and cyclone 10 for unburnt carbon combustion fluidized bed furnace, or cyclone 10 and cyclone 2 for unburnt carbon combustion fluidized bed furnace, or unburned carbon combustion fluidized bed furnace Fine powder desulfurization agent extracted from the cyclone 10,
Fly ash consisting of unburned carbon, etc. is introduced into the granulator 5, and on the other hand, the granular desulfurizing agent is classified in advance into powdered desulfurizing agent and granular desulfurizing agent, and the granular desulfurizing agent is directly transferred to the main combustion fluidized bed boiler 8. The powdered desulfurization agent is added to the granulator 5 together with water and granulated with the fly ash, and then the granules are supplied to the main combustion fluidized bed boiler 8. Note that when the strength of the granulated material is insufficient, a hardening agent such as cement may be added to the granulated material.

Examples Example 1 FIG. 1 shows a case where fly ash and limestone are mixed and granulated, and the granulated material is supplied to a fluidized bed. The exhaust gas from the fluidized bed boiler 1 is introduced into a cyclone 2 for primary dust collection, and the exhaust gas from the cyclone 2 is introduced into a dust collection device 3 such as an electrostatic precipitator, a bag filter, or a sand filter dust collector. Next time, after collecting dust,
In the conventional method of discharging from the chimney 4, fly ash consisting of fine limestone, unburned carbon, etc. extracted from the cyclone 2 and the dust collector 3 is introduced into the granulator 5, and the ash is pulverized into the granulator 5.
For example, after granulating by adding uncut limestone with a grain size of 3 mm or less and water, the granulated product is supplied to the fluidized bed of the fluidized bed boiler 1. Note that part or all of the fly ash collected by the dust collector 3 may be discharged outside the system. If all of the fly ash is discharged outside the system, only the collected fly ash from the cyclone 2 will be supplied to the granulator 5. Furthermore, if the strength of the granules is insufficient, cement or the like may be added as a hardening agent. Reference numeral 6 denotes a fluidized medium overflow pipe, through which the overflowed fluidized medium is introduced into the granulating device 5, where it is mixed with fly ash, limestone, water, and, if necessary, a hardening agent, and granulated. In this case, the overflowing fluid medium acts as a kind of hardening agent.

Example 2 FIG. 2 shows a case where fly ash and part of limestone are mixed and granulated, and the granulated material is supplied to a fluidized bed. Fly ash consisting of fine limestone, unburned carbon, etc. extracted from the cyclone 2 and the dust collector 3 is introduced into the granulator 5. On the other hand, powdered limestone, for example, uncut limestone with a particle size of 3 mm or less, is introduced into a classifier 7 such as a sieve to preliminarily separate powdered limestone (for example, particle size of less than 1 mm) and granular limestone (for example, particle size of 1 to 3 mm). The granular limestone is directly supplied to the fluidized bed of the fluidized bed boiler 1, and the granulated limestone is added to the granulator 5 together with water and granulated with the fly ash. Feed into fluidized bed. Other configurations and operations are the same as in FIG. 1.

Example 3 Figure 3 shows a main combustion fluidized bed boiler (hereinafter referred to as MBC) and an unburnt carbon combustion fluidized bed furnace (hereinafter referred to as
The figure shows a case in which fly ash and limestone are mixed and granulated in a device having a CBC system (CBC), and the granulated material is supplied to a fluidized bed. That is, the exhaust gas from MBC 8 is introduced into cyclone 2 for primary dust collection, and the exhaust gas from cyclone 2 is introduced into an electrostatic precipitator.
After being introduced into a dust collection device 3 such as a bag filter or sand filter dust collector for secondary dust collection, it is released from the chimney 4, and a part of the fly ash extracted from the cyclone 2 is introduced into the CBC9. In the method of introducing the exhaust gas from the cyclone into the cyclone 10 for an unburned carbon combustion fluidized bed furnace (CBC) to collect dust, the pulverized limestone and unburned carbon extracted from the cyclone 2, the dust collector 3 and the cyclone 10 for the CBC. The fly ash consisting of such as It is supplied to the fluidized bed of the combustion fluidized bed boiler 8. In addition, all of the fly ash extracted from Cyclone 2 may be introduced into CBC9.
In this case, the fly ash extracted from the dust collector 3 and the CBC cyclone 10 will be supplied to the granulator 5. In addition, part or all of the fly ash collected by the dust collector 3 may be discharged outside the system, and if all the fly ash is discharged outside the system, the CBC cyclone 10 and the cyclone 2
Cyclone 1 for collecting fly ash or CBC from
The collected fly ash from 0 will be supplied to the granulator 5. Reference numeral 11 denotes a CBC fluid medium overflow pipe, which introduces the overflowing fluid medium into the granulating device 5, where it is mixed with fly ash, limestone, water, and if necessary, a hardening agent, and granulated. in this case,
The overflowing fluid medium acts as a kind of hardening agent. The other configurations and operations are the same as those in FIG. 1.

Example 4 FIG. 4 shows a case where a part of limestone from fly ash is mixed and granulated in an apparatus having MBC and CBC, and the granulated material is supplied to a fluidized bed. Fly ash consisting of fine limestone, unburned carbon, etc. extracted from the cyclone 2, dust collector 3, and CBC cyclone 10 is introduced into the granulator 5.
On the other hand, powdered limestone, for example, uncut limestone with a particle size of 3 mm or less, is introduced into a classifier 7 such as a sieve to preliminarily separate powdered limestone (for example, particle size of less than 1 mm) and granular limestone (for example, particle size of 1 to 3 mm). The granular limestone is directly supplied to the fluidized bed of the main combustion fluidized bed boiler 8, and the powdered limestone is added to the shaping device 5 together with water and granulated with the fly ash. It is fed to the fluidized bed of the bed boiler 8. Other configurations and operations are similar to those in FIG. 3.

Effects of the Invention According to the method of the present invention, since the granulated waste has a longer residence time in the fluidized bed than the powder, combustion efficiency can be improved with a smaller amount than in the case of the powder. Furthermore, by granulating limestone with fly ash, even when the limestone particle size is made into powder with a particle size smaller than the fly ash particle size, the residence time can be extended and the bed height can be maintained. In this way, even small granular limestone can provide a long residence time, so fly ash consisting of fine limestone, unburned carbon, etc. extracted from desulfurization performance is introduced into the granulator 5. on the other hand,
Powdered limestone, for example, uncut limestone with a particle size of 3 mm or less, is introduced into a classifier 7 such as a sieve, and is pre-classified into powdered limestone (for example, particle size of less than 1 mm) and granular limestone (for example, particle size of 1 to 3 mm). Then, the granular limestone is directly supplied to the fluidized bed of the main combustion fluidized bed boiler 8, and the powdered limestone is added to the granulator 5 together with water and granulated with the fly ash. 8 fluidized bed. Other configurations and operations are similar to those in FIG. 3.

Effects of the Invention According to the method of the present invention, since granulated ash has a longer residence time in the fluidized bed than powder, combustion efficiency can be improved with a smaller amount than in the case of powder. Furthermore, by granulating limestone with fly ash, even when the limestone particle size is made into powder with a particle size smaller than the fly ash particle size, the residence time can be extended and the bed height can be maintained. In this way, even limestone with a small particle size can have a long residence time, making it possible to improve _{desulfurization} performance. As a result, it is possible to reduce the amount of fresh limestone, and furthermore, since there is no need to undercut the limestone, excellent effects such as cost reduction can be achieved.

[Brief explanation of the drawing]

Figures 1 to 4 show examples of the present invention, and Figure 1 shows a mixture of fly ash and limestone and granulation.
A flow sheet showing a method of supplying to a fluidized bed (Example 1), Figure 2 is a flow sheet showing a method of mixing fly ash and a portion of limestone, granulating it, and supplying it to a fluidized bed (Example 2) , Figure 3 shows a method of mixing fly ash and limestone, granulating the mixture, and supplying it to a fluidized bed in an apparatus having a main combustion fluidized bed boiler (MBC) and an unburned carbon combustion fluidized bed furnace (CBC) (Example) 3); FIG. 4 is a flow sheet showing a method (Example 4) of mixing and granulating some fly ash and limestone and supplying it to a fluidized bed in an apparatus having MBC and CBC; 5 and 6 show the conventional method, FIG. 5 is a flow sheet showing the once-through method, and FIG. 6 is a flow sheet showing the ash recycling method. 1...Fluidized bed boiler, 2...Cyclone, 3...
...Dust collector, 4...Chimney, 5...Pelletizer, 6
...Fluid medium overflow pipe, 7...Classifier,
8... Main combustion fluidized bed boiler (MBC), 9... Unburned carbon combustion fluidized bed furnace (CBC), 10... Cyclone for unburnt carbon combustion fluidized bed furnace (CBC), 1
1...Fluid medium overflow pipe.

Claims (1)

[Claims] 1. A method in which exhaust gas from a fluidized bed boiler is introduced into a cyclone for primary dust collection, and exhaust gas from the cyclone is introduced into a dust collector for secondary dust collection, the cyclone and the dust collector Alternatively, fly ash consisting of fine desulfurizing agent, unburned carbon, etc. extracted from the cyclone is introduced into a granulator, and after granulation by adding powdered desulfurizing agent and water, the granulated material is placed in a fluidized bed. A method for supplying a desulfurizing agent and fly ash granules to a fluidized bed boiler, the method comprising supplying a desulfurizing agent and fly ash granules to a fluidized bed boiler. 2 In a method in which exhaust gas from a fluidized bed boiler is introduced into a cyclone for primary dust collection, and exhaust gas from the cyclone is introduced into a dust collector for secondary dust collection, the cyclone and dust collector, or the extraction from the cyclone. The fly ash consisting of the fine powder desulfurization agent, unburned carbon, etc. is introduced into the granulation equipment, while
The granular desulfurizing agent is classified in advance into powdered desulfurizing agent and granular desulfurizing agent, the granular desulfurizing agent is directly supplied to the fluidized bed boiler, and the granular desulfurizing agent is added to the granulator together with water to combine with the fly ash. A method for supplying a desulfurizing agent and fly ash granules to a fluidized bed boiler, which comprises supplying the granulated material to a fluidized bed boiler after granulation. 3 The exhaust gas from the main combustion fluidized bed boiler is introduced into a cyclone for primary dust collection, the exhaust gas from the cyclone is introduced into a dust collector for secondary dust collection, and a portion of the fly ash extracted from the cyclone is Alternatively, in a method of introducing the entire unburned carbon-burning fluidized bed furnace into an unburned carbon-burning fluidized bed furnace and introducing the exhaust gas from the unburned carbon-burning fluidized bed furnace into a cyclone for the unburned carbon-burning fluidized bed furnace to collect dust, the cyclone, dust collector and A cyclone for an unburned carbon-burning fluidized bed furnace, or a dust collector and a cyclone for an unburnt carbon-burning fluidized bed furnace, or a cyclone and a cyclone for an unburnt carbon-burning fluidized bed furnace, or a cyclone for an unburnt carbon-burning fluidized bed furnace. The fly ash consisting of the fine powder desulfurization agent and unburned carbon is introduced into the granulator, and after granulation with the addition of powder desulfurization agent and water, the granules are supplied to the main combustion fluidized bed boiler. A method for supplying desulfurization agent and fly ash granulation to a fluidized bed boiler, characterized by: 4 The exhaust gas from the main combustion fluidized bed boiler is introduced into a cyclone for primary dust collection, the exhaust gas from the cyclone is introduced into a dust collector for secondary dust collection, and a portion of the fly ash extracted from the cyclone is Or, in a method of introducing the entire unburned carbon-burning fluidized bed furnace into an unburned carbon-burning fluidized bed furnace, and introducing the exhaust gas from the unburned carbon-burning fluidized bed furnace into a cyclone for the unburned carbon-burning fluidized bed furnace to collect dust, the cyclone, dust collector and A cyclone for an unburned carbon-burning fluidized bed furnace, or a dust collector and a cyclone for an unburnt carbon-burning fluidized bed furnace, or a cyclone and a cyclone for an unburnt carbon-burning fluidized bed furnace, or a cyclone for an unburnt carbon-burning fluidized bed furnace. The fly ash made up of the fine powder desulfurization agent, unburned carbon, etc. is introduced into the granulation equipment, and the powdered desulfurization agent is classified in advance into powdered desulfurization agent and granular desulfurization agent, and the granular desulfurization agent is directly After supplying the main combustion fluidized bed boiler and adding the powdered desulfurization agent together with water to the granulator and granulating it with the fly ash,
A method for supplying a desulfurizing agent and fly ash granules to a fluidized bed boiler, the method comprising supplying granules to a main combustion fluidized bed boiler.