JP2001212429A - Corrosion component removing method of waste treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing corrosion components in a waste treatment equipment which is capable of easily and efficiency removing the corrosion components produced by waste combustion of chlorine-base plastics, or the like, at a low cost, thereby enabling the higher temperature and higher pressure of a waste heat boiler. SOLUTION: This method for removing the corrosion components in the waste treatment equipment for supplying wastes to a fluidized bed furnace 3, recovering the waste heat of the waste gases generated in this fluidized bed furnace 3 or a combustion melting furnace 4 behind the same with a heat recovering device and removing the corrosion components included in pyrolytic gas consists in removing the corrosion components from the pyrolytic gas by supplying granular CaO reacting with the corrosion components to a fluidized bed to effect the contact reaction of the corrosion components in the pyrolytic gas produced in the fluidized bed with a granular CaO surface layer by utilizing the swirling motion of the fluidized bed and discharging the reacted granular CaO together with fluidized sand out of the fluidized bed furnace 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing corrosive components in a waste treatment facility for introducing heat of exhaust gas generated in the process of burning waste such as municipal waste into a heat recovery device and recovering heat. is there.

[0002]

2. Description of the Related Art Conventionally, a facility for incinerating waste such as municipal waste in a fluidized bed furnace is provided with an exhaust heat recovery device for recovering exhaust gas heat generated by combustion in order to save energy. As the heat recovery device, an air preheater, a heat exchanger, a boiler and the like are prepared.

[0003] Municipal waste contains many components having a relatively high calorific value, such as paper and plastics, and dust is contained in exhaust gas.
A waste heat boiler with a structure in which dust hardly accumulates is used. The high-pressure steam generated by the waste heat boiler is used as a drive source for driving a steam turbine of a generator.

However, when chlorine-based plastic waste such as polyvinyl chloride or rubber is incinerated in the fluidized-bed furnace, highly corrosive HCl (hydrogen chloride) or SO _x (sulfur oxide) is generated. When the exhaust gas containing these HCl and SO _x is introduced into the waste heat boiler, particularly, the HCl chemically reacts with the water pipe and the heat transfer surface of the waste heat boiler in a high temperature state,
Corrosion occurs severely.

As is known, this corrosion has a high temperature dependency and the progress of the corrosion is accelerated as the temperature of the atmosphere increases. Therefore, conventionally, the temperature of the superheated steam of the waste heat boiler is set to about 300 ° C. so that the high temperature corrosion does not proceed. Operation is restricted to the following. Therefore, the efficiency of the steam turbine using the superheated steam generated by the waste heat boiler as a driving source cannot be improved, and as a result, the power generation efficiency of the generator cannot be increased.

Therefore, for example, in the method for removing hydrogen chloride described in Japanese Patent Application Laid-Open No. H11-309338, an HCl-containing gas is passed through a reaction layer filled with granular deHCl reactants, and HCl is passed through the deHCl reactant surface layer. A method has been proposed in which a chloride compound is produced by a contact reaction, and the produced chloride compound is discharged out of the system together with the reacted reagent for removing HCl to remove HCl.

[0007]

In the above-mentioned method for removing hydrogen chloride, granular quicklime having a particle diameter of 2 to 10 mm or the like is charged into a reactor as a dehydrochlorinating agent, and combustion exhaust gas containing HCl is supplied to the reactor. Introduce and contact reaction with granular quicklime,
The HCl reactant generated on the surface of the HCl removing reagent is removed from the HC.
l It is removed outside the system together with the reactant. However, most of the reaction is performed only in the surface layer at a depth of about 0.5 mm from the surface of the granular material, so that the removal efficiency is not continued in a reactor having a limited filling amount. The agent must be removed from the reactor and regenerated so that it can be used for the reaction. Therefore, HC
In addition to providing a 1-removing device, a complicated circulating device for circulating the regenerated HCl-removing agent to the reactor was required, and high cost was unavoidable.

The present invention has been made in consideration of the above-mentioned problems in the desalination method in a waste treatment facility, and can easily and inexpensively reduce corrosive components generated by combustion of waste such as chlorine-based plastics. It is an object of the present invention to provide a method for removing corrosive components in a waste treatment facility, which can efficiently remove the waste heat, thereby making it possible to increase the temperature and pressure of the waste heat boiler.

[0009]

According to a first aspect of the present invention, waste is supplied to a fluidized-bed furnace, and exhaust heat of exhaust gas generated in the fluidized-bed furnace or a subsequent combustion-melting furnace is recovered by a heat recovery device. In a method for removing corrosive components in waste treatment equipment, which collects and removes corrosive components that corrode metals from pyrolysis gas generated in a fluidized-bed furnace, a reactant reacting with the corrosive components flows through a fluidized-bed furnace. The fluidized bed is fed into the bed, and the corrosive components in the pyrolysis gas generated in the fluidized bed are contact-reacted with the reactant surface layer using the swirling motion of the fluidized bed. This is a method for removing corrosive components in a waste treatment facility for removing corrosive components from pyrolysis gas by discharging.

A second aspect of the present invention is a method for removing corrosive components in a waste treatment facility in which corrosive components are removed from a reacted reactant and then circulated and supplied to a fluidized bed.

According to the present invention, the corrosive component is removed by scraping off the surface layer of the reactant, and the corrosive component is removed and the regenerated reactant having a predetermined particle size is discharged. This is a method for removing corrosive components in a waste treatment facility that circulates and supplies sand to a fluidized bed.

A fourth aspect of the present invention is a method for removing corrosive components in a waste treatment facility, in which a corrosive component is removed and then classified to have a predetermined particle size.

A fifth aspect of the present invention is a method for removing corrosive components in a waste treatment facility in which the reactant is a calcium compound and the corrosive components include hydrogen chloride and sulfur oxides.

According to the first aspect of the present invention, when a chlorine-based plastic such as polyvinyl chloride is thermally decomposed in a fluidized-bed furnace and a large amount of corrosive components such as hydrogen chloride are generated, the corrosive component is removed from the fluidized-bed furnace. Reacts with the surface layer of the granular reactant supplied to the substrate and is adsorbed on its surface. Therefore, if the reacted reactant is discharged from the fluidized-bed furnace, the corrosive components accompanying the reactant can be removed.

According to the second aspect of the present invention, the unreacted reactant can be circulated through the fluidized bed and recycled.

According to the third aspect of the present invention, the corrosive component adsorbed on the surface can be separated from the reactant by shaving off the surface layer of the reactant discharged from the fluidized-bed furnace. The reactant from which the corrosive component has been stripped can be recycled for reaction with the corrosive component as long as it satisfies a predetermined particle size. In supplying the regenerated reactant to the fluidized bed furnace, an existing conveyor for circulating fluidized sand in the fluidized bed furnace can be used.

According to the fourth aspect of the present invention, the predetermined particle size can be obtained by performing classification.

According to the fifth aspect of the present invention, the reactant is composed of a calcium compound and can adsorb corrosive components such as hydrogen chloride and sulfur oxide.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows the overall configuration of a waste treatment facility to which the method for removing corrosive components according to the present invention is applied. Note that the waste treatment facility in the present embodiment utilizes a pyrolysis gasification and melting system.

In FIG. 1, waste as waste is temporarily stored in a waste pit 1 and is put into a hopper 1b by a crane 1a. The refuse discharged from the hopper 1b is introduced into a crusher 1c to be crushed finely, and then charged into the fluidized bed furnace 3 at a constant volume by a duster 2.

In the fluidized-bed furnace 3, partial combustion is performed under the condition of an air ratio of 0.2 to 0.4, and low-temperature pyrolysis is performed while maintaining the sand layer temperature at 500 to 600 ° C. All of the input refuse other than incombustibles extracted from the lower part of the hearth are guided to the combustion melting furnace 4 directly connected (to the downstream side) with the fluidized bed furnace 3.

On the other hand, the incombustibles extracted from the lower part of the hearth pass through the screw conveyor 5 and the vibrating feeder 6 and a magnetic separator and an aluminum separator (not shown).
Iron and fluidized sand are separated from each other.
It is returned to the sand layer and reused.

The pyrolysis gas containing ash generated in the fluidized bed furnace 3 is led to the combustion and melting furnace 4 as exhaust gas of the fluidized bed furnace 3,
It is further combusted under the condition of a total air ratio of 1.3. In the combustion melting furnace 4, high-temperature combustion of about 1200 ° C. or more is performed, and ash is melted and separated as slag, and harmful substances in gas such as dioxin are decomposed. Reference numeral 7 denotes a slag discharge device, and reference numeral 8 denotes a slag water conveying device for cooling and solidifying the slag.

The melting furnace exhaust gas discharged from the combustion melting furnace 4 is heat-recovered by a waste heat boiler 9, and the high-temperature, high-pressure steam generated by the waste heat boiler 9 is sent to a steam turbine 10 a, and is supplied to a steam generator 10 b. It becomes the driving force. Also, waste heat boiler 9
The temperature of the exhaust gas sent from the gas cooler 11 is further reduced by the gas cooler 11, and the exhaust gas is removed by the bag filter 12. The purified exhaust gas then passes through an induction fan 13 and a denitration device 14
Through the chimney 15.

FIG. 2 is an enlarged view of the configurations of the fluidized bed furnace 3, the combustion melting furnace 4 and the waste heat boiler 9.

In the figure, a dispersion plate 3a having a number of air injection ports is provided at the bottom of the fluidized bed furnace 3, and a wind box 3b is formed below the dispersion plate 3a. When a fluidizing gas is introduced into the wind box 3b by the forced blower 3c, the dispersion plate 3a
Fluidized air is injected upward through the air injection port of
A fluidized bed B made of sand particles is formed above the dispersion plate 3a. Above the fluidized bed B, a dust inlet 3d and a main burner (not shown) for starting are provided, and a free board 3e is formed above the dust inlet 3d.

A pyrolysis gas discharge port 3f is provided at the furnace top, and a noncombustible substance discharge port 3g for extracting noncombustibles is provided at the lower part of the furnace floor. Of the incombustibles extracted from the lower part of the hearth, fluidized sand is returned to the fluidized bed furnace 3 via the conveyor 3h.

On the other hand, in the combustion melting furnace 4, the pyrolysis gas generated in the fluidized bed furnace 3 flows tangentially into the primary combustion area 4a, is burned while swirling, and the molten ash is collected on the wall and slag is collected. Be transformed into Next, the combustion gas that has passed through the throttle 4b collides with the slag separation portion bottom surface 4c, and collects fine ash to form molten slag. These slags are discharged from the outlet 4d. Note that combustion air is introduced into the primary combustion region 4a from a blower 4e.

When the exhaust gas from the melting furnace introduced into the waste heat boiler 9 passes through the radiant heat transfer surface 9a composed of a membrane wall, the waste gas flows between the water flowing through a plurality of heat transfer tubes arranged vertically. The heat exchange takes place. The waste heat boiler 9 has a superheater 9 for heating the saturated steam to an appropriate temperature.
d, 9c, and a large number of pipes constituting an economizer 9b and the like for preheating the feed water of the waste heat boiler 9 using the residual heat of the combustion gas. In addition, 9e is a steam separator.

In the above configuration, the pyrolysis gas generated in the fluidized-bed furnace 3 passes through the combustion-melting furnace 4, becomes the melting furnace exhaust gas, and flows to the waste heat boiler 9. Since the waste heat boiler 9 is originally assumed to contain dust and corrosive gas, it is made to have a structure in which dust is not easily deposited, and a device such as lowering the gas flow velocity to avoid abrasion of the heat transfer surface is provided. The water pipe is made of a material resistant to corrosion.

However, in the waste treatment facility, the quality of the waste introduced into the fluidized bed furnace 3 is inevitably fluctuated. When a large amount of chlorine-based plastic is introduced, corrosive gas containing corrosive components such as HCl is generated. A large amount is generated and flows to the waste heat boiler 9. Then, the large amount of corrosive gas that has reached the waste heat boiler 9 severely corrodes the water pipe and the heat transfer surface.

In order to solve this problem, the conventional pyrolysis gasification and melting system has a passive corrosion countermeasure that operates while suppressing the superheated steam temperature of the waste heat boiler 9 so as not to accelerate the progress of corrosion. Had been taken.

[0034] In contrast, in the present invention, corrosion components generated in the fluidized bed furnace 3, HCl specifically generated by pyrolysis in a fluidized layer, a gas containing corrosive components such as SO _x,
The particles are positively contact-reacted with granular CaO (quick lime) as a reactant supplied into the fluidized bed to remove them.

That is, in the fluidized bed, the swirling motion is actively performed by the injection of fluidized air, and the granular CaO supplied to the fluidized bed is swirled with the fluidized sand while being dispersed in the fluidized bed by the swirling motion. Exercise. In addition,
As a method of supplying granular CaO, it is sufficient to simply supply the CaO in a lump to the upper part of the fluidized bed.

On the other hand, the waste put into the fluidized bed, for example, chlorine plastic waste, is taken into the fluidized bed by the swirling motion of the fluidized bed and is thermally decomposed in the sand layer maintained at 500 to 600 ° C. Will be HCl generated by thermal decomposition
The gas contacts and reacts with the granular CaO moving in the sand layer in the process of ascending the fluidized bed, and the corrosive component is adsorbed on the granular CaO.

Therefore, the pyrolysis gas discharged from the fluidized-bed furnace 3 has no corrosive components removed, and the waste heat boiler 9
Can prevent the flow of corrosive gas. If it is not necessary to consider the influence of corrosion in the waste heat boiler 9, the waste heat boiler 9 can be set to a high-temperature, high-pressure boiler specification, and as a result, the power generation efficiency of the generator 10b can be increased.

FIG. 3 is a flowchart showing a method for removing a corrosive component according to the present invention.

Referring to FIG.
O is supplied to the fluidized bed furnace 3 (steps S1 and S2). The particle size of the supplied CaO is preferably in the range of 1 to 10 mm. If the particle size is less than 1 mm, it is difficult to classify with the fluidized sand, and if the particle size is more than 10 mm, the reaction efficiency with the corrosive gas decreases.

The supplied particulate CaO is contacted reacted HCl, and SO _x generated from pyrolyzed municipal solid waste in the sand, the reactants are produced granulated CaO surface layer (see the following reaction formula). That is, a reaction product is formed and attached on the surface of the granular CaO as a core, and as a result, the corrosive component is adsorbed on the granular CaO. The granular CaO is
In the process of being supplied to the fluidized-bed furnace 3, the reaction is performed in a state where the particle diameter is slightly reduced. In addition, the above-mentioned granular CaO
Is a non-reacted portion.

CaO + 2HCl → CaCl ₂ + H ₂ O CaO + SO ₂ → CaSO _{3 The} reacted granular CaO is formed by the fact that the hearth of the fluidized-bed furnace 3 is formed in a mortar structure and the swirling motion of the fluidized sand causes the formation of aluminum or the like. Incombustibles outlet 3 with incombustibles and liquid sand
g and is sent to the screw conveyor 5 (see FIG. 1) (step S3).

The reacted granular CaO transported by the screw conveyor 5 together with the fluidized sand and incombustibles is then supplied to the first classifier (steps S4 to S6).

In this first classifier, 10 mm of aluminum or the like is used.
Is sieved and discharged out of the system (step S7).

On the other hand, the incombustible material of 10 mm or less, that is, the incombustible material containing the reacted granular CaO is further subjected to a separation device, and the reaction product adsorbed on the granular CaO is separated and removed (step S8). In addition, trommel etc. can be used as a separation device.

The incombustibles discharged from this separation device include:
Includes granular CaO, silica sand as fluidized sand, and reaction products (including granular CaO whose part of the surface layer has been shaved off) separated by a separation device.

The incombustibles are further sent to a second classifier (steps S9 to S11), where silica sand and granular CaO having a particle size of 0.5 mm or more and pulverized Ca having a particle size of less than 0.5 mm are used.
O and reaction products.

The pulverized CaO of less than 0.5 mm and the reaction products are subjected to an intermediate treatment (prevention of elution of heavy metals) together with the fly ash collected by the exhaust gas treatment device, and then discharged out of the system (step S12). ).

On the other hand, a predetermined particle size, that is, 0.5 mm or more
Granular CaO and silica sand of 0 mm or less are returned into the fluidized-bed furnace 3 via the conveyor 3h, and are recycled (Step S13). As described above, when returning the granular CaO to the fluidized-bed furnace 3, the existing conveyor 3h for returning the silica sand to the fluidized-bed furnace 3 can be used, so that it is not necessary to newly provide a dedicated return path.

Table 1 shows the desalting efficiencies obtained by the above-described methods for removing corrosive components.

[0050]

[Table 1] The reactant of the present invention is the same as the particulate C shown in the above embodiment.
aO is most preferable because it can reduce the cost, but is not limited thereto, and slaked lime Ca (OH) ₂ , calcium carbonate Ca
It can also be composed of a calcium compound such as CO ₃ .

In the above embodiment, the corrosion component is H
Has been described taking the Cl as an example, not limited thereto, it can be removed for corrosive components of the SO _x and the like generated by the combustion of the rubber waste.

[0052]

As is apparent from the above description,
According to the first aspect of the present invention, for example, when a chlorine-based plastic such as polyvinyl chloride is thermally decomposed in a fluidized-bed furnace and a corrosive component such as hydrogen chloride is generated, the corrosive component is supplied to the fluidized-bed furnace. The corrosive component can be removed by reacting the reactant with the surface layer of the reactant and discharging the reacted reactant from the fluidized-bed furnace.

According to the second aspect of the present invention, the unreacted reactant can be circulated through the fluidized bed and recycled.

According to the third aspect of the present invention, the corrosive component adsorbed on the surface can be separated from the reactant by shaving off the surface layer of the reactant discharged from the fluidized bed furnace. The reactant from which the corrosive component has been stripped can be recycled for reaction with the corrosive component as long as it satisfies a predetermined particle size. Further, when supplying the regenerated reactant to the fluidized bed furnace, an existing conveyor for circulating the fluidized sand in the fluidized bed furnace can be used, so it is necessary to newly provide a device for circulating the regenerated reactant. There is no advantage.

According to the fourth aspect of the present invention, the predetermined particle size can be obtained by performing classification.

According to the fifth aspect of the present invention, the reactant is composed of a calcium compound, and can adsorb corrosive components such as hydrogen chloride and sulfur oxide.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a configuration of a waste treatment facility to which a method for removing a corrosive component according to the present invention is applied.

FIG. 2 is an enlarged view of a fluidized bed furnace, a combustion melting furnace, and a waste heat boiler shown in FIG.

FIG. 3 is a flowchart illustrating a corrosion component removing method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 garbage pit 2 dust feeder 3 fluidized bed furnace 3 g incombustible discharge 3 h conveyor 4 combustion and melting furnace 9 waste heat boiler

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23G 5/30 ZAB F23J 1/00 A F23L 15/00 A B01D 53/34 134A 124Z F23J 1/00 B09B 3 / 00 ZAB F23L 15/00 F term (reference) 3K023 QA11 3K061 NA01 NA09 NA14 NA19 4D002 AA02 AA19 AA21 AC04 BA03 BA05 BA13 BA14 BA16 CA09 DA05 DA11 EA02 GA01 GB03 GB12 HA03 HA08 4D004 AA46 AC05 BA02 CA28 CB29

Claims (5)

[Claims] A waste is supplied to a fluidized-bed furnace, and exhaust heat of exhaust gas generated in the fluidized-bed furnace or a subsequent combustion-melting furnace is recovered by a heat recovery device, and heat generated in the fluidized-bed furnace is recovered. In a method for removing a corrosive component in a waste treatment facility for removing a corrosive component that is a component that corrodes a metal from a cracked gas, a reactant reacting with the corrosive component is supplied to a fluidized bed of the fluidized-bed furnace, The corrosive component in the generated pyrolysis gas is brought into contact with the reactant surface layer using the swirling motion of the fluidized bed, and the reacted reactant is discharged from the fluidized bed furnace together with the fluidized sand from the fluidized bed furnace. And removing a corrosive component from the pyrolysis gas. 2. The method for removing corrosive components in a waste treatment facility according to claim 1, wherein the corrosive components are removed from the reacted reactant and then circulated and supplied to the fluidized bed. 3. The corrosive component is removed by scraping off the reactant surface layer, and the reactant regenerated by removing the corrosive component and having a predetermined particle size is removed together with the discharged fluidized sand. 3. The method for removing corrosive components in a waste treatment facility according to claim 1, wherein the corrosive component is circulated and supplied to the fluidized bed. 4. The method for removing corrosive components in a waste treatment facility according to claim 3, wherein after the corrosive components are removed, classification is performed by performing classification. 5. The method for removing corrosive components in a waste treatment facility according to claim 1, wherein said reactant comprises a calcium compound, and said corrosive components include hydrogen chloride and sulfur oxides.