JPH11200818A - Energy recovering method from exhaust gas and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power generation efficiency by generating preheated air by exchanging heat between exhaust gas and clean air, generating steam by heating a steam turbine condensate by the temperature-dropped exhaust gas, and superheating this steam again by using the preheated air. SOLUTION: An inflammable component is burnt here by sending by inflammable gas component, solid combustibles and the ash content to a melting furnace 2 by partically burning garbage 7 inputted to a gasifying furnace 1 in a reducing atmosphere. Preheated air 8 is generated by heating air 6 by a first heat exchanger 5 by the exhaust gas 4 by completely burning the generated high temperature exhaust gas by a secondary combustion chamber 5. Exhaust gas 9 generates steam 12 in the next place by heating a condensate 10 from a condensate tank 11 by a boiler 13. Electric power is generated by a steam turbine 17 by using this superheated steam 16 by obtaining steam (superheated steam) 16 of 350 to 550 deg.C by superheating this steam 12 again by the preheated air 8 by being introduced to a second heat exchanger 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recovering energy from combustion or incineration residue of flue gas, and more particularly to industrial waste such as municipal solid waste, waste plastic, waste oil, and solidification of garbage. Fuel (Refu
se Derived Fuel (hereinafter referred to as RDF), incineration process of sewage sludge, etc. and treatment process by gasification and melting system, or incineration ash discharged from incinerator, melting process by burning coal, petroleum, etc. or heating by electric energy The present invention relates to a method and an apparatus for recovering energy that can be applied to a computer.

[0002]

2. Description of the Related Art In recent years, a thermal recycling system has been established that not only targets so-called "garbage" such as municipal solid waste, industrial waste, RDF, and sewage sludge but also positions it as an effective energy source. Has been proposed. BACKGROUND ART Conventionally, as a method of recovering energy of high-temperature exhaust gas generated by combustion of refuse or melting treatment of incineration residues, a method of recovering steam with a boiler, back pressure, bleeding, and generating electricity with a condensing turbine has been used. More recently, the following four types of power generation systems have been researched and developed as power generation systems aimed at obtaining electric power with high efficiency in the process of burning solid waste.

(1) As high-efficiency power generation by material development,
This is a method to improve the power generation efficiency by developing incinerators and super heater materials that can withstand corrosive components such as hydrogen chloride generated by burning garbage and raising the steam temperature or pressure. The feature is that the environmental load due to fuel burning other than refuse is small, but the problem is that it is technically and economically difficult to develop materials that can withstand molten salt corrosion.

(2) As a method of generating electricity by RDF, a method of dechlorination and desulfurization by converting garbage into a solidified fuel mixed with lime or the like to raise the steam temperature or pressure is used. Since it is difficult to generate power, these facilities only convert to solid fuel,
Consolidate DF to generate high-efficiency power at large-scale facilities.

(3) As combined power generation with a gas turbine,
A method that uses a high-quality fuel such as natural gas to generate electricity with a gas turbine, and reheats the waste heat from the waste heat boiler with the waste heat of the gas turbine to increase the power generation efficiency of the steam turbine. It is.

(4) As a method of power generation by a fuel reheating method, there is a method in which steam from a refuse power generation boiler is reheated by reheating by using a high quality fuel such as heavy oil to increase the power generation efficiency of a steam turbine. It is considered to be effective in small-scale incineration facilities, but the problem is that high-quality fuel is required separately and the cost is high.

Conventionally, when the surface temperature of a heat transfer tube for heat recovery becomes 400 ° C. or higher due to chlorine gas generated by the combustion of a chlorine-containing polymer such as vinyl chloride in the flue gas of refuse, for example. Corrosion of the heat transfer tube became remarkable, and the superheated steam temperature could not be raised.
This has hindered high-temperature power generation due to high temperatures.
Recently, regarding the corrosion of this heat transfer tube, molten salts attached to the heat transfer tube (such as sodium chloride and potassium chloride in garbage)
Was found to accelerate corrosion, and the superheated steam temperature in conventional waste power generation had to be 300 ° C. or less. For this reason, it is said that in order to put the above-mentioned high-efficiency power generation methods (1) and (2) to practical use, it is necessary to create conditions for avoiding corrosion.

In the above-mentioned power generation systems (3) and (4), which are called super garbage power generation, the exhaust gas at 450 to 700 ° C. is heat-exchanged by a boiler instead of directly raising the temperature of the exhaust gas to generate power. The heat is recovered as steam at around 400 ° C., and the steam temperature is further increased by using the waste heat of the gas turbine or the heat obtained by refueling to perform high-efficiency power generation. In these systems, steam is reheated by the heat of the combustion exhaust gas of a fuel containing almost no molten salt or hydrogen chloride component, so that there is very little concern about corrosion of the heat transfer tubes. However, these systems require additional fuels such as natural gas, coal and petroleum to reheat the steam, and these fuels are costly and reduce the carbon dioxide emissions from the use of fossil fuel resources. There were problems such as an increase or the need for large-scale facilities.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and does not corrode the heat transfer tube of the steam superheater due to the exhaust gas generated from the combustible combustion facility or the incineration residue melting facility, and eliminates the problem of water vapor. Method and apparatus for recovering energy from exhaust gas that can increase power generation efficiency by reheating superheated water vapor from a boiler without the need for natural gas or fossil fuel for reheating and increasing the temperature Is provided.

[0010]

In order to solve the above-mentioned problems, if the steam is reheated using the high-temperature air obtained from the high-temperature exhaust gas by using the high-temperature-compatible heat exchanger according to the present invention,
Generally, it is difficult to raise the temperature to 300 ° C. or more due to corrosion of chlorine or molten salt.
It is possible to overheat. That is, the present invention relates to a method for recovering energy from exhaust gas generated from a combustion facility for combustibles or a melting facility for incineration residues, wherein heat exchange is performed between the exhaust gas and clean air to generate preheated air, and the exhaust gas having a lowered temperature is used for steam. Turbine condensate is heated by a boiler to generate steam at 250 to 450 ° C, and the steam is reheated to 350 to 550 ° C using the preheated air. Then, high-efficiency power generation is performed by the steam turbine using the superheated steam. Things.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the method for recovering energy from exhaust gas of the present invention, in recovering energy from exhaust gas, after exchanging heat between exhaust gas and clean air to generate preheated air, steam turbine condensate is recovered by a boiler using the exhaust gas whose temperature has dropped. The gist is to generate steam by heating, then reheat the generated steam by using the preheated air, and generate electricity with a steam turbine using the reheated steam. Further, the energy recovery apparatus from exhaust gas of the present invention includes a first heat exchanger that exchanges heat between exhaust gas and clean air to generate preheated air, a steam turbine that supplies superheated steam and generates power, Condensate the first
A boiler configured to generate steam at a temperature lower than that of the preheated air by heating the exhaust gas at a lower temperature in a heat exchanger; and a second heat exchanger configured to exchange heat between the preheated air and the steam to generate the superheated steam. The gist is to have

In the present invention, it is desirable to increase the temperature of the superheated steam to 350 to 550 ° C. in order to recover energy from the exhaust gas and improve the power generation efficiency. For that purpose, preheat air for reheating steam is 450 to 7
The temperature of the combustible combustion exhaust gas or the molten exhaust gas of the incineration residue, which is the heat exchange heat source for the preheated air, is desirably 900 to 1200 ° C.

In the above energy recovery method, the equipment for generating exhaust gas is not particularly limited, but it is preferable to use exhaust gas generated by burning combustibles or exhaust gas obtained by melting incineration residues. The equipment that burns such combustible materials and generates exhaust gas may be any equipment that generates exhaust gas at about 900 to 1200 ° C., and is not particularly limited. Such facilities include incinerators (e.g., stoker type and fluidized bed type) that completely burn combustibles, gasify combustibles in a reducing atmosphere, and completely combust the generated combustible gas to melt ash. And a gasification and melting furnace for obtaining slag (for example, a gasification and melting system using a fluidized bed gasification furnace and a rotary melting furnace, a vertical direct gasification and melting furnace, and a kiln-type gasification and melting furnace).

The combustible materials include municipal solid waste, industrial waste such as waste plastic and waste oil, RDF,
Examples include flammable substances such as sewage sludge, coal, petroleum, and flammable gas, or aggregates containing these flammable substances.

As equipment for melting incineration residues and generating exhaust gas, incineration residues can be turned into slag, and 900 to 1
Any equipment that generates exhaust gas at about 200 ° C. may be used, and is not particularly limited. The method of heating the incineration residue to make it slag is not particularly limited, and examples thereof include a heating method using combustion of coal or petroleum or a heating method using electric energy. As a facility for melting incineration residues by such a method, for example, an ash melting furnace (electric heating type, plasma arc type, etc.) for melting incinerated ash discharged from a combustible incinerator to obtain slag Surface melting type, coke bed type) and the like.

A heat exchanger (first heat exchanger) for exchanging exhaust gas with clean air to generate preheated air includes:
A heat exchanger using a material which is not corroded by a combustible combustion exhaust gas containing molten salt or hydrogen chloride or a molten exhaust gas of an incineration residue at a high temperature of about 900 to 1200 ° C., preferably using ceramic beads as a heat medium It is preferable to use a high temperature compatible heat exchanger.

In the heat exchanger (second heat exchanger) for reheating the steam, the preheated air that comes into contact with the heat transfer tube is heated to about 450 to 700 ° C. at a temperature of about 450 to 700 ° C. In order to use clean air containing no, it is not particularly necessary to use a material having corrosion resistance, and it is not particularly limited as long as it is a heat exchanger capable of heat exchange with high efficiency. Steam superheaters are preferred in terms of heat exchange efficiency.

The preheated air after reheating is still 400-700
Since the temperature of ° C is maintained, it can be used as combustion air for a combustion device or the like. If such preheated air is used as combustion air for combustibles, the temperature inside the furnace is stabilized, so that combustion is stabilized, and high-temperature exhaust gas is obtained, facilitating energy recovery. As the clean air used as the combustion air, besides ordinary outside air, oxygen-enriched air in which oxygen has been enriched by existing oxygen generation equipment can also be used. In the combustion using oxygen-enriched air, the temperature of the exhaust gas can be easily raised, so that a high-temperature exhaust gas useful for energy recovery can be easily obtained. In addition, since the amount of exhaust gas after heat exchange also decreases, the load on exhaust gas treatment equipment (appropriate combination of gas cooling equipment, denitration equipment, desulfurization equipment, dust removal equipment, dioxin removal equipment, etc.) can be reduced, and these equipment can be made compact. It is also possible to make it.

The steam turbine for generating power using superheated steam is not particularly limited as long as it is a steam turbine capable of generating power with high efficiency. Although a water turbine is mentioned, a condensing turbine is preferable among them because of its high efficiency.

Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 shows a process chart of the present invention in a gasification and melting furnace for municipal solid waste by a combination of a gasification furnace and a melting furnace. In FIG. 1, the refuse 7 charged into the gasifier 1 is reduced to 4 in a reducing atmosphere (air ratio = 0.2 to 0.4).
Partial combustion is performed at 50 to 700 ° C., and combustible gas components, solid combustibles, ash, and the like are sent to the melting furnace 2. Non-combustible wastes 22 such as aluminum, iron, and glass are removed from the lower part of the gasification furnace 1 to the outside. Is discharged to Combustible components burn at 1200 to 1500 ° C. in the melting furnace 2 (air ratio =
0.6 to 0.8), and the ash is melted and discharged as slag 23. This high-temperature exhaust gas is further completely burned (air ratio = 0.3 or less) in the secondary combustion chamber 3, and 900 to
Exhaust gas 4 at 1200 ° C. is discharged. The exhaust gas 4 becomes exhaust gas 9 whose temperature has dropped to 600 to 900 ° C. in the first heat exchanger 5, while heating the air 6 to 450 to 7
A preheated air 8 of 00 ° C. is generated. The exhaust gas 9 heats the condensate 10 from the condensate tank 11 in the boiler 13 to 250.
After generating steam 12 at ~ 450 ° C., the exhaust gas 19 is processed by an exhaust gas processing device 25 configured by an appropriate combination of, for example, a gas cooling device, a dust removal device, a denitration device, a desulfurization device, and a dioxin removal device, and the processed exhaust gas 19. Is exhausted from the chimney 14 to the outside by the induction blower 21 as exhaust gas 26. The steam 12 is reheated by the preheated air 8 in the second heat exchanger 15 to become steam (superheated steam) 16 at 350 to 550 ° C., and the steam turbine 17 generates electric power to generate electricity 18. On the other hand, the preheated air 8 heat-exchanged in the second heat exchanger 15 is 400 to
It becomes preheated air 20 of 650 ° C., gasification furnace 1, melting furnace 2
And it is supplied to the secondary combustion chamber 3 as combustion air.

FIG. 2 shows a process chart of the present invention in the combustion of municipal waste by an incinerator. In FIG. 2, incinerator 2
The refuse 7 put in 4 is burned in an oxidizing atmosphere,
Further, the combustible components in the exhaust gas are completely burned in the secondary combustion chamber 3. The non-combustible waste 22 and the incineration residue 27 in the refuse 7 are discharged to the outside from the lower part of the incinerator 24 and recycled. 900-1 generated in the secondary combustion chamber 3
The exhaust gas 4 at 200 ° C. is heat-exchanged with the air 6 in the first heat exchanger 5 to become exhaust gas 9 at 600 to 900 ° C. and preheated air 8 at 450 to 700 ° C. which does not contain exhaust gas components.
Exhaust gas 9 is condensed from condensate tank 11 in boiler 13
After heating 0 to generate steam 12 at 250 to 450 ° C., the steam 12 is treated by an exhaust gas treatment device 25 configured by an appropriate combination of, for example, a gas cooling device, a dust removal device, a denitration device, a desulfurization device, and a dioxin removal device. The treated exhaust gas 19 is exhausted to the outside as an exhaust gas 26 from the chimney 14 by the induction blower 21. The water vapor 12 is second
Reheated by the preheated air 8 in the heat exchanger 15,
It is converted into steam (superheated steam) 16 at 550 ° C., and is generated by a steam turbine 17 to generate electricity 18. The preheated air 8 heat-exchanged in the second heat exchanger 15 is 40
It becomes preheated air 20 at 0 to 650 ° C. and is supplied to the incinerator 24 as combustion air.

FIG. 3 shows a process chart of the present invention in the melting treatment of incineration residues such as incineration ash by a surface melting type ash melting furnace. In FIG. 3, the incineration residue (for example, the incineration residue obtained in the incinerator 24) put into the melting furnace 2 27.
Is melted at 1200 to 1500 ° C. by heating by burning the fuel 28 in an oxidizing atmosphere, and is discharged as slag 23 to the outside. On the other hand, in the high temperature exhaust gas, unburned components in the exhaust gas are completely burned in the secondary combustion chamber 3, and the exhaust gas 4 of 900 to 1200 ° C. generated in the secondary combustion chamber 3 is the first exhaust gas.
The heat is exchanged with the air 6 in the heat exchanger 5, and 600 to 90
Exhaust gas 9 at 0 ° C. and 450-7 containing no exhaust gas components
It becomes preheated air 8 of 00 ° C. The exhaust gas 9 heats the condensate 10 from the condensate tank 11 in the boiler 13 to 250-45.
After generating steam 12 at 0 ° C., the exhaust gas 19 is processed by an exhaust gas processing device 25 configured by an appropriate combination of, for example, a gas cooling device, a dust removal device, a denitration device, a desulfurization device, and a dioxin removal device. The air is exhausted from the chimney 14 to the outside as the exhaust gas 26 by the induction blower 21. The steam 12 is reheated by the preheated air 8 in the second heat exchanger 15, becomes steam (superheated steam) 16 at 350 to 550 ° C., generates electricity by the steam turbine 17, and generates electricity 18. The preheated air 8 heat-exchanged in the second heat exchanger 15 is preheated air 20 at 400 to 650 ° C.
And supplied to the melting furnace 2 and the secondary combustion chamber 3 as combustion air.

[0023]

As described above, according to the present invention, in recovering energy from flue gas generated by combustion of combustibles or melting of incineration residues, natural gas or petroleum is used to superheat steam. Energy recovery costs can be reduced because the burning (reheating) of fossil fuels is not required. In addition, the heat exchanger efficiently exchanges heat energy from high-temperature exhaust gas into clean air, and uses this air to reheat steam with the steam superheater. Corrosion can be avoided, the steam can be heated to 350-550 ° C,
It is possible to generate power with high efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing an energy recovery process from waste gasification and melting treatment by a combination of a gasification furnace and a melting furnace, which is an example of the present invention.

FIG. 2 is a diagram showing an energy recovery process from waste incineration by an incinerator as an example of the present invention.

FIG. 3 is a diagram showing an energy recovery process from a melting treatment of incineration residues by a surface melting furnace as an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasifier 2 Melting furnace 3 Secondary combustion chamber 4 Exhaust gas 5 First heat exchanger 6 Air 7 Garbage 8 Preheat air 9 Exhaust gas 10 Condensate 11 Condensate tank 12 Steam 13 Boiler 14 Chimney 15 Second heat exchanger 16 Steam (Superheated steam) 17 Steam turbine 18 Electricity 19 Exhaust gas 20 Preheated air 21 Induced blower 22 Non-combustible waste 23 Slag 24 Incinerator 25 Exhaust gas treatment device 26 Exhaust gas 27 Incineration residue 28 Fuel

 ──────────────────────────────────────────────────の Continuing from the front page (71) Applicant 000001834 Sanki Kogyo Co., Ltd. 1-4-1, Yurakucho, Chiyoda-ku, Tokyo (72) Inventor Satoshi Kawanaka 23 Uji Kozakura, Uji-shi, Kyoto Unitika Research Center Office (72) Inventor Katsuyuki Mukai 23 Uji Kozakura, Uji-city, Kyoto Prefecture Unitika Corporation Central Research Laboratory (72) Inventor Takashi Watanabe 1-112-19 Kitahorie, Nishi-ku, Osaka-shi, Osaka Kurimoto Ironworks Co., Ltd. 72) Inventor Seiichiro Enatsu 4845 Mishima-shi, Shizuoka Toray Engineering Co., Ltd. (72) Inventor Haruo Miyata 1-4-1 Yurakucho, Chiyoda-ku, Tokyo Sanki Kogyo Co., Ltd.

Claims (9)

[Claims] 1. When recovering energy from exhaust gas, heat exchange is performed between the exhaust gas and clean air to generate preheated air, and then the steam turbine condensate is heated by the boiler using the exhaust gas whose temperature has dropped to generate steam. And then reheat the generated steam using the preheated air,
A method for recovering energy from exhaust gas, wherein power is generated by a steam turbine using the reheated steam. 2. When recovering energy from the exhaust gas, heat exchange is performed between the exhaust gas at 900 to 1200 ° C. and clean air to generate preheated air at 450 to 700 ° C.
The steam turbine condensate is heated by a boiler with exhaust gas whose temperature has dropped to 0 to 900 ° C to generate steam at 250 to 450 ° C, and then the generated steam is reheated to 350 to 550 ° C using the preheated air. The method for recovering energy from exhaust gas according to claim 1, wherein power is generated by a steam turbine using the reheated steam. 3. The method for recovering energy from exhaust gas according to claim 1, wherein the exhaust gas is an exhaust gas generated from a combustible combustion facility. 4. The method for recovering energy from exhaust gas according to claim 3, wherein the combustibles are municipal solid waste, industrial waste, solidified waste fuel, sewage sludge, coal, oil, and combustible gas. . 5. The method for recovering energy from exhaust gas according to claim 1, wherein the exhaust gas is an exhaust gas generated from a facility for melting incineration residues. 6. A first heat exchanger for exchanging heat between exhaust gas and clean air to generate preheated air, a steam turbine for supplying electric power by supplying superheated steam, and condensing water from the turbine to the first heat. A boiler that generates steam at a temperature lower than that of the preheated air by heating with exhaust gas cooled at a low temperature in an exchanger, and a second heat exchanger that generates heat of the superheated steam by exchanging heat between the preheated air and the steam. An energy recovery device from exhaust gas, comprising: 7. The apparatus for recovering energy from exhaust gas according to claim 6, wherein the steam turbine is constituted by a condensing turbine. 8. The apparatus for recovering energy from exhaust gas according to claim 6, wherein the first heat exchanger comprises a heat exchanger using ceramic beads as a heat medium. 9. The apparatus for recovering energy from exhaust gas according to claim 6, wherein the second heat exchanger is constituted by a steam superheater.