JP2001280863A - Heat exchanger and electric power generator comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger which is not corroded by corrosive components contained in refuse or combustion exhaust gas of fuel and producing high temperature high pressure vapor, and an electric power generator performing high efficiency power generation using vapor heated by means of the heat exchanger. SOLUTION: An inner heat transfer tube 21 is contained in an outer heat transfer tube 20 touching combustion exhaust gas and the space between the outer heat transfer tube 20 and the inner heat transfer tube 21 is filled with heating medium. The heating medium is air, nitrogen gas, or a powdery solid. The outer heat transfer tube 20 is made of heat resistant cast steel, ceramics or heat resistant metal. Temperature of combustion exhaust gas is set at 1000 deg.C-1300 deg.C and temperature on the face of the outer heat transfer tube 20 touching combustion exhaust gas is set at 700 deg.C or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for obtaining high-temperature and high-pressure steam using high-temperature exhaust gas generated when various wastes and fuels are burned or gasified, and heated by the heat exchanger. The present invention relates to a power generation device that generates power using steam.

[0002]

2. Description of the Related Art As a method of utilizing thermal energy generated when various kinds of wastes and fuels are burned for power generation, combustion heat is recovered as steam in a waste heat boiler and then supplied to a steam turbine to generate power. The method is generally adopted. FIG. 14 shows an example of a conventional waste combustion power generation system according to such a method.

In a conventional waste combustion power generation system, waste is burned in an incinerator (or gasification and melting furnace) 11, and the combustion exhaust gas is heat-exchanged in a waste heat boiler 13 to recover superheated steam. The superheated steam obtained by the waste heat boiler 13 is supplied to a steam turbine 14 and power is generated by a generator directly connected to the steam turbine 14. Electric power obtained by the power generation is consumed in the waste incineration plant and sold to a power company. The combustion exhaust gas that has passed through the waste heat boiler 13 passes through a preheater 15 such as an air preheater or an economizer, and a dust removal device 16 such as a bag filter, and is discharged into the atmosphere from a chimney as clean exhaust gas.

[0004] The power generation efficiency of such steam turbine power generation largely depends on the temperature of the superheated steam supplied to the steam turbine, and the higher the steam temperature, the higher the power generation efficiency. However, in the conventional waste combustion power generation system, the limit of the steam temperature obtained by heat exchange is about 400 ° C., and as a result, the power generation efficiency is only about 20%. The reason why the steam temperature cannot be raised to 400 ° C. or more is that corrosive gas such as HCl generated by combustion of waste and NaC
This is because the heat transfer tube of the heat exchanger is corroded by a molten salt such as 1, KCl. The mechanism of this corrosion is complex and is thought to be caused by various factors overlapping. In addition, as a cause of corrosion, NaCl, KCl, and the like are larger than HCl, and the heat transfer tubes are corroded at an accelerated rate due to the melting and attachment of the salts to the heat transfer tubes. Hereinafter, the relationship between the corrosion and the steam temperature will be described.

[0005] Fig. 15 shows the corrosion pattern on the surface of the metal heat transfer tube using the combustion exhaust gas temperature and the heat transfer tube surface temperature as parameters, as estimated from a corrosion test using a municipal solid waste incinerator. As shown in the figure, there are four corrosion regions, namely, a "severe corrosion region", a "corrosion progress region", a "corrosion reduction region", and a "non-corrosion region" according to the combustion exhaust gas temperature and the heat transfer tube surface temperature. Normally, the surface temperature of the heat transfer tube is about 30 degrees higher than the superheated steam temperature.
° C, the superheated steam temperature in the heat transfer tube is 400
In the case of ° C., the heat transfer tube surface temperature becomes 430 ° C., which is about 30 ° C. higher than the internal steam temperature. At this time, from FIG. 15, the vicinity of the combustion exhaust gas temperature of 600 ° C. is a boundary between the “corrosion progressing region” and the “corrosion reducing region” or the “non-corrosive region”.

[0006] This is because when the temperature of the combustion exhaust gas entering the boiler bank portion (portion where evaporating water pipes are densely packed) of the waste heat boiler of the municipal solid waste incinerator is 600 ° C or more,
This is consistent with the phenomenon that the salts adhere to the heat transfer tubes and block the exhaust gas passage. That is, it is considered that the boundary between the state in which the salt is molten and the state in which the salt is solidified is around 600 ° C. This temperature coincides with the solidification temperature of the composite salt composed of NaCl, KCl, or the like. That is, the melting point of a single component of the salt is N
Although aCl is 800 ° C and KCl is 776 ° C, the solidification temperature is 550 to 650 because the salts are melted to form a composite salt.
° C. The solidification temperature varies slightly depending on the quality of the waste.

Here, as shown in FIG. 15, when the saturated steam is recovered, the temperature of the saturated steam is as low as about 310 ° C. even at a pressure of about 10 MPa, so that the steam enters the “non-corrosive area” and the metal transfer occurs. Corrosion can be avoided by using heat tubes. However, when recovering superheated steam, the temperature of the steam is 400 ° C. or higher, and when a metal heat transfer tube is used, its surface is corroded. Therefore, in order to obtain a superheated steam of 400 ° C. or more while avoiding the “corrosion progressing region” in FIG. 15, the combustion exhaust gas needs to be at 500 to 600 ° C.

In this case, although the heat transfer tube does not corrode, the temperature difference between the combustion exhaust gas (500 to 600 ° C.) and the superheated steam (400 ° C. or more) is small. However, there is a problem that the heat transfer area becomes large and the equipment becomes large. Also, the combustion exhaust gas is 500 ~
Even if the temperature is 600 ° C., when the outer surface temperature of the heat transfer tube becomes 430 ° C. or higher, the corrosion enters the “corrosion reduction region”, so that slight corrosion proceeds. Therefore, when the combustion exhaust gas is used in this temperature range, the selection of the material for the heat transfer tube becomes an important problem. Here, since the outer surface temperature of the heat transfer tube is higher than the superheated steam temperature by about 30 ° C., the allowable corrosion limit of the superheated steam temperature (upper limit of the steam temperature in a non-corrosive region) is about 400 ° C. In this case, due to the problem of drain attack on the steam turbine, the steam pressure is suppressed to about 3.9 MPa, so that the power generation efficiency is limited to about 20% as described above.

On the other hand, in recent years, high-efficiency power generation by material development has been attempted in order to obtain a high steam temperature and increase power generation efficiency by developing a corrosion-resistant metal material. However, such material development involves technical and economic difficulties. In addition, RDF (Refuse Derived
RDF power generation using garbage that has been converted to Fuel has also been attempted. According to this method, since lime or the like is added to the RDF, generation of HCl can be reduced, but corrosion due to the molten salt occurs to the same extent as in the past. Therefore, the superheated steam of 500 ° C.
If it is attempted to obtain from the combustion exhaust gas of 800 ° C. or more, the surface temperature of the heat transfer tube becomes about 530 ° C., which corresponds to “a severely corroded area” in FIG. 15, so that the heat transfer tube cannot be protected from corrosion.

[0010] Further, there is super refuse power generation in which steam recovered by a waste heat boiler is heated using exhaust gas from a gas turbine to increase the power generation efficiency of the steam turbine. However, this super garbage power generation consumes a large amount of fuel such as light oil, and therefore has a problem in economy. In addition, there is also a super-waste-type power generation system that reheats the steam from the waste heat boiler with additional fuel to increase the efficiency of the power generation of the steam turbine by overheating, but this power generation also uses a large amount of fuel. There is a problem with economy.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been made in consideration of such problems as corrosion of salts and the like contained in exhaust gas generated when waste or fuel is burned or gasified. Provided is a heat exchanger that can obtain high-temperature and high-pressure steam without being corroded by components, and a power generation device that can perform high-efficiency power generation by steam or the like heated by the heat exchanger, or It is intended to obtain valuable gas efficiently.

[0012]

In order to solve the problems in the prior art, a heat exchanger according to the present invention comprises a heat transfer pipe in which steam or water flows inside a heat transfer outer tube which contacts exhaust gas. The heat transfer medium is interposed between the heat transfer outer tube and the heat transfer inner tube.

[0013] Further, the power generation apparatus of the present invention supplies combustion exhaust gas generated when waste or fuel is burned in a combustor or gasifier or valuable gas generated when gasified to a waste heat boiler to generate steam. In a power generating apparatus that generates and supplies the steam to a steam turbine and generates power by a generator connected to the steam turbine, the heat exchanger is disposed between an exhaust gas outlet of a combustor or a gasifier and a waste heat boiler. And supplying the combustion exhaust gas and the like after the heat exchange by the heat exchanger to the waste heat boiler, and supplying steam generated by the supplied combustion exhaust gas and the like of the waste heat boiler to the heat exchanger. It is characterized by the following.

That is, heat exchange in which steam or water is circulated inside between a waste heat boiler and a combustor such as a combustion furnace or a gasification and melting furnace or a gasification furnace such as a fluidized bed gasification furnace or a kiln furnace. The outer surface of the heat exchanger is covered with a container (shell) so as not to be directly exposed to the flue gas or the product gas from the furnace, and air, oxygen, and the like are provided between the container and the heat exchanger. Oxygenated gas, steam mixed oxygen,
A heat medium such as nitrogen gas or a mixed gas thereof, solid particles of a substance having high thermal conductivity such as copper and silicon carbide, and sand is placed, and the heat inside the heat exchanger is generated by heat of combustion exhaust gas or the like via the heat medium. Is heated to superheated steam or water. In particular, a heat exchanger equipped with a heat transfer inner tube and a heat transfer outer tube with a double tube structure is provided, and steam flows inside the heat transfer inner tube, and between the heat transfer inner tube and the heat transfer outer tube. By interposing a gas such as air or nitrogen gas as a heat medium,
The superheated steam is heated by the heat of the combustion exhaust gas or the like.

In the conventional method in which the superheated steam is passed through the heat transfer tube and the heat transfer tube is directly heated by the combustion exhaust gas, the heat transfer coefficient of the film on the steam side is large. The temperature becomes closer to the steam temperature (about 400 ° C.) on the lower temperature side than the temperature (about 1300 ° C.), and the temperature of 700 ° C. or more cannot be maintained. That is, since the condition of the "severely corroded area" in FIG.
As shown by the curve A, the influence of molten salt corrosion is severe, so that the corrosion progresses rapidly. On the other hand, in the method of the present invention, the heat transfer outer tube is heated by the combustion exhaust gas or the gas generated by gasification (such as the combustion exhaust gas). There is a gas such as air, and the heat transfer coefficient of the film on the air side is smaller than that of steam. Therefore, the outer surface temperature of the heat transfer outer tube approaches the temperature on the high temperature side, so that the high temperature of 700 ° C or more can be maintained. become. That is, the outer surface of the heat transfer outer tube is shown in FIG.
Can be operated under the condition of “corrosion reduction area” of FIG.
Since the influence of molten salt corrosion can be avoided as shown by, the rate of progress of corrosion is considerably reduced. As a result, the heat transfer outer tube
It can be manufactured and used with existing metal materials.

For example, even when a heat transfer tube made of heat-resistant cast steel or metal is used, a heat transfer outer tube exposed to combustion exhaust gas or the like is shown in FIG.
5 can be used in the “corrosion reduction region” where the problem of molten salt corrosion hardly occurs. Even the heat-resistant cast steel, which is resistant to corrosion, could not be used for heat transfer tubes by the conventional method, but can be effectively used by the present invention.

Further, in the conventional method, the heat transfer outer tube which is in direct contact with the combustion exhaust gas or the like has to be provided with a pressure-resistant specification when the inside is steam, but the present invention does not require the pressure-resistant specification. Therefore, there is no need to use materials specified in laws and regulations such as boiler structural standards and technical standards for thermal power plants for power generation. Therefore, a ceramic material that does not easily cause the problem of molten salt corrosion, which has been conventionally difficult to use, can be used for the heat transfer outer tube.

The high-temperature flue gas and the like come into contact with the outer surface of the heat transfer outer tube, thereby heating a gas such as air between the heat transfer outer tube and the heat transfer inner tube and radiating the gas through the heat transfer outer tube. Heat transfer can heat the heat transfer inner tube. When the outer surface of the heat transfer outer tube is at least 700 ° C., the corrosive action due to the molten salt contained in the combustion exhaust gas or the like is reduced. This is because if the outer surface temperature of the outer tube of the heat transfer tube is 700 ° C. or more, it enters the “corrosion reduction region” of FIG. In this way, a gas such as air between the heat transfer outer tube and the heat transfer inner tube is heated to 700 ° C. or more, and the superheated steam of about 400 ° C. obtained by the waste heat boiler is removed from the air of 700 ° C. or more. By heating with such a gas, superheated steam of about 500 ° C. can be easily obtained. Since the gas used for heating the superheated steam inside the heat transfer tube is not combustion exhaust gas or the like, the problem of molten salt corrosion of the heat transfer tube as in the related art does not occur.

Further, since gas such as air is a heat medium,
The heat transfer coefficient does not decrease due to the adhesion of dust, and the heat transfer inner tube can be made compact. By supplying the superheated steam having a high temperature of 500 ° C. or more to the steam turbine, high-efficiency power generation with a power generation efficiency of 30% or more can be achieved.

Conventionally, in order to avoid the problem of corrosion of the heat transfer tube due to the molten salt, the outer surface temperature of the heat transfer tube had to be set to about 500 ° C. or lower (see curve A in FIG. 16). Also,
As the operating conditions, as shown in FIG. 15, the temperature of the combustion exhaust gas had to be 600 ° C. or less. For this reason,
The temperature difference ΔT between the temperature of the high-temperature flue gas and the steam temperature in the heat transfer tube (including the superheated steam tube in the waste heat boiler) cannot be large, so the heat transfer area must be increased. However, in the present invention, the temperature difference ΔT can be made large, so that the heat transfer area can be small. The steam flowing into the heat transfer inner pipe may be not only superheated steam but also saturated steam. In this case, a radiant heat transfer section 55 shown in FIG.

FIG. 16 shows the difference in the corrosion rate of the heat transfer tube due to the combustion exhaust gas in the conventional art and the present invention. Conventional method of directly heating superheated steam by combustion exhaust gas (curve A
Since the heat transfer coefficient of the film on the steam side is large, the outer surface temperature of the heat transfer tube is shifted to the low-temperature steam side instead of the high-temperature combustion exhaust gas side, and is exposed to the "severely corroded area" in FIG. On the other hand, in the method of the present invention (indicated by curve B), a gas such as air between the heat transfer outer tube and the heat transfer inner tube is heated by the combustion exhaust gas or the like. In the case of air, since the heat transfer coefficient of the film on the air side is smaller than that of steam, the outer surface temperature of the heat transfer tube is shifted to the exhaust gas side, and enters the “corrosion reduction region” of FIG. As a result, the heat transfer outer tube can be made of an existing metal material because corrosion of molten salt can be avoided.

Here, the difference in the pipe surface temperature due to the difference in the film heat transfer coefficient of the fluid will be described. The tube surface temperature Tw is calculated by the following equation. Tw = T− {hio / (hio + hio)} × (T−
t) where T: exhaust gas temperature t: heat receiving gas temperature ho: film heat transfer coefficient of exhaust gas hio: film heat transfer coefficient of heat receiving gas 1) When the heat receiving side is superheated steam, T = 1200 ° C., t = 500 ° C, ho @ 116W / m ²
℃, hi {2330 W / m ² ℃ (in the case of superheated steam, the value is very high), the tube surface temperature Tw is given by: Tw = 1200− {2330 / (2330 + 116)} × (1200−500) = 533 ° C and enters the "severely corroded area" shown in FIG. 2) When the heat receiving side is air, T = 1200 ° C., t = 700
° C, ho ≒ 116W / m ² ℃, hi ≒ 116W / m ²
° C (a low value in the case of a gas such as air), the tube surface temperature Tw becomes Tw = 1200-{116 / (116 + 116)} x (1200-700) = 950 ° C, and a severely corroded area is formed. can avoid.

Further, in the present invention, since the heat medium inserted between the heat transfer outer tube and the heat transfer inner tube can be air at normal pressure, the material of the heat transfer outer tube can be a ceramic material.
Whether the material is metal or ceramics is determined according to the use conditions. In the case of a conventionally used metallic heat transfer tube, when the surface of the tube becomes 800 ° C. or higher, the strength is remarkably reduced. In recent years, heat-resistant cast steel that can be used even at 1100 ° C. has been developed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a power generator according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of the power generation device according to the present embodiment. As shown in the figure, the power generator according to the present invention performs an incinerator or a gasification / melting furnace or gasification furnace 11, a heat exchanger 12, a waste heat boiler 13, a steam turbine 14, a preheater 15, and dust removal. A bag filter 16 is basically provided.

In an incinerator, a gasification melting furnace, or a gasification furnace 11, waste or combustible material such as coal is gasified by complete combustion or partial combustion, thereby producing high-temperature CO ₂ ,
Combustion exhaust gas mainly composed of H ₂ O or medium calorie mainly composed of CO and H ₂ (2,500 to 4500 kcal / Nm ³
(10500-18900 kJ / m ³ )) to low calories (1000-1500 kcal / Nm ³ (4200-
6300 kJ / m ³ )) flammable gas is generated. The combustion exhaust gas or combustible gas generated in the incinerator, gasification melting furnace, or gasification furnace 11 passes through the heat exchanger 12 according to the present invention, and is guided to the waste heat boiler 13. In the waste heat boiler 13, a pressure of 10 MPa and a temperature of 40 MPa are supplied from the supplied water.
Generates superheated steam at about 0 ° C. The waste heat boiler 13
May produce saturated steam.

The superheated steam (or saturated steam) generated in the waste heat boiler 13 is supplied to the heat exchanger 12 and is heated to about 500 ° C. by the following heat exchange. 500
The superheated steam heated to about ° C is supplied to the steam turbine 14 and used for power generation.

The heat exchanger 12 is provided with a waste heat boiler 13 in a heat transfer outer tube 20 which comes into contact with combustion exhaust gas or product gas.
A heat exchanger having a structure in which a heat transfer inner tube 21 for flowing steam from the container is housed, and a gas such as air as a heat medium is interposed between the heat transfer outer tube 20 and the heat transfer inner tube 21 ( Charge). The heat transfer outer tube 20 is made of heat-resistant metal or ceramic.

In the heat exchanger 12, a gas (heat medium) such as air between the heat transfer outer tube 20 and the heat transfer inner tube 21 is heated to 500 ° C. or more, preferably 700 to 8 by combustion exhaust gas or generated gas.
Heat to 00 ° C. The superheated steam or the saturated steam supplied from the waste heat boiler 13 is heat-exchanged with a gas such as the air heated to 700 ° C. or more, and is heated to about 500 ° C. In addition, as a gas used as a heat medium, an inert gas such as air or nitrogen is preferable.

On the other hand, the combustion exhaust gas or product gas that has exited from the waste heat boiler 13 is supplied to an air preheater constituting the preheater 15 by air or a gasifying agent (oxygen) used in an incinerator, a gasification melting furnace, or the gasification furnace 11. , Steam, or a mixed gas thereof), and the boiler feedwater is further heated by an economizer (not shown). The combustion exhaust gas or product gas whose temperature has dropped due to the heat recovery is removed by a bag filter 16 and then discharged from the stack as a clean gas in the case of the combustion exhaust gas. Used as fuel for power generation by fuel cells, gas engines, and the like.

Hereinafter, the heat exchanger 12 according to the present invention will be described in more detail. FIG. 2 is a schematic configuration diagram of the first embodiment of the heat exchanger 12 according to the present invention, and FIG.
FIG. 2 is a cross-sectional view taken along a line A, and is a cross-sectional view of a one-loop type heat exchanger. FIG. 3B is a sectional view of a two-loop type heat exchanger. As shown in FIG. 2, a heat transfer outer tube 20 is disposed so as to protrude into a flow passage G through which a high-temperature combustion exhaust gas or product gas flows.
It is fixed to 0. A heat transfer inner tube 21 bent into a hairpin shape is housed in the heat transfer outer tube 20.
The heat transfer inner tube 21 is heated by the waste heat boiler 13
Superheated steam of about 00 to 600 ° C. is supplied. That is, the superheated steam supplied from the waste heat boiler 13 flows through the heat transfer inner tubes 21 from the low-temperature steam header 41, is heated, then gathers in the high-temperature steam header 42, and then is supplied to the steam turbine 14. .

The space between the heat transfer outer tube 20 and the heat transfer inner tube 21 is filled with air as a heat medium. The air is sealed by a sealing material 40 having a shape.
The heat exchanger shown in FIGS. 2 and 3A is a so-called one-loop type heat exchanger, in which the inner heat transfer tube 21 is bent once near the closed end in the outer heat transfer tube 20. I have. FIG.
The heat exchanger shown in (b) is a two-loop type heat exchanger, in which the heat transfer inner pipe 21 is bent near the closed end in the heat transfer outer pipe 20 and then near the open end. It is bent and then bent again near the closed end.

The heat transfer outer tube 20 has a temperature of 700 ° C. or higher, preferably 850 ° to 1100 ° C. due to radiant heat transfer and convective heat transfer from a high-temperature combustion exhaust gas or product gas at 900 to 1500 ° C.
Heated. In this temperature range, the lower the temperature, the slower the corrosion rate of the material, especially the metallic material, and therefore, it is desirable to lower the temperature of the material constituting the outer tube 20 in order to extend the useful life of the material.

Since the outer surface temperature of the heat transfer inner tube 21 is at most about 430 ° C., the heat transfer inner tube 20 is positively brought close to the heat transfer outer tube 20 as shown in FIGS. Can be cooled. That is, when the temperature of the heat transfer outer tube 20 is 8
In the range of 50 to 1100 ° C., the heat transfer inner pipe 2
Radiation heat transfer is more dominant than convective heat transfer in heat transfer to the heat transfer tube 1. By arranging the heat transfer inner tube 21 so as to be close to the entire inner surface of the heat transfer outer tube 20, the heat transfer inner tube is formed by radiant heat transfer. 2
The heat is transferred to 1 and the outer tube 20 is cooled. The embodiment shown in FIG. 4 to be described later is more preferable in the sense of being close to the entire inner surface of the heat transfer outer tube 20.

In the case of recovering heat from combustion exhaust gas having a high temperature of 1000 ° C. or more as in the present invention, the heat transfer
In the case of heat transfer on the inner surface of 0, radiant heat transfer is overwhelmingly superior to convective heat transfer, and the amount of radiant heat transfer is the difference between the temperature of the combustion exhaust gas and the absolute temperature of the surface temperature of the heat transfer outer tube 20 raised to the fourth power. Since it is proportional, the amount of heat transfer can be increased by lowering the surface temperature of the heat transfer outer tube 20. As a result, the amount of heat transfer per unit area can be increased,
The heat transfer area can be reduced. For example, when the surface temperature of the heat transfer outer tube 20 is 1100 ° C. and 850 ° C., and the difference in the amount of heat transfer when the temperature of the combustion exhaust gas is 1200 ° C. is compared, the surface temperature of the heat transfer outer tube 20 is 1100 ° C.
The heat transfer amounts Q ₁ and Q _{2 at the} temperatures of ℃ and 850 ° C. are as follows: Q ₁ = αA ((1200 + 273) ⁴ − (1100 + 273) ⁴ ) = 1.15 × 10 ¹² αA Q ₂ = αA ((1200 + 273) ⁴ − (850 + 273) ) ⁴ ) = 3.12 × 10 ¹² αA Here, α: radiation constant A: heat transfer area, and the ratio of the _two is Q ₂ / Q ₁ = 2.17. Therefore, by lowering the surface temperature of the heat transfer outer tube 20 by 250 ° C., a heat exchange of 2.17 times is possible with the same heat transfer area. In other words, to achieve the same heat exchange amount, 1 /
A heat transfer area of 2.17 is sufficient. As described above, if the heat transfer area exposed to the high-temperature exhaust gas can be reduced, the cost will be greatly reduced.

As a material of the heat transfer outer tube 20, ceramics such as alumina or silicon carbide, a nickel-chromium heat-resistant alloy, a heat-resistant cast steel, or the like can be used. According to an exposure test performed by the present inventors, silicon carbide was most preferred as ceramics. When silicon carbide is used for the heat transfer outer tube 20, the surface temperature of the heat transfer outer tube 20 is 1100 ° C. or less,
Preferably, the temperature is kept at 1050 ° C. or lower. This is because silicon carbide reacts with water vapor and an alkali metal in a high temperature range to form water glass on the surface, and the thinning proceeds due to evaporation of the water glass. If the silicon carbide is kept at 1050 ° C. or lower, even if water glass is formed on the surface, it does not evaporate, and thus hardly loses its thickness. When a piece of SiC, alumina, and silicon nitride was exposed to the high-temperature exhaust gas of the gasification and melting furnace for one month, the alumina and silicon nitride were completely melted, but the thickness of silicon carbide was reduced from 10 mm to 5 mm. He kept the original form of the meat. Also,
Significant wall thinning in the flow direction of combustion exhaust gas or product gas,
There was little wall thinning where the flow was weak. If the surface temperature of SiC is set to 1050 ° C. or less, the wall thickness in the flow direction of the combustion exhaust gas or the like hardly occurs.

Further, when the heat transfer outer tube 20 made of a metal material is used, it has been found that a material which is based on nickel or chromium and in which an appropriate amount of tungsten or alumina is further blended is used. However, in the case of using the heat transfer outer tube 20 made of a metal material, if the temperature control is performed as in the case of ceramics, it is not possible to use the heat transfer semi-permanently, but the life is determined by the material, the wall thickness of the tube, and the use conditions. . Therefore, it is necessary to select the appropriate material, pipe wall thickness, and operating conditions according to the purpose. However, metal materials are easier to control in quality than ceramics. Can be demonstrated. When heat-resistant cast steel is used for the heat transfer outer tube 20, a JIS SCH material is preferable.

As described above, in the temperature range of 850 ° C. to 1100 ° C., the lower the temperature is, the more advantageous the corrosion resistance of the metal material is. Therefore, to extend the life of the heat transfer outer tube 20, It is preferred to lower the temperature. Therefore, in the case of the structure as shown in FIGS.
The operation of lowering the temperature of the outer heat transfer tube 20 by lowering the steam temperature inside the inner heat transfer tube 21 is also effective. For example, when the steam temperature is lowered by 100 ° C., the temperature of the heat transfer outer tube 20 is also lowered by 50 to 80 ° C., and the corrosive environment is reduced. In particular, since a metal material has a critical point of corrosion between 850 ° C. and 1000 ° C., it is preferable to keep the temperature at or below that temperature from the viewpoint of improving durability. According to the exposure test performed by the inventors, the nickel-chromium-based metal material has a critical point around 950 ° C. Therefore, the temperature of the heat transfer outer tube 20 of the metal material should be maintained at 950 ° C. or less. Was important. In this case, in order to keep the heat transfer outer tube 20 shown in FIG.
It is necessary to keep the steam temperature inside the 550 ° C. or lower.

Further, although the heat transfer outer tube 20 may be a dense body,
It may be a porous body like a filter. When the heat transfer outer tube 20 made of a porous body is employed, a very small amount of gas such as air, nitrogen, or steam is sealed by slightly increasing the external pressure of the heat transfer outer tube 20. Can leak out to the outer surface of the heat transfer outer tube 20. The leaked sealed gas cools the heat transfer outer tube 20 and also has an effect of preventing corrosive combustion exhaust gas and the like from directly contacting the heat transfer outer tube 20, thereby dramatically improving the corrosion resistance of the heat transfer outer tube 20. Can be improved. It is feared that the amount of heat exchange is reduced due to leakage of the sealed gas. However, since heat transfer in a high-temperature region is dominated by radiation, this heat transfer loss can be ignored.

The air or nitrogen gas interposed between the heat transfer outer tube 20 and the heat transfer inner tube 21 may be circulated or filled. Alternatively, solid particles having high thermal conductivity are filled between the heat transfer outer tube 20 and the heat transfer inner tube 21,
Promoting heat transfer between the outer heat transfer tube 20 and the inner heat transfer tube 21 is also an effective method. Specifically, for example, when solid particles of a substance having high thermal conductivity such as copper and silicon carbide are filled between the heat transfer outer tube 20 and the heat transfer inner tube 21 as a heat medium, the heat transfer coefficient is a gas such as air. Only 3 to 5 times higher than in the case where only the heat transfer outer tube 2 is filled.
The surface temperature of 0 also decreases. Of course, the substance that can be used as the heat medium may be other than copper or silicon carbide, provided that the substance has excellent heat conductivity.

FIG. 4 is a schematic structural view of a heat exchanger 12 according to a second embodiment of the present invention. As shown in the figure, the heat transfer inner tube 21 in the present embodiment has a cylindrical outer tube portion 21a having a closed end and an open end, and a cylindrical outer tube portion 21a disposed in the outer tube portion 21a and having open ends. And an inner cylindrical portion 21b. As shown in FIG. 4, the low-temperature steam flows in from one end of the inner cylinder portion 21b, is discharged from an opening at the tip, and flows into the tip portion of the outer cylinder portion 21a. Then, the fluid flows out from the other end of the outer cylinder 21a through the annular flow path 21c between the inner cylinder 21b and the outer cylinder 21a. During this time, the steam is heated by the heat transfer surface of the outer cylindrical portion 21a, and is discharged as high-temperature steam.

Next, a second embodiment of the power generator according to the present invention will be described in detail with reference to the drawings. Note that portions that are not particularly described are the same as those in the first embodiment. FIG. 5 is a block diagram illustrating a configuration of the power generation device according to the present embodiment. The figure shows that using a fluidized-bed gasification furnace and a swirling melting furnace, waste is gasified in a fluidized-bed gasification furnace to produce combustible gas, and the melting furnace together with the unburned carbon (char) and fly ash produced The system is the same until it is completely burned and a high temperature atmosphere is obtained, and the char and fly ash are melted to obtain molten slag (gasification combustion). An example in which the present invention is applied to a system (two-stage gasification) for obtaining a valuable flammable gas by burning and also obtaining a high-temperature atmosphere to obtain molten slag is shown.

The waste is first introduced into a fluidized-bed gasification furnace 51, and the temperature is 450 to 650 ° C., preferably 500 to 600 ° C.
At a low oxygen ratio to be pyrolyzed and gasified by partial combustion.
The gasifying agent supplied at this time is oxygen-containing gas such as air, oxygen, steam, CO ₂ or a mixed gas thereof. Since the inside of the fluidized bed gasification furnace 51 has a low fluidized bed temperature and is in a reducing atmosphere, metals such as iron, copper, and aluminum can be recovered in an unoxidized state.

The pyrolysis gas containing char, tar and the like generated in the fluidized bed gasification furnace 51 is sent to the swirling melting furnace 52 and burned or partially burned at a high temperature of 1200 to 1500 ° C. The gasifying agent supplied at this time is oxygen-containing gas such as air, oxygen, steam, CO ₂ or a mixed gas thereof. In the case of gasification combustion, gas combustion is mainly performed, so that a low air ratio combustion of about 1.3 in total is possible, whereby the amount of exhaust gas can be significantly reduced. In either case, since combustion or partial combustion occurs at a high temperature of 1200 ° C. or more, complete decomposition of tar or dioxins is possible. Moreover, the slag can be efficiently separated by the swirling flow. By cooling the slag, heavy metals can be contained in a glassy solid.

A heat exchanger 53 and a waste heat boiler 54 are connected to the melting furnace 52, and the heat exchanger 53 is provided before the radiant heat transfer section 55 of the waste heat boiler 54. The heat exchanger 53 includes a heat transfer outer tube 20 and a heat transfer inner tube 21 shown in FIGS.
Is used. The heat transfer outer tube of the heat exchanger 53 uses heat-resistant cast steel, heat-resistant metal, silicon carbide (ceramics), or the like, and heats the air between the heat transfer outer tube and the heat transfer inner tube to 500 ° C. or more, preferably 700 ° C. ~
Heat to 800 ° C. At this time, the temperature of the exhaust gas generated by gasification combustion, that is, the temperature of the combustion exhaust gas or the pyrolysis gas generated by the two-stage gasification is preferably from 1000 to 1300 ° C, and preferably about 1200 ° C in order to avoid the adhesion of ash. As described above, the temperature difference ΔT between the flue gas or the like and the air between the heat transfer outer tube and the heat transfer inner tube can be made larger than before, so that the heat transfer area can be reduced, and the heat exchanger 53 can be reduced in size and size. It can be shaped.

500 ° C. or higher, preferably 700-8 ° C., depending on the combustion exhaust gas or generated gas (these gases, ie, the exhaust gas).
The air between the heat transfer outer tube and the heat transfer inner tube heated to 00 ° C. exchanges heat with superheated steam (or saturated steam) via the heat transfer inner tube, and the superheated steam inside the heat transfer inner tube. (Or saturated steam) 4
It heats to 00-600 degreeC, Preferably it is heated to about 500 degreeC.
Pressure increased about 10MPa inside the heat transfer inner tube, temperature 5
The superheated steam of about 00 ° C. is supplied to a steam turbine 56, and the power is directly generated by a power generator. This allows
While avoiding the problem of molten salt corrosion, the power generation end efficiency is about 30 ~
32% is achieved. The higher the temperature of the superheated steam, the higher the power generation end efficiency can be.

In the radiant heat transfer section 55, superheated steam of about 400 ° C. is generated using the combustion exhaust gas or the like that has passed through the heat exchanger 53. The temperature of the combustion exhaust gas and the like that has passed through the radiant heat transfer section 55 drops to about 600 ° C., but the problem of molten salt corrosion does not occur as shown in FIG. The temperature of the flue gas at the outlet of the waste heat boiler 54 is about 350 ° C. The boiler feed water is preheated by the economizer 57, and the air supplied to the melting furnace 52 is cooled by the air preheater 58.
Preheat to 0-300 ° C. After the flue gas and the like whose temperature has dropped to about 160 ° C. is removed by a dust remover such as a bag filter 59, the flue gas is discharged from the stack as clean flue gas, and the gas obtained by the two-stage gasification is C
O, with _{H 2} mainly hydrogen concentration 15% to 50%, CO concentration 1
The generated gas of 0% to 35% is used as a raw material for the chemical industry of a valuable gas refining plant or as a fuel for power generation by a fuel cell, a gas engine, or the like.

Here, air is used as an example of the heat medium between the heat transfer outer tube 20 and the heat transfer inner tube 21 of the heat exchanger 53. However, the present invention is not limited to this. it is obvious. Since the pressure of the portion of the heat exchanger 53 between the heat transfer outer tube 20 and the heat transfer inner tube 21 is normal pressure or at most 0.3 MPa, the heat transfer outer tube needs to have a pressure-resistant structure. Absent. Accordingly, a ceramic heat transfer outer tube may be used, or a cast steel tube may be used. The installation place of the heat exchanger 53 is not limited to the position before the radiant heat transfer section 55 of the waste heat boiler 54,
It may be anywhere between 2 and the waste heat boiler 54. For example, a duct may be provided after the melting furnace 52 and installed in the duct.

Hereinafter, another embodiment of the power generator according to the present invention will be described in detail with reference to the drawings. 6 to 13 described below, the same reference numerals as those in FIG. 5 indicate members or elements having the same functions or functions as those in FIG. FIG. 6 is a block diagram showing the configuration of the power generation device according to the third embodiment of the present invention. The figure shows an example in which the present invention is applied to a system in which waste is gasified and then gasified and burned (gasification and melting) or two-stage gasification using a fluidized bed gasification furnace and a swirling melting furnace. .

The structure of the third embodiment is basically the same as that of the second embodiment, except that a gasifying agent is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube. Then, a method is shown in which after flowing between the heat transfer outer tube and the heat transfer inner tube, it is used as a gasifying agent for the gasification furnace or the melting furnace 51. When the gasifying agent is introduced into the gasification furnace or the melting furnace 51, an oxygen-containing gas such as air, steam, CO ₂ , H ₂ O, or a mixed gas thereof is used. On the other hand, as for the gaseous heat medium used as a heat medium between the heat transfer outer tube and the heat transfer inner tube, the water vapor excessively lowers the outer surface temperature of the heat transfer outer tube, leading to a severe corrosion region temperature. Therefore, it is not very preferable. However, it can be used by mixing with other gases.

By supplying a high-temperature gas heated by the heat exchanger 53 to the gasification furnace or melting furnace 51 as a gasifying agent, in order to maintain the temperature of the furnace, it is necessary to use a combustion gas used for raising the temperature. The amount of oxygen can be reduced. That is, the amount of the raw material that is converted into combustion heat decreases, and the amount that is gasified relatively increases, so that more generated gas can be obtained. For this reason, in gasification combustion in which gasification is performed in the low-temperature gasification furnace 51 and complete combustion is performed in the melting furnace 52 using the generated gas as fuel, a richer combustible gas can be obtained from the low-temperature gasification furnace 51, It is easy to raise the temperature in the furnace 52, and the operation can be easily stabilized. It is also effective when the quality of the waste to be put into the gasifier is municipal waste with a high water content.

In FIG. 6, the gasifying agent is supplied to the air preheater 58.
Is heated between the heat transfer outer tube 20 and the heat transfer inner tube 21 of the heat exchanger 53, and then supplied as a gasifying agent to the fluidized bed gasification furnace 51 or the melting furnace 52. Regarding the supply of steam, when the amount of steam required for gasification is insufficient, steam is injected after flowing through the heat exchanger, or the steam is supplied through a supply line separate from the gasifier supply system via the heat exchanger. From the viewpoint of promoting gasification in the fluidized bed and making the temperature uniform, a fluidized bed furnace in which the fluidized medium in the fluidized bed forms a circulating flow by fluidizing gas or the like is preferable, and the melting furnace is also used. The swirling flow type is preferable in promoting gasification.

FIG. 7 is a block diagram showing the configuration of the power generator according to the fourth embodiment of the present invention. FIG. 1 shows an example in which the present invention is applied to a system in which waste is gasified and then subjected to two-stage combustion (gasification-melting) or two-stage gasification using a fluidized-bed gasification furnace and a swirling melting furnace. . The configuration of the fourth embodiment is basically the same as the configurations of the second and third embodiments, except that a gasifying agent is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube. Then, after flowing between the heat transfer outer tube and the heat transfer inner tube, the temperature of the gasifying agent to be supplied to the gasification furnace or the melting furnace by a method used as a gasifying agent for the gasification furnace or the melting furnace. This is a method intended for control.

The gas source supplied to the gasification furnace or the melting furnace is supplied from the heat exchanger 53 and the air preheater 58. The agent is mixed and supplied to a gasification furnace or a melting furnace. Thereby, the temperature of the gasifying agent to be supplied can be changed according to the temperature inside the gasification furnace or the melting furnace. For example, when the furnace temperature, fluidized bed temperature, etc. are abnormally high, the gasification agent is supplied from the supply system A that supplies the gasification agent via the air preheater 58, so that the valve of the supply system A In order to increase the opening of the valve 60 and conversely introduce a smaller amount of the gasifying agent from the supply system B for supplying the gasifying agent via the heat exchanger 53, the opening of the valve 61 of the supply system B is reduced to a small value. By doing so, the temperature of the gasifying agent introduced into the gasification furnace or the melting furnace decreases, and the temperature in the furnace and the temperature of the fluidized bed can be reduced to normal ranges.

Conversely, when the furnace temperature, fluidized bed temperature and the like are abnormally low, the gasification agent is supplied from the supply system B for supplying the gasification agent through the heat exchanger 53, so that the gasification agent is supplied. In order to increase the opening of the valve 61 of the system B and conversely introduce a smaller amount of the gasifying agent from the supply system A for supplying the gasifying agent via the air preheater 58, the opening of the valve 60 of the supply system A is increased. Squeeze small. By doing so, the temperature of the gasifying agent introduced into the gasification furnace or the melting furnace rises, and the furnace temperature and the fluidized bed temperature can be raised to normal ranges. The gasifying agent for both the supply systems A and B is oxygen-containing gas such as air, oxygen, water vapor, CO _2, or a mixed gas thereof.

FIG. 8 is a block diagram showing the configuration of the power generator according to the fifth embodiment of the present invention. FIG. 1 shows an example in which the present invention is applied to a system in which waste is gasified and then subjected to two-stage combustion (gasification-melting) or two-stage gasification using a fluidized-bed gasification furnace and a swirling melting furnace. . The configuration of the fifth embodiment is basically the same as that of the second to fourth embodiments, except that the gasifying agent is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube. After using and passing between the heat transfer outer tube and the heat transfer inner tube, a part of the high-temperature superheated steam obtained in the heat exchanger is This is a method of supplying to a gasification furnace or a melting furnace. The gasifying agent to be used is the same as that used in the above examples. This system introduces the superheated steam obtained by the heat exchanger and the high-temperature gasifying agent passed through the heat exchanger into the gasification furnace or melting furnace. Gasification has progressed due to the high water vapor, especially in the process of obtaining flammable valuable gases such as chemical recycling systems,
It is effective when treating multi-water waste such as municipal waste.

After the gasifying agent is superheated by the air preheater 58, it is heated by the heat exchanger 53 and supplied to the gasification furnace 51 or the melting furnace 52. On the other hand, the steam heated by the economizer 57 is further heated by the waste heat boiler 54 and the radiant heat transfer unit 55, and then introduced into the heat transfer inner tube of the heat exchanger 53, where it becomes superheated steam. A part of the superheated steam obtained in the heat exchanger 53 is supplied to the turbine 56, and the remaining part is supplied to the gasification furnace 51 or the melting furnace 52 as a gasifying agent. Both may be mixed and supplied to the gasification furnace 51 or the melting furnace 52, or may be supplied separately. The control of the supply amount of steam is performed by a valve or the orifice 62.

FIG. 9 is a block diagram showing the configuration of the power generator according to the sixth embodiment of the present invention. The figure shows an example in which the present invention is applied to a system in which waste is gasified and then gasified and burned (gasification and melting) or two-stage gasification using a fluidized bed gasification furnace and a swirling melting furnace. . The configuration of the sixth embodiment is basically the same as the configurations of the second to fifth embodiments, except that a gasifying agent is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube. Then, after flowing between the heat transfer outer tube and the heat transfer inner tube, a part or heat of the high-temperature superheated steam obtained in the heat exchanger is used in a method of using as a gasifying agent for a gasification furnace or a melting furnace. In this method, a part of the steam before being introduced into the exchanger is temporarily mixed with a gasifying agent supplied through the heat exchanger. The gasifying agent to be used is the same as that used in the above examples.

The steam obtained by the economizer 57 or a part of the steam obtained by the waste heat boiler 54 or the radiant heat transfer section 55 or the steam obtained by the heat exchanger 53 reaches the heat exchanger via the air preheater 58. The mixed gas is mixed in the passage of the gasifying agent, and the mixed gas is supplied between the heat transfer inner tube and the heat transfer outer tube of the heat exchanger 53 and is heated by the heat exchanger 53. It is supplied to a furnace 52. When the difference ΔT between the outer surface temperature of the heat transfer outer tube and the temperature of the combustion exhaust gas (or product gas) is reduced or it is desired to increase the temperature, the steam is supplied to the heat transfer inner tube and the heat transfer outer tube of the heat exchanger 53. The temperature of the outer surface of the heat transfer outer tube is reduced by mixing it with the gasifying agent supplied during the process so that it can be adjusted or adjusted, and the outer surface temperature of the heat transfer outer tube and the combustion exhaust gas (or generated gas) Temperature difference Δ
T can be made large, so that the heat exchanger 53
The amount of heat input to the heat exchanger can be increased.

FIG. 10 is a block diagram showing the configuration of a power generator according to the seventh embodiment of the present invention. The figure shows an example in which the present invention is applied to a system in which waste is gasified and then gasified and burned (gasification and melting) or two-stage gasification using a fluidized bed gasification furnace and a swirling melting furnace. . The gasifying agent is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube of the heat exchanger 53, and after flowing between the heat transfer outer tube and the heat transfer inner tube, the obtained high temperature This is a method to use gas effectively.

The configuration of the seventh embodiment is basically the same as that of the second to sixth embodiments, except that the melting furnace 52
In order to maintain the fire resistance of the wall of the furnace, a pipe (cooling pipe 65) for cooling the inside of the refractory wall or the outer wall surface of the refractory wall is provided, and cooling water is supplied to the cooling pipe. Further, in the flow path of the flue gas between the melting furnace 52 and the waste heat boiler 54, the heat exchanger 53 of the present invention and the existing high-temperature air heater 63 are provided between the melting furnace 52 and the waste heat boiler 54.
They are arranged in parallel or in a serial order.
Here, “parallel” means that the gas discharged from the melting furnace 52 is divided into the heat exchanger 53 and the high-temperature air heater 63 and enters almost simultaneously, and each gas discharged from the heat exchanger 53 and the high-temperature air heater 63 Refers to an arrangement that directly reaches the waste heat boiler 54, and the series refers to a case where the gas discharged from the melting furnace 52 enters a certain device (for example, the heat exchanger 53), and the gas discharged therefrom is the next gas. The gas that enters the other device (for example, the high-temperature air heater 63) as it is, and then exits from the next another device directly, reaches the waste heat boiler 54. The order of the series may be the heat exchanger 53 followed by the hot air heater 63 or vice versa. Heat exchanger 53 or hot air heater 63
Is an oxygen-containing gas such as air serving as a gasifying agent for the gasification furnace 51 or the melting furnace 52, oxygen, nitrogen, CO _2, or a mixed gas thereof, or a mixture of these gases with a slight amount of water vapor (gasifying agent). ) Is circulated and heated by the high temperature exhaust gas of the melting furnace.

In addition, there is a super heater 64,
The gasifying agent heated by the heat exchanger 53 and / or the high-temperature air heater 63 is introduced into the waste heat boiler 54.
Alternatively, a part or all of the high-temperature steam obtained by the radiant heat transfer unit 55 or the heat exchanger 53 or the high-temperature steam obtained by mixing the high-temperature steam may be partially or entirely converted into the super heater 64.
Superheated by the gasifying agent heated in. Heat exchanger 53
When the gasifying agent heated by both of the hot air heater 63 and the high-temperature air heater 63 is introduced into the super heater 64, the gasifying agent passes through the heat exchanger 53 to reach the high-temperature air heater 6, and then is introduced into the super heater. Flow, and vice versa, to the heat exchanger after passing through the high-temperature air heater, or the flow to be introduced into the super heater, or the gasifying agent passes through the heat exchanger 53 and the high-temperature air heater 6 separately. However, each gasifier that has passed may flow directly to the super heater.

Next, the flow of FIG. 10 will be described. In the gasification furnace 51, combustible materials such as wastes are kept at a low temperature (450 ° C to 650 ° C,
(Preferably 500 ° C. to 600 ° C.), and the combustible gas obtained therefrom is partially or completely burned in the melting furnace 52 to obtain a high temperature of 1300 ° C. or more. The flue gas is then deprived of heat by several devices or processes and subjected to detoxification treatment. In the case of gasification combustion, the flue gas is exhausted to the atmosphere, and in the case of two-stage gasification, it is flammable. The valuable gas is used in a gas purification plant, a power generation facility using a fuel cell, a gas engine, or the like.

The cooling water supplied to the cooling water pipe 65 of the refractory wall of the melting furnace 52 becomes high-temperature steam by the heat of the melting furnace 51. The steam obtained by the cooling water pipe is led to the heat transfer inner pipe of the heat exchanger 53, where it is further heated and the turbine 56
Supplied to On the other hand, the gasifying agent that has passed through the air preheater 58 is heated by the high-temperature air heater 63 and further guided to the heat exchanger 53 to be overheated. Here, first, the heat exchanger 53
Alternatively, the flow may reach the high-temperature air heater 63 via. The superheated high temperature gasifying agent is used as a gasifying agent for the gasification furnace 51 or the melting furnace 52 via the super heater 64. In the super heater 64, the waste gas is heated by the waste heat boiler 54 through the economizer 57, and the high temperature steam obtained through the radiant heat transfer unit 55 is introduced. The high temperature steam is superheated by the high temperature gasifying agent in the super heater. Is done. The superheated steam obtained by the superheater 64 is sent to the turbine 56 together with the superheated steam that has passed through the heat transfer inner tube of the heat exchanger 53.

Generally, the melting furnace 52 and the like have a cooling pipe for cooling the refractory wall and supply cooling water, but the state after cooling is collected as high-temperature steam. This high-temperature steam differs from the state of the steam obtained in the waste heat boiler 54 and the radiant heat transfer part in temperature, quantity pressure, and the like. In order to effectively use both of them for steam turbine power generation, it was necessary to give appropriate temperatures and calories to the respective steams so that the temperature and pressure conditions were equivalent. In the present invention, a large amount of steam passing through the waste heat boiler 54 is used to heat low-temperature steam with a large amount of high-temperature air by the super heater 64 as compared with the steam passing through the cooling pipe 65, so that the amount passing through the cooling pipe 65 is small. By heating the relatively high-temperature steam in the heat exchanger 53, both can be turned into superheated steam under substantially the same temperature and pressure conditions.

As described above, when there are a plurality of locations where steam is generated, there are differences in the temperature, pressure, amount, etc. of the generated steam for each location. A plurality of superheaters for steam superheating are provided in accordance with each equivalent, and a high-temperature air heater 63 or a heat exchanger 53 is formed from flue gas according to the temperature and amount of the heating steam supplied to each superheater. The high-temperature gasifying agent obtained through the super-heater is supplied to each super heater, and a plurality of high-temperature air heaters 63 and heat exchangers 53 can obtain heat from the flue gas so as to be easily distributed to each super heater. This arrangement is an effective method for obtaining homogeneous superheated steam.

FIG. 11 is a block diagram showing the configuration of the power generator according to the eighth embodiment of the present invention. FIG. 1 shows an example in which the present invention is applied to a system in which waste is gasified and then gasified and combustion or two-stage gasification is performed using a fluidized-bed gasification furnace and a swirling melting furnace. In this method, a gaseous heat medium such as air or nitrogen gas is used as a heat medium between the heat transfer outer tube and the heat transfer inner tube of the heat exchanger 53, and the obtained high-temperature steam is used effectively. The gasifying agent to be used is the same as that used in the above examples. The configuration of the eighth embodiment is basically the same as the configuration of the seventh embodiment, except that the gasifying agent is not supplied to the heat exchanger 53. This case is suitable when the amount of steam obtained by the waste heat boiler 54 is small.

FIG. 12 is a block diagram showing the configuration of the power generator according to the ninth embodiment of the present invention. The figure shows an example in which the present invention is applied to a system in which waste is gasified and then gasified and burned (gasification and melting) or two-stage gasification using a fluidized bed gasification furnace and a swirling melting furnace. . The gasifying agent is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube of the heat exchanger 53, and after flowing between the heat transfer outer tube and the heat transfer inner tube, the obtained high temperature This is a method to use gas effectively. The gasifying agent to be used is the same as that used in the above examples.
The configuration of the ninth embodiment is basically the same as the configuration of the seventh embodiment, except that the gasifying agent superheated by the high-temperature air heater 63 is once superheated by the waste heat boiler 54 and the radiant heat transfer. It is used to superheat the high-temperature steam obtained in the portion 55, and thereafter, the gasifying agent is passed between the heat transfer inner tube and the heat transfer outer tube of the heat exchanger 53, and the heat exchanger 53 becomes hot again. The gasifying agent is introduced into the gasification furnace 51 or the melting furnace 52.
Due to the relatively small amount of high-temperature steam obtained in the waste heat boiler and the gasifying agent heated again in the heat exchanger 53, as described in the third embodiment shown in FIG. Because you can get more
It is suitable for a system for recovering valuable combustible gas.

FIG. 13 is a block diagram showing the configuration of the power generator according to the tenth embodiment of the present invention. FIG. 1 shows an example in which the present invention is applied to a system in which waste is gasified and then gasified and combustion or two-stage gasification is performed using a fluidized-bed gasification furnace and a swirling melting furnace. Gasifier to heat exchanger 53
It is used as a gaseous heat medium between the heat transfer outer tube and the heat transfer inner tube, and after flowing between the heat transfer outer tube and the heat transfer inner tube, the obtained high-temperature gas is effectively used. is there. The configuration of the tenth embodiment is basically the same as the configurations of the seventh and ninth embodiments, except that the gasifying agent superheated by the high-temperature air heater 63 is replaced by the superheater 64 with the waste heat boiler 54 or the like. It is used to superheat the high-temperature steam obtained in the radiant heat transfer section 55, and then the gasifying agent is supplied to the gasification furnace 51 and the melting furnace 52. On the other hand, a gasifying agent is passed between the heat transfer inner tube and the heat transfer outer tube of the heat exchanger 53 through a system (supply system B) different from the system (supply system A) supplied to the super heater 64, Heat exchanger 5
The gasifying agent which has become high temperature in 3 is mixed with the gasifying agent discharged from the super heater 64 and introduced into the gasification furnace 51 or the melting furnace 52.

As a result, the gasification furnace 51 and the melting furnace 5
The temperature of the gasifying agent supplied to 2 is adjusted. For example,
If the furnace temperature, fluidized bed temperature, etc. are abnormally high,
Supply system A for supplying gasifying agent via super heater 64
In order to introduce a larger amount of the gasifying agent, the opening degree of the valve 60 of the supply system A is increased, and conversely, a smaller amount of the gasifying agent is introduced from the supply system B that supplies the gasifying agent via the heat exchanger 53. Therefore, the opening of the valve 61 of the supply system B is reduced to a small value.
By doing so, the temperature of the gasifying agent introduced into the gasification furnace or the melting furnace decreases, and the temperature in the furnace and the temperature of the fluidized bed can be reduced to normal ranges.

Conversely, when the furnace temperature, fluidized bed temperature and the like are abnormally low, the gasification agent is supplied from the supply system B for supplying the gasification agent through the heat exchanger 53, so that the gasification agent is supplied. In order to increase the opening of the valve 61 of the system B and conversely introduce a smaller amount of the gasifying agent from the supply system A for supplying the gasifying agent via the super heater 64, the opening of the valve 60 of the supply system A is reduced. squeeze. By doing so, the temperature of the gasifying agent introduced into the gasification furnace or the melting furnace rises, and the temperature in the furnace and the temperature of the fluidized bed can be raised to normal ranges. The gasifying agent in each of the supply systems A and B is an oxygen-containing gas such as air, oxygen, nitrogen, CO _2, or a mixed gas thereof, or a mixture of these gases with a small amount of water vapor.

In the case of the gasification and melting system in the gasification and combustion of waste, low air ratio operation can be performed, so that the boiler efficiency can be increased, the power consumption of the ventilation equipment is greatly reduced, and the power for melting ash is unnecessary. Therefore, the power transmission end efficiency is greatly improved. Needless to say, high-efficiency thermal recycling is not high-efficiency power generation but high-efficiency power transmission. In addition, operation is possible without using auxiliary fuel, which is reasonable and economical. In addition, in a two-stage gasification chemical recycling system that generates valuable chemical gas, abundant combustible gas can be obtained from a low-temperature gasification furnace, the operation is easily stabilized, and a high temperature in the melting furnace can be achieved. The amount of consumed oxygen can be reduced. Here, Table 1 shows a comparative example of the power transmission end efficiency of each method regarding the high-efficiency thermal recycling.

[0072]

[Table 1]

In Table 1, 4 MPa × 400 ° C., 4M
Pa × 400 ° C. and 10 MPa × 500 ° C. are the pressure and temperature of the superheated steam in each system. According to Table 1, the method of generating power by obtaining superheated steam of high temperature and high pressure (10 MPa × 500 ° C.) using the gasification and melting system shown in FIG. 5 (gasification and melting-II) has a power transmission efficiency of 28.1%.
And the highest. The combination of the incinerator and the ash melting furnace has a high power generation efficiency, but the power consumption in the ash melting furnace is large, so that the power transmission efficiency is reduced to 11.2%. In addition, it is shown that the conventional system (gasification and melting-I) that generates power using superheated steam (4 MPa × 400 ° C.) heated directly by heating with combustion exhaust gas has low power generation efficiency and power transmission efficiency.

[0074]

As described above, according to the present invention, a heat transfer outer tube is provided in a flow path of exhaust gas generated when high temperature combustion or gasification occurs, and the heat transfer inner tube is arranged in the heat transfer outer tube. The heating medium consisting of gas such as air filled between the heat transfer outer tube and the heat transfer inner tube is heated, and then the steam in the heat transfer inner tube is heated by the high-temperature heat medium. About 500 ℃ or 500 ℃ while avoiding molten salt corrosion from exhaust gas etc.
The above superheated steam can be obtained. This makes it possible to obtain a power generation end efficiency of 30% or more.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a power generator according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram in a first embodiment of a heat exchanger according to the present invention.

FIG. 3A is a cross-sectional view taken along line AA of FIG. 2 and is a cross-sectional view of a one-loop type heat exchanger. (B) is a sectional view of a two-loop type heat exchanger.

FIG. 4 is a schematic configuration diagram of a second embodiment of the heat exchanger according to the present invention.

FIG. 5 is a block diagram showing a configuration of a power generator according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a power generator according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a power generator according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration of a power generator according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a power generator according to a sixth embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a power generator according to a seventh embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a power generator according to an eighth embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a power generator according to a ninth embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of a power generator according to a tenth embodiment of the present invention.

FIG. 14 is a block diagram showing a configuration of a conventional power generation device.

FIG. 15 is a diagram showing the relationship between corrosion by combustion exhaust gas temperature (horizontal axis) and pipe surface temperature (vertical axis).

FIG. 16 is a graph showing a corrosion rate with respect to a heat transfer tube surface temperature, wherein a curve A shows a conventional direct heat exchange method, and a curve B shows an indirect heat exchange method of the present invention.

[Explanation of symbols]

 Reference Signs List 11 combustion furnace or gasification melting furnace or gasification furnace 12, 53 heat exchanger 13, 54 waste heat boiler 14, 56 steam turbine 15, 58 air preheater 20 heat transfer outer tube 21 heat transfer inner tube 21a outer tube 21b Cylinder 51 Fluidized bed gasifier 52 Melting furnace 55 Radiant heat transfer unit 60, 61 Valve 62 Orifice 63 High temperature air heater 64 Super heater 65 Cooling pipe

Continued on the front page (72) Inventor Tetsuhisa Hirose 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside the Ebara Corporation (72) Inventor Akira Uchino 11-1 Asahi-cho Haneda, Ota-ku, Tokyo Ebara Corporation (72) Inventor Akisaku Fujinami 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Kei Kei Matsuoka 11-1 Haneda Asahi-cho, Ota-ku Tokyo (Reference) 3G081 BA02 BB00 BC13 BD00 3L103 AA35 AA44 BB05 CC18 CC27 DD38

Claims (8)

[Claims] 1. A heat transfer inner tube for flowing steam therein is placed in a heat transfer outer tube that comes into contact with combustion exhaust gas, and a heat medium is interposed between the heat transfer outer tube and the heat transfer inner tube. Characterized heat exchanger. 2. The heat exchanger according to claim 1, wherein the heat medium is air or nitrogen gas. 3. The heat exchanger according to claim 1, wherein the heat medium is solid particles. 4. The heat exchanger according to claim 1, wherein the heat transfer outer tube is made of heat-resistant cast steel or ceramics. 5. The heat exchanger according to claim 1, wherein the heat transfer outer tube is formed of a heat-resistant metal. 6. The method according to claim 1, wherein the temperature of the flue gas is 1000 ° C. to 1300 ° C., and the temperature of the outer surface of the heat transfer outer tube in contact with the flue gas is 700 ° C. or higher. Heat exchanger. 7. The heat exchanger according to claim 1, wherein the steam is generated by supplying a flue gas after heat exchange by the heat exchanger to a waste heat boiler. 8. A power generation device that supplies combustion exhaust gas generated in a combustor to a waste heat boiler to generate steam, supplies the steam to a steam turbine, and generates power by a generator connected to the steam turbine. The heat exchanger according to any one of claims 1 to 6, wherein the waste heat boiler supplies the combustion exhaust gas after heat exchange by the heat exchanger to the waste heat boiler. A power generator, wherein steam generated by the generated combustion exhaust gas is supplied to the heat exchanger.