JP4376137B2 - Power generation system - Google Patents

Description

  The present invention relates to a power generation system using a Stirling engine.

  As a power generation system using waste heat generated by incineration of waste, there is a system using a steam turbine. In addition to recovering combustible gas by pyrolyzing waste, this combustible gas is used as a gas engine. Some generators are rotated by directing and burning them.

By the way, a power generation system using a Stirling engine has been proposed as a clean one (for example, see Patent Document 1).
In the power generation system disclosed in Patent Document 1, low-temperature clean air is introduced into a tubular heating chamber portion (heating passage) and heated by high-temperature exhaust gas flowing outside thereof (so-called gas-gas heat exchange). The high temperature portion of the Stirling engine is heated by the air flowing in the heating chamber portion (heated by
JP2003-20993

  The power generation by the steam turbine is not practical in a small incinerator because the efficiency is remarkably reduced when the waste incineration amount is 100 t / d or less. In addition, when the waste is pyrolyzed, combustible gas can be recovered, but sensible heat is not effectively used.

  On the other hand, for a system that generates power using a Stirling engine using exhaust gas, the exhaust gas contains corrosive components, and there is concern about corrosion at the high temperature part of the Stirling engine, and transmission due to adhesion of dust in the exhaust gas. There is a risk of thermal degradation or wear damage due to dust.

  Therefore, in Patent Document 1, in order to heat the high temperature portion of the Stirling engine, heat is generated in the order of high temperature exhaust gas flowing in the flue → air flowing in the heating chamber portion composed of silicon carbide → high temperature portion of the Stirling engine. By moving, the working fluid in the Stirling engine is heated, and there is a problem that the heat efficiency is very poor.

  Then, an object of this invention is to provide the electric power generation system which can aim at the improvement of thermal efficiency.

In order to solve the above problems, a power generation system according to claim 1 is a power generation system that generates power by driving a generator by a Stirling engine using heat of exhaust gas as a heat source,
Inside the casing that houses the high temperature part of the Stirling engine and forms a heat exchange chamber, an inner pipe part is provided, and there is an outer passage and an inner passage. While inserting a heating tube with a double tube structure provided,
Exhaust gas is supplied to the outer passage of the heating tube and discharged from the inner passage .

Moreover, the electric power generation system which concerns on Claim 2 coat | covers the ceramic on the outer surface of the heating tube in the electric power generation system of Claim 1 at least.

Furthermore, the power generation system according to claim 3 is configured such that the heating tube is detachable from the casing in the power generation system according to claim 1 or 2 .

  According to the above configuration, since the heating pipe that guides the exhaust gas is arranged in the heat exchange chamber that houses the high temperature part in the Stirling engine, the heat of the exhaust gas is transferred to the working fluid on the Stirling engine side by radiation, Compared to a structure in which, for example, clean air is supplied between the heating pipe and the high temperature part is heated, corrosion on the high temperature part side due to exhaust gas is prevented and thermal efficiency can be improved.

Also, the radiation efficiency can be improved by coating the surface of the heating tube with ceramic.
Furthermore, since the heating tube is configured to be detachable from the casing, when the heating tube is corroded or dust is attached, it can be easily replaced.

[Embodiment]
Hereinafter, a power generation system according to an embodiment of the present invention will be described.
In the power generation system according to the present embodiment, for example, high-temperature combustion exhaust gas discharged from an incinerator is guided to a high-temperature part of a Stirling engine, the working fluid is heated to drive the Stirling engine, and the generator is rotated. It generates electricity. Of course, the working fluid is cooled in the low temperature part of the Stirling engine.

  Since the gist of the present invention lies in the high temperature part (heating part) of the Stirling engine, the explanation will be made with a focus on this part, and explanations of other components such as an incinerator and generator will be omitted. To do.

  As shown in FIG. 1, for the Stirling engine 1 used in this power generation system, that is, for rotating the generator, for example, helium gas (a gas with a small molecular weight that moves quickly) is used as a working fluid. A cylinder (also a cylindrical casing) 2 in which a piston is movably arranged is formed, and the upper working fluid chamber side of the cylinder 2 is a high temperature part. The lower working fluid chamber side (or a space chamber communicating with the lower working fluid chamber) is made a low temperature portion (also called a low temperature cooling portion).

  The high temperature part will be described. A casing 12 that forms a heating chamber (an example of a heat exchange chamber) 11 is provided by covering (accommodating) the entire upper portion of the cylinder 2, and the heating chamber 11 in the casing 12 includes The upper wall of the casing 12 is arranged such that a large number of inverted U-shaped heat transfer tubes 13 are arranged in an annular shape when viewed from above, and the heating tube 14 is located at the center of the group of these heat transfer tubes 13 arranged in an annular shape. It is inserted through the part (inserted into the heating chamber) and detachably attached via the flange part 15 (made removable).

  The heat transfer tube 13 is for heating the working fluid, and one end side thereof is connected to the upper part of the cylinder 2 (communication with the upper working fluid chamber) and the other end side is connected (communication) to the low temperature part. The working fluid is circulated between the high temperature part and the low temperature part.

The heating tube 14 has a double-pipe structure, and high-temperature exhaust gas from the incinerator is introduced into the outer passage (which is an annular passage) 14a, and inside the communication portion 14b at the inner tip. The exhaust gas is configured to enter the passage 14c and be led out from the inner passage 14c to the outside. Specifically, as shown in FIG. 1, an inner tube portion 14 d is arranged inside the heating tube 14 so as to have a clearance from the inner surface of the heating tube 14 at the tip.

  Further, the heating tube 14 is made of silicon carbide (SiC) and is made of a ceramic material that is easily radiated with heat (in the case of radiation, at least the outer surface of the heating tube 14 is coated with silicon carbide. As long as it has been.)

  Although FIG. 1 shows the case where only one cylinder 2 is provided, usually a plurality of, for example, four cylinders are arranged on the same circumference, and the heating tube 14 is arranged at the center thereof. However, an annular inner header and an outer header are respectively provided at the end of each heat transfer tube 13 on the cylinder 2 side (high temperature part side) and the end of the low temperature part. Connected to the upper working fluid chamber and the low temperature part.

  In the above configuration, when high-temperature exhaust gas is supplied to the heating pipe 14, it flows into the outer passage 14 a and heats the surface of the heating pipe 14. Then, the radiant heat from the heating tube 14 heats the group 13 of heat transfer tubes arranged in an annular shape around the heating tube 14, and the working fluid flowing through the inside is heated.

The heated working fluid is guided into the cylinder 2 to push down the piston, and then moves to the low temperature portion to be cooled.
That is, since the working fluid is heated and cooled, the piston in the cylinder 2 filled with the working fluid is reciprocated. Finally, the reciprocating movement of the piston is converted into a rotational motion to rotate the generator. Power is generated.

Here, a description will be given of the result of a thermal study on the configuration of the present embodiment and the conventional configuration.
The calculation for the case of supplying sufficient energy to the generator, for example, energy equivalent to 50 kW, is as follows.

First, the case of the conventional configuration is obtained.
The exhaust gas inlet temperature is 1000 ° C. (Ta _in ), the outlet temperature is 950 ° C. (Ta _out ), the clean air inlet temperature is 300 ° C. (Tb _in ), and the outlet temperature is 900 ° C. (Tb _out ). The amount of air is 180 kg / h (0.05 kg / s), and the heat transfer rate is 20 because it is a high temperature. As shown in the following formula, the heat exchange is about 6 m ^2. Area is required.

  The logarithm average temperature difference ΔTm (° C.) between the exhaust gas and the clean air is obtained by the following equation (1).

但し、（１）式中、ΔＴ１＝Ｔａ_ｉｎ−Ｔｂ_ｏｕｔ、ΔＴ２＝Ｔａ_ｏｕｔ−Ｔｂ_ｉｎである_。

However, in the formula (1), ΔT1 = Ta _in −Tb _out and ΔT2 = Ta _out −Tb _{in .}

  If hot air equivalent to 50 kW (E) [25 ° C. reference (Ts)] is supplied to the Stirling engine, the required air volume V (kg / s) is obtained by the following equation (2).

上記（２）式中、ｃは比熱（ＫＪ／ｋｇ・Ｋ）である。

In the above formula (2), c is specific heat (KJ / kg · K).

  Accordingly, the exchange heat quantity Q in the heat exchange section is obtained by the following equation (3), and the necessary heat exchange area A is obtained by the following equation (4).

但し、（４）式中、κは熱透過率（今回は２０を使用する）、ψは修正係数（今回は１．０を使用する）である。

However, in the equation (4), κ is a heat transmittance (20 is used this time), and ψ is a correction coefficient (1.0 is used this time).

Next, the case of the configuration of this embodiment is obtained.
In this case, a heating tube 14 made of silicon carbide (so-called ceramic) heated with high-temperature exhaust gas is disposed in the immediate vicinity of the high-temperature portion of the Stirling engine, and the high-temperature portion of the Stirling engine is radiated from the heating tube 14. That is, a case where the heat transfer tube 13 group is heated is shown.

Usually, since the radiant heat is proportional to the fourth power of the absolute temperature, the temperature of the heating tube 14 on the high temperature side is 1000 ° C., the heat transfer tube 13 on the heated side is 900 ° C., and the radiation heat release rate is 0.8. As shown in the calculation, 50 kW of energy can be supplied at about 1.5 m ² .

  That is, the radiant energy E is expressed by the following equation (5).

但し、（５）式中、εは黒度（セラミックの場合は０．８である。なお、金属の場合は０．３となる）である。

However, in the formula (5), ε is blackness (0.8 for ceramics, 0.3 for metals).

  Therefore, when the radiant energy E from the heating tube 14 is obtained, the following equation (6) is obtained. Based on this, when the area A corresponding to energy of 50 kW is obtained, the following equation (7) is obtained.

すなわち、本実施の形態の構成とすることにより、従来の構成の場合に比べて、必要熱交換面積を大幅に減らすことができ、装置（発電システム）のコンパクト化（小型化）を図り得るとともに、装置（発電システム）の構造の簡単化を図ることができる。

That is, by adopting the configuration of the present embodiment, the required heat exchange area can be greatly reduced compared to the conventional configuration, and the device (power generation system) can be made compact (downsized). The structure of the device (power generation system) can be simplified.

  As described above, as the heating means in the high temperature part of the Stirling engine, the heat transfer tube 13 through which the working fluid on the Stirling engine side is flowed is heated by the radiant heat from the heating tube 14 through which the exhaust gas is guided. Compared to the case where heating is performed by heat transfer and heat conduction through clean air flowing between the exhaust gas side and the high temperature part of the Stirling engine as in the configuration, corrosion by the exhaust gas on the heat transfer tube 13 side is prevented. In addition, it is possible to improve the efficiency of one step in the heat transfer path, that is, to improve the heat efficiency, and thus a power generation system having a compact and simple structure can be obtained.

  By the way, in FIG. 1 of the said embodiment, although it illustrated as what inserted only one heating tube 14 in the center of the heat exchanger tube 13 arrange | positioned cyclically | annularly, as shown to FIG. 3 and FIG. A plurality of heating tubes 14 (for example, three on the inner side and 12 on the outer side) can be respectively arranged on the inner side and the outer side of the group 13 of heat transfer tubes. Of course, also in this case, each heating tube 14 is detachably attached to the casing 12 via the flange plate 16.

In this way, since the heat transfer tube 13 group is heated by the radiant heat from the heating tube 14 group arranged inside and outside thereof, more efficient heating can be performed.
In addition, as shown in FIG. 5, about the inner side heating tube 14 arrange | positioned at the center of the heat exchanger tube 13 group, the outer channel | paths 14a of each heating tube 14, and inner channel | paths 14c are gathered together, respectively, and the collection pipe part 14d , 14e may be connected to the outside.

Moreover, in the said embodiment, although the double tube was employ | adopted as a heating tube, a U-shaped tube can also be employ | adopted like a heat exchanger tube, for example.
In the above embodiment, silicon carbide, that is, ceramic is used as the material of the heating tube. However, the heating tube may be made of cast iron, heat-resistant alloy, or the like. In this case, those having a surface coated with a ceramic such as silicon carbide may be used.

  Further, in the above embodiment, by providing an auxiliary burner in the middle of the exhaust gas path, the exhaust gas temperature can be increased when the exhaust gas temperature is low.

It is principal part sectional drawing of the Stirling engine used for the electric power generation system which concerns on embodiment of this invention. It is BB sectional drawing of FIG. It is principal part sectional drawing concerning the modification of the Stirling engine. It is CC sectional drawing of FIG. It is principal part sectional drawing which concerns on the other modification of the Stirling engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirling engine 2 Cylinder 11 Heating chamber 12 Casing 13 Heat transfer tube 14 Heating tube 15 Flange part 16 Flange plate

Claims (3)

A power generation system that generates power by driving a generator with a Stirling engine that uses the heat of exhaust gas as a heat source,
Inside the casing that houses the high temperature part of the Stirling engine and forms a heat exchange chamber, an inner pipe part is provided, and there is an outer passage and an inner passage. While inserting a heating tube with a double tube structure provided,
A power generation system, characterized in that exhaust gas is supplied to the outer passage of the heating pipe and discharged from the inner passage . The power generation system according to claim 1 , wherein ceramic is coated on at least an outer surface of the heating tube. The power generation system according to claim 1 , wherein the heating tube is configured to be detachable from the casing.

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