Heat exchange – With thermal or acoustical blocker
Reexamination Certificate
2001-11-06
2004-01-13
Ciric, Ljiljana (Department: 3743)
Heat exchange
With thermal or acoustical blocker
C165S136000, C165S901000, C165S905000, C110S302000
Reexamination Certificate
active
06675880
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the air heater for recovering a heat of exhaust gas from an incinerator for disposing wastes. More particularly, the invention relates to an apparatus for heating air that is capable of recovering heat energy out of burnt exhaust gas of elevated temperature by heat exchange with air and hence of using the resultant heat energy to advantage, where exhaust gas occurs during incineration of wastes (in which are included combustibles of general wastes such as municipal wastes disposed of by households and offices and also of industrial wastes such as waste plastics, shredded car dusts, waste office equipment, waste electronic equipment, waste cosmetic containers and the like) in a incinerator for municipal wastes and in an incinerator for industrial wastes. The invention also relates to an apparatus for disposing of wastes which is provided with the above heating apparatus.
BACKGROUND ART
An incinerator for municipal wastes and an incinerator for industrial wastes have been equipped with an apparatus for heating high-temperature air in order to recover and utilize the heat energy of burnt gas of elevated temperature derived by incinerating those wastes. This heating apparatus of high-temperature air is so designed that heat is recovered by allowing air to flow through a heat transfer conduit formed of a metal, followed by heating of the air on heat exchange with the burnt gas of elevated temperature. The heat energy thus recovered is utilized as a heat source in decomposing wastes thermally, in generating electricity and in other systems.
In
FIG. 49
, there is shown one form of a conventional heating apparatus of high-temperature air. A burning melting portion
49
is located upwardly of a burning melting furnace
53
, and a heating apparatus
1
of high-temperature air is disposed downwardly of that apparatus. In the burning melting portion
49
, gas and air for use in combustion are supplied to a burner
56
so as to burn combustible components such as wastes at a high temperature of about 1300° C. so that a melted slug
53
f
and a burnt exhaust gas G are generated. Usually, the burnt exhaust gas G contains dust (refuse) and constitutes a highly corrosive gas including corrosive materials such as chlorine and hydrogen chloride which, however, depend on the kind of wastes. In such furnace, the burnt exhaust gas flows at a temperature of 1000-1100° C. and at a flow rate of about 2-3 m/sec. The heating apparatus
1
of high-temperature air is essentially constructed with a heat transfer conduit
9
arranged to recover the heat from the burnt exhaust gas G of high temperature stated above. For the heating apparatus
1
of high-temperature air to entrap heated air in a large quantity, the heat transfer conduit
9
is structured to be elongate and is usually disposed in a plurally paralleled posture.
It is required, therefore, that such heat transfer conduit located in the incineration furnace and exposed to a high temperature and to a highly corrosive gas atmosphere should be sufficiently durable, in respect of both the material and the structure, with respect to the corrosive gas of elevated temperature noted above. As means for imparting improved corrosion resistance to the heating apparatus of high-temperature air, it is thought that a stud pin could be welded to the heat transfer conduit formed of a metal, and an castable refractory material could be placed in surrounded relation to that pin and that refractory bricks basically of a rectangular parallelopiped shape could be arranged with their joints connected lengthwise and widthwise. These systems permit such a refractory material to act as a physical barrier against convection and mutual diffusion in a corrosive gas phase, and therefore, can somewhat prevent the heat transfer conduit from getting corroded.
Problems to be Solved by the Invention
However, each such system leads to cracked refractory material, eventually resulting in corroded and impaired fixing jig for the refractory material, or in damaged and detached refractory material itself, because of the difference in thermal expansion which arises from combination of different materials between the refractory material and the metallic heat transfer conduit. This causes a serious corrosion phenomenon in which the metallic heat transfer conduit becomes corrosively damaged, creating the problem that the heating apparatus of high-temperature air suffers from shortened service life and hence from reduced working efficiency with consequent decline in the efficiency of heat recovery upon heat exchange.
Moreover, the heat transfer conduit has the problem that it is rather elongate and hence liable to be thermally deformable and bendable. Another problem is that since a plurality of heat transfer conduits are disposed in parallel to each other, dust contained in an exhaust gas gets deposited between those conduits, thus inviting reduced efficiency of heat recovery based on heat exchange.
One object of the present invention is to attain prolonged service life in an apparatus for heating high-temperature air and also to make the apparatus highly efficiently workable, thereby gaining improved efficiency of heat recovery through heat exchange. For other objects, the invention provides an apparatus for heating high-temperature air which is less thermally deformable and less susceptible to dust deposition, and further an apparatus for disposing of wastes which is provided with such heating apparatus.
Disclosure of the Invention
In order to achieve the foregoing objects, the present invention is constructed as will be described hereinbelow.
In the invention recited in claim 1, there is provided an apparatus for heating high-temperature air characterized in that such appratus is located for use in an atmosphere containing a gas of elevated temperature and has a heat transfer conduit disposed to heat, by means of heat exchange with the gas of elevated temperature, air to be heated and caused to flow through the heat transfer conduit, and such heat transfer conduit comprises a heat transfer pipe arranged to flow the air to be heated therethrough, and a refractory protective pipe formed of a refractory material and held in coaxially covered relation to the heat transfer pipe with a gapping defined between the protective pipe and the heat transfer pipe.
According to this invention, the heat transfer pipe (usually formed of a metal) and the refractory protective pipe formed of a refractory material are less susceptible, by the provision of such gapping, to mutual propagation of those effects attributable to different thermal expansion of the different materials used for formation of both pipes. This makes it possible to reduce damaged and detached portion of the refractory material which tends to result from such varied thermal expansion.
In the invention recited in claim 2, there is provided an apparatus for heating high-temperature air characterized in that such apparatus is located for use in an atmosphere containing a gas of elevated temperature and has a heat transfer conduit disposed to heat, by means of heat exchange with the gas of elevated temperature, air to be heated and flowing through the heat transfer conduit, and such heat transfer conduit comprises an inner heat transfer pipe formed of a metal and opened at a tip thereof, and an outer heat transfer pipe formed of a refractory material and held in coaxially covered relation to the inner metallic heat transfer pipe with a spacing defined between the outer and inner pipes, and after being caused to flow through the inner metallic heat transfer pipe, the air to be heated is heated with the gas of elevated temperature while the former air is being passed at from the open tip of the inner pipe through the spacing between the inner and outer pipes.
In this invention, damaged and detached portion of the refractory material due to the different thermal expansion stated above can likewise be reduced by the provision of such gap passage.
The invention recited in claim 3 is as set forth
Harada Yasuaki
Kiuchi Hidehiro
Miura Kenzo
Namba Masao
Shimamura Kazuo
Ciric Ljiljana
Mitsui Engineering and Shipbuilding Company Limited
Parkhurst & Wendel L.L.P.
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