Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including heat exchanger for reaction chamber or reactants...
Reexamination Certificate
1996-01-25
2001-04-03
Straub, Gary P. (Department: 1754)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including heat exchanger for reaction chamber or reactants...
C501S134000, C165S009200, C165S905000, C165SDIG003, C165SDIG004
Reexamination Certificate
active
06210645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a honeycomb regenerator for recovering a waste heat in an exhaust gas by passing the exhaust gas and a gas to be heated alternately therethrough, which is constructed by stacking a plurality of honeycomb structural bodies and especially relates to the honeycomb regenerator used in an exhaust gas having a high temperature or a corrosive exhaust gas having a high temperature.
2. Related Art Statement
In a combustion heating furnace used for an industries such as a blast furnace, an aluminum melting furnace, a glass melting furnace or the like, a regenerator used for improving a heat efficiency, in which a firing air is pre-heated by utilizing a waste heat of an exhaust gas, has been known. As such regenerators, Japanese Patent Laid-Open Publication No. 58-26036 (JP-A-58-26036) discloses a regenerator utilizing ceramic balls, and also Japanese Patent Laid-Open Publication No. 4-251190 (JP-A-4-251190) discloses a regenerator utilizing honeycomb structural bodies.
In the known regenerator mentioned above, at first an exhaust gas having a high temperature is brought into contact with the ceramic balls or the honeycomb structural bodies to store a waste heat of the exhaust gas in the regenerator, and then a gas to be heated having a low temperature is brought into contact with the thus pre-heated regenerator to heat the gas to be heated, thereby utilizing the waste heat in the exhaust gas effectively.
Among the known regenerators mentioned above, in the case of using the ceramic balls, since a contact area between the ceramic balls and the exhaust gas is small due to a large gas-flowing resistivity of the ceramic balls, it is not possible to perform a heat exchanging operation effectively. Therefore, there occurs a drawback such that it is necessary to make a dimension of the regenerator large.
Contrary to this, in the case of using the honeycomb structural bodies, since a geometrically specific surface thereof is large as compared with a volume thereof, it is possible to perform the heat exchanging operation effectively even by a compact body. However, in an actual industrial heating furnace such as a glass melting furnace and a ceramic firing furnace, an operating temperature becomes over 1400° C. Therefore, if a honeycomb regenerator constructed by cordierite honeycomb structural bodies, which are widely used in a field of automobiles as a catalyst carrier, is applied to the heating furnaces mentioned above, the cordierite honeycomb structural bodies become soft and in an extreme case melted. This is because a softening temperature of the cordierite honeycomb structural bodies is about 1400° C. In this case, the honeycomb regenerator cannot be used.
Moreover, in order to improve anti-corrosive properties, a prior art honeycomb regenerator is known, which is constructed by stacking anti-corrosive honeycomb structural bodies and cordierite honeycomb structural bodies. However, the honeycomb regenerator mentioned above cannot be used in a blasting furnace where the temperature reaches about 1300° C. and foreign substances such as an iron scale are included in an exhaust gas. For Example, if use is made of an alumina honeycomb structural body as the anti-corrosive honeycomb structural body, the alumina honeycomb structural body is not reacted with the iron scale, and thus it is no problem. However, in the blasting furnace, an abrupt temperature change occurs during a normal operation. In this case, the alumina honeycomb structural body is susceptible to breakage by the abrupt temperature change mentioned above, since alumina has a high thermal expansion coefficient and a low thermal shock resistance. Further, if the other anti-corrosive honeycomb structural bodies such as mullite, SiC are used, mullite and SiC have a high thermal expansion coefficient, and thus the honeycomb structural bodies are also susceptible to breakage due to an abrupt temperature change as is the same as the alumina honeycomb structural body. Moreover, in order to improve anti-corrosive properties, it is thought that the size of one honeycomb structural body is made small, but in this case a handling operation of the honeycomb regenerator becomes troublesome.
Further, in a heating furnace using a heavy fuel oil, SOx is generated due to a sulfur component included in the heavy oil and is reacts with a water component at a temperature under a dew point of SOx, so that a diluted sulfuric acid is generated. Therefore, if use is made of the cordierite honeycomb structural body in the atmosphere mentioned above, the cordierite honeycomb structural body is corroded.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate the drawbacks mentioned above and to provide a honeycomb regenerator which can perform a heat exchanging operation effectively even in an exhaust gas having a high temperature and in an exhaust gas having a high temperature and a corrosive property.
According to a first embodiment of the invention, a honeycomb regenerator for recovering a waste heat in an exhaust gas by alternately passing an exhaust gas and a gas to be heated therethrough, constructed by stacking a plurality of honeycomb structural bodies, compromising (a) honeycomb structural bodies arranged in a high temperature portion, in which a temperature thereof is over 1250° C. during a normal operation of a furnace, are made of aluminum-titanate as a main crystal phase or a combination of aluminum-titanate and mullite, and (b) honeycomb structural bodies arranged in a low temperature portion are made of cordierite and/or mullite as a main crystal phase.
According to a second embodiment of the invention, a honeycomb regenerator for recovering a waste heat in an exhaust gas by alternately passing an exhaust gas and a gas to be heated therethrough, constructed by stacking a plurality of honeycomb structural bodies, comprising (a) honeycomb structural bodies arranged in a high temperature portion, to which said exhaust gas having a high temperature is contacted, are made of aluminum-titanate as a main crystal phase or a combination of aluminum-titanate and mullite, (b) said honeycomb structural bodies arranged in a middle temperature portion, in which a temperature is at least over 1200° C., are made of alumina as a main crystal phase, and (c) honeycomb structural bodies arranged in a low temperature portion, in which a temperature is lower than that of said alumina honeycomb structural bodies, are made of one material or a combination of materials selected from a group of cordierite, mullite and a porcelain having a corrosion resistivity.
REFERENCES:
patent: 4143704 (1979-03-01), Kandakov et al.
patent: 4379109 (1983-04-01), Simpson
patent: 4421702 (1983-12-01), Oda et al.
patent: 4533584 (1985-08-01), Takeuchi et al.
patent: 4767731 (1988-08-01), Asami et al.
patent: 2 545 917 A1 (1984-05-01), None
patent: 58-26036 (1983-02-01), None
patent: 4-251190 (1992-09-01), None
Kotani Wataru
Kumazawa Kazuhiko
NGK Insulators Ltd.
Straub Gary P.
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