Cogeneration system using waste-heat gas generated in micro...

Power plants – Combustion products used as motive fluid – For nominal other than power plant output feature

Reexamination Certificate

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C060S039500, C060S039511, C062S238300, C062S480000

Reexamination Certificate

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06519946

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
The present invention is based on Japanese Patent Application No. 2000-174319, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a waste-heat gas driven cogeneration system using waste-heat gas generated from a micro gas turbine so that a cold heat output can be obtained efficiently.
2. Description of the Related Art
Public attention has been paid to a micro gas turbine electric power plant as a distributed electric source recently. The plant uses natural gas or biogas as fuel and the fuel is burned to operate a small-sized gas turbine to thereby generate electric power. However, it cannot be said that energy efficiency in the plant is sufficiently high. Because a large amount of energy is lost as waste heat into exhaust gas, it may be said that the plant is adapted to a cogeneration system for recovering waste heat and using it efficiently. In the background art, a cogeneration system for obtaining hot water by use of waste heat has been proposed from this point of view.
In the background-art cogeneration system for obtaining hot water, however, total efficiency is low and it is hardly worth using the cogeneration system when there is no need for hot water.
On the other hand, electric power is in great demand particularly in the field of freezers and coolers in summer, so that public hopes are put on a cogeneration system capable of supplying cold heat also from the point of view of leveling electric power. From this point of view, there may be conceived a method in which steam is generated from waste-heat gas to thereby operate a freezer using lithium bromide. It is however impossible to obtain a coolant at a temperature not higher than 5° C. because water is used as a coolant theoretically in this method. It is therefore difficult to apply this method to refrigeration. On the other hand, it is conceived that this method is applied to an ammonia absorption type refrigerator in which a coolant in a freezing temperature range can be obtained by use of steam.
Ammonia to be used as a coolant in this refrigerator is however harmful to the human body. Leaking of ammonia to the outside may be caused by corrosion or the like, if a material to be used is selected by mistake. If leaking of ammonia to the outside occurs once, there is a problem in worries about damages such as very great damage to the human body, an offensive odor deposited on peripheral goods and particularly prohibition against foods. It cannot be said that this system is adapted for small-scale industry and private use expected as a distributed electric source. It is conceived that application of this system to private districts and the field of foods is difficult practically.
SUMMARY OF THE INVENTION
The present invention is designed upon such circumstances as the background and an object of the present invention is to provide a waste gas-driven cogeneration system in which thermal energy is obtained effectively from waste heat of exhaust gas generated from a micro gas turbine so that the thermal energy can be used as a driving source to generate cold heat for refrigeration or cooling.
That is, in order to solve the above object, according a first aspect of the present invention, there is provided a cogeneration system using micro gas turbine waste-heat gas, comprising: a micro gas turbine; a driving portion having a high-temperature-side hydrogen storage alloy container and for operating through direct or indirect heat exchange between the high-temperature-side hydrogen storage alloy container and waste-heat gas from the micro gas turbine and a cold-heat heat medium to thereby absorb and release hydrogen; and a cold heat output portion having a low-temperature-side hydrogen storage alloy container and for absorbing and releasing hydrogen by use of the low-temperature-side hydrogen storage alloy container in accordance with the operation of the driving portion to generate cold heat, transmit the cold heat to a cooling heat medium to thereby externally supply the cold heat through the cooling heat medium.
According to a second aspect of the present invention, in the cogeneration system using micro gas turbine waste-heat gas as defined in the first aspect, the heat exchange between the waste-heat gas from the micro gas turbine and the high-temperature-side container is performed indirectly through steam generated by heat of the waste-heat gas.
According to a third aspect of the present invention, in the cogeneration system using micro gas turbine waste-heat gas as defined in the first or second aspect, the driving portions and the cold heat generating portions are provided multistageously respectively so that waste-heat gas subjected to heat exchange in the pre-stage driving portion is further subjected to heat exchange in the post-stage driving portion to thereby make the post-stage driving portion operate.
According to a fourth aspect of the present invention, in the cogeneration system using micro gas turbine waste-heat gas as defined in the third aspect, heat exchange is performed between the waste-heat gas from the micro gas turbine and the pre-stage high-temperature-side container indirectly through steam generated by heat of the waste-heat gas whereas after the heat exchange, and further heat exchange is performed directly between the waste-heat gas after the first heat exchange and the post-stage high-temperature-side container.
According to a fifth aspect of the present invention, the cogeneration system using micro gas turbine waste-heat gas, as defined in any one of the first through fourth aspects, further comprises a hot water generator for generating hot water by performing heat exchange between water of the hot water generator and the waste-heat gas after the waste-heat gas is subjected to the heat exchange in the driving portion.
According to the present invention, waste heat generated from the micro gas turbine is used as a driving source. To use such waste heat, direct or indirect heat exchange is performed between exhaust gas with the waste heat, that is, waste-heat gas and a high-temperature-side hydrogen storage alloy container to thereby recover thermal energy.
Incidentally, for improvement of energy efficiency in the micro gas turbine, the temperature is raised by heat exchange between air taken in the turbine and the waste-heat gas to thereby improve power generating efficiency. As a result, the temperature of the waste-heat gas finally discharged from the micro gas turbine becomes low about 300° C. As described above, a cogeneration system for recovering heat from waste-heat gas and recycling the heat in order to improve energy efficiency in the micro gas turbine plant has been discussed. In the existing situation, nothing but hot water can be obtained because the temperature of waste-heat gas is low as described above. Hence, cold heat necessary for use in coolers and refrigerators particularly in summer cannot be obtained.
According to a first embodiment of the present invention, waste-heat gas by which the background-art heat-driving type cooler system cannot be driven is imported from the micro gas turbine and subjected to direct heat exchange with the hydrogen storage alloy container to thereby generate cold heat. Hence, a refrigeration output can be obtained in a freezing temperature range which can be adapted for small-scale industry and private use, food industry use, etc. This system can be used as a high-energy-efficiency system in a food factory, a convenience store, a supermarket, a hospital, a hotel, or the like. Moreover, this system can be provided as a cogeneration system using a micro gas turbine free from any problem in leaking an offensive odor, or the like.
According to a second embodiment of the present invention, waste-heat gas at a high temperature without heat exchange with intake air can be used to make it possible to attain improvement of energy-utilizing efficiency though power generating efficiency in the micro gas turbine is reduced. That is, he

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