Power plants – Combustion products used as motive fluid – With combustible gas generator
Reexamination Certificate
1999-04-29
2001-06-12
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
With combustible gas generator
C060S736000
Reexamination Certificate
active
06244038
ABSTRACT:
THE BACKGROUND OF THE INVENTION AND PRIOR ART
The present invention relates to a combustion plant for a combustion process, comprising a combustion chamber in which combustion of a fuel is to take place while producing combustion gases, a gasifying device which is arranged to produce a combustible gas and a degassed combustible rest product, and transportation means which are arranged to discharge said rest products from the gasifying device and supply it to the combustion chamber for combustion of the rest product in the combustion chamber.
The present invention will now be discussed and enlightened in different applications in connection to a pressurized fluidized bed, a so called PFBC-power plant (Pressurized Fluidized Bed Combustion). However, the invention is not delimited to such applications, but can be employed in all possible types of heat and power plants, for example in connection to different types of gas turbine plants.
It is known to combust different fuels in a bed of particulate, non-combustible material which is supplied with combustion air from below through nozzles in such a way that the bed becomes fluidized. The combustion gases formed during the combustion process pass a freeboard above the bed, whereafter they are purified and guided to a gas turbine. The combustion gases drive the gas turbine which in its turn drives an electric generator on one hand and a compressor which supplies the pressure vessel with compressed air on the other hand. In the bed the fuel is combusted at a temperature in the order of 850° C. To be able to maintain this temperature at a required level it is known to arrange an additional combustion in the freeboard above the bed. This additional combustion may take place by means of a burner in which the combustible gas from a gasifying plant is combusted. By such a gasifying plant it is known to gasify coal and produce said combustible gas and a degassed rest product, such as coke (“char coal”). This rest product can be delivered to the combustion chamber and be combusted in the fluidized bed. However, it is difficult to transport the degassed rest product from the gasifying device to the combustion chamber because the rest product has a very high temperature and is also combustible. This means that valves and other control members that are necessary for this transport must be made of temperature-resistant and accordingly, expensive materials. Moreover, the degassed rest product cannot be transported by means of air due to the risk of self-ignition, but instead inert gases, such as nitrogen, must be employed, also resulting in the operation of the plant becoming expensive.
SE-B-458 955 shows a PFBC-plant with a pressure vessel in which a combustion chamber and a gasifying reactor are arranged. The combustible gases generated in the gasifying reactor are conducted to a topping combustion chamber located outside the pressure vessel and for increasing the temperature of the combustion gases before these ones are conducted to a gas turbine. The combustion chamber and the gasifying reactor are only separated by a separation wall which, in its bottom part, permits passage of combustible material between the gasifying reactor and the combustion chamber.
SUMMARY OF THE INVENTION
The object of the present invention is to remedy the above problems and more precisely to accomplish a combustion plant with a gasifying device the degassed rest product of which can be taken advantage of in a simple way and combusted in the combustion chamber of the combustion plant.
This object is obtained by the combustion plant initially defined, which is characterized by means which are arranged to cool said rest product which is discharged from the gasifying device. Through the inventive measure the handling of the degassed rest product is substantially facilitated. The rest product can now be transported by means of conventional aids, such as for example pressurized air, without the risk of self-ignition in the transportation system. Furthermore, the valves and control members employed to control the supply of the rest product to the combustion chamber may be of a conventional type and, accordingly, do not need to be adjusted to high temperatures.
According to one embodiment of the invention, said cooling means are connected to means which are arranged to recover the heat gained during the cooling of the rest product in said process. In that way the total efficiency of the combustion plant can be kept at a high level. Thereby, said recovery means may advantageously be arranged to heat the fuel before it is fed into the combustion chamber. By preheating and drying the fuel, for example coal, in this way before it is supplied to the combustion chamber, also the combustion in the fluidized bed is facilitated. Furthermore, the plant may comprise means for feeding an absorbent into the combustion chamber, the recovery means possibly being arranged to heat the absorbent before it is fed into the combustion chamber.
According to another embodiment of the invention, a circuit conduit is arranged to conduct a medium between said cooling means and said recovery means, said cooling means being arranged to transmit the heat of the rest product to said medium, and the recover y means being arranged to emit the heat of the medium.
According to another embodiment of the invention, said transportation means comprise a supply conduit downstream of said cooling means, which conduit is connected to the combustion chamber and arranged to supply the combustion chamber with said rest product by means of pressurized gas containing oxygen. Thanks to the inventive cooling such a gas containing oxygen can be employed without any risk of self-ignition in the supply conduit. The employment of such gas containing oxygen, such as for example air, is favourable in comparison to the employment of other inert gases in this context such as for example nitrogen gas, as it is often accessible and also the cheapest one. Advantageously, said transportation means comprise a discharge conduit with a discharging device which is arranged to make a continuous discharge of the combustible rest product from the gasifying device possible. Thereby, advantageously, the discharge conduit comprises said cooling means, and these are arranged upstream of the discharging device. In that way, the discharging device can be made of relatively simple components comprising a first valve member, a container arranged downstream of the first valve member, and a second valve member arranged downstream of the container.
According to another embodiment of the invention an additional combustion device is arranged to make a control of the temperature of the combustion gases possible through combustion of the combustible gas. Thereby, a channel member may be arranged to conduct said combustion gas from the combustion chamber to one or more gas turbine steps for extracting energy therefrom, the additional combustion device being arranged in the channel member upstream of at least one of the gas turbine steps. In that way the combustion gases can be given a temperature which corresponds to optimum operational conditions for the gas turbine, that is a temperature of approximately 1200-1500° C. Furthermore, the combustion chamber may be enclosed in a pressure vessel and enclose a pressurized fluidized bed, the additional combustion device possibly comprising a burner which is arranged to accomplish a combustion in the combustion chamber in a space downstream of the bed. In that way the possibilities to control the temperature in the combustion chamber, especially at a low load, are improved, and it can be made sure that the combustion gases leaving the combustion chamber always have generally the same temperature.
REFERENCES:
patent: 3991557 (1976-11-01), Donath
patent: 4253409 (1981-03-01), Wormser
patent: 4470255 (1984-09-01), Rowlands et al.
patent: 4896497 (1990-01-01), Pillai
patent: 5134841 (1992-08-01), Rehwinkel et al.
patent: 5469698 (1995-11-01), Garcia-Mallol
patent: 0 468 357 A1 (1992-01-01), None
patent: 0 503 77
Brannstrom Roine
Lovgren Anders
Veenhuizen Dirk
Asea Brown Boveri AB
Casaregola Louis J.
Connolly Bove & Lodge & Hutz LLP
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