Gas: heating and illuminating – Generators – Cupola
Patent
1991-10-11
1997-04-29
Kepplinger, Esther
Gas: heating and illuminating
Generators
Cupola
48 73, 48 77, 48210, 48202, 422139, 422145, 422147, C10J 372
Patent
active
056244690
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method and apparatus for recovering heat from solid material discharged from hot processes such as combustion or gasification processes and/or from cleaning processes of hot gases. In particular, the invention relates to the reuse of recovered heat in hot processes, and more specifically, it is suitable for recovering heat from the ashes of gasification or combustion processes.
Handling of the ashes derived from the combustion and gasification processes is problematic. For one thing, the hot ash has to be cooled before storing, and for another, spreading of ash and especially the finest ash particles after cooling causes environmental hazards.
Efforts have been made to get rid of fine ash by agglomerating it by means of heating such either in a combustion chamber or in a separate agglomerating means, whereby the ash released from the process becomes more applicable to storage.
It has also been suggested to use ash for drying of fuel. For example, Swedish patent application 8501563-4 discloses mixing of hot ash with fuel prior to feeding the fuel into a combustion chamber. In this case, the moisture possibly contained in the fuel is either absorbed in the ash or evaporates. The fuel becomes drier and it is easier to handle in the equipment constructed for treating conventional dry material. At the same time, however, the quantity of ash circulating in the process becomes greater, which is less desirable in terms of energy economy.
Efforts have also been made to cool and agglomerate ash by mixing water therewith in order to receive ash which is more appropriate for storage, such as is disclosed in DE patent specification 31 01 847. In this disclosure, the cooling water constitutes a problem because the temperature of the water is low, it is difficult to utilize its heat. Depending on the method of cooling and amounts of water, the temperature of the cooling water of ash is generally below 200.degree. C. The water is too cold to be added in the steam circuit. On the other hand, the temperature of the cooling water is not much different from the temperature of the boiler water. Therefore, the cooling water cannot be used for heating of the boiler water with means of reasonable size. Discharging of water and not utilizing its heat is not a good solution either in terms of heat economy.
It is known from U.S. Pat. No. 4,244,706 a gasification process where both gaseous and solid products from the gasification are simultaneously cooled by direct heat exchange with water in a char cooling -device. Thus cooled product gas and vaporized water are separated from the solids and further cooled in order to condensate water and organic materials such as phenols and other aromatics, which are to be recycled. Cooling is accomplished by indirect heat transfer in a heat exchanger. The cooled condensate is mixed with fresh make-up water and thereafter mixed with coal in a mixing tank. The resulting mixture is preheated before being introduced into the gasifier.
It is known through U.S. Pat. No. 4,111,158 a method to cool bed material discharged from a fluidized bed reactor in order to control the bed temperature in the fluidized bed reactor. The bed material is discharged from the reactor into a heat exchanger where the material is cooled indirectly. The cooled bed material is thereafter recycled into the fluidized bed reactor.
The solids required for gasification and combustion processes have to be fed undisturbed into the combustion chamber and in such a manner that the various substances are distributed as evenly as possible over the cross sectional area of the entire combustion chamber. Feeding of dry, fine material, for example, into a pressurized combustion chamber calls for rather complicated equipment. Conveyance of dry material in the pipework prior to feeding it into the combustion chamber is both energy-consuming and difficult. For example, transfer of fine coal causes dusting and the fine coal itself is clearly explosive.
To avoid the above
REFERENCES:
patent: 2782913 (1957-01-01), Donath
patent: 4111158 (1978-09-01), Reh et al.
patent: 4244706 (1981-01-01), Forney et al.
patent: 4276021 (1981-06-01), Karnofsky et al.
patent: 4461629 (1984-07-01), Arisaki
patent: 4542621 (1985-09-01), Andersson et al.
Isaksson Juhani
Ollila Harry
Foster Wheeler Energia OY
Kepplinger Esther
Tran Lien
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