Drying and gas or vapor contact with solids – Process – Gas or vapor contact with treated material
Patent
1998-04-16
2000-10-31
Wilson, Pamela
Drying and gas or vapor contact with solids
Process
Gas or vapor contact with treated material
34478, 34 73, F26B 300
Patent
active
061383813
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to treatment of moist fuel in connection with a power production process, for instance in a steam power plant. The treatment comprises drying of the fuel, which typically may be a biomass fuel.
TECHNOLOGICAL BACKGROUND
It is well known that drying of humid fuel, such as biomass fuel, produces essential advantages in connection with the subsequent combustion of the fuel. Separate drier systems for e.g. biomass fuel have been constructed. Drying heat is then produced, for instance in a separate furnace, wherein part of the moist fuel, is consumed. Flue gases from the oven are used to dry the fuel, for instance in a rotary drier. The moist flue gases from the drier may be condensed for recovery of heat that may be used to pre-dry the fuel to a certain extent before the latter is fed to the drier.
It is likewise known to utilise flue gas condensation in connection with conventional combustion of moist fuel, for instance in a hot water boiler. In this case, the high moisture contents obtained in the flue gases due to the moisture in the fuel are utilised.
PURPOSE OF THE INVENTION
A primary object of the present invention is to provide a process for treatment of moist fuel which in an efficient manner combines fuel drying with flue gas condensation.
A further object of the invention is to provide a process for treatment of moist fuel which in a simple manner may be integrated into conventional power production processes.
Yet another object of the invention is to provide a process for treatment of moist fuel which offers considerable environmental advantages.
A further object of the invention is to provide a process for treatment of moist fuel which is easily adaptable to different power production processes and operational conditions.
SUMMARY OF THE INVENTION
The above objects are achieved by means of a process and a plant possessing the characteristic features defined in the appended claims.
Thus, the invention is based on the knowledge of the advantage of combining drying of moist fuel by means of the conventional combustion air supplied to the combustion section in a power production process with condensing of flue gases from the power production process, said flue gases having become moisture-laden in said drying process. The thus dried fuel preferably is used as the fuel for combustion in the associated combustion section of the power production processing section. The fuel may be used directly after drying or after suitable intermediate storage.
By power production process should in this connection be understood a process essentially producing power and/or heat. Typically, it could be a condensing power plant or a combined power and heating plant based on a steam turbine cycle, a directly or indirectly heated steam turbine cycle, or a combined gas turbine and steam cycle.
By combustion air should be understood air that normally is supplied to the combustion section of the power production process, as a rule air at a low temperature supplied directly from the environment.
The invention involves utilisation in one and the same system of the gas flow passing through the system, without the latter being negatively affected. In an advantageous manner the basis is the combustion section or boiler proper, based on which such modifications of the system as are necessary to the invention can be made easily. It should be noted that the principal process as such may be practically unaffected and that the drier section of the system may handle its own flow of fuel to be dried and that said flow may be entirely independent of the fuel flow which at a certain instant is adequate for the combustion section of the system.
By using combustion air as a medium for drying the fuel it becomes possible to keep the drying temperature low and in addition emissions from the dried fuel will be treated efficiently in the combustion section, since all essential drying medium passes therethrough. In addition, according to the invention intake and discharge of fuel into and out of
REFERENCES:
patent: 5215670 (1993-06-01), Girovich
patent: 5237757 (1993-08-01), Wiedmann et al.
patent: 5263266 (1993-11-01), Schmidt
Joyce Andrea M.
Vattenfall AB (Publ.)
Wilson Pamela
LandOfFree
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