TUKIAINEN, Sampo (Pispalanharju 25, TAMPERE, FI-33250, FI)
Claims :
1. Method for feeding of solid fuel into a process space (1) , such as a firebox, gas chamber or like, by means of a supply arrangement (2) , which comprises an intermediate container (2c) that is to be opened and closed by feeding means (2a) and discharge means (2b) , whereby the level of the fuel (Pa) therein is being kept within set limits by feeding the fuel (Pa) into the intermediate container (2c) by using the feeding means (2a) , when the intermediate container is kept closed by means of the discharge means (2b) , whereby the fuel is being discharged from the intermediate container by using the discharge means (2b) for bringing the fuel into the process space (1) , when the intermediate container is kept closed by the feeding means (2a) , and whereby a flow of process gas taking place from the process space (1) to the surroundings through the supply arrangement (2) for fuel is being prevented by pressurizing the intermediate container (2c) and the discharge means at a pressure that is essentially higher that the pressure in the process space (1) , characterized in that solid fuel (Pa) is being fed into the process space (1) by dropping the same from above by means of a transport conveyor (2bl) , which brings about a counter pressure with respect to the combustion process, and a discharge apparatus (2b2) of open-shut -type, both of the above belonging to the discharge means (2b) .
2. Method according to claim 1, characterized, in that the supply arrangement (2) for fuel, being used with overpressure, is being pressurized by air that is being transmitted preferably by a combustion or gasifying air blower arrangement for the combustion process that takes place in the process space, which air is being brought into the intermediate container (2c) with a volume flow (V) that corresponds essentially to the amount of the fuel being fed to the process space (1) , whereby an air flow (w) takes place from the intermediate container (2c) via the transport conveyor (2bl) through the discharge apparatus (2b2), existing in open-position, into the process space (1) .
3. Method according to claim 1 or 2, characterized in that the fuel (Pa) is being fed into the process space (1) by means of a continuous drive transport conveyor (2bl), which is preferably steplessly adjustable and essentially gas tight with respect to the surroundings, such as a scraper, screw conveyor or like operated in a frequency converter adjusted manner and that feeds the fuel, being discharged from the intermediate container (2c) , into the process space (1) with a volume flow corresponding to the desired capacity of the combustion process.
4. Supply arrangement for feeding of solid fuel into a process space (1) , such as a firebox, gas chamber or like, which comprises an intermediate container (2c) that is to be opened and closed by feeding means (2a) and discharge means (2b) , whereby the level of the fuel (Pa) therein is kept within set limits by feeding the fuel (Pa) into the intermediate container (2c) by using the feeding means (2a) , when the intermediate container is kept closed by means of the discharge means (2b) , whereby the fuel is discharged from the intermediate container by using the discharge means (2b) for bringing the fuel into the process space (1) , when the intermediate container is kept closed by the feeding means (2a) , and whereby a flow of process gas taking place from the process space ( 1 ) to the surroundings through the supply arrangement (2) for fuel is prevented by pressurizing the intermediate container (2c) and the discharge means at a pressure that is essentially higher that the pressure in the process space (1) , characterized in that solid fuel (Pa) is being fed into the process space (1) by dropping the same from above by means of a transport conveyor (2bl) , which brings about a counter pressure with respect to the combustion process, and a discharge apparatus (2b2) of open-shut -type, both of the above belonging to the discharge means (2b) .
5. Supply arrangement according to claim 4, characterized in that the supply arrangement (2) for fuel that is used with overpressure, is pressurized by air that is brought into the intermediate container (2c) with a volume flow (V) that corresponds essentially to the amount of the fuel being fed to the process space (1) , whereby an air flow (w) takes place from the intermediate container (2c) via the transport conveyor (2bl) through the discharge apparatus (2b2), existing in open-position, into the process space (1) .
6. Supply arrangement according to claim 5, characterized in that the air, being used for pressurizing of the intermediate container (2c) , is led by a combustion or gasifying air blower arrangement for the combustion process that takes place in the process space (1) .
7. Supply arrangement according to any of the above claims 4-6, characterized in that the transport conveyor (2bl) that feeds the fuel (Pa) into the process space (1) , is a continuous drive scraper, screw conveyor or like.
8. Supply arrangement according to claim 7 , characterized in that the transport conveyor (2bl) is arranged to be used steplessly, such as adjusted by a frequency converter, in order to feed the fuel that has been discharged from the intermediate container (2c) into the process space (1) with a volume flow corresponding to the desired capacity of the combustion process.
9. Supply arrangement according to any of the above claims 4-8, characterized in that the intermediate container (2c) and the transport conveyor
(2bl) are arranged by essentially gas tight structures with respect to the surroundings.
10. Supply arrangement according to any of the above claims 4-9, characterized in that the feeding means (2a) and the discharge apparatus (2b2) belonging to the discharge means are arranged by ball, spherical valves or like, the size of which being between DN 75- DN 200 and particularly, when using wood chips, preferably DN 150. |
Method and supply arrangement for feeding of solid fuel
The invention relates to a method for feeding of solid fuel into a process space, such as a firebox, gas chamber or like, by means of a supply arrangement, which comprises an intermediate container that is to be opened and closed by feeding means and discharge means, whereby the level of the fuel therein is being kept within set limits by feeding the fuel into the intermediate container by using the feeding means, when the intermediate container is kept closed by means of the discharge means. The fuel is being discharged from the intermediate container by using the discharge means for bringing the fuel into the process space, when the intermediate container is kept closed by the feeding means.
For the purpose described above it is know to use e.g. an apparatus of so called lock-hopper -type, which comprises an intermediate container that can be closed by upper and lower valves. This kind of an apparatus is being used in a way that the upper valve is being opened, whereafter the intermediate container is being filled with fuel. After this the upper valve is being closed, whereafter the fuel may fall down into the process space through the opened lower valve. After this the lower valve is being closed.
An alternative way in this context is such, that a desired stoking of fuel is being brought on top of the upper valve, whereafter the upper valve is being opened and the stoking of fuel is being allowed to fall down into the intermediate container. After this the upper valve is being closed, whereafter the fuel falls, when the lower valve is opened, into the
process space, whereafter the lower valve is being closed.
Due to its operating principle, a lock-hopper -apparatus of the above type can not be totally gas tight. This is why an amount of gas corresponding to the volume of the fuel that has been fed gets drifted from the process space into the intermediate container during each and every feed cycle. This gas gets released to the surroundings when the intermediate container is being charged with the following stoking of fuel. There is also an other problem related to the operation of the lock-hopper apparatus, whereby the stoking of fuel is firstly brought on top of the valve, where it is expected to flow through when the valve gets opened. Supply of solid fuel carried out in this way requires, however, particularly due to a hanging up -problem generally valves with very big openings (at least of size DM 250) , which are very expensive. This is why a type of operating principle as described above has been found unreliable in practice. A third problem related to the type of apparatus described above is caused by the stoking- based supply of fuel into the process space, being obligatory in this context. In this respect particularly a combustion process with a character of a gasifying process requires in practice a continuous and stepless supply of fuel that follows the capacity of the combustion process in order to operate optimally. These kinds of solutions, can not, however, be carried out by apparatuses of ordinary lock-hopper -type, but instead complicated solutions and apparatuses, which are in practice very hard to adjust, are required, in order to achieve at least a satisfactory operating of the gasifying process.
It is the aim of the method according to the present invention to achieve a decisive improvement in the problems described above and thus to raise essentially the level of prior art. In order to achieve this aim, the method according to the invention is primarily characterized by that a flow of process gas taking place from the process space to the surroundings through the supply arrangement for fuel is being prevented by pressurizing the intermediate container at a pressure that is essentially higher than the pressure in the process space and by feeding the fuel into the process space by means of a transport conveyor, which brings about a counter pressure with respect to the combustion process, and a discharge apparatus of open-shut -type, both of the above belonging to the discharge means .
As the most important advantages of the method according to the invention may be mentioned the simplicity and efficiency of its operating principle and use. By the method according to the invention it is possible to carry out reliably enough over- pressurized supply of solid fuel, being strived after for a very long time, with a very simple supply arrangement from a technical point of view. A flow of process gas from the process space through the supply arrangement for fuel to the surroundings can be totally eliminated thanks to the invention, due to the pressure in the intermediate container being essentially higher than the pressure in the process space, which is why a flow of process gas therefrom towards the supply arrangement is not possible. The supply arrangement for solid fuel, being used with overpressure, is being pressurized advantageously by a combustion or gasifying air arrangement for the combustion process that takes place in the process
space, which air is being brought into the intermediate container with a volume flow that corresponds essentially to the amount of fuel, being fed into the process space. In this case, an air flow is taking place in practice from the intermediate container by transmission of the transport conveyor through the opened discharge means into the process space, and not under any circumstances vice versa.
Advantageous embodiments of the method according to the invention have been presented in the dependent claims related to the same.
The invention relates also to a supply arrangement operating according to the method, which arrangement has being defined in greater detail in the preamble of the independent claim related to the same . The primarily characteristic features of the supply arrangement according to the invention have been defined in the characterizing part of the corresponding claim.
By means of the supply arrangement according to the invention it is possible to carry out supply of fuel particularly for a combustion process, which is very demanding from the technical point of view, first of all in a continuously operating manner and on the other hand in a way that process gases from the process space may not get drifted therefrom to the surroundings. This has been made possible by a very simple supply arrangement technically by pressurizing an intermediate container thereof into a pressure that is essentially higher than the pressure in the process space and by feeding the fuel by means of a transport conveyor, which brings about a counter pressure with respect to the combustion process, and a discharge
apparatus of open-shut -type, both of the above belonging to the discharge means. A supply arrangement for solid fuel, being carried out according to the invention and used with overpressure, can be pressurized with air that is fed into the intermediate container with a volume flow corresponding essentially to the amount of fuel, being fed into the process space, thanks to which a flow of air takes place from the intermediate container through the transport conveyor and the discharge means, existing in open- position, into the process space, and not vice versa. At its simplest, the air, being used for pressurizing of the intermediate container, is being led from the combustion or gasifying air arrangement of the combustion process that takes place in the process space, thanks to which the pressurization as such does not require extra devices with respect to traditional solutions .
Advantageous embodiments of the supply arrangement according to the invention have been described in the dependent claims related to the same.
In the following description, the invention is being depicted in greater detail with reference to the attached drawings, in which,
in figure 1 is shown the operating principle of an apparatus of lock-hopper -type according to prior art, and
in figure 2 is shown the operating principle of a supply arrangement operating according to the method according to the invention.
The invention relates to a method for feeding of solid fuel into a process space 1, such as a firebox, gas chamber or like, by means of a supply arrangement 2, which comprises an intermediate container 2c that is to be opened and closed by feeding means 2a and discharge means 2b, whereby the level of the fuel Pa therein is being kept within set limits, advantageously automatically and controlled i.e. by level measuring means 2d, as shown in figure 1, by feeding the fuel Pa into the intermediate container 2c by using the feeding means 2a, when the intermediate container is kept closed by means of the discharge means 2b. The fuel is being discharged from the intermediate container by using the discharge means 2b for bringing the fuel into the process space 1, when the intermediate container is kept closed by the feeding means 2a. A flow of process gas taking place from the process space 1 to the surroundings through the supply arrangement 2 for fuel is being prevented on the principle shown in figure 2 by pressurizing the intermediate container 2c at a pressure, which is essentially higher that the pressure in the process space 1 and by feeding the solid fuel Pa into the process space 1 by means of a transport conveyor 2bl, which brings about a counter pressure with respect to the combustion process, and a discharge apparatus 2b2 of open-shut -type, both of the above belonging to the discharge means 2b.
The supply arrangement 2 for fuel, being used with overpressure, is being pressurized by air that is being transmitted advantageously by a combustion or gasifying air blower arrangement for the combustion process that takes place in the process space 1, which air is being brought into the intermediate container 2c with a volume flow V that corresponds essentially
to the amount of the fuel being fed into the process space 1, whereby an air flow w takes place from the intermediate container 2c via the transport conveyor 2bl through the discharge apparatus 2b2 , existing in open-position, into the process space 1. In this connection it is possible to take advantage of the air that is brought directly from the air blower arrangement for the combustion process, taking place in the process space, since the air that is led from this source to the combustion process will suffer greater pressure losses, whereby a lower pressure level will be caused naturally in the combustion process, when compared to the intermediate container that is pressurized by "free blow".
As a further advantageous embodiment, the fuel Pa is being fed into the process space 1 by means of a continuous drive transport conveyor 2bl, which is advantageously steplessly adjustable and essentially gas tight with respect to the surroundings, such as a scraper, screw conveyor or like operated in a frequency converter adjusted manner and that feeds the fuel, being discharged from the intermediate container 2c, into the process space 1 with a volume flow corresponding to the desired capacity of the combustion process.
The invention relates also to a supply arrangement for carrying out the method described above, which is based on the fact that a flow of process gas taking place from the process space 1 to the surroundings through the supply arrangement 2 for fuel is prevented by pressurizing the intermediate container 2c at pressure that is essentially higher that the pressure in the process space 1 and by feeding solid fuel Pa into the process space 1 by means of a transport
conveyor 2bl, which brings about a counter pressure with respect to the combustion process, and a discharge apparatus 2b2 of open-shut -type, both of the above belonging to the discharge means 2b.
The supply arrangement 2 for fuel, being used with overpressure, is pressurized by air that is brought into the intermediate container 2c with a volume flow V that corresponds essentially to the amount of the fuel being fed to the process space 1, by influence of which an air flow w takes place from the intermediate container 2c via the transport conveyor 2bl through the discharge apparatus 2b2 , existing in open- position, into the process space 1.
The air, being used for pressurizing of the intermediate container 2c, is led as an advantageous embodiment by a combustion or gasifying air blower arrangement for the combustion process that takes place in the process space 1. According to the advantageous embodiment shown in figure 2, the intermediate container 2c is equipped furthermore with a draught valve 3, which aids feeding of the intermediate container 2c by letting out an amount of air that corresponds to the amount of fuel being fed therein, and with an explosion door 5. In the substitute air channel there has been arranged correspondingly a closing valve 4. The feeding means 2a and the draught valve 3 are coupled with each other to operate simultaneously in a way that they are both in open-position when the substitute air valve 4 is closed and in closed-position when the substitute air valve 4 is open.
Furthermore as an advantageous embodiment in practice, the transport conveyor 2bl that feeds the fuel Pa into
the process space 1 is a continuous drive scraper, screw conveyor or like. Furthermore the intermediate container 2c and the transport conveyor 2bl are carried out advantageously by essentially gas tight structures with respect to the surroundings.
As a further advantageous embodiment the transport conveyor 2bl is arranged to be used steplessly, such as adjusted by a frequency converter, in order to feed the fuel that has been discharged from the intermediate container 2c into the process space 1 with a volume flow that corresponds to the desired capacity of the combustion process.
The feeding means 2a and the discharge apparatus 2b2 belonging to the discharge means are arranged in simplicity by ball, spherical valves or like, the size of which being between DN 75-DN 200 and particularly, when using wood chips, preferably DN 150. In the supply arrangement according to the invention it is possible to use smaller sized valves than in traditional solutions, which is thanks to the fact that the transport conveyor of the supply arrangement brings the solid fuel in a controlled manner as a continuous flow, which furthermore falls down through an open discharge means 2b2 into the process space. In this way it is possible to avoid those hanging up - problems related to traditional solutions, because the fuel is not being gathered into a loaf before dropping the same into the process space.
It is clear, that the invention is not limited to the solutions presented or described above, but instead it can be varied within the basic idea of the invention according to the operating purpose and embodiments respectively. It is thus first of all possible to
provide the supply arrangement, being exploited in the method, with more abundant equipment and automation, such as e.g. for monitoring of a hanging up - phenomenon in the intermediate container or with a view to other corresponding exceptional disturbance situations, which may be caused e.g. due to very nonhomogeneuous , wet or frozen solid fuel. It is furthermore naturally possible to provide the intermediate container e.g. with detectors for monitoring of temperature or pressure, by guidance of which the process can be halted under extreme situations. It is furthermore naturally possible to equip the intermediate container and/or the transport conveyor with visual monitoring devices, such as sight glasses or like.
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