EP2746661B1 - Combustion facility - Google Patents

Description

The invention relates to a combustion system for burning a main fuel and additional fuels with a first train, with at least one main burner for burning a main fuel and with a fluidized bed.

The invention further relates to a method for burning a main fuel and additional fuels, in a combustion system for burning additional fuels with a first train, with at least one main burner for burning a main fuel and with a fluidized bed.

In industrial locations where flammable waste materials are generated, it has proven effective to build combustion power plants. In this way, the mass and volume of the waste materials generated can be greatly minimized on the one hand, and on the other hand, the location can cover part or all of its energy requirements itself. Fluidized bed furnaces are often used for this. However, these have the disadvantage that, due to the high temperatures prevailing inside the incineration plant, not all of the substances that are produced can be burned. Many waste materials, such as concentrates from particleboard production, lyes from paper and pulp production, waste from bioethanol production or agricultural residues, form ashes that have a melting point that is below the normal combustion temperature of such a plant. If these substances are burned in conventional plants, the described ashes or their melts can come into contact with the fluidized bed. As a result, sintering of the bed material occurs, which ultimately severely affects the fluidization in the fluidized bed, and also leads to excessive deposits on the walls. The bed material therefore requires expensive additives and has to be exchanged frequently, and the system requires frequent cleaning work, which, particularly as a result of the shutdown of the furnace, further high Costs. It is here, for example, from the EP 0 862 019 A1 , EP 0 748 983 A1 ,
DE 199 10 530 A1 and US 3,208,411 Plants with grate firing are known in which the gases are post-burned. The US 3,843,339 , BE1018137A3 , US 2007 / 0234937A1 and EP343535A2 show plants with fluidized bed boilers. The object of the invention is therefore to provide a method for burning such additional fuels which avoids or reduces the disadvantages mentioned above.

This object is achieved by an incinerator of the type mentioned at the outset, which is characterized in that an additional burner for burning additional fuels, the ashes of which have a melting point of less than 800 ° C., is arranged in a region which is at least partially separated from the fluidized bed by a guide device .

This object is further achieved by a method of the type mentioned at the outset, which is characterized in that ashes produced during the combustion of the additional fuels with an additional burner are guided with a guide device into an area separated from the main burner and the additional fuel is burned in an area of the incineration plant, in which gases produced during the combustion of the main fuel are cooled to a temperature below 800 ° C., in particular below 700 ° C., the ashes having a melting point below 800 ° C.

All fuels, the combustion of which has proven to be unproblematic with regard to the ash melting points, for example lignin, are conceivable as the main fuel. Additional fuels can be, for example, alkalis from pulp or paper production. The one when burning this Additional fuels produced ashes can have a melting point below 800 ° C depending on the composition. The temperatures in the combustion chamber in the combustion area are usually above 800 ° C. If the additional fuels are burned in a separate area, as provided in accordance with the invention, the ash can no longer - or can only be greatly reduced - get into the fluidized bed.

Another advantage of such an arrangement is that by burning the additional fuels in an at least partially separated area, in which gases have already cooled below the critical temperature, i.e. the ash melting point of the additional fuels, it is avoided that the ashes of the additional fuels melt and lead to the negative effects listed above.

Lyes from paper and pulp production and lignin as additives and main fuels are only given as examples. The invention can equally be used in other combustions in which the additional fuels have a significantly lower ash melting point than the main fuels.

According to a preferred embodiment, the additional burner is arranged in the first train and the guide device is an orifice. A separate space is thus constructively created, the orifice preferably being arranged below the burner, so that possibly falling, possibly melted, ashes of the additional fuel are collected by the orifice. The separated area can have its own access through which collected ashes of the additional fuels can be removed.

According to an alternative entirely, particularly preferred Embodiment, the additional burner is arranged in a second train and the guide device is a partition between the first and second train. Thus, only a few changes are necessary compared to the conventional design of such incineration plants in order to make it possible to burn additional fuels in the same plants as the main fuels, without the described negative effects on efficiency or the described increase in operating costs due to increased service requirements of the plant to have.

According to a preferred embodiment of the method, the gases are led from the fluidized bed through a first train and the combustion of the additional fuels takes place exclusively in a second train. The resulting flow, which leads away from the fluidized bed and towards the location of the combustion of the additional fuels, additionally helps to prevent spatial separation, that ashes generated during the combustion of the additional fuels reach the fluidized bed and lead there to the described negative effects.
According to an alternative or additional embodiment of the method, gases from the combustion of the main fuel and / or the additional fuel are returned to the fluidized bed. As a result, the temperature that arises during the combustion drops and a small time and / or spatial distance is necessary in order to cool down to the desired uncritical temperature.

Further preferred and advantageous embodiments of the invention are the subject of the remaining subclaims.

Fig. 1

eine erste Ausführungsform einer erfindungsgemäßen Verbrennungsanlage und

Fig. 2

eine zweite Ausführungsform einer erfindungsgemäßen Verbrennungsanlage.

The invention is further explained below with reference to the drawings. These show in a highly schematic representation:

Fig. 1

a first embodiment of an incinerator according to the invention and

Fig. 2

a second embodiment of an incinerator according to the invention.

Apart from the changes according to the invention, the systems shown are designed as is customary in the prior art. It is therefore only generally mentioned that the system has discharge and supply lines, heat exchangers and ash and exhaust gas treatment devices.

The Fig. 1 shows an incinerator 1 with a first train 2, a second train 3 and a third train 4. There is a fluidized bed 5 at the lower end of the first train 2. A first burner 6 for burning the main fuel is arranged directly above the fluidized bed 5. An arrow 7 shows a gas flow leading away from the fluidized bed 5 and from the first burner 6. The gas cools on the way to the second train 3, in which an additional burner 8 is located. In the second train 3, the temperature has already dropped, so that melting of the ashes 10 of those additives which are burned with the additional burner 8 and have a lower ash melting point is reduced or avoided. However, even if ash melts, it does not fall onto the fluidized bed 5. Ash and exhaust gases are transported with the gas flow 7 via the third train 4 to a hood 9, where they are treated further. In this case, the partition 12 between the first train 2 and the second train 3 acts as a guide device. Ash particles 10 that are too heavy to be carried away by the flow collect in the transition area between the second train 3 and the third train 4 Advantageously, an access (not shown) for removing the ash 10 can be provided at this point.

The Fig. 2 shows a second embodiment of an incinerator according to the invention. In this, the second burner 8 is still arranged in the first train 2. The undesired contact between the fluidized bed 5 and ash particles 10, which are too heavy to be carried away by the flow, are prevented in this case by an aperture 11. Access to the removal of the ash particles 10 can also be provided here.

In summary, an embodiment of the invention can be described as follows:
In an incineration plant 1 for burning additional fuels with a first train 2, with at least one main burner 6 for burning a main fuel and with a fluidized bed 5, ashes are formed when the additional fuels are burned with an additional burner 8 with a guide device 11, 12 into one of the main burner 6 separate area.

Claims (8)

1. Combustion system (1) for combustion of a main fuel and auxiliary fuels with a first pass (2), comprising at least one main burner (6) to burn the main fuel and with a fluidized bed (5), characterised in that an auxiliary burner (8) to burn auxiliary fuels from which the ash has a melting point of less than 800°C is arranged in an area that is at least partly separated from the fluidized bed (5) by a guide (11, 12).
2. Combustion system (1) according to claim 1, characterised in that the auxiliary burner (8) is disposed in the first pass (2) and the guide (11, 12) is a baffle (11)
3. Combustion system (1) according to claim 1, characterised in that the auxiliary burner (8) is disposed in a second pass (3) and the guide (11,12) is a partition wall (12) between the first and second pass (2, 3).
4. Method for combustion of a main fuel and auxiliary fuels in a system (1) for combustion of auxiliary fuels with a first pass (2), which has at least one main burner (6) to burn the main fuel and with a fluidized bed (5), characterised in that the ash produced when the auxiliary fuel is burned in an auxiliary burner (8) is directed with a guide (11, 12) into an area of the combustion system (1) that is separated from the main burner (6) and the auxiliary fuel is burned in an area of the combustion system (1) where gases that form when the main fuel is burned are cooled to a temperature below 800 °C, especially under 700 °C, where the ash has a melting point below 800 °C.
5. Method according to claim 4, characterised in that the gases from the fluidized bed (5) are directed to a first pass (2) and the auxiliary fuels are burned in a second pass (3).
6. Method according to one of claims 4 to 5, characterised in that the gases from combustion of the main fuel and/or the auxiliary fuel are returned to the fluidized bed (5).
7. Method according to one of Claims 4 to 6, characterised in that combustion is sub-stoichiometric.
8. Method according to one of claims 4 to 7, characterised in that the auxiliary fuel is fed to combustion in powdered or liquid form.

Images