FI69695B - ELEKTRISK TAENDNINGSLOESNING FOER FLYTBAEDDSPANNA - Google Patents

Description

69695 1 Electric fluidized bed boiler ignition solution Elektrisk tändningslösning för flytbäddspanna 5

The invention relates to a fluidized bed boiler ignition solution for igniting fuel, in which an electric heating element is used, which is placed in the fluidized bed combustion part of the boiler.

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Small boilers using solid fuels such as coal, peat and wood are usually based on grate combustion. There are long-term experiences with grate boilers, they are simple and cheap in structure. The disadvantages are the modest efficiency and the combustion results, which are detrimental to the environment, especially when driving with a small load.

When the fuel is large (eg halos or logs), the fuel supply to the boiler is automatically expensive. For many fuels, such as peat or straw pellets or certain coal grades, the melting and sintering of ash into a cake on top of the grate hinders the use of those fuels. Various mechanical devices can be used to remove sintered slag, but often such mechanisms interfere with combustion in a small boiler.

Known small boilers with grate combustion have numerous non-25 points. Efficiency is poor with varying loads. The suitability of small boilers for varying fuels is also poor.

In addition, the work input in small boilers is high.

Fluidized bed boilers are usually large in size and complex in structure, making them unsuitable for the small boiler class.

Fluidized bed small boilers with a fluidized bed combustion section are also known, as well as good efficiency even at part loads. In this case, the combustion is as complete as possible and various solid fuels can be used in the boiler.

The fluidized bed small boiler is ignited either electrically or in larger rooms with oil or gas. When oil or gas is used for ignition, the ignition takes place in such a way that the oil or gas burner heats the sand mattress directly or hot flue gases are used in fluidization. In the latter case, the fluidizing air blower blows air into a separate preheating chamber equipped with an oil or gas burner. The burner burns air from the fluidized air stream.

The fluidized bed small boiler has previously been electrically ignited by placing an electric heating resistor in an inlet line leading to the boiler air supply connection, as disclosed, for example, in U.S. Patent No. 4,183,308. In this case, it is a normal electric air heater and the disadvantage of this known solution is the poor heat transfer to the air.

The object of the invention is to provide an improvement on the currently known ignition solutions used in 15 1 non-bed small boilers. A more detailed object of the invention is to provide an electric ignition solution which enables a more efficient transfer of heat to a floating sand mattress and to make the ignition period as short as possible.

The objects of the invention are achieved by an ignition solution, characterized in that the electric heating element is located above the first air supply point required to start the boiler leading to the boiler combustion part, and above the electric air heating element the second air supply point required for normal operation of the boiler.

In a preferred embodiment of the invention, the electric heating element is located above the air supply point required for starting the boiler, but below the second upper air supply point required for normal use. In this case, the heating element operates in a floating sand bed or suspension and the shape of the heating element can be conical, coil-shaped or of any shape. Likewise, the electric heater can be brought into the sand mattress from any direction.

The invention will be explained in detail with reference to a preferred embodiment of the invention shown in the figure of the accompanying drawing, to which, however, the invention is not intended to be exclusively limited.

3,69695 1 Figure 1 shows a fluidized bed heating boiler in a schematic cross-section.

Figure 2 shows a schematic cross-section of a preferred embodiment of an ignition solution according to the invention.

In the embodiment according to Figure 1, the boiler is generally indicated by reference number 10. The boiler 10 has a fluidized bed combustion section 11. The water space is indicated by reference number 10 and the outer jacket of boiler 10 is provided with insulation 13. The fuel supply point can be indicated by reference number 14. Fuel use a screw feeder, piston feeder or pneumatic feeder. The whistle-shaped air distribution pipes are marked with reference number 15 and the compressed air supply line with reference number 16. Reference-15 number 17 indicates an air box. The fluidizing sand removal screw is indicated by reference numeral 18a and the ash removal screw by reference numeral 18b, respectively.

The cross-sectional area of the fluidized bed combustion section 11 of the boiler 10 increases from the bottom upwards and the combustion section 11 is provided in whole or in part with thermal insulation 19. In this embodiment, the thermal insulation layer 19 of the combustion section 11 is formed by masonry. As a result, the thermal insulation of the combustion part 11 also decreases from the bottom up.

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In the embodiment according to Figure 2, the electric heating element 20b is located above the first air supply point 16 leading to the combustion part 11 of the boiler 10, but below the second air supply point 16a. In this embodiment, the air supply arrangement is such that an air distribution pipe 23 of arbitrary shape is mounted on the lower part of the combustion part 11, with holes or slits 24 at its lower edge, which communicate with the air inlet 16. In particular, when lowering the boiler, through the feed arrangement 16. In Fig. 4, the dashed line 35 indicates a second air and air tube 23a of arbitrary shape located in the combustion part 11, which has holes or slits 24a, respectively, and which communicates with the air inlet connection 16a. In the normal operating condition of the boiler, 696 95 sa air is led to the combustion part 11 via the air supply point 16a. Placing the heating element 20b as shown in Fig. 4 enhances the operation of the heating element 20b, because when the boiler 10 is ignited, the electric heater 20b is located above the air supply point, the heating resistor 20b

Claims (2)

6. C 9 5 A fluidized bed boiler ignition solution for igniting fuel using an electric heating element 5 (20b) located in a fluidized bed combustion section (11) of a boiler (10), characterized in that the electric heating element (20b) is located in the boiler (10b). above the first air supply point (16) required to start the boiler leading to the combustion part (11), and that above the electric heating element (20b) there is a second air supply point (16a) required for normal operation of the boiler. 15 20 25 30 35