Incinerator system

Abstract

The invention relates to an incinerator system for burning biomass, in particular wood pellets, comprising a combustion chamber (1) with a nozzle bottom (2) above which a fluidized bed (3) comprising a bulk quantity of solid particles, preferably quartz sand, is arranged, an ignition unit (4), a combustion air supply (5) and a fuel supply (6). The ignition unit (4) comprises two ignition electrodes (7) or a spark plug for generating an arc, the tips of the two ignition electrodes (7) or the tip of the spark plug being arranged in the combustion chamber (1) in the vertical direction above the fluidized bed (3), which is stationary in the switched-off state, and substantially below an inlet opening (8) of the fuel supply (6).

Description

INCINERATOR PLANT Technical area

[0001] The invention relates to a combustion furnace system for the combustion of biomass, in particular wood pellets, comprising a combustion chamber with a nozzle base, above which a fluidized bed of a bed of solid particles, preferably quartz sand, is arranged, an ignition unit, a combustion air supply, and a fuel supply. State of the art

[0002] Fluidized bed combustion furnaces are typically used in large facilities, such as power plants, where they operate around the clock. However, in smaller systems, such as those used for heating, hot water production, and electricity generation for single-family homes, the systems do not run continuously but cyclically and therefore require repeated re-ignition. EP2827059A describes an example of such a combustion furnace system for use in private homes. Here, the air supplied for the start-up process is preheated, for example, by an electric hot air gun, to reach the ignition temperature for the fuel.

[0003] Biomass ignition in pellet stoves with automatic ignition is usually achieved using heating elements or hot air. The igniters used require approximately 600 to 1000 watts of power and are subject to significant wear due to the high temperatures they generate.

[0004] DE20321670U shows a pellet fuel burner that is ignited with a discharge electrode in a guide tube. The electrodes themselves remain at a distance from the pellets. The design is accordingly complex and unsuitable for use in a fluidized-bed combustion chamber. Description of the invention

[0005] The object of the present invention is to improve an incinerator system, such as that described in EP 2827059 A1, so that the ignition process, which is frequently required, especially in private use, can be carried out significantly more energy-efficiently. The device should be simple and cost-effective in construction and have a long service life with low maintenance requirements.

[0006] This object is achieved according to the invention in that the ignition unit comprises two ignition electrodes or a spark plug for generating an arc, wherein the tips of the two ignition electrodes or the tip of the spark plug are arranged in the combustion chamber in a vertical direction above the fluidized bed, which is at rest in the switched-off state, and substantially below an inlet opening of the fuel supply. In the proposed solution, the tips of the ignition electrodes or the tip of the spark plug protrude directly into the combustion chamber and generate an arc when a voltage is applied. The fuel, which is introduced into the combustion chamber via the fuel supply, comes to rest on the at rest fluidized bed exactly between the two ignition electrodes or close to the tip of the spark plug and is ignited by the plasma of the arc. For example, only about 150 W are required for the ignition device to reliably ignite the fuel.

[0007] A further preferred feature is that the tips of the ignition electrodes or the tip of the spark plug lie within the moving fluidized bed during operation of the incinerator. As soon as the incinerator is started up, the surface of the fluidized bed, now flushed with air, is higher than the surface of the stationary fluidized bed and also flows around the tips of the ignition electrodes or the tip of the spark plug. This has the advantage that any soot produced during the ignition process is removed from the tips of the ignition electrodes by the solid particles of the fluidized bed. The ignition electrodes are therefore always completely soot-free and clean with each new start-up, which also means they require less maintenance.

[0008] It is also a preferred feature that the inlet opening of the combustion air supply is also positioned substantially above the tips of the ignition electrodes or the tip of the spark plug, so that the incoming air flow is essentially perpendicular to the surface of the fluidized bed, which is at rest in the off state. The introduced combustion air facilitates the ignition process and stretches the arc toward the fluidized bed, allowing the resulting plasma to efficiently envelop and ignite the fuel provided.

[0009] Finally, it is a further preferred feature that a control unit is provided via which the starting process can be controlled when commissioning the incineration furnace system, wherein for the starting process the control unit first feeds fuel into the combustion chamber, which comes to rest on the stationary fluidized bed, then generates an arc via the ignition electrodes or the spark plug, which ignites the fuel located between the tips of the ignition electrodes or near the tip of the spark plug, wherein if necessary the combustion air supply can be controlled via the control unit in order to stretch the arc in the direction of the fluidized bed by the incoming air flow, and wherein after the ignition of the fuel the ignition electrodes or the spark plug can be deactivated again by the control unit and the air supply can be activated through the nozzle base in order to set the fluidized bed in motion.It is advantageous to control the entire start-up process via a dedicated control unit. This allows individual parameters to be saved for each system and adjusted if necessary. Possible adjustable parameters include the amount of fuel introduced, the ignition duration, the amount and speed of the combustion air introduced, the time at which the air supply through the nozzle base is switched on to fluidize the fluidized bed, etc. Short description of the drawings

[0010] The invention will now be described in detail using an exemplary embodiment and with the aid of the accompanying figures. Figure 1 shows a schematic side sectional view through the combustion chamber of an incineration furnace system according to the invention, and Figure 2 shows a schematic cross-sectional view through the combustion chamber of an incineration furnace system according to the invention. Way(s) of carrying out the invention

[0011] Fig. 1 shows a very schematic side sectional view of a combustion chamber 1 of an incinerator plant according to the invention. Located in the combustion chamber 1 is a fluidized bed 3, shown here at rest in the switched-off state, which is formed from a bed of, for example, quartz sand. A nozzle base 2 is provided beneath the fluidized bed 3 and is connected to an air supply 9 via a plurality of openings. The air supply 9 serves to fluidize the fluidized bed 3 and to supply combustion air during operation of the plant. The air supply 9 is arranged externally along the combustion chamber 1 so that the incoming air is appropriately preheated via heat exchanger surfaces before entering the nozzle base 2.

[0012] An ignition unit 4 is arranged above the fluidized bed 3, with the tips of the ignition electrodes 7 located above the surface of the stationary fluidized bed 3. Directly above the tips of the ignition electrodes 7 is the inlet opening 8 for the fuel supply 6, through which fuel, for example, in the form of wood pellets, is introduced. In the example shown, the combustion air supply 5 is also fed into the combustion chamber 1 via the same pipe as the fuel supply 6, with a common inlet opening 8.

[0013] Fig. 2 shows the system from Fig. 1 in a schematic cross-sectional view in the area of ​​the common pipe for the combustion air supply 5 and fuel supply 6. It is understood that the fuel supply 6 can also be formed separately, and the combustion air supply 5 can be arranged, for example, next to it or in a ring around it.

[0014] When the system is switched off, the introduced fuel rests in the area between the tips of the ignition electrodes 7. When the ignition electrodes 7 are switched on, an arc is created between the two tips, with the resulting plasma being blown toward the fuel or the surface of the fluidized bed 3 by the air introduced via the combustion air supply 5, thus efficiently igniting the fuel.

[0015] The ignition process consumes significantly less energy than conventional ignition devices. Once sufficient fuel has been ignited, the fluidized bed 3 can be activated. The movement of the sand bed of the fluidized bed 3 causes the tips of the ignition electrodes 7 to enter the fluidized bed 3 and be freed from any soot that may have formed during the ignition process. This ensures that they are completely clean again during the next ignition process and thus retain their full functionality even after repeated ignition processes.

Claims

Combustion furnace system for the combustion of biomass, in particular wood pellets, comprising a combustion chamber (1) with a nozzle base (2) above which a fluidized bed (3) consisting of a bed of solid particles, preferably quartz sand, is arranged, an ignition unit (4), a combustion air supply (5), and a fuel supply (6), characterized in that the ignition unit (4) comprises two ignition electrodes (7) or a spark plug for generating an electric arc, wherein the tips of the two ignition electrodes (7) or the tip of the spark plug are arranged in the combustion chamber (1) in a vertical direction above the fluidized bed (3) which is stationary when switched off and substantially below an inlet opening (8) of the fuel supply (6). Combustion furnace system according to claim 1, characterized in that the tips of the ignition electrodes (7) or the tip of the spark plug are located within the moving fluidized bed (3) during operation of the combustion furnace system. Combustion furnace system according to claim 1 or 2, characterized in that the inlet opening of the combustion air supply (5) is also arranged substantially above the tips of the ignition electrodes (7) or the tip of the spark plug and the incoming airflow is thus oriented substantially normal to the surface of the fluidized bed (3) which is at rest in the switched-off state. Combustion furnace system according to one of claims 1 to 3, characterized in that a control unit is provided by which the start-up process can be controlled when the combustion furnace system is put into operation, wherein for the start-up process the control unit first directs fuel into the combustion chamber (1), which comes to rest on the stationary fluidized bed (3), then generates an arc via the ignition electrodes (7) or via the spark plug, which ignites the fuel located between the tips of the ignition electrodes (7) or near the tip of the spark plug, wherein the combustion air supply (5) can optionally be controlled via the control unit in order to extend the arc in the direction of the fluidized bed (3) by the incoming airflow, and wherein after ignition of the fuel the ignition electrodes (7) or the spark plug can be deactivated again by the control unit and the air supply can be activated through the nozzle base (2).to set the fluidized bed (3) in motion.

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