EP2228603A2 - Method for adjusting the output of a solid fuel oven and oven with corresponding output adjustment - Google Patents

Abstract

The method involves connecting a primary combustion chamber (10) with a flue gas course (60) by a passage opening (11), where the passage opening is locked by a flue gas flap (65). A secondary combustion chamber (20) is connected with the flue gas course through a secondary exhaust gas channel (25). A temperature sensor (28) is arranged in the secondary exhaust gas channel, where the temperature sensor regulates a primary air flow rate based on the temperature in the secondary exhaust gas channel, and a secondary air flow rate is kept constant. An independent claim is also included for a solid fuel furnace.

Description

The invention relates to a method for regulating the performance of a solid fuel furnace according to the preamble of claims 1 and 2.

The invention further relates to furnaces each having a control of the type described above.

An oven of the type mentioned is from the EP 1 340 943 A2 known. The known from the prior art furnace has an upper and a lower chamber, a so-called primary and a so-called secondary chamber, which are interconnected by a bottom, wherein the bottom has a bottom opening. Located in the area of the bottom opening a rust for receiving the fuel. In addition, in the region of the grate, the furnace has openings for supplying the primary air and, in addition, in the region of the bottom, and in particular in the area of the bottom opening, openings for the secondary air. From the lower chamber outgoing an exhaust duct is provided, which opens into the flue of the chimney. The upper combustion chamber is also provided with a passage to the flue. For shutting off either the transition from the upper combustion chamber to the flue gas duct or the opening from the exhaust gas duct to the flue gas duct, a pivotable flap is provided. This flap is manually operated. In addition, there is a further control flap on the side of the furnace in the region of the bottom between the two combustion chambers, which is manually actuated by a lever. Depending on the position of the control flap, the fresh air supply, namely primary and secondary side, regulated.

The operation of this known furnace is such that in the burn-through mode, ie during heating of the furnace, the flap occupies a position in the region of the flue so that the transition from the upper combustion chamber to the flue is completely opened. At the same time, the position of the butterfly valve is such that it provides for maximum primary air supply. The consequence of this is that during this burnout during firing the burning material located on the grate, for example wood, "burns up". After firing, the furnace must be manually switched to "underfire mode". This is done in detail by the fact that the flap is pivoted in the region of the flue; It is estimated by the operator how far the flap must close the transition opening of the primary chamber to the flue, in order to ensure that the combustion actually takes place in the lower chamber, that is to say that the flame strikes down into the lower combustion chamber. If such a switching of the flap does not occur, there is a risk of overheating both the furnace and the flue. At this point, it should be noted that the operation of the furnace in underburden mode has the further advantage that this reduces both the carbon monoxide and the particulate matter content. This is because relatively high temperatures prevail in the lower combustion chamber. That is, the goal is always that the switchover to the subfire mode is achieved as quickly as possible.

As already stated elsewhere, in the furnace according to the prior art, the switching takes place manually. That is, it may well be forgotten to pivot the flap in the flue so that the oven operates completely in burn-through mode. In such a case, or even if switched to the underfire mode too late, resulting in power peaks, which, as already stated, lead to elevated temperatures in the primary chamber and in the flue, where appropriate, may cause damage, and the above Finally, reduce the efficiency, since most of the heat escapes in the burn-through mode directly through the flue into the chimney.

Next is a general problem in the batch burning of solid fuels that outgas strong, such. As wood, that the combustion process has a pronounced peak power in the first third of the burning cycle. In order to avoid emissions of unburned gases, the uncontrolled operation of the air supply, especially the secondary air, must be designed for this peak power. If primary and secondary air are adjusted together, this also results in a high primary air flow, which increases the power peak. After this peak power, in which most of the fuel charge is burned, then follows a phase of residual combustion of the charcoal with a unnecessarily high excess air. The problem is more evident the more fuel is used.

From this it becomes clear that the control of the furnace by hand is extremely difficult and therefore requires increased attention. In particular, in the vast majority of cases, it will be unavoidable that power peaks will result during the burnup, which will lead to an early burning off of the burning material and which, at correspondingly high temperatures during burnout, may result in damage to the furnace or in the flue gas pass.

The object underlying the invention is therefore to make a scheme with which a limitation of power peaks is possible with the aim of a continuous output of the furnace, this goal is to be achieved substantially automated.

This object is achieved with the features of claims 1 and 2.

From this the following becomes clear. At the beginning of the burn-through, the transition opening from the primary combustion chamber to the flue is completely opened. In order to get into the subfire mode, this flue gas flap is at least partially closed. The consequence of this is that the secondary exhaust gas channel is flowed through with exhaust gases from the secondary combustion chamber. At this time, the temperature in the secondary exhaust passage increases. Depending on the burning behavior of the fuel in the first combustion chamber now the flue gas flap is always closed, that is, the transition opening between the primary combustion chamber and the flue gas is reduced in cross-section more and more, with the result that the temperature in the Secondary flue gas continues to rise. Upon reaching a predetermined temperature range between 250 ° C and 400 ° C is now reduced by the first temperature sensor, the primary air flow, the secondary air flow rate is kept at least constant. The reduction of the primary air volume flow by a control device, which is in communication with the first temperature sensor, can be achieved by arranging a pivotable primary air damper in a primary air duct of the furnace, the position of which, as already stated, can be regulated by the first temperature sensor is.

Another variant is that the cross section of the bottom or wall opening of the bottom or the wall between the two combustion chambers is variable, as seen from the side of the primary combustion chamber, so that the secondary air flow is not affected by the reduction of the primary air volume flow , The consequence of this is that the burn-off behavior is kept substantially constant with temperature control.

As already explained elsewhere, the transition opening from the primary combustion chamber to the flue gas pass is at least partially shut off by a flue gas flap. The outlet of the secondary flue gas duct to the flue is also lockable. This means that during the burn-through phase, the transition opening between the primary chamber and the flue is completely open or substantially completely open and parallel to the outlet of the secondary exhaust gas channel is shut off. The opening of the secondary exhaust gas duct takes place in parallel with the shut-off of the transition opening between the primary combustion chamber and the flue gas duct. In this context, it is provided that a single flue gas flap is provided for shutting off the outlet of the secondary exhaust gas channel and the transition opening. hereby It is achieved that virtually automatically a reduction in the transitional opening between the primary combustion chamber and flue gas duct has an increase in the passage of the secondary exhaust gas channel to the flue gas train result.

In this context, it is provided in particular that a second temperature sensor is provided in the flue substantially immediately after the transition opening from the primary combustion chamber to the flue, through which the position of the flue gas flap is controlled in dependence on the temperature at the second temperature sensor. Overall, not only the power limit of the furnace is now achieved with the goal of a constant burning behavior, but this also opens up the possibility to virtually automate the operation of the furnace. Because the temperature, which measures the second temperature sensor after the transition opening, is characteristic of the progress of the burning material in the burn-through process. If this second temperature sensor indicates a high temperature, then in order to avoid damage to both the primary combustion chamber and the flue gas pass, the exhaust gas flow from the primary combustion chamber is to be reduced. A corresponding change in the position of the flue gas flap takes place in the temperature range between 150 ° C and 300 ° C, but preferably at about 200 ° C. This means that when reaching a temperature of about 200 ° C in the flue immediately after the transition opening, the flue gas flap from the position in the state of burning - ie during burnout, in which the transition opening was opened by the primary combustion chamber and the secondary exhaust duct - now angled Position assumes so that the transition opening is closed to the extent that the secondary exhaust duct is opened. By such a temperature-dependent control of both the primary air supply and the position of the flue gas flap not only a homogenization of the burn is achieved with the aim of avoidance of power peaks, but it is also increased by the temperature-controlled control and ease of use.

A furnace with a control of the type described above is characterized by the change of the free cross section in the wall or bottom opening by a slider. This can happen, on the one hand, that the slide has two relatively movable, in particular rotatable, disks with individual openings, which have the advantage that, in accordance with the orientation of the openings in the slide, a visually appealing flame pattern is achieved.

According to a further feature of the invention it is provided that in the secondary combustion chamber, a thermal energy storage is arranged. Such an energy store does not primarily have the task of storing the heat in the oven and to allow a uniform heat dissipation, but it serves in particular a reduction of the CO content in the exhaust gas. This insofar as when the burning power is reduced, due to the progress of the burning of the fuel, through the energy storage, which is for example designed as a fireclay plate, the exhaust gas temperature is maintained at least over a certain period of time so high that a residual gas combustion is guaranteed.

According to a further feature of the invention, it is provided that in one embodiment, the bottom of the primary combustion chamber is formed so that on the one hand has a passage to the secondary combustion chamber and on the other hand receives the ash as ash box. According to the second embodiment, the ash box is located at the bottom of the primary combustion chamber. Through the opening in the floor or the wall so only the fly ash, ie the entrained with the flow particles. With low ash load in the secondary combustion chamber can be better mixing of the flue gases with the secondary air can be achieved by appropriate installations. Good mixing of the pyrolysis gases with the secondary air ultimately ensures a reduction of the CO content in the exhaust gas. As a further advantage eliminates the ugly sight of the ashes in the secondary combustion chamber and the latter can be made more free. The standing grate in the primary combustion chamber can be attached to the ash box and is therefore very well accessible for cleaning.

It has already been pointed out elsewhere that if the primary air volume flow is reduced, the secondary air volume flow is at least kept constant. This is done in the simplest case in that the volume flow can be regulated separately both in the secondary air duct and in the primary air duct.

According to a further advantageous feature of the invention, it is provided that the primary air channel opens in the upper region of the primary combustion chamber, that is, the primary air flows through the primary combustion chamber from top to bottom. In contrast to the prior art, in which both the primary air and the secondary air are introduced laterally into the furnace housing, it is ensured by the separation according to the invention that the volume flows do not interfere, and that the primary air also serves to flush the pane without the flow direction must be reversed. The secondary air duct for the supply of the secondary air volume flow is provided in the region of the bottom or the wall between the combustion chambers.

Figur 1

zeigt eine erste Ausführungsform des Ofens mit übereinander angeordneten Brennkammern;

Figur 2

zeigt eine zweite Ausführungsform mit nebeneinander angeordneten Brennkammern in einer Vorderansicht im Schnitt gemäß der Linie II-II aus Fig. 3;

Figur 3

zeigt einen Schnitt gemäß der Linie III-III aus Fig. 2;

Figur 4

zeigt einen Schnitt gemäß der Linie IV-IV aus Fig. 3.

With reference to the drawings, the invention will be explained in more detail by way of example; Here, the drawings show a schematic structure of the respective furnace.

FIG. 1

shows a first embodiment of the furnace with stacked combustion chambers;

FIG. 2

shows a second embodiment with juxtaposed combustion chambers in a front view in section along the line II-II Fig. 3 ;

FIG. 3

shows a section along the line III-III Fig. 2 ;

FIG. 4

shows a section along the line IV-IV Fig. 3 ,

The components of both oven variants are identical in function; they are hereinafter referred to differently only by the addition of a letter, since they have a different position in the oven partially.

The furnace, generally designated 1, has two chambers, namely the primary combustion chamber 10, 10a and the secondary combustion chamber 20, 20a. The opening discs are 12, 22; 12a, 22a. The primary combustion chamber 10, 10a and the secondary combustion chamber 20, 20a are separated by the bottom 30 or the wall 30a as a whole. The bottom 30 or the wall 30a have an opening 31, 31a wherein, moreover, in the bottom or in the wall, a secondary air channel 32, 32a is provided, which serves to supply the secondary air volume flow. In addition, the furnace has a primary air duct 40, 40a which has a primary air flap 45, 45a, by means of which the volumetric flow can be changed. The air flows of both channels are controlled or regulated separately. The ash box 33, 33a, connected to the standing grid 34, 34a, is arranged on the floor.

In front of the opening 31, 31a is a slide 35, 35a, which communicates with the temperature measuring point 28, 28a, and controlled by the cross section of the opening changed.

The secondary combustion chamber 20, 20a has an opening to the secondary exhaust port 25, 25a. The secondary exhaust duct 25, 25a opens into the flue 60, 60a. Between the primary combustion chamber 10, 10a and the flue 60, 60a is located at 11, 11a designated transition opening, the secondary exhaust duct 25, 25a opens into the same flue 60, 60a. The secondary exhaust duct 25, 25a is closed by the flue gas flap 65, 65a, which is arranged pivotably on the furnace, into a position "A" (burn-through). In position "B" (underburner) closes the flue gas flap 65, 65 a, the transition opening 11 between the primary combustion chamber and flue gas.

The invention now particularly relates to the arrangement of the first temperature sensor in the secondary exhaust gas channel 25, 25a, in particular in the region of the bottom 30 or the wall 30a. The arranged there temperature sensor 28, 28a is connected to a lever mechanism and ensures, for example in the formation as a bimetal that depending on the measured temperature by the slider 35, 35a, the bottom or wall opening 31, 31a is reduced or enlarged. Optionally, however, the temperature sensor may also be in communication with the fresh air supply door 45, 45a and thus regulate the supply of primary air. In fact, it is the case that the primary air volume flow is regulated both by the change in the free cross section of the bottom or wall opening 31, 31a and by the immediate change in the primary air volume flow.

In addition, located in the flue gas immediately after the transition opening 11, 11 a, a second temperature sensor 68, 68 a of the position of the flue gas flap 65, 65 a controls.

The mode of operation of the furnace is as follows. During the firing, ie in the burn-through or overfire mode, the flue gas flap 65, 65a is in position "A" and thus blocks the secondary exhaust duct 25, 25a to the flue 60, 60a. That is, all flue gases formed during burnout escape through the transition opening into the flue 60, 60a. The supply of primary air is maximum. In this mode, the air from the channel 32, 32a acts as primary air. Now, if a temperature of about 200 ° C determined by the second temperature sensor 68, 68a, then the flue gas flap 65, 65a in the direction of the arrow 69, ie to the transition opening 11, 11a, pivoted. The consequence of this is that the flames due to the suction and the at least partially closed transition opening 11, 11a and corresponding thereto the opening of the secondary exhaust gas channel in the secondary combustion chamber 20, 20a turn over. If a temperature is determined by the first temperature sensor 28, 28a, which is approximately at 300 ° C to 350 ° C, the primary air volume flow is reduced. This is done in detail either by the fact that the free cross-section of the bottom or wall opening between the two combustion chambers is reduced, or by the fact that the flap 45, 45a is pivoted in the primary air flow accordingly. That is, the combustion is stopped. This naturally reduces the temperature at the temperature sensor 28, 28a. This has the consequence that the primary air volume flow increases, which is accomplished in detail by the fact that the free cross section of the bottom or wall opening between the combustion chambers increases or according to the position of the flap 45, 45a provides for an increase of the primary air volume flow. Here, the performance of the furnace increases because, as already stated, the primary air volume flow, ie the supply of fresh air, is increased. Correspondingly, the secondary air volume flow decreases in percentage. It has already been explained in this connection that the secondary air volume flow and the primary air volume flow amount correlate with each other. If the temperature at the temperature sensor 68, 68a now drops below about 200 ° C., then the flue gas flap 65, 65a opens in accordance with the arrow 69a. In the end, this means that the secondary exhaust gas channel is progressively closed by the flue gas flap 65, 65a. The firing material in the primary chamber continues to burn upwards, which ensures that the flue gases can escape directly upwards into the flue.

The oven also has a heat storage 70, 70 a, which is arranged in the secondary combustion chamber 20. Due to the burnup in the secondary combustion chamber in the underfire mode, this memory 70, 70a is heated and ensures reduced combustion power due to increasing burnup of the fuel that the temperature in the secondary combustion chamber still remains relatively high over a certain period of time, which promotes the combustion of the residual gases.

Claims (15)

A method for controlling the performance of a solid fuel furnace (1) having two superposed combustion chambers (10, 20) separated by a floor (30) but still communicating with each other through at least one floor opening (31), the secondary combustion chamber (20) communicates with a flue gas duct (60) through a secondary off-gas duct (25), the primary combustion chamber (10) communicating with the flue gas duct (60) through a transition opening (11), the transition opening (11) through a flue gas damper (65) is at least partially closed, wherein both a primary and a secondary air supply is provided
characterized,
in that a first temperature sensor (28) is arranged in the secondary exhaust gas channel (25), which regulates the primary air volume flow as a function of the temperature in the secondary exhaust gas channel (25), the secondary air volume flow being kept at least constant. A method for controlling the performance of a solid fuel furnace (1) having two juxtaposed combustion chambers (10a, 20a) separated by a wall (30a) but still communicating with each other through at least one wall opening (31a), the secondary combustion chamber (20a) communicates with a flue gas duct (60a) through a secondary off-gas passage (25a), the primary combustion chamber (10a) communicating with the flue (60a) through a transition opening (11a), the transition opening (11a) through a flue gas damper (65a) is at least partially closed, with both a primary and a secondary air supply is provided
characterized,
in that a first temperature sensor (28a) is arranged in the secondary exhaust gas channel (25a) which regulates the primary air volume flow as a function of the temperature in the secondary exhaust gas channel (25), the secondary air volume flow being kept at least constant. Method according to claim 2,
characterized,
that the wall opening (31 a) is located in the lower quarter of the height of the wall (30 a). Method according to one of the preceding claims,
characterized,
in that the cross-section of the bottom opening (31) or the wall opening (31 a) between the two combustion chambers (10, 20, 10a, 20a) is variable as a function of the temperature in the secondary exhaust gas duct (25, 25a). Method according to one of the preceding claims,
characterized,
that the outlet of the secondary exhaust channel (25, 25a) to the flue (60a 60) is shut off. Method according to one of the preceding claims,
characterized,
that in the flue (60, 60a) substantially immediately after the hole (11, 11a) of the primary combustion chamber (10, 10a) to the flue (60, 60a), a second temperature sensor (68, 68a) is arranged, through which the position of the Flue gas flap (65, 65a) is regulated as a function of the temperature at the second temperature sensor (68, 68a). Method according to one of the preceding claims,
characterized,
that the volume flow in the secondary air duct (32, 32a) and / or in the primary air duct (40, 40a) is regulated separately. Furnace operated by a power control method according to claims 1 to 7,
characterized,
in that the free cross-section of the bottom or wall opening (31, 31a) in the base (30) or the wall (30a) is variable. Oven according to claim 8,
characterized,
that for changing the free cross section of the bottom opening (31) or wall opening (31a), a slider (35, 35a) is provided. Oven according to claim 8 and 9,
characterized,
in that a heat store (70, 70a) is arranged in the secondary combustion chamber (20, 20a). Oven according to one of the preceding claims 8 to 10,
characterized,
in that the bottom of the first combustion chamber (10, 10a) is designed as an ash box (33, 33a) which receives the ash. Oven according to one of the preceding claims 8 to 11,
characterized,
in that the furnace (1) has a primary air channel (40, 40a), wherein in the primary air channel (40, 40a) a pivotable primary air flap (45, 45a) is arranged, which communicates with the first temperature sensor (28, 28a). Oven according to one of the preceding claims 8 to 12,
characterized,
in that a single flue gas flap (65, 65a) is provided for shutting off the outlet of the secondary waste gas channel (25, 25a) and the transition opening (11, 11a). Oven according to one of the preceding claims 8 to 13,
characterized,
that the primary air duct (40, 40a) in the upper region of the primary combustion chamber (10, 10a) opens. Oven according to one of the preceding claims 8 to 14,
characterized,
that the secondary air channel (32, 32a) in the region of the bottom (30) or the wall (30a) between the two combustion chambers (10, 20; 10a, 20a) in the furnace (1) opens.

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