DE60110100T2 - METHOD FOR THE AUTOMATIC CONTROL OF A SOLID FUEL BURNER - Google Patents

Abstract

The invention relates to a method for automatized combustion of solid fuel in a combustion apparatus which comprises a burner (1) which is connected to a boiler (400) and has a feeding-in opening (63, 62) for fuel and an outlet opening (3) which opens in a combustion chamber (401) inside the boiler which comprises a convection unit (402) and a flue gas pipe (407) for waste flue gases containing CO2 and not combusted O2, the combustion apparatus comprising a device (27) for feeding combustion air into the burner, and a fuel charge feeder (200, 212) for fuel provided to be driven by a motor (211), here called fuel charge feeding motor, the operation of the fuel charge feeding motor (211) being regulated by command from a control unit (300) in dependency on measured values transmitted to the control unit (300) in dependency on measured values transmitted to the control unit (300) and in dependency of the heat power the burner shall generate, and a measuring device (408) arranged for measuring the content of CO2 and or O2 in the flue gases. The invention is characterized by said measuring device (408) transmitting measuring signal to said cotrol unit (300) regarding the contents of the flue gases and that the contenets of the flue gases is regualted by means of the control unit (300) regulated the fuel charge feeding motor with reference to the values measured in the flue gases, maintaining an optimal content of the gas measured by the measuring device (408) in the flue pipe (407). The invention also relates to a combustion apparatus in which the above mentioned procedure is being applied.

Description

The invention relates to a method for automatically combusting a solid fuel in a combustion apparatus having a burner connected to a boiler and having a fuel supply port and an exhaust port opening into a combustion chamber within the boiler comprising a convection unit and a waste gas exhaust pipe containing CO ₂ and unburned O ₂ , the combustion device including a device for supplying combustion air to the burner, and a fuel-supply-type fuel-supply device driven by a motor, the engine being referred to herein as a fuel-filling supply motor, the operation of the Fuel supply supply motor is controlled by commands from a control unit in response to measured values sent to the control unit and depending on the heating power to be generated by the burner, and with a measuring device to the CO ₂ content and / or to measure the O ₂ content in the flue gases.

BACKGROUND THE INVENTION

solid fuels have a number of significant advantages over heating oil; they are in general cheaper, they are in big Quantities available and they are part of a natural one Circulation and pollute, despite their emission of carbon dioxide, the environment is not, as it is on wood or other renewable organic products based. Nevertheless, solid fuels are only in a comparatively small extent in used in modern society. The main reason for this Condition is likely that it is easy to burn of heating oil to automate, but relatively difficult, to automate the burning of solid fuels, and it is especially difficult, the burning of solid fuels so too Automate that to efficient combustion at all Performance levels comes without emitting products with the fuel gases, the harm the environment.

With WO99 / 28678, for example, is a combustion device shown for solid fuel, the efficient way many of the problems with the automatic Control triggers. However, as with other known arrangements in this field Difficulty in controlling under certain circumstances undesirable Maintenance and / or too unwanted Complexity of the control programs and / or the included Equipment lead. This is because the claims which today put to a combustion device for solid fuels will mean that a quality is expected which, in view of on emissions, the best combustion devices for heating oil. A specific problem encountered with solid fuels, the in combustion devices for heating oil does not exist, is the quality difference between different deliveries, and also within them Delivery. Solid fuels often rank in weight per unit volume, Density and size between different charges sometimes even in the same charge. As a result, the optimization of the combustion efficiency becomes Combustion device for Solid fuels through a constant varying weight per unit volume of the fuel difficult. From the point of view of efficiency, it is desirable that almost all oxygen that is fed to the combustion chamber, after a complete finished combustion, ie. in the flue gases, which are expelled through an exhaust pipe. The fact is, that if there is an insufficient amount of oxygen in the combustion chamber supplied will be produced, unburned pyrolytic gases that the risk of an explosion.

In Related to the solid fuel combustion device has become pointed out that the supervisory staff often for security reasons the setting of the fuel lowers so that it is never possible that variations in fuel quality cause saturation. Instead becomes a larger excess of air and thus a lower efficiency accepted. Accordingly, lies the reason for that in the steadily varying weight per unit volume of the solid fuel in connection with the difficulties, the efficiency without security risk to be able to optimize. The Difficulties in the optimization are among others at the long time delay between the burning and the possibility of changing the To cause proportions in the flue gases, i. it goes a long time Time from the point where new fuel begins to burn to the point where the flue gases are measured from this new fuel and can be analyzed.

So far conducted Attempts to automatically control combustion were always based on a change of air supply. By changing the air supply also other variables for the Way in which the combustion takes place, and thus also for the quantity at remaining oxygen content in the combustion gases crucial are, changed. Many different attempts have been made so far been, for various reasons However, there is no satisfactory solution to these problems.

It is true that in DE-U-20007801 a method is already described, according to the preamble of claim 1, wherein the measuring device, a measurement signal on the contents of the flue gas sends to the control unit, wherein the contents of the flue gas are controlled by means of the control unit, which adjusts the fuel filling feed motor with respect to the flue gas measured values. The supply of combustion air is kept substantially constant during the time in which the flue gas content is adjusted. This solves some of the above problems, but there are still significant tax difficulties due to the process of providing continuous feed. This is related to the long time delay between combustion and the ability to establish a change in the levels in the flue gases. A difficult problem is also that the fuel fill feed screw must operate at different rotational speeds, which means, among other things, that the motor must be overcompensated to ensure operation, even at low rotational speeds, due to rotational speed control. Moreover, such a further difficulty in the control technology itself is added by the fact that a continuously variable rotational speed is to be handled, in particular if in many cases this has to be adapted to changed nominal values.

SHORT DISCLOSURE THE INVENTION

It Object of the invention to solve the above problems, what by a method of the kind described in the preamble, characterized in that the fuel supply motor is intermittent works and the burner supplies fuel fillings, and that, if the measurement signal from the measuring device suggesting that the contents of the flue gas above is a desired value, the control unit determines the operating time of the fuel supply motor, dependent from the value of the measurement signal, and affects either the operating time elevated or reduced to the contents of the flue gas to a desired Set target value, so that an optimum of the measuring device in the flue gas tube measured gas content is maintained.

thanks This new way of thinking brings many unexpected benefits and it is possible Safely ensure that the combustion device at the highest Efficiency works and at the same time prevents the risk of explosion becomes. Further, surprisingly shown that the life of the material of the drum interior essential elevated is up to twice the life. This probably depends on the optimized residual oxygen content during combustion together.

• – wird die Luftzufuhr durch ein von einem Motor angetriebenes Gebläse gewährleistet, wobei die Drehgeschwindigkeit dieses Motors während der Einstellung bzw. Regelung des Rauchgasinhalts auf konstantem Niveau gehalten wird;
• – fällt eine Änderung der Betriebszeit des Brennstofffüllungszufuhrmotors größer aus, wenn der Gehalt an Restsauerstoff den Sollwert überschreitet;
• – darf nach einer Änderung der Betriebszeit des Brennstofffüllungszufuhrmotors ein bestimmtes Zeitintervall verstreichen, bevor eine mögliche zusätzliche Anpassung erfolgt, um eine notwendige Zeitverzögerung abzuwarten, um den Effekt der zuletzt durchgeführten Änderung zu sehen, wobei das Zeitintervall vorzugsweise zwischen 30 Sekunden und 5 Minuten, stärker bevorzugt über 1 Minute, liegt, und der Änderungsbetrag der Impulslänge des Brennstofffüllungszufuhrmotors bei einer Anpassung nach unten wenigstens doppelt so groß ist wie bei einer Anpassung nach oben;
• – ist wenigstens der größere Teil der in der Verbrennungsvorrichtung enthaltene Motoren, vorzugsweise eines Rührmotors, eines Gebläsemotors und eines Brennstofffüllungszufuhrmotors, zum Rotieren gemäß einer Anzahl verschiedener Programme vorgesehen, die derselben Anzahl verschiedener Leistungsstufen entsprechen, die zwischen einer niedrigsten Leistungsstufen zur Aufrechterhaltung des Brennvorgang und einer höchsten Leistungsstufen aufgeteilt sind, wobei die Temperatur des Heißwassers in einer Heißwasserleitung vorzugsweise an eine Steuereinheit gesendet wird, um eine Leistungsstufe automatisch auszuwählen; und
• – liefert die Zufuhrvorrichtung für die Brennstofffüllung mithilfe des Brennstofffüllungszufuhrmotors den Brennstoff in Form von Füllungen bzw. Chargen an die Einfüllvorrichtung, die kontinuierlicher als die Zufuhrvorrichtung für die Brennstofffüllung arbeitet, und den eingefüllten Brennstoff verteilt, so dass er als gleichmäßiger Ausfluss in den Brenner eingeführt wird.

According to further aspects of the invention

• - The air supply is ensured by a fan driven by a motor, wherein the rotational speed of this motor is maintained during the adjustment of the flue gas content at a constant level;
• A change in the operating time of the fuel filling feed motor is greater when the residual oxygen content exceeds the target value;
• After a change in the operating time of the fuel charge supply motor, a certain time interval may elapse before a possible additional adjustment to wait for a necessary time delay to see the effect of the last change made, the time interval preferably between 30 seconds and 5 minutes, more preferably over 1 minute, and the amount of change of the pulse width of the fuel filling supply motor when downwardly adjusted is at least twice as large as in an upward adjustment;
• At least the greater part of the motors contained in the combustion device, preferably a stirring motor, a fan motor and a fuel filling supply motor, is arranged to rotate in accordance with a number of different programs corresponding to the same number of different power levels lying between a lowest power level to maintain the burning process and a the highest power levels are divided, wherein the temperature of the hot water in a hot water line is preferably sent to a control unit to automatically select a power level; and
• By means of the fuel filling supply motor, the fuel filling supply device supplies the fuel in the form of charges to the filling device, which operates more continuously than the fuel filling device, and distributes the filled fuel so that it is introduced into the burner as a uniform outflow ,

Further Features and aspects of the invention will become apparent from the following description a preferred embodiment clear.

SUMMARY THE DRAWINGS

In the following description of a preferred embodiment the invention is referred to the accompanying drawings, in which:

1 partially schematically shows the automated combustion apparatus according to the invention;

2 a preferred movement pattern ei a fuel filling supply device suitable for use with the invention;

3 shows a graph of power / performance mode of a control program suitable for use with the invention;

4 a preferred embodiment of a performance optimization according to the invention;

5 the same as 4 but in other circumstances shows.

DETAILED DESCRIPTION OF THE INVENTION

In 1 For example, a combustion apparatus that may be configured to operate in accordance with the invention is shown. The main components of the combustion device are a burner assembly 100 , a fuel-filling supply arrangement 200 and a control unit 300 , The burner assembly 100 is with a boiler shown schematically 400 connected, which may be of conventional type. In the kettle 400 is a combustion chamber 401 arranged with a convection unit 402 connected is. With the convection unit 402 are lines 403 for hot water as well as an exhaust pipe 407 connected to the removal of combustion gases / flue gases. In the exhaust pipe 407 is a measuring device 408 arranged, the content of residual oxygen in the combustion gases to the control unit 300 sends. This measuring device 408 is suitably formed by a lambda probe. In the hot water pipe 403 a temperature sensor is arranged, which adjusts the temperature of the hot water to the control unit 300 sends.

In the burner assembly 100 is a solid fuel burner 1 included, which is circular cylindrical according to the preferred embodiment shown and is rotatable about a slightly inclined axis of rotation. He has an outer flange 24 for fixing the entire burner assembly 100 on a boiler door of the boiler shown schematically 400 on, leaving an opening 3 for the combustion gases at the front end of the burner into the combustion chamber 401 the boiler opens. The interior of the burner forms a primary or main combustion chamber 13 and a secondary or afterburning chamber 14 ,

Other components of the burner assembly 100 are a fan 27 for combustion air, a blower motor 22 , also called second motor in this text, for the rotation of the blower 27 (Alternatively, two or more fans with associated motors may be provided, including a blower with an engine for blowing primary combustion air into the primary or main combustion chamber 13 and another motorized blower for blowing secondary combustion air into the secondary or afterburning chamber 14 ), a coreless filling screw 40 in a fuel filler pipe 18 for a solid fuel in particulate form, a filling engine 41 , also called fourth motor in this text, for rotating the filling screw 40 , a stirring motor 34 , also called first motor in the text, for rotating the reactor drum 1 around the inclined axis of rotation 2 , and the lower part of a downpipe 42 for the fuel. The inclined angle of the reactor drum 1 to the horizontal plane, eliminating the front opening 3 The reactor drum for the combustion gas is inclined upward, is about 8 to 15 degrees depending on the size, the inclination angle is reduced as the size increases.

The rear end wall of the reactor drum 1 is double-walled, as well as the main part of the cylindrical part. The space between the inner ones 55, 66 and the outer walls is with 54 designated. The inner walls 55 . 66 are with holes 55 in the cylindrical part as well as in the rear end part for the introduction of combustion air into the main combustion chamber 13 fitted. The holes in the inner cylindrical wall 66 are denser in the back of the primary combustion chamber 13 and slightly less densely distributed in the front part. Further, the gap 54 divided by longitudinal, radially oriented lamellar partitions in the cylindrical part of the reactor drum into channels, and in the rear end of the drum partitions are arranged, which form between them arc-shaped channels for combustion air. The partition walls in the rear part are connected to those in the cylindrical part, so that each sector-shaped channel communicates in the end wall with a longitudinal channel in the cylindrical part, but only with one and not with further such longitudinal channels. The airflows through these channels may be adjusted by valve elements (not shown) which direct the combustion air primarily or substantially into the lower rear portions of the combustion chamber, which are below an inner smaller drum 60 in the back of the reactor drum 1 are arranged as described in more detail below. The combustion air is thus primarily or substantially in these parts of the main combustion chamber 13 introduced, in which the fuel is collected during combustion. As an alternative or additive, two or more fans may be provided which transport air into the primary combustion chamber and the secondary combustion chamber, respectively, as mentioned above. This can be particularly advantageous in particular for burners with high powers, ie of the order of magnitude of 1 MW or more.

The rear, inner wall 65 the drum 1 and in particular the rear part of the cylindrical inner wall 65 the drum 1 forms the fire grate of the burner 1 , At the same time, the drum with its inner walls forms a rotatable device for stirring the fuel in the burner. To further ensure the stirring of the fuel are on the inside of the reactor drum 1 activators 56 arranged, stretching the entire way back to the end wall 65 extend and the rotation of the reactor drum 1 consequences.

The inner, smaller drum 60 is cylindrical and has a perforated jacket. According to the embodiment, the drum consists of a sheet metal drum with holes in the jacket, but a net drum is also conceivable. The holes in the coat are with 61 designated. These are so small that their diameter or their largest dimension is a maximum of 10 mm, preferably a maximum of 8 mm, so that no fuel particles can escape to any appreciable extent through them. At the front is the drum 60 completely open. This opening is with 62 designated. The drum 60 is coaxial with the reactor drum 1 and surrounds a central filling opening 63 that the mouth of the filler pipe 18 for the fuel that flows through the filling screw 40 is filled. The diameter of the drum 60 is slightly larger than the opening 63 , In the annular space 64 between the filling opening 63 and the drum 60 has the rear end wall 65 the reactor drum 1 No inlet openings for combustion air. The drum 60 is at the rear end wall of the reactor drum 1 welded. The fuel inlet tube 18 is of a concentric, tubular drive shaft 19 surrounded, which also serves as an air supply pipe. In the cylindrical room 20 between the filler pipe 18 and the drive shaft 19 are in the same way as in the cylindrical space 54 arranged between the cylindrical outer and inner walls of the drum longitudinal, radially oriented partitions extending between the tube 18 and the wave 19 extend so that longitudinal channels are defined between these walls in the same way as the channels between the walls of the cylindrical part of the drum 1 , Every partition in the room 20 is thus with one and only one partition in the room 54 connected. Thus, a system is formed of channels which are separated from each other - in the embodiment 8th Such channels - which are from the rear end of the tube 19 the entire route to the front end of the main combustion chamber 13 extend where the channels through an annular end wall 47 Are completed.

The back part of the drum 1 , which corresponds to about half the length of the drum, is of a double-walled housing 25 surrounded, which is obliquely cut off at an angle corresponding to the inclination angle of the drum and by a flange 24 for fastening the burner assembly to a boiler door or boiler wall is completed by means of screws. The part of the device which is in 1 to the left of the flange 24 lies, thus extends into the combustion chamber 401 in the kettle 400 while the parts to the right of the flange 24 lie outside the boiler.

The combustion air is passed through the blower 27 through an air inlet 27A pulled and through air ducts 51 and via the not-shown valve system (a throttle valve) in the air inlet tube or the air inlet shaft 19 pushed, and of its interior 20 further into the channels in the intermediate space 54 and finally through the holes 54 into the combustion chamber 13 ,

For driving the fan 27 , the drum 1 and the filling screw 40 through the blower motor 22 , the stirring motor 34 and the filling motor 41 In each case, power transmission devices (not shown) are provided, which may, however, conventionally consist of shafts, chains, belts or other conventional elements. The filling screw 40 can through the filling motor in a direction opposite to that of the drum 1 be rotated.

The fuel in the downpipe 42 falls down immediately through the filling screw 40 pushed further. If due to a malfunction of the filling screw 40 does not transport the fuel fast enough to keep up with the fuel falling through the downcomer, an amount of fuel collects in the lower part of the downcomer 42 at. This is not desirable, especially for security reasons.

Therefore, in order to limit the amount of such accumulated fuel, a level monitor becomes 70 in the downpipe 42 arranged to send a signal to the control unit 300 to send when the amount of fuel in the lower part of the downpipe to the level monitoring device 70 increases, allowing the further transport of fuel to the downpipe 42 is stopped. According to the embodiment, this volume corresponds to only three liters. In the lower part of the downpipe 42 is also a temperature monitor 71 arranged, which sends a signal to the control unit 300 sends when the temperature exceeds a certain set temperature, so that the burner is turned off in an emergency, which means that the filling of fuel and combustion air to the burner and the rotation of the drum are stopped. As an additional security measure, there is a section 72 of the downpipe of a non - combustible plastic hose, which will be melted off if the temperature in the downer in this section is equal to still exceeds a certain temperature. As yet another safety measure is the upper section 73 the downspout is laterally offset so that no fuel would fall down onto the burner assembly when the plastic section 70 would be melted down.

It is understood that the burner assembly shown 100 can be changed in large areas. For example, the rotating drum 1 no matter if she has an inner, smaller drum 60 contains or not, be positioned completely horizontally. In this case, however, the drum should taper forward from the rear wall, ie taper conically so that the bottom of the drum has approximately the same inclination as shown in the described embodiments, in which case the fuel will also be at the bottom of the rear one Part of the drum collects where the supply of primary air is concentrated. It is further conceivable that there is no sharp edge at the transition between the rear end wall and the side wall corresponding to the shell of the drum, but instead, for example, a beveled transition. A burner that contains no corners, z. However, for example, with the approximate shape of an egg or pear cut off at both ends, where the more pointed portion is directed forward to the outlet opening, is a design that is most appropriate from some viewpoints. Also in this case, the burner is suitably double-walled with the space between the walls divided into channels, or otherwise provided with channels for combustion air from the air inlet pipe surrounding the central fuel filler pipe and further outwards and forwards.

According to the shown preferred embodiment, the fuel filling device is 200 with a storage container 201 for fuel 202 in particulate form, preferably in the form of pellets, via an external screw conveyor 203 connected in a conveyor pipe 204 can be rotated obliquely upwards by means of a fifth motor, which external motor here 205 is called. In the upper end of the conveyor pipe 203 the transported fuel falls through a downpipe 207 in a fuel storage facility 208 , A feed pipe 210 for the fuel filling, which is inclined upwards, has a rear inlet opening for fuel from the storage facility 208 , In the feed pipe 210 for the fuel filling is a feed screw 212 arranged for the fuel filling, which is rotatable with variable frequency, in particular intermittently rotatable, by means of a fuel filling supply motor 201 , The pipe 210 closes at its upper end the upper filling end of the downpipe 42 where a smoke detector 213 is provided in the case of smoke in the downpipe 92 a signal to the control unit 300 to stop all motors in the combustion device. A temperature monitoring device 217 is in the upper part of the downpipe 42 or above. When the temperature is in the range of temperature monitoring arrangement 217 rises above a certain set value, sends the temperature monitoring device 217 that does not depend on electric current, issue a command directly to a non-current-dependent valve, allowing water to a sprinkler 214 at the top of the downpipe 42 is supplied to sprinkle the overheated area with water.

The principles of operation of the combustion device shown are also based on the control unit being able to be set to a number of fixed power levels; according to the embodiment on eight power levels. The principle of the invention to use a number of fixed power levels greatly simplifies the adjustment of the devices. By "power level" is meant that the burner 1 at each power level generates a certain heat output, in the convection unit 402 of the boiler 400 for heating the water in the boiler 400 can be used. In one example of the invention, which does not limit the principles of the invention, is the maximum output of the burner 100 KW, which corresponds to the power level E8, see 3 , The power level E1 is a maintenance level at which the burner generates 2 KW. In the power stages E2, E3, E4 ... E7, the burner generates 10, 25, 40, 55, 70 and 85 KW, respectively, through the control of the control unit 300 , The temperature of the water in a hot water pipe 403 is suitably by means of a thermometer 404 measured with a resistive element which sends an analogue signal having a magnitude related to the temperature. The measured signal is transmitted via an analog-to-digital converter 405 . 5 , to a main CPU 308 (Computer Processing Unit, ie a microprocessor or a so-called PROM) on the control unit 300 transfer. The basic principle is that the generated power of the burner 1 is changed to a higher power level, z. From the power stage E6, at which the burner produces 70 KW, to the power stage E7, at which the burner generates 85 KW when the temperature in the hot water conduit 403 a certain predetermined span falls below a certain setpoint, e.g. B. 80 ° C. Correspondingly, a change is made to a higher power level when the temperature in the hot water line falls above the upper range of the setpoint. In this way, the generated power of the burner may fluctuate between fixed power levels, but this does not mean that the operating mode of the combustion device is given a choppy manner, as will become apparent from the following. On the contrary, the change between the different levels of performance takes place despite his seemingly erratic in nature, resulting in high combustion efficiency and very low emission of undesirable products in the flue gases. Now, let's explain how the burner assembly 100 and the feeder assembly 200 the fuel filling in cooperation with each other depending on the control unit 300 operate at different power levels, for simplicity, assuming that the level of residual oxygen is within an acceptable range.

In 2 schematically are the intermittent movement patterns of the burner and the fuel filling feed screw 212 shown. The fan motor is rotating 22 and the other engines in a state of equilibrium with velocities tuned to each other in such a manner that the amount per unit time of injected combustion air corresponds to the amount required for optimum combustion per unit time of fuel charged. The combustion air is thereby through the inlet 27A retracted and through the lines 51 through the openings 55 in the walls 65 . 55 of the fire grate / burner 1 blown. The burner 1 rotates intermittently in pulses of 1 second, alternating with 3 seconds rest periods. The fuel filling feed screw 212 Intermittently performs fuel fillings during 5 second pulses alternating with 40 second rest periods in which the fuel fill feed screw does not move. The fuel filling feed screw 212 gets the pellets from the interim storage 208 , which always by means of the external screw 203 and her engine 205 which start to work as soon as the fuel level in the intermediate storage 208 dropped below a certain level, which is indicated by a level meter 215 is registered, which is located there, and the control unit 300 the external engine 205 stops.

The fillings or batches of pellets passing through the downpipe 42 fall down, fall all the way down into the filler pipe 18 and then be through the continuously rotating filling screw 40 pushed forward. While in the tube 18 through the snail 40 pushed forward, the pellets are also distributed, ie the fillings through the downpipe 42 to the snail 40 fall, be through the snail 40 distributed such that the fuel supplied to the inner basket has the shape of a comparatively smooth flow. The leveling force is increased by the fact that the screw 40 has no core. In the basket 60 The pellets are preheated before the fuel is the drum / basket 60 through his mouth 42 leaves, leaving it in the form of a river, in the drum / basket 60 even further leveled, falls down on the sloping floor / rust, passing through the inner perforated mantle 66 of the burner / drum 1 is formed.

By adjusting the fuel fill and the amount of combustion air in accordance with the control program, the burner generates 10 KW at power level E2 shortly after the power stage has been changed according to the example. In the case of insufficient power, a change to power level E3 (see 3 ) is performed automatically to increase the output power after a period of time which is also set in the control program.

In the power stages E3 to E8 the burner rotates 1 continuously at a certain controlled speed. The filling of the pellets by means of the fuel filling feed screw 212 in the fuel filling unit 200 is increased and proportional to it also the amount of combustion air passing through the blower 27 is blown per unit time, leaving the burner 1 generates the desired power at each power level. The fuel filling feed screw 212 however, it is still rotated intermittently, but with shorter pauses between fuel fill pulses at each higher power level. The filler screw rotates continuously at a constant speed at all power levels E3 to E8 to provide the desired uniform flow of pellets into the burner.

The power-up procedure continues to move from stage E3 to stage E4, then stage E5, etc., each stage having a duration that is predetermined in the program, e.g. B. two minutes. This incremental increase in the power generated by the burner continues until the predetermined temperature of the water in the hot water line 42 is reached, z. B. 80 ° C. If this z. B. occurs at a power level E7, in which the power generated according to the example 85 is KW, and if the desired accuracy in the control unit 300 is set to + 2 ° C, the following occurs when the temperature of the water in the hot water line 302 would rise to 82 ° C: the supply of fuel fillings by means of the fuel charge supply unit 200 , and the rotational speed of the drum 1 , are immediately set to the values that apply to the next lower power level, in this case the power level E6, while the fan 207 continue combustion air into the combustion chamber 13 according to the program for performance level E7. The blower continues to blow an excess of combustion air until the excess fuel in the burner has been burned so that the remaining amount of fuel in the burner / drum meets the conditions during power level E6. This post blowing period, suitably 1 to 5 minutes, preferably about 2 minutes, will be in the computer in the control unit 300 programmed to avoid the risk of generating pyrolytic gases (risk of explosion), which can happen if an insufficient amount of oxygen is added. Thereafter, the rotational speed of the fan 27 reduced to the normal rotational speed for the power level E6. The burner now continues to operate at power level E6 according to the predetermined program. This lasts as long as the temperature is kept within 80 + 2 ° C. Under normal conditions, if the changes in ambient temperature and hot water consumption are not significant, the temperature will slowly drop to 78 ° C. Then, immediately, or with some delay to avoid oscillations in the system, which may be difficult to control, is switched back to the power level E7. In this way, the combustion device can be made to oscillate in a controlled mode between two power levels. Since it is possible to operate a variety of different power levels, including delays between power levels, there is therefore no great leap in performance. The system can therefore be called modulating because it adapts at all times to the power requirements of the building in which the combustion device is located.

If at this stage the measuring device 408 in the exhaust pipe 407 should send, that the residual oxygen content is not within a predetermined value or setpoint, so sends that the residual oxygen content (eg by measuring the CO ₂ content) is too high, this is to the control unit 300 sent, so the processor 308 ensures that an automatic adjustment is made according to the invention, with the aim of restoring an optimal residual oxygen content, and thereby optimum combustion efficiency. As is well known to those skilled in the art, it is a good approach to use the knowledge that a burned oxygen molecule results in about one carbon dioxide molecule. Furthermore, the oxygen content of air is normally about 21%. For safety reasons, the device should be set to use a maximum of 20 of the 21 parts of available oxygen. Thus, it is possible to measure the consumption in the other way - by measuring the carbon dioxide. According to most systems known today, it is sufficient if the residual oxygen content is around 5%. As in 4 shown, the pulse for fuel filling increases to compensate for a reduction in the CO ₂ content (increased residual oxygen content) of the measuring device 408 was measured. In order to prevent overcompensation, which would in the worst case lead to an explosion, the increase of the filling time is carried out with relatively small control steps. Preferably, the increase is performed in increments of at most 10%, more preferably an increase of 2 to 6%, in which case an increase in the operating time of the fuel fill feed screw 211 of between 0.1 and 0.3 seconds. This leads to an additional feed of fuel without changing other variables, so it is fed a constant amount of air. After a certain desired time interval, suitably 2 minutes, a new message of the residual oxygen content is sent by the measuring device 408 is sent, and if at that time the target value has not yet been reached, a further change of the same size of the operating time of the fuel filling feed screw 211 carried out. It will be appreciated that instead of percentages requiring a continuous computation function of the processor, fixed, smaller step units may also be used, eg, steps of 0.1 second to possibly simplify the system under some circumstances. This adjustment will continue until the measuring device 408 finally signals that the residual oxygen content is within a desired set point. Suitably, this setpoint is an interval which is preferably 4% to 9% for the residual oxygen content. Certain burners with a large power range can also be set to different setpoints within different power intervals, e.g. For example, to a first set point (eg maximum 6%) for the lower power ranges (2 - 30 Pmax), a slightly lower set point (eg 5%) in the middle power ranges (30 - 60% of Pmax) and a even lower setpoint (eg 4%) for the highest power values.

In 5 is a reverse situation to that in 4 shown shown. Namely, there is shown a situation where a new fuel charge having a higher calorific value than the previously fed combustion fillings was fed. As a result, a larger amount of oxygen is needed than in the previous filling / batch, resulting in a higher content of CO ₂ in the flue gases. As a result, the measuring device signals 408 if the flue gases have reached this level, the CO ₂ content is too high, ie the residual oxygen content is too low. Since such a faulty situation means a potential explosion hazard, the control system should be programmed to make a larger change in the rule in this situation. When such a measurement situation is sent, the control unit decreases 300 , as in 5 shown, the operating time of the fuel filling feed screw 211 automatically by about 15%, ie in this case, a reduction in operating time by about 0.8 seconds. As a result, in most cases, the amount of residual oxygen dra increase, since a large surplus of oxygen is then available. In conjunction with the next scheduled measurement, after about 2 minutes, it is normally determined that the residual oxygen content is above the setpoint interval, ie CO ₂ is below the interval. Thus, the automatic will slowly compensate for the residual oxygen up, as in 4 until it is within the setpoint again. It is understood that during this adjustment of the residual oxygen content, the automatic is suitably kept at a single power level with respect to the power levels, with the control unit keeping the other values at the same level.

The Invention is not limited to that shown above, but may be within within the scope of the following claims. The expert Understands that the invention together with many different devices for solid fuels can be used, which differs from the above preferred example can differ significantly. It goes without saying that the invention does not depend on the exact Details, e.g. of the burner, the feed channels for air etc. depends.

Claims (10)

Method for automatically burning a solid fuel in a combustion device with a burner ( 1 ), with a boiler ( 400 ) and a feed opening ( 63 . 62 ) for fuel and an outlet opening ( 3 ), which enters a combustion chamber ( 401 ) within the boiler, which is a convection unit ( 402 ) and an exhaust pipe ( 407 ) for waste flue gases containing CO ₂ and unburned O ₂ , said combustion device comprising a device ( 27 ), which supplies combustion air to the burner, and one of a motor ( 211 ) powered feeding device ( 200 . 212 ) for the fuel filling, wherein the engine is referred to herein as a fuel filling supply engine, wherein the operation of the fuel filling supply motor ( 211 ) via commands from a control unit ( 300 ) is controlled in dependence on the control unit ( 300 ) and depending on the heat output to be generated by the burner and with a measuring device ( 408 ) in order to measure the CO ₂ content and / or the O ₂ content in the flue gases, wherein the measuring device sends a measurement signal about the contents of the flue gas to the control unit ( 300 ), whereby the flue gas content is controlled by the control unit ( 300 ), which in turn adjusts the fuel fill feed motor in response to the flue gas readings, wherein the supply of combustion air is maintained substantially constant during the time the flue gas contents are adjusted, characterized in that the fuel fill feed motor ( 211 ) intermittently and the fuel in the form of fillings to the burner ( 1 ) and that if the measurement signal concerning the smoke gas content is supplied by the measuring device ( 408 ) exceeds a setpoint, the control unit ( 300 ) the operating time of the fuel filling supply motor ( 211 ), depending on the value of the measurement signal, and extends or shortens the operating time for adjusting the flue gas content up to a desired setpoint, whereby an optimum of the measuring device ( 408 ) in the exhaust pipe ( 407 ) gas content is maintained. Method according to claim 1, characterized in that that a change the operating time of the fuel filling supply motor more pronounced, though the content of residual oxygen in the flue gases falls below the nominal value, as if the content of residual oxygen exceeds the nominal value. Method according to claim 1, characterized in that one of a motor ( 22 ) powered blower ( 27 ) provides the air supply, the rotational speed of this engine ( 22 ) is kept at a constant level during adjustment of the flue gas content. A method according to claim 2, characterized in that, after changing the operating time of the fuel filling supply motor ( 211 ), a certain time interval (T) may elapse before a possible additional adjustment takes place, wherein a necessary time delay is to be seen to see the effect of the last change made, and the time interval (T) is preferably between 30 seconds and 5 minutes more advantageously over 1 minute. A method according to claim 4, characterized in that the amount of change in the pulse lengths of the fuel filling supply motor ( 211 ) is at least twice as large when adjusting downwards as when adjusting upward. A method according to claim 1, characterized in that at least the main part of the motors contained in the combustion device ( 34 . 22 . 211 ), preferably a stirring motor ( 34 ), a blower motor ( 22 ) and a fuel charge supply motor ( 211 ), for rotating according to a number of different programs corresponding to the same number of different power levels, which in turn are between a lowest power level (E1) for sustaining the burn and a highest power level (E8). A method according to claim 6, characterized in that the temperature of the water in a Hot water pipe ( 403 ) to the control unit ( 300 ) is sent to automatically select a power level. Method according to one of the preceding claims, characterized in that the supply device ( 200 . 212 ) for the fuel filling by means of the fuel filling supply motor ( 211 ) fills the fuel into a filling device which operates more continuously than the fuel filling supply device and to distribute the filled fuel so that it is introduced into the burner as a uniform outflow. Method according to one of the preceding claims, characterized in that different nominal values are used in different power ranges, wherein a low set value for the content of residual oxygen, or vice versa for CO ₂ , is used in higher power ranges than in lower power ranges. Method according to claim 9, characterized in that that change the setpoint from the lowest power range to the highest power range between 10 - 300 % is, with the change advantageously exceeds 30.