EP3026339A1 - Solid fuel burner - Google Patents

Abstract

The invention relates to a solid fuel burner (10) having a fuel supply (12), a burner muffle (20) and at least one combustion air supply (30). It is envisaged that the burner muffle is subdivided into a main load muffle (22) and a partial load muffle (21), wherein the main muffle and the partial load muffle have a rotationally symmetrical basic shape and the axes of rotation (25) coincide. The main muffle adjoins directly to the part muffle.

Furthermore, the invention relates to a method for operating a solid-fuel burner (10), in which the combustion air supply (30) is controlled such that the flame up to about 30% of the maximum power of the solid-fuel burner (10) substantially in the partial load muffle (21 ) is located.

Description

The invention relates to a solid fuel-fired burner with a fuel supply by means of conveying air, with a burner muffle and with at least one combustion air supply.

Such solids-fired burners are used, for example, in a hot gas generator in process plants. Examples include grinding plants for grinding coal, cement clinker, granulated blastfurnace, raw meal or other moist, especially mineral, to be shredded materials. Also in the gypsum, sugar and potash industries, lignite or hard coal fired hot gas generators are used. Generic burners can also be used in other firing systems such as for waste heat boiler for steam generation.

There are a variety of burner technologies for oils, gases and solid fuels known. Due to increased fuel costs and resources, there is a desire to substitute solid fuels for precious energy sources such as natural gas and oil. Through the development of improved solid fuel burner systems For the purposes of the invention, solid fuels can be, for example, rock or lignite dust, biomass dust or mixtures thereof.

A generic burner is for example from the DE 197 06 077 A1 known. In this burner, solid which is crushed and called fuel dust is pneumatically conveyed into a combustion chamber and burned by supplying combustion air. On the output side, the burner is a burner muffle, a supply for the gas to be heated and a mixing part is provided, which is then arranged on the burner muffle.

Another burner is out of the DE 102 32 373 A1 known, which is a further development of the burner DE 197 25 613 A1 for firing with solids represents. This type of burner is also referred to by the manufacturer as a pulse burner.

In these burners, pulverized coal is transported with a gaseous carrier medium, which may preferably be air, and blown into a reaction space by means of an injection lance. The injection lance leads from the burner head to the point of the largest diameter of the conical reaction space and has a deflection hood at the outlet end.

The combustion air is supplied via a radial blade grid at the head end of the reaction space. The blade grid and part of the reaction space are surrounded by an air collecting housing in which the combustion air is to be calmed and from which the combustion air is to reach the reaction space via the blade grid. Due to its flow pattern, the burner generates a large range of turbulent fluctuation movements. As a result, the burner dust after its exit from the Umlenkhaube to the air guide vane, which is provided in the region of the burner head, transported back and heated by a swirling helical flame to about 1,000 ° C and ignited. The flame jet itself has a very strong impulse and produces a very fast recirculation of the gas. In the further development, the main focus was on increasing the flame stability and the flame jet speed.

However, such and other solid-fuel burners available on the market only have a control range of 1: 4. However, as shown in the following example, this control range is not sufficient for many applications of a burner. Therefore, currently still on recycle burner with gaseous or liquid fuels, which are more expensive by the combustion of precious energy in operation. One approach to remedy this is the use of so-called dual burners, which are operated either solid fuel depending on the required performance or in areas where operating with solid fuels is not possible to be fired with gas or oil. In dual burners, some operating conditions are also achieved by simultaneously burning solid fuels with gas or oil together.

One application of burners is hot gas generators. Hot gas generators are used, for example, in grinding mills in the grinding of coal to produce hot process gas. The ground coal can be used for example in coal gasification or pig iron or steel production in the PCI process (Pulverized Coal Injection).

In coal grinding plants with an air-flow mill, for example a spherical roller mill, a roller ring mill or a vertical roller mill of the Loesche type, moist raw coal is subjected to the mentioned mill drying with the supply of hot gases and ground to pulverized coal. In a downstream separation unit, such as a filter, the ground coal dust is separated from the coal dust gas mixture. Further applications of hot gas generators are found in drying plants for a variety of organic and mineral substances.

The necessary control ranges of the burner or of the hot gas generator are determined by the parameters of the following heat-consuming systems. This consumption depends in particular on the sometimes highly fluctuating moisture of the material to be ground and dried, the necessary throughput of the heat-consuming apparatus, in this case the grinding unit, and the ambient temperature.

In the following, a required control range is explained in more detail by means of an example of a grinding drying of hard coal with a Loesche type vertical roller mill.

The possible minimum and maximum throughput of such a roller mill is between 40% and 100%. This means that the mill has a control ratio of 1: 2.5.

If a minimum throughput coincides with a very low moisture content of the material to be ground and a relatively high outside temperature, only a relatively small amount of heat energy is needed for drying. A maximum heat energy consumption results at maximum throughput of the roller mill, with maximum permissible moisture of the material to be ground and dried and a relatively low outside temperature.

For example, when milling coal at a minimum throughput of 32 t / h with 5% moisture and an outside temperature of 35 ° C, approximately 1.695 MW is needed for drying. In the maximum case, assuming a maximum throughput of 80 t / h, a humidity of 15% and an outside temperature of only 5 ° C, a heat quantity of 13.8 MW is required.

This results in a necessary control ratio of 13.8: 1.695 to achieve the two extreme operating points and all intermediate operating points, which is approximately equal to a ratio of 1: 8.14. Such a high control ratio can not be achieved with the known solids-fired burners. These usually have, as already described, a maximum control ratio of 1: 4. Therefore, gas generators or oil burners are predominantly used in hot gas generators. These are fired, for example, in coal gasification plants with synthesis gas and in PCI plants for the blast furnace process with blast furnace gas.

To replace the known oil or gas fired burners with solid fuel burners, the solid fuel burners must achieve a control ratio of 1: 8 to 1:10.

The invention is therefore based on the object of specifying a solid-fueled burner and a method for its operation, which achieves a high control ratio of 1: 8 or higher.

This object is achieved by a solid fuel burner with the features of claim 1 and a method for operating a solid fuel burner with the features of claim 10.

Further advantageous embodiments are specified in the dependent claims, the description and in the figures.

According to the invention, the generic solid-fueled burner is further developed in that the burner muffle is subdivided into a main-load muffle and a partial-load muffle, wherein the partial-load muffle covers 5% to 10% of the volume of the main muffle having. The part-load muffle itself is essentially conical with a rotationally symmetrical basic shape, which has an axis of rotation. The main load muff, in turn, likewise has a rotationally symmetrical basic shape with an axis of rotation. The axis of rotation of the main muffle and the axis of rotation of the part load muffle are in extension to each other. In other words, this can also be a single axis of rotation. Furthermore, the main muffle is provided immediately after the part load muffle.

The invention is based on the finding that generic burners are usually designed only for one operating point, usually at 100% burner power. If now such a dimensioned burner driven with a lower load, so both the amount of combustion air supplied and the amount of fuel supplied is reduced. It has been found that from about 30% to 40% of the maximum load on a burner optimized for maximum load, the speeds at the burner head are so low that proper self-sustaining combustion can no longer be maintained and the burner fails, because the flame collapses. This is due to the fact that the flow rates of the combustion air and the fuel are very low, so that there is no sufficient mixing of the combustion air with the pulverized fuel and on the other hand that the supporting effect of the burner muffle is eliminated, since the flame far away from this. In addition, this plays an inadequate coordination of the combustion air-fuel ratio into it.

Therefore, it is a basic idea of the invention to dimension the burner for part-load and full load in the manner of a two-stage system to plan and execute. According to the invention, the burner muffle is subdivided into a main-load muffle and a partial-load muffle. The part load muffle has a much smaller volume than the main load muffle. This results in the advantage that, if the burner is operated with, for example, only 20% of its maximum power, the flame can withdraw into the part load muffle and since it has a smaller volume, yet can be supported by the muffle wall. Due to the smaller volume and the outflow velocities of the combustion air and the fuel are sufficient so that the flame does not go out. However, the burner is in full load operation or driven close to it, the flame of the burner can extend from the partial load muffle to the main muffle and occupy the entire space in the burner muffle, which is also referred to as the reaction space. In this case, the part of the flame which is outside the part load muffle is supported by the main load muffle.

In this context, the burner head, ie the area in which at least the fuel is supplied to the burner muffle or the combustion chamber, is located near or at the beginning of the partial load muffle. In other words, the burner muffle consists of a small-volume part-load muffle, which widens in the direction of the burner mouth and converts to the bulky main muffle. This can be achieved, for example, in the form of two cylinders or cone-like structures arranged concentrically on the same axis of rotation, wherein a transition from the partial load muffle to the main load muffle is provided substantially in the radial direction.

It is preferred if the combustion air supply is carried out at least three parts. Here, a first combustion air supply and a second combustion air supply for supplying combustion air are formed in the partial load muffle. A third combustion air supply is provided for supplying combustion air into the main load muffle.

By dividing the combustion air supply into different partial flows, a good and targeted combustion of the fuel can be achieved, as targeted a certain ratio of the combustion air to the fuel can be maintained. Thus, for example, if the burner is operated only with 30% of its maximum load, and the burner flame is located substantially in the part load muffle, are also supplied via the different combustion air supply the combustion air mainly in the part load muffle. This serves on the one hand for a good mixing of the fuel with the combustion air, which in turn enables efficient combustion and, on the other hand, prevents a collapse of the flame. Another advantage of the division is that the individual feeds of the combustion air supply are each smaller. As a result, the combustion air supplies are operated at higher flow rates, which positively influences the stability of the flame.

This is particularly advantageous in a low load or power range, since only small amounts of combustion air can be selectively supplied at certain points.

An important principle in the combustion of solids is the maintenance of the temperature in the combustion chamber below the so-called ash softening point. If this temperature were exceeded, caking would occur on the burner muffle, which would reduce the efficiency of the burner - or would prevent the operation after a short time. Therefore, solid fuel burners are generally operated at a lambda value between 1.4 and 2.0.

As a result, in order to maintain the lambda value, the quantities of combustion air, both locally and temporally, must be adapted differently to the pulverulent fuel as a function of the thermal heat output. This local and temporal supply of combustion air can be achieved by the use of the division of the combustion air supply according to the invention

If now the burner according to the invention is operated in part-load operation, for example at 30% of the maximum load, it must be ensured that the required lambda value is present in the region of the flame. This can in turn be achieved by keeping the volume flow of the combustion air for the third combustion air supply relatively low and directing the majority of the combustion air via the first and / or second combustion air supply directly into the partial load muffle, since in this operating state the flame is substantially in the part load muffle is located. In other words, a large part of the combustion air is conducted into the part-load muffle.

In principle, the first and the second combustion air supply can be arranged arbitrarily in the region of the partial load muffle. It is advantageous if the first combustion air supply and the second combustion air supply are designed as an annular gap around the axis of rotation, wherein the first combustion air supply is provided closer to the axis of rotation than the second combustion air supply. With this construction, on the one hand, the combustion air can be injected well and evenly into the partial load muffle. Assuming that the fuel is injected relatively close to the axis of rotation, it turns out that way also a good mixing of the combustion air with the fuel. On the other hand, this provides the fuel with a sufficient amount of combustion air for combustion.

A further advantage of this arrangement - the first combustion air feed closer to the axis of rotation than the second combustion air feed - is that the principle which has already been described with respect to the main load muffle and the partial load muffle is also continued here. If the burner is operated at the lower end of its power range, for example at 10% of the maximum power, the required combustion air tends to be supplied by the first combustion air supply, which is closer to the axis of rotation, since in this operating state the flame is also smaller , However, if the burner is operated at 30% or 80% of its maximum load, combustion air can also be introduced into the part-load muffle through the second combustion air feed, resulting in sufficient combustion air supply for the corresponding load conditions.

In this regard, it is preferable that the ratio of the exit cross-sectional areas of the combustion air of the first combustion air supply to the exit cross-sectional areas of the combustion air of the second combustion air supply is 1: 8 to 1:10. This means that the outlet cross-sectional areas of the first combustion air supply are made smaller than those of the second combustion air supply. This in turn makes it possible that the volume flow at assumed equal exit velocity of the combustion air of the first combustion air supply is less than the second combustion air supply. This in turn ensures that the flame is optimally supported and sufficient combustion air can be made available depending on the load condition of the burner.

In principle, the outlet cross-sectional areas of the combustion air of the third combustion air supply can be made arbitrarily large. However, it has proven to be advantageous if the ratio of the sum of the outlet cross-sectional areas of the combustion air of the first combustion air supply and the second combustion air supply to the outlet cross-sectional areas of the combustion air of the third combustion air supply is 1: 7 to 1:11. In other words, the dimensioning of the outlet cross-sectional areas is such that, assuming an same flow rate through the outlet cross-sectional areas of the third combustion air supply, which conduct combustion air into the main muffle, significantly more combustion air can be supplied as by the two combustion air supply lines, which conduct combustion air into the part load muffle.

This ensures that in a load condition of, for example, 70% or more, in particular in the main muffle sufficient combustion air is available to achieve the best possible combustion of the fuel. This also supports the expansion of the burner flame during main load operation, which can be, for example, in the range between 30% and 100% of the maximum load.

To even better offer different amounts of combustion air depending on the load state of the burner of the flame, it is provided that fans for conveying the combustion air to the combustion air supply lines are present and that the maximum design speed of the first and the second combustion air supply 1.8 to 2.5 times is greater than the maximum design speed of the third combustion air supply. Such a design ensures that, on the one hand, sufficient combustion air is available as a function of the various operating states of the burner, but that a sufficiently high lambda value is present in order to prevent reaching the ash softening point. The different maximum design speeds also affect a twisting of the combustion air in the burner muffle, thereby achieving better combustion.

In a preferred embodiment, the second and / or the third combustion air supply in each case two or more independent combustion air feeds are executed with independent cross-sections. This is particularly advantageous for burners with a maximum power of more than 10 MW. This division is based on the finding that, as previously described in general, even with burners, which are designed for example for a maximum load of more than 100 MW, it is advantageous to further divide the combustion air supply, so that in each case an optimal supply to the one Combustion air quantity as well as in relation to the position of the supply line in the Brennermuffel the combustion air is possible. This allows for a sufficiently high lambda values and on the other hand a sufficiently high mixing within the burner muffle, so that a good combustion is achieved.

In this regard, it is preferred if the second and / or third combustion air supply are each divided in the ratio of about 30:70 of the outlet cross-sectional areas of the combustion air, wherein the outlet for the smaller combustion air flow is provided closer to the axes of rotation. In other words, for example, the second combustion air supply is split into two separate combustion air supply lines, wherein the part of the second combustion air embodiment located further in the vicinity of the rotation axis has 30% of the cross-sectional area and the more external part of the second combustion air supply has 70% of the exit cross-sectional area. In the same way, the third combustion air supply can be divided into two, with one part having 30% and the other 70% of the total outlet cross-sectional areas. It has been found that such a division satisfies particularly well the requirements of the different operating conditions. This also takes into account that in the wall of the burner muffle a cooling air flow is advantageous to reduce the thermal load on the burner muffle. This is supported by the fact that the external cross-sectional areas are dimensioned larger than the inside, so that here a larger amount of air can flow. The two parts of the second or third combustion air supply can also be operated with different maximum design speeds.

In a preferred embodiment, at the outlet of at least the first and the second combustion air feeds, swirl devices are provided for influencing the combustion air flows in a circular orbit about the axes of rotation within the part-load and main-load burner muffle. This ensures that a so-called swirl or whirl combustion chamber is generated. In other words, a gas flow sets in, which rotates or runs around the axes of rotation in a spiral or helical manner. The vortex profile of the gas flow thus generated in the combustion chamber forces the fuel particles due to the centrifugal force acting on a circular path on the outer walls of the combustion chamber. As a result, the residence time of the fuel particles in the burner muffle or in the combustion zone of the combustion chamber, which is formed by the burner muffle, increases, whereby a better more complete combustion can be achieved.

Furthermore, the invention relates to a method for operating a solid-fueled burner. Such a burner has at least a first combustion air supply, a second combustion air supply and a third combustion air supply. In addition, it has a burner muffle, which consists of a partial load muffle and a main load muffle, wherein the first and the second combustion air supply for the supply of combustion air are designed in the part load muffle. The third combustion air supply is designed to supply combustion air into the main muffle. According to the invention, the solids-fired hot gas generator is operable in a continuous operating state between about 10% to 100% of its maximum power. It is further provided that the combustion air supply is controlled such that a flame is up to about 30% of the maximum power of the solids-fired hot gas generator substantially within the part load muffle.

The method is also based on the explained finding that in generic solid-fuel burners it is not possible to achieve operating states which are below about 40% of the maximum designed output. The reason for this is that at a load range of 20% to 30% of the maximum load, the flow rates of both the combustion air and the fuel supply are so low that the flame is broken off or collapsed. This is also caused by the fact that the flame of the burner muffle is so far away that no supporting effect through the burner muffle is more present.

According to the invention it is therefore provided that the combustion air supply is controlled such that the flame retreats from an amount of about 30% of the maximum power of the entire burner muffle, which is formed by the Hauptlastmuffel and the partial load muffle, substantially in the part load muffle. This is smaller volume than the bulky Hauptlastmuffel. As a result, on the one hand, the flame is better supported in the part load muffle. On the other hand, with a smaller flow volume of the combustion air as well as delivery volume of the fuel supply a sufficiently good mixing and thus a combustion achieved so that the flame does not collapse. This makes it possible to operate the solid-fueled burner continuously between 10% or less up to 100% of its maximum power.

It is preferably provided that during operation by 10% of the maximum power of the solid-fueled burner, the second and third combustion air supply are operated at about 10% of their maximum design speed and that the first combustion air supply is operated at about 70% of its maximum design speed.

In addition to the outlet cross-sectional areas of the combustion air supply lines, the speed with which the combustion air is blown out defines the volume of combustion air per unit time. This is decisive for influencing the burning behavior. The flow rate is a common factor to influence this volume of combustion air per unit time, since the exit cross-sectional areas are determined by design.

In the context of the invention, the maximum design speed can be understood as meaning, in particular, the flow rate that is present when the burner is operated at 100% of its power.

By operating the second and third combustion air supply at about 10% of their maximum design speed and the first combustion air supply at about 70% of their maximum design speed, it is achieved that, when operated at 10% of the burner's maximum output, the relatively small flame is mainly due to the first combustion air supply is supplied with combustion air. If this combustion air supply is relatively close to the axes of rotation and the outlet of the delivery air of the fuel supply, then the flame is sufficiently supplied with combustion air and additionally supported. If the first combustion air supply is designed such that it directs its combustion air into the part-load muffle, it is also achieved by the process control according to the invention that, above all, combustion air reaches the part-load muffle. As a result, a supply of the flame, which has retreated into the partial load muffle, additionally supported.

In an operation of the burner between about 10% and about 30% of the maximum power of the solid-fueled burner, it is preferable to continuously increase or boost the first combustion air supply from 70% to 100% of its maximum design speed. Additionally or alternatively, the second combustion air supply can be continuously increased from 10% to 20% of its maximum design speed. By one or both of these measures it is achieved that, although sufficiently more combustion air is supplied to the flame, so that it can burn with up to 30% of the maximum power, but the supply is mainly by the combustion air supply in the part load muffle. This ensures that the flame is still mainly located in the part load muffle. Here it is sufficiently supported and does not coincide, so that even a burner operation at only 10% to 30% of the maximum power of the solid-fuel burner is possible.

When operating between 30% and 100% of the maximum output of the solid-fueled burner, it is advantageous to continuously increase the second combustion air supply from 20% to 100% of its maximum design speed. By this design, the increased combustion air requirement of the flame is taken into account. The second combustion air supply is located at the edge of the partial load muffle, so that by increasing the volume flow through the second combustion air supply, the flame is well supplied with additional air in the part of the partial mast, on the other hand also extending the flame is extended into the main muffle.

In principle, the flow velocity of the combustion air can be increased by the third combustion air supply in operation from 30% of the maximum power. It is preferred in this case if the flow rate is continuously increased from 10% to 100% of its maximum design speed when operating between 40% and 100% of the maximum power of the solid-fueled burner.

By such a design is from 40%, a substantial portion of the combustion air supplied via the third combustion air supply. This introduces its combustion air directly into the main muffle. Since, as already mentioned, from 30%, the combustion flame also tends to extend into the main muffle, it is now necessary also to provide enough combustion air here. By significantly larger dimensions of the maximum possible flow rate of combustion air through the third combustion air supply is achieved that, especially in the upper power range, mainly combustion air is fed directly into the main load muffle. Thus, a sufficiently good combustion is possible.

Fig. 1:

einen Schnitt durch eine vereinfachte Konstruktion des erfindungsgemäßen Brenners;

Fig. 2:

einen Schnitt durch einen erfindungsgemäßen Brenner mit verdeutlichter Verbrennungsluftzufuhr;

Fig. 3:

ein Diagramm zur Erläuterung der Betriebsweise eines erfindungsgemäßen Brenners;

Fig. 4:

einen Schnitt durch den Bereich der Teillastmuffel eines erfindungsgemäßen Brenners; und

Fig. 5:

eine vergrößerte Ansicht der Zuführungen zur Teillastmuffel aus Fig. 4.

The invention will be explained in more detail with reference to embodiments and schematic drawings. In these drawings show:

Fig. 1:

a section through a simplified construction of the burner according to the invention;

Fig. 2:

a section through a burner according to the invention with clarified combustion air supply;

3:

a diagram for explaining the operation of a burner according to the invention;

4:

a section through the region of the part load muffle of a burner according to the invention; and

Fig. 5:

an enlarged view of the leads to the part load muffle Fig. 4 ,

In Fig. 1 a section is shown by a schematic diagram of a burner 10 according to the invention. The burner shown is a solids-fired burner 10. The solids are supplied via the fuel supply 12 at the burner head, in which, for example, pulverized coal is blown into a burner muffle 20 by means of conveying air.

The burner muffle 20 is formed in two parts in the burner 10 according to the invention. It consists of a partial load muffle 21 and a main load muffle 22, which adjoins the part load muffle 21. The partial load muffle 21 as well as the main load muffle 22 are rotationally symmetrical and arranged so that the respective rotational symmetry axis 25 coincides. The partial load muffle 21 has approximately 5% to 10% of the volume of the main load muffle 22.

According to the invention, it is provided that the solid-fuel fired burner 10 shown in sketched form has a high control ratio of 1:10. This is achieved by defining a partial load range I and a main load range II in the reaction space through the two-part burner muffle 20. The reaction space is the internal volume of the burner muffle 20. If the burner 10 is operated at a low load or power, for example 10% of its maximum load, the operating parameters are adjusted such that the burner flame is substantially in the partial load range I. If the burner 10 is started up and operated, for example, with 70% of its maximum load or maximum power, then the now existing burner flame extends from the partial load range I to far into the partial load range II.

This behavior of the flame is achieved by the control of combustion air supplies 30. In Fig. 1 For this purpose, three combustion air supply lines 31, 32, 33 are provided. The first and the second combustion air supply 31, 32 lead their combustion air in the partial load muffle 21. The third combustion air supply 33 is arranged such that its combustion air is supplied directly into the main load muffle 22.

In solid burners of the prior art, it has not been possible to achieve a load operation of 30% or less of the maximum power. According to the invention, it was recognized that this was due inter alia to insufficient support of the flame by the burner muffle 20. Also, in the prior art, the air supply is insufficiently arranged, so that there is a tearing and going out of the flame, since not enough combustion air is available at the necessary locations.

This was counteracted according to the invention by providing a two-piece burner muffle 20 was provided. This makes it possible, in a low-load or part-load operation, which extends to about 30% of the maximum power of the burner 10, to provide a flame substantially only in the partial load range I. Nevertheless, in order to achieve a high performance, the main load area II is formed much larger in volume, so that there is enough space for adequate combustion with sufficient fuel available.

In Fig. 2 is a further sketch of a section through a burner 10 according to the invention shown, in which now the various feeds into the burner interior or the burner muffle 20 are shown.

The burner muffle of the burner 10 is again designed in two parts and has a partial load muffle 21 and a main load muff 22. The partial load muffle 21 has a substantially conical shape. It widens from the burner head in the direction of the main load muffle 22. The angle of the cone is here preferably between 15 ° and 25 °.

At the part load muffle 21, the main load muffle 22 connects. This has at the beginning of a cone-like basic shape, which later merges into a cylinder-like shape. Both parts of the muffle 20 are rotationally symmetrical about a rotation axis 25 executed.

In the center of the axis of rotation 25 is located at the beginning of the burner head to the partial load muffle 21, a starting burner 13. To the starting burner 13, an annular gap is provided, which is provided as a fuel supply 12. By means of this annular gap, for example, pulverized coal can be blown into the burner interior or reaction space by means of a carrier medium, such as air. In principle, of course, other solid, crushed fuels can be blown thereby.

Around the annular gap of the fuel supply 12, a further annular gap is provided concentrically. This is connected to the first combustion air supply 31. In the region of the exit of the first combustion air in the partial load range I at the burner head swirling means 41 are provided in order to be able to impart a directional impulse to the exiting combustion air.

Subsequent to the annular gap for the first combustion air feed 31, a second annular gap is provided, which is connected to the second combustion air feed 32. This annular gap also ends in the partial load muffle 21. At the transition of the annular gap for the second combustion air 32 into the partial load region I, swirl devices 42 are likewise provided in order to be able to impart a swirl impulse to the incoming combustion air.

Furthermore, openings are still provided for supplying the third combustion air 33 in the region of the main load muffle 22. It is essential here at their position that the openings lead directly into the main load muffle, ie in the main load area II and not in the partial load range I. Thus, the proportion of combustion air, which is supplied via the third combustion air supply 33, are passed directly into the main load muffle ,

The following is with reference to the Fig. 3 now the operation of the burner 10 according to the invention explained in more detail. Here, by an arrangement of the first, second and third combustion air supply lines 31, 32, 33 corresponding to the Fig. 2 went out.

In the diagram of Fig. 3 is given on the abscissa, the power P of the burner 10 of the invention in percent. On the ordinate, the ratio of the exit velocity to the maximum designed exit velocity of the combustion air supply lines 31, 32, 33 is shown. Here, the value 1 represents an existing exit speed corresponding to the maximum designed speed.

By means of the exit velocity and the outlet cross section of the corresponding combustion air feed 31, 32, 33, the respective volume flow of combustion air can be calculated. The maximum design speeds for the combustion air supply 31, 32, 33 can be determined depending on the fuel used, for example lignite or hard coal, as well as the intended use of the burner.

The diagram shows three different curves, labeled a, b and c. The curve a relates to the first combustion air supply 31, the curve b, the second combustion air supply 32 and the curve c, the third combustion air supply 33. The addition of the combustion air supplied via the various combustion air feeds 31, 32, 33 gives the total amount of combustion air. This can be derived from the desired lambda value and the desired burner load. The total combustion air supply is then split among the various combustion air supplies 31, 32, 33.

At a power of 10% of the maximum possible power of the burner, the first combustion air supply 31 is operated at 70% of its design speed. The second combustion air supply 32 and the third combustion air supply 33 are each operated at 10% of their maximum design speed. This operating state with 10% of the maximum design speed is also referred to as the cooling air position. This means that a large part of the combustion air is blown into the partial load range I. This in turn has the consequence that, since relatively little fuel is blown into the combined burner muffle 20, the flame is mainly in the partial load range I.

When the burner is raised from 10% to 30% of the maximum power, the first combustion air supply 31 is continuously increased to its maximum value. The second combustion air supply 23 is continuously increased to about 20% of its maximum delivery speed, whereas the third combustion air supply 33 continues to operate at 10% of its maximum design speed. This continuous startup of the air supply via the first and second combustion air feeds 31, 32 has the effect that a higher combustion air volume is available in the partial load range I. This combustion air volume is stressed by the flame, which is operated with the solid fuel. Of course, when the load is raised from 10% to 30%, the amount of fuel per time is also increased. Due to the design according to the invention, the flame of the burner 10 continues to remain substantially in the partial load range I and can thus continue to be supported by the partial load muffle 21.

Now, if the burner from the 30% load range are raised to full load, the first combustion air supply 31 is still operated at full load, that is, at its maximum Auslegegeschwindigkeit. The second combustion air supply 32 is continuously increased. That is, the blow-off speed is continuously increased from 20% of the maximum lay-up speed to 100% of the maximum lay-up speed, so that 100% of the maximum lay-up speed is present at 100% of the power of the burner 10.

The blow-off rate of the third combustion air supply 33 is maintained to about 40% of the maximum load of the burner at 10% of the design speed. From the range around 40% of the maximum burner output, this also increases continuously until it reaches its maximum design speed at 100% of maximum burner power.

By this control, in particular the second and third combustion air supply 32, 33, the burner flame extends only from about 30% of the maximum power of the burner in the main load range II. From 30% or 40%, the flame has such a strength that no longer There is a risk that it breaks off or goes out due to a stall of the combustion air. In other words, the flame migrates gradually from about 30% of the maximum power from the partial load muffle 21 into the main load muffle 22.

Another functionality of the combustion air supplied via the third combustion air feed 33 is that the wall-like burnout zones of the muffle 20 can hereby also be cooled. As a result, lower requirements can be made of the materials of the burner muffle 20.

With this method according to the invention, it is possible to continuously operate the solid fuel burner 10 according to the invention from a 10% power to 100% power. This means a control range of 1:10.

Thus, it is thus possible to use solid-fuel burners for hot gas generators in grinding drying plants, as they were discussed by way of example in the introduction to the description.

In Fig. 4 is a more detailed view of a section through a burner 10 according to the invention shown and in Fig. 5 is an enlargement of the burner head to the part load muffle 21 Fig. 4 shown.

In the following, reference will now be made to a more detailed construction of the air ducts and other elements of the burner 10 according to the invention arranged in this area with reference to both FIGS. 4 and 5 received. The area which in Fig. 4 denoted by A is in Fig. 5 shown enlarged.

As already stated, the burner 10 according to the invention is essentially rotationally symmetrical. Centrally in the region of the axis of rotation 25, a starting burner 13 is arranged with its feed 52. This is operated for example with gas or oil. It serves to start the burner 10 according to the invention. For this purpose, the starting burner 13 is first operated for a time until a sufficiently high temperature is present in the muffle 20 in order to start the actual solid fuel-fired burner 10.

Around the start burner 13 extends around an annular gap, which is connected to a fuel supply 12. About this coal dust can be blown with conveying air in the partial load range I, for example.

With a further annular gap around the annular gap for the fuel supply 12, the first combustion air supply 31 is connected. Before entering the partial load range I within the partial load sleeve 21, swirl devices 41, which can also be referred to as swirl blades, are arranged in the annular gap in order to be able to impart a twist in helical form about the central axis 25 to the injected combustion air.

Similarly, a further annular gap for the second combustion air supply 32 is arranged around the annular gap for the first combustion air supply 31. Again, swirl devices 42 or swirl vanes are again provided shortly before the outlet in order to twist the combustion air which is thereby blown out.

At the part load muffle 21, the main load muffle 22 connects. In this, the third combustion air supply 31 is guided. This feed is not carried out again in the embodiment shown here via an annular gap, but a supply 60 for the third combustion air leads into an air distributor 61 for the third combustion air. This in turn is connected to outlet openings 62 for the third combustion air. These openings lead into the main load area II, ie into the interior or reaction space of the main load muff 22. In other words, the air distribution 61 is connected to the interior of the main load muff 22 by means of a mask having the outlet opening 62. Through the openings 62 for the third combustion air supply of the combustion air also a swirl can be given up.

Into the muffle 20 projects laterally a pilot burner 51 into it. This is used to start the starting burner 13.

In principle, normal external air can be supplied as combustion air through the first, second and third combustion air feeds 31, 32, 33. If the burner 10 according to the invention is used in a hot gas generator, in particular for coal grinding plants, then it is advantageous to supply a mixture of outside air and oxygen-poor air or recirculated air via the third combustion air feed 33. This is necessary because the hot process gases used in mill grinding in coal grinding plants must have a maximum oxygen content of 10% in order to prevent dust explosions.

With the burner design according to the invention and the operating method according to the invention, it is therefore possible to specify and operate a solid fuel burner, which has a control ratio of up to 1:10.

Claims (15)

Solid-fueled burner (10)
with a fuel supply (12) by means of conveying air,
with a burner muffle (20) and
with at least one combustion air supply (30)
characterized,
in that the burner muffle (20) is subdivided into a main load muffle (22) and a partial load muffle (21),
that the part-load muffle (21) comprises 5% to 10% of the volume of the main load muffle (22)
that the part-load muffle (21) has a conical, rotationally symmetrical basic shape with an axis of rotation (25),
that the main load muffle (22) has a rotationally symmetrical basic shape with an axis of rotation (25),
wherein the axis of rotation (25) of the main load muffle (22) lies in an extension of the axis of rotation (25) of the partial load muffle (21), and
that the main load muffle (22) immediately subsequent to the partial load muffle (21) is provided. Solid-fuel burner according to claim 1,
characterized,
in that the combustion air feed (30) is designed in at least three parts, in that a first combustion air feed (31) and a second combustion air feed (32) are provided for feeding combustion air into the partial load muffle (21) and
in that a third combustion air feed (33) for supplying combustion air is formed in the main load muffle (22). Solid-fuel burner according to claim 2,
characterized,
that the first combustion air supply (31) and the second combustion air supply (32) are designed as an annular gap about the axes of rotation (25) and
that the first combustion air supply (31) is provided closer to the axes of rotation (25) than the second combustion air supply (32). Solid-fuel burner according to one of claims 2 or 3,
characterized,
in that the ratio of the outlet cross-sectional areas of the combustion air of the first combustion air supply (31) to the outlet cross-sectional areas of the combustion air of the second combustion air supply (32) is 1: 8 to 1:10. A solid-fuel burner according to any one of claims 2 to 4,
characterized,
in that the ratio of the sum of the outlet cross-sectional areas of the combustion air of the first combustion air supply (31) and the second combustion air supply (32) to the outlet cross-sectional areas of the combustion air of the third combustion air supply (33) is 1: 7 to 1:11. Solid-fuel burner according to one of claims 2 to 5,
characterized,
in that blowers are provided for conveying the combustion air to the combustion air feeds (31, 32, 33) and
in that the maximum design speed of the first (31) and second (32) combustion air supplies is 1.8 to 2.5 times greater than the maximum design speed of the third combustion air supply (33). Solid-fuel burner according to one of Claims 2 to 6,
characterized,
that the second (32) and / or the third (33) combustion air supply in a burner with a maximum power of more than 10 MW in each two or more independent combustion air feeds (32, 33) are executed with independent cross-sections. Solid-fuel burner according to claim 7,
characterized,
that the second (32) and / or the third (33) combustion air supply in each case in the ratio of about 30:70 of the outlet cross-sectional areas of the combustion air are divided, the outlet for the smaller combustion air flow is provided closer to the rotation axes (25) , Solid-fuel burner according to one of claims 1 to 8,
characterized,
in that at the outlet of at least the first and the second combustion air feeds (31, 32) swirling means (41, 42) are provided for influencing the combustion air flows in a circular path about the axes of rotation (25) within the part load (21) and main load muffles (22). Method for operating a solid-fueled burner (10)
with at least one first combustion air feed (31), a second combustion air feed (32) and a third combustion air feed (33),
with a partial load muffle (21) and a main load muffle (22),
wherein the first (31) and the second (32) combustion air supply for the supply of combustion air in the part load muffle (21) are designed and the third combustion air supply (33) for supplying combustion air into the main load muffle (22) is designed
characterized,
that the solid fuel burner (1) is operable in a continuous operating state between 10% to 100% of its maximum power (P), and
in that the combustion air feeds (31, 32, 33) are regulated in such a way that a flame is located approximately within the partial load muffle (21) up to approximately 30% of the maximum power P of the solids-fired burner (1). Method according to claim 10,
characterized,
that, when operated at 10% of the maximum power (P) of the solid-fueled burner (1), the second (32) and third (33) combustion air supplies are operated at about 10% of their maximum design speed;
that the first combustion air supply (31) is operated at approximately 70% of its maximum design speed. Method according to one of claims 10 or 11,
characterized,
that when operating between about 10% and about 30% of the maximum power (P) of the solid-fueled burner (1), the first combustion air supply (31) is continuously increased from 70% to 100% of its maximum design speed. Method according to one of claims 10 to 12,
characterized,
that when operating between about 10% and about 30% of the maximum power (P) of the solid-fueled burner (1), the second combustion air supply (32) is continuously increased from 10% to 20% of its maximum design speed. Method according to one of claims 10 to 13,
characterized,
that when operating between about 30% and 100% of the maximum power (P) of the solids-fired burner (10), the second combustion air supply (32) is continuously increased from 20% to 100% of its maximum design speed. Method according to one of claims 10 to 14,
characterized,
that at an operation between about 40% and 100% of the maximum power (P) of the solid-fuel burner (10), the third combustion air supply (33) is continuously increased from 10% to 100% of its maximum design speed.

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