Method for operating a burner of a rotary kiln

Abstract

The present invention relates to a method for operating a burner (14) of a rotary kiln (10), wherein the gas streams supplied to the rotary kiln (10) comprise in total more than 50 vol.% oxygen, wherein the burner (14) has a burner opening (20) from which a fuel-gas mixture is discharged, and wherein at least one state variable of the burner flame (16), in particular the ignition gap (18), the flame shape, the flame length and / or the flame width, is determined, wherein the flow rate, the quantity and / or the impulse of the fuel-gas mixture and / or the fuel properties are controlled in an open-loop / closed-loop manner depending on the determined state variable. The invention also relates to a rotary kiln (10) for burning raw meal to produce cement clinker, said rotary kiln comprising: a burning zone formed inside the rotary kiln (10); a burner (14) having a burner opening (20) for discharging a fuel-gas mixture into the burning zone; a measuring device (22) which is designed and positioned in such a way that it determines at least one state variable of the burner flame (16), in particular the ignition gap (18), the flame length and / or the flame width, the rotary kiln (10) having an open-loop / closed-loop control device which is designed in such a way that it controls, in an open-loop / closed-loop manner, the flow rate, the quantity and / or the impulse of the fuel / gas mixture and / or the fuel properties depending on the determined state variable.

Description

[0001] The invention relates to a method for operating a rotary kiln, in particular a burner within the rotary kiln, wherein the rotary kiln is operated with an oxygen-rich gas.

[0002] Rotary kilns are commonly used in the cement and mineral industries and are used, for example, to burn preheated cement raw meal to produce cement clinker.

[0003] It is known from the prior art to introduce oxygen-containing gas into the rotary kiln or calciner of a cement production plant for the combustion of carbon-containing fuels. To reduce the amount of exhaust gas and avoid complex purification processes, it is known, for example, from DE 10 2018 206 673 A1, to use a combustion gas that is as oxygen-rich as possible, so that the CO2 content in the exhaust gas is high and the storage of the CO2 or its separation in the exhaust gas stream is facilitated. DE 10 2018 206 673 A1 discloses the introduction of an oxygen-rich gas into the cooler inlet area to preheat the gas and cool the clinker.

[0004] When using oxygen-enriched combustion gases with a high oxygen content of at least 30% to 100%, very high temperatures can develop in the furnace. If these high temperatures occur over a prolonged period or continuously near the wall of the furnace, they can result in damage to the furnace's inner wall. There is also a risk of very high temperatures developing at the burner, particularly the burner nozzle.

[0005] From CN 111 521 003 A an intelligently controlled oxygen system and a method for oxygen-enriched firing of a furnace are known.

[0006] From WO 2017 / 121449 A1 an evaluation and control method for multi-fuel burners and an evaluation and control arrangement therefor are known.

[0007] From DE 10 2006 060 869 A1 a method for controlling the operation of a rotary kiln burner is known.

[0008] EP 1 637 823 A1 discloses a metal melting furnace and a method and use for melting metals.

[0009] Based on this, it is the object of the present invention to provide a method for operating a rotary kiln, in particular a burner, wherein a safe operation of the rotary kiln is ensured and at the same time an exhaust gas with a high CO 2 content is obtained.

[0010] This object is achieved according to the invention by a method having the features of independent method claim 1 and by a rotary kiln according to independent claim 9. Advantageous further developments emerge from the dependent claims.

[0011] A method for operating a rotary kiln, in particular a burner of a rotary kiln, comprises, according to a first aspect, the gas streams supplied to the rotary kiln consisting in total of more than 50 vol% oxygen, wherein an oxygen-rich atmosphere is preferably formed within the rotary kiln with an oxygen content of more than 30 vol%, preferably more than 50 vol%, in particular more than 75 vol%. The oxygen-rich atmosphere is in particular the average oxygen content within the entire rotary kiln, wherein local regions with an oxygen content of less than 50 vol% can occur. The burner has a burner mouth from which a fuel-gas mixture is discharged into the interior of the rotary kiln, in particular the combustion chamber, and wherein at least one state variable of the burner flame, in particular the ignition distance, the flame shape, the flame length and / or the flame width, is determined.The flow velocity, the quantity and / or the momentum of the fuel-gas mixture and / or the fuel properties are controlled / regulated depending on and preferably to influence the determined state variable.

[0012] The fuel properties are preferably the fuel moisture content, fuel composition, calorific value and / or grain size of the fuel.

[0013] The kiln is in particular a rotary kiln and preferably part of a cement production plant, the cement production plant comprising, for example: a preheater for preheating raw meal, a calciner for calcining the preheated raw meal, a rotary kiln with a burner for firing the calcined hot meal to cement clinker and a cooler for cooling the cement clinker.

[0014] The rotary kiln comprises a burner, such as a burner lance and / or a single-channel or multi-channel burner for firing the calcined hot meal into cement clinker. The rotary kiln has a combustion gas inlet for admitting a combustion gas into the rotary kiln with an oxygen content of 50% to 100% by volume, in particular at least 50% by volume, preferably at least 75% by volume. The combustion gas inlet is preferably located in the kiln head, to which the cooler is connected. In particular, the combustion gas is formed at least partially from the cooler exhaust air. Optionally, the burner has a combustion gas inlet, in particular for controlling and regulating the flame parameters, via which a combustion gas is introduced into the kiln. This combustion gas can differ in composition from the combustion gas supplied via the cooler.In a special embodiment, this combustion gas has an oxygen content of between 0 and 100%, in particular a maximum of 21%, preferably a maximum of 10%.

[0015] A preheater of the cement production plant preferably comprises a plurality of cyclone stages, each with at least one cyclone for separating solids from the gas stream. In the preheater, the raw meal fed into the uppermost, first cyclone stage is preheated in countercurrent to the kiln exhaust gases, passing successively through the cyclone stages.

[0016] The calciner is preferably located between the last and penultimate cyclone stages. This calciner has a riser pipe into which the raw meal is heated by means of a calciner furnace. In particular, the raw meal is deacidified and calcined in the calciner.

[0017] The raw meal preheated in the preheater and calcined in the calciner is then fed to the rotary kiln. The rotary kiln has, in particular, a rotary tube rotatable about its longitudinal axis, which is preferably slightly inclined in the conveying direction of the material to be burned, so that the material is moved in the conveying direction by the rotation of the rotary tube and gravity. The kiln preferably has, at one end, a material inlet for admitting preheated, calcined raw meal and, at the end opposite the material inlet, a material outlet for discharging the burned clinker into the cooler. At the material outlet end of the kiln, a kiln head is preferably arranged, which has the burner for burning the material, in particular a fuel lance and / or a single-channel or multi-channel burner.The rotary kiln preferably has a sintering zone in which the material is at least partially melted and in particular has a temperature of 1500°C to 1900°C, preferably 1450°C to 1750°C. The sintering zone comprises, for example, the kiln head and in particular a sector of the rotary kiln at the rear end, preferably the rear third of the kiln in the conveying direction of the material.

[0018] The oxygen-containing combustion gas is, for example, fed entirely or partially directly into the kiln head, wherein the kiln head has, for example, a combustion gas inlet. Preferably, the combustion gas is fed entirely or partially into the kiln via the material outlet of the kiln. The combustion gas supplied to the kiln has, for example, an oxygen content of more than 30 vol% to 75 vol%, in particular more than 50 vol%, preferably more than 95 vol%. The combustion gas consists, for example, entirely of pure oxygen, in which case the oxygen content of the combustion gas is 100%. The burner can be, for example, a burner lance and / or a single-channel or multi-channel burner. A cooler for cooling the cement clinker is preferably connected to the material outlet of the kiln.

[0019] The cooler preferably has a conveying device for conveying the bulk material in the conveying direction through the cooling gas chamber. The cooling gas chamber is preferably arranged directly downstream of the cooler inlet, in particular the kiln material outlet, in the flow direction of the bulk material to be cooled, so that the clinker falls from the rotary kiln into the cooling gas chamber and, in particular, the heated cooling gas stream from the cooler enters the rotary kiln and at least partially forms the combustion gas.

[0020] The burner of the rotary kiln is preferably a single burner lance and / or a single-channel or multi-channel burner with a plurality of coaxially arranged tubes or channels. The burner is preferably mounted on the wall, in particular the inner wall, of the kiln head, in particular on a static area of ​​the rotary kiln, and extends in particular in the axial direction, preferably centrally into the rotary kiln's rotary tube.

[0021] The burner comprises, for example, a plurality of tubes, in particular four tubes, which are arranged coaxially to one another and have different diameters. A central tube is arranged in the middle and forms a central channel. The central tube with the smallest diameter is used to transport, in particular, lumpy fuel, such as substitute fuels made from waste or production residues, such as old tires. A carrier gas is passed through the central tube together with the fuel, which serves to pneumatically transport the fuel. The carrier gas is in particular a low-oxygen gas with an oxygen concentration of 0 to 30 vol%, in particular 2 to 20 vol%, preferably 10 to 15 vol%, most preferably less than 10 vol%. The transport gas preferably has a CO2 concentration of 70 to 95 vol%, in particular 80 to 90 vol%, preferably more than 75 vol%.The remaining portion of the transport gas preferably comprises oxygen and / or water vapor and / or another inert gas component. The central tube is preferably connected to a fuel source, in particular lumpy refuse-derived fuel, and a transport gas source.

[0022] A swirl gas tube is preferably arranged coaxially around the central tube, forming a swirl gas channel. The swirl gas channel preferably serves to conduct a swirl gas with an oxygen content of 0 to 100 vol%, in particular 0 to 75 vol%, preferably less than 10 vol%. The swirl gas channel is preferably connected to a source of the swirl gas. The swirl gas tube extends, for example, axially, toward the burner orifice, beyond the central tube.

[0023] The fuel tube is preferably arranged coaxially to the swirl gas tube and forms a fuel channel. It is preferably designed to conduct a fine-particle fuel, such as coal, as well as a carrier gas for pneumatically transporting the fuel through the fuel channel. The carrier gas preferably has an oxygen content of 0 to 30 vol%, in particular 2 to 20 vol%, preferably less than 10 vol%. The transport gas preferably has a CO2 concentration of 70 to 95 vol%, in particular 80 to 90 vol%, preferably more than 75 vol%. The remaining portion of the transport gas preferably comprises oxygen and / or water vapor. The fuel tube preferably extends axially, in the direction of the burner mouth, over the central tube and out of the swirl gas tube. The fuel channel is preferably connected to a source of the carrier gas and the, in particular, fine-grained fuel.Instead of the finely divided fuel, a liquid or gaseous fuel can also be used, which is introduced into the combustion chamber under pressure without any portion of the transport gas.

[0024] The axial gas tube is preferably arranged coaxially around the fuel tube, forming an axial gas channel and preferably serving to conduct an axial gas. The axial gas preferably has an oxygen content of 0 to 100 vol%, in particular 0 to 75 vol%, preferably less than 10 vol%, with the axial gas channel preferably being connected to a source of the axial gas. The axial gas tube extends, in particular, in the axial direction, toward the burner orifice, over the central tube, the fuel tube, and the swirl gas tube.

[0025] The fuel-gas mixture preferably comprises the carrier gas, the axial gas and / or the swirl gas, as well as a fine-grained fuel and / or a coarse-grained fuel, in particular a substitute fuel. The carrier gas, swirl gas and / or the axial gas comprise at least partially or completely exhaust gas from the rotary kiln or exhaust gas from the cement production plant. The axial gas and the swirl gas preferably have a higher flow velocity relative to the carrier gas, so that the axial gas and the swirl gas preferably impart a swirl impulse to the mixture of fuel and carrier gas. In particular, the swirl gas tube, in particular the burner mouth, is designed such that the swirl gas has a substantially tangential flow direction relative to the burner axis.Preferably, the axial gas tube, in particular the burner mouth, is designed such that the axial gas has a substantially axial flow direction relative to the burner axis.

[0026] The terms "control" and "regulation" refer to processes in automation technology. The term "regulation" refers to a process in which a variable, the controlled variable, is continuously recorded, compared with another variable, the reference variable, and influenced to achieve an adjustment to the reference variable. The term "control" refers to a process in which at least one input variable influences other variables as output or control variables based on the inherent laws of the system. The term "adjustment" encompasses both "control" and "regulation."

[0027] The ignition distance is the distance, preferably in the axial direction of the rotary kiln, between the burner orifice and the flame. In particular, the ignition distance is the smallest distance between the burner orifice and the burner flame. The flame length is preferably the extension of the burner flame in the axial direction of the rotary kiln, while the flame width is the extension of the burner flame in the radial direction of the rotary kiln.

[0028] According to a first embodiment, the state variable of the burner flame is compared with a limit value or limit range, and if the determined state variable deviates from the limit value or limit range, the flow velocity, the quantity and / or the momentum of the fuel-gas mixture and / or the fuel properties are adjusted. Preferably, each state variable of the burner flame has a respective limit value or limit range. The limit range preferably comprises a maximum value and a minimum value, wherein falling below the limit range comprises falling below the minimum value, and exceeding the limit value comprises exceeding the maximum value. Such control makes it possible to prevent damage to the burner by monitoring the state variables of the burner flame.

[0029] According to a further embodiment, the ignition distance is determined and compared with an ignition distance limit value or limit range, wherein if the determined ignition distance deviates from the ignition distance limit value or limit range, the fuel moisture content, the grain size of the fuel, the CO2 content of the fuel-gas mixture and / or the oxygen content of the fuel-gas mixture is increased or decreased.

[0030] If the determined ignition distance falls below the ignition distance limit value or limit range, the fuel moisture content and / or the grain size of the fuel is preferably increased. If the determined ignition distance exceeds the ignition distance limit value or limit range, the fuel moisture content and / or the grain size of the fuel is preferably reduced. In particular, if the ignition distance limit value or limit range is undershot, fine-grained material such as lime powder or gypsum powder is fed through the burner, in particular through the fuel duct and / or the axial gas duct, into the combustion zone of the rotary kiln. This prevents ignition of the fuel near the burner mouth. It is also conceivable to increase the flow velocity of the carrier gas if the ignition distance limit value or limit range is undershot.

[0031] According to a further embodiment, the burner has an axial gas channel through which an axial gas flows and exits the burner mouth in a substantially axial direction of the burner, and a swirl gas channel through which a swirl gas flows and exits the burner mouth in a substantially tangential direction of the burner. Preferably, the ignition distance is determined and compared with an ignition distance limit value or limit range, wherein, if the determined ignition distance deviates from the ignition distance limit value or limit range, the flow velocity, the oxygen content and / or the CO2 content of the axial gas and / or the swirl gas is increased or decreased. Preferably, only axial gas flows through the axial gas channel, and only swirl gas flows through the swirl gas channel in accordance with the preceding description.Adjusting the flow velocities of the axial gas and the swirl gas ensures a corresponding impulse on the mixture of fuel and carrier gas as it exits the burner orifice, so that the flame shape can be adjusted accordingly.

[0032] According to a further embodiment, the flame length is determined and compared with a flame length limit or limit range. If the determined flame length deviates from the flame length limit or limit range, the flow velocity and / or momentum of the fuel-gas mixture is increased or decreased. The flow velocity of the fuel-gas mixture is preferably adjusted by adjusting the flow velocities of the axial gas, swirl gas, and / or carrier gas, whereby such an adjustment preferably ensures optimal mixing between the fuel and the gases.

[0033] According to a further embodiment, the flame length and / or flame width is determined and compared with a flame length / flame width limit value or limit range. If the determined flame length or flame width deviates from the flame length / flame width limit value or limit range, water vapor, CO2, and / or solid particles are introduced into the combustion zone. Preferably, the water vapor, CO2, and / or solid particles are introduced into the rotary kiln, in particular the combustion zone, via the burner and / or via a separate line. Adding water vapor, CO2, and / or solid particles results, for example, in a delay in ignition and / or improved or reduced thermal expansion of the burner flame.

[0034] According to a further embodiment, the burner has an axial gas channel through which an axial gas flows and exits the burner orifice in a substantially axial direction of the burner, and a swirl gas channel through which a swirl gas flows and exits the burner orifice in a substantially tangential direction of the burner. If the determined flame length deviates from the flame length limit or limit range, the flow velocity of the axial gas in the axial gas channel and of the swirl gas in the swirl gas channel is increased or decreased.

[0035] If the determined flame length falls below the flame length limit or limit range, the flow velocity of the axial gas in the axial gas channel is preferably increased and / or the flow velocity of the swirl gas in the swirl gas channel is preferably reduced. If the determined flame length exceeds the flame length limit or limit range, the flow velocity of the axial gas in the axial gas channel is preferably reduced and / or the flow velocity of the swirl gas in the swirl gas channel is preferably increased. The flow velocity of the carrier gas is preferably unchanged depending on the determined flame length.

[0036] According to the invention, the exhaust gas from the rotary kiln is at least partially fed to the burner. Preferably, the exhaust gas from the rotary kiln forms the carrier gas at least partially or completely. In particular, the exhaust gas from the rotary kiln is fed partially or completely to the burner via the burner or via a line arranged separately from the burner. The exhaust gas is, for example, at least partially exhaust gas from the cement production plant.

[0037] According to a further embodiment, the state variable of the burner flame is determined using a camera, in particular an infrared camera.

[0038] The invention also encompasses a rotary kiln for burning raw meal to produce cement clinker, comprising a combustion zone formed within the rotary kiln, a burner with a burner orifice for discharging a fuel-gas mixture into the combustion zone, and a measuring device designed and arranged to determine at least one state variable of the burner flame, in particular the ignition distance, the flame length, and / or the flame width. The rotary kiln has a control / regulation device designed to control / regulate the flow velocity, the quantity, and / or the momentum of the fuel-gas mixture, and / or the fuel properties as a function of the determined state variable.

[0039] The embodiments and advantages described with reference to the method for operating a burner of a rotary kiln also apply, in accordance with the device, to the rotary kiln for burning raw meal to cement clinker.

[0040] The measuring device is preferably designed to transmit the determined data, in particular the state variables of the burner flame, to the control / regulation device. The rotary kiln preferably has one or a plurality of gas inlets for admitting combustion gas, in particular oxygen. The gas inlets of the rotary kiln are preferably connected to at least one or more gas sources containing a gas with an oxygen content of more than 50 vol%. The control / regulation device is preferably designed to set an oxygen content of more than 50 vol%, in particular more than 75 vol%, preferably more than 90 vol% within the rotary kiln, in particular the combustion zone. The oxygen content within the kiln is preferably greater than 50 vol% overall, although individual regions with an oxygen content of less than 50 vol% may occur locally.

[0041] According to one embodiment, the control / regulation device is designed such that it compares the state variable of the burner flame with a limit value or limit range and, in the event of a deviation of the determined state variable from the limit value or limit range, adjusts the flow velocity, the quantity and / or the momentum of the fuel-gas mixture and / or the fuel properties.

[0042] According to a further embodiment, the measuring device is designed such that it determines the ignition distance and the control / regulation device is designed such that it compares the determined ignition distance with an ignition distance limit value or limit range and, in the event of a deviation of the determined ignition distance from the ignition distance limit value or limit range, increases or decreases the fuel moisture, the grain size of the fuel, the CO2 content of the fuel-gas mixture and / or the oxygen content of the fuel-gas mixture.

[0043] According to a further embodiment, the burner has an axial gas channel designed such that an axial gas flows through it and exits the burner mouth in a substantially axial direction of the burner, and wherein the burner has a swirl gas channel designed such that a swirl gas flows through it and exits the burner mouth in a substantially tangential direction of the burner, and the measuring device is designed such that it determines the ignition distance. The control / regulation device is designed such that, if the determined ignition distance deviates from a predetermined ignition distance limit value or limit range, it increases or decreases the flow velocity, the oxygen content, and / or the CO2 content of the axial gas and / or the swirl gas.

[0044] According to a further embodiment, the measuring device is designed to determine the flame length. The control / regulation device is preferably designed to compare the determined flame length with a flame length limit or limit range and, if the determined flame length deviates from the flame length limit or limit range, to increase or decrease the flow velocity and / or momentum of the fuel-gas mixture.

[0045] According to a further embodiment, the rotary kiln has a line for feeding water vapor, CO2, and / or solid particles into the combustion zone, wherein the measuring device is designed to determine the flame length and the control / regulation device is designed to compare the determined flame length with a flame length limit value or limit range, and if the determined flame length deviates from the flame length limit value or limit range, water vapor, CO2, and / or solid particles are fed into the combustion zone. Preferably, the rotary kiln has a line separate from the burner for feeding water vapor, CO2, and / or solid particles into the combustion zone. The line and / or the burner are preferably connected to a source of water vapor, CO2, and / or solid particles.

[0046] According to a further embodiment, the burner has an axial gas channel designed such that an axial gas flows through it and exits the burner mouth in a substantially axial direction of the burner. The burner has a swirl gas channel designed such that a swirl gas flows through it and exits the burner mouth in a substantially tangential direction of the burner. The control / regulation device is preferably designed such that, in the event of a deviation of the determined flame length from the flame length limit value or limit range, it increases or decreases the flow velocity of the axial gas in the axial gas channel and of the swirl gas in the swirl gas channel.

[0047] According to the invention, the rotary kiln has an exhaust gas outlet, wherein the burner is connected to the exhaust gas outlet for conducting at least part of the exhaust gas into the burner.

[0048] According to a further embodiment, the measuring device is a camera, in particular an infrared camera. Description of the drawings

[0049] The invention is explained in more detail below using several embodiments with reference to the accompanying figures. Fig. 1 shows a schematic representation of a burner in a rotary kiln in a partial sectional view according to one embodiment. Fig. 2 shows a schematic representation of a burner in a longitudinal sectional view according to one embodiment.

[0050] Fig. 1 shows a rotary kiln 10 with a rotary tube 12 and a burner 14 arranged within the rotary tube 12. The burner 14 is preferably arranged on a Fig. 1The burner 14 is attached to the inner wall (not shown) of the rotary kiln 12, wherein the inner wall is a static inner wall that does not rotate with the rotary kiln's rotary tube. For example, the burner 14 is attached to the end wall arranged at the end region of the rotary tube or extends through it.

[0051] The rotary tube 12 is preferably arranged to be rotatable about its longitudinal axis and is oriented in particular in a downward direction towards the furnace head, in particular the burner 14, so that the material to be burned is conveyed within the rotary tube by gravity and by the rotation of the rotary tube 12 in the direction of the burner 14.

[0052] Fig. 1further shows a schematic representation of the flame 16 of the burner 14 and the ignition distance 18. The ignition distance 18 is the distance, preferably in the axial direction of the rotary kiln 10, between the burner 14 and the flame 16. The burner 14 has a burner orifice 20, which forms the axial end of the burner 14 and from which the fuel exits the burner 14. In particular, the ignition distance 18 is the smallest distance between the burner orifice 20 and the flame 16.

[0053] The rotary kiln 10 preferably has a measuring device, in particular a camera 22, preferably an infrared camera, which is designed and arranged to determine the ignition gap 18. The camera 22 is preferably attached to the inner wall of the rotary kiln 10, for example, to the rotary tube 12 or the kiln head. It is also conceivable for the camera 22 to be attached to a static inner wall of the kiln head or outside the rotary kiln 10. The measuring device is preferably designed to determine the flame shape, flame length, and flame width. The measuring device is preferably designed such that it detects a flame when the temperature exceeds a value of 1600°C and / or when combustion of the fuel occurs. The measuring device preferably comprises a cooling device for cooling the measuring device.

[0054] Fig. 2showed the burner 14 in a sectional view, wherein only the end region of the burner 14 extending into the rotary tube 12 with the burner mouth 20 is shown.

[0055] The burner 14 comprises, for example, four tubes which are arranged coaxially to one another and have different diameters. The central tube 24 with the smallest diameter is used to transport, in particular, lumpy fuel, such as, for example, substitute fuels made from waste or old tires. The central tube 24 forms a central channel 26. Together with the fuel, a carrier gas is passed through the central tube 24 and serves to pneumatically transport the fuel. The carrier gas is, in particular, a low-oxygen gas with an oxygen concentration of 0 to 35 vol%, in particular 2 to 20 vol%, preferably 10 to 15 vol%, most preferably less than 10 vol%. The transport gas preferably has a CO2 concentration of 70 to 95 vol%, in particular 80 to 90 vol%, preferably more than 75 vol%. The remaining portion of the transport gas preferably comprises oxygen, nitrogen and / or water.The central pipe 24 is preferably connected to a source of fuel, in particular lumpy substitute fuel, and a source of the transport gas.

[0056] Arranged coaxially to the central tube 24, for example, is the swirl gas tube 28, which forms a swirl gas channel 30. The swirl gas channel 30 is preferably formed between the inner wall of the swirl gas tube 28 and the outer wall of the central tube 24 and preferably serves to conduct a swirl gas. The swirl gas tube 28 extends, for example, in the axial direction, in the direction of the burner mouth 20, beyond the central tube 24. The swirl gas preferably has an oxygen content of 0 to 100 vol%, in particular 30 to 75 vol%, preferably more than 90 vol%. The swirl gas channel 30 is preferably connected to a source for the swirl gas.

[0057] Arranged coaxially to the swirl gas tube 28, for example, is the fuel tube 32, which forms a fuel channel 34. The fuel channel 34 is formed between the inner wall of the fuel tube 32 and the outer wall of the swirl gas tube 28 and preferably serves to conduct a finely divided fuel, such as coal, as well as to conduct a carrier gas for pneumatically transporting the fuel through the fuel channel 34. The fuel tube 32 extends, for example, in the axial direction, in the direction of the burner mouth 20, over the central tube 24 and out of the swirl gas tube 28. The carrier gas preferably has an oxygen content of 0 to 30 vol%, in particular 2 to 20 vol%, preferably 10 to 15 vol%, most preferably less than 10 vol%. Preferably, the transport gas has a CO 2 concentration of 70 to 95 vol%, in particular 80 to 90 vol%, preferably more than 75 vol%.The remaining portion of the transport gas preferably comprises oxygen, nitrogen, and / or water. The fuel channel 34 is preferably connected to a source of the carrier gas and the, in particular, fine-grained fuel.

[0058] Arranged coaxially to the fuel tube 32, for example, is the axial gas tube 36, which forms an axial gas channel 38. The axial gas channel 38 is formed in particular between the inner wall of the axial gas tube 36 and the outer wall of the fuel tube 32 and preferably serves to conduct an axial gas. The axial gas tube 36 extends, for example, in the axial direction, in the direction of the burner mouth 20, over the central tube 24, the fuel tube 32, and the swirl gas tube 28. The axial gas preferably has an oxygen content of 0 to 100 vol%, in particular 30 to 75 vol%, preferably more than 90 vol%. The axial gas channel 38 is preferably connected to a source for the axial gas.

[0059] The main flow direction of the gases is indicated by the arrow. The axial gas and the swirl gas preferably have a high flow velocity relative to the carrier gas. The flow direction of the axial gas is essentially in the axial direction of the burner, while the flow direction of the swirl gas is essentially tangential to the burner. The swirl gas and the axial gas preferably serve to impart an axial and swirl impulse to the fuel exiting the burner orifice 20, in particular from the fuel channel 30 and the central channel 26.

[0060] The central channel 26, the swirl gas channel 30, the fuel channel 34, and the axial gas channel 38 are each connected to a device for adjusting the flow rate and / or quantity of the respective gas, such as the carrier gas, axial gas, or swirl gas. The device for adjusting the flow rate and / or quantity of the gas is, for example, a valve, a fan, a nozzle, and / or a diffuser.

[0061] The rotary kiln 10 has a control / regulation device connected to the camera 22 for transmitting the data determined by the camera 22, in particular the ignition distance, the flame length, and / or the flame width. The control / regulation device is preferably connected to the device for adjusting the flow velocity and / or the gas quantity and is designed to control / regulate the flow velocity and / or the gas quantity of the gases flowing through the central channel 26, the swirl gas channel 30, the fuel channel 34, and the axial gas channel 38. The control / regulation device is preferably designed to adjust the flow velocity and / or the gas quantity depending on the determined ignition distance, the flame length, and / or the flame width, preferably increasing, decreasing, or leaving it unchanged.

[0062] Preferably, the determined state variable of the burner flame is compared with a predetermined limit value or boundary range, and if the determined state variable deviates from the limit value or boundary range, the flow velocity, the quantity and / or the momentum of the carrier gas and / or the fuel properties are adjusted. It is also conceivable that the flow velocity, the quantity and / or the momentum of the carrier gas and / or the fuel properties are controlled in such a way that a respective predetermined value of the flow velocity, quantity and / or the momentum of the carrier gas and / or the fuel properties is assigned to the determined state variable, so that the flow velocity, the quantity and / or the momentum of the carrier gas and / or the fuel properties are adjusted to the respective predetermined value depending on the determined state variable.

[0063] For example, the ignition distance is determined and compared with an ignition distance limit or threshold range. If the determined ignition distance falls below the ignition distance limit or threshold range, the fuel moisture content and / or the fuel grain size are increased. If the determined ignition distance exceeds the ignition distance limit or threshold range, the fuel moisture content and / or the fuel grain size are reduced.

[0064] For example, if the ignition distance limit or limit range is undershot, the CO2 content in the carrier gas is increased and preferably the oxygen content of the carrier gas is reduced. If the determined ignition distance 18 exceeds the ignition distance limit or limit range, for example, the CO2 content in the carrier gas is reduced and preferably the oxygen content of the carrier gas is increased. For example, if the determined ignition distance from the ignition distance limit or limit range is undershot, fine-grained material, such as lime powder or gypsum powder, is fed through the burner 14, in particular through the fuel channel 34 and / or the axial gas channel 38, into the combustion zone of the rotary kiln 10.

[0065] The burner 14 has a central channel 26 through which fuel flows together with a carrier gas. Furthermore, the burner 12 has a swirl gas channel 26 through which the swirl gas flows. The burner 12 also has an axial gas channel 38 through which the axial gas flows. In particular, the burner 12 has a fuel channel 34 through which fuel flows together with a carrier gas.

[0066] In particular, if the ignition distance limit value or limit range is undershot, the flow velocity and / or the quantity of carrier gas, in particular in the central channel 26 and / or the fuel channel 34, is increased. If the determined ignition distance 18 exceeds the ignition distance limit value or limit range, the flow velocity and / or the quantity of carrier gas, in particular in the central channel 26 and / or the fuel channel 34, is reduced. Preferably, if the ignition distance limit value or limit range is undershot, the flow velocity of the axial gas in the axial gas channel 38 is increased, and if the ignition distance limit value or limit range is exceeded, it is reduced. Preferably, if the ignition distance limit value or limit range is undershot, the flow velocity of the swirl gas in the swirl gas channel 30 is increased, and if the ignition distance limit value or limit range is exceeded, it is reduced.

[0067] For example, the flame length is determined and compared with a flame length limit value or limit range. If the determined flame length falls below the flame length limit value or limit range, the flow velocity of the axial gas in the axial gas channel 38 and the swirl gas in the swirl gas channel 30 is reduced, for example, and increased if it is exceeded. The flow velocity of the carrier gas, for example, does not change depending on the determined flame length. For example, if the flame length deviates from the flame length limit value or limit range, water vapor, CO2, and / or solid particles are fed into the combustion zone. The feed takes place, for example, via the burner or via at least one additional line.The solid particles are introduced in particular through the central channel or the fuel channel, with the water vapor and / or CO2 preferably being introduced into the combustion zone through the axial gas channel 38 and / or the swirl gas channel 30. The solid particles are, for example, cement raw meal, limestone flour, calcined cement raw meal, and / or fuel ash, which stimulate the thermal radiation within the rotary kiln and thus influence the expansion of the burner flame.

[0068] If the determined flame length falls below the flame length limit value or limit range, the feed of water vapor, CO 2 and / or solid particles is increased, for example, whereas the feed is reduced if the flame length limit value or limit range is undershot.

[0069] For example, the flame shape is determined and compared with a plurality of predetermined flame shapes. Preferably, each flame shape is assigned a respective predetermined value of the flow velocity, quantity, and / or momentum of the carrier gas and / or the fuel properties, so that the flow velocity, quantity, and / or momentum of the carrier gas and / or the fuel properties are adjusted to the respective predetermined value depending on the determined flame shape. The flame shape is, for example, the two-dimensional or three-dimensional extension of the burner flame within the rotary kiln. List of reference symbols

[0070] 10Rotary kiln 12Rotary kiln 14Burner 16Burner flame 18Ignition gap 20Burner orifice 22Measuring device / camera 24Central tube 26Central duct 28Swirl gas tube 30Swirl gas duct 32Fuel tube 34Fuel duct 36Axial gas tube 38Axial gas duct

Claims

1. A process for operating a burner (14) of a rotary kiln (10), wherein the gas streams supplied to the rotary kiln (10) comprise in total more than 50% by volume of oxygen, wherein the burner (14) has a burner orifice (20) from which a fuel-gas mixture is discharged and wherein at least one state variable of the burner flame (16), in particular the ignition distance (18), the flame shape, the flame length and / or the flame width, is determined, characterized in that the flow velocity, the amount and / or the momentum of the fuel-gas mixture and / or the fuel properties is under open-loop / closed-loop control in accordance with the determined state variable, wherein the exhaust gas from the rotary kiln (10) is supplied at least in part to the burner (14).

2. The process as claimed in claim 1, wherein the state variable of the burner flame (16) is compared with a limit value or limit range and, if the determined state variable deviates from the limit value or limit range, the flow velocity, the amount and / or the momentum of the fuel-gas mixture and / or the fuel properties is adjusted.

3. The process as claimed in either of the preceding claims, wherein the ignition distance (18) is determined and compared with an ignition distance limit value or limit range and wherein, if the determined ignition distance (18) deviates from the ignition distance limit value or limit range, the fuel moisture content, the particle size of the fuel, the CO2 content of the fuel-gas mixture and / or the oxygen content of the fuel-gas mixture is increased or decreased.

4. The process as claimed in any of the preceding claims, wherein the burner (14) has an axial gas channel (38) through which an axial gas flows and exits the burner orifice (20) in the essentially axial direction of the burner (14) and a swirl gas channel (30) through which a swirl gas flows and exits the burner orifice (20) in essentially the tangential direction of the burner (14) and wherein the ignition distance (18) is determined and compared with an ignition distance limit value or limit range and wherein, if the determined ignition distance (18) deviates from the ignition distance limit value or limit range, the flow velocity, the oxygen content and / or the CO2 content of the axial gas and / or of the swirl gas is increased or decreased.

5. The process as claimed in any of the preceding claims, wherein the flame length is determined and compared with a flame length limit value or limit range and wherein, if the determined flame length deviates from the flame length limit value or limit range, the flow velocity and / or the momentum of the fuel-gas mixture is increased or decreased.

6. The process as claimed in any of the preceding claims, wherein the flame length is determined and compared with a flame length limit value or limit range and wherein, if the determined flame length deviates from the flame length limit value or limit range, water vapor, CO2 and / or solid particles are fed into the combustion zone.

7. The process as claimed in claim 5, wherein the burner (14) has an axial gas channel (38) through which an axial gas flows and exits the burner orifice (20) in the essentially axial direction of the burner (14) and a swirl gas channel (30) through which a swirl gas flows and exits the burner orifice (20) in essentially the tangential direction of the burner (14) and wherein, if the determined flame length deviates from the flame length limit value or limit range, the flow velocity of the axial gas in the axial gas channel and of the swirl gas in the swirl gas channel is increased or decreased.

8. The process as claimed in any of the preceding claims, wherein the state variable of the burner flame (16) is determined using a camera (22), in particular an infrared camera.

9. A rotary kiln (10) for burning raw meal to cement clinker having a combustion zone designed within the rotary kiln (10), a burner (14) having a burner orifice (20) for discharging a fuel-gas mixture into the combustion zone, a measuring device (22) that is designed and arranged such that it determines at least one state variable of the burner flame (16), in particular the ignition distance (18), the flame length and / or the flame width, characterized in that the rotary kiln (10) has an open-loop / closed-loop control device designed such that it provides open-loop / closed-loop control of the flow velocity, the amount and / or the momentum of the fuel-gas mixture and / or the fuel properties in accordance with the determined state variable, wherein the rotary kiln (10) has an exhaust gas outlet and the burner (14) is connected to the exhaust gas outlet for conducting at least part of the exhaust gas into the burner (14).

10. The rotary kiln as claimed in claim 9, wherein the open-loop / closed-loop control device is designed such that it compares the state variable of the burner flame (16) with a limit value or limit range and, if the determined state variable deviates from the limit value or limit range, it adjusts the flow velocity, the amount and / or the momentum of the fuel-gas mixture and / or the fuel properties.

11. The rotary kiln as claimed in claim 9 or 10, wherein the measuring device (22) is designed such that it determines the ignition distance (18) and the open-loop / closed-loop control device is designed such that it compares the determined ignition distance (18) with an ignition distance limit value or limit range and wherein, if the determined ignition distance (18) deviates from the ignition distance limit value or limit range, the fuel moisture content, the particle size of the fuel, the CO2 content of the fuel-gas mixture and / or the oxygen content of the fuel-gas mixture is increased or decreased.

12. The rotary kiln as claimed in any of claims 9 to 11, wherein the burner (14) has an axial gas channel (38) designed such that an axial gas flows through it and exits the burner orifice (20) in the essentially axial direction of the burner (14), and wherein the burner (14) has a swirl gas channel (30) that is designed such that a swirl gas flows through it and exits the burner orifice (20) in essentially the tangential direction of the burner (14) and the measuring device (22) is designed such that it determines the ignition distance (18) and wherein the open-loop / closed-loop control device is designed such that, if the determined ignition distance (18) deviates from a predetermined ignition distance limit value or limit range, it increases or decreases the flow velocity, the oxygen content and / or the CO2 content of the axial gas and / or of the swirl gas.

13. The rotary kiln as claimed in any of claims 9 to 12, wherein the measuring device (22) is designed such that it determines the flame length and the open-loop / closed-loop control device is designed such that it compares the determined flame length with a flame length limit value or limit range and, if the determined flame length deviates from the flame length limit value or limit range, the flow velocity and / or the momentum of the fuel-gas mixture is increased or decreased.

14. The rotary kiln as claimed in any of claims 9 to 13, wherein the rotary kiln (10) has a conduit for feeding water vapor, CO2 and / or solid particles into the combustion zone and wherein the measuring device (22) is designed such that it determines the flame length and the open-loop / closed-loop control device is designed such that it compares the determined flame length with a flame length limit value or limit range and, if the determined flame length deviates from the flame length limit value or limit range, water vapor, CO2 and / or solid particles are fed into the combustion zone.

15. The rotary kiln as claimed in claim 13, wherein the burner has an axial gas channel (38) designed such that an axial gas flows through it and exits the burner orifice (20) in the essentially axial direction of the burner (14), and wherein the burner (14) has a swirl gas channel (30) that is designed such that a swirl gas flows through it and exits the burner orifice (20) in essentially the tangential direction of the burner (14) and wherein the open-loop / closed-loop control device is designed such that, if the determined flame length deviates from the flame length limit value or limit range, it increases or decreases the flow velocity of the axial gas in the axial gas channel (38) and of the swirl gas in the swirl gas channel (30).

16. The rotary kiln as claimed in any of claims 9 to 15, wherein the measuring device (22) is a camera, in particular an infrared camera.

Images