HYDRAULIC-BINDER ROTARY-FURNACE OPERATION

Abstract

Method of operating a rotary furnace for the production of hydraulic binder so as to reduce ring formation therein, whereby the longitudinal temperature profile in the furnace is varied during furnace operation by injecting at least one fluid other than the main fuel(s) the primary oxidizer and hot air from the material cooler with at least one continuously or discontinuously varying injection parameter.

Claims

1-15. (canceled)

16. A method of operating a rotary furnace for the production of a hydraulic binder, comprising the steps of: providing a furnace having a substantially cylindrical shape with a longitudinal axis which is inclined with respect to the horizontal, an upper end, a lower end and a substantially cylindrical wall, the length of the furnace being at least 9 times the diameter of the furnace, and preferably from 9 to 40 times the diameter of the furnace, the furnace comprising a burner assembly at its lower end; rotating the furnace around the longitudinal axis; feeding a material to be pyroprocessed to the furnace at its upper end, the material to be pyroprocessed thereby traveling downwards through the furnace under the effect of gravity and being pyroprocessed in the furnace by heat generated by combustion of a main fuel in the furnace and leaving the furnace at its lower end as pyroprocessed material; transferring the pyroprocessed material from the furnace to an air-cooled material cooler, to produce cooled pyroprocessed material and hot air; injecting the main fuel and primary combustion oxidizer into the furnace with the burner assembly so as to generate partial combustion of the main fuel with the primary combustion oxidizer, a flame generated by combustion of the main fuel with the primary and secondary oxidizer being directed substantially parallel to the longitudinal axis of the furnace; feeding hot air from the material cooler to the furnace at its lower end as secondary oxidizer so as to substantially complete combustion of the main fuel; evacuating flue gas from the upper end of the furnace; and varying a longitudinal temperature profile within the furnace during furnace operation by injecting, into the furnace, at least one fluid other than the main fuel, the primary oxidizer and the secondary oxidizer, wherein the variation of the longitudinal temperature profile is achieved by continuously or discontinuously varying at least one injection parameter of the fluid injection into the furnace.

17. The method of claim 16, wherein the fluid is injected with a continuously or discontinuously varying injection velocity.

18. The method of claim 16, wherein the fluid is injected with a continuously or discontinuously varying the injection direction.

19. The method of claim 16, wherein the fluid is injected from one or more continuously or discontinuously varying points of injection.

20. The method of claim 16, wherein the fluid is injected with a continuously or discontinuously varying the injection flow rate of the fluid.

21. The method of claim 16, wherein a temperature the fluid injected is continuously or discontinuously varied.

22. The method of claim 16, wherein the fluid is injected by one or more lances located at the lower end of the furnace.

23. The method of claim 16, wherein the fluid is a gas.

24. The method of claim 23, wherein the fluid contains a gas selected from the group consisting of: oxygen, air, CO.sub.2, steam and recycled flue gas, and mixtures thereof.

25. The method of claim 16, wherein the fluid is a liquid.

26. The method of claim 16, wherein the fluid is an auxiliary fuel which is injected into the furnace by an auxiliary burner located at the lower end of the furnace.

27. The method of claim 26, wherein the auxiliary burner also injects an auxiliary combustion oxidizer for burning the auxiliary fuel.

28. The method of claim 16, wherein the injection parameter is varied as a function of a temperature of the cylindrical wall detected at a given location along the length of the rotary furnace.

29. The method of claim 16, wherein the injection parameter is varied as a function of a pressure drop over the rotary furnace.

30. The method of claim 16, wherein the hydraulic binder is cement or lime.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0060] FIG. 1 is a schematic representation of the impact of the variation of the injection momentum of oxygen in accordance with the present invention on the global momentum of the furnace and on the temperature at distinct longitudinal positions within the furnace;

[0061] FIG. 2 is a schematic representation of the impact of the variation of the global momentum in the furnace caused by the variation of the injection momentum of oxygen in accordance with the present invention on the longitudinal temperature profile in the furnace and the longitudinal location of ring formation;

[0062] FIG. 3 is a schematic partial representation of a hydraulic-binder production unit according to the state of the art comprising a rotary pyroprocessing furnace.

[0063] FIG. 4 is a schematic partial representation of a hydraulic-binder production unit of the type illustrated in FIG. 3, but adapted for use in one embodiment of the method of the present invention;

[0064] FIG. 5 is a further schematic partial representation of a hydraulic-binder production unit of the type illustrated in FIG. 3, but adapted for use in a second embodiment of the method of the present invention;

[0065] FIG. 6 is a schematic representation in longitudinal cross section and in front view of an oxygen lance suitable for use in the method of the present invention, including in the production units illustrated in FIGS. 4 and 5;

[0066] FIG. 7 is a schematic front view of a burner assembly equipped with a suitable lance as illustrated in FIG. 6 and suitable for use in the method according to the present invention, including in the production unit illustrated in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0067] Although the example relates specifically to a rotary cement furnace, similar considerations apply to other rotary hydraulic-binder furnaces, such as rotary lime furnaces.

[0068] The final conversion of meal into cement clinker, which is usually performed in a rotary cement furnace, is a sintering reaction between the principle reactants lime (CaO) and dicalcium silicate (C2S) remaining solids. This solid to solid conversion is greatly enhanced by the presence of 20 to 30% liquid phase formed from the calcium alumina ferrite (C3AF) and tricalcium aluminate (C3A) phases plus the alkalis, sulfates and magnesia.

[0069] Co-existence of these various phases along the kiln creates a gradient of material viscosity and stickiness depending on temperature and composition of the material mix and of the atmosphere in contact therewith, causing localized formation of a thick coating, build-up or ring of sticky material on the cylindrical furnace wall.

[0070] The current practice of burning alternative fuels, such as shredded tires, organic waste, etc., as (part of) the main fuel in the rotary furnace, thereby introducing a substantial amount of impurities like sulfur and chlorine into the process, tends to promote ring formation and increases the need for a solution to the problem.

[0071] Various types and locations of rings are reported in the literature according to their location in the furnace: [0072] Ring at the lower end of the rotary furnace

[0073] These rings are mainly associated with overheating of refractory lining and overproduction of the liquid phase of the granular material. To counteract this phenomenon, it is known to select the process parameters at the start of furnace operation, in particular to select a sufficient secondary air flow so as to achieve adequate cooling the furnace wall, to select a sufficiently low secondary air temperature, to position the burner assembly deeper into the furnace or to operate the burner assembly so as to generate a tight flame when said flame tends to lift towards the lining of the furnace. [0074] Ring at the upper end of the rotary furnace

[0075] These rings are mainly due to the formation of spurrite/sulfate spurrite, possibly arising from reductive burning conditions at some point in the kiln and recirculation of sulfate.

[0076] These rings are particularly problematic as they are located too far back from the lower end of the furnace to be effectively removed by gun firing. It has been proposed to destroy said rings by firing CO.sub.2 charges through the cylindrical wall when ports for the firing of such charges are provided. In any case, the kiln has to be stopped frequently and has to be allowed to cool down before the rings can be physically removed. The only known solution not requiring frequent kiln stoppage is to select the process parameters, and in particular the selection of raw meal and the main fuel at the start of furnace operation, so as to prevent a sulfate excess in the hot material. However, this is often not possible due to the need for regional sourcing of raw meal and of the main fuel for cost reasons. [0077] Ring in the burning zone in the middle of the rotary furnace

[0078] These rings are associated with (re)circulation in the furnace atmosphere of dust particles, in particular fuel ash and material dust such as clinker dust, for example entrained with the secondary combustion air from the cooler. When reaching a sufficiently high temperature in the flame, the dust particles melt and are carried up the kiln where they stiffen again and stick to the furnace wall, forming generally elongated rings. These rings can usually be destroyed mechanically by firing a gun, but this requires significant furnace downtime and can damage refractory lining.

[0079] It is also known to try to reduce dust production and/or dust (re)circulation by operating the burner assembly so as to shorten and tighten the flame, however this does not entirely eliminate ring formation in the middle of the rotary furnace, but merely reduces the required frequency of furnace shut-down or the ring length. Indeed shortening the flame requires increasing the flow of primary air and thereby gas recirculation at the burner tip, so that dust from the cooler is carried less far into the furnace, resulting in smaller rings.

[0080] In accordance with the present invention, the longitudinal temperature profile within the furnace is varied during furnace operation resulting in a corresponding variation of the longitudinal heat transfer profile and/or material composition profile along the rotary furnace.

[0081] During furnace operation, i.e. in the course of continued furnace operation, the longitudinal temperature profile is varied during furnace operation by injecting at least one fluid other than the main fuel, the primary oxidizer and the secondary oxidizer under continuously or discontinuously varying injection parameters. A wide range of fluids can be injected thereto. The fluid can be gaseous or liquid. It can comprise or consist of a further or auxiliary oxidizer, a further or auxiliary fuel, a combination of auxiliary fuel and auxiliary oxidizer, combustion gases generated by the combustion of an auxiliary fuel, steam, CO.sub.2, oxygen, recycled combustion gases, etc. In general, due to its promotion of complete fuel combustion, it is preferred to inject oxygen or an oxygen-containing fluid. In accordance with the present invention, at least one injection parameter of said oxygen injection, such as velocity and/or flow rate and/or temperature, is varied to a sufficient degree so as to generate a corresponding variation in the longitudinal temperature profile of the furnace.

[0082] In practice, the furnace operator selects the fluid and the injection parameters of the fluid, including, but not only the injection parameter(s) which is (are) varied in accordance with the invention, so as to maximize the impact of the parameter variation on the longitudinal temperature profile of the furnace, but without appreciable negative impact on the furnace output, on the product quality or on the profitability of the process. The selection of the momentum with which the fluid is injected is generally particularly relevant in this respect. The injection momentum of the fluid is advantageously selected at between 5% and 50% of the global momentum of the furnace, preferably between 10% and 30%. This is in particular the case when the fluid is oxygen.

[0083] By means of the invention, it is prevented that at a given point along the length of the furnace, the temperature of the material and furnace atmosphere and their composition stabilize or remain at a combination likely to promote ring formation.

[0084] FIG. 1 illustrates the impact over time of a continuous non-periodic and non-cyclic variation of the injection momentum of a fluid jet consisting of oxygen on the temperature of the furnace wall/of the material in the furnace at a given longitudinal position of the furnace.

[0085] In this manner, the present invention substantially limits ring growth at specific locations in the rotary furnace by shifting the occurrence of conditions which promote ring growth along the length of the rotary furnace. This is illustrated in FIG. 2.

[0086] As shown in the example of FIG. 2, when the rotary furnace kiln operates with a global momentum M1, the associated longitudinal temperature & composition profile creates a zone at distance X1 from the burner assembly where said conditions promote ring formation.

[0087] After a given period of furnace operation, for example after a predetermined number of hours of operation or when probable ring formation is detected (e.g. a decrease in cylindrical wall temperature and/or an increase in the pressure drop over the furnace) the momentum of oxygen injection into the furnace is changed so as to change the global momentum from level M1 to level M2, thereby modifying the material and atmosphere temperature and composition in zone X1 to halt ring growth in said zone and preferably before stabilization of said ring. In this new process operation phase, the conditions suitable for ring formation have now moved to a new location X2 along the rotary furnace. After some further hours of production or, as indicated above, when there are new indications of ring formation within the furnace, the momentum of oxygen injection is again adjusted, for example so as to return to the initial global momentum level M1.

[0088] In the latter case, furnace operation alternating between operation at global momentum level M1 and global momentum level M2, the variation of the oxygen injection parameter is discontinuous. When the variations of oxygen injection momentum take place at fixed time intervals, the variation is periodic.

[0089] When the changes in the longitudinal temperature profile are sufficiently large, the present invention furthermore makes it possible to destabilize and decrease or destroy rings that have formed in the furnace at a previous stage in the process.

[0090] FIG. 1 illustrates the impact over time of a continuous non-periodic and non-cyclic variation of the injection momentum of a fluid jet consisting of oxygen on the temperature of the furnace wall/of the material in the furnace at two distinct longitudinal positions of the furnace. As shown in FIG. 1, the momentum of the oxygen jet was varied sufficiently so as to change the temperature at the two longitudinal positions (and consequently of the longitudinal temperature profile in the furnace).

[0091] However, the changes in the oxygen momentum do not generate significant changes in the global furnace momentum. Stable furnace operation and productivity are thus maintained in spite of the changes in the oxygen injection momentum.

[0092] Rotary furnace or kiln 10 presents an inclined longitudinal axis around which it rotates. Material to be pyroprocessed, such as uncalcined or partially calcined meal is introduced into rotary furnace 10 via kiln inlet 11 located at the upper end of furnace 10. The material travels through rotating furnace 10 under the effect of gravity and cylindrical wall rotation and is pyroprocessed by the heat generated by combustion of the main fuel(s) 31 inside furnace 10. It is indeed common practice to use the cheapest possible appropriate fuel or fuel combination for mineral pyroprocessing in order to keep production costs low.

[0093] The fumes or flue gases 51 generated in the furnace are evacuated at the upper end of furnace 10 via exhaust duct 50. When, for example, a precalciner (not illustrated) is present upstream of the rotary furnace (in the flow direction of the material), at least part of the flue gases may be directed towards said precalciner via said exhaust duct 50.

[0094] At the lower end of furnace 10, the pyroprocessed mineral material is transferred from furnace 10 to material cooler 20.

[0095] In cooler 20, the pyroprocessed material is cooled by means of cooling air 21.

[0096] For the combustion of the main fuel(s) 31, a main burner or burner assembly 30 is provided in the kiln hood 12 at the lower end of furnace 10. This main burner 30 is typically designed so as to permit the efficient combustion of a range of fuels, including alternative and low-calorific-value fuels 31.

[0097] In addition to the main fuel(s) 31, main burner 30 also injects primary combustion oxidizer 32, typically primary combustion air, into the furnace so as to generate partial burning of the main fuel(s) 31 with the primary oxidizer 32. Combustion of the main fuel(s) 31 is thereafter completed by further combustion with secondary combustion oxidizer 22. Hot air 22 from cooler 20 is used as secondary combustion oxidizer and is injected into furnace 10 at the lower end of furnace 10 separately from main burner 30.

[0098] In the illustrated embodiment shown in FIG. 3, a further portion 23 of the hot air from cooler 20 is used as tertiary air and transported from kiln hood 12 to a calciner (not shown) via tertiary air duct 40.

[0099] In the production unit illustrated in FIG. 4, a fluid injection device 60 is installed within burner assembly 30 (for example in channels 33 and/or 34 in FIG. 7).

[0100] The burner assembly illustrated in FIG. 7 is adapted for burning two types of main fuel. A first primary main fuel is injected through annual primary-fuel injection passage 311. The primary combustion air is divided in two air flows. A first axial primary-air flow is injected into the furnace via annular axial air passage 321 surrounding primary-fuel injection passage 311. A second radial primary-air flow is injected via annular radial air passage 322 located adjacent and within primary-fuel injection passage 311. The burner assembly further comprises a core element inside air passage 322. Multiple through passages or channels are provided in said core element, and more particularly, primary fuel passage 312 for the injection of primary fuel into the rotary furnace and the above-mentioned two additional channels 33 and 34. The injection parameters of the primary air are fixed in function of the nature and the flow rates of the primary fuel(s).

[0101] As many existing rotary kiln burner assemblies already present one or more such spare through passages or channels which, in normal furnace operation, are not used for injecting media into the furnace, the installation of a fluid injection device for use in the method of the invention is often possible without changes to the structure or design of the burner assembly 30 of the furnace 10.

[0102] In the production unit illustrated in FIG. 5, the fluid injection device 60 is mounted separately from burner assembly 30. Injection device 60 is shown mounted below burner assembly 30, but may also be mounted above or to the side of burner assembly 30, provided this does not interfere with the good functioning of the furnace.

[0103] An advantageous choice of additional fluid 61 is oxygen.

[0104] In accordance with the present invention, injection device 60 is used to inject a fluid, referred to as additional fluid, other than main fuel(s) 31, primary oxidizer 32 and secondary oxidizer 22, into the furnace. Injection device 60 is more specifically used to inject the additional fluid 61 into the furnace and to vary at least one injection parameter of the additional fluid during furnace operation so as thereby to achieve a change in the longitudinal temperature profile in the furnace while maintaining adequate productivity and pyroprocessed product quality.

[0105] One way of implementing the present invention is to vary the injection velocity or momentum of the additional fluid 61, and thereby to vary the longitudinal temperature profile in the furnace.

[0106] This may be achieved using a lance with two nozzles as injection device 60. Typically, one nozzle will surround the other, for example in a coaxial arrangement. An example of such a lance is illustrated in FIG. 6. The illustrated lance has a longitudinal axis 600, an inner supply pipe 68, which terminates in inner injection nozzle 66 and an outer supply pipe 67 which terminates in outer injection nozzle 65. Inner injection nozzle 66 defines inner injection opening 63 and the space between inner injection nozzle 66 and outer injection nozzle 65 defines outer injection opening 64. Such a lance 60 makes it possible to vary the oxygen injection velocity and injection momentum even at constant oxygen mass flow rates through lance 60, by switching the oxygen injection between (a) oxygen injection substantially through one of injection opening 63 and 64 only and (b) oxygen injection through both the inner and the outer openings 63, 64.

[0107] Lance 60 may thus be used for the discontinuous stepwise variation of the oxygen injection velocity or momentum by switching lance operation between a first and second phase during furnace operation. For example, during a first phase the oxygen is fed to both injection openings 63 and 64 to provide a low oxygen injection velocity, whereas during a second phase, inner nozzle 66 is fed with most of the oxygen (for example 90%) to inject a higher velocity or momentum oxygen jet into the furnace. The remaining 10% of the oxygen flow is injected through outer opening 64 to ensure cooling of the outside of the lance and prevent thermal damage thereof. When the flow cross section area of inner injection opening 63 differs substantially from the flow cross section area of outer injection opening 64, further variations in the oxygen injection velocity and momentum can be realized at the same oxygen injection mass flow rate. It is naturally also possible to vary the oxygen injection velocity or momentum by varying the oxygen mass flow rate through the lance and combine a variation of fluid flow rate with a variation of injection velocity.

[0108] It is also possible to install two or more distinct additional-fluid injection devices 60 for use in accordance with the present invention. For example, several injection devices 60 may be installed, each with their own point of injection and/or injection direction into the furnace. In that case, the longitudinal temperature profile of the furnace may be varied during furnace operation by varying the additional fluid flow through the different injection devices.

[0109] It is also possible to provide several variable-momentum lances as described above, each capable of injecting oxygen at low and high momentum at constant oxygen mass flow rate.

[0110] When the furnace is equipped with two such lances, for example one in channel 33 and one in channel 34 of the burner assembly shown in FIG. 7 or two lances at different positions around burner assembly 30 in FIG. 5 or at different locations in the rotary furnace, and to operate, during a first phase, one of said lances to inject oxygen at high momentum, the other to inject oxygen at low momentum, and thereafter to switch to a second phase in which the first of said two lances injects oxygen at low momentum and the second of the two lances injects oxygen at high momentum. By thus switching between the first phase and the second phase during furnace operation, it is again possible to vary the longitudinal temperature profile in the furnace even without varying the mass flow rate of oxygen injected into the furnace as additional fluid.

[0111] It is further possible, optionally in combination with one of the above embodiments, to vary the longitudinal temperature profile in the furnace by varying the temperature of the additional fluid injected into the furnace, for example by preheating said fluid to different temperatures by means of heat exchange with the flue gases from the hydraulic binder production plant or with cooling gas from the cooler.

EXAMPLE

[0112] The present invention and its advantages are illustrated in the following non-limiting example of the implementation of the method according to the present invention.

[0113] In a prior-art rotary kiln for the production of cement clinker of the type illustrated in FIG. 3, with an internal length of 65 m and equipped with a burner 30 as illustrated in FIG. 7, but without injection lance in either of channels 33 and 34, substantial ring formation took place at a distance between 20 m and 30 m from burner 30, resulting in significant reductions in production capacity. On the outside of the furnace, the formation of said rings within the furnace could be observed in that the shell temperature (i.e. the temperature on the outside of the cylindrical kiln wall) dropped significantly due to the insulating effect of the ring deposits.

[0114] In accordance with the present invention, an oxygen lance of the pipe-in-pipe type shown in FIG. 6 was installed in passage 34 in the central core element of burner 30 (as shown in FIG. 7).

[0115] A solenoid valve (not shown) at the inlet end of said oxygen lance controlled the distribution of the oxygen injected respectively through inner injection opening 63 and outer injection opening 64.

[0116] Using said oxygen lance and the associated solenoid valve, oxygen was injected into the kiln at constant flow rate of 600 Nm.sup.3/h, but with cyclic variations of the oxygen injection velocity.

[0117] The cyclic variation consisted of two phases.

[0118] During the first phase, the solenoid valve was closed and all of the oxygen, except for a minor sweeping fraction, was injected through the inner injection opening 63 at a first injection velocity in the range of 120 m/s to 140 m/s, preferably at 120 m/s. The sweeping oxygen fraction was injected through the outer injection opening 64. Said sweeping oxygen fraction was obtained from the oxygen supply line by bypassing the solenoid valve and was limited to the amount of oxygen required to maintain the outer injection nozzle 65 at a sufficiently low temperature to avoid thermal damage thereof and to prevent particle-laden gases from the kiln atmosphere to travel up said outer nozzle 65 during the first phase.

[0119] During the second phase of the cycle, the solenoid valve was open and the oxygen was distributed over and injected through the inner injection opening 63 and the outer injection opening 64, resulting in a lower oxygen injection velocity between 60 m/s and 90 m/s, preferably of 60 m/s.

[0120] Switching between the two phases took place every 12 hours.

[0121] When the method according to the present invention was used, there was no significant loss of production capacity due to the formation of ring deposits.

[0122] In those areas where during prior-art kiln operation ring formation was observed, i.e. at between 20 m and 30 m from the burner, the temperature of the kiln shell was on average 200 C. higher than during prior-art kiln operation.

[0123] Compared to prior-art operation, a production increase of appr. 12 tonnes of clinker per tonne of oxygen injected was observed.

[0124] This is all the more remarkable as oxygen lancing into the kiln at constant oxygen injection parameters resulted in a significantly lower production increase of 2 to 4 tonnes of clinker per tonne of oxygen injected. The method according to the invention was not only effective in preventing the formation of rings in the rotary kiln. Indeed, when the method according to the invention was used after a period of prior-art operation of the kiln, the method according to the invention permitted the destabilization and destruction of the earlier formed rings.

[0125] Although the invention has been described herein with respect to rotary furnaces for the production of hydraulic binders, it will be appreciated that it can be useful for all rotary furnaces in which ring formation during furnace operation presents a problem.

[0126] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0127] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0128] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of comprising. Comprising is defined herein as necessarily encompassing the more limited transitional terms consisting essentially of and consisting of; comprising may therefore be replaced by consisting essentially of or consisting of and remain within the expressly defined scope of comprising.

[0129] Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0130] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0131] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0132] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

LEGEND

[0133] 10: rotary kiln/furnace [0134] 11: kiln inlet/upper end [0135] 12: kiln hood [0136] 20: material cooler [0137] 21: cold cooling air [0138] 22: secondary air/hot cooling air [0139] 23: tertiary air [0140] 30: main burner assembly [0141] 31: main fuel(s) [0142] 32: primary air/primary oxidizer [0143] 33: channel for fluid injection device [0144] 34: channel for fluid injection device [0145] 40: tertiary air duct [0146] 50: flue gas exhaust duct [0147] 51: flue gases [0148] 60: fluid injection device/lance [0149] 61: additional fluid(s) [0150] 63: inner injection opening [0151] 64: outer injection opening [0152] 65: outer injection nozzle [0153] 66: inner injection nozzle [0154] 67: outer supply pipe [0155] 68: inner supply pipe [0156] 311: primary fuel [0157] 312: secondary fuel [0158] 321: primary air axial flow [0159] 322: primary air radial flow [0160] 600: longitudinal axis of fluid injection device