Fuel blowing-in method

Abstract

To provide a fuel blowing-in method which enables using a combustible gas as a fuel for clinker burning, while suppressing increase of a generation volume of NOx.SOLUTION: This method is a fuel blowing-in method which blows a fuel in a rotary kiln for cement burning through a burner. The burner includes a plurality of flow channels partitioned by a plurality of concentric cylindrical members. The method has a process (a) in which a combustible gas is blowed in through a combustible gas flow channel belonging to the plurality of flow channels, while a primary air is blowed in through an air flow channel belonging to the plurality of flow channels and different from the combustible gas flow channel. The process (a) is executed in a condition in which a relative ratio of a circumferential direction momentum of a synthetic gas of the primary air blowed in from the air flow channel and the combustible gas blowed in from the combustible gas flow channel to an axial direction momentum of the synthetic gas is within a range of 0.06 to 0.44.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a method for injecting a fuel-laden air stream into the interior of a rotary kiln for burning cement. [Background technology]

[0002] The production of cement requires firing at temperatures exceeding 1,400°C. A chemical reaction during this firing process causes limestone, the main raw material, to decarbonate (CaCO3 → CaO + CO2). For these reasons, it is known that a large amount of CO2 is generated during the cement production process.

[0003] Approximately 40% of the CO2 generated in the cement manufacturing process is derived from energy sources such as fossil fuel and electricity consumption. For this reason, in consideration of the impact on global warming, consideration is being given to using combustible gases such as natural gas, which has a lower CO2 emission intensity than coal, the main fuel used until now, and synthetic methane (e-methane) made from CO2, as a substitute for the main fuel or as a supplementary fuel to the main fuel.

[0004] The following Patent Document 1 discloses a technology in which a burner that injects a main fuel such as coal is provided with a dedicated port separate from the port through which the main fuel is fed, and ammonia gas, a type of combustible gas, is injected into a rotary kiln for burning cement from this dedicated port. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-185122 Summary of the Invention [Problem to be solved by the invention]

[0006] Because combustible gas is a gas, it tends to burn faster than coal, which is a solid. Therefore, when combustible gas is used as a fuel for cement burning by injecting it from a burner, the combustion reaction of combustible gas proceeds more rapidly than that of coal, making it more likely to form localized high-temperature areas inside the rotary kiln.

[0007] More specifically, coal combustion involves the combustion of volatile matter released into the gas phase by pyrolysis (volatile matter combustion) and the combustion of solid matter known as fixed carbon (char combustion). While volatile matter combustion ends quickly, char combustion takes time and is the rate-limiting step for the overall combustion reaction. Natural gas combustion, on the other hand, is a gas-phase combustion only, so combustion is completed earlier than coal. Therefore, replacing coal with combustible gas as fuel can result in localized high-temperature areas (a tendency toward shorter flames) within the rotary kiln, potentially increasing thermal NOx emissions.

[0008] Because NOx is one of the sources of air pollution, the cement industry is also being asked to reduce the amount of NOx contained in exhaust gases. If the amount of NOx generated increases, it becomes necessary to increase the amount of denitrification agents used to reduce the amount of NOx contained in exhaust gases, which leads to an increase in cement production costs.

[0009] In view of the above problems, the present invention aims to provide a fuel injection method that makes it possible to use combustible gas as fuel for clinker burning while suppressing an increase in the amount of NOx generated. [Means for solving the problem]

[0010] The present invention provides a fuel injection method for injecting a fuel-containing airflow into a rotary kiln for cement burning through a burner, the method comprising: The burner includes a plurality of flow paths partitioned by a plurality of concentric cylindrical members, a step (a) of blowing a flammable gas as the fuel through a flammable gas flow path belonging to the plurality of flow paths and blowing primary air through an air flow path belonging to the plurality of flow paths and different from the flammable gas flow path; at least one of the flammable gas flow path and the air flow path has a turning angle with respect to the axial direction of the burner, The step (a) is characterized in that it is carried out under conditions in which the relative ratio β of the circumferential momentum of the synthesis gas of the primary air blown from the air flow passage and the combustible gas blown from the combustible gas flow passage to the axial momentum of the synthesis gas is within a range of 0.06 to 0.44.

[0011] The above method can suppress both the amount of NO produced by the Zeldovich mechanism (Zeldovich NO) and the amount of NO produced by the reaction of N2 contained in the combustion air with CH, CH2, etc. in the flame (Prompt NO). Details will be described later.

[0012] The primary air composite momentum, circumferential momentum, and axial momentum are calculated by numerical calculations once the primary air flow rate, flow velocity, and swirl angle values ​​are determined. The combustible gas composite momentum, circumferential momentum, and axial momentum are calculated once the combustible gas flow rate, flow velocity, gas density, and swirl angle values ​​are determined. The gas density of the combustible gas is uniquely determined by the type of combustible gas used.

[0013] The axial momentum and circumferential momentum of the synthesis gas of the primary air and the combustible gas can be calculated by calculation using the flow rates, flow velocities, and swirl angles of the primary air and the combustible gas. In other words, by adjusting the flow rates, flow velocities, and swirl angles of the primary air and the combustible gas during step (a) so that the relative ratio β falls within the range of 0.06 to 0.44, it becomes possible to inject the combustible gas as fuel into the rotary kiln while suppressing the amount of NOx generated.

[0014] The relative ratio β is more preferably within the range of 0.15 to 0.30.

[0015] In the step (a), the circumferential momentum of the synthesis gas is 0.6 kg m / s2 ]~4.5[kg·m / s 2 ] and the axial momentum of the synthesis gas is within 4.0 [kg m / s 2 ]~10.2[kg·m / s 2 It is also acceptable to set the condition to be within the range of [ ].

[0016] At least one of the flammable gas flow path and the air flow path may have a turning angle of 40° or less with respect to the axial direction of the burner. In this case, it is more preferable that at least one of the flammable gas flow path and the air flow path has a turning angle of 11° to 40° with respect to the axial direction of the burner. [Effects of the Invention]

[0017] According to the present invention, it is possible to suppress an increase in the amount of NOx generated while using combustible gas as fuel for burning clinker. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing a part of a cement manufacturing facility in which a fuel injection device is attached to a rotary kiln for cement burning. [Figure 2] FIG. 2 is an example of a plan view schematically illustrating a tip portion of a burner on the rotary kiln side. [Figure 3] FIG. 10 is another example of a plan view schematically showing the tip portion of the burner on the rotary kiln side. [Figure 4] 1 is a diagram showing a schematic diagram of a combustible gas being blown into a rotary kiln from the tip of a burner. [Figure 5] 1 is a diagram for explaining the decomposition of the velocity vector of gas injected from the tip of the burner into an axial component of the burner and a directional component perpendicular to the axial direction. [Figure 6] 1 is a schematic diagram of a test facility used in verifying the examples. [Figure 7] 1 is a graph showing the temperature distribution in a kiln. [Figure 8] This is a graph showing the NOx concentration in the exhaust gas and the peak temperature inside the kiln at different levels. [Figure 9] 1 is a graph in which the conditions of each level (#1 to #8) are plotted based on the values ​​of the axial momentum Mx of the synthesis gas of combustible gas and air and the circumferential momentum Mt of the synthesis gas. [Figure 10] 10 is a graph showing the relationship between the relative ratio β of the circumferential momentum Mt to the axial momentum Mx of the synthesis gas and the rate of increase in the NOx concentration in the exhaust gas. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of a fuel injection method according to the present invention will be described with reference to the accompanying drawings. The drawings are schematic illustrations, and the dimensional ratios in the drawings do not necessarily correspond to the actual dimensional ratios. Furthermore, the dimensional ratios between the drawings do not necessarily correspond to each other.

[0020] 1 is a cross-sectional view showing a part of a cement production facility 1 in which a fuel injection device is attached to a rotary kiln for cement burning, as an example suitable for carrying out the fuel injection method of this embodiment. The cement production facility 1 includes a rotary kiln 2 and a kiln hood 4 connected to the rotary kiln 2.

[0021] The rotary kiln 2 is a device that produces cement clinker (hereinafter referred to as "clinker 5") by burning clinker raw materials. Typically, the clinker raw materials are calcined via a preheater (not shown) installed upstream and flow into the kiln's base. The rotary kiln 2 has a horizontal cylindrical shape that is slightly inclined downward toward the downstream side (toward the kiln hood 4), and burns the clinker raw materials (or partially burned clinker) while rotating.

[0022] The upstream side of the kiln hood 4 is connected to the downstream end of the rotary kiln 2 and surrounds the downstream end of the rotary kiln 2. The lower side of the kiln hood 4 is connected to the clinker cooler 3. A burner 10 is fixed to the downstream wall surface 4a of the kiln hood 4. A portion of the downstream wall surface 4a of the kiln hood 4 is typically in the form of an openable door, which is opened when repairing the rotary kiln 2 or installing or replacing the burner 10.

[0023] Burners 10 attached to the kiln hood 4 burn the clinker raw material descending inside the rotary kiln 2. After burning, the clinker 5 falls toward the clinker cooler 3 disposed below the kiln hood 4 and is cooled in the clinker cooler 3.

[0024] The temperature of the burned clinker 5 is 1000°C or higher, typically about 1200°C to 1500°C. This clinker 5 is cooled by the ambient air AA1 at room temperature (about 20°C to 30°C) sent in from a cooling fan (not shown) connected to the clinker cooler 3. The cooled clinker 5 is discharged from the outlet end of the clinker cooler 3 and stored in a clinker silo (not shown).

[0025] The air AA1 that flows into the clinker cooler 3 is heat exchanged with the high-temperature clinker 5 and then supplied as secondary air AA2 into the rotary kiln 2. This secondary air AA2 is used as combustion air in the burner 10.

[0026] 1 also shows an XYZ coordinate system in which the vertical direction is the Z direction, the axial direction of the rotary kiln 2 on the kiln hood 4 side is the X direction, and the direction perpendicular to the X and Z directions is the Y direction. The same applies to FIGS. 2 and 3.

[0027] FIG. 2 is an example of a plan view schematically illustrating the tip portion of the burner 10 on the rotary kiln 2 side. The burner 10 shown in FIG. 2 has multiple concentrically arranged flow paths (11, 12). Each of the flow paths (11, 12) is formed independently. Specifically, the burner 10 has a combustible gas flow path 11 for blowing combustible gas G1 into the rotary kiln 2 and an air flow path 12 for blowing combustion air G2 into the rotary kiln 2. Note that the burner 10 may have flow paths other than the combustible gas flow path 11 and the air flow path 12. For example, as shown in FIG. 3, the burner 10 may have flow paths 13 and 14 in addition to the combustible gas flow path 11 and the air flow path 12. Here, air may also be blown in from the flow paths 13 and 14.

[0028] The flow rate of the flammable gas G1 blown in from the flammable gas flow path 11 and the flow rate of the air G2 blown in from the air flow path 12 are configured to be independently controllable using an adjustment valve or the like (not shown).

[0029] In the fuel injection method of this embodiment, the flow rates of the combustible gas G1 and air G2 are adjusted so that the relative ratio β of the circumferential momentum of the synthesis gas of the combustible gas G1 and air G2 injected from the burner 10 to the axial momentum of the synthesis gas is within the range of 0.06 to 0.44.

[0030] 4 and 5, the combined momentum M of the flammable gas G1 is calculated as follows. g and the combined momentum M of air G2 a A method for calculating the relative ratio β of the circumferential momentum of the synthesis gas of the combustible gas G1 and the air G2 to the axial momentum of the synthesis gas will be described below.

[0031] As shown in FIG. 4, the flammable gas flow passage 11 is rotated at a rotation angle θ g In this case, the combustible gas G1 blown into the rotary kiln 2 from the burner 10 has a rotation angle θ gAlthough not shown, the air flow passage 12 rotates at a swirl angle θ a In this case, the air G2 blown into the rotary kiln 2 from the burner 10 also exhibits a swirling flow corresponding to the swirl angle θ2.

[0032] For convenience of explanation, the combustible gas G1 and the air G2 are collectively referred to as "gas G0." When the gas G0 is blown through a flow path with a swirl angle θ at a flow velocity Vg (see FIG. 5), the flow velocity Vg is decomposed into a component (Vg cos θ) parallel to the burner axis A10 and a component (Vg sin θ) perpendicular to the burner axis A10.

[0033] Here, the combined momentum M of the combustible gas G1 g [kg m / s 2 ] is the circumferential momentum M of the combustible gas G1 gt [kg m / s 2 ] and the axial momentum M of the combustible gas G1 gx [kg m / s 2 ] is used to calculate using the following formula (1).

[0034]

number

[0035] Here, the flow rate of the combustible gas G1 is G g [Nm 3 / h], and the flow rate is V g [m / s], density is ρ g [kg / m 3 ], then the circumferential momentum M of the combustible gas G1 gt [kg m / s 2 ] is the axial momentum M gx [kg m / s 2 ] are calculated using the following formula (3). In formulas (2) and (3), θ g indicates the turning angle of the flammable gas flow path 11.

[0036]

number

[0037] Similarly, the combined momentum M of the combustion air G2 a [kg m / s 2 ] can be calculated using the circumferential momentum and axial momentum of the air G2. However, as shown in Figure 3, when multiple air flow paths for blowing the air G2 are provided (flow paths 12, 13, 14), it is necessary to calculate the combined momentum of the air G2 blown from each of the flow paths.

[0038] Assuming that there are i channels into which air G2 is blown (i is a natural number), the combined momentum M of air G2 is a [kg m / s 2 ] is the circumferential momentum M of the air G2 blown through the passage i (i=1, 2, ...) ati [kg m / s 2 ] and the axial momentum M of the air G2 axi [kg m / s 2 ] is used to calculate using the following formula (4).

[0039]

number

[0040] Here, for the air G2 blown through the flow path i (i=1, 2, ...), the flow rate is G ai [Nm 3 / h], and the flow rate is V ai [m / s], density is ρ ai [kg / m 3 ], the circumferential momentum M of the air G2 blown through the passage i ati [kg m / s 2 ] is the axial momentum M axi [kg m / s 2 ] are calculated using the following formula (6). In formulas (5) and (6), θ ai indicates the turning angle of the i-th air flow path i.

[0041]

number

[0042] Also, the axial momentum M of the composite gas of combustible gas G1 and air G2 x The circumferential momentum M of the synthesis gas with respect to t The relative ratio β is derived from the following equation (7).

[0043]

number

[0044] That is, the circumferential momentum M of the combustible gas G1 is determined by the flow rate, flow velocity, and density of the combustible gas G1 blown through the combustible gas flow path 11 and the rotation angle of the combustible gas flow path 11. gt and axial momentum M gx Similarly, the value of the circumferential momentum M of the air G2 blown from each passage i (i=1, 2, ...) is determined based on the values ​​of the flow rate, flow velocity, and density of the combustion air G2 blown through the air passages (12, 13, ...) and the value of the swirl angle of the air passages (12, 13, ...). ati and axial momentum M axi In other words, the axial momentum M of the composite gas of combustible gas G1 and air G2 is determined by the above values. x The circumferential momentum M of the synthesis gas with respect to t The relative ratio β is determined.

[0045] The density ρ of the flammable gas G1 blown through the flammable gas flow path 11 is g is a physical quantity determined by the type of combustible gas G1 used. Also, the density ρ of the combustion air G2 blown in through the air flow passages (12, 13, ...) aiis also a physical quantity determined by the air G2. That is, in the fuel injection method of the present embodiment, the values ​​of the flow rate, flow velocity, and swirl angle of the combustible gas G1 injected through each combustible gas flow path 11 and the values ​​of the flow rate, flow velocity, and swirl angle of the combustion air G2 injected through the air flow paths (12, 13, ...) are adjusted so that the value of the relative ratio β falls within the range of 0.06 to 0.44.

[0046] The fact that an increase in the amount of NOx produced can be suppressed by adjusting the blowing conditions of the combustible gas G1 and the combustion air G2 so that the relative ratio β falls within the range of 0.06 to 0.44 will be described with reference to examples. [Example]

[0047] FIG. 6 is a schematic diagram of the test equipment used in the verification of the examples. The test equipment 20 includes a kiln front 22, a kiln 23, and a kiln end 24. The test equipment 20 was configured so that combustible gas G1 and combustion air G2 could be blown into the kiln 23 through a burner 21 from the kiln front 22 side. The kiln 23 was a cylindrical member with a diameter of 450 mm and a length of 8,340 mm. The test equipment 20 was equipped with multiple thermometers 25 for measuring the temperature at each axial position within the kiln 23. Air G3 to be introduced into the kiln 23 was blown in from the bottom side of the kiln front 22. This air G3 simulated secondary air introduced into the kiln from the clinker cooler.

[0048] Table 1 shows the composition of the combustible gas G1 used in the verification.

[0049] [Table 1]

[0050] As shown in Fig. 3, a burner 21 was used in which flow paths 11 to 14 were connected. A combustion environment was created in the kiln 23 by blowing combustible gas G1 through flow path 11 and air G2 through flow paths 12 to 14. The NOx concentration of the exhaust gas extracted from the kiln end 24 connected to the kiln 23 was measured. A known NOx concentration measuring device was used to measure the NOx concentration of the exhaust gas.

[0051] (Adjusting the turning angle) The rotation angle of the combustible gas flow path 11 was changed within a range of 11° to 40°, and other conditions were kept constant. Combustible gas G1 and air G2 were blown into the kiln 23 from the burner 21, and the temperature distribution inside the kiln 23 and the NOx concentration of the exhaust gas were measured. The flow rate and flow velocity of the air flow blown into the kiln 23 through the air flow paths (12, 13, 14) were set to simulate the air flow injection conditions when pulverized coal is used as the main fuel, which is conventionally used. The gas flowing through each path (11-14) was at room temperature.

[0052] The verification results are shown in Figures 7 and 8. Figure 7 is a graph showing the temperature distribution inside the kiln 23, showing the relationship between the axial distance from the tip of the burner 21 and the measured temperature. Figure 8 is a graph showing the NOx concentration in the obtained exhaust gas and the peak temperature inside the kiln 23 for each level. Figures 7 and 8 show the results when the turning angle of the combustible gas flow path 11 is 11° and 40°.

[0053] According to Fig. 8, when the swirl angle of the combustible gas G1 is relatively large (40°), the peak temperature inside the kiln 23 is higher and the NOx concentration in the exhaust gas is also higher than when the swirl angle is relatively small (11°). Note that, according to the temperature distribution shown in Fig. 7, it was confirmed that the temperature distribution at a swirl angle of 11° is generally close to the temperature distribution in a conventional cement kiln that uses pulverized coal as the main fuel.

[0054] The results in Figure 7 show that when the swirl angle of the combustible gas G1 is reduced, the location of the peak temperature in the kiln 23 moves axially away from the tip of the burner 21. This is thought to be because, as the swirl angle of the combustible gas G1 decreases, the vector component of the airflow of the combustible gas G1 relative to the axial direction of the burner 21 increases, making it easier for the combustible gas G1 to move away from the burner 21. This means that the combustible gas G1 is more likely to move away from the tip of the burner 21, which is hot, in a short time, before the degree of mixing with the air G2 progresses. As a result, the peak temperature in the kiln 23 decreases. This is reflected in Figure 8, where the peak temperature is lower when the swirl angle is 11° than when the swirl angle is 40°.

[0055] Conversely, if the swirl angle of the combustible gas G1 is too high, the mixing of the combustible gas G1 and the air G2 progresses in the high-temperature region near the tip of the burner 21. As a result, it is believed that the amount of NOx generated increases.

[0056] (Adjustment of relative ratio β) Next, using the test equipment 20, the flow rate, flow velocity, and swirl angle of the gases (G1, G2) blown from each flow path (11 to 14) were changed to measure the axial momentum M of the synthesis gas of the combustible gas G1 and the air G2. x and circumferential momentum M t The effect on the NOx concentration in exhaust gas was evaluated by changing the momentum M. x ,M t The values ​​calculated based on the above-mentioned formulas (1) to (7) were used as the values ​​of .

[0057] The test standards are shown in Table 2. The evaluation results are shown in Table 2 and FIGS.

[0058] [Table 2]

[0059] The results were judged based on a comparison with the NOx concentration in the exhaust gas when the fuel flow and air flow were introduced into the kiln 23 under conventional conditions, using pulverized coal as the main fuel. In detail, a case where the NOx concentration in the exhaust gas was significantly lower than before was given an "Evaluation A," a case where the NOx concentration in the exhaust gas was higher than in Evaluation A but lower than before was given an "Evaluation B," and a case where the NOx concentration in the exhaust gas was higher than before was given an "Evaluation C."

[0060] According to FIG. 10, the axial momentum M of the synthetic gas of combustible gas G1 and air G2 injected from the burner 10 x Circumferential momentum M t It has been confirmed that by adjusting the relative ratio β to within the range of 0.06 to 0.44, the NOx concentration in exhaust gas can be reduced more than before.

[0061] When the relative ratio β is too low, the axial momentum M x This means that the temperature of the combustible gas G1 and the air G2 becomes too high. At this time, the combustible gas G1 and the air G2 tend to move in the axial direction of the burner 10, which reduces the mixing efficiency of the fuel (combustible gas G1) and the air G2 and suppresses the combustion reaction. It is believed that excessive suppression of the fuel reaction creates an excessively fuel-rich combustion environment inside the kiln 23, which increases the prompt NO and increases the NOx concentration in the exhaust gas.

[0062] On the other hand, when the relative ratio β is too high, the circumferential momentum M t This means that the temperature of the combustible gas G1 and the air G2 becomes too high. At this time, the combustible gas G1 and the air G2 tend to mix more easily before they move away from the tip of the burner 10 in the axial direction, accelerating the combustion reaction. This is thought to increase the peak temperature inside the kiln 23, increase NO produced by the Zeldovich mechanism (Zeldovich NO), and increase the NOx concentration in the exhaust gas.

[0063] In contrast, by injecting the combustible gas G1 and the air G2 into the kiln 23 so that the relative ratio β falls within the range of 0.06 to 0.44, it is possible to burn the cement raw materials while suppressing the amounts of both Zeldovich NO and Prompt NO produced.

[0064] The circumferential momentum of the synthesis gas, M t If the value of is too small, the combustible gas G1 and the air G2 may not be mixed sufficiently in the kiln 23, resulting in incomplete combustion. t If the value of θ itself is too large, that is, if the swirl angle θ is too high, the combustible gas G1 or the air G2 will flow through each flow path with high momentum, which may increase the pressure loss of the burner 21 and make it difficult to ensure the supply pressure of the combustible gas G1 and the air G2.

[0065] Also, the axial momentum of the synthesis gas, M x If the value of is too small, the combustible gas G1 and the air G2 will be mixed near the tip of the burner 21, promoting combustion, which may change the thermal history in the kiln 23 or cause the equipment to burn out due to excessively high temperatures. x If the value of is too large, in other words, if the flow rate is too fast, the pressure loss of the burner 21 increases, and it may become difficult to ensure the supply pressure of the combustible gas G1 and the air G2.

[0066] From this perspective, the circumferential momentum M of the synthesis gas t to 0.6 [kg m / s 2 ]~4.5[kg·m / s 2 ] and the axial momentum M x is 4.0 kg m / s 2 ]~10.2[kg·m / s 2 This is also evident from the results shown in FIG.

[0067] It is understood from the results in Table 2 that the effect of suppressing the amount of NOx produced can be further enhanced by setting the relative ratio β within the range of 0.15 to 0.30.

[0068] The results shown in Table 2 and Figures 9 and 10 show that when air G2 is blown not only through the flow path 12 but also through the flow paths 13 and 14, the circumferential momentum M of the synthesis gas is calculated based on the values ​​calculated in accordance with the above formulas (1) to (7). t and axial momentum M x The relative ratio β was calculated from the ratio of these. However, even when air G2 is blown only from the flow path 12, the circumferential momentum M of the synthesis gas calculated in accordance with the above formulas (1) to (7) can be calculated. t and axial momentum M x Based on this, it is expected that the amount of NOx generated can be suppressed by adjusting the flow rate, flow velocity, and swirl angle of the combustible gas G1 and the flow rate, flow velocity, and swirl angle of the air G2 so that the relative ratio β between the two is within the range of 0.06 to 0.44. [Explanation of symbols]

[0069] 1: Cement manufacturing facility 2: Rotary kiln 3: Clinker cooler 4: Kilnhood 4a: Downstream wall 5: Clinker 10: Burner 11: Flammable gas flow path 12: Air flow path 13: Flow path 14: Flow path 20: Testing facilities 21: Burner 22: Front of the kiln 23: Kiln 24: Bottom of the kiln 25:Thermometer A10: Burner shaft G1: Flammable gas G2: Air G3: Air

Claims

1. A fuel injection method for injecting a fuel-containing airflow into a rotary kiln for cement burning through a burner, comprising: The burner includes a plurality of flow paths partitioned by a plurality of concentric cylindrical members, a step (a) of blowing a flammable gas as the fuel through a flammable gas flow path belonging to the plurality of flow paths and blowing primary air through an air flow path belonging to the plurality of flow paths and different from the flammable gas flow path, at least one of the flammable gas flow path and the air flow path has a turning angle with respect to the axial direction of the burner, a fuel injection method characterized in that the step (a) is carried out under conditions such that a relative ratio of a circumferential momentum of a synthesis gas of the primary air injected from the air passage and the combustible gas injected from the combustible gas passage to an axial momentum of the synthesis gas is within a range of 0.06 to 0.

44.

2. In the step (a), the circumferential momentum of the synthesis gas is 0.6 [kg m / s 2 ]~4.5[kg・m / s 2 ] and the axial momentum of the synthesis gas is 4.0 [kg m / s 2 ]~10.2[kg・m / s 2 2. The fuel injection method according to claim 1, wherein the fuel injection is carried out under conditions such that the temperature is within the range of [0.01].

3. 3. The fuel injection method according to claim 1, wherein the swirl angle is 40 degrees or less.

4. 4. The fuel injection method according to claim 3, wherein the swirl angle is between 11° and 40°.

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