Cement kiln precalciner and cement firing system

Abstract

The application provides a cement kiln external decomposing furnace and a cement firing system, wherein the cement kiln external decomposing furnace comprises a decomposing furnace body and a connecting pipeline, the lower end of the decomposing furnace body is provided with an air inlet for connecting with a kiln tail flue of a rotary kiln, and the upper end of the decomposing furnace body is connected with the inlet of a cyclone through the connecting pipeline; the decomposing furnace body comprises a reduction section and a decomposing section, the outside of the decomposing furnace body is provided with a blast pipe, the air outlet end of the blast pipe is communicated with the inside of the decomposing furnace body, the air outlet end of the blast pipe is located between the reduction section and the decomposing section, the included angle between the air outlet direction of the blast pipe and the axis of the decomposing furnace body is an acute angle, and the blast pipe gradually extends downward along the direction from the air outlet end to the air inlet end. In this way, the third air enters the decomposing furnace body along the flow direction of the cement raw material and the fuel through the blast pipe, the resistance of the fuel and the cement raw material flowing upward can be reduced, and then the energy consumption can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cement production equipment, and particularly relates to a cement kiln external decomposing furnace and a cement firing system. BACKGROUND

[0002] The decomposing furnace is a key equipment for realizing cement clinker production scaling and is a landmark technology of modern cement industry. The decomposing furnace mainly disperses cement raw materials and fuel in hot air flow, utilizes relative movement of material particles in the flow field in the furnace to realize high dispersion, uniform mixing and distribution and rapid heat exchange, so as to improve combustion efficiency, heat transfer efficiency and clinker decomposition of raw materials entering the kiln.

[0003] The fuel and cement raw materials in the decomposing furnace move from bottom to top under the action of the fan. In order to ensure sufficient combustion of the fuel, three times of air is needed to be introduced into the decomposing furnace, but the introduction of the three times of air often increases the resistance of the fuel and the cement raw materials in the decomposing furnace to flow upward, and further increases the energy consumption of the decomposing furnace.

[0004] Therefore, how to solve the problem of high energy consumption of the decomposing furnace in the prior art has become an important technical problem to be solved by the person skilled in the art. SUMMARY

[0005] The present application provides a cement kiln external decomposing furnace and a cement firing system to solve the problem of high energy consumption of the decomposing furnace in the prior art.

[0006] The present application provides a cement kiln external decomposing furnace, which comprises a decomposing furnace body and a connecting pipeline, a gas inlet for connecting with a kiln tail gas chamber of a rotary kiln is arranged at a lower end of the decomposing furnace body, and an inlet of a cyclone is connected with an upper end of the decomposing furnace body through the connecting pipeline.

[0007] The decomposing furnace body comprises a reduction section and a decomposing section, an air supply pipe is arranged outside the decomposing furnace body, an air outlet end of the air supply pipe is in communication with the inside of the decomposing furnace body, the air outlet end of the air supply pipe is located between the reduction section and the decomposing section, an included angle between an air outlet direction of the air supply pipe and an axis of the decomposing furnace body is an acute angle, and the air supply pipe gradually extends downward along a direction from the air outlet end to an air inlet end.

[0008] According to the cement kiln external decomposing furnace provided by the present application, the included angle between the air outlet direction of the air supply pipe and the axis of the decomposing furnace body is 30-50 degrees.

[0009] The connecting pipeline comprises a first straight pipe section, a bent pipe section and a second straight pipe section, the first straight pipe section, the bent pipe section and the second straight pipe section are formed as an integrated structure, one end of the first straight pipe section away from the bent pipe section is connected with the decomposition furnace body, and the axis of the first straight pipe section coincides with the axis of the decomposition furnace body.

[0010] The first straight pipe section and the second straight pipe section are arranged along a vertical direction, the bent pipe section comprises an upper half pipe part and a lower half pipe part.

[0011] The upper half pipe part is connected with the first straight pipe section and the second straight pipe section in a smooth manner, and the cross section of the upper half pipe part is arc-shaped.

[0012] The lower half pipe part comprises two connection plates arranged in an inclined manner, the upper ends of the two connection plates are connected in a one-to-one correspondence, the side edges of the two connection plates are connected with the upper half pipe part to form a closed tubular cavity structure, and the lower ends of the two connection plates are connected with the first straight pipe section and the second straight pipe section.

[0013] The cross-sectional area of the connecting pipeline is 70%-80% of the cross-sectional area of the decomposition furnace body.

[0014] The length of the reduction section along the axis direction of the decomposition furnace body is 9-10 meters.

[0015] The cross-sectional shape of the reduction section is rectangular.

[0016] The lower end of the reduction section is provided with a first fuel inlet and a first raw material inlet.

[0017] The lower end of the decomposition section is provided with a second fuel inlet and a second raw material inlet, and the second fuel inlet and the second raw material inlet are located above the air outlet end of the air supply pipe.

[0018] The decomposition section has a necked part.

[0019] The cement burning system comprises the cement kiln external decomposition furnace.

[0020] The cement kiln external decomposing furnace provided by the application is provided with an air supply pipe outside the decomposing furnace body, and the included angle between the air outlet direction of the air supply pipe and the axis of the decomposing furnace body is an acute angle. The air outlet end of the air supply pipe is communicated with the inside of the decomposing furnace body, and the air supply pipe gradually extends downward along the direction from the air outlet end to the air inlet end, so as to ensure that the air outlet direction of the air supply pipe and the flow direction of the fuel and the cement raw material in the inside of the decomposing furnace body are acute angles, that is, the tertiary air enters the decomposing furnace body along the flow direction of the fuel and the cement raw material through the air supply pipe, which is beneficial to reducing the resistance of the fuel and the cement raw material flowing upward, and further reducing the energy consumption.

[0021] Further, in the cement firing system provided by the application, since the cement kiln external decomposing furnace is provided, the various advantages as described above are also provided. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0023] Fig. 1 is a structural schematic view of the cement kiln external decomposing furnace provided by the application;

[0024] Fig. 2 is a sectional view of the elbow section of the connecting pipeline provided by the application;

[0025] Fig. 3 is a top view of the decomposing furnace body provided by the application.

[0026] REFERENCE SIGNS:

[0027] 1: connecting pipeline; 2: cyclone barrel; 3: reduction section; 4: decomposing section; 5: air supply pipe; 6: first straight pipe section; 7: second straight pipe section; 8: upper half pipe part; 9: connecting plate; 10: first fuel inlet; 11: first raw material inlet; 12: second fuel inlet; 13: second raw material inlet; 14: necked part. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the application clearer, the technical solutions in the application will be described clearly and completely below in combination with the drawings in the application. Obviously, the described embodiments are some embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the application.

[0029] The following will be described in combination withFigs. 1-3 The present application discloses a cement kiln precalciner.

[0030] As Figs. 1-3 shown in the drawings, the cement kiln precalciner provided by the embodiments of the present application comprises a precalciner body and a connecting pipeline 1, an air inlet is arranged at the lower end of the precalciner body, the air inlet is connected with the kiln tail flue of the rotary kiln, so that the flue gas in the rotary kiln can flow into the interior of the precalciner body, and the heat of the flue gas of the rotary kiln can be recycled and utilized.

[0031] The connecting pipeline 1 is arranged at the upper end of the precalciner body, and the upper end of the precalciner body is connected with the inlet of a cyclone 2 through the connecting pipeline 1, the cyclone 2 is generally referred to as the fifth-stage cyclone in the cement clinker burning system, the cyclone 2 has a solid outlet and a gas outlet, the decomposition products of the cement raw meal after decomposition include solid products and gaseous products, the solid products include calcium oxide, and the gaseous products include carbon dioxide. The solid products and the gaseous products enter the cyclone 2 together, and under the action of the cyclone 2, the solid products flow out through the solid outlet of the cyclone 2, and the gaseous products flow out through the gas outlet of the cyclone 2.

[0032] Since the flue gas output by the rotary kiln contains a large amount of nitrogen oxides, the nitrogen oxides need to be reduced, so that the flue gas meets the emission requirements.

[0033] The precalciner body comprises a reduction section 3 and a decomposition section 4, the reduction section 3 is used for treating the nitrogen oxides, and the decomposition section 4 is used for decomposing the cement raw meal.

[0034] A large amount of heat is needed when the cement raw meal is decomposed, and the heat is derived from the complete combustion of the fuel. In the embodiment, an air supply pipe 5 is arranged outside the precalciner body, the air outlet end of the air supply pipe 5 is in communication with the interior of the precalciner body, and the air outlet end of the air supply pipe 5 is arranged between the reduction section 3 and the decomposition section 4, so as to supply the decomposition section 4 with the gas with a high oxygen content as the tertiary air, so as to ensure the complete combustion of the fuel. Specifically, the air supply pipe 5 can be connected with a grate cooler in the production site.

[0035] When the reduction section 3 reduces the nitrogen oxides, the carbon monoxide generated when the fuel is incompletely combusted is mainly used. Arranging the air outlet end of the air supply pipe 5 between the reduction section 3 and the decomposition section 4 can avoid the influence of the tertiary air on the reduction process.

[0036] The angle between the air outlet direction of the air supply pipe 5 and the axis of the decomposing furnace body is an acute angle, and the air supply pipe 5 gradually extends downward along the direction from the air outlet end to the air inlet end, so that the air outlet direction of the air supply pipe 5 and the flow direction of the fuel and the cement raw material in the decomposing furnace body are in an acute angle, that is, the tertiary air enters the decomposing furnace body along the flow direction of the fuel and the cement raw material through the air supply pipe 5, which is beneficial to reduce the resistance of the fuel and the cement raw material flowing upward, thereby reducing the energy consumption, and solving the problem of high energy consumption of the decomposing furnace in the prior art.

[0037] In the embodiment of the present application, the angle between the air outlet direction of the air supply pipe 5 and the axis of the decomposing furnace body is 30-50 degrees, and specifically, the angle between the air outlet direction of the air supply pipe 5 and the axis of the decomposing furnace body can be set to 40 degrees. According to the comparison of the test data, after adjusting the air outlet direction of the air supply pipe 5, the overall resistance of the cement kiln external decomposing furnace is about 700 Pa, which is reduced by more than 300 Pa compared with the decomposing furnace in the prior art.

[0038] In the embodiment, the connecting pipeline 1 includes a first straight pipe section 6, a bent pipe section and a second straight pipe section 7. The two ends of the bent pipe section are connected with the first straight pipe section 6 and the second straight pipe section 7 respectively, and the first straight pipe section 6, the bent pipe section and the second straight pipe section 7 are formed in an integrated structure. Specifically, the first straight pipe section 6, the bent pipe section and the second straight pipe section 7 can be integrally formed, which is beneficial to ensure the reliability and stability of the connecting pipeline 1. Alternatively, the first straight pipe section 6, the bent pipe section and the second straight pipe section 7 can be separately processed, and then connected with each other by welding or the like.

[0039] The end of the first straight pipe section 6 of the connecting pipeline 1 away from the bent pipe section is connected with the decomposing furnace body, and the axis of the first straight pipe section 6 coincides with the axis of the decomposing furnace body. The end of the second straight pipe section 7 of the connecting pipeline 1 away from the bent pipe section is connected with the inlet of the cyclone 2.

[0040] In the embodiment, the axes of the first straight pipe section 6 and the second straight pipe section 7 are arranged in a vertical direction, the cross sections of the first straight pipe section 6 and the second straight pipe section 7 are circular, and the diameters of the first straight pipe section 6 and the second straight pipe section 7 are equal.

[0041] The bent pipe section includes an upper half pipe part 8 and a lower half pipe part. Specifically, the two ends of the upper half pipe part 8 are smoothly connected with the first straight pipe section 6 and the second straight pipe section 7 respectively. The cross section of the upper half pipe part 8 is arc-shaped, and specifically, the upper half pipe part 8 can be circular arc-shaped with a diameter equal to that of the first straight pipe section 6 and the second straight pipe section 7.

[0042] The lower half pipe part comprises two connecting plates 9, the upper ends of the two connecting plates 9 are connected one by one in correspondence, the two connecting plates 9 are both arranged obliquely, the two connecting plates 9 both have an included angle with the vertical plane, so that the two connecting plates 9 also have an included angle. The side edges of the two connecting plates 9 are connected with the upper half pipe part 8 to form a closed tubular cavity structure, and the lower ends of the two connecting plates 9 are respectively connected with the first straight pipe section 6 and the second straight pipe section 7 in a closed manner.

[0043] Compared with the prior art in which the upper half pipe part 8 and the lower half pipe part of the elbow pipe section are both arranged in a circular arc cross-section structure, in the embodiment of the present application, the lower half pipe part is arranged as two inclined connecting plates 9, which is beneficial to the sliding of dust or material and avoids the accumulation of dust or material in the lower half pipe part, thereby avoiding the increase of resistance caused by the reduction of the space for the material to pass through the elbow pipe section due to the accumulation of dust or material, and further reducing the energy consumption.

[0044] In the traditional design, the cross-sectional area of the connecting pipe 1 is generally set to be 50%-60% of the cross-sectional area of the decomposing furnace body, and in the embodiment of the present application, the cross-sectional area of the connecting pipe 1 is set to be 70%-80% of the cross-sectional area of the decomposing furnace body, which effectively increases the volume of the cement kiln external decomposing furnace as a whole. In addition, through comparison of test data, the wind speed in the connecting pipe 1 of the traditional design is 18-20 meters per second, and the wind speed in the connecting pipe 1 of the embodiment of the present application is 13-15 meters per second. The increase of the cross-sectional area of the connecting pipe 1 reduces the wind speed in the connecting pipe 1, thereby reducing the flow speed of the fuel and the cement raw material in the connecting pipe 1, prolonging the passing time of the fuel and the cement raw material in the connecting pipe 1, which is beneficial to improve the decomposition rate of the cement raw material, and is beneficial to the full combustion of the fuel, improves the burnout rate of the fuel, and avoids the damage of the fuel combustion to the cyclone 2.

[0045] In the specific embodiment, the cross-sectional area of the connecting pipe 1 can be set to be 75% of the cross-sectional area of the decomposing furnace body.

[0046] In the embodiment of the present application, the first fuel inlet 10 and the first raw material inlet 11 are arranged at the lower end of the reduction section 3, and the first coal injection pipe can be arranged at the first fuel inlet 10 for injecting and burning the pulverized coal into the inside of the reduction section 3. The oxygen content in the flue gas in the rotary kiln is low, and the fuel is not fully combusted in the reduction section 3, producing carbon monoxide for reduction treatment of nitrogen oxides.

[0047] To ensure sufficient reduction reaction, the length of the reduction section 3 along the axis of the decomposition furnace body is set to 9-10 meters in the embodiment of the present application, and when the wind speed in the reduction section 3 is 10 meters per second, the reaction time of carbon monoxide and nitrogen oxides in the reduction section 3 can be ensured to be at least 0.8 seconds, the reduction reaction time is increased, more than 40% of the nitrogen oxides can be stably removed, the denitrification efficiency is improved, and the environmental pollution is reduced.

[0048] In the embodiment, the cross-sectional shape of the reduction section 3 is set to a rectangle. Compared with the prior art in which the cross-sectional shape of the reduction section 3 is set to a circle, when the side length of the rectangle is equal to the diameter of the circle, the cross-sectional shape of the reduction section 3 is set to a rectangle, the cross-sectional area of the reduction section 3 is increased, the wind speed of the reduction section 3 is reduced, the passing time of the nitrogen oxides and the like in the reduction section 3 is prolonged, and the sufficient reduction reaction is facilitated. In addition, through flow field simulation, the cross-sectional shape of the reduction section 3 is set to a rectangle, so that the flue gas flow field in the reduction section 3 is more uniform and stable.

[0049] The first raw material inlet 11 is used to transport the cement raw material to the reduction section 3, and specifically, the first raw material inlet 11 can be connected with the solid outlet of the fourth stage cyclone in the cement firing system. The solid flowing out of the solid outlet of the fourth stage cyclone is the cement raw material, and the temperature thereof is about 500 degrees, which is relatively low compared with the temperature of the reduction section 3, can neutralize the temperature in the reduction section 3, avoid the temperature of the reduction section 3 being too high, and effectively prevent the skinning.

[0050] In the embodiment, the second fuel inlet 12 and the second raw material inlet 13 are arranged at the lower end of the decomposition section 4, and the second fuel inlet 12 and the second raw material inlet 13 are both located above the air outlet end of the air supply pipe 5. The second coal injection pipe can be arranged at the second fuel inlet 12, which is used to inject and burn the pulverized coal in the decomposition section 4. The tertiary air transported through the air supply pipe 5 has a high oxygen content, which can make the fuel burn sufficiently and release a large amount of heat.

[0051] The second raw material inlet 13 is used to transport the cement raw material to the decomposition section 4, and the cement raw material entering the decomposition section 4 will be decomposed by heat.

[0052] In the embodiment, the necking portion 14 is arranged in the decomposition section 4, and when the cement raw material and the fuel rise to the necking portion 14, the necking portion 14 makes the airflow speed suddenly increase, the cement raw material and the fuel are ejected at the necking portion 14, the cement raw material and the fuel are further mixed uniformly, the cement raw material is heated uniformly and sufficiently, and the decomposition rate of the cement raw material is improved.

[0053] In another aspect, the embodiment of the present application also provides a cement burning system, which comprises the cement precalciner provided by any of the above embodiments. The cement precalciner provided by any of the above embodiments can make the tertiary air enter the precalciner body along the flow direction of the fuel and the cement raw material through the air supply pipe 5, which is beneficial to reduce the resistance of the upward flow of the fuel and the cement raw material, and has the advantage of low energy consumption. Therefore, the cement burning system provided by the embodiment of the present application also has the advantage of low energy consumption. The derivation process of the beneficial effects of the cement burning system in the embodiment of the present application is similar to the derivation process of the beneficial effects of the cement precalciner, and thus is not described here.

[0054] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A cement kiln external calciner, characterized in that: It includes a decomposition furnace body and a connecting pipeline. The lower end of the decomposition furnace body is provided with an air inlet for connecting to the kiln tail smoke chamber of the rotary kiln. The upper end of the decomposition furnace body is connected to the inlet of the cyclone through the connecting pipeline. The decomposition furnace body includes a reduction section and a decomposition section. An air supply pipe is provided on the outside of the decomposition furnace body. The air outlet end of the air supply pipe is connected to the interior of the decomposition furnace body. The air outlet end of the air supply pipe is located between the reduction section and the decomposition section. The angle between the air outlet direction of the air supply pipe and the axis of the decomposition furnace body is an acute angle. The air supply pipe gradually extends downward from the air outlet end to the air inlet end. The connecting pipeline includes a first straight pipe section, a curved pipe section, and a second straight pipe section, wherein the first straight pipe section, the curved pipe section, and the second straight pipe section form an integrated structure, and an end of the first straight pipe section away from the curved pipe section is connected to the decomposition furnace body, and the axis of the first straight pipe section coincides with the axis of the decomposition furnace body; The axis of the first straight pipe section and the axis of the second straight pipe section are both arranged in the vertical direction, and the curved pipe section includes an upper half pipe portion and a lower half pipe portion; The two ends of the upper half pipe portion are smoothly connected to the first straight pipe section and the second straight pipe section respectively, and the cross section of the upper half pipe portion is arc-shaped; The lower half pipe portion includes two obliquely arranged connecting plates, the upper ends of the two connecting plates are connected to each other in a one-to-one correspondence, and the sides of the two connecting plates are connected to the upper half pipe portion to form a closed tubular cavity structure, and the lower ends of the two connecting plates are respectively connected to the first straight pipe section and the second straight pipe section; The cross-section of the reduction section is rectangular.

2. The cement kiln calciner according to claim 1, characterized in that: The angle between the air outlet direction of the air supply pipe and the axis of the decomposition furnace body is 30-50 degrees.

3. The cement kiln calciner according to claim 1, characterized in that: The cross-sectional area of ​​the connecting pipeline is 70%-80% of the cross-sectional area of ​​the decomposition furnace body.

4. The cement kiln calciner according to claim 1, characterized in that: The length of the reduction section along the axis of the decomposition furnace body is set to 9-10 meters.

5. The cement kiln external calciner according to claim 1, characterized in that: The lower end of the reduction section is provided with a first fuel inlet and a first raw material inlet; A second fuel inlet and a second raw material inlet are provided at the lower end of the decomposition section, and both the second fuel inlet and the second raw material inlet are located above the air outlet end of the air supply pipe.

6. The cement kiln external calciner according to claim 1, characterized in that: The decomposition section has a necked portion.

7. A cement burning system, characterized in that: It comprises the cement kiln external calciner as described in any one of claims 1 to 6.

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