A high-efficiency preheating coal-fired power generation boiler

Abstract

The present invention relates to the technical field of coal-fired power generation boilers, and specifically to a high-efficiency preheating type coal-fired power generation boiler, comprising a boiler body, a coal mill for preparing coal powder, a burner for burning coal powder to heat the inner cavity of the boiler body, an air preheater arranged at the tail end of the flue of the boiler body for collecting flue gas heat, and a heat mixing device for secondary drying and heating the coal powder prepared by the coal powder machine, wherein the coal mill is connected to the burner through a coal powder pipeline, the coal mill is connected to the air preheater through a hot air pipeline, the heat mixing device is arranged in the coal powder pipeline, and the hot mixing device introduces the hot air in the hot air pipeline into the hot mixing device through a hot air branch pipe to perform secondary drying and heating on the coal powder flowing through the coal powder pipeline. The present invention utilizes the hot air generated by the air preheater to perform secondary drying and heating on the coal powder, thereby improving the combustion rate of the coal powder in the boiler.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas waste heat recovery, and in particular to a high-efficiency preheating type coal-fired power generation boiler. Background Art

[0002] Coal-fired power generation boilers use the heat generated by the combustion of coal powder to convert the water flowing through the inner wall of the boiler into superheated steam, and then transport the superheated steam heated to the rated temperature to the steam turbine to generate electricity.

[0003] In the prior art, during the process of a coal mill grinding raw coal into coal powder, hot air is needed to heat and dry the coal. The source of hot air is usually to send cold air from the outside into the air preheater of the flue at the tail end of the boiler through a blower. The cold air is heated by the high-temperature flue gas to become hot air and enters the hot air duct. A part of the hot air in the hot air duct is sent to the coal mill to heat and dry the raw coal. At the same time, this part of air is also the medium for conveying the coal powder made by the coal mill. The coal powder made by the coal mill is sent to the burner through the coal powder duct by this part of hot air. The mixture of coal powder and air discharged from the coal mill enters the furnace through the burner to burn and heat the inner cavity of the boiler. Another part of the hot air in the hot air duct directly enters the furnace through the burner to participate in the combustion of coal powder.

[0004] The higher the degree of dryness and temperature of the coal powder before combustion, the faster the coal powder burns in the boiler and the more heat is generated. During the process of grinding the coal powder, the temperature of the high-temperature hot air from the air preheater is greatly reduced after the raw coal in the coal mill is dried. The existing technology does not reheat the ground coal powder and preheat it again. It is impossible to effectively continue to heat and dry the ground coal powder again to reduce the water content of the coal powder and increase the temperature of the coal powder, so that the combustion rate of the coal powder cannot be further improved. Summary of the invention

[0005] The object of the present invention is to provide a high-efficiency preheating type coal-fired power generation boiler, which can achieve the purpose of increasing the combustion rate of coal by providing a heat mixing device to perform secondary heating and drying on coal powder.

[0006] To achieve the above object, the basic scheme of the present invention is as follows:

[0007] A high-efficiency preheating type coal-fired power generation boiler comprises a boiler body, a coal mill for preparing coal powder, a burner for burning coal powder to heat the inner cavity of the boiler body, an air preheater arranged at the tail end of the flue of the boiler body for collecting flue gas heat, and a heat mixing device for secondary drying and heating the coal powder prepared by the coal mill. The coal mill is connected to the burner through a coal powder pipeline. The coal mill introduces hot air generated by the air preheater into the coal mill through a hot air pipeline to dry the coal in the coal mill and sends the coal powder generated by the coal mill into the burner through the coal powder pipeline by the hot air flow entering the coal mill. The heat mixing device is arranged in the coal powder pipeline. The heat mixing device introduces the hot air in the hot air pipeline into the heat mixing device through a hot air branch pipe to perform secondary drying and heating on the coal powder flowing through the coal powder pipeline.

[0008] The principle and beneficial effects of the basic scheme of a high-efficiency preheating coal-fired power generation boiler of the present invention are:

[0009] The flue gas of the boiler is preheated and recovered through the air preheater to form a high-temperature airflow for drying the raw coal in the pulverizer and for conveying the pulverized coal prepared by the pulverizer. A hot mixing device is set in the pulverized coal pipeline to use the high-temperature airflow for secondary drying and preheating of the pulverized coal to increase the dryness and temperature of the pulverized coal and increase the combustion rate of the pulverized coal in the boiler.

[0010] Furthermore, the heat mixing device includes a plurality of mixing barrels arranged in sequence along the length direction of the pulverized coal pipeline, the mixing barrel is coaxial with the pulverized coal pipeline, the maximum outer diameter of the mixing barrel is smaller than the inner diameter of the pulverized coal pipeline, the mixing barrel is fixedly connected to the pulverized coal pipeline through a connecting rod, the mixing barrel is a dumbbell-shaped cylinder with one end closed so that the mixing barrel forms an annular recess located in the middle of the mixing barrel, a front annular protrusion near the closed end of the mixing barrel with an outer diameter larger than the outer diameter of the annular recess, and a rear annular protrusion away from the closed end of the mixing barrel with an outer diameter larger than the outer diameter of the annular recess, and the mixing barrel is close to one end of the coal mill. The mixed flow barrel has a closed end, and the inner cavity of the mixed flow barrel is formed with a fine channel corresponding to the annular recess, a front diffusion cavity corresponding to the front annular protrusion and having an inner diameter larger than the inner diameter of the fine channel, and a rear diffusion cavity corresponding to the rear annular protrusion and having an inner diameter larger than the inner diameter of the fine channel. One end of the hot air branch pipe extends from the closed end of the mixed flow barrel into the inner cavity of the mixed flow barrel along the axial direction of the mixed flow barrel, and the other end of the hot air branch pipe passes through the pipe wall of the pulverized coal pipe and is connected with the hot air pipe. The side walls of the annular recess, the front annular protrusion and the rear annular protrusion are all provided with air flow holes that connect the inner and outer spaces of the mixed flow barrel.

[0011] Through the above arrangement, the coal powder flows back and forth between the coal powder pipeline and the inner cavity of the mixing barrel multiple times, sometimes fast and sometimes slow, to form turbulence, so that the coal powder can be fully contacted with the high-temperature air from the hot branch pipe, so that the coal powder is heated again to increase the temperature and reduce the moisture content, so that the coal powder can be burned fully and quickly in the burner.

[0012] Furthermore, the outer diameter of the rear annular protrusion is greater than the outer diameter of the front annular protrusion, which can further reduce the air flow rate outside the annular recess, so that more coal powder flowing outside the annular recess can be sucked into the fine channel for heating.

[0013] Furthermore, the closed end of the mixing drum is formed with a conical surface coaxially arranged with the mixing drum and converging toward the coal mill. The setting of the conical surface can reduce wind resistance and evenly disperse the coal powder airflow in front of the mixing drum into the gap between the mixing drum and the coal powder pipeline, thereby improving the adsorption efficiency of the airflow holes on the coal powder.

[0014] Furthermore, the annular concave portion is connected to the front annular convex portion and the rear annular convex portion by a conical transition.

[0015] Furthermore, an exhaust fan is arranged on the hot air duct to speed up the flow rate of the hot air in the hot air duct. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a high-efficiency preheating type coal-fired power generation boiler of the present invention.

[0017] Figure 2 This is a schematic diagram of the layout of the heat mixing device in the pulverized coal pipeline.

[0018] Figure 3 Schematic diagram of the mixed flow barrel structure. DETAILED DESCRIPTION

[0019] The following is further described in detail through specific implementation methods:

[0020] The reference numerals in the drawings of the specification include:

[0021] Boiler body 10, flue 101, connecting rod 102, coal mill 201, burner 202, air preheater 203, pulverized coal duct 204, hot air duct 205, hot air branch pipe 206, mixing flow barrel 30, annular recess 301, detailed channel 3011, front annular protrusion 302, front diffusion chamber 3021, rear annular protrusion 303, rear diffusion chamber 3031, air flow hole 304, exhaust fan 40.

[0022] A high-efficiency preheating coal-fired power generation boiler in this embodiment, such as Figure 1As shown, it includes a boiler body 10, a coal mill 201 for preparing coal powder, a burner 202 for burning coal powder to heat the inner cavity of the boiler body 10, an air preheater 203 arranged at the tail of the flue 101 of the boiler body 10 for collecting flue gas heat, and a hot mixing device for secondary drying and heating the coal powder prepared by the coal mill. The coal mill 201 is connected to the burner 202 through a coal powder pipeline 204, and the coal mill 201 introduces the hot air generated by the air preheater 203 into the coal mill 201 through a hot air pipeline 205. The coal in the coal mill 201 is dried and the pulverized coal generated by the coal mill 201 is sent to the burner 202 through the pulverized coal pipeline 204 by the hot air flow entering the coal mill 201. The heat mixing device is arranged in the pulverized coal pipeline 204. The heat mixing device introduces the hot air in the hot air pipeline 205 into the heat mixing device through the hot air branch pipe 206 to perform secondary drying and temperature raising on the pulverized coal flowing through the pulverized coal pipeline 204. The hot air branch pipe 206 is provided with a booster pump to increase the flow rate of the high-temperature air entering the inner cavity of the heat mixing passage 30 from the hot air branch pipe 206.

[0023] like Figure 1 As shown, an exhaust fan 40 is arranged on the hot air duct 205 to accelerate and pressurize the hot air generated by the air preheater 203 and transport it to the coal mill 201 and the heat mixing device through the hot air duct 205. Figure 2 As shown, the heat mixing device includes three mixing barrels 30 arranged in sequence along the length direction of the pulverized coal pipeline 204. The specific number of the mixing barrels 30 can be flexibly set according to the amount of pulverized coal and is not limited by the number of this embodiment. The mixing barrel 30 is coaxial with the pulverized coal pipeline 204. The maximum outer diameter of the mixing barrel 30 is smaller than the inner diameter of the pulverized coal pipeline 204 so that a gap is formed between the mixing barrel 30 and the inner wall of the pulverized coal pipeline 204 to accommodate the flow of airflow mixed with pulverized coal. A plurality of connecting rods 102 are evenly distributed on the outer wall of the mixing barrel 30, one end of the connecting rod 102 is fixedly connected to the outer wall of the mixing barrel 30, and the other end of the connecting rod 102 is fixedly connected to the pulverized coal pipeline 204.

[0024] like Figure 3As shown, the mixing barrel 30 is a dumbbell-shaped cylinder with one end closed, and the end of the mixing barrel 30 close to the coal mill 201 is a closed end. The mixing barrel 30 is formed with an annular recess 301 located in the middle of the mixing barrel 30, a front annular protrusion 302 close to the closed end of the mixing barrel 30, and a rear annular protrusion 303 away from the closed end of the mixing barrel 30. The outer diameters of the front annular protrusion 302 and the rear annular protrusion 303 are both larger than the outer diameter of the annular recess 301, so that the gap between the annular recess 301 and the pulverized coal pipeline 204 is larger than the gap between the front annular protrusion 302 and the rear annular protrusion 303 and the pulverized coal pipeline 204. When the airflow mixed with pulverized coal in the pulverized coal pipeline 204 flows through the outside of the mixing barrel 30, the flow velocity is reduced in the gap between the annular recess 301 and the pulverized coal pipeline 204. In order to further reduce the airflow velocity outside the annular concave portion 301, the outer diameter of the rear annular convex portion 303 is set to be larger than the outer diameter of the front annular convex portion 302. In order to reduce the resistance of the mixing barrel 30 to the airflow in the pulverized coal pipeline 204, the annular concave portion 301 is provided with a conical transition connection with the front annular convex portion 302 and the rear annular convex portion 303.

[0025] like Figure 3 As shown, the closed end of the mixing barrel 30 is formed with a conical surface coaxially arranged with the mixing barrel 30 and converging toward the direction of the coal mill 201. The setting of the conical surface can reduce wind resistance and evenly disperse the coal powder airflow from the direction of the coal mill 201 into the gap between the mixing barrel 30 and the coal powder pipeline 204. The inner cavity of the mixing barrel 30 is formed with a detailed channel 3011 corresponding to the annular concave portion 301, a front diffusion cavity 3021 corresponding to the front annular convex portion 302, and a rear diffusion cavity 3031 corresponding to the rear annular convex portion 303. The front diffusion cavity 3021 and the rear diffusion cavity 3031 are The inner diameters of the detailed channels 3011 and the hot air branch pipe 206 are larger than those of the detailed channels 3011 and the hot air branch pipe 206. One end of the hot air branch pipe 206 extends from the closed end of the mixing barrel 30 into the inner cavity of the mixing barrel 30 along the axial direction of the mixing barrel 30. The other end of the hot air branch pipe 206 passes through the pipe wall of the pulverized coal pipe 204 and is connected with the hot air pipe 205. The hot air branch pipe 206 is sealed and fixedly connected with the pulverized coal pipe 204. The side walls of the annular recess 301, the front annular protrusion 302 and the rear annular protrusion 303 are all provided with air flow holes 304 that connect the inner and outer spaces of the mixing barrel 30.

[0026] The working principle and beneficial effects of the present invention are:

[0027] The air preheater 203 absorbs the heat of the flue gas in the flue 101 to form high-temperature gas. The exhaust fan 40 transports the hot air in the air preheater 203 to the coal mill 201 through the hot air duct 205 to dry the coal body in the coal mill 201. A part of the hot air is sent to each mixed flow barrel 30 in the heat mixing device through the hot air branch pipe 206. The coal powder prepared by the coal mill 201 is driven by the hot air entering the coal mill 201 and transported to the burner 202 on the boiler body 10 through the coal powder pipeline 204 to burn and heat the inner cavity of the boiler body 10.

[0028] When the airflow mixed with coal powder flows through the mixing barrel 30, the conical surface on the closed end of the mixing barrel 30 forces the airflow mixed with coal powder to be evenly distributed and dispersed to flow through the gap between the front annular protrusion 302 on the mixing barrel 30 and the coal powder pipeline 204. Since the gap between the front annular protrusion 302 and the coal powder pipeline 204 is small, the airflow mixed with coal powder accelerates when flowing through the gap between the front annular protrusion 302 and the coal powder pipeline 204 and forms a negative pressure in the gap. At the same time, part of the high-temperature air enters the front diffusion chamber 3021 in the mixing barrel 30 through the hot air branch pipe 206. Since the inner diameter of the front diffusion chamber 3021 is larger than the inner diameters of the detailed channel 3011 and the hot air branch pipe 206, the high-temperature air from the hot air branch pipe 206 has a reduced flow velocity and increased pressure in the front diffusion chamber 3021. The negative pressure generated in the gap between the front annular protrusion 302 and the pulverized coal pipeline 204 absorbs part of the high-temperature air in the front diffusion chamber 3021 through the air flow holes 304 and enters the gap between the front annular protrusion 302 and the pulverized coal pipeline 204 to contact the pulverized coal and heat the pulverized coal.

[0029] The pulverized coal airflow that flows through the gap between the front annular protrusion 302 and the pulverized coal pipeline 204 then enters the gap between the annular recess 301 and the pulverized coal pipeline 204. Since the gap between the annular recess 301 and the pulverized coal pipeline 204 is larger than the gap between the front annular protrusion 302 and the rear annular protrusion 303 and the pulverized coal pipeline 204, the pulverized coal airflow will reduce its flow rate in the gap between the annular recess 301 and the pulverized coal pipeline 204 and form turbulence to promote the contact time between the pulverized coal and the high-temperature airflow. At the same time, the high-temperature airflow after passing through the front diffusion chamber 3021 flows through the detailed channel 3011 in the mixing barrel 30. Similarly, negative pressure is generated in the detailed channel 3011 and the pulverized coal airflow in the gap between the annular recess 301 and the pulverized coal pipeline 204 is sucked into the detailed channel 3011 through the airflow holes 304 on the side wall of the annular recess 301, and contacts with the high-temperature gas in the detailed channel 3011 to heat the pulverized coal. The pulverized coal airflow flowing through the detailed channel 3011 finally enters the rear diffusion chamber 3031 to reduce the flow velocity and form turbulence. The airflow holes 304 on the side wall of the rear annular protrusion 303 also enable the pulverized coal airflow in the rear diffusion chamber 3031 to circulate and exchange with the pulverized coal airflow outside the rear annular protrusion 303, so that the pulverized coal airflow after passing through the mixing barrel 30 flows to the next mixing barrel 30 at a uniform speed for reheating.

[0030] Compared with simply introducing hot air into the coal mill and the coal powder pipeline to heat the coal powder, the present invention provides a mixing barrel so that the coal powder flowing through the mixing barrel generates turbulence and is fully in contact with the high-temperature air, thereby improving the preheating efficiency of the coal powder and effectively preventing the coal powder from settling and accumulating in the coal powder pipeline, thereby improving the coal powder transportation efficiency; by drying and preheating the coal powder multiple times, the dryness of the coal powder and the temperature of the coal powder are effectively improved, the combustion rate of the coal powder is increased, and the release of the heat of the coal powder is accelerated to increase the heating rate of the boiler.

[0031] The above are only embodiments of the present invention, and the common knowledge such as the known specific structures and characteristics in the scheme are not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A high-efficiency preheating type coal-fired power generation boiler, comprising a boiler body, a coal mill for preparing coal powder, a burner for burning coal powder to heat the inner cavity of the boiler body, and an air preheater arranged at the tail end of the flue of the boiler body for collecting flue gas heat, the coal mill is connected to the burner through a coal powder pipeline, the coal mill introduces hot air generated by the air preheater into the coal mill through a hot air pipeline to dry the coal in the coal mill, and the coal powder generated by the coal mill is sent to the burner through the coal powder pipeline through the hot air, characterized in that: A heat mixing device is arranged in the pulverized coal pipeline, and the heat mixing device introduces the hot air in the hot air pipeline into the heat mixing device through the hot air branch pipe to perform secondary drying and temperature raising on the pulverized coal flowing through the pulverized coal pipeline; The hot mixing device comprises a plurality of mixing barrels arranged in sequence along the length direction of the pulverized coal pipeline, the mixing barrel is coaxially arranged with the pulverized coal pipeline, the maximum outer diameter of the mixing barrel is smaller than the inner diameter of the pulverized coal pipeline, the mixing barrel is fixedly connected with the pulverized coal pipeline through a connecting rod, the mixing barrel is a dumbbell-shaped cylinder with one end closed so that the mixing barrel forms an annular concave portion located in the middle of the mixing barrel, a front annular convex portion with an outer diameter larger than the outer diameter of the annular concave portion near the closed end of the mixing barrel, and a rear annular convex portion with an outer diameter larger than the outer diameter of the annular concave portion away from the closed end of the mixing barrel, and the end of the mixing barrel close to the coal mill is The closed end, the inner cavity of the mixing barrel is formed with a fine channel corresponding to the annular recess, a front diffusion cavity corresponding to the front annular protrusion and having an inner diameter larger than the inner diameter of the fine channel, and a rear diffusion cavity corresponding to the rear annular protrusion and having an inner diameter larger than the inner diameter of the fine channel. One end of the hot air branch pipe extends into the inner cavity of the mixing barrel along the axial direction of the mixing flow barrel from the closed end of the mixing flow barrel, and the other end of the hot air branch pipe passes through the pipe wall of the pulverized coal pipe and is connected with the hot air pipe. The side walls of the annular recess, the front annular protrusion and the rear annular protrusion are all provided with air flow holes that connect the inner and outer spaces of the mixing flow barrel.

2. A high-efficiency preheating coal-fired power generation boiler according to claim 1, characterized in that: The outer diameter of the rear annular protrusion is greater than the outer diameter of the front annular protrusion.

3. A high-efficiency preheating coal-fired power generation boiler according to claim 2, characterized in that: The closed end of the mixing flow barrel is formed with a conical surface which converges toward the coal mill and is coaxially arranged with the mixing flow barrel.

4. A high-efficiency preheating coal-fired power generation boiler according to claim 3, characterized in that: The annular concave portion is connected to the front annular convex portion and the rear annular convex portion through a conical surface transition.

5. A high-efficiency preheating coal-fired power generation boiler according to claim 4, characterized in that: The hot air duct is provided with an exhaust fan for accelerating the flow rate of the hot air in the hot air duct.

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