A heat exchanger structure for boiler flue gas waste heat utilization system

Abstract

The present invention discloses a heat exchanger structure for a boiler flue gas waste heat utilization system, which includes a shell, a gas channel and a pressurizing device, wherein an air intake section, a heat exchange section and an exhaust section are sequentially arranged in the gas flow direction in the gas channel, wherein the air intake section is provided with a concentrically mounted inner tube body and an outer tube body, wherein an air window with an oblique flow guide surface is provided between the inner tube body and the outer tube body, and a honeycomb heat exchanger is formed in the annular surface at the rear of the air window as a first-stage heat exchanger; and the heat exchange section includes a heat exchange chamber, wherein an oblique flow guide plate is provided at the outlet position corresponding to the honeycomb heat exchanger, and a plurality of heat exchange plates arranged in parallel and equidistantly and obliquely arranged are provided in the heat exchange chamber as a second-stage heat exchanger. The present invention can divert the superheated flue gas and process it in two parts, and utilize the internal structure for diversion, guidance and mixed flow diffusion, and can simultaneously recover the sensible heat and latent heat of the superheated flue gas, and has a high waste heat recovery rate.

Description

Technical Field

[0001] The invention relates to the technical field of waste heat recovery structures and devices, and in particular to a heat exchanger structure used in a boiler flue gas waste heat utilization system. Background Art

[0002] In the existing technology, the most important loss in boiler operation is the flue gas heat loss. The combustion products in the boiler contain a large amount of water vapor. The high-temperature water vapor has both sensible heat and latent heat. Directly discharging it into the atmosphere without waste heat recovery will cause energy waste and environmental pollution. Flue gas waste heat resource loss is the most important waste heat resource loss, accounting for 60-70% of boiler waste heat resource loss. Generally speaking, the actual flue gas temperature of boilers used by boiler companies is generally higher than the design temperature, generally 120℃ to 150℃. The heat carried away by the flue gas causes great energy waste, and still has a certain recovery value. Reducing flue gas losses and rationally utilizing flue gas waste heat are particularly important for saving energy and improving the economy of related factories and mines.

[0003] In order to reduce energy waste, relevant enterprises generally adopt corresponding flue gas waste heat recovery devices to recover flue gas heat. The commonly used flue gas waste heat recovery devices in the prior art are mainly flue gas heat exchangers, which are widely used in various chemical fields such as petroleum, coal, and power, and are used to convert and recycle the heat energy of high-temperature flue gas generated by combustion. However, due to the structural design defects and the limitations of their own working mechanism, the heat exchange efficiency of the flue gas heat exchanger in the prior art is not high. If the flue gas treatment volume per unit time needs to be increased, the system will be too large, the cost will be high, and the operation and maintenance costs will be high; there are also pressurized high-temperature flue gas to improve the heat exchange efficiency, but the contact time of the pressurized high-temperature flue gas in the heat exchange structure of the flue gas heat exchanger is too short, which will lead to a small temperature difference in the heat transfer of the low-temperature flue gas and a reduced heat transfer coefficient, resulting in the flue gas after waste heat recovery still having a high temperature, and it is impossible to ensure that the sensible heat and latent heat of the flue gas are completely absorbed.

[0004] Therefore, under the current background of strict energy conservation and emission reduction policies, it is urgent to develop a flue gas waste heat recovery device so that the heat in the boiler exhaust system can be fully utilized to achieve deep energy conservation and reduce pollution, and promote the coordinated development of the environment and the economy. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a heat exchanger structure for a boiler flue gas waste heat utilization system, which can efficiently recover the exhaust gas waste heat to solve the defects of the above technical background.

[0006] The technical problem solved by the present invention is achieved by adopting the following technical solutions:

[0007] A heat exchanger structure for a boiler flue gas waste heat utilization system is arranged on a boiler smoke pipe, comprising a shell, a gas channel for conveying smoke is arranged in the shell, and a pressurizing device for pressurizing the superheated smoke in the boiler smoke pipe is arranged at the front end of the gas channel, and an air intake section, a heat exchange section and an exhaust section are arranged in sequence in the gas flow direction in the gas channel;

[0008] The air inlet section includes an outer tube body, the front end of the outer tube body is connected to the air outlet end of the boiler smoke pipe, and the rear end is provided with an inner tube body, the inner tube body is concentrically arranged with the outer tube body, and its inner diameter is 1 / 3 to 1 / 2 of the inner diameter of the outer tube body, and an air window is arranged between the inner tube body and the outer tube body for connection, and a honeycomb heat exchanger is formed in the annular surface between the inner tube body and the outer tube body inside the air window as the first-stage heat exchanger; the air window is provided with an oblique guide surface, so as to introduce part of the superheated flue gas coming out of the boiler smoke pipe into the honeycomb heat exchanger through the oblique guide surface for the first heat exchange;

[0009] The heat exchange section includes a heat exchange cavity whose inner diameter is larger than the inner diameter of the outer tube. The heat exchange cavity is provided with an oblique guide plate at the outlet position corresponding to the honeycomb heat exchanger. The guide plate is used to form a swirl in the heat exchange cavity under the guidance of the guide plate for the flue gas that has undergone the first heat exchange in the honeycomb heat exchanger. At the same time, a plurality of heat exchange plates are also provided in the heat exchange cavity. The heat exchange plates are arranged in parallel with equal intervals and in an oblique direction, maintaining an angle of 30-45° with the axial direction of the heat exchange section and maintaining an angle of 65-70° with the swirl direction of the swirl.

[0010] In the present invention, the heat exchanger structure divides the superheated flue gas in the flue through the concentrically arranged inner tube body and outer tube body. Part of the superheated flue gas directly enters the heat exchange section through the inner tube body, while the other part enters the honeycomb heat exchanger for the first heat exchange through the guiding effect of the guide plate. This honeycomb heat exchanger is also called a honeycomb jacket heat exchanger. Its heat transfer coefficient is 2 to 3 times higher than that of the traditional plate heat exchanger. At the same time, this honeycomb heat exchanger also has better structural stability. When the pressurizing device pressurizes and injects the high-temperature flue gas, the high-temperature flue gas can be heated to a certain temperature. Under high pressure, the heat exchange efficiency can still be guaranteed while the structure does not deform, and it can self-depressurize, which is safer to use. The flue gas after the first heat exchange in the honeycomb heat exchanger still has a certain pressure after entering the heat exchange section. Under the action of the oblique guide plate, a vortex is formed in the heat exchange cavity, forming two counter-heat flows with different temperatures and directions with the part of the superheated flue gas that directly enters the heat exchange section through the inner tube body, and the contact time of the flue gas on the heat exchange plate and the heat exchange efficiency are increased through the interaction of the counter-heat flows.

[0011] As a further limitation, the inner diameter of the heat exchange cavity is preferably 1.2 to 1.5 times the inner diameter of the outer tube.

[0012] As a further limitation, a heat-insulating insulation layer is provided between the shell and a gas passage provided in the shell, and the heat-insulating insulation layer is filled with heat-insulating material to improve heat utilization and reduce heat loss.

[0013] As a further limitation, the cross-section of the inclined guide surface arranged on the air window is a continuous concave arc surface, and the concave arc surface is provided with reinforcing ribs arranged along the axial direction of the outer tube body, and the channel between adjacent reinforcing ribs on the air intake section is used as a diversion channel.

[0014] As a further limitation, the heat exchange bracket part in the honeycomb heat exchanger is formed of a high temperature resistant and high thermal conductivity metal material and is subjected to anti-corrosion surface treatment, preferably a zirconium alloy heat exchange bracket or an aluminum alloy heat exchange bracket with an anti-corrosion coating on the surface.

[0015] As a further limitation, the sum of the cross-sectional areas of the heat exchange plates accounts for 35-40% of the area of ​​the corresponding heat exchange cavity cross-section.

[0016] As a further limitation, a heat-conducting air duct is arranged on the surface of the heat exchange plate, and the heat-conducting air duct is a wavy groove structure, arranged on the surface of the heat exchange plate and along the length direction of the surface of the heat exchange plate, and extends out of the surface of the heat exchange plate at both ends.

[0017] As a better utilization method, the pressurizing device pressurizes the superheated flue gas to 1.0~1.5MPa and then sends it into the heat exchanger structure for processing. The temperature of the heat medium replaced from the honeycomb heat exchanger and the heat exchange plate can be stabilized at 60~70℃, directly acting on the heat transfer plate to thermally dry the coal briquettes on the surface of the heat transfer plate.

[0018] Beneficial effects: The heat exchanger structure of the present invention for a boiler flue gas waste heat utilization system has high heat exchange efficiency, compact structure and controllable volume. The double duct structure is set to divert the superheated flue gas after the pressurization layer treatment, and a part of the diverted superheated flue gas is subjected to the first heat exchange through a honeycomb heat exchanger, and the part of the flue gas after the heat exchange is mixed with the superheated flue gas that has not undergone the first heat exchange by using the design of the duct to form flue gas cyclones of different temperatures, and the sensible heat and latent heat are exchanged between the flue gases at two different temperatures through the flue gas cyclone, and mixed flow heat is exchanged with the heat exchange plates, and the sensible heat and latent heat in the flue gas are recovered at the same time, thereby improving the utilization rate of the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a preferred embodiment of the present invention.

[0020] Among them: 1. Insulation material filling layer; 2. Shell; 3. Heat exchange cavity; 4. Heat exchange plate; 5. Oblique guide plate; 6. Inner tube body; 7. Honeycomb heat exchanger; 8. Air window; 9. Outer tube body. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0022] See also Figure 1 A heat exchanger structure for a boiler flue gas waste heat utilization system. In this embodiment, the heat exchanger structure for a boiler flue gas waste heat utilization system includes a shell 2 wrapped around the outside, a gas channel is formed on the inside of the shell 2, and an interlayer space with a thermal insulation material filling layer 2 is provided between the gas channel and the shell 2.

[0023] The gas passage in the shell 2 is divided into three sections from the direction of the flue gas flow, namely, the air intake section, heat exchange section and exhaust section corresponding to letters a, b and c, wherein the front end of the air intake section corresponding to letter a is connected to the air outlet end of the boiler smoke pipe through the outer tube body 9, which is used to receive the air outlet of the boiler smoke pipe. At the same time, a pressurizing device for pressurizing the superheated flue gas in the boiler smoke pipe is also connected between the outer tube body 9 and the air outlet end of the boiler smoke pipe. The superheated flue gas in the boiler smoke pipe passes into the inner side of the outer tube body 9 after being pressurized. At the same time, an inner tube body 6 is arranged at the rear of the air intake section a, and the inner tube body 6 is arranged concentrically with the outer tube body 9, and its inner diameter is 1 / 3 of the inner diameter of the outer tube body 9. An annular cavity is formed between the inner tube body 6 and the outer tube body 9, and an air window 8 is arranged at the front end of the annular cavity, and a honeycomb heat exchanger 7 is arranged in the annular cavity.

[0024] The heat exchange section b is arranged after the air inlet section a, and its main body is an outward expansion cavity, namely, the heat exchange cavity 3. The inner diameter of the heat exchange cavity 3 is 1.3 times the inner diameter of the outer tube. The lower part thereof corresponds to the honeycomb heat exchanger 7 and is provided with an oblique guide plate 5 of the same height as the corresponding annular surface of the honeycomb heat exchanger 7. The oblique guide plate 5 is formed on the lower cavity wall of the heat exchange cavity 3 and is used to guide the flue gas after heat exchange by the honeycomb heat exchanger 7 and form an external vortex in the heat exchange cavity 3. At the same time, a plurality of parallel heat exchange plates 4 are also arranged in the heat exchange cavity 3 above the oblique guide plate 5. These heat exchange plates 4 are obliquely arranged. The heat exchanger 4 is arranged at an angle of 36° to the central axis of the heat exchange section, and at an angle of 70° to the swirl direction formed by the smoke passing through the honeycomb heat exchanger 7 under the action of the oblique guide plate 5, and the sum of the cross-sectional areas of these heat exchange plates 4 under any cross section accounts for 36% of the area of ​​the cross section of the corresponding heat exchange cavity 3; and in order to increase the contact area between the single plate of the heat exchange plate 4 and the smoke, heat conduction air ducts are arranged on the plate surfaces of both sides of the heat exchange plate 4. These heat conduction air ducts are wavy groove structures, which are arranged on the plate surface of the heat exchange plate 4 and along the plate surface length direction of the heat exchange plate 4, and extend out of the plate surface of the heat exchange plate 4 at both ends.

[0025] In this embodiment, the exhaust section c is arranged at the upper part of the heat exchange section b, which is an extension of the heat exchange chamber 3. Its upper part is open, and the opening is used as a smoke exhaust port. In this case, the smoke that has completed sufficient heat exchange in the heat exchange chamber 3 is in a dispersed state after the swirl action of the heat exchange chamber 3, and is discharged in all directions at the end of the exhaust section c as shown in the figure; in another embodiment, the exhaust section c can also be set as a closing structure, that is, the dispersed smoke flow is gathered and discharged at the rear of the heat exchange chamber 3.

[0026] When the heat exchanger structure of this embodiment is in use, the superheated flue gas in the boiler smoke pipe is pressurized to 1.2MPa by the pressurizing device and then axially sent to the air inlet section a as shown in the figure. The flow of the flue gas airflow entering the air inlet section a is shown by the arrow in the figure. A part of it directly enters the heat exchange cavity 3 axially through the inner tube body 6, and the other part enters the honeycomb heat exchanger 7 through the air window 8 for the first heat exchange. In this embodiment, in order to obtain a better air intake effect and air intake amount, the surface of the air window 8 is a continuous concave arc surface to form a guiding airflow at the position of the air window 8. At the same time, since the incoming flue gas is pressurized flue gas, the structure can be strengthened by setting reinforcing ribs axially arranged along the outer tube body on the inner side of the air window 8 corresponding to the inner side of the air window 8 position, and the channel between the adjacent reinforcing ribs on the air intake section is used as a diversion channel.

[0027] In this embodiment, the heat exchange bracket part in the honeycomb heat exchanger 7 is formed of a heat exchange bracket made of a zirconium alloy material with high temperature resistance and high thermal conductivity. After the part of the smoke passing through the air window 8 passes through the honeycomb heat exchanger 7 for the first heat exchange, it is discharged from the tail of the honeycomb heat exchanger 7 and enters the outer annular surface position of the heat exchange cavity 3, and is guided by the oblique guide plate 5 at the position corresponding to the oblique guide plate 5 to form a Figure 1 The swirl shown in the figure has a different temperature and direction from the flue gas that directly enters the heat exchange chamber 3 axially through the inner tube body 6. The two flue gas flows are mixed and turbulent through the action of the heat exchange plate 4 set at a specific angle. The interaction between the airflows excites the latent heat in the flue gas and converts it into sensible heat that is more easily recovered. On the one hand, the heat recovery rate of the heat exchange plate 4 for the flue gas can be improved. At the same time, the swirling flue gas after turbulence can stay in the heat exchange chamber 3 for a longer time, which is also beneficial to the heat recovery rate of the flue gas. The recovered flue gas flow becomes irregular in motion after mixing and turbulence, that is, it moves irregularly in the exhaust section c and is discharged in a dispersed manner.

[0028] After the boiler superheated flue gas in a saturated state passes through the heat exchanger structure with the above structure and undergoes heat recovery twice, the temperature of the heat medium on the honeycomb heat exchanger 7 and the heat exchange plate 4 can be stabilized at 60-70°C, and is directly exported to act on the heat transfer plate to heat dry the briquette on the surface of the heat transfer plate. Neither secondary heating nor cooling treatment is required, and it can be used to dry the moisture content of the wet briquette formed by the die from about 14% to about 6% of the formed state, which is very convenient and practical.

[0029] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A heat exchanger structure for a boiler flue gas waste heat utilization system, comprising a shell arranged on a boiler flue gas pipe, characterized in that: A gas channel for conveying flue gas is provided in the shell, and a pressurizing device for pressurizing the superheated flue gas in the boiler smoke pipe is provided at the front end of the gas channel, and an air intake section, a heat exchange section and an exhaust section are arranged in sequence in the gas flow direction in the gas channel; The air inlet section includes an outer tube body, the front end of the outer tube body is connected to the air outlet end of the boiler smoke pipe, and the rear end is provided with an inner tube body, the inner tube body is concentrically arranged with the outer tube body, and its inner diameter is 1 / 3 to 1 / 2 of the inner diameter of the outer tube body, and an air window is arranged between the inner tube body and the outer tube body for connection, and a honeycomb heat exchanger is formed in the annular surface between the inner tube body and the outer tube body inside the air window as the first-stage heat exchanger; the air window is provided with an oblique guide surface, so as to introduce part of the superheated flue gas coming out of the boiler smoke pipe into the honeycomb heat exchanger through the oblique guide surface for the first heat exchange; The heat exchange section includes a heat exchange cavity whose inner diameter is larger than the inner diameter of the outer tube. The heat exchange cavity is provided with an oblique guide plate at the outlet position corresponding to the honeycomb heat exchanger. The guide plate is used to guide the flue gas that has undergone the first heat exchange in the honeycomb heat exchanger to form a swirl in the heat exchange cavity under the guidance of the guide plate. At the same time, a plurality of heat exchange plates are also provided in the heat exchange cavity. The heat exchange plates are arranged in parallel with equal spacing and in an oblique direction, maintaining an angle of 30-45° with the axial direction of the heat exchange section, and maintaining an angle of 65-70° with the swirl direction of the swirl. The cross section of the oblique flow guide surface arranged on the air window is a continuous concave arc surface, and the concave arc surface is provided with reinforcing ribs arranged along the axial direction of the outer tube body, and the channel between the adjacent reinforcing ribs on the air inlet section is used as a diversion channel; A heat-conducting air duct is arranged on the plate surface of the heat exchange plate, and the heat-conducting air duct is a wave-shaped groove structure, which is arranged on the plate surface of the heat exchange plate and along the length direction of the plate surface of the heat exchange plate, and extends out of the plate surface of the heat exchange plate at both ends.

2. The heat exchanger structure for boiler flue gas waste heat utilization system according to claim 1 is characterized in that: The inner diameter of the heat exchange cavity is 1.2 to 1.5 times the inner diameter of the outer tube.

3. The heat exchanger structure for boiler flue gas waste heat utilization system according to claim 1, characterized in that: A heat-insulating insulation layer is arranged between the shell and a gas channel arranged in the shell, and the heat-insulating insulation layer is filled with heat-insulating material.

4. The heat exchanger structure for boiler flue gas waste heat utilization system according to claim 1, characterized in that: The heat exchange support part in the honeycomb heat exchanger is formed of a high-temperature resistant and high-thermal conductive metal material and is subjected to an anti-corrosion surface treatment.

5. The heat exchanger structure for the boiler flue gas waste heat utilization system according to claim 4 is characterized in that: The heat exchange bracket in the honeycomb heat exchanger is a zirconium alloy heat exchange bracket.

6. The heat exchanger structure for boiler flue gas waste heat utilization system according to claim 4, characterized in that: The heat exchange bracket in the honeycomb heat exchanger is an aluminum alloy heat exchange bracket with an anti-corrosion coating electroplated on the surface.

7. The heat exchanger structure for the boiler flue gas waste heat utilization system according to claim 1, characterized in that: The sum of the cross-sectional areas of the heat exchange plates accounts for 35-40% of the area of ​​the corresponding heat exchange cavity cross-section.

8. The heat exchanger structure for boiler flue gas waste heat utilization system according to claim 1, characterized in that: The pressurizing device pressurizes the superheated flue gas to 1.0-1.5 MPa and then sends it into the heat exchanger structure for processing. The heat medium displaced from the honeycomb heat exchanger and the heat exchange plate is applied to the heat conduction plate, and the heat conduction plate is used as the hot drying surface of the briquette.

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