High temperature axial flow fan unit

Abstract

The present invention relates to a high-temperature axial flow fan unit, wherein an impeller (2) is mounted on a drive shaft (13) of an outer sleeve support tube (3), and the support tube (3) passes through the hot flue gas area of ​​the bottom plate of the flue gas ascending channel; the motor and drive device of the unit can be placed in a low temperature area to avoid being affected by the high temperature flue gas. In order to prevent the hot flue gas from being retained or refluxed, the cross section of the lower half of the hot flue gas chamber (4) behind the impeller (2) is enlarged on both sides, and the pressure is increased by reducing the hot flue gas flow rate to compensate for the pressure loss caused by the change in the flue gas flow direction. The support tube (3) is combined with a metal chassis (34) placed on a shock absorber (17) to form a unit. The temperature protection tube (5) is coated with a ceramic heat insulation coating (6) so that the hot flue gas does not contact the support tube (3), and the support tube (3) is fixed on a base (16). The impeller (2) generates a negative pressure for sucking in cooling air and is cleaned by a compressed air spray gun (37).

Description

Technical Field

[0001] The present invention relates to a method for constructing a high-temperature axial flow fan unit for conveying large-flow, 500-900°C hot flue gas, which can be made large enough, the flue gas is only slightly accelerated and the energy consumption is minimized. In this way, it is possible to convey the high-temperature flue gas through the flue gas channel under negative pressure, and in particular, the high-temperature axial flow fan can be used to convey a large-flow, high-temperature hot flue gas from a biomass combustion system to a large coal-fired boiler without pressure. Background Art

[0002] The motor of a common axial flow fan is placed in the center of the airflow, so there is no axial flow fan that can actually be used to transport high-temperature gas. The motor of a radial fan is placed outside the airflow, so the temperature of the transmitted flue gas can be as high as 1000°C. However, due to the swirl and change of flow direction of the airflow, the efficiency of a radial fan is often lower than that of an axial flow fan, so it is difficult for a radial fan to achieve large-volume airflow transmission.

[0003] The construction of large high-temperature radial fans is more complicated because the high-alloy heat-resistant steel materials required for high-temperature flue gases have high thermal expansion, which often causes the impeller and fan housing to change or deform in size.

[0004] The shell shape required for radial fans is difficult to manufacture with ceramic materials, while hot flue gas containing corrosive components (such as alkali metal dissolves or chlorine) often requires the use of ceramic materials because dust particles in the flue gas will grind the oxide layer on the metal surface that has been corroded by alkali metal dissolves or chlorine.

[0005] The impeller motor unit of the previous axial flow fan is always fixed in the airflow. This structure will also make the impeller motor unit a resistance to airflow or smoke. If the impeller motor unit adds a high-temperature resistant outer coating, the gas resistance will increase because the shell becomes thicker. The pressure on the impeller blades will also change during rotation. In extreme cases, vibration will occur until the impeller blades are damaged. This is very important because the high temperature state has already put the impeller blade material in a fragile and sensitive stress state.

[0006] The hot flue gas from the straw burning system can even form a dust layer on the fan blades and cause imbalance, and there is currently no suitable cleaning method. Since high-temperature axial flow fans have not yet been put into practical use due to technological development limitations, even less is known about how to cool high-temperature axial flow fans.

[0007] The technology involved in building a long channel to transport positive pressure flue gas at a large flow rate and maintain a high-reliability seal under thermal expansion is very complex. However, it would be much safer if the flue gas could be transported under negative pressure. However, this requires the construction of a new type of axial flow induced draft fan that has not been put into practical use so far. Summary of the invention

[0008] The purpose of the present invention is to build a high-temperature axial flow fan that can transport high-temperature flue gas at a large flow rate through a flue gas conveying channel under negative pressure. The conveyed flue gas can also be flue gas containing dust and corrosive substances. At the same time, it is necessary to ensure that the power system and bearings of the fan are not affected by high temperature, and there is almost no pressure change when the fan impeller rotates.

[0009] The structure should be suitable for the application of ceramic materials, while the long-term and high-reliability operation of the fan can be achieved through a reliable cooling system and an impeller dust removal device.

[0010] According to the present invention, the high-temperature axial flow fan is implemented by fixing the impeller of the axial flow fan on a long drive shaft, and the drive shaft is installed in a long support tube. The support tube is wrapped by a temperature protection tube and passes through the hot smoke chamber and the bottom plate of the smoke rising channel arranged at an elevation angle to change the flow direction of the smoke.

[0011] The hot flue gas chamber is arranged behind the impeller along the direction of flue gas flow. The hot flue gas passage to the impeller has no deflectors or obstacles that cause the hot flue gas to change direction. The hot flue gas flows into the impeller evenly with almost no pressure difference on the circular cross section. The support pipe and the wrapped temperature protection pipe are arranged in the hot flue gas chamber along the direction of hot flue gas flow. The hot flue gas flow changes its flow direction after passing through the bottom plate at an elevation angle.

[0012] The upper part of the hot flue gas flowing into the impeller can flow freely, while the hot gas in the lower part will flow through a space approximately 0.8-1.3 times the diameter of the temperature protection tube. However, since the flow space of the hot flue gas has been fully enlarged, hot flue gas reflow will not occur.

[0013] At this time, the hot smoke chamber whose cross-sectional area is enlarged by at least half will slow down the hot smoke flow, and part of the kinetic energy of the hot smoke flow is converted into pressure to compensate for the pressure loss caused by the change in the direction of the hot smoke flow.

[0014] The initial cross-section and shape of the hot flue gas chamber do not change in the upper part, which, combined with the distance the flue gas has to travel to reach the impeller, results in almost no pressure difference when the impeller rotates.

[0015] After the hot flue gas exhaust channel behind the high-temperature axial flow fan unit is changed into a cone, part of the kinetic energy of the hot flue gas flow will be recovered because the hot flue gas flow is converted into negative pressure and decelerated by the hot flue gas flow, which can reduce the power consumption of the high-temperature axial flow fan unit.

[0016] A temperature protection tube coated with a ceramic heat-insulating coating is arranged on the periphery of the support tube, which protects the support tube from contact with the hot flue gas. The temperature protection tube is firmly connected to the load-bearing foundation through the support member so that it will not vibrate, which makes the external ceramic heat-insulating coating of the temperature protection tube have a long service life. The temperature protection tube channel passing through the bottom plate of the flue gas ascending channel can also be sealed with ceramic material.

[0017] The support tube can be securely connected via a solid support to a metal chassis which is mounted on a shock absorber and carries a counterweight which compensates for the torque forces generated by the impeller pull.

[0018] The drive shaft is installed in the center of the hot flue gas chamber. The drive shaft is connected to a hub to absorb the axial tension generated by the rotation of the impeller. The drive shaft is in a tension state to help stabilize the concentricity. The inside of the drive shaft is hollow for cooling air to pass through.

[0019] The impeller includes an aerodynamic cap that meets the negative pressure in front of the impeller and effectively delivers the cooling air required by the drive shaft. There is a free gap between the cap and the rim, and the negative pressure of the gas flowing through it will be enhanced, so that fresh air for cooling will be sucked in from the outside and inside of the drive shaft to cool the drive shaft. After the cooling air enters the impeller cap, it will also cool the connection area between the fan blades and the hub or rim.

[0020] The fan blades are welded to the conical wheel rim, which means that even the fast-flowing hot flue gases after the impeller will generate negative pressure, which is further enhanced by the small blades. According to the principle of radial fans, these small blades generate further negative pressure. The negative pressure here is used to draw in cooling air from the outside through the space between the temperature protection tube and the support tube and the inner space of the support tube.

[0021] In order to achieve smooth operation, all fixed parts of the high-temperature axial flow fan unit are built very solidly, and counterweights are arranged for the support tube to prevent vibration of the support tube due to mass inertia.

[0022] A compressed air spray gun which can move radially and includes a nozzle is arranged in front of the impeller. This device is used to remove dust accumulated on the impeller fan blades.

[0023] The outer walls of all spaces carrying hot flue gases are made of steel plates, on which a certain number of cooling reinforcement plates and structural reinforcement plates are welded. Steel hooks are welded to the inner side of the outer wall steel plates to fix the refractory ceramic layer, and an insulation layer is arranged under the refractory ceramic layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A side view of a high temperature axial fan unit is shown.

[0025] Figure 2 A horizontal cross-section of a high-temperature axial flow fan unit is shown.

[0026] Figure 3 A vertical section view of a high temperature axial flow fan unit viewed from the driver side is shown.

[0027] Figure 4 A side cross-sectional view of a high temperature axial flow fan unit is shown.

[0028] In the figure: 1-hot flue gas channel, 2-impeller, 3-support tube, 4-hot flue gas chamber, 5-temperature protection tube, 6-ceramic thermal insulation coating, 7-bottom plate of flue gas rising channel, 8-hot flue gas discharge channel, 9-opening, 10-fan blade, 11-motor, 12-V-belt drive, 13-drive shaft, 14-air inlet, 15-base, 16-base, 17-shock absorber, 18-support, 19-bearing jacket, 20-rolling bearing, 21-seal, 22-oil channel, 23-mass Body, 24-shaft, 25-hub, 26-wheel disc, 27-rim, 28-small blades, 29-cap, 30-central area, 31-perforation, 32-welding connection, 33-cooling oil tank, 34-metal chassis, 35-counterweight, 36-duct, 37-compressed air spray gun, 38-handle, 39-nozzle, 40-steel plate, 41-cooling reinforcement plate, 42-insulation layer, 43-refractory ceramic layer, 44-steel hook, 45-cooling air exhaust port, 46-cooling air, 47-screw. DETAILED DESCRIPTION

[0029] Application examples of the present invention will be explained in more detail below with reference to the accompanying drawings.

[0030] exist Figure 1 A side view of a high temperature axial flow fan unit is shown in FIG. 1 , which is designed to transport 400 m3 of 3 / second of hot flue gas and produces a flue gas pressure of about -1800Pa.

[0031] The hot flue gas is transported from the straw combustion system (not shown) through a relatively long hot flue gas channel (1). The inner dimension of the hot flue gas channel is 3.7m x 3.7m, and gradually narrows to a circular shape with a diameter of 3.7m in the direction of the fan. The diameter of the axial flow fan impeller (2) is 3.5m. The hot flue gas velocity in the hot flue gas channel (1) before the impeller (2) is only slightly increased, thereby minimizing the energy consumption of the high-temperature axial flow fan unit.

[0032] The impeller (2) is positioned by a support tube (3), which passes through the elevation angle hot flue gas ascending channel bottom plate (7) of the hot flue gas chamber (4) behind the impeller (2). In this embodiment, the elevation angle of the flue gas ascending channel bottom plate (7) is set to 30-40°. The support tube (3) can be made of stainless steel or ordinary carbon steel. In this embodiment, the diameter is 800 mm and the wall thickness is 50 mm. This makes it very hard and heavy, so that the influence of vibration can be offset to a certain extent.

[0033] The support tube (3) is wrapped by a temperature protection tube (5), and the outside of the temperature protection tube (5) is coated with a ceramic heat insulation coating (6). In this embodiment, the outer diameter of the temperature protection tube is 1100 mm. The hot flue gas flowing into the upper part of the hot flue gas chamber (4) after the impeller (2) is not blocked here, but the hot flue gas flowing into the lower part of the hot flue gas chamber (4) will change its flow direction to a certain extent when flowing through the outer surface of the temperature protection tube (5). However, because the cross-sectional area on both sides of the lower part of the hot flue gas chamber (4) is enlarged, the flue gas will not flow back to the impeller (2) and cause the impeller to vibrate when rotating.

[0034] Figure 2 The top view shows that the lower half of the hot flue gas chamber (4) is designed to be open on both sides, which will reduce the flow rate of the hot flue gas and convert its kinetic energy into pressure. The cross-sectional expansion will not only compensate for the reduced hot flue gas flow rate caused by the coated temperature protection tube (5), but also compensate for the pressure loss caused by the change in the hot flue gas flow direction caused by the bottom plate (7) of the flue gas ascending channel.

[0035] The lower part of the hot flue gas chamber (4) has a width equal to the diameter of the temperature protection tube (1100 mm in this example) added on both sides. The hot flue gas discharge channel (8) after the hot flue gas chamber (4) is also conical to enlarge the cross-sectional area of ​​the flue gas discharge.

[0036] The reduced velocity of the hot flue gas will form an induced draft negative pressure, thereby alleviating the fan drive and reducing the fan power consumption. In this embodiment, the hot flue gas is introduced into the hot flue gas opening (9) of the coal-fired boiler not shown in the figure, and the inner size of the hot flue gas opening (9) here is 7mx7m.

[0037] exist Figure 3 It can be seen that the cross-section of the lower part of the hot smoke chamber (4) is expanded, while the cross-section of the upper part of the hot smoke chamber (4) is not expanded because there is no obstacle when the hot smoke flows.

[0038] The impeller (2) comprises eight fan blades (10), which are made of high alloy fire-resistant stainless steel and are aerodynamically designed in a conventional manner. The output power of the motor (11) in this example is 1300 kW, which is transmitted to the drive shaft (13) via a V-belt drive (12). The interior of the drive shaft (13) is hollow and can be cooled by sucking air through an air inlet (14) in the center of the drive shaft (13).

[0039] The support tube (3) is supported by a strong base frame (15) which is connected to a solid metal chassis (34). The metal chassis (34) is located on a base (16) of a concrete structure, and a shock absorber (17) is arranged between the metal chassis (34) and the base (16).

[0040] The temperature protection tube (5) having the ceramic heat-insulating coating (6) is not in contact with the support tube (3) but is directly connected to the base (16) through the support member (18). This can prevent the vibration of the impeller (2) of the high-temperature axial fan unit from being transmitted to the temperature protection tube (5) and the outer wall steel plate (40) of the hot flue gas chamber (4). This can keep the ceramic heat-insulating coating (6) of the temperature protection tube (5) intact and functional for a long time. The temperature protection tube (5) passes through the bottom plate (7) of the flue gas ascending channel and is also sealed with refractory ceramic material.

[0041] Figure 4 The internal structure of the impeller (2) and the bearing is dissected in depth. In order to avoid oscillation and vibration and realize the smooth operation of the impeller (2), each fixed component is configured with a suitable deadweight. In this embodiment, the outer diameter of the support tube (3) is 800 mm and the tube wall thickness is 50 mm, which can increase the deadweight of the support tube (8) and improve the operation stability.

[0042] The bearing sleeve (19) carrying the rolling bearing (20) and including the seal (21) is made of solid material. When installing the high-temperature axial flow fan unit, a mass body (23) inserted into the support tube (3) can be optionally provided to prevent the impeller (2) and the bearing from slightly unstable operation due to dust accumulation on the impeller (2). In this embodiment, the mass body (23) is made of low-quality iron and weighs about 4600 kg.

[0043] The average distance between the support tube (3) and the temperature protection tube (5) is 8 cm. The temperature protection tube (5) is fixed by a support member (18) and the distance between the support tube (3) and the temperature protection tube (5) can be adjusted during the final assembly of the high-temperature axial flow fan unit.

[0044] The weight of the rotating parts should be as light as possible. The shaft (24) is about 8 meters long in this embodiment and is composed of a drawn tube with a diameter of 210 mm and a wall thickness of 25 mm. The drawn tube material is a steel material with better strength. The shaft (24) carries the hub (25) of the impeller (2).

[0045] The wheel disc (26) and the conical wheel rim (27) are made of low alloy heat-resistant steel, whose thermal expansion coefficient is higher than that of ordinary carbon steel. The stress generated by the part of the impeller (2) contacting the outside due to the increase in temperature can be balanced in the wheel disc (26).

[0046] The fan blades (10) can be made of the same high alloy refractory steel as the gas turbine blades, but in order to minimize the influence of the tension between the two different materials, the welded connection (32) between the rim (27) and the fan blades (10) can be made as short as possible.

[0047] The small blades (28) connected to the wheel (26) can bring additional negative pressure for conveying cooling air as in radial fans. The cap (29) is placed in front of the impeller (2) to provide better flow and temperature protection, and can also generate negative pressure to suck in cooling air (46) through the drive shaft (13). The cap (29) can be made of a thin but highly heat-resistant metal material. The central area (30) is used to fix the cap (29). In this embodiment, it is fixed with screws (47) and then sealed with a filler made of lightweight ceramic.

[0048] Cooling air (46) enters the support tube (3), the space between the support tube (3) and the temperature protection tube (5), and the air inlet hole (14) of the drive shaft (13) from the outside through an adjustable opening (not shown in the figure) in a set amount and further passes through the through hole (31) in the shaft (24).

[0049] The negative pressure in front of the fan blades (10) sucks the cooling air (46) out of the borehole (31), so that the flue gas temperature is, for example, 720°C while the operating temperature of the cap (29) is only 630°C, and such a temperature difference is tolerable by the material itself.

[0050] The important, very strong welded connection (32) between the rim (27) and the fan blade (10) also provides a certain degree of protection and cooling. The high alloy stainless steel of the fan blade (10) has a thermal conductivity of only about 15% of that of ordinary carbon steel, which is also very helpful in achieving the above protection and cooling.

[0051] The high temperature axial flow fan unit in this example is used to transfer the hot flue gas at about 850°C from the external straw combustion system to the impeller (2) at a speed of 400m / s. 3 / second to the coal-fired boiler not shown in the figure, which is equivalent to about 100MW of heat transfer. 3 / second, cooling air (46) gradually heated to 200°C is added to the hot flue gas, which only accounts for a very small part of the hot flue gas fed to the coal-fired boiler.

[0052] By strengthening the ceramic heat-insulating coating (6) of the temperature protection tube (5) and increasing the supply of cooling air, in principle the high-temperature axial flow fan unit in this embodiment can be used to transport hot flue gas with a maximum temperature of 900°C.

[0053] The multi-protected rolling bearing (20) requires bearing lubricating oil. For this purpose, a cooling oil tank (33) with an oil pump is arranged outside the rolling bearing (20). The temperature of the oil returning from the rolling bearing (20) can provide a signal for correctly setting the cooling air volume and cooling oil volume.

[0054] The drive shaft (13) and the V-belt drive (12) can be arranged in the low temperature zone in any form, and it is best to provide pressurized oil cooling. A common axial thrust bearing (not shown in this figure) can also be configured to absorb the tension exerted by the impeller (2) on the drive shaft (13).

[0055] If the high temperature axial flow fan unit generates a pressure of -1800Pa in the hot flue gas channel (1), a pulling force of about 16KN will act on the drive shaft (13) through the impeller (2), but when equipped with a fixed and solid metal chassis (34), this force will not affect the stability of the drive shaft (13) during operation. In addition, the torque force generated can be balanced by the counterweight (35). In this embodiment, the mass of the counterweight (35) is 2100kg and can be made of concrete blocks.

[0056] Dust in the hot flue gas from the straw burning system will also be deposited on the fan blades (10) and may cause the fan blades (10) to move unbalanced. Therefore, according to the high-temperature axial flow fan unit shown in the figure, two devices for cleaning the impeller (2) during operation can be arranged in front and behind. The cleaning device cleans the impeller (2) by sliding a compressed air spray gun (37) in the guide tube (36) and inserting the handle (38) into the hot flue gas channel (1) in front of or behind the impeller (2).

[0057] In this embodiment, a 0.1 MPa compressed air jet is blown into the rotating fan blade (10) through a nozzle (39) with a diameter of 5 mm, and the compressed air spray gun (37) can be slowly pushed in and pulled out.

[0058] The walls of the hot flue gas channel (1), the hot flue gas chamber (4) and the hot flue gas discharge channel (8) are composed of steel plates (40). A certain amount of short cooling reinforcement plates (41) can be welded on the outside of the wall steel plates (40). In engineering practice, the external structure of the steel plate (40) wall is stable.

[0059] A thick, high-quality heat-insulating layer (42) can be arranged inside the wall steel plate (40) to reduce the heat transfer to the steel plate (40). The heat-insulating layer can be made of materials such as vermiculite concrete. A refractory ceramic layer (43) made of hard, wear-resistant, fire-resistant ceramic concrete and other materials is arranged above the heat-insulating layer. In this embodiment, the thickness of the heat-insulating layer (42) is 15 cm, and the thickness of the refractory ceramic layer (43) is 8 cm.

[0060] The ceramic heat insulating layer (43) can be fixed by welding with steel hooks (44) made of stainless steel, which has only low thermal conductivity. The steel hooks (44) welded in the heat insulating layer (42) can play a role in reducing the tension in the concrete. The diameter of the steel hooks (44) in this embodiment is 5 mm, and the distance between them is about 10 cm. The refractory concrete can also be arranged with a separating steel plate with an expansion joint.

[0061] The present invention enables high-temperature hot flue gas to be transported to a coal-fired boiler system at a large flow rate, which means that a biomass combustion system, especially a biomass combustion system using straw, can be placed at a certain distance and maintain a layout space with the coal-fired boiler.

[0062] The long-distance and safe transmission of large-volume, high-temperature hot flue gas can simplify the construction or renovation planning of smaller thermal systems, allowing other users of hot flue gas to use biomass such as straw as fuel.

Claims

1. A high temperature axial flow fan unit, comprising an impeller with aerodynamically designed fan blades, a drive shaft, a driver, a hot flue gas channel for providing the gas to be transported, and a hot flue gas discharge channel; It is characterized in that The impeller (2) is fixed on a long drive shaft (13), and the drive shaft (13) is installed in a long support tube (3). The support tube (3) is covered by a temperature protection tube (5) and passes through a hot smoke chamber (4). The hot smoke chamber (4) includes a hot smoke ascending channel bottom plate (7) with an elevation angle of 30-40 degrees to change the direction of hot smoke flow. The hot smoke chamber (4) has a cross-sectional area enlarged on both sides of its lower half by not less than 0.8-1.3 times the diameter of the temperature protection tube (5).

2. The high temperature axial flow fan unit according to claim 1, It is characterized in that The cross-sectional area of ​​the hot flue gas discharge channel (8) increases in the direction of flue gas flow.

3. The high temperature axial flow fan unit according to claim 1, It is characterized in that The temperature protection tube (5) is covered with a ceramic heat-insulating coating (6) on the outside to prevent hot flue gas from contacting the support tube (3) and the base (16).

4. The high temperature axial flow fan unit according to claim 1, It is characterized in that The support tube (3) forms a unit with a chassis (15) having a metal chassis (34), which is mounted on a shock absorber (17).

5. The high temperature axial flow fan unit according to claim 4, It is characterized in that The metal chassis (34) includes a counterweight (35).

6. The high temperature axial flow fan unit according to claim 1, It is characterized in that The interior of the long drive shaft (13) is a hollow perforated (31) structure, and cooling air (46) can flow through the hollow perforated (31).

7. The high temperature axial flow fan unit according to claim 1, It is characterized in that The impeller (2) comprises a cap (29), and a cooling air outlet (45) formed by the cap (29) and the rim (27) can be used to release cooling air (46).

8. The high temperature axial flow fan unit according to claim 7, It is characterized in that The wheel rim (27) is conical and has small blades (28) arranged on the wheel disc (26).

9. The high temperature axial flow fan unit according to claim 1, It is characterized in that The support tube (3) uses a mass body (23) which plays a role in stable operation and balance.

10. The high temperature axial flow fan unit according to claim 1, It is characterized in that Compressed air spray guns (37) movable in radial direction and equipped with nozzles (39) are arranged in front and behind the impeller (2).

11. The high temperature axial flow fan unit according to any one of claims 1 to 10, It is characterized in that The walls of the hot flue gas channel (1), the hot flue gas chamber (4), and the hot flue gas discharge channel (8) are all made of steel plates (40), a certain number of short cooling reinforcement plates (41) are welded on the outer side of the wall steel plates (40), a certain number of steel hooks (44) are welded on the inner side thereof, a refractory ceramic layer (43) is fixed on the steel hooks (44), and a thick heat insulation layer (42) is arranged under the refractory ceramic layer (43).

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