Waste heat recovery device and waste heat recovery method for high-temperature aluminum oxide roasting furnace

Abstract

The invention relates to the technical field of aluminum oxide production, in particular to a waste heat recovery device and method for a high-temperature aluminum oxide roasting furnace, and the device comprises a flue gas aluminum oxide particle waste heat utilization mechanism and a water vapor waste heat utilization mechanism. The flue gas after roasting of aluminum hydroxide can be subjected to primary dust removal, aluminum oxide particles with heat after dust removal and separation are conveyed to the fluidized bed through the spiral conveyor, the gas is heated after the aluminum oxide particles are in contact with the gas in the fluidized bed, and the gas with heat is introduced into the heat exchange accessory, so that utilization of the heat of the aluminum oxide particles in the flue gas is realized; the flue gas subjected to primary dust removal makes contact with circulating water, water vapor in the flue gas makes contact with water to achieve phase change, latent heat is converted into heat of the circulating water to the maximum extent, the circulating water exchanges heat with a heat dissipation pipe in the heat exchange box, gas in the heat dissipation pipe is heated and conveyed to a heat exchange accessory, and utilization of the heat of the water vapor in the flue gas is achieved. The energy consumption is reduced, the production cost is reduced, and energy conservation and emission reduction of production are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of alumina production, and in particular to a waste heat recovery device and a waste heat recovery method for a high-temperature alumina roasting furnace. Background Art

[0002] Aluminum hydroxide roasting is a key step in the Bayer process and the last processing step in the alumina plant. It decomposes and filters the aluminum hydroxide filter cake, roasts it in a roasting furnace to remove attached water, deeply heats it to remove crystallization water, and transforms the crystal form to produce the product alumina.

[0003] However, the roasting of aluminum hydroxide is a very important link in the production of alumina and is one of the processes that consumes the most heat energy in the alumina production process.

[0004] The roasting process of aluminum hydroxide is essentially a dehydration process. The water content of dry aluminum hydroxide is 34.6%, plus 3-5% of water attached to the surface of aluminum hydroxide. The essence of aluminum hydroxide roasting is to remove all of the approximately 38% of the water in the aluminum hydroxide. Therefore, the roasting process of aluminum hydroxide inevitably consumes a lot of energy to achieve.

[0005] At present, most of the aluminum hydroxide roasting furnaces used are gas suspension roasting furnaces. The design of this type of furnace has fully considered the recovery and utilization of heat energy. However, the flue gas of the roasting furnace contains a lot of heat during the roasting process. The heat source of the flue gas is actually steam containing a lot of water and hot alumina particles. If the heat energy and water in the flue gas can be recovered, it is actually an energy-saving project that turns waste into treasure. At the same time, the alumina product after roasting still contains a lot of heat that has not been utilized. If the roasting flue gas and the heat of the alumina product can be utilized, it can not only minimize the comprehensive energy consumption of alumina production and reduce the production cost of alumina, but also maximize the energy conservation and emission reduction of alumina production. Summary of the Invention

[0006] In response to the technical problem that when aluminum hydroxide is roasted to produce alumina, the flue gas emitted by the roasting furnace and the waste heat of the alumina product are difficult to utilize, the present invention provides a waste heat recovery device and a waste heat recovery method for a high-temperature alumina roasting furnace, which can reuse the flue gas emitted by the roasting furnace and the waste heat of the alumina product, save energy consumption, reduce the production cost of alumina, and achieve energy conservation and emission reduction in alumina production.

[0007] The technical solutions of the present invention are as follows: In the first aspect, the present invention provides a waste heat recovery device for a high-temperature alumina roasting furnace, comprising a roasting furnace, wherein the smoke outlet of the roasting furnace is connected to the air inlet of a first dust collector, the air outlet at the top of the first dust collector is connected to the aeration element in the spray tower through a first pipeline, the air outlet at the top of the spray tower is connected to the chimney through a second pipeline, a spray element is provided just above the aeration element, the water inlet end of the spray element is connected to the water outlet end of a radiating pipe through a third pipeline, the radiating pipe is located in a closed heat exchange box, the water inlet end of the radiating pipe is connected to the lower part of the spray tower through a fourth pipeline, and the upper portion of the heat exchange box is provided with a spray element. An air inlet and an air outlet are respectively provided on the end face and the lower end face. The air inlet is connected to the first blower through a pipe, the air outlet is connected to the air inlet of the heat exchange accessory through the fifth pipeline, and the air outlet of the heat exchange accessory is connected to the second pipeline through the sixth pipeline; a screw conveyor is provided under the roasting furnace, and the feed port of the screw conveyor is located directly below the discharge port at the bottom of the roasting furnace, and the discharge port of the screw conveyor is connected to the feed end of the fluidized bed through a feeding pipe, and the air outlet on the side of the fluidized bed is connected to the second dust collector, and the air outlet on the top of the second dust collector is connected to the fifth pipeline through the seventh pipeline.

[0008] Furthermore, the discharge end at the bottom of the first dust collector is connected to the first return pipe and the second return pipe, the end of the first return pipe is connected to the roasting furnace, and the end of the second return pipe is connected to the feed port of the screw conveyor.

[0009] Furthermore, a first material valve is provided on the first return pipe, and a second material valve is provided on the second return pipe.

[0010] Furthermore, the aeration element includes a hollow aeration plate with a plurality of aeration tubes disposed on its lower end surface. The aeration plate is connected to the first pipeline. The aeration plate increases the aeration area, and downward aeration increases the contact area between gas and liquid, thereby improving heat exchange.

[0011] Furthermore, the seventh pipeline is provided with a first fan, the sixth pipeline is provided with a second fan, and the fourth pipeline is provided with a circulating water pump.

[0012] Furthermore, the heat dissipation pipe is an S-shaped or spiral heat dissipation pipe.

[0013] Furthermore, the spraying parts are divided into at least two groups, and each group of spraying parts includes a plurality of spray heads.

[0014] Furthermore, the heat exchange accessories include heat exchange tubes in the alkali solution preparation tank.

[0015] Furthermore, a drain pipe is provided at the lower portion of the outer shell of the spray tower.

[0016] In a second aspect, the present invention provides a method for recovering waste heat from a high-temperature alumina roasting furnace, comprising the following steps: S1, aluminum hydroxide is fed into the roasting furnace for roasting, and the flue gas after roasting enters the first dust collector; S2. The flue gas after dust removal enters the spray tower, which stores circulating water. The flue gas is sprayed out from the aeration element and contacts the circulating water for heat exchange. S3, the circulating water after heat exchange enters the heat dissipation pipe and exchanges heat with the first blower and is cooled. The cooled circulating water enters the spray tower and is sprayed out through the spray element; S4. The circulating water sprayed downwards contacts the rising flue gas again for heat exchange. The flue gas is cooled by heat exchange and then discharged into the chimney. The heated air in the heat exchange box enters the heat exchange accessories for heat exchange and then is discharged through the chimney. S5. After roasting is completed, the material is discharged from the bottom of the roasting furnace into the screw conveyor and transported to the fluidized bed. The second blower blows air into the fluidized bed and the heated air is discharged through the air outlet at the top of the second dust collector and enters the heat exchange accessory for heat exchange.

[0017] The beneficial effects of the present invention are: (1) The present invention can perform preliminary dust removal on the flue gas after the roasting of aluminum hydroxide. After the dust removal and separation, the hot alumina particles are transported to the fluidized bed through a screw conveyor. After the alumina particles come into contact with the gas in the fluidized bed, the gas is heated. The hot gas is introduced into the heat exchange accessory, thereby realizing the utilization of the heat of the alumina particles in the flue gas.

[0018] (2) The present invention can bring the flue gas after preliminary dust removal into contact with circulating water. The water vapor in the flue gas contacts the water to achieve phase change, converting the latent heat into the heat of the circulating water to the greatest extent. The circulating water exchanges heat with the heat pipe in the heat exchange box. The gas in the heat pipe is heated and transported to the heat exchange accessories, thereby realizing the utilization of the heat of the water vapor in the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 It is a structural diagram of Example 1 of the specific implementation method of the present invention.

[0021] Figure 2 It is a schematic diagram of the structure of an aeration component according to a specific embodiment of the present invention.

[0022] In the figure, 1-first fan, 2-second dust collector, 3-second blower, 4-feeding pipe, 5-screw conveyor, 6-fluidized bed, 7-seventh pipeline, 8-roasting furnace, 9-second return pipe, 10-second material valve, 11-first return pipe, 12-first material valve, 13-first dust collector, 14-first pipeline, 15-second pipeline, 16-spraying element, 17-drain pipe, 18-aeration element, 181-aeration plate, 182-aeration pipe, 19-circulating water pump, 20-fourth pipeline, 21-heat exchange box, 22-fifth pipeline, 23-heat exchange accessories, 24-sixth pipeline, 25-second fan, 26-chimney, 27-heat pipe, 28-first blower, 29-air inlet, 30-third pipeline, 31-spray tower, 32-air outlet. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0024] Example 1 Combine Figure 1 The present invention provides a waste heat recovery device for a high-temperature alumina roasting furnace, comprising a roasting furnace 8, wherein the smoke outlet of the roasting furnace 8 is connected to the air inlet of a first dust collector 13, the air outlet at the top of the first dust collector 13 is connected to an aeration member 18 in a spray tower 31 through a first pipeline 14, the air outlet at the top of the spray tower 31 is connected to a chimney 26 through a second pipeline 15, a spray member 16 is provided just above the aeration member 18, the water inlet end of the spray member 16 is connected to the water outlet end of a heat dissipation pipe 27 through a third pipeline 30, the spray member 16 is divided into three groups, each group of the spray member 16 includes a plurality of spray heads, the heat dissipation pipe 27 is an S-shaped heat dissipation pipe and is located in a closed heat exchange box 21, the water inlet end of the heat dissipation pipe 27 is connected to the water outlet end of a heat dissipation pipe 27 through a fourth pipeline 20 The lower part of the spray tower 31 is connected, and the upper and lower end surfaces of the heat exchange box 21 are respectively provided with an air inlet 29 and an air outlet 32. The air inlet 29 is connected to the first blower 28 through a pipeline, and the air outlet 32 is connected to the air inlet of the heat exchange accessory 23 through the fifth pipeline 22, and the air outlet of the heat exchange accessory 23 is connected to the second pipeline 15 through the sixth pipeline 24; a screw conveyor 5 is provided below the roasting furnace 8, and the feed port of the screw conveyor 5 is located directly below the discharge port at the bottom of the roasting furnace 8, and the discharge port of the screw conveyor 5 is connected to the feed end of the fluidized bed 6 through the feeding pipe 4, and the air outlet on the side of the fluidized bed 6 is connected to the second dust collector 2, and the air outlet at the top of the second dust collector 2 is connected to the fifth pipeline 22 through the seventh pipeline 7.

[0025] The discharge end at the bottom of the first dust collector 13 of the present invention is connected to the first return pipe 11 and the second return pipe 9. The end of the first return pipe 11 is connected to the roasting furnace 8, and the end of the second return pipe 9 is connected to the feed port of the screw conveyor 5. The first return pipe 11 is provided with a first valve 12, and the second return pipe 9 is provided with a second valve 10. The function is that in the early stage of roasting, due to insufficient roasting of aluminum hydroxide, some aluminum hydroxide particles are carried out with the flue gas. At this time, the first valve 12 is opened and the second valve 10 is closed to return the captured aluminum hydroxide particles to the roasting furnace 8. When the roasting process is stable, the flue gas carries out aluminum oxide particles. At this time, the first valve 12 is closed and the second valve 10 is opened to send the captured aluminum oxide particles to the screw conveyor 5 and then transport them to the fluidized bed 6.

[0026] Combine Figure 2 The aeration element 18 of the present invention includes a hollow aeration plate 181 with a plurality of aeration tubes 182 disposed on its lower end. The aeration plate 181 is connected to the first pipeline 14. The aeration plate 181 increases the aeration area, and downward aeration increases the contact length between the gas and the liquid, thereby improving the heat exchange effect.

[0027] In the present invention, the seventh pipeline 7 is provided with a first fan 1, the sixth pipeline 24 is provided with a second fan 25, and the fourth pipeline 20 is provided with a circulating water pump 19, which respectively provide power to the gas or liquid in the pipeline.

[0028] The heat exchange accessory 23 of the present invention includes a heat exchange tube in the alkali solution preparation tank. The alkali solution preparation tank is suitable for the alkali dissolution stage of producing alumina by the Bayer process. The alkali dissolution needs to be carried out at high temperature. The present invention can preheat the alkali solution during preparation, effectively utilizing heat.

[0029] A drain pipe 17 is provided at the lower portion of the outer shell of the spray tower 31 of the present invention. Its function is that the conversion of water vapor into water will cause the water level of the circulating water in the spray tower 31 to increase. The drain pipe 17 provided by the present invention can discharge the high liquid level water for utilization, thereby saving water resources.

[0030] Example 2 A method for recovering waste heat from a high-temperature alumina roasting furnace, using the waste heat recovery device for a high-temperature alumina roasting furnace in Example 1, comprises the following steps: S1, aluminum hydroxide is fed into the calcining furnace 8 for calcination, and the flue gas after calcination enters the first dust collector 13; S2. The dust-removed flue gas enters the spray tower 31, which stores circulating water. The flue gas is sprayed out of the aeration element 18 and contacts the circulating water for heat exchange. S3, the circulating water after heat exchange enters the heat dissipation pipe 27 and is cooled by the first blower 28 after heat exchange. The cooled circulating water enters the spray tower 31 and is sprayed out through the spray element 16; S4. The circulating water sprayed downward contacts the rising flue gas again for heat exchange. The flue gas is cooled by heat exchange and discharged into the chimney 26. The heated air in the heat exchange box 21 enters the heat exchange accessory 23 for heat exchange and is discharged through the chimney 26. S5. After roasting is completed, the material is discharged from the bottom of the roasting furnace 8 into the screw conveyor 5 and transported to the fluidized bed 6. The second blower 3 blows air into the fluidized bed 6, and the heated air is discharged through the air outlet at the top of the second dust collector 2 and enters the heat exchange accessory 23 for heat exchange.

[0031] Although the present invention has been described in detail with reference to the accompanying drawings and in conjunction with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be easily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A waste heat recovery device for a high-temperature alumina roasting furnace, comprising a roasting furnace, wherein the smoke outlet of the roasting furnace is connected to the air inlet of a first dust collector, characterized in that: The air outlet at the top of the first dust collector is connected to the aeration part in the spray tower through the first pipeline, and the air outlet at the top of the spray tower is connected to the chimney through the second pipeline. A spray part is provided directly above the aeration part, and the water inlet end of the spray part is connected to the water outlet end of the heat dissipation pipe through the third pipeline. The heat dissipation pipe is located in the closed heat exchange box, and the water inlet end of the heat dissipation pipe is connected to the lower part of the spray tower through the fourth pipeline. The upper end face and the lower end face of the heat exchange box are respectively provided with an air inlet and an air outlet, the air inlet is connected to the first blower through a pipeline, the air outlet is connected to the air inlet of the heat exchange accessory through the fifth pipeline, and the air outlet of the heat exchange accessory is connected to the second pipeline through the sixth pipeline; a screw conveyor is provided under the roasting furnace, and the feed port of the screw conveyor is located directly below the discharge port at the bottom of the roasting furnace, and the discharge port of the screw conveyor is connected to the feed end of the fluidized bed through a feeding pipe, the air outlet on the side of the fluidized bed is connected to the second dust collector, and the air outlet at the top of the second dust collector is connected to the fifth pipeline through the seventh pipeline.

2. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: The discharge end at the bottom of the first dust collector is connected to the first return pipe and the second return pipe. The end of the first return pipe is connected to the roasting furnace, and the end of the second return pipe is connected to the feed port of the screw conveyor.

3. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 2, characterized in that: The first material return pipe is provided with a first material valve, and the second material return pipe is provided with a second material valve.

4. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: The aeration element comprises an aeration plate with a hollow structure. A plurality of aeration pipes are arranged on the lower end surface of the aeration plate. The aeration plate is connected to the first pipeline.

5. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: The seventh pipeline is provided with a first fan, the sixth pipeline is provided with a second fan, and the fourth pipeline is provided with a circulating water pump.

6. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: The heat dissipation pipe is an S-shaped or spiral heat dissipation pipe.

7. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: The spraying parts are divided into at least two groups, and each group of spraying parts includes a plurality of spraying heads.

8. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: The heat exchange accessories include heat exchange tubes in the alkali solution preparation tank.

9. The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1, characterized in that: A drain pipe is provided at the lower part of the outer shell of the spray tower.

10. A method for recovering waste heat from a high-temperature alumina roasting furnace, characterized in that: The waste heat recovery device for a high-temperature alumina roasting furnace according to claim 1 comprises the following steps: S1, aluminum hydroxide is fed into the roasting furnace for roasting, and the flue gas after roasting enters the first dust collector; S2. The flue gas after dust removal enters the spray tower, which stores circulating water. The flue gas is sprayed out from the aeration element and contacts the circulating water for heat exchange. S3, the circulating water after heat exchange enters the heat dissipation pipe and exchanges heat with the first blower and is cooled. The cooled circulating water enters the spray tower and is sprayed out through the spray element; S4. The circulating water sprayed downwards contacts the rising flue gas again for heat exchange. The flue gas is cooled by heat exchange and then discharged into the chimney. The heated air in the heat exchange box enters the heat exchange accessories for heat exchange and then is discharged through the chimney. S5. After roasting is completed, the material is discharged from the bottom of the roasting furnace into the screw conveyor and transported to the fluidized bed. The second blower blows air into the fluidized bed and the heated air is discharged through the air outlet at the top of the second dust collector and enters the heat exchange accessory for heat exchange.

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