A waste heat utilization system and method based on alumina production

Abstract

The application provides a waste heat utilization system based on alumina production, which comprises a heat pump unit, a preheating desalted water tank and a heating desalted water tank; the input end of the heat pump unit is used for connecting the end of a multi-effect evaporator in alumina production, so as to recover the waste heat of exhaust steam generated in the last effect in the process of producing alumina by the multi-effect evaporator; the first output end of the heat pump unit is connected with the heating desalted water tank, the preheating desalted water tank is connected with the heating desalted water tank through a pipeline, and the preheating desalted water tank is used for providing desalted water; the heat pump unit is used for transmitting the waste heat of exhaust steam to the heating desalted water tank, and heating the desalted water of the heating desalted water tank by using the waste heat of exhaust steam. The system of the application utilizes the characteristic that the desalted water needs to be heated when being added into a desalted water receiver, for example, an oxygen removal tank, and uses the waste heat of exhaust steam at the end of the multi-effect evaporator in alumina production to heat the desalted water of the heating desalted water tank, so that the resources are effectively utilized and the economic benefits are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste heat utilization, and particularly relates to a waste heat utilization system and method based on alumina production. BACKGROUND

[0002] Alumina is a high-hardness compound and is widely used in industry and various fields. A multi-effect evaporator is used in alumina production. A large amount of waste heat is generated in the last effect in the process of producing alumina by using the multi-effect evaporator.

[0003] However, in the related art, the large amount of waste heat generated in the last effect is not effectively utilized, which causes great waste of resources and increases the cost. SUMMARY

[0004] To solve or partially solve the technical problem that a large amount of waste heat generated in the process of producing alumina by using the multi-effect evaporator is not effectively utilized in the related art, thereby causing great waste of resources, the present application provides a waste heat utilization system and method based on alumina production.

[0005] In a first aspect, the present application provides a waste heat utilization system based on alumina production, comprising a heat pump unit, a preheating desalted water tank and a heating desalted water tank.

[0006] The input end of the heat pump unit is used to connect the last end of the multi-effect evaporator for alumina production, so as to recover the waste heat of the last effect generated in the process of producing alumina by using the multi-effect evaporator.

[0007] The first output end of the heat pump unit is connected to the heating desalted water tank.

[0008] The preheating desalted water tank is connected to the heating desalted water tank through a pipeline, and the preheating desalted water tank is used to provide desalted water.

[0009] The heat pump unit is used to transmit the waste heat to the heating desalted water tank, and the waste heat is used to heat the desalted water of the heating desalted water tank. The heating desalted water tank is connected to a desalted water receiver through a pipeline.

[0010] In the above scheme, the system further comprises a heating pipeline, the second output end of the heat pump unit is connected to the heating pipeline, a first butterfly valve is arranged on the heat pump unit, the first butterfly valve is used to switch the output path of the heat pump unit, so as to realize switching output of the heat pump unit from the first output end or the second output end; when the heat pump unit outputs from the second output end, the heat pump unit is used to transmit the waste heat to the heating pipeline for heating.

[0011] In the scheme, the first butterfly valve is used for adjusting the heat pump unit to output from the second output end in the heating period, and is also used for adjusting the heat pump unit to output from the first output end in the non-heating period.

[0012] In the scheme, the system further comprises a steam supply pipeline, a pipeline block plate and a second butterfly valve. The steam supply pipeline is also used for connecting the end of the multiple-effect evaporator in the alumina production and is bypassed with the input end of the heat pump unit. The second butterfly valve is connected between the end of the multiple-effect evaporator and the input end of the heat pump unit and is used for, when turned on, delivering the waste heat of the exhaust steam of the end of the multiple-effect evaporator to the input end of the heat pump unit. The pipeline block plate is connected between the end of the multiple-effect evaporator and the steam supply pipeline and is used for, when closed, blocking the flow between the end of the multiple-effect evaporator and the steam supply pipeline, and for, when opened, delivering the waste heat of the exhaust steam of the end of the multiple-effect evaporator to the steam supply pipeline.

[0013] In the scheme, the system further comprises a cooling tower and a cooling unit. The cooling tower and the cooling unit are respectively connected to the heat pump unit and are used for providing a vacuum environment for the heat pump unit. The heat pump unit is further used for connecting the cooling tower in the heating period and connecting the cooling unit in the non-heating period.

[0014] In the scheme, the system further comprises a first desalted water supply pump. The first desalted water supply pump is connected to the pipeline between the preheating desalted water tank and the heating desalted water tank and is used for transmitting the desalted water in the preheating desalted water tank to the heating desalted water tank.

[0015] In the scheme, the desalted water receiver comprises a deaerated water tank. The system further comprises a second desalted water supply pump. The second desalted water supply pump is connected to the pipeline between the heating desalted water tank and the deaerated water tank. The first end of the second desalted water supply pump is connected to the heating desalted water tank as an inlet main pipe. The second end of the second desalted water supply pump is connected to the deaerated water tank as an outlet main pipe. The second desalted water supply pump is used for transmitting the heated desalted water in the heating desalted water tank to the deaerated water tank.

[0016] In the scheme, the system further comprises a return water pipe and a third butterfly valve. The third butterfly valve is connected to the return water pipe. The first end of the return water pipe is connected to the input end of the heat pump unit. The second end of the return water pipe is respectively connected to the first end of the second desalted water supply pump, the second end of the second desalted water supply pump and the heating desalted water tank. The third butterfly valve is used for being opened when the heat pump unit fails, so as to realize the continuous supply of the desalted water from the heating desalted water tank to the desalted water receiver.

[0017] In the second aspect of the present application, a waste heat utilization method based on the alumina production is provided. The method is used in the system as above and comprises the following steps.

[0018] obtaining a heating period;

[0019] confirming a heating period and a non-heating period according to the heating period;

[0020] in the heating period, controlling the first butterfly valve to output the heat pump unit from the second output end for transmitting the waste steam waste heat to the heating pipeline for heating;

[0021] in the non-heating period, controlling the first butterfly valve to output the heat pump unit from the first output end for transmitting the waste steam waste heat to the heating desalted water tank.

[0022] In the above scheme, if the heat pump unit is detected to be damaged, the third butterfly valve is opened to realize continuous supply of desalted water from the heating desalted water tank to the desalted water receiver.

[0023] The application provides a waste heat utilization system and method based on alumina production, wherein the system comprises a heat pump unit, a preheating desalted water tank and a heating desalted water tank; the input end of the heat pump unit is used for connecting the end of a multi-effect evaporator in alumina production, for recycling waste steam waste heat generated in the last effect in the process of producing alumina by the multi-effect evaporator; the first output end of the heat pump unit is connected with the heating desalted water tank, the preheating desalted water tank is connected with the heating desalted water tank through a pipeline, and the preheating desalted water tank is used for providing desalted water; the heat pump unit is used for transmitting the waste steam waste heat to the heating desalted water tank and heating the desalted water of the heating desalted water tank by using the waste steam waste heat; and the heating desalted water tank is connected with a desalted water receiver through a pipeline. The system of the application connects the end of the multi-effect evaporator in alumina production to the heating desalted water tank through the heat pump unit, utilizes the characteristic that the desalted water needs to be heated when being added to the desalted water receiver, for example, an oxygen removal tank, and uses the waste steam waste heat of the end of the multi-effect evaporator in alumina production to heat the desalted water of the heating desalted water tank, so that resources are effectively utilized, waste of resources is avoided, and cost is saved.

[0024] The method of the present application obtains a heating period; confirms a heating period and a non-heating period according to the heating period; in the heating period, controls the first butterfly valve to output the heat pump unit from the second output end, for transmitting the waste steam waste heat to the heating pipeline for heating; in the non-heating period, controls the first butterfly valve to output the heat pump unit from the first output end, for transmitting the waste steam waste heat to the heating desalted water tank. Through the method of the present application, the waste steam waste heat at the end of the multiple-effect evaporator in the alumina production can be effectively controlled to be used for heating in the heating period, and the waste steam waste heat at the end of the multiple-effect evaporator in the alumina production can be used for heating the desalted water of the heating desalted water tank in the non-heating period, resources are effectively utilized, and the existing system can be directly improved with low improvement cost, the utilization efficiency in the non-heating period is further improved without affecting the original heating, and the cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the present application. Furthermore, the same reference numerals are used throughout the drawings to denote the same components. In the drawings:

[0026] Figure 1 a block diagram of a waste heat utilization system based on alumina production according to an embodiment of the present application is shown;

[0027] Figure 2 a flow chart of a waste heat utilization method based on alumina production according to an embodiment of the present application is shown;

[0028] Figure 3 a block diagram of a waste heat utilization system based on alumina production according to an application embodiment of the present application is shown;

[0029] 1-heat pump unit; 2-preheating desalted water tank; 3-heating desalted water tank; 4-heating pipeline; 5-first butterfly valve; 6-desalted water receiver; 7-steam supply pipeline; 8-pipeline blocking plate; 9-second butterfly valve; 10-first desalted water supply pump; 11-second desalted water supply pump; 12-backwater pipe; 13-third butterfly valve; DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be accurately conveyed to those skilled in the art.

[0031] Alumina is a high hardness compound, which is widely used in industry and various fields. The production of alumina uses multi-effect evaporator, and a large amount of steam exhaust waste heat is generated in the last effect in the process of producing alumina by using multi-effect evaporator.

[0032] However, in the related art, the large amount of steam exhaust waste heat generated in the last effect is not effectively utilized, which causes great waste of resources and increases the cost.

[0033] For example, the steam exhaust waste heat of the last effect of the multi-effect evaporator in the alumina production process is usually directly discharged into the air, causing a large amount of waste of waste heat. In the related art, the technology is improved, that is, the waste heat is used for heating. For example, in actual application, an A area has a heat station responsible for winter heating of Shan Alumina and surrounding dormitory area. Two absorption heat pump units are built in the station, which uses steam as a driving heat source to recover the steam exhaust waste heat of the last effect of the multi-effect evaporator in the alumina production process to heat the heating circulating water. One heat pump unit is always on during the heating period, and the two heat pump units are idle during the non-heating period. Therefore, the steam exhaust waste heat can be effectively used for heating. However, the heating time is limited in a year, and the production of alumina by using multi-effect evaporator is carried out all year round, so the steam exhaust waste heat cannot be effectively utilized.

[0034] In order to solve the above problems, the application discloses a waste heat utilization system based on alumina production, which fully considers the characteristic that the desalted water needs to be heated in the process of being supplied to the deaerator, and supplies the waste heat generated by the production of alumina by using multi-effect evaporator to the process of desalted water. Specifically, in actual application, the 6# and 7# boilers of a thermal power plant need to supply about 400-600t / h of desalted water, most of the time is operated under the condition of 600t / h, the initial temperature is about 54℃, which is supplied to the 6# and 7# boilers by a desalted water pump house, most of the desalted water is supplied to the deaerator, and needs to be heated to about 160℃ by steam extracted by a steam turbine generator set, which needs to consume a large amount of new steam. The steam exhaust waste heat of the last effect of the multi-effect evaporator in the alumina production process is wasted during the non-heating period, so the application combines the two, and uses the steam exhaust waste heat of the last effect of the multi-effect evaporator in the alumina production process to heat the desalted water supply.

[0035] Specifically, the application discloses a waste heat utilization system based on alumina production, which relates to a new energy-saving process of a self-provided power plant based on waste heat utilization of an alumina production process, and the corresponding specific application field can be a new process field of waste heat utilization and energy saving of a self-provided power plant.

[0036] According to a first aspect of the application, the application provides a waste heat utilization system based on alumina production, as shown in Figure 1 Figure 1 ​A block diagram of a waste heat utilization system based on alumina production according to one embodiment of the application is shown. The system of the application comprises a heat pump unit 1, a preheating desalted water tank 2 and a heating desalted water tank 3. The heat pump unit 1 of the application can be two groups, or multiple groups according to actual application; the preheating desalted water tank 2 of the application can be three groups, or multiple groups according to actual application; the heating desalted water tank 3 of the application can be one group, or multiple groups according to actual application.

[0037] The input end of the heat pump unit 1 of the application is used to connect the end of the multiple-effect evaporator of alumina production, for recovering the waste heat of the exhaust steam generated in the last effect in the process of producing alumina by the multiple-effect evaporator; the first output end of the heat pump unit 1 is connected to the heating desalted water tank 3, the preheating desalted water tank 2 is connected to the heating desalted water tank 3 through a pipeline, and the preheating desalted water tank 2 is used to provide desalted water; the heat pump unit 1 is used to transmit the waste heat of the exhaust steam to the heating desalted water tank 3, and to heat the desalted water of the heating desalted water tank 3 by using the waste heat of the exhaust steam; the heating desalted water tank 3 is connected to the desalted water receiver 6 through a pipeline.

[0038] The system of the application uses the waste heat of the exhaust steam of the end of the multiple-effect evaporator of alumina production to heat the desalted water of the heating desalted water tank 3 by connecting the end of the multiple-effect evaporator of alumina production to the heating desalted water tank 3 through the heat pump unit 1, and taking advantage of the characteristic that the desalted water needs to be heated when being added to the desalted water receiver 6, such as an oxygen removal tank, which effectively utilizes resources, avoids waste of resources, and saves costs. Moreover, the application can fully utilize existing idle equipment and facilities, integrate process flows, exchange heat sources and cold sources, avoid exhaust of waste heat of the exhaust steam, and improve the temperature of the cold source.

[0039] In one embodiment of the application, the system of the application further comprises a heating pipeline 4, and the second output end of the heat pump unit 1 is connected to the heating pipeline 4; a first butterfly valve 5 is arranged on the heat pump unit 1, and the first butterfly valve 5 is used to switch the output path of the heat pump unit 1, so as to realize switching output of the heat pump unit 1 from the first output end or the second output end; when the heat pump unit 1 outputs from the second output end, the heat pump unit 1 is used to transmit the waste heat of the exhaust steam to the heating pipeline 4 for heating.

[0040] In one embodiment of the application, the first butterfly valve 5 is used to adjust the heat pump unit 1 to output from the second output end during the heating period; and is also used to adjust the heat pump unit 1 to output from the first output end during the non-heating period.

[0041] By the above system of the present application, the first butterfly valve 5 can be switched according to the heating period and the non-heating period, so that the system of the present application can be directly applied to the scheme of using the waste heat of the exhaust steam at the end of the multiple-effect evaporator for heating, which can effectively reduce the conversion cost without making too many modifications to the equipment. Moreover, the first butterfly valve 5 can be used for switching control, and the waste heat of the exhaust steam generated in the process of producing aluminum oxide by the multiple-effect evaporator is fully utilized, which will not cause resource waste in any period, further reducing the production cost and improving the economic benefit.

[0042] In an embodiment of the present application, the system further comprises a steam supply pipeline 7, a pipeline blocking plate 8 and a second butterfly valve 9. The steam supply pipeline 7 is also used to connect the end of the multiple-effect evaporator for producing aluminum oxide and is bypassed with the input end of the heat pump unit 1. The second butterfly valve 9 is connected between the end of the multiple-effect evaporator and the input end of the heat pump unit 1 and is used to deliver the waste heat of the exhaust steam at the end of the multiple-effect evaporator to the input end of the heat pump unit 1 when it is turned on in the forward direction. The pipeline blocking plate 8 is connected between the end of the multiple-effect evaporator and the steam supply pipeline 7 and is used to block the flow between the end of the multiple-effect evaporator and the steam supply pipeline 7 when it is closed. When it is opened, the waste heat of the exhaust steam at the end of the multiple-effect evaporator is delivered to the steam supply pipeline 7.

[0043] By the above system of the present application, the steam supply pipeline 7, the pipeline blocking plate 8 and the second butterfly valve 9 are added, which can temporarily deliver the waste heat of the exhaust steam at the end of the multiple-effect evaporator to the steam supply pipeline 7 when the heating pipeline 4 of the heating period needs to be maintained or the heat pump unit 1, the preheating desalted water tank 2 and the heating desalted water tank 3 in the system of the present application need to be repaired in the non-heating period, so as to further avoid the waste of the waste heat of the exhaust steam. At the same time, this embodiment can also be applied to the scene where the waste heat of the exhaust steam needs to be directly utilized. When the rear end needs to directly utilize the waste heat of the exhaust steam, the pipeline blocking plate 8 can be controlled to be opened for a long time, and the second butterfly valve 9 can be controlled to continuously supply steam to the steam supply pipeline 7, which can improve the utilization efficiency of the waste heat of the exhaust steam, avoid resource waste, further reduce the production cost and improve the economic benefit.

[0044] In an embodiment of the present application, the system further comprises a cooling tower and a cooling unit, which are respectively connected to the heat pump unit 1 for providing a vacuum environment for the heat pump unit 1. The heat pump unit 1 is further used to connect the cooling tower in the heating period and connect the cooling unit in the non-heating period.

[0045] Through the above-mentioned system of the present application, the present application provides two sets of independent and adaptive cooling schemes for the heating period and the non-heating period, especially for the vacuum pump cooling water of the heat pump unit 1, in the heating period, the cooling tower is used for cooling, and in the non-heating period, the water chiller is used for cooling, so as to solve the problem of cooling of the vacuum pump cooling water throughout the year. Therefore, the applicability is further improved by using the method of the present application.

[0046] In an embodiment of the present application, the system further comprises a first desalted water supply pump 10 connected to the pipeline between the preheating desalted water tank 2 and the heating desalted water tank 3, for transmitting the desalted water in the preheating desalted water tank 2 to the heating desalted water tank 3.

[0047] The first desalted water supply pump 10 of the present application can have three, of which the specifications can be: two Q = 470 m 3 / h, H = 60 m; one Q = 250 m 3 / h, H = 60 m. The pipeline for transmitting the desalted water in the preheating desalted water tank 2 to the heating desalted water tank 3 of the present application can use seamless steel pipe.

[0048] Through the above-mentioned system of the present application, the present application provides the first desalted water supply pump 10 for the transmission of desalted water, which can stably and effectively transmit the desalted water of the preheating desalted water tank 2 to the heating desalted water tank 3 for heating.

[0049] In an embodiment of the present application, the desalted water receiver 6 comprises a deaerated water tank, of course, other desalted water receivers 6 can be provided according to needs, wherein the desalted water receiver 6 of the present application is required to be added after heating, and not all desalted water receivers 6. The system of the present application further comprises a second desalted water supply pump 11 connected to the pipeline between the heating desalted water tank 3 and the deaerated water tank, the first end of the second desalted water supply pump 11 being connected to the heating desalted water tank 3 as an inlet main pipe, and the second end of the second desalted water supply pump 11 being connected to the deaerated water tank as an outlet main pipe; for transmitting the heated desalted water in the heating desalted water tank 3 to the deaerated water tank.

[0050] The second desalted water supply pump 11 of the present application can have five, which can be adjusted according to the actual needs of the system.

[0051] Through the above-mentioned system of the present application, the present application transmits the heated desalted water in the heating desalted water tank 3 to the deaerated water tank by using the second desalted water supply pump 11, for use of the deaerated water tank.

[0052] In a specific application, the thermal power plant 6# and 7# boiler needs to supply about 400-600t / h of desalination water, most of the time in the 600t / h operating condition, the initial temperature is about 54℃, supplied to the 6# and 7# furnace by the desalination water pump house, most of the desalination water is supplied to the deaerator, and needs to be heated to about 160℃ by the steam extracted by the steam turbine generator set, therefore, the second desalination water supply pump 11 of the present application can withstand the hot water pump of 160℃ temperature.

[0053] In an embodiment of the present application, the system further comprises a return pipe 12 and a third butterfly valve 13, the third butterfly valve 13 is connected to the return pipe 12, the first end of the return pipe 12 is connected to the input end of the heat pump unit 1, the second end is connected to the first end of the second desalination water supply pump 11, the second end of the second desalination water supply pump 11 and the heating desalination water tank 3 respectively, and the third butterfly valve 13 is used to open when the heat pump unit 1 fails, to realize continuous supply of desalination water from the heating desalination water tank 3 to the desalination water receiver 6.

[0054] Through the above-mentioned system of the present application, the present application adds an emergency mechanism, when the heat pump unit 1 fails and cannot heat and transmit the desalination water to the desalination water receiver 6, the first end of the second desalination water supply pump 11, the second end of the second desalination water supply pump 11 and the desalination water in the heating desalination water tank 3 can be heated and transmitted to the desalination water receiver 6 by using the return pipe 12 and the third butterfly valve 13 of the present application and opening the third butterfly valve 13. Further avoid the waste of resources, at the same time, the present application can also temporarily open the third butterfly valve 13 during the repair to realize the backflow, avoid the waste of resources during the repair of the heat pump unit 1.

[0055] The above discloses the content of the first aspect of the present application, and the content of the second aspect of the present application will be disclosed below. According to the second aspect of the present application, a waste heat utilization method based on alumina production is provided, as shown in Figure 2 Figure 2 A flow chart of a waste heat utilization method based on alumina production according to an embodiment of the present application is shown. The method of the present application utilizes the above-mentioned system, specifically, the above-mentioned system of the present application is provided with a processor, wherein the processor can control the opening and closing of each butterfly valve, therefore, the following method of the present application can be applied in the processor, the method comprises steps S210-S240:

[0056] Step S210: obtaining a heating period.

[0057] The heating period can be automatically set according to the predetermined season, for example, winter is the heating period, and other times are non-heating periods. At the same time, the heating period can also be set according to the actual needs of the user, for example, the user can set a specific time point as the heating period.

[0058] Step S220: confirming the heating period and the non-heating period according to the heating period.​

[0059] The processor can confirm the heating period and the non-heating period according to the heating period, and perform step S230 and step S240 based on the heating period and the non-heating period respectively.

[0060] Step S230: In the heating period, the first butterfly valve 5 is controlled to output the heat pump unit 1 from the second output end for transmitting the waste steam waste heat to the heating pipeline 4 for heating.

[0061] When in the heating period, the processor can control the first butterfly valve 5 to output the heat pump unit 1 from the second output end for transmitting the waste steam waste heat to the heating pipeline 4 for heating.

[0062] Further, if the butterfly valve used by the user cannot be controlled by the processor, step S230 can also be, in the heating period, sending a prompt signal to the display to remind the user to open the first butterfly valve 5.

[0063] Step S240: In the non-heating period, the first butterfly valve 5 is controlled to output the heat pump unit 1 from the first output end for transmitting the waste steam waste heat to the heating desalted water tank 3.

[0064] When in the non-heating period, the processor can control the first butterfly valve 5 to output the heat pump unit 1 from the first output end for transmitting the waste steam waste heat to the heating desalted water tank 3.

[0065] Therefore, the method of the present application can effectively control the waste steam waste heat at the end of the multiple-effect evaporator in the alumina production in the heating period for heating, and use the waste steam waste heat at the end of the multiple-effect evaporator in the alumina production in the non-heating period for heating the desalted water in the heating desalted water tank 3, effectively utilize the resources, and can be improved directly on the existing system, with low improvement cost, further improve the utilization efficiency in the non-heating period without affecting the original heating, and reduce the cost.

[0066] In an embodiment of the present application, if it is detected that the heat pump unit 1 is damaged, the third butterfly valve 13 is opened to continuously supply desalted water from the heating desalted water tank 3 to the desalted water receiver 6.

[0067] With the method, when the heat pump unit 1 fails to heat and transmit the desalted water to the desalted water receiver 6, the backwater pipe 12 and the third butterfly valve 13 of the application are used, and the third butterfly valve 13 is opened to heat and transmit the desalted water in the first end of the second desalted water supply pump 11, the second end of the second desalted water supply pump 11 and the heating desalted water tank 3 to the desalted water receiver, further avoiding the waste of resources.

[0068] The specific embodiments of the application are introduced above, and the application embodiments of the application are further introduced next.

[0069] As shown in Figure 3 , Figure 3 A block diagram of a waste heat utilization system based on alumina production according to an application embodiment of the application is shown. It is found in the implementation of the application that there is a heat station in A area for winter heating of Shanxi Aluminium and surrounding dormitory areas. Two absorption heat pump units are built in the station to recover waste heat of exhaust steam of the last effect evaporator in the alumina production process to heat the heating circulating water. One heat pump unit is always on during the heating period, and the two heat pump units are idle during the non-heating period. The 6# and 7# boilers of the thermal power plant in B area need to supply about 400-600 t / h of desalted water, and most of the time is operated at 600 t / h, with an initial temperature of about 54℃. The desalted water is supplied to the 6# and 7# boilers from the desalted water pump house, and most of the desalted water is supplied to the deaerator, which needs to be heated to about 160℃ by steam extracted from the low-pressure steam turbine, consuming a large amount of new steam.

[0070] However, the above two areas work independently and do not cooperate. In summary, one heat pump unit in A area is idle all year round, causing waste of equipment; the waste heat of exhaust steam of the last effect evaporator in the alumina production process is idle in the non-heating season, causing waste of resources; and the desalted water of the thermal power plant in B area is operated at 400-600 t / h all year round, with sufficient cold source.

[0071] The application embodiment of the application can make full use of the existing idle equipment and facilities, integrate the process flow, exchange the heat source and the cold source, avoid exhaust of waste heat, and improve the temperature of the cold source.

[0072] The application utilizes three water tanks (4#, 7# and 8#) in the desalted water area on the north side of the 6# and 7# unit plant of the thermal power plant in B area, which are transformed into preheating desalted water tanks. Three desalted water supply pumps (two Q=470 m3 / h, H=60 m, and one Q=250 m3 / h, H=60 m) are arranged in the water treatment plant pump house to deliver the desalted water to the east line heat station.

[0073] The pipeline for delivering the desalted water from the water treatment plant pump house to the east line heat station is made of seamless steel pipe, and the old pipeline in the old thermal power plant is used. (II) Steam pipeline about 160 meters, using the old pipe section need to take measures to isolate the steam system. Desalination water pipeline to the east line heat station, respectively, with the two heat pump unit water inlet pipeline fork, using the first butterfly valve and the original system isolation. From the two heat pump unit outlet pipe respectively connected backwater pipe, using the third butterfly valve and the original system isolation, combined for DN350 backwater main pipe, laid to the existing south desalination water supply pump outlet pipe, and set aside to desalination water tank and water supply pump inlet pipe. Desalination water pump house now has 5 desalination water supply pump replaced with hot water pump, unchanged specifications.

[0074] Among them, the heat pump unit vacuum pump cooling water of the east line heat station (corresponding to the A area) now uses the method of natural cooling of the circulating water pool, a cooling tower and a cold water unit are newly installed, the cooling tower is used for cooling during the heating period, and the cold water unit is used for cooling during the non-heating period, so as to solve the cooling water cooling problem of the vacuum pump throughout the year.

[0075] Through the above method of the present application, resources can be effectively utilized, resource waste can be avoided, cost can be saved, and economic benefits can be improved. Through accounting, from January to September 2024, the heat pump unit of the east line heat station consumes 67657t of new steam, which is equivalent to 196844GJ of heat, and the desalination water of the B area absorbs 373156GJ of heat. Through this new process, 176311GJ of waste heat is utilized, and the economic benefit is 811.03 million yuan according to the unit price of heating heat of 46 yuan / GJ.

[0076] Among them, the A area of the present application can generate a large amount of waste heat through two production processes, one is the roasting furnace flue gas, and the other is the evaporation system exhaust steam. The comparison and calculation of the two waste heat utilization schemes are as follows:

[0077] 1. Calculation of roasting furnace flue gas waste heat heating desalination water:

[0078] High-temperature flue gas heating desalination water can be realized by installing a flue gas-water heat exchanger on the flue, and the simple calculation is as follows:

[0079] The flue gas amount is Q = 12 x 104Nm 3 / h, and the flue gas temperature is 160℃

[0080] The flue gas density p = 1.32 kg / Nm 3 , and the specific heat of flue gas C = 0.24 kcal / kg.℃

[0081] When the flue gas is reduced from 160℃ to 100℃, the heat release is:

[0082] QBY = 120000 * 1.32 * 0.24 * (160-100) = 228 x 104kcal / h

[0083] The desalted water quantity fluctuation range of the thermal power plant is 400-600 t / h, and the value is 420 t / h, and the heat required when heating from 54°C to 83°C is:

[0084] QHS = 420 * 1000 * 1 * (83-54) = 1218 * 104 kcal / h

[0085] According to the above calculation, in the case that the flue gas temperature is reduced by 60°C, the heat provided by the calcination furnace flue gas is only (228 / 1218) * 100% ≈ 18.7% of the required heat, which cannot meet the heat required for heating the desalted water of the thermal power plant.

[0086] 2. Evaporation waste heat utilization calculation:

[0087] The heat pump unit has been successfully operated for nearly three years (heating season) in the A area using evaporation waste heat. The heat supply capacity of the unit can reach the value in the above table, i.e. (30000 KW * (860 Kcal / KW)) = 2580 * 104 kcal / h, which can meet the heat required for heating the maximum 781 t / h of heating water from 50°C to 83°C or above. The heat pump manufacturer has carried out checking calculation on the unit according to the working condition of the desalted water, and confirms that the heat pump unit can meet the heating of 400-600 t / h of desalted water from 54°C to 90.7°C.

[0088] 3. Comparison of schemes

[0089] Through the above two waste heat utilization heat calculation comparisons, the calcination furnace flue gas waste heat cannot meet the heat requirement, while the evaporation waste heat can achieve the purpose of the project. Therefore, the heat pump unit is adopted in the present application to absorb the heat generated by the evaporation waste heat to heat the desalted water for the boiler of the thermal power plant.

[0090] 4. At the same time, the present application is based on the above scheme and has been calculated. The heat pump manufacturer has carried out checking calculation on the unit according to the working condition of the desalted water, and confirms that the heat pump unit can meet the heating of 400-600 t / h of desalted water from 54°C to 90.7°C.

[0091] 60-110 t / h of desalted water enters the shaft seal heater as its cooling water. Since the higher the inlet water temperature, the less conducive to the condensation of the steam seal leakage, the maximum inlet water temperature of the shaft seal heater is not more than 85°C, and the working condition comparison calculation is as follows:

[0092] (1) Working condition one: heating from 54°C to 90.7°C. The desalted water (54°C) before preheating is transported to the shaft seal heater through the original water pump (Q = 100 m3 / h, H = 50 m, N = 22 kW) and pipeline, the total amount of desalted water is 600 t / h, and the water consumption of the shaft seal heater is 100 t / h, so the water quantity through the heat pump unit is 500 t / h. At this time, the heat raised by the desalted water through the heat pump:

[0093] Q1 = CMAt = 4.18 * 500 * 1000 * (90.7 - 54) = 7.67 * 107 kJ / h

[0094] (2) Case two: heated from 54℃ to 85℃. The total amount of desalinated water is 600t / h, all of which passes through the heat pump unit. At this time, the heat raised by the desalinated water through the heat pump:

[0095] Q2 = CMAt = 4.18 * 600 * 1000 * (85 - 54) = 7.77 * 107 kJ / h

[0096] (3) After checking with the heat pump manufacturer, the COP of the heat pump unit in case one is approximately 1.62, and the COP of the heat pump unit in case two is approximately 1.65.

[0097] In summary, the heating capacity and performance coefficient (cop) of the heat pump unit in case two are slightly higher than those in case one, so the energy saving benefit of case two is slightly higher than that of case one.

[0098] In summary, the desalinated water supplied by the thermal power plant to the deaerator of the boiler has an initial temperature of about 54℃, and needs to be heated to about 160℃ by steam extracted from the low-pressure turbine of the steam turbine generator set, consuming a large amount of new steam. The heat pump unit in the heat station is used to raise the desalinated water supplied by the thermal power plant to the boiler in the south area to above 85℃; for the alumina plant, because the heat pump unit consumes more evaporative exhaust steam throughout the year, it can alleviate the problem of insufficient cooling capacity of the evaporative cooling tower in summer and high load operation of the evaporative circulating water pump, reducing the operating cost of the alumina plant; due to the improvement of the evaporative cooling effect, the evaporative capacity can be improved, thereby improving the production capacity of the alumina plant. Through process modification, the existing resources in Area A and Area B are revitalized, the waste heat of the evaporative cooler on the east line is utilized, the desalinated water of the thermal power plant is heated, and new steam is saved.

[0099] Therefore, the scheme of the present application can therefore, the present application can utilize the above-mentioned industrial and mining combination system to utilize the waste heat of alumina production, which can effectively utilize resources, avoid waste of resources, save costs, and improve economic benefits.

[0100] In the specification provided herein, a large number of specific details are described. However, it can be understood that embodiments of the present application can be practiced without these specific details. In some examples, well-known methods, structures and techniques are not shown in detail in order not to obscure understanding of the present specification.

[0101] Similarly, it is to be understood that the embodiments of the present application can be placed into practice notwithstanding modifications to form yet further embodiments of the present application. As such, the terms and expressions of the foregoing description are used solely by way of the example thereof, but to the extent possible no limitation is intended to the details of the construction described herein other than as described in the claims. The foregoing description, for purposes of illustration and example, sets forth preferred embodiments of the present application. However, it is understood that the present application can be practiced in other specific forms that are not expressly described herein. Indeed, any and all combinations of features described herein can be implemented without departing from the scope of the present application. Accordingly, any and all variations from the preferred embodiments described herein that fall within the scope of the present application are intended to be embraced by the claims set forth below.

[0102] Those skilled in the art can appreciate that modules in the apparatus in the embodiments can be adaptively changed and disposed in one or more apparatuses different from the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and further can be divided into multiple sub-modules or sub-units or sub-components. Any combination of all the features disclosed in the specification (including the accompanying claims, abstract and drawings), and any method or apparatus so disclosed, can be taken in any combination unless otherwise explicitly stated (in particular, although specific embodiments can be discussed or shown above or below, unless otherwise explicitly stated each feature or combination of features can be replaced by alternative features serving the same, equivalent or similar purpose). Unless explicitly stated otherwise, each feature disclosed in the specification (including the accompanying claims, abstract and drawings) can be replaced by alternative features serving the same, equivalent or similar purpose.

[0103] Further, those skilled in the art could understand that although some embodiments herein include certain features rather than others included in other embodiments, the combination of features of different embodiments means to be within the scope of the present application and form different embodiments. For example, in the following claims, any one of the claimed embodiments can be used in any combination.

[0104] Various component embodiments of the present application can be implemented in hardware, or as software modules running in one or more processors, or in combinations thereof. As will be appreciated by one skilled in the art, a microprocessor or digital signal processor (DSP) can be used in practice to implement some or all of the functionality of some or all of the components of the gateway, proxy electronic device, system according to embodiments of the present application. The present application can also be implemented as a program of instructions for performing part or all of the methods described herein, e.g., a computer program and a computer program product. Such program of the present application can be stored on a computer readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, or provided on a carrier medium, or in any other form.

[0105] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps other than those listed in a claim. The word 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements. The application can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the system claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The use of the word 'at least' followed by a list of one or more items means that any item in the list can be present or there can be more than one of a certain item. The use of the terms 'first','second' and 'third', etc. does not limit the quantity and / or order of those terms. These terms are used to distinguish between two entities or steps involved with the application and are not necessarily used to describe a 'first','second' or 'third' or the like by their appearance or order of appearance in the claims or description.

[0106] Although preferred embodiments of the application have been described herein, additional changes and modifications can be suggested to one skilled in the art once given the benefit of the basic inventive concept. Accordingly, the scope of the present application is intended to embrace all such changes and modifications as fall within the scope of the appended claims.

[0107] The above-described embodiments are merely given as examples and are not intended to limit the scope of the present application. Various modifications made within the scope of the application based on the principles of the application should be considered as falling within the scope of the application.

Claims

1. A waste heat utilization system based on aluminum oxide production, characterized by, The system comprises a heat pump unit, a preheating desalted water tank and a heating desalted water tank. An input end of the heat pump unit is connected to an end of a multi-effect evaporator in an alumina production process, for recycling waste steam heat generated in the last effect of the multi-effect evaporator in the alumina production process. A first output end of the heat pump unit is connected to the heating desalted water tank. The preheating desalted water tank is connected to the heating desalted water tank through a pipeline, and the preheating desalted water tank is used to provide desalted water. The system further comprises a heating pipeline, and a second output end of the heat pump unit is connected to the heating pipeline. A first butterfly valve is arranged on the heat pump unit, and the first butterfly valve is used to switch an output path of the heat pump unit, so that the heat pump unit is switched to output from the first output end or the second output end. When the heat pump unit outputs from the second output end, the heat pump unit is used to transmit the waste steam heat to the heating pipeline for heating. The first butterfly valve is used to adjust the heat pump unit to output from the second output end during a heating period, and is also used to adjust the heat pump unit to output from the first output end during a non-heating period. The system further comprises a cooling tower and a cooling unit, and the cooling tower and the cooling unit are respectively connected to the heat pump unit, for providing a vacuum environment for the heat pump unit.

2. The system of claim 1, wherein, During the heating period, the heat pump unit is connected to the cooling tower, and during the non-heating period, the heat pump unit is connected to the cooling unit. The desalted water receiver comprises a deaerated water tank, and the system further comprises a second desalted water supply pump. The second desalted water supply pump is connected to a pipeline between the heating desalted water tank and the deaerated water tank. A first end of the second desalted water supply pump is connected to the heating desalted water tank as an inlet main pipe. A second end of the second desalted water supply pump is connected to the deaerated water tank as an outlet main pipe. The system further comprises a return water pipe and a third butterfly valve. The third butterfly valve is connected to the return water pipe. A first end of the return water pipe is connected to the input end of the heat pump unit. A second end of the return water pipe is respectively connected to the first end of the second desalted water supply pump, the second end of the second desalted water supply pump and the heating desalted water tank. The third butterfly valve is used to be opened when the heat pump unit fails, so that the heating desalted water tank continuously supplies desalted water to the desalted water receiver. The system further comprises a steam supply pipeline, a pipeline block plate and a second butterfly valve. The steam supply pipeline is also used to be connected to an end of a multi-effect evaporator in an alumina production process, and is bypassed to the input end of the heat pump unit. The second butterfly valve is connected between the end of the multi-effect evaporator and the input end of the heat pump unit. When the second butterfly valve is turned on, waste steam heat of the end of the multi-effect evaporator is transmitted to the input end of the heat pump unit. The pipeline block plate is connected between the end of the multi-effect evaporator and the steam supply pipeline. When the pipeline block plate is closed, the flow between the end of the multi-effect evaporator and the steam supply pipeline is blocked. When the pipeline block plate is opened, waste steam heat of the end of the multi-effect evaporator is transmitted to the steam supply pipeline.

3. The system of claim 2, wherein, The system further comprises a first desalted water supply pump connected to the pipeline between the preheating desalted water tank and the heating desalted water tank, for transmitting the desalted water in the preheating desalted water tank to the heating desalted water tank.

4. A method for utilizing waste heat based on alumina production, characterized by, The method is used for the system as claimed in claim 3, and the method comprises: acquiring a heating period; confirming a heating period and a non-heating period according to the heating period; in the heating period, controlling the first butterfly valve to output the heat pump unit from the second output end, for transmitting the exhaust steam waste heat to the heating pipeline for heating; in the non-heating period, controlling the first butterfly valve to output the heat pump unit from the first output end, for transmitting the exhaust steam waste heat to the heating desalted water tank.

5. The method of claim 4, wherein, if the heat pump unit is detected to be damaged, the third butterfly valve is opened to realize continuous supply of desalted water from the heating desalted water tank to the desalted water receiver.

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