Waste heat utilization system and method based on aluminum oxide production

Abstract

The invention provides a waste heat utilization system based on aluminum oxide production. The waste heat utilization system comprises a heat pump unit, a preheating desalting water tank and a heating desalting water tank. The input end of the heat pump unit is used for being connected with the tail end of a multi-effect evaporator for aluminum oxide production and used for recycling dead steam waste heat generated in the last effect in the aluminum oxide production process of the multi-effect evaporator. The first output end of the heat pump unit is connected with the heating desalted water tank, and the preheating desalted water tank is connected with the heating desalted water tank through a pipeline and used for providing desalted water; the heat pump unit is used for transmitting the waste heat of the dead steam to the heating desalting water tank and heating the desalted water in the heating desalting water tank by using the waste heat of the dead steam. According to the system, the characteristic that desalted water needs to be heated when being added into a desalted water receiver such as a deoxygenation water tank is utilized, waste heat of dead steam at the tail end of the multi-effect evaporator for aluminum oxide production is used for heating the desalted water of the heating desalted water tank, resources are effectively utilized, and economic benefits are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat utilization, and in particular to a waste heat utilization system and method based on alumina production. Background Art

[0002] Alumina is a high-hardness compound that is widely used in industry and various fields. The production of alumina uses a multiple-effect evaporator. In the process of using a multiple-effect evaporator to produce alumina, a large amount of exhaust steam and waste heat will be generated in the last effect.

[0003] However, in the related art, a large amount of waste heat from exhaust steam generated by the final effect is not effectively utilized, resulting in a huge waste of resources and increased costs. Summary of the invention

[0004] In response to the problems existing in the prior art, the embodiments of the present invention provide a waste heat utilization system and method based on alumina production, so as to solve or partially solve the technical problem in the related technology that a large amount of exhaust steam waste heat in the process of producing alumina by a multiple-effect evaporator is not effectively utilized, resulting in a huge waste of resources.

[0005] In a first aspect of the present invention, there is provided 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 to the end of the multi-effect evaporator for aluminum oxide production, and is used to recover the exhaust steam waste heat generated by the end effect of the multi-effect evaporator in the process of aluminum oxide production;

[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 transfer the exhaust steam waste heat to the heating desalted water tank, and use the exhaust steam waste heat to heat the desalted water in the heating desalted water tank; the heating desalted water tank is connected to the desalted water receiver through a pipeline.

[0010] In the above scheme, the system also includes a heating pipe, and the second output end of the heat pump unit is connected to the heating pipe; the heat pump unit is provided with a first butterfly valve, and the first butterfly valve is used to switch the output path of the heat pump unit to enable the heat pump unit to switch the 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 transfer the exhaust steam waste heat to the heating pipe for heating.

[0011] In the above scheme, the first butterfly valve is used to adjust the heat pump unit to output from the second output end during the heating period; and is also used to adjust the heat pump unit to output from the first output end during the non-heating period.

[0012] In the above scheme, the system also includes a steam supply pipeline, a pipeline plugging plate and a second butterfly valve. The steam supply pipeline is also used to connect the end of the multi-effect evaporator for 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 multi-effect evaporator and the input end of the heat pump unit, and is used to transport the exhaust steam and waste heat at the end of the multi-effect evaporator to the input end of the heat pump unit when forward conduction occurs; the pipeline plugging plate is connected between the end of the multi-effect evaporator and the steam supply pipeline, and is used to block the flow between the end of the multi-effect evaporator and the steam supply pipeline when closed; and transport the exhaust steam and waste heat at the end of the multi-effect evaporator to the steam supply pipeline when opened.

[0013] In the above scheme, the system also includes a cooling tower and a cooling unit, and the cooling tower and the cooling unit are respectively connected to the heat pump unit to provide a vacuum environment for the heat pump unit. The heat pump unit is also used to connect the heat pump unit to the cooling tower during the heating period; and to connect the cooling unit during the non-heating period.

[0014] In the above scheme, the system also includes a first desalted water supply pump, which is connected to the pipeline between the preheating desalted water tank and the heating desalted water tank, and is used to transfer the desalted water in the preheating desalted water tank to the heating desalted water tank.

[0015] In the above scheme, the desalted water receiver includes a deoxygenated water tank, and the system also includes a second desalted water supply pump, which is connected to the pipeline between the heating desalted water tank and the deoxygenated 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, and the second end of the second desalted water supply pump is connected to the deoxygenated water tank as an outlet main pipe; it is used to transfer the heated desalted water in the heating desalted water tank to the deoxygenated water tank.

[0016] In the above scheme, the system also includes a return pipe and a third butterfly valve, the third butterfly valve is connected to the return pipe, the first end of the return pipe is connected to the input end of the heat pump unit, and the second end 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, and the third butterfly valve is used to open when the heat pump unit fails, so as to enable the heating desalted water tank to continuously supply desalted water to the desalted water receiver.

[0017] The second aspect of the present invention provides a method for utilizing waste heat based on alumina production, which is used in the above system and comprises:

[0018] Get the heating cycle;

[0019] Identify heating and non-heating periods based on the heating cycle;

[0020] During the heating period, the first butterfly valve is controlled to output the heat pump unit from the second output end, so as to transfer the exhaust steam waste heat to the heating pipeline for heating;

[0021] During the non-heating period, the first butterfly valve is controlled to output the heat pump unit from the first output end, so as to transfer the exhaust 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 enable the heated desalted water tank to continuously supply desalted water to the desalted water receiver.

[0023] The present invention 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 to connect to the end of a multiple-effect evaporator for alumina production, and is used to recover the exhaust steam waste heat generated in the last effect of the multiple-effect evaporator in the process of producing alumina; the 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 heat pump unit is used to transmit the exhaust steam waste heat to the heating desalted water tank, and use the exhaust steam waste heat to heat the desalted water in the heating desalted water tank; the heating desalted water tank is connected to a desalted water receiver through a pipeline. The system of the present application connects the end of the multi-effect evaporator for aluminum oxide production to a heating desalted water tank through a heat pump unit, utilizing the property that desalted water needs to be heated when added to a desalted water receiver, such as a deoxygenation tank, and uses the exhaust steam waste heat at the end of the multi-effect evaporator for aluminum oxide production to heat the desalted water in the heating desalted water tank, thereby effectively utilizing resources, avoiding waste of resources, and saving costs.

[0024] The method of the present application is to obtain the heating cycle; confirm the heating period and the non-heating period according to the heating cycle; in the heating period, control the first butterfly valve to output the heat pump unit from the second output end, so as to transfer the exhaust steam and waste heat to the heating pipe for heating; in the non-heating period, control the first butterfly valve to output the heat pump unit from the first output end, so as to transfer the exhaust steam and waste heat to the heating desalted water tank. Through the method of the present application, the exhaust steam and waste heat at the end of the multi-effect evaporator for aluminum oxide production can be effectively controlled to be used for heating during the heating period, and the exhaust steam and waste heat at the end of the multi-effect evaporator for aluminum oxide production can be used to heat the desalted water in the heating desalted water tank during the non-heating period, which effectively utilizes resources, and can be directly improved on the existing system, with low transformation cost. Without affecting the original heating, the utilization efficiency of the non-heating period is further improved, and the cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

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

[0027] Figure 2 A flow chart of a method for utilizing waste heat based on alumina production according to an embodiment of the present invention 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 invention 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-pipe plugging plate; 9-second butterfly valve; 10-first desalted water supply pump; 11-second desalted water supply pump; 12-return pipe; 13-third butterfly valve; DETAILED DESCRIPTION

[0030] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying 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. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0031] Alumina is a high-hardness compound that is widely used in industry and various fields. The production of alumina uses a multiple-effect evaporator. In the process of using a multiple-effect evaporator to produce alumina, a large amount of exhaust steam and waste heat will be generated in the last effect.

[0032] However, in the related art, a large amount of waste heat from exhaust steam generated by the final effect is not effectively utilized, resulting in a huge waste of resources and increased costs.

[0033] For example, the exhaust steam waste heat from the end effect of the multi-effect evaporator in the alumina production process is usually directly discharged into the air, resulting in a large amount of waste heat. In the related art, the technology can be improved, that is, the waste heat can be used for heating. For example, in actual application, a thermal power station is built in area A to be responsible for winter heating of Shan Aluminum and surrounding dormitory areas. There are two absorption heat pump units in the station, which use steam as the driving heat source to recover the exhaust steam waste heat from the end effect of the multi-effect evaporator in the alumina production process to heat the heating circulating water. During the heating period, one heat pump unit is often turned on, and during the non-heating period, two heat pump units are idle and stopped. Therefore, the exhaust steam waste heat can be effectively used for heating. However, the heating time is limited in a year, and the production of alumina using a multi-effect evaporator is carried out all year round, so the exhaust steam waste heat cannot be effectively utilized.

[0034] In order to solve the above problems, the present application discloses a waste heat utilization system based on alumina production. The present application fully considers the characteristic that the desalted water needs to be heated during the process of supplying to the deaerator, and supplies the waste heat generated by the production of alumina by the multi-effect evaporator to the process of desalting water. Specifically, in practical applications, the 6# and 7# boilers of the thermal power plant need to supply about 400 to 600 t / h of desalted water, and most of the time they operate at 600 t / h. The initial temperature is about 54°C, which is supplied to the 6# and 7# furnaces by the desalted water pump room. Most of the desalted water is supplied to the deaerator and needs to be heated to about 160°C by the steam extracted by the steam turbine generator set at low pressure, which requires a large amount of new steam. As for the exhaust steam waste heat of the last effect of the multi-effect evaporator in the alumina production process, it is wasted during the non-heating period. Therefore, the present application combines the two and uses the exhaust steam 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 present application discloses a waste heat utilization system based on alumina production, which involves a new energy-saving process for self-contained power plants based on the utilization of waste heat in the alumina production process. The corresponding specific application field can be a new process field for energy-saving by utilizing waste heat in self-contained power plants.

[0036] According to a first aspect of the present invention, the present application provides a waste heat utilization system based on alumina production, such as Figure 1 As shown, Figure 1A block diagram of a waste heat utilization system based on alumina production according to an embodiment of the present invention is shown. The system of the present application includes 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 present application can be two groups, or multiple groups can be set according to actual application conditions; the preheating desalted water tank 2 of the present application can be three groups, or multiple groups can be set according to actual application conditions; the heating desalted water tank 3 of the present application can be one group, or multiple groups can be set according to actual application conditions.

[0037] The input end of the heat pump unit 1 of the present application is used to connect to the end of the multi-effect evaporator for alumina production, and is used to recover the exhaust steam waste heat generated in the last effect of the multi-effect evaporator in the process of producing alumina; the first output end of the heat pump unit 1 is connected to the heating desalted water tank 3, and 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 transfer the exhaust steam waste heat to the heating desalted water tank 3, and use the exhaust steam waste heat to heat the desalted water in the heating desalted water tank 3; the heating desalted water tank 3 is connected to the desalted water receiver 6 through a pipeline.

[0038] The system of the present application connects the end of the multi-effect evaporator for aluminum oxide production to the heating desalted water tank 3 through a heat pump unit 1, and utilizes the characteristic that the desalted water needs to be heated when added to the desalted water receiver 6, such as a deoxygenation tank, and uses the exhaust steam waste heat at the end of the multi-effect evaporator for aluminum oxide production to heat the desalted water in the heating desalted water tank 3, thereby effectively utilizing resources, avoiding waste of resources, and saving costs. Moreover, the present application can make full use of existing idle equipment and facilities, integrate process flows, exchange heat sources and cold sources, avoid exhaust steam waste heat discharge, and increase the cold source temperature.

[0039] In one embodiment of the present application, the system of the present application also includes a heating pipe 4, and the second output end of the heat pump unit 1 is connected to the heating pipe 4; a first butterfly valve 5 is provided 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 that the heat pump unit 1 can switch the output 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 transfer the exhaust steam waste heat to the heating pipe 4 for heating.

[0040] In one embodiment of the present 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] Through the above-mentioned system of the present application, the first butterfly valve 5 can be used for switching according to the heating period and the non-heating period. Therefore, the system of the present application can be directly applied to the scheme of using the exhaust steam and waste heat at the end of the multi-effect evaporator for heating, which can effectively reduce the conversion cost without making too many modifications to the equipment. Moreover, the present application can use the first butterfly valve 5 for switching control, and make full use of the large amount of exhaust steam and waste heat generated in the process of producing alumina by the multi-effect evaporator. No matter in which period, it will not cause waste of resources, further reducing production costs and improving economic benefits.

[0042] In one embodiment of the present application, the system also includes a steam supply pipe 7, a pipe plug 8 and a second butterfly valve 9. The steam supply pipe 7 is also used to connect the end of the multi-effect evaporator for alumina production, 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 multi-effect evaporator and the input end of the heat pump unit 1, and is used to transport the exhaust steam and waste heat at the end of the multi-effect evaporator to the input end of the heat pump unit 1 when forward conduction occurs; the pipe plug 8 is connected between the end of the multi-effect evaporator and the steam supply pipe 7, and is used to block the flow between the end of the multi-effect evaporator and the steam supply pipe 7 when closed; when opened, the exhaust steam and waste heat at the end of the multi-effect evaporator are transported to the steam supply pipe 7.

[0043] Through the above-mentioned system of the present application, the present application adds a steam supply pipeline 7, a pipeline plugging plate 8 and a second butterfly valve 9. When the heating pipeline 4 needs to be maintained during the heating period, or when 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 during the non-heating period, the exhaust steam waste heat at the end of the multi-effect evaporator can be temporarily transported to the steam supply pipeline 7 through the cooperation of the second butterfly valve 9 and the pipeline plugging plate 8, thereby further avoiding the waste of exhaust steam waste heat. At the same time, this embodiment can also be applied to the scene where the exhaust steam waste heat needs to be directly utilized. When the back end needs to directly utilize the exhaust steam waste heat, the present application can directly control the pipeline plugging plate 8 to be opened for a long time, and at the same time control the second butterfly valve 9 to continuously supply gas to the steam supply pipeline 7, which can improve the utilization efficiency of the exhaust steam waste heat, avoid waste of resources, further reduce production costs, and improve economic benefits.

[0044] In one embodiment of the present application, the system also includes a cooling tower and a cooling unit, and the cooling tower and the cooling unit are respectively connected to the heat pump unit 1 to provide a vacuum environment for the heat pump unit 1. The heat pump unit 1 is also used to connect the heat pump unit 1 to the cooling tower during the heating period; and to connect to the cooling unit during the non-heating period.

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

[0046] In one embodiment of the present application, the system also includes a first desalted water supply pump 10, which is connected to a pipeline between the preheating desalted water tank 2 and the heating desalted water tank 3, and is used to transfer 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 may have three, wherein the specification may be: two using Q=470m 3 / h, H = 60m; 1 unit uses Q = 250m 3 / h, H = 60m. The pipeline for transferring the desalted water in the preheating desalted water tank 2 to the heating desalted water tank 3 can be adopted. Seamless steel pipe.

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

[0049] In one embodiment of the present application, the desalted water receiver 6 includes a deoxygenated water tank. Of course, the present application can set up other desalted water receivers 6 as needed, wherein the desalted water receiver 6 of the present application needs to be added after heating the desalted water, rather than all desalted water receivers 6. The system of the present application also includes a second desalted water supply pump 11, which is connected to the pipeline between the heated desalted water tank 3 and the deoxygenated water tank. The first end of the second desalted water supply pump 11 is connected to the heated desalted water tank 3 as an inlet main pipe, and the second end of the second desalted water supply pump 11 is connected to the deoxygenated water tank as an outlet main pipe; it is used to transfer the heated desalted water in the heated desalted water tank 3 to the deoxygenated water tank.

[0050] The present application may include five second desalted water supply pumps 11, and the number of pumps 11 may also be adjusted according to actual needs of the system.

[0051] Through the above system of the present application, the present application utilizes the second desalted water supply pump 11 to transfer the heated desalted water in the heating desalted water tank 3 to the deoxygenated water tank for use in the deoxygenated water tank.

[0052] In specific applications, the 6# and 7# boilers of the thermal power plant need to supply desalted water of about 400 to 600 t / h, and most of the time they operate at 600 t / h. The initial temperature is about 54°C, and it is supplied to the 6# and 7# boilers by the desalted water pump room. Most of the desalted water is supplied to the deaerator and needs to be heated to about 160°C by steam extracted at low pressure from the steam turbine generator set. Therefore, the second desalted water supply pump 11 of the present application is a hot water pump that can withstand a temperature of 160°C.

[0053] In one embodiment of the present application, the system also includes 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, and the second end is respectively connected to 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, the third butterfly valve 13 is used to open when the heat pump unit 1 fails, so as to realize the continuous supply of desalted water from the heating desalted water tank 3 to the desalted water receiver 6.

[0054] Through the above system of the present application, the present application adds an emergency mechanism. When the heat pump unit 1 fails and cannot heat the desalted water and transmit it to the desalted water receiver 6, the return pipe 12 and the third butterfly valve 13 of the present application can be used, and the third butterfly valve 13 can be opened to heat the first end of the second desalted water supply pump 11, the second end of the second desalted water supply pump 11 and the desalted water in the heating desalted water tank 3 and transmit them to the desalted water receiver 6. Further avoid the waste of resources, at the same time, the present application can also temporarily open the third butterfly valve 13 during overhaul to achieve reflux, avoiding waste of resources when the heat pump unit 1 is overhauled.

[0055] The first aspect of the present application is disclosed above, and the second aspect of the present application is disclosed below. According to the second aspect of the present invention, a method for utilizing waste heat from aluminum oxide production is provided, such as Figure 2 As shown, Figure 2 The flowchart of the method for utilizing waste heat based on alumina production according to one embodiment of the present invention is shown. The method of the present application is used on the above system. Specifically, the above 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 to the processor, and the method includes steps S210 to S240:

[0056] Step S210: Obtain the heating cycle.

[0057] The heating cycle 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 cycle 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: confirm the heating period and non-heating period according to the heating cycle.

[0059] The processor may confirm a heating period and a non-heating period according to the heating cycle, and perform steps S230 and S240 respectively based on the heating period and the non-heating period.

[0060] Step S230: During the heating period, the first butterfly valve 5 is controlled to output the heat pump unit 1 from the second output end, so as to transfer the exhaust steam waste heat to the heating pipe 4 for heating.

[0061] During the heating period, the processor can control the first butterfly valve 5 to output the heat pump unit 1 from the second output end, so as to transfer the exhaust steam waste heat to the heating pipe 4 for heating.

[0062] Furthermore, if the butterfly valve used by the user cannot be controlled by the processor, step S230 may also be to send a prompt signal to the display during the heating period to remind the user to open the first butterfly valve 5.

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

[0064] When it is not a heating period, the processor can control the first butterfly valve 5 to output the heat pump unit 1 from the first output end, so as to transfer the exhaust steam waste heat to the heating desalted water tank 3 .

[0065] Therefore, the method of the present application obtains the heating cycle; confirms the heating period and the non-heating period according to the heating cycle; in the heating period, controls the first butterfly valve 5 to output the heat pump unit 1 from the second output end, for transmitting the exhaust steam and waste heat to the heating pipe 4 for heating; in the non-heating period, controls the first butterfly valve 5 to output the heat pump unit 1 from the first output end, for transmitting the exhaust steam and waste heat to the heating desalted water tank 3. Through the method of the present application, the exhaust steam and waste heat at the end of the multi-effect evaporator for aluminum oxide production can be effectively controlled to be used for heating during the heating period, and the exhaust steam and waste heat at the end of the multi-effect evaporator for aluminum oxide production can be used to heat the desalted water in the heating desalted water tank 3 during the non-heating period, which effectively utilizes resources, and can be directly improved on the existing system, with low transformation cost, and further improves the utilization efficiency of the non-heating period without affecting the original heating, thereby reducing costs.

[0066] In one 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 achieve the heating of the desalted water tank 3 to continuously supply desalted water to the desalted water receiver 6 .

[0067] By using this method, when the heat pump unit 1 fails and cannot heat the desalted water and transmit it to the desalted water receiver 6, the return pipe 12 and the third butterfly valve 13 of the present application can be used, and the third butterfly valve 13 can be opened to heat the first end of the second desalted water supply pump 11, the second end of the second desalted water supply pump 11 and the desalted water in the heating desalted water tank 3 and transmit them to the desalted water receiver, further avoiding waste of resources.

[0068] The above introduces the specific embodiments of the present application. Next, the application embodiments of the present application will be further introduced.

[0069] like Figure 3 As shown, Figure 3 The block diagram of a waste heat utilization system based on alumina production according to an application embodiment of the present invention is shown. During the implementation of this application, it was found that a thermal power station was built in area A to provide winter heating for Shan Aluminum and surrounding dormitory areas. Two absorption heat pump units are built in the station, which use steam as the driving heat source to recover the exhaust heat of the last effect of the multi-effect evaporator in the alumina production process to heat the heating circulating water. During the heating period, one heat pump unit is always open, and during the non-heating period, two heat pump units are idle and stopped. The 6# and 7# boilers of the thermal power plant in area B need to supply about 400 to 600 t / h of desalted water, and most of the time they operate at 600 t / h. The initial temperature is about 54°C, which is supplied to 6# and 7# furnaces by the desalted water pump room. Most of the desalted water is supplied to the deaerator, which needs to be heated to about 160°C by steam extracted at low pressure from the steam turbine generator set, consuming a large amount of new steam.

[0070] However, the two areas are working independently and not in coordination. In general, one heat pump unit in area A is idle all year round, resulting in equipment waste; the multi-effect evaporator in alumina production is running all year round, and the exhaust steam and waste heat of the last effect are idle in the non-heating season, resulting in resource waste; the thermal power plant in area B runs desalted water at 400--600t / h all year round, with sufficient cold source.

[0071] The application embodiments of the present invention can make full use of existing idle equipment and facilities, integrate process flows, exchange heat sources and cold sources, avoid exhaust steam waste heat discharge, and increase the cold source temperature.

[0072] This application utilizes the three water tanks (4#, 7#, 8#) in the first phase desalted water area on the north side of the 6# and 7# unit buildings of the thermal power plant in area B and transforms them into pre-preheating desalted water tanks. Three desalted water supply pumps (2 Q=470m3 / h, H=60m, 1 Q=250m3 / h, H=60m) are installed in the pump room of the chemical water workshop to transport the desalted water to the East Line Thermal Power Station.

[0073] The pipeline used to transport desalted water from the pump room of the water treatment plant to the East Line Heating Station is Seamless steel pipe, using old thermal power plant (II) The steam pipeline is about 160 meters long. If the old pipe section is used, measures must be taken to isolate it from the steam system. The desalted water pipeline transported to the East Line Thermal Power Station is respectively connected to the water inlet pipelines of the two heat pump units and isolated from the original system by the first butterfly valve. The return water pipes are connected from the outlet pipes of the two heat pump units respectively, and the third butterfly valve is used to isolate it from the original system. They are combined into a DN350 return water main pipe, which is laid to the existing outlet main pipe of the desalted water supply pump in the South District, and a bypass is set up to connect to the desalted water tank and the inlet main pipe of the water supply pump. The existing 5 desalted water supply pumps in the desalted water pump room are replaced with hot water pumps with unchanged specifications.

[0074] Among them, the vacuum pump cooling water of the heat pump unit of the East Line Thermal Power Station (corresponding to area A) now adopts the natural cooling method of circulating water pool. A new cooling tower and a chiller are installed. The cooling tower is used for cooling during the heating period, and the chiller is used for cooling during the non-heating period to solve the vacuum pump cooling water cooling problem throughout the year.

[0075] Through the above method of the present application, resources can be effectively utilized, waste of resources can be avoided, costs can be saved, and economic benefits can be improved. Through accounting, from January to September 2024, the heat pump unit of the East Line Thermal Power Station consumed 67,657 tons of new steam, with a heat conversion of 196,844 GJ, and the desalted water in area B heated and absorbed 373,156 GJ of heat. After this new process, 176,311 GJ of waste heat was utilized. According to the heating heat unit price of 46 yuan / GJ, the economic benefit was 8.1103 million yuan.

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

[0077] 1. Calculation of desalted water heated by waste heat from roasting furnace flue gas:

[0078] High-temperature flue gas heating desalted water can be achieved by installing a flue gas-water heat exchanger on the flue. The simple calculation is as follows:

[0079] The flue gas volume is Q = 12 × 104 Nm 3 / h, flue gas temperature is 160℃

[0080] Smoke density ρ=1.32kg / Nm 3 , specific heat of flue gas C = 0.24kcal / kg.℃

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

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

[0083] The fluctuation range of desalted water in thermal power plants is 400~600t / h, and the value is 420t / h. The heat required to heat from 54℃ to 83℃ is:

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

[0085] According to the above calculation, when the flue gas temperature is reduced by 60°C, the heat provided by the roasting furnace flue gas is only (228 / 1218)*100%≈18.7% of the required heat, which is far from meeting the heat required for heating the desalted water in the thermal power plant.

[0086] 2. Calculation of waste heat utilization of evaporation exhaust steam:

[0087] The heat pump unit has been successfully operated in area A using evaporation exhaust steam for nearly three years (heating season). The unit's heat supply can reach the value in the above table, that is, (30000KW*(860Kcal / KW))=2580×104kcal / h, which can meet the heat required for heating the maximum 781t / h of heating water from 50℃ to 83℃ or above. The heat pump manufacturer has verified and calculated the unit based on the working conditions of desalted water, confirming that the heat pump unit can meet the heating of 400~600t / h of desalted water from 54℃ to 90.7℃.

[0088] 3. Comparison of solutions

[0089] Through the calculation and comparison of the above two types of waste heat, the waste heat from the roasting furnace flue gas does not meet the heat requirements, while the evaporation waste heat can achieve the purpose of this project. Therefore, this application adopts the solution of using the heat pump unit to absorb the heat produced by evaporation exhaust steam to heat the desalted water for the thermal power plant boiler.

[0090] 4. At the same time, this application was calculated based on the above scheme. The heat pump manufacturer calibrated and calculated the unit according to the working conditions of the desalted water and confirmed that the heat pump unit can meet the heating of 400-600t / h desalted water from 54°C to 90.7°C.

[0091] 60~110t / h of desalted water enters the shaft seal heater as its cooling water. Since the higher the inlet water temperature, the more unfavorable it is for the cooling and condensation of the steam seal leakage, considering that the maximum inlet water temperature of the shaft seal heater does not exceed 85℃, the working condition comparison calculation is as follows:

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

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

[0094] (2) Working condition 2: heating from 54℃ to 85℃. The total amount of desalted water is 600t / h, all of which passes through the heat pump unit. At this time, the heat added by the desalted water through the heat pump is:

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

[0096] (3) After verification by the heat pump manufacturer, the COP of the heat pump unit under operating condition 1 is ≈1.62, and the COP of the heat pump unit under operating condition 2 is ≈1.65.

[0097] In summary, the heating capacity and coefficient of performance (COP) of the heat pump unit in operating condition 2 are slightly higher than those in operating condition 1, so the energy-saving benefit of operating condition 2 is slightly higher than that of operating condition 1.

[0098] In summary, the initial temperature of the desalted water supplied to the boiler deaerator of the thermal power plant is about 54°C, which needs to be heated to about 160°C by the steam extracted from the steam turbine generator set at low pressure, consuming a large amount of new steam. The heat pump unit in the thermal power station is used to raise the 54°C desalted water supplied to the boiler in the southern area of ​​the thermal power plant to above 85°C; for the alumina plant, because the heat pump unit consumes more evaporation exhaust steam throughout the year, it can alleviate the problems of insufficient heat dissipation capacity of the cooling tower of the evaporation system in summer and high-load operation of the evaporation circulation water pump, thereby reducing the operating cost of the alumina plant; due to the improvement of the evaporative cooling effect, the evaporation output can be increased, thereby increasing the production capacity of the alumina plant. Through process transformation, the existing resources in areas A and B are activated, and the waste heat of the East Line evaporator is used to heat the desalted water of the thermal power plant and save new steam.

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

[0100] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0101] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly recited in each claim. More specifically, as reflected in the claims below, inventive aspects lie in less than all the features of the individual embodiments disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0102] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition they may be divided into a plurality of submodules or subunits or subcomponents. Except that at least some of such features and / or processes or units are mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature providing the same, equivalent or similar purpose.

[0103] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims below, any one of the claimed embodiments may be used in any combination.

[0104] The various component embodiments of the present invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. It should be understood by those skilled in the art that a microprocessor or digital signal processor (DSP) may be used in practice to implement some or all functions of some or all components of a gateway, proxy electronic device, or system according to an embodiment of the present invention. The present invention may also be implemented as a device or apparatus program (e.g., a computer program and a computer program product) for executing part or all of the methods described herein. Such a program implementing the present invention may be stored on a computer-readable medium, or may be in the form of one or more signals. Such a signal may be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

[0105] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc., does not indicate any order. These words may be interpreted as names.

[0106] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A waste heat utilization system based on alumina production, characterized in that: It includes 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 to connect to the end of the multi-effect evaporator for aluminum oxide production, and is used to recover the exhaust steam waste heat generated by the end effect of the multi-effect evaporator in the process of aluminum oxide production; The 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 heat pump unit is used to transfer the exhaust steam waste heat to the heating desalted water tank, and use the exhaust steam waste heat to heat the desalted water in the heating desalted water tank; the heating desalted water tank is connected to the desalted water receiver through a pipeline.

2. The system according to claim 1, characterized in that The system also includes a heating pipeline, and the second output end of the heat pump unit is connected to the heating pipeline; the heat pump unit is provided with a first butterfly valve, and the first butterfly valve is used to switch the output path of the heat pump unit to enable the heat pump unit to switch the 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 transfer the exhaust steam waste heat to the heating pipeline for heating.

3. The system according to claim 2, characterized in that The first butterfly valve is used to adjust the heat pump unit to output from the second output end during the heating period; and is also used to adjust the heat pump unit to output from the first output end during the non-heating period.

4. The system according to claim 3, characterized in that The system also includes a steam supply pipeline, a pipeline plugging plate and a second butterfly valve. The steam supply pipeline is also used to connect the end of the multi-effect evaporator for 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 multi-effect evaporator and the input end of the heat pump unit and is used to transport the exhaust steam and waste heat at the end of the multi-effect evaporator to the input end of the heat pump unit when forward conduction occurs. The pipeline plugging plate is connected between the end of the multi-effect evaporator and the steam supply pipeline and is used to block the flow between the end of the multi-effect evaporator and the steam supply pipeline when closed; and transport the exhaust steam and waste heat at the end of the multi-effect evaporator to the steam supply pipeline when opened.

5. The system according to claim 4, characterized in that The system also includes a cooling tower and a cooling unit, wherein the cooling tower and the cooling unit are respectively connected to the heat pump unit to provide a vacuum environment for the heat pump unit. The heat pump unit is also used to connect the heat pump unit to the cooling tower during the heating period and to connect to the cooling unit during the non-heating period.

6. The system according to claim 5, characterized in that The system further comprises a first desalted water supply pump connected to a 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.

7. The system according to claim 6, characterized in that The desalted water receiver includes a deoxygenated water tank, and the system also includes a second desalted water supply pump, which is connected to the pipeline between the heating desalted water tank and the deoxygenated 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, and the second end of the second desalted water supply pump is connected to the deoxygenated water tank as an outlet main pipe; it is used to transfer the heated desalted water in the heating desalted water tank to the deoxygenated water tank.

8. The system according to claim 7, characterized in that The system also includes a return pipe and a third butterfly valve, wherein the third butterfly valve is connected to the return pipe, wherein the first end of the return pipe is connected to the input end of the heat pump unit, and the second end 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, and the third butterfly valve is used to open when the heat pump unit fails, so as to enable the heating desalted water tank to continuously supply desalted water to the desalted water receiver.

9. A method for utilizing waste heat from alumina production, characterized in that: Using the system as claimed in claim 8, the method comprises: Get the heating cycle; Identify heating and non-heating periods based on the heating cycle; During the heating period, the first butterfly valve is controlled to output the heat pump unit from the second output end, so as to transfer the exhaust steam waste heat to the heating pipeline for heating; During the non-heating period, the first butterfly valve is controlled to output the heat pump unit from the first output end, so as to transfer the exhaust steam waste heat to the heating desalted water tank.

10. The method according to claim 9, characterized in that If it is detected that the heat pump unit is damaged, the third butterfly valve is opened to enable the heated desalted water tank to continuously supply desalted water to the desalted water receiver.

Images