Alumina mother liquor evaporation system capable of reducing multi-effect evaporation steam consumption

Abstract

The utility model relates to an aluminum oxide mother liquor evaporation system capable of reducing multi-effect evaporation steam consumption, which comprises a plurality of evaporators which are sequentially arranged, a steam jet mixer, a steam outlet pipe and a steam outlet pipe, the steam jet mixer is provided with a steam inlet, a steam suction port and a mixed steam outlet connected with the first-effect evaporator, the aluminum oxide mother liquor evaporation system further comprises a steam supplementing pipeline connected between the steam suction port and the last-effect secondary steam pipeline, and a steam compressor is arranged on the steam supplementing pipeline. Due to the fact that the last-effect secondary steam contains more latent heat, by means of the scheme, the last-effect secondary steam can be used for replacing part of new steam, the latent heat of the last-effect secondary steam is effectively recycled, and energy consumption of an evaporation system is reduced; and meanwhile, the amount of last-effect secondary steam entering the water cooler can be reduced, so that the load of a circulating water system of the water cooler is reduced, and the operation cost of the circulating water system is reduced.

Description

Technical Field

[0001] This utility model relates to the field of metallurgical and chemical technology, and in particular to an alumina mother liquor evaporation system that can reduce steam consumption in multi-effect evaporation. Background Technology

[0002] The alumina mother liquor evaporation system is a crucial piece of equipment in alumina production. Mother liquor evaporation is a vital step in the alumina production process, responsible for maintaining the liquid volume balance, providing a suitable concentration of alkali solution for leaching or raw material slurry preparation, and removing carbon and alkali accumulated during production. Evaporation is the main energy-consuming unit in alumina production and a critical step in maintaining liquid volume balance.

[0003] Currently, alumina mother liquor evaporation systems such as Figure 1 As shown, it includes evaporators 2 connected in sequence with multiple effects, ranging from 3 to 7 effects; the more effects, the more energy-efficient the evaporator. Along the steam flow, the first evaporator is called the first-effect evaporator 1, and the last evaporator is called the last-effect evaporator 3. The steam produced by the last effect of the multi-effect evaporator is called the last-effect secondary steam. In existing alumina production evaporation systems, the last-effect secondary steam enters the water cooler 4 (also called the large steam condenser), where it directly contacts and exchanges heat with low-temperature circulating water. This steam is condensed and enters the circulating water. After absorbing the last-effect steam, the temperature of the circulating water increases. The heated circulating water then returns to the cooling tower 6 for cooling via the water seal tank 5. Due to the continuous influx of condensate from the last-effect steam in the evaporation system, a portion of the circulating water in the evaporation system needs to be discharged to maintain the water balance of the circulating water system.

[0004] Furthermore, the secondary steam from the last effect of the alumina evaporation system accounts for approximately 30% of the total steam volume. Under current evaporation process conditions, the temperature of this secondary steam is generally between 50 and 60°C. Due to its low temperature and pressure, its energy quality is poor, making recovery and utilization difficult. However, the volume of this secondary steam is large, and it contains a significant amount of latent heat, accounting for 30% to 40% of the evaporator's heat recovery. Approximately 1800 MJ of heat is carried away per ton of alumina secondary steam. In existing technology, the energy of this secondary steam from the last effect is absorbed by the circulating water. To maintain system energy balance, the circulating water system uses a cooling tower to remove this energy from the system, consuming a large portion of energy during the cooling tower's operation. According to relevant calculations, 10 to 15 m³ of secondary steam from the last effect needs to be injected into the water cooler to absorb 1 ton of secondary steam. 3 For a mainstream 1 million-ton alumina production line, the required circulating water volume is 5000-7000 m³. 3 The transportation of this portion of circulating water per hour will consume a large portion of energy. Utility Model Content

[0005] The purpose of this invention is to provide an alumina mother liquor evaporation system that can recover and reuse the secondary steam from the final effect, and reduce the energy consumption of circulating water transportation in the water-cooling system, thereby reducing the steam consumption of multi-effect evaporation.

[0006] To solve the above-mentioned technical problems, the technical solution of the alumina mother liquor evaporation system of this utility model, which can reduce the steam consumption of multi-effect evaporation, is as follows:

[0007] An alumina mother liquor evaporation system capable of reducing steam consumption in multi-effect evaporation includes evaporators arranged in sequence with multiple effects. The secondary steam produced by the last-effect evaporator is connected to a water cooler via a last-effect steam pipe. The alumina mother liquor evaporation system also includes a steam jet mixer, which has a steam inlet, a steam suction port, and a mixed steam outlet connected to the first-effect evaporator. The alumina mother liquor evaporation system also includes a make-up steam pipe connected between the steam suction port and the secondary steam pipe of the last effect, and a steam compressor is installed on the make-up steam pipe.

[0008] Furthermore, the steam inlet pressure is not less than 0.025 MPa.

[0009] Furthermore, there are multiple steam jet mixers connected in series. The steam intake port of each steam jet mixer is connected to the final-effect steam pipeline through its corresponding make-up steam pipeline, and each make-up steam pipeline is equipped with a steam compressor.

[0010] Furthermore, the number of evaporators should not be less than three.

[0011] The beneficial effects of this utility model are as follows: In this utility model, the secondary steam discharged from the final-effect evaporator does not completely enter the water cooler for water cooling. Instead, a portion of the secondary steam is pressurized by the steam compressor on the make-up steam pipeline and sent to the steam jet mixer. After being pressurized, the secondary steam mixes with the new steam and is then used as a heat source to power the first-effect evaporator. Since the secondary steam contains a lot of latent heat, this scheme can replace part of the new steam with the secondary steam, effectively recovering the latent heat of the secondary steam and reducing the energy consumption of the evaporation system. At the same time, it can also reduce the amount of secondary steam entering the water cooler, thereby reducing the load on the water cooler's circulating water system and lowering the operating cost of the circulating water system. Attached Figure Description

[0012] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments with reference to the accompanying drawings. In the drawings, several embodiments of this disclosure are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding portions, wherein:

[0013] Figure 1This is a schematic diagram of the structure of the alumina mother liquor evaporation system in the background technology of this utility model;

[0014] Figure 2 This is a schematic diagram of the structure of an embodiment of an alumina mother liquor evaporation system that can reduce the steam consumption of multi-effect evaporation in this utility model;

[0015] 1. First-effect evaporator; 2. Evaporator; 3. Last-effect evaporator; 4. Water cooler; 5. Water seal tank; 6. Cooling tower; 7. Water pump; 8. Vacuum pump; 9. Last-effect steam pipeline; 10. Steam compressor; 11. Make-up steam pipeline; 12. Steam jet mixer; 13. Steam inlet; 14. Steam suction port; 15. Mixed steam outlet. Detailed Implementation

[0016] To facilitate understanding of this utility model, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings show preferred embodiments of this utility model. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this utility model.

[0017] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0018] An example of an implementation of an alumina mother liquor evaporation system in this invention that can reduce steam consumption in multi-effect evaporation is shown below. Figure 2 As shown:

[0019] The system includes evaporators 2 arranged in sequence with multiple effects. In this embodiment, there are 7 evaporators. Along the steam conveying direction, the evaporator located at the front is called the first-effect evaporator 1, and the evaporator located at the back is called the last-effect evaporator 3. The last-effect secondary steam produced by the last-effect evaporator is connected to the water cooler 4 via the last-effect steam pipeline 9. The water cooler 4 is also connected to a circulating cooling water circuit, which is equipped with a water seal tank 5, a cooling tower 6, and a water pump 7.

[0020] The upper end of the water cooler 4 is connected to an exhaust pipe, and a vacuum pump 8 is installed on the exhaust pipe. The non-condensable gas in the water cooler can be discharged by the vacuum pump.

[0021] The alumina mother liquor evaporation system also includes a steam jet mixer 12, which has a steam inlet 13, a steam suction port 14, and a mixed steam outlet 15 connected to the first-effect evaporator. The steam inlet 13 is located at the front end of the steam jet mixer, the mixed steam outlet 15 is located at the rear end of the steam jet mixer 12, and the steam suction port 14 is located on the outer periphery of the steam jet mixer. When new steam enters through the steam inlet, the new steam is high-pressure supersaturated steam. It then passes through a constriction section for natural pressurization and acceleration before being discharged through the steam jet mixer and connected to the steam supply line of the first-effect evaporator. The acceleration of the new steam creates a negative pressure at the suction port, which further helps to increase the inlet steam pressure. The alumina mother liquor evaporation system also includes a make-up steam pipe 11 connecting the steam suction port 14 and the final-effect secondary steam pipe 9. A steam compressor 10 is installed on the make-up steam pipe 11. Through the pressurization of the steam compressor 10, the inlet steam pressure at the suction port is not less than 0.025 MPa.

[0022] In this embodiment, there is one steam jet mixer 12. In other embodiments of this utility model, there may be multiple steam jet mixers connected in series. The steam inlet of each steam jet mixer is connected to the final steam pipeline through its corresponding make-up steam pipeline, and each make-up steam pipeline is equipped with a steam compressor.

[0023] During operation, the new steam that has not been treated by the evaporator enters through the steam jet mixer and is then ejected through the steam jet mixer. It then passes through each effect evaporator for evaporation. The secondary steam discharged from the last effect evaporator is directly sent to the water cooler for water cooling. The other secondary steam discharged from the last effect evaporator enters the make-up pipe, is then pressurized by the steam compressor, and enters the steam jet mixer through the steam suction port. It mixes with the new steam entering through the steam inlet to form a lower pressure steam, which then flows to the first effect evaporator through the mixed steam outlet.

[0024] Since the secondary steam in the last effect contains a lot of latent heat, this scheme can replace part of the new steam with the secondary steam in the last effect, effectively recover the latent heat of the secondary steam in the last effect, and reduce the energy consumption of the evaporation system. After adopting this scheme, the amount of secondary steam entering the water cooler in the last effect is reduced, which can reduce the load on the circulating water system and reduce the operating cost of the circulating water system.

[0025] In the foregoing description of this specification, unless otherwise expressly specified and limited, the terms "fixed," "installed," "connected," or "joined" should be interpreted broadly. For example, the term "joined" can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can refer to the internal communication of two components or the interaction between two components. Therefore, unless otherwise expressly limited in this specification, those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0026] Based on the above description in this specification, those skilled in the art will also understand that terms used, such as "upper," "lower," "front," "rear," "left," "right," "length," "width," "thickness," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," "circumferential," "center," "longitudinal," "transverse," "clockwise," or "counterclockwise," are terms indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings of this specification. They are only for the purpose of facilitating the explanation of the present invention and simplifying the description, and do not imply that the device or element involved must have the specific orientation, or be constructed and operated in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms should not be understood or interpreted as limitations on the present invention.

[0027] Furthermore, the terms "first" or "second," etc., used in this specification to refer to numbers or ordinal numbers are for descriptive purposes only and should not be construed as indicating, explicitly or implicitly, relative importance or specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this specification, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. An alumina mother liquor evaporation system capable of reducing steam consumption in multi-effect evaporation, comprising evaporators arranged in sequence with multiple effects, wherein the secondary steam produced by the last-effect evaporator is connected to a water cooler via a last-effect steam pipeline, characterized in that: The alumina mother liquor evaporation system also includes a steam jet mixer, which has a steam inlet, a steam suction port, and a mixed steam outlet connected to the first-effect evaporator. The alumina mother liquor evaporation system also includes a make-up steam pipe connected between the steam suction port and the last-effect secondary steam pipe, and a steam compressor is installed on the make-up steam pipe.

2. The alumina liquor evaporation system of claim 1, wherein: The steam inlet pressure is not less than 0.025 MPa.

3. The alumina liquor evaporation system of claim 1, wherein: The steam jet mixer may be single or multiple, with multiple steam jet mixers connected in series. The steam intake port of each steam jet mixer is connected to the final-effect steam pipeline through its corresponding make-up steam pipeline, and each make-up steam pipeline is equipped with a steam compressor.

4. The alumina liquor evaporation system of claim 1, wherein: The number of evaporators shall not be less than three.

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