A process for utilizing waste heat in alumina production

Abstract

The invention discloses a process method for utilizing waste heat in alumina production, which belongs to the technical field of waste heat utilization in alumina production, and comprises the following steps: S1, exchanging heat between decomposition mother liquor and evaporated secondary water through a first heat exchanger, increasing the temperature of the decomposition mother liquor, and reducing the temperature of the evaporated secondary water; S2, storing the heated decomposition mother liquor in a mother liquor tank, continuing to heat exchange the evaporated secondary water with industrial water through a second heat exchanger after cooling, increasing the temperature of the industrial water, further reducing the temperature of the evaporated secondary water, exchanging heat through a second heat exchanger, increasing the temperature of the industrial water, and reducing the temperature of the evaporated secondary water; S3, loading the heated industrial water into a dissolution water cooler and a raw water tank in a water treatment workshop, and storing the evaporated secondary water after cooling in a storage tank; S4, heating the evaporated secondary water, and sending it to the dissolution water cooler after heating. The invention fully recovers the gas heat source, and achieves a certain degree of reduction in the overall production energy consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of waste heat utilization in alumina production, and in particular relates to a process method for utilizing waste heat in alumina production. Background Art

[0002] Alumina is an important chemical substance and is usually produced by the Bayer process. The basic principle of the Bayer process is to convert aluminum hydroxide into sodium aluminate with concentrated sodium hydroxide solution, and then re-precipitate the aluminum hydroxide by dilution and adding aluminum hydroxide seeds. The remaining sodium hydroxide solution is reused to process the next batch of bauxite, thus achieving continuous production.

[0003] In the Bayer process of producing alumina, there are many heat exchange equipment, and industrial water is often used as a heat exchange cold source. This method will cause serious scaling of equipment and pipelines, resulting in a significant reduction in heat exchange efficiency. A certain alumina plant project is equipped with a gas furnace and boiler system. The gas produced by the gas furnace needs to be cooled from 230°C to about 150°C in the heat pipe heat exchanger before it can enter the bag filter. After further cooling, the gas temperature is reduced from 150°C to about 50°C in the deamination tower before it can enter the desulfurization tower for desulfurization. The heat exchange cold medium water of the heat pipe heat exchanger and the deamination tower is industrial water. Because the water quality contains a lot of calcium and magnesium ions, it is easy to cause scaling of equipment and pipelines after long-term use after heating, resulting in low equipment heat exchange efficiency and a large amount of pipeline cleaning work. Summary of the invention

[0004] The present invention overcomes the deficiencies of the prior art and provides a process for utilizing waste heat in alumina production to solve the problems existing in the prior art.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a process for utilizing waste heat in alumina production, comprising the following steps:

[0006] S1, exchanging heat between the decomposition mother liquor and the evaporated secondary water through a first heat exchanger, thereby increasing the temperature of the decomposition mother liquor and reducing the temperature of the evaporated secondary water;

[0007] S2, the heated decomposition mother liquor is stored in the mother liquor tank, the cooled evaporated secondary water is further heat exchanged with the industrial water through the second heat exchanger, the temperature of the industrial water is increased, and the temperature of the evaporated secondary water is further decreased, and the temperature of the industrial water is increased and the temperature of the evaporated secondary water is decreased by heat exchange through the second heat exchanger;

[0008] S3, the heated industrial water is loaded into the dissolution water cooler and the raw water tank of the water treatment workshop, and the cooled evaporated secondary water is loaded into the storage tank for storage;

[0009] S4, heating the evaporated secondary water and sending it to the dissolution water cooler after heating.

[0010] In a preferred embodiment of the present invention, both the first heat exchanger and the second heat exchanger are plate heat exchangers.

[0011] In a preferred embodiment of the present invention, in step S3, a driving pump is used to transport the evaporated secondary water in the storage tank to the deammoniation cooling tower and the third heat exchanger to exchange heat with the coal gas and to transport the evaporated secondary water to the flocculant water tank for storage.

[0012] In a preferred embodiment of the present invention, the third heat exchanger is a heat pipe heat exchanger.

[0013] In a preferred embodiment of the present invention, in step S4, the evaporated secondary water heated in the third heat exchanger is sent to the flat plate washing water tank and the ash hot water tank respectively, and the evaporated secondary water after heating in the deammoniation cooling tower is sent to the dissolution water cooler.

[0014] In a preferred embodiment of the present invention, the temperature of the evaporated secondary water is 75° C. after being heated in the deammoniation cooling tower.

[0015] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0016] The evaporated secondary water of the present invention undergoes two heat exchange processes of first cooling and then heating, and is combined with production to fully recover the gas heat source, thereby achieving a certain degree of reduction in the overall production energy consumption; after the evaporated secondary water replaces the industrial water, the amount of pipeline cleaning is greatly reduced, and the operating efficiency of the equipment is improved; the heated industrial water can be supplied to multiple work sections, which not only ensures that heat is not wasted, but also can adjust production in time according to changes in the water volume of the system; and the water use requirements for flocculants are strict, and the water quality requirements are guaranteed after the evaporated secondary water after cooling is used to configure the flocculant. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0018] Figure 1 is an operation block diagram of a preferred embodiment of the present invention;

[0019] Figure 2 A flowchart of a preferred embodiment of the present invention; DETAILED DESCRIPTION

[0020] The following will disclose multiple embodiments of the present invention with drawings. For the purpose of clear description, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. That is, in some embodiments of the present invention, these practical details are not necessary. In addition, for the purpose of simplifying the drawings, some conventional structures and components will be depicted in a simple schematic manner in the drawings.

[0021] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present invention. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] This embodiment provides a process method for utilizing waste heat in alumina production, so that the evaporated secondary water undergoes two heat exchange processes of first cooling and then heating. Combined with the production, the gas heat source is fully recovered, and a certain degree of reduction in the overall production energy consumption is achieved. After the evaporated secondary water replaces the industrial water, the amount of pipeline cleaning is greatly reduced, and the operating efficiency of the equipment is improved. The heated industrial water can be supplied to multiple work sections, which not only ensures that heat is not wasted, but also can adjust the production in time according to the changes in the water volume of the system. In addition, the water use requirements for flocculants are strict. After the evaporated secondary water after cooling is used to prepare the flocculant, the water quality requirements are guaranteed.

[0023] Combination Figure 1 and Figure 2 As shown, the process method for utilizing waste heat in alumina production in this embodiment includes the following steps:

[0024] S1, exchanging heat between the decomposition mother liquid and the evaporated secondary water through a first heat exchanger, thereby increasing the temperature of the decomposition mother liquid and reducing the temperature of the evaporated secondary water. The first heat exchanger in this embodiment is a plate heat exchanger;

[0025] S2, the heated decomposition mother liquor is stored in the mother liquor tank, the cooled evaporated secondary water is further heat exchanged with the industrial water through the second heat exchanger, the temperature of the industrial water is increased, and the temperature of the evaporated secondary water is further decreased, and the heat is exchanged through the second heat exchanger, the temperature of the industrial water is increased, and the temperature of the evaporated secondary water is decreased. The second heat exchanger in this embodiment is a plate heat exchanger;

[0026] S3, the heated industrial water is loaded into the dissolution water cooler and the raw water tank of the water treatment workshop, the cooled evaporated secondary water is loaded into the storage tank for storage, and the evaporated secondary water in the storage tank is transported to the deammoniation cooling tower and the third heat exchanger by a driving pump to exchange heat with the coal gas and to the flocculant water tank for storage. The third heat exchanger in this embodiment is a heat pipe heat exchanger;

[0027] S4. The evaporated secondary water is heated up and sent to the dissolution water cooler after heating. The evaporated secondary water heated up in the third heat exchanger is sent to the flat plate washing water tank and the ash hot water tank respectively. The evaporated secondary water after heating up in the deammoniation cooling tower is sent to the dissolution water cooler. After the evaporated secondary water is heated up in the deammoniation cooling tower, the temperature is 75°C.

[0028] In the actual use of the process method for utilizing waste heat in the production of alumina in this embodiment, an alumina plant is equipped with three gas furnaces and two evaporation stations, which can produce 570t / h of evaporated secondary water at 65°C. First, the evaporated secondary water is mixed with the decomposition mother liquor (500m 3 / h, 48℃) for heat exchange (the temperature of the decomposition mother liquor also needs to be raised to 90℃ before evaporation and concentration, so it is reasonable to use the decomposition mother liquor to recover the heat of the evaporated secondary water), the temperature of the evaporated secondary water is reduced to 50℃, and the temperature of the decomposition mother liquor is raised to 60℃ and then directly sent to the decomposition mother liquor tank. This process is the first stage of heat exchange; the evaporated secondary water coming out of the first heat exchanger directly enters the second heat exchanger and then exchanges heat and cools with industrial water (330t / h, 25℃), so that the temperature of the evaporated secondary water is reduced to 35℃ to meet the conditions for heat exchange at the gas station and is stored in the newly added cold water tank; the heated industrial water (48℃) can go to the dissolution water cooler and continue to heat up for red mud washing water, or it can be used for domestic hot water and the chemical water raw water tank. This process is the second stage of heat exchange.

[0029] The evaporation of secondary water cooling water in the previous stage is completed, and the next stage is two heat exchange processes: the evaporation of secondary water and the gas in the three heat pipe heat exchangers of the gas station, and the evaporation of secondary water and the gas in the three deamination towers of the gas station. The evaporation of secondary water in the cold water tank is pumped to the gas station for heat exchange with the gas in the heat pipe heat exchanger, and the gas temperature is reduced from 230℃ to 150℃ to meet the conditions for entering the bag filter. The evaporation of secondary water temperature is heated to 90℃ and directly used as flat plate washing water and hot water for ash removal; this process is over. In the next process, the evaporation of secondary water in the cold water tank is pumped to the gas station for heat exchange with the gas in the deamination tower, and the gas temperature is reduced from 150℃ to 50℃ to meet the desulfurization conditions. The evaporation of secondary water is heated from 35℃ to 75℃ and then sent to the water cooler to continue heating and sent to the red mud washing tank. The 35℃ evaporation of secondary water can also be sent to flocculant water.

[0030] Although the present invention has been described above with reference to various embodiments, it should be understood that many changes and modifications may be made without departing from the scope of the present invention. That is, the methods, systems or devices discussed above are all examples. Various configurations may appropriately omit, replace or add various processes or components. For example, in alternative configurations, the method may be performed in an order different from the order described, and / or various stages may be added, omitted and / or combined. Moreover, the features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. In addition, with the development of technology, many elements are merely examples and do not limit the scope of the present disclosure or claims.

[0031] Specific details are given in the specification to provide a thorough understanding of the exemplary configurations including implementations. However, the configurations can be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary details to avoid obscuring the configurations. This description provides only example configurations and does not limit the scope, applicability, or configurations of the claims. On the contrary, the foregoing description of the configurations will provide those skilled in the art with an enabling description for implementing the described techniques. Various changes may be made to the functions and arrangements of the elements without departing from the spirit or scope of the present disclosure.

[0032] In addition, although each operation may describe the operation as a sequential process, many operations may be performed in parallel or simultaneously. In addition, the order of the operations may be rearranged. A process may have additional steps. In addition, examples of methods may be implemented by hardware, software, firmware, middleware, code, hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or code, program code or code segments for performing the necessary tasks may be stored in a non-transitory computer-readable medium such as a storage medium, and the described tasks are performed by a processor.

[0033] In summary, it is intended that the above detailed description is considered to be illustrative rather than restrictive, and it should be understood that the claims (including all equivalents) are intended to limit the spirit and scope of the present invention. The above embodiments should be understood to be only used to illustrate the present invention and not to limit the scope of protection of the present invention. After reading the content of the record of the present invention, the technician can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall into the scope limited by the claims of the present invention.

Claims

1. A process for utilizing waste heat in alumina production, characterized in that: The following steps are involved: S1, exchanging heat between the decomposition mother liquor and the evaporated secondary water through a first heat exchanger, thereby increasing the temperature of the decomposition mother liquor and reducing the temperature of the evaporated secondary water; S2, the heated decomposition mother liquor is stored in the mother liquor tank, and the cooled evaporated secondary water and industrial water are introduced into the second heat exchanger, and heat is exchanged through the second heat exchanger to increase the temperature of the industrial water and reduce the temperature of the evaporated secondary water; S3, the heated industrial water is loaded into the dissolution water cooler and the raw water tank of the water treatment workshop, and the cooled evaporated secondary water is loaded into the storage tank for storage; S4, heating the evaporated secondary water and sending it to the dissolution water cooler after heating; In step S3, a driving pump is used to transport the evaporated secondary water in the storage tank to the deammoniation cooling tower and the third heat exchanger to exchange heat with the coal gas, and the evaporated secondary water is transported to the flocculant water tank for storage; In step S4, the evaporated secondary water heated in the third heat exchanger is sent to the flat plate washing water tank and the ash hot water tank respectively, and the evaporated secondary water heated in the deammoniation cooling tower is sent to the dissolution water cooler.

2. The process for utilizing waste heat in alumina production according to claim 1, characterized in that: The first heat exchanger and the second heat exchanger are both plate heat exchangers.

3. The process for utilizing waste heat in alumina production according to claim 1, characterized in that: The third heat exchanger is a heat pipe heat exchanger.

4. The process for utilizing waste heat in alumina production according to claim 1, characterized in that: After the evaporated secondary water is heated in the deammoniation cooling tower, the temperature is 75°C.

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