Alumina production high temperature evaporation water recycling system

Abstract

The present application relates to the technical field of evaporative water recovery system, and more particularly to a high-temperature evaporative water recovery system for alumina production, which separates high-temperature condensate water from low-temperature condensate water, uses the low-temperature condensate water for low-temperature workstations, and sends the high-temperature condensate water to a deaerator for auxiliary heating of the deoxygenation process of the deaerator, so as to make the deoxygenated water reach a saturation temperature and maximize the deoxygenation effect. The heat of the condensate water is used for heat exchange with the deaerator, which not only reduces the heating power and energy of the original heating coil in the deaerator and saves the energy consumption of external heating, but also gradually cools the high-temperature condensate water to meet the requirements of high-pressure boiler makeup water recovery. The condensate water is not only recovered in terms of heat, but also used in various areas, realizing all-round recovery and utilization of the condensate water and green energy saving.

Description

Technical Field

[0001] This invention relates to the technical field of evaporation water recovery systems, and more particularly to a high-temperature evaporation water reuse system for alumina production. Background Technology

[0002] Alumina is a white, amorphous, powdery inorganic substance commonly used as an analytical reagent and adsorbent. It is primarily extracted from bauxite and other materials, requiring several major production processes: raw material preparation (preparing the raw ore slurry), leaching (dissolving the alumina component from the raw ore slurry into a sodium aluminate solution), sedimentation (separating the crude liquid and red mud composed of adhering alkali and various impurities from the slurry; the separated crude liquid is then filtered through a leaf filter to obtain a refined liquid), decomposition (mixing the refined slurry with seed crystals and progressively cooling and stirring it in various decomposition tanks to fully precipitate aluminum hydroxide), and roasting (roasting the filtered crude material at high temperatures to finally obtain the finished alumina). To fully utilize the mother liquor, an evaporation workshop is set up to concentrate the circulating mother liquor, removing excess water that enters the mother liquor during the process and achieving the required mother liquor concentration.

[0003] However, the evaporation process generates a large amount of high-temperature condensate, which contains acidic and alkaline components and is rich in oxygen. These components can oxidize and corrode the high-pressure boiler, failing to meet the quality standards for high-pressure boiler feedwater (GB / T12145-2016). A mixed bed is needed to remove the harmful components in the condensate. However, after initial recovery, the temperature of the condensate reaches as high as 75°C, while the inlet water temperature of the mixed bed needs to be controlled below 45°C. Therefore, the condensate needs to be cooled before being injected into the mixed bed. Currently, during the cooling process, the heat dissipation of the condensate cannot be fully utilized, resulting in heat loss.

[0004] Therefore, the present invention provides a high-temperature evaporation and water recycling system for alumina production, which improves the heat utilization rate of condensate recovery water. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art by proposing a high-temperature evaporation and water recycling system for alumina production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-temperature evaporation and water recycling system for alumina production is characterized by comprising five sets of parallel exchangers, which are connected in parallel to a high-temperature demineralized water tank and a normal-temperature demineralized water tank. The high-temperature demineralized water tank and the normal-temperature demineralized water tank are connected in parallel to a main pipe. A gate valve is provided on the main pipe. A low-temperature demineralized water pump and a high-temperature demineralized water pump are respectively connected on both sides of the gate valve on the main pipe. The low-temperature demineralized water pump is connected to a low-temperature water tank. The high-temperature demineralized water pump is connected to a deaerator. The deaerator is connected to a return water tank.

[0008] The main pipe sidewall is connected to a recovery pipe via an isolation valve, and the recovery pipe is connected to a regeneration system.

[0009] Preferably, each group of exchangers includes a primary mixed bed and a secondary mixed bed connected in series, with the outlet of the secondary mixed bed connected in parallel to a high-temperature demineralized water tank and a normal-temperature demineralized water tank, respectively.

[0010] Preferably, the low-temperature demineralized water in the low-temperature water tank is used for condenser makeup water and high-pressure feed water pump sealing water.

[0011] Preferably, the outlet of the secondary mixed bed is connected to the high-temperature demineralized water tank via a DN250 pipe.

[0012] Preferably, multiple sets of both the low-temperature demineralized water pump and the high-temperature demineralized water pump are provided, with the inlet of all the low-temperature demineralized water pumps connected to a common low-temperature inlet header, and the inlet of all the high-temperature demineralized water pumps connected to a common high-temperature inlet header.

[0013] Preferably, the outlet of the high-temperature demineralized water tank is connected to the high-temperature water inlet header via a DN300 pipe.

[0014] Preferably, all primary and secondary mixed beds contain both cation and anion resins, and both the anion and cation resins are high-temperature resistant resins.

[0015] Compared with the prior art, the present invention provides a high-temperature evaporation and water recycling system for alumina production, which has the following beneficial effects.

[0016] 1. This invention separates high-temperature condensate from low-temperature condensate. The low-temperature condensate is used in low-temperature work areas (condenser makeup water, high-pressure feedwater pump sealing water), while the high-temperature condensate is transported to the deaerator to provide auxiliary heating for the deaerator's deoxygenation process, promoting the deaerator water to reach saturation temperature and maximizing the deaeration effect. The heat from the condensate is used to exchange heat with the deaerator, which not only reduces the heating power and energy consumption of the original heating pipes in the deaerator, saving energy consumption from external heating, but also allows the high-temperature condensate to gradually cool down, meeting the feedwater recovery requirements of the high-pressure boiler. After heat exchange, the high-temperature condensate is recycled, enabling both high-temperature and low-temperature condensate to be used in various areas, achieving comprehensive condensate recycling, saving energy and water consumption, and realizing green energy conservation.

[0017] 2. This invention utilizes ion exchange to improve water recycling, reduce heat loss, reduce coal consumption, and achieve green, clean, and energy-saving practices.

[0018] 3. In this invention, the anion and cation exchange resins in the mixed bed are all made of high-temperature resistant resins, which improves the heat resistance of the mixed bed and eliminates the need for cooling of condensate before it is fed into the mixed bed, thereby reducing the process flow and simplifying the operation steps.

[0019] Other advantages, objectives and features of the invention will be set forth in part in the description which follows; and in part will be apparent to those skilled in the art upon examination of the following description; or may be learned from practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the basic condensate recovery system of Embodiment 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the improved condensate recovery system according to Embodiment 2 of the present invention.

[0022] Figure 3 This is a schematic diagram of the combined condensate recovery system of Embodiment 3 of the present invention.

[0023] In the diagram: 1. Primary mixed bed; 2. Secondary mixed bed; 3. High-temperature demineralized water tank; 4. Normal-temperature demineralized water tank; 5. First main pipe; 6. Second gate valve; 7. Low-temperature demineralized water pump; 8. High-temperature demineralized water pump; 9. Deaerator; 10. Low-temperature water tank; 11. DN250 pipeline; 12. DN300 pipeline. Detailed Implementation

[0024] The following will refer to the appendices in the embodiments of the present invention. Figure 1-3 The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] Example 1: In order to improve the heat utilization rate of high-temperature condensate, this example provides a high-temperature evaporation water reuse system for alumina production, including five sets of parallel exchangers. Each set of exchangers includes a primary mixed bed 1 and a secondary mixed bed 2 connected in series (mixed bed is short for mixed ion exchanger). The inlet and outlet water of the primary mixed bed 1 and the secondary mixed bed 2 of the first set are isolated to form a separate system.

[0026] See attached document Figure 1As shown, the outlet of the secondary mixed bed 2 is connected to a high-temperature demineralized water tank 3 and a normal-temperature demineralized water tank 4 via a water supply pipe. Both the inlet and outlet of the high-temperature demineralized water tank 3 and the normal-temperature demineralized water tank 4 are equipped with a first gate valve. The high-temperature demineralized water tank 3 and the normal-temperature demineralized water tank 4 are connected in parallel to a first main pipe 5. A second gate valve 6 is installed on the first main pipe 5. A low-temperature demineralized water pump 7 and a high-temperature demineralized water pump 8 are connected on both sides of the gate valve on the first main pipe 5. The low-temperature demineralized water pump 7 and the high-temperature demineralized water pump 8 are connected to a second main pipe. An isolation valve is installed on the second main pipe between the low-temperature demineralized water pump 7 and the high-temperature demineralized water pump 8. The end of the second main pipe connected to the low-temperature demineralized water pump 7 is connected to a low-temperature water tank 10. The end of the second main pipe connected to the high-temperature demineralized water pump 8 is connected to a deaerator 9.

[0027] In this embodiment, all primary mixed beds 1 and secondary mixed beds 2 contain regenerable cation and anion resins. The anions and cations of the salts contained in the condensate are exchanged by the resins after passing through the mixed bed, resulting in highly pure water. The condensate is initially recycled at a temperature of approximately 75 degrees Celsius. According to the specifications, the inlet water temperature of the mixed bed can only be controlled at 40 degrees Celsius. Therefore, both the anion and cation resins are high-temperature resistant resins to improve the heat resistance of the mixed bed.

[0028] In this embodiment, a return water tank is provided to collect all the high-temperature condensate. The return water tank is connected to the primary mixed bed 1 via a return water pump.

[0029] In this embodiment, multiple sets of both the low-temperature demineralized water pump 7 and the high-temperature demineralized water pump 8 are provided to improve pipeline transportation efficiency.

[0030] The specific usage process of this embodiment is as follows:

[0031] Start the return water pump to draw the high-temperature condensate in the return water tank into the primary mixed bed 1 for ion exchange to remove harmful components. The condensate filtered from the primary mixed bed 1 will be injected back into the secondary mixed bed 2 for secondary filtration to improve the purification effect of the condensate.

[0032] If the purified condensate is below room temperature (less than 30℃), the first gate valve at the inlet of the room temperature demineralized water tank 4 is opened, and the low-temperature condensate is injected into the room temperature demineralized water tank 4. Specific chemical reagents are used to remove impurities and salts from the water, further improving the purification effect of the condensate, so that the treated condensate can meet the qualification requirements. After demineralization, the first gate valve at the outlet of the room temperature demineralized water tank 4 is opened, and the low-temperature demineralized water pump 7 is started to inject the treated condensate into the low-temperature water tank 10. The low-temperature demineralized water in the low-temperature water tank 10 is used for condenser makeup water, high-pressure feed water pump sealing water and other low-temperature work positions.

[0033] If the purified condensate exceeds room temperature, the first gate valve at the inlet of the high-temperature demineralized water tank 3 is opened, allowing the high-temperature condensate to be injected into the tank for impurity and desalination. Then, the first gate valve at the outlet of the tank 3 is opened, and the high-temperature demineralized water pump 8 is started, sending the treated high-temperature condensate to the deaerator 9. This provides auxiliary heating for the deaerator 9's deoxygenation process, ensuring the deoxygenated water reaches saturation temperature and maximizing the deoxygenation effect. The heat from the condensate is used to exchange heat with the deaerator 9, which not only reduces... This reduces the heating power and energy consumption of the original internal heating pipes of the deaerator 9, saving energy consumption from external heating. For example, it reduces coal consumption when heating the boiler and reduces electricity consumption when heating with electricity. According to estimates, based on the use of an additional 50t of evaporation return water per hour, the original operating temperature is increased by 31℃, resulting in an annualized benefit of 50×24×30×12×31×1000×4.2 / 29270=1921 tons of standard coal. Moreover, it allows the high-temperature condensate to gradually cool down, meeting the requirements for feedwater recovery of the high-pressure boiler, thus achieving green energy saving.

[0034] Example 2: This example optimizes the pipeline based on Example 1, as shown in the attached figure. Figure 2 As shown, a DN250 pipe is opened on the side wall of the water supply pipe. A third gate valve is installed between the DN250 pipe and the delivery pipe. The water supply pipe is only connected to the ambient temperature demineralized water tank 4. The first main pipe 5 is divided into a low-temperature inlet main pipe and a high-temperature inlet main pipe at the second gate valve 6. The inlets of all low-temperature demineralized water pumps 7 are connected to the low-temperature inlet main pipe, and the inlets of all high-temperature demineralized water pumps 8 are connected to the high-temperature inlet main pipe. The high-temperature inlet main pipe is connected to the high-temperature demineralized water tank 3 via a DN300 pipe. The second main pipe is disconnected at the second gate valve 6 and the isolation valve, respectively, and connected to the low-temperature water tank 10 and the deaerator 9, thereby enabling... Low-temperature condensate and high-temperature condensate are completely separated. The high-temperature condensate is dedicated to the deaerator 9, and its heat is directly utilized. The original low-temperature condensate is still used for the low-temperature workstation. The separation of the two means that the pipes used to transport condensate at different temperatures are made of different materials, and therefore have different prices. The price of the pipes used to transport high-temperature condensate is higher than that used to transport low-temperature condensate. Originally, high-temperature and low-temperature condensate shared a single pipe. Now, after separation, the cost of laying the pipes is reduced. The separation of one pipe into two pipes increases the pressure resistance and fault tolerance of the pipes. After the pipes are separated, the frequency of valve opening and closing is reduced, making operation more convenient and the process simpler.

[0035] Example 3 retains the basic piping of Example 1 in Example 2, so that it can be used in an emergency if any pipe in either set of piping has a problem.

[0036] Example 4: In order to further improve the recycling rate of condensate, in this example, the side wall of the first main pipe 5 is connected to a recovery pipe via an isolation valve. The recovery pipe is connected to a mixed bed regeneration system. After the mixed bed has been used for a certain period of time, the ion adsorption in the cation and anion resins inside it becomes saturated and can no longer exchange with the ions in the condensate, thereby greatly reducing the purification effect of the mixed bed. In order to restore the mixed bed, acid and alkali solutions need to be injected alternately into the mixed bed. The hydrogen ions and hydroxide ions in the acid and alkali solutions exchange with the cations and anions adsorbed on the cation and anion resins respectively, thereby consuming the saturated state of the cation and anion resins and restoring them to their original state, thereby restoring the function of the mixed bed.

[0037] Regeneration steps for mixed-bed cation and anion exchange resins:

[0038] 1. Backwashing and stratification: The anion and cation resins are separated into layers through repeated washing.

[0039] 2. Close the backwash inlet valve of the mixed bed and check whether the resin in the mixed bed has completely separated into layers;

[0040] 3. Draining water: After the cation and anion resins have completely separated into layers, open the positive wash drain valve to drain the water from the mixed bed until it is about 10cm away from the surface of the resin layer.

[0041] 4. Add regenerated solution: Adding regenerated solution promotes the cation and anion exchange of the mixed bed resin;

[0042] 5. Displacement: The ion-saturated state of the mixed resin is mitigated through displacement;

[0043] 6. Mixing of cation and anion resins: The ions after displacement are remixed to produce regenerated resin.

[0044] 7. Forward washing: Wash until the effluent meets the standards before it can be used for standby or put into operation.

[0045] In this embodiment, the flange of the middle drain header of the mixing bed device is moved to the outside of the mixing bed tank for easy assembly and replacement.

[0046] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A high-temperature evaporation and water recycling system for alumina production, characterized in that, It includes five sets of parallel exchangers, which are connected in parallel to a high temperature demineralized water tank (3) and a normal temperature demineralized water tank (4). The high temperature demineralized water tank (3) and the normal temperature demineralized water tank (4) are connected in parallel to a main pipe. A gate valve is provided on the main pipe. A low temperature demineralized water pump (7) and a high temperature demineralized water pump (8) are respectively connected on both sides of the gate valve on the main pipe. The low temperature demineralized water pump (7) is connected to a low temperature water tank (10). The high temperature demineralized water pump (8) is connected to a deaerator (9). The deaerator (9) is connected to a return water tank. The side wall of the main pipe is connected to a recovery pipe via an isolation valve, and the recovery pipe is connected to a regeneration system. Each of the exchangers in the group includes a primary mixed bed (1) and a secondary mixed bed (2) connected in series. The outlet of the secondary mixed bed (2) is connected in parallel with the high temperature demineralized water tank (3) and the normal temperature demineralized water tank (4), respectively. The low-temperature demineralized water pump (7) and the high-temperature demineralized water pump (8) are provided in multiple sets. The inlets of all low-temperature demineralized water pumps (7) are connected to a low-temperature water inlet header, and the inlets of all high-temperature demineralized water pumps (8) are connected to a high-temperature water inlet header. All primary mixed beds (1) and secondary mixed beds (2) contain cation resin and anion resin, and both anion resin and cation resin are high-temperature resistant resins. Regeneration steps for mixed-bed cation and anion exchange resins: Step 1: Backwashing and Separation: Repeated washing is used to separate the anion and cation resins into layers; Step 2: Close the backwash inlet valve of the mixed bed and check whether the resin in the mixed bed has completely separated into layers; Step 3: Draining water: After the cation and anion resins have completely separated into layers, open the positive wash drain valve to drain the water in the mixed bed until the water level is 10cm away from the surface of the resin layer. Step 4: Add regenerated solution: Add regenerated solution to promote cation and anion exchange in the mixed bed resin; Step 5: Displacement: The ion saturation state of the mixed resin is mitigated by displacement; Step 6: Mixing of cation and anion resins: The ions after displacement are remixed to produce regenerated resin; Step 7: Forward washing: Wash until the effluent meets the standards before it can be used for standby or put into operation.

2. The high-temperature evaporation and water recycling system for alumina production according to claim 1, characterized in that, The low-temperature demineralized water in the low-temperature water tank (10) is used for condenser makeup water and high-pressure feed water pump sealing water.

3. The high-temperature evaporation and water recycling system for alumina production according to claim 1, characterized in that, The outlet of the secondary mixed bed (2) is connected to the high-temperature demineralized water tank (3) via a DN250 pipe (11).

4. The high-temperature evaporation and water recycling system for alumina production according to claim 1, characterized in that, The outlet of the high-temperature demineralized water tank (3) is connected to the high-temperature water inlet header via a DN300 pipe (12).

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