Salt leaching tank and salt manufacturing device comprising same

Abstract

The utility model relates to a salt leaching tank. The salt leaching tank comprises a settling area, a rinsing area and an elutriation area which are sequentially divided from top to bottom, wherein the rinsing area comprises a main body section and an inverted trapezoidal section, a stirring mechanism is arranged at the top of the salt leaching tank and comprises a motor and a stirring rod, the motor is arranged at the top of the salt leaching tank, the stirring rod extends through an opening in the top of the salt leaching tank, passes through the settling area and enters the main body section of the rinsing area, and a feeding mechanism is further arranged at the top of the salt leaching tank. An overflow port is formed in the side wall of the settlement area; the washing area is a salt leg, and the inverted trapezoidal section is connected with the salt leg. The utility model provides a novel salt leaching tank which can be used for quickly cleaning crystals and effectively removing impurities in the crystals. The utility model further provides a salt making device comprising the salt leaching tank.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment technology, specifically relating to a salt washing tank and a salt making device including the same. Background Technology

[0002] Currently, the amount of high-salinity wastewater generated from coal chemical production is increasing daily. High-salinity wastewater refers to wastewater with a total salt content greater than 1% by mass. This type of wastewater contains a large amount of organic and inorganic substances and is a common and difficult-to-treat type of wastewater. In order to improve the recycling of water resources and protect the ecological environment, zero-discharge and resource utilization of coal chemical wastewater is imperative.

[0003] Zero-discharge resource utilization of coal chemical wastewater refers to treating wastewater generated in coal mines and coal chemical production projects, partially reusing it to the production line after it meets standards, and separating the remaining concentrated brine through evaporation and crystallization to produce product salt which is sold to downstream manufacturers (chlor-alkali chemical, textile, papermaking, etc.) as raw materials. Compared with traditional wastewater treatment, zero-discharge resource utilization of coal chemical wastewater presents two challenges. First, facing increasingly stringent environmental policies, enterprises have higher requirements for the continuous and stable operation of their facilities. Wastewater discharge is not allowed, and complete reuse and resource utilization are required. If the facility's operation is unstable, it will force the shutdown of production facilities, leading to unpredictable losses. Second, if the crystalline salt produced by "zero discharge" does not meet the standards for use by downstream manufacturers, it will cause new solid waste problems arising from the treated wastewater. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this utility model is to provide a salt washing tank, which includes a settling zone, a rinsing zone and a washing zone divided from top to bottom; wherein, the top of the salt washing tank is provided with a stirring mechanism, which includes a motor and a stirring rod. The motor is located at the top of the salt washing tank, and the stirring rod extends through the opening at the top of the salt washing tank, preferably the opening at the center of the top, through the settling zone and into the main body of the rinsing zone. The top of the salt washing tank is also provided with a feeding mechanism, and the side wall of the settling zone is provided with an overflow port; the washing zone is a salt leg, and an inverted trapezoidal section is connected to the salt leg.

[0005] An inverted trapezoidal segment refers to a segment whose longitudinal cross-section is an inverted trapezoid.

[0006] This utility model's salt washing tank, as part of a salt-making apparatus, is internally divided into three zones: the upper zone is a settling zone with an overflow port on the side wall, allowing the clear liquid to overflow into the mother liquor tank at the front of the washing tank, where it can be used for further evaporation in the crystallization section of the salt-making apparatus; the middle zone is a rinsing zone, where a stirring mechanism is activated to accelerate the recrystallization of the washed crystals, promoting the separation of impurities such as COD from the crystals; the lower zone is a washing zone with salt legs for washing, where a prepared, subsaturated pure solution can be used for countercurrent washing, both replacing the mother liquor components and accelerating the recrystallization of the washed crystals, further promoting the separation of impurities such as COD from the crystals. Using this utility model's salt washing tank significantly improves the purity of salt crystals, reduces the content of impurities such as COD, while also increasing washing efficiency and reducing energy consumption.

[0007] Preferably, the stirring rod is a paddle type, a spiral type, or an anchor type. Different types of stirring rods can be selected according to the characteristics of the salt crystals and the requirements for salt washing, so as to improve stirring efficiency, promote uniform recrystallization of crystals, and separate impurities.

[0008] Preferably, the stirring mechanism also includes a frequency converter connected to the motor for adjusting the motor speed. Adjusting the stirring speed via the frequency converter can adapt to the needs of different salt washing stages, optimize the salt washing effect, and reduce energy consumption.

[0009] Preferably, the cross-sectional areas of the settling zone, rinsing zone, and washing zone decrease sequentially. A larger cross-sectional area in the settling zone reduces the fluid velocity and promotes the settling of impurity particles; a smaller cross-sectional area in the washing zone increases the washing liquid velocity and enhances the countercurrent washing effect.

[0010] Preferably, the salt washing tank also includes a temperature control mechanism, optionally located on the side wall of the main section in the rinsing zone. The temperature control mechanism can precisely control the temperature of the rinsing zone, optimize the recrystallization process, and improve the purity of the salt crystals and the salt washing efficiency.

[0011] Preferably, the side wall of the salt leg has one or more washing liquid inlets for providing washing liquid to wash the salt; and / or, the salt leg has one or more discharge ports, which may be located at the bottom of the salt leg and / or on the side wall of the salt leg. The multi-inlet design enables countercurrent washing, effectively displacing the mother liquor components, while the multiple locations of the discharge ports facilitate flexible discharge of salt crystals and improve operational convenience.

[0012] Preferably, the height ratio of the main section to the inverted trapezoidal section of the rinsing zone is 1:0.8 to 1:1.2, and the height ratio of the rinsing zone to the washing zone is 1:0.7 to 1:2.5; and / or the height of the rinsing zone accounts for 1 / 4 to 1 / 2 of the total height of the salt washing tank, and the height of the washing zone accounts for 1 / 3 to 2 / 3 of the total height of the salt washing tank; and / or the transverse cross-sectional area of ​​the main section is larger than that of the inverted trapezoidal section, and the angle between the sidewall of the inverted trapezoidal section and the vertical direction is 15°-25°; and / or the transverse cross-sectional area of ​​the main section is 1.20-2.00m². 2 The base area where the inverted trapezoidal segment connects to the salt leg is 0.20-0.40 m². 2 In this invention, the total height of the salt washing tank is the height from the top of the settling zone to the bottom of the rinsing zone. These features effectively achieve thorough stirring of the crystals in the rinsing zone and enhance the displacement of impurities by the countercurrent washing liquid during rinsing, significantly improving the whiteness of the product.

[0013] Another aspect of this invention provides a salt-making apparatus, comprising a crystallization section, a primary thickening centrifugation section, a salt washing section, and an optional secondary thickening centrifugation section connected in sequence, wherein the salt washing section includes a salt washing tank as described above. By integrating the salt washing tank into the salt-making apparatus, the salt-making process is made highly efficient and continuous, improving the purity of the salt product and production efficiency.

[0014] Preferably, the crystallization section includes a salt precipitation tank and a nitrate precipitation tank, and the primary thickening centrifugation section and the secondary thickening centrifugation section each include one or more thickeners and centrifuges. The thickeners may optionally be equipped with salt legs and weight sensors.

[0015] In use, the thickener receives the suspension discharged from the salt washing tank and concentrates it. The thickener is equipped with a salt leg that allows for counter-current rinsing, effectively removing impurities and mother liquor residue from the salt crystals, significantly improving the purity of the crystallized salt and thickening efficiency. Additionally, a weight sensor on the thickener detects the solid-liquid ratio. Once a suitable ratio is reached, the material in the thickener is fed into a centrifuge for dehydration of the concentrated material.

[0016] Preferably, the salt precipitation tank is sequentially connected to the primary salt thickener, primary salt centrifuge, and the aforementioned salt washing tank in the primary thickening centrifugation section, and the secondary salt thickener and secondary salt centrifuge in the secondary thickening centrifugation section. Similarly, the nitrate precipitation tank is sequentially connected to the primary nitrate thickener, primary nitrate centrifuge, and the aforementioned salt washing tank in the primary thickening centrifugation section, and the secondary nitrate thickener and secondary nitrate centrifuge in the secondary thickening centrifugation section. Through multi-stage thickening and salt washing processes, the salt and nitrate can be further purified, the impurity content reduced, and the quality of the final product improved.

[0017] More preferably, the sodium chloride (salt) obtained by the salt-making device of this utility model shall at least meet the requirements for whiteness and total organic carbon (TOC) of the secondary standard for industrial wet salt specified in T / CCT002-2019 "Sodium Chloride for Industrial Use as a By-product of Coal Chemical Industry", and the obtained sodium sulfate (nitrate) shall at least meet the requirements for TOC of Class B Grade I product specified in T / CCT001-2019 "Sodium Sulfate for Industrial Use as a By-product of Coal Chemical Industry", and more preferably meet the requirements for whiteness and TOC of Class A Grade I product. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the salt washing tank of this utility model;

[0019] Figure 2 This is a schematic diagram of the connection of the salt-making device of this utility model. Detailed Implementation

[0020] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0021] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the utility model.

[0023] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0024] The above solution will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrating the present invention and do not limit the scope of this application.

[0025] The salt washing tank in this embodiment adopts a zoned structure design, divided from top to bottom into an upper settling zone, a middle rinsing zone, and a lower washing zone. It utilizes saturated washing mother liquor or salt washing mother liquor to wash the crystalline salt produced by evaporation and crystallization, thoroughly washing away impurities remaining on the surface of the crystalline salt that affect purity, accelerating recrystallization, and promoting the separation of impurities, including COD, from the crystals. This design fully guarantees the purity and whiteness of the produced salt, meeting the usage standards of downstream manufacturers.

[0026] Figure 1 A schematic diagram of the salt washing tank in this embodiment is shown, as follows: Figure 1 As shown, the rinsing zone of the salt washing tank in this embodiment includes a main body section and an inverted trapezoidal section. The top of the salt washing tank is equipped with a stirring mechanism, which includes a motor and a stirring rod. The motor is located at the top of the salt washing tank, and the stirring rod extends through the central opening at the top of the salt washing tank, passes through the settling zone, and enters the main body section of the rinsing zone. The top of the salt washing tank is also equipped with a feeding mechanism, and the side wall of the settling zone is equipped with an overflow port. The washing zone is a salt leg, and the inverted trapezoidal section is connected to the salt leg.

[0027] Specifically, in this embodiment, the height ratio of the main section to the inverted trapezoidal section of the rinsing zone is approximately 1:1, and the ratio of the height H2 of the rinsing zone to the height H3 of the washing zone is 1:0.8. The height H2 of the rinsing zone accounts for approximately 1 / 2 of the total height H of the salt washing tank, and the height H3 of the washing zone accounts for approximately 1 / 3 of the total height H of the salt washing tank. The transverse cross-sectional area of ​​the main section of the rinsing zone is larger than that of the inverted trapezoidal section. In this embodiment, the angle between the sidewall of the inverted trapezoidal section and the vertical direction is approximately 20°; the transverse cross-sectional area of ​​the main section is 1.77m². 2 The base area where the inverted trapezoidal segment connects to the salt leg is 0.28 m². 2In this embodiment, a paddle-type agitator is used, extending from the central opening at the top of the brine washing tank to the lower part of the main body section in the rinsing zone. The agitation mechanism also includes a frequency converter connected to a motor for adjusting the motor's speed. Of course, in other embodiments of this invention, the agitator can also be spiral or anchor-type, selected according to different crystal characteristics and the requirements of the subsequent salt products. In this embodiment, the feeding mechanism can be used for feeding, solution reflux, and replenishing water to the brine washing tank.

[0028] In this embodiment, the side wall of the salt leg is provided with three washing liquid inlets for providing washing liquid to wash the salt; and the salt leg is provided with two discharge ports, one of which is located at the bottom of the salt leg and the other is located on the side wall of the salt leg.

[0029] In this embodiment, the upper part of the salt washing tank is a settling zone, and an overflow port is provided on the side wall. During use, the clear liquid overflows into the mother liquor tank at the front of the salt washing tank. The clear liquid can be used for further evaporation and crystallization in the crystallization section of the salt making device. The middle rinsing zone is equipped with frequency conversion stirring. Stirring and rinsing can adjust the stirring speed, accelerate crystal recrystallization, and promote the separation of components such as COD that encapsulate the crystals. The lower washing zone is equipped with salt legs for washing. During use, a pure solution with a concentration lower than saturation is used for countercurrent washing (for example, when cleaning crystals whose main component is sodium chloride, a pure sodium chloride solution with a concentration lower than saturation is used for washing). This replaces the components of the mother liquor and accelerates recrystallization, promoting the separation of components such as COD that encapsulate the crystals.

[0030] In this embodiment, the lateral cross-sectional areas of the settling zone, rinsing zone, and washing zone decrease sequentially. A larger cross-sectional area in the settling zone facilitates rapid separation and overflow of the clarified liquid, thereby improving the overall processing efficiency of the brine washing tank.

[0031] In this embodiment, the salt washing tank also includes a temperature control mechanism, which is located on the side wall of the main body section in the rinsing zone. In this embodiment, the temperature control mechanism includes a temperature sensor, a heating / cooling device, and a controller. During use, the controller controls the operation of the heating / cooling device based on the signal fed back from the temperature sensor, achieving precise temperature control within the salt washing tank. The specific washing temperature varies depending on the type of crystalline salt being washed. For example, when washing crystalline salt whose main component is sodium chloride, the temperature inside the washing tank is above 75°C and typically below 100°C; when washing crystalline salt whose main component is sodium sulfate, the temperature inside the washing tank is above 50°C and typically below 70°C.

[0032] The salt washing tank in this embodiment is part of the salt-making apparatus. In this embodiment, the salt-making apparatus includes a crystallization section, a primary thickening centrifugation section, a salt washing section, and a secondary thickening centrifugation section connected in sequence.

[0033] like Figure 2As shown, the salt precipitation tank is sequentially connected to the primary salt thickener, primary salt centrifuge, and salt washing tank in the primary thickening centrifugation section, and the secondary salt thickener and secondary salt centrifuge in the secondary thickening centrifugation section. Similarly, the nitrate precipitation tank is sequentially connected to the primary nitrate thickener, primary nitrate centrifuge, and salt washing tank in the primary thickening centrifugation section, and the secondary nitrate thickener and secondary nitrate centrifuge in the secondary thickening centrifugation section.

[0034] In this embodiment, specifically taking coal chemical wastewater with a COD of 280-400 ppm as an example, after pretreatment (e.g., filtration), the wastewater first enters the crystallization section to crystallize sodium chloride (salt) and sodium sulfate (nitrate) separately. In the crystallization section, the COD in the salt and nitrate tanks is controlled to be ≤7000 ppm during crystallization to avoid excessive enrichment of COD and other colorimetric components. Crystallization can be performed using an FC crystallizer or an Oslo crystallizer; in this embodiment, the salt and nitrate tanks are FC crystallizers.

[0035] In the primary thickening centrifugation section, there are separate primary salt thickeners and centrifuges, and primary nitrate thickeners and centrifuges. Both the primary salt and primary nitrate thickeners have salt legs. The solution enters from the inlet of the thickener and is countercurrently washed along the leg wall. The primary salt thickener is washed with the clear liquid generated in the salt precipitation tank or the subsequent secondary washing mother liquor. The primary nitrate thickener is washed with the four-effect concentrated liquid generated in the nitrate precipitation tank or the subsequent secondary nitrate washing mother liquor. The centrifuges are also divided into salt centrifuges and nitrate centrifuges. The thickeners increase the slurry concentration, and the centrifuges perform solid-liquid separation to obtain crystals. The thickeners and centrifuges work together to achieve efficient solid-liquid separation. In this embodiment, the centrifuge is a horizontal centrifuge. Of course, in other embodiments of this invention, a vertical centrifuge or a screw discharge centrifuge can also be used.

[0036] In this embodiment, a weight sensor is installed on the thickener. When the thickener reaches the weight within the designed range, the centrifuge is started. Therefore, the centrifuge is set to operate intermittently. When the weight of the thickener is lower than the designed range, the discharge from the outlet of the salt / nitrate tank to the thickener is stopped. The thickener continues to thicken the slurry to increase the solid-liquid ratio, thereby ensuring that the water content of the crystals is low after centrifugation.

[0037] The secondary thickening centrifugation section is set up similarly to the primary thickening centrifugation section. The secondary thickener for salt and the secondary thickener for nitrate are also equipped with salt legs. The washing solution is also the same, using the clear liquid produced in the salt precipitation tank or the mother liquor produced in the salt washing tank, and the four-effect concentrated liquid produced in the nitrate precipitation tank or the mother liquor produced in the nitrate washing tank, respectively, to improve the quality of salt and nitrate particles.

[0038] In this embodiment, the solution processing capacity of the primary thickening centrifugation section is greater than that of the secondary thickening centrifugation section. This design allows the entire device to adapt to different wash water additions. During use, if the COD of the salt or nitrate precipitation tank exceeds the design value, the salt washing tank can be adjusted to use multiple times the amount of water for washing as needed, thereby ensuring the purity and whiteness of the product.

[0039] After the above processing, sodium chloride crystals were obtained from the salt secondary centrifuge, and sodium sulfate crystals were obtained from the nitrate secondary centrifuge. The sodium chloride crystals had a whiteness of 83 and COD < 20 mg / kg, meeting the first-grade standard for industrial wet salt specified in T / CCT002-2019 "Industrial Sodium Chloride, a By-product of Coal Chemical Industry". The sodium sulfate crystals had a whiteness of 85 and COD < 35 mg / kg, meeting the Class A first-grade standard in T / CCT001-2019 "Industrial Sodium Sulfate, a By-product of Coal Chemical Industry".

[0040] The embodiments of this utility model have been described in detail above, but the content described is only a preferred embodiment of this utility model and should not be considered as limiting the scope of implementation of this utility model. Any equivalent improvements made by those skilled in the art without departing from the scope of this utility model should still fall within the patent coverage of this utility model.

Claims

1. A brine washing tank characterized by, The salt washing tank includes a settling zone, a rinsing zone, and a washing zone, divided from top to bottom. The rinsing zone includes a main section and an inverted trapezoidal section. A stirring mechanism is located at the top of the salt washing tank, comprising a motor and a stirring rod. The motor is located at the top of the salt washing tank, and the stirring rod extends through an opening at the top of the salt washing tank, passes through the settling zone, and enters the main section of the rinsing zone. A feeding mechanism is also located at the top of the salt washing tank, and an overflow port is located on the side wall of the settling zone. The washing zone is a salt leg, and the inverted trapezoidal section is connected to the salt leg.

2. The brine washing tank according to claim 1, characterized in that, The stirring rod is a paddle type, a spiral type, or an anchor type; and / or, the stirring rod extends through the main body section of the settling zone into the rinsing zone through the opening at the center of the top of the salt washing tank.

3. The brine wash tank of claim 1, wherein, The stirring mechanism also includes a frequency converter connected to the motor for adjusting the motor speed.

4. The brine wash tank of claim 1, wherein, The cross-sectional areas of the settling zone, the rinsing zone, and the washing zone decrease sequentially.

5. The brine wash tank of claim 1, wherein, The salt washing tank also includes a temperature control mechanism, which is optionally located on the side wall of the main body section in the rinsing zone.

6. The salt washing tank according to claim 1, characterized in that, The salt leg has one or more washing liquid inlets on its side wall for providing washing liquid to wash the salt; and / or, the salt leg has one or more discharge ports, which may be located at the bottom of the salt leg and / or on the side wall of the salt leg.

7. The salt washing tank according to claim 1, characterized in that, The height ratio of the main section to the inverted trapezoidal section of the rinsing zone is 1:0.8 to 1:1.2, the height ratio of the rinsing zone to the washing zone is 1:0.7 to 1:2.5; and / or the height of the rinsing zone accounts for 1 / 4 to 1 / 2 of the total height of the salt washing tank, the height of the washing zone accounts for 1 / 3 to 2 / 3 of the total height of the salt washing tank; and / or the lateral cross-sectional area of the main section is greater than that of the inverted trapezoidal section, the angle between the side wall of the inverted trapezoidal section and the vertical direction is 15°-25°; and / or the lateral cross-sectional area of the main section is 1.20-2.00 m 2 , the bottom area of the connection between the inverted trapezoidal section and the salt leg is 0.20-0.40 m 2 .

8. A salt-making apparatus, characterized in that, The salt-making apparatus includes a crystallization section, a primary thickening centrifugation section, a salt washing section, and an optional secondary thickening centrifugation section connected in sequence, wherein the salt washing section includes a salt washing tank as described in any one of claims 1-7.

9. The salt-making apparatus according to claim 8, characterized in that, The crystallization section includes a salt precipitation tank and a nitrate precipitation tank. The primary thickening centrifugation section and the secondary thickening centrifugation section each include one or more thickeners and centrifuges. The thickener may optionally be equipped with a salt leg and a weight sensor.

10. The salt-making apparatus according to claim 9, characterized in that, The salt precipitation tank is sequentially connected to the primary salt thickener, primary salt centrifuge, the salt washing tank as described in any one of claims 1-7, the secondary salt thickener and secondary salt centrifuge in the secondary thickening centrifuge section, and the nitrate precipitation tank is sequentially connected to the primary nitrate thickener, primary nitrate centrifuge, the salt washing tank as described in any one of claims 1-7, the secondary nitrate thickener and secondary nitrate centrifuge in the secondary thickening centrifuge section.

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