A method for pre-treatment and concentration of high-salinity wastewater in winter

Abstract

The invention relates to the technical field of frozen wastewater concentration, and specifically discloses a method for pre-treatment and concentration of high-salt wastewater in winter, comprising: S1: transporting raw high-salt wastewater to an outdoor flow channel through a sewage pump, the width of the outdoor flow channel is greater than the depth, the high-salt wastewater flows at a low speed through the outdoor flow channel to a separation process, and the temperature of the high-salt wastewater changes from room temperature to low temperature to room temperature, S2: putting an ice crystal nucleation auxiliary medium into the high-salt wastewater with the help of a floating medium, S3: the primary ice crystal filtrate is slightly melted at the end of the low temperature to room temperature stage, promoting the formation of a salt water channel; with the help of a floating medium, the liquid above the middle layer of the waste liquid is preferentially ice crystals, and enters the low temperature to room temperature stage, at which time the temperature gradually increases, the ice crystals are melted, the salt water channel travel is accelerated, and the impurities are promoted to be discharged, thereby obtaining pure ice crystals. This process can greatly reduce the energy consumption of freezing treatment of high-salt wastewater, and at the same time, the high-salt wastewater is concentrated, the volume of wastewater to be subsequently treated is reduced, and the equipment load is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of frozen wastewater concentration, in particular to a method for pre-treatment and concentration of high-salt wastewater in winter. Background Art

[0002] As an important wastewater desalination technology, freeze concentration methods currently include FGM, FCM, FBM, and FCBM. At low temperatures, water molecules begin to slowly condense and form tiny crystal nuclei, and then the water molecules are arranged and expanded around the crystal nuclei. In this process, salt substances will be discharged through the salt discharge channel in the crystal. There are pores in the internal structure of ice crystals. Combined with gravity, these pores merge with salt impurities to form brine channels, and then the entrained salt impurities are discharged from the ice body through the brine channels to purify the ice crystals. The ice formation rate is inversely proportional to the desalination rate.

[0003] In order to further promote ice crystal formation, ice nucleators are often used. For example, nanocellulose crystals can accelerate ice crystal growth by 500 times and increase ice crystal size by 37%. The Institute of Physics and Chemistry of the Chinese Academy of Sciences discovered a molecular targeted natural ice nucleator and found that it was related to the effective exposure of cellulose hydroxyl groups on the (-110) surface. Therefore, accelerating ice crystal formation through nucleators has application value in wastewater treatment.

[0004] The above content explains the principle of freeze concentration desalination, the relationship between desalination rate and ice formation rate, and the promotion principle of ice crystal nucleating agent on ice crystal formation. However, factory wastewater is often produced continuously, and how to ensure that the freeze concentration method can be continuously concentrated in continuous wastewater treatment is a problem that needs to be solved.

[0005] A Chinese patent discloses a method for treating saline wastewater by freeze concentration, and its publication number is (CN104803433A). The patent uses a crystallizer to crystallize ice crystals, and then takes out the ice crystals and melts them to obtain frozen water. However, after the ice crystals crystallize, there is no gravity sedimentation time, and the salt discharge channel is not fully opened, and a part of it still remains in the ice body. If the crystallization time of the crystallizer is increased, the subsequent waste liquid cannot be continuously fed into the crystallizer, because it is easy to cause temperature changes and crystallization cannot be achieved. Therefore, the subsequent waste liquid needs to be stopped and waited or multiple equipment needs to be added for alternating operation, which increases costs. Summary of the invention

[0006] The object of the present invention is to provide a method for pre-treatment and concentration of high-salt wastewater in winter to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for pre-treatment and concentration of high-salinity wastewater in winter, comprising:

[0009] S1: The raw water of high-salinity wastewater is transported to the outdoor flow channel through a sewage pump. The high-salinity wastewater flows at a low speed through the outdoor flow channel to the separation process. The temperature of the high-salinity wastewater changes from room temperature to low temperature to room temperature.

[0010] S2: placing the ice crystal nucleation auxiliary medium into the high-salinity wastewater with the help of the floating medium, the floating medium flows with the high-salinity wastewater in the outdoor flow channel, the floating medium is located in the upper layer of the high-salinity wastewater, and the upper and lower layers of the high-salinity wastewater are filtered and separated at the end of the low-temperature-room temperature stage to obtain the primary concentrated liquid and the primary ice crystal filtrate;

[0011] S3: The primary ice crystal filtrate melts slightly at the end of the low temperature-room temperature stage, promoting the formation of brine channels and producing a small amount of melted liquid, which flows back into the primary concentrated liquid to obtain the final concentrated liquid and purify the ice crystals;

[0012] S31: During the slight melting of the primary ice crystal filtrate at the end of the low temperature to room temperature stage, a vibration process is added to promote the separation of ice crystals from the ice crystal nucleation auxiliary medium, and the ice crystal nucleation auxiliary medium is transferred to the S2 process for delivery;

[0013] S4: The final concentrated liquid is injected into the high-salt wastewater evaporator for evaporation and crystallization. The purified ice crystals are added with low-temperature clean water and transported to the condensation heat exchange section of the high-salt wastewater evaporator as a heat exchange medium to cool the steam, and refluxed and collected to obtain the ice crystal melted mixed clean water.

[0014] As a further solution of the present invention: S11: the outdoor flow channel is a variable stroke flow channel. When the outdoor temperature is lower than 0 degrees, the low temperature section flow channel stroke is reduced. When the outdoor temperature is higher than 0 degrees, the low temperature section flow channel stroke is increased, and an auxiliary cooling process is added in the low temperature section flow channel stroke.

[0015] As a further solution of the present invention: S12: when the outdoor temperature is below 0 degrees, the flow path stroke of the low-temperature section is increased, and at the same time, the flow path stroke of the low-temperature section-room temperature section is increased and the room temperature section temperature in the low-temperature section-room temperature section is increased.

[0016] As a further solution of the present invention: S21: a plurality of cellulose nanowires are selected as an auxiliary medium for ice crystal nucleation, nanocellulose crystals are adhered to the surface of the cellulose nanowires, one end of the plurality of cellulose nanowires floats on the surface layer of the waste liquid with the assistance of a floating medium, and the other end of the cellulose nanowires floats between the surface layer of the waste liquid and the middle layer of the waste liquid through the floating medium.

[0017] As a further solution of the present invention: S31: During the slight melting of the primary ice crystal filtrate at the end of the low temperature to room temperature stage, a vibration process is added to promote the separation of ice crystals and ice crystal nucleation auxiliary medium, and the ice crystal nucleation auxiliary medium is transferred to the S2 process for delivery.

[0018] As a further solution of the present invention: the width of the outdoor flow channel in S1 is greater than the depth of the outdoor flow channel.

[0019] As a further solution of the present invention: the outdoor flow channel in S1 is arranged inclined.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] In cold seasons, high-salinity wastewater uses the room temperature-low temperature-room temperature method to form wastewater ice crystals by utilizing the low temperature characteristics of the outdoors. In the room temperature-low temperature process, affected by the external low temperature environment, the retention time outside is increased under low flow rate conditions, thereby gradually producing ice crystals. The concentrated liquid is gradually moved to the bottom of the flow channel under the influence of gravity, so that the waste liquid in the flow channel begins to stratify. With the help of floating media, the ice crystal nucleation auxiliary medium is located above the middle layer of the high-salinity wastewater flow channel, so that the liquid above the middle layer of the waste liquid preferentially produces ice crystals, which is conducive to subsequent stratification and collection. Therefore, after the ice crystals are formed, they enter the low temperature-room temperature stage. At this time, the temperature gradually increases, the ice crystals melt, the brine channel travel is accelerated, and the impurities are promoted to be discharged, thereby obtaining pure ice crystals. This process can greatly reduce the energy consumption of high-salinity wastewater freezing treatment, while concentrating high-salinity wastewater, reducing the volume of wastewater for subsequent treatment, and reducing equipment load. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 This is a schematic diagram of a method for pre-treatment and concentration of high-salinity wastewater in winter. DETAILED DESCRIPTION

[0024] See also Figure 1 In this embodiment, S1: the high-salt wastewater raw water is transported to the outdoor flow channel through a sewage pump. The width of the outdoor flow channel is greater than the depth. The high-salt wastewater flows at a low speed through the outdoor flow channel to the separation process. The temperature of the high-salt wastewater changes from room temperature to low temperature to room temperature.

[0025] In this embodiment, in the cold season, the low temperature characteristics of the outdoor are utilized to further concentrate the high-salt wastewater by freeze concentration, and pure liquid is extracted. Without using a refrigeration medium or only using a small amount of refrigeration medium to increase the flow time of the waste liquid outside, the ice formation rate can be controlled, the gravity action time can be increased, and the desalination rate can be improved. The high-salt wastewater is also easy to achieve by using the room temperature-low temperature-room temperature method. It only needs to separate the wastewater raw water storage workshop and the high-salt wastewater treatment workshop, and an outdoor flow channel is arranged between the raw water storage workshop and the high-salt wastewater treatment workshop. The wastewater output from the raw water workshop gradually reaches the lowest temperature as it approaches the outdoor flow channel. At the same time, when it flows to the high-salt wastewater treatment workshop through the end of the outdoor flow channel, the temperature gradually rises to room temperature. In this process, affected by the external low temperature environment, the retention time outside is increased under low flow rate conditions, thereby gradually generating ice crystals, and the concentrated liquid is gradually located below the flow channel under the influence of gravity, so that the waste liquid in the flow channel begins to be stratified.

[0026] In this embodiment, S2: the ice crystal nucleation auxiliary medium is introduced into the high-salt wastewater with the help of the floating medium. The floating medium flows with the high-salt wastewater in the outdoor flow channel. The floating medium is located in the upper layer of the high-salt wastewater, and the upper and lower layers of the high-salt wastewater are filtered and separated at the end of the low-temperature-room temperature stage to obtain the primary concentrated liquid and the primary ice crystal filtrate.

[0027] In this embodiment, in order to accelerate the travel of ice crystals and strengthen the stratification of waste liquid, an ice crystal nucleation auxiliary medium is required. In order to better improve the stratification effect, the ice crystal nucleation auxiliary medium is located above the middle layer of the high-salt wastewater flow channel with the help of a floating medium, so that the liquid above the middle layer of the waste liquid preferentially produces ice crystals, which is conducive to subsequent stratification collection. After stratification, the lower layer is the primary concentrated liquid. Under the low temperature of the outdoor flow channel, the waste liquid produces ice crystals in the upper layer of the liquid with the auxiliary effect of the ice crystal nucleation auxiliary medium. However, under the low temperature environment, the salt water channel in the ice crystal is difficult to open completely. Therefore, after the ice crystal is formed, it enters the low temperature-room temperature stage. At this time, the temperature gradually increases, the ice crystals melt, the travel of the salt water channel is accelerated, and the impurities are promoted to be discharged, thereby obtaining pure ice crystals.

[0028] In this embodiment, S3: the primary ice crystal filtrate slightly melts at the end of the low temperature-room temperature stage, promoting the formation of brine channels and producing a small amount of melted liquid, which flows back into the primary concentrated liquid to obtain the final concentrated liquid and purify the ice crystals.

[0029] In this embodiment, a filtering and conveying mechanism can be provided in the separation stage to filter and convey the ice crystals in the liquid, and the melted liquid generated during the conveying process drops from the filtering surface of the filtering and conveying mechanism to the concentrated liquid below, thereby obtaining pure ice crystals. Pure ice crystals can be melted to obtain clean water, and the content of clean water after concentration is reduced, which reduces the volume occupied in the subsequent evaporation process, thereby increasing the volume of the final evaporation treatment wastewater raw water.

[0030] In this embodiment, S4: the final concentrated liquid is injected into the high-salt wastewater evaporator for evaporation and crystallization, and the purified ice crystals are added to low-temperature clean water and transported to the condensation heat exchange section in the high-salt wastewater evaporator as a heat exchange medium to cool the steam, and refluxed and collected to obtain ice crystal melted mixed clean water.

[0031] In this embodiment, the concentrated liquid evaporates in the evaporator, and the generated steam enters the condenser for heat exchange. At this time, the purified ice crystals are combined with low-temperature clean water as a heat exchange medium and transported to the condenser to cool the pipeline. After the steam is cooled in the pipeline, condensate is generated, and the ice crystals melt at this time to obtain ice crystal melt mixed clean water.

[0032] In this embodiment, S11: the outdoor flow channel is a variable stroke flow channel. When the outdoor temperature is lower than 0 degrees, the low temperature section flow channel stroke is reduced. When the outdoor temperature is higher than 0 degrees, the low temperature section flow channel stroke is increased, and an auxiliary cooling process is added in the low temperature section flow channel stroke.

[0033] In this embodiment, when the outdoor temperature is below 0 degrees, the freezing rate of the waste liquid increases, which can easily lead to a decrease in the desalination rate. Therefore, the low-temperature section flow path is reduced to reduce the freezing rate and ensure the desalination rate, while still being able to concentrate the waste liquid.

[0034] In this embodiment, when the outdoor temperature is higher than 0 degrees, the low temperature section flow path needs to be increased, and the waste liquid in the low temperature section flow path is further cooled by means of an auxiliary cooling process so that ice crystals can form. Compared with direct freezing of water, the amount of refrigeration medium used is reduced.

[0035] In this embodiment, S12: when the outdoor temperature is lower than 0 degrees, the low temperature section flow path stroke is increased, and at the same time, the low temperature section - room temperature section flow path stroke is increased and the room temperature section temperature in the low temperature section - room temperature section is increased.

[0036] In this embodiment, in order to improve the concentration effect, in a low-temperature environment, the flow path of the low-temperature section is increased to increase the freezing rate. At the same time, the flow path of the low-temperature section-room temperature section is increased and the temperature of the room temperature section in the low-temperature section-room temperature section is increased. Under the condition of high freezing rate, the formation of brine channels is promoted by increasing the temperature, and impurities are discharged, thereby improving the concentration effect.

[0037] In this embodiment, S21: a plurality of cellulose nanowires are selected as an auxiliary medium for ice crystal nucleation, nanocellulose crystals are adhered to the surface of the cellulose nanowires, one end of the plurality of cellulose nanowires floats on the surface layer of the waste liquid with the assistance of a floating medium, and the other end of the cellulose nanowire floats between the surface layer of the waste liquid and the middle layer of the waste liquid through the floating medium.

[0038] In this embodiment, the structure of the cellulose nanowires is similar to that of the nanocellulose crystals. The density of the nanocellulose crystals is greater than the density of water and greater than the density of brine. Therefore, the nanocellulose crystals will sink to the bottom in the water. Therefore, the cellulose nanowires are used as the main body, and the ends of multiple cellulose nanowires are connected to a floating medium. The floating medium can be any object that can float above the liquid surface, such as a plastic hollow ball, and the other end of the cellulose nanowire is fixed with another floating medium. The floating medium allows the other end of the cellulose nanowire to extend toward the middle layer of the liquid, and a large number of nanocellulose crystals are adhered to the outside of the cellulose nanowires by bonding. This design method allows the ice crystal nucleation auxiliary medium to cover the middle layer of the liquid surface, inducing the preferential production and enrichment of ice crystals above the middle layer of the wastewater. During the flow process, a small amount of nanocellulose crystals will fall off, and a small amount of ice crystals will be produced in the lower layer of the waste liquid. Therefore, when filtering, further filtering or no filtering of the bottom can be considered.

[0039] In this embodiment, S31: During the slight melting of the primary ice crystal filtrate at the end of the low temperature-room temperature stage, a vibration process is added to promote the separation of ice crystals from ice crystal nucleation auxiliary medium, and the ice crystal nucleation auxiliary medium is transferred to the S2 process for delivery. Since a large amount of ice crystals are enriched in the upper layer of the waste liquid, and the cellulose nanowires are also affected by the adhering nanocellulose crystals to produce ice crystals, the vibration process is conducive to the separation of ice crystals from cellulose nanowires, so that the cellulose nanowires can be reused. During use, multiple ice crystal nucleation auxiliary media are delivered and cover the upper area of ​​the wastewater.

[0040] In this embodiment, the width of the outdoor flow channel in S1 is greater than the depth of the outdoor flow channel. Increasing the flow channel width makes it easier for the surface to exchange temperature with the external environment.

[0041] In this embodiment, the outdoor flow channel in S1 is inclined. The inclined setting reduces the power required for the waste liquid to flow slowly, and the low-speed flow is achieved by converting gravity and kinetic energy.

[0042] What has been described above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for pre-treatment and concentration of high-salinity wastewater in winter, characterized in that: include: S1: The raw water of high-salinity wastewater is transported to the outdoor flow channel through a sewage pump. The high-salinity wastewater flows at a low speed through the outdoor flow channel to the separation process. The temperature of the high-salinity wastewater changes from room temperature to low temperature to room temperature. S11: The outdoor flow channel is a variable stroke flow channel. When the outdoor temperature is below 0 degrees, the low temperature section flow channel stroke is reduced. When the outdoor temperature is above 0 degrees, the low temperature section flow channel stroke is increased, and an auxiliary cooling process is added in the low temperature section flow channel stroke. S2: placing the ice crystal nucleation auxiliary medium into the high-salinity wastewater with the help of the floating medium, the floating medium flows with the high-salinity wastewater in the outdoor flow channel, the floating medium is located in the upper layer of the high-salinity wastewater, and the upper and lower layers of the high-salinity wastewater are filtered and separated at the end of the low-temperature-room temperature stage to obtain the primary concentrated liquid and the primary ice crystal filtrate; S21: A plurality of cellulose nanowires are selected as the ice crystal nucleation auxiliary medium, nanocellulose crystals are adhered to the surface of the cellulose nanowires, one end of the plurality of cellulose nanowires is floated on the surface layer of the waste liquid with the assistance of the floating medium, and the other end of the cellulose nanowire is floated between the surface layer of the waste liquid and the middle layer of the waste liquid through the floating medium; S3: The primary ice crystal filtrate melts slightly at the end of the low temperature-room temperature stage, promoting the formation of brine channels and producing a small amount of melted liquid, which flows back into the primary concentrated liquid to obtain the final concentrated liquid and purify the ice crystals; S31: During the slight melting of the primary ice crystal filtrate at the end of the low temperature to room temperature stage, a vibration process is added to promote the separation of ice crystals from the ice crystal nucleation auxiliary medium, and the ice crystal nucleation auxiliary medium is transferred to the S2 process for delivery; S4: The final concentrated liquid is injected into the high-salt wastewater evaporator for evaporation and crystallization. The purified ice crystals are added with low-temperature clean water and transported to the condensation heat exchange section of the high-salt wastewater evaporator as a heat exchange medium to cool the steam, and refluxed and collected to obtain the ice crystal melted mixed clean water.

2. A winter high-salinity wastewater pretreatment and concentration method according to claim 1, characterized in that: The outdoor flow channel width in S1 is greater than the outdoor flow channel depth.

3. A winter high-salinity wastewater pretreatment and concentration method according to claim 1, characterized in that: The outdoor flow channel in S1 is tilted.

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