Dissolved air flotation device with desilting function and seawater desalination pretreatment process

Abstract

The invention relates to the technical field of seawater desalination pretreatment, in particular to a dissolved air flotation device with a desilting function and a seawater desalination pretreatment process, and the dissolved air flotation device comprises a water distribution channel, a coagulation and flocculation system, an air flotation tank, a water outlet system and a deslagging system which are integrally designed and sequentially communicated; the bottom of the water distribution channel and the bottom of the coagulation and flocculation system are both designed to be in a conical hopper type. Sand discharging floral tubes are laid at the bottoms of the water distribution channel, the coagulation and flocculation system and the air floatation tank, the opening directions of a plurality of sand discharging openings in the sand discharging floral tubes are obliquely downward, and deposited sand grains are discharged in a self-pressing mode. According to the dissolved air flotation device, by arranging the continuous desilting channel and laying the desilting floral tubes, deposited sand grains can be effectively discharged, the effective volume utilization rate of the air flotation tank is improved, the stability of the treatment effect of the dissolved air flotation device is ensured, and the seawater desalination pretreatment efficiency is improved; through the integrated design, the occupied area can be reduced to the maximum extent; the problems in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater desalination pretreatment processes, and particularly relates to a dissolved air flotation device with a sand discharge function and a seawater desalination pretreatment process. Background Art

[0002] With the growth of the global population and the development of the economy, the demand for fresh water resources is increasing day by day. However, due to the scarcity of fresh water resources, its supply faces serious challenges. Given that the ocean contains rich seawater resources, seawater desalination has become an important solution to address this challenge. Seawater desalination aims to remove salts and impurities from seawater to make it fresh water resources directly usable by humans. During the seawater desalination process, it is first necessary to pretreat the seawater to remove suspended solids, organic matter, microorganisms and other pollutants to prevent these pollutants from clogging and damaging the subsequent desalination equipment. Among them, the dissolved air flotation device is a commonly used device in the seawater desalination pretreatment process. Its working principle is to dissolve air in water through a dissolved air system and release a large number of tiny bubbles under appropriate conditions. These bubbles will attach to the suspended particles in the water, reducing the density of the suspended particles and causing them to rise to the water surface to form scum. Subsequently, the scum is removed by a scraper. Therefore, through the dissolved air flotation device, suspended solids and part of the organic matter in seawater can be effectively removed, providing good inlet conditions for subsequent desalination processes such as reverse osmosis and distillation, ensuring the smooth progress of the seawater desalination process, and helping to improve the seawater desalination efficiency. However, there are many problems to be solved urgently in traditional dissolved air flotation devices. Specifically, for example, traditional dissolved air flotation devices usually occupy a large area and do not have a sand discharge function. When encountering extreme typhoon weather, the sand content in seawater will increase significantly. These mud and sand particles are small and have a large density. After being affected by their own gravity, they will deposit at the bottom of the dissolved air flotation device, forming a dense sand deposit layer. These sand deposit layers are different in nature from the loose sludge deposited under traditional flotation or sedimentation tanks. The loose sludge has fluidity and is easier to be discharged. However, due to the friction between sand particles and the pressure generated by accumulation, these sand deposit layers will form a bridge above the sludge discharge pipe, resulting in that traditional dissolved air flotation devices often cannot completely discharge these sand particles. This is extremely likely to cause a large amount of sand to deposit at the bottom of the flotation tank. A large amount of sand deposited at the bottom of the flotation tank will not only clog the sand discharge system, but even clog the air release heads. It will also occupy the effective volume of the flotation tank. Furthermore, it will seriously affect the treatment effect and treatment efficiency of the dissolved air flotation device for seawater. In addition, once the above-mentioned clogging occurs, the inspection, maintenance and repair are difficult and costly, which also brings great trouble to the seawater desalination pretreatment work.

[0003] The present invention provides a dissolved air flotation device with a sand discharge function and a seawater desalination pretreatment process to solve the problems existing in the prior art, such as the traditional dissolved air flotation device not having a sand discharge function, a large floor area, low efficiency and high cost in seawater desalination pretreatment. Summary of the Invention

[0004] The object of the present invention is to provide a dissolved air flotation device with a sand discharge function and a seawater desalination pretreatment process to solve the problems existing in the prior art, such as the traditional dissolved air flotation device not having a sand discharge function, a large floor area, low efficiency and high cost in seawater desalination pretreatment.

[0005] The technical solution of the present invention is: a dissolved air flotation device with a sand discharge function, including an integrated design of a water distribution channel, a coagulation and flocculation system, a flotation tank, a slag discharge system and an effluent system, which are connected in sequence; wherein, the bottoms of the water distribution channel and the coagulation and flocculation system are both designed in a conical hopper shape; A dissolved air release head connected to a dissolved air tank is arranged in the flotation tank, and a slag scraper travels above; a continuous sand discharge channel is arranged at the bottom of the flotation tank; The slag discharge system includes a slag tank arranged on one side of the flotation tank and communicating with the upper part of the flotation tank, and a slag discharge tank communicating with the slag tank; The effluent system includes an effluent tank communicating with one side of the flotation tank; Sand discharge perforated pipes and reverse blowing air pipes are laid at the bottoms of the water distribution channel, the coagulation and flocculation system and the flotation tank; the reverse blowing air pipe is arranged at the upper end of the sand discharge perforated pipe and is parallel to the sand discharge perforated pipe; The sand discharge perforated pipe is connected to the slag discharge tank through an external sand discharge pipeline; the opening directions of several sand discharge openings on the sand discharge perforated pipe are all obliquely downward, and the deposited sand grains are discharged by self-pressure; The reverse blowing air pipe is connected to an external reverse blowing pipeline through a first valve; Several air blowing openings with opening directions all obliquely downward are arranged on the reverse blowing air pipe.

[0006] Preferably, in the flotation tank, the slope of the sand discharge channel is 40°-60°; the sand discharge perforated pipe is laid in the sand discharge channel; The coagulation and flocculation system includes a coagulation tank and a flocculation tank that are interconnected and both designed with conical hoppers at the bottom; the coagulation tank communicates with the upper part of the water distribution channel, and the upper part of the flocculation tank communicates with the flotation tank; the sand discharge perforated pipes are respectively laid at the bottoms of the coagulation tank and the flocculation tank. Preferably, the opening center line directions of the air blowing openings and the sand discharge openings are both obliquely downward at 40°-50° Preferably, the segments of the external backwashing pipeline near the water distribution channel, the coagulation and flocculation system, and the air flotation tank are all designed in a "Ji" shape, and their heights are respectively higher than the maximum liquid level height in the adjacent water distribution channel, the coagulation and flocculation system, or the air flotation tank.

[0007] Preferably, the external backwashing pipeline is connected to the external sand discharge pipeline through a second valve.

[0008] Preferably, the dissolved air flotation device further includes a return water dual-source system; the return water dual-source system includes a dual-source switching device; one end of the dual-source switching device is connected to the dissolved air release head through a return pipeline, and the other end is respectively connected to the water outlet tank and the subsequent filtration system through a return pipeline.

[0009] Preferably, an adjustable water outlet weir is provided on one side of the air flotation tank connected to the slag tank.

[0010] Preferably, a stirring device is provided on the slag discharge tank; A slag tank flushing system or a screw slag conveyor may also be provided on the slag discharge tank.

[0011] The present invention also provides a seawater desalination pretreatment process, which uses the above-mentioned dissolved air flotation device with a sand discharge function to pretreat seawater; the process includes the following steps: S1. First, the seawater is transported to the water distribution channel for mixing and sedimentation treatment. After that, the seawater flows into the coagulation and flocculation system, and the deposited sand grains are discharged through the sand discharge perforated pipe. S2. The seawater flowing into the coagulation and flocculation system forms flocculent alum flowers with impurities and lighter sand grains under the action of coagulants and flocculants. Part of the sand grains are deposited at the bottom of the coagulation and flocculation system and are discharged through the sand discharge perforated pipe. S3. The formed flocculent alum flowers and part of the sand grains flow into the air flotation tank with the seawater. After the flocculent alum flowers are combined with the bubbles released by the dissolved air release head, they float upward and are scraped into the slag tank by the slag scraper. Part of the sand grains are deposited in the sand discharge channel and are discharged through the sand discharge perforated pipe. After that, the seawater in the air flotation tank flows into the water outlet tank. During operation, the sand discharge situation is monitored in real time. When the sand grain bridging phenomenon occurs, the first valve is opened, and the air released through the backwashing air pipe is used to destroy the bridging. When the external sand discharge pipeline is blocked, the second valve is opened, and the high-pressure gas transported through the external backwashing pipeline is used to dredge the external sand discharge pipeline. S4. The seawater flowing into the water outlet tank is transported to the subsequent filtration system for further treatment, or part of it is refluxed to the dissolved air tank and flows into the air flotation tank through the dissolved air release head, and the other part flows into the subsequent filtration system. S5. The flocculated alum flocs scraped into the slag tank and the sand grains discharged from the sand discharge pipeline are both transported through the pipeline to the slag discharge tank and discharged after treatment.

[0012] Compared with the prior art, the advantages of the present invention are as follows: (1) This application is applied to seawater desalination. In view of the characteristics of the environment and seawater itself, the upper end of the air flotation tank realizes the separation of pollutants based on the air flotation principle, and the lower end of the air flotation tank realizes the discharge of sand grains based on the self-pressure principle, overcoming the limitation that the traditional air flotation tank can only separate floating scum through air flotation; specifically, by setting a continuous sand discharge channel in the air flotation tank and laying sand discharge perforated pipes at the bottom of the water distribution channel, coagulation and flocculation system, and air flotation tank, the sand grains deposited in the water distribution channel, coagulation and flocculation system, and air flotation tank can be effectively discharged, improving the effective volume utilization rate of the water distribution channel, coagulation and flocculation system, and air flotation tank, ensuring the stability of the treatment effect of the dissolved air flotation device, and improving the efficiency of seawater desalination pretreatment; moreover, by setting an anti-blowing air pipe and an external anti-blowing pipeline, not only can the phenomenon of sand grain bridging be prevented during the sand discharge process, but also the blocked external sand discharge pipeline can be dredged in time, effectively reducing the maintenance difficulty and frequency of the dissolved air flotation device, reducing the maintenance cost, and further reducing the cost of seawater desalination pretreatment; at the same time, through the integrated design of the dissolved air flotation device, the floor area can be minimized; it solves the problems existing in the prior art that the traditional dissolved air flotation device does not have a sand discharge function, has a large floor area, low efficiency and high cost in seawater desalination pretreatment.

[0013] (2) The dissolved air flotation device with a sand discharge function and the seawater desalination pretreatment process provided by the present invention are provided with a double water source system for return water in the dissolved air flotation device. According to the monitoring results of the sand grain content, the return water source can be switched through the double water source switching device of the double water source system for return water, ensuring that the air release heads are not blocked, making the dissolved air flotation device have stronger adaptability when dealing with seawater with different sand grain contents, and ensuring the stable operation of the dissolved air flotation device.

[0014] (3) The dissolved air flotation device with a sand discharge function and the seawater desalination pretreatment process provided by the present invention are provided with an adjustable water outlet weir, a slag tank flushing system or a screw slag conveyor, which can reduce the moisture content of the floating scum and ensure the smooth discharge of the floating scum, thereby reducing the amount of floating scum in the seawater of the water outlet tank, and contributing to the subsequent treatment of seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the drawings and embodiments: Figure 1 is a structural schematic diagram of the dissolved air flotation device described in the present invention; Figure 2 is a structural schematic diagram of the water distribution channel - coagulation and flocculation system - air flotation tank described in the present invention; Figure 3 This is a cross-sectional view of the dissolved air flotation tank of the present invention; Figure 4 This is a cross-sectional view of the dissolved air flotation tank of the present invention; Figure 5 This is a schematic structural view of the coagulation tank of the present invention; Wherein: 1, water distribution channel; 2, coagulation and flocculation system; 21, coagulation tank; 22, flocculation tank; 3, dissolved air flotation tank; 31, adjustable effluent weir; 32, dissolved air release head; 33, dissolved air tank; 34, dual water source switching device; 35, flow stabilizer plate; 4, slag discharge system; 41, slag trough; 42, slag discharge tank; 43, stirring device; 5, effluent system; 51, effluent tank; 52, effluent pump; 6, sand discharge channel; 7, slag scraper; 8, sand discharge perforated pipe; 81, sand discharge port; 82, external sand discharge pipeline; 9, reverse blowing air pipe; 91, blowing port; 92, external reverse blowing pipeline; 93, first valve; 94, second valve. Specific embodiments

[0016] The following further elaborates on the content of the present invention in conjunction with specific embodiments: In the description of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "bottom", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0017] A dissolved air flotation device with a sand discharge function, as Figure 1 shown, includes a water distribution channel 1, a coagulation and flocculation system 2, a dissolved air flotation tank 3, a slag discharge system 4, and an effluent system 5 that are integrally designed and connected in sequence; adopting an integrated intensive design makes the structure of the dissolved air flotation device compact and can minimize the floor area to the greatest extent. Among them, the bottoms of the water distribution channel 1 and the coagulation and flocculation system 2 are both designed as conical hoppers, and the conical hopper design can make the sand grains naturally slide to the bottoms of the water distribution channel 1 and the coagulation and flocculation system 2 under the action of gravity; a dissolved air release head 32 connected to the dissolved air tank 33 is provided in the dissolved air flotation tank 3, and a slag scraper 7 travels above the dissolved air flotation tank 3; a continuous sand discharge channel 6 is provided at the bottom of the dissolved air flotation tank 3; and, as Figure 2As shown in the figure, several water distribution channels 1, coagulation and flocculation systems 2, and air flotation tanks 3 in the dissolved air flotation device are arranged side by side. The sand discharge channels 6 of each air flotation tank 3 are arranged parallel to the length direction of the air flotation tank 3, that is, longitudinally arranged. Longitudinally arranging the sand discharge channels 6 can ensure that the dissolved air flotation device can discharge mud independently and smoothly, and also helps to reduce the floor area of the dissolved air flotation device. The slag discharge system 4 includes a slag tank 41 arranged on one side of the air flotation tank 3 and communicating with the upper part of the air flotation tank 3. The water outlet system 5 includes a water outlet tank 51 communicating with one side of the air flotation tank 3. Sand discharge perforated pipes 8 are laid at the bottoms of the water distribution channels 1, coagulation and flocculation systems 2, and air flotation tanks 3, and the sand discharge perforated pipes 8 are communicated with an external sand discharge pipeline 82 for discharging the sand grains deposited in the water distribution channels 1, coagulation and flocculation systems 2, and air flotation tanks 3. The opening directions of several sand discharge openings 81 on the sand discharge perforated pipes 8 are all obliquely downward, and the deposited sand grains are discharged by self-pressure under the action of the liquid level difference.

[0018] In the air flotation tank 3, the slope of the sand discharge channel 6 laid at its bottom is 40 - 60°; the sand discharge perforated pipe 8 is laid in the sand discharge channel 6. This design enables the sand grains to quickly move along the large-slope sand discharge channel 6 towards the sand discharge openings 81 under the action of gravity and water flow, facilitating the effective discharge of sand grains and reducing the deposition of sand grains at the bottom of the air flotation area. The dissolved air release head 32 is arranged in the floating selection area of the air flotation tank 3. A flow stabilizer plate 35 is also arranged in the air flotation area of the air flotation tank 3, which helps to improve the sedimentation rate of sand grains in seawater. The slag scraper 7 travels on the liquid surface in the air flotation tank 3 and is close to the position of the slag tank 41 for scraping the floating slag into the slag tank 41. An adjustable water outlet weir 31 is arranged above the side of the air flotation tank 3 communicating with the slag tank 41. The weir plate of the adjustable water outlet weir 31 is made of a material with a certain flexibility and can bend downward when subjected to an external force and return to its original state after the external force disappears. Furthermore, it can effectively fine-tune the water outlet liquid level according to the treatment volume to avoid phenomena such as a large amount of water being carried by the floating slag or the floating slag not being scraped out due to too low a slag level. In addition, the weir plate of the adjustable water outlet weir 31 can also be made of a rigid plate. In this case, a lifting power system such as a lifting cylinder or a lifting electric cylinder needs to be equipped, and the height of the weir plate is precisely controlled through a valve. The coagulation and flocculation system 2 includes a coagulation tank 21 and a flocculation tank 22 that are interconnected and both designed with a conical hopper at the bottom. The coagulation tank 21 communicates with the upper part of the water distribution channel 1, and the upper part of the flocculation tank 22 communicates with the air flotation tank 3. Sand discharge perforated pipes 8 are respectively laid at the bottoms of the coagulation tank 21 and the flocculation tank 22. For the sand discharge perforated pipes 8 laid at the bottoms of the water distribution channel 1, coagulation tank 21, flocculation tank 22, and air flotation tank 3, the opening center line directions of the sand discharge openings 81 are all obliquely downward at 40° - 50°.

[0019] The slag discharging system 4 further includes a slag discharging pit 42; the slag discharging pit 42 is connected to the slag trough 41 through a pipeline; the external sand discharging pipeline 82 is also connected to the slag discharging pit 42, and is used to centrally transport the sand particles deposited at the bottoms of the water distribution channel 1, the coagulation and flocculation system 2, the air flotation tank 3, etc. to the slag discharging pit 42 for subsequent treatment; due to the poor uniformity and stability of the floating slag, in order to ensure the uniformity and stability of the floating slag, in this application, a stirring device 43 is provided on the slag discharging pit 42 for stirring the floating slag transported to the slag discharging pit 42; in addition, due to the poor fluidity of the floating slag, a slag trough scouring system or a screw slag conveyor may also be provided on the slag discharging pit 42 to prevent a large amount of accumulation in the slag discharging pit 42 and difficult discharge due to the poor fluidity of the floating slag.

[0020] Seawater contains a large amount of mud and sand, especially sand, and when encountering extreme typhoon weather, the sand content in seawater will increase significantly; due to the small particle size and large density of these mud and sand, after being affected by their own gravity, they are deposited at the bottoms of the water distribution channel 1, the coagulation and flocculation system 2 and the air flotation tank 3, forming a dense sand particle deposition layer. This causes a bridging phenomenon during the process of discharging sand particles through the sand discharging perforated pipe 8 under the action of the liquid level difference. This is not the same as the loose sludge deposited under the traditional sedimentation tank. The loose sludge has fluidity, while in this application, based on the friction between sand particles, the pressure generated by accumulation, etc., as Figure 3 shown, when the sand particles on the periphery of the sand discharging perforated pipe 8 and the sand discharging port 81 are discharged, the sand particles above them are prone to form a bridge. Therefore, in this application, as Figure 4 shown, the bottoms of the water distribution channel 1, the coagulation and flocculation system 2 and the air flotation tank 3 are all provided with back blowing air pipes 9, and the back blowing air pipes 9 are connected to the external back blowing pipeline 92 through the first valves 93; the back blowing air pipes 9 are arranged at the upper ends of the sand discharging perforated pipes 8 and are parallel to the sand discharging perforated pipes 8; the pipe diameters of the back blowing air pipes 9 are smaller than those of the sand discharging perforated pipes 8; a number of air blowing ports 91 with the opening directions all inclined downward are also provided on the back blowing air pipes 9, and the opening center line directions of the air blowing ports 91 are also inclined downward at 40° - 50°. By blowing air into the bottoms of the water distribution channel 1, the coagulation and flocculation system 2 and the air flotation tank 3 through the back blowing air pipes 9, a flowing air current is introduced into the space below the area where the bridge is formed, destroying the bridging phenomenon, and effectively avoiding the bridging phenomenon during the discharge of the sand particles deposited at the bottoms of the water distribution channel 1, the coagulation and flocculation system 2 and the air flotation tank 3, ensuring that the sand particles can be smoothly discharged from the bottoms of the water distribution channel 1, the coagulation and flocculation system 2 and the air flotation tank 3.

[0021] To avoid the phenomenon of seawater flowing back into the external back blowing pipeline 92 when starting or stopping blowing air into the bottoms of the water distribution channel 1, the coagulation and flocculation system 2 and the air flotation tank 3, as Figure 5As shown, the segments of the external backwashing pipeline 92 near the water distribution channel 1, the coagulation and flocculation system 2, and the air flotation tank 3 are all designed in a "Ji" shape, and their heights are respectively higher than the maximum liquid level heights in their adjacent water distribution channel 1, coagulation and flocculation system 2, or air flotation tank 3; that is, the segment of the external backwashing pipeline 92 connected to the backwashing air pipe 9 in the water distribution channel 1 is designed in a "Ji" shape, and the height of this "Ji" shape is higher than the maximum liquid level height in the water distribution channel 1; similarly, the segments of the external backwashing pipeline 92 respectively connected to the backwashing air pipes 9 in the coagulation and flocculation system 2 and the air flotation tank 3 are also designed in a "Ji" shape, and their heights are respectively higher than the maximum liquid level heights in the coagulation and flocculation system 2 and the air flotation tank 3.

[0022] During the process of discharging the sand particles deposited at the bottoms of the water distribution channel 1, the coagulation and flocculation system 2, and the air flotation tank 3 through the sand discharge perforated pipe 8 and the external sand discharge pipeline 82, the external sand discharge pipeline 82 and the sand discharge perforated pipe 8 may be blocked; therefore, in this application, the external backwashing pipeline 92 is also connected to the external sand discharge pipeline 82 through the second valve 94; at this time, the external backwashing pipeline 92 can be used as a high-pressure air pipe to convey high-pressure gas into the external sand discharge pipeline 82; when the sand particles block the external sand discharge pipeline 82 and the sand discharge perforated pipe 8, the second valve 94 can be opened, and high-pressure gas can be introduced into the external sand discharge pipeline 82 and the sand discharge perforated pipe 8 through the external backwashing pipeline 92 to dredge the blocked external sand discharge pipeline 82 and sand discharge perforated pipe 8 and ensure smooth sand and sludge discharge. In addition, the external backwashing pipeline 92 may not be connected to the external sand discharge pipeline 82, but instead a pipeline separately laid and connected to the external sand discharge pipeline 82 can be used as a high-pressure air pipe to dredge the blocked external sand discharge pipeline 82 and sand discharge perforated pipe 8.

[0023] The dissolved air flotation device further includes a return water dual-source system; the return water dual-source system includes a dual-source switching device 34; one end of the dual-source switching device 34 is connected to the dissolved air releasing head 32 through a return pipeline, and the other end is respectively connected to the water outlet tank 51 and the subsequent filtration system through a return pipeline. In this application, the return water dual-source system enables the return water to select the air flotation effluent or the effluent of the subsequent filtration system, such as ultrafiltration, sand filtration and other systems; that is, under normal circumstances, the return water selects the air flotation effluent to ensure the normal operation of the dissolved air flotation; and when the sand particle content in the air flotation effluent exceeds the standard, it can be switched to the effluent of the subsequent filtration system, thereby effectively avoiding the blockage of the dissolved air releasing head 32 due to the return water carrying sand particles and achieving the ensure good air releasing effect of the dissolved air flotation. The water outlet system 5 further includes a water outlet pump 52, the input end of the water outlet pump 52 is connected to the water outlet tank 51, and the output end is connected to the dual-source switching device 34 or the subsequent filtration system.

[0024] The present invention also provides a seawater desalination pretreatment process, which uses the above-mentioned dissolved air flotation device with sand discharge function to pretreat seawater; specifically, it includes the following steps: S1. First, convey the seawater to the distribution channel for mixing and sedimentation treatment. Then, the seawater flows into the coagulation and flocculation system, and the deposited sand grains are discharged through the sand discharge perforated pipe; S2. For the seawater flowing into the coagulation and flocculation system, under the action of the coagulant and flocculant, the impurities and lighter sand grains therein form flocculent alum flowers. Part of the heavier sand grains settle at the bottom of the coagulation and flocculation system under the action of gravity and are discharged through the sand discharge perforated pipe; S3. The formed flocculent alum flowers and part of the sand grains flow into the air flotation tank with the seawater. The bubbles released by the dissolved air diffuser head will combine with the flocculent alum flowers, causing them to float, and are scraped into the slag tank by the slag scraper. Part of the sand grains settle in the sand discharge channel and are discharged by self-pressure through the sand discharge perforated pipe under the action of the liquid level difference. Then, the seawater in the air flotation tank flows into the outlet tank; During the operation, it is also necessary to monitor the sand discharge situation in real time. When the sand grain bridging phenomenon occurs, open the first valve, and use the air released by the back blowing air pipe to destroy the bridging; when the external sand discharge pipeline is blocked, open the second valve, and use the high-pressure gas conveyed through the external back blowing pipeline to dredge the external sand discharge pipeline; S4. Convey the seawater flowing into the outlet tank to the subsequent filtration system for further treatment through the outlet water pump. Or, part of it flows back to the dissolved air tank through the reflux pipe and flows into the air flotation tank through the dissolved air diffuser head, and the other part flows into the subsequent filtration system for further treatment; S5. The flocculent alum flowers scraped into the slag tank and the sand grains discharged from the sand discharge pipeline are both conveyed to the slag discharge tank through pipelines and discharged after treatment.

[0025] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A dissolved air flotation device with a sand discharge function, comprising an integrated design of a water distribution channel (1), a coagulation and flocculation system (2), a flotation tank (3), a slag discharge system (4), and an effluent system (5) that are connected in sequence; characterized in that, The bottoms of the water distribution channel (1) and the coagulation and flocculation system (2) are both designed in a conical hopper shape; In the flotation tank (3), there is a dissolved air release head (32) connected to a dissolved air tank (33), and a slag scraper (7) travels above; at the bottom of the flotation tank (3), there is a continuous sand discharge channel (6); The slag discharge system (4) includes a slag tank (41) arranged on one side of the flotation tank (3) and connected to the upper part of the flotation tank (3), and a slag discharge tank (42) connected to the slag tank (41); The effluent system (5) includes an effluent tank (51) connected to one side of the flotation tank (3); The bottoms of the water distribution channel (1), the coagulation and flocculation system (2), and the flotation tank (3) are all provided with sand discharge perforated pipes (8) and reverse blowing air pipes (9); the reverse blowing air pipes (9) are arranged at the upper ends of the sand discharge perforated pipes (8) and are parallel to the sand discharge perforated pipes (8); The sand discharge perforated pipes (8) are connected to the slag discharge tank (42) through an external sand discharge pipeline (82); the opening directions of several sand discharge openings (81) on the sand discharge perforated pipes (8) are all obliquely downward, and the deposited sand grains are discharged by self-pressure; The reverse blowing air pipes (9) are connected to an external reverse blowing pipeline (92) through a first valve (93); Several blowout openings (91) with opening directions all obliquely downward are arranged on the reverse blowing air pipes (9).

2. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: In the flotation tank (3), the slope of the sand discharge channel (6) is 40° - 60°; the sand discharge perforated pipes (8) are laid in the sand discharge channel (6); The coagulation and flocculation system (2) includes a coagulation tank (21) and a flocculation tank (22) that are connected to each other and the bottoms of which are both designed in a conical hopper shape; the coagulation tank (21) is connected to the upper part of the water distribution channel (1), and the upper part of the flocculation tank (22) is connected to the flotation tank (3); the sand discharge perforated pipes (8) are respectively laid at the bottoms of the coagulation tank (21) and the flocculation tank (22).

3. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: The opening center line directions of the blowout openings (91) and the opening center line directions of the sand discharge openings (81) are both obliquely downward at 40° - 50°.

4. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: The segments of the external reverse blowing pipeline (92) close to the water distribution channel (1), the coagulation and flocculation system (2), and the flotation tank (3) are all designed in a "zigzag" shape, and the heights are respectively higher than the maximum liquid level heights in the adjacent water distribution channel (1), coagulation and flocculation system (2), or flotation tank (3).

5. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: The external reverse blowing pipeline (92) is connected to the external sand discharge pipeline (82) through a second valve (94).

6. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: The dissolved air flotation device also includes a dual water source system for return water; the dual water source system for return water includes a dual water source switching device (34); one end of the dual water source switching device (34) is connected to the dissolved air release head (32) through a return pipeline, and the other end is connected to the water outlet pool (51) and the subsequent filtration system through the return pipeline.

7. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: An adjustable water outlet weir (31) is provided on one side of the air flotation tank (3) that is in communication with the slag trough (41).

8. A dissolved air flotation device with sand removal function according to claim 1, characterized in that: The slag discharge pool (42) is provided with a stirring device (43); The slag discharge pool (42) may also be provided with a slag trough flushing system or a screw slag conveyor.

9. A seawater desalination pretreatment process, characterized in that: The method of pre-treating seawater by using the dissolved air flotation device with sand removal function described in any one of items 1 to 8 above comprises the following steps: S1, first transporting seawater to the water distribution channel (1) for mixing and sedimentation treatment, then the seawater flows into the coagulation and flocculation system (2), and the deposited sand is discharged through the sand discharge flower pipe (8); S2, the seawater flowing into the coagulation and flocculation system (2), under the action of the coagulant and flocculant, the impurities and lighter sand particles therein form flocs, and part of the sand particles are deposited at the bottom of the coagulation and flocculation system (2) and discharged through the sand discharge pipe (8); S3, the formed flocs and part of the sand flow into the flotation tank (3) along with the seawater, the flocs combine with the bubbles released by the dissolved air release head (32) and float up, and are scraped into the slag tank (41) by the scraper (7), part of the sand is deposited in the sand discharge channel (6), and is discharged by self-pressure through the sand discharge pipe (8) based on the liquid level difference, and then the seawater in the flotation tank (3) flows into the water outlet tank (51); During operation, the sand discharge situation is monitored in real time. When sand bridges occur, the first valve (93) is opened, and the bridges are destroyed by air released through the back-blowing pipe (9). When the external sand discharge pipeline (82) is blocked, the second valve (94) is opened, and the external sand discharge pipeline (82) is unblocked by high-pressure gas delivered through the external back-blowing pipeline (92); S4, transporting the seawater flowing into the outlet pool (51) to a subsequent filtration system for further treatment, or partially returning the seawater to the dissolved air tank (33) and flowing into the flotation pool (3) through the dissolved air release head (32), and the other part flowing into the subsequent filtration system; S5. The flocs scraped into the slag tank (41) and the sand discharged from the sand discharge pipeline are transported to the slag discharge pool (42) through the pipeline and discharged after being processed.

Images