Vanadium precipitation wastewater treatment system

Abstract

The utility model discloses a vanadium precipitation wastewater treatment system which comprises a vanadium removal reaction tank, a silicon removal reaction tank and a chromium removal reaction tank which are independently arranged and are connected in sequence; each reaction tank is provided with a feeding mechanism and a stirring mechanism. By adopting the system disclosed by the utility model, the step-by-step recycling of vanadium and chromium in the vanadium precipitation wastewater can be realized, and the economic utilization value of chromium-containing sludge is improved as high-concentration total silicon contained in the vanadium precipitation wastewater is removed by arranging the silicon removal reaction tank.

Description

TECHNICAL FIELD

[0001] The utility model relates to wastewater treatment technical field especially relates to a vanadium precipitation wastewater treatment system. BACKGROUND

[0002] In the steel smelting industry, vanadium and chromium have significant harmfulness. Dust or smoke generated by vanadium compounds in the smelting process can cause respiratory diseases after inhalation, and even lead to pulmonary fibrosis after long-term exposure. Skin contact can also cause dermatitis. In addition, compounds formed by vanadium at high temperatures can accelerate equipment corrosion and increase maintenance costs. The main harm of chromium comes from hexavalent chromium, which has strong oxidizing properties and poses a serious threat to human health, and can cause lung cancer, skin ulcers and other diseases. Hexavalent chromium is easily dissolved in water and difficult to degrade after polluting the environment. Vanadium and chromium accumulate in the environment, which can pollute soil and water and destroy the ecological balance. Therefore, in the steel smelting process, the use and discharge of vanadium and chromium need to be strictly controlled.

[0003] The traditional vanadium pentoxide industrial wastewater treatment process only detoxifies toxic substances in acidic wastewater, i.e. reduces and neutralizes vanadium and chromium, but does not stepwise recover and utilize valuable metals vanadium and chromium. Moreover, the large amount of calcium and chromium waste residue formed by precipitation has high water content, which is not easy to store and reprocess, and external discharge will cause secondary pollution. Therefore, a vanadium precipitation wastewater treatment system is needed that can stepwise recover and utilize vanadium and chromium, and at the same time better meet environmental protection requirements. SUMMARY

[0004] In order to solve the above technical problems existing in the prior art, the utility model provides a vanadium precipitation wastewater treatment system, which comprises independently arranged vanadium removal reaction tank, silicon removal reaction tank and chromium removal reaction tank, wherein the vanadium removal reaction tank, silicon removal reaction tank and chromium removal reaction tank are connected in sequence; the reaction tank is provided with a feeding mechanism and a stirring mechanism.

[0005] Preferably, the system further comprises an ammonia evaporation tower, an evaporation device for concentrating sodium sulfate, a first crystallization device for obtaining sodium sulfate crystals and a second crystallization device for obtaining sodium chloride crystals connected in sequence, wherein the discharge port of the chromium removal reaction tank is connected with the feeding port of the ammonia evaporation tower.

[0006] In the utility model, vanadium and chromium in wastewater are recovered step by step by respectively arranging vanadium removal reaction tank and chromium removal reaction tank, compared with the conventional vanadium removal wastewater treatment system, the economic value of vanadium mud and chromium mud obtained in the system can be improved. In addition, the utility model additionally arranges silicon removal reaction tank between vanadium removal reaction tank and chromium removal reaction tank, so that high concentration total silicon doped in the chromium mud obtained subsequently can be avoided. The system adopting the utility model can also obtain ammonia, sodium sulfate and sodium chloride products by additionally arranging ammonia tower, first crystallization device and second crystallization device, so that the economic benefit of wastewater treatment can be improved significantly.

[0007] Preferably, the system further comprises a calcium removal reaction tank, which is arranged between the chromium removal reaction tank and the ammonia tower and is used for removing calcium in the wastewater. Arranging the calcium removal reaction tank before the ammonia tower helps to improve the yield of ammonia water subsequently.

[0008] Preferably, the system further comprises a plate-and-frame filter press, which is connected with the discharge port of one or more of the vanadium removal reaction tank, the silicon removal reaction tank, the chromium removal reaction tank and the calcium removal reaction tank and is used for separating solid and liquid of the filtrate discharged from each reaction tank to obtain sludge and purified filtrate.

[0009] Preferably, the system comprises two plate-and-frame filter presses, one of which is arranged between the vanadium removal reaction tank and the silicon removal reaction tank and is used for obtaining vanadium-containing sludge, and the other of which is connected with the discharge port of the chromium removal reaction tank and is used for obtaining chromium-containing sludge.

[0010] Preferably, one or more of the vanadium removal reaction tank, the silicon removal reaction tank, the chromium removal reaction tank and the calcium removal reaction tank is provided with a sedimentation mechanism for improving the sedimentation effect of solids in the reaction tank. In an embodiment of the utility model, the sedimentation mechanism is a baffle. For example, a plurality of baffles are arranged on the inner side wall of the tank body of the vanadium removal reaction tank at intervals, and the baffles are perpendicular to the inner side wall of the tank body. The baffles increase the flow path of the liquid in the tank body, thereby improving the sedimentation effect of solids in the reaction tank. Similar arrangement can also be made in the silicon removal reaction tank, the chromium removal reaction tank and the calcium removal reaction tank.

[0011] Preferably, the system further comprises an ammonia gas absorption device, the feed inlet of which is connected with the discharge port of the ammonia tower and is used for absorbing ammonia gas to obtain ammonia water.

[0012] Preferably, the ammonia tower is a large-pore guide sieve plate type ammonia tower, which is composed of a bottom liquid storage section, a heating distillation section and a distributor. The heating distillation section contains a total of 20-40 sieve plates, and the heat exchange area of the distributor is 5-20 m 2 .

[0013] Preferably, the system further comprises a sand filter tank connected to the outlet of the calcium removal reaction tank for removing suspended solids and particulate matters in the filtrate discharged from the calcium removal reaction tank.

[0014] Preferably, the system further comprises one or more intermediate water tanks connected to the outlet of one or more of the chromium removal reaction tank, the calcium removal reaction tank and the ammonia distillation tower for storing the filtrate discharged from the outlet.

[0015] Preferably, the reaction tank comprises a tank cover and a tank body, and the inner bottom surface of one or more of the vanadium removal reaction tank, the silicon removal reaction tank and the chromium removal reaction tank is conical, and the included angle between the generatrix of the cone and the horizontal direction is greater than 6°, which can be preferably less than 10°. This shape is beneficial to the discharge of materials in the reaction tank and avoids the retention of materials in the reaction tank.

[0016] Preferably, the stirring mechanism is arranged at the center of the top of the tank cover.

[0017] Preferably, the feeding mechanism is arranged on the tank cover.

[0018] Preferably, the paddle of the stirring rod in the stirring mechanism is anchor-shaped, paddle-shaped or frame-shaped.

[0019] The vanadium precipitation wastewater treatment system provided by the present application realizes step-by-step treatment of vanadium, silicon and chromium by independently arranging the vanadium removal reaction tank, the silicon removal reaction tank and the chromium removal reaction tank, significantly improves the purity and economic value of vanadium sludge and chromium sludge, and avoids the pollution of silicon to chromium sludge. The calcium removal reaction tank added in the system effectively reduces the interference of calcium ions on subsequent ammonia water recovery, and further improves the ammonia water yield. Through the combination of the plate-and-frame filter press and the sedimentation mechanism, the system realizes efficient solid-liquid separation, ensures sufficient sludge recovery and further wastewater treatment. In addition, the arrangement of the ammonia distillation tower and the ammonia gas absorption device realizes efficient recovery of ammonia gas, reduces resource waste and environmental pollution. The conical bottom design of the reaction tank avoids material residues and improves the utilization rate of the device. Moreover, ammonia, sodium sulfate and sodium chloride products can be obtained through the treatment system, and the salts in the wastewater are fully utilized. The overall system is modular, efficient and environmentally friendly, and is suitable for wastewater treatment and resource recovery in the vanadium chemical industry, and has significant technical and economic advantages. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A connection schematic diagram of a vanadium precipitation wastewater treatment system in another specific embodiment of the present application is shown.

[0021] Figure 2 A connection schematic diagram of a vanadium precipitation wastewater treatment system in another specific embodiment of the present application is shown. DETAILED DESCRIPTION

[0022] The following embodiments of the present application will be described in greater detail by the specific embodiments, and other advantages and effects of the present application can be easily understood by those skilled in the art from the content disclosed in the present specification. Although the present application will be described in combination with the preferred embodiments, this does not mean that the features of the present application are limited to the embodiments. On the contrary, the purpose of describing the present application in combination with the embodiments is to cover other options or modifications that can be extended based on the claims of the present application. In order to provide a deep understanding of the present application, many specific details will be included in the following description. The present application can also be implemented without using these details. In addition, in order to avoid confusion or obscure the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0023] It should be noted that in the present specification, similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0024] In the description of the present embodiments, it should also be noted that unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present embodiments can be understood according to the specific circumstances.

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0026] According to one embodiment of the present application, with reference to Figure 1 When the vanadium precipitation wastewater treatment system of the present embodiment is used to treat vanadium precipitation wastewater, vanadium precipitation wastewater with vanadium content of about 350mg / L, total chromium content of about 2500mg / L and silicon content of about 2000mg / L is used, and the vanadium precipitation wastewater is first treated to remove vanadium. The vanadium removal reaction tank includes a tank body and a tank cover, the tank body is a cylinder, the inner bottom surface is conical, and the angle between the generatrix of the cone and the horizontal direction is 8°. The foot of the tank body is a circular tube, and a sedimentation mechanism is provided on the inner wall of the tank body. The tank cover is circular and has a convex arc surface. A feeding mechanism and a stirring mechanism are provided on the tank cover. The stirring mechanism is provided at the center of the top of the tank cover, and the paddle of the stirring rod is paddle-shaped. The feeding mechanism is also provided on the tank cover. The sedimentation mechanism is a plurality of partitions provided on the inner side wall of the tank body at intervals, and the partitions are perpendicular to the side wall of the tank body. The structure of the reaction tank is not shown.

[0027] When in use, the vanadium-containing wastewater is fed into the tank through the feeding mechanism provided on the vanadium removal reaction tank, and at the same time, the iron salt, flocculant and liquid alkali are added into the tank through the feeding mechanism for precipitating vanadium in the wastewater. The stirring mechanism is used to help the precipitation, and the partition plate is used to increase the flow path of the liquid in the tank and improve the sedimentation effect of the solid in the reaction tank. The sludge containing a large amount of vanadium-containing precipitate is discharged through the discharge port provided at the bottom of the tank, and the first filtrate is discharged into the silicon removal reaction tank. The bottom of the tank of the vanadium removal reaction tank is conical and the inner surface forms a certain angle with the horizontal direction, so that the vanadium-containing sludge in the tank can be fully discharged. In other embodiments of the present application, if the tank is not provided with a precipitation mechanism such as a partition plate, the wastewater containing vanadium-containing precipitate can be separated into filtrate and vanadium-containing sludge by an additional plate-and-frame filter press device.

[0028] In the present embodiment, the silicon removal reaction tank has the same structure as the above-mentioned vanadium removal reaction tank. The first filtrate is fed into the tank through the feeding mechanism of the silicon removal reaction tank, and at the same time, the aluminum salt, flocculant and liquid alkali are also added into the silicon removal reaction tank through the feeding mechanism. In the silicon removal reaction tank, the aluminum salt is used to precipitate the silicon in the first filtrate to remove the silicon in the wastewater, and the silicon-containing sludge and the second filtrate are obtained. The silicon-containing sludge is discharged, and the second filtrate is discharged into the chromium removal reaction tank.

[0029] In the present embodiment, the chromium removal reaction tank has the same structure as the above-mentioned silicon removal reaction tank and vanadium removal reaction tank. The second filtrate is fed into the tank through the feeding mechanism of the chromium removal reaction tank, and at the same time, the reducing agent, flocculant and liquid alkali are also added into the chromium removal reaction tank through the feeding mechanism. In the chromium removal reaction tank, the chromium in the wastewater is reduced and precipitated, and the chromium-containing sludge and the third filtrate are obtained.

[0030] The vanadium content in the vanadium-containing sludge is determined by parallel sampling more than 4 times, and the vanadium recovery rate is calculated to be >90%; and the chromium content in the chromium-containing sludge is determined by parallel sampling more than 4 times, and the chromium recovery rate is calculated to be >99%.

[0031] As shown in Figure 1 , an ammonia tower, a first evaporation device, a first crystallization device and a second crystallization device are sequentially arranged after the chromium removal reaction tank for obtaining ammonia, sodium sulfate and sodium chloride respectively.

[0032] In the present embodiment, the ammonia tower is a large-pore guide sieve plate type ammonia tower, which is composed of a tank bottom liquid storage section, a heating distillation section and a condenser. The heating distillation section contains a total of 30 sieve plates, and the heat exchange area of the condenser is 15 m 2 .

[0033] The first evaporation device is an MVR evaporator, and the evaporation temperature is 80-120℃. In the first evaporation device, preliminary concentration is carried out to obtain evaporation mother liquor.

[0034] The first crystallization device can be a DTB crystallizer or an OSLO crystallizer. In the present embodiment, the OSLO crystallizer is selected, and the temperature for crystallization is 100-120℃, so as to obtain anhydrous sodium sulfate crystals and a crystallization mother liquor.

[0035] The second crystallization device comprises an evaporator and a crystallizer, the evaporator is an MVR evaporator, and the crystallizer is an OSLO crystallizer. The temperature for crystallization is 25-35℃ or 90-120℃. The cooling crystallization at 25-35℃ or the evaporation crystallization at 90-120℃ can be used to obtain sodium chloride.

[0036] The sodium sulfate obtained by the processing system of the present embodiment meets the first-class product standard of type II in the Industrial Anhydrous Sodium Sulfate (GB / T6009-2014); the sodium chloride obtained meets the first-class standard of refined industrial salt (industrial dry salt) in the Industrial Salt (GB / T5462-2015); the ammonia water concentration can reach 15-20%, which meets the external sales standard.

[0037] According to another embodiment of the present application, referring to Figure 2 , the system structure is basically the same as that in Figure 1 , and the difference lies in that a plate-and-frame filter press is additionally arranged between each reaction tank for fully separating solid and liquid; a calcium removal reaction tank and a sand filter tank are additionally arranged in sequence between the chromium removal reaction tank and the ammonia distillation tower; a plurality of intermediate water tanks are additionally arranged for storing the filtrate from the discharge port; and an ammonia gas absorption device is additionally arranged in connection with the discharge port of the ammonia distillation tower to realize efficient recovery of ammonia gas.

[0038] In the present embodiment, the calcium removal reaction tank has the same structure as the chromium removal reaction tank. The filtrate from the chromium removal reaction tank enters the tank body of the calcium removal reaction tank through the feeding mechanism of the calcium removal reaction tank, and at the same time, lime or sodium hydroxide is put into the calcium removal reaction tank through the feeding mechanism to precipitate calcium. The reacted wastewater enters the plate-and-frame filter press for solid-liquid separation to obtain a precipitate and a filtrate. The precipitate is discarded, and the filtrate enters the intermediate water tank for temporary storage and then enters the sand filter tank to remove suspended solids and particulate matter in the filtrate.

[0039] The filtrate after sand filtration enters the ammonia distillation tower.

[0040] In the present embodiment, the ammonia distillation tower is a large-pore guide sieve plate type ammonia distillation tower, which is composed of a bottom liquid storage section, a heating distillation section, and a splitter. The heating distillation section contains a total of 30 sieve plates, and the heat exchange area of the splitter is 15m 2 . The separated ammonia at the top of the tower is absorbed by the ammonia gas absorption device. In the present embodiment, the ammonia gas absorption device is a cylindrical absorption tank containing water, and ammonia gas forms ammonia water after entering the absorption device for external sales.

[0041] The deamination filtrate is discharged from the bottom of the tower into an intermediate water tank for temporary storage and then into a first evaporation device. In this embodiment, the first evaporation device is an MVR evaporator, and the evaporation temperature is 80-120 DEG C. The first evaporation device is used for preliminary concentration, and an evaporation mother liquor is obtained. Of course, in other embodiments of the present application, the evaporator can also be a multiple-effect evaporator. The condensed water produced in the evaporation process can be reused in the system.

[0042] The evaporation mother liquor is introduced into a first crystallization device, which can be a DTB crystallizer or an OSLO crystallizer. In this embodiment, the OSLO crystallizer is selected, and the crystallization temperature is 100-120 DEG C. Anhydrous sodium sulfate crystals and a crystallization mother liquor are obtained.

[0043] The crystallization mother liquor is introduced into a second crystallization device. In this embodiment, the second crystallization device includes an evaporator and a crystallizer. The evaporator is an MVR evaporator, and the crystallizer is an OSLO crystallizer. The crystallization temperature is 25-35 DEG C or 90-120 DEG C. Cooling crystallization at 25-35 DEG C or evaporation crystallization at 90-120 DEG C can be used to obtain sodium chloride. In this embodiment, sodium chloride is obtained by evaporation crystallization at 90-120 DEG C. Part of the crystallization residual liquid is returned to the vanadium precipitation wastewater for wastewater treatment.

[0044] The system of this embodiment can further improve the vanadium recovery rate and the chromium recovery rate. The vanadium recovery rate is as high as 90% or more, and the chromium recovery rate is as high as 99% or more. The recovery efficiency of ammonia, sodium sulfate and sodium chloride is further improved, and the industrial standard is further improved.

[0045] The vanadium precipitation wastewater treatment system provided by the present application realizes step-by-step removal of vanadium and chromium by the independently arranged vanadium removal reaction tank and chromium removal reaction tank, significantly improves the purity and recovery value of vanadium mud and chromium mud, and avoids pollution of silicon to chromium mud. The arrangement of the ammonia stripping tower and the ammonia gas absorption device realizes efficient recovery of ammonia gas, reduces resource waste and environmental pollution. In addition, the system realizes efficient recovery of salt resources such as sodium sulfate and sodium chloride by the combination of the MVR evaporator and the OSLO crystallizer, and fully recovers the salts in the wastewater. The overall system has the advantages of modularity, high efficiency and environmental protection, is suitable for wastewater treatment and resource recovery in the vanadium chemical industry, and has significant technical and economic advantages.

[0046] Although the present application has been illustrated and described with reference to certain preferred embodiments thereof, it should be understood by those skilled in the art that the foregoing is a further detailed description of the present application in connection with specific embodiments, and the specific implementation of the present application should not be limited to these descriptions. Those skilled in the art can make various changes in form and details without departing from the spirit and scope of the present application, including making a number of simple deductions or substitutions.

Claims

1. A vanadium precipitation wastewater treatment system, characterized in that, The system comprises independently arranged vanadium removal reaction tank, silicon removal reaction tank and chromium removal reaction tank, which are connected in sequence; the reaction tanks are each provided with feeding mechanism and stirring mechanism.

2. The system of claim 1, wherein, The system further comprises ammonia evaporation tower, evaporation device for concentrating sodium sulfate, first crystallization device for obtaining sodium sulfate crystals and second crystallization device for obtaining sodium chloride crystals connected in sequence, wherein the discharge port of the chromium removal reaction tank is connected with the feeding port of the ammonia evaporation tower.

3. The system of claim 2, wherein, The system further comprises calcium removal reaction tank, which is arranged between the chromium removal reaction tank and the ammonia evaporation tower, for removing calcium in the wastewater.

4. The system of any one of claims 1-3, wherein, The system further comprises plate and frame filter press, which is connected with the discharge port of one or more of the vanadium removal reaction tank, the silicon removal reaction tank and the chromium removal reaction tank, for solid-liquid separation of the filtrate discharged from each reaction tank to obtain sludge and purified filtrate.

5. The system of any one of claims 1-3, wherein, The system comprises two plate and frame filter presses, one of which is arranged between the vanadium removal reaction tank and the silicon removal reaction tank, for obtaining vanadium-containing sludge; the other is connected with the discharge port of the chromium removal reaction tank, for obtaining chromium-containing sludge.

6. The system of any one of claims 1-3, wherein, One or more of the vanadium removal reaction tank, the silicon removal reaction tank and the chromium removal reaction tank is provided with precipitation mechanism.

7. The system of claim 6, wherein, The precipitation mechanism is composed of multiple partitions, which are arranged on the inner side wall of the tank body of the reaction tank and are perpendicular to the inner side wall of the tank body.

8. The system of claim 3, wherein, The system further comprises sand filter tank, which is connected with the discharge port of the calcium removal reaction tank, for removing suspended solids and particulate matter in the filtrate discharged from the calcium removal reaction tank.

9. The system of claim 3, wherein, The system further comprises one or more intermediate water tanks, which are connected with the discharge port of one or more of the chromium removal reaction tank, the calcium removal reaction tank and the ammonia evaporation tower, for storing the filtrate discharged from the discharge port.

10. The system of any one of claims 1-3, wherein, The reaction tank comprises tank cover and tank body, the inner bottom surface of the tank body of one or more of the vanadium removal reaction tank, the silicon removal reaction tank and the chromium removal reaction tank is conical, and the included angle between the generatrix of the cone and the horizontal direction is greater than or equal to 6°.

11. The system of claim 10, wherein, The stirring mechanism is arranged at the center of the top of the tank cover, and the feeding mechanism is arranged on the tank cover; and / or the paddle of the stirring rod in the stirring mechanism is anchor type, paddle type or frame type.

Images