Harmless and resourceful treatment method of extraction liquid after vanadium extraction of stone coal

Abstract

The invention relates to the technical field of sewage treatment, and particularly provides a harmless and resourceful treatment method for extraction liquid obtained after vanadium extraction of stone coal. The device mainly comprises a pretreatment unit, a concentration unit, a reaction unit 1, a calcination and magnetic separation unit, a reaction unit 2, a reaction unit 3, an ammonia recovery unit and a tail water treatment unit. Iron oxide and alumina slag in the sewage are recycled, sulfate radicals in the sewage are recycled to prepare gypsum, environmental pollution caused by the fact that the substances enter the environment is avoided, economic benefits can be generated through recycling, and meanwhile through multi-section concentration, the final concentrated water amount is reduced, and the disposal cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and specifically provides a method for harmless and resourceful treatment of extract liquid after vanadium extraction from stone coal. Background Art

[0002] Stone coal is a low-quality "coal" with a much higher content of inorganic components than organic components. Among them, stone coal with a V2O5 content of more than 0.8% can be used as a vanadium ore resource. At present, the conventional process for extracting vanadium from stone coal is roasting first and then leaching, that is, first destroying the mineral structure of stone coal and dissolving vanadium oxide into vanadate, then leaching it from solid phase to liquid phase, and extracting refined vanadium from the solution.

[0003] The stone coal roasting vanadium extraction process has obvious advantages, such as strong universality, low cost, high vanadium leaching rate, and easy vanadium recovery. However, its disadvantages are also prominent, such as the large amount of residual wastewater produced, complex composition, and a large amount of heavy metal ions, especially iron and aluminum ions.

[0004] At present, most of the treatment methods for extract wastewater are direct recycling. However, as the number of recycling increases, the iron and aluminum ions in the extract will be enriched. If the enriched iron and aluminum ions cannot be removed, the vanadium extraction rate will be affected, and the phase separation effect of the extraction process will gradually deteriorate. Therefore, exploring appropriate methods to treat extract wastewater has become an important bottleneck restricting the development of the stone coal vanadium extraction industry.

[0005] Therefore, finding a more reasonable, economical and effective method to treat the wastewater is an urgent problem to be solved in the stone coal vanadium extraction industry. If the heavy metals such as iron and aluminum can be recycled and reused to create certain economic benefits, it can not only solve the problem of wastewater treatment at the source, but also provide technical support for the further development of the stone coal vanadium extraction industry.

[0006] In view of this, this application is hereby filed. Summary of the invention

[0007] One of the purposes of the present application is to provide a method for harmless and resourceful treatment of the extract from stone coal for vanadium extraction, so as to treat the extract from stone coal for vanadium extraction in a low-cost, easy-to-operate and environmentally friendly manner.

[0008] In order to achieve the above purpose, this application adopts the following technical solutions:

[0009] A method for harmless and resourceful treatment of extracting liquid after vanadium extraction from stone coal, comprising the following steps:

[0010] (1) Pretreatment: The wastewater is treated by oil separation flotation, filtration and pre-oxidation in sequence before entering the concentration unit to remove oil, suspended solids and most organic matter;

[0011] The deep vanadium wastewater is sequentially treated by reaction clarification and filtration before entering the reaction unit 1 to remove suspended solids and vanadium pentoxide;

[0012] (2) Concentration unit: The pre-treated raffinate wastewater is first subjected to ultrafiltration to remove suspended solids, and then concentrated and reduced by acid-resistant reverse osmosis. It then enters the reaction unit 1, and the collected produced water is reused or reprocessed;

[0013] (3) Reaction unit 1: By controlling the pH value, the iron and aluminum ions in the sewage are precipitated to form iron-aluminum sludge, which enters the calcination and magnetic separation unit, and the sewage enters the reaction unit 2;

[0014] (4) Calcination and magnetic separation unit: The iron and aluminum sludge is dehydrated, dried, calcined and magnetically separated to recover iron and aluminum;

[0015] (5) Reaction unit 2: adding calcium ions and controlling pH value, the sulfate ions in the sewage are removed by forming precipitation, the precipitation is filtered, and the sewage enters reaction unit 3;

[0016] (6) Reaction unit 3: carbonate ions are added and pH value is controlled. Residual calcium sulfate in the sewage is removed by precipitation. A small amount of calcium carbonate sludge is produced. The calcium carbonate sludge is filtered and the sewage enters the ammonia recovery unit.

[0017] (7) Ammonia recovery unit: Ammonia water in sewage is recovered through a deammonification tower, and the deammonified sewage is reused or enters a tail water treatment unit;

[0018] (8) Tail water treatment unit: remove organic matter and residual ammonia nitrogen in the wastewater through advanced oxidation, and then reduce the tail water and recover the produced water through evaporation and concentration processes such as TVR; the produced water is reused or reprocessed, and the concentrated liquid is returned to the reaction unit 1 or neutralized and discharged.

[0019] Furthermore, in step (1), the raffinate wastewater first enters the regulating tank 1 and then undergoes oil separation and flotation treatment to adjust the water volume and balance the water quality, thereby ensuring load balance in subsequent treatment units;

[0020] Preferably, in step (1), the regulating tank 1 is made of reinforced concrete or an anti-corrosion assembled tank, aerated or mechanically stirred, with a hydraulic retention time of 4 to 12 hours, and a rectangular or cylindrical shape;

[0021] Preferably, in step (1), the oil separation flotation adopts dissolved air flotation, the hydraulic retention time is 1-1.5 h, the dissolved air pressure is 0.3-0.55 MPa, the dissolved air time is 1-3 min, the diameter of the microbubble is 30-100 μm, and the horizontal flow rate is 4-6 mm / s;

[0022] Preferably, in step (1), the filtration treatment of the raffinate wastewater adopts an inclined plate sedimentation tank, the diameter of the inclined tube is 25 mm to 80 mm, the inclination angle of the inclined plate is 45° to 60°, the material is PP material, and the sedimentation time is 0.5 to 1.5 h;

[0023] Preferably, in step (1), the pre-oxidation treatment is: the oxidant is H2O2 or O2, preferably H2O2, the addition concentration of H2O2 is 0.1%~1%, the inlet pH is 1.5~3.5, the reaction temperature is 140℃~200℃, and the reaction pressure is 0.5~2MPa.

[0024] Furthermore, in step (1), the deep vanadium wastewater first enters the regulating tank 2 and then undergoes reaction clarification treatment to regulate the water volume and balance the water quality, thereby ensuring load balance in subsequent treatment units;

[0025] Preferably, in step (1), the regulating tank 2 is made of reinforced concrete or an anti-corrosion assembled tank, aerated or mechanically stirred, with a hydraulic retention time of 4 to 12 hours, and a rectangular or cylindrical shape;

[0026] Preferably, in step (1), the reaction clarification treatment equipment has an inlet pipe flow rate of 1-1.2 m / s, a total hydraulic retention time of 1-1.5 h, wherein the hydraulic retention time of the reaction section is 10-20 min, and 1-3 sludge thickening buckets are provided, and the volume of the sludge thickening bucket is 1%-4% of the volume of the clarification tank;

[0027] Preferably, in step (1), the vanadium sludge produced after the reaction clarification treatment is filtered by a dehydrator and then centrally disposed, and the wastewater returns to the regulating tank 2 or enters the reaction unit 1; the pressure of the dehydrator is 0.6-1MPa, and the moisture content of the vanadium sludge after dehydration is less than 60%;

[0028] Preferably, in step (1), the deep vanadium wastewater is filtered and treated using an inclined plate sedimentation tank, the diameter of the inclined tube is 25 mm to 80 mm, the inclined plate has an inclination angle of 45° to 60°, the material is PP material, and the sedimentation time is 0.5 to 1.5 h.

[0029] Furthermore, in step (2), the ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5-8 mm, the length of the membrane tube is 3-4 m, the membrane pore size is 20-50 nm, and the membrane material is PVDF;

[0030] Preferably, in step (2), the acid-resistant reverse osmosis adopts a spiral reverse osmosis, the filtration pore size of the reverse osmosis membrane is 0.5-2 nm, and the operating flux of the membrane is 20-35 L / (m 2 ‧h), operating pressure is 0.6~1MPa, maximum transmembrane pressure difference is 2.5bar, and inlet water temperature is 15~40℃;

[0031] Preferably, a bag filter and a core filter are arranged after the reverse osmosis water inlet pump, the bag filter has a filtration pore size of 5 μm, and the core filter has a filtration pore size of 1 μm.

[0032] Furthermore, in step (3), the pH value is controlled by adding alkali, wherein the alkali is ammonia water or NaOH, preferably ammonia water, and the concentration of ammonia water added is 20% to 30%. After adding ammonia water, the pH value is adjusted to 4.7 to 5, and the reaction stirring speed is 60 to 130 r / min. After the reaction, the reaction is allowed to naturally precipitate for 0.5 to 1 hour, and the iron-aluminum sludge at the bottom is filtered by a plate-frame filter, and the filter cake is placed in the iron-aluminum sludge stacking area. The filtration pressure of the plate-frame filter is 0.5 to 2.5 MPa, and the filtration area is 15 to 30 m 2 The filtration accuracy is 0.5~10μm.

[0033] Furthermore, in step (4), the temperature of the dehydration and drying section is 80-300°C, the moisture content is 10%, and the drying time is 2-6 hours; the temperature of the calcination section is 950-1200°C, and the calcination time is 0.5-4 hours.

[0034] Furthermore, in step (5), the calcium ion source is quicklime or slaked lime, the lime concentration is 10% to 90%, the pH is controlled at above 12, and the reaction stirring speed is 50 to 100 r / min; after the reaction, the natural precipitation is carried out for 0.5 to 1 hour, and the bottom precipitation is filtered by a plate-frame filter to make gypsum from the filter cake. The filtration pressure of the plate-frame filter is 0.5 to 2.5 MPa, and the filtration area is 40 to 100 m 2 The filtration accuracy is 50~200μm.

[0035] Furthermore, in step (6), the source of carbonate ions is sodium carbonate, the configuration concentration of sodium carbonate is 10% to 30%, the pH is controlled at above 12, the reaction stirring speed is 50 to 100 r / min, and anchor frame stirring is adopted; after the reaction, natural precipitation is carried out for 1 to 2 hours, and the calcium carbonate precipitate at the bottom is filtered by a plate and frame machine, and the filter cake is placed in the calcium carbonate sludge pile, the filtration pressure of the plate and frame machine is 0.5 to 2.5 MPa, and the filtration area is 3 to 10 m 2 The filtration accuracy is 25~250μm.

[0036] Furthermore, in step (7), the deamination tower adopts a stripping method, the operating pressure of the stripping tower is 0.35~1MPa, the top temperature is less than 60°C, the bottom temperature is about 145~180°C, the spacing between plates is 400mm~500mm, and steam heating is adopted, the temperature of the steam is 180°C~220°C, and the pressure is 1~1.5MPa.

[0037] Furthermore, in step (8), the advanced oxidation is performed by electrolytic oxidation, and the current density of the electrolytic oxidation device is 1 to 10 A / dm 2 The material is diamond doped with boron or titanium substrate coated with graphene. The hydraulic retention time of the electrolytic oxidation device is 10-60 minutes. The shell and tube heat exchanger or plate heat exchanger is used for cooling to ensure that the temperature of the liquid in the electrolytic device is lower than 60°C.

[0038] In step (8), the concentration is carried out by TVR evaporation concentration, the supply steam pressure of the TVR evaporation concentration is above 0.3 MPa, and the evaporation temperature is 40-80°C.

[0039] Compared with the prior art, the technical effects of this application are:

[0040] The harmless and resource-based treatment technology for the extract from vanadium extraction from stone coal disclosed in the present application not only recovers the iron oxide and bauxite slag in the sewage, but also recovers the sulfate ions therein to make gypsum, thereby preventing these substances from entering the environment and causing environmental pollution, but also recovers them to generate economic benefits. At the same time, through multi-stage concentration, the final concentrate volume is reduced, thereby reducing disposal costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The various technical features of the present application and the relationship between them are further explained below with reference to the accompanying drawings. The accompanying drawings are exemplary, and some technical features are not shown in actual proportion. In addition, some drawings may omit technical features that are commonly used in the technical field to which the present application belongs and are not essential for understanding and implementing the present application, or additional technical features that are not essential for understanding and implementing the present application may be shown. In other words, the combination of the various technical features shown in the accompanying drawings is not used to limit the present application. In addition, throughout the present application, the same figure numbers refer to the same content. The specific description of the drawings is as follows:

[0042] Figure 1 This is the main process flow chart for the harmless and resourceful treatment of the extract liquid after vanadium extraction from stone coal in this application. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present application, the technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0044] The wastewater after vanadium extraction from stone coal contains certain organic matter. Due to the high content of heavy metals, it is difficult to remove this organic matter with conventional treatment methods.

[0045] The present application provides a method for harmless and resourceful treatment of extract liquor after vanadium extraction from stone coal, which mainly includes "pretreatment + concentration unit + reaction unit 1 + calcination and magnetic separation unit + reaction unit 2 + reaction unit 3 + ammonia recovery unit + tail water treatment unit".

[0046] Step (1), pretreatment: the extract wastewater is successively subjected to oil separation flotation treatment, filtration treatment and pre-oxidation treatment before entering the concentration unit to remove oil, suspended matter and most organic matter; the deep vanadium wastewater is successively subjected to reaction clarification treatment and filtration treatment before entering the reaction unit 1 to remove suspended matter and vanadium pentoxide.

[0047] In some embodiments, the raffinate wastewater first enters the regulating tank 1 and then undergoes oil separation and flotation treatment, and the deep vanadium wastewater first enters the regulating tank 2 and then undergoes reaction clarification treatment to adjust the water volume and balance the water quality to ensure load balance in subsequent treatment units.

[0048] In some embodiments, regulating tank 1 and regulating tank 2 are made of reinforced concrete or anti-corrosion assembled tanks, aerated and stirred or mechanically stirred, preferably aerated and stirred, with a hydraulic retention time of 4 to 12 h (for example, but not limited to 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h), preferably 6 to 8 h, and the shape is a rectangular parallelepiped or a cylinder.

[0049] In some embodiments, the oil separation flotation adopts dissolved air flotation, the hydraulic retention time is 1~1.5 h (for example, it can be but not limited to 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h), the dissolved air pressure is 0.3~0.55 MPa (for example, it can be but not limited to 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa or 0.55 MPa), the dissolved air time is 1~3 min (for example, it can be but not limited to 1 min, 1.5 min, 2 min, 2.5 min or 3 min), the diameter of the microbubble is 30-100 μm, and the horizontal flow rate is 4~6 mm / s.

[0050] In some embodiments, the filtration treatment of the raffinate wastewater and the filtration treatment of the deep vanadium wastewater adopts an inclined plate sedimentation tank, the diameter of the inclined tube is 25 mm~80 mm (for example, but not limited to 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm or 80 mm), preferably 40~60 mm, the inclination angle of the inclined plate is 45°~60°, the material is PP material, and the sedimentation time is 0.5~1.5h, preferably 1h.

[0051] In some embodiments, the pre-oxidation treatment is as follows: the oxidant is H2O2 or O2, preferably H2O2, the addition concentration of H2O2 is 0.1%~1% (for example, it can be but not limited to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%), the inlet pH is 1.5~3.5 (for example, it can be but not limited to 1.5, 1.7, 2, 2.3, 2.5, 2.7, 3, 3.2 or 3.5), preferably 1.5~2.5, the reaction temperature is 140℃~200℃ (for example, it can be but not limited to 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃), and the reaction pressure is 0.5~2MPa (for example, it can be but not limited to 0.5 MPa, 0.7 MPa, 1 MPa, 1.2 MPa, 1.5 MPa, 1.7MPa or 2MPa).

[0052] In some embodiments, the equipment for reaction clarification treatment has a water inlet flow rate of 1-1.2 m / s (for example, but not limited to 1 m / s, 1.1 m / s or 1.2 m / s), a total hydraulic retention time of 1-1.5 h (for example, but not limited to 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h), wherein the hydraulic retention time of the reaction section is 10-20 min (for example, but not limited to 10 min, 12 min, 14 min, 16 min, 18 min or 20 min), 1-3 sludge thickening buckets are provided, preferably 2-3, and the volume of the sludge thickening buckets is 1%-4% of the volume of the clarification tank, preferably 2%-4%.

[0053] In some embodiments, the vanadium sludge produced after the reaction clarification treatment is filtered by a dehydrator and then disposed of centrally, and the wastewater returns to the regulating tank 2 or enters the reaction unit 1; the pressure of the dehydrator is 0.6~1MPa, and the moisture content of the vanadium sludge after dehydration is less than 60%.

[0054] Step (2), concentration unit: the pretreated raffinate wastewater is first subjected to ultrafiltration to remove suspended solids therein, and then concentrated and reduced by acid-resistant reverse osmosis, and then enters the reaction unit 1, and the collected produced water is reused or reprocessed.

[0055] In some embodiments, the ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5-8 mm, preferably 8 mm, the length of the membrane tube is 3-4 m, the membrane pore size is 20-50 nm (can be but not limited to 20 nm, 30 nm, 40 nm or 50 nm), and the membrane material is PVDF. The produced water enters the ultrafiltration water production tank, and the concentrated water returns to the regulating tank. When the SS of the wastewater in the regulating tank reaches 30 g / L, it is discharged into the sludge tank.

[0056] In some embodiments, the acid-resistant reverse osmosis adopts a spiral reverse osmosis, the filtration pore size of the reverse osmosis membrane is 0.5-2 nm, preferably 0.56-0.7 nm, and the operating flux of the membrane is 20-35 L / (m 2 ‧h), preferably 25~35 L / (m 2 ‧h), operating pressure is 0.6~1MPa, maximum transmembrane pressure difference is 2.5bar, and inlet water temperature is 15~40℃.

[0057] In some embodiments, a bag filter and a core filter are provided after the reverse osmosis water inlet pump, wherein the bag filter has a filtration pore size of 5 μm, and the core filter has a filtration pore size of 1 μm.

[0058] Step (3), reaction unit 1: by controlling the pH value, the iron ions and aluminum ions in the sewage are precipitated to form iron-aluminum sludge, the iron-aluminum sludge enters the calcination and magnetic separation unit, and the sewage enters the reaction unit 2.

[0059] In some embodiments, the pH value is controlled by adding alkali, the alkali is ammonia water or NaOH, preferably ammonia water, the concentration of ammonia water is 20%~30% (for example, but not limited to 20%, 22%, 24%, 26%, 28% or 30%), after adding ammonia water, the pH is adjusted to 4.7~5, the reaction stirring speed is 60~130r / min; after the reaction, it is naturally precipitated for 0.5~1h, preferably 1h. After the bottom iron-aluminum sludge is filtered by a plate-frame machine, the filter cake is placed in the iron-aluminum sludge stacking place, the filtration pressure of the plate-frame machine is 0.5~2.5MPa, preferably 0.5~1.6MPa, and the filtration area is 15~30m 2 The filtration accuracy is 0.5~10μm.

[0060] Step (4), calcination and magnetic separation unit: the iron-aluminum sludge is sequentially dehydrated, dried, calcined and magnetically separated to recover iron and aluminum.

[0061] In some embodiments, the temperature of the dehydration and drying section is 80-300°C, preferably 80-200°C, the moisture content is dried from 60% to about 10%, and the drying time is 2-6h (for example, but not limited to 2h, 3h, 4h, 5h or 6h). The temperature of the calcination section is 950-1200°C (for example, but not limited to 950°C, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C), and the calcination time is 0.5-4h (for example, but not limited to 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h).

[0062] Step (5), reaction unit 2: adding calcium ions and controlling the pH value, the sulfate ions in the sewage are removed by forming precipitation, the precipitation is filtered, and the sewage enters the reaction unit 3.

[0063] In some embodiments, the calcium ion source is quicklime or slaked lime, the lime concentration is 10% to 90% (for example, but not limited to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%), preferably 30% to 70%, the pH is controlled at above 12, preferably 14 and above, the reaction stirring speed is 50 to 100 r / min; after the reaction, the natural precipitation is 0.5 to 1 hour, the bottom precipitation is filtered by a plate and frame machine, and the filter cake is made into gypsum, the filtration pressure of the plate and frame machine is 0.5 to 2.5 MPa, and the filtration area is 40 to 100 m 2 The filtration accuracy is 50~200μm.

[0064] Step (6), reaction unit 3: carbonate ions are added and the pH value is controlled. The residual calcium sulfate in the sewage is removed by precipitation, and a small amount of calcium carbonate sludge is produced. The calcium carbonate sludge is filtered and the sewage enters the ammonia recovery unit.

[0065] In some embodiments, the source of the carbonate ion is sodium carbonate, the configuration concentration of the sodium carbonate is 10% to 30%, preferably 30%, the pH is controlled at above 12, preferably 14 and above, the reaction stirring speed is 50 to 100 r / min, and anchor frame stirring is adopted; after the reaction, natural precipitation is carried out for 1 to 2 hours, and the calcium carbonate precipitate at the bottom is filtered by a plate and frame machine, and the filter cake is placed in the calcium carbonate sludge stacking place. The filtration pressure of the plate and frame machine is 0.5 to 2.5 MPa, and the filtration area is 3 to 10 m 2 The filtration accuracy is 25~250μm.

[0066] Step (7), ammonia recovery unit: recover ammonia water in the sewage through a deammonification tower, and the deammonified sewage is reused or enters a tail water treatment unit.

[0067] In some embodiments, the deamination tower adopts a stripping method, the operating pressure of the stripping tower is 0.35~1MPa (for example, it can be but not limited to 0.35 MPa, 0.45 MPa, 0.55 MPa, 0.65 MPa, 0.75 MPa, 0.85 MPa, 0.95 MPa or 1 MPa), preferably 0.5~0.7MPa, the top temperature is less than 60°C, the bottom temperature is about 145~180°C (for example, it can be but not limited to 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or 180°C), preferably 155~165°C, the spacing between plates is 400mm~500mm, preferably 500mm, steam heating is adopted, the temperature of the steam is 180°C~220°C, and the pressure is 1~1.5MPa.

[0068] Step (8), tail water treatment unit: remove organic matter and residual ammonia nitrogen in the sewage through advanced oxidation, and then reduce the tail water and recover the produced water through evaporation and concentration processes such as TVR; the produced water is reused or reprocessed, and the concentrated liquid is returned to the reaction unit 1 or neutralized and discharged.

[0069] In some embodiments, the advanced oxidation is performed by electrolytic oxidation, and the current density of the electrolytic oxidation device is 1-10 A / dm 2 , preferably 1~5 A / dm 2 The material is diamond doped with boron or titanium substrate coated with graphene, preferably diamond doped with boron, and the hydraulic retention time of the electrolytic oxidation device is 10-60 minutes, preferably 10-30 minutes. A shell and tube heat exchanger or a plate heat exchanger is used for cooling to ensure that the temperature of the liquid in the electrolytic device is lower than 60°C.

[0070] In some embodiments, the concentration adopts TVR evaporation concentration, the supply steam pressure of the TVR evaporation concentration is above 0.3 MPa, the evaporation temperature is 40-80°C (for example, but not limited to 40°C, 50°C, 60°C, 70°C or 80°C), 1 kg of new steam can utilize approximately 0.3 kg of secondary steam, and the condensate water production rate is about 95%.

[0071] In some embodiments, the scraper adopts a chain and chain plate type or a traveling type, and the scraper moves at a speed of 50-100 mm / s. Reverse scraping is recommended, but forward scraping is also possible. The outlet weir adopts a movable adjustable weir or a thin-walled weir.

[0072] In view of the technical problems existing in the prior art, this application provides a technology for comprehensively treating organic matter in a reasonably designed high-salt environment. First, a mild oxidation technology is provided, using H2O2 or O2 as an oxidant, at a pH of 1.5 to 3.5, a reaction temperature of 140°C to 200°C, and a reaction pressure of 0.5 to 2MPa, to oxidize the organic matter in the residual wastewater into CO2 and other substances to be discharged from the system. Secondly, an advanced oxidation technology is used, and under the action of an external electric field, the current density is generally 1 to 10 A / dm 2 , the material is selected from diamond doped with boron or titanium substrate coated with graphene, etc., to achieve efficient purification of organic matter in water through physical and chemical effects. Finally, preferably, steam is used as the heat source, TVR evaporation technology is used, the evaporation temperature is 40~80℃, the solid and liquid in the wastewater are separated, and the evaporated water vapor is condensed into condensate, and the condensate water production rate is about 95%.

[0073] Furthermore, the present application also provides a more comprehensive resource recovery technology, which not only recovers the iron and aluminum, but also recovers the sulfate ions to make gypsum. The recovered iron, aluminum and gypsum can create economic value and reduce processing costs.

[0074] Furthermore, the present application also provides a comprehensive reduction and recovery technology to minimize the generation of concentrated water, using membrane treatment technology at the front end of the treatment to reduce the treated residual wastewater by half, and reuse the reverse osmosis produced water. Preferably, TVR concentration is used at the back end of the treatment to minimize the amount of concentrated water to achieve the purpose of fully recycling resources.

[0075] The embodiments of the present application will be described in detail below in conjunction with the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be considered to limit the scope of the present application. If no specific conditions are specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer.

[0076] Example 1

[0077] The vanadium extraction project of a vanadium-containing shale mine in Hunan produces a total of 3180m³ / d of wastewater, including 3000m³ / d (125m³ / h) of residual wastewater and 180m³ / d (7.5m³ / h) of vanadium precipitation wastewater. The water quality parameters are shown in Table 1.

[0078] Table 1 Main element contents of residual wastewater in Example 1

[0079] pH value of residual wastewater: 2.0~2.5

[0080] Table 2 Main element contents of deep vanadium wastewater in Example 1

[0081] pH value of vanadium precipitation wastewater: 2.0±0.5

[0082] As shown in Table 1, the residual wastewater mainly contains SO4 2- , Fe, K, Al and other elements, COD (chemical oxygen demand) content is about 300mg / L, SS (suspended solids) is about 100mg / L. Deep vanadium wastewater mainly contains SO4 2- NH4 + , Cl - Elements such as COD content is about 30mg / L, SS is about 30mg / L. The effluent is required to meet the secondary standard limit of "Comprehensive Sewage Discharge Standard" (GB8978-1996), COD ≤ 120mg / L, SS ≤ 30mg / L, ammonia nitrogen ≤ 50mg / L. With this process method, the effluent can meet the owner's requirements, and the system is stable. The technical parameters of the main process sections are as follows.

[0083] (1) Pretreatment: After the wastewater is treated by a regulating tank, oil separation flotation, filtration, pre-oxidation and other facilities, Fe 2+ Oxidized to Fe 3+ The SS of the pre-treated effluent was 52.48 mg / L and the COD was 112.89 mg / L. After the deep vanadium wastewater was clarified by reaction and filtered, the SS of the pre-treated effluent was 0 mg / L, the COD was 29.97 mg / L, and the NH4 + It is 1865.35mmol / L.

[0084] (2) Concentration unit: After pretreatment, the raffinate wastewater is concentrated and reduced by ultrafiltration and acid-resistant reverse osmosis. The SS of the produced water is 0 mg / L and the COD is 29.97 mg / L. The produced water is reused or reprocessed, and the SS of the concentrated water is 17 mg / L and the COD is 223.76 mg / L.

[0085] (3) Reaction unit 1: After the deep vanadium wastewater is pretreated and the residual wastewater is treated in the concentration unit, it enters the reaction unit 1, and after reaction precipitation and filtration, 8.75m 3 / h 40% solid content of ferric hydroxide aluminum slag and 68.46m 3 / h of filtrate, the ferric hydroxide aluminum slag is further dehydrated and separated through calcination and magnetic separation, and the filtrate enters the reaction unit 2.

[0086] (4) Calcination and magnetic separation process: The drying time is 2 to 4 hours, the calcination time is 0.5 to 2 hours, and then the iron oxide and bauxite slag are separated by magnetic separation to obtain 0.5 t / h Fe2O3 and 2.87 t / h Al2O3.

[0087] (5) Reaction unit 2: Add 6.23t / h 50% Ca(OH)2 solution to remove SO4 2-The reaction forms 30.16 t / h of gypsum, which is separated by plate and frame filtration.

[0088] (6) Reaction unit 3: Add 30% 2.1m 3 / h of Na2CO3 solution, the remaining Ca 2+ A precipitate is formed, and the reaction is allowed to settle naturally for 1 to 2 hours. The calcium carbonate precipitate at the bottom is separated by plate and frame filtration to obtain 2.12 t / h of calcium carbonate precipitate with a moisture content of 60%.

[0089] (7) Ammonia recovery unit: The deammoniation tower adopts the steam stripping method, the operating pressure is 0.5~0.7MPa, the spacing between plates is 500mm, and 8.13 Nm is added per hour. 3 Steam at 180℃~200℃ evaporates and recovers ammonia in the solution with a recovery rate of 95%. The deammoniated solution is either reused or enters the tail water treatment unit.

[0090] (8) Tail water treatment unit: The solution is first electrolytically oxidized with a current density of 1-5 A / dm 2 The electrode material is diamond doped with boron, and the hydraulic retention time of the electrolytic oxidation device is 10~30min. The TVR evaporation temperature is 40~80℃. After evaporation and condensation, 42.28t / h of condensate is produced, and the condensate water production rate is about 95%. The condensate is combined with the water produced by the concentration unit and finally reused or reprocessed. The final effluent COD is 16.75mg / L, SS is 0, and ammonia nitrogen is 21.56mg / L, all of which meet the secondary standard limit of the "Comprehensive Sewage Discharge Standard" (GB8978-1996). 2.23t / h of concentrated liquid is produced, which is either returned to reaction unit 1 or discharged after neutralization according to the water quality and operation conditions.

[0091] Note that the above are only preferred embodiments of the present application and the technical principles used. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present application. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the technical concept of the present application, all of which belong to the protection scope of the present application.

Claims

1. A method for harmless and resourceful treatment of extractant after vanadium extraction from stone coal, characterized in that: The steps include: (1) Pretreatment: The wastewater is treated by oil separation flotation, filtration and pre-oxidation in sequence before entering the concentration unit to remove oil, suspended solids and most organic matter; The deep vanadium wastewater is sequentially treated by reaction clarification and filtration before entering the reaction unit 1 to remove suspended solids and vanadium pentoxide; (2) Concentration unit: The pre-treated raffinate wastewater is first subjected to ultrafiltration to remove suspended solids, and then concentrated and reduced by acid-resistant reverse osmosis. It then enters the reaction unit 1, and the collected produced water is reused or reprocessed; (3) Reaction unit 1: By controlling the pH value, the iron and aluminum ions in the sewage are precipitated to form iron-aluminum sludge, which enters the calcination and magnetic separation unit, and the sewage enters the reaction unit 2; (4) Calcination and magnetic separation unit: The iron and aluminum sludge is dehydrated, dried, calcined and magnetically separated to recover iron and aluminum; (5) Reaction unit 2: adding calcium ions and controlling pH value, the sulfate ions in the sewage are removed by forming precipitation, the precipitation is filtered, and the sewage enters reaction unit 3; (6) Reaction unit 3: carbonate ions are added and pH value is controlled. Residual calcium sulfate in the sewage is removed by precipitation. A small amount of calcium carbonate sludge is produced. The calcium carbonate sludge is filtered and the sewage enters the ammonia recovery unit. (7) Ammonia recovery unit: Ammonia water in sewage is recovered through a deammonification tower, and the deammonified sewage is reused or enters a tail water treatment unit; (8) Tail water treatment unit: remove organic matter and residual ammonia nitrogen in the wastewater through advanced oxidation, and then reduce the tail water and recover the produced water through evaporation and concentration processes such as TVR; the produced water is reused or reprocessed, and the concentrated liquid is returned to the reaction unit 1 or neutralized and discharged.

2. The processing method according to claim 1, characterized in that: In step (1), the residual wastewater first enters the regulating tank 1 and then undergoes oil separation and flotation treatment to adjust the water volume and balance the water quality to ensure load balance in subsequent treatment units; In step (1), the regulating tank 1 is made of reinforced concrete or an anti-corrosion assembled tank, aerated or mechanically stirred, with a hydraulic retention time of 4 to 12 hours, and a rectangular or cylindrical shape; In step (1), the oil separation flotation adopts dissolved air flotation, the hydraulic retention time is 1-1.5 h, the dissolved air pressure is 0.3-0.55 MPa, the dissolved air time is 1-3 min, the diameter of the microbubble is 30-100 μm, and the horizontal flow rate is 4-6 mm / s; In step (1), the filtration treatment of the raffinate wastewater adopts an inclined plate sedimentation tank, the diameter of the inclined tube is 25 mm to 80 mm, the inclination angle of the inclined plate is 45° to 60°, the material is PP material, and the sedimentation time is 0.5 to 1.5 h; In step (1), the pre-oxidation treatment is as follows: the oxidant is H2O2 or O2, the H2O2 addition concentration is 0.1%~1%, the inlet water pH is 1.5~3.5, the reaction temperature is 140℃~200℃, and the reaction pressure is 0.5~2MPa.

3. The processing method according to claim 1, characterized in that: In step (1), the deep vanadium wastewater first enters the regulating tank 2 and then undergoes reaction clarification treatment to adjust the water volume and balance the water quality to ensure load balance in subsequent treatment units; In step (1), the regulating tank 2 is made of reinforced concrete or an anti-corrosion assembled tank, aerated or mechanically stirred, with a hydraulic retention time of 4 to 12 hours, and a rectangular or cylindrical shape; In step (1), the reaction clarification treatment equipment has an inlet pipe flow rate of 1-1.2 m / s, a total hydraulic retention time of 1-1.5 h, wherein the hydraulic retention time of the reaction section is 10-20 min, and 1-3 sludge thickening buckets are provided, and the volume of the sludge thickening buckets is 1%-4% of the volume of the clarification tank; In step (1), the vanadium sludge produced after the reaction clarification treatment is filtered by a dehydrator and then centrally disposed of, and the wastewater returns to the regulating tank 2 or enters the reaction unit 1; the pressure of the dehydrator is 0.6-1MPa, and the moisture content of the vanadium sludge after dehydration is less than 60%; In step (1), the deep vanadium wastewater is filtered and treated using an inclined plate sedimentation tank, the diameter of the inclined tube is 25 mm to 80 mm, the inclined plate has an inclination angle of 45° to 60°, the material is PP material, and the sedimentation time is 0.5 to 1.5 h.

4. The processing method according to claim 1, characterized in that: In step (2), the ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5-8 mm, the length of the membrane tube is 3-4 m, the membrane pore size is 20-50 nm, and the membrane material is PVDF; In step (2), the acid-resistant reverse osmosis adopts a spiral reverse osmosis, the filtration pore size of the reverse osmosis membrane is 0.5-2 nm, the operating flux of the membrane is 20-35 L / (m2‧h), the operating pressure is 0.6-1 MPa, the maximum transmembrane pressure difference is 2.5 bar, and the inlet water temperature is 15-40°C; A bag filter and a core filter are arranged after the reverse osmosis water inlet pump. The filter pore size of the bag filter is 5 μm, and the filter pore size of the core filter is 1 μm.

5. The processing method according to claim 1, characterized in that: In step (3), the pH value is controlled by adding alkali, wherein the alkali is ammonia water or NaOH, and the concentration of ammonia water is 20% to 30%. After the addition of ammonia water, the pH value is adjusted to 4.7 to 5, and the reaction stirring speed is 60 to 130 r / min. After the reaction, the reaction is allowed to naturally precipitate for 0.5 to 1 hour, and the iron-aluminum sludge at the bottom is filtered by a plate-frame filter, and the filter cake is placed in the iron-aluminum sludge stacking area. The filtration pressure of the plate-frame filter is 0.5 to 2.5 MPa, the filtration area is 15 to 30 m2, and the filtration accuracy is 0.5 to 10 μm.

6. The processing method according to claim 1, characterized in that: In step (4), the temperature of the dehydration and drying section is 80-300°C, the moisture content is 10%, and the drying time is 2-6 hours; the temperature of the calcination section is 950-1200°C, and the calcination time is 0.5-4 hours.

7. The processing method according to claim 1, characterized in that: In step (5), the calcium ion source is quicklime or slaked lime, the lime concentration is 10% to 90%, the pH is controlled at above 12, and the reaction stirring speed is 50 to 100 r / min; after the reaction, the natural sedimentation is 0.5 to 1 hour, and the bottom sediment is filtered by a plate and frame filter press, and the filter cake is made into gypsum. The filtration pressure of the plate and frame filter press is 0.5 to 2.5 MPa, the filtration area is 40 to 100 m2, and the filtration accuracy is 50 to 200 μm.

8. The processing method according to claim 1, characterized in that: In step (6), the source of the carbonate ions is sodium carbonate, the configuration concentration of the sodium carbonate is 10% to 30%, the pH is controlled at above 12, the reaction stirring speed is 50 to 100 r / min, and anchor frame stirring is adopted; after the reaction, natural precipitation is carried out for 1 to 2 hours, and the calcium carbonate precipitate at the bottom is filtered by a plate and frame machine, and the filter cake is placed in the calcium carbonate sludge pile. The filtration pressure of the plate and frame machine is 0.5 to 2.5 MPa, the filtration area is 3 to 10 m2, and the filtration accuracy is 25 to 250 μm.

9. The processing method according to claim 1, characterized in that: In step (7), the deamination tower adopts a stripping method, the operating pressure of the stripping tower is 0.35~1MPa, the top temperature is less than 60°C, the bottom temperature is 145~180°C, the spacing between plates is 400mm~500mm, and steam heating is adopted. The temperature of the steam is 180°C~220°C and the pressure is 1~1.5MPa.

10. The processing method according to claim 1, characterized in that: In step (8), the advanced oxidation adopts electrolytic oxidation, the current density of the electrolytic oxidation device is 1-10 A / dm2, the material is diamond doped with boron or titanium substrate coated with graphene, the hydraulic retention time of the electrolytic oxidation device is 10-60min, and a shell and tube heat exchanger or a plate heat exchanger is used for cooling to ensure that the temperature of the liquid in the electrolytic device is lower than 60°C; In step (8), the concentration is carried out by TVR evaporation concentration, the supply steam pressure of the TVR evaporation concentration is above 0.3 MPa, and the evaporation temperature is 40-80°C.

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