First, the characteristics and harm of mineral processing wastewater Dressing wastewater harmful substances mainly heavy metal ions, various organic and inorganic flotation agent when used in ore flotation, including highly toxic cyanide, cyanide compounds like chromium. The wastewater also contains various insoluble coarse particles and fine particles dispersed impurities. The ore dressing wastewater often contains sulfates, chlorides or hydroxides such as sodium, magnesium and calcium. The acid in the ore dressing wastewater is mainly formed by the mixing of sulfur-containing minerals with water and water. The pollutants in the ore dressing wastewater mainly include suspended solids, acid and alkali, heavy metals and arsenic , fluorine, mineral processing chemicals, chemical oxygen-consuming substances and other pollutants such as oils, phenols, ammonium, phosphines and the like. The hazards of heavy metals such as copper , lead , zinc , chromium, mercury and arsenic ions and their compounds are well known. The main hazards of other pollutants are as follows: (1) Suspended matter: Suspended matter in water can occur, such as blocking fish gills, affecting the photosynthesis of algae to interfere with the living conditions of aquatic organisms. If the concentration of suspended solids is too high, it can also cause river siltation, which can cause soil compaction. . If used as domestic water, suspended matter is a substance that makes people feel uncomfortable, and it is a carrier of bacteria and viruses, which is potentially harmful to the human body. Even when heavy metal compounds are present in the suspension, they are released into the water under certain conditions (pH drop of the water body, ionic strength, change in concentration of the organic chelating agent, etc.). (2) Xanthate: that is, xanthate, which is a pale yellow powder, has a pungent odor and is easily decomposed, and the odor smell valve is 0.005 mg/L. Fish and shrimp in water bodies contaminated with xanthine have an unpleasant smell of yellow medicinal herbs. Xanthate is easily soluble in water, unstable in water, especially under acidic conditions, and its decomposition product CS can be sulfur pollutant. Therefore, the maximum allowable concentration of butylxanthate in ground water in China is 0.005 mg/L, while the concentration of sodium butylxanthate in the former Soviet Union water is 0.001 mg/L. (3) of black powder: disulfide dihydroxy phosphate as a main component, impurities contained include formic acid, phosphoric acid, cresol sulfur and hydrogen sulfide. It has a dark brown oily liquid, slightly soluble in water, and has a smell of hydrogen sulfide. It is also a source of pollution such as phenol and phosphorus in mineral processing wastewater. (4) Pine oil: it is 2# flotation oil, the main component is terpene alcohol. Yellow-brown oily transparent liquid, insoluble in water, is a non-toxic dressing agent, but has a loose fragrance, so it can cause changes in the sensory performance of water. Since pine oil is a foaming agent, it is easy to cause unpleasant foam on the water surface. (5) Cyanide: a highly toxic substance, which enters the human body and is hydrolyzed into hydrocyanic acid by the action of gastric acid and absorbed by the stomach and then enters the blood. Hydrocyanic acid in the blood can bind to the iron ions of cytochrome oxidase to form oxidized high-iron cytochrome acidase, thereby losing the ability to transmit oxygen, causing tissue hypoxia to cause poisoning. However, cyanide can be removed by self-purification in the water body. Therefore, if this property is used to extend the residence time of the ore dressing wastewater in the tailings pond, it can be brought to the discharge standard. (6) Sulfide: Under normal circumstances, S and HS will affect the hygienic condition of water in water, and generate hydrogen sulfide under acidic conditions. When the content of hydrogen sulfide in water exceeds 0.5mg/L, it is toxic to fish and can detect the odor emitted by it; the hydrogen olfactory valve in the atmosphere is l0mg/m. In addition, low concentrations of CS, which are volatile in water, enter the body through breathing and skin, and long-term exposure can cause poisoning, leading to the neurological disease Charcote carbon disulfide. (7) Chemical Oxygen Consumption: Chemical oxygen demand is a quantitative alternative indicator of oxygen-consuming organic matter in water. Oxygen consumption in ore dressing wastewater is mainly a mineral processing agent remaining in water. The water quality of some metal mine beneficiation wastewater is shown in the table. Second, the treatment method of mineral processing wastewater pollutants For the pollution in the above wastewater, the treatment units that can be used are as follows: Suspended matter: mainly used in preprecipitation, coagulation/precipitation. Acid-alkaline wastewater: wastewater neutralization method, tailings alkalinity and acidity. Heavy metal ions: adjustment of raw water pH co-precipitation or flotation technology, sulfide precipitation, lime-flocculation precipitation, adsorption technology (including biosorption), chelate resin method, ion exchange method, artificial wetland technology. Xanthate, black medicine: iron salt coagulation / precipitation method, bleaching powder oxidation, Fenton oxidation degradation method, artificial wetland technology. Cyanide: natural purification method, hypochlorite/liquid chlorine oxidation, hydrogen peroxide oxidation method, iron complex combination method, insoluble salt precipitation method, acidification-volatile re-neutralization method, zinc sulfate-sulfuric acid method, sulfur dioxide Air oxidation method, electrolytic oxidation method, ozone oxidation method, ion exchange method, biodegradation method, artificial wetland. Sulfide: mutual precipitation with heavy metal-containing wastewater, stripping method, air oxidation method, chemical precipitation method, chemical oxidation method, biochemical oxidation method. Chemical oxygen consumption: coagulation / precipitation, biodegradation, advanced oxidation, adsorption. (1) Treatment of ore dressing wastewater by coagulation inclined tube sedimentation method The wastewater from the workshop is firstly separated into solid and liquid by a grit chamber, and the grit of the grit chamber is discharged into the tailings field through the unloading gate. The supernatant liquid overflowing from the grit chamber is mixed and then enters the reactor to fully coagulate the reaction, and then flows into the inclined tube precipitator to further remove fine particles and harmful substances, and the sludge of the inclined tube precipitator passes through the valve. Arranged to the tailings sand field. After passing this process, the wastewater reaches the national allowable discharge standard. According to the requirements of environmental protection, the water from the inclined pipe settler enters the clear water tank, and is returned to the workshop with a clean water pump to save water, and the wastewater is closed in a closed circuit to achieve zero discharge. The process flow is shown in Figure 1. (2) Coagulation sedimentation-activated carbon adsorption-reuse process This method is currently used in the domestic selection of more ore processing wastewater reuse method. Through the research on the ore dressing wastewater of different mines, it is found that different amounts of different agents or the same agent are applied to the same ore dressing wastewater, and the results are different. But their common points are as follows: 1 Condenser effect comparison test: Polyferric sulfate (PFS), mixed aluminum chloride (PAC) and alum were used as coagulation precipitants respectively. The results showed that the use of alum as a coagulant is economical and reasonable, and the optimum dosage is generally Controlled at around 30mg/L. 2 Effect of polyacrylamide PAM on coagulation effect: The addition of PAM further improves the coagulation treatment effect of wastewater, but because it is an organic polymer, the COD value in water rises. In practice, the effect of coagulation treatment is Considering the combination of changes and COD values, the input amount of PAM is generally 0.2 mg/L. 3 The effect of sedimentation time on wastewater: The standing time after coagulation was established to be 30 min. 4 adsorption test: the amount of powdered activated carbon is less than the amount of granular activated carbon, basically in the case of half of it, the same effect can be achieved. At the same time, since the powdered activated carbon easily enters the concentrate and does not accumulate in the water cycle, it is selected as the adsorbent. The optimum amount is generally 50 to 100 mg/L. 5 Flotation test: After the wastewater is coagulated and precipitated, and activated carbon is adsorbed, it can be reused, and has no effect on the beneficiation index. After alum (30mg / L), PAM (0.2mg / L)} Kunming sedimentation, and then purified by powder activated carbon (50 ~ 100rag / L) process, the effluent water quality not only meets the national mine wastewater discharge standards, but also shows that the reuse results show The wastewater treated by the process can not only be reused, but also does not affect the beneficiation index. In the process of beneficiation, the amount of flotation reagent is also reduced, which brings considerable economic benefits to the enterprise. At the same time, due to the reuse of wastewater, the daily consumption of fresh water is reduced. This is more of a social significance for reducing pollution and purifying the environment for water shortage in China. The method has simple process, good effect and broad industrial application prospects. (III) Comprehensive method for resource utilization of ore dressing wastewater After a large number of water treatment tests and mineral processing comparison experiments, the professionals have summarized a better solution to solve the ore dressing wastewater. Taking lead-zinc ore as an example, the process flow is shown in Figure 2. Due to the different water quality of various wastewaters, the regulating tank plays a role in regulating water quality and water volume during the recycling process. The coagulation sedimentation tank enhances the mixing of the coagulant and the waste water, so that the fine particles grow and become a suspended matter which can be removed by precipitation. The reaction tank is used for further deepening of the wastewater, and the defoaming agent is used to react the excess foaming agent in the wastewater to weaken the influence on the flotation index. Third, the tailings pond water treatment technology introduction The tailings pond is a large-volume sedimentation-storage pond that can be built on a dam, using slopes on slopes, slopes, rivers or flats. A drainage well and a drain pipe are arranged in the pool, or a drainage ditch is opened along the edge, and the tailings water is clarified and purified in the pool and discharged. The suspended solids in the tailings water are stored at the bottom of the tank. The wastewater stays in the pool for at least one night. This method can effectively remove suspended solids in wastewater, and the content of heavy metals and flotation reagents is also reduced. The longer the residence time, the better the treatment. The overflow water in the tailings pond can be recycled. Re-election, magnetic separation and simple flotation of a single metal ore have low water quality requirements, water recycling rate of up to 80%, or no drainage at all. When the tailings particles are extremely fine and partially colloidal, a coagulant can be added to the tailings water to accelerate the clarification process and improve the treatment effect. If lime is added to the tailings water, 60-70% of the xanthate and black medicine can be removed. If the supernatant of the tailings pond does not meet the discharge standards, it should be further processed. Commonly used treatment methods are: 1 removal of heavy metals by lime neutralization and roast dolomite adsorption. To remove 1 mg of copper, 0.81 mg of lime is needed, 1 mg of nickel requires 0.88 mg of lime, and the pH requirement is controlled to be 8.5 or more. Copper and lead ions can be removed by adsorption of calcined dolomite having a particle size of less than 0.1 mm. Removal of 1 mg of copper requires 25 mg of dolomite, and 1 mg of lead requires dolomite 2.5 mg. 2 Removal of flotation agent by ore adsorption method, using lead-zinc ore to adsorb organic flotation agent, removing 1 mg of organic flotation agent requires lead-zinc ore 200 mg. Treatment with activated carbon adsorption is more effective, but expensive. 3 Cyanide-containing wastewater mainly uses chemical oxidation method, such as bleaching powder oxidation method; it can also remove cyanide by ferrous sulfate lime method and lead-zinc ore method, adding 200 grams of ore per gram of cyanide, which can remove simple cyanide by about 90%, or compound cyanide The compound is about 70%. High concentration of cyanide-containing wastewater can recover sodium cyanide. The process of purifying the overflow water of the tailings pond by lead-zinc ore and lime method is shown in the figure. Fourth, the ore dressing wastewater treatment project case (1) Treatment of ore dressing wastewater by cyclone flocculation At present, the wastewater treatment of ferrous metal mines in China is mostly carried out by ordinary concentrating machines, and the water purification effect is poor. For example, a mine will pump 485m3/h of wastewater into a natural concentrator with a diameter of 18m for natural precipitation. When the effluent is 425m3/h, the overflow concentration is as high as 9996mg/L, which does not meet the requirements of national industrial wastewater discharge standards. To this end, some concentrators installed ordinary concentrators on sloping plates and converted them into sloping plate sedimentation tanks. Although the effect of the sedimentation tank is better, the transformation cost is high, the service life is short, the utility is easy to block, and the maintenance workload is large. In order to make full use of the original processing equipment of the concentrator, we proposed to change the concentrator with a diameter of 18m into a cyclone flocculation sedimentation tank. According to a small test, if the effluent concentration is controlled below 300 mg/L, the treatment load is only 0.3 m3/m2•h, but after the anionic polyacrylamide is added to the modified cyclone flocculation sedimentation tank, the treatment load is applied. The amount can reach 2m3/m2•h, that is, the processing efficiency of the cyclone flocculation sedimentation tank is 7 times that of the ordinary concentrator. 1 Reform of the thickener The 18m diameter ordinary concentrator was changed into a cyclone flocculation sedimentation tank. It is carried out on the basis of the original ordinary concentrator structure, that is, a cyclone reactor is installed between the center pillar and the truss, and its shape is a truncated cone shape, and a multi-layer swirling guide plate is installed inside (see the figure). 1). The modified cyclone flocculation sedimentation tank has the following characteristics: 1 Does not destroy the structure of the original ordinary thickener, not only utilizes the original enrichment facility, but also significantly improves the purification efficiency of the wastewater; 2 Anionic polyacrylamide is added near the inlet of the cyclone flocculation reactor, and the hydrocyclone can be fully utilized for the reaction without adding a mechanical stirrer; 3 The swirling flocculation sedimentation tank adopts deep influent water, which greatly shortens the sedimentation distance of the solid particles, so that the medium and coarse particles quickly sink into the compression layer, relatively reducing the concentration of the middle and upper water bodies of the pool body, and forcing the fine particles into the concentration. Upper part of the higher compression zone. Due to the collision of dense particles, their energy is greatly reduced, so that a considerable amount of fine particles can not float up, and the underflow concentration is correspondingly increased. 4 The upper part of the cyclone flocculation reactor has a small diameter, a large diameter at the lower part, and a continuously variable speed of the water flow, which meets the requirements of rapid mixing of the coagulation reaction and slow flocculation. After the water leaves the reactor, there is still a swirling process, which gradually spreads. The “flocs†continue to grow, and the effluent and influent flows in opposite directions. After passing through the concentrated layer, they enter the clear water area and then overflow to the periphery, which is radiated from the upper part of the ordinary thickener. The flow is much better. 2 flocculant equipment 2.1 static test The concentration of 300mg/L of ore dressing wastewater was used as the test solution (pH=8.12), and the poly-iron, poly-aluminum, polyacrylamide, etc. were screened at room temperature in a 100 mL measuring cylinder and a 40 mm diameter and 2 m high precipitation tube. The order of promoting sedimentation effect between various flocculants was evaluated from the sedimentation speed of floc and the turbidity of supernatant. It was confirmed that the anionic polyacrylamide had the best sedimentation effect on the treatment of the beneficiation wastewater. The test curve is shown in Figure 2. 2.2 Industrial test The process flow is shown in Figure 3. The selected anionic polyacrylamide has a molecular weight of 7 to 8 million, a concentration of 0.1%, and an amount of 2.3 g/m3. In the actual operation, when the original influent concentration is 21540mg/L, pH=8.05, and the temperature is 6 degrees, after the anionic polyacrylamide is added, the effluent concentration is 33 mg/L, and the removal rate can reach 99.85%. 2.3 Dosing equipment 1 Mixing drum: a mixing drum with a diameter of 1.7 m and a volume of 3 m3. Consider 4h mixing cycle, one work, one standby. 2 Dosing pump: In order to facilitate automatic control of dosing, XF-101 metering pump was selected. One job, one spare. 3 Storage tank: According to the concentration of anionic polyacrylamide of 0.1%, the mixing drum can work continuously and can be discharged one by one, and the designed volume is 7m3. (2) Chemical coagulation treatment of ore dressing wastewater A mining company Hechi tin reselection method is employed to achieve separation and clay minerals, rocks and other impurities, where the ore rock since not the same, resulting in the changing of the wastewater discharged from the washing process. Mineral processing wastewater is the main source of emission pollution in the mining industry. It has the characteristics of large water volume and high suspended solid content. After the company's wastewater is naturally settled by the tailings pond, the overflow water is discharged directly into the nearby river. The discharged wastewater is insufficiently sedimented, the sediment content is large, the suspended matter content is high, and the appearance is dark brown and turbid. The wastewater quality: COD is 100-400mg/L, SS is l100-8000Hlg/L, turbidity is 2500-4000NTU, pH=7.0-8.0, water volume is 2000-3000m3/d, the main pollutant is suspended matter, which is directly discharged. Environmental pollution. Research content: Select high-efficiency flocculant to find the best coagulation conditions suitable for the treatment of the beneficiation wastewater, including the control of coagulant dosage and pH value, and provide relevant parameters selection, design reference and design for the wastewater treatment project. Guide production operations. Experimental reagents and instruments Reagents: polyaluminum chloride (PAC), FeCl3•6H2O (FC), polyferric sulphate (PFS), polyaluminum silicate (PSA), prepared concentration (mass fraction) are 5%; 5% Ca(OH) 2, solution; polyacrylamide (anionic, molecular weight 8 million), mass fraction 0.1%. Instrument: PHS-3C pH meter, JJ4-six electric agitator, HACH2100AN turbidity meter. experimental method Use 5 500HLJ beakers, put 300mL of raw water separately, add a certain amount of flocculant, put it on the mixer platform, stir quickly, then stir slowly, the stirring intensity is 100r/min and 50r/min respectively, stirring time Each is lmin, the fine particles of the wastewater and the colloidal substance are thoroughly mixed and reacted to form a floc, which is allowed to stand for 15 minutes. The supernatant in the beaker is extracted with a 100 mL syringe (23 cm below the liquid surface, the volume is about 40 mL), and the turbidity is measured. Measured 3 times to average). Engine Cylinder Liner,Engine Parts Cylinder Liner,Car Engine Cylinder Liners,Car Engine Liners KINCON POWER TECHNOLOGY CO.,LTD , https://www.kinconparts.com
The ore dressing wastewater includes the beneficiation process drainage, the tailings pond overflow water and the mine drainage. The ore dressing process drainage is generally transported to the tailings pond together with the tailings slurry, collectively referred to as tailings water; therefore, the ore dressing wastewater treatment is also referred to as tailings water treatment.