System and method for removing copper ions from oily wastewater

Abstract

The invention discloses a system and a method for removing copper ions in oily wastewater, and belongs to the field of water treatment. A mechanical cavitation strengthening-flocculation process is adopted and comprises the following specific steps: firstly, heating sewage, keeping the temperature of the sewage at 50-70 DEG C, then adding alkali, controlling the pH value within the range of 8-11, keeping the temperature of the pretreated wastewater at 25-40 DEG C, feeding the pretreated wastewater into a cavitation-flocculation tank at the flow rate of 30-50L / h for cavitation flocculation, filtering filtrate in an intermediate tank, and circularly feeding the filtrate into the cavitation-flocculation tank for 3-10 times, during the period, precipitates in the residual pool enter the waste liquid pool through flushing, waste residues are recycled, and waste liquid circularly enters the sewage pool. The method solves the problems that a single flocculation method adsorbs copper ions, wastewater treatment is not thorough, a traditional process is complex, operation cost is high and the like, realizes high efficiency of treatment of the copper ions in the oil-containing wastewater, is applied to treatment of the oil-containing wastewater in the field of mechanical manufacturing and processing, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for removing copper ions from oily wastewater by adopting a mechanical cavitation enhancement-adsorption / flocculation process. Background Art

[0002] With the rapid development of the machinery manufacturing industry in recent years, the mechanical processing industry is a typical water-consuming industry, and the amount of oily wastewater discharged by enterprises is also increasing, which contains a large number of heavy metal ions such as Cr(VI), Fe(III), Cu(II) and Pb(II). These metal ions are toxic and extremely harmful to the human body and the environment, so the treatment of wastewater generated by mechanical manufacturing and processing has gradually attracted people's attention.

[0003] Copper is widely used in metallurgy, machinery manufacturing, electroplating, chemistry and other industries. During the mechanical processing and forming process, copper materials will enter the cutting fluid and react with the cutting fluid, so that copper ions exist in the cutting fluid, thus forming oily wastewater containing copper ions. Therefore, it is necessary to develop a new method to remove copper ions from oily wastewater in the mechanical processing industry, increase the removal of copper ions in wastewater, make it meet national emission standards, and then eliminate the pollution of copper ions to the surrounding environment caused by the discharge of wastewater.

[0004] The phenomenon of hydraulic cavitation refers to the process of formation, growth and collapse of steam or cavitation bubbles in liquid or on the liquid-solid interface when the local pressure inside the liquid is reduced to the saturated vapor pressure corresponding to the liquid temperature. Hydraulic cavitation produces high-speed shock waves and microjets with local high temperature and high pressure, which squeeze or impact the oil-water interface film and destroy it, achieving demulsification. For example, heavy metal ions such as copper ions are released from oil-in-water or oil-in-water, achieving the effect of removing heavy metals from oil-containing wastewater. In addition, the energy release and cavitation effect of the cavitation process can strengthen the reaction process.

[0005] Hydraulic cavitation has the characteristics of simple process, easy industrialization and high energy utilization, and has broad application prospects in the fields of chemical industry, environmental protection, etc. At present, in the technology of removing heavy metal ions from sludge, flocculants are first added to the sludge water and then ultrasonic treatment is performed, or ultrasonic treatment is first performed to destroy the sludge flocs, bacterial flocs and cell bodies, and then inorganic-organic flocculation precipitation treatment is performed. The above methods have achieved good results in sludge dehydration and removal of heavy metal ions. However, ultrasonic cavitation is suitable for fields with low bubble demand and high dimensional accuracy requirements, and the cavitation volume is small, so it is difficult to industrialize on a large scale. If multiple ultrasonic cavitation equipment are set up, it will consume a lot of electricity and the operating cost will be high. Summary of the invention

[0006] The present invention aims at the problems existing in the prior art and provides a system for removing copper ions from oily wastewater. The present invention is achieved through the following technical solutions:

[0007] A system for removing copper ions from oily wastewater, the system comprising in sequence: a sewage tank, a pretreatment tank, a cavitation-flocculation module, an intermediate tank, a clear water tank and a waste liquid tank;

[0008] The downstream of the sewage pool is connected to the upstream of the pretreatment pool by a one-way valve; the downstream of the pretreatment pool is connected to the upstream of the cavitation-flocculation module by a one-way valve, and a pressurizing mechanism is provided between the pretreatment pool and the cavitation-flocculation module; the cavitation-flocculation module includes a cavitation generator, a flocculant injector and a flocculation pool; a first plate-frame filter is provided in the flocculation pool;

[0009] The downstream of the cavitation-flocculation module is connected to the upstream of the intermediate tank by a one-way valve, and a second plate-frame filter is provided in the intermediate tank; a circulation loop is connected between the downstream of the intermediate tank and the upstream of the cavitation-flocculation module, and the circulation loop is connected to the upstream of the pressurizing mechanism; a one-way valve is provided on the circulation loop;

[0010] The downstream of the intermediate tank is connected to the upstream of the clean water tank by a one-way valve.

[0011] Preferably, a heater and a flow meter are provided in the connection section between the sewage tank and the pretreatment tank; and an agitator, a pH detector and a thermometer are provided in the pretreatment tank.

[0012] Preferably, a heat exchanger is provided in the connection section between the pretreatment tank and the cavitation-flocculation module; the heat exchanger is arranged between the circulation loop and the pressurizing mechanism; and the pressurizing mechanism adopts a first pump.

[0013] Preferably, the circulation loop is provided with a second pump.

[0014] Preferably, the pretreatment tank, the cavitation-flocculation module and the intermediate tank are all connected to the waste liquid tank by a one-way valve; and the waste liquid tank is connected to the sewage tank.

[0015] Preferably, the cavitation generator and the flocculant injector are both placed in the flocculation tank; the liquid inlet of the cavitation generator is connected to the pretreatment tank, and the liquid outlet of the cavitation generator is connected to the first plate and frame filter; the other end of the cavitation generator is connected to the flocculant injector.

[0016] Preferably, the cavitation generator and the flocculant injector are both placed outside the flocculation tank; the liquid inlet of the cavitation generator is connected to the pretreatment tank, and the liquid outlet of the cavitation generator is connected to the flocculation tank; the other end of the cavitation generator is connected to the flocculant injector.

[0017] The present invention also aims to provide a system for removing copper ions from oily wastewater for use in a method for removing copper ions from wastewater, which is achieved through the following technical solutions:

[0018] The method for removing copper ions from oily wastewater comprises the following process steps:

[0019] S1. Introduce the sewage in the sewage pool into the pretreatment tank, heat the sewage solution to 50-70°C by a heater and maintain it, and add alkali solution to the pretreatment tank to control the pH value of the sewage solution to 8-11, so that copper ions react with the alkali solution to generate copper hydroxide and produce suspended particles;

[0020] S2, the treated wastewater in the pretreatment tank is kept at a temperature of 25-40°C after passing through a heat exchanger, and is sent to the cavitation-flocculation module at a flow rate of 30-50L / h, and a pressure of 0.2-4MPa is given to the cavitation generator, and a flocculant is added at the same time to obtain a primary cavitation liquid;

[0021] S3, introducing the primary cavitation liquid obtained in step S2 into the intermediate tank for filtration;

[0022] S4, sending the filtrate obtained in step S3 into the cavitation-flocculation module at a flow rate of 30-50 L / h to repeat step S2 for 3-10 times;

[0023] S5, introducing the filtrate obtained in step S4 into a clear water tank;

[0024] S6. After the operation is completed, the sediment in the pretreatment tank, cavitation-flocculation module, and intermediate tank can be flushed to the waste liquid tank for solid-liquid separation, solids can be recovered, and the filtrate can be discharged into the sewage tank for the next cycle.

[0025] Furthermore, the flocculant and coagulant aid are one of polyaluminium chloride (PAC), polyacrylamide (PAM), ferric chloride (FeCl3) and ferrous sulfate (FeSO4), or a combination of two or more thereof.

[0026] Furthermore, in step S2, the working steps of the cavitation-flocculation module are: the treated wastewater in the pretreatment tank is introduced into the cavitation generator, and when hydraulic cavitation occurs, the flocculant solution is released to the cavitation generator through the flocculant injector, and the flocculant moves forward with the cavitation bubbles to obtain the cavitated feed liquid.

[0027] Furthermore, in step S2, the cavitated feed liquid is passed into a first plate-and-frame filter to intercept the precipitate and obtain a filtered feed liquid.

[0028] Furthermore, in step S2, the cavitated feed liquid is passed into a flocculation tank, the precipitate is intercepted by a first plate-and-frame filter, and a filtered feed liquid is obtained.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. When the cavitation generator produces hydraulic cavitation effect, flocculant is added in time. A large number of cavitation bubbles generated by cavitation make the flocculant and cavitation liquid fully mixed, enhance the flocculation effect, and effectively improve the removal effect and rate of copper ions.

[0031] 2. The continuous formation and collapse of tiny bubbles produced by hydraulic cavitation, accompanied by huge pressure pulses, instantaneous local high temperature and high pressure around the bubbles, as well as strong shock waves and mechanical effects such as microjets, release heavy metal ions such as copper ions from water-in-oil or oil-in-water, thereby accelerating the full combination and flocculation of flocculants and copper ions.

[0032] 3. Through multiple cycles of cavitation, the flocculant is fully combined with the copper ions in the oily wastewater, so that the copper ions in the oily wastewater are removed more thoroughly.

[0033] 4. The sediment in the pretreatment tank, cavitation-flocculation module, and intermediate tank is flushed to the waste liquid tank for solid-liquid separation, the solid is recovered, and the waste liquid is recycled into the sewage tank, reducing the treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the technical roadmap of the present invention.

[0035] Figure 2 This is a diagram of the equipment structure of embodiment 1 of the present invention including the cavitation-flocculation module.

[0036] Figure 3 This is a diagram of the equipment structure of Embodiment 2 of the present invention including the cavitation-flocculation module.

[0037] Among them, there are sewage tank 1, one-way valve 11, heater 12, flow meter 13, pretreatment tank 2, agitator 21, pH detector 22, thermometer 23, heat exchanger 24, first pump 25, second pump 26, flocculation tank 3, cavitation generator 31, flocculant injector 32, first plate and frame filter 33, second plate and frame filter 34, intermediate tank 4, clean water tank 5, and waste liquid tank 6. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with the embodiments and drawings.

[0039] like Figure 1 As shown, a system for removing copper ions from oily wastewater comprises a sewage tank, a pretreatment tank, a cavitation-flocculation module, an intermediate tank, a clear water tank and a waste liquid tank which are arranged in sequence;

[0040] like Figure 2As shown, the sewage tank 1 is connected to the pretreatment tank 2 by a one-way valve 11, and a heater 12 and a flow meter 13 are provided in the connection section; an agitator 21, a pH detector 22 and a thermometer 23 are provided in the pretreatment tank 2. The pretreatment tank 2 is connected to the cavitation-flocculation module by a one-way valve 11, and a heat exchanger 24 and a first pump 25 are provided in the connection section.

[0041] The cavitation-flocculation module is composed of a cavitation generator 31, a flocculant injector 32 and a flocculation tank 3; a first plate-frame filter 33 is provided in the flocculation tank 3;

[0042] The cavitation-flocculation module is connected to the intermediate tank 4 by a one-way valve 11, and a second plate-frame filter 34 is provided in the intermediate tank 4; the intermediate tank 4 and the cavitation-flocculation module are also connected to a circulation loop, and the circulation loop is connected before the heat exchanger 24 and the first pump 25; a one-way valve is provided on the circulation loop;

[0043] A second pump 26 is provided on the circulation loop;

[0044] The middle tank 4 is connected to the clean water tank 5 by a one-way valve 11;

[0045] The pretreatment tank 2 , the cavitation-flocculation module, and the intermediate tank 4 are all connected to the waste liquid tank 6 by a one-way valve; the waste liquid tank 6 is connected to the sewage tank 1 .

[0046] There are two implementations of the cavitation-flocculation module:

[0047] Implementation 1:

[0048] like Figure 2 As shown, the cavitation generator 31 and the flocculant injector 32 are both placed in the flocculation tank 3.

[0049] The liquid inlet end of the cavitation generator 31 is connected to the pretreatment tank 2, and the liquid outlet end of the cavitation generator 31 is connected to the first plate-frame filter 33; the other end of the cavitation generator 31 is connected to the flocculant injector 32;

[0050] Working principle of cavitation-flocculation module implementation method 1:

[0051] The treated wastewater in the pretreatment tank 2 is introduced into the cavitation generator 31. When hydraulic cavitation occurs, the flocculant solution or the coagulant aid solution is timely released to the cavitation generator 31 through the flocculant injector 32. The flocculant moves forward with the cavitation bubbles. The cavitated liquid obtained is mixed with the cavitated flocculant liquid and discharged from the liquid outlet of the generator to the first plate and frame filter 33. The first plate and frame filter 33 intercepts the precipitate and the filtrate is transported to the intermediate tank 4.

[0052] The flocculant injector 32 is a flexible container immersed in the flocculation tank. The negative pressure is generated due to the hydraulic cavitation effect, which creates a pressure difference inside and outside the cavitation generator, squeezing the flocculant solution into the cavitation generator.

[0053] Implementation 2:

[0054] like Figure 3 As shown, the cavitation generator 31 and the flocculant injector 32 are both placed outside the flocculation tank 3 .

[0055] The liquid inlet end of the cavitation generator (31) is connected to the pretreatment tank 2, the liquid outlet end of the cavitation generator (31) is connected to the flocculation tank (3), and the other end of the cavitation generator (31) is connected to the flocculant injector (32); a first plate-frame filter (33) is provided in the flocculation tank (3).

[0056] Working principle of cavitation-flocculation module implementation 2:

[0057] The treated wastewater in the pretreatment tank 2 is introduced into the cavitation generator 31. When hydraulic cavitation occurs, the flocculant solution is released to the cavitation generator 31 through the flocculant injector 32. The flocculant moves forward with the cavitation bubbles. The cavitated liquid obtained is mixed with the cavitated flocculant and discharged from the liquid outlet of the cavitation generator to the flocculation tank 3. The precipitate is intercepted by the first plate and frame filter 33 in the flocculation tank 3, and the filtrate of the flocculation tank 3 is transported to the intermediate tank 4.

[0058] The following is a further description of a method for removing copper ions from oily wastewater according to the present invention in conjunction with specific embodiments. The following are only specific embodiments of the present invention.

[0059] Embodiment 1:

[0060] The sewage in the sewage pool 1 is introduced into the pretreatment pool 2, and the sewage solution is heated to 50°C and maintained by the heater 12. At the same time, NaOH is added to the treatment pool 2 to control the pH value of the sewage solution at 8, so that the copper ions react with NaOH to generate copper hydroxide suspended particles. The temperature is maintained at 25°C through the heat exchanger 24, and the copper ions are sent to the cavitation-flocculation module at a flow rate of 30L / h. Under the given pressure of 0.2Mpa of the cavitation generator, polyaluminum chloride and polyacrylamide are added through the flocculant feeder 32 and stirred evenly, so that the precipitate containing copper ions produces flocs under the flocculation effect. The precipitate is intercepted by the first plate and frame filter 33, and the filtrate enters the intermediate pool (4), and is intercepted again by the second plate and frame filter 34. After interception, the filtrate is introduced from the intermediate pool (4) into the cavitation-flocculation module again for circulation. The cavitation operation is repeated 5 times to obtain the circulated cavitation liquid, which is introduced into the clear water pool. At this time, Cu 2+ The removal rate reached 85.05%.

[0061] Embodiment 2-16:

[0062] Other embodiments were tested with reference to Example 1, and the technical parameters and results are shown in Table 1 below:

[0063] Table 1 Technical parameters and results of each case

[0064]

[0065]

[0066] Comparative Example 1:

[0067] The removal rate of Cu2+ was determined without using a mechanical cavitation device.

[0068] First, the sewage solution in the sewage pool is introduced into the primary reactor, and the sewage solution is heated to 60°C and maintained. At the same time, NaOH is added to the primary reactor to control the pH value of the sewage solution at 8, so that the copper ions react with NaOH to generate copper hydroxide precipitation, and the precipitation is intercepted by the plate and frame filter press. The filtrate is introduced into the secondary reactor, polyaluminum chloride and polyacrylamide are added and stirred evenly, so that the precipitate containing copper ions produces flocs under flocculation, and the precipitation is intercepted by the plate and frame filter press. The sewage solution is introduced from the secondary reactor into the intermediate tank. Sampling, at this time, the removal rate of Cu2+ reaches 80%.

Claims

1. A system for removing copper ions from oily wastewater, characterized in that: The system comprises in sequence: a sewage tank, a pretreatment tank, a cavitation-flocculation module, an intermediate tank, a clear water tank and a waste liquid tank; The downstream of the sewage tank is connected to the upstream of the pretreatment tank by a one-way valve; the downstream of the pretreatment tank is connected to the upstream of the cavitation-flocculation module by a one-way valve, and a pressurizing mechanism is provided between the pretreatment tank and the cavitation-flocculation module; the cavitation-flocculation module includes a cavitation generator, a flocculant injector and a flocculation tank; a first plate-frame filter is provided in the flocculation tank; The downstream of the cavitation-flocculation module is connected to the upstream of the intermediate tank by a one-way valve, and a second plate-frame filter is provided in the intermediate tank; a circulation loop is connected between the downstream of the intermediate tank and the upstream of the cavitation-flocculation module, and the circulation loop is connected to the upstream of the pressurizing mechanism; a one-way valve is provided on the circulation loop; The downstream of the intermediate tank is connected to the upstream of the clean water tank by a one-way valve.

2. A system for removing copper ions from oily wastewater according to claim 1, characterized in that: A heater and a flow meter are arranged in the connection section between the sewage pool and the pretreatment pool; and an agitator, a pH detector and a thermometer are arranged in the pretreatment pool.

3. A system for removing copper ions from oily wastewater according to claim 1, characterized in that: A heat exchanger is provided in the connection section between the pretreatment tank and the cavitation-flocculation module; the heat exchanger is arranged between the circulation loop and the pressurizing mechanism; the pressurizing mechanism adopts a first pump.

4. A system for removing copper ions from oily wastewater according to claim 1, characterized in that: A second pump is provided on the circulation loop.

5. The system for removing copper ions from oily wastewater according to claim 1, characterized in that: The pretreatment tank, the cavitation-flocculation module, and the intermediate tank are all connected to the waste liquid tank by a one-way valve; and the waste liquid tank is connected to the sewage tank.

6. The system for removing copper ions from oily wastewater according to claim 1, characterized in that: The cavitation generator and the flocculant injector are both placed in the flocculation tank; the liquid inlet end of the cavitation generator is connected to the pretreatment tank, and the liquid outlet end of the cavitation generator is connected to the first plate-frame filter; the other end of the cavitation generator is connected to the flocculant injector.

7. The system for removing copper ions from oily wastewater according to claim 1, characterized in that: The cavitation generator and the flocculant injector are both placed outside the flocculation tank; the liquid inlet end of the cavitation generator is connected to the pretreatment tank, and the liquid outlet end of the cavitation generator is connected to the flocculation tank; the other end of the cavitation generator is connected to the flocculant injector.

8. A method for removing copper ions from oily wastewater using a system for removing copper ions from oily wastewater according to any one of claims 1 to 7, wherein the method for removing copper ions from oily wastewater is characterized in that: The following steps are involved: S1. Introduce the sewage in the sewage pool into the pretreatment tank, heat the sewage solution to 50-70°C by a heater and maintain it, and add alkali solution to the pretreatment tank to control the pH value of the sewage solution to 8-11, so that copper ions react with the alkali solution to generate copper hydroxide and produce suspended particles; S2. The treated wastewater in the pretreatment tank is passed through a heat exchanger and maintained at a temperature of 25-40°C, and is sent to the cavitation-flocculation module at a flow rate of 30-50 L / h. The cavitation generator is given a pressure of 0.2-4 MPa, and flocculants and coagulants are added at the same time to obtain a primary cavitation liquid; S3, introducing the primary cavitation liquid obtained in step S2 into the intermediate tank for filtration; S4, sending the filtrate obtained in step S3 into the cavitation-flocculation module at a flow rate of 30-50 L / h to repeat step S2 for 3-10 times; S5, introducing the filtrate obtained in step S4 into a clear water tank; S6. After the operation is completed, the sediment in the pretreatment tank, cavitation-flocculation module, and intermediate tank can be flushed to the waste liquid tank for solid-liquid separation, solids can be recovered, and the filtrate can be discharged into the sewage tank for the next cycle.

9. The method for removing copper ions from oily wastewater using a system for removing copper ions from oily wastewater according to claim 8, characterized in that: The flocculant and coagulant aid are one of polyaluminium chloride (PAC), polyacrylamide (PAM), ferric chloride (FeCl3) and ferrous sulfate (FeSO4) or a combination of two or more thereof.

10. The method for removing copper ions from oily wastewater using a system for removing copper ions from oily wastewater according to claim 8, characterized in that: In step S2, the working steps of the cavitation-flocculation module are: the treated wastewater in the pretreatment tank is introduced into the cavitation generator, and when hydraulic cavitation occurs, the flocculant solution is released to the cavitation generator through the flocculant injector, and the flocculant moves forward with the cavitation bubbles to obtain the cavitated feed liquid.

11. The method for removing copper ions from oily wastewater using a system for removing copper ions from oily wastewater according to claim 10, characterized in that: In step S2, the cavitated feed liquid is passed into a first plate-and-frame filter to intercept the precipitate and obtain a filtered feed liquid.

12. The method for removing copper ions from oily wastewater using a system for removing copper ions from oily wastewater according to claim 10, characterized in that: In step S2, the cavitated feed liquid is passed into a flocculation tank, the precipitate is intercepted by a first plate-and-frame filter, and a filtered feed liquid is obtained.

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