CN101811757B - Air-assisted electro-coagulation algae water separation device and using method thereof - Google Patents

Abstract

A gas-assisted electric flocculation algae-water separation device and a use method thereof belong to the technical field of sewage treatment. The device includes a tower body, a main shaft, a concentric cylindrical electrode plate, a mechanical transmission device, a connecting rod mechanism, a floating ball device, a gas distributor, a pulse gas supply device and other parts. The device uses an even number of concentric cylinders as the cathode and anode of electroflocculation, which are distributed in a staggered manner, has a large surface area of the plates, high electrocoagulation efficiency, and can effectively prevent the adsorption and precipitation of microalgae on the electrode surface. The flow direction of the liquid in the tower is opposite to the sedimentation direction of the microalgae, forming a cross flow, which can enhance mass transfer and improve the efficiency of electrocoagulation. The floating ball device can make the moving parts such as the main shaft in the tower and the concentric cylindrical electrode plates of the anode and cathode in a floating state, which can reduce the operating load of the transmission motor. The device of the invention can realize the continuous operation of microalgae electric flocculation and air flotation collection, the basic structure is easy to enlarge and implement, and is suitable for large-scale industrial continuous operation requirements.

Description

A gas-assisted electric flocculation algae water separation device and its application method

technical field

The invention belongs to the technical field of sewage treatment, and in particular relates to a gas-assisted electric flocculation algae water separation device and a use method thereof, which are used for the separation and purification of algae water rich in microalgae water bodies.

Background technique

Water resources are one of the key resources for human survival. With the acceleration of urbanization and industrial development, human beings are putting more and more pressure on the ecological environment of precious water resources. A large amount of industrial wastewater and domestic sewage are discharged into rivers, lakes and reservoirs, resulting in the continuous increase of ammonia, nitrogen and phosphorus nutrients in the water, the eutrophication of the lake water is becoming more and more serious, and the ecosystem is degraded. According to the latest statistics, 88.6% of the 133 large lakes in my country have water eutrophication. In eutrophic water bodies, cyanobacteria and other microbial algae reproduce explosively in a large area, which not only inhibits the growth of other algae, reduces the transparency of the water body, but also discharges toxic metabolites into the water body. In addition, after a large number of blue-green algae die, it will cause a serious shortage of dissolved oxygen in the water body, resulting in foul smell. Severe water pollution has adverse effects on the ecological environment and human production and life, and poses a serious threat to human health. In the summer of 2007, severe cyanobacteria blooms occurred successively in Taihu Lake, Chaohu Lake and Dianchi Lake. Dongting Lake and Baiyangdian Lake are also threatened by eutrophication to varying degrees. At the end of May 2008, the most serious cyanobacteria event in history broke out in Taihu Lake, which led to a serious water crisis for Wuxi residents. Therefore, how to solve this problem has aroused widespread concern from all walks of life.

If the water body rich in microalgae can be separated and treated with algae water, it should have positive significance for purifying the water body. At present, the separation and collection methods of microalgae mainly include: centrifugation, filtration, flocculation and sedimentation, etc. Due to the extremely fine particle size of the microalgae, the efficiency of the centrifugation method is low. In order to effectively separate the algae water, the centrifuge needs to be operated at a relatively high speed, which consumes a lot of energy. Most of the filtration methods use membrane filtration equipment, but the membrane is easy to clog after a period of time, and the regeneration and reuse process is complicated, so continuous operation cannot be realized. The method of flocculation and sedimentation generally adds various chemical flocculants, which is likely to cause secondary pollution of water bodies.

In recent years, the process of separating algal water by electrocoagulation has attracted great attention. The mechanism of electrocoagulation separation of microalgae mainly includes: ① electro-oxidation damages microalgae organisms and leads to agglomeration and flocculation; ② metal ions dissolved from the electrode when the active metal electrode is used are used as flocculants to produce flocculation; ③ water electrolysis process. Hydrogen and oxygen are separated by air flotation for microalgae. Compared with other algal water separation methods, electrocoagulation has the advantages of high separation efficiency, no need to add chemical flocculants, easy operation and controllable process. Electrocoagulation has been tried for the separation of different microalgal water bodies: Alfafara and Nakano et al. used electrocoagulation to remove Microcystis sp. in lake water (Alfafara C.G., Nakano K., Nomura N., Igarashi T., Matsumura M.J.Chem.Technol.Biotechnol., 2002,77,871); Poelman and DePauw etc. have verified that electrocoagulation is used for the recovery of microalgae such as various green algae and diatoms through experiments (Poelman E., DePauw N., Jeurissen B., Resour. Conserv. Recy., 1997, 19, 1). However, there are still problems in the electrocoagulation separation process of microalgae: ① After flocculation, the microalgae cells precipitate on the electrode surface and are adsorbed on the electrode surface. The effective electrode plate area decreases, resulting in a decrease in electrocoagulation efficiency. If a trough device is used, continuous operation is difficult due to the need to frequently descale the electrode surface during operation. ②The electrolysis gas production is not large, and the air flotation efficiency is low. ③The industrial scale-up of the trough-type electroflocculation device is also unfavorable, the equipment structure is complex, and maintenance is not easy. Therefore, there is no industrialized report on microalgae electroflocculation.

The method of separating microalgae by air flotation has also been reported. However, most of them need to add chemical flocculants in advance to pre-flocculate the microalgae to be separated, and then use the surface adsorption of the rising air bubbles to catch the aggregated microalgae and move upward to realize the separation of algae and water. Due to the large surface area of the micro-bubbles blown into the water body, the adsorption and separation efficiency is high; at the same time, the bubbles may coalesce and break the wall during the rising process, and the energy generated by the explosion of the burst bubbles further promotes the reunion of microalgae in the water body. However, there is no industrial report on the separation of microalgae by air flotation. In addition to the need to add chemical flocculants, which may easily cause secondary pollution of the water body, there are also problems in the scale-up and continuous operation of the equipment.

Therefore, how to effectively combine the two technologies of electrocoagulation and air flotation to develop a continuous device for microalgae electroflocculation is of great significance. It is necessary to develop a microalgae electrocoagulation device that can meet the requirements of continuous industrial operation in order to exert its power. The advantages of flocculation in the separation of microalgae make it valuable for popularization and application.

Contents of the invention

The purpose of the present invention is to provide a gas-assisted electric flocculation algae water separation device and its use method, so as to overcome the defect that the current microalgae electric flocculation equipment is difficult to realize industrial continuous operation.

The device of the present invention includes a tower body, a main shaft, a concentric cylindrical electrode plate, a mechanical transmission device, a connecting rod mechanism, a floating ball device, a gas distributor, a pulse air supply device and the like; The center hole, the upper end of the main shaft is located outside the tower body and connected with the connecting rod mechanism; the lower end of the main shaft is located inside the tower body and connected with the floating ball device, and the upper part of the main shaft (the main shaft is made of metal) is located outside the tower body. Two circular conductive metal plates are installed for use. The wires are respectively softly connected to the positive and negative poles of a DC power supply (the voltage of the DC power supply is 6-24 volts, and the current is 1-1.5 amperes); The lower ends are connected; the gas distributor is set under the concentric cylinder at the lower part of the tower; the pulse gas supply device is powered by a pulse AC power supply, and supplies gas to the gas distributor in an intermittent manner.

The tower body is a cylindrical structure, and the upper and lower parts are designed with enlarged closed cavities. Among them, the center of the top surface of the cylindrical cavity on the upper part of the tower body is open; the bottom end surface of the cylindrical cavity on the lower part of the tower body is a conical structure, and a slag discharge port is provided to connect with the valve. The material of the tower body is metal or plastic, and the lining of the tower body is anti-corrosion coating.

The upper part of the tower body is located on the side of the cavity of the expansion section, and an overflow outlet is provided; the upper part of the tower body is located below the cavity of the expansion section, and a feed liquid inlet is connected to the valve; the lower part of the tower body is located above the cavity of the expansion section, and there is a material The liquid outlet is connected with the valve.

The voltage and current of the DC power supply can be adjusted according to technological requirements. The anode metal plate is a circular surface; the cathode metal plate is a ring structure, and there are gaps between the rings, and the distance between the rings is fixed by four mutually orthogonal conductive metal plates. The anode and cathode metal plates are respectively connected to the main shaft with insulating material and fixed with a positioning device 4 . The anode and cathode metal plates on the main shaft are separated by insulating material.

A series of concentric cylinders are respectively welded on the anode and cathode metal plates on the main shaft. Even pairs of anode and cathode concentric cylinders are staggered, and the distance between the concentric cylinders is 1-10 mm. The materials of the concentric cylinders are all conductive metal materials. The cathode concentric cylinders are welded on four mutually orthogonal conductive metal plates, and the thickness of the conductive metal plates fixing the cathode concentric cylinders is 1 to 4 mm; each anode concentric cylinder has four long and narrow gaps. The width L is 5-10 mm, and the conductive metal plate fixing the cathode concentric cylinder passes through the slit without contacting the anode concentric cylinder.

The mechanical transmission device is located outside the tower and includes a link mechanism and an eccentric wheel connected thereto. The connecting rod mechanism is connected to the upper end of the main shaft through a fixed shaft sleeve; the eccentric wheel is driven to rotate by a motor. When the motor rotates, the main shaft vibrates up and down. The amplitude and frequency of the main shaft can be adjusted, the amplitude of the main shaft can be adjusted by adjusting the eccentricity of the eccentric wheel, and the vibration frequency of the main shaft can be adjusted by changing the motor speed.

The floating ball device is a spindle-shaped hollow floating ball device, and the floating ball device can make moving parts such as the main shaft in the tower and the concentric cylindrical electrode plates of the anode and cathode in a floating state. The material of the float device can be metal or plastic, and the outer surface is treated with anticorrosion.

The gas distributor consists of a gas distribution head and a protective cover. The protective cover is set above the gas distribution head, and the distance between it and the gas distribution head should not hinder the gas blowing. The protective cover is fixed on the main shaft with a positioning device, and its function is to prevent the falling solid particles from clogging the gas distribution head. The gas distribution head is made of ceramic-based porous material, and the hollow cavity is connected to the air supply pipe. The gas supply device bubbles air and other gases from the gas distribution head; the size of the bubbles is controlled by the micropore diameter on the surface of the gas distribution head.

The gas supply duration and gas volume of the pulse gas supply device can be adjusted according to the process requirements. The air supply duration can be realized by adjusting the pulse AC power frequency, and the air supply volume can be realized by adjusting the power of the pulse AC power supply to generate different air pressures. The pulse gas supply device is connected with the gas supply pipeline, and a valve is arranged in the middle. The air supply of the pulse blowing device is 1 to 5 minutes, the interval is 30 seconds to 1 minute, and the air pressure is 1 to 4 MPa.

The use method of the present invention is as follows: the feed liquid containing microalgae is pumped in from the feed inlet, and the cathode and anode conductive concentric cylindrical electrode plates connected to the main shaft and the main shaft are driven by the motor to reciprocate up and down. After electrification, the microalgae in the feed liquid produce flocculation, agglomeration and sedimentation under the action of the electric field. The gas distributor in the lower part of the tower is pulsed and intermittently blasted to generate a large number of bubbles. The surface of the rising bubbles adsorbs the flocculated microalgae and then carries the microalgae to move up the tower body. Bubbles may coalesce and break walls during their ascent, and the energy generated by the bursting of bubbles will further promote the reunion of microalgae in the water body. The agglomerated microalgae are further coalesced during the ascent process, and the particles grow up, and are finally brought by the air bubbles to the liquid surface of the cavity in the upper part of the tower body. The height of the liquid level in the cavity of the enlarged section on the upper part of the tower body is below the microalgae outlet 7 and above the feed liquid inlet 16, and the microalgae enriched on the liquid surface can flow out from the overflow port 7 and be collected. The microalgae in the feed liquid are separated from the algae and water under the action of electrocoagulation and air flotation, and the clear liquid from which the microalgae has been removed flows out from the feed liquid outlet at the lower part of the tower above the cavity of the expansion section.

The flow rate ratio between the feed liquid inlet and the feed liquid outlet is 1:0.5-1:1, and the preferred flow rate ratio is 1:0.85-1:0.95.

The advantages of the present invention are:

1. Adopt a series of concentric cylindrical cathode and anode electrode plates to vibrate up and down, or/and the gas distributor in the lower part of the tower body for pulsed intermittent air blowing, the purpose of which is to effectively prevent the microalgae rising with the bubbles from adsorption and precipitation on the electrode surface, and improve Electrocoagulation efficiency.

2. A series of concentric cylinders are used as the cathode and anode electrode plates of the electrocoagulation device, and the even numbered pairs are staggered to increase the surface area of the electrodes as much as possible to improve the electrocoagulation efficiency.

3. The flow direction of the liquid in the tower is opposite to the movement direction of the agglomerated, flocculated and settled microalgae, forming a cross flow, which can enhance mass transfer and improve the efficiency of electrocoagulation.

4. The floating ball device is adopted, and the buoyancy of the water body is used to make the moving parts in the tower (including the main shaft and the cathode and anode cylindrical electrode plates connected to it) in a floating state, which can reduce the operating load of the transmission motor.

5. The gas-assisted electric flocculation algae water separation device of the present invention can realize the continuous operation of microalgae electric flocculation and air flotation collection, and the purification effect of various microalgae-rich water bodies after treatment by the device can reach the national first-class water quality standard.

6. The basic structure of the device of the present invention is simple, easy to scale up and implement, and is suitable for large-scale industrial continuous operation requirements. Under the condition of a certain tower cavity volume, controlling the flow rate ratio between the feed liquid inlet and the feed liquid outlet, controlling the applied voltage and current of the cathode and anode concentric cylindrical electrode plates, and controlling the gas supply interval and the gas volume of the pulse gas supply device can be controlled. The processing power of the device is controlled.

After the device of the present invention has been used for a period of time, if the device needs to be shut down for maintenance, the slag discharge port and valve located in the cylindrical cavity at the lower part of the tower body can be opened to clean the tower body and discharge slag.

Description of drawings

Fig. 1 is a structural schematic diagram of the novel gas-assisted electroflocculation algae water separation device of the present invention. Among them, mechanical transmission device 1, connecting rod mechanism 2, fixed bushing 3, positioning device 4, anode concentric cylinder electrode plate 5, cathode concentric cylinder electrode plate 6, overflow outlet 7, tower body 8, protective cover 9, Gas distributor 10, pulse gas supply device 11, feed liquid outlet 12, float device 13, slag discharge port 14, main shaft 15, feed liquid inlet 16, DC power supply 17, valve 18.

Fig. 2 is a three-dimensional assembly view of the cathode and anode concentric cylindrical electrode plates of the present invention, and the cathode and anode concentric cylindrical electrode plates are fixed by four mutually orthogonal conductive metal plates.

Fig. 3 is a top view of the anode concentric cylinder electrode plate 5, and each anode concentric cylinder has four long and narrow gaps.

Fig. 4 is a front view of the anode concentric cylinder electrode plate 5, the width L of the slit should be greater than the thickness of the conductive metal plate fixing the cathode concentric cylinder, and leave a gap.

FIG. 5 is a top view of the electrode plate 6 of the cathode concentric cylinder, and the cathode concentric cylinder is welded on four mutually orthogonal conductive metal plates.

FIG. 6 is a rotated sectional view of the cathode concentric cylindrical electrode plate 6 .

Fig. 7 is a top view of the schematic structure of the gas distributor of the present invention.

Fig. 8 is a perspective view of a schematic structural view of the gas distributor of the present invention.

Figure 9 is a top view of the protective cover.

Figure 10 Front view of the protective cover.

Detailed ways

The device of the present invention includes a tower body 8, a main shaft 15, cathode and anode concentric cylindrical electrode plates 5, 6, a mechanical transmission device 1, a connecting rod mechanism 2, a floating ball device 13, a gas distributor 10, a pulse gas supply device 11 and other parts; The main shaft 15 passes through the central hole at the top of the cylindrical cavity on the upper part of the tower body 8, and the upper end of the main shaft 15 is located outside the tower body 8 and is connected with the linkage mechanism 2; the lower end of the main shaft 15 is located in the tower body 8 and is connected with the float device 13, The upper part of the main shaft 15 is located outside the tower body, and two cathode and anode concentric cylindrical electrode plates 5 and 6 are installed, which are respectively softly connected to the positive pole and the negative pole of a DC power supply 17 with wires; In the cavity, the floating ball device 13 is connected to the lower end of the main shaft 15; the gas distributor 10 is arranged under the concentric cylinder at the lower part of the tower body 8; the pulse gas supply device 11 is powered by a pulse AC power supply and supplies gas to the gas distributor intermittently.

Example 1 Separation of algal hydroelectric flocculation and air flotation collection of cyanobacteria in Dianchi Lake, Kunming

The device of the present invention is used to investigate the separation effect of algae hydroelectric flocculation in the water body of cyanobacteria in Dianchi Lake, Kunming. Control the flow rate ratio of the feed liquid inlet 16 and the feed liquid outlet 12 to be 1:0.95, the applied voltage of the DC power supply 17 is 24 volts, the current is 1.5 amperes, the air supply time of the pulse blowing device 11 is 1 minute, the interval is 30 seconds, and the air pressure is 4.0 MPa , during the continuous separation and collection process, the microalgae biomass was measured on the clear liquid at the feed liquid outlet 12, and the microalgae yield was 98.5%.

Example 2 Separation of algal hydroelectric flocculation and air flotation collection of cyanobacteria in Taihu Lake, Wuxi

The device of the invention is used to investigate the separation effect of algae hydroelectric flocculation in Wuxi Taihu cyanobacteria water body. Control the flow rate ratio of the feed liquid inlet 16 and the feed liquid outlet 12 to be 1:0.85, the applied voltage of the DC power supply 17 is 24 volts, the current is 1.5 amperes, the air supply time of the pulse blowing device 11 is 5 minutes, the interval is 1 minute, and the air pressure is 2.0 MPa , during the continuous separation and collection process, the microalgae biomass was measured on the clear liquid at the feed liquid outlet 12, and the microalgae yield was 99.0%.

Example 3 Separation of algal hydroelectric flocculation and air flotation collection of microalgae in spirulina culture solution

The device of the invention is used to investigate the effect of hydroelectric flocculation separation of microalgae in spirulina culture solution. Control the flow rate ratio of the culture solution inlet 16 and the clear liquid outlet 12 to be 1:0.9, the applied voltage of the DC power supply 17 is 6 volts, the current is 1.0 ampere, and the gas supply time of the pulse blowing device 11 is 2 minutes with an interval of 45 seconds , air pressure 1.0MPa, during the continuous separation and collection process, the microalgae biomass was measured on the clear liquid at the feed liquid outlet 12, and the yield of spirulina was 97.5%.

Claims (9)

1. an air-assisted electro-coagulation algae water separation device, comprise tower body, main shaft, concentric drums battery lead plate, mechanical drive, linkage assembly, floating ball device, gas distributor and Gas puffing device; It is characterized in that: main shaft (15) passes the centre hole on tower body (8) top cylinder shape cavity top, and main shaft (15) upper end is positioned at that tower body (8) is outer to be connected with linkage assembly (2); Main shaft (15) lower end is positioned at tower body (8) and is connected with floating ball device (13), main shaft (15) top is positioned at the tower body outside two anode and cathode concentric drums battery lead plates (5,6) is installed, and does to be flexible coupling with positive pole and the negative pole of a direct current power supply (17) respectively with wire; Floating ball device (13) is positioned at tower body (8) inner bottom part expanding reach cavity, and floating ball device (13) is connected with main shaft (15) lower end; Gas distributor (10) is arranged at concentric drums below, tower body (8) bottom; Gas puffing device (11) is by the pulse ac Power supply, with intermittent mode to the gas distributor air feed.

2. device according to claim 1 is characterized in that: tower body (8) is the cylinder barrel shaped structure, and top and the bottom all are designed with the expanding reach enclosed cavity; The top end face center drilling of tower body top cylinder shape cavity; The bottom face of tower body lower cylindrical cavity is conical structure, is provided with a slag notch (14) and is connected with valve; The material of tower body is metal or plastics, and the tower body liner is corrosion protection coating; The side that tower body top is positioned at the expanding reach cavity is provided with an overflow outlet (7); Tower body top is positioned at the below of expanding reach cavity, is provided with a liquor inlet (16) and is connected with valve; The tower body bottom is positioned at the top of expanding reach cavity, is provided with a material liquid outlet (12) and is connected with valve.

3. device according to claim 1, it is characterized in that: the voltage and current of described direct supply is according to the processing requirement adjustment, and anode metal plate is disc; The cathodic metal plate is circular ring structure, and interannular leaves the space, and ring spacing is fixed with four mutually orthogonal conductive metal sheets; Anode is connected with main shaft with insulating material respectively with the cathodic metal plate, and fixing with locating device (4); Separate with insulating material between the anode on main shaft and cathodic metal plate.

4. device according to claim 1, is characterized in that: be welded with respectively a series of concentric drums on the anode on main shaft and cathodic metal plate; Anode and negative electrode concentric drums even-even are interspersed, 1～10 millimeter of concentric drums spacing; The concentric drums material is conductive metallic material; The negative electrode concentric drums is welded on four mutually orthogonal conductive metal sheets, and the thickness of the conductive metal sheet of fixed negative pole concentric drums is 1～4 millimeter; Each anode concentric drums all leaves four long and narrow gaps, and slit width L is 5～10 millimeters, and the conductive metal sheet of fixed negative pole concentric drums passes from slit, does not contact with the anode concentric drums.

5. device according to claim 1, it is characterized in that: described floating ball device (13) is fusiform hollow float device, and floating ball device makes tower inner main axis (15) and anode and cathode concentric drums battery lead plate (5,6) moving parts be in floating state; The floating ball device material is metal or plastics, and outside surface is done rotproofing.

6. device according to claim 1, it is characterized in that: described gas distributor (10) is comprised of a gas distribution head and a shield cap (9); Shield cap (9) is located at above gas distribution head, shield cap (9) shield cap is fixed on main shaft with locating device, gas distribution head is made by the ceramic base porous material, the gas distribution head inner chamber is hollow to be connected with air duct, by Gas puffing device (11), gas is sent from the gas distribution head bubbling; The air feed of pulse air-blowing device (11) is 1～5 minute, interval 30 seconds～1 minute, air pressure 1～4MPa.

7. device according to claim 1, is characterized in that, the voltage of direct supply (17) is 6～24 volts, and electric current is 1～1.5 ampere.

8. air-assisted electro-coagulation algae water separation device using method claimed in claim 1, it is characterized in that, the feed liquid that contains little algae pumps into from opening for feed (16), be connected to anode and cathode conductive concentric cylinder electrode plate (5,6) on main shaft (15) with main shaft (15) under motor drives, do up and down reciprocatingly vibration; After energising, the little algae in feed liquid produces flocculation reunion sedimentation under electric field action; The intermittently air-blowing of tower body lower gas sparger (10) pulsed produces a large amount of bubbles; Carry little algae after little algae of rising bubble surface adsorption flocculation to tower body top motion; Bubble might occur to gather also at uphill process, broken wall, and the energy that the bubble explosion of breaking produces further impels the little algae in water body to reunite; Little algae of reuniting is further poly-in uphill process, and also particle is grown up, and is finally brought to the fluid surface of tower body top expanding reach cavity by bubble; Liquid level is below overflow outlet (7) in the expanding reach cavity of tower body top, and more than liquor inlet (16), on liquid level, little algae of enrichment can export from overflow (7) and flows out and collect; Little algae in feed liquid complete under electricity flocculation and two kinds of effects of air supporting algae moisture from, and the clear liquid of having removed little algae is positioned at material liquid outlet (12) outflow of expanding reach cavity top from the tower body bottom.

9. method according to claim 8, is characterized in that, the velocity ratio of liquor inlet (16) and material liquid outlet (12) is 1: 0.85～1: 0.95.

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