A method for coagulation flocculation precipitation using a fluidized bed

Abstract

The present application provides a kind of coagulation flocculation precipitation method using fluidized bed, including coaxial setting middle cylinder, outer tube and inner tube, the bottom of inner tube is provided with water inlet device, water baffle is arranged between inner tube and middle cylinder, guide vane assembly is arranged in the lower part of middle cylinder and outer tube, and the lower part is sedimentation zone;Upper part of outer tube is provided with water outlet;After wastewater enters device, it goes up in inner tube, goes down between middle cylinder and inner tube, and under the action of water baffle, large particle flocculation body is produced by collision and aggregation;Realize separation at bottom, and part of inner circulation is in inner tube.The coagulation flocculation precipitation reaction of the present application is carried out in the inner circulation type fluidized bed reaction device, realizes the coagulation, flocculation and precipitation process in the same device, saves the cost of site and equipment, improves equipment utilization rate;Flocculation body after condensation can be directly precipitated and removed, can greatly reduce reaction time and processing cost, equipment process is simple, easy to operate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater treatment, and relates to a method for coagulation and flocculation sedimentation, in particular a method for coagulation and flocculation sedimentation treatment of wastewater by using an internal circulation fluidized bed. BACKGROUND

[0002] Coagulation and flocculation is an important step in the water treatment process, and the purpose is to coagulate the pollutants such as suspended solids, organic matter, heavy metal ions, etc. in water into larger particles through chemical reactions, so as to facilitate subsequent separation and removal. The coagulant generally uses aluminum or iron salts, and the flocculant generally uses high molecular polymers.

[0003] Both coagulation and flocculation are to coagulate pollutants into larger particles through chemical reactions and physical actions. Coagulation is to attract small particles and make them into larger aggregates through interaction forces, while flocculation is to make particles collide with each other in liquid phase through interaction forces to form larger particles, which are then removed by rising or sinking.

[0004] The coagulation and flocculation sedimentation treatment process can be divided into a coagulation stage, a flocculation stage and a sedimentation stage. The coagulation stage is rapid coagulation of the reagent and wastewater, and small alunite flowers are formed in a very short time, and the water flow is usually in a turbulent state. The flocculation stage is a stage in which the alunite flowers become larger and thicker, and appropriate turbulent state is required. The sedimentation stage is the process of flocculation settling, and slow water flow is required. In order to improve the sedimentation efficiency, inclined pipes or guide pipes are often used. The traditional coagulation and flocculation sedimentation reaction needs a coagulation tank for coagulation treatment, a flocculation tank for flocculation reaction, and a sedimentation tank for sedimentation reaction. The number of equipment is large, the land occupation is large, the treatment process is long, and the foreign countries have developed a reaction device with the functions of flocculation and sedimentation in one, but these products have the disadvantages of uneven water distribution, complex equipment, high investment cost, etc. SUMMARY

[0005] In view of the above problems, the present application provides a method for coagulation and flocculation sedimentation by using a fluidized bed. According to the principle of coagulation and flocculation, a specially designed internal circulation fluidized bed reactor device is used, so that the wastewater has different fluid flow states in different areas in the reactor. The coagulation tank and the sedimentation tank can be integrated to form an integrated reaction device, which is compact in structure and saves land occupation. The internal circulation quantity is used instead of external circulation to reduce energy consumption, improve the mixing effect of the flocculant, and improve the flocculation and sedimentation effect.

[0006] In order to achieve the above technical purposes, the technical scheme of the present application is as follows:

[0007] The present application provides a method for coagulation and flocculation precipitation by using a fluidized bed, which is carried out by using an internal circulation type fluidized bed reaction device, wherein the internal circulation type fluidized bed reaction device comprises a middle cylinder, an outer cylinder and an inner cylinder arranged coaxially, the bottom of the inner cylinder, the middle cylinder and the outer cylinder are communicated, at least one water inlet device is arranged at the bottom of the inner cylinder and connected with a water inlet arranged on the wall of the device or outside the device, the upper end of the inner cylinder extends to the upper part of the middle cylinder, the opening at the upper end is communicated with the inside of the middle cylinder, the top of the middle cylinder and the outer cylinder is jointly sealed and an exhaust port is arranged, a water baffle is arranged between the inner cylinder and the middle cylinder, a flow guide plate assembly is arranged at the lower part of the middle cylinder and the outer cylinder and fixed on the inner wall of the outer cylinder, and the lower part of the flow guide plate assembly is the precipitation zone of the outer cylinder; a water outlet is arranged at the upper part of the outer cylinder.

[0008] The method for coagulation and flocculation precipitation is as follows: after the treated wastewater is adjusted by acid and alkali, the wastewater and the coagulation and flocculation agent enter the device from the water inlet, the wastewater and the coagulation and flocculation agent enter the inner cylinder rapidly under the water inlet pressure, and then are mixed rapidly, and then reach the upper part of the middle cylinder and continue to be mixed, and flocculation is generated to form flocculation bodies; the wastewater flows downward between the middle cylinder and the inner cylinder, and the flow direction is changed constantly under the action of the water baffle, so that the small particle flocculation bodies in the wastewater collide constantly to generate large particle flocculation bodies; after the wastewater reaches the bottom of the middle cylinder, the large particle flocculation bodies will be subjected to sedimentation, and after passing through the flow guide plate, the large particle flocculation bodies are settled in the precipitation zone at the bottom of the reactor, part of the small particles will enter the inner cylinder again for internal circulation under the driving of the water inlet, and the other part of the small particles will enter between the middle cylinder and the inner cylinder with the wastewater and be subjected to sedimentation, and after passing through the flow guide plate, the small particles are settled in the precipitation zone, the treated clean water is discharged through the water outlet, and the precipitate in the precipitation zone is discharged through the bottom sludge outlet.

[0009] Further, at least one exhaust port is arranged at the top of the middle cylinder and between the middle cylinder and the outer cylinder.

[0010] Further, the lower part of the flow guide plate is conical.

[0011] Further, the opening at the bottom of the inner cylinder is arranged as a horn-shaped baffle outward, the included angle between the baffle and the horizontal plane is 10°-80°, preferably 20°-60°, and the ratio of the length of the baffle to the distance between the middle cylinder wall and the inner cylinder wall is 1:1.5-8, preferably 1:2-4.

[0012] Further, the position of the liquid outlet on the wall of the outer cylinder is lower than the reaction liquid level in the reaction device.

[0013] Further, one end of the water baffle is connected with the inner wall of the middle cylinder or the outer wall of the inner cylinder, and the water baffles are arranged staggeredly, one end of the water baffle is connected with the inner wall of the middle cylinder or the outer wall of the inner cylinder at a fixed angle with the horizontal plane, the other end extends to the opposite direction and leaves a gap with the next water baffle.

[0014] Further, the angle between the water baffle and the horizontal plane is 5°-80°, preferably 10°-60°, and most preferably 15°-45°; the ratio of the length of the water baffle to the distance between the middle cylinder and the inner cylinder is 1:1-5, preferably 1:1.2-3.5, and the ratio of the distance between the connection points of two adjacent water baffles on the same side to the height of the inner cylinder is 1:2-15, preferably 1:3-10.

[0015] Further, the angle between the water baffles on the same side or different sides and the horizontal direction is the same or different, and the length of the water baffles is the same or different.

[0016] Further, the lower edge of the inner cylinder is higher than the lower edge of the middle cylinder, and the ratio of the height difference between the lower edge of the inner cylinder and the lower edge of the middle cylinder to the height of the inner cylinder is 1:3-15, preferably 1:4-10.

[0017] Further, the flow guide plate assembly comprises several flow guide plates at an angle to the horizontal plane, the angle being 20°-80°, preferably 30°-70°, and the ratio of the length of the flow guide plate to the diameter of the straight portion of the outer cylinder is 1:5-30, preferably 1:8-15.

[0018] Further, the ratio of the diameter of the reaction device to the height of the reaction device is 1:1-30, preferably 1:3-12; the ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the middle cylinder is 100:20-80, preferably 100:30-60; the ratio of the cross-sectional area of the middle cylinder to the cross-sectional area of the inner cylinder is 100:1-60, preferably 100:3-20, and the ratio of the length of the middle cylinder to the length of the inner cylinder is 100:20-90, preferably 100:30-60.

[0019] Further, the water outlet is located below the liquid level in the reaction device.

[0020] Further, the water inlet device is a device with mixing and water distribution functions, which can fully mix the medicament and water, such as a static mixer or other prior art device that can achieve this function.

[0021] Further, a flow guide plate is arranged in the inner cylinder to make the wastewater flow upward more smoothly.

[0022] Further, the pH of the wastewater to be treated is 5-10, preferably 6-9. The average residence time of the wastewater to be treated in the reaction device is 0.1-6h, preferably 0.3-2h, and most preferably 0.5-1h.

[0023] Further, gas can be optionally mixed into the water inlet, and the volume ratio of the water inlet to the gas is 1:0-30, preferably 1:0-10. The gas is one or a mixture of several of air, nitrogen, oxygen, and tail gas generated by biochemical treatment.

[0024] The technical solution of the present application has the following advantages:

[0025] (1) The coagulation, flocculation and precipitation processes are completed in the same device, saving the cost of site and equipment and improving the utilization rate of equipment.

[0026] (2) The flocculation body after agglomeration can be directly precipitated and removed, which can greatly reduce the reaction time and treatment cost, and the equipment process is simple and easy to operate.

[0027] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The figure is a schematic diagram of the internal circulating fluidized bed reaction device of Example 1. DETAILED DESCRIPTION

[0029] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but in no way limit the present application.

[0030] Example 1

[0031] This example provides an internal circulating fluidized bed reaction device, such as Figure 1As shown: including coaxially arranged inner cylinder 5, middle cylinder 4 and outer cylinder 3, the bottom of inner cylinder 5, middle cylinder 4 and outer cylinder 3 are communicated, the bottom of inner cylinder 5 is provided with water inlet mixing and water distribution device 11, which is connected to water inlet 1, water inlet 1 is arranged on the outer cylinder wall, the upper end of inner cylinder 5 extends to the middle upper part of middle cylinder 4, the upper end opening is communicated with the inside of middle cylinder 4, the top of middle cylinder 4 and the top of outer cylinder 3 are jointly sealed, the top of middle cylinder 4 is provided with exhaust port 10, and each of the top of middle cylinder 4 and the top of outer cylinder 3 is provided with exhaust port 23 and exhaust port 24; Water baffle 6 is arranged between inner cylinder 5 and middle cylinder 4, one end of water baffle 6 is connected to the inner wall of middle cylinder or the outer wall of inner cylinder, and the water baffles are staggered, the water baffles are inclined downward at an angle of 30° with the horizontal plane, one end of the water baffles is sealingly connected to the inner wall of middle cylinder or the outer wall of inner cylinder, the other end of the water baffles extends to the opposite direction, and a gap is left between the water baffles of adjacent levels, the length of the water baffles is 1:1.5 times the distance from the inner wall of middle cylinder to the outer wall of inner cylinder. A guide plate assembly 7 is arranged in the lower part of middle cylinder 4 and the outer cylinder 3 and is fixed to the inner wall of outer cylinder, the guide plate assembly 7 includes a plurality of guide plates, the guide plates are centered on a central axis, the bottom of the guide plates is inclined inward, the guide plates are distributed at a certain angle with the horizontal plane, and the length of the guide plates is 1:10 times the diameter of the outer cylinder; The lower part of guide plate assembly 7 is a conical sedimentation zone 8 of outer cylinder, and the bottom is provided with a sludge discharge port 9; The upper wall of outer cylinder 3 is provided with liquid outlet I 21 and liquid outlet II 22, and the positions of liquid outlet I 21 and liquid outlet II 22 are lower than the liquid level in the reaction device; The ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the middle cylinder is 100:45, the ratio of the cross-sectional area of the middle cylinder to the cross-sectional area of the inner cylinder is 100:7, and the height-diameter ratio of the reaction device is 6.

[0032] The bottom opening of inner cylinder 5 is arranged as an outwardly flared baffle, the baffle has an angle of 30° with the horizontal plane, and the length of the baffle is 1:2 times the distance between the wall of middle cylinder and the wall of inner cylinder.

[0033] Example 2

[0034] This embodiment provides a method for treating wastewater by using the reaction device of example 1, the process is as follows:

[0035] The wastewater to be treated is adjusted by acid and alkali, and then enters the water inlet device 11 from the water inlet 1 together with the coagulation flocculant. The wastewater and the coagulation flocculant enter the inner cylinder 5 quickly through the water inlet device 11, and are quickly mixed in the inner cylinder 5. Then, the mixed wastewater reaches the upper part of the middle cylinder 4 to continue mixing and flocculation, and forms flocculation bodies. The mixed wastewater flows downward between the middle cylinder 4 and the inner cylinder 5, and the flow direction is changed constantly by the water baffle 6, so that the small flocculation bodies in the wastewater collide and gather to form large flocculation bodies. Then, the large flocculation bodies reach the bottom of the middle cylinder 4, and then are settled to the sedimentation area 8 at the bottom of the reactor through the flow guide plate assembly 7. Part of the small flocculation bodies is driven by the water to enter the inner cylinder 5 for internal circulation, and part of the small flocculation bodies enters between the middle cylinder 4 and the inner cylinder 5 and is settled through the flow guide plate assembly 7. The treated clear water is discharged through the water outlet I 21 and the water outlet II 22, and the sediment in the sedimentation area is discharged through the bottom sludge outlet 9.

[0036] Example 3

[0037] The wastewater of a chemical plant has a turbidity of 546 NTU. The pH of the wastewater is adjusted to 8-9, and then the polymeric aluminum ferric chloride flocculant is added, and the concentration of the flocculant is controlled to be 0.8 g / L. The residence time of the wastewater in the reactor is controlled, and after continuous operation for 6 h, the sample is taken from the effluent for analysis, and the results are shown in the following table.

[0038]

[0039]

[0040] Comparative Example 1

[0041] The wastewater of a chemical plant has a turbidity of 546 NTU. The pH of the wastewater is adjusted to 8-9, and then the polymeric aluminum ferric chloride flocculant is added, and the concentration of the flocculant is controlled to be 0.8 g / L. The coagulation flocculation and sedimentation are carried out by intermittent stirring. After the sedimentation is completed, the turbidity of the supernatant is 49.1 NTU, and the turbidity removal rate is 91.0%.

[0042] As can be seen from the above experimental results, the fluidized bed coagulation flocculation and sedimentation reactor of the present application has the functions of coagulation, flocculation and sedimentation, and forms an integrated reactor device. The structure is compact, the land occupation is saved, the internal circulation amount is large, the mixing effect of the flocculant is improved, and the flocculation and sedimentation effect is improved.

Claims

1. A method for coagulation, flocculation, and sedimentation using a fluidized bed, characterized in that, The reaction is carried out using an internal circulation fluidized bed reactor, which includes a coaxially arranged middle cylinder, outer cylinder, and inner cylinder. The bottoms of the inner cylinder, middle cylinder, and outer cylinder are connected. At least one water inlet device is provided at the bottom of the inner cylinder and connected to a water inlet located on the reactor wall or outside the reactor. The upper end of the inner cylinder extends to the upper middle part of the middle cylinder, and its upper opening communicates with the interior of the middle cylinder. The tops of the middle cylinder and the outer cylinder are jointly sealed and equipped with vents. A water-blocking baffle is provided between the inner cylinder and the middle cylinder. A flow guide plate assembly is provided in the lower part of the middle cylinder and in the outer cylinder and fixed to the inner wall of the outer cylinder. The lower part of the flow guide plate assembly is the sedimentation zone of the outer cylinder. A water outlet is provided at the upper part of the outer cylinder. The lower edge of the inner cylinder is higher than the lower edge of the middle cylinder. The method for coagulation, flocculation, and sedimentation is as follows: After acid-base adjustment, the wastewater to be treated enters the device together with the coagulating flocculant through the inlet. The wastewater and coagulating flocculant enter the inner cylinder rapidly under the inlet pressure and mix quickly. Then, they reach the upper part of the middle cylinder and continue to mix, producing flocculation and forming flocs. The wastewater flows downward between the middle and inner cylinders. Under the action of the baffle, the flow direction is constantly changed, causing the small flocs formed in the wastewater to collide and aggregate to form large flocs. After the wastewater reaches the bottom of the middle cylinder, the large flocs will settle and settle to the sedimentation zone at the bottom of the reactor after passing through the guide plate. Some small particles will re-enter the inner cylinder for internal circulation under the influence of the inlet water. Other small particles will enter the space between the middle and inner cylinders with the wastewater and settle, settling to the sedimentation zone after passing through the guide plate. The treated water is discharged through the outlet, and the sediment in the sedimentation zone is discharged through the bottom sludge discharge port.

2. The method according to claim 1, characterized in that, The sedimentation zone at the bottom of the guide plate is conical.

3. The method according to claim 1, characterized in that, The bottom opening of the inner cylinder is configured as an outward-facing trumpet-shaped baffle, with the baffle forming an angle of 10°-80° with the horizontal plane, and the ratio of the baffle length to the distance between the middle cylinder wall and the inner cylinder wall is 1:1.5-8.

4. The method according to claim 1, characterized in that, One end of the water-proof baffle is connected to either the inner wall of the middle cylinder or the outer wall of the inner cylinder, and they are arranged in an alternating pattern. The water-proof baffles are inclined downward at a fixed angle to the horizontal plane. One end of the baffle is sealed to the inner wall of the middle cylinder or the outer wall of the inner cylinder, and the other end extends in the opposite direction, leaving a gap with the next level water-proof baffle.

5. The method according to claim 1, characterized in that, The angle between the water-proof baffle and the horizontal plane is 5°-80°. The ratio of the length of the water-proof baffle to the distance between the middle cylinder and the inner cylinder is 1:1-5. The ratio of the distance between the connection points of two adjacent water-proof baffles on the same side on the cylinder wall to the height of the inner cylinder is 1:2-15.

6. The method according to claim 1, characterized in that, The ratio of the height difference between the lower edge of the inner cylinder and the lower edge of the middle cylinder to the height of the inner cylinder is 1:3-15.

7. The method according to claim 1, characterized in that, The guide vane assembly includes several guide vanes that form a certain angle with the horizontal plane, with the angle being 20°-80°; the ratio of the length of the guide vane to the diameter of the straight section of the outer cylinder is 1:5-30.

8. The method according to claim 1, characterized in that, The ratio of the diameter to the height of the reaction device is 1:1-30.

9. The method according to claim 1, characterized in that, The outlet is positioned below the liquid level inside the reaction device.

10. The method according to claim 1, characterized in that, The pH of the wastewater to be treated is 5-10, and the average residence time of the wastewater in the reaction device is 0.1-6h.

11. The method according to claim 1, characterized in that, Gas can be selectively mixed into the influent, with a volume ratio of influent to gas of 1:0-30.

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