A high solid content fully mixed anaerobic reactor

Abstract

The present invention belongs to the technical field of anaerobic digestion, and specifically relates to a high solid content fully mixed anaerobic reactor, comprising an anaerobic digestion tank and a filtering and separating device arranged outside the anaerobic digestion tank, the filtering and separating device comprising a shell and a filtering element arranged in the shell, the shell being connected in series with the anaerobic digestion tank through a pipeline to form a circulation loop, the filtering element comprising a hollow rotating shaft and a disc-shaped hollow ceramic membrane, the disc-shaped hollow ceramic membrane being sleeved along its axial direction and fixed on the outer periphery of the hollow rotating shaft, the hollow rotating shaft being connected to the inside of the disc-shaped hollow ceramic membrane through a through hole in its side wall, and the filtered clear liquid being discharged from the filtering and separating device through the hollow rotating shaft. The reactor is suitable for processing raw materials of high viscosity materials, such as thermal hydrolysis sludge, restaurant kitchen waste, etc., to increase solid concentration or organic load through anaerobic digestion, and at the same time solves the problems of increasing the solid content of anaerobic digestion liquid and filtering the digestion liquid, and the solid content of anaerobic digestion can reach 12%.

Description

Technical Field

[0001] The invention belongs to the technical field of anaerobic digestion, and in particular relates to a high-solid content fully mixed anaerobic reactor. Background Art

[0002] Anaerobic digestion is a commonly used technology for treating organic solid waste and organic wastewater, and is particularly important for waste reduction, stabilization and resource utilization.

[0003] The most common reactor for anaerobic digestion is the fully mixed type, which has the advantages of wide application range, easy control, and simple structure, but its disadvantage is that the digester has a low operating load, that is, the solid content of the digester is low, generally not exceeding 5%. Low load operation leads to low unit volume biogas production, large tank body, high investment and operation costs, and low solid content of digestate reduces the efficiency of solid-liquid separation. At present, the only way is to concentrate the material before entering the anaerobic digester. On the one hand, flocculants will be added, which will have an adverse effect on anaerobic microorganisms and biochemical reactions; on the other hand, high-concentration feed will lead to feeding difficulties, thereby increasing pumping requirements, such as the need to change the screw pump to a plunger pump, which ultimately leads to an increase in investment costs. In addition, as the amount of solid matter in the anaerobic digestion reaction decreases, the solid content of the sludge will also be reduced to a certain extent compared to the feed, and the feed needs to be increased to a higher concentration than the actual anaerobic digestion. Summary of the invention

[0004] The object of the present invention is to provide a fully mixed anaerobic reactor to overcome the problems of high suspended matter in filtrate, low denitrification load and low efficiency, and poor removal effect of difficult-to-degrade COD in existing fully mixed anaerobic reactors.

[0005] The present invention provides a high-solid content fully mixed anaerobic reactor, including an anaerobic digestion tank and a filtering and separating device arranged outside the anaerobic digestion tank, the filtering and separating device includes a shell and a filtering element arranged in the shell, the shell is connected in series with the anaerobic digestion tank through a pipeline to form a circulation loop, the filtering element includes a hollow rotating shaft and a disc-shaped hollow ceramic membrane, the disc-shaped hollow ceramic membrane is sleeved along its axial direction and fixed on the outer periphery of the hollow rotating shaft, the hollow rotating shaft is connected to the inside of the disc-shaped hollow ceramic membrane through the through hole of its side wall, and the filtered clear liquid is discharged from the filtering and separating device through the hollow rotating shaft. Preferably, one end of the hollow rotating shaft is closed, and the other end is provided with a filtrate outlet.

[0006] As a preferred solution, in order to facilitate separation of high solid content solution, the discharge pipe of the filtering separation device is connected to the upper reaction zone of the anaerobic digester, and the inlet pipe of the filtering separation device is connected to the lower reaction zone of the anaerobic digester.

[0007] As a preferred solution, in order to ensure the filtering effect, the pore size of the disc-shaped hollow ceramic membrane is 0.05 μm to 2 μm, and the material is selected from one of aluminum oxide, zirconium oxide, titanium dioxide and silicon oxide.

[0008] As a preferred solution, a circulating pump is connected in series to the liquid inlet pipe, and the pump extracts the anaerobic digestion liquid and sends it to the filtration separation device. The pressure is controlled by a valve, and the anaerobic digestion liquid is subjected to dynamic cross-flow filtration by filtration separation. The membrane filtration flux is controlled at 15-20L / m2·h, the filtration pressure is controlled at 0.1MPa-0.6Mpa, and the rotation speed of the rotating shaft is controlled at 400-900rpm / min. With the high-speed rotation of the disc-shaped hollow ceramic membrane, a high shear force is generated on the surface of the disc-shaped hollow ceramic membrane to form a cyclonic sweep flow, so that the filter cake layer on the surface of the membrane is very thin to avoid blockage as much as possible.

[0009] Furthermore, during the start-up period of anaerobic digestion, the hydraulic retention time of anaerobic digestion is adjusted by adjusting the feed amount until the biogas production is stable and the methane content in the biogas is greater than 55%. During the stable period, the digestate in the anaerobic digestion tank is quantitatively pumped into the filtration separation device every day, and the membrane permeate is quantitatively discharged. When the solid content of the digestate reaches the target value (8% to 12%), the filtration is stopped.

[0010] As a preferred solution, in order to increase the filtration area and improve the filtration efficiency, a plurality of the disc-shaped hollow ceramic membranes are coaxially arranged.

[0011] As a preferred embodiment, the outer surface of the disc-shaped hollow ceramic membrane is provided with ridge-shaped protrusions, and the ridge-shaped protrusions are perpendicular to the tangent direction of the disc-shaped hollow ceramic membrane. Such a setting can generate turbulence when the disc-shaped hollow ceramic membrane is rotary-cut and rubbed with the digestive liquid, thereby forming a larger positive pressure in front of the ridge-shaped protrusions to impact the filter cake, and forming an area with a certain vacuum degree behind the ridge-shaped protrusions, thereby better stripping off the filter cake, avoiding blockage, and maintaining sufficient membrane filtration flux.

[0012] Furthermore, in order to reduce the accumulation of filter cake at the center of the disc-shaped hollow ceramic membrane, the height of the ridge-like protrusions decreases from one end of the rotating shaft to the end away from the rotating shaft. The higher ridge-like protrusions produce a greater impact force in the front and a greater vacuum in the back, thereby compensating for the problem of insufficient filter cake removal force caused by insufficient shear force and centrifugal force due to the low linear velocity at the center.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The present invention separates the anaerobic digester from the filtration separation device, and the cross-flow filtration formed by the disc-shaped hollow ceramic membrane is relatively stable, easy to clean the membrane and does not affect the normal operation of the anaerobic digester.

[0015] (2) The diaphragm of the filtration separation device provided by the present invention is a disc-shaped hollow ceramic membrane. Its high-speed rotation can increase the flow rate of the fluid inside the membrane assembly, increase the shear force, impact force and vacuum degree of the fluid, and can not only more effectively reduce the deposition of pollutants on the membrane surface under the action of pump pressure, but also can peel off pollutants that are not tightly adsorbed on the membrane surface, effectively reducing the pollution of the ceramic membrane assembly.

[0016] (3) This device has significant tolerance and controllability for anaerobic digestion liquid mud indicators such as suspended solids and organic matter, so it can meet the anaerobic digestion treatment requirements of different raw materials (sludge, thermal hydrolysis sludge, food waste, leachate, etc.) and different temperatures (medium temperature and high temperature, 35℃~55℃). BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention.

[0018] Figure 1 This is a schematic structural diagram of a high solid content fully mixed anaerobic reactor according to Example 1 of the present invention.

[0019] Figure 2 Schematic diagram of the top view of the disc-shaped hollow ceramic membrane in the high solid content fully mixed anaerobic reactor of Example 1 of the present invention.

[0020] The figure includes: 1-feed pipe; 2-discharge pipe; 3-anaerobic digester; 4-agitator and motor; 5-circulation pump; 6-motor; 7-hollow rotating shaft; 8-disc-shaped hollow ceramic membrane; 81-prismatic protrusion; 9-pressure gauge; 10-reflux valve; 11-clear liquid outlet pipe; 12-housing; 13-biogas collection pipe. DETAILED DESCRIPTION

[0021] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product instructions are used.

[0022] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", etc. indicating the orientation or state relationship are based on the orientation or state relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0023] In the following examples, the instruments and equipment used without indicating the manufacturer are all conventional products that can be purchased through regular channels. The methods described are conventional methods unless otherwise specified, and the raw materials described can be obtained from public commercial channels unless otherwise specified.

[0024] Example 1

[0025] like Figure 1 and Figure 2 As shown, this embodiment provides a high solid content fully mixed anaerobic reactor, including an anaerobic digestion tank 3 and a filtering and separating device arranged outside the anaerobic digestion tank, wherein a stirring device 4 is arranged in the anaerobic digestion tank 3, a discharge pipe 2 is arranged at the bottom of the reaction zone, a feed pipe 1 is arranged in the middle of the reaction zone, a biogas collecting pipe 13 is arranged at the top of the anaerobic digestion tank 3, the filtering and separating device comprises a shell 12 and a filtering element arranged in the shell, the shell 12 is connected in series with the anaerobic digestion tank 3 through a pipeline to form a circulation loop, the liquid inlet pipe of the pipeline is led out through the lower part of the reaction zone of the anaerobic digestion tank, and a circulation pump 5 and a pressure gauge 9 are connected in series in sequence, the liquid discharge pipe is connected in series with a reflux valve 10, and is connected to the upper part of the reaction zone of the anaerobic digestion tank, the filtering element comprises a hollow rotating shaft 7 and a disc-shaped hollow ceramic membrane 8, the disc The pore size of the sheet-like hollow ceramic membrane 8 is 0.05 μm to 2 μm, and the material is at least one of aluminum oxide, zirconium oxide, titanium dioxide and silicon oxide. In this embodiment, zirconium oxide is selected. The disc-shaped hollow ceramic membrane 8 is sleeved and fixed on the outer periphery of the hollow rotating shaft 7 along its axial direction. The hollow rotating shaft 7 of the disc-shaped hollow ceramic membrane 8 is connected to the inside of the disc-shaped hollow ceramic membrane 8 through the through hole of its side wall. The disc-shaped hollow ceramic membrane 8 is coaxially arranged with multiple disc-shaped hollow ceramic membranes to increase the filtration area. At the same time, the outer surface of the disc-shaped hollow ceramic membrane 8 is provided with a prismatic protrusion 81, which is perpendicular to the tangent direction of the disc-shaped hollow ceramic membrane, and the height of the prismatic protrusion 81 decreases from one end of the rotating shaft to the end away from the rotating shaft, and the maximum height is preferably 1 cm, and the minimum height is not less than 0.1 cm. One end of the hollow rotating shaft 7 is connected to the motor 6, and the other end is connected to the clear liquid outlet pipe 11, so that the filtered clear liquid is discharged from the filtration separation device through the hollow rotating shaft 7.

[0026] The effective volume of the anaerobic fully mixed reactor is 10L, and the reactor operating temperature is 55°C.

[0027] The COD of restaurant kitchen waste wastewater is 74000 mg / L and the solid content is 9.11%.

[0028] The membrane area of ​​the filtration separation device is 0.1m 2 , membrane pore size: 0.2μm.

[0029] (1) Anaerobic reactor startup:

[0030] The anaerobic reactor and its stirring device 4 are started, and anaerobic digestate or flocculent sludge is inoculated in the anaerobic reactor. A small amount of feed is fed through the feed pipe 1 every day. The feed amount = reactor effective volume / hydraulic retention time, that is, 10 / 30 = 0.33L. The hydraulic retention time is set to 30 days. The daily feed amount = discharge amount, and the material is discharged through the discharge pipe 2. In this way, the material is discharged and fed every day, and the culture is continuously carried out for 7 to 10 days; the gas composition of the biogas produced by the anaerobic reactor is detected. When the methane concentration in the measured gas composition is ≥55%, and the pH range is 6.8 to 7.8, the reactor inoculation and startup process can be considered to be completed.

[0031] (2) Anaerobic reactor concentration improvement:

[0032] A: After the reactor is inoculated, the kitchen waste slurry with a solid content of 6-10% is gradually added to the anaerobic reactor, the hydraulic retention time is controlled to 15 days, the initial reactor volume load is to control the concentration of volatile fatty acids and alkalinity in the anaerobic reactor during the feeding period, and the concentration ratio of volatile fatty acids to alkalinity is controlled below 0.2, the methane concentration in the biogas is ≥55%, and the organic matter degradation rate is >70%. At this time, the solid content in the anaerobic digester is about 6.3%.

[0033] B: Open the circulation pump 5 and the valve 10, pump the anaerobic digestion liquid into the filter container 12, perform dynamic cross-flow filtration on the anaerobic digestion liquid, and obtain the clear liquid through the clear liquid outlet pipe 11 tank, and the concentrated liquid is refluxed to the anaerobic digestion tank through the concentrated liquid, and the filtration pressure is maintained by controlling the opening of the reflux valve 10; the speed of the rotating shaft is controlled at 400-900rpm / min, and 900rpm / min is selected in this embodiment, the filtration pressure is controlled at 0.1MPa-0.6Mpa, and 0.2MPa in this embodiment, and the membrane flux is controlled at 15-20L / m 2 h, in this implementation it is 20L / m 2 After about 0.25h of filtration, 0.42L of clear liquid was filtered out, and the solid content in the anaerobic digester was about 10.5%.

[0034] Example 2

[0035] The device structure of this embodiment is the same as that of embodiment 1. The effective volume of the anaerobic fully mixed reactor is 10 L, and the operating temperature of the reactor is 40°C.

[0036] The solid content of sludge thermal hydrolysis liquid is 8.21%.

[0037] The membrane area of ​​the filtration separation device is 0.1m 2 , membrane pore size: 2μm.

[0038] ① Anaerobic reactor start-up:

[0039] The anaerobic reactor and its stirring device 4 are started, and anaerobic digestate or flocculent sludge is inoculated in the anaerobic reactor. A small amount of feed is fed through the feed pipe 1 every day. The feed amount = reactor effective volume / hydraulic retention time, that is, 10 / 30 = 0.33L. The hydraulic retention time is set to 30 days. The daily feed amount = discharge amount, and the material is discharged through the discharge pipe 2. In this way, the material is discharged and fed every day, and the culture is continuously carried out for 7 to 10 days; the gas composition of the biogas produced by the anaerobic reactor is detected. When the methane concentration in the measured gas composition is ≥55%, and the pH range is 6.8 to 7.8, the reactor inoculation and startup process can be considered to be completed.

[0040] ② Anaerobic reactor concentration increase:

[0041] A: After the reactor is inoculated, the sludge thermal hydrolysis slurry with a solid content of about 8.5% is gradually added to the anaerobic reactor, the hydraulic retention time is controlled to 15 days, and the initial reactor volume load is to control the concentration of volatile fatty acids and alkalinity in the anaerobic reactor during the feeding period, and control the concentration ratio of volatile fatty acids to alkalinity below 0.2, the methane concentration in the biogas is ≥55%, and the organic matter degradation rate is >45%. At this time, the solid content in the anaerobic digester is about 5.1%.

[0042] B: Open the circulation pump 5 and the valve 10, pump the anaerobic digestion liquid into the filter container 12, perform dynamic cross-flow filtration on the anaerobic digestion liquid, and obtain the clear liquid through the clear liquid outlet pipe 11 tank, and the concentrated liquid is refluxed to the anaerobic digestion tank through the concentrated liquid, and the filtration pressure is maintained by controlling the opening of the reflux valve 10;

[0043] The rotation speed of the rotating shaft is controlled at 400-900 rpm / min, and 900 rpm / min is selected in this embodiment. The filtration pressure is controlled at 0.1 MPa-0.6 MPa, and 0.1 MPa is selected in this embodiment. The membrane flux is controlled at 15-20 L / m 2 h, in this implementation it is 15L / m 2 After about 0.25h of filtration, 0.33L of clear liquid was filtered out, and the solid content in the anaerobic digestion tank was about 8.4%.

[0044] Regarding the selection of the above parameter range values, ordinary technicians in this field can make adjustments based on actual conditions, and this application will not go into details.

[0045] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, such as simply adjusting the parameters within or near the specified parameter range, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A high solid content fully mixed anaerobic reactor, characterized in that: The invention comprises an anaerobic digestion tank and a filtering and separating device arranged outside the anaerobic digestion tank, wherein the filtering and separating device comprises a shell and a filtering element arranged in the shell, wherein the shell is connected in series with the anaerobic digestion tank through a pipeline to form a circulation loop, wherein the filtering element comprises a hollow rotating shaft and a disc-shaped hollow ceramic membrane, wherein the disc-shaped hollow ceramic membrane is sleeved along its axial direction and fixed on the outer periphery of the hollow rotating shaft, wherein the hollow rotating shaft is connected with the inside of the disc-shaped hollow ceramic membrane through a through hole in its side wall, and the filtered clear liquid is discharged from the filtering and separating device through the hollow rotating shaft; wherein the outer surface of the disc-shaped hollow ceramic membrane is provided with a prismatic protrusion, wherein the prismatic protrusion is perpendicular to the tangent direction of the disc-shaped hollow ceramic membrane; and wherein the height of the prismatic protrusion decreases from one end of the rotating shaft to the end away from the rotating shaft.

2. The high solid content fully mixed anaerobic reactor according to claim 1, characterized in that: The liquid discharge pipe of the filtering and separating device is connected to the upper part of the reaction zone of the anaerobic digestion tank, and the liquid inlet pipe of the filtering and separating device is connected to the lower part of the reaction zone of the anaerobic digestion tank.

3. The high solid content fully mixed anaerobic reactor according to claim 2, characterized in that: The pore size of the disc-shaped hollow ceramic membrane is 0.05 μm to 2 μm, and the material is at least one of aluminum oxide, zirconium oxide, titanium dioxide and silicon oxide.

4. The high solid content fully mixed anaerobic reactor according to claim 2, characterized in that: The liquid inlet pipe is connected in series with a circulation pump, and the membrane filtration flux is controlled at 15-20 L / m 2 ·h, the filtration pressure is controlled at 0.1 MPa~0.6 MPa, and the rotation speed of the rotating shaft is controlled at 400~900 rpm / min.

5. The high solid content fully mixed anaerobic reactor according to claim 1, characterized in that: A plurality of the disc-shaped hollow ceramic membranes are coaxially arranged.

6. A method for improving the solid content of anaerobic digestion, using the high solid content fully mixed anaerobic reactor according to claim 1, characterized in that: During the start-up period of anaerobic digestion, the hydraulic retention time of anaerobic digestion is adjusted by adjusting the feed rate until the biogas production is stable and the methane content in the biogas is greater than 55%; during the stabilization period, the digestate in the anaerobic digester is pumped into the filtration separation device in a quantitative manner every day, and the membrane permeate is discharged in a quantitative manner; when the solid content of the digestate reaches 8%~12%, the filtration is stopped.

Images