Method for conditioning and deeply dewatering co-digested sludge by means of bubble stripping-carbon adsorption

Abstract

The present invention relates to the technical field of dewatering, and provides a method for conditioning and deeply dewatering co-digested sludge by means of bubble stripping-carbon adsorption, which method is used for removing water contained in a mixture obtained after anaerobic co-digestion of pyrohydrolysis sludge and garbage. The dewatering method comprises: adding an inorganic agent to the mixture for a reaction with a protein component in the mixture, wherein generated protein foam is used for stripping grease on the surface of sludge; adding an oil absorbing agent to the mixture from which grease has been removed, so as to adsorb the grease; adding a flocculating agent to the mixture that has been subjected to grease adsorption, and performing convergent flocculation on sludge flocs; and putting the flocculated mixture into a mechanical dewatering device, and performing filter pressing on the mixture. After the sludge is conditioned by using the dewatering method, the binding capacity of the grease and the sludge is reduced, the hydrophobicity of the sludge is improved, and the strength of the floc sludge is enhanced, thereby improving the pressing effect, and achieving the requirements of deep dewatering.

Description

A method for achieving synergistic digestion sludge conditioning and deep dehydration by bubble stripping and carbon adsorption Technical Field

[0001] The present invention belongs to the technical field of dehydration, and more specifically, relates to a method for realizing synergistic digestion sludge conditioning-deep dehydration by means of bubble stripping-carbon adsorption. Background Art

[0002] Currently, plate and frame pressing dehydration has become one of the main methods for reducing the volume of municipal sludge. The sludge needs to be conditioned to a certain degree of hydrophobicity before entering the plate and frame filter press. After the mud has been conditioned more fully, its water absorption and water retention capacity is reduced. After a certain period of pressing in the plate and frame filter press, the moisture content of the mud cake can be reduced to below 60%.

[0003] Due to differences in mud quality, there will be differences in sludge conditioning methods, types of reagents and dosages of reagents. Therefore, for sludge with special mud quality, specific conditioning methods need to be developed to ensure the mud conditioning effect and improve the conditioning efficiency.

[0004] Thermal hydrolysis sludge refers to the product of municipal sludge after high temperature (150-180℃) and high pressure (0.6-0.8MPa) hydrothermal treatment. The median particle size of the residual sludge and conventional sludge is 80μm-120μm, and the specific surface area is 300-500cm 2 / g. After thermal hydrolysis, the concentration of soluble substances in the sludge supernatant is greatly increased, the sludge particle size is reduced, and the specific surface area is greatly increased. The median particle size of thermal hydrolysis sludge is 5μm to 10μm, and the specific surface area is 3000 to 5000cm 2 / g.

[0005] Co-anaerobic digestion sludge refers to the product of co-anaerobic digestion of municipal sludge with food waste after thermal hydrolysis treatment. The sludge after co-anaerobic digestion is more difficult to condition and dehydrate. The capillary absorption time (CST) of the sludge after thermal hydrolysis and anaerobic digestion alone is usually between 400 and 1700 seconds, while the capillary absorption time (CST) of the sludge after co-anaerobic digestion is usually between 2000 and 3000 seconds. The conditioning and dehydration difficulty of the sludge after co-anaerobic digestion is significantly higher than that of thermal hydrolysis anaerobic digestion sludge.

[0006] The dosage of hydrophobic modifiers for thermal hydrolysis anaerobic digestion sludge is usually controlled at 2.5-3%, while the dosage of hydrophobic modifiers for conditioning sludge / food waste co-anaerobic digestion sludge in the same period will be increased to 4%-6%, and the dosage of hydrophobic modifiers will be significantly increased.

[0007] There is a large amount of fat in the products of the anaerobic digestion of thermal hydrolysis sludge and food waste. The fat forms a strong adsorption bond with the high specific surface area sludge, which effectively isolates the hydrophobic modification agent from the improvement of the hydrophobicity of proteins and polysaccharides in sludge polymers. As a result, the sludge after the anaerobic digestion cannot be effectively conditioned, resulting in an excessively high moisture content in the dehydrated cake from the plate and frame press dehydration.

[0008] In summary, the sludge obtained by the anaerobic digestion of thermal hydrolysis sludge and food waste is a special type of sludge that is difficult to condition and difficult to dewater compared to the anaerobic digestion of thermal hydrolysis sludge alone, and has higher technical requirements for the conditioning and dewatering process and chemicals.

[0009] Summary of the Invention

[0010] The purpose of the present invention is to address the deficiencies in the existing technology by providing a method for co-digestion sludge conditioning and deep dehydration by bubble stripping-carbon adsorption, so as to solve the problems in the above-mentioned background technology of the products of the co-anaerobic digestion of thermal hydrolysis sludge and food waste, namely, the strong binding ability of oil and fat with thermal hydrolysis sludge makes it difficult to remove, resulting in the sludge after the co-anaerobic digestion having obvious hydrophobicity, high difficulty in conditioning, low sludge floc strength, poor pressing effect and high moisture content of the mud cake.

[0011] To achieve the above objectives, the present invention provides a method for co-digestion sludge conditioning and deep dehydration by bubble stripping-carbon adsorption, which is used to remove water from a mixture of thermally hydrolyzed sludge and garbage after co-anaerobic digestion. The dehydration method comprises:

[0012] Inorganic agents are added to the mixture to react with the protein components in the mixture. The generated protein foam is used to remove grease from the surface of the sludge.

[0013] Adding oil absorbing agent to the degreased mixture to absorb the grease;

[0014] Add flocculating agent to the mixture after grease adsorption to achieve sludge floc convergence and flocculation;

[0015] The flocculated mixture is put into a mechanical dehydration device for filter pressing.

[0016] Preferably, an inorganic agent is added to the mixture to react with the protein component in the mixture, and the generated protein foam is used to strip the grease on the sludge surface. The addition amount of the inorganic agent is set to 0.02-0.06t / tDS, and the inorganic agent is a protein reaction agent.

[0017] Preferably, adding an oil absorbing agent to the degreased mixture to adsorb the grease comprises setting the addition amount of the oil absorbing agent to 0.01-0.05 t / tDS, and the oil absorbing agent is a carbon-based material.

[0018] Preferably, adding a flocculant to the mixture after grease adsorption to perform sludge floc convergence and flocculation includes: setting the addition amount of the flocculant to 0.004-0.010 t / tDS, and the flocculant is an organic flocculant.

[0019] Preferably, the flocculated mixture is put into a mechanical dehydration device, and the filter pressing of the mixture includes: pumping the mixture into the mechanical dehydration device, wherein the mechanical dehydration device is a plate and frame filter press.

[0020] Preferably, the thermal hydrolysis temperature of the sludge is set to 150-180° C., and the thermal hydrolysis time of the sludge is set to 30 minutes.

[0021] Preferably, the ratio of thermally hydrolyzed sludge to garbage for anaerobic digestion is set to 1:1 to 3:1, the temperature for anaerobic digestion is set to 40±1°C, and the duration of anaerobic digestion is set to 15d to 25d.

[0022] Preferably, after the inorganic agent is added to the mixture, the mixture is stirred, the stirring frequency is set to 50 Hz, and the stirring time is set to 20-40 minutes.

[0023] Preferably, after adding the oil absorbing agent to the degreased mixture, the mixture is stirred, the stirring frequency is set to 50 Hz, and the stirring time is set to 5 to 20 minutes.

[0024] Preferably, after adding the flocculating agent to the mixture after the oil is adsorbed, the mixture is stirred, the stirring frequency is set to 40-50 Hz, and the stirring time is set to 1-2 minutes.

[0025] The present invention provides a method for realizing synergistic digestion sludge conditioning-deep dehydration by means of bubble stripping-carbon adsorption, and its beneficial effects are as follows: the inorganic agent of the dehydration method is used to react with the protein component in the mixture, and the generated protein foam is used to strip the grease on the surface of the sludge, and the grease is migrated to the upper foam layer of the sludge conditioning tank, thereby realizing the separation of the sludge and the grease; the oil absorbing agent of the dehydration method is used to adsorb the grease, weaken the effect of the sludge adsorbing the grease, or isolate the grease from the sludge, support the sludge flocs, and form a water filter. The dewatering method removes the moisture between the sludge flocs and enhances the filtration capacity of the sludge cake, effectively reducing the moisture content of the dewatered cake. The flocculant of this dewatering method is used to converge and flocculate the sludge flocs and increase the floc particle size. The mechanical dewatering equipment of this dewatering method completes the dewatering cake with a moisture content of less than 60% after filter pressing. After conditioning by this dewatering method, the binding ability of oil and sludge is reduced, the sludge hydrophobicity is improved, the floc sludge strength is improved, and then the pressing effect is improved, achieving the requirement of deep dehydration.

[0026] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0028] FIG1 shows a flow chart of a dehydration method for deoiling according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0030] The present invention provides a method for achieving collaborative digestion sludge conditioning and deep dehydration by bubble stripping and carbon adsorption, which is used to remove water contained in a mixture of thermally hydrolyzed sludge and garbage after collaborative anaerobic digestion. The dehydration method comprises:

[0031] Inorganic agents are added to the mixture to react with the protein components in the mixture. The generated protein foam is used to remove grease from the surface of the sludge.

[0032] Adding oil absorbing agent to the degreased mixture to absorb the grease;

[0033] Add flocculating agent to the mixture after grease adsorption to achieve sludge floc convergence and flocculation;

[0034] The flocculated mixture is put into a mechanical dehydration device for filter pressing.

[0035] Specifically, in order to solve the problem that the products after the anaerobic digestion of thermal hydrolysis sludge and food waste are difficult to remove due to the strong binding ability of grease with thermal hydrolysis sludge, resulting in obvious hydrophobicity, high difficulty in conditioning, low sludge floc strength, poor squeezing effect and high moisture content of mud cake after anaerobic digestion, the present invention provides a method for achieving sludge conditioning and deep dehydration of synergistic digestion by bubble stripping-carbon adsorption. The sludge can be municipal sludge with an organic content of 45% to 75%. The garbage can be food waste. The mixture is placed in a conditioning tank. The inorganic agent of the dehydration method is used to react with the protein component in the mixture. The generated protein foam is used to strip off the grease on the surface of the sludge and migrate the grease to the upper part of the sludge conditioning tank. In the foam layer, the separation of sludge and grease is achieved. The oil absorption agent of this dehydration method is used for grease adsorption, weakening the effect of sludge adsorbing grease, or isolating grease and sludge, supporting sludge flocs, forming water filtration channels and draining moisture between sludge flocs, enhancing the water filtration capacity of sludge cake, and effectively reducing the moisture content of dehydrated cake. The flocculating agent of this dehydration method is used for sludge floc convergence and flocculation, increasing the floc particle size. After the mechanical dehydration equipment of this dehydration method is completed by filter pressing, the moisture content of dehydrated cake is less than 60%. After conditioning by this dehydration method, the binding ability of grease and sludge is reduced, the sludge hydrophobicity is improved, the floc sludge strength is improved, and then, the pressing effect is improved, achieving the requirements of deep dehydration.

[0036] Preferably, an inorganic agent is added to the mixture to react with the protein component in the mixture, and the generated protein foam is used to strip the grease on the sludge surface. The addition amount of the inorganic agent is set to 0.02-0.06t / tDS, and the inorganic agent is a protein reaction agent.

[0037] Specifically, an inorganic agent is added to the conditioning tank, and the protein reaction agent can further be aluminum sulfate, iron sulfate or aluminum ferric sulfate;

[0038] The dry solid content of conditioned sludge is used as the basis for calculating the dosage of the agent, and the dosage of the inorganic agent is set at 0.02-0.06t / tDS;

[0039] After the inorganic agent is added, the stirring power and stirring time are controlled to ensure uniform stirring. Usually, the preferred stirring frequency is 50 Hz and the stirring time is 20 to 60 minutes.

[0040] Inorganic agents can improve the hydrophobicity of sludge flocs and act on the protein components in the sludge to produce a large amount of protein foam. The foam strips off the grease adsorbed on the sludge surface and migrates the grease to the upper foam layer of the conditioning tank, thereby separating the sludge and grease.

[0041] Preferably, adding an oil absorbing agent to the degreased mixture to adsorb the grease comprises setting the addition amount of the oil absorbing agent to 0.01-0.05 t / tDS, and the oil absorbing agent is a carbon-based material.

[0042] Specifically, the oil absorbing agent is continuously added into the conditioning tank. The carbon-based material can be coconut shell charcoal, wood charcoal, coal-based activated carbon or sludge charcoal with a particle size of 2.00 to 0.25 mm and a specific surface area of ​​400 to 1000 m 2 / g, iodine value is 200~900mg / g;

[0043] The dosage of oil absorption agent is 0.01~0.05t / tDS;

[0044] After the addition of the oil absorbing agent, the carbon-based material is fully moistened to complete the adsorption of oil and fat, and the stirring frequency and stirring time are controlled. Under normal circumstances, the preferred stirring frequency is 50Hz and the stirring time is 5 to 20 minutes;

[0045] Oil absorbing agents can absorb grease, weaken the effect of sludge adsorbing grease, or isolate grease and sludge, support sludge flocs, form water filtration channels, and drain moisture between sludge flocs, thereby enhancing the water filtration capacity of sludge cake and effectively reducing the moisture content of dehydrated cake.

[0046] Preferably, adding a flocculant to the mixture after grease adsorption to perform sludge floc convergence and flocculation includes: setting the addition amount of the flocculant to 0.004-0.010 t / tDS, and the flocculant is an organic flocculant.

[0047] Specifically, the flocculant is continuously added into the conditioning tank, and the organic flocculant can further be cationic polyacrylamide (CPAM);

[0048] The dosage of flocculation agent is 0.004~0.010t / tDS;

[0049] After the flocculant is added, the stirring power and duration are controlled to ensure that the sludge flocs are completely flocculated and the flocs are not loose. Generally, the preferred stirring frequency is 40-50 Hz and the stirring time is 1-2 minutes.

[0050] The flocculant can complete the convergence of sludge flocs in the entire conditioning tank, increase the floc particle size, and improve the strength of the floc sludge.

[0051] Preferably, the flocculated mixture is put into a mechanical dehydration device, and the filter pressing of the mixture includes: pumping the mixture into the mechanical dehydration device, wherein the mechanical dehydration device is a plate and frame filter press.

[0052] Specifically, after the filter press is completed, the moisture content of the dehydrated cake is less than 60%.

[0053] Preferably, the thermal hydrolysis temperature of the sludge is set to 150-180°C, and the thermal hydrolysis time of the sludge is set to 30 minutes;

[0054] The ratio of thermally hydrolyzed sludge and garbage for anaerobic digestion is set at 1:1 to 3:1, the temperature of anaerobic digestion is set at 40±1°C, and the duration of anaerobic digestion is set at 15d to 25d.

[0055] Specifically, after the coordinated anaerobic digestion treatment, the capillary absorption time (CST) of the mixture is 1200-2500s, and the oil content is 2-4%.

[0056] Example 1

[0057] The mixture of thermally hydrolyzed sludge and garbage after anaerobic digestion is as follows:

[0058] After municipal sludge was treated with thermal hydrolysis at 165°C for 30 minutes, the thermally hydrolyzed sludge and food waste were mixed in a 2:1 ratio to complete a mesophilic synergistic anaerobic digestion reaction. The mesophilic synergistic anaerobic digestion reaction temperature was 40±1°C, and the mesophilic synergistic anaerobic digestion reaction time was 22 days. The solid content of the sludge after synergistic anaerobic digestion was 5.6%, and the capillary suction time (CST) was 1815 seconds.

[0059] The mud conditioning is as follows:

[0060] Add inorganic agent: aluminum ferric sulfate to the sludge in the conditioning tank at a dosage of 0.026t / tDS. After the addition of the inorganic agent is completed, stir at a frequency of 50Hz for 40 minutes.

[0061] Add oil absorption agent: coal-based activated carbon, particle size: 0.55-0.25 mm, specific surface area: 800 m2 / g, iodine value: 900 mg / g; dosage: 0.03 t / tDS. After the oil absorption agent is added, the stirring frequency is 50 Hz; the stirring time is 10 min.

[0062] Add flocculating agent: cationic polyacrylamide (CPAM), the dosage is: 0.0076t / tDS; stirring frequency: 50Hz, stirring time: 2min.

[0063] Mechanical dehydration and mud cake moisture content are as follows:

[0064] The plate and frame filter press is used as the deep dehydration machine. The filter plate size of the plate and frame filter press is 200cm*200cm. The mud input capacity of the plate and frame filter press is 42m 3 After the plate and frame filter press is fed, it is pressed for 8000s at a pressure of 1.6-2.0MPa to obtain a plate and frame mud cake with a moisture content of 55.84%.

[0065] Example 2

[0066] The mixture of thermally hydrolyzed sludge and garbage after anaerobic digestion is as follows:

[0067] After municipal sludge was treated with thermal hydrolysis at 165°C for 30 minutes, the thermally hydrolyzed sludge and food waste were mixed in a 2:1 ratio to complete a mesophilic anaerobic digestion reaction. The mesophilic anaerobic digestion temperature was 40±1°C, and the mesophilic anaerobic digestion time was 22 days. The solid content of the sludge after anaerobic digestion was 5.2%, and the capillary suction time (CST) was 2610 seconds.

[0068] The mud conditioning is as follows:

[0069] Add inorganic agent: aluminum ferric sulfate to the sludge in the conditioning tank at a dosage of 0.028t / tDS. After the addition of the inorganic agent is completed, stir at a frequency of 50Hz for 40 minutes.

[0070] Add oil-absorbing agent: coal-based activated carbon, particle size: 0.55-0.25mm, specific surface area: 800m2 / g, iodine value: 900mg / g; dosage: 0.035t / tDS. After the oil-absorbing agent is added, stir at 50Hz for 10 minutes.

[0071] Add flocculating agent: cationic polyacrylamide (CPAM), the dosage is: 0.0069t / tDS; stirring frequency: 50Hz, stirring time: 2min.

[0072] Mechanical dehydration and mud cake moisture content are as follows:

[0073] The plate and frame filter press is used as the deep dehydration machine. The filter plate size of the plate and frame filter press is 200cm*200cm. The mud input capacity of the plate and frame filter press is 42m 3 After the plate and frame filter press is fed, it is pressed for 8000s at a pressure of 1.6-2.0MPa to obtain a plate and frame mud cake with a moisture content of 59.45%.

[0074] Example 3

[0075] The mixture of thermally hydrolyzed sludge and garbage after anaerobic digestion is as follows:

[0076] After municipal sludge was treated with thermal hydrolysis at 165°C for 30 minutes, the thermally hydrolyzed sludge and food waste were mixed in a 2:1 ratio to complete a mesophilic synergistic anaerobic digestion reaction. The mesophilic synergistic anaerobic digestion reaction temperature was 40±1°C, and the mesophilic synergistic anaerobic digestion reaction time was 22 days. The solid content of the sludge after synergistic anaerobic digestion was 5.3%, and the capillary suction time (CST) was 2433 seconds.

[0077] The mud conditioning is as follows:

[0078] Add inorganic agent: aluminum ferric sulfate to the sludge in the conditioning tank at a dosage of 0.027t / tDS. After the addition of the inorganic agent is completed, stir at a frequency of 50Hz for 40 minutes.

[0079] Add oil absorption agent: coal-based activated carbon, particle size: 0.55-0.25mm, specific surface area: 800m 2 / g, iodine value: 500mg / g; dosage: 0.03t / tDS. After the oil absorption agent is added, the stirring frequency is 50Hz and the stirring time is 10min.

[0080] Add flocculating agent: cationic polyacrylamide (CPAM), the dosage is: 0.0089t / tDS; stirring frequency: 50Hz, stirring time: 2min.

[0081] Mechanical dehydration and mud cake moisture content are as follows:

[0082] The plate and frame filter press is used as the deep dehydration machine. The filter plate size of the plate and frame filter press is 200cm*200cm. The mud input capacity of the plate and frame filter press is 42m 3 After the plate and frame filter press is fed, it is pressed for 8000s at a pressure of 1.6-2.0MPa to obtain a plate and frame mud cake with a moisture content of 58.51%.

[0083] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for realizing cooperative digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption, which is used to remove the water contained in the mixture of thermally hydrolyzed sludge and garbage after cooperative anaerobic digestion, characterized in that: The dehydration method includes: Inorganic agents are added to the mixture to react with the protein components in the mixture, and the generated protein foam is used to remove grease from the surface of the sludge; Adding oil absorbing agent to the degreased mixture to absorb the grease; Adding flocculating agent to the mixture after absorbing oil and fat to achieve sludge floc convergence and flocculation; The flocculated mixture is put into a mechanical dehydration device for filter pressing.

2. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: Inorganic agents are added to the mixture to react with protein components in the mixture. The generated protein foam is used to strip grease from the surface of the sludge. The dosage of the inorganic agent is set to 0.02-0.06 t / tDS, and the inorganic agent is a protein reaction agent.

3. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: Adding an oil absorbing agent to the degreased mixture to adsorb the grease includes: setting the addition amount of the oil absorbing agent to 0.01-0.05 t / tDS, and the oil absorbing agent is a carbon-based material.

4. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: Adding a flocculant to the mixture after the oil and fat is adsorbed to carry out sludge floc convergence and flocculation, including: setting the dosage of the flocculant to 0.004-0.010 t / tDS, and the flocculant is an organic flocculant.

5. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: The flocculated mixture is put into a mechanical dehydration device, and the filter pressing of the mixture includes: pumping the mixture into the mechanical dehydration device, and the mechanical dehydration device is a plate and frame filter press.

6. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: The thermal hydrolysis temperature of the sludge is set at 150-180°C, and the thermal hydrolysis time of the sludge is set at 30 minutes.

7. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: The ratio of thermally hydrolyzed sludge to garbage for anaerobic digestion is set at 1:1 to 3:1, the temperature of anaerobic digestion is set at 40±1°C, and the duration of anaerobic digestion is set at 15d to 25d.

8. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: After the inorganic agent is added to the mixture, the mixture is stirred, the stirring frequency is set to 50 Hz, and the stirring time is set to 20-40 minutes.

9. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: After adding the oil absorbing agent to the degreased mixture, the mixture is stirred, the stirring frequency is set to 50 Hz, and the stirring time is set to 5 to 20 minutes.

10. The method of realizing synergistic digestion sludge conditioning and deep dehydration by air bubble stripping and carbon adsorption according to claim 1, characterized in that: After adding the flocculating agent to the mixture after the oil is adsorbed, the mixture is stirred, the stirring frequency is set to 40-50 Hz, and the stirring time is set to 1-2 minutes.

Images