A sludge modification and separation method

Abstract

The present invention relates to the technical field of environmentally friendly sludge recovery, and in particular to a sludge modification and separation method. The method comprises the following steps: adding ferrous sulfite and glutaraldehyde to the sludge to be treated, stirring the reaction, adding a chelating agent and a flocculant, and adjusting the pH, stirring the reaction to obtain a solid-liquid mixture; performing solid-liquid separation on the solid-liquid mixture to obtain inorganic gravel, organic sludge, and a supernatant; using a washing agent to wash the organic sludge to obtain a washing liquid and residual sludge; repeatedly performing solid-liquid separation and washing on the residual sludge to obtain a supernatant and high-purity organic sludge; and drying the high-purity organic sludge to obtain biomass fuel. The present invention can effectively separate the sludge, and the obtained inorganic gravel has a low organic content, which is convenient for subsequent application in fields such as building materials; the high-purity organic sludge is dried to obtain biomass fuel, and has a high high calorific value; and is conducive to subsequent resource utilization.

Description

Technical Field

[0001] The invention relates to the technical field of environmentally friendly sludge recovery, and in particular to a sludge modification and separation method. Background Art

[0002] Sludge is a flocculent substance with a high water content and a mixture of solids and liquids. It is produced in large quantities during processes such as sewage treatment, sediment dredging, and oilfield production. For example, for every 10,000 tons of municipal sludge processed, 10-20 tons (assuming a 90% water content) of sludge are generated. Sludge is not only a large quantity but also contains toxic and hazardous substances such as parasite eggs, heavy metals, pathogenic microorganisms, and persistent organic matter. Effective treatment and disposal are essential to prevent secondary contamination of groundwater and soil, posing a threat to environmental safety and public health.

[0003] Sludge itself has a low calorific value and high moisture content. Standalone incineration cannot meet the heat balance of drying and incineration, requiring the addition of large amounts of fuel. Co-incineration faces the same dilemma. Anaerobic sludge fermentation requires significant investment, and without thermal hydrolysis, the actual biogas yield is low, making the final biogas liquid and residue difficult to handle and dispose of. Aerobic composting, however, is affected by the high moisture content of the incoming sludge, requiring large amounts of auxiliary materials, resulting in low treatment efficiency and high odor production. This limits the final fertilizer product's potential for disposal. Economical and efficient sludge-water separation technology is a prerequisite for effective sludge treatment and disposal, and is key to achieving sludge reduction and resource utilization.

[0004] Therefore, the present invention provides a sludge modification and separation method that can effectively separate sludge and facilitate subsequent resource utilization. Summary of the Invention

[0005] The object of the present invention is to provide a sludge modification and separation method, which can solve the above technical problems.

[0006] The present invention provides a sludge modification and separation method, comprising the following steps:

[0007] S1. Add ferrous sulfite and glutaraldehyde to the sludge to be treated, stir and react for 30-50 minutes, add a chelating agent and a flocculant, adjust the pH to 6-8, stir and react for 40-80 minutes to obtain a solid-liquid mixture;

[0008] S2. The solid-liquid mixture is subjected to solid-liquid separation to obtain inorganic gravel and organic sludge, and a supernatant;

[0009] S3. The organic sludge is eluted using an eluent to obtain an eluent and residual sludge;

[0010] S4. Repeating solid-liquid separation and elution of the residual sludge to obtain a supernatant and high-purity organic sludge; and drying the high-purity organic sludge to obtain biomass fuel.

[0011] Preferably, the mass percentages of the components in step S1 are: 90-99 wt % of the sludge to be treated, 0.4-3.0 wt % of ferrous sulfite, 0.2-2.0 wt % of glutaraldehyde, 0.3-5.0 wt % of chelating agent, and 0.1-4.0 wt % of flocculant.

[0012] Preferably, the chelating agent is any one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, and aminotrimethylenephosphonic acid.

[0013] Preferably, the flocculant is any one or more of polyaluminium chloride, polyferric sulfate, polyacrylamide and polydimethyldiallylammonium chloride.

[0014] Preferably, the specific steps of step S2 are: sending the solid-liquid mixture into a cyclone solid-liquid separation device at a flow rate of 2-4 m / s, centrifuging at a speed of 1000-1500 r / min, and throwing inorganic sand and gravel toward the wall of the device to form an underflow and discharge downward; the organic sludge and liquid phase form an overflow and are discharged from the overflow port above to obtain a mixture of organic sludge and supernatant.

[0015] Preferably, the specific steps of step S3 are: slowly adding a leaching agent to the organic sludge, stirring at 50-300 r / min for 1-4 hours, allowing the organic sludge to fully react with the leaching agent, and then performing solid-liquid separation to obtain a leaching liquid and residual sludge.

[0016] Preferably, the eluent comprises calcium chloride and citric acid, the concentration of the calcium chloride is 0.1-0.5 mol / L, and the concentration of the citric acid is 0.05-0.5 mol / L.

[0017] Preferably, the mass ratio between the sum of the mass of the calcium chloride and the citric acid and the organic sludge is (0.05-0.5):1.

[0018] Preferably, the specific steps of drying the high-purity organic sludge in step S4 are: using a plate and frame filter press to preliminarily dehydrate the high-purity organic sludge to obtain a mud cake with a water content of 30-50%, and drying the mud cake to a water content of 10-15% to obtain biomass fuel.

[0019] Preferably, the method further comprises step S5. Adding a reducing agent to the supernatant obtained in step S2 and step S4 and the eluent obtained in step S3, stirring the reaction for 20-30 minutes, and then performing solid-liquid separation to obtain a precipitate.

[0020] Beneficial effects:

[0021] The sludge modification and separation method provided by the present invention can effectively separate sludge, and the organic matter content in the obtained inorganic gravel is low, which is convenient for subsequent application in fields such as building materials; after drying the high-purity organic sludge, biomass fuel is produced, and it has a high high calorific value, which is conducive to subsequent resource utilization.

[0022] The method provided by the present invention uses ferrous sulfite, a chelating agent, and a flocculant to pretreat the sludge, disrupting the viscosity of the EPS (Emulsified Polystyrene) (EPS) in the sludge and enabling better separation of the inorganic and organic components in the sludge. Glutaraldehyde treatment allows for full penetration into the sludge during the pretreatment process, killing microorganisms, bacteria, and viruses in the sludge, preventing their spread during the subsequent separation process and improving biosafety during the treatment process.

[0023] The present invention adds a reducing agent to the supernatant and the eluent to carry out a reaction, thereby analyzing inorganic groups such as iron, aluminum and phosphorus therein, which is convenient for subsequent recycling. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] The sludge to be treated is the sludge collected from the municipal sewage treatment plant.

[0028] Example 1

[0029] A sludge modification and separation method comprises the following steps:

[0030] S1. Adding ferrous sulfite and glutaraldehyde to the sludge to be treated, stirring for 40 minutes, then adding a chelating agent, ethylenediaminetetraacetic acid, and a flocculant, polyacrylamide, and adjusting the pH to 6-8. Stirring for 60 minutes to obtain a solid-liquid mixture. This reduces inorganic components such as iron, aluminum, and phosphorus in the sludge to ions that dissolve in the liquid phase, facilitating subsequent separation and recovery.

[0031] The mass percentage of each component is: 98 wt% of the sludge to be treated, 0.5 wt% of ferrous sulfite, 0.5 wt% of glutaraldehyde, 0.7 wt% of the chelating agent, and 0.3 wt% of the flocculant.

[0032] S2. The solid-liquid mixture is fed into a cyclone solid-liquid separation device at a flow rate of 3 m / s and centrifuged at a speed of 1000 r / min. The inorganic gravel is thrown toward the wall and discharged downward to form an underflow; the organic sludge and liquid phase form an overflow and are discharged from the upper overflow port to obtain a mixture of organic sludge and supernatant;

[0033] S3. Slowly add an eluent to the organic sludge and stir at 100 rpm for 2 h to allow the organic sludge and the eluent to react fully, followed by solid-liquid separation to obtain an eluent and residual sludge; the eluent comprises calcium chloride and citric acid, wherein the concentration of the calcium chloride is 0.1 mol / L, the concentration of the citric acid is 0.2 mol / L, the mass ratio of the calcium chloride to the citric acid is 1:1, and the mass ratio of the sum of the mass of the calcium chloride and the citric acid to the organic sludge is 0.2:1;

[0034] S4. The solid-liquid separation and elution of the remaining sludge were repeated three times to obtain a supernatant and high-purity organic sludge; the high-purity organic sludge was initially dehydrated using a plate and frame filter press to obtain a mud cake with a moisture content of 30%, and the mud cake was dried to a moisture content of 10%, and the drying was completed to obtain biomass fuel;

[0035] Step S5. Add a reducing agent to the supernatant obtained in steps S2 and S4, and the eluent obtained in step S3. Stir the mixture for 30 minutes, then perform solid-liquid separation to obtain a precipitate. The precipitate mainly contains iron and aluminum salts and phosphate salts. The iron and aluminum salts can be recycled back to the sewage treatment plant as a phosphorus removal agent, and the phosphate salts can be recycled as phosphate fertilizer.

[0036] The content of organic components in the inorganic gravel separated in Example 1 is no more than 3%, and the higher calorific value of the biomass fuel is 3500 kcal / kg.

[0037] Example 2

[0038] A sludge modification and separation method comprises the following steps:

[0039] S1. Add ferrous sulfite and glutaraldehyde to the sludge to be treated, stir and react for 30 minutes, then add chelating agent diethylenetriamine pentaacetic acid, aminotrimethylenephosphonic acid and flocculant polyaluminum chloride, polyferric sulfate, and adjust the pH to 6-8. Stir and react for 40 minutes to obtain a solid-liquid mixture;

[0040] The mass percentage of each component is: 96 wt % of the sludge to be treated, 1.5 wt % of ferrous sulfite, 0.6 wt % of glutaraldehyde, 1.0 wt % of the chelating agent, and 0.9 wt % of the flocculant.

[0041] S2. The solid-liquid mixture is fed into a cyclone solid-liquid separation device at a flow rate of 2 m / s and centrifuged at a speed of 1200 r / min. The inorganic gravel is thrown toward the wall and discharged downward as an underflow; the organic sludge and liquid phase form an overflow and are discharged from the overflow port above to obtain a mixture of organic sludge and supernatant;

[0042] S3. Slowly add an eluent to the organic sludge and stir at 50 rpm for 4 hours to allow the organic sludge and the eluent to react fully, followed by solid-liquid separation to obtain an eluent and residual sludge; the eluent comprises calcium chloride and citric acid, wherein the concentration of the calcium chloride is 0.5 mol / L, the concentration of the citric acid is 0.05 mol / L, the mass ratio of the calcium chloride to the citric acid is 1:1, and the mass ratio of the sum of the mass of the calcium chloride and the citric acid to the organic sludge is 0.05:1;

[0043] S4. The residual sludge is repeatedly subjected to solid-liquid separation and leaching to obtain a supernatant and high-purity organic sludge; the high-purity organic sludge is initially dehydrated using a plate and frame filter press to obtain a mud cake with a moisture content of 40%, and the mud cake is dried to a moisture content of 12%, and the drying is completed to obtain biomass fuel;

[0044] Step S5. Add a reducing agent to the supernatant obtained in step S2 and step S4 and the eluent obtained in step S3, stir and react for 20 minutes, then perform solid-liquid separation to obtain a precipitate.

[0045] The content of organic components in the inorganic gravel separated in Example 2 is no more than 10%, and the higher calorific value of the biomass fuel is 2700 kcal / kg.

[0046] Example 3

[0047] A sludge modification and separation method comprises the following steps:

[0048] S1. Add ferrous sulfite and glutaraldehyde to the sludge to be treated, stir and react for 50 minutes, then add the chelating agent hydroxyethylethylenediaminetriacetic acid and the flocculant polydimethyldiallyl ammonium chloride, adjust the pH to 6-8, stir and react for 80 minutes to obtain a solid-liquid mixture;

[0049] The mass percentage of each component is: 99wt% of sludge to be treated, 0.4wt% of ferrous sulfite, 0.2wt% of glutaraldehyde, 0.3-5.0wt% of chelating agent, and 0.1wt% of flocculant.

[0050] S2. The solid-liquid mixture is fed into a cyclone solid-liquid separation device at a flow rate of 4 m / s and centrifuged at a speed of 1500 r / min. The inorganic gravel is thrown toward the wall and discharged downward to form an underflow; the organic sludge and liquid phase form an overflow and are discharged from the overflow port above to obtain a mixture of organic sludge and supernatant;

[0051] S3. Slowly add an eluent to the organic sludge and stir at 300 r / min for 1 hour to allow the organic sludge and the eluent to fully react, followed by solid-liquid separation to obtain an eluent and residual sludge; the eluent comprises calcium chloride and citric acid, wherein the concentration of the calcium chloride is 0.3 mol / L, the concentration of the citric acid is 0.5 mol / L, the mass ratio of the calcium chloride to the citric acid is 1:1, and the mass ratio of the sum of the mass of the calcium chloride and the citric acid to the organic sludge is 0.5:1;

[0052] S4. The residual sludge was subjected to five repeated solid-liquid separation and elution to obtain a supernatant and high-purity organic sludge; the high-purity organic sludge was initially dehydrated using a plate and frame filter press to obtain a mud cake with a water content of 50%, and the mud cake was dried to a moisture content of 15%, and the drying was completed to obtain biomass fuel;

[0053] Step S5. Add a reducing agent to the supernatant obtained in step S2 and step S4 and the eluent obtained in step S3, stir and react for 25 minutes, then perform solid-liquid separation to obtain a precipitate.

[0054] The organic content of the inorganic gravel separated in Example 3 is no more than 2%, and the higher calorific value of the biomass fuel is 3700 kcal / kg.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sludge modification and separation method, characterized in that: The following steps are involved: S1. Adding ferrous sulfite and glutaraldehyde to the sludge to be treated, stirring and reacting for 30-50 minutes, adding a chelating agent and a flocculant, and adjusting the pH to 6-8, stirring and reacting for 40-80 minutes to obtain a solid-liquid mixture, wherein the chelating agent is any one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, and aminotrimethylenephosphonic acid; S2. The solid-liquid mixture is subjected to solid-liquid separation to obtain inorganic gravel and organic sludge, and a supernatant; S3. The organic sludge is eluted with an eluent to obtain an eluent and residual sludge, wherein the eluent comprises calcium chloride and citric acid, the concentration of the calcium chloride being 0.1-0.5 mol / L, and the concentration of the citric acid being 0.05-0.5 mol / L; S4. Repeating the solid-liquid separation and leaching of the remaining sludge to obtain a supernatant and high-purity organic sludge; the high-purity organic sludge is dried to obtain biomass fuel; S5. Add a reducing agent to the supernatant obtained in step S2 and step S4 and the eluent obtained in step S3, stir and react for 20-30 minutes, then perform solid-liquid separation to obtain a precipitate.

2. The sludge modification and separation method according to claim 1, characterized in that: The mass percentages of the components in step S1 are: 90-99 wt % of the sludge to be treated, 0.4-3.0 wt % of ferrous sulfite, 0.2-2.0 wt % of glutaraldehyde, 0.3-5.0 wt % of the chelating agent, and 0.1-4.0 wt % of the flocculant.

3. The sludge modification and separation method according to claim 2, characterized in that: The flocculant is any one or more of polyaluminium chloride, polyferric sulfate, polyacrylamide and polydimethyldiallylammonium chloride.

4. The sludge modification and separation method according to claim 1, characterized in that: The specific steps of step S2 are: feeding the solid-liquid mixture into a cyclone solid-liquid separation device at a flow rate of 2-4 m / s, centrifuging at a speed of 1000-1500 r / min, and throwing inorganic sand and gravel toward the wall of the device to form an underflow for discharge; The organic sludge and liquid phase form an overflow and are discharged from the overflow port above to obtain a mixture of organic sludge and supernatant.

5. The sludge modification and separation method according to claim 1, characterized in that: The specific steps of step S3 are: slowly adding the eluent to the organic sludge, stirring at 50-300 r / min for 1-4 hours, allowing the organic sludge to fully react with the eluent, and then performing solid-liquid separation to obtain eluent and residual sludge.

6. The sludge modification and separation method according to claim 1, characterized in that: The mass ratio of the sum of the mass of the calcium chloride and the citric acid to the organic sludge is (0.05-0.5):

1.

7. The sludge modification and separation method according to claim 1, characterized in that: The specific steps of drying the high-purity organic sludge in step S4 are: using a plate and frame filter press to preliminarily dehydrate the high-purity organic sludge to obtain a mud cake with a water content of 30-50%, and drying the mud cake to a water content of 10-15% to obtain biomass fuel.