Method for extracting plastic precursor from sludge
By adopting multi-level warm zone filtering devices and liquid-liquid extraction technology in the sludge treatment, the recovery rate of plastic preparation has been successfully improved, and the problem of resource loss and environmental pollution in traditional sludge treatment has been solved. Recycling with sludge resources of the economy.
Patent Information
- Application Number
- CN202411573569.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-06
- Publication Date
- 2025-01-28
AI Technical Summary
The prior art is difficult to efficiently extract plastic precursors in sludge treatment, resulting in loss of valuable resources and environmental pollution.
The multi-stage warm zone filtering device binding liquid-liquid extraction technology is used to extract different types of plastic forethers from the sludge. This method adapts to the dissolving temperature of different plastic pre -bodies by setting up low temperature, medium temperature and high temperature sections, and achieve efficient separation extraction.
It significantly improves the recovery rate of plastic front body in the sludge, reduces environmental pollution, saves energy, and is suitable for various types of sludge treatment. It has strong universality and application potential.
Smart Images
Figure CN119371714A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of plastic recycling and environmental protection, and in particular to a method for extracting plastic precursors from sludge. Background Art
[0002] With the increasing global concern about plastic pollution, the recycling and reuse of plastic waste has become an important environmental protection task. Plastics are widely used in packaging, construction, electronic products and other fields. However, their degradation time in the natural environment is extremely long, leading to serious ecological pollution. In addition, a large amount of sludge is also generated during the production and treatment of plastics. This sludge not only occupies a large amount of land resources, but may also cause secondary pollution to water and soil.
[0003] As an inevitable by-product of urban sewage treatment, industrial wastewater treatment and agricultural drainage, sludge has a complex composition and usually contains a large amount of organic matter, inorganic matter, bacteria and chemicals. Depending on the source of the sludge, the composition of urban sludge, industrial sludge and agricultural sludge will vary. For example, urban sludge generally contains rich organic matter, while industrial sludge may contain heavy metals and other industrial chemicals. Agricultural sludge may be rich in nutrients such as nitrogen and phosphorus, which have the potential to be converted into valuable resources under appropriate conditions.
[0004] In recent years, studies have shown that there may be some precursors or degradation products in sewage sludge that can be used to synthesize plastics, especially during pyrolysis or chemical treatment. These precursors can be converted into monomers at high temperatures or under specific chemical conditions and thus used in the production of recycled plastics. Nevertheless, traditional sewage sludge treatment methods, such as incineration and pyrolysis, often lead to the loss of valuable plastic precursors.
[0005] To solve this problem, scientists have begun to explore new sludge resource technology, including extracting reusable organic components from sludge through physical, chemical and biological methods. Liquid-liquid extraction, pyrolysis, chemical degradation and other methods have been proposed, but they still face challenges such as low efficiency, poor selectivity and high economic cost in practical applications.
[0006] Therefore, developing an efficient and economical sludge treatment and plastic precursor extraction method can effectively realize the recycling and utilization of sludge resources, which not only helps to reduce plastic pollution, but also provides a new way out for sludge treatment, and has important economic and social value. Summary of the invention
[0007] The object of the present invention is to provide a method for extracting plastic precursors from sludge. The method can extract different types of plastic precursors in different temperature zones by setting a multi-stage temperature zone filtering device, thereby improving the efficiency of resource recovery.
[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0009] The present invention provides a method for extracting plastic precursors from sludge, comprising the following steps:
[0010] Step 1: Sludge pretreatment: Collect sludge samples and sieve to remove impurities with particle diameters greater than 2 mm. Dry the sludge samples at a temperature of 60-80°C for 12 to 24 hours until the moisture content drops below 5%. Crush the dried sludge samples to a particle size of less than 0.5 mm.
[0011] Step 2, solvent extraction: the crushed sludge is mixed with an organic solvent in a mass ratio of 1: (3-10), soaked at room temperature for 12-48 hours, and then filtered. The filtered solution is evaporated under reduced pressure at a temperature of 40-60° C. and concentrated to 10-30% of the original volume using a rotary evaporator to remove most of the solvent and concentrate the plastic precursor.
[0012] Step 3, multi-stage slow flow filtration and liquid-liquid extraction, set a multi-stage slow flow filtration device, divided into three temperature sections, set to low temperature zone 20-30 ° C, medium temperature zone 40-50 ° C and high temperature zone 60-70 ° C, respectively, to adapt to the dissolution temperature of different plastic precursors. The concentrated solution is gradually introduced into the multi-stage filtration device, and first filtered in the low temperature section to extract the plastic precursor dissolved at a lower temperature. Repeat this process in the medium temperature section and the high temperature section to extract different plastic precursors dissolved at medium and high temperatures, ensuring that the filtration rate of each temperature section is 5-20mL / min to ensure sufficient dissolution and separation. Collect the filtrate from each temperature section, and after standing for 15-30 minutes, mix it with the aqueous phase solvent in a volume ratio of 1: (1-3) for liquid-liquid extraction to promote the transfer of the plastic precursor. During the liquid-liquid extraction process, stir the mixed liquid at a stirring rate of 100-500rpm, collect the organic phase, and obtain the plastic precursor.
[0013] Particularly, in step 1, the sludge is urban sludge, industrial sludge or agricultural sludge.
[0014] In particular, in step one, the sieving step is to use a sieve with a mesh diameter of 2 mm, pour the sludge sample into the sieve, and gently vibrate or shake it to force particles smaller than 2 mm to pass through the sieve, while particles larger than 2 mm are retained on the sieve.
[0015] Particularly, in step 2, the reduced pressure condition of the reduced pressure evaporation step is 20-100 mmHg.
[0016] In particular, in step three, the filtering device is a pressure filter, a membrane filter or a stacked filter with a temperature regulating function, which can be precisely controlled according to the required temperature.
[0017] In particular, the plastic precursors extracted in the low temperature zone include degradation products of polyvinyl alcohol (PVA) and polyvinyl chloride (PVC); the plastic precursors extracted in the medium temperature zone include degradation products of polypropylene (PP) and polyethylene terephthalate (PET); and the plastic precursors extracted in the high temperature zone include degradation products of polystyrene (PS) and polyethylene (PE).
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] 1. Efficient recovery. The present invention can achieve efficient separation and extraction of different types of plastic precursors through multi-stage temperature zone filtration and liquid-liquid extraction technology. The multi-stage temperature zone takes into account the degradation temperature of different plastics at the same time, which significantly improves the recovery rate of plastic precursors in sludge.
[0020] 2. Environmental benefits: This method uses low-energy solvent extraction and temperature zone filtration technology. Compared with the traditional high-temperature carbonization method, it can not only effectively reduce environmental pollution, but also save energy.
[0021] 3. Wide applicability: The method of the present invention is suitable for the treatment of various types of sludge, including urban sludge, industrial sludge and agricultural sludge, and has strong universality and application potential.
[0022] 4. Economic benefits: the plastic precursors recovered by this method can be further converted into valuable raw materials, reducing the cost of waste treatment and having good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is a flow chart of the present invention, illustrating the various steps of extracting plastic precursors from sludge, including sludge pretreatment, solvent extraction, multi-stage filtration and liquid-liquid extraction. DETAILED DESCRIPTION
[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0025] Example 1: Extraction of plastic precursors from municipal sludge
[0026] Urban sludge mainly comes from sewage treatment plants and contains rich organic matter and degradable plastic components.
[0027] Sludge pretreatment: Municipal sludge samples were collected and sieved using a sieve with a mesh diameter of 2 mm to remove impurities with particle diameters greater than 2 mm. The sieved sludge was dried at 70°C for 18 hours until the moisture content dropped below 5%. The dried sludge was then crushed to a particle size of less than 0.5 mm.
[0028] Solvent extraction: The crushed sludge was mixed with dichloromethane in a mass ratio of 1:5 and soaked at room temperature for 24 hours. After filtration, the obtained solution was evaporated under reduced pressure at 50°C and concentrated to 20% of the original volume.
[0029] Multi-stage filtration and liquid-liquid extraction: The concentrated liquid was introduced into a multi-stage slow flow filtration device, and the low temperature zone was set to 25°C, the medium temperature zone was set to 45°C, and the high temperature zone was set to 65°C. Filter in sequence and collect the filtrate in each temperature zone. After standing for 30 minutes, the filtrate was mixed with deionized water in a volume ratio of 1:2 for liquid-liquid extraction. During the liquid-liquid extraction process, the mixed liquid was stirred at a stirring rate of 200rpm, and the organic phase was collected. The degradation products of polyvinyl alcohol (PVA) and polyvinyl chloride (PVC) were extracted.
[0030] Example 2: Extraction of plastic precursors from industrial sludge
[0031] Industrial sludge usually contains heavy metals and chemicals, and the extraction process requires special attention to safety and environmental impact.
[0032] Sludge pretreatment: Collect industrial sludge samples and remove impurities with particle diameter greater than 2 mm by sieving. Dry the sludge at 80°C for 15 hours to reduce the moisture content to less than 5%. Crush to a particle size of less than 0.5 mm.
[0033] Solvent extraction: Mix the crushed sludge with ethanol in a mass ratio of 1:4 and soak at room temperature for 36 hours. After filtering, evaporate under reduced pressure at 45°C and concentrate to 15% of the original volume.
[0034] Multi-stage filtration and liquid-liquid extraction: A multi-stage slow flow filtration device was set up, with the low temperature zone at 20°C, the medium temperature zone at 40°C, and the high temperature zone at 60°C. The filtration was performed in sequence, and the liquid in each temperature zone was collected. After standing for 20 minutes, liquid-liquid extraction was performed using ethanol aqueous solution as the extraction solvent, with a volume ratio of 1:1. During the liquid-liquid extraction process, the mixed liquid was stirred at a stirring rate of 300rpm, and the degradation products of polypropylene (PP) were extracted.
[0035] Example 3: Plastic Precursor Extraction from Agricultural Sludge
[0036] Agricultural sludge is rich in organic matter and nutrients and is suitable for the extraction of plastic precursors.
[0037] Sludge pretreatment: Agricultural sludge samples were collected and sieved to remove impurities with particle diameter greater than 2 mm. The sludge was dried at 65°C for 20 hours until the moisture content dropped below 5%. The sludge was crushed to a particle size of less than 0.5 mm.
[0038] Solvent extraction: The crushed sludge was mixed with acetone in a mass ratio of 1:6 and soaked at room temperature for 12 hours. After filtration, the obtained solution was evaporated under reduced pressure at 40°C and concentrated to 10% of the original volume.
[0039] Multi-stage filtration and liquid-liquid extraction: The concentrated liquid was introduced into a multi-stage slow flow filtration device, with the low temperature zone at 20°C, the medium temperature zone at 50°C, and the high temperature zone at 70°C. Filter in sequence and collect the filtrate in each temperature zone. After standing for 25 minutes, it was mixed with deionized water at a volume ratio of 1:1.5 for liquid-liquid extraction. During the liquid-liquid extraction process, the mixed liquid was stirred at a stirring rate of 500rpm, and the degradation products of polyethylene terephthalate (PET) were extracted.
[0040] Figure 1 Some of the key steps included are:
[0041] 1. Collect sludge samples: obtain sludge samples to be treated.
[0042] 2. Screening to remove large particles of impurities: Use a sieve to remove impurities with a diameter greater than 2 mm.
[0043] 3. Drying: Dry the sludge at a controlled temperature to reduce the moisture content.
[0044] 4. Crushing: Crushing the dried sludge to a particle size of less than 0.5 mm to increase the surface area.
[0045] 5. Solvent extraction: Mix the crushed sludge with an organic solvent and soak it to promote dissolution.
[0046] 6. Filtration: Filter to remove solid residue and retain dissolved substances.
[0047] 7. Evaporation under reduced pressure: Concentrate the solution under controlled temperature to remove most of the solvent.
[0048] 8. Multi-stage slow flow filtration: A multi-stage filtration device is set up, divided into different temperature sections to extract plastic precursors.
[0049] 9. Liquid-liquid extraction: Mix the filtrate from each temperature zone with the aqueous solvent, let it stand and extract to collect the organic phase.
[0050] The method provided by the present invention is very suitable for continuous industrial processes.
[0051] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.
Claims
1. A method for extracting plastic precursors from sludge, characterized in that: The method comprises the following steps: Step 1: Collect sludge samples, sieve to remove impurities with a particle diameter greater than 2 mm, dry the sludge samples at a temperature of 60-80° C. for 12 to 24 hours until the moisture content drops below 5%, and crush the dried sludge samples to a particle size less than 0.5 mm; Step 2: Mix the crushed sludge and the organic solvent in a mass ratio of 1: (3-10), soak at room temperature for 12-48 hours, and then filter, evaporate the filtered solution under reduced pressure at a temperature of 40-60° C., and concentrate it to 10-30% of the original volume using a rotary evaporator to remove most of the solvent and concentrate the plastic precursor; Step 3, multi-stage slow flow filtration and liquid-liquid extraction, set up a multi-stage slow flow filtration device, divided into three temperature sections, set to low temperature zone 20-30°C, medium temperature zone 40-50°C and high temperature zone 60-70°C, respectively, to adapt to the dissolution temperature of different plastic precursors; the concentrated solution is gradually introduced into the multi-stage filtration device, first filtered in the low temperature section to extract the plastic precursor dissolved at a lower temperature, and then the process is repeated in the medium temperature section and the high temperature section to extract different plastic precursors dissolved at medium and high temperatures, ensuring that the filtration rate of each temperature section is 5-20mL / min to ensure sufficient dissolution and separation; finally, the filtrate of each temperature section is collected, and after standing for 15-30 minutes, it is mixed with the aqueous phase solvent in a volume ratio of 1: (1-3) to perform liquid-liquid extraction to promote the transfer of the plastic precursor; during the liquid-liquid extraction process, the mixed liquid is stirred at a stirring rate of 100-500rpm, and the organic phase is collected to obtain the plastic precursor.
2. The method according to claim 1, wherein the sludge is urban sludge, industrial sludge or agricultural sludge.
3. According to the method described in claim 1, in step 1, the sieving step is to use a sieve with a mesh diameter of 2 mm, pour the sludge sample into the sieve, and gently vibrate or shake it to cause particles smaller than 2 mm to pass through the sieve, while particles larger than 2 mm are retained on the sieve.
4. The method according to claim 1, wherein in step 2, the reduced pressure condition of the reduced pressure evaporation step is 20-100 mmHg.
5. According to the method of claim 1, in step 3, the filtering device is a pressure filter, a membrane filter or a stacked filter with a temperature regulating function, which can be accurately controlled according to the required temperature.
6. According to the method of claim 1, in step 3, the plastic precursor extracted in the low temperature zone includes degradation products of polyvinyl alcohol and polyvinyl chloride; the plastic precursor extracted in the medium temperature zone includes degradation products of polypropylene and polyethylene terephthalate; and the plastic precursor extracted in the high temperature zone includes degradation products of polystyrene and polyethylene.