CN115124211A - Method for stabilizing heavy metal in sludge thermochemical treatment and safely recycling sludge - Google Patents
Method for stabilizing heavy metal in sludge thermochemical treatment and safely recycling sludge Download PDFInfo
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- CN115124211A CN115124211A CN202211043771.XA CN202211043771A CN115124211A CN 115124211 A CN115124211 A CN 115124211A CN 202211043771 A CN202211043771 A CN 202211043771A CN 115124211 A CN115124211 A CN 115124211A
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/10—Treatment of sludge; Devices therefor by pyrolysis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
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Abstract
The invention provides a method for stabilizing heavy metal in sludge thermochemical treatment and safely recycling sludge, belonging to the field of environmental pollution control. The method analyzes and identifies the concentration of heavy metals in the sludge, carries out pyrolysis carbonization treatment or high-temperature sintering treatment on the sludge which is lower than the preset heavy metal standard limit value, and carries out high-temperature sintering treatment on the sludge which is higher than the preset heavy metal standard limit value. The leaching value of heavy metal in the material obtained by pyrolysis and carbonization is lower than the heavy metal limit value of European biochar certification standard, and the material can be used as a sewage treatment sludge-based biochar adsorption material, an advanced oxidation catalysis material and the like. The leaching value of heavy metal in the product obtained by high-temperature sintering treatment is lower than the limit value of the national industry standard for leaching heavy metal from sludge ceramsite, and the product can be used as building material and the like. The invention can realize the stabilization of heavy metals in the sludge and the safe resource utilization of the sludge.
Description
Technical Field
The invention belongs to the field of environmental pollution control, and particularly relates to a method for stabilizing heavy metal in sludge thermochemical treatment and safely recycling sludge.
Background
Sludge is always considered as a collection of pollutants in the sewage treatment process, various pollutants, especially heavy metals, seriously hinder the resource utilization of the pollutants, and the research and development of a safe sludge resource method are urgently needed. Although the existing sludge biochemical treatment method realizes the passivation of heavy metals in sludge to a certain extent, can recover biomass energy, and can partially use the product as garden utilization, the heavy metals do not disappear in the process, the repeated garden utilization brings about the problems of heavy metal accumulation and re-release, and contradicts with safe resource utilization, thereby limiting the outlet of sludge. The heavy metal can be solidified and stabilized through thermochemical treatment, and the obtained product can better realize the safe recycling of the sludge, but a consistent method for stabilizing and safely recycling the heavy metal in the thermochemical treatment of the sludge is not available at present.
Disclosure of Invention
The thermochemical treatment technology of the sludge mainly comprises sludge incineration, sludge gasification, cement kiln cooperative treatment, hydrothermal carbonization, sludge pyrolysis, sludge high-temperature sintering and the like. In consideration of safety, treatment cost and operation and maintenance cost, the sludge-based biochar material prepared by sludge pyrolysis and the light ceramsite prepared by sludge sintering can realize the recovery of biomass energy and the stabilization of heavy metals in sludge, and in addition, the operation cost is low, so that the safe recycling of sludge is realized at low cost.
On the basis, in consideration of the solidification rate of heavy metals in the sludge in the thermochemical treatment process and the disposal risk thereof, it is particularly important to refer to the concentration of heavy metals in the raw sludge in the selection of the heat treatment manner of the sludge.
In view of the foregoing, the main object of the present invention is to provide a method for stabilizing heavy metals and safely recycling sludge by thermochemical treatment of sludge, so as to stabilize heavy metals in sludge and safely recycle sludge by thermochemical treatment, thereby promoting the development of sludge safety treatment technology.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for stabilizing heavy metals in sludge thermochemical treatment and safely recycling sludge, as shown in figure 1, wherein the method comprises the following steps:
the method comprises the following steps: analyzing and identifying the concentration of heavy metals in the sludge, carrying out pyrolysis carbonization treatment or high-temperature sintering treatment on the sludge which is lower than a preset heavy metal standard limit value, and carrying out high-temperature sintering treatment on the sludge which is higher than the preset heavy metal standard limit value. In this step, the following is included:
1. further, the heavy metal includes at least one of: cadmium, mercury, lead, chromium, arsenic, nickel, zinc and copper.
2. Further, a pretreatment method for analyzing and identifying the concentration of heavy metals in sludge implements CJ/T221-2005 sludge inspection method for municipal wastewater treatment plants.
3. Furthermore, the preset heavy metal standard limit value referred to for analyzing and identifying the concentration of heavy metals in the sludge is actually formulated by selecting the lowest value of the heavy metal index in the two standards according to GB/T23486-.
Step two: the thermochemical treatment of the sludge identified by the concentration of the heavy metal is specifically carried out in the following two forms:
the first method is as follows: and carrying out pyrolysis carbonization treatment on the sludge. Comprises the following steps:
1. deeply dehydrating the sludge before the pyrolysis carbonization treatment, and reducing the water content in the sludge to 60-70% after the deep dehydration treatment.
2. Further, low-temperature drying treatment is carried out on the deeply dehydrated sludge, so that the water content in the sludge is reduced to 10% -30%, and the temperature of the low-temperature drying treatment is 65-95 ℃.
3. Further, the sludge after the low-temperature drying treatment is subjected to pyrolysis carbonization treatment to obtain a sludge-based biochar material and pyrolysis gas.
4. Further, the parameters of the pyrolysis carbonization treatment include: the pyrolysis carbonization time is 20-120 min; the pyrolysis carbonization temperature is 400-800 ℃. The pyrolysis temperature is adjusted according to the product application, the heavy metal content in the sludge and other factors; the residence time of the pyrolysis products is determined according to the organic content of the sludge, and the residence time is prolonged along with the increase of the organic content.
5. Further, the leaching value of heavy metals in the sludge-based biochar material generated in the pyrolysis carbonization process is lower than the heavy metal limit of the European biochar certification standard (EBC, ver, 10.1, 2022), wherein the heavy metal leaching concentration limit in the sludge pyrolysis carbonization product in the embodiment of the invention is established according to the heavy metal limit of the European biochar certification standard (as shown in Table 2), and the pretreatment method for detecting the leaching of heavy metals in the sludge pyrolysis carbonization product is implemented by HJ/T299 and 2007 sulfuric acid-nitric acid method for leaching toxicity of solid wastes.
6. Further, the sludge-based biochar material generated by pyrolysis and carbonization can be used as a high-grade oxidation catalyst in ozone high-grade oxidation, Fenton catalytic oxidation and persulfate oxidation; the composite adsorbent is used as an adsorbent in sewage strengthening primary treatment, effluent strengthening dephosphorization and antibiotic removal.
The second method comprises the following steps: and (4) carrying out high-temperature sintering treatment on the sludge. Comprises the following steps:
1. and (3) conditioning and dehydrating the sludge before high-temperature sintering treatment, wherein the water content in the dehydrated sludge is 60-80%.
2. Further, the dewatered sludge and the additive are fully mixed according to a certain proportion to obtain a mixture.
3. Further, the additive comprises one or more of clay, feedwater sludge, municipal sludge, river sediment, lake sediment, dredging sediment, and mineral binder.
4. Further, according to the performance of the sludge sintered product and the immobilization target requirement of heavy metals, the content of oxides in the mixture after doping the sludge after different drying processes comprises the following steps: SiO 2 2 ：24%~46%，Al 2 O 3 ：11%~26%，Fe 2 O 3 : 3.5-8.0%, CaO: 2.25% -7.0%, MgO: 1.2% -4.0%. SiO in the mixture 2 The stability of the crystal structure in the product can be ensured; al (Al) 2 O 3 The rigidity and the strength of the product can be improved, and the crystallization rate and the stability of the crystal structure are important; fe 2 O 3 Oxide decomposition occurs at high temperature to form a new structure; CaO maintains good thermal stability; MgO can reduce the eutectic point of the material, promote self-bonding and pore-forming of the raw material, and influence crystal formation.
5. Further, after the mixture is extruded and dried by using a granulator, the mixture is sintered at a high temperature to obtain a sintered product.
6. Further, the temperature of the high-temperature sintering treatment process is 1000-1300 ℃; the time of the high-temperature sintering treatment is as follows: 20-120 min. The residence time of the sintered product is determined according to the organic content in the raw materials of the mixture, and the residence time is prolonged along with the increase of the organic content. In addition, the determination of the sintering temperature can also be adjusted according to factors such as product application, raw material heavy metal content and the like, and the higher the sintering temperature is, the higher the heavy metal solidification rate is.
7. Further, the leaching value of the heavy metal in the sintered product is lower than the heavy metal leaching limit of the national industry standard sludge ceramsite (JC/T2621-.
8. Further, the sintered product can be used as a building material.
According to the technical scheme, the method for stabilizing the heavy metal in the thermochemical treatment of the sludge and safely recycling the sludge has the following beneficial effects:
(1) in the invention, the sludge-based biochar material obtained by pyrolysis and carbonization can be used as an adsorption material, a catalytic material and the like; the sintered product obtained by high-temperature sintering treatment has good performance and low production cost, can meet the industrial requirements, and can be used as building materials and the like. In addition, heavy metals in the sludge after pyrolysis carbonization treatment and high-temperature sintering treatment can be stabilized in solid products, and the use safety of the solid products is ensured.
(2) In the invention, the pyrolysis gas obtained by pyrolysis and carbonization can be converted into heat energy or electric energy, so that the energy utilization of the pyrolysis gas is realized.
(3) According to the invention, the concentrations of heavy metals in the sludge are firstly analyzed and identified, different thermochemical treatment methods are provided for the sludge with different concentrations of heavy metals, a consistent reference is provided for realizing stabilization and safe resource treatment of the heavy metals in the sludge, the development of sludge treatment industry is facilitated, ecological safety is ensured and maintained, and the practicability and environment-friendly goal of sludge treatment are realized.
Drawings
FIG. 1 is a flow chart of a method for stabilizing heavy metals and safely recycling sludge in thermochemical treatment of sludge in the embodiment of the invention.
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Example 1
The method comprises the following steps of carrying out pyrolysis carbonization treatment on sludge of a certain domestic sewage treatment plant to realize safe resource utilization of the sludge, wherein the contents of cadmium (2 mg/kg), mercury (3 mg/kg), lead (120 mg/kg), chromium (100 mg/kg), arsenic (12 mg/kg), nickel (20 mg/kg), zinc (400 mg/kg) and copper (300 mg/kg) are all lower than preset heavy metal standard limit values. The water content of the sludge is 98.7 percent, the organic matter content is 55 percent, and the conditioned sludge is subjected to plate-frame dehydration to reduce the water content of the sludge to 65 percent. And drying the dewatered sludge by adopting a low-temperature heat pump at the drying temperature of 80 ℃, and reducing the water content of the sludge to 15% by low-temperature drying. And conveying the low-temperature dried sludge to a continuous pyrolysis device through a conveyor belt, wherein the pyrolysis temperature is 700 ℃, and the retention time is 50 min. Pyrolysis gas generated in the sludge pyrolysis process is converted into heat energy in a combustion mode for utilization. The sludge-based biochar material generated after the sludge pyrolysis is pretreated by HJ/T299-2007 sulfuric acid-nitric acid method for solid waste leaching toxicity leaching method, and the heavy metal leaching value in the obtained sludge-based biochar material is lower than the heavy metal limit value of European biochar certification standard. The sludge-based biochar material prepared by the method can be used as a catalyst for removing new pollutants in sewage.
Example 2
The method comprises the following steps of carrying out pyrolysis carbonization treatment on sludge of a certain municipal sewage treatment plant to realize safe resource utilization of the sludge, wherein the contents of cadmium (1 mg/kg), mercury (2 mg/kg), lead (220 mg/kg), chromium (200 mg/kg), arsenic (17 mg/kg), nickel (30 mg/kg), zinc (800 mg/kg) and copper (400 mg/kg) are all lower than preset heavy metal standard limit values. The water content of the sludge is 98.5 percent, the organic matter content is 45 percent, and the conditioned sludge is subjected to plate-frame dehydration to reduce the water content of the sludge to 65 percent. Drying the dewatered sludge by a low-temperature heat pump at the drying temperature of 80 ℃, and reducing the water content of the sludge to 20% by low-temperature drying. And conveying the low-temperature dried sludge into a pyrolysis device through a conveyor belt, wherein the pyrolysis temperature is 750 ℃, and the retention time is 45 min. Pyrolysis gas generated in the sludge pyrolysis process is converted into heat energy in a combustion mode for utilization. The sludge-based biochar material generated after the sludge pyrolysis is pretreated by HJ/T299-2007 sulfuric acid-nitric acid method for solid waste leaching toxicity leaching method, and the heavy metal leaching value in the obtained sludge-based biochar material is lower than the heavy metal limit value of European biochar certification standard. The sludge-based biochar material can be used for treating phosphorus-containing wastewater in a sewage treatment plant.
Example 3
The sludge of sewage treatment plants in certain tanning industrial parks, wherein the total chromium content is 1250mg/kg of dry sludge, is subjected to high-temperature sintering treatment to realize the safe resource utilization of the sludge.The water content of the sludge is 95 percent, and the water content of the sludge is reduced to 80 percent through filter pressing dehydration. Uniformly mixing the sludge and the clay according to the mass ratio of 1:1, then placing the mixture in a granulator to obtain a ceramsite blank with the particle size of 8mm, drying the ceramsite blank, conveying the ceramsite blank into a continuous sintering device through a conveyor belt, sintering the ceramsite blank at 1000 ℃ for 70min, and cooling the material to obtain the sintered ceramsite product. The pretreatment method for detecting the leaching of the heavy metals in the ceramsite executes GB/T30810 'determination method for leachable heavy metals in cement mortar', the leaching amount of Cr in the ceramsite is 11 mu g/g, which is 0.88 percent of the Cr content in the original sludge and is lower than the limit value of the national industry standard for leaching the heavy metals in the sludge ceramsite. The bulk density of the prepared ceramsite is 675-850 kg/m 3 The water absorption rate is 3-6%, the sum of the crushing rate and the wear rate is 0.75-1%, and the cylinder pressure strength is 14-17 MPa, so that the material can be used as a building material.
Example 4
The sludge of a sewage treatment plant in a certain electroplating industrial park has the total zinc content and the total copper content of 2600mg/kg of dry sludge and 1000mg/kg of dry sludge respectively, and is subjected to high-temperature sintering treatment to realize safe recycling. And (3) carrying out filter pressing dehydration on the sewage sludge and the river sediment to reduce the water content to 80%. Mixing the treated sewage sludge and the river sediment according to the mass ratio of 3:1, manufacturing a ceramsite blank with the particle size of 6mm by using a granulator, and drying. And sintering the dried ceramsite blank at 1200 ℃, keeping the temperature for 60min, and cooling the material to obtain the sintered ceramsite product. The pretreatment method for detecting the leaching of the heavy metals of the ceramsite executes GB/T30810 'determination method for leachable heavy metals in cement mortar', and the leaching amounts of Zn and Cu in the ceramsite are respectively 20 mug/g and 8.5 mug/g, which are 0.77 percent and 0.85 percent of the Zn and Cu contents of the original sludge and are lower than the national industry standard limit value of the leaching of the heavy metals of the sludge ceramsite. The prepared ceramsite can be used as a building material.
Claims (4)
1. A method for stabilizing heavy metal in sludge thermochemical treatment and safely recycling sludge is characterized by comprising the following steps:
the method comprises the following steps: analyzing and identifying the concentration of heavy metals in the sludge, performing pyrolysis carbonization treatment or high-temperature sintering treatment on the sludge which is lower than a preset heavy metal standard limit, and performing high-temperature sintering treatment on the sludge which is higher than the preset heavy metal standard limit;
step two: the thermochemical treatment of the sludge identified by the concentration of the heavy metal is specifically carried out by the following two modes:
the method I comprises the following steps: the sludge pyrolysis carbonization treatment comprises the following steps: deep dehydration and low-temperature drying treatment are carried out on the sludge, pyrolysis carbonization treatment is carried out for 20min to 120min at the pyrolysis temperature of 400 ℃ to 800 ℃, the leaching value of heavy metals in the obtained sludge-based biochar material is lower than the heavy metal limit value of European biochar certification standard, and pyrolysis gas realizes energy conversion and utilization;
the second method comprises the following steps: the high-temperature sintering treatment of sludge comprises the following steps: and (3) conditioning and dehydrating the sludge, mixing the dehydrated sludge and an additive, granulating, drying, and sintering at the sintering temperature of 1000-1300 ℃ for 20-120min to obtain a sintered product, wherein the leaching value of heavy metals in the sintered product is lower than the national industrial standard limit value of leaching heavy metals from sludge ceramsite.
2. The method for stabilizing heavy metals in sludge thermochemical treatment and recycling sludge as claimed in claim 1, wherein the heavy metals include at least one of the following: cadmium, mercury, lead, chromium, arsenic, nickel, zinc and copper.
3. The method for stabilizing heavy metals and recycling sludge through thermochemical treatment according to claim 1, wherein in the second step, the method further comprises the steps of mixing the dewatered sludge with an added additive, extruding, granulating and molding before the sludge is subjected to high-temperature sintering treatment;
wherein, the oxide content in the mixture after the additive is added comprises: 24% -46% SiO 2 、11%~26% Al 2 O 3 、3.5%~8.0% Fe 2 O 3 、2.25%~7.0% CaO、1.2%~4.0% MgO。
4. The method for stabilizing heavy metals in sludge thermochemical treatment and recycling sludge as claimed in claim 1, wherein in the second step, the additive comprises: one or more of clay, water supply sludge, municipal sludge, river sediment, lake sediment, dredging sediment and mineral binder.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH05220499A (en) * | 1992-02-12 | 1993-08-31 | Hitachi Plant Eng & Constr Co Ltd | Sludge disposal method |
| JP2008221206A (en) * | 2007-02-13 | 2008-09-25 | Metawater Co Ltd | Dust collection method of exhaust gas from sludge incinerator |
| CN102815925A (en) * | 2012-07-13 | 2012-12-12 | 哈尔滨工业大学 | Method for preparation of ceramsites by using sludge and river sediment and harmlessness treatment and immobilization of heavy metals |
| CN110054476A (en) * | 2019-05-13 | 2019-07-26 | 江苏捷豋环保能源有限公司 | A method of haydite is prepared using domestic sludge cracking gas-producing sintering industrial sludge |
| CN110981130A (en) * | 2019-12-11 | 2020-04-10 | 湖南省建筑设计院有限公司 | Method for judging utilization path of heavy metal polluted bottom mud |
| CN112159063A (en) * | 2020-10-26 | 2021-01-01 | 哈尔滨工业大学 | Sludge pyrolysis safe resource utilization process |
-
2022
- 2022-08-30 CN CN202211043771.XA patent/CN115124211A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05220499A (en) * | 1992-02-12 | 1993-08-31 | Hitachi Plant Eng & Constr Co Ltd | Sludge disposal method |
| JP2008221206A (en) * | 2007-02-13 | 2008-09-25 | Metawater Co Ltd | Dust collection method of exhaust gas from sludge incinerator |
| CN102815925A (en) * | 2012-07-13 | 2012-12-12 | 哈尔滨工业大学 | Method for preparation of ceramsites by using sludge and river sediment and harmlessness treatment and immobilization of heavy metals |
| CN110054476A (en) * | 2019-05-13 | 2019-07-26 | 江苏捷豋环保能源有限公司 | A method of haydite is prepared using domestic sludge cracking gas-producing sintering industrial sludge |
| CN110981130A (en) * | 2019-12-11 | 2020-04-10 | 湖南省建筑设计院有限公司 | Method for judging utilization path of heavy metal polluted bottom mud |
| CN112159063A (en) * | 2020-10-26 | 2021-01-01 | 哈尔滨工业大学 | Sludge pyrolysis safe resource utilization process |
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