Cooperative integrated treatment method for medical waste incineration slag

Abstract

The invention discloses a cooperative and integrated treatment method for medical waste incineration slag, which comprises the following steps: step 1, crushing, screening and magnetically separating the medical waste incineration slag, and recovering magnetic metal components in the medical waste incineration slag; 2, the slag subjected to magnetic separation in the step 1 is subjected to multi-stage water washing, and filtrate containing soluble salt and heavy metal and purified slag are obtained; 3, sequentially carrying out heavy metal reaction sedimentation treatment and evaporation desalting treatment on the filtrate in the step 2 to realize graded recovery of heavy metals and soluble salts; and 4, drying the slag purified in the step 2, and treating the dried slag through a sand making process to obtain the building raw material. By means of the method, beneficial metal in the medical waste incineration slag can be recycled, the content of heavy metal and soluble salt in the medical waste incineration slag are reduced, and resource utilization of the medical waste incineration slag is achieved.

Description

Technical Field

[0001] This invention relates to the field of solid waste disposal materials technology, and in particular to a synergistic integrated treatment method for medical waste incineration slag. Background Technology

[0002] In recent years, with the continuous development of society, the output of medical waste in my country has also been increasing. How to safely and stably dispose of medical waste has become a key focus of social concern. Among many disposal methods, high-temperature incineration has become the main method for disposing of medical waste in China due to its advantages such as volume reduction and safety. High-temperature incineration of medical waste produces approximately 20-25 wt% medical waste incineration ash. According to the hazardous waste exemption list in the "National Hazardous Waste List (2021 Edition)," the bottom ash produced from medical waste incineration meets the requirements of the "Regulations on the Management of Municipal Solid Waste Landfills." The "Pollution Control Standard" (GB16889) requires medical waste to be disposed of in landfills, and the entire process is not managed as hazardous waste. Medical waste incineration ash contains large amounts of heavy metals, such as nickel, copper, and lead. The heavy metal content in its leachate is far below the requirements for direct landfilling. Furthermore, medical waste incineration ash also contains a large amount of soluble salts, making it difficult to utilize as a building material. Currently, medical waste incineration ash is mainly disposed of centrally through hazardous waste centers, which significantly increases treatment costs.

[0003] Therefore, there is an urgent need to develop a new process for the resource utilization of medical waste incinerator slag to solve the current problem of difficult disposal and recycling of medical waste incinerator slag. Summary of the Invention

[0004] The present invention aims to solve the current problem of how to recycle and utilize medical waste incinerator slag, and provides a synergistic integrated treatment method for medical waste incinerator slag.

[0005] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows: A method for the integrated co-processing of medical waste incinerator slag includes the following steps: Step 1: Crush, screen and magnetically separate the medical waste incinerator slag to recover the magnetic metal components; Step 2: The slag after magnetic separation in Step 1 is subjected to multi-stage water washing to obtain filtrate containing soluble salts and heavy metals and purified slag. Step 3: The filtrate from Step 2 is subjected to heavy metal reaction sedimentation treatment and evaporation desalination treatment in sequence to achieve the graded recovery of heavy metals and soluble salts; Step 4: Dry the slag purified in Step 2, and process the dried slag into building materials through a sand making process.

[0006] Specifically, the recovered magnetic metal components are compounds of iron (Fe), nickel (Ni), and cobalt (Co).

[0007] Specifically, the heavy metals in step 3 include chromium (Cr), nickel (Ni), copper (Cu), lead (Pb), etc. Because these heavy metals are not magnetic, magnetic separation cannot remove them (nickel itself is not magnetic, but some nickel compounds are magnetic).

[0008] Furthermore, in step 1, the sieve aperture is 20-50mm.

[0009] Furthermore, in step 1, the surface magnetic induction intensity during the magnetic separation process is controlled at 5000 GS-10000 GS.

[0010] Furthermore, in step 2, the multi-stage washing includes a primary washing and a secondary washing.

[0011] Furthermore, in the primary water washing method, the mass ratio of slag to water is 1:2, the water washing pH is 2.2-2.5, the water washing temperature is set at 20-40℃, and the water washing time is 2-4 hours.

[0012] Furthermore, in the secondary water washing method, the mass ratio of slag to water after the primary water washing is 1:1.2, the water washing temperature is set at 20-40℃, and the water washing time is 2-4 hours. Furthermore, the heavy metal reaction sedimentation treatment includes the following method: the filtrate is introduced into a heavy metal reaction tank, and a heavy metal precipitant and a flocculant are added to the heavy metal reaction tank. The concentrations of the heavy metal precipitant and the flocculant are 30-100 mg / L and 20-50 mg / L, respectively. The filtrate after the reaction is introduced into a heavy metal sedimentation tank to separate the heavy metal sludge.

[0013] Among them, heavy metal scavengers can complex with heavy metals to form solids, such as inorganic or organic heavy metal scavengers like sodium sulfide, dithiocarbamate, and trithiotriazine trisodium salt; flocculants can accelerate solid precipitation, such as polyaluminum chloride and polyacrylamide.

[0014] Furthermore, in step 3, the evaporation desalination treatment includes the following steps: filtering, evaporating, concentrating, and centrifuging the wastewater after heavy metal reaction sedimentation treatment to obtain soluble salts.

[0015] Furthermore, the evaporation adopts a MED triple-effect evaporator. The steam at the evaporator inlet is steam from the medical waste incinerator boiler, with a temperature of 220-240℃. A heat pump is installed at the steam inlet, which can return part of the steam at the evaporator outlet to the heat pump for reuse.

[0016] Furthermore, in step 4, the drying temperature is 60-70℃; the sand diameter in the sand making process is 2-10mm.

[0017] The present invention has the following beneficial effects: This invention relates to a treatment method specifically designed for medical waste incineration slag, aiming to achieve integrated and coordinated disposal of medical waste incineration slag within medical waste incineration plants. Medical waste incineration slag contains a large amount of recyclable metals, some of which can be recovered and reused after crushing, screening, and magnetic separation. Furthermore, medical waste incineration slag also contains a large amount of heavy metals and soluble salts, posing environmental risks. Additionally, the chloride salts present can affect its strength when used as a building material. Multi-stage washing can separate heavy metals and soluble salts from the slag, enabling the medical waste incineration slag to be used as a recyclable material. The recycling of environmentally friendly and high-strength building material raw materials is achieved through the following processes: the filtrate containing soluble salts and heavy metals generated from water washing undergoes heavy metal reaction sedimentation and evaporation desalination to achieve graded treatment of heavy metals and soluble salts without generating secondary polluted water. Furthermore, the water used in the process can be recycled. High-temperature steam generated from the medical waste incinerator is used as the heat source for evaporation desalination, further reducing the energy consumption of the evaporation process. The slag after water washing has a high water content. The moisture content is reduced by a dryer, and the medical waste incinerator slag, after being processed by a sand making machine, can be directly recycled as a building material. Attached Figure Description

[0018] Figure 1 For process flow diagram; Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Example A method for the integrated co-processing of medical waste incinerator slag, characterized by comprising the following steps: Step 1: Crush, screen, and magnetically separate the medical waste incinerator slag to recover the metal components; The metal components are iron, cobalt, and nickel; the sieve aperture is 50 mm; the sieve tool is not limited to a drum screen; the drum screen has an inclination angle of 5°; the drum screen outlet is connected to a magnetic separator; the slag residue is sent to a crusher for crushing; the crushed slag is then sent back to the drum screen for further sieving; the surface magnetic induction intensity during the magnetic separation process is controlled between 5000 GS and 10000 GS.

[0022] Step 2: The slag after magnetic separation in Step 1 is subjected to multi-stage water washing to obtain filtrate containing soluble salts and heavy metals and purified slag.

[0023] The multi-stage washing process includes primary and secondary washing. In the primary washing method, the mass ratio of slag to water is 1:2, the washing pH is 2.2-2.5, the washing temperature is 30℃, and the washing time is 3 hours. After washing, the slag undergoes solid-liquid separation through a gravity filter. The separated filtrate undergoes subsequent heavy metal reaction sedimentation treatment and evaporation desalination treatment. Specifically, a gas collection hood is installed above the primary washing tank and connected to the primary air fan of the medical waste incinerator, which can send the waste gas generated during the washing process into the incinerator for high-temperature treatment.

[0024] In the two-stage washing method, the mass ratio of slag to water after the first-stage washing is 1:1.2, and the washing time is set to 2 hours. The washed slag is separated into solid and liquid by gravity filter, and the filtrate from the second-stage washing is recycled for use in the first-stage washing tank.

[0025] Step 3: The filtrate from Step 2 is subjected to heavy metal reaction sedimentation treatment and evaporation desalination treatment in sequence to achieve graded recovery of heavy metals and soluble salts.

[0026] The heavy metal reaction sedimentation treatment includes the following method: the filtrate is introduced into the heavy metal reaction tank, and heavy metal scavenging agent and flocculant are added to the heavy metal reaction tank. The concentrations of the heavy metal scavenging agent and flocculant are 30-100 mg / L and 20-50 mg / L, respectively. The filtrate after reaction is introduced into the heavy metal sedimentation tank to separate the heavy metal sludge.

[0027] Evaporation desalination treatment includes the following steps: filtering, evaporating, concentrating, and centrifuging the wastewater after heavy metal reaction sedimentation treatment to obtain soluble salts.

[0028] Specifically, the wastewater is filtered sequentially through a multi-media filter and a precision filter to remove suspended solids and microorganisms. It then flows into a MED triple-effect evaporator. The concentrated liquid is collected using a thickener, and soluble salts are separated by a centrifuge and transported off-site for processing. The evaporator inlet steam is sourced from the medical waste incinerator boiler, with a temperature of 220-240℃. A heat pump is installed at the steam inlet, allowing a portion of the evaporator outlet steam to be recycled back to the heat pump for reuse.

[0029] Step 4: Dry the slag purified in Step 2, and process the dried slag into building materials through a sand making process.

[0030] In step 4, the slag is dried by a DC rotary dryer. The hot air used for drying is provided by a steam heat exchanger. The steam source is low-temperature steam discharged from the desalination process, and the temperature is 60-70℃. The diameter of the sand produced in the sand making process is 2-10mm.

[0031] Test case In step 1, the magnetic separation recovery rate was 21.14%. It should be noted that magnetic separation recovers all magnetic materials, including magnetic metals and some magnetic slag. In step 2, the remaining mass of the slag after water washing was 70.28% of the initial mass, and the overall slag recovery rate was 98.42%. In step 3, 0.21% of heavy metal sludge was separated. In the evaporation desalination process, a total of 1.24% of soluble salts were separated.

[0032] The content of some heavy metals in the slag leachate was determined by ICP-MS, as shown in Table 1. It should be noted that this leachate was obtained by first drying the original slag and the washed slag, then soaking and filtering it with acid solution. The heavy metal content in the filtrate was then measured. Environmental standards in many countries have requirements for the heavy metal content in leachate, such as the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" and the "Pollution Control Standard for Municipal Solid Waste Landfills". The contents of Cr, Ni, Cu and Ba in the untreated original medical waste incineration slag are relatively high. Among them, the leaching content of Ni is 19 times the limit of GB16889-2024 "Pollution Control Standard for Municipal Solid Waste Landfills". Furthermore, the average Ni content was 191.6 mg / Kg, exceeding the soil pollution risk screening value of 100 mg / Kg in GB15618-2018 "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)"; the average Cu content was 364.08 mg / Kg, also exceeding the soil pollution risk screening value of 100 mg / Kg in GB 15618-2018 "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)". After secondary washing, the heavy metal leaching content of the slag was significantly reduced, with the leaching concentrations of Cr, Ni, Cu, and Ba decreasing by 96.75%, 96.94%, 94.12%, and 88.40%, respectively, and meeting the standard limit requirements of GB18599-2001 "Pollution Control Standard for General Industrial Solid Waste Storage and Disposal Sites" (2013 revised edition). Testing revealed that the water-soluble chloride ion content in the untreated medical waste incineration slag was 6.40 g / kg, exceeding the maximum chloride ion content of 0.6 g / kg for 100-year concrete structures required by GB 50010-2010 "Code for Design of Concrete Structures," representing 10.6 times the standard limit. After secondary washing, the water-soluble chloride ion content of the slag decreased to 0.53 g / kg, a reduction of 91.72%, and still met the standard limit of GB 50010-2010 "Code for Design of Concrete Structures." The pH value of the slag after secondary washing was 6.73. The leaching concentration of heavy metals and pH value of the washed slag met the limit requirements of GB5085.3-2007 "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" and GB5085.1-2007 "Identification Standard for Hazardous Waste: Corrosivity Identification." In conclusion, the washed slag is classified as general industrial solid waste and can be recycled as building materials.

[0033] Table 1 Heavy Metal Content Detection Table Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0034] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for the integrated co-processing of medical waste incinerator slag, characterized in that, Includes the following steps: Step 1: Crush, screen and magnetically separate the medical waste incinerator slag to recover the magnetic metal components; Step 2: The slag after magnetic separation in Step 1 is subjected to multi-stage water washing to obtain filtrate containing soluble salts and heavy metals and purified slag. Step 3: The filtrate from Step 2 is subjected to heavy metal reaction sedimentation treatment and evaporation desalination treatment in sequence to achieve the graded recovery of heavy metals and soluble salts; Step 4: Dry the slag purified in Step 2, and process the dried slag into building materials through a sand making process.

2. The method for the integrated treatment of medical waste incineration slag according to claim 1, characterized in that, In step 1, the sieve aperture is 20-50mm.

3. The method for the integrated treatment of medical waste incineration slag according to claim 1, characterized in that, In step 1, the surface magnetic induction intensity during the magnetic separation process is controlled between 5000 GS and 10000 GS.

4. The method for the integrated co-processing of medical waste incinerator slag according to claim 1, characterized in that, In step 2, the multi-stage washing includes a primary washing and a secondary washing.

5. The method for the integrated treatment of medical waste incineration slag according to claim 4, characterized in that, The mass ratio of slag to water is 1:2, the pH of the water washing is 2.2-2.5, the water washing temperature is set at 20-40℃, and the water washing time is 2-4 hours.

6. The method for the integrated treatment of medical waste incineration slag according to claim 4, characterized in that, In the secondary water washing method, the mass ratio of slag to water after primary water washing is 1:1.2, the water washing temperature is set at 20-40℃, and the water washing time is 2-4 hours.

7. The method for the integrated co-processing of medical waste incinerator slag according to claim 1, characterized in that, The heavy metal reaction sedimentation treatment includes the following method: the filtrate is passed into a heavy metal reaction tank, and a heavy metal precipitant and a flocculant are added to the heavy metal reaction tank. The concentrations of the heavy metal precipitant and the flocculant are 30-100 mg / L and 20-50 mg / L, respectively. The filtrate after the reaction is passed into a heavy metal sedimentation tank to separate the heavy metal sludge.

8. The method for the integrated treatment of medical waste incineration slag according to claim 1, characterized in that, In step 3, the evaporation desalination process includes the following steps: filtering, evaporating, concentrating, and centrifuging the wastewater after heavy metal reaction sedimentation to obtain soluble salts.

9. The method for the integrated treatment of medical waste incineration slag according to claim 8, characterized in that, Evaporation uses a MED triple-effect evaporator. The steam at the evaporator inlet is steam from the medical waste incinerator boiler, with a temperature of 220-240℃. A heat pump is installed at the steam inlet, which can return part of the steam at the evaporator outlet to the heat pump for reuse.

10. The method for the integrated co-processing of medical waste incinerator slag according to claim 1, characterized in that, In step 4, the drying temperature is 60-70℃; the sand diameter in the sand making process is 2-10mm.

Images