CN114769297A - Method for trapping and separating heavy metals in waste incineration fly ash - Google Patents
Method for trapping and separating heavy metals in waste incineration fly ash Download PDFInfo
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
- B09B5/00—Operations not covered by a single other subclass or by a single other group in this subclass
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0066—Preliminary conditioning of the solid carbonaceous reductant
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/10—Dry methods smelting of sulfides or formation of mattes by solid carbonaceous reducing agents
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention discloses a method for trapping and separating heavy metals in waste incineration fly ash. The method takes waste incineration fly ash as a main raw material, biomass as a reducing agent, acid-washing sludge as a trapping agent and a cosolvent, heavy metals in the waste incineration fly ash and the acid-washing sludge are reduced into a metal phase by adopting a melting method, and iron oxide in the acid-washing sludge is reduced into an iron alloy phase solid solution. The reduced heavy metal is enriched in the ferroalloy phase solid solution, so that the heavy metal is captured and the heavy metal pollution is avoided. The acid-washing sludge reduces the viscosity of the slag, and the metal phase and the slag phase are separated through heterogeneous deposition. The invention realizes the cooperative treatment of the waste incineration fly ash, the acid pickling sludge and the biomass, realizes the purpose of treating waste by waste and changing waste into valuable, can use the treated slag as building material aggregate or raw materials of cementing materials and the like, and can use the obtained ferroalloy as a hardening and tempering agent in the metallurgical industry.
Description
Technical Field
The invention relates to the technical field of waste incineration fly ash treatment, in particular to a method for trapping and separating heavy metals in waste incineration fly ash.
Background
Solidification/stabilization treatment technology is the most popular global heavy metal innocent treatment method, and the mobility of heavy metals can be reduced by converting hazardous wastes into chemically stable solids. After the heavy metals are solidified/stabilized, the morphology, mobility and bioavailability of the heavy metals may shift unpredictably over time during service, presenting potential environmental risks. The heavy metal extraction and separation technology separates heavy metals from the waste incineration fly ash, so that the potential risk of the heavy metals to the environment is fundamentally eliminated, and the heavy metal extraction and separation technology has important significance for long-term service of the waste incineration fly ash in the resource treatment process of the waste incineration fly ash.
The waste incineration fly ash is particulate matter in flue gas collected by a dust remover and the like in the waste incineration process. Typically neutralized reactants collected by a cyclone, electrostatic precipitator, or bag-type dust collector. In the process of waste incineration, heavy metals are usually concentrated in fine particles, and part of the heavy metals with lower boiling points are discharged to the environment in gaseous form. Heavy metal with low boiling point volatilizes when the waste is burned, heavy metal steam can be concentrated to form aerosol particles to be captured at a low-temperature section, heavy metal which can not be condensed can be directly absorbed by waste burning fly ash in a steam state, and the main actions of the heavy metal in the process comprise uniform nucleation for generating fine smoke particles and heterogeneous deposition on the surface of the fly ash. The pickling sludge is derived from an acid rolling process in stainless steel production, and the surface of stainless steel is usually pickled by adopting strong acid or mixed acid of hydrofluoric acid, nitric acid, sulfuric acid and the like to remove an oxide layer on the surface of a plate blank. The surface oxide layer reacts with acid to produce a heavy metal-containing pickle liquor whose concentration is highly correlated with the stainless steel composition. The concentrations of the total chromium and the total nickel in the stainless steel pickling waste liquid reach 150mg/L and 100mg/L respectively, and the concentrations seriously exceed the standard. The pickling waste liquid is generally treated by lime neutralization and precipitation, so that the environmental risk is reduced. In the precipitation process, heavy metals such as chromium and nickel enter a slag phase to form acid-washing sludge. The acid-washing sludge contains a large amount of ferric oxide and calcium fluoride, and is a good cosolvent and a trapping agent. The waste incineration fly ash and the acid-washing sludge are dangerous wastes in the name list of Chinese dangerous wastes and contain various and a large amount of potential dangerous heavy metals. The harmless treatment of the acid-washing sludge and the waste incineration fly ash is widely researched at home and abroad.
Solidification/stabilization treatment technology is the most popular global heavy metal innocent treatment method, and the mobility of heavy metals can be reduced by converting hazardous wastes into chemically stable solids. The current state-of-the-art techniques for curing/stabilizing heavy metals include landfill capping, cement curing/stabilization, thermal treatment and electrokinetic remediation. Heat treatment techniques including sintering, vitrification and fusion are currently the most common techniques for the disposal of hazardous waste, including the melting of solid waste at 1100-1500 ℃ to form amorphous or crystalline phases, with heavy metals removed or immobilized during the thermal conversion process. After the heavy metal is solidified/stabilized, the form, mobility and bioavailability of the heavy metal may be unpredictably changed over time in the service process, and the heavy metal has potential environmental risks. The heavy metal extraction and separation technology can separate heavy metals from the waste incineration fly ash, fundamentally eliminates the potential risk of the heavy metals to the environment, and has important significance for realizing the long-term service of the waste incineration fly ash in the resource treatment process. The heavy metal extraction and separation technology uses an extracting agent which is mainly a reagent with higher cost, and the heavy metal is separated after being dissolved in a liquid phase, so that the heavy metal extraction and separation technology has the defects of complex process flow and high cost.
The invention patent CN110607454B (New Zhongtian environmental protection limited company) discloses a method for extracting heavy metals from secondary fly ash generated by burning garbage, which comprises the steps of adding active carbon into the secondary fly ash, mixing uniformly, compressing the mixture into blocks, packaging, wrapping and storing for later use. The method saves the transportation cost by mixing the secondary fly ash of the garbage incineration with the activated carbon and packaging and transporting the mixture, simultaneously adsorbs harmful substances, reduces the damage of the fly ash to the environment, breaks the fly ash into nano particles, adds sodium carbonate into water to dissolve the nano particles completely to prepare a separation solvent, effectively desulfurizes, puffs and permeates the fly ash particles, softens the water quality, improves the effective extraction rate of heavy metals, replaces copper powder by zinc powder, and distills ZnCl by layered filtration2Powder, PbCl2The powder and the magnetic-philic metal impurities have high purity of the heavy metal after effective separation. The invention physically adsorbs the heavy metals in the fly ash by using the activated carbon, then separates the heavy metals by using the separation solvent, and extracts the heavy metals by distillation and magnetic separation.
Chinese invention patent CN201010248266.X (ecological environment research center of Chinese academy of sciences) discloses a method for extracting harmful heavy metals from incineration fly ash by supercritical fluid, Na and K in fly ash and heavy metals in exchange binding state are separated by pretreatment, so as to achieve the purposes of fly ash reduction and harmful heavy metal enrichment; in the supercritical treatment process, a small amount of hydrochloric acid is generated in the reaction process by the action of adding the auxiliary agent in advance, and the hydrochloric acid reacts with harmful heavy metals in the fly ash to dissolve out the heavy metals. Because a small amount of hydrochloric acid is generated in the reaction process, the hydrochloric acid can be consumed by heavy metals in the fly ash in time, and the corrosion to reaction facilities is avoided. The toxicity leaching experiment of the treated solid residue shows that the leaching amount of the heavy metal is lower than the national specified limit value, and the solid residue can be safely buried or recycled. However, the invention adopts supercritical treatment and adds the auxiliary agent, so the process flow is long, the cost is high and the operation is troublesome.
Disclosure of Invention
The invention provides a method for collecting and separating heavy metal in waste incineration fly ash, which is beneficial to realizing the reclamation of dangerous waste in China and has obvious social, economic and environmental benefits. Meanwhile, the waste incineration fly ash, the acid pickling sludge and the biomass are cooperatively treated, so that the waste is treated by waste, the waste is changed into valuable, the treated slag can be used as building material aggregates or raw materials of cementing materials and the like, and the obtained ferroalloy can be used as a modifier in the metallurgical industry.
In order to solve the problems of the prior art, the invention adopts the technical scheme that:
a method for catching and separating heavy metals in waste incineration fly ash is characterized in that the waste incineration fly ash is used as a main raw material, biomass is used as a reducing agent, acid-washing sludge is used as a catching agent and a cosolvent, heavy metals in the waste incineration fly ash and the acid-washing sludge are reduced into a metal phase by adopting a melting method, iron oxide in the acid-washing sludge is reduced into an iron alloy phase solid solution, the reduced heavy metals are enriched into the iron alloy phase solid solution, the heavy metal catching is realized, and the heavy metal pollution is avoided; the acid-washing sludge reduces the viscosity of the slag, and the metal phase and the slag phase are separated through heterogeneous phase deposition.
The method for trapping and separating the heavy metals in the waste incineration fly ash comprises the following steps:
step one, proportioning
30-60 wt.% of waste incineration fly ash, 1-30 wt.% of acid-washed sludge and 20-40 wt.% of biomass, wherein the mass of the waste incineration fly ash, the acid-washed sludge and the biomass is 100 wt.%; the content of iron oxide in the acid-washing sludge is not less than 10 wt.%, and the content of calcium fluoride in the acid-washing sludge is not less than 20 wt.%;
step two, mixing
Uniformly mixing the waste incineration fly ash, the acid-washing sludge and the biomass to obtain a mixture;
step three, melting and heterogeneous separation
Heating and melting the mixture, carrying out heat preservation treatment to realize heavy metal reduction, reducing iron oxide into an iron alloy phase solid solution, and carrying out-phase separation on the melted product to obtain an iron alloy phase and a slag phase; flue gas treatment: the flue gas generated in the melting process is treated by a flue gas quenching device and rapidly cooled to below 200 ℃, so that the secondary synthesis of dioxin is avoided;
step four, discharging the metal phase
Casting the solid solution of the ferroalloy phase through an iron outlet to obtain a metal phase;
step five, deslagging
The slag phase flows out through a slag outlet to obtain a slag phase.
The improvement is that the temperature for heating and melting in the third step is 1100-.
As an improvement, the metal phase in the fourth step is used as a quenching and tempering agent in the metallurgical industry.
And 5, improving the application of the slag phase in the step five in building material aggregate or cementing material.
The principle of the invention for trapping and separating heavy metals in waste incineration fly ash is as follows:
1. reducing ferric oxide and heavy metal in the acid-washing sludge and heavy metal in the waste incineration fly ash by using organic carbon in the biomass to obtain a metal phase, wherein the iron content in the acid-washing sludge is higher to form an iron-containing alloy solid solution, and the heavy metal is trapped in the iron alloy solid solution;
2. the liquid metal has high density, is positioned at the bottom of the melt, has low slag phase density, is positioned at the upper part of the melt, and is layered by heterogeneous deposition of a metal phase and a slag phase;
3. the pickling sludge contains a large amount of calcium fluoride, is a good cosolvent, reduces the viscosity of a slag phase and is easy to deposit a metal phase at the bottom.
Has the advantages that:
compared with the prior art, the method for collecting and separating the heavy metals in the waste incineration fly ash takes the waste incineration fly ash as a main raw material, utilizes biomass as a reducing agent, takes the acid-washed sludge as a collecting agent and a cosolvent, reduces the heavy metals in the waste incineration fly ash and the acid-washed sludge into a metal phase by adopting a melting method, and reduces iron oxide in the acid-washed sludge into an iron alloy phase solid solution. The reduced heavy metal is enriched in the ferroalloy phase solid solution, so that the heavy metal is captured and the heavy metal pollution is avoided. The acid-washing sludge reduces the viscosity of the slag, and the metal phase and the slag phase are separated through heterogeneous deposition. The invention realizes the cooperative treatment of the waste incineration fly ash, the acid pickling sludge and the biomass, realizes the purposes of treating waste by waste and changing waste into valuable, can use the treated slag as building material aggregate or raw materials of cementing materials and the like, and can use the obtained ferroalloy as a modifier in the metallurgical industry, and has the advantages of simple process, low cost, strong operability and high additional value, and the specific summary is as follows:
1. the method for trapping and separating the heavy metals in the waste incineration fly ash solves the problems of low treatment efficiency, high cost, high energy consumption, long process flow and the like of the waste incineration fly ash, thoroughly solves the problem of heavy metal pollution, is favorable for realizing the recycling of hazardous wastes in China, and has remarkable social, economic and environmental benefits;
2. the method is characterized in that waste incineration fly ash, acid-washing sludge and biomass are cooperatively treated to develop a new method for separating and extracting heavy metals in the waste incineration fly ash and the acid-washing sludge;
3. the carbon source in the biomass is used as a reducing agent, so that the cost of the reducing agent is reduced, and the resource utilization of the biomass is realized;
4. the pickling sludge contains a large amount of ferric oxide and calcium fluoride, and can be used as a trapping agent and a cosolvent, so that the energy consumption is reduced, and heavy metal trapping is realized;
5. dioxin in the waste incineration fly ash is decomposed into small molecular chloride after being melted at high temperature, and is rapidly cooled to below 200 ℃ through a flue gas quenching device, so that the dioxin is prevented from being synthesized again;
6. the method utilizes the cooperation of the waste incineration fly ash and the acid-washing sludge, the slag obtained after treatment can be used as building material aggregate or raw materials of cementing materials and the like, the obtained ferroalloy can be used as a modifier in the metallurgical industry, and the added values of the waste incineration fly ash, the acid-washing sludge and the biomass are increased.
Drawings
FIG. 1 is a process flow chart of the method for collecting and separating heavy metals in waste incineration fly ash of the present invention.
Detailed Description
The following examples will give the skilled person a more complete understanding of the present invention, but do not limit the invention in any way.
Waste incineration fly ash: the dust collector and the like collect the particulate matters in the flue gas in the waste incineration process.
Pickling sludge: the stainless steel pickling sludge is derived from an acid rolling process in stainless steel production, and the surface of the stainless steel is usually pickled by adopting strong acid or mixed acid of hydrofluoric acid, nitric acid, sulfuric acid and the like to remove an oxide layer on the surface of a plate blank. The pickling waste liquid is generally treated by lime neutralization and precipitation, so that the environmental risk is reduced. In the precipitation process, heavy metals such as chromium, nickel and the like enter a slag phase to form stainless steel pickling sludge.
Example 1
59 wt.% of waste incineration fly ash, 1 wt.% of acid-washed sludge and 40 wt.% of biomass are uniformly mixed to obtain a mixture, wherein the content of iron oxide in the acid-washed sludge is not lower than 10 wt.%, and the content of calcium fluoride in the acid-washed sludge is not lower than 20 wt.%. The mixture is heated to 1100 ℃ for melting and heat preservation for 3h, and the organic carbon in the biomass is utilized to reduce the heavy metal ions in the waste incineration fly ash and the acid-washing sludge into liquid metal. The iron oxide in the acid-washed sludge is reduced to a solid solution of ferroalloy phase. The reduced heavy metal is enriched in the ferroalloy phase solid solution, so that the heavy metal is captured and the heavy metal pollution is avoided. The liquid metal has high density and is positioned at the bottom of the melt; the slag phase has low density and is positioned at the upper part of the melt. Liquid metal is cast through a taphole to obtain a metal phase, and the metal phase can be used as a quenching and tempering agent in the metallurgical industry; the slag phase flows out through a slag outlet and is naturally cooled to obtain the slag phase which can be used for building materials, thereby realizing high-value utilization. And the flue gas generated in the melting process is subjected to quenching treatment, and is rapidly cooled to below 200 ℃ to avoid the re-synthesis of dioxin.
Experiments were conducted by changing some of the parameter indexes in example 1, specifically as shown in table 1, referring to the operation steps in example 1, and setting examples 2 to 20.
TABLE 1 table for values of different parameters of method for trapping and separating heavy metals in waste incineration fly ash
The invention realizes the cooperative treatment of the waste incineration fly ash, the acid pickling sludge and the biomass, realizes the purpose of treating waste by waste and changing waste into valuable, can use the treated slag as building material aggregate or raw materials of cementing materials and the like, and can use the obtained ferroalloy as a hardening and tempering agent in the metallurgical industry.
Claims (5)
1. A method for catching and separating heavy metals in waste incineration fly ash is characterized in that the waste incineration fly ash is used as a main raw material, biomass is used as a reducing agent, acid-washing sludge is used as a catching agent and a cosolvent, a fusion method is adopted to reduce the heavy metals in the waste incineration fly ash and the acid-washing sludge into a metal phase, iron oxide in the acid-washing sludge is reduced into an iron alloy phase solid solution, and the reduced heavy metals are enriched into the iron alloy phase solid solution, so that heavy metal catching is realized, and heavy metal pollution is avoided; the acid-washing sludge reduces the viscosity of the slag, and the metal phase and the slag phase are separated through heterogeneous phase deposition.
2. The method for collecting and separating the heavy metals in the waste incineration fly ash according to claim 1, specifically comprising the following steps:
step one, preparing materials
30-60 wt.% of waste incineration fly ash, 1-30 wt.% of acid-washed sludge and 20-40 wt.% of biomass, wherein the mass of the waste incineration fly ash, the acid-washed sludge and the biomass is 100 wt.%; the content of iron oxide in the acid-washing sludge is not less than 10 wt%, and the content of calcium fluoride in the acid-washing sludge is not less than 20 wt%;
step two, mixing
Uniformly mixing the waste incineration fly ash, the acid-washing sludge and the biomass to obtain a mixture;
step three, melting and heterogeneous separation
Heating and melting the mixture, carrying out heat preservation treatment to realize heavy metal reduction, reducing iron oxide into an iron alloy phase solid solution, and carrying out-phase separation on the melted product to obtain an iron alloy phase and a slag phase; flue gas treatment: the flue gas generated in the melting process is treated by a flue gas quenching device and rapidly cooled to below 200 ℃, so that the secondary synthesis of dioxin is avoided;
step four, metal phase is produced
Casting the ferroalloy phase solid solution through a taphole to obtain a metal phase;
step five, deslagging
The slag phase flows out through the slag outlet to obtain the slag phase.
3. The method for capturing and separating heavy metals in waste incineration fly ash as claimed in claim 2, wherein the temperature for heating and melting in the third step is 1100-1600 ℃, and the temperature is maintained for 0.5-3.0 h.
4. The method for capturing and separating the heavy metals in the waste incineration fly ash according to claim 2, wherein the metal phase is applied as a conditioner in the metallurgical industry in the fourth step.
5. The method for capturing and separating the heavy metals in the waste incineration fly ash according to claim 2, wherein the slag phase is applied to building aggregate or cementing material in step five.
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| CN118497486A (en) * | 2024-05-30 | 2024-08-16 | 北方工业大学 | A method for preparing ferroalloy and geopolymer materials using waste incineration fly ash and iron tailings |
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