A method for reusing and processing waste incineration fly ash
By sintering and washing fly ash after pelletizing it, the problem of incomplete removal of chloride salts and thermally stable heavy metals in existing technologies has been solved, enabling low-cost and efficient fly ash reuse. The resulting dry slag can be used in building materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN ZHIHENG ENVIRONMENTAL SAFETY ENG TECH CO LTD
- Filing Date
- 2023-11-22
- Publication Date
- 2026-08-04
AI Technical Summary
Existing technologies struggle to effectively remove chlorides and some thermally stable heavy metals when processing fly ash from waste incineration. This can lead to the ash potentially corroding steel reinforcement when used as a building material, and the process is complex and costly.
First, fly ash is granulated and then sintered to remove dioxins and heat-sensitive heavy metals. Then, the sintered fly ash is quenched and washed with water to remove soluble heavy metals and chloride salts. The resulting dry slag can be used as a raw material for building material preparation and can also be recycled from flue gas and chlorine-containing wastewater.
This method achieves efficient removal of harmful substances from fly ash, reduces costs, improves resource recycling rates, and produces dry slag suitable as a building material raw material.
Smart Images
Figure CN117443911B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of incineration fly ash treatment technology, specifically to a method for recycling and treating waste incineration fly ash. Background Technology
[0002] Currently, common methods for treating and disposing of municipal solid waste include landfill, incineration, and composting. Among these, incineration has advantages such as high volume reduction, high waste reduction, and destruction of toxic and hazardous substances, and is widely adopted by various countries. However, along with municipal solid waste incineration, a large amount of fly ash is generated, which accumulates heavy metals, soluble chlorides, dioxins, and other persistent organic pollutants. Pollution control during the collection, storage, transportation, pretreatment, resource recovery, and landfill disposal of incineration fly ash is crucial to its environmental impact.
[0003] For example, patent CN103822211A discloses a method for the gelling and sintering treatment of waste incineration fly ash, including: S1, pre-treating the waste incineration fly ash before sintering to form solidified fly ash; S3, transporting the solidified fly ash to an incinerator for sintering municipal solid waste, and generating accumulated waste incineration fly ash. This method utilizes the incinerator used in waste incineration for sintering, requiring only that the waste incineration fly ash and municipal solid waste be transported together to the incinerator for combustion. No additional sintering conditions or equipment are needed, and no additional technical difficulties need to be overcome. It is low-cost, has a short process, is easy to operate, and is convenient to implement and widely applicable in engineering projects. Furthermore, during the gelling and sintering process, the heavy metals and dioxins in the waste incineration fly ash are burned at high temperatures, resulting in stable sintered slag that does not pollute the environment and can be utilized as a resource.
[0004] The above-mentioned scheme discloses a method of solidifying the fly ash from waste incineration and then sending it into the incinerator to be sintered together with municipal solid waste. Sintering the fly ash can remove most of the heavy metals and dioxins in the fly ash, but some chloride salts and some thermally stable heavy metals are still not removed. When the ash is used as a building material, the chloride salts in the ash may corrode the steel bars, causing adverse effects.
[0005] For example, patent CN104070054B discloses a method for reducing the volume of waste incineration fly ash through sintering. This technology is particularly suitable for the treatment and disposal of waste incineration fly ash with a salt content of less than 20%. By adding a dechlorination flux to the fly ash, the volatilization of heavy metals and the decomposition of dioxins are enhanced. Heavy metals and chlorides are highly concentrated in the secondary fly ash within a relatively low temperature range. Further enrichment of pollutants and reduction of fly ash volume are achieved through water washing of the secondary fly ash. After washing, the fly ash is returned to a rapid sintering unit for complete degradation of dioxin-like pollutants. The washing liquid is evaporated and concentrated using the waste heat of the sintering system to recover salt. The concentrated liquid and sludge obtained from evaporation, as well as the sintered body obtained above, are either safely landfilled or recycled.
[0006] This patented method involves adding a dechlorination flux to fly ash, causing chloride salts to volatilize into the flue gas during fly ash sintering. The secondary fly ash is then washed with water to remove chloride salts. While this method can remove chloride salts, it has drawbacks. It requires the collection and rapid cooling of the secondary fly ash, making it difficult to effectively utilize the thermal energy of the secondary fly ash. Furthermore, the secondary sintering of the fly ash is a complex and energy-intensive process, resulting in high costs.
[0007] For example, patent CN115646442A discloses a method for preparing adsorbents using fly ash from municipal solid waste incineration, belonging to the field of adsorbent preparation. The method includes: S1, preparing an ash carrier: removing harmful gases from the fly ash; water washing pretreatment: adding a measured amount of water to the fly ash and soaking it; alkaline washing pretreatment: adding sodium hydroxide solution to the fly ash, soaking it, and then washing it with water; S2, mixing: mixing the medium-ash carrier with sodium tetraborate decahydrate and calcium carbonate in a certain mass ratio, adding a small amount of deionized water, mixing and stirring until viscous, and then forming the stirred raw materials into spherical materials; S3, sintering: placing the prepared spherical materials into a high-temperature tubular resistance furnace for calcination to obtain the adsorbent material; S4, modification: using zinc sulfate solution and ammonia water to modify the processed adsorbent material, followed by sintering to obtain the adsorbent.
[0008] This patent uses a method of washing with water before sintering, which can remove chloride salts. However, the fly ash after washing with water needs to be dried. Natural drying takes a long time and occupies a large area, while forced drying requires an external heat source and has high energy consumption. It is also easy to generate secondary dust during transportation. In addition, the wastewater from the water washing process contains a large number of heavy metal ions, which makes it inconvenient to recycle chloride salts and increases costs. Summary of the Invention
[0009] The purpose of this invention is to address the problems existing in the prior art by providing a method for the reuse and treatment of waste incineration fly ash. The fly ash is first granulated and then sintered to remove dioxins and heat-sensitive heavy metals. The sintered fly ash is then quenched and washed with water to remove soluble heavy metals and chloride salts. The resulting dry slag contains fewer harmful substances and can be used as a raw material for building material preparation.
[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for recycling and treating fly ash from waste incineration includes the following steps: S1. Add modifier to fly ash from waste incineration and use mechanical molding to obtain fly ash pellets; S2. The fly ash pellets are preheated and then sintered to discharge medium-temperature flue gas; S3. The sintered fly ash particles are quenched with water to form ash residue. The ash residue is washed with water to form wet residue and chlorine-containing wastewater. The wet residue is dehydrated to form dry residue.
[0011] Fly ash, water, and the modifier are initially mixed according to a predetermined mass ratio after being metered, and then stirred and mixed by a mixer to achieve uniform mixing of fly ash and modifier, forming a gel solid. The gel solid is then fed into a granulator and extruded to obtain fly ash granules.
[0012] The fly ash particles are placed in a cool, ventilated environment for curing, which increases the strength of the fly ash particles and solidifies some of the heavy metal components.
[0013] The medium-temperature flue gas is subjected to secondary combustion to form high-temperature flue gas. The high-temperature flue gas is then introduced into a waste heat boiler for heat exchange to form low-temperature flue gas. The low-temperature flue gas is then introduced into a purification device for purification to obtain purified flue gas and concentrated fly ash. A solidifying agent and a chelating agent are added to the concentrated fly ash to obtain stable fly ash, which is then landfilled.
[0014] Before entering the waste heat boiler, a portion of the high-temperature flue gas is introduced into a preheating device for heat exchange with the fly ash particles. After the heat exchange, the flue gas with a lower temperature merges with the flue gas from the waste heat boiler outlet and enters the purification device.
[0015] Flocculant and softener are added to the chlorine-containing wastewater to form sludge sediment. The supernatant is then filtered using a first filter membrane to obtain a chlorine-containing solution. The sludge is added to the wet sludge and dried together to form dry sludge.
[0016] The chlorine-containing solution is filtered through a second filter membrane to obtain a divalent ion solution and a monovalent ion salt solution. The monovalent ion salt solution is then filtered through a third filter membrane to obtain purified water and a concentrated chloride salt solution. The concentrated chloride salt solution is then evaporated and crystallized to obtain refined chloride salt.
[0017] The divalent ion solution is filtered through a fourth filter membrane to obtain purified water and a concentrate. A solidifying agent and a chelating agent are added to the concentrate to obtain stable fly ash, which is then landfilled.
[0018] Compared with the prior art, the beneficial effects of the present invention are: First, fly ash is granulated and then sintered to remove dioxins and heat-sensitive heavy metals. Then, the sintered fly ash is quenched and washed with water to remove soluble heavy metals and chloride salts. The resulting dry slag contains fewer harmful substances and can be used as a raw material for building material preparation.
[0019] The sintering flue gas is used to preheat the pellets, and the resulting chlorine-containing wastewater is filtered to obtain refined salt and purified water. The purified water is used for conditioning, water quenching, and water washing, resulting in high resource recycling rate and lower cost. Attached Figure Description
[0020] Figure 1 This is an overall flow chart of the waste incineration fly ash reuse treatment method of the present invention; Figure 2 This is a flowchart of the preprocessing process of the present invention; Figure 3 This is a flowchart of the sintering process and flue gas treatment of the present invention; Figure 4 This is a flowchart of the ash and chlorine-containing wastewater treatment process of the present invention. Detailed Implementation
[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely 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.
[0022] like Figures 1 to 4 As shown, a method for recycling and treating fly ash from waste incineration includes the following steps: S1. Add modifier to fly ash from waste incineration and use mechanical molding to obtain fly ash pellets; Modifiers are used to agglomerate fly ash into clumps. Mechanical forming can be accomplished by using a granulator to compress large ash clumps into fly ash granules with a certain strength, which facilitates transportation, reduces secondary ash generation during sintering, and increases the volatilization rate of heavy metals during sintering.
[0023] S2. After preheating the fly ash pellets, sinter them and discharge the medium-temperature flue gas; heat and sinter the pellets at a temperature of 600-900℃ to remove decomposable and volatile organic substances and some heavy metals from the pellets through pyrolysis.
[0024] S3. The sintered fly ash particles are quenched with water to form ash residue. The ash residue is washed with water to form wet residue and chlorine-containing wastewater. The wet residue is dehydrated to form dry residue. The granules are quenched and washed (rinsing / soaking / washing) to remove soluble salts from the quenched slag. Sodium chloride / potassium chloride in the soluble salt solution is then separated and recovered using softening precipitation, membrane separation (UF, NF, RO / DTRO) and concentration crystallization. This process transforms fly ash into a raw material for building material preparation that meets reuse requirements (dioxins 30 ng-teq / kg, heavy metals meeting national standards, and soluble chlorine <2%). At the same time, most of the chloride salts in the fly ash are separated and recovered.
[0025] This application first granulates fly ash and then sinters it to remove dioxins and heat-sensitive heavy metals. Then, the sintered fly ash is quenched and washed with water to further remove soluble heavy metals and chloride salts. The final dry slag has fewer harmful substances and can be used as a raw material for building material preparation.
[0026] This application uses the sintering flue gas for preheating the pellets, filters the resulting chlorine-containing wastewater to obtain refined salt and purified water, and uses the purified water for conditioning, water quenching, and water washing, resulting in high resource recycling rate and lower cost.
[0027] The modifier is prepared by mixing a gelling agent, a fluxing agent, and a reducing agent in a mass ratio of 15:3:6. The gelling agent is made from a silicon-aluminum based gelling material, the fluxing agent is made from industrial waste residue, and the reducing agent is a carbon-based mineral material, such as pulverized coal or petroleum coke powder.
[0028] Fly ash, water, and a modifier are initially mixed at a mass ratio of 100:8–16:5–15, and then stirred in a mixer for 5–10 minutes to ensure uniform mixing and the formation of a gelatinous substance. This gelatinous substance is then fed into a granulator and extruded to produce fly ash granules with a diameter of 10–30 mm. The granulator is existing technology; for example, it can utilize two grooved rollers that roll together.
[0029] To stabilize fly ash pellets, they should be cured in a humid environment at 25–30°C with warm air for 3–7 days to increase their strength and solidify some heavy metal components. Alternatively, a curing container can be used, with warm air continuously flowing into it to improve curing efficiency.
[0030] The temperature range of the medium-temperature flue gas emitted after sintering is 600–900℃. To reduce the harmful substances in the secondary flue gas after sintering, the flue gas from fly ash sintering needs to reach above 900℃ and be maintained for a certain period of time to remove harmful substances. Therefore, the medium-temperature flue gas undergoes secondary combustion to form high-temperature flue gas of 900–1000℃. This high-temperature flue gas is then introduced into a waste heat boiler for heat exchange, reducing its temperature to 100–200℃. The low-temperature flue gas is then purified by a purification device to obtain purified flue gas and concentrated fly ash. A solidifying agent and a chelating agent are added to the concentrated fly ash to produce stable fly ash, which is then landfilled. The chelating agent is an organic sulfide, which reacts with heavy metals to form stable complexes, meeting the landfill requirements for heavy metal leaching concentration limits.
[0031] In order to achieve rational use of resources and save energy, a portion of the high-temperature flue gas before entering the waste heat boiler is introduced into a preheating device to exchange heat with the fly ash particles. After the heat exchange, the temperature of the flue gas drops to about 200°C and merges with the flue gas from the outlet of the waste heat boiler into the purification device.
[0032] Chlorine-containing wastewater from washing contains a significant amount of sludge and calcium and magnesium ions. The sludge needs to be filtered first. Flocculants and softeners are added to the chlorine-containing wastewater to form sludge sediment. The supernatant is then filtered through a first filtration membrane, such as a UF membrane, to obtain a chlorine-containing solution. The sludge is then added to the wet sludge mixture and dried together to form dry sludge. The flocculant used is an aqueous solution prepared from an inorganic flocculant (such as aluminum sulfate) and an organic anionic flocculant, polyacrylamide (PAM). This solution is added to the wastewater, causing compression of the electrical double layer, destabilizing the suspended particles in the wastewater. The particles aggregate, increasing in size and forming flocs. Once the flocs reach a certain size, they detach from the aqueous phase under gravity, thus removing a large amount of suspended solids and achieving water treatment. Sodium bicarbonate solution can be used as a softener, which also helps to precipitate some of the calcium and magnesium ions in the chlorine-containing wastewater.
[0033] After removing sludge and most of the calcium and magnesium ions, the chlorine-containing solution is filtered through a second filtration membrane, such as a nanofiltration membrane, to obtain a divalent ion solution and a monovalent ion salt solution in a mass ratio of 1:4. The monovalent ion salt solution contains Na+. + K + Cl - NO3 - H - OH - Etc., divalent ion solutions contain Ca 2+ Mg 2+ SO2 2- CO 2- The monovalent ion salt solution is filtered through a third filtration membrane, such as an RO reverse osmosis membrane, to obtain purified water and concentrated chloride solution. The concentrated chloride solution is then evaporated and crystallized to obtain refined chloride salt.
[0034] The divalent ion solution is filtered through a fourth filter membrane, such as a DTRO reverse osmosis filter membrane, to obtain purified water and concentrate. A solidifying agent and a chelating agent are added to the concentrate to produce stable fly ash, which is then landfilled.
[0035] The purified water obtained through the above steps can be returned to fly ash conditioning, water quenching, water washing, and waste heat boiler heat exchange, thereby improving resource utilization and saving energy.
[0036] 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.
Claims
1. A waste incineration fly ash recycling treatment method, characterized by, Includes the following steps: S1. Add modifier to fly ash from waste incineration and use mechanical molding to obtain fly ash pellets; S2. The fly ash agglomerates are preheated and then sintered to discharge medium-temperature flue gas. The medium-temperature flue gas is then subjected to secondary combustion to form high-temperature flue gas. A portion of the high-temperature flue gas is introduced into a preheating device for heat exchange with the fly ash agglomerates, and the remainder is introduced into a waste heat boiler for heat exchange to form low-temperature flue gas. The flue gas whose temperature drops after heat exchange with the fly ash agglomerates is combined with the low-temperature flue gas from the outlet of the waste heat boiler and enters a purification device to obtain purified flue gas and concentrated fly ash. A solidifying agent and a chelating agent are added to the concentrated fly ash to obtain stable fly ash, which is then landfilled. S3. The sintered fly ash particles are quenched with water to form ash residue. The ash residue is washed with water to form wet residue and chlorine-containing wastewater. The wet residue is dehydrated to form dry residue.
2. The method of claim 1, wherein the fly ash is obtained from a waste incineration plant. Fly ash, water, and the modifier are initially mixed according to a predetermined mass ratio after being metered, and then stirred and mixed by a mixer to achieve uniform mixing of fly ash and modifier, forming a gel solid. The gel solid is then fed into a granulator and extruded to obtain fly ash granules.
3. The method of claim 1, wherein the fly ash is obtained from a waste incineration plant. The fly ash particles are placed in a cool, ventilated environment for curing, which increases the strength of the fly ash particles and solidifies some of the heavy metal components.
4. The method of claim 1, wherein the fly ash is obtained from a waste incineration plant. The temperature range of the low-temperature flue gas is 100–200°C, the temperature range of the medium-temperature flue gas is 600–900°C, and the temperature range of the high-temperature flue gas is 900–1000°C.
5. The method of claim 1, wherein the fly ash is obtained from a waste incineration plant. Flocculant and softener are added to the chlorine-containing wastewater to form sludge sediment. The supernatant is then filtered using a first filter membrane to obtain a chlorine-containing solution. The sludge is added to the wet sludge and dried together to form dry sludge.
6. The method of claim 5, wherein the fly ash is obtained from a waste incineration plant. The chlorine-containing solution is filtered through a second filter membrane to obtain a divalent ion solution and a monovalent ion salt solution. The monovalent ion salt solution is then filtered through a third filter membrane to obtain purified water and a concentrated chloride salt solution. The concentrated chloride salt solution is then evaporated and crystallized to obtain refined chloride salt.
7. The method of claim 6, wherein the fly ash is obtained from a waste incineration plant. The divalent ion solution is filtered through a fourth filter membrane to obtain purified water and a concentrate. A solidifying agent and a chelating agent are added to the concentrate to obtain stable fly ash, which is then landfilled.
8. The method of claim 1, wherein the fly ash is obtained from a waste incineration plant. The modifier is prepared by mixing a gelling agent, a fluxing agent, and a reducing agent in a mass ratio of 15:3:
6. The gelling agent is made from a silicon-aluminum based gelling material, the fluxing agent is made from industrial waste residue, and the reducing agent is made from a carbon-based mineral material.