Method and device for preparing deacidifier from domestic waste incineration fly ash

Abstract

The present invention relates to a method and device for preparing a deacidifier from domestic waste incineration fly ash. The method comprises the following steps: primary conversion: converting various types of minerals in domestic waste incineration fly ash into metal carbonate minerals; secondary conversion: converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high-alkalinity deacidifier; and optionally, tertiary conversion before deacidification application: hydrating the metal oxides to enable same to become a deacidifier having high activity, wherein the domestic waste incineration fly ash is generated by deacidification of domestic waste incineration flue gas, the primary conversion is carried out in an aqueous solution and a conversion reagent comprises water-soluble carbonate and / or water-soluble bicarbonate, and the secondary conversion is carried out at a temperature exceeding 700°C. The method of the present invention realizes harmlessness, reduction and resource utilization of domestic waste incineration fly ash, prevents environmental release and ecological burden of toxic and harmful substances, and has good techno-economic feasibility.

Description

A method and equipment for preparing deacidifying agent from fly ash of municipal solid waste incineration Technical Field

[0001] This invention relates to the field of waste treatment technology, specifically to a method and equipment for preparing a deacidifying agent from fly ash from municipal solid waste incineration. Background Technology

[0002] Fly ash from municipal solid waste incineration is a secondary pollutant that is trapped and settled during the flue gas purification process of municipal solid waste incineration systems. It accounts for approximately 3-5% of the total incinerated waste and easily accumulates high concentrations of heavy metals such as lead (Pb), chromium (Cr), mercury (Hg), cadmium (Cd), and copper (Cu), with concentrations exceeding soil background levels by 10-100 times. Furthermore, the salt content in fly ash is as high as 20-30%. Fly ash is recognized as hazardous waste both domestically and internationally, and its safe disposal has become a global issue. Currently, the main treatment technologies for municipal solid waste incineration fly ash include safe landfill after stabilization and solidification, co-processing in cement kilns, and sintering and vitrification followed by use as aggregate.

[0003] As a pretreatment step for safe landfilling, stabilization technologies mainly include chemical stabilization and physical-thermal stabilization. Chemical stabilization aims to reduce the toxicity of substances in fly ash by adding stabilizers, thereby lowering the leaching risk and reducing the environmental risk associated with toxic substances, especially heavy metals. Commonly used organic stabilizers include dithiocarbamates (DTC), mercaptopolyamines, EDTA polymers, and sulfur-containing polysaccharides; inorganic stabilizers include lime, sodium sulfide, sulfates, phosphates, carbonates, silicates, and iron oxides. Thermal stabilization and thermal sintering involve heating the fly ash to a temperature at which particle bonding occurs and reorganizing the chemical phases within the fly ash. Generally, the temperature for such thermal stabilization processes is between 1000 and 1200°C, and stabilizers are often added synergistically. The sintered product has reduced porosity, high strength, and is difficult for heavy metals to leach. The drawbacks of stabilization technology are that the stabilizer itself may slowly decompose and degrade in the environment, so its long-term stability is not reliable; in room temperature stabilization / solidification landfill, water-soluble salts can cause the solidified body to crack, leading to the leaching of heavy metals.

[0004] Cement kiln co-processing technology involves adding fly ash to cement raw materials during cement production and sintering them together (1200–1500℃) to co-process fly ash from municipal solid waste incineration. This technology offers significant social and environmental benefits, is mature, and has a well-established standard system. However, a drawback is that toxic heavy metals are actually transferred to the cement product and can be released back into the environment during the cement's use and life cycle. Cement kiln co-processing has strict limits on chloride salts in fly ash, requiring deep washing of the fly ash beforehand.

[0005] Fly ash contains a large amount of valuable metals such as zinc, lead, and copper. The academic and industrial communities have long developed numerous extraction and leaching technologies for these metals in municipal solid waste incineration fly ash. Chemical extraction technology aims to extract these valuable metals through the addition of specific extractants for recycling. Commonly used extractants include hydrochloric acid, nitric acid, sulfuric acid, sodium hydroxide, sodium carbonate, ammonia, and chelating agents; among these, sulfuric acid, hydrochloric acid, and nitric acid can extract most metals; sodium hydroxide and sodium carbonate can selectively extract amphoteric metals such as Zn and Pb. However, the drawback of chemical extraction technology is the need for large amounts of acidic or alkaline extractants, and the regeneration of these extractants is also relatively difficult. Therefore, the industry has been seeking environmentally friendly methods for the treatment of municipal solid waste incineration fly ash. Summary of the Invention

[0006] Therefore, on the one hand, the present invention provides a method for preparing a deacidifying agent from fly ash of municipal solid waste incineration, which includes the following steps:

[0007] The primary conversion process transforms various types of minerals in the fly ash from municipal solid waste incineration into metallic carbonate minerals.

[0008] Secondary conversion transforms the obtained metallic carbonate minerals into corresponding metal oxides, yielding a high-alkalinity deacidifying agent; and

[0009] Optionally, the three-stage conversion before deacidification application hydrates the metal oxide, giving it high deacidification activity.

[0010] The fly ash from the municipal solid waste incineration is generated from the deacidification treatment of the flue gas from the municipal solid waste incineration.

[0011] The primary conversion is carried out in an aqueous solution and the conversion reagent contains water-soluble carbonates and / or water-soluble bicarbonates.

[0012] The secondary conversion is carried out at temperatures exceeding 700°C.

[0013] On the other hand, the present invention provides a method for preparing a deacidifying agent from fly ash from municipal solid waste incineration, the method comprising:

[0014] The primary conversion involves adding an aqueous solution of water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the municipal solid waste incineration fly ash, stirring and reacting to convert various types of minerals in the municipal solid waste incineration fly ash into metallic carbonate minerals.

[0015] In the secondary conversion, after the primary conversion and liquid-solid separation, the resulting solid powder of metallic carbonate minerals is subjected to a secondary conversion at a temperature >700℃ to form metallic oxides, yielding a high-alkalinity deacidifying agent; and

[0016] The three-stage transformation before deacidification application hydrates the metal oxides to give them high deacidification activity.

[0017] Furthermore, this invention provides a method for preparing a deacidifying agent from fly ash from municipal solid waste incineration, comprising the following steps:

[0018] (1) Before the primary conversion, the fly ash from the municipal solid waste incineration is first washed with water to remove water-soluble components, especially metal salts and chloride-containing salts, and then the washed fly ash is obtained by liquid-solid separation.

[0019] (2) Add an aqueous solution of water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the water-washed fly ash, stir and react, and convert the various types of minerals in the water-washed fly ash into metallic carbonate minerals through primary conversion.

[0020] (3) After a second liquid-solid separation, the resulting solid powder of metallic carbonate minerals is subjected to a secondary conversion into metal oxides at a temperature >700℃ to obtain a high-alkalinity deacidifying agent; and

[0021] (4) The three-stage transformation before deacidification application hydrates the metal oxide to give it high deacidification activity.

[0022] In a preferred embodiment, the conversion reagents used for the primary conversion include sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate solution, or any combination thereof. The conversion solution of ammonium carbonate and / or ammonium bicarbonate can be prepared on-site by passing carbon dioxide through an ammonia solution.

[0023] In a preferred embodiment, the concentration range of the aqueous conversion reagent is 0.1-5.0M; and / or, the liquid-to-solid ratio of the aqueous conversion reagent to fly ash is (1-100):1; and / or, the temperature range of the primary conversion is 0-100℃; and / or, the time of the primary conversion is 0.5-48h.

[0024] Preferably, the concentration range of the aqueous solution of the conversion reagent in the primary conversion is 0.5-4.5M, the liquid-solid ratio of the aqueous solution of the conversion reagent to fly ash in the primary conversion is (2-20):1, and the primary conversion time is 1-24h.

[0025] In a preferred embodiment, the conversion reagent further includes an auxiliary agent, wherein the auxiliary agent is carbon dioxide.

[0026] In a preferred embodiment, the conversion reagents for ammonium carbonate and / or ammonium bicarbonate are prepared on-site by passing carbon dioxide through an aqueous ammonia solution.

[0027] In a preferred embodiment, the municipal solid waste incineration fly ash is generated by treating the flue gas from municipal solid waste incineration fly ash using the lime method, wherein the flue gas treatment method includes at least one of wet, semi-wet and dry methods; or, the municipal solid waste incineration fly ash is untreated fly ash and / or aged fly ash.

[0028] Preferably, the silica content in the fly ash from municipal solid waste incineration does not exceed 20% by weight, more preferably not more than 10% by weight.

[0029] In a preferred embodiment, the metal carbonate minerals are preferably dried before the secondary conversion after the primary conversion to generate metal carbonate minerals and liquid-solid separation, at a drying temperature of 40-300℃.

[0030] In a preferred embodiment, the method of the present invention further includes the following steps: reusing the obtained deacidifying agent for flue gas treatment of municipal solid waste incineration fly ash, and then repeating the method of the present invention for preparing deacidifying agent from municipal solid waste incineration fly ash.

[0031] Finally, the present invention also provides an apparatus for preparing a deacidifying agent from fly ash of municipal solid waste incineration, comprising:

[0032] --Fly ash collection device, used to collect fly ash from municipal solid waste incineration;

[0033] --Reaction device, used to convert various types of minerals in fly ash from municipal solid waste incineration into metallic carbonate minerals;

[0034] --A heat treatment apparatus for converting the obtained metallic carbonate minerals into corresponding metallic oxides to obtain a high-alkalinity deacidifying agent; and

[0035] --Optionally, a hydration device is used to hydrate metal oxides to give them high deacidification activity.

[0036] In a preferred embodiment, the device further includes a washing device located between the fly ash collection device and the reaction device.

[0037] This invention achieves the harmlessness, volume reduction, and resource recovery of hazardous solid waste fly ash from municipal solid waste incineration, effectively addressing the environmental release and ecological burden of toxic and harmful substances from this type of waste. The invention uses a two-stage conversion process to prepare a high-alkalinity metal oxide deacidifying agent from municipal solid waste incineration fly ash. Before deacidification application, a tertiary conversion process hydrates the metal oxide, giving it high deacidification activity. The technical and economic feasibility of this invention is excellent, with processing costs only a few hundred yuan. It produces a reusable deacidifying agent and zinc- and lead-rich materials, resulting in a profit margin. Attached Figure Description

[0038] Figure 1 shows a process flow diagram of one embodiment of the method according to the present invention;

[0039] Figure 2(a) shows a scanning electron microscope image of the original fly ash (i.e., before water washing) in Example 1;

[0040] Figure 2(b) shows a scanning electron microscope image of the fly ash after water washing in Example 1;

[0041] Figure 2(c) shows a scanning electron microscope image of the fly ash after water washing / calcination in Example 1;

[0042] Figure 2(d) shows a scanning electron microscope image of the hydrated deacidifying agent obtained in Example 1;

[0043] Figure 3(a) shows the XRD pattern of the original fly ash in Example 1;

[0044] Figure 3(b) shows the XRD patterns of different solid products during the conversion of the original fly ash in Example 1;

[0045] Figures 4(a)-(d) show the effect of the liquid-to-solid ratio on the alkalinity of the deacidifying agents obtained from the conversion of fly ash A, B, C and D in Example 3, respectively.

[0046] Figure 5 shows the effect of reaction time on alkalinity in the primary conversion in Example 6.

[0047] Figures 6(a)-(d) show the comparison of alkalinity effects of fly ash A, B, C and D obtained under different conversion methods (where I, II, III and IV represent the alkalinity effects of no conversion reagent, CaO added, CaCO3 added and the deacidifying agent obtained in Example 1 of this invention, respectively). Detailed Implementation

[0048] The following embodiments illustrate various features and advantages provided by aspects of this disclosure and are in no way intended to limit this disclosure and the appended claims.

[0049] In this invention, unless otherwise specified, all operations are performed at room temperature (25°C) and normal pressure (101 kPa).

[0050] In this invention, unless otherwise specified, all embodiments and preferred embodiments of this application can be combined to form new technical solutions.

[0051] In this invention, unless otherwise specified, all technical features and preferred technical features of this application can be combined to form new technical solutions.

[0052] my country's total municipal solid waste treatment volume reaches 250 million tons, of which approximately 180 million tons are incinerated, roughly generating about 10 million tons of fly ash annually. Fly ash contains complex heavy metals and is also enriched with pollutants such as dioxins and chlorides. Its leaching concentration exceeds the upper limit for hazardous waste identification, leading to its classification as hazardous waste by various countries worldwide. Improper disposal methods can cause severe environmental damage. This invention can prepare a high-alkalinity deacidifying agent from municipal solid waste incineration fly ash through a two-stage conversion process. Before deacidification application, a tertiary conversion process hydrates the metal oxides to give it high deacidification activity. The composition of fly ash from municipal solid waste incineration is very complex. Its main components are water-soluble mixed salts and insoluble mixed minerals of various metal ions such as Ca, Mg, Zn, Pb, Fe, and Al. Its acidic anionic ligands are mainly hydroxide, carbonate, sulfate, silicate, fluoride, and chlorinated silicate ions. The above-mentioned metal ions and anionic ligands are randomly combined or coupled together, intersecting and containing each other, thus forming a highly complex and mixed mixture of salts and minerals, which exists in the fly ash in powder or colloidal form and is difficult to decompose thermally.

[0053] The inventors unexpectedly discovered that, firstly, by using water-soluble carbonates and / or water-soluble bicarbonates as conversion reagents, various types of minerals in municipal solid waste incineration fly ash are uniformly converted into metallic carbonate minerals through a conversion reaction; these metallic carbonate minerals are then converted into metal oxides at relatively low temperatures (e.g., 700-1000℃), resulting in a metallic oxide deacidifying agent with extremely high total alkalinity and effective alkalinity; the metallic oxide deacidifying agent is further hydrated before deacidification application to achieve high deacidification activity. Secondly, the prepared deacidifying agent can be recycled for use in the treatment of municipal solid waste incineration fly ash flue gas (e.g., as a deacidifying agent in fly ash deacidification treatment), and multiple recycling cycles can yield zinc and lead enriched materials with high recovery value. Thirdly, the resulting tailings, after appropriate treatment, can be evaporated and concentrated to obtain water-soluble metal salts or discharged into sodium brine bodies, without causing any toxic impact on the environment. Fourth, this invention achieves the harmlessness, reduction, and resource utilization of hazardous solid waste fly ash from municipal solid waste incineration, effectively addressing the environmental release and ecological burden of toxic and harmful substances from this type of hazardous waste, and significantly reducing its carbon footprint. Finally, the technical and economic feasibility of this invention in converting municipal solid waste incineration fly ash into a high-alkalinity and high-activity deacidifying agent is excellent, with a processing cost of only a few hundred yuan. The resulting reusable deacidifying agent and zinc- and lead-rich materials can generate a profit. Therefore, the method of this invention simultaneously achieves significantly better economic benefits.

[0054] In view of this, on the one hand, the present invention provides a method for preparing a deacidifying agent from fly ash of municipal solid waste incineration, which includes the following steps:

[0055] The primary conversion process transforms various types of minerals in the fly ash from municipal solid waste incineration into metallic carbonate minerals.

[0056] Secondary conversion transforms the resulting metallic carbonate minerals into corresponding metal oxides, yielding a high-alkalinity deacidifying agent; and

[0057] Optionally, a three-stage conversion is performed, and the metal oxide is hydrated before deacidification to give it high deacidification activity.

[0058] The fly ash from municipal solid waste incineration is produced by deacidifying the flue gas from municipal solid waste incineration.

[0059] The primary conversion is carried out in an aqueous solution and the conversion reagent contains water-soluble carbonates and / or water-soluble bicarbonates.

[0060] The secondary conversion is carried out at temperatures exceeding 700°C;

[0061] Preferably, the deacidifying agent is reused for flue gas treatment of fly ash from municipal solid waste incineration, such as deacidification treatment of flue gas from municipal solid waste incineration.

[0062] Through the two-stage conversion of this invention, municipal solid waste incineration fly ash can be finally converted into a metal oxide deacidifying agent with high total alkalinity and effective alkalinity. The three-stage conversion before deacidification application hydrates the metal oxide, giving it high deacidification activity. This deacidifying agent can be reused for the treatment of flue gas from municipal solid waste incineration fly ash, forming a closed loop in the treatment process.

[0063] In a preferred embodiment, the municipal solid waste incineration fly ash refers to fly ash from a municipal solid waste incineration power plant generated from the deacidification treatment of municipal solid waste incineration flue gas.

[0064] In a preferred embodiment, the deacidifying agent used in the deacidification treatment of municipal solid waste incineration flue gas is the deacidifying agent prepared by the method of the present invention.

[0065] On the other hand, the present invention provides a method for preparing a deacidifying agent from fly ash from municipal solid waste incineration, the method comprising:

[0066] The primary conversion involves adding an aqueous solution of water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the municipal solid waste incineration fly ash, stirring and reacting to convert various types of minerals in the municipal solid waste incineration fly ash into metallic carbonate minerals.

[0067] In the secondary conversion, after the primary conversion and liquid-solid separation, the resulting solid powder of metallic carbonate minerals is subjected to a secondary conversion at temperatures above 700°C into metallic oxides, yielding a high-alkalinity deacidifying agent; and

[0068] The three-stage transformation before deacidification involves hydrating the metal oxides to give them high deacidification activity.

[0069] In this invention, unless otherwise specified, the term "liquid-to-solid ratio" refers to the volume / mass ratio (L / kg) of the aqueous solution of the water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to fly ash. It can be understood that when the fly ash is washed with water and dried, the term "liquid-to-solid ratio" refers to the volume / mass ratio (L / kg) of the aqueous solution of the water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the washed fly ash (dried, i.e., water-free).

[0070] In this invention, the term "mineral" should be understood to refer to the general term for all metals and their salts, oxides and hydroxides present in fly ash.

[0071] In this invention, liquid-solid separation can be performed using conventional separation methods in the art, such as filtration separation, centrifugal separation, or gravity separation.

[0072] In this invention, the heating in the secondary conversion can be carried out in conventional heating equipment in the art, such as a muffle furnace, as long as the heating temperature of this invention (i.e., greater than 700°C, for example 700°C-1200°C, preferably 750-1100°C, for example 800-1000°C or 850-1000°C) can be achieved.

[0073] In a preferred embodiment, the heating time in the secondary conversion can be 0.5 to 10 hours, such as 1 to 8 hours or 2 to 4 hours.

[0074] In this invention, hydration can be carried out by directly adding the obtained metal oxide to water, and the resulting deacidifying agent suspension can be directly applied to deacidification treatment; alternatively, liquid-solid separation can be performed and the resulting solid component dried to obtain deacidifying agent powder, which can then be applied to deacidification treatment. During the hydration process, most of the metal oxide is converted into metal hydroxide, thereby activating the alkali capacity (alkalinity) and achieving high deacidification activity. The effective component of the high-activity deacidifying agent obtained after hydration is a mixture of metal oxide and metal hydroxide, which is referred to here as "metal (hydrogen) oxide" for convenience. Therefore, in the context of this invention, the deacidifying agent after hydration is also referred to as "metal (hydrogen) oxide deacidifying agent". The water used in this invention can be municipal water or water recovered from the method of this invention.

[0075] Furthermore, this invention provides a method for preparing a deacidifying agent from fly ash from municipal solid waste incineration, comprising the following steps:

[0076] (1) Before the primary conversion, the fly ash from the municipal solid waste incineration is first washed with water to remove water-soluble components, especially metal salts and chloride-containing salts, and then the washed fly ash is obtained by liquid-solid separation.

[0077] (2) Add an aqueous solution of water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the water-washed fly ash, stir and react, and convert the various types of minerals in the water-washed fly ash into metallic carbonate minerals through primary conversion.

[0078] (3) After a second liquid-solid separation, the resulting solid powder of metallic carbonate minerals is subjected to a secondary conversion into metal oxides at a temperature >700℃ to obtain a high-alkalinity deacidifying agent; and

[0079] (4) The three-stage transformation before deacidification application hydrates the metal oxide to give it high deacidification activity.

[0080] Washing the fly ash with water before primary conversion to remove water-soluble components, especially metal salts and chloride-containing salts, can reduce its impact on subsequent primary conversion.

[0081] In a preferred embodiment, the conversion reagent used in the primary conversion includes sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, or any combination thereof; preferably, the concentration range of the aqueous solution of the conversion reagent is 0.1-5.0M; and / or, the liquid-to-solid ratio of the aqueous solution of the conversion reagent to fly ash is (1-100):1; and / or, the temperature range in the primary conversion is 0-100℃, preferably 5-80℃, more preferably 20-60℃, and even more preferably 30-50℃.

[0082] In a preferred embodiment, the conversion reagent used for the primary conversion comprises a mixture of sodium carbonate and sodium bicarbonate in a molar ratio of (0.1-4):1, preferably (0.5-2):1.

[0083] The inventors of this invention discovered that when the concentration of the primary conversion reagent exceeds 4.5 M, sintering occurs in the material obtained after secondary conversion, thereby destroying its original ultrafine powder structure and making it unsuitable for recycling as a deacidifying agent. Therefore, preferably, in the primary conversion, the concentration range of the aqueous solution of the conversion reagent is 0.5-4.5 M, preferably 0.7-4.0 M, more preferably 1-3.5 M, and even more preferably 2-3.5 M, and the liquid-solid ratio of the aqueous solution of the conversion reagent to fly ash in the primary conversion is (2-20):1.

[0084] In a preferred embodiment, the liquid-to-solid ratio of the aqueous solution of the conversion reagent to fly ash can be (2-16):1, preferably (3-12):1, more preferably (4-8):1, and even more preferably (4-6):1.

[0085] In a preferred embodiment, the primary conversion time can be 0.5-48h, preferably 1-40h, more preferably 4-35h, even more preferably 10-30h, and even more preferably 20-25h.

[0086] In one implementation, the conversion reagent used for the primary conversion is ammonium carbonate and / or ammonium bicarbonate. The advantage of using ammonium carbonate and / or ammonium bicarbonate as conversion reagents compared to sodium carbonate is that the former is cheaper, and the residual filtrate generated after the primary conversion can be used as fertilizer after purification.

[0087] In a preferred embodiment, the conversion reagent further includes an auxiliary agent, namely carbon dioxide. Although carbon dioxide itself cannot be used as a primary conversion reagent, and carbon dioxide alone cannot uniformly convert the various phases in fly ash into metallic carbonate minerals, carbon dioxide, as an auxiliary agent, can adjust the pH of the system to a certain extent, thereby reducing the alkaline leaching of heavy metals during primary conversion and saving some of the conversion reagent consumption.

[0088] In a preferred embodiment, the conversion reagents for ammonium carbonate and / or ammonium bicarbonate are prepared on-site by passing carbon dioxide through an aqueous ammonia solution.

[0089] In a preferred embodiment, the municipal solid waste incineration fly ash is generated from the treatment of flue gas from municipal solid waste incineration fly ash using the lime method, wherein the flue gas treatment method includes at least one of wet, semi-wet, and dry methods; or, the municipal solid waste incineration fly ash is untreated fly ash and / or aged fly ash. Preferably, the silica content in the municipal solid waste incineration fly ash does not exceed 20% by weight, more preferably not more than 10% by weight, and even more preferably not more than 5% by weight. A side effect of silica in municipal solid waste incineration fly ash is that it readily reacts with metal oxides at high temperatures during secondary conversion to form metal silicate minerals, thereby reducing the alkalinity of the deacidifying agent.

[0090] In a preferred embodiment, the metal carbonate minerals are preferably dried before the secondary conversion following the primary conversion to produce metal carbonate minerals and liquid-solid separation (e.g., to reduce their moisture content to a suitable range, typically 0 to 15% by weight, preferably 0 to 5% by weight), at a drying temperature of 40-300°C. The drying time can be selected as needed and is not particularly limited here.

[0091] In a preferred embodiment, the primary conversion reaction can be carried out in a single-stage reactor or through two-stage or multi-stage operation. The specific operation can be selected based on the throughput and the processing capacity of the equipment.

[0092] In a preferred embodiment, the liquid phase obtained by liquid-solid separation can be reused in the corresponding grade step, discharged into sodium brine after treatment, or concentrated and evaporated.

[0093] In this invention, the liquid phase after liquid-solid separation contains soluble components, which can be partially recycled back into the process or concentrated and evaporated using the heat generated in the process, and the resulting salt can be used for commercial purposes.

[0094] As shown in Figure 1, in a preferred embodiment, fly ash (6) obtained from the lime-process treatment of municipal solid waste incineration fly ash is added to a washing device (1) for washing to remove water-soluble components from the fly ash. Then, liquid-solid separation is performed, and the resulting solid phase (12) is sent to a reaction device (2) for primary conversion. At the same time, a portion (111) of the resulting liquid phase (11) is returned to the washing device (1), and the remaining portion (112) is treated as waste liquid (7). In the reaction device (2), the solid phase (12) is reacted with an aqueous sodium carbonate solution for primary conversion. After the reaction, liquid-solid separation is performed, and the resulting solid phase (22) is sent to a heat treatment device (3) for heating for secondary conversion to obtain a high-alkalinity deacidifying agent. At the same time, a portion (211) of the liquid phase (21) obtained after liquid-solid separation is returned to the reaction device (2), and the remaining portion (212) is treated as waste liquid (7). After the secondary conversion is completed, the high alkalinity deacidifying agent obtained in the heat treatment device (3) is transported to the hydration device (4) for tertiary conversion, so that it is hydrated to obtain metal (hydrogen) oxide (5) with high deacidification activity.

[0095] Furthermore, the method for preparing a deacidifying agent from municipal solid waste incineration fly ash of the present invention further includes the following steps: reusing the obtained deacidifying agent for flue gas treatment of municipal solid waste incineration fly ash, and then repeating the method for preparing a deacidifying agent from municipal solid waste incineration fly ash of the present invention. During this cycle, lead and / or zinc in the municipal solid waste incineration fly ash will be enriched. When the zinc content is not less than 1% by weight and / or the lead content is not less than 0.5% by weight, a portion of the material can be supplied to smelting enterprises as raw materials for lead and zinc smelting. The zinc and lead content in the recycled deacidifying agent can be determined according to the national standard HJ 781-2016. Specifically, 0.25g of fly ash sample is weighed and placed in a polytetrafluoroethylene digestion tube. Nitric acid (65-68%), hydrofluoric acid (40%), and perchloric acid (70-72%) are added in a ratio of 10mL:10mL:5mL. Digestion is carried out in a graphite digester at 200℃ for 6 hours until about 1-2mL of digestate remains. After digestion, 2mL of nitric acid is added to dissolve the residue. After cooling, the volume was adjusted to 25 mL, filtered, and the lead and zinc content was analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0096] The deacidifying agent obtained by this invention is recycled for the treatment of flue gas from municipal solid waste incineration fly ash. Multiple recycling yields zinc- and lead-enriched materials with high recovery value. Typically, after four cycles of use, the zinc enrichment concentration in the fly ash and deacidifying agent material can exceed 1%, and the lead enrichment concentration is approximately 0.5%. Such materials can be sold to lead-zinc smelting enterprises. Therefore, this invention also provides a method for enriching lead and / or zinc in municipal solid waste incineration fly ash, comprising the following steps: first, performing the method of preparing a deacidifying agent from municipal solid waste incineration fly ash according to this invention, and then recycling the obtained deacidifying agent for the flue gas treatment of the municipal solid waste incineration fly ash.

[0097] Finally, the present invention also provides an apparatus for preparing a deacidifying agent from fly ash of municipal solid waste incineration, comprising:

[0098] --Fly ash collection device, used to collect fly ash from municipal solid waste incineration;

[0099] --Reaction device, used to convert various types of minerals in fly ash from municipal solid waste incineration into metallic carbonate minerals;

[0100] --A heat treatment apparatus for converting the obtained metallic carbonate minerals into corresponding metallic oxides to obtain a high-alkalinity deacidifying agent; and

[0101] --Optionally, a hydration device hydrates the metal oxides before deacidification application, giving them high deacidification activity.

[0102] In a preferred embodiment, the apparatus further includes a washing device located between the fly ash collection device and the reaction device.

[0103] In a preferred embodiment, the washing device is used to wash the fly ash from municipal solid waste incineration to remove water-soluble components, and after liquid-solid separation, the solid components are transported to the reaction device for primary conversion.

[0104] After the fly ash from municipal solid waste incineration is washed and separated into liquid and solid states, it can be pre-dried. Therefore, in a preferred embodiment, a heating device is provided between the downstream of the washing device and the upstream of the reaction device for pre-drying the fly ash after washing and separation (the drying temperature can be, for example, 40-300°C, preferably 50-200°C).

[0105] In a preferred embodiment, the reaction apparatus may be a reactor (tank) equipped with a stirring device. In a preferred embodiment, the reaction apparatus further includes a metering device for adding an aqueous solution of the conversion reagent; preferably, the metering device and the corresponding piping are alkali-resistant.

[0106] In a preferred embodiment, the heat treatment apparatus is used to convert the obtained metal carbonate minerals into corresponding metal oxides, and the heating temperature can be greater than 700°C, for example 700°C-1200°C, preferably 750-1100°C, for example 800-1000°C or 850-1000°C. The heat treatment apparatus can be a conventionally used heating device in the art, such as a muffle furnace. Preferably, the heat of the heating device comes from the heat generated by the incineration of municipal solid waste.

[0107] In a preferred embodiment, the hydration device is a hydration reaction device, such as a reactor (tank), which receives the metal oxide obtained by heating in a heat treatment device and hydrates it with water in the hydration device. To prevent the water temperature from becoming too high during hydration, the hydration device may also include a heat exchanger for heat exchange.

[0108] In a preferred embodiment, a drying device for drying the resulting hydrated product may also be included downstream of the hydration device.

[0109] In a preferred embodiment, a conveying device (e.g., a conveyor belt) is provided between the heat treatment apparatus and the hydration apparatus to transport the metal oxide obtained from the heat treatment apparatus to the hydration apparatus for hydration reaction.

[0110] Furthermore, the equipment for preparing deacidifying agents from municipal solid waste incineration fly ash of the present invention can be directly integrated with municipal solid waste incineration equipment, particularly with fly ash treatment devices used in municipal solid waste incineration equipment. In this way, fly ash can be recycled and metals such as lead and / or zinc can be enriched in the fly ash.

[0111] This invention achieves the harmlessness, volume reduction, and resource recovery of hazardous solid waste fly ash from municipal solid waste incineration, effectively addressing the environmental release and ecological burden of toxic and harmful substances from this type of waste. The invention uses a two-stage conversion process to prepare a high-alkalinity metal oxide deacidifying agent from municipal solid waste incineration fly ash. Before deacidification application, a tertiary conversion process hydrates the metal oxide, giving it high deacidification activity. This invention demonstrates excellent technical and economic feasibility, with processing costs of only a few hundred yuan. It produces a reusable deacidifying agent and zinc- and lead-rich materials, resulting in a profit margin.

[0112] Example

[0113] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0114] In this invention, total alkalinity refers to the total amount of alkaline substances in the aqueous solution, including all substances that can consume acid and contribute to alkalinity in an aqueous solution with a titration endpoint of pH 3.0, such as hydroxides, carbonates, and bicarbonates. Effective alkalinity refers to the amount of substances that can consume acid and contribute to alkalinity in an aqueous solution with a titration endpoint of pH 8.0, primarily the content of hydroxides. The specific methods for determining total alkalinity and effective alkalinity are as follows:

[0115] A certain amount of solid sample was placed in a beaker, deionized water was added, and the liquid-to-solid ratio (by weight) was controlled at 10:1. The sample was magnetically stirred and titrated with 2M HNO3 solution at room temperature until acidic, with pH 3.0 as the titration endpoint. The amount of acid consumed was the total alkalinity. Then, 2M NaOH solution was used for back titration until alkaline, with pH 8.0 as the titration endpoint. The difference between the amount of acid consumed in the former titration and the amount of alkalinity consumed in the latter titration was the effective alkalinity. For ease of measurement and comparison with control examples, in all examples, the alkalinity was evaluated by the number of moles of nitric acid consumed per unit mass of the deacidifying agent powder sample obtained from secondary conversion (rather than the volume of the deacidifying agent emulsion obtained after hydration). Titration errors generally vary between different batches, but relatively consistent titration errors can occur within the same batch of experiments.

[0116] The four fly ash samples selected in this invention are all fly ash from municipal solid waste incineration produced by the lime-method deacidification treatment of municipal solid waste incineration flue gas, and are respectively designated as: fly ash A, fly ash B, fly ash C and fly ash D.

[0117] Example 1

[0118] 500g of municipal solid waste incineration fly ash (original fly ash A, B, C, and D) were placed in a reaction vessel, and deionized water was added at a water-to-fly ash ratio (L / Kg) of 10:1. The mixture was stirred in water for 2 hours, filtered to remove soluble salt components, and then dried in an electric heating drying oven at 60℃ for 24 hours to obtain the first solid phase, i.e., the water-washed fly ash. 15g of the above water-washed fly ash (after drying, the same below) was placed in a polyethylene bottle, and a 20% (equivalent to 1.89M, the same below) conversion reagent Na2CO3 solution was added, with a liquid-to-solid ratio (L / Kg, the same below) of 4:1. The mixture was reacted at room temperature for 12 hours, and the liquid and solid were separated. The unreacted Na2CO3 on the surface of the solid was then washed away with water, filtered, and dried to obtain the second solid phase, i.e., metallic carbonate minerals. The second solid phase was subjected to a secondary conversion in a muffle furnace at 900℃ for 3 hours to generate the third solid phase (i.e., metal oxides), yielding a high-alkalinity deacidifying agent. The third solid phase was hydrated in water to obtain a deacidifying agent emulsion, at which point the alkalinity of the deacidifying agent was fully activated. The total alkalinity and effective alkalinity of the original fly ash and the obtained deacidifying agent emulsion were titrated using 2M HNO3 solution and 2M NaOH solution, respectively. Alkalinity was evaluated based on the number of moles of nitric acid required per unit mass of the original fly ash and per unit mass of the deacidifying agent powder sample obtained through secondary conversion.

[0119] The total alkalinity and effective alkalinity of the four types of raw fly ash and the resulting metal (hydrogen) oxide deacidifying agent are shown in Table 1. The total alkalinity of raw fly ash A, B, C, and D are 8.00, 7.90, 9.05, and 8.35 mol / kg, respectively, and the total alkalinity of the metal (hydrogen) oxide deacidifying agent are 29.99, 29.31, 30.29, and 31.24 mol / kg, respectively. Their total alkalinity is 3.75, 3.71, 3.35, and 3.74 times that of the corresponding raw fly ash. The effective basicities of the original fly ash A, B, C, and D were 7.10, 7.12, 8.30, and 7.28 mol / kg, respectively. The effective basicities of the metal (hydr)oxide deacidifying agents were 27.42, 26.68, 27.59, and 28.69 mol / kg, respectively. The effective basicities of the obtained metal (hydr)oxide deacidifying agents were 3.86, 3.75, 3.32, and 3.94 times that of the corresponding original fly ash products. This indicates that the obtained deacidifying agent products have very high basicity and corresponding deacidification activity.

[0120] Table 1. Summary of Total Alkalinity and Effective Alkalinity of Four Types of Raw Fly Ash and Obtained Metal (Hydrogen) Oxide Deacidifying Agents

[0121] The deacidifying agent product obtained in this invention is compared with commonly used industrial caustic soda, soda ash, lime, or slaked lime, as shown in Table 2. The total alkalinity of the product is higher than that of caustic soda (NaOH) with a purity of 98.0%, and its alkali capacity is also significantly higher than that of soda ash (Na2CO3) with a purity of 99.2%. The effective alkalinity of the deacidifying agent product obtained in this invention is comparable to that of Class II standard lime (CaO).

[0122] Table 2 Comparison of alkalinity between the metal (hydrogen) oxide deacidifying agent of this invention and commonly used industrial alkalis.

[0123] Taking fly ash C as an example, the morphology and particle size changes of the original fly ash transformed into a metal (hydrogen) oxide deacidifying agent were characterized by scanning electron microscopy (see Figure 2). The original fly ash (Figure 2(a)) was densely aggregated with large particle clusters. After water washing, the agglomeration was still significant (Figure 2(b)), with nearly spherical clusters distributed. The water-washed / calcined fly ash (Figure 2(c)) had a more irregular structure than the water-washed fly ash, but particle aggregation was still obvious, which may be due to the collapse of its nearly spherical cluster structure caused by calcination. Compared with the original fly ash, the metal (hydrogen) oxide deacidifying agent obtained in this invention (Figure 2(d)) has significantly enhanced dispersibility and significantly reduced particle size.

[0124] XRD was used to characterize the changes in crystalline phases in different solid products during the transformation of fly ash C from raw fly ash to a metal (hydrogen) oxide deacidifying agent (Figure 3). The composition of municipal solid waste incineration fly ash is very complex, mainly consisting of water-soluble mixed salts and insoluble mixed minerals of various metal ions such as Na, K, Ca, Mg, Zn, Pb, Fe, and Al. Its acidic anionic ligands are mainly chloride ions, hydroxide ions, carbonate ions, sulfate ions, silicate ions, fluoride ions, and chlorosilicate ions. The above-mentioned various metal ions and anionic ligands randomly combine or couple together, intersecting and containing each other, thus forming a highly complex and mixed mixture of salts, amorphous minerals, or crystalline minerals, which are present in the fly ash in powder or colloidal form. The crystalline minerals present in the original fly ash exhibit characteristic diffraction peaks of chlorides (NaCl, KCl), carbonates (CaCO3), sulfates (CaSO4), zinc carbonate (ZnCO3), silicates (Mg2SiO4), sulfides (FeS2), oxides (Al2O3), and elemental metals (Cd). Using sodium carbonate as a conversion reagent, these minerals are uniformly converted into metallic carbonate minerals through a conversion reaction. The diffraction peaks belonging to carbonates in the primary conversion products are very strong, with strong diffraction peaks belonging to CaCO3 and Pb3(CO3)2(OH)2 also appearing, indicating that the main product of the primary conversion is carbonates. After a secondary conversion, the metallic carbonate minerals are converted into metallic oxides at a relatively low temperature. The secondary conversion products mainly show diffraction peaks belonging to metallic oxides, including those belonging to CaO, MgO, and (CaO). 12 The diffraction peaks of (Al2O3)7 indicate that the secondary conversion mainly formed various metal oxide components with very high total and effective basicity. X-ray fluorescence analysis (XRF) also shows that the main components of the secondary conversion products are metal oxides of Ca, Mg, Fe, Al, and Zn, with various metal oxides accounting for up to 90% of the total matter. Tertiary conversion, which involves hydrating the metal oxide mixture to achieve high deacidification activity, mainly produces metal hydroxides and some metal oxides, such as the diffraction peaks of Ca(OH)2 and MgO. It should be noted that XRD cannot reveal the changes in amorphous mineral phases at different conversion stages, and phase components with a content below 5% are sometimes difficult to detect. The examples in this document merely use XRD to illustrate the changes in crystalline phases in different solid products during different conversion stages from original fly ash to a high-activity metal (hydrogen) oxide deacidifying agent.

[0125] Example 2

[0126] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the water-washed fly ash. Take 15g of the above water-washed fly ash into a polyethylene bottle, and add Na2CO3 solutions with concentration gradients of 6%, 10%, 20%, 30%, and 40%, respectively, with a liquid-to-solid ratio of 4:1. React at room temperature for 12h, first separate the liquid and solid, then wash away the incompletely reacted Na2CO3 on the surface of the solid with water, filter, and dry to obtain the second solid phase, i.e., metal carbonate minerals. The second solid phase is subjected to a secondary conversion at 900℃ in a muffle furnace for 3h to generate the third solid phase, i.e., the metal oxide deacidifying agent. The third solid phase is hydrated in water to obtain a deacidifying agent emulsion, and the alkalinity of the deacidifying agent is fully activated. The alkalinity determination and evaluation methods of the obtained deacidifying agent are the same as above. In this example, the data of total alkalinity and effective alkalinity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the four fly ashes as a function of Na2CO3 concentration are shown in Table 3. In this embodiment, the total alkalinity and effective alkalinity of the metal (hydr)oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D initially increased with the increase of the Na2CO3 concentration, reaching a saturation peak at a certain concentration. When the Na2CO3 concentration was 6%, the total alkalinity of the corresponding metal (hydr)oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D was 26.54-28.14 mol / kg, and the effective alkalinity was 24.03-25.81 mol / kg. When the Na2CO3 concentration increased to 10%, the total alkalinity of the corresponding metal (hydr)oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D was 27.46-29.61 mol / kg, and the effective alkalinity was 25.81-27.15 mol / kg. When the Na₂CO₃ concentration reached 20%, the total basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D was 29.31-31.24 mol / kg, and the effective basicity was 26.68-28.69 mol / kg. Compared with a conversion concentration of 6%, when the Na₂CO₃ concentration reached 20%, the total basicity of fly ash A, B, C, and D increased by 13.00%, 9.61%, 7.64%, and 13.84%, respectively, and the effective basicity increased by 14.11%, 8.19%, 6.90%, and 14.58%, respectively. This indicates that increasing the concentration of the conversion reagent Na₂CO₃ can enhance the effect of the first-stage conversion, thereby increasing the deacidification capacity and activity of the final product. When the Na2CO3 concentration was further increased to 30%, the total alkalinity and effective alkalinity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D increased by only 1%-6% compared with the concentration of the conversion reagent at 20%. That is, the total alkalinity increased by only 0.77%, 2.49%, 5.77%, and 1.02%, respectively, and the effective alkalinity increased by only 0.51%, 2.47%, 6.13%, and 1.92%, respectively.Similarly, when a 40% Na₂CO₃ solution was added, the total alkalinity and effective alkalinity showed almost no change compared to a 30% conversion reagent concentration, with the difference being less than the error. This indicates that when a sufficient concentration of Na₂CO₃ is added, the concentration of the conversion reagent is no longer the determining factor for increasing the total alkalinity and effective alkalinity of the final product, the metal (hydrogen) oxide deacidifying agent. Even more concerning, when the Na₂CO₃ concentration reaches or exceeds 4.5M (equivalent to a concentration of 48%), the material obtained after secondary conversion frequently exhibits sintering, destroying the original ultrafine powder structure and rendering it unsuitable for recycling as a deacidifying agent.

[0127] Table 3. Summary of alkalinity changes of the metal (hydrogen) oxide deacidifying agent obtained from fly ash conversion in Example 2.

[0128] Example 3

[0129] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the water-washed fly ash. Take 15g of the above water-washed fly ash into a polyethylene bottle, add a 20% Na2CO3 solution, and the liquid-to-solid ratios are 2:1, 4:1, 6:1, 8:1, 12:1, and 16:1, respectively. React the fly ash at room temperature for 12 hours, first separating the liquid and solid, then washing away the unreacted Na2CO3 on the solid surface with water, filtering and drying to obtain the second solid phase, i.e., metallic carbonate minerals. Perform a secondary conversion on the second solid phase in a muffle furnace at 900℃ for 3 hours to generate the third solid phase, i.e., a metal oxide deacidifying agent. Fully hydrate the third solid phase in water to obtain a deacidifying agent emulsion, and the alkalinity of the deacidifying agent is fully activated. The alkalinity determination and evaluation methods of the obtained deacidifying agent are the same as above.

[0130] In this embodiment, the effect of the liquid-to-solid ratio on the total basicity and effective basicity of the metal (hydrogen) oxide deacidifying agents obtained from fly ash conversion is shown in Figure 4. When the liquid-to-solid ratio is 2:1, the total basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from fly ash A, B, C, and D is below 29 mol / kg, and the effective basicity is below 26 mol / kg. When the liquid-to-solid ratio is 4:1, the total basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the above four fly ash conversions is 29.19-30.17 mol / kg, and the effective basicity is 26.57-28.57 mol / kg. Compared with the case of liquid-to-solid ratio of 2:1, the total basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from fly ash A, B, C, and D conversions increased by 7.70%, 5.37%, 7.21%, and 9.54%, respectively, and the effective basicity increased by 8.24%, 7.86%, 8.55%, and 12.67%, respectively. When the liquid-to-solid ratio increased to 6:1, compared with the metal (hydrogen) oxide deacidifying agent prepared under a liquid-to-solid ratio of 4:1, the changes in total basicity and effective basicity were both less than the error. Further increasing the liquid-to-solid ratio to 8:1, 12:1, and 16:1, the total basicity and effective basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the four fly ash conversions no longer increased. This indicates that a liquid-to-solid ratio of 4:1 is sufficient for effective primary conversion.

[0131] Example 4

[0132] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the water-washed fly ash. Take 50g of the above water-washed fly ash into a polyethylene bottle, add a 20% Na2CO3 solution with a liquid-to-solid ratio of 4:1, and react the fly ash at room temperature for 12 hours. First, separate the liquid and solid phases, then wash away the unreacted Na2CO3 with water, filter and dry to obtain the second solid phase, i.e., metallic carbonate minerals. Divide the second solid phase into five equal parts and perform secondary conversion in a muffle furnace at 700℃, 800℃, 850℃, 900℃, and 1000℃ for 3 hours respectively to generate the third solid phase, i.e., the metal oxide deacidifying agent. Place the third solid phase in water for full hydration to obtain a deacidifying agent emulsion, and the alkalinity of the deacidifying agent is fully activated. The alkalinity determination and evaluation methods are the same as above.

[0133] In this embodiment, the data on the relationship between the secondary conversion temperature and the fly ash conversion effect are shown in Table 4. When the secondary conversion temperature is 700℃, the total basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D is 24.76-26.50 mol / kg, and the effective basicity is 22.41-24.20 mol / kg, indicating that the secondary conversion is insufficient at this temperature and has not yet reached saturation. When the secondary conversion temperature is increased to 800℃, the total basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the conversion of fly ash A, B, C, and D ranges from 27.99 to 29.29 mol / kg, and the effective basicity is 25.60 to 26.81 mol / kg. Compared to 800℃, when the secondary conversion temperature was increased to 850℃, the total basicity and effective basicity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from fly ash A, B, C, and D all showed a slight increase. The total basicity increased by 3.87%, 5.86%, 4.85%, and 7.90%, respectively, and the effective basicity increased by 5.43%, 5.78%, 4.81%, and 6.81%, respectively. When the secondary conversion temperature was raised to 900℃, the total basicity and effective basicity values ​​of the corresponding metal (hydrogen) oxide deacidifying agents obtained from the four fly ash conversions were not significantly different from the corresponding values ​​under the secondary conversion condition at 850℃, and were basically lower than their error values. This indicates that the secondary conversion in the fly ash was fully completed at this point, and the carbonate components from the primary conversion were completely decomposed and converted into the corresponding metal oxides.

[0134] Table 4. Summary of alkalinity changes of the deacidifying agent for metal (hydrogen) oxides obtained from fly ash conversion in Example 4.

[0135] Example 5

[0136] Take 10g of municipal solid waste incineration fly ash (original fly ash A, B, C, and D) into a reaction vessel and conduct the following experimental designs: (1) Add 6% and 10% Na2CO3 solutions directly to the original fly ash, with a liquid-to-solid ratio of 2:1; (2) Add 20% Na2CO3 solution directly to the original fly ash, with liquid-to-solid ratios of 2:1 and 4:1. Then react at room temperature for 12h and separate the liquid and solid. Wash away the unreacted Na2CO3 on the surface of the solid with water, filter and dry to obtain the first solid phase, and place it in a muffle furnace for high-temperature calcination at 900℃ for 3h to obtain the second solid phase. Place the second solid phase in water for full hydration to obtain a deacidifying agent emulsion. The alkalinity determination and evaluation methods are the same as above.

[0137] As shown in Table 5, when the concentration of the conversion reagent Na₂CO₃ is 6% (liquid-to-solid ratio 2:1), the total basicity of the obtained metal (hydr)oxide deacidifying agent is 17.83-21.53 mol / kg, and the effective basicity is 16.54-20.29 mol / kg. When the concentration of the conversion reagent is 10% (liquid-to-solid ratio 2:1), the total basicity of the obtained metal (hydr)oxide deacidifying agent varies from 20.95-24.95 mol / kg, and the effective basicity varies from 19.59-23.35 mol / kg. When the concentration of Na₂CO₃ is 20% (liquid-to-solid ratio 2:1), the total basicity of the metal (hydr)oxide deacidifying agent varies from 23.50-25.43 mol / kg, and the effective basicity is 22.12-24.16 mol / kg. When the Na₂CO₃ concentration was 20% (liquid-to-solid ratio 4:1), the total basicity of the metal (hydr)oxide deacidifying agent varied from 24.70 to 27.15 mol / kg, and the effective basicity was 23.39 to 25.87 mol / kg. Compared with the method in Example 1 where desalination was performed first followed by primary conversion (at the same liquid-to-solid ratio), the total basicity and effective basicity of the metal (hydr)oxide deacidifying agent obtained by direct conversion were 82.36%-90.28% and 85.30%-93.37% of the latter, respectively. This is because the presence of a large amount of water-soluble salts in the original fly ash affected the efficiency of the primary conversion. The effect of water-soluble salts on the conversion was particularly significant at lower liquid-to-solid ratios and lower conversion reagent concentrations, but the effect was relatively weakened at higher liquid-to-solid ratios and higher conversion reagent concentrations. Compared with Example 1 where water washing was used to remove water-soluble salts before primary conversion, the reagent consumption was greater and the reusability of the conversion reagent was reduced when the original fly ash was directly converted.

[0138] Table 5. Summary of alkalinity changes of the deacidifying agent for metal (hydrogen) oxides obtained from fly ash conversion in Example 5.

[0139] Example 6

[0140] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the fly ash after washing. Take 5g of the fly ash C after washing and place it in 12 polyethylene bottles. Add a 10% Na2CO3 solution to each bottle, with a liquid-to-solid ratio of 4:1 and a reaction temperature of 35℃. Then, measure the alkalinity at intervals of 0.5, 1, 2, 3, 4, 6, 8, 10, 13, 24, 32, and 48 hours. After solid-liquid separation, wash away any unreacted Na2CO3 with water, filter, and dry to obtain the second solid phase. Perform a secondary conversion on the second solid phase in a muffle furnace at 900℃ for 3 hours to obtain the third solid phase. Hydrate the third solid phase thoroughly in water to obtain a metal (hydrogen) oxide deacidifying agent suspension. The alkalinity determination and evaluation methods are the same as above.

[0141] As shown in Figure 5, the time of the primary conversion reaction significantly affects the total alkalinity and effective alkalinity of the final deacidifying agent. After 0.5 h of primary conversion, the total alkalinity and effective alkalinity increased from the initial 21.47 and 19.78 mol / kg to 23.44 and 21.26 mol / kg, respectively; after 1 h of primary conversion, they continued to increase rapidly to 25.90 and 24.15 mol / kg; after 4 h of primary conversion, the total alkalinity and effective alkalinity increased to 27.11 and 25.35 mol / kg, respectively; and after 10 h of primary conversion, the total alkalinity and effective alkalinity continued to increase to 28. The total alkalinity and effective alkalinity reached 29.31 and 26.97 mol / kg respectively after 13 hours of primary conversion, indicating that the conversion was close to equilibrium. After 24 hours of primary conversion, the total alkalinity and effective alkalinity reached 29.47 and 27.17 mol / kg respectively. During the 24-48 hour period of primary conversion, the total alkalinity and effective alkalinity remained stable at 29.47-29.75 mol / kg and 27.17-27.55 mol / kg respectively.

[0142] Example 7

[0143] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the fly ash after washing. Take 5g of the fly ash C after washing and place it in a polyethylene bottle. Add an aqueous solution of Na2CO3 / NaHCO3 (single or mixed) with a total concentration of 1.5M as the conversion reagent, setting the molar ratios as 1:0, 2:1, 1:1, 1:2, and 0:1, where the liquid-to-solid ratio of the aqueous solution of the conversion reagent to the fly ash after washing is 4:1. React at room temperature for 12 hours, first separating the liquid and solid, then washing the surface of the solid with water to remove any incompletely reacted mixed conversion liquid, filtering, and drying to obtain the second solid phase. Perform a secondary conversion in a muffle furnace at 900℃ for 3 hours to obtain the third solid phase. Hydrate the third solid phase in water to obtain a metal (hydrogen) oxide deacidifying agent emulsion.

[0144] The basicity of the corresponding metal (hydr)oxide deacidifying agents is shown in Table 6. The total basicity and effective basicity of the deacidifying agent obtained by using Na₂CO₃ alone are 28.95 and 27.25 mol / kg, respectively. When using NaHCO₃ as an auxiliary agent alone, the total basicity and effective basicity of the obtained deacidifying agent are 27.46 and 25.18 mol / kg, respectively. When Na₂CO₃ and NaHCO₃ are combined, the total basicity and effective basicity of the obtained deacidifying agent are 27.26 and 25.10 mol / kg, respectively, when n(Na₂CO₃):n(NaHCO₃) = 2:1. When n(Na₂CO₃):n(NaHCO₃) = 1:1 and 1:2, the total basicity of the obtained deacidifying agent is 27.71 and 27.56 mol / kg, respectively, and the effective basicity is 25.39 and 25.26 mol / kg, respectively.

[0145] Table 6: Summary of the effects of the conversion agent combination in Example 7

[0146] Example 8

[0147] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the water-washed fly ash. Take 5g of water-washed fly ash C into a polyethylene bottle, and add 1.5M (NH4)2CO3 solution and NH4HCO3 solution respectively, with a liquid-to-solid ratio of 4:1. React at room temperature for 12h, first separate the liquid and solid, then wash the unreacted mixed conversion liquid on the surface of the solid with water, filter, and dry to obtain the second solid phase. Perform a secondary conversion on the second solid phase in a muffle furnace at 900℃ for 3h to obtain the third solid phase. Hydrate the third solid phase in water to obtain a metal (hydrogen) oxide deacidifying agent emulsion. The total alkalinity of the corresponding metal (hydrogen) oxide deacidifying agents obtained from (NH4)2CO3 solution and NH4HCO3 solution were 27.34 and 26.81 mol / kg, respectively, and the effective alkalinity were 25.25 and 24.72 mol / kg, respectively. Compared with sodium carbonate, the advantage of using ammonium carbonate or ammonium bicarbonate as conversion reagent is that the former is cheaper and the residual filtrate generated after primary conversion can be used as fertilizer after purification treatment.

[0148] Example 9

[0149] Repeat the first step of Example 1 to obtain the first solid phase, i.e., the water-washed fly ash. Take 5g of water-washed fly ash C into a polyethylene bottle, add a 10% Na2CO3 solution (liquid-solid ratio 4:1), and simultaneously purge CO2 gas under atmospheric pressure for 1 hour, then stop purging and continue the reaction at room temperature for 12 hours. Separate the liquid and solid phases, then wash the unreacted mixed conversion liquid on the solid surface with water, filter, and dry to obtain the second solid phase. Perform a secondary conversion on the second solid phase in a muffle furnace at 900℃ for 3 hours to obtain the third solid phase. Hydrate the third solid phase in water to obtain a metal (hydr)oxide deacidifying agent emulsion. The total basicity and effective basicity of the obtained metal (hydr)oxide deacidifying agent are 28.15 and 26.46 mol / kg, respectively. Experiments show that carbon dioxide itself cannot be used as a primary conversion reagent; using carbon dioxide alone cannot uniformly convert the various phases in fly ash into metal carbonate minerals. Carbon dioxide, as an auxiliary agent, can adjust the pH of the system to a certain extent, thereby reducing the alkaline leaching of heavy metals during primary conversion.

[0150] Example 10

[0151] Step 1 in Example 1 was repeated to obtain the first solid phase, i.e., the fly ash after water washing. A primary conversion system containing the conversion reagents (NH4)2CO3 and NH4HCO3 was prepared in situ using the following two methods.

[0152] (1) Take 5g of fly ash into a reaction vessel, add 5% ammonia solution, the liquid-solid ratio is 6:1, stir magnetically at room temperature and introduce CO2 gas until the pH of the reaction system is 9.0-9.5, then stop the gas introduction, continue to stir magnetically for 8 hours, and then filter and dry to obtain the second solid phase;

[0153] (2) Add a 5% ammonia solution to the reaction vessel, stir magnetically at room temperature and introduce CO2 in situ to generate a conversion liquid containing (NH4)2CO3 and NH4HCO3. Stop the gas flow, add 5g of water-washed fly ash to the system, the liquid-solid ratio is 6:1, stir magnetically for 8 hours and then filter and dry to obtain the second solid phase.

[0154] The second solid phase was subjected to a secondary conversion at 900℃ for 3 hours in a muffle furnace to obtain the third solid phase. The third solid phase was then fully hydrated in deionized water to obtain a suspension of metal (hydrogen) oxide deacidifying agent. The alkalinity determination and evaluation methods were the same as above. The obtained total alkalinities were 27.40 mol / kg and 26.88 mol / kg, respectively, and the effective alkalinities were 25.84 mol / kg and 25.08 mol / kg, respectively.

[0155] Example 11

[0156] The activity of the deacidifying agent obtained in the above typical examples, i.e., the actual acid neutralization efficiency of the deacidifying agent within 10 minutes, was determined as follows: 1 g of the deacidifying agent prepared from fly ash C was placed in a 50 mL conical flask, and deoxygenated deionized water (40°C warm water) was added at a liquid-to-solid ratio of 40:1. The flask was immediately sealed with a sealing film to isolate it from air. After hydration for about 2 minutes, 5 drops of phenolphthalein reagent were added. 4M hydrochloric acid was rapidly titrated until just colorless and maintained at this abrupt change point for 10 minutes. The amount of acid consumed was recorded. The molar mass of hydrochloric acid consumed per kilogram of deacidifying agent is the activity. As shown in Table 7, the activities of untreated fly ash C and calcined fly ash C were only 2.36 and 7.24 mol / kg, respectively. Under the typical conversion parameters of Examples 1-10, the activity of the deacidifying agent prepared from fly ash C was as high as 21-23.4 mol / kg, which is 9-10 times that of the original fly ash, exhibiting extremely high deacidifying activity. The activity of the deacidifying agent is as high as 80% or more of its total alkalinity, indicating that most of the alkalinity capacity contained in the obtained deacidifying agent has actual deacidifying activity.

[0157] Table 7 Activity of deacidifying agent prepared from fly ash C under typical conversion parameters

[0158] As can be seen from the above embodiments, the present invention provides a simple and effective solution for fly ash resource utilization. Through a three-stage conversion process, the metal oxides and their corresponding hydroxide components are progressively enriched and purified, ultimately yielding a metal (hydrogen) oxide deacidifying agent with ultra-high alkalinity and corresponding activity, thus realizing the resource utilization of fly ash. The categorized study of staged fly ash and comprehensive fly ash emphasizes the universality of the present invention for fly ash resource utilization. The method provided by the present invention is not only simple and efficient, but also has the prospect of large-scale industrial application. From an environmental impact perspective, it can solve the fly ash disposal problem; from an efficiency perspective, it can basically achieve the self-circulation of metal (hydrogen) oxide deacidifying agents in waste incineration plants. The above-described embodiments are preferred embodiments of the present invention. It should be noted that several improvements and modifications can be made without departing from the conversion principle and purpose of the present invention, and these improvements and modifications should be considered within the scope of protection of the present invention.

[0159] Comparative Example 1

[0160] This comparative example uses the first solid phase of fly ash A, B, C, and D from the first step of Example 1, which is washed with water. This fly ash is directly treated in a muffle furnace at 900°C for 3 hours to obtain water-washed and calcined fly ash without primary conversion. After thorough hydration in water, its alkalinity is measured. As shown in Figure 6 (where I corresponds to the total alkalinity and effective alkalinity of this comparative example, and IV corresponds to the total alkalinity and effective alkalinity of the deacidifying agent product obtained in Example 1 of this invention), the total alkalinity of the corresponding third solid phase of the four fly ashes in this comparative example is 18.34, 20.54, 23.84, and 22.74 mol / kg, respectively, while the effective alkalinity is only 17.24, 18.38, 22.14, and 21.44 mol / kg. The alkalinity is too low for deacidification applications. The total alkalinity of the deacidifying agent obtained by this invention was 29.46, 28.93, 29.77, and 30.77 mol / kg, respectively, and the effective alkalinity was 26.89, 26.32, 27.07, and 28.22 mol / kg, respectively. The total alkalinity and effective alkalinity of the water-washed-calcined fly ash were only 62.25%, 71.00%, 80.08%, 73.90% and 64.11%, 69.83%, 81.79%, 75.97% of the metal (hydr) oxide deacidifying agent obtained by this invention, respectively, which is far lower than the corresponding metal (hydr) oxide deacidifying agent obtained by this invention.

[0161] Comparative Example 2

[0162] In this comparative example, 20% (wt%) of analytical grade CaO powder was added to the first solid phase (i.e., the fly ash after water washing) of fly ash A, B, C, and D in the first step of Example 1 and mixed thoroughly to obtain a second solid phase. The second solid phase was treated in a muffle furnace at 900°C for 3 hours to obtain fly ash conversion products with added CaO. After being fully hydrated in water, the alkalinity was measured. As shown in Figure 6 (where II corresponds to the total alkalinity and effective alkalinity of this comparative example, and IV corresponds to the total alkalinity and effective alkalinity of the deacidifying agent product obtained in Example 1 of this invention), the total alkalinity of the four fly ash products obtained in this comparative example were 21.21, 22.72, 24.79, and 23.83 mol / kg, respectively, and the effective alkalinity were 20.21, 21.62, 23.39, and 22.53 mol / kg, respectively. In this comparative example, 20% (wt%) of analytical grade CaO was added to each of the four types of fly ash. However, compared with water-washed calcined fly ash, the total basicity and effective basicity only increased by 10.20%, 10.61%, 3.98%, 4.79% and 17.23%, 17.63%, 5.65%, 5.08%, respectively. Compared with the metal (hydr)oxide deacidifying agent of this invention, the total basicity and effective basicity of the fly ash conversion product with added CaO in this comparative example were only 72.00%, 78.53%, 83.27%, 77.45% and 75.16%, 82.14%, 86.41%, 79.84%, respectively, still far lower than the corresponding metal (hydr)oxide deacidifying agent obtained. This is because even with the addition of a certain amount of CaO, the activity of alkaline substances in unconverted calcined fly ash remains low, resulting in insufficient release of effective basicity during acid-base titration.

[0163] Comparative Example 3

[0164] In this comparative example, 20% (wt%) of analytical grade CaCO3 powder was added to the first solid phases (i.e., the water-washed fly ash) of fly ash A, B, C, and D in the first step of Example 1 and mixed thoroughly to obtain the second solid phase. The second solid phase was treated in a muffle furnace at 900°C for 3 hours to obtain water-washed calcined fly ash with added CaCO3. After being fully hydrated in water, the alkalinity was measured. As shown in Figure 6 (where III corresponds to the total alkalinity and effective alkalinity of this comparative example, and IV corresponds to the total alkalinity and effective alkalinity of the deacidifying agent product obtained in Example 1 of this invention), the total alkalinity of the corresponding third solid phases of the four fly ashes in this comparative example were 19.54 mol / kg, 20.36 mol / kg, 21.76 mol / kg, and 21.54 mol / kg, respectively, and the effective alkalinity were 17.54 mol / kg, 18.56 mol / kg, 20.01 mol / kg, and 19.29 mol / kg, respectively. In this comparative example, 20% (wt%) of CaCO3 was added to each of the four types of fly ash. However, compared with the water-washed-calcined fly ash, the total alkalinity and effective alkalinity were actually lower, with differences of 1.2%, -0.18%, -2.08%, -1.2% and 0.3%, 0.18%, -2.13%, -2.15%, respectively. The total alkalinity and effective alkalinity of the fly ash conversion product with added CaCO3 in this comparative example were only 66.33%, 70.38%, 73.09%, 70.00% and 65.24%, 70.52%, 73.92%, 68.36% of the metal (hydr)oxide deacidifying agent in this invention, respectively, still far lower than the corresponding metal (hydr)oxide deacidifying agent obtained from the invention. This is because the activity of alkaline substances in unconverted calcined fly ash remains low even with the addition of an appropriate amount of CaCO3, resulting in insufficient release of effective alkalinity.

[0165] In the three comparative examples above, the activity range of the product obtained from fly ash C was 16.5–17.2 mol / kg (as shown in Table 8), which was much lower than the activity of the deacidifying agent obtained from fly ash C in the examples (21–23.4 mol / kg).

[0166] Table 8 shows the activity of the products prepared from fly ash C in the above comparative examples.

Claims

A method for preparing a deacidifying agent from fly ash from municipal solid waste incineration, comprising the following steps: The primary conversion process transforms various types of minerals in the fly ash from municipal solid waste incineration into metallic carbonate minerals. Secondary conversion transforms the obtained metallic carbonate minerals into corresponding metallic oxides, yielding a high-alkalinity deacidifying agent. and Optionally, the three-stage conversion before deacidification application hydrates the metal oxide, giving it high deacidification activity. The fly ash from the municipal solid waste incineration is produced by deacidifying the flue gas from the municipal solid waste incineration process; The primary conversion is carried out in an aqueous solution and the conversion reagent contains water-soluble carbonates and / or water-soluble bicarbonates. The secondary conversion is carried out at temperatures exceeding 700°C. The method according to claim 1, wherein the method comprises the following steps: The primary conversion involves adding an aqueous solution of water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the municipal solid waste incineration fly ash, stirring and reacting to convert various types of minerals in the municipal solid waste incineration fly ash into metallic carbonate minerals. In the secondary conversion, after the primary conversion and liquid-solid separation, the resulting solid powder of metallic carbonate minerals is subjected to a secondary conversion at a temperature >700℃ to form metallic oxides, yielding a high-alkalinity deacidifying agent; and The three-stage transformation before deacidification involves hydrating the metal oxides to give them high deacidification activity. The method according to claim 1, wherein the method comprises the following steps: (1) Before the primary conversion, the fly ash from the municipal solid waste incineration is first washed with water to remove water-soluble components, especially metal salts and chloride-containing salts, and then the washed fly ash is obtained by liquid-solid separation. (2) Add an aqueous solution of water-soluble carbonate and / or water-soluble bicarbonate conversion reagent to the water-washed fly ash, stir and react, and convert the various types of minerals in the water-washed fly ash into metallic carbonate minerals through primary conversion. (3) After a second liquid-solid separation, the resulting solid powder of metallic carbonate minerals is subjected to a secondary conversion into metal oxides at a temperature >700℃ to obtain a high-alkalinity deacidifying agent; and (4) The three-stage transformation before deacidification application hydrates the metal oxide to give it high deacidification activity. The method according to any one of claims 1-3, wherein the conversion reagent used for the primary conversion includes sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, or any combination thereof; Preferably, the concentration range of the aqueous solution of the conversion reagent is 0.1-5.0M; and / or, the liquid-to-solid ratio of the aqueous solution of the conversion reagent to fly ash is (1-100):1; and / or, the temperature range of the primary conversion is 0-100℃; and / or, the time of the primary conversion is 0.5-48h. Preferably, the concentration range of the aqueous solution of the conversion reagent in the primary conversion is 0.5-4.5M, the liquid-solid ratio of the aqueous solution of the conversion reagent to fly ash in the primary conversion is (2-20):1, and the primary conversion time is 1-24h. The method according to any one of claims 1-4, wherein the conversion reagent further comprises the auxiliary agent carbon dioxide. According to any one of claims 1-5, the municipal solid waste incineration fly ash is generated by treating the flue gas of municipal solid waste incineration fly ash using the lime method, wherein the flue gas treatment method includes at least one of wet method, semi-wet method and dry method, or the municipal solid waste incineration fly ash is untreated fly ash and / or aged fly ash. According to any one of claims 1-6, the metal carbonate minerals are dried before the secondary conversion following the primary conversion to generate metal carbonate minerals and liquid-solid separation, at a drying temperature of 40-300°C. The method according to any one of claims 1-7 further includes the following step: The obtained deacidifying agent is reused for flue gas treatment of fly ash from municipal solid waste incineration, and then the method is repeated. A device for preparing a deacidifying agent from fly ash from municipal solid waste incineration, comprising: --Fly ash collection device, used to collect fly ash from municipal solid waste incineration; --Reaction device, used to convert various types of minerals in fly ash from municipal solid waste incineration into metallic carbonate minerals; --Heat treatment equipment, used to convert the obtained metallic carbonate minerals into corresponding metallic oxides to obtain a high-alkalinity deacidifying agent; and --Optionally, a hydration device is used to hydrate metal oxides to give them high deacidification activity. The apparatus according to claim 9, wherein the apparatus further comprises a washing device located between the fly ash collection device and the reaction device.

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