Method and equipment for preparing deacidification agent from household garbage incineration fly ash

Abstract

The invention relates to a method and equipment for preparing a deacidification agent from household garbage incineration fly ash, and the method comprises the following steps: primary conversion: converting various minerals in the household garbage incineration fly ash into metal carbonate minerals; secondary conversion: converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high-alkalinity deacidification agent; and optionally, performing three-stage conversion before deacidification application, and hydrating the metal oxide to obtain a deacidification agent with high activity; wherein the household garbage incineration fly ash is generated by performing deacidification treatment on household garbage incineration flue gas; the primary conversion is carried out in an aqueous solution, and a conversion reagent contains water-soluble carbonate and / or water-soluble bicarbonate; the secondary conversion is carried out at a temperature of more than 700 DEG C. According to the method, harmlessness, reduction and recycling of the household garbage incineration fly ash are achieved, environmental release and ecological burden of toxic and harmful substances are prevented, and the technical economic feasibility is good.

Description

Technical Field

[0001] The invention relates to the technical field of waste treatment, and in particular to a method and equipment for preparing a deacidifying agent from fly ash from the incineration of domestic waste. Background Art

[0002] Fly ash from the incineration of municipal solid waste is a secondary pollutant that is intercepted and settled during the flue gas purification process of the municipal solid waste incineration system. Its output accounts for about 3-5% of the total amount of incinerated waste. It is easy to enrich high-concentration heavy metals, such as lead (Pb), chromium (Cr), mercury (Hg), cadmium (Cd), copper (Cu), etc., and its content exceeds the soil background by 10-100 times. In addition, the salt content in fly ash is as high as 20-30%. Fly ash is recognized as a hazardous waste both in my country and internationally, and its safe disposal has become a global issue. At present, the treatment technologies for fly ash from the incineration of municipal solid waste are mainly divided into safe landfill after stabilization and solidification, cement kiln coordinated disposal, and sintering and melting and vitrification as filling aggregate.

[0003] As a pre-treatment for safe landfill, stabilization technology mainly includes chemical stabilization and physical thermal stabilization. Chemical stabilization technology aims to add stabilizers to reduce the toxicity of toxic substances in fly ash, making the risk of leaching smaller, thereby reducing the environmental risks of toxic substances in fly ash, especially heavy metals. Commonly used organic stabilizers include dithiocarbamate (DTC), mercaptopolyamine, EDTA polymer, sulfonated polysaccharide, etc.; inorganic stabilizers include lime, sodium sulfide, sulfate, phosphate, carbonate, silicate and iron oxide, etc. Thermal stabilization and thermal sintering involve heating the fly ash to a temperature where particles combine and reorganizing the chemical phases in the fly ash. Generally, the temperature of this type of thermal stabilization process is between 1000 and 1200°C and stabilizers are often added in coordination. The sintered product has reduced porosity and high strength and heavy metals are difficult to leach. The disadvantage of stabilization technology is that the stabilizer itself may slowly decompose and degrade in the environment, so long-term stability is not reliable; in room temperature stabilization / solidification landfill, water-soluble salts will cause the solid body to crack and cause heavy metals to leach out.

[0004] Cement kiln co-processing technology is to add fly ash to cement raw materials during cement production and sinter them together (1200-1500℃), and co-process fly ash from the incineration of domestic waste. It has significant social and environmental benefits, mature technology, and a complete standard system. The disadvantage of cement kiln co-processing technology is that toxic heavy metals are actually transferred to cement products and will be released into the environment again during the use and life cycle of cement. Cement kiln co-processing has strict restrictions on chloride salts in fly ash, and fly ash needs to be deeply washed with water beforehand.

[0005] Fly ash contains a large amount of valuable metals such as zinc, lead and copper. Academia and industry have developed many extraction and leaching technologies for the above-mentioned valuable metals in fly ash from the incineration of domestic waste. Chemical extraction technology aims to extract valuable metals by adding specific extractants to achieve the purpose of recycling. Commonly used extractants include hydrochloric acid, nitric acid, sulfuric acid, sodium hydroxide, sodium carbonate, ammonia water and chelating agents; among them, 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 disadvantage of chemical extraction technology is that a large amount of acidic or alkaline extractants are required, and the regeneration of the extractants is also difficult. Therefore, the industry has been seeking methods for environmentally friendly treatment of fly ash from the incineration of domestic waste. Summary of the invention

[0006] To this end, on the one hand, the present invention provides a method for preparing a deacidifying agent from fly ash from the incineration of domestic waste, which comprises the following steps:

[0007] Primary conversion, converting various types of minerals in the fly ash from the incineration of domestic waste into metal carbonate minerals;

[0008] Secondary conversion, converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high basicity deacidification agent; and

[0009] Optionally, a tertiary conversion prior to deacidification is used to hydrate the metal oxide to give it a high deacidification activity;

[0010] The domestic waste incineration fly ash is produced by deacidification treatment of domestic waste incineration flue gas;

[0011] The primary conversion is carried out in an aqueous solution and the conversion reagent comprises a water-soluble carbonate and / or a water-soluble bicarbonate;

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

[0013] In another aspect, the present invention provides a method for preparing a deacidifying agent from fly ash from incineration of domestic waste, the method comprising:

[0014] Primary conversion, adding an aqueous solution of a water-soluble carbonate and / or water-soluble bicarbonate conversion agent to the domestic waste incineration fly ash, stirring and reacting, and converting various types of minerals in the domestic waste incineration fly ash into metal carbonate minerals;

[0015] Secondary conversion: after the primary conversion is completed and the liquid-solid separation is carried out, the solid phase powder of the obtained metal carbonate mineral is secondary converted into metal oxides at a temperature of >700°C to obtain a high basicity deacidification agent; and

[0016] The tertiary conversion before deacidification application hydrates the metal oxides to give them high deacidification activity.

[0017] In another aspect, the present invention provides a method for preparing a deacidifying agent from fly ash from the incineration of domestic waste, comprising the following steps:

[0018] (1) Before the primary conversion, the fly ash from the incineration of domestic waste 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) adding an aqueous solution of a water-soluble carbonate and / or water-soluble bicarbonate conversion agent to the washed fly ash, stirring and reacting, and converting various types of minerals in the washed fly ash into metal carbonate minerals through primary conversion;

[0020] (3) after liquid-solid separation again, the solid phase powder of the obtained metal carbonate mineral is converted into metal oxides at a temperature of >700°C to obtain a high basicity deacidification agent; and

[0021] (4) The tertiary conversion before deacidification application hydrates the metal oxides to give them high deacidification activity.

[0022] 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 solution or any combination thereof. The conversion solution of ammonium carbonate and / or ammonium bicarbonate can be prepared on-site by introducing carbon dioxide into an ammonia solution.

[0023] In a preferred embodiment, the concentration range of the conversion reagent aqueous solution is 0.1-5.0M; and / or, the liquid-to-solid ratio of the conversion reagent aqueous solution to fly ash is (1-100):1; and / or, the temperature range in the primary conversion is 0-100°C; 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 time of the primary conversion is 1-24h.

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

[0026] In a preferred embodiment, the conversion reagent for ammonium carbonate and / or ammonium bicarbonate is prepared in situ by passing carbon dioxide into an aqueous ammonia solution.

[0027] In a preferred embodiment, the domestic waste incineration fly ash is produced by treating the flue gas of domestic waste incineration fly ash by a lime method, and the flue gas treatment method includes at least one of a wet method, a semi-wet method and a dry method, or the domestic waste incineration fly ash is untreated fly ash and / or aged fly ash.

[0028] Preferably, the content of silicon dioxide in the domestic waste incineration fly ash does not exceed 20% by weight, more preferably does not exceed 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, and the drying temperature is 40-300°C.

[0030] In a preferred embodiment, the method of the present invention further comprises the following steps: recycling the obtained deacidifying agent for flue gas treatment of domestic waste incineration fly ash, and then cyclically carrying out the method of the present invention for preparing the deacidifying agent from domestic waste incineration fly ash.

[0031] Finally, the present invention also provides a device for preparing a deacidifying agent from fly ash from incineration of domestic waste, comprising:

[0032] --Fly ash collection device, used to collect fly ash from the incineration of domestic waste;

[0033] --Reaction device, used to convert various types of minerals in fly ash from the incineration of domestic waste into metal carbonate minerals;

[0034] -- a heat treatment device for converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high basicity deacidification agent; and

[0035] - Optionally, a hydration device for hydrating the metal oxide to give it a high deacidification activity.

[0036] In a preferred embodiment, the apparatus further comprises a washing device, which is located between the fly ash collecting device and the reaction device.

[0037] The method of the present invention achieves the harmlessness, reduction and resource utilization of fly ash from the incineration of domestic waste, which is a hazardous solid waste, and well solves the environmental release and ecological burden of toxic and harmful substances in such hazardous waste. The present invention prepares fly ash from the incineration of domestic waste into a high-alkalinity metal oxide deacidification agent through two-stage conversion, and hydrates the metal oxide through three-stage conversion before deacidification application, so that it has a high deacidification activity. The technical and economic feasibility of the method of the present invention is very good, the processing cost is only a few hundred yuan, and a reusable deacidification agent and zinc-lead-rich materials are prepared, and a profit surplus can be achieved by comparison of the two. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A process flow diagram according to an embodiment of the method of the present invention is shown;

[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 washed fly ash in Example 1;

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

[0042] Figure 2 (d) shows a scanning electron micrograph 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 phase products during the conversion of raw fly ash in Example 1;

[0045] Figure 4 (a)-(d) respectively show the effect of the liquid-to-solid ratio on the alkalinity of the deacidification agent obtained by converting fly ashes A, B, C and D in Example 3;

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

[0047] Figure 6 (a)-(d) respectively show the comparison of the alkalinity effects of the materials obtained by fly ash A, B, C and D under different conversion methods (where Ⅰ, Ⅱ, Ⅲ and Ⅳ respectively represent the alkalinity effects of no conversion agent, addition of CaO, addition of CaCO3 and the deacidification agent obtained in Example 1 of the present invention). DETAILED DESCRIPTION

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

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

[0050] In the present invention, unless otherwise specified, all embodiments and preferred embodiments of the present application can be combined with each other to form a new technical solution.

[0051] In the present invention, unless otherwise specified, all technical features and preferred technical features of the present application can be combined with each other to form a new technical solution.

[0052] The total amount of domestic waste in my country is 250 million tons, of which about 180 million tons are incinerated. It is roughly estimated that about 10 million tons of fly ash are produced each year. Fly ash contains heavy metals with complex components and is enriched with pollutants such as dioxins and chloride salts. The leaching concentration exceeds the identification upper limit of hazardous wastes and is defined as hazardous waste by countries around the world. Unreasonable treatment methods will cause serious damage to the environment. The present invention can prepare domestic waste incineration fly ash into a high alkalinity deacidification agent through two-stage conversion, and hydrate the metal oxide through three-stage conversion before deacidification application to make it have high deacidification activity. The composition of fly ash from the incineration of domestic waste 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, Al, etc., and its acidic anion ligands are mainly hydroxide, carbonate, sulfate, silicate, fluoride, chlorosilicate, etc. The above-mentioned various metal ions and various anion ligands are randomly combined or coupled together, cross and contain each other, thus forming a highly complex and mixed mixture of salts and minerals, which exist in the fly ash in the form of powder or colloid and are difficult to decompose thermally.

[0053] The inventor unexpectedly found that, first, by using water-soluble carbonates and / or water-soluble bicarbonates as conversion reagents, various types of minerals in the fly ash from the incineration of domestic waste are uniformly converted into metal carbonate minerals through conversion reactions; metal carbonate minerals are converted into metal oxides at relatively low temperatures (e.g., 700-1000°C), and metal oxide deacidifiers with extremely high total alkalinity and effective alkalinity are obtained; the metal oxide deacidifier is hydrated before deacidification to give it a high deacidification activity. Thirdly, the prepared deacidifier can be recycled and reused for the treatment of flue gas from fly ash from the incineration of domestic waste (such as being used as a deacidifier in the deacidification treatment of fly ash), and multiple recycling can obtain zinc-lead enriched materials with high recovery value. Thirdly, the tail liquid produced can be evaporated and concentrated to obtain water-soluble metal salts or discharged into sodium salt bodies after appropriate treatment, without any toxic effects on the environment. Fourth, the harmlessness, reduction and resource utilization of hazardous solid wastes such as fly ash from the incineration of domestic waste are achieved, which well solves the environmental release and ecological burden of toxic and harmful substances in such hazardous wastes, and also significantly reduces the carbon footprint. Finally, the technical and economic feasibility of the present invention is very good in that fly ash from the incineration of domestic waste is prepared into a deacidifying agent with high basicity and high activity by conversion, and the processing cost is only a few hundred yuan. A reusable deacidifying agent and zinc-lead-rich materials are prepared, and a profit surplus can be achieved by comparison. Therefore, the method of the present invention can achieve significantly better economy at the same time.

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

[0055] Primary conversion, converting various types of minerals in the fly ash from the incineration of domestic waste into metal carbonate minerals;

[0056] Secondary conversion, converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high basicity deacidification agent; and

[0057] Optionally, in the third stage conversion, the metal oxide is hydrated before the deacidification application to make it have high deacidification activity;

[0058] The domestic waste incineration fly ash is produced by deacidification treatment of domestic waste incineration flue gas;

[0059] The primary conversion is carried out in an aqueous solution and the conversion reagent comprises a water-soluble carbonate and / or a water-soluble bicarbonate;

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

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

[0062] Through the two-stage conversion of the present invention, the fly ash from the incineration of domestic waste can be finally converted into a metal oxide deacidification agent with high total alkalinity and effective alkalinity; the three-stage conversion before deacidification hydrates the metal oxide to make it have high deacidification activity. The deacidification agent can be reused for the treatment of fly ash flue gas from the incineration of domestic waste, forming a closed loop of the treatment process.

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

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

[0065] In another aspect, the present invention provides a method for preparing a deacidifying agent from fly ash from incineration of domestic waste, the method comprising:

[0066] Primary conversion, adding an aqueous solution of a water-soluble carbonate and / or water-soluble bicarbonate conversion agent to the domestic waste incineration fly ash, stirring and reacting, and converting various types of minerals in the domestic waste incineration fly ash into metal carbonate minerals;

[0067] Secondary conversion: after the primary conversion is completed and the liquid-solid separation is carried out, the solid phase powder of the obtained metal carbonate mineral is secondary converted into metal oxides at a temperature of >700°C to obtain a high basicity deacidification agent; and

[0068] The tertiary conversion before deacidification application hydrates the metal oxides to give them high deacidification activity.

[0069] In the present 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 the fly ash. Here, it can be understood that when the fly ash is washed 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., free of water).

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

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

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

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

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

[0075] In another aspect, the present invention provides a method for preparing a deacidifying agent from fly ash from the incineration of domestic waste, comprising the following steps:

[0076] (1) Before the primary conversion, the fly ash from the incineration of domestic waste 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) adding an aqueous solution of a water-soluble carbonate and / or water-soluble bicarbonate conversion agent to the washed fly ash, stirring and reacting, and converting various types of minerals in the washed fly ash into metal carbonate minerals through primary conversion;

[0078] (3) after liquid-solid separation again, the solid phase powder of the obtained metal carbonate mineral is converted into metal oxides at a temperature of >700°C to obtain a high basicity deacidification agent; and

[0079] (4) The tertiary conversion before deacidification application hydrates the metal oxides to give them high deacidification activity.

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

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

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

[0083] The inventors of the present invention have found that when the concentration of the primary conversion reagent exceeds 4.5M, the material obtained after the secondary conversion undergoes sintering, thereby destroying its original ultrafine powder structure and being unsuitable for recycling as a deacidification agent. Therefore, preferably, in the primary conversion, the concentration range of the conversion reagent aqueous solution may be 0.5-4.5M, preferably 0.7-4.0M, more preferably 1-3.5M, and even more preferably 2-3.5M, and the liquid-to-solid ratio of the conversion reagent aqueous solution to the 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 the fly ash may 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 time for primary conversion may be 0.5-48 h, preferably 1-40 h, more preferably 4-35 h, still more preferably 10-30 h, further preferably 20-25 h.

[0086] In one embodiment, the conversion reagent used in the primary conversion is ammonium carbonate and / or ammonium bicarbonate. The advantages of using ammonium carbonate and / or ammonium bicarbonate as the conversion reagent compared to sodium carbonate are 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, which is carbon dioxide. Although carbon dioxide itself cannot be used as a primary conversion reagent, and the use of carbon dioxide alone cannot uniformly convert various phases in fly ash into metal carbonate minerals, as an auxiliary agent, carbon dioxide can adjust the pH of the system to a certain extent, thereby reducing the alkaline dissolution of heavy metals during the primary conversion, while saving part of the consumption of the conversion reagent.

[0088] In a preferred embodiment, the conversion reagent for ammonium carbonate and / or ammonium bicarbonate is prepared in situ by passing carbon dioxide into an aqueous ammonia solution.

[0089] In a preferred embodiment, the fly ash from the incineration of domestic waste is produced by treating the flue gas of fly ash from the incineration of domestic waste by lime method, and the flue gas treatment method includes at least one of wet method, semi-wet method and dry method, or the fly ash from the incineration of domestic waste is untreated fly ash and / or aged fly ash. Preferably, the content of silicon dioxide in the fly ash from the incineration of domestic waste does not exceed 20% by weight, more preferably does not exceed 10% by weight, and even more preferably does not exceed 5% by weight. The side effect of silicon dioxide in the fly ash from the incineration of domestic waste is reflected in that it reacts with metal oxides at high temperature in the secondary conversion to easily generate metal silicate minerals, thereby reducing the alkalinity of the deacidifying agent.

[0090] In a preferred embodiment, the metal carbonate mineral is preferably dried before the secondary conversion after the primary conversion to generate the metal carbonate mineral and the liquid-solid separation (for example, to reduce its water content to a suitable range, such as usually 0 to 15% by weight, preferably 0 to 5% by weight), and the drying temperature may be 40-300° C. The drying time may be selected as required and is not particularly limited here.

[0091] In a preferred embodiment, the primary conversion reaction can be achieved in a single-stage reactor, or can be completed by two-stage or multi-stage operation. Here, which operation can be specifically selected according to the processing capacity and the processing ability of the equipment.

[0092] In a preferred embodiment, the liquid phase obtained by liquid-solid separation can be recycled to the corresponding step, discharged into a sodium salt water body after treatment, or concentrated and evaporated.

[0093] In the present invention, the liquid phase obtained through liquid-solid separation contains soluble components, which can be partially recycled to the process, or can be concentrated and evaporated using the heat generated in the process, and the obtained salt can be used for commercial purposes.

[0094] like Figure 1 As shown, in a preferred embodiment, fly ash (6) obtained from lime treatment of fly ash from incineration of domestic waste is added to a washing device (1) for water washing to remove water-soluble components in the fly ash, and then liquid-solid separation is performed, and the obtained solid phase (12) is transported to a reaction device (2) for primary conversion; at the same time, a portion (111) of the obtained liquid phase (11) is returned to the washing device (1), and the remaining portion (112) is subjected to waste liquid treatment (7). In the reaction device (2), the solid phase (12) is reacted with an aqueous sodium carbonate solution to perform a primary conversion, and liquid-solid separation is performed after the reaction is completed. The obtained solid phase (22) is transported to a heat treatment device (3) for heating and secondary conversion to obtain a high alkalinity deacidification agent; at the same time, a portion (211) of the liquid phase (21) obtained by liquid-solid separation is returned to the reaction device (2), and the remaining portion (212) is subjected to waste liquid treatment (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 a metal (hydr) oxide (5) with high deacidification activity.

[0095] In addition, the method for preparing a deacidification agent from fly ash from incineration of domestic waste of the present invention further comprises the following steps: the obtained deacidification agent is reused for flue gas treatment of fly ash from incineration of domestic waste, and then the method for preparing a deacidification agent from fly ash from incineration of domestic waste of the present invention is circulated. In this circulation process, lead and / or zinc in fly ash from incineration of domestic waste will be enriched, and when the content of zinc is not less than 1% by weight and / or the content of lead is not less than 0.5% by weight, part of the material can be provided to the smelting enterprise as raw materials for lead and zinc smelting. The zinc and lead content in the recycling of the deacidification agent can be determined according to the national standard HJ 781-2016 method. 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, and digested in a 200°C graphite digester for 6 hours until the digestion solution remains about 1-2mL, and 2mL of nitric acid is added to dissolve the residue after the digestion is completed. After cooling, the volume was adjusted to 25 mL, and after filtering, the lead and zinc contents were analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0096] The deacidifying agent obtained by the present invention is recycled and used for the flue gas treatment of fly ash from the incineration of domestic waste, and the zinc-lead enriched material with high recovery value is obtained by multiple recycling. Generally, after the deacidifying agent is recycled four times, the zinc enrichment concentration in the fly ash and the deacidifying agent material can exceed 1%, and the lead enrichment concentration is about 0.5%. Such materials can be sold to lead and zinc smelting enterprises. Therefore, the present invention also provides a method for enriching lead and / or zinc in fly ash from the incineration of domestic waste, which comprises the following steps: firstly, the method for preparing a deacidifying agent from fly ash from the incineration of domestic waste of the present invention is carried out, and then the obtained deacidifying agent is recycled for the flue gas treatment of the fly ash from the incineration of domestic waste.

[0097] Finally, the present invention also provides a device for preparing a deacidifying agent from fly ash from incineration of domestic waste, comprising:

[0098] --Fly ash collection device, used to collect fly ash from the incineration of domestic waste;

[0099] --Reaction device, used to convert various types of minerals in fly ash from the incineration of domestic waste into metal carbonate minerals;

[0100] -- a heat treatment device for converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high basicity deacidification agent; and

[0101] - Optionally, a hydration device to hydrate the metal oxide before deacidification application to give it a high deacidification activity.

[0102] In a preferred embodiment, the apparatus further comprises a washing device, which is located between the fly ash collecting device and the reaction device.

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

[0104] After washing and liquid-solid separation of the fly ash from the incineration of domestic waste, a pre-drying treatment may be performed. Therefore, in a preferred embodiment, there is also a heating device between the downstream of the washing device and the upstream of the reaction device, which is used to pre-dry the fly ash after washing and liquid-solid separation (the drying temperature may be, for example, 40-300° C., preferably 50-200° C.).

[0105] In a preferred embodiment, the reaction device may be a reactor (tank) with a stirring device. In a preferred embodiment, the reaction device further comprises a metering device for adding a conversion reagent aqueous solution, and preferably, the metering device and the corresponding pipeline are alkali-resistant.

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

[0107] In a preferred embodiment, the hydration device is a hydration reaction device, such as a reaction kettle (tank), which is used to receive the metal oxide obtained by heating the heat treatment device and hydrate with the water in the hydration device. In order to prevent the water temperature from being too high due to hydration, the hydration device may also include a heat exchange device for heat exchange.

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

[0109] In a preferred embodiment, a conveying device (such as a conveyor belt, etc.) is further provided between the heat treatment device and the hydration device, which is used to convey the metal oxide obtained from the heat treatment device to the hydration device for hydration reaction.

[0110] In addition, the device for preparing a deacidifying agent from fly ash from the incineration of domestic waste of the present invention can also be directly combined with a domestic waste incineration device, in particular, combined with a fly ash treatment device used in the domestic waste incineration device. In this way, the fly ash can be recycled and the metals such as lead and / or zinc in the fly ash can be enriched.

[0111] The method of the present invention achieves the harmlessness, reduction and resource utilization of hazardous solid waste fly ash from the incineration of domestic waste, and well solves the environmental release and ecological burden of toxic and harmful substances in such hazardous waste. The present invention prepares fly ash from the incineration of domestic waste into a high-alkalinity metal oxide deacidifier through a two-stage conversion, and hydrates the metal oxide through a three-stage conversion before deacidification application to make it have a high deacidification activity. The technical and economic feasibility of the method of the present invention is very good, the processing cost is only a few hundred yuan, and a reusable deacidifier and zinc-lead-rich materials are prepared, and a profit surplus can be achieved by comparison of the two.

[0112] Example

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

[0114] In the present invention, the 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 the aqueous solution with pH 3.0 as the titration endpoint, such as hydroxides, carbonates, bicarbonates, etc.; the effective alkalinity refers to the substances that can consume acid and contribute to alkalinity in the aqueous solution with pH 8.0 as the titration endpoint, mainly the content of hydroxides. The determination methods of total alkalinity and effective alkalinity are as follows:

[0115] A certain amount of solid sample is placed in a beaker, deionized water is added, and the liquid-solid ratio (by weight) is controlled to be 10:1, and magnetic agitation is used at room temperature to titrate the solution to acidity, and the acid amount consumed as the titration end point is total alkalinity with a pH value of 3.0; then 2M NaOH solution is used to back-titrate to alkalinity with a pH value of 8.0 as the titration end point, and the acid amount consumed by the former and the alkali amount difference consumed by the back titration are effective alkalinity. For the convenience of measurement and comparison with reference examples, the deacidification agent powder sample obtained by the secondary conversion of unit mass is used in all embodiments to do the mass accounting (rather than the deacidification agent emulsion obtained after hydration to do the volume accounting) The number of moles of nitric acid consumed is evaluated for alkalinity. The titration error of different batches generally differs, but a more consistent titration error can occur in the same batch of experiments.

[0116] The four fly ash samples selected in the present invention are all domestic waste incineration fly ashes produced by deacidification of domestic waste incineration flue gas by lime method, and are respectively recorded as: fly ash A, fly ash B, fly ash C and fly ash D.

[0117] Example 1

[0118] Take 500g of domestic waste incineration fly ash (original fly ash A, B, C and D) in a reaction container, add deionized water, the water to fly ash ratio (L / Kg) is 10:1, stir it in water for 2h, filter to remove soluble salt components, and then dry it in an electric heating blast drying oven with a setting parameter of 60℃ for 24h to obtain the first solid phase, that is, washed fly ash. Take 15g of the above washed fly ash (after drying, the same below) in a polyethylene bottle, add a conversion reagent Na2CO3 solution with a concentration of 20% (equivalent to 1.89M, the same below), the liquid-solid ratio (L / Kg, the same below) is 4:1, react at room temperature for 12h, separate the liquid and solid, and then wash the unreacted Na2CO3 on the solid surface with water, filter and dry to obtain the second solid phase, that is, metal carbonate minerals. The second solid phase is converted in a muffle furnace at 900℃ for 3h to generate a third solid phase (i.e., metal oxide) to obtain a high basicity deacidification agent. The third solid phase is placed in water for hydration to obtain a deacidifier emulsion, at which time the alkaline capacity of the deacidifier is fully activated. The total alkalinity and effective alkalinity of the original fly ash and the obtained deacidifier emulsion are titrated using 2M HNO3 solution and 2M NaOH solution, respectively. The alkalinity is evaluated by the number of moles of nitric acid required to be consumed per unit mass of the original fly ash and per unit mass of the deacidifier powder sample obtained by the secondary conversion.

[0119] The total alkalinity and effective alkalinity of the four raw fly ashes and the resulting metal (hydr) oxide deacidifiers are shown in Table 1. The total alkalinity of the raw fly ashes 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 (hydr) oxide deacidifiers are 29.99, 29.31,

[0120] 30.29 and 31.24 mol / kg, and their total alkalinity is 3.75, 3.71, 3.35 and 3.74 times of the original fly ash respectively. The effective alkalinity of the original fly ash A, B, C and D is 7.10, 7.12, 8.30 and 7.28 mol / kg respectively, and the effective alkalinity of the metal (hydr) oxide deacidifier is 27.42, 26.68, 27.59 and 28.69 mol / kg respectively. The effective alkalinity of the obtained product metal (hydr) oxide deacidifier is 3.86, 3.75, 3.32 and 3.94 times of the original fly ash respectively. It shows that the obtained deacidifier product has very high alkalinity and corresponding deacidification activity.

[0121] Table 1 List of total alkalinity and effective alkalinity of four kinds of raw fly ash and the resulting metal (hydroxide) deacidification agent products

[0122]

[0123] The caustic soda, soda ash, lime or slaked lime commonly used in the industry are used as references for comparison, as shown in Table 2. The total alkalinity of the deacidification agent product obtained by the present invention 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 deacidification agent product obtained by the present invention is equivalent to that of lime (CaO) of Class II standard.

[0124] Table 2 Comparison of basicity of metal (hydroxide) deacidifier of the present invention and common industrial alkali

[0125]

[0126] Taking fly ash C as an example, scanning electron microscopy was used to characterize the morphology and particle size changes of the original fly ash to the metal (hydr)oxide deacidification agent (see Figure 2 ). Original fly ash ( Figure 2 (a)) The particles are densely aggregated in clusters of large particles. The agglomeration is still quite significant after washing. Figure 2 (b)) are distributed in nearly spherical clusters. Washed / calcined fly ash ( Figure 2 (c)) The structure of the fly ash after washing is more irregular, but the particle aggregation is still obvious, which may be due to the collapse of its nearly spherical cluster structure caused by calcination. The metal (hydr) oxide deacidification agent ( Figure 2 (d)) Compared with the original fly ash, the dispersibility is significantly enhanced and the particle size is significantly reduced.

[0127] XRD was used to characterize the changes in the crystal phases of different solid products during the process of fly ash C being converted from raw fly ash to metal (hydroxide) deacidification agent. Figure 3). The composition of fly ash from the incineration of domestic waste is very complex. The main components are water-soluble mixed salts and insoluble mixed minerals of various metal ions such as Na, K, Ca, Mg, Zn, Pb, Fe, Al, etc., and their acidic anion ligands are mainly chloride ions, hydroxides, carbonates, sulfates, silicates, fluorides, chlorosilicates, etc. The above-mentioned various metal ions and various anion ligands are randomly combined or coupled together, cross-linked and contained with each other, thus forming a highly complex and mixed mixture of salts, amorphous minerals or crystalline minerals, which exist in the fly ash in the form of powder or colloid. From the perspective of the crystalline minerals presented in the original fly ash, there are characteristic diffraction peaks of chlorides (NaCl, KCl), carbonates (CaCO3), sulfates (CaSO4), zinc carbonate (ZnCO3), silicates (Mg2SiO4), sulfides (FeS2), oxides (Al2O3) and metal elements (Cd). Using sodium carbonate as a conversion reagent, they are uniformly converted into metal carbonate minerals through conversion reactions. The diffraction peaks attributable to carbonates in the primary conversion products are very strong, and there are strong diffraction peaks attributable to CaCO3 and Pb3(CO3)2(OH)2, indicating that the main product of the primary conversion is carbonate. After the secondary conversion, metal carbonate minerals are converted into metal oxides at a relatively low temperature. The secondary conversion products mainly have diffraction peaks attributable to metal oxides, including CaO, MgO and (CaO) 12 The diffraction peak of (Al2O3)7 indicates that the secondary conversion mainly forms various metal oxide components, and has very high total alkalinity and effective alkalinity. 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, and the proportion of various metal oxides can reach 90% of the total substance. Through the tertiary conversion, the metal oxide mixture is hydrated to have a high deacidification activity. The tertiary conversion products are mainly attributed to metal hydroxides and some metal oxides, such as the diffraction peaks of Ca(OH)2 and MgO. It should be noted that XRD cannot show the change law of amorphous mineral phases in different transformation stages, and the phase components with a content of less than 5% are sometimes difficult to detect. In the embodiment, only XRD is used as an example to illustrate the change law of crystalline phases in different solid phase products in different transformation stages of the original fly ash into a high-activity metal (hydride) oxide deacidifier.

[0128] Example 2

[0129] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 15g of the washed fly ash in a polyethylene bottle, add Na2CO3 solution with concentration gradients of 6%, 10%, 20%, 30%, and 40%, respectively, and the liquid-solid ratio is 4:1. React at room temperature for 12 hours, first separate the liquid and solid, then wash the unreacted Na2CO3 on the solid surface with water, filter and dry to obtain the second solid phase, i.e., metal carbonate minerals. The second solid phase is converted in a muffle furnace at 900°C for 3 hours to generate the third solid phase, i.e., metal oxide deacidifier. The third solid phase is placed in water for hydration to obtain a deacidifier emulsion, and the alkalinity of the deacidifier is fully activated. The alkalinity determination and evaluation method of the obtained deacidifier is the same as above. In this embodiment, the total alkalinity and effective alkalinity of the corresponding metal (hydride) oxide deacidifiers obtained from the four fly ashes vary with the Na2CO3 concentration as shown in Table 3. In this embodiment, the total basicity and effective basicity of the metal (hydroxide) deacidification agent obtained by the conversion of fly ashes A, B, C and D increase with the increase of the concentration of the conversion reagent Na2CO3. The overall performance is that it first increases, and then reaches a saturation peak when it is increased to a certain concentration. When the concentration of Na2CO3 is 6%, the total basicity of the corresponding metal (hydroxide) deacidification agent obtained by the conversion of fly ashes A, B, C and D is 26.54-28.14mol / kg, and the effective basicity is 24.03-25.81mol / kg. When the concentration of Na2CO3 increases to 10%, the total basicity of the corresponding metal (hydroxide) deacidification agent obtained by the conversion of fly ashes A, B, C and D is 27.46-29.61mol / kg, and the effective basicity is 25.81-27.15mol / kg. When the concentration of Na2CO3 reaches 20%, the total alkalinity of the corresponding metal (hydr) oxide deacidification agents obtained by the conversion of fly ash A, B, C and D is 29.31-31.24 mol / kg, and the effective alkalinity is 26.68-28.69 mol / kg. Compared with the conversion concentration of 6%, when the concentration of Na2CO3 reaches 20%, the total alkalinity of fly ash A, B, C and D increases by 13.00%, 9.61%, 7.64% and 13.84%, respectively, and the effective alkalinity increases by 14.11%, 8.19%, 6.90% and 14.58%, respectively, which shows 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 concentration of Na2CO3 continued to increase to 30%, the total alkalinity and effective alkalinity of the corresponding metal (hydr)oxide deacidification agents obtained by the conversion of fly ash A, B, C and D were only 1%-6% higher than the concentration of the conversion reagent with a concentration of 20%, that is, the total alkalinity was only increased by 0.77%, 2.49%, 5.77% and 1.02%, respectively, and the effective alkalinity was only increased by 0.51%, 2.47%, 5.77% and 1.02%, respectively.

[0130] 6.13% and 1.92%. Similarly, when a 40% Na2CO3 solution is added, the total alkalinity and effective alkalinity are almost unchanged compared to the 30% conversion reagent concentration, and the difference between the two is less than the error. This shows that when a sufficient concentration of Na2CO3 is added, the concentration of the conversion reagent is no longer a determining factor in the increase in the total alkalinity and effective alkalinity of the final product, the metal (hydr)oxide deacidification agent. What's worse is that when the concentration of Na2CO3 reaches or exceeds 4.5M (equivalent to a concentration of 48%), the material obtained after the secondary conversion often undergoes sintering, which destroys the original ultrafine powder structure and is no longer suitable for recycling as a deacidification agent.

[0131] Table 3 Basicity change data of metal (hydroxide) deacidification agent obtained by fly ash conversion in Example 2

[0132]

[0133] Example 3

[0134] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 15 g of the washed fly ash in polyethylene bottles, add 20% Na2CO3 solution, and the liquid-solid ratio is 2:1, 4:1, 6:1, 8:1, 12:1, 16:1, respectively. React the fly ash at room temperature for 12 hours, separate the liquid and solid first, then wash the unreacted Na2CO3 on the solid surface with water, filter and dry to obtain the second solid phase, i.e., metal carbonate minerals. The second solid phase is converted in a muffle furnace at 900°C for 3 hours to generate a third solid phase, i.e., a metal oxide deacidifier. The third solid phase is placed in water for full hydration to obtain a deacidifier emulsion, and the alkalinity of the deacidifier is fully activated. The alkalinity determination and evaluation method of the obtained deacidifier are the same as above.

[0135] In this embodiment, the effect of liquid-to-solid ratio on the total basicity and effective basicity of the metal (hydr)oxide deacidification agent obtained by fly ash conversion is as follows: Figure 4As shown. When the liquid-solid ratio is 2:1, the total alkalinity of the corresponding metal (hydroxide) deacidifiers obtained by converting fly ashes A, B, C and D is less than 29 mol / kg, and the effective alkalinity is less than 26 mol / kg. When the liquid-solid ratio is 4:1, the total alkalinity of the corresponding metal (hydroxide) deacidifiers obtained by converting the above four fly ashes is 29.19-30.17 mol / kg, and the effective alkalinity is 26.57-28.57 mol / kg. Compared with the case where the liquid-solid ratio is 2:1, the total alkalinity of the corresponding metal (hydroxide) deacidifiers obtained by converting fly ashes A, B, C and D increased by 7.70%, 5.37%, 7.21% and 9.54% respectively, and the effective alkalinity increased by 8.24%, 7.86%, 8.55% and 12.67% respectively. When the liquid-solid ratio increases to 6:1, compared with the metal (hydroxide) deacidifier obtained under the condition of a liquid-solid ratio of 4:1, the changes in total alkalinity and effective alkalinity are less than the error. When the liquid-solid ratio continues to increase to 8:1, 12:1 and 16:1, the total alkalinity and effective alkalinity of the corresponding metal (hydroxide) deacidifiers obtained from the four fly ash conversions no longer increase. This shows that the primary conversion can be effectively carried out when the liquid-solid ratio reaches 4:1.

[0136] Example 4

[0137] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 50 g of the washed fly ash in a polyethylene bottle, add a 20% Na2CO3 solution, and the liquid-solid ratio is 4:1. The fly ash is reacted at room temperature for 12 hours, first liquid-solid separation, and then the unreacted Na2CO3 is washed with water, filtered and dried to obtain the second solid phase, i.e., metal carbonate minerals. The second solid phase is divided into five equal parts, and the secondary conversion is carried out at 700°C, 800°C, 850°C, 900°C, and 1000°C in a muffle furnace for 3 hours to generate the third solid phase, i.e., the metal oxide deacidifier. The third solid phase is placed in water for full hydration to obtain a deacidifier emulsion, and the alkalinity of the deacidifier is fully activated. The alkalinity determination and evaluation methods are the same as above.

[0138] In this embodiment, the data of the secondary conversion temperature change and the fly ash conversion effect are shown in Table 4. When the secondary conversion temperature is 700°C, the total basicity of the corresponding metal (hydr) oxide deacidification agent obtained by the conversion of fly ashes 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 not sufficient at this temperature and has not reached the saturation value. When the secondary conversion temperature is increased to 800°C, the total basicity of the corresponding metal (hydr) oxide deacidification agent obtained by the conversion of fly ashes 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 with 800℃, when the secondary conversion temperature is increased to 850℃, the total basicity and effective basicity of the corresponding metal (hydroxide) deacidification agents obtained by the conversion of fly ash A, B, C and D are still slightly increased, with 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 is increased to 900℃, the total basicity and effective basicity values ​​of the corresponding metal (hydroxide) deacidification agents obtained by the four fly ash conversions are not much different from the corresponding values ​​under the secondary conversion conditions of 850℃, and are basically lower than their error values, indicating that the secondary conversion in the fly ash has been fully completed at this time, and the carbonate components of the primary conversion are completely decomposed and converted into the corresponding metal oxides.

[0139] Table 4 Basicity change data of metal (hydroxide) deacidification agent obtained by fly ash conversion in Example 4

[0140]

[0141] Example 5

[0142] Take 10g of domestic waste incineration fly ash (original fly ash A, B, C and D) in the reaction container and carry out the following experimental designs: (1) directly add 6% and 10% Na2CO3 solutions to the original fly ash, with a liquid-solid ratio of 2:1; (2) directly add 20% Na2CO3 solution to the original fly ash, with a liquid-solid ratio of 2:1 and 4:1. Then react at room temperature for 12 hours and separate the liquid and solid, then wash with water to remove the unreacted Na2CO3 on the solid surface, filter and dry to obtain the first solid phase, place it in a muffle furnace and calcine it at 900℃ for 3 hours to obtain the second solid phase. The second solid phase is placed in water to fully hydrate to obtain a deacidifier emulsion. The alkalinity determination and evaluation methods are the same as above.

[0143] As shown in Table 5, when the conversion reagent Na2CO3 concentration is 6% (liquid-solid ratio 2:1), the total basicity of the obtained metal (hydroxide) deacidification agent is 17.83-21.53mol / kg, and the effective basicity is 16.54-20.29mol / kg. When the conversion reagent concentration is 10% (liquid-solid ratio 2:1), the total basicity of the obtained metal (hydroxide) deacidification agent changes at 20.95-24.95mol / kg, and the effective basicity changes at 19.59-23.35mol / kg. When the Na2CO3 concentration is 20% (liquid-solid ratio 2:1), the total basicity of the metal (hydroxide) deacidification agent changes at 23.50-25.43mol / kg, and the effective basicity is 22.12-24.16mol / kg. When the concentration of Na2CO3 is 20% (liquid-solid ratio 4:1), the total alkalinity of the metal (hydroxide) deacidifier varies between 24.70-27.15 mol / kg, and the effective alkalinity is between 23.39-25.87 mol / kg. Compared with the first desalination and then primary conversion (same liquid-solid ratio) in Example 1, the total alkalinity and effective alkalinity of the metal (hydroxide) deacidifier obtained by direct conversion are 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 affects the efficiency of the primary conversion. The effect of water-soluble salts on conversion is particularly significant at a lower liquid-solid ratio and a lower conversion reagent concentration, but the effect is relatively weakened when the liquid-solid ratio is higher and the conversion reagent concentration is higher. Compared with Example 1, which first washes and removes water-soluble salts and then performs primary conversion, the reagent consumption increases when the original fly ash is directly converted, and the reusability of the conversion reagent decreases.

[0144] Table 5 Basicity change data of metal (hydroxide) deacidification agent obtained by fly ash conversion in Example 5

[0145]

[0146] Example 6

[0147] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 5 g of washed fly ash C in 12 polyethylene bottles, add 10% Na2CO3 solution, the liquid-solid ratio is 4:1, the reaction temperature is 35°C, and then measure at intervals of 0.5, 1, 2, 3, 4, 6, 8, 10, 13, 24, 32, and 48 hours, respectively, wherein after solid-liquid separation, wash away the incompletely reacted Na2CO3 with clean water, filter and dry to obtain the second solid phase. The second solid phase is subjected to secondary conversion at 900°C in a muffle furnace for 3 hours to obtain the third solid phase. The third solid phase is placed in clean water for full hydration to obtain a metal (hydr) oxide deacidification agent suspension. The alkalinity determination and evaluation methods are the same as above.

[0148] Depend on Figure 5It can be seen that the time of the primary conversion reaction significantly affects the total alkalinity and effective alkalinity of the final deacidification agent. After 0.5h of primary conversion reaction, 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 1h of primary conversion reaction, they continued to increase rapidly to 25.90 and 24.15 mol / kg; after 4h of primary conversion, the total alkalinity and effective alkalinity increased to 27.11 and 25.35 mol / kg; after 10h of primary conversion, the total alkalinity and effective alkalinity continued to increase to 28. 83 and 26.6 mol / kg; 13 hours after the primary conversion, the total alkalinity and effective alkalinity reached 29.31 and 26.97 mol / kg, and the conversion was basically close to equilibrium; 24 hours after the primary conversion, the total alkalinity and effective alkalinity reached 29.47 and 27.17 mol / kg; within the range of 24-48 hours of primary conversion, the total alkalinity and effective alkalinity were stable at 29.47-29.75 mol / kg and 27.17-27.55 mol / kg, respectively.

[0149] Example 7

[0150] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 5 g of washed fly ash C in a polyethylene bottle, add a single or mixed solution of Na2CO3 / NaHCO3 with a total concentration of 1.5 M as the aqueous solution of the conversion reagent, and set the molar ratio to 1:0, 2:1, 1:1, 1:2, 0:1, respectively, wherein the liquid-solid ratio of the aqueous solution of the conversion reagent to the washed fly ash is 4:1, react at room temperature for 12 hours, separate the liquid and solid first, and then wash the mixed conversion liquid that has not completely reacted on the solid surface with water, filter and dry to obtain the second solid phase. The second solid phase is subjected to secondary conversion at 900°C in a muffle furnace for 3 hours to obtain a third solid phase. The third solid phase is placed in water for full hydration to obtain a metal (hydr) oxide deacidification agent emulsion.

[0151] The alkaline capacity of the corresponding metal (hydride) oxide deacidifier obtained is shown in Table 6. The total alkalinity and effective alkalinity of the deacidifier obtained by converting with Na2CO3 alone are 28.95 and 27.25 mol / kg, respectively. When NaHCO3 is used as an auxiliary agent alone, the total alkalinity and effective alkalinity of the deacidifier obtained are 27.46 and 25.18 mol / kg, respectively. When Na2CO3 and NaHCO3 are matched, when n(Na2CO3):n(NaHCO3)=2:1, the total alkalinity and effective alkalinity of the deacidifier obtained are 27.26 and 25.10 mol / kg, respectively. When n(Na2CO3):n(NaHCO3)=1:1 and 1:2, the total alkalinity of the deacidifier obtained is 27.71 and 27.56 mol / kg, respectively, and the effective alkalinity is 25.39 and 25.26 mol / kg, respectively.

[0152] Table 6 Summary of the effects of the conversion agent compounding in Example 7

[0153]

[0154] Example 8

[0155] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 5 g of washed fly ash C in polyethylene bottles, add 1.5 M (NH4)2CO3 solution and NH4HCO3 solution, respectively, with a liquid-solid ratio of 4:1, react at room temperature for 12 hours, first separate the liquid and solid, then wash the unreacted mixed conversion liquid on the solid surface with water, filter and dry to obtain the second solid phase. The second solid phase is subjected to secondary conversion at 900°C in a muffle furnace for 3 hours to obtain the third solid phase. The third solid phase is placed in water for full hydration to obtain a metal (hydr)oxide deacidifying agent emulsion. The total alkalinity of the corresponding metal (hydro)oxide deacidifiers obtained from (NH4)2CO3 solution and NH4HCO3 solution are 27.34 and 26.81 mol / kg, respectively, and the effective alkalinity are 25.25 and 24.72 mol / kg, respectively; the advantage of using ammonium carbonate or ammonium bicarbonate as the conversion agent compared to sodium carbonate is that the former is cheaper and the residual filtrate produced after the first-level conversion can be used as fertilizer after purification.

[0156] Example 9

[0157] Repeat the first step in Example 1 to obtain the first solid phase, i.e., washed fly ash. Take 5 g of washed fly ash C in a polyethylene bottle, add a 10% Na2CO3 solution (liquid-to-solid ratio of 4:1), and then introduce CO2 gas under atmospheric pressure for 1 hour, then stop ventilation, and continue to react at room temperature for 12 hours. Liquid-solid separation, then wash the unreacted mixed conversion liquid on the solid surface with water, filter and dry to obtain the second solid phase. The second solid phase is converted in a muffle furnace at 900°C for 3 hours to obtain the third solid phase. The third solid phase is placed in water for full hydration to obtain a metal (hydroxide) deacidification agent emulsion. The total alkalinity and effective alkalinity of the corresponding metal (hydroxide) deacidification agent obtained are 28.15 and 26.46 mol / kg, respectively. Experiments show that carbon dioxide itself cannot be used as a primary conversion reagent, and the use of carbon dioxide alone cannot uniformly convert 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 dissolution of heavy metals during the primary conversion.

[0158] Example 10

[0159] Repeat step 1 in Example 1 to obtain the first solid phase, namely the washed fly ash. A primary conversion system comprising conversion reagents (NH4)2CO3 and NH4HCO3 was prepared in situ according to the following two methods.

[0160] (1) 5 g of fly ash was placed in a reaction tank, and a 5% ammonia solution was added to the reaction tank, with a liquid-to-solid ratio of 6:1. The reaction tank was stirred magnetically at room temperature and CO2 gas was introduced until the pH value of the reaction system was 9.0-9.5, and then the gas was stopped. The reaction was continued with magnetic stirring for 8 h, and then filtered and dried to obtain a second solid phase.

[0161] (2) adding a 5% ammonia solution into the reaction tank, introducing CO2 with magnetic stirring at room temperature to generate a conversion solution containing (NH4)2CO3 and NH4HCO3 in situ, stopping the ventilation, and then adding 5 g of washed fly ash into the system with a liquid-to-solid ratio of 6:1. After reacting for 8 hours with magnetic stirring, filtering and drying to obtain a second solid phase;

[0162] The second solid phase was subjected to secondary conversion at 900°C for 3h in a muffle furnace to obtain a third solid phase. The third solid phase was placed in deionized water for full hydration to obtain a metal (hydr)oxide deacidification agent suspension. The alkalinity determination and evaluation methods were the same as above. The total alkalinity obtained was 27.40 mol / kg and 26.88 mol / kg, and the effective alkalinity was 25.84 mol / kg and 25.08 mol / kg, respectively.

[0163] Embodiment 11

[0164] The activity of the deacidifier obtained in the above typical embodiment, that is, the actual acid neutralization efficiency of the deacidifier within 10 minutes, is determined as follows: take 1g of the deacidifier prepared from fly ash C in a 50mL conical flask, add deoxygenated deionized water (40℃ warm water) at a liquid-to-solid ratio of 40:1 and immediately use a sealing film to isolate the air, and drip 5 drops of phenolphthalein reagent after hydration for about 2 minutes. Rapidly titrate 4M hydrochloric acid until it is just colorless and keep it at this mutation point for 10 minutes, record the acid consumption, and the molar mass of hydrochloric acid consumed per kilogram of deacidifier is the activity. It can be seen from Table 7 that the original fly ash C without any treatment and the original fly ash C after calcination only have an activity of only 2.36 and 7.24 mol / kg; under the typical conversion parameters of Examples 1 to 10, the activity of the deacidifier prepared from fly ash C is as high as 21 to 23.4 mol / kg, which is 9 to 10 times the activity of the original fly ash, and has extremely high deacidification activity. The activity of the deacidifying agent is as high as more than 80% of the total alkalinity of the deacidifying agent, indicating that most of the alkaline capacity contained in the obtained deacidifying agent has actual deacidifying activity.

[0165] Table 7 Activity of deacidifier prepared from fly ash C under typical conversion parameters

[0166]

[0167] It can be seen from the above embodiments that the present invention provides a simple and effective fly ash resource utilization scheme. Through the three-stage conversion process, the metal oxides and their corresponding hydroxide components are enriched and purified step by step, and finally a metal (hydroxide) oxide deacidifier with ultra-high basicity and corresponding activity is obtained, thereby realizing the resource utilization of fly ash. The study of staged fly ash and comprehensive fly ash is classified into different categories, which emphasizes the universality of the present invention for the resource application of fly ash. The method provided by the present invention is not only simple and efficient, but also has the prospect of large-scale industrial application. From the perspective of environmental impact, the disposal problem of fly ash can be solved; from the perspective of benefits, the self-circulation of metal (hydroxide) oxide deacidifiers in waste incineration plants can be basically realized. The above-mentioned embodiments are preferred embodiments of the present invention. It should be pointed out that without departing from the conversion principle and purpose of the present invention, several improvements and modifications can be made, and these improvements and modifications should be regarded as the scope of protection of the present invention.

[0168] Comparative Example 1

[0169] This comparative example uses the first solid phase water-washed fly ash of fly ash A, B, C and D in the first step of Example 1, and directly treats it in a muffle furnace at 900°C for 3 hours to obtain water-washed-calcined fly ash without primary conversion, and then places it in water for full hydration to measure the alkalinity. Figure 6 It can be seen that (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 deacidification agent product obtained in Example 1 of the present invention), the total alkalinity of the corresponding third solid phase of the four fly ashes described in this comparative example is 18.34, 20.54, 23.84 and 22.74 mol / kg, respectively, and the effective alkalinity is only 17.24, 18.38, 22.14 and 21.44 mol / kg, and the alkalinity is too low to be used for deacidification. The total alkalinity of the deacidification agent obtained by the present invention is 29.46, 28.93, 29.77 and 30.77 mol / kg, respectively, and the effective alkalinity is 26.89, 26.32, 27.07 and 28.22 mol / kg, respectively. The total alkalinity and effective alkalinity of the washed-calcined fly ash are only 62.25%, 71.00%, 80.08%, 73.90% and 64.11%, 69.83%, 81.79%, 75.97% of the metal (hydr) oxide deacidifier in the present invention, respectively, which are much lower than the corresponding product metal (hydr) oxide deacidifier obtained.

[0170] Comparative Example 2

[0171] In this comparative example, 20% (weight %) of analytically pure CaO powder was added to the first solid phase (i.e., washed fly ash) 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 a fly ash conversion product with CaO added, which was then placed in water for full hydration and then the alkalinity was measured. Figure 6 It can be seen (wherein 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 deacidification agent product obtained in Example 1 of the present invention), the total alkalinity of the four fly ash products obtained in this comparative example is 21.21, 22.72, 24.79 and 23.83 mol / kg, respectively, and the effective alkalinity is 20.21, 21.62, 23.39 and 22.53 mol / kg, respectively. 20% (weight %) of analytical pure CaO was added to the four fly ashes described in this comparative example, but the total alkalinity and effective alkalinity were only increased by 10.20%, 10.61%, 3.98%, 4.79% and 17.23%, 17.63%, 5.65%, 5.08%, respectively, compared with the washed-calcined fly ash. The total basicity and effective basicity of the fly ash conversion product with CaO added in this comparative example are only 72.00%, 78.53%, 83.27%, 77.45% and 75.16%, 82.14%, 86.41%, 79.84% of the metal (hydr) oxide deacidification agent of the present invention, respectively, which are still far lower than the corresponding product metal (hydr) oxide deacidification agent obtained. This is because even if a certain amount of CaO is added to the unconverted calcined fly ash, the activity of its alkaline substances is still low, resulting in the inability to fully release the effective basicity in the acid-base titration.

[0172] Comparative Example 3

[0173] In this comparative example, 20% (weight %) of analytically pure CaCO3 powder was added to the first solid phase (i.e., washed fly ash) of fly ash A, B, C, and D in the first step of Example 1, respectively, and the mixture was fully mixed to obtain a second solid phase; the second solid phase was treated at 900°C for 3 hours in a muffle furnace to obtain washed calcined fly ash with CaCO3 added, which was then placed in water for full hydration to determine the alkalinity. Figure 6It can be known that (wherein 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 deacidification agent product obtained in Example 1 of the present invention), the total alkalinity of the corresponding third solid phase of the four fly ashes described in this comparative example is 19.54mol / kg, 20.36mol / kg, 21.76mol / kg and 21.54mol / kg, respectively, and the effective alkalinity is 17.54mol / kg, 18.56mol / kg, 20.01mol / kg and 19.29mol / kg, respectively. 20% (weight %) of CaCO3 was added to the four fly ashes described in this comparative example, but the total alkalinity and effective alkalinity were compared with the washed-calcined fly ashes, and the alkalinity was reduced, that is, the difference was 1.2%, -0.18%, -2.08%, -1.2% and 0.3%, 0.18%, -2.13%, -2.15%, respectively. The total basicity and effective basicity of the fly ash conversion product with CaCO3 added in this comparative example are only 66.33%, 70.38%, 73.09%, 70.00% and 65.24%, 70.52%, 73.92%, 68.36% of the metal (hydr) oxide deacidification agent in the present invention, respectively, which are still far lower than the corresponding product metal (hydr) oxide deacidification agent obtained. This is because the activity of the alkaline substances in the unconverted calcined fly ash is still low even if an appropriate amount of CaCO3 is added, resulting in the inability to fully release the effective basicity.

[0174] The activity range of the products obtained from fly ash C in the above three comparative examples is 16.5-17.2 mol / kg

[0175] (as shown in Table 8), which is much lower than the activity of the deacidifying agent obtained from fly ash C in the example (21-23.4 mol / kg).

[0176] Table 8 Activity of the products prepared from fly ash C in the above comparative examples

[0177]

Claims

1. A method for preparing a deacidifying agent from fly ash from the incineration of domestic waste, comprising the following steps: Primary conversion, converting various types of minerals in the fly ash from the incineration of domestic waste into metal carbonate minerals; Secondary conversion, converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high basicity deacidification agent; and Optionally, a tertiary conversion prior to deacidification is used to hydrate the metal oxide to give it a high deacidification activity; The domestic waste incineration fly ash is produced by deacidification treatment of domestic waste incineration flue gas; The primary conversion is carried out in an aqueous solution and the conversion reagent comprises a water-soluble carbonate and / or a water-soluble bicarbonate; The secondary conversion is carried out at temperatures exceeding 700°C.

2. The method according to claim 1, wherein the method comprises the following steps: Primary conversion, adding an aqueous solution of a water-soluble carbonate and / or water-soluble bicarbonate conversion agent to the domestic waste incineration fly ash, stirring and reacting, and converting various types of minerals in the domestic waste incineration fly ash into metal carbonate minerals; Secondary conversion: after the primary conversion is completed and the liquid-solid separation is carried out, the solid phase powder of the obtained metal carbonate mineral is secondary converted into metal oxides at a temperature of >700°C to obtain a high basicity deacidification agent; and The tertiary conversion before deacidification application hydrates the metal oxides to give them high deacidification activity.

3. The method according to claim 1, wherein the method comprises the following steps: (1) Before the primary conversion, the fly ash from the incineration of domestic waste 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) adding an aqueous solution of a water-soluble carbonate and / or water-soluble bicarbonate conversion agent to the washed fly ash, stirring and reacting, and converting various types of minerals in the washed fly ash into metal carbonate minerals through primary conversion; (3) after liquid-solid separation again, the solid phase powder of the obtained metal carbonate mineral is converted into metal oxides at a temperature of >700°C to obtain a high basicity deacidification agent; and (4) The tertiary conversion before deacidification application hydrates the metal oxides to give them high deacidification activity.

4. The method according to any one of claims 1 to 3, wherein the conversion reagent used for the primary conversion comprises sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate or any combination thereof; Preferably, the concentration range of the conversion reagent aqueous solution is 0.1-5.0M; and / or, the liquid-to-solid ratio of the conversion reagent aqueous solution to fly ash is (1-100):1; and / or, the temperature range in the primary conversion is 0-100°C; 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 time of the primary conversion is 1-24h.

5. The method according to any one of claims 1 to 4, wherein the conversion reagent further comprises an auxiliary agent carbon dioxide.

6. The method according to any one of claims 1 to 5, wherein the domestic waste incineration fly ash is produced by treating domestic waste incineration fly ash flue gas by a lime method, and the flue gas treatment method includes at least one of a wet method, a semi-wet method and a dry method, or the domestic waste incineration fly ash is untreated fly ash and / or aged fly ash.

7. The method according to any one of claims 1 to 6, wherein the metal carbonate minerals are first dried before the secondary conversion after the primary conversion to generate metal carbonate minerals and liquid-solid separation, and the drying temperature is 40-300°C.

8. The method according to any one of claims 1 to 7, further comprising the following steps: The obtained deacidifying agent is recycled for flue gas treatment of fly ash from incineration of domestic waste, and then the method is circulated.

9. A device for preparing a deacidifying agent from fly ash from the incineration of domestic waste, comprising: --Fly ash collection device, used to collect fly ash from the incineration of domestic waste; --Reaction device, used to convert various types of minerals in fly ash from the incineration of domestic waste into metal carbonate minerals; --a heat treatment device for converting the obtained metal carbonate minerals into corresponding metal oxides to obtain a high basicity deacidification agent; and - Optionally, a hydration device for hydrating the metal oxide to give it a high deacidification activity.

10. The apparatus according to claim 9, wherein the apparatus further comprises a washing device, wherein the washing device is located between the fly ash collecting device and the reaction device.

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