Method for co-production of glass and micro-fertilizer from biomass-coal mixed combustion ash melting-solidification and valuable element recovery

Abstract

The present disclosure provides a method for co-production of glass and micro-fertilizer by melting and solidifying biomass-coal ash and recycling valuable elements, which belongs to the technical fields of high-temperature metallurgy, hazardous waste treatment, special glass, micro-fertilizer preparation and the like. The method comprises: mixing solid-state ash after biomass and coal powder mixed combustion with a first fluxing agent, and forming a uniform and amorphous silicate glass body by heating treatment; and subjecting the silicate glass body to leaching treatment in a first acid solution, and subjecting the leaching solution to purification, concentration, crystallization or spray drying treatment to obtain high-purity micro-fertilizer and glass body. The present disclosure uses high-temperature melting technology to vitrify the entire ash system, completely destroys all lattices, permanently locks heavy metals in the glass network structure, and at the same time, by virtue of the chemical inertness of the glass body, valuable elements such as potassium and phosphorus are recycled by selective acid leaching to prepare high-stability glass body filler and high-purity chemical micro-fertilizer, respectively.

Description

Technical Field

[0001] This disclosure belongs to the technical fields of high-temperature metallurgy, hazardous waste treatment, special glass, micro-fertilizer preparation, etc., and specifically relates to a method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing glass and micro-fertilizer. Background Technology

[0002] Combustion power generation, as one of the main methods of energy supply, generates a large amount of combustion residues, such as fly ash and bottom ash. Traditional fly ash and bottom ash have been widely studied and applied in building materials such as cement, concrete, and road construction, achieving a high level of resource utilization. However, with the energy structure shifting towards low-carbon transformation, the co-combustion of biomass and pulverized coal, as an effective emission reduction technology, is increasingly being used in power plants both domestically and internationally. The mixed combustion ash produced in this process (hereinafter referred to as "mixed combustion ash") has significantly different physicochemical properties from traditional coal ash, posing new challenges to existing resource utilization technologies. The high content of alkali metals and chloride ions in mixed combustion ash, if directly used in cement concrete, may lead to a series of durability problems such as concrete efflorescence, volume expansion, and steel corrosion. Its unstable mineral composition also affects the chemical stability and mechanical properties as a building material raw material. At the same time, the abundant potassium, phosphorus, and other plant nutrients in mixed combustion ash, if simply landfilled or used at a low value with the ash residue, represents a waste of valuable resources. For mixed combustion ash with a particularly high risk of heavy metal pollution, simple sorting or hydrothermal methods may not be sufficient to meet the most stringent environmental protection requirements. Therefore, to address the aforementioned technical problems, an ultimate processing technology is needed that can "encapsulate" all harmful substances in a stable crystal lattice while simultaneously recovering valuable elements. Summary of the Invention

[0003] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizer.

[0004] One aspect of this disclosure provides a method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers, the method comprising: The solid ash residue from the co-combustion of biomass and pulverized coal is mixed with the first flux and then heated to form a homogeneous, amorphous silicate glass. The silicate glass is leached in a first acid solution, and the leachate is purified, concentrated, crystallized, or spray-dried to obtain high-purity micro-fertilizer and glass.

[0005] Optionally, the first flux may be borax, waste glass powder, or phosphate.

[0006] Optionally, the content ratio of the solid ash to the first flux is 1:(0.3-0.5); The solid ash slag is mixed with the first flux and then heated at a temperature of 1200-1400°C for 2-4 hours.

[0007] Optionally, the first acid solution is citric acid or dilute nitric acid, with a concentration of 5-10%; The silicate glass body is leached in the first acid solution at a temperature of 60-80°C for 4-8 hours.

[0008] Optionally, the micronutrient fertilizer is a potassium salt micronutrient fertilizer and / or a phosphate micronutrient fertilizer; The vitreous body has a network structure.

[0009] Another aspect of this disclosure proposes a method for the melting and solidification of biomass-coal powder co-combustion ash residue, along with the recovery of valuable elements and the co-production of vitreous material and micro-fertilizer, the method comprising: The solid ash residue after co-combustion of biomass and pulverized coal is leached in a second acid solution to form a primary micro-fertilizer solution. The primary micro-fertilizer solution is filtered to obtain filter residue containing heavy metals. The filter residue is mixed with a second flux and then heated to obtain high-purity micro-fertilizer and vitreous.

[0010] Optionally, the second acid solution is acetic acid; The solid ash residue after mixing biomass and coal powder is leached in a second acid solution at a temperature of 40-60℃ for 2-4 hours.

[0011] Optionally, the second flux is borax, waste glass powder, or phosphate; The ratio of the filter residue to the second co-solvent is 1:(0.4-0.6).

[0012] Optionally, the filter residue is mixed with the flux and then heated to a temperature of 1200-1400°C for 2-4 hours.

[0013] Optionally, the micronutrient fertilizer is a potassium salt micronutrient fertilizer and / or a phosphate micronutrient fertilizer; The vitreous body has a network structure.

[0014] This disclosure provides a method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers, which has the following advantages compared to the prior art: 1. This disclosure employs high-temperature melting technology to vitrify the entire ash slag system, completely destroying all crystal lattices and permanently locking heavy metals within the glass network structure. Then, utilizing the chemical inertness of the glass, valuable elements such as potassium and phosphorus are recovered through selective acid leaching, producing highly stable glass fillers and high-purity chemical micro-fertilizers, respectively. 2. The molten vitrification method used in this disclosure is one of the most reliable technologies for treating high-concentration hazardous waste, and can achieve permanent harmless treatment. 3. The vitreous produced by the method disclosed herein is a high-grade industrial raw material with a much higher added value than ordinary building materials, and the recovered micro-fertilizer has high purity, making it a high-end agricultural input. 4. The method disclosed herein maximizes the utilization of co-combustion ash without generating any secondary waste; 5. The method disclosed herein is particularly suitable for treating highly polluting and high-risk ash residues that are difficult to handle by physical sorting and hydrothermal methods, representing a new direction in solid waste treatment. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating a specific embodiment of the method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers. Figure 2 This is a flowchart illustrating another specific embodiment of the method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0017] like Figure 1 As shown, this disclosure provides a method S100 for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers, specifically including the following steps S110~S120: S110. The solid ash residue after co-combustion of biomass and pulverized coal is mixed with the first flux and then heated to form a uniform, amorphous silicate glass.

[0018] In step S110, the first flux is borax, waste glass powder or phosphate, etc. For example, borax is preferred, and the content ratio of ash residue to the first flux is 1:(0.3-0.5).

[0019] In step S110, the solid ash slag is mixed with the flux and then heated to a temperature of 1200-1400°C for 2-4 hours. At this temperature, it is in a molten state, and all solid particles melt and form a uniform, amorphous silicate glass. Heavy metal ions are firmly bound in a huge silicon-oxygen tetrahedral network, and their mobility and bioavailability are minimized.

[0020] It should be noted that this embodiment does not specifically limit the melting equipment. For example, an electric arc furnace, plasma torch, or rotary kiln can be used. The solid ash and flux are uniformly mixed and then fed into the melting equipment. The mixture is kept at a high temperature for a sufficient time to achieve complete homogenization, and then rapidly cooled or cast to obtain a "heavy metal-cured glass". This material has stable physical properties and is chemically inert, making it safe for use in the manufacture of microcrystalline glass, high-grade ceramic glazes, or as aggregate for paving bricks.

[0021] In step S110, the original co-fired ash and flux are directly mixed and then fed into a high-temperature furnace in one go, where they are completely melted and vitrified at 1200-1400°C. This step is a thorough detoxification process, entraining all components into the glass phase to generate a homogeneous primary glass.

[0022] S120. The silicate glass is leached in a first acid solution. The leachate is then purified, concentrated, crystallized, or spray-dried to obtain high-purity micro-fertilizer and glass.

[0023] In step S120, the first acid solution is citric acid or dilute nitric acid, and the solid-liquid ratio of the silicate glass to the first acid solution is 1g:(3-10)mL, for example, preferably 1:5. In addition, the concentration of the first acid solution is preferably 0.5-2mol / L. For example, when using citric acid, its concentration is preferably 1-2mol / L, and when using dilute nitric acid, its concentration is preferably 0.5-2mol / L.

[0024] In step S120, the silicate glass is leached in the first acid solution at a temperature of 60-80°C, preferably 60°C, 65°C, 70°C, etc., for a time of 4-8 hours.

[0025] In step S120, the molten and cooled glass is broken into small pieces. Taking advantage of the different resistances of various elements within the glass to acids, leaching is performed using acids of specific concentrations (such as citric acid or dilute nitric acid) under specific conditions. Since salts formed from alkali metals such as potassium and sodium in the glass are more soluble in acid, nutrients such as potassium and phosphorus can be selectively leached by controlling the type, concentration, and temperature of the acid. Heavy metals, however, are almost entirely unleached because they are firmly bound within the glass framework.

[0026] In step S120, the micronutrient fertilizer is a potassium salt micronutrient fertilizer and / or a phosphate micronutrient fertilizer.

[0027] In step S120, when borax or waste glass powder (mainly composed of SiO2, Na2O, and CaO) is used as a flux, SiO2 and Al2O3 in the ash become the main formants and intermediates of the glass network, forming a Na2O (or K2O) - CaO (or MgO) - Al2O3 - B2O3 - SiO2 multi-component glass system. Among them, B2O3 is a strong flux and network formant, which can significantly reduce the melting temperature and improve the chemical stability of the glass.

[0028] In step S120, when phosphates (such as sodium phosphate, apatite, etc.) are used as fluxes, P2O5 becomes a network formation that is equally important as or even dominant over SiO2, forming a Na2O-CaO-Al2O3-P2O5-SiO2 phosphate-silicate composite glass system. This type of glass is resistant to heavy metals (especially Pb, which has a strong affinity for phosphate ions). 2+ Cd 2+ Zn 2+ (etc.) have stronger solidification ability because many heavy metals can form stable phosphate crystals themselves.

[0029] In addition, in step S120, the basic framework of the glass is an amorphous, long-range disordered but short-range ordered continuous network structure, mainly composed of SiO4 tetrahedra connected by bridging oxygen (Si-O-Si) to form a three-dimensional random network framework. This is the basis for the chemical inertness and high strength of the glass. When B2O3 is present, BO3 triangles or BO4 tetrahedra will be formed, which will interpenetrate and fuse with the silicon-oxygen network, making the network more compact and strong. When P2O5 is present, PO5 tetrahedra will be formed, which will also participate in the network construction.

[0030] Further, in step S120, the alkali metals (Na) in the ash and flux are... + K + ) and alkaline earth metals (Ca 2+ Mg 2 + ) ions, acting as network modifiers, break bridging oxygen bonds (Si-O-Si) in the silicon-oxygen network, forming non-bridging oxygen bonds (Si-O). - This reduces the melt viscosity, making it easier to melt and form. Meanwhile, the target heavy metal ions (such as Pb)... 2+ Cd 2+ Cr 3+ Cu 2+ In the molten state, substances such as Al can replace or occupy the positions of network modifiers, or act as network intermediates. 3+ Fe 3+Some of these heavy metal ions participate in network formation. These heavy metal ions are firmly bound by electrostatic forces to negatively charged non-bridging oxygen (Si-O). - The glass is embedded in the voids of a rigid silicon-oxygen (or boron-oxygen, phosphorus-oxygen) network framework. Because the glass is a supercooled liquid, its structure is macroscopically frozen, and the activation energy required for the diffusion and migration of heavy metal ions is extremely high, so they can hardly move or leach out at room temperature.

[0031] In this embodiment, the leachate is treated to produce a high-purity micro-fertilizer. The leached glass residue, due to the further locking of heavy metals and the denser surface structure resulting from acid etching, exhibits higher environmental safety and can be used as a common roadbed material or concrete admixture. Simultaneously, the continuous covalent bond network of the formed glass exhibits extremely strong resistance to water, acids, and alkalis. Heavy metal ions are physically isolated and chemically bonded, resulting in a leaching rate far lower than that of physical coating methods such as cement curing.

[0032] like Figure 2 As shown, this disclosure provides a method S200 for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers, specifically including the following steps S210~S220: S210. The solid ash residue after co-combustion of biomass and pulverized coal is leached in a second acid solution to form a primary micro-fertilizer solution.

[0033] In step S210, the second acid solution is preferably acetic acid. The solid-liquid ratio of the solid ash and the second acid solution is 1g:(5-15)mL. The original mixed ash is first leached with weak acid to preferentially dissolve elements such as potassium and calcium in the biomass ash to form a primary micro-fertilizer solution.

[0034] In step S210, the concentration of the second acid solution is preferably 5-10%, and the leaching temperature is 40-60°C, for example, preferably 40°C, 50°C, 60°C, etc., and the time is 2-4 hours.

[0035] S220. After filtering the primary micro-fertilizer solution, a filter residue containing heavy metals is obtained. The filter residue is mixed with a second flux and then heated to obtain a high-purity micro-fertilizer or vitreous body.

[0036] In step S220, the second flux is borax, waste glass powder, or phosphate, etc. Furthermore, the mass ratio of filter residue to the second flux is 1:(0.4-0.6).

[0037] In step S220, the micronutrient fertilizer is either potassium salt micronutrient fertilizer or phosphate micronutrient fertilizer.

[0038] In step S220, the heating temperature is preferably 1200-1400°C, and the time is 2-4.

[0039] In step S220, the leached filter residue is mixed with a specific flux (such as borax, waste glass powder, sodium silicate, etc.) in a certain proportion. The mixture is then melted at a high temperature (using equipment such as an electric arc furnace or plasma torch). During this process, all mineral lattices are completely destroyed, forming a homogeneous, high-temperature silicate melt. The high-temperature melt is then rapidly cooled (quenched) or cast into an amorphous glass. Heavy metal ions are firmly captured and solidified in a dense silica-oxygen network structure, reducing their leaching toxicity to extremely low levels and achieving permanent stabilization.

[0040] It should be noted that both of the above methods aim to solve the core problem of how to simultaneously achieve the permanent harmlessness of high-risk co-fired ash and the precise high-value recovery of valuable elements. Both methods utilize key technologies such as melt vitrification and selective acid leaching to separate and recover valuable elements from high-risk co-fired ash and permanently solidify heavy metals.

[0041] It should be further noted that, in some preferred embodiments, a process of melting followed by leaching is preferred. Because the original ash slag has a complex composition, heavy metals may exist in various unstable forms. Melting first forces all elements to dissolve and redistribute them within a uniform amorphous glass network. Potassium and sodium in the network act as network modifiers and have weak binding forces with the silicon-oxygen network, while phosphorus typically exists in the form of phosphate clusters. This makes their selective response to acid consistent and predictable, facilitating selective stripping through precise control of acidity, temperature, and time, thereby improving the leaching rate and selectivity of the target elements.

[0042] The following will further illustrate the method of melting and solidifying biomass-pulverized coal co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizers with specific embodiments: Example 1 This example illustrates a method for the melting and solidification of biomass-pulverized coal co-combustion ash residue, along with the recovery of valuable elements and the co-production of vitreous material and micronutrients, comprising the following steps: Step 1: Mix the solid ash residue from the co-combustion of biomass and pulverized coal with borax, and heat-treat it to form a homogeneous, amorphous silicate glass. In step 1, the ratio of solid ash to borax is 1:0.4, the heat treatment temperature is 1300°C, and the time is 3 hours.

[0043] Step 2: The silicate glass is leached in citric acid solution. The leachate is then purified, concentrated, crystallized, or spray-dried to obtain high-purity phosphate micro-fertilizer and high-borosilicate glass.

[0044] In step 2, the solid-liquid ratio of the silicate glass to the citric acid solution is 1:5, the leaching temperature is 70°C, and the time is 6 hours.

[0045] Example 2 This example presents another method for the melting and solidification of biomass-coal powder co-combustion ash residue, along with the recovery of valuable elements and the co-production of vitreous and micronutrient fertilizers, including the following steps: Step 1: The solid ash residue after co-combustion of biomass and pulverized coal is leached in acetic acid solution to form a primary micro-fertilizer solution; In step 1, the solid-liquid ratio of the solid ash residue to the acetic acid solution is 1:10, the leaching treatment temperature is 50℃ and the time is 3h, and the primary micro-fertilizer solution obtained after leaching is mainly a mixed solution of potassium acetate and calcium acetate, and contains some potassium dihydrogen phosphate, etc.

[0046] Step 2: After filtering the primary micro-fertilizer solution, a filter residue containing heavy metals is obtained. The filter residue is mixed with phosphate and heated to obtain high-purity crystalline potassium acetate and potassium ammonium phosphate compound fertilizer and porous ceramic glass.

[0047] In step 2, the ratio of filter residue to phosphate content is 1:0.5, the heating temperature is 1300°C, and the time is 3 hours.

[0048] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizer, characterized in that, The method includes: The solid ash residue from the co-combustion of biomass and pulverized coal is mixed with the first flux and then heated to form a homogeneous, amorphous silicate glass. The silicate glass is leached in a first acid solution, and the leachate is purified, concentrated, crystallized, or spray-dried to obtain high-purity micro-fertilizer and glass.

2. The method according to claim 1, characterized in that, The first flux is borax, waste glass powder or phosphate.

3. The method according to claim 1, characterized in that, The content ratio of the solid ash to the first flux is 1:(0.3-0.5); The solid ash slag is mixed with the first flux and then heated at a temperature of 1200-1400°C for 2-4 hours.

4. The method according to claim 1, characterized in that, The first acid solution is citric acid or dilute nitric acid; The silicate glass body is leached in the first acid solution at a temperature of 60-80°C for 4-8 hours.

5. The method according to claim 1, characterized in that, The micronutrient fertilizer is a potassium salt micronutrient fertilizer and / or a phosphate micronutrient fertilizer; The vitreous body has a network structure.

6. A method for melting and solidifying biomass-coal powder co-combustion ash residue, recovering valuable elements, and co-producing vitreous and micro-fertilizer, characterized in that, The method includes: The solid ash residue after co-combustion of biomass and pulverized coal is leached in a second acid solution to form a primary micro-fertilizer solution. The primary micro-fertilizer solution is filtered to obtain filter residue containing heavy metals. The filter residue is mixed with a second flux and then heated to obtain high-purity micro-fertilizer and vitreous.

7. The method according to claim 6, characterized in that, The second acid solution is acetic acid; The solid ash residue after mixing biomass and coal powder is leached in a second acid solution at a temperature of 40-60℃ for 2-4 hours.

8. The method according to claim 6, characterized in that, The second flux is borax, waste glass powder, or phosphate; The ratio of the filter residue to the second co-solvent is 1:(0.4-0.6).

9. The method according to claim 6, characterized in that, The filter residue is mixed with the flux and then heated at 1200-1400°C for 2-4 hours.

10. The method according to claim 6, characterized in that, The micronutrient fertilizer is a potassium salt micronutrient fertilizer and / or a phosphate micronutrient fertilizer; The vitreous body has a network structure.

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