Purification and modification system of heavy metal chloride salts in waste incineration fly ash

Abstract

The present invention relates to the technical field of waste incineration treatment, and in particular to a purification and modification system based on heavy metal chloride salts in waste incineration fly ash, comprising a hopper, a grate furnace, an evaporator, a superheater, an economizer, a deacidification tower, a lime powder tank, a bag filter and a chimney arranged in sequence along the flue gas flow direction, the bag filter is also connected to a water washing tower, the water washing tower is respectively connected to a first collecting bin and a second collecting bin, the first collecting bin and the second collecting bin are respectively connected to a modifier, the first collecting bin is used to collect the precipitate after the heavy metal chloride salt is purified, the second collecting bin is used to collect the washed fly ash, the modifier is used to mix and grind the precipitate and the washed fly ash to achieve the modification of the washed fly ash, and spray the modified fly ash back into the flue. The above technical scheme can effectively realize the resource utilization of heavy metal chloride salts.

Description

Technical Field

[0001] The invention relates to the technical field of waste incineration treatment, in particular to a purification and modification system based on heavy metal chloride salts in waste incineration fly ash. Background Art

[0002] With the acceleration of urbanization and the growth of population, the amount of domestic waste has increased dramatically, and waste incineration has been widely used as an effective way to dispose of waste. Waste incineration fly ash contains a large amount of heavy metal chloride salts (such as zinc chloride, ferric chloride, calcium chloride, magnesium chloride, ferric chloride, etc.). If these heavy metal chloride salts are not handled properly, they will not only cause waste of resources, but also cause serious pollution to the environment. At present, the use of water washing to treat waste incineration fly ash is one of the effective means to recover heavy metal chloride salts. Through water washing, heavy metal ions can be transferred to the solution to form a fly ash water washing solution. Therefore, it is necessary to study the resource utilization of heavy metal chloride salts in waste incineration fly ash. Summary of the invention

[0003] The invention provides a purification and modification system for heavy metal chloride salts in waste incineration fly ash, which can effectively realize the resource utilization of heavy metal chloride salts.

[0004] The present invention provides a purification and modification system for heavy metal chloride salts in waste incineration fly ash, comprising:

[0005] It includes a hopper, a grate furnace, an evaporator, a superheater, an economizer, a deacidification tower, a lime powder tank, a bag filter and a chimney which are arranged in sequence along the flue gas flow direction. The bag filter is also connected to a water washing tower, which is respectively connected to a first collecting bin and a second collecting bin, the first collecting bin and the second collecting bin are respectively connected to a modifier, the first collecting bin is used to collect precipitates after purification of heavy metal chloride salts, the second collecting bin is used to collect washed fly ash, and the modifier is used to mix and grind the precipitates and the washed fly ash to achieve modification of the washed fly ash, and spray the modified fly ash back into the flue.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: by connecting the bag filter to the water washing tower, and connecting the water washing tower to the first collecting bin and the second collecting bin respectively, and connecting the first collecting bin and the second collecting bin to the modifier respectively, the first collecting bin can be used to collect the precipitate after the heavy metal chloride salt is purified, and the second collecting bin can be used to collect the washed fly ash, and the modifier can be used to mix and grind the precipitate and the washed fly ash to achieve the modification of the washed fly ash, that is, the modified fly ash can be used to remove heavy metals, and finally the modified fly ash is sprayed back into the flue, thereby realizing the purification of heavy metal chloride salts and the modification of garbage incineration fly ash based on the heavy metal chloride salts in the garbage incineration fly ash, thereby effectively realizing the resource utilization of heavy metal chloride salts. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0008] Figure 1 It is a schematic diagram of a purification and modification system for heavy metal chloride salts in waste incineration fly ash provided by one embodiment of the present invention;

[0009] Figure 2 The present invention provides a flowchart of a method for purifying heavy metal chloride salts in waste incineration fly ash according to an embodiment of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0011] Please refer to Figure 1 The embodiment of the present invention provides a purification and modification system for heavy metal chloride salts in waste incineration fly ash, comprising a hopper, a grate furnace, an evaporator, a superheater, an economizer, a deacidification tower, a lime powder tank, a bag filter and a chimney arranged in sequence along the flue gas flow direction. The bag filter is also connected to a water washing tower, which is respectively connected to a first collecting bin and a second collecting bin, and the first collecting bin and the second collecting bin are respectively connected to a modifier. The first collecting bin is used to collect precipitates after purification of heavy metal chloride salts, and the second collecting bin is used to collect washed fly ash. The modifier is used to mix and grind the precipitates and washed fly ash to achieve modification of the washed fly ash, and spray the modified fly ash back into the flue.

[0012] In this embodiment, the bag filter is connected to a water washing tower, and the water washing tower is connected to the first collecting bin and the second collecting bin respectively, and the first collecting bin and the second collecting bin are connected to the modifier respectively. In this way, the first collecting bin can be used to collect the precipitate after the heavy metal chloride salt is purified, and the second collecting bin can be used to collect the washed fly ash, and the modifier can be used to mix and grind the precipitate and the washed fly ash to achieve the modification of the washed fly ash, that is, the modified fly ash can be used to remove heavy metals, and finally the modified fly ash is sprayed back into the flue, thereby realizing the purification of heavy metal chloride salts and the modification of waste incineration fly ash based on the heavy metal chloride salts in the waste incineration fly ash, thereby effectively realizing the resource utilization of heavy metal chloride salts.

[0013] It should be noted that heavy metal chloride salts are important functional substances in the fly ash modification process. In the preparation process of modified fly ash, heavy metal chloride salts gasify and expand during high-temperature pyrolysis, which promotes the fly ash raw materials to obtain a loose skeleton of primary pore structure. The activation mechanism of heavy metal chloride salts on fly ash structure is mainly gasification, oxidation and reconstruction. Representative heavy metal chloride salt activators include zinc chloride, ferric chloride, calcium chloride, magnesium chloride, ferric chloride, etc. In the fly ash modification process, the heavy metal chloride salts in the fly ash modification mechanism is to form surface carbon-chlorine active groups, which promote the fly ash to Hg 0 Produce specific chemical adsorption.

[0014] In one embodiment of the present invention, flue gas sampling positions using CEMS are provided at the inlet of the deacidification tower, between the deacidification tower and the lime powder tank, and at the outlet of the bag filter.

[0015] In one embodiment of the present invention, the modifier is connected to the flue gas sampling position between the deacidification tower and the lime powder tank to spray the modified fly ash back to the flue gas sampling position (generally speaking, activated carbon can be sprayed at the flue gas sampling position, and in order to reduce costs, the modified fly ash can be sprayed here).

[0016] In one embodiment of the present invention, a third collecting bin and a compressed air source are provided between the modifier and the flue gas sampling position, the third collecting bin is used to collect the modified fly ash, and the compressed air source is used to spray the fly ash in the third collecting bin to the flue gas sampling position.

[0017] As an effective wastewater treatment method, evaporation crystallization technology can convert harmful substances in wastewater into solid form through evaporation and crystallization processes, which is convenient for subsequent treatment and resource utilization. However, the existing evaporation crystallization methods mostly use fixed temperature for operation, but the solubility and crystallization rate of different heavy metal ions and precipitants at different temperatures vary greatly. The traditional single temperature control often cannot take into account the optimal crystallization conditions of multiple heavy metal ions, which may lead to problems such as low crystallization efficiency, low product purity or excessive energy consumption. In addition, it is affected by various environmental factors, such as ambient temperature, humidity, air pressure, and the initial pH value of wastewater, which will affect the evaporation crystallization process. However, the existing evaporation crystallization methods rarely consider these environmental and wastewater characteristic parameters, lack of comprehensive analysis and utilization of these parameters, and cannot achieve precise control of temperature during the evaporation crystallization process.

[0018] To solve the above technical problems, please refer to Figure 2 , a method for purifying heavy metal chloride salts, comprising:

[0019] Step S1, based on the fly ash washing solution treatment scheme, extracting the type of heavy metal ion precipitant used for fly ash washing solution treatment;

[0020] Step S2, measuring the composition of the fly ash washing solution to obtain a heavy metal ion concentration profile of the aqueous solution and an initial pH value of the fly ash washing solution; the heavy metal ion concentration profile of the aqueous solution includes several heavy metal ion concentrations;

[0021] Step S3, using a pre-constructed precipitate prediction model, comprehensively analyzing the type of heavy metal ion precipitant, the heavy metal ion concentration profile of the aqueous solution, and the initial pH value of the fly ash washing solution to obtain the crystallization characteristics of the precipitate obtained by evaporation and crystallization of the aqueous solution; the precipitate crystallization characteristics include the precipitate type and the concentration of each type of precipitate;

[0022] Step S4: Real-time collection of environmental data information of the location of the fly ash washing solution; the environmental data information includes environmental temperature, environmental humidity and environmental pressure

[0023] Step S5, inputting the crystallization characteristics of the precipitate into a pre-constructed dissolution-crystallization equilibrium model to obtain a precipitate crystallization step temperature set, and correcting the precipitate crystallization step temperature set using environmental data information to obtain an environmentally corrected precipitate crystallization step temperature set;

[0024] Step S6: Using the corrected precipitation crystallization step temperature set as the evaporation crystallization temperature control strategy, the evaporation crystallization temperature of the fly ash washing solution is controlled to purify different heavy metal chloride salts in the waste incineration fly ash.

[0025] In this embodiment, by conducting a detailed component analysis of the fly ash washing solution, combined with the type of heavy metal ion precipitant and the heavy metal ion concentration profile of the aqueous solution, the precipitation of heavy metal ions can be predicted more accurately, which is helpful to select the most suitable temperature range in the evaporation crystallization process, improve the crystallization efficiency, and ensure the high purity of the product; through the constructed dissolution crystallization equilibrium model, the optimal crystallization temperature range can be accurately calculated according to the characteristics of different heavy metal ions, avoiding unnecessary energy consumption and reducing operating costs; the present invention not only considers the characteristics of the wastewater itself, but also monitors environmental data information in real time, such as temperature, humidity, air pressure, etc., as well as the initial pH value of the wastewater. The comprehensive analysis of the above-mentioned multiple factors can better adapt to changes in the external environment and enhance the flexibility and stability of the treatment process; by precisely controlling the evaporation crystallization process, valuable metals and other resources can be effectively recovered from the wastewater, reducing resource waste, which is in line with the concept of sustainable development.

[0026] Described below Figure 2 How the various steps are performed.

[0027] For step S1:

[0028] In the waste incineration fly ash treatment process, evaporation crystallization technology is a key subsequent treatment step, which is used to efficiently separate and recover heavy metal ions from the fly ash washing solution; and in order to ensure the efficiency of the evaporation crystallization process and the purity of the product, it is very important to select a suitable type of heavy metal ion precipitant; the main task of step S1 is to determine the type of heavy metal ion precipitant used in the evaporation crystallization process; this step involves the selection and identification of the precipitant, ensuring that the selected precipitant can form a stable precipitate with the heavy metal ions in the fly ash washing solution, thereby facilitating subsequent crystallization separation.

[0029] When selecting a heavy metal ion precipitant, multiple factors need to be considered, including the affinity of the precipitant to heavy metal ions, the stability of the formed precipitate, the environmental friendliness of the precipitant, and cost-effectiveness; common heavy metal ion elements in waste combustion fly ash require the selection of precipitants with strong affinity for these heavy metal ions; common precipitants include EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), CTAB (hexadecyltrimethylammonium bromide), etc.; these precipitants can effectively react with various heavy metal ions in fly ash to form water-soluble precipitates, thereby realizing the migration of heavy metal ions from fly ash solids to aqueous solutions.

[0030] In practical applications, the following factors are considered when selecting heavy metal ion precipitants:

[0031] The affinity and selectivity of the precipitant for the target heavy metal ions ensures that the target heavy metal ions can be extracted preferentially without affecting other non-target ions;

[0032] The stability of the precipitate formed by the precipitant and heavy metal ions in the aqueous solution ensures that it will not precipitate or dissociate prematurely during the subsequent evaporation and crystallization process;

[0033] The cost-effectiveness, biodegradability and environmental friendliness of the precipitant ensure that the entire treatment process is both economical and environmentally friendly;

[0034] The reactivity of the precipitant with other fly ash components under water washing conditions can avoid unnecessary side reactions that affect the extraction rate of heavy metal ions;

[0035] Therefore, step S1 is not just to simply obtain a certain type of heavy metal ion precipitant, but to scientifically and rationally determine the optimal type and amount of precipitant suitable for the extraction of heavy metal ions in the fly ash to be treated through experimental research and technical comparison, laying the foundation for the subsequent evaporation and crystallization steps, ensuring that the heavy metal ions can be efficiently separated and converted into a solid crystalline form that is easy to recover.

[0036] For step S2:

[0037] Step S2 in the process of coal fly ash treatment mainly involves detailed heavy metal ion quantitative analysis and pH determination of the washed fly ash solution to determine the actual concentration of various heavy metal ions in the solution and the initial pH value of the fly ash washing solution; the specific operation includes the following steps:

[0038] S21. Sample preparation and pretreatment: A certain amount of sample is extracted from the fly ash washing solution to ensure that the sample can truly reflect the heavy metal ion composition of the entire solution; considering the state of the solution and possible interfering substances, sampling should be carried out on the basis of uniform mixing of the solution; the sample needs to go through a series of pretreatment steps to improve the detection accuracy; for example, the solution needs to be filtered, centrifuged and other steps to remove insoluble solid impurities to avoid affecting subsequent detection;

[0039] S22. Heavy metal ion analysis method: Use analytical instruments and techniques to measure the concentration of heavy metal ions in samples. Commonly used analysis methods include but are not limited to:

[0040] a. Atomic absorption spectrometry: The concentration of heavy metal ion elements is determined by measuring the intensity of light of a specific wavelength absorbed by impurity atoms in the sample; this method is simple to operate and has high sensitivity, and is suitable for the determination of a variety of heavy metal ion elements;

[0041] b. Inductively coupled plasma emission spectrometry: This method is a highly sensitive and high-resolution spectral analysis method that can simultaneously determine multiple elements, including heavy metal ions; this method is suitable for rapid and accurate determination of heavy metal ions;

[0042] c. Inductively coupled plasma mass spectrometry: This method is a highly sensitive and selective analytical method that can simultaneously determine multiple elements and can detect extremely low concentrations of heavy metal ions. This method is suitable for the determination of trace heavy metal ions in water washing solutions.

[0043] d. Ion chromatography: Ion chromatography is an analytical method for separating and determining ions, and can separate and determine heavy metal ions in water washing solutions; this method is simple to operate and is suitable for quantitative analysis of heavy metal ions in water washing solutions;

[0044] S23. Integration of heavy metal ion concentration data: After measuring each heavy metal ion separately, record the concentration data of each ion, usually expressed in milligrams per liter (mg / L) or molar concentration; summarize all the measurement results to create a detailed "heavy metal ion concentration portrait of aqueous solution". The heavy metal ion concentration portrait of aqueous solution is essentially a visual expression that intuitively shows the concentration distribution of various heavy metal ions contained in the solution.

[0045] S24, initial pH value of fly ash washing solution: The initial pH value of the wastewater is an important factor affecting the form of heavy metal ions and the reaction effect of the precipitant; under different pH conditions, the reaction path of heavy metal ions and precipitants changes, thereby affecting the crystallization characteristics of the precipitate; therefore, step S4 also needs to measure the initial pH value of the fly ash washing solution in real time, and use it as an important input parameter of the evaporation crystallization temperature control strategy; use a pH meter to directly measure the initial pH value of the fly ash washing solution.

[0046] In this step, by constructing a concentration profile of heavy metal ions in aqueous solution, the originally complex laboratory test data can be converted into an intuitive graphical expression, so that non-professionals can also quickly understand and grasp the specific distribution and relative concentration relationship of various heavy metal ions in aqueous solution, enhancing the interpretability and communication efficiency of the data; the concentration profile of heavy metal ions in aqueous solution helps to quickly identify potential environmental risk factors, such as which heavy metal ions exceed the standard seriously, and their potential harm to soil, water sources, and ecosystems, and then guide the adoption of targeted governance measures; in the field of environmental monitoring and industrial wastewater treatment, the concentration profile of heavy metal ions in aqueous solution provides clear and standardized data records, which is convenient for monitoring The regulatory authorities review the pollution discharge status of enterprises to ensure that they comply with relevant environmental protection laws and regulations; through a detailed description of the heavy metal ion concentration of fly ash washing solution, it can help enterprises control heavy metal ion pollution from the source, optimize production processes, reduce heavy metal ion emissions, and promote the development of resource recycling technology; scientists and decision makers can conduct in-depth research based on concentration portraits, explore the migration and transformation laws of heavy metal ions, evaluate the effectiveness of governance technologies, and provide a scientific basis for policy formulation and environmental restoration projects; the long-term accumulated heavy metal ion concentration portraits of aqueous solutions can be used to track changes in pollution trends, predict future environmental evolution, and provide strong data support for environmental planning and long-term governance goal setting.

[0047] For step S3:

[0048] Step S3 is a key step in the evaporation crystallization temperature control method, which involves inputting the type of heavy metal ion precipitant, the heavy metal ion concentration profile of the aqueous solution and the initial pH value of the fly ash washing solution into a pre-trained precipitation prediction model to output the precipitation crystallization characteristics obtained by evaporation crystallization of the aqueous solution, and specifically includes the following steps:

[0049] S31. Preparation of input information: Before starting step S3, three preparations for input data need to be completed: on the one hand, the type of heavy metal ion precipitant is obtained, which is to understand the type of precipitant used in the evaporation crystallization process; different precipitants have different complexing abilities and effects on heavy metal ions, so understanding the type of precipitant is crucial for predicting the crystallization characteristics of the precipitate; on the other hand, the heavy metal ion concentration profile of the aqueous solution is obtained. Through the determination of heavy metal ions in the fly ash washing solution in step S2, a heavy metal ion concentration profile of the aqueous solution containing several heavy metal ion concentrations has been obtained; this profile provides specific concentration information for each heavy metal ion, which is the basic data for predicting the crystallization characteristics of the precipitate; thirdly, through the determination of the pH value of the fly ash washing solution in step S2, the initial pH value of the fly ash washing solution is obtained;

[0050] S32. Application of the sediment prediction model: After obtaining the above three input information, input them into the pre-trained sediment prediction model; the sediment prediction model is constructed based on a large amount of experimental data and machine learning algorithms, and can predict the type of sediment that may be formed under different conditions and the concentration of each type of sediment according to the input precipitant type, heavy metal ion concentration information and initial pH value of the fly ash washing solution;

[0051] S33. Interpretation of output results: The output results of the precipitation prediction model are the crystallization characteristics of the precipitate obtained by evaporation and crystallization of the aqueous solution, including the type of precipitate and the concentration of each type of precipitate. By understanding the types and concentrations of various precipitates, their crystallization behaviors at different temperatures can be more accurately determined, thereby formulating a more reasonable evaporation crystallization temperature control strategy.

[0052] More specifically, the precipitation prediction model is built based on complex chemical kinetics and thermodynamics principles to simulate and predict the types of precipitation that may be formed by different heavy metal ions and specific precipitants in different pH environments during the evaporation crystallization process and their corresponding concentrations. The following are the specific steps for establishing the model:

[0053] S321. Data collection and preprocessing: Collect a large amount of experimental data, including the types of precipitates formed by different heavy metal ions and various precipitants under different temperatures, concentrations and acid-base conditions, as well as their solubility, crystallization rate and other information; organize and standardize the data on the reaction between heavy metal ions and precipitants in fly ash washing solution to ensure the accuracy of the data input into the model;

[0054] S322. Establish a basic chemical reaction model: clarify the chemical reaction mechanism between heavy metal ions and precipitants, including coordination number, stability constant (such as stability constant Ks), reaction rate constant, etc.; based on the principles of chemical kinetics, describe the rate equation for the formation of precipitates by heavy metal ions and precipitants, as well as the law of change of the solubility of precipitates with temperature during evaporation and crystallization;

[0055] S323. Build a machine learning or deep learning model: Use the existing experimental data set to train the model. You can choose machine learning methods such as multivariate regression analysis, support vector machine, neural network, etc. You can also use deep learning architecture to simulate complex nonlinear relationships. The goal of the model is to predict the expected crystallization characteristics of various precipitates after the evaporation crystallization process under given heavy metal ion concentration, precipitant type and pH value, including but not limited to precipitate type, concentration and possible crystal morphology;

[0056] S324, Model verification and optimization: Use independent experimental data to verify the model and adjust model parameters to improve prediction accuracy; multiple iterations of training and calibration are required until the model can more accurately reflect the actual situation and predict reasonable and stable precipitate crystallization characteristics under different initial conditions.

[0057] The significance of step S3 is to establish a mapping relationship from heavy metal ion concentration, precipitant type and pH value to precipitate crystallization characteristics; this mapping relationship can not only help predict the type and concentration of precipitates that may be formed under different conditions, but also provide important reference information for subsequent evaporation and crystallization temperature control; through this step, the evaporation and crystallization process can be controlled more accurately, the recovery efficiency of heavy metal ions and product quality can be improved, and energy consumption and environmental pollution can be reduced.

[0058] For step S4:

[0059] Step S4 is to collect the environmental data information of the location of the fly ash washing solution in real time, and its main purpose is to obtain the environmental factors that affect the evaporation and crystallization process, so as to more accurately control the temperature of the evaporation and crystallization; the details are as follows:

[0060] Ambient temperature: Ambient temperature directly affects the evaporation rate and the physical and chemical properties of the solution, such as solubility, viscosity and latent heat of evaporation. Use temperature sensors to monitor the ambient temperature of the fly ash washing solution treatment facility in real time.

[0061] Ambient humidity: Ambient humidity reflects the water vapor content in the air. High humidity will slow down the evaporation rate and affect the efficiency of the crystallization process. The humidity level in the air is recorded by the humidity sensor. Real-time monitoring of ambient humidity helps to adjust the working state of the evaporation equipment in time to ensure the smooth progress of the evaporation crystallization process.

[0062] Ambient air pressure: Changes in air pressure will affect the diffusion rate and condensation temperature of steam during the evaporation process, thereby affecting the efficiency of evaporation crystallization; using a barometer to measure the local atmospheric pressure, by real-time monitoring of air pressure, the steam flow and condensation conditions during the evaporation process can be precisely controlled;

[0063] Step S4 provides key input parameters for the evaporation crystallization temperature control method by real-time collection and processing of environmental data information; through step S4, refined control of the evaporation crystallization process can be achieved, promoting the further development and application of fly ash washing solution treatment technology.

[0064] For step S5:

[0065] Step S5 is one of the key steps in the evaporation crystallization temperature control method, which involves inputting the crystallization characteristics of the precipitate into a pre-built dissolution crystallization equilibrium model, obtaining a set of precipitate crystallization step temperatures, and correcting the set of precipitate crystallization step temperatures using environmental data information; each gradient in the corrected set corresponds to the optimal crystallization temperature of at least one precipitate and the corresponding crystallization time.

[0066] First, the crystallization characteristics of the precipitate are input into the pre-built dissolution-crystallization equilibrium model to obtain the implementation steps of the precipitate crystallization step temperature set, which are as follows:

[0067] S51. Construction of dissolution-crystallization equilibrium model: Based on the principles of thermodynamics and phase equilibrium theory, which describe how substances transform between liquid and solid at different temperatures and concentrations; collect solubility data of various heavy metal ion precipitates at different temperatures; these data can be obtained through experimental measurements or found in existing scientific literature; use the collected data to train or develop a mathematical model that can predict whether a certain precipitate will crystallize at a given temperature and concentration;

[0068] S52. Input the crystallization characteristics of the precipitate: The type of precipitate refers to the type of precipitant that binds to the heavy metal ions. Different precipitants may affect the solubility of heavy metal ions. The concentration data of each precipitate is crucial to predict its behavior in solution. The higher the concentration, the greater the possibility of reaching saturation and crystallization.

[0069] S53, run the dissolution crystallization equilibrium model: input the precipitate type and concentration data into the model; the model will simulate the dissolution and crystallization behavior of various precipitates at different temperatures based on the input data and internal algorithms; the model will output the solubility curves and possible crystallization conditions of each precipitate at different temperatures;

[0070] S54. Generate a set of step temperatures for crystallization of precipitates: According to the prediction results of the model, determine the temperature at which each precipitate reaches the maximum solubility and starts to crystallize; in addition to temperature, the time of crystallization is also a key factor; the model needs to predict or determine the time required for each precipitate to complete crystallization at the optimal temperature; based on the optimal crystallization temperature and duration of various precipitates, construct a step-by-step temperature set; this set will guide the temperature adjustment during the evaporation crystallization process;

[0071] S55. Consider the actual operating conditions: the performance and capacity of the evaporation crystallization equipment may limit the temperature adjustment range; energy consumption needs to be considered in actual operation, and an operating temperature that is both efficient and energy-saving should be selected; the experience of the operators is also very important, and they can adjust the temperature predicted by the model according to the actual situation;

[0072] S56. Continuous optimization and updating: As actual operations proceed, more experimental data can be collected, which can be used to verify and update the model; based on the newly collected data and actual operation experience, the model is adjusted and optimized to improve its predictive accuracy and adaptability.

[0073] In this step, by determining the optimal crystallization temperature and duration of each precipitate, it can be ensured that during the evaporation crystallization process, various precipitates are crystallized under the most suitable conditions, thereby greatly improving the crystallization efficiency; since each precipitate is crystallized under the optimal conditions, the purity of the resulting product will be higher, thereby ensuring the product quality; this is particularly important for industries that need to recover high-purity heavy metal ions; by optimizing the crystallization process, energy can be used more efficiently and unnecessary energy consumption can be reduced; this not only helps to reduce production costs, but also meets the current environmental protection requirements of energy conservation and emission reduction; since the model is constructed based on thermodynamic principles and phase equilibrium theory, it can adapt to precipitates of different types and concentrations; this means that the method has strong flexibility and can adapt to different production environments and needs; with the continuous accumulation of data in actual operation, the model can be continuously optimized and updated; this enables the method to continuously adapt to new production conditions and needs, and maintain its long-term effectiveness and competitiveness; by providing a set of precipitate crystallization step temperatures, the method provides decision support for temperature control in the production process; this allows operators to adjust the temperature of the evaporation crystallization process more scientifically and accurately, thereby improving production efficiency and product quality.

[0074] Specifically, the method for constructing the dissolution-crystallization equilibrium model includes:

[0075] S511. Collect a large amount of experimental data or consult relevant literature to obtain the solubility data of different heavy metal ions and specific precipitants at different temperatures, as well as the kinetic data of these precipitates during the crystallization process (such as crystallization rate); these data are the basis for constructing a dissolution-crystallization equilibrium model;

[0076] S512. Based on the principles of thermodynamics, especially the principle of minimization of Gibbs free energy, an equation describing the dissolution-crystallization equilibrium can be established; for example, the solubility product constant Ksp can be used to express the dissolution equilibrium relationship of sparingly soluble salts at a specific temperature; for precipitates, the stability constant of complex formation may also need to be considered and incorporated into the thermodynamic model;

[0077] S513. Considering that the crystallization process involves not only dissolution equilibrium but also kinetic factors such as crystal growth rate, the crystallization kinetic equation should be integrated into the model, such as the JMAK (Johnson-Mehl-Avrami-Kolmogorov) equation or other applicable kinetic models to reflect the variation of crystallization rate with time and temperature.

[0078] S514. Combining the above thermodynamic and kinetic theories, develop a mathematical model that can predict the solubility and crystallization characteristics of different precipitates at different temperatures and concentrations through multivariate nonlinear regression, machine learning or other appropriate mathematical methods; the model should be able to predict the optimal crystallization conditions, including the optimal crystallization temperature and the corresponding required crystallization time, based on the input precipitant type, heavy metal ion type and their initial concentration in the solution;

[0079] S515. Use experimental data to calibrate and verify the model, and iteratively optimize parameters to ensure that the model has high prediction accuracy for the actual system; in addition, the model should also have a certain generalization ability to cope with fly ash washing solutions of different sources or compositions;

[0080] S516. Using the optimized dissolution-crystallization equilibrium model, a series of most suitable crystallization temperatures are calculated for each precipitate and its actual concentration in the fly ash washing solution, and matched with the corresponding crystallization time, thereby forming a set of precipitate crystallization step temperatures.

[0081] More specifically, the mathematical model for predicting the solubility and crystallization properties of different precipitates at different temperatures and concentrations is:

[0082] T opt (C m ,C c )=dln(C m / C c )+e;

[0083] t crystal (T,C m ,C c )=f(TT opt ) / (gC m +hC c );

[0084] Where T represents the initial temperature, which can be set uniformly or measured in real time, and the unit is Celsius; C m Represents the concentration of heavy metal ions in moles per liter; C c represents the concentration of the precipitant in moles per liter; T opt (C m ,C c ) represents the optimal crystallization temperature of the precipitate at a specific heavy metal ion and precipitant concentration, in degrees Celsius; t crystal (T,C m ,C c) represents the time required for the precipitate formed by heavy metal ions and precipitant to completely crystallize from the solution at the initial temperature, in minutes; d, e, f, g, and h are parameters obtained by fitting experimental data, which are used to describe the relationship between solubility, optimal crystallization temperature, crystallization time and input variables.

[0085] In this step, by considering the three key variables of temperature, heavy metal ion concentration and precipitant concentration, the model can provide personalized solutions for different fly ash washing solutions to meet the needs of efficient separation of heavy metal ions under different conditions; the model can predict solubility and help determine when the solution will reach saturation, thereby determining the optimal time to start evaporation and crystallization; at the same time, predicting the optimal crystallization temperature helps to avoid premature or late crystallization, ensuring crystallization efficiency and product quality; according to the changes in input parameters, the model can dynamically adjust the crystallization temperature and required time, making the entire evaporation and crystallization process more efficient and energy-saving, optimizing resource allocation, and reducing unnecessary energy consumption and time costs; the model not only considers thermodynamic equilibrium (solubility), but also kinetic factors (crystallization temperature and time), which makes it possible to take into account both crystallization rate and crystallization effect in actual operation, thereby improving the robustness and controllability of the entire process; by means of mathematical models, complex chemical reactions and thermodynamic principles are converted into operational process parameters, providing clear guidance for technicians, so that they can more confidently control and optimize the evaporation and crystallization process in actual operation.

[0086] The above precipitation crystallization step temperature set is generated under ideal conditions. In actual operation, the influence of environmental factors needs to be considered. The specific implementation steps for correcting the precipitation crystallization step temperature set using environmental data information are as follows:

[0087] Based on the environmental data information, the correction factor is calculated to adjust the solubility and crystallization rate of the precipitate;

[0088] Temperature correction factor: adjust the solubility and crystallization rate of the precipitate according to the change of ambient temperature; linear or nonlinear regression methods can be used to establish a temperature correction factor model based on experimental data;

[0089] Humidity correction factor: High humidity will slow down the evaporation rate and affect the efficiency of the crystallization process; the humidity correction factor model can be established using empirical formulas or experimental data;

[0090] Pressure correction factor: Changes in air pressure affect the diffusion rate and condensation temperature of vapor during evaporation. The pressure correction factor model can be established using the ideal gas law or experimental data.

[0091] Step temperature correction for precipitation crystallization: According to the temperature correction factor, each temperature gradient is adjusted to ensure the best crystallization effect at the actual ambient temperature. According to the humidity and air pressure correction factors, the crystallization time at each temperature gradient is adjusted to ensure the best crystallization efficiency under the actual ambient conditions.

[0092] For example, suppose an ideal set of precipitation crystallization step temperatures is obtained through the dissolution crystallization equilibrium model, as shown in the following table:

[0093]

[0094] The collected environmental data information is:

[0095] Ambient temperature: 25℃

[0096] Ambient humidity: 70%

[0097] Ambient air pressure: 1013hPa;

[0098] The calibration process is:

[0099] Temperature correction factor: Assume that for every 1°C increase in temperature, the solubility increases by 1% and the crystallization rate increases by 2%;

[0100] Corrected temperature gradient: 60°C + 25 × 0.01 = 60.25°C

[0101] Corrected crystallization time: 30×(1+25×0.02)=31.5min

[0102] Humidity correction factor: Assume that for every 10% increase in humidity, the crystallization time is extended by 5%;

[0103] Corrected crystallization time: 31.5×(1+7×0.05)=35.2125min

[0104] Air pressure correction factor: Assume that for every 10hPa increase in air pressure, the crystallization time is shortened by 1%;

[0105] Corrected crystallization time: 35.2125×(1-1×0.01)=34.860375min;

[0106] According to the above correction factors, each temperature gradient is adjusted to obtain the corrected precipitation crystallization step temperature set:

[0107]

[0108] Through the above steps, it can be ensured that in actual operation, the evaporation crystallization process can be carried out under optimal conditions, thereby improving crystallization efficiency and product quality, while reducing energy consumption and environmental pollution; by comprehensively considering factors such as ambient temperature, humidity, and air pressure, the precipitation crystallization step temperature set is corrected, which can achieve refined control of the evaporation crystallization process and promote the further development and application of fly ash washing solution treatment technology.

[0109] For step S6:

[0110] Step S6 is an actual operation step based on the above series of preliminary analysis and calculations. The core of step S6 is to accurately control the evaporation and crystallization process of the fly ash washing solution according to the corrected precipitation crystallization step temperature set to achieve efficient, orderly and targeted separation and recovery of heavy metal ions. It specifically includes the following steps:

[0111] S61, according to the precipitate crystallization step temperature set corrected in step S5, various parameters of the evaporation crystallization equipment are set in advance; this set includes the temperature and corresponding time window of each heavy metal ion precipitate under its respective optimal crystallization conditions;

[0112] S62, when starting the evaporation crystallization operation, firstly, according to the first set of data in the precipitate crystallization step temperature set, the optimal crystallization temperature suitable for a certain heavy metal ion precipitate is selected to ensure that the internal working area of ​​the evaporation crystallizer can be stably maintained at this temperature;

[0113] S63. The evaporation crystallizer uses an advanced temperature control system to monitor and adjust the working temperature in real time to ensure that it is accurately maintained at the predetermined optimal crystallization temperature; in addition, it is also necessary to equip the corresponding sensors to detect changes in the solution state, such as the solution's conductivity, density, etc. These changes indirectly reflect the precipitation of heavy metal ions;

[0114] S64, according to the crystallization time given in the crystallization step temperature combination of the precipitate, accurately control the duration of each stage; for example, if the optimal time required for the crystallization of the copper ion precipitate is two hours, then after reaching this time point, even if the crystallization has not yet been completely completed, it will switch to the temperature setting of the next stage as planned;

[0115] S65. When one stage of crystallization is completed, the device will automatically or manually switch to the next optimal crystallization temperature to meet the crystallization requirements of the precipitate of another heavy metal ion; this cycle will be repeated until all target heavy metal ions have experienced their respective optimal crystallization conditions;

[0116] S66. After each temperature stage, collect the corresponding heavy metal ion precipitate crystal products, and analyze and verify their purity and yield to confirm whether the crystallization process has achieved the expected results. At the same time, the remaining solution needs to be tested for heavy metal ion concentration again to determine whether there are heavy metal ions that have not been effectively separated. During the actual operation, technicians will continuously calibrate and optimize the model predictions based on the actual crystallization effects to ensure the efficiency and sustainability of the entire evaporation crystallization process.

[0117] In this step, the crystallization step temperature set of the precipitate calculated based on the dissolution crystallization equilibrium model can realize the refined and personalized control of the evaporation crystallization process, and select the best crystallization temperature and time for different heavy metal ions, thereby improving the separation efficiency and recovery purity; by accurately adjusting the temperature, it avoids the waste of resources and inefficient crystallization that may be caused by traditional fixed temperature control, so that each heavy metal ion can crystallize under the most appropriate time and temperature conditions, thereby maximizing the resource recovery rate; equipped with advanced temperature control systems and sensors, real-time monitoring of the state changes of the solution, can timely adjust the process parameters to ensure that the crystallization process is always in the best state, and according to the actual The actual situation can be optimized; the temperature is gradually switched according to the precipitate crystallization step temperature set, which can realize the orderly separation of heavy metal ions, avoid mutual interference, and ensure the smooth completion of the crystallization of each heavy metal ion; through the analysis and verification of the product purity and yield after each stage, as well as the detection of the heavy metal ion concentration in the remaining solution, a closed-loop feedback system is formed, so that the entire evaporation and crystallization process can be continuously optimized and its performance and stability can be continuously improved; through the above-mentioned precise control and optimization means, the efficiency, energy saving and environmental protection of the entire evaporation and crystallization process are ensured, which is conducive to the sustainable utilization of heavy metal ion resources in fly ash and reduces pollution to the environment.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A purification and modification system for heavy metal chloride salts in waste incineration fly ash, characterized in that: It includes a hopper, a grate furnace, an evaporator, a superheater, an economizer, a deacidification tower, a lime powder tank, a bag filter and a chimney which are arranged in sequence along the flue gas flow direction. The bag filter is also connected to a water washing tower, which is respectively connected to a first collecting bin and a second collecting bin, the first collecting bin and the second collecting bin are respectively connected to a modifier, the first collecting bin is used to collect precipitates after purification of heavy metal chloride salts, the second collecting bin is used to collect washed fly ash, and the modifier is used to mix and grind the precipitates and the washed fly ash to achieve modification of the washed fly ash, and spray the modified fly ash back into the flue.

2. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 1, characterized in that: Flue gas sampling positions using CEMS are arranged at the inlet of the deacidification tower, between the deacidification tower and the lime powder tank, and at the outlet of the bag filter.

3. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 2, characterized in that: The modifier is connected to a flue gas sampling position between the deacidification tower and the lime powder tank to spray the modified fly ash back to the flue gas sampling position.

4. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 3, characterized in that: A third collecting bin and a compressed air source are provided between the modifier and the flue gas sampling position. The third collecting bin is used to collect the modified fly ash, and the compressed air source is used to spray the fly ash in the third collecting bin to the flue gas sampling position.

5. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to any one of claims 1 to 4, characterized in that: The heavy metal chloride salt is purified by the following method: Based on the fly ash washing solution treatment scheme, the types of heavy metal ion precipitants used in fly ash washing solution treatment are extracted; The components of the fly ash washing solution were determined to obtain the concentration profile of heavy metal ions in the aqueous solution and the initial pH value of the fly ash washing solution; Using the pre-built precipitation prediction model, the type of heavy metal ion precipitant, the heavy metal ion concentration profile of the aqueous solution and the initial pH value of the fly ash washing solution were comprehensively analyzed to obtain the crystallization characteristics of the precipitate obtained by evaporation and crystallization of the aqueous solution; Real-time collection of environmental data information of the location of the fly ash washing solution; the environmental data information includes environmental temperature, environmental humidity and environmental air pressure; Inputting the crystallization characteristics of the precipitate into a pre-built dissolution-crystallization equilibrium model to obtain a precipitate crystallization step temperature set, and correcting the precipitate crystallization step temperature set using environmental data information to obtain an environmentally corrected precipitate crystallization step temperature set; The corrected precipitation crystallization step temperature set is used as the evaporation crystallization temperature control strategy to control the evaporation crystallization temperature of the fly ash washing solution to purify different heavy metal chloride salts in the waste incineration fly ash.

6. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 5, characterized in that: The heavy metal ion concentration profile of the aqueous solution includes several heavy metal ion concentrations, and the precipitate crystallization characteristics include precipitate types and concentrations of each type of precipitate.

7. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 6, characterized in that: In the precipitate crystallization step temperature set, each gradient corresponds to the optimal crystallization temperature and corresponding crystallization time of at least one precipitate.

8. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 7, characterized in that: The method for constructing a dissolution crystallization equilibrium model comprises: Obtain the solubility data of different heavy metal ions and specific precipitants at different temperatures, as well as the kinetic data of the precipitates corresponding to different heavy metal ions during the crystallization process; Based on thermodynamics and kinetics, a mathematical model of the dissolution-crystallization equilibrium model is constructed to predict the optimal crystallization conditions, including the optimal crystallization temperature and the corresponding required crystallization time, according to the input precipitant type, heavy metal ion species, and their initial concentrations in the solution; The dissolution-crystallization equilibrium model was calibrated and validated using experimental data, and the parameters were iteratively optimized.

9. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 8, characterized in that: The mathematical model of the dissolution crystallization equilibrium model is: T opt (C m ,C c )=dln(C m / C c )+e; t crystal (T,C m ,C c )=f(T-T opt ) / (gC m +hC c ); Where T represents the initial temperature; C m Represents the concentration of heavy metal ions; C c represents the concentration of the precipitant; T opt (C m ,C c ) represents the optimal crystallization temperature of the precipitate at a specific heavy metal ion and precipitant concentration; t crystal (T,C m ,C c ) represents the time required for the precipitate formed by heavy metal ions and the precipitant to completely crystallize from the solution at the initial temperature; d, e, f, g, and h are parameters obtained by fitting the experimental data, which are used to describe the relationship between solubility, optimal crystallization temperature, crystallization time and the input variables.

10. The purification and modification system based on heavy metal chloride salts in waste incineration fly ash according to claim 9, characterized in that: The method for controlling the evaporation crystallization temperature of the fly ash washing solution based on the precipitate crystallization step temperature set comprises: According to the crystallization step temperature set of the precipitate, set the operating parameters of the evaporation crystallization equipment; According to the first set of data in the crystallization step temperature set of the precipitate, the optimal crystallization temperature corresponding to the heavy metal ion precipitate is set; The evaporation crystallization equipment monitors and adjusts the working temperature in real time through the temperature control system, and maintains it at the set optimal crystallization temperature; According to the crystallization time of the precipitate crystallization step temperature combination, the duration of the corresponding step temperature is controlled; When the crystallization of a step temperature is completed, the evaporation crystallization equipment switches to the next optimal crystallization temperature to meet the crystallization requirements of the precipitation of another heavy metal ion; the cycle is repeated until all target heavy metal ions have experienced their respective optimal crystallization conditions.

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