Comprehensive evaluation method for fly ash quality

Abstract

The invention provides a comprehensive evaluation method for fly ash quality, and relates to the field of building materials and environmental science. Through combination of multiple physical and chemical indexes, the quality of the fly ash is comprehensively evaluated by using a comprehensive method of fuzzy mathematics and statistics. According to the method, physical characteristics of fly ash are detected through modern detection equipment; and chemical properties; detecting, and comprehensively evaluating the quality of fly ash samples from different sources by using a fuzzy comprehensive evaluation model to generate a comprehensive score. Through the evaluation result, the fly ash can be scientifically classified according to different application requirements, and reliable guidance is provided for building materials, soil remediation, fly ash high-value utilization and the like. The evaluation system has the advantages of systematization and comprehensiveness, a scientific basis can be provided for comprehensive utilization of the fly ash, and social and economic benefits are maximized.

Description

Technical Field

[0001] The invention relates to the fields of building materials and environmental science, in particular to a comprehensive evaluation method for fly ash quality. Background Art

[0002] Fly ash is a solid waste produced when coal is burned. Since fly ash contains various chemical components, the main components include silica, alumina, iron oxide, calcium compounds, etc., it can be used as an additive for building materials such as concrete, cement, bricks, and ceramics. The quality of fly ash directly affects its use in building materials such as concrete and bricks. Traditional evaluation methods mostly focus on single indicators, such as fineness, water demand, etc., and lack systematic evaluation indicators. Therefore, it is necessary to develop a comprehensive evaluation method to comprehensively evaluate the quality of fly ash.

[0003] At present, researchers have found that the physical and chemical properties of fly ash have a significant impact on the application of fly ash in the circular economy. Fly ash can be used in soil remediation, solid waste treatment, pollutant adsorption, etc., but the utilization rate in the extraction of useful components and high value-added utilization is less than 5%, and the overall comprehensive utilization rate is low. With the continuous development of science and technology, the scientific research on fly ash is also deepening, and its potential areas of utilization are gradually increasing. The comprehensive utilization of fly ash has achieved the transformation of waste into treasure and reduced the pressure on other non-renewable resources. In addition, scientists are also exploring the use of waste fly ash to prepare high-value-added chemicals and functional materials, such as catalysts, adsorbents, polymer precursors, silicon-aluminum substrates, etc., to give it new functions and values. The principle of fly ash utilization is to focus on ash utilization technology, organically combine its comprehensive utilization benefits and social benefits, absorb and learn from advanced technologies in developed countries, and improve the comprehensive utilization technology of fly ash.

[0004] Patent No. CN108008069A provides an evaluation method for automatically uploading and processing data by connecting to a fly ash physical and chemical property detection instrument through an intelligent terminal. It mainly focuses on the application of fly ash in the building materials industry, especially in concrete, cement and fly ash bricks. Although this method also provides a comprehensive evaluation system in the fly ash quality evaluation system, it focuses more on safety evaluation (such as radionuclide content and heavy metal leaching) and evaluation of building materials related indicators. It lacks a scientific and systematic evaluation method combining multiple indicators, and the application guidance is not direct and specific enough. Therefore, it is very important to provide an evaluation method that is obviously innovative in terms of scientificity, comprehensiveness and application guidance, especially in the establishment of a comprehensive evaluation system and the scientificity of combining multiple indicators, for the quality evaluation and comprehensive utilization of fly ash. Summary of the invention

[0005] The purpose of the present invention is to provide a comprehensive evaluation method for fly ash quality to promote its efficient utilization.

[0006] The present invention provides a comprehensive evaluation method for the quality of fly ash, which comprehensively evaluates the quality of fly ash by combining physical and chemical multi-index analysis, so as to provide a scientific basis for its efficient use in building materials and other environmental applications. The method is based on the main physical properties (such as particle distribution, specific surface area, density, etc.) and chemical properties (such as silicon dioxide content, aluminum oxide content, alkali content, trace metal elements, etc.) of fly ash, and uses a combination of fuzzy mathematics and statistics to comprehensively evaluate the quality of fly ash from different sources.

[0007] A comprehensive evaluation method for fly ash quality comprises the following steps:

[0008] S1. Sample pretreatment, including collecting fly ash samples from different sources, drying to constant weight, and grinding to a certain particle size;

[0009] S2, physical and chemical index testing;

[0010] Includes the following:

[0011] a. Particle distribution: The size and distribution of fly ash particles are measured by a laser particle size analyzer, with the parameter range being 10%-40% of the data set;

[0012] b. Specific surface area: The specific surface area of ​​fly ash was measured using a specific surface area analyzer, with the parameter range being 15%-35% of the data set;

[0013] c. Density: The density of fly ash was determined by gas displacement method or liquid displacement method, and the parameter range was 20%-40% of the data set;

[0014] d. Silica content: X-ray fluorescence spectrometer was used to analyze the silica content in fly ash, with the parameter range being 25%-50% of the data set;

[0015] e. Alumina content: measures the content of alumina, with the parameter range being 20%-40% of the data set;

[0016] f. Alkali content: The alkali content of fly ash is determined by wet chemical method or ion chromatography, and the parameter range is 15%-35% of the data set;

[0017] g. Trace Metal Elements: Measure the content of heavy metals and other trace elements in fly ash, with the parameter range being 10%-30% of the data set.

[0018] S3, comprehensive evaluation model, using the combination of fuzzy mathematics and statistics to standardize the test results, weight indicators, perform fuzzy mathematical operations and statistical analysis to form a comprehensive evaluation score;

[0019] The following steps are involved:

[0020] a. Standardization of indicators, standardization of all physical and chemical test results;

[0021] b. Index weighting: weight each index according to the demand for fly ash in different application scenarios;

[0022] c. Fuzzy mathematical operation, using fuzzy comprehensive evaluation method to process the standardized indicators;

[0023] d. Statistical analysis: statistical analysis is performed on the comprehensive scores of each sample, and fly ash samples with similar scores are classified by clustering method. The comprehensive membership parameter range is:

[0024] Comprehensive membership > 0.75 is “excellent”;

[0025] 0.5<comprehensive membership<0.75 is “good”;

[0026] 0.25<comprehensive membership<0.5 is “medium”;

[0027] The comprehensive membership degree <0.25 is “poor”.

[0028] S4. Application of comprehensive evaluation scores: provide guidance on the application of fly ash based on the comprehensive evaluation scores;

[0029] Includes the following:

[0030] a. Application in building materials, fly ash with high comprehensive score will be used preferentially in concrete, cement and bricks;

[0031] b. Application in soil remediation and pollutant adsorption, select fly ash samples with high specific surface area and appropriate trace metal content;

[0032] c. Preparation of high value-added products, screening out fly ash samples suitable for the preparation of catalysts, adsorbents and other functional materials.

[0033] S5. Feedback and improvement of evaluation results, and optimize the parameters in the evaluation system according to the actual application effects.

[0034] Specifically, the feedback and improvement of the evaluation results include optimizing the indicator weights and standardization method parameters in the evaluation system according to the feedback on the effect of fly ash application.

[0035] The establishment of the comprehensive evaluation system of the present invention aims to provide a comprehensive fly ash quality evaluation framework. The first step of the evaluation system is to select appropriate evaluation indicators. These indicators should be able to fully reflect the quality of fly ash and the performance of subsequent comprehensive utilization of fly ash.

[0036] Pretreatment of fly ash samples is a critical step as it ensures that the samples represent the overall characteristics of their source. Pretreatment involves collecting fly ash samples from multiple coal-fired power plants, which should cover different combustion conditions and coal types to ensure the broad applicability of the evaluation results. After sample collection, it is necessary to dry in a controlled environment, usually in an oven at 60°C to 80°C, until the sample reaches a constant weight to eliminate the effect of moisture on subsequent testing. This facilitates accurate physical and chemical analysis.

[0037] The present invention uses modern testing equipment to test the physical and chemical indicators of the pretreated fly ash sample. These indicators include but are not limited to particle distribution, specific surface area, density, silicon dioxide content, aluminum oxide content, alkali content and trace metal element content. These test results will provide key data for the quality evaluation of fly ash.

[0038] The present invention: establishes a membership function for each evaluation index, which maps the actual measured value of the index to the interval [0,1], indicating the degree to which the index meets the evaluation criteria. The membership function can be linear or nonlinear, depending on the characteristics of the index and the evaluation requirements. Determine the weight: determine the weight of each evaluation index, and the weight reflects the importance of each index in the comprehensive evaluation. The weight can be determined by expert scoring, hierarchical analysis method (AHP) or other objective methods.

[0039] The present invention adopts a fuzzy mathematical evaluation model, which can process and integrate multiple physical and chemical indicators to form a comprehensive evaluation score through weighted comprehensive calculation. In this process, each indicator is weighted according to its importance in affecting the quality of fly ash. For example, for concrete applications, particle distribution and silica content may be given higher weights, while for soil remediation applications, specific surface area and trace metal content may be more critical. The fuzzy mathematical model converts qualitative evaluation into quantitative scores by constructing a membership function, making the evaluation results more objective and accurate.

[0040] The present invention classifies the quality of different fly ash samples according to the obtained comprehensive evaluation scores. This classification will guide the selection of fly ash in specific applications. For example, fly ash with a high score may be more suitable for the production of high-strength concrete, while fly ash with a low score may require further processing before use.

[0041] The present invention achieves accurate matching by correlating the comprehensive evaluation score of fly ash with its performance in building materials. The comprehensive evaluation score of fly ash is compared with performance data in actual applications, such as strength development, durability and workability in concrete. Through this correlation analysis, it is possible to determine which fly ash samples are most suitable for specific building materials, thereby optimizing their utilization in building materials.

[0042] In addition, the evaluation method of the present invention is not limited to the field of building materials, but can also be extended to other fields, such as soil remediation, pollutant adsorption, and the preparation of high value-added materials. In the field of soil remediation, the evaluation method can help select fly ash with a suitable specific surface area and trace metal content to improve the efficiency of soil remediation. In the field of pollutant adsorption, the evaluation method can guide the selection of fly ash with specific chemical properties to improve the adsorption efficiency. When preparing high value-added materials, the evaluation method can screen out fly ash samples suitable for the preparation of catalysts, adsorbents and other functional materials, thereby improving the performance and value of the materials.

[0043] Compared with the prior art, the present invention has the following technical advantages:

[0044] 1) A systematic and comprehensive evaluation system that can fully reflect the quality of fly ash;

[0045] 2) Combine multiple physical and chemical indicators to ensure the scientificity and accuracy of the evaluation results;

[0046] 3) The evaluation results can directly guide the efficient utilization of fly ash and provide a reliable scientific basis for different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0048] In order to achieve the purpose and effect of the present invention, the present invention provides two specific implementation methods so as to better scientifically evaluate the comprehensive quality of fly ash. The implementation details of each step will be specifically described below:

[0049] Example 1: This example provides a method for evaluating fly ash quality under laboratory conditions

[0050] S1. Sample pretreatment

[0051] Before evaluating the quality of fly ash, the fly ash sample must be pretreated to ensure that the sample is representative and uniform. The pretreatment steps include the following:

[0052] Sample collection: Collect fly ash samples from different sources to ensure that the samples have different physical and chemical properties to reflect the diversity of fly ash.

[0053] Sample drying: Place the sample in an oven at 60℃-80℃ and dry it to constant weight to avoid interference of moisture on the measurement results.

[0054] S2. Physical and chemical index testing

[0055] In the comprehensive quality evaluation method of the present invention, the physical and chemical indicators of fly ash are the core components of the evaluation. Through modern testing equipment, multiple physical and chemical properties of the sample are analyzed, including but not limited to the following:

[0056] Physical properties:

[0057] Particle distribution: The size and distribution of fly ash particles are measured by a laser particle size analyzer to obtain data such as the median particle size and distribution range to evaluate its filling performance in building materials.

[0058] Specific surface area: The specific surface area of ​​fly ash is measured using a specific surface area analyzer (such as the BET method) to provide a basis for subsequent adsorption performance and reaction activity.

[0059] Density: The density of fly ash is measured by gas displacement method or liquid displacement method, and its influence on material density and mechanical properties is analyzed.

[0060] Chemical properties:

[0061] Silica content: X-ray fluorescence spectrometer (XRF) was used to analyze the silica content in fly ash to determine its effect on cement hydration reaction and mechanical properties.

[0062] Alumina Content: The content of alumina is measured to evaluate the activity of fly ash and its potential application in cement.

[0063] Alkali content: The alkali content of fly ash is determined by wet chemical methods or ion chromatography to analyze its alkali-aggregate reaction risk in concrete.

[0064] Trace Metal Elements: Measure the content of heavy metals and other trace elements in fly ash to evaluate its potential impact in environmental applications such as soil remediation and pollutant adsorption.

[0065] S3. Comprehensive evaluation model

[0066] After the physical and chemical tests are completed, the comprehensive quality of fly ash is analyzed through an evaluation model combining fuzzy mathematics and statistics. The implementation steps of the model are as follows:

[0067] Standardization of indicators: First, all the results of physical and chemical tests are standardized to eliminate the impact of the dimension on the comprehensive score. All data are converted to the same scale range through Min-Max normalization or Z-score normalization.

[0068] Constructing particle size function and index weighting: Establish membership function for each evaluation index, and weight each index according to the needs of fly ash in different application scenarios. For example, in concrete application, particle distribution and silica content have higher weights, while in soil remediation, specific surface area and trace metal content have higher weights.

[0069] Fuzzy mathematical operation: The standardized indicators are processed using the fuzzy comprehensive evaluation method. By constructing a membership function, each indicator is converted into a fuzzy evaluation matrix, and fuzzy operations are performed to generate a comprehensive evaluation score.

[0070] Statistical analysis: The comprehensive scores of each sample were statistically analyzed, and fly ash samples with similar scores were classified by clustering method, and finally fly ash sample categories of different grades were obtained.

[0071] S4. Application of comprehensive evaluation scores

[0072] According to the comprehensive evaluation scores and classification results, guidance is provided on the application of fly ash in building materials and other fields. The specific application methods are as follows:

[0073] Application in building materials: Fly ash with high comprehensive scores is used preferentially in concrete, cement and bricks to improve the strength and durability of the materials. For different grades of fly ash, it is matched with the use performance to optimize its use effect in building materials.

[0074] Application in soil remediation and pollutant adsorption: In view of the needs of soil remediation and pollutant adsorption, fly ash samples with high specific surface area and appropriate trace metal content are selected to achieve optimal utilization in ecological restoration.

[0075] Preparation of high value-added products: Through a comprehensive evaluation system, fly ash samples suitable for the preparation of catalysts, adsorbents and other functional materials are screened out to realize their application in high value-added products.

[0076] Further reprocessing: Some low-scoring and unqualified fly ash requires further processing, such as activation treatment.

[0077] S5. Feedback and improvement of evaluation results

[0078] The evaluation system of the present invention also includes a feedback mechanism for the fly ash evaluation results. In practical applications, according to the feedback of the fly ash application effect, the parameters such as the index weight and the standardization method in the evaluation system are optimized to further improve the comprehensive utilization efficiency of the fly ash.

[0079] Example 2: This example provides a method for evaluating and monitoring fly ash quality in real time under field conditions.

[0080] Another specific implementation method of the present invention is to conduct real-time quality evaluation and monitoring in the on-site environment where fly ash is produced. The specific steps are as follows:

[0081] S1. On-site sample collection:

[0082] (1) Install automated sampling equipment at the fly ash emission points of coal-fired power plants to collect fly ash samples in a timed or continuous manner.

[0083] (2) Ensure that the sampling equipment is able to collect fly ash from different time periods and under different combustion conditions to ensure the representativeness of the sample.

[0084] S2. On-site pretreatment system:

[0085] (1) Install drying equipment on site, such as a hot air drying oven, to quickly dry the collected fly ash samples.

[0086] (2) The dried samples are ground into a particle size suitable for analysis using an automated grinding system to reduce sample processing time and improve efficiency.

[0087] S3. On-site physical and chemical index testing:

[0088] (1) Deploy portable or fixed laser particle size analyzers to measure the distribution of fly ash particles in real time.

[0089] (2) Use a portable surface area analyzer, such as a dynamic flow analyzer, to quickly determine the surface area of ​​fly ash.

[0090] (3) Deploy a density meter on site to measure the density of fly ash through an automated system.

[0091] (4) Use a portable X-ray fluorescence spectrometer (XRF) to conduct on-site rapid analysis of the chemical composition of fly ash.

[0092] S4. On-site fuzzy mathematical evaluation model:

[0093] (1) The on-site detection data is transmitted to the on-site control center, and the fuzzy mathematical evaluation model is used for real-time data processing.

[0094] (2) Constructing a fuzzy evaluation matrix: Combine the membership value and weight to construct a fuzzy evaluation matrix.

[0095] (3) Fuzzy operations: Perform fuzzy matrix operations, such as fuzzy multiplication or fuzzy weighted average, to generate a comprehensive evaluation score.

[0096] (4) Dynamically adjust the weight of each indicator based on real-time data to adapt to changes in the on-site environment and different application requirements.

[0097] S5. On-site application of comprehensive evaluation scores:

[0098] (1) The comprehensive evaluation scores generated in real time are used to guide on-site fly ash handling and application decisions.

[0099] (2) Adjust the fly ash application strategy in real time based on the comprehensive evaluation score

[0100] (3) Fly ash with higher evaluation scores can be directly used in on-site construction material production, mix proportioning in concrete production or soil remediation projects.

[0101] (4) For fly ash with lower evaluation scores, further treatment such as activation or chemical modification is carried out on site.

[0102] S6. On-site feedback and system optimization:

[0103] (1) Establish a field feedback mechanism to collect field data on the effects of fly ash application, such as setting time and strength development of concrete.

[0104] (2) Based on on-site feedback, adjust the evaluation model parameters in real time to optimize the quality evaluation and application effect of fly ash.

[0105] (3) Through this on-site implementation method, real-time monitoring and rapid response of fly ash quality can be achieved, improving the efficiency and effect of fly ash comprehensive utilization, while reducing environmental pollution and resource waste. This method is particularly suitable for occasions with strict requirements on fly ash quality, such as large-scale construction projects or environmental remediation projects.

[0106] Through the above steps, the fly ash comprehensive quality evaluation method of the present invention can not only comprehensively and accurately evaluate the quality of fly ash, but also scientifically screen and classify fly ash according to different application requirements, thereby improving the application efficiency of fly ash in circular economy and environmental protection, and achieving higher social and economic benefits.

Claims

1. A comprehensive evaluation method for fly ash quality, characterized in that: The following steps are involved: S1. Sample pretreatment, including collecting fly ash samples from different sources, drying to constant weight, and grinding to a certain particle size; S2, physical and chemical index testing; S3, comprehensive evaluation model, using the combination of fuzzy mathematics and statistics to standardize the test results, weight indicators, perform fuzzy mathematical operations and statistical analysis to form a comprehensive evaluation score; S4. Application of comprehensive evaluation scores: provide guidance on the application of fly ash based on the comprehensive evaluation scores; S5. Feedback and improvement of evaluation results, and optimize the parameters in the evaluation system according to the actual application effects.

2. A comprehensive evaluation method for fly ash quality according to claim 1, characterized in that: The physical and chemical index detection includes the following contents: a. Particle distribution: The size and distribution of fly ash particles are measured by a laser particle size analyzer, with the parameter range being 10%-40% of the data set; b. Specific surface area: The specific surface area of ​​fly ash was measured using a specific surface area analyzer, with the parameter range being 15%-35% of the data set; c. Density: The density of fly ash was determined by gas displacement method or liquid displacement method, and the parameter range was 20%-40% of the data set; d. Silica content: X-ray fluorescence spectrometer was used to analyze the silica content in fly ash, with the parameter range being 25%-50% of the data set; e. Alumina content: measures the content of alumina, with the parameter range being 20%-40% of the data set; f. Alkali content: The alkali content of fly ash is determined by wet chemical method or ion chromatography, and the parameter range is 15%-35% of the data set; g. Trace Metal Elements: Measure the content of heavy metals and other trace elements in fly ash, with the parameter range being 10%-30% of the data set.

3. The comprehensive evaluation method for fly ash quality according to claim 1, characterized in that: The comprehensive evaluation model includes the following steps: a. Standardization of indicators, standardization of all physical and chemical test results; b. Index weighting: weight each index according to the demand for fly ash in different application scenarios; c. Fuzzy mathematical operation, using fuzzy comprehensive evaluation method to process the standardized indicators; d. Statistical analysis: statistical analysis is performed on the comprehensive scores of each sample, and fly ash samples with similar scores are classified by clustering method. The comprehensive membership parameter range is: Comprehensive membership > 0.75 is "excellent"; 0.5<comprehensive membership<0.75 is "good"; 0.25<comprehensive membership<0.5 is "medium"; The comprehensive membership degree <0.25 is "poor".

4. The comprehensive evaluation method for fly ash quality according to claim 1, characterized in that: The comprehensive evaluation score application includes the following: a. Application in building materials, fly ash with high comprehensive score will be used preferentially in concrete, cement and bricks; b. Application in soil remediation and pollutant adsorption, select fly ash samples with high specific surface area and appropriate trace metal content; c. Preparation of high value-added products, screening out fly ash samples suitable for the preparation of catalysts, adsorbents and other functional materials.

5. The comprehensive evaluation method for fly ash quality according to claim 1, characterized in that: The feedback and improvement of the evaluation results include optimizing the indicator weights and standardization method parameters in the evaluation system according to the feedback of the fly ash application effect.

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