Method for optimizing ratio response curved surface and evaluating equivalent toxicity inhibition efficiency of composite smoke suppressant

Abstract

The invention discloses a composite smoke suppressant ratio response curved surface optimization and equivalent toxicity suppression efficiency evaluation method in the technical field of road asphalt, which comprises the following steps: 1) initially determining the raw material type and single mixing amount range of a composite smoke suppressant through a single mixing smoke suppression test and an LOI limit oxygen index test; 2) designing a multi-factor orthogonal rotation combination test, establishing a Quadratic model between the ratio of the composite smoke suppressant and the asphalt VOCs inhibition effect, and generating a response curved surface to obtain an optimal ratio; (3) applying the composite smoke suppressant with the optimized ratio to asphalt, quantitatively detecting the VOCs of the smoke suppression asphalt, and calculating the total toxic equivalent of the VOCs of the asphalt smoke; 4) calculating the equivalent toxicity inhibition efficiency of the composite smoke suppressant, the proportion of the components of the composite smoke suppressant can be optimized efficiently, the smoke inhibition efficiency of the smoke suppressant can be evaluated, and the problems that the number of experimental components of the current smoke suppressant is too large, and the inhibition efficiency of the smoke suppressant on high-toxicity substances is difficult to evaluate are solved.

Description

Technical Field

[0001] The invention relates to the technical field of road asphalt, and in particular to an optimized ratio of an asphalt smoke suppressant and a method for evaluating the toxicity suppression efficiency. Background Art

[0002] Asphalt pavement has become the most commonly used pavement structure due to its good road performance, smoothness, and noise-free advantages. However, asphalt, as a product of petroleum distillation, will release a large amount of asphalt fume during the mixing, paving and thermal regeneration of asphalt mixtures. These asphalt fumes will not only cause serious air pollution and affect the visibility of construction in tunnels, but also most of the components in asphalt fume are classified as Class II carcinogens by the World Health Organization, which will cause great harm to the health of road construction workers. Therefore, reducing the fume generated by asphalt during high-temperature heating from the source, or adopting effective fume treatment devices to purify the fume generated during construction, is of great significance to protecting the environment and the physical and mental health of road workers, and is also a necessary measure to build a "resource-saving and environmentally friendly" society.

[0003] In order to improve the safety of asphalt pavement and reduce smoke emissions during the production and paving of asphalt mixtures, researchers have proposed the preparation of smoke-suppressing asphalt. At present, the research on smoke-suppressing asphalt mainly focuses on reducing the mixing temperature, physical pore adsorption, electrostatic adsorption, and fixation of light components of asphalt. Practice has shown that these methods have good flame retardant and smoke-suppressing effects, can essentially improve the environmental protection and safety of asphalt pavement, reduce pollutant emissions during the paving of asphalt mixtures, and have good application prospects.

[0004] The current method for preparing smoke-suppressing asphalt is mainly to add smoke-suppressing additives into it to achieve the effect of reducing smoke emissions. The current additives can be roughly divided into three types: adsorbents, flame retardants and polymer smoke suppressants. Adsorbents are mostly loose porous structures or have the ability to spontaneously generate polarity to achieve the ability to adsorb asphalt smoke. Flame retardants have the effect of isolating oxygen in asphalt to prevent the oxidation of organic matter and reduce the generation of volatile organic compounds (VOCs). Alkali metal hydroxides such as magnesium hydroxide can absorb a large amount of heat when heated to lower the temperature of asphalt and reduce smoke generation. At the same time, a dense insulating layer is produced to isolate the asphalt from oxygen to achieve flame retardant and smoke suppression effects;

[0005] In recent years, compounding smoke suppressants of different types, properties and characteristics in a certain proportion to prepare a composite smoke suppressant has become the mainstream of smoke suppressant asphalt research. There is a synergistic effect between different types of smoke suppressants, which has a better smoke suppression effect than single smoke suppressants. However, there is a lack of efficient optimization methods for the selection of different types of smoke suppressants and the ratio between the components of composite smoke suppressants. At the same time, existing studies have shown that most of the total smoke components suppressed by smoke suppressants are low-hazard substances such as water and tar, and there is a lack of evaluation indicators and means for the actual suppression effect of smoke suppressants on high-hazard substances in asphalt smoke. Summary of the invention

[0006] In view of the shortcomings in the prior art, the present invention provides a response surface optimization method for the ratio of composite smoke suppressants and an equivalent toxicity inhibition efficiency evaluation method, which can efficiently optimize the ratio between the components of the composite smoke suppressant. In order to more comprehensively evaluate the performance of the composite smoke suppressant while reflecting its environmental protection and economy, new evaluation indicators are proposed, and the toxicity reduction effect of the smoke suppressant is quantitatively evaluated, so as to solve the problems of too many test groups for the ratio of smoke suppressant components and difficulty in evaluating the equivalent toxicity inhibition efficiency.

[0007] The object of the present invention is achieved by: a composite smoke suppressant ratio response surface optimization and equivalent toxicity inhibition efficiency evaluation method, characterized in that it includes the following steps:

[0008] Step 1) Preliminarily determine the types of raw materials and single dosage range of the composite smoke suppressant;

[0009] Step 2) design a multi-factor orthogonal rotation combination test, establish a Quadratic model between the ratio of the composite smoke suppressant and the VOCs inhibition effect of asphalt, optimize the mathematical model, generate a response surface, and obtain the optimal ratio of the smoke suppressant;

[0010] Step 3) applying the composite smoke suppressant with optimized ratio to asphalt, using asphalt smoke high temperature enrichment device and GC-MS to quantitatively detect the VOCs of the smoke suppressant asphalt, and calculating the total toxic equivalent of the VOCs of the asphalt smoke;

[0011] Step 4) Calculate the equivalent toxicity suppression efficiency of the composite smoke suppressant, evaluate the proportion of highly toxic substances in the total amount of smoke suppressed by the smoke suppressant, and assess the actual suppression effect of the composite smoke suppressant on the toxicity of asphalt smoke.

[0012] Furthermore, in step 1), the raw materials of the composite smoke suppressant include: nano-magnesium hydroxide, zeolite and expandable graphite, and the optimal dosage range of each smoke suppressant is determined by a single factor smoke suppression rate test based on a gravimetric method.

[0013] Furthermore, the test device used in the single-factor smoke suppression rate test is an asphalt flue gas high-temperature enrichment device, including: an air drying device, an asphalt high-temperature oil bath heating device, an asphalt flue gas enrichment device, an exhaust gas purification device, and an air pump, which are connected in sequence through a conduit. The air passes through the air drying device and absorbs moisture before flowing into the asphalt high-temperature oil bath heating device. The asphalt high-temperature oil bath heating device provides a temperature of not less than 180°C and a stirring rate of 300r / min, so that the asphalt is evenly heated to produce asphalt flue gas; the asphalt flue gas enrichment device is composed of a polytetrafluoroethylene (PTFE) hydrophobic filter membrane and a filter membrane box. Polytetrafluoroethylene has excellent organic adsorption properties; the exhaust gas purification device can absorb harmful gases in the exhaust gas and discharge them into the air. The air pump provides a stable airflow rate in the device, so that the asphalt flue gas is enriched on the PTFE filter membrane through the rubber conduit, which can be weighed and tested in the next step.

[0014] Furthermore, step 2) is specifically as follows: using Design-Expert 13 software, selecting the surrounding range value of the result for a single factor, designing a multi-factor orthogonal rotation combination test, taking the dosage of the smoke suppressant material as the independent variable q, and the smoke suppression rate as the dependent variable ε, establishing a Quadratic mathematical model of the dosage of each component of the smoke suppressant and the smoke suppression rate through an orthogonal test, and generating a response surface to obtain the optimal formula of the compound smoke suppression asphalt;

[0015] The Quadratic mathematical model is in the form of:

[0016]

[0017] Among them: n and N are the types of smoke suppressant materials, q x is the dosage of each smoke suppressant component, A, B, C are the coefficients of different terms in the regression equation;

[0018] Furthermore, the collection process of the smoke-suppressing asphalt in step 3) is as follows: the smoke is enriched onto a hydrophobic PTFE filter membrane using an asphalt smoke high-temperature enrichment device, and the filter membrane is placed in a trichloroethylene solution to prepare an asphalt smoke headspace sample using an ultrasonic extraction method.

[0019] Furthermore, the detection in step 3) is specifically as follows: a headspace gas chromatograph is used to perform a full SCAN scan on the asphalt flue gas sample, and a qualitative result is obtained by comparing it with the spectral library to determine the specific harmful component VOC i And prepare the VOC to be tested i Standard sample, establish the standard response curve y = a for this component i x+b i , SIM selective ion scanning was performed on specific components using gas chromatography-mass spectrometry to separate VOC i The response value y i Substitute the standard curve into the calculation to obtain the VOCi mass concentration x in the sample solutioni ; Then combined with the sample mass m i The VOC i The mass ratio of the ingredients w i Quantitative test of smoke suppressants on VOC i emission reduction effect.

[0020] Further, in step 3), asphalt flue gas VOC i The mass ratio w i The calculation formula is as follows:

[0021] VOC in asphalt flue gas i Quality Ratio

[0022] Where: w i For this VOC i The proportion of the component in each kilogram of smoke, mg / Kg;

[0023] m i is the mass of asphalt fume adsorbed by the filter paper, that is, the mass of asphalt fume dissolved in 10mL trichloroethylene solution, mg;

[0024] x i is the mass concentration of VOCi in the sample solution, mg / L.

[0025] Furthermore, in step 4), the threat of asphalt smoke to human health mainly depends on the toxicity of equivalent asphalt smoke and the mass of asphalt smoke ingested by the human body. In order to consider the threat of the above two factors to human health at the same time and comprehensively judge the actual filtration efficiency of the smoke suppressant on the toxicity of the smoke generated by asphalt combustion, the equivalent toxicity inhibition efficiency (ETE) of the smoke suppressant is now defined to describe the proportion of the amount of smoke suppressant to inhibit the toxicity of asphalt smoke VOCs in the total amount of smoke inhibition. The calculation formula is as follows:

[0026]

[0027] Where, ETE is the equivalent toxicity inhibition efficiency; Δw i VOC before and after using smoke suppressant i Mass ratio change rate, mg / Kg; TE i For VOC i The numerator is the sum of the mass ratio change rate of each VOC above the detection limit multiplied by its equivalent toxicity factor, that is, the comprehensive change of equivalent toxicity of all VOCs in asphalt smoke; Δm is the change in smoke production in the heating test before and after the use of smoke suppressant, mg.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adopts the response surface method and simulation experiments to optimize the composition ratio of the composite smoke suppressant, which greatly reduces the number of experimental groups; utilizes a self-made asphalt flue gas high-temperature enrichment device, and utilizes the weight difference of the filter membrane instead of the traditional asphalt mass difference, thereby improving the test accuracy; this composite smoke suppressant composition ratio response surface optimization and equivalent toxicity inhibition efficiency evaluation method, uses GC-MS to detect VOCs in asphalt flue gas, and can achieve quantitative detection and evaluation of the emission reduction effect of the smoke suppressant in VOCs, which provides a theoretical basis and practical reference for further improving the performance of smoke suppressant asphalt and the development of asphalt flue gas emission detection standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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 only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 It is a schematic diagram of the structure of the asphalt flue gas high temperature enrichment device in the present invention.

[0031] Figure 2 It is a flow chart of the present invention.

[0032] Figure 3 This is the response surface diagram of the present invention.

[0033] Among them, 1 is an air drying device, 2 is an asphalt high-temperature oil bath heating device, 3 is an asphalt flue gas enrichment device, 4 is an exhaust gas purification device, and 5 is an air pump. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] As shown in the figure, a composite smoke suppressant ratio response surface optimization and equivalent toxicity inhibition efficiency evaluation method includes the following steps:

[0036] Step 1) In this embodiment, the smoke suppression materials initially selected are nano-magnesium hydroxide powder (100-200nm), zeolite powder (200 mesh), and expandable graphite (100 mesh). 70# road petroleum asphalt is selected for material preparation. The three materials in various dosages are added to the asphalt in an asphalt high-temperature shear instrument and sheared for 30 minutes at 200°C and 3000r / min to fully blend.

[0037] Step 2) Determine the initial dosage of several materials in the smoke suppressant through single factor experiments, combined with Figure 1 The test device used in the single factor smoke suppression rate test is an asphalt smoke high temperature enrichment device, including: an air drying device 1, an asphalt high temperature oil bath heating device 2, an asphalt smoke enrichment device 3, an exhaust gas purification device 4, and an air pump 5, which are connected in sequence through a conduit. The air passes through the air drying device 1 and then flows into the asphalt high temperature oil bath heating device 2 after absorbing moisture. The asphalt high temperature oil bath heating device 2 provides a temperature of not less than 180°C and a stirring rate of 300r / min, so that the asphalt is evenly heated to produce asphalt smoke; the asphalt smoke enrichment device 3 is made of polytetrafluoroethylene It is composed of a PTFE hydrophobic filter membrane and a filter membrane box. Polytetrafluoroethylene has excellent organic adsorption. The exhaust gas purification device 4 can absorb harmful gases in the exhaust gas and discharge them into the air. The air pump 5 provides a stable air flow rate in the device, so that the asphalt smoke is enriched on the PTFE filter membrane through the rubber tube, and can be weighed and tested in the next step. The prepared single-doped smoke suppression asphalt is placed in a three-necked flask of the asphalt smoke high-temperature enrichment device, and the heating temperature is set to 200°C, the air flow rate is 1L / min, and the heating time is 3min. The smoke suppression rate test based on the weight method is carried out. The dosage corresponding to the maximum smoke suppression rate of each material is obtained. Taking the optimal dosage as the center point, the optimal dosage ranges of the three materials are obtained as follows: magnesium hydroxide 4%-12%, zeolite 0.5%-1%, and expandable graphite 2%-6%.

[0038] Step 3) Design-Expert 13.0 software was used to design a multi-factor orthogonal rotation combination test for the range of values ​​around the single factor selection results. A total of 15 groups of rotation orthogonal combination experiments were designed with the dosage of the three materials as the independent variable and the smoke suppression rate as the response value. Combined with the test results in Table 1 and Table 2, the correlation significance between each factor and the response value smoke suppression rate was calculated to optimize the model, and finally the mathematical model regression equation between the dosage of each material and the response value was obtained as follows:

[0039] ω=-14.73750+21.779A+25.74B-9.49125C+0.089AC+1.545BC-1.05469A 2 -

[0040] 14.58B 2 +0.0525C 2R 2 =0.9853

[0041] Where R 2 The closer it is to 1, the smaller the error between the model and the actual value, and the more accurate the model.

[0042] Combination Figure 3 Through mathematical models and response surface analysis, the optimal dosage ratio of each material is obtained as follows: 9.75% nano-magnesium hydroxide, 0.88% zeolite, and 2.16% expandable graphite. At this time, the highest theoretical smoke suppression rate of 93.2% can be achieved.

[0043] Step 4: Prepare the optimized asphalt sample with the best ratio, use GC-MS to perform a full scan of the asphalt flue gas sample, and obtain the name of each substance through comparative analysis of the NIST 2014MS Library mass spectrum library, and obtain the qualitative results, as shown in Table 3. Configure GC-MS with mixed standard solutions at 5 concentration levels, and use the least squares method to establish the standard response curve y=a for 7 VOCs i x+b i , as shown in Table 4.

[0044] Step 5, prepare the headspace samples of smoke suppression asphalt and control group matrix asphalt, use GC-MS to perform SIM selective ion scanning on the 7 VOCs detected, obtain the response values ​​of the 7 VOCs, substitute the response value y into the standard curve, and calculate the mass ratio of each VOC in combination with formula (1), as shown in Table 5.

[0045] Step 6, the equivalent toxicity inhibition efficiency of the composite smoke suppressant optimized by the response surface is calculated by the formula in claim 8, and a single 8% nano magnesium hydroxide powder is selected as a comparative smoke suppressant, and the calculation results of the equivalent toxicity inhibition efficiency of the two are shown in Table 6. It can be concluded that the ETE of the asphalt smoke suppressant optimized based on the response surface is significantly improved compared with that of the single nano magnesium hydroxide, indicating that the composite smoke suppressant optimized by the response surface has a stronger inhibitory effect on highly toxic substances in the flue gas and has a better equivalent toxicity inhibition efficiency for asphalt flue gas.

[0046] Table 1 Orthogonal experimental design and experimental results

[0047]

[0048]

[0049] Table 2 Significance analysis of factors in multi-factor orthogonal test (P<0.05 indicates that the item is significant, P<0.0001 indicates that the factor is highly significant)

[0050]

[0051] Table 3 GC-MS test results

[0052]

[0053] Table 4 VOCs standard curve and correlation coefficient

[0054]

[0055] Table 5 Asphalt smoke generation in high temperature smoke enrichment test

[0056]

[0057] Table 6 Calculation results of equivalent toxicity inhibition efficiency

[0058]

[0059] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A response surface optimization method for compound smoke suppressant ratio and equivalent toxicity inhibition efficiency evaluation method, characterized in that: The following steps are involved: Step 1) Preliminarily determine the type of raw materials and single doping range of the composite smoke suppressant according to the smoke suppression effect and the minimum combustion oxygen concentration through single doping smoke suppression test and LOI limiting oxygen index test; Step 2) design a multi-factor orthogonal rotation combination test, establish a Quadratic model between the ratio of the composite smoke suppressant and the VOCs inhibition effect of asphalt, optimize the mathematical model, generate a response surface, and obtain the optimal ratio of the smoke suppressant; Step 3) The composite smoke suppressant with optimized ratio is applied to asphalt, and the VOCs of the smoke suppressant asphalt are quantitatively detected by using an asphalt smoke high-temperature enrichment device and GC-MS to calculate the total toxic equivalent of the asphalt smoke VOCs. Step 4) Calculate the equivalent toxicity suppression efficiency of the composite smoke suppressant, evaluate the proportion of highly toxic substances in the total amount of smoke suppressed by the smoke suppressant, and assess the actual suppression effect of the composite smoke suppressant on the toxicity of asphalt smoke.

2. The method for optimizing the ratio of composite smoke suppressant and evaluating the VOCs inhibition effect of asphalt according to claim 1 is characterized in that: The types of raw materials of the composite smoke suppressant in step 1) include but are not limited to: nano magnesium hydroxide, nano montmorillonite, carbon nanotubes, zeolite, expanded graphite and organosilicon compounds. The synergistic effect of the composite formula of the smoke suppressant is considered. Based on the principles of nano adsorption, film-forming flame retardancy and oxygen isolation, three smoke suppressants, expanded graphite, nano magnesium hydroxide and zeolite, which have mutually enhanced smoke suppression effects, are selected to compensate for the defects of the smoke suppression function of a single material, and a single factor smoke suppression rate test based on the weight method is used to determine the optimal dosage range of each smoke suppressant.

3. The composite smoke suppressant ratio response surface optimization and equivalent toxicity inhibition efficiency evaluation method according to claim 2 is characterized in that: The test device used in the single-factor smoke suppression rate test is an asphalt smoke high-temperature enrichment device, including: an air drying device (1), an asphalt high-temperature oil bath heating device (2), an asphalt smoke enrichment device (3), an exhaust gas purification device (4), and an air pump (5), which are connected in sequence through a conduit. The air passes through the air drying device (1). The air drying device absorbs moisture and then flows into the asphalt high-temperature oil bath heating device (2). The asphalt high-temperature oil bath heating device (2) provides a temperature of not less than 180°C and a stirring rate of 300r / min, so that the asphalt is evenly heated to produce asphalt smoke; the asphalt smoke enrichment device (3) is composed of a polytetrafluoroethylene (PTFE) hydrophobic filter membrane and a filter membrane box. Polytetrafluoroethylene has excellent organic adsorption properties; the exhaust gas purification device (4) can absorb harmful gases in the exhaust gas and discharge them into the air. The air pump (5) provides a stable air flow rate in the device, so that the asphalt smoke is enriched on the PTFE filter membrane through the rubber conduit, and can be weighed and tested in the next step.

4. The method for response surface optimization of composite smoke suppressant ratio and evaluation of equivalent toxicity inhibition efficiency according to any one of claims 1 to 4, characterized in that: Step 2) is specifically as follows: using Design-Expert 13 software, selecting the surrounding range value of the result for a single factor, designing a multi-factor orthogonal rotation combination test, taking the dosage of smoke suppressant material as the independent variable q, and the smoke suppression rate as the dependent variable ε, establishing a Quadratic mathematical model of the dosage of each component of the smoke suppressant and the smoke suppression rate through an orthogonal test, and generating a response surface to obtain the optimal formula of the compound smoke suppression asphalt; The Quadratic mathematical model is in the form of: Among them: n and N are the types of smoke suppressant materials, q x is the dosage of each smoke suppressant component, A, B, C are the coefficients of different terms in the regression equation.

5. The method for response surface optimization of composite smoke suppressant ratio and evaluation of equivalent toxicity inhibition efficiency according to any one of claims 1 to 4, characterized in that: The collection process of the smoke-suppressing asphalt in step 3) is as follows: the smoke is enriched onto a hydrophobic PTFE filter membrane using an asphalt smoke high-temperature enrichment device, and the filter membrane is placed in a trichloroethylene solution to prepare an asphalt smoke headspace sample using an ultrasonic extraction method.

6. The method for response surface optimization of composite smoke suppressant ratio and evaluation of equivalent toxicity inhibition efficiency according to any one of claims 1 to 4, characterized in that: The specific detection in step 3) is as follows: a headspace gas chromatograph is used to perform a full SCAN scan on the asphalt flue gas sample, and a qualitative result is obtained by comparing it with the spectral library to determine the specific harmful component VOC i And prepare the VOC to be tested i Standard sample, establish the standard response curve y = a for this component i x+b i , SIM selective ion scanning was performed on specific components using gas chromatography-mass spectrometry to separate VOC i The response value y i Substitute the standard curve into the calculation to obtain the VOCi mass concentration x in the sample solution i ; Then combined with the sample mass m i The VOC i The mass ratio of the ingredients w i , VOC in asphalt flue gas i The mass ratio w i The calculation formula is as follows: VOC in asphalt flue gas i Quality Ratio Where: w i For this VOC i The proportion of the component in each kilogram of flue gas, mg / Kg; m is the flue gas release in this heating test, that is, the mass of asphalt flue gas adsorbed by the filter paper or the mass of asphalt flue gas dissolved in 10mL of trichloroethylene solution, mg; x i is the mass concentration of VOCi in the sample solution, mg / L.

7. The method for optimizing the ratio of composite smoke suppressants and evaluating the equivalent toxicity inhibition efficiency according to any one of claims 1 to 4, characterized in that asphalt The threat of smoke to human health mainly depends on the toxicity of equivalent asphalt smoke and the quality of asphalt smoke ingested by the human body. In order to consider the threat of the above two factors to human health at the same time and comprehensively evaluate the actual filtration efficiency of smoke suppressants on the toxicity of smoke produced by asphalt combustion, the equivalent toxicity inhibition efficiency (ETE) of smoke suppressants is defined to describe the proportion of the amount of smoke suppressants inhibiting the toxicity of asphalt smoke VOCs in the total amount of smoke inhibition. The calculation formula is as follows: Where, ETE is the equivalent toxicity inhibition efficiency; Δw i VOC before and after using smoke suppressant i Mass ratio change rate, mg / Kg; TE i For VOC i The numerator is the sum of the mass ratio change rate of each VOC above the detection limit multiplied by its equivalent toxicity factor, that is, the sum of the equivalent toxicity changes of all VOCs in asphalt smoke; Δm is the change in smoke production in the asphalt smoke high-temperature enrichment test before and after the use of smoke suppressant, mg.

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