A composite dust suppressant applicable to open-pit mine transportation roads and its preparation method

Abstract

A composite dust suppressant applicable to open-pit mine transportation roads and its preparation method, belonging to the technical field of preparation of composite dust suppressants for dust prevention and control. To overcome the deficiencies of existing dust suppressants such as single function, high price, toxicity, and secondary pollution, the present invention effectively combines four functional materials: a binder, a surfactant, a water retention agent, and a hygroscopic agent. The binder is xanthan gum, the surfactant is rhamnolipid, the water retention agent is glycerol, and the hygroscopic agent is magnesium chloride. The prepared composite dust suppressant has the advantages of low cost, good hygroscopic and water retention performance, high compressive strength and wind erosion resistance, and high dust reduction efficiency compared with traditional dust suppressants. It is a composite dust suppressant with continuous dust suppression effect, safety and high efficiency applicable to open-pit mine transportation roads, and is of great significance for dust prevention and control of open-pit mine transportation roads.

Description

Technical Field

[0001] The present invention relates to the technical field of dust suppressants, and particularly to a composite dust suppressant suitable for the transportation roads of open-pit mines. Background Art

[0002] As one of the ways of solid mining, open-pit mining is widely used due to its safety and high efficiency, but environmental problems such as dust pollution also follow. Therefore, the problem of dust control in open-pit mines has gradually become a research hotspot in the field of mine environmental protection. Currently, the commonly used dust reduction methods can be divided into physical dust suppression such as wet type and chemical dust suppression.

[0003] Wet dust suppression is widely used because of its simplicity and convenience, but its dust suppression duration is short, cost is high, and efficiency is low, making it difficult to achieve long-term dust suppression. Chemical dust suppression is to capture, adsorb, and agglomerate dust particles and lock them in a network structure to achieve dust reduction, which is one of the effective methods for treating dust problems. Although there are many types of dust suppressants, common problems include single function, high price, toxicity, secondary pollution, and limited application in open-air environments. It is mainly manifested that the wetting type dust suppressant has poor bonding performance and a very long curing time (usually 5 - 10 days); the coagulating type dust suppressant has a high cost and poor salt tolerance; the bonding type dust suppressant using residue oil, asphalt, etc. as raw materials has poor hygroscopicity and problems such as toxicity, difficult degradation, and pollution of water and soil. Although some effective dust suppressants have been developed, it is still necessary to develop an environmentally friendly, highly efficient, and low-cost composite dust suppressant to solve the problem of road dust in open-pit mine transportation.

[0004] Xanthan gum is considered a powerful organic gum in the world. It is inexpensive, widely sourced, and has good thickening, emulsifying, suspending properties and stability. However, the slow penetration speed and low penetration efficiency of xanthan gum limit its application as a binder on the transportation roads of open-pit mines. Summary of the Invention

[0005] The present invention provides a composite dust suppressant suitable for the transportation roads of open-pit mines and its preparation method. Its main components include a binder, a surfactant, a hygroscopic agent, and a water retention agent. The surfactant is combined with xanthan gum, and the binder and the surfactant are uniformly mixed by a mixing method, and then the hygroscopic water retention agent is added to prepare a composite dust suppressant suitable for the transportation roads of open-pit mines, which is convenient to operate, has a low economic cost, and has a good dust suppression effect.

[0006] The composite dust suppressant of the present invention includes a binder, a surfactant, a water retention agent, and a hygroscopic agent. According to the mass ratio with water, the dosages of the binder and the surfactant are each 0.1% - 0.2%, and the dosages of the water retention agent and the hygroscopic agent are each 2% - 4%. Among them, the binder is xanthan gum, and the surfactant is rhamnolipid.

[0007] Preferably, the water retaining agent is glycerol.

[0008] Preferably, the hygroscopic agent is magnesium chloride.

[0009] The preparation method of the composite dust suppressant suitable for open-pit mine transportation roads comprises the following steps:

[0010] S1: Add 2%-4% xanthan gum to deionized water at 50-70°C according to the mass ratio with deionized water, and stir until a uniform xanthan gum solution is obtained;

[0011] S2: Add 2%-4% rhamnolipid dropwise to the stirred xanthan gum solution according to the mass ratio of rhamnolipid to deionized water, and stir until a uniformly mixed xanthan gum / rhamnolipid solution is obtained;

[0012] S3: Add 5%-7% of glycerol and magnesium chloride to deionized water according to the mass ratio of deionized water.

[0013] Continue stirring until a well-mixed solution is obtained;

[0014] S4: The solutions prepared by S2 and S3 are fully mixed in a volume ratio of 1-2:1-2, and stirred until a uniform mixed solution is obtained, which is a composite dust suppressant solution. The mixed solution is placed in a freeze dryer and dried, and then ground to obtain a composite dust suppressant powder.

[0015] Furthermore, the stirring described in S3 is performed at room temperature.

[0016] Furthermore, the stirring in S4 is performed at 50-70°C.

[0017] Furthermore, the drying time described in S4 is 12 hours.

[0018] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0019] The present invention combines xanthan gum and rhamnolipid, which not only utilizes the thickening, emulsification, suspension characteristics and stability of the xanthan gum organic gum, but also utilizes rhamnolipid, a biological surfactant, to reduce the surface tension of water and improve the penetration rate of the xanthan gum. The present invention can be used under atypical temperature, pH and salinity conditions, is non-toxic and biodegradable.

[0020] The present invention prepares a composite dust suppressant by compounding a surfactant with a main binder and then adding a hygroscopic water-retaining agent. Due to the adhesiveness of the binder, the wettability of the surfactant, and the water retention and water absorption of the hygroscopic water-retaining agent, the dust suppressant has good anti-evaporation property, anti-wind erosion property, compressive resistance, and high dust suppression efficiency. In addition, the preparation process of the composite dust suppressant meets the on-site application conditions, is simple and convenient to operate, and has low cost, making it a composite dust suppressant suitable for the transportation roads of open-pit mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0022] Figure 1 It is a diagram of the moisture absorption experiment process

[0023] Figure 2 It is a diagram of the change of water content with time at different humidities

[0024] Figure 3 It is a diagram of the change of water content with time under different temperature conditions

[0025] Figure 4 It is a diagram of the compression experiment process

[0026] Figure 5 It is a compressive strength curve diagram of the specimen

[0027] Figure 6 It is the microscopic change on the surface of dust samples A (left) and B (right) at a magnification of 1000 times

[0028] Figure 7 It is a schematic diagram of dust reduction simulation DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the technical problems, technical solutions, and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0030] Preparation process of the composite dust suppressant:

[0031] (1) According to the mass ratio with deionized water, add 2%-4% of xanthan gum to deionized water at 50-70 °C, and stir until a uniform xanthan gum solution is obtained;

[0032] (2) According to the mass ratio with deionized water, gradually add 2%-4% of rhamnolipid to the above-mentioned stirred xanthan gum solution, and stir until a uniformly mixed xanthan gum / rhamnolipid solution is obtained;

[0033] (3) adding 5% to 7% of glycerol and magnesium chloride to deionized water in a mass ratio to deionized water, and stirring continuously at room temperature until a uniformly mixed solution is obtained;

[0034] (4) The solutions prepared in (2) and (3) are fully mixed in a volume ratio of 1-2:1-2, and stirred at 50-70° C. until a uniform mixed solution is obtained, which is the composite dust suppressant solution. The mixed solution is placed in a freeze dryer and dried for 12 h, and then ground to obtain a composite dust suppressant powder.

[0035] Example 1: Response Surface Methodology

[0036] In this embodiment, the different ratios of the components of the composite dust suppressant are optimized by the response surface method to obtain the optimal ratio with the highest adhesion and anti-evaporation properties of the composite dust suppressant and a moderate pH value. The design is carried out according to the central composite design principle of Box-Benhnken, with xanthan gum, rhamnolipid, glycerol and magnesium chloride as independent variables, and pH value, viscosity and anti-evaporation properties as response values, and a four-factor three-level experimental design is carried out. The independent variable factors and their levels of this experimental design are shown in Table 1.

[0037] Table 1 Experimental independent variable factors and their levels

[0038]

[0039]

[0040] According to the four factors and three levels determined by BBD, the response surface test required 27 independent experiments in total using Design-Expert 13 software. The response surface test design results are shown in Table 2 Table 2 Response surface analysis factor combinations and experimental results

[0041]

[0042] According to the calculation results in Table 2, quadratic polynomials were used for fitting, and the regression equations of viscosity, pH value and anti-evaporation were obtained as shown in equations (1)-(3):

[0043]

[0044] The results of the analysis of variance of the regression models for different response values are shown in Table 3. It can be seen from the table that the F values corresponding to the three response values are 132.21, 14.75, and 28.09 respectively, and the values of Prob>F are all < 0.0001, indicating that the model is significant. In addition, the values of Prob > F in the lack-of-fit terms are 0.1635, 0.7920, and 0.3818, all of which are evaluated as insignificant, indicating that the model is less affected by errors. In summary, the quadratic equation model has a significant regression, the lack-of-fit term is insignificant, and the fitting result is good. Therefore, the optimal ratio of each component of the composite chemical dust suppressant obtained by using this model is: 0.15% xanthan gum, 0.15% rhamnolipid, 3.2% glycerol, and 2.8% magnesium chloride. The predicted viscosity is 79.31 mPa·s, the pH value is 6.53, and the anti-evaporation property is 5.36%.

[0045] Table 3 Analysis of variance of the regression models for each response value

[0046]

[0047]

[0048] Prepare the dust suppressant solution according to the optimal ratio, test its viscosity, pH, and anti-evaporation property. Each group of experiments is carried out three times, and the obtained data is compared with the predicted values to analyze the rationality and effectiveness of the model optimization results. The results are shown in Table 4.

[0049] Table 4 Comparison of the results of the verification test

[0050]

[0051] The viscosity, pH value, and anti-evaporation property of the dust suppressant measured by experiments are close to the values predicted by the response surface model, indicating that this model is reasonable and effective and can correctly predict the three response values of viscosity, pH value, and anti-evaporation property. Therefore, the optimized ratio result is correct. Under the optimal ratio, the viscosity of the dust suppressant is 81.98 mPa·s, the pH value is 6.48, and the anti-evaporation property is 5.20%. In the subsequent examples, the dust suppressant under the optimal ratio obtained from this experiment is used, which is abbreviated as the optimal dust suppressant.

[0052] Example 2: Determination of moisture absorption rate

[0053] Prepare eight groups of 20.00 g of dry dust in petri dishes, spray 5 mL of the optimal dust suppressant and deionized water respectively, let it stand for 30 minutes, and then put it into a blast drying oven at 100 °C for 1 h and take it out. At room temperature (i.e., 25 °C), set the humidity of the GDJS-400A high and low temperature humidity test chamber to 30%, 50%, 70%, and 90% respectively. Put the dust samples containing the optimal dust suppressant solution and deionized water into the test chamber for experiments. Take out the petri dishes every hour to weigh and record the data, and conduct the experiment for a total of 5 hours. The test process is as followsFigure 1 as shown

[0054] The variation of the moisture content of the dust samples with the moisture absorption time at different humidities is as Figure 2 shown. It can be seen from the figure that after drying in a forced-air drying oven at 100 °C for 1 h, the moisture contents of the four groups of dust samples sprayed with deionized water are all lower than those of the dust samples sprayed with the dust suppressant, indicating that the addition of the dust suppressant can effectively inhibit the evaporation of water. At different humidities, as the moisture absorption time increases, the moisture content of the dust samples gradually increases, but as the humidity increases, the growth rate of the moisture content continuously increases. Therefore, the addition of the dust suppressant effectively increases the moisture absorption rate of the dust samples, and the greater the humidity, the more obvious its effect.

[0055] Example 3: Anti-evaporation experiment

[0056] Weigh 10.00 g of dry dust into 8 petri dishes with a diameter of 75 mm, add 4 groups of 5.00 g of deionized water and 4 groups of 5.00 g of the optimal dust suppressant solution respectively, let it stand for 30 minutes, and put it into a forced-air drying oven after the solution is completely mixed with the dust samples. Set the temperatures of the forced-air drying oven to 25 °C, 35 °C, 45 °C and 55 °C respectively, record a set of data every 30 minutes, and calculate the moisture content of the dust samples. The test time is 5 h.

[0057] The results of the anti-evaporation experiment are as Figure 3 shown. It can be seen from the figure that the dust samples sprayed with the optimal dust suppressant have better anti-evaporation effect than those sprayed with deionized water. At the same temperature, the longer the drying time, the smaller the moisture content of the dust samples, and the moisture content of the dust samples sprayed with water decreases more slowly than that of the dust samples sprayed with the dust suppressant solution. As the temperature increases, the rate of decrease of the moisture content of the dust samples gradually accelerates, and the final moisture content becomes smaller and smaller. However, at higher temperatures, the dust suppressant can still keep the dust at a certain humidity.

[0058] Example 4: Anti-erosion experiment

[0059] Weigh 20.00 g of dry dust with an electronic balance and place it on a glass plane. Spray 1 mL of the optimal dust suppressant solution and deionized water evenly on the surface of the dust, place it at room temperature and dry for 6 h, then put it into a forced-air drying oven at 60 °C and dry for 6 h, and record the initial weight; finally, place the dust samples in an environment with different wind speeds for erosion, record the weight every hour, calculate the loss rate at this moment, and conduct it for 5 h. The calculation formula is shown in Equation (4):

[0060]

[0061] where: E——loss rate, %;

[0062] W 前 ——mass of the dust sample before erosion, g;

[0063] W 后 —— mass of the dust sample after erosion, g

[0064] A hard shell with hardness was formed on the surfaces of the dusts sprayed with water and the dust suppressant. Under the long-term action of wind force, holes appeared in the hard shell formed on the surface of the dust sprayed with water. The appearance of the holes aggravated the damage of the wind force to the hard shell on the dust surface, causing the holes to continue to increase. The internal dust would be lifted by the wind force from the holes, forming a hollow shape. Finally, the hard shell at the top collapsed under the action of the wind force and lost its wind erosion resistance. However, the surface morphology of the dust sample sprayed with the dust suppressant remained basically unchanged, with basically no holes and still having wind erosion resistance. Therefore, it can be concluded from the experimental process diagram that the addition of the dust suppressant made the surface of the dust form a hard shell with certain wind erosion resistance, which can well protect the internal dust from being lifted again by the wind force.

[0065] The experimental data of wind erosion resistance are shown in Table 5. The overall loss rate of the dust samples sprayed with the dust suppressant is lower than that of the dust samples sprayed with deionized water. At a low wind speed of 3 m / s, the wind force is too small to damage the hard shell formed on the surface of the dust sample, and its loss rate mainly comes from the unconsolidated dust particles on the surface; at a wind speed of 6 m / s, the wind force increases, causing a small number of small holes to appear in the hard shell on the dust surface. At this time, the loss rate mainly comes from the dust particles falling from the hole parts; at a wind speed of 10 m / s, the loss rates of the two groups of dust samples increase significantly, and the loss rate mainly comes from the loss of dust particles inside the holes. Therefore, the addition of the dust suppressant greatly improves the wind erosion resistance of the dust, especially at high wind speeds, and its improvement effect is more obvious, which is consistent with the analysis results of the previous experimental process.

[0066] Table 5 Statistical table of the loss rate of dust samples eroded at different wind speeds for 5 h

[0067]

[0068]

[0069] Example 5: Corrosion experiment

[0070] According to the "Full immersion test method for uniform corrosion of metallic materials in laboratory" (GB10124 - 88), the corrosion of the dust suppressant solution to metals was tested. Three metal coupons of 2024 aluminum alloy, Q235B carbon steel and 316 stainless steel with dimensions of 50 mm (length) × 25 mm (width) × 2 mm (height) were prepared, immersed in alcohol for cleaning, taken out and dried and weighed after cleaning; they were respectively immersed in 20 mL of deionized water and the optimal dust suppressant solution, taken out after soaking for 72 h, cleaned with alcohol, dried and weighed, and the corrosion rate was calculated according to the formula. The calculation formula is shown in Equation (5):

[0071]

[0072] Where: X——corrosion rate, mm / a;

[0073] M 前 ——mass of metal sheet before corrosion, g;

[0074] M 后 ——mass of metal sheet after corrosion, g;

[0075] A——surface area of metal sheet, cm 2 ;

[0076] T——test time, h;

[0077] D——density of metal sheet, g / cm 3 .

[0078] From the perspective of surface morphology, the corrosion degree of carbon steel in deionized water is the highest. There is basically no change on the surfaces of aluminum alloy and stainless steel. There are varying degrees of corrosion marks on the surfaces of aluminum alloy and carbon steel in the dust suppressant, but there is basically no change on the surface of stainless steel.

[0079] The corrosion rates of different metal sheets are calculated as shown in Table 6. Deionized water causes the least damage to stainless steel, with a corrosion rate of only 0.0012 mm / a, while the damage to carbon steel is the most serious, reaching 0.0397 mm / a; similar to deionized water, the dust suppressant has the least impact on stainless steel, with a corrosion rate of only 0.0024 mm / a, and the damage to carbon steel is the most serious, being 0.0496 mm / a. Therefore, it is recommended to use stainless steel as much as possible for metals in contact with the dust suppressant solution in actual production to reduce corrosion. The corrosion rates of both solutions for aluminum alloy are 0.0036 mm / a, and the corrosion rates of the dust suppressant solution for stainless steel and carbon steel are both greater than that of deionized water, indicating that the dust suppressant solution has a certain degree of corrosiveness. However, the corrosion rates of the two solutions are similar, and the corrosion rate of the dust suppressant meets the requirements of "Technical Conditions for Dust Suppression Technology in Railway Coal Transportation - Part 1: Dust Suppressant". Therefore, this dust suppressant can be applied in actual production.

[0080] Table 6 Corrosion Rates of Different Metal Sheets

[0081]

[0082] Example 6: Compression Experiment

[0083] Weigh 50.00 g of dry dust with an electronic balance and pour it into a mold with a diameter of 30 mm. Pour in 20 mL of deionized water and the optimal dust suppressant solution and mix evenly. Place it in a 100 °C blast drying oven and dry it for 12 h until it reaches a constant weight. After the sample cools to room temperature, demold and polish it to prepare a solidified dust column specimen. Use an Edberg HP series digital push-pull force gauge to conduct a compression test. Rotate the screw until the specimen is crushed. The test process is as followsFigure 4 as shown

[0084] The compressive curves of the deionized water and dust suppressant specimens are as Figure 5 shown. During the entire compression process, a small fracture and a large fracture occurred in the deionized water specimen as a whole. The small fracture was mainly caused by the voids existing in the specimen. The occurrence of the large fracture indicated that cracks began to appear on the surface of the specimen, and its compressive strength reached the peak. The dust suppressant specimen had two small fractures and two large fractures. The occurrence of the first large fracture indicated that the surface of the specimen began to fracture, and the occurrence of the second large fracture indicated that large fractures occurred again in the places where the surface of the specimen was not damaged. At this time, the surface could no longer bear greater force, and the compressive strength reached the peak. The hard shell formed on the surface of the deionized water specimen could only withstand one large fracture, while the surface of the dust suppressant specimen still had good compressive capacity after experiencing one large fracture until the second large fracture occurred, and its compressive capacity decreased. At this time, the forces causing complete damage to the surfaces of the two specimens were 0.27 kN and 0.50 kN respectively. As described above, the addition of the dust suppressant effectively improved the compressive strength of the dust, could well resist external forces, and played a good consolidation role.

[0085] Example 7: Scanning electron microscope experiment

[0086] Spray 5 mL of deionized water and the optimal dust suppressant evenly on the surface of 10 g of dust, and label them A and B respectively. Then put the two groups of dust samples into a freeze-drying oven and dry them for 12 hours, and then take out the dust samples. Stick the conductive glue tightly on the metal sample to ensure that the edge does not exceed the sample stage. Spread the dust sample evenly on the conductive glue, and blow off the floating powder on the surface of the experimental sample. Put it into a Quorum SC7620 sputtering coater for gold spraying to improve the conductivity and secondary electron yield of the sample. Set the vacuum degree to 0.2 mbar, the current size to 10 mA, and the gold spraying time to 90 s. Use a Czech TESCAN MIRA LMS scanning electron microscope for shooting. First, select a landmark point in the sample through the knob dial, adjust it to the center position of the image, and after magnifying it to a certain multiple, adjust the knobs such as astigmatism, brightness, and contrast to obtain a clear image.

[0087] Observe and compare the microscopic surface morphologies of the two groups of dust samples at 1000 times and greater magnification, as Figure 6As shown, it can be found that the surface of the dust samples in Group A is generally relatively uniform. This is because after the dust samples in Group A are sprayed with water, some small-sized dust particles are wetted and coagulated on the larger-sized dust particles. These dust particles are extremely easy to break away from the dust body under the action of external forces and disperse in the air, causing dust flying. While the surface of the dust particles in Group B is distributed with many dust particles of different sizes, indicating that under the action of the dust suppressant, even the relatively larger-sized dust particles can adhere tightly to the large-sized particles. However, since the moisture has not been completely dried, there is still a part of the combined large particles remaining in the dust samples of Group A. After the dust samples in Group B are dried and ground, some of the small particles adhering to the surface of the large particles will fall off, so there are still some fine particles in the microscopic surface image of the dust samples in Group B. Generally speaking, this dust suppressant has a good dust fixation and suppression effect.

[0088] Example 8: Dust reduction simulation experiment

[0089] To test the dust reduction efficiency of the optimal dust suppressant, a simulated roadway of 0.5×0.5×3 m was built using an aluminum profile bracket and a transparent plastic film. An axial flow fan was placed at the front of the roadway to simulate the dust raising state; a funnel was installed at the top, and dust was added through the funnel to ensure that the dust could be evenly scattered into the roadway; two spray devices were added at 2 m in the roadway, and water or the optimal dust suppressant was added through spraying to ensure that the spray range covered the entire square cross-section, creating a spray dust reduction atmosphere and avoiding the formation of a single beam of solution, which may cause uneven contact between the solution and the dust and affect the dust reduction efficiency; an IFC-2 type dust sampler was used to measure the dust concentration in the roadway at the end of the roadway. The air volume was set at 20 L / min, and the sampling time was 5 min. The experimental schematic diagram is as Figure 7 shown.

[0090] This experiment was divided into two groups of experiments for total dust and respirable dust. For each group of experiments, the dust concentrations in three cases of without water, with water, and with the dust suppressant were tested, and the dust reduction efficiencies of water and the dust suppressant were calculated. Three parallel tests were carried out and the average value was taken. The calculation formulas for dust concentration and dust reduction efficiency are shown in Equations (6) and (7):

[0091]

[0092] In the formula: C——Measured dust concentration, g / m 3 ;

[0093] W1——Mass of the filter membrane before sampling, g;

[0094] W2——Mass of the filter membrane after sampling, g;

[0095] q——Sampling flow rate, L / min;

[0096] t——Sampling time, min;

[0097]

[0098] Where: η——dust removal efficiency, %;

[0099] C1——dust concentration in the roadway before spraying, g / m 3 ;

[0100] C2——dust concentration in the roadway after spraying, g / m 3 .

[0101] The dust removal efficiencies of water and dust suppressant for total dust and respirable dust are shown in Tables 7 and 8. It can be seen from the tables that the average dust removal efficiency of water for total dust is 66.84%, and the dust removal efficiency of the dust suppressant for total dust has been increased to 91.38%; the dust removal efficiency of water for respirable dust is 54.64%, and the dust removal efficiency of the dust suppressant for respirable dust has been increased to 81.22%. Therefore, the dust suppressant has a better dust removal efficiency compared with water, can effectively reduce the concentrations of total dust and respirable dust, and is of great significance for actual production applications.

[0102] Table 7 Dust removal efficiencies of two solutions for total dust

[0103]

[0104] Table 8 Dust removal efficiencies of two solutions for respirable dust

[0105]

[0106]

[0107] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claimed rights.

Claims

1. A preparation method of a composite dust suppressant applicable to the transportation roads of open-pit mines, characterized in that, The invention comprises xanthan gum, rhamnolipid, glycerol and magnesium chloride. According to the mass ratio with deionized water, the amount of xanthan gum and rhamnolipid is 0.1%-0.2% respectively, and the amount of glycerol and magnesium chloride is 2%-4% respectively. The specific preparation steps are as follows: S1: Add xanthan gum to deionized water at 50-70°C according to the mass ratio of xanthan gum to deionized water, and stir until a uniform xanthan gum solution is obtained; S2: adding rhamnolipid dropwise to the stirred xanthan gum solution according to the mass ratio of rhamnolipid to deionized water, and stirring until a uniformly mixed xanthan gum / rhamnolipid solution is obtained; S3: adding glycerol and magnesium chloride to deionized water in a mass ratio to deionized water, and continuously stirring until a uniformly mixed solution is obtained; S4: The solutions prepared by S2 and S3 are fully mixed in a volume ratio of 1-2:1-2, and stirred until a uniform mixed solution is obtained, which is a composite dust suppressant solution. The mixed solution is placed in a freeze dryer and dried, and then ground to obtain a composite dust suppressant powder.

2. The preparation method according to claim 1, characterized in that, The stirring described in S3 is performed at room temperature.

3. The preparation method according to claim 1, characterized in that, The stirring in S4 is performed at 50-70°C.

4. The preparation method according to claim 1, characterized in that, The drying time described in S4 is 12 h.

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