A method for preventing the separation and maintaining the stability of fly ash slurry

Abstract

The present application belongs to the field of fly ash slurry stable transportation, and particularly relates to a method for preventing fly ash slurry stratification and keeping stable. The method is: extracting large leafed wood ear saponin; preparing sodium silicate from fly ash; selecting the best component ratio of saponin and sodium silicate, and adding fly ash slurry. The present application has the advantages of being more green and sustainable for fly ash slurry transportation, avoiding stratification solidification in fly ash secondary treatment, and adopting natural surfactant compared with commercial specific surface activator hexadecyl trimethyl ammonium bromide. The viscosity, surface tension and concentration of fly ash slurry are tested and compared, which not only reduces the surface tension of fly ash slurry to reduce stratification and aggregation, but also adds sodium silicate to the fly ash slurry system to generate sodium aluminosilicate, which significantly improves the stability of fly ash slurry.

Description

Technical Field

[0001] This invention belongs to the field of stable transportation of fly ash slurry, and specifically relates to a method for preventing fly ash slurry from separating and maintaining its stability. Background Technology

[0002] The amount of coal ash produced by coal combustion is increasing year by year, resulting in a large amount of fly ash. Currently, with the development of carbon sequestration technology, fly ash has become an ideal carbon sequestration material. Wet mineralization carbon sequestration is currently considered an ideal carbon sequestration technology.

[0003] Fly ash is made into a slurry and transported through pipelines to the goaf of a coal mine to absorb carbon dioxide. In the aforementioned wet fly ash transportation process, slurry stratification is a common problem, preventing the effective components from being delivered to the appropriate locations. Fine fly ash particles in the slurry phase agglomerate. Therefore, the primary goal is to maintain the fly ash particles in a dispersed state, ensuring that the fly ash is uniformly distributed in the slurry, preventing slurry deposition that could cause pipeline blockage and safety issues such as pipe bursts. Therefore, a stable and uniform distribution of the fly ash slurry is extremely important.

[0004] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a method for preventing the stratification of fly ash slurry and maintaining its stability, the method comprising the following steps:

[0006] (1) Collect fresh leaves of large-leaf wood ear fungus, dry them, grind and pulverize them to obtain leaf powder;

[0007] (2) The leaf powder is mixed with water and extracted to obtain an extract;

[0008] (3) The extract was distilled under reduced pressure to obtain a solid saponin plant extract;

[0009] (4) Mix fly ash, solid sodium hydroxide and water, and introduce carbon dioxide under stirring conditions to obtain a sodium silicate mixture; then filter and dry in sequence to obtain a high-purity sodium silicate solution.

[0010] (5) The solid saponin plant extract and the high-purity sodium silicate solution are mixed and diluted with water to obtain a surfactant mixture; then the surfactant mixture is added to the fly ash slurry.

[0011] Preferably, in step (2), the mass ratio of the leaf powder to water is 1:10 to 12.

[0012] Preferably, in step (2), the extraction temperature is 70-80°C and the extraction time is 3-5 hours (the higher the temperature, the shorter the extraction time; too long a time will lead to the decomposition of the active ingredients; the smaller the powder particles and the more agitation is performed during extraction, the higher the dissolution efficiency and the shorter the extraction time).

[0013] Preferably, in step (2), the extraction is performed 3 to 5 times.

[0014] Preferably, in step (3), the temperature of the vacuum distillation is 40-45°C and the pressure of the vacuum distillation is 0.15-0.20 MPa.

[0015] Preferably, in step (4), the mass ratio of fly ash, solid sodium hydroxide and water is 40:1:200.

[0016] Preferably, in step (4), the stirring speed is 100-800 r / min.

[0017] Preferably, in step (4), the pressure of introducing carbon dioxide is 3 to 10 bar.

[0018] Preferably, in step (4), the drying temperature is 180-200°C and the drying time is 2-2.5 hours.

[0019] Preferably, in step (5), the concentration of solid saponin plant extract in the surfactant mixture is 0.010-0.020 g / mL, and the concentration of sodium silicate is 0.003-0.004 g / mL; the mass ratio of the surfactant mixture to fly ash slurry is 1:10.

[0020] It should be noted that the surface activity of solid saponin plant extract (water extract of Auricularia auricula-judae) was detected using a surface tension meter. Subsequent observations showed that its saturation point range was 0.010 g / mL to 0.020 g / mL (CMC), which is considered the optimal concentration of saponins in the surfactant.

[0021] The beneficial effects of this invention are as follows:

[0022] The advantages of this invention are that it enables greener and more sustainable transportation of fly ash slurry, avoids stratification and solidification during secondary treatment of fly ash, and compared with commercial surface area enhancers such as cetyltrimethylammonium bromide, it uses natural surfactants. Through comparative tests on the viscosity, surface tension, and concentration of fly ash slurry, it not only reduces the surface tension of fly ash slurry, thereby reducing stratification and sedimentation, but also, by adding sodium silicate to the fly ash slurry system, the generated sodium aluminosilicate has a significant effect on improving the stability of fly ash slurry. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a SEM image (scale bar 5μm) of a standard fly ash slurry with added surfactant.

[0025] Figure 2 This is a SEM image (scale bar 5μm) of standard fly ash slurry without the addition of surfactant. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] Example 1

[0028] This embodiment provides a method for preventing the stratification of fly ash slurry and maintaining its stability, the method comprising the following steps:

[0029] (1) Collect 10g of fresh leaves of large-leaf wood ear fungus, dry them, and then grind them into powder using a mortar and pestle to obtain leaf powder;

[0030] (2) Place the leaf powder in a Soxhlet extractor and add 10 times the mass of water to the leaf powder. Extract at 70°C for 4 hours. Filter using a Buchner funnel. Extract the filter residue again with 100 mL of water and filter. Repeat the operation 3 times to obtain the extract (combined).

[0031] (3) The extract is first filtered, and then distilled under reduced pressure until the water evaporates to dryness to obtain a solid saponin plant extract.

[0032] (4) Take 200g of water, 1g of solid sodium hydroxide and 40g of fly ash, pour them into the reactor, stir at 800r / min for 5min, introduce carbon dioxide into the reactor at room temperature, maintain the pressure at 3bar, wait for the pressure to rise to 10bar, stir at 100r / min for 45min to obtain sodium silicate mixture, filter with a filter, dry the sodium silicate solution at 200℃ for 2 hours to obtain high purity sodium silicate solution;

[0033] (5) The solid saponin plant extract and the high-purity sodium silicate solution are mixed and diluted with water, and stirred at 300 r / min for 3 min to obtain a surfactant mixture; wherein, the concentration of the solid saponin plant extract in the surfactant mixture is 0.010 g / mL and the concentration of sodium silicate is 0.004 g / mL; then the surfactant mixture is added to the fly ash slurry to prevent the fly ash slurry from separating and to maintain stability; wherein, the mass ratio of the surfactant mixture to the fly ash slurry is 1:10.

[0034] Example 2

[0035] This embodiment provides a method for preventing the stratification of fly ash slurry and maintaining its stability, the method comprising the following steps:

[0036] (1) Collect 10g of fresh leaves of large-leaf wood ear fungus, dry them, and then grind them into powder using a mortar and pestle to obtain leaf powder;

[0037] (2) Place the leaf powder in a Soxhlet extractor and add 12 times the mass of water to the leaf powder. Extract at 80°C for 3 hours. Filter using a Buchner funnel. Extract the residue again with 100 mL of water and filter. Repeat the operation 5 times to obtain the extract (combined).

[0038] (3) The extract is first filtered, and then distilled under reduced pressure until the water evaporates to dryness to obtain a solid saponin plant extract.

[0039] (4) Take 200g of water, 1g of solid sodium hydroxide and 40g of fly ash, pour them into the reactor, stir at a rate of 800r / min for 5min, introduce carbon dioxide into the reactor at room temperature, maintain the pressure at 3bar, and when the pressure rises to 10bar, stir at a rate of 100r / min for 45min to obtain a sodium silicate mixture, filter it with a filter, and dry the sodium silicate solution at 180℃ for 2.5 hours to obtain a high-purity sodium silicate solution;

[0040] (5) The solid saponin plant extract and the high-purity sodium silicate solution are mixed and diluted with water, and stirred at 300 r / min for 5 min to obtain a surfactant mixture; wherein, the concentration of the solid saponin plant extract in the surfactant mixture is 0.020 g / mL and the concentration of sodium silicate is 0.004 g / mL; then the surfactant mixture is added to the fly ash slurry to prevent the fly ash slurry from separating and to maintain stability; wherein, the mass ratio of the surfactant mixture to the fly ash slurry is 1:10.

[0041] Improved example

[0042] Based on Example 1, improvements were made to the extracted solid saponin plant extract (aqueous extract of saponins from Auricularia auricula-judae). Further purification and removal of impurities were performed as follows: After water extraction, the solvent was recovered, the residue was dissolved in water, and insoluble matter was filtered out. Two-phase extraction was performed in the aqueous solution using diethyl ether (a strongly lipophilic organic solvent). Saponins are insoluble in these strongly lipophilic solvents and remain in the aqueous phase, while impurities such as oils and fat-soluble pigments dissolve in the lipophilic solvent and are separated from the saponins. After removing these impurities, two-phase extraction was continued in the aqueous solution using n-butanol, a strongly hydrophilic solvent. Saponins dissolve in n-butanol, while some strongly hydrophilic impurities such as sugars, proteins, and tannins remain in the water and are separated from the saponins. The n-butanol solution was collected, evaporated to dryness under reduced pressure, and pure solid saponins were obtained.

[0043] Test case

[0044] In fly ash slurry, the greater the attraction between fly ash particles, the lower the stability and solid concentration in the slurry. The inventors tested the effect of the concentration of Auricularia auricula-judae saponin aqueous extract on the surface tension of fly ash slurry, and the results are shown in Table 1.

[0045] Table 1

[0046] 946 0.0025 896 0.0030 746 0.0051 685 0.0064 605 0.0071 545 0.0078 468 0.0085 435 0.0100 397 0.0150 385 0.0200

[0047] When the concentration of the aqueous extract of saponins from Auricularia auricula-judae is 0.0100–0.0200 g / mL, the surface tension is 435–385 mPa·s, which can well meet the actual application requirements.

[0048] When the concentration of *Auricularia auricula-judae* saponins was fixed (0.010 g / mL), the concentration of sodium silicate significantly affected the apparent viscosity of the fly ash slurry, as shown in Table 2. The results showed that the best effect was achieved when the sodium silicate concentration was 0.004 g / mL. Sodium silicate (Na2SiO3) is an ionic compound with detergent activity. Due to a specific interaction between the silanol hydrogens in its complex molecules, the hydrophobic portion of *Auricularia auricula-judae* saponins adheres to the surface of fly ash, while the hydrophilic sugar chains are hydrated. This interaction forms a spatial barrier around each particle and inhibits particle-to-particle bonding. Therefore, it can be used as a suitable dispersant for the stable transport of fly ash slurry. It has stabilizing and transporting effects, allowing the slurry to settle in the ash pit after being transported there, thereby minimizing environmental pollution. The main objective of this invention is to use the maximum amount of natural extract and the minimum amount of sodium silicate to form a stable slurry within an acceptable viscosity range. Secondly, adding sodium silicate to the fly ash slurry helps the fly ash settle and stabilize. The secondary reaction product is sodium aluminosilicate (NAS). NAS compounds are typically formed in alkali-activated materials, and in the presence of sodium-based activators, they are combined with fly ash. The formation of NAS gel helps fly ash particles stabilize and settle after treatment and dehydration, thereby preventing air pollution caused by fly ash particles.

[0049] Table 2

[0050] 397 0.001 345 0.002 275 0.003 239 0.004

[0051] Further, two standard fly ash slurries were taken. The surfactant mixture obtained in Example 1 was added to the first standard fly ash slurry, while the second was not added. The microstructure of the two slurries was then analyzed, observing the interparticle spacing and particle morphology. The fly ash samples underwent XRD analysis (as shown in Table 3), and the results were obtained from SEM micrographs (e.g., ...). Figure 1 , Figure 2 (As shown) The particle spacing of fly ash in the first sample is significantly reduced compared to the second sample. Therefore, Auricularia auricula-judae saponins and sodium silicate can be suitable alternatives to the commercial dispersant CTAB.

[0052] Table 3

[0053]

[0054]

[0055] As shown in Table 3, this part explains that the high silicon and aluminum content in fly ash can serve as a precursor for sodium silicate and the subsequent product sodium aluminosilicate.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preventing stratification and maintaining stability of fly ash slurry, characterized in that, The method includes the following steps: (1) Collect fresh leaves of large-leaf wood ear fungus, dry them, grind and pulverize them to obtain leaf powder; (2) The leaf powder is mixed with water and extracted to obtain an extract; (3) The extract was distilled under reduced pressure to obtain a solid saponin plant extract; (4) Mix fly ash, solid sodium hydroxide and water, and introduce carbon dioxide under stirring conditions to obtain a sodium silicate mixture; then filter and dry in sequence to obtain a high-purity sodium silicate solution; (5) The solid saponin plant extract and the high-purity sodium silicate solution are mixed and diluted with water to obtain a surfactant mixture; then the surfactant mixture is added to the fly ash slurry; wherein: in the surfactant mixture, the concentration of the solid saponin plant extract is 0.010~0.020g / mL, the concentration of sodium silicate is 0.003~0.004g / mL; the mass ratio of the surfactant mixture to the fly ash slurry is 1:

10.

2. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (2), the mass ratio of the leaf powder to water is 1:10~12.

3. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (2), the extraction temperature is 70~80℃ and the extraction time is 3~5h.

4. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (2), the extraction is performed 3 to 5 times.

5. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (4), the mass ratio of fly ash, solid sodium hydroxide and water is 40:1:

200.

6. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (4), the stirring speed is 100~800 r / min.

7. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (4), the pressure of the introduced carbon dioxide is 3~10 bar.

8. The method for preventing stratification and maintaining stability of fly ash slurry according to claim 1, characterized in that, In step (4), the drying temperature is 180~200℃ and the drying time is 2~2.5h.

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