Method for preventing coal ash slurry from layering and keeping stability

Abstract

The invention belongs to the field of stable transportation of coal ash slurry, and particularly relates to a method for preventing coal ash slurry from layering and keeping the coal ash slurry stable. The method comprises the following steps: extracting Auricularia macrophylla saponin; preparing sodium silicate from the fly ash; and selecting saponin and sodium silicate with the optimal component ratio, and adding the fly ash slurry. The method has the advantages that the coal ash slurry can be transported more greenly and continuously, layering and curing conditions in secondary treatment of the coal ash are avoided, and compared with a commercial specific surface activating agent cetyltrimethylammonium bromide, the natural surfactant is adopted, and the viscosity, surface tension and concentration test comparison of the coal ash slurry can be greatly improved. The surface tension of the fly ash slurry is reduced, layering coagulation is reduced, sodium silicate is added into a fly ash slurry system, and generated sodium aluminosilicate has a remarkable improvement effect on the stability of the fly ash slurry.

Description

Technical Field

[0001] The invention belongs to the field of stable transportation of fly ash slurry, and in particular relates to a method for preventing fly ash slurry from stratifying and maintaining stability. Background Art

[0002] The amount of coal ash produced by coal combustion increases year by year, and a large amount of fly ash will be produced. At present, with the development of carbon fixation technology, fly ash has become an ideal carbon fixation material. At present, wet mineralization carbon fixation is an ideal carbon fixation technology.

[0003] The fly ash is made into slurry and transported to the coal mine goaf through pipelines to absorb carbon dioxide. In the above wet fly ash transportation process, slurry stratification is a common transportation problem, and the effective ingredients cannot be transported to the corresponding location. The fine fly ash particles in the slurry phase flocculate. Therefore, the primary goal is to keep the fly ash particles in a dispersed state so that the fly ash is evenly present in the slurry, avoiding slurry deposition causing pipeline blockage and avoiding safety problems such as pipe bursts. Therefore, it is extremely important to have a stable and uniform distribution of fly ash slurry.

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

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for preventing fly ash slurry from stratifying and maintaining stability, the method comprising the following steps:

[0006] (1) collecting fresh leaves of Auricularia auricularia auricula, drying them, grinding them and obtaining leaf powder;

[0007] (2) mixing the leaf powder with water for extraction to obtain an extract;

[0008] (3) distilling the extract under reduced pressure to obtain a solid saponin plant extract;

[0009] (4) mixing fly ash, solid sodium hydroxide and water, and introducing carbon dioxide under stirring conditions to obtain a sodium silicate mixture; then filtering and drying in sequence to obtain a high-purity sodium silicate solution;

[0010] (5) Mix and dilute the solid saponin plant extract and the high-purity sodium silicate solution with water to obtain a surfactant mixture; and then add the surfactant mixture to the fly ash slurry.

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

[0012] Preferably, in step (2), the leaching temperature is 70-80° C., and the leaching time is 3-5 h (the higher the temperature, the shorter the leaching time; too long a time will lead to decomposition of the active ingredients; smaller powder particles and disturbance during leaching can improve dissolution efficiency and reduce leaching time).

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

[0014] Preferably, in step (3), the temperature of the reduced pressure distillation is 40-45° C., and the pressure of the reduced pressure 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 to 800 r / min.

[0017] Preferably, in step (4), the pressure of the introduced 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 h.

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

[0020] It should be noted that the surface activity of solid saponin plant extracts (Auricularia auricula water extract) was tested using a surface tensiometer. Subsequent observations showed that the saturation point range was 0.010 g / mL to 0.020 g / mL (CMC), which is the optimal concentration of saponins in surfactants.

[0021] The beneficial effects of the present invention are:

[0022] The advantages of the present invention are that it can transport fly ash slurry in a greener and more sustainable manner, avoid stratification and solidification in secondary treatment of fly ash, and compared with the commercial surface active agent hexadecyltrimethylammonium bromide, the present invention adopts a natural surfactant, and compares the viscosity, surface tension and concentration of the fly ash slurry through tests, which not only reduces the surface tension of the fly ash slurry, thereby reducing stratification and coagulation, but also adds sodium silicate to the fly ash slurry system to generate sodium aluminosilicate, which has a significant effect on improving the stability of the fly ash slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0025] Figure 2 This is the SEM image of the standard fly ash slurry without adding surfactant mixture (scale 5μm). DETAILED DESCRIPTION

[0026] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0027] Example 1

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

[0029] (1) Collect 10 g of fresh leaves of Auricularia auricularia auricula, dry them, and grind them into powder using a mortar to obtain leaf powder;

[0030] (2) placing the leaf powder in a Soxhlet extractor, adding water 10 times the mass of the leaf powder, extracting at 70° C. for 4 h, filtering with a Buchner funnel, extracting the residue again with 100 mL of water, filtering with suction, repeating the operation 3 times, and obtaining an extract (after merging);

[0031] (3) filtering the extract first, and then performing reduced pressure distillation until the water is evaporated to dryness, thereby obtaining a solid saponin plant extract;

[0032] (4) 200 g of water, 1 g of solid sodium hydroxide, and 40 g of fly ash were poured into a reactor and stirred at a rate of 800 r / min for 5 min. At room temperature, carbon dioxide was introduced into the reactor to maintain the pressure at 3 bar. When the pressure rose to 10 bar, the mixture was stirred at a rate of 100 r / min for 45 min to obtain a sodium silicate mixture. The mixture was filtered with a filter and the sodium silicate solution was dried at 200° C. for 2 hours to obtain a 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 minutes to obtain a surfactant mixture; wherein, in the surfactant mixture, the concentration of the solid saponin plant extract is 0.010 g / mL, and the concentration of sodium silicate is 0.004 g / mL; and the surfactant mixture is added to the fly ash slurry to prevent the fly ash slurry from stratifying and maintaining 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 fly ash slurry from stratifying and maintaining stability, the method comprising the following steps:

[0036] (1) Collect 10 g of fresh leaves of Auricularia auricularia auricula, dry them, and grind them into powder using a mortar to obtain leaf powder;

[0037] (2) placing the leaf powder in a Soxhlet extractor, adding water 12 times the mass of the leaf powder, extracting at 80° C. for 3 h, filtering with a Buchner funnel, extracting the residue again with 100 mL of water, filtering with suction, repeating the operation 5 times, and obtaining an extract (after merging);

[0038] (3) filtering the extract first, and then performing reduced pressure distillation until the water is evaporated to dryness, thereby obtaining a solid saponin plant extract;

[0039] (4) 200 g of water, 1 g of solid sodium hydroxide, and 40 g of fly ash were poured into a reactor and stirred at a rate of 800 r / min for 5 min. At room temperature, carbon dioxide was introduced into the reactor to maintain the pressure at 3 bar. When the pressure rose to 10 bar, the mixture was stirred at a rate of 100 r / min for 45 min to obtain a sodium silicate mixture. The mixture was filtered with a filter and the sodium silicate solution was dried at 180° C. 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 minutes 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 the sodium silicate is 0.004 g / mL; and the surfactant mixture is added to the fly ash slurry to prevent the fly ash slurry from stratifying and maintaining stability; wherein the mass ratio of the surfactant mixture to the fly ash slurry is 1:10.

[0041] Improvement example

[0042] Based on Example 1, an improvement is made. The solid saponin plant extract (Auricularia auricula saponin water extract) after extraction needs to be further impurity-removed and purified. The operation steps are as follows: after extraction with water, the solvent is recovered, the residue is dissolved in water, the insoluble matter is filtered out, and ether (a strongly lipophilic organic solvent) is added to the aqueous solution for two-phase extraction. Saponins are insoluble in these strongly lipophilic solvents and remain in the aqueous phase, while impurities such as oils, fat-soluble pigments, etc. are transferred to the lipophilic solvent and separated from the saponins. After removing these impurities, the highly hydrophilic n-butanol is used as the solvent to continue the two-phase extraction in the aqueous solution. The saponins are transferred to the n-butanol, and some highly hydrophilic impurities such as sugars, proteins, and substances remain in the water and are separated from the saponins. The n-butanol solution is collected and evaporated to dryness under reduced pressure to obtain pure saponin solids.

[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 saponin water extract on the surface tension of fly ash slurry, and the results are shown in Table 1.

[0045] Table 1

[0046] Surface tension (mpa.s) Saponin concentration (g / mL) 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 Auricularia auricula saponin water extract is 0.0100-0.0200 g / mL, the surface tension is 435-385 mpa.s, which can better meet actual usage requirements.

[0048] When the concentration of Auricularia auricula saponin is fixed (0.010g / mL), the concentration of sodium silicate has a significant effect on the apparent viscosity of the fly ash slurry, as shown in Table 2. The results show that the best effect is achieved when the concentration of sodium silicate is 0.004g / mL. Sodium silicate (Na2SiO3) is an ionic compound with washing activity. Due to a certain specific interaction between the silanol hydrogen of its composite molecules, the hydrophobic part of Auricularia auricula saponin is attached to the surface of the fly ash, and the hydrophilic sugar chain is hydrated. This interaction forms a spatial barrier around each particle and inhibits the combination between particles. Therefore, it can be used as a suitable dispersant for the stable transportation of fly ash slurry. It has a stabilizing and transporting effect, so that the slurry can be precipitated in the ash pond after being transported to the ash pond, thereby minimizing environmental pollution. The main goal of the present invention is to use the maximum amount of natural extracts and the minimum amount of sodium silicate to form a stable slurry within an acceptable viscosity range. Secondly, adding sodium silicate to fly ash slurry helps the settlement and stabilization of fly ash. The secondary reaction product is sodium aluminosilicate (NAS). The formation of NAS-type compounds usually exists in alkali-activated materials and is combined with fly ash in the presence of sodium-based activators. The formation of NAS gel helps the fly ash particles to stabilize and settle after treatment and dehydration, thereby preventing air pollution caused by fly ash particles.

[0049] Table 2

[0050] Apparent viscosity (mpa.s) Sodium silicate concentration (g / mL) 397 0.001 345 0.002 275 0.003 239 0.004

[0051] Furthermore, two portions of standard fly ash slurry were taken, and the surfactant mixture obtained in Example 1 was added to the first portion of the standard fly ash slurry, while the second portion was not added. Thereafter, the microscopic morphology of the slurries of the two components was analyzed, and the particle spacing and particle morphology thereof were observed. The fly ash sample was subjected to XRD analysis (as shown in Table 3), and it can be seen from the SEM micrograph (as shown in Table 3). Figure 1 , Figure 2 As shown in the figure, the distance between the fly ash particles in the first portion is significantly reduced compared with the second portion. Therefore, Auricularia auricula saponin and sodium silicate can be used as suitable substitutes for the commercial dispersant CTAB.

[0052] Table 3

[0053]

[0054]

[0055] As can be seen from Table 3, the explanation for this part is that the silicon and aluminum contents in fly ash are high, which can serve as a foundation for sodium silicate and the subsequent product sodium aluminosilicate.

[0056] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preventing fly ash slurry from stratifying and maintaining stability, characterized in that: The method comprises the following steps: (1) collecting fresh leaves of Auricularia a ... (2) mixing the leaf powder with water for extraction to obtain an extract; (3) distilling the extract under reduced pressure to obtain a solid saponin plant extract; (4) mixing fly ash, solid sodium hydroxide and water, and introducing carbon dioxide under stirring to obtain a sodium silicate mixture; then filtering and drying 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; and the surfactant mixture is then added to the fly ash slurry.

2. The method for preventing fly ash slurry from stratifying and maintaining stability 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 fly ash slurry from stratifying and maintaining stability according to claim 1, characterized in that: In step (2), the extraction temperature is 70-80° C., and the extraction time is 3-5 hours.

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

5. The method for preventing fly ash slurry from stratifying and maintaining stability according to claim 1, characterized in that: In step (3), the temperature of the reduced pressure distillation is 40-45° C., and the pressure of the reduced pressure distillation is 0.15-0.20 MPa.

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

200.

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

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

9. The method for preventing fly ash slurry from stratifying and maintaining stability according to claim 1, characterized in that: In step (4), the drying temperature is 180-200° C., and the drying time is 2-2.5 h.

10. The method for preventing fly ash slurry from stratifying and maintaining stability according to claim 1, characterized in that: In step (5), in the surfactant mixture, the concentration of the solid saponin plant extract 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 the fly ash slurry is 1:10.

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