Modifier for dewatering modification treatment of engineering waste slurry and use method of modifier

Abstract

The invention relates to the field of waste slurry treatment, in particular to a modifier for dewatering modification treatment of engineering waste slurry and a use method of the modifier. The modifier comprises the following components in parts by weight: 40-50 parts of dust collecting powder, 30-45 parts of dried desulfurized gypsum, 10-25 parts of cement and 5-10 parts of nano calcium oxide; the sum of the parts by weight of the components is 100 parts. The components of the modifier cooperate with each other, and the modifier has a good precipitation modification effect, can be rapidly cured, has good strength, is low in cost, can fully utilize various engineering recycled materials, and is green and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of waste mud treatment, and particularly relates to a modifier for the dewatering modification treatment of engineering waste mud and its application method. Background Technology

[0002] Sludge has a high water content (usually >80%) and high viscosity, and traditional treatment methods (landfill, stockpiling) lead to land resource occupation and secondary pollution problems. At the same time, off-site treatment costs are high (for example, the cost of off-site treatment of sludge from a construction site accounts for 15% to 20% of the total project cost).

[0003] On the other hand, the rapid economic development in my country's eastern coastal areas and the construction in the central and western regions have created a huge demand for roadbed fill. Roadbed engineering, in particular, consumes a large amount of high-quality soil and gravel resources, and over-exploitation will exacerbate soil erosion and damage river ecosystems. Developing modified waste mud and other materials into environmentally friendly roadbed fillers not only contributes to environmental protection but also enables resource reuse, yielding significant economic and social benefits. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a modifier for the dewatering modification treatment of engineering waste mud and its application method, which can make full use of solid waste, achieve rapid dewatering of engineering waste mud, and modify the mud to facilitate transportation or use as a geosynthetic material for filling.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a modifier for the treatment of engineering waste mud by precipitation, comprising the following components in parts by weight: 40-50 parts of dust collection powder, 30-45 parts of dried desulfurized gypsum, 10-25 parts of cement, and 5-10 parts of nano-calcium oxide; the sum of the parts by weight of the above components is 100 parts.

[0007] In some embodiments, the modifier comprises the following components in parts by weight: 40-50 parts of dust collection powder, 30-35 parts of dried desulfurized gypsum, 10-18 parts of cement, and 7-10 parts of nano-calcium oxide; the sum of the parts by weight of the above components is 100 parts.

[0008] In some embodiments, the dust collection powder is obtained by modifying electrostatic dust collection powder from steel electric arc furnaces or cement-based material premixing production lines with a silane coupling agent, with a particle size ≤45μm and a specific surface area ≥500m². 2 / kg. Silane coupling agents can reduce the stickiness of the extremely fine particles of the electrostatic precipitator, which is beneficial for the mixing of the modifier and the slurry. In some specific embodiments, the electrostatic precipitator powder can be collected from the electrostatic precipitator silo of the premixing production line.

[0009] In some embodiments, the dust collecting powder is obtained by heating electrostatic dust collecting powder to 80-90°C, spraying it with a 0.1-1 wt% silane coupling agent atomized liquid, stirring and mixing for 30-50 minutes, and then inertizing it with nitrogen gas. In some preferred embodiments, the silane coupling agent is KH560, KH550, etc.

[0010] In some embodiments, the main component of the dried desulfurized gypsum is CaSO4·0.5H2O, with the content of CaSO4·0.5H2O ≥95wt% and CaSO3 ≤wt5%. Further, in some embodiments, the dried desulfurized gypsum is obtained by calcining power plant desulfurized gypsum at 120–180°C to convert it into hemihydrate gypsum (building gypsum), followed by immediate steam aging and stabilization. After 20–40 minutes, it is removed, dried, and pulverized to obtain a particle size ≤0.15mm. Specifically, the dried gypsum can be ground and sieved (using a 0.15mm square-hole sieve) to collect the residue.

[0011] In some embodiments, the nano-calcium oxide is dispersed using an organic solvent-coupling agent. Specifically, the nano-calcium oxide powder is first ultrasonically dispersed in anhydrous ethanol to obtain a suspension. Then, 0.1–1 wt% of a silane coupling agent atomized solution is added to the suspension, and surface modification is performed by stirring. In a preferred embodiment, the nano-calcium oxide powder is ultrasonically dispersed in anhydrous ethanol for 1 hour, followed by the addition of 0.1–1 wt% of a silane coupling agent atomized solution to the suspension, and surface modification is performed by stirring for 30 minutes. In some preferred embodiments, the silane coupling agent is KH570, KH550, etc.

[0012] In some embodiments, the cement is at least one of PI cement, P.II cement, PO cement, and PC cement, and has a strength grade ≥42.5.

[0013] The modifier of the present invention can be obtained by mixing the components in the prescribed amounts, and the preparation method is simple.

[0014] In another aspect, the present invention also provides a method for using the modifier, wherein the modifier is directly mixed with the mud and allowed to stand and dry for more than 24 hours to obtain solidified mud, which is then transported or used directly for filling.

[0015] In some embodiments, the modifier is used at 5% to 20% of the weight of the mud, and the water content of the mud is 50% to 500%. After being added, the mud can be quickly solidified.

[0016] In particular, the dosage should be adjusted according to the project requirements. When the solidified mud needs to be transported off-site, a low dosage can be selected. When the water content of the mud is too high (over 300%), the temperature is low (below 15℃), or the project schedule is tight and rapid solidification is required, a higher dosage should be selected.

[0017] The beneficial effects of this invention are:

[0018] The main functions of the modifier of this invention on engineering waste mud are as follows: 1) The dust collector is a fine dust particle captured by electrostatics. It has a large specific surface area and can adsorb water in the mud, increasing the mud viscosity. At the same time, the dust collector can fill the gaps between particles in the mud, optimizing the particle size distribution of the mud. 2) The main component of the dried desulfurization gypsum is CaSO4·0.5H2O, which can react with water in the mud to form CaSO4·2H2O, increasing the mud viscosity. At the same time, CaSO4·2H2O promotes the hydration of cement and dust collector, accelerates the formation of ettringite, and accelerates the thickening and solidification of the mud. 3) The reaction of cement and water to generate CS~H and Ca(OH)2 provides the main components for binding the solid particles of the mud and also provides the alkaline environment required for the hydration reaction. 4) Nano-calcium oxide reacts with water in the slurry to generate calcium hydroxide, supplementing the alkaline conditions. Simultaneously, it, along with active silica and active alumina in the dust collection powder, replenishes the calcium, silicon, and aluminum substances generated during the hydration reaction of the modifier, promoting rapid reaction between the modifier and the slurry. Under alkaline conditions, the water-soluble components of cement, dust collection powder, and nano-calcium oxide undergo a secondary hydration reaction, enhancing the slurry solidification effect. 5) The dried desulfurized gypsum reacts with divalent calcium ions (CaO) in the nano-calcium oxide. 2+ It has a very high charge density and can very effectively compress the electric double layer, replacing monovalent cations (such as sodium ions, Na+) on soil colloids. + This invention effectively improves soil structure and enhances the soil's soil-stabilizing effect. Therefore, the components of the modifier in this invention work synergistically to achieve excellent precipitation-modifying effects. Furthermore, the raw materials used in the modifier are inexpensive and can fully utilize recycled materials from various engineering projects, making it environmentally friendly. Attached Figure Description

[0019] Figure 1 Images showing the curing effect of different dosages of modifier after 24 hours. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0021] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples.

[0023] The dust collection powder used in the following examples was obtained by heating electrostatic dust collection powder collected from the electrostatic dust collection chamber of the premixing production line to 80°C, simultaneously spraying it with 0.1wt% KH550 atomized liquid, mixing and stirring in a kneader for 30 minutes, and then inertizing it with nitrogen gas for 10 minutes while continuing to knead and stir. The powder had the following properties: D99 = 43 μm, D90 = 23 μm, D50 = 10 μm, D10 = 1.2 μm, and a specific surface area of ​​534 m². 2 / g.

[0024] The dried desulfurized gypsum is produced by calcining power plant desulfurized gypsum at 150℃ to convert it into hemihydrate gypsum (building gypsum). It is then immediately stabilized by short-term steam aging, and removed after 30 minutes. The particle size is 0.12 mm. The gypsum contains 95.7 wt% CaSO4·0.5H2O and 3.5% CaSO3.

[0025] Nano calcium oxide is obtained by ultrasonically dispersing nano calcium oxide powder in anhydrous ethanol for 1 hour, then adding 0.5 wt% KH570 silane coupling agent atomized liquid to the suspension, stirring for 30 minutes for surface modification, and then drying, grinding, and sieving (0.15 mm square hole sieve).

[0026] I. Preparation and Formulation Optimization of Modifiers in Examples

[0027] Example 1

[0028] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 40 parts dust collection powder, 35 parts dried desulfurized gypsum, 15 parts P.O42.5 cement, and 10 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0029] Example 2

[0030] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 42 parts dust collection powder, 30 parts dried desulfurized gypsum, 20 parts P.O42.5 cement, and 8 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0031] Example 3

[0032] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 45 parts dust collection powder, 30 parts dried desulfurized gypsum, 18 parts P.O42.5 cement, and 7 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0033] Example 4

[0034] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 50 parts dust collection powder, 30 parts dried desulfurized gypsum, 10 parts P.II 52.5 cement, and 10 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0035] Example 5

[0036] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 40 parts dust collection powder, 45 parts dried desulfurized gypsum, 10 parts P.O42.5 cement, and 5 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0037] Example 6

[0038] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 35 parts dried desulfurized gypsum, 55 parts P.O42.5 cement, and 10 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0039] Example 7

[0040] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 40 parts dust collection powder, 15 parts P.O42.5 cement, and 45 parts nano-calcium oxide. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0041] Example 8

[0042] This embodiment provides a modifier for the treatment of engineering waste mud dewatering. The formula, by weight, is as follows: 40 parts dust collection powder, 45 parts dried desulfurized gypsum, and 15 parts P.O42.5 cement. The above-mentioned raw materials are uniformly mixed to obtain the modifier.

[0043] The formulations of the modifiers in Examples 1 to 8 are shown in Table 1.

[0044] Table 1. Modifier formulations for Examples 1-8

[0045] Example 1 2 3 4 5 6 7 8 Dust collection powder 40 42 45 50 40 0 40 40 Drying desulfurized gypsum 35 30 30 30 45 35 0 45 cement 15 20 18 10 10 55 15 15 Nano calcium oxide 10 8 7 10 5 10 45 0

[0046] II. Application Examples

[0047] Using the modifier from the above embodiments, a type of engineering waste mud with a water content of 220% was selected as the object to be solidified. At a dosage of 8% (i.e., the modifier added was 8% of the mud weight), the fluidity and fluidity loss of the mixture of modifier and mud were tested after 2 hours, 4 hours, and 24 hours (fluidity test mold: a hollow cylindrical barrel 150mm high and 76mm in diameter). The unconfined compressive strength of the solidified mud was tested at 1 day, 2 days, and 3 days. A comparative example was also set up; details are as follows.

[0048] Application Example 1

[0049] 8 kg of the modifier from Example 1 was directly mixed with 100 kg of engineering waste mud with a water content of 220% and allowed to stand and dry for more than 24 hours.

[0050] Application Examples 2-8

[0051] Referring to Application Example 1, 8 kg of the modifier prepared in Examples 2 to 8 were directly mixed with 100 kg of engineering waste mud with a water content of 220% and allowed to stand and dry for more than 24 hours.

[0052] Comparative Example 1

[0053] This comparative example is a blank control group, and the mud is not treated in any way.

[0054] Comparative Example 2

[0055] In this comparative example, PO 42.5 cement was used as a modifier for the dewatering modification treatment of engineering waste mud. Specifically, 8 kg of PO 42.5 cement was directly mixed with 100 kg of engineering waste mud with a moisture content of 220% and allowed to stand and dry for more than 24 hours.

[0056] The specific curing effect is shown in Table 2.

[0057] Table 2 Application Examples and Comparative Examples: Slurry Solidification Effect

[0058]

[0059] As can be seen from the results in Table 1, the modifiers of the present invention have good curing effects, especially Examples 1, 3, and 4, with Example 1 showing the best effect.

[0060] In the examples where one of the key components was missing (Examples 6-8), the modifier's solidification effect on the mud was weaker, similar to Comparative Example 2. All components in the modifier play a crucial role in mud solidification, and their solidification and modification capabilities were significantly weakened when any component was missing.

[0061] Furthermore, the dust collection powder in the modifier and the active silica-alumina component in the cement can react rapidly with the water in the engineering waste mud under the synergistic effect of calcined desulfurized gypsum and nano calcium oxide, reducing the excess free water in the system. The large amount of calcium hydroxide produced by hydration provides a highly alkaline environment, which promotes the rapid formation of more stable hydrated calcium silicate, hydrated calcium aluminate, hydrated calcium sulfoaluminate and other components in the silica-alumina phase of the system, thereby improving the early strength.

[0062] III. Optimization Experiment of Modifier Dosage

[0063] Based on the formulation of Example 1, slurry solidification experiments were conducted with different admixture amounts (5%, 10%, 15%, 20%), resulting in Examples 1A, 1B, 1C, and 1D. The solidification effects were compared with those of Comparative Example 1 (PO 42.5 cement, admixture 8%). Specific results are shown in Table 3 and... Figure 1 As shown, where Figure 1 Images showing the curing effect of different dosages of modifier after 24 hours.

[0064] Table 3 Results of the experiment on the optimization of modifier dosage

[0065]

[0066] It can be seen that the higher the admixture dosage, the better the rapid solidification effect of the mud. For a certain project's waste mud with a moisture content of 220%, adding 10% of the modifier from Example 1 and drying it for 24 hours allowed it to granulate, meeting the conditions for transport by dump trucks.

[0067] The results above show that this invention uses dust collection powder and calcined desulfurized gypsum to prepare the modifier, making full use of solid waste generated by power plants and premixing plants, thus reducing the accumulation of solid waste to a certain extent. Simultaneously, the dust collection powder in the modifier reacts rapidly with the water in the engineering waste slurry under the synergistic effect of calcined desulfurized gypsum and nano-calcium oxide, reducing excess free water in the system. The large amount of calcium hydroxide produced during hydration provides a highly alkaline environment, promoting the rapid formation of more stable hydrated calcium silicate, hydrated calcium aluminate, and hydrated calcium sulfoaluminate from the silica-alumina phase in the system, improving early strength, exhibiting good curing effect, and being low-cost and environmentally friendly.

[0068] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A modifier for modified treatment of dewatering of an engineering sludge, characterized by The dust collecting powder, the baked desulfurization gypsum, the cement and the nano calcium oxide are mixed in a weight ratio of 40-50:30-45:10-25:5-10.

2. The modifying agent of claim 1, wherein The dust collecting powder, the baked desulfurization gypsum, the cement and the nano calcium oxide are mixed in a weight ratio of 40-50:30-35:10-18:7-10.

3. The modifying agent according to claim 1 or 2, characterized in that, The dust collecting powder is a steel arc furnace dust collecting powder or a cement-based material premix process production line electrostatic dust collecting powder modified by a silane coupling agent, with a particle size of ≤45 μm and a specific surface area of ≥500 m 2 / kg.

4. The modifying agent of claim 3, wherein The dust collecting powder is obtained by heating the electrostatic dust collecting powder to 80-90 DEG C, spraying a silane coupling agent mist liquid with a concentration of 0.1-1wt%, stirring and mixing for 30-50 min, and then introducing nitrogen for inertization.

5. The modifier of claim 1 or 2, wherein The baked desulfurization gypsum mainly contains CaSO4·0.5H2O, and the content of the main component CaSO4·0.5H2O is ≥95wt%, and CaSO3≤5wt%.

6. The modifying agent of claim 5, wherein, The baked desulfurization gypsum is obtained by calcining the desulfurization gypsum from a power plant at 120-180 DEG C to convert it into hemihydrate gypsum, then introducing steam for aging and stabilization, and then taking out the baked and crushed product after 20-40 min, with a particle size ≤0.15mm.

7. The modifier of claim 1 or 2, wherein The nano calcium oxide is prepared by first dispersing the nano calcium oxide powder in anhydrous ethanol to obtain a suspension, then adding 0.1-1wt% of a silane coupling agent mist liquid to the suspension, and stirring to perform surface modification.

8. The modifying agent according to claim 1 or 2, characterized in that, The cement is at least one of P.I cement, P.II cement, P.O cement and P.C cement, and the strength grade is ≥42.

5.

9. The method of using a modifier of any of claims 1-8, wherein, The modifier is directly stirred with the mud until uniform, and then left to stand and dry for 24h or more.

10. The method of use of claim 9, wherein, The amount of the modifier is 5%-20% of the weight of the mud, and the water content of the mud is 50%-500%.

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