CN118978368A

CN118978368A - A kind of sludge solidifying agent and its preparation method and application

Info

Publication number: CN118978368A
Application number: CN202411059716.9A
Authority: CN
Inventors: 符文妍; 陈建宝; 黄宏; 陈耿; 沙马什布; 李玉花
Original assignee: HAINAN LANDAO ENVIRONMENTAL PROTECTION INDUSTRY CO LTD
Current assignee: HAINAN LANDAO ENVIRONMENTAL PROTECTION INDUSTRY CO LTD
Priority date: 2024-08-02
Filing date: 2024-08-02
Publication date: 2024-11-19

Abstract

本发明提出了一种淤泥固化剂及其制备方法和应用，属于固化剂和固体废弃物资源化利用技术领域，该固化剂按照质量百分数计，原料包括：水泥45％～65％、矿粉18％～30％、粉煤灰9％～20％和固化剂母料8％～10％。即本发明利用矿粉、粉煤灰等固废材料实现滩涂淤泥固化及稳定化，且无需加入特殊添加剂，具有价格低廉，材料简单优点。此外，本发明对粉煤灰、纸浆厂制浆碱回收绿泥等固体废弃物进行资源化利用，增加经济收益的同时，减轻了生态环境的污染问题；同时本发明可原地固化淤泥，固化速度快，可以大大缩短施工工期，降低施工成本，适用于大规模的淤泥、软基础处理；且本发明制备得到的淤泥固化土满足公路工程施工要求，具有优异的抗压性能。The present invention proposes a sludge solidifying agent and its preparation method and application, which belongs to the technical field of solidifying agent and solid waste resource utilization. The raw materials of the solidifying agent include: 45% to 65% cement, 18% to 30% mineral powder, 9% to 20% fly ash and 8% to 10% solidifying agent masterbatch according to mass percentage. That is, the present invention uses solid waste materials such as mineral powder and fly ash to realize the solidification and stabilization of tidal flat sludge, and no special additives are needed, which has the advantages of low price and simple materials. In addition, the present invention makes resource utilization of solid wastes such as fly ash and green mud recovered from pulping alkali in pulp mills, which increases economic benefits while reducing the pollution problem of the ecological environment; at the same time, the present invention can solidify sludge in situ, with a fast solidification speed, which can greatly shorten the construction period and reduce the construction cost, and is suitable for large-scale sludge and soft foundation treatment; and the sludge solidified soil prepared by the present invention meets the requirements of highway engineering construction and has excellent compressive strength.

Description

Silt curing agent and preparation method and application thereof

Technical Field

The invention belongs to the technical field of curing agents and solid waste recycling, and particularly relates to a sludge curing agent and a preparation method and application thereof.

Background

Soft soil refers to fine-grained soil with high natural water content, large pore ratio, high compressibility and low shear strength. Is generally referred to as soft clay, mucky soil, muddy peat soil, peat and other weak soil. The highway subgrade is defined as: cohesive soil with a standard number of less than 4, an unconfined compressive strength of less than 50kPa, a water content of greater than 50% and sandy soil with a standard number of less than 10 and a water content of greater than 30% are collectively referred to as soft soil. According to the specification of the design and construction technical Specification of the embankment of the highway soft soil foundation (JTJ 017-96): the soft soil meets three indexes of natural water content of not less than 35% or liquid limit, natural pore ratio of not less than 1.0, cross plate shearing strength of less than 35 kPa.

The sludge is soft soil with high natural water content and porosity ratio of not less than 1.5, and has rheological property and thixotropic property; the building is a modern sediment formed under the condition of slow still water or slow water flow and under the action of microorganisms, is rich in organic matters, is often gray black, has the characteristics of low strength, high compressibility, high water permeability, low shear strength, poor earthquake resistance and the like, and is easy to cause the subsidence of the building if silt exists in the foundation.

Along with the increase of the construction quantity of highway infrastructure in China, coastal city highway construction relates to a sludge soft soil working section, so that the sludge generated by dredging river channels and waterways and the sludge generated by highway engineering construction soft soil are huge in generation quantity, the traditional treatment method of the sludge generated by dredging is to adopt sea throwing and soil replacement backfill construction, but the original sludge is required to be stored in a place after soil replacement, so that new pollution is caused; the soft soil sludge generated by dredging can not meet the requirements of highway engineering construction due to the property of the soft soil sludge, and can not be directly recycled; therefore, stabilization and harmless treatment of dredging soft soil sludge become an engineering problem to be solved urgently.

The curing agent is a material which bonds soil particles by adopting a chemical method or a biological method. By doping the curing agent into the soil body, the aims of improving the strength of the soil body, reducing the deformation of the soil body and reducing the permeability of the soil body can be achieved within the time required by design. At present, the research results of the sludge curing agent are more, but most of the results are more complicated in materials, more severe in application conditions and complex in process flow.

In order to solve the problem, the invention provides the curing agent for the soft soil sludge for highway engineering construction, which has the advantages of simple material and low price, and then the sludge in the construction section is subjected to in-situ curing, so that the compressive strength, the bearing ratio and the like of the cured sludge soil can meet the requirements of highway engineering construction, and the curing agent can be used in the original site and other civil engineering, and simultaneously, the industrial solid waste fly ash, mineral powder and the like can be used for waste resource utilization when the curing agent is prepared, the pollution is avoided, the engineering cost is saved, and the curing agent has important social benefit and application value.

Disclosure of Invention

In order to solve the technical problems, the invention provides the silt curing agent, the preparation method and the application thereof, the total mixing amount of the fly ash and the solid waste of the granulated blast furnace slag powder can be improved to 45%, the recycling effect of industrial waste is achieved, good environmental benefits are generated, energy conservation and environmental protection are realized, and the price is low; the prepared curing agent can improve the curing speed and strength of the sludge, can realize the requirement of curing large-scale sludge in situ, reduces the construction cost, and simultaneously, the curing soil meets the construction requirement of actual highway engineering.

In order to achieve the above purpose, the present invention provides the following technical solutions:

one of the technical schemes of the invention is as follows:

the sludge curing agent comprises the following raw materials in percentage by mass:

45-65% of cement, 18-30% of mineral powder, 9-20% of fly ash and 8-10% of curing agent master batch.

Preferably, the cement is a pozzolanic portland cement;

The mineral powder is granulated blast furnace slag powder;

the preparation process of the mineral powder comprises the steps of drying and ball milling water quenched blast furnace slag, and then drying and dewatering the water quenched blast furnace slag by a dryer to obtain high-fineness and high-activity granulated blast furnace slag powder which is also called as mineral powder;

the fly ash is power plant fly ash, and belongs to primary fly ash.

Preferably, the curing agent masterbatch comprises the following raw materials: limestone, iron powder, fly ash and a composite mineralizer.

Further, the mass ratio of the limestone, the iron powder, the fly ash and the composite mineralizer is 65:2:30:3.

Furthermore, the composite mineralizer is desulfurized gypsum and fluorite, and the mass ratio of the desulfurized gypsum to the fluorite is 3:1.

Preferably, the preparation method of the curing agent masterbatch comprises the following steps: and uniformly mixing the raw materials, sintering at high temperature, and ball milling to obtain the curing agent master batch.

Further, the specific conditions of the high-temperature sintering are as follows: sintering at 1400-1500 deg.c for 2.5-3.5 hr.

Preferably, the ball milling in the preparation process of mineral powder and the ball milling in the preparation method of the curing agent master batch are one or two of a vertical roller mill system, a vibration mill or a Raymond mill; the ball milling time is 25-30 min, the fineness of the powder is 250-350 meshes, and the water content is less than 0.5%.

The second technical scheme of the invention is as follows:

The preparation method of the sludge curing agent comprises the following steps:

and uniformly mixing the raw materials, and preparing the sludge curing agent by using a dry powder stirring method.

Preferably, the dry powder stirring method comprises the following specific steps: stirring the raw materials for 30-40 min at a low speed of 140+/-5 r/min.

The third technical scheme of the invention:

the sludge curing agent is applied to curing soft soil sludge in highway engineering construction and/or recycling green sludge from pulping alkali in pulp factories.

Preferably, the mixing amount of the sludge curing agent is 5-10% of the total mass of the soft soil sludge for highway engineering construction and the green sludge recovered by pulping alkali of a pulp mill.

The following raw material components in the sludge curing agent have the following roles in the sludge curing process:

And (3) cement: the cement mineral phase C ₃S、C₂S、C₃A、C₄ AF and calcium sulfate generate hydration reaction to generate hydration products such as C-S-H, C-A-H, AFm, AFt, CH, and the cementing action form among powder particles with different particle sizes, sand grains and gravel grains forms a structural whole with certain strength, so that the strength of the solidified soil is improved. The water in the cement and the sludge reacts with CaO+H ₂O→Ca(OH)₂, and the generated OH ^- ions ionized from Ca (OH) ₂ effectively neutralize acidic substances in the sludge, so that the pH is improved, and an alkaline environment is provided for the solidification process of the sludge.

Mineral powder: slag is industrial waste discharged after mineral separation or smelting, wherein the content of glass bodies is high, the potential activity is high, but the activity can be activated only by grinding into powder; the invention adopts a physical excitation (mechanical grinding) method to reduce the particle fineness, increase the specific surface area and improve the vitreous phase content and the volcanic ash reactivity of the mineral powder which is mainly a CaO-Al ₂O₃-SiO₂ system, thereby improving the speed and strength of the reaction with sludge. Wherein, the mineral powder can fill the pores in the sludge, reduce the porosity and improve the compactness of the sludge.

Fly ash: the fly ash is an industrial solid waste discharged from coal-fired power plants, the early fly ash has lower activity and can only be used for filling, and soluble substances contained in the fly ash gradually react with Ca (OH) ₂ along with the continuous growth of the age to generate a gelled substance with certain strength.

Limestone: the hydration reaction of CaO and the moisture in the sludge helps to reduce the moisture content of the sludge, ca (OH) ₂ is generated, which can be ion-exchanged with clay particles and adsorbed between the particles to form a solidified product, and Ca (OH) ₂ in the hardened material can be recrystallized and carbonized to form CaCO ₃ in the sludge solidification process, which can make the material more rigid and increase the solidification strength in the sludge solidification process. The alkaline component of the limestone can effectively improve the pH of the sludge, so that the decomposition of organic matters and the solidification of harmful substances are promoted, and the solidification strength is improved.

Iron powder: c ₃ S and C ₂ S are generated in the high-temperature calcination process, the liquid limit amount of the iron powder can be increased, the C ₂ S can be promoted to absorb f-CaO back to form C ₃ S, the hardening speed of cement clinker is improved, the cementing effect is enhanced, and after the iron powder reacts with water in sludge, a hardened body with high strength and good durability can be formed, and the solidification strength of the sludge is improved.

Composite mineralizing agent: on one hand, SO ₃ in gypsum can reduce the liquid limit viscosity of cement formation and increase the liquid limit quantity, which is beneficial to the formation of C ₃ S, and on the other hand, 2C ₂S·CaSO₄ and C ₄A₃ S which are early strength minerals can be formed, SO that the solidification speed and strength of sludge can be effectively improved.

CaF ₂ in fluorite can generate hydrofluoric acid under the action of high temperature to generate SiF ₄ and CaF, and the reaction promotes carbonate decomposition to destroy SiO ₂ crystal lattice; caF ₂ and other components generate calcium fluosilicate, calcium fluoaluminate and the like through solid phase reaction, so that C ₂ S and C ₃ S are effectively generated, the curing reaction is enhanced, and the curing strength and crack resistance of the sludge are improved.

Compared with the prior art, the invention has the following advantages and technical effects:

The silt curing agent disclosed by the invention can be used for curing and stabilizing silt generated by dredging river channels and waterways and soft soil silt for highway engineering construction; the curing agent adopts simple raw materials with wide sources, comprises solid waste slag, fly ash and the like, and realizes the comprehensive treatment of resources on the waste materials such as slag, fly ash, pulp mill pulping alkali recycling green mud and the like, thereby saving resources and producing good environmental benefit; on the other hand, the sludge does not need to be added with special additives or treated in special process environments, and the sludge under different natural conditions can be proportioned and blended with curing agents, so that the curing speed and the strength can reach the actual engineering requirements. The method can be used for curing and treating large-scale sludge in situ, has simple construction method, saves the total engineering cost, and solves the problems of water, soil and environmental pollution and the like.

Detailed Description

Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.

The invention discloses a curing agent for highway engineering construction soft soil silt, which comprises the following raw materials in percentage by mass: 45-65% of cement, 18-30% of mineral powder (granulated blast furnace slag powder), 9-20% of fly ash and 8-10% of curing agent master batch.

In some preferred embodiments, the cement is a pozzolanic portland cement having a strength of 32.5MPa and a specific surface area of 393.8m ²/kg.

In some preferred embodiments, the granulated blast furnace slag powder has a specific surface area of 372.0m ²/kg.

In some preferred embodiments, the fly ash is the primary solid waste discharged from a coal-fired power plant, and has a specific surface area of 409.8m ²/kg, which is the primary fly ash.

In some preferred embodiments, the curative masterbatch has a specific surface area of 440.4m ²/kg; wherein, the curing agent master batch comprises the following raw materials according to the mass ratio, limestone, iron powder, fly ash, desulfurized gypsum and fluorite=65:2:30:2.25:0.75. The chemical composition and content (wt.%) of each raw material are shown in table 1 below:

TABLE 1

Raw materials	CaO	SiO2	Al₂O₃	Fe₂O₃	MgO	SO₃	CaF₂
								Limestone powder	52.26	3.10	0.94	0.57	0.68	0	0
Iron powder	8.11	17.80	5.95	65.84	0.93	0	0
								Fly ash	5.60	48.40	37.31	5.12	2.22	0	0
Desulfurized gypsum	32.12	2.72	1.40	4.59	2.18	40.12	0
								Fluorite stone	11.56	11.10	1.40	0.50	1.90	0	56.12

The invention discloses a preparation method of a curing agent for highway engineering construction soft soil silt, which specifically comprises the following steps:

Step 1, weighing limestone, iron powder, fly ash and a composite mineralizer (desulfurized gypsum and fluorite) according to a mass ratio, uniformly mixing the raw materials, sintering the mixture at a high temperature of 1400-1500 ℃ for 2.5-3.5 hours, ball-milling the obtained substances into powder to obtain a curing agent master batch, and sealing and storing the curing agent master batch for later use;

Step 2, carrying out drying and ball milling on water quenched blast furnace slag, and then carrying out drying and dehydration treatment by a dryer to obtain high-fineness and high-activity granulated blast furnace slag powder, which is also called as mineral powder, and sealing and storing for later use;

Step 3, accurately weighing the powder materials of all the components according to the mass percentage, placing all the raw material components (curing agent master batch, cement, mineral powder and fly ash) into a cement mortar stirrer, and stirring for 30-40 min at a low speed of 140+/-5 r/min to ensure that the powder materials are uniformly mixed to obtain a silt curing agent with the powder density of 2.82g/cm ³;

In addition, the invention also discloses application of the curing agent in highway engineering soft soil silt, which comprises the following concrete steps: uniformly mixing the sludge dug in the construction section, the green mud recovered by pulping alkali of a pulp mill and a curing agent, and performing in-situ natural curing;

wherein the mass ratio of the curing agent is 5-10% of the total mass of the mud and the recycled green mud of pulping alkali.

The raw materials used in the examples of the present invention are all commercially available.

The parts used in the examples of the present invention are parts by weight unless otherwise specified.

The technical scheme of the invention is further described by the following examples.

Example 1

(One) a preparation method of the curing agent, which comprises the following steps:

Step 1, weighing limestone, iron powder, fly ash and a composite mineralizer (desulfurized gypsum and fluorite) according to a mass ratio, uniformly mixing the raw materials, then sintering the mixture at a high temperature of 1400 ℃ for 3.0h, ball milling the obtained material (the ball milling time is 30min, the fineness is 350 meshes, the water content is 0.44%) to obtain a curing agent master batch, and sealing and storing the curing agent master batch for later use;

Step 2, drying (the drying temperature is 250 ℃ and the time is 1.5 h), ball milling (the ball milling time is 30min, the fineness is 325 meshes, the water content is 4.50%), drying and dehydration (the drying temperature is 105 ℃ and the dehydration is 0.48%) are carried out by a dryer, and then high-fineness and high-activity slag micro powder, also called mineral powder, is obtained after the process treatment, and is stored in a sealed manner for standby;

And 3, stirring 45.46% of raw cement, 27.27% of granulated blast furnace slag powder, 18.18% of fly ash and 9.09% of curing agent master batch for 40min at a low speed of 140+/-5 r/min according to mass percent, so that the powder materials are uniformly mixed, and obtaining the sludge curing agent 1.

And (II) the steps of solidifying the sludge and the green mud are as follows:

The mixture of the green mud (with the water content of 97.7 percent and the same as the following) recovered by the pulp alkali of the pulp mill and the sludge 1 (each detection index of the sludge 1 is shown in the table 2) is cured by adopting the sludge curing agent 1 at the room temperature of 25 ℃, and the mixing amount of the sludge curing agent 1 is 5 percent of the total mass of the sludge 1 and the green mud recovered by the pulp alkali of the pulp mill (wherein the mass ratio of the sludge 1 to the green mud is 90:10), so that the obvious curing is realized in 48 hours, and the rapid curing test speed of the sludge is indicated.

Note that: the method for curing the sludge and the green mud in the step (II) refers to a method for curing the sludge and the green mud in 2.2 sludge curing methods in Wang Jiangying silicate report paper "ultra-high water content lake phase sludge curing test and filling performance analysis".

TABLE 2

Example 2

The difference from example 1 is that,

The detection indexes of the sludge 2 used for the solidification in the step (two) are shown in table 3.

Other conditions were the same as in example 1.

TABLE 3 Table 3

Example 3

The difference from example 1 is that,

The raw material types and the dosage proportion of the curing agent in the step (I) are as follows: 63.64% of cement, 18.18% of granulated blast furnace slag powder, 9.09% of fly ash and 9.09% of curing agent master batch.

And the detection indexes of the sludge 3 used for solidification in the step (two) are shown in table 4.

Other conditions were the same as in example 1.

TABLE 4 Table 4

Example 4

The difference from example 1 is that,

The detection indexes of the sludge 4 used for the solidification in the second step are shown in Table 5.

Other conditions were the same as in example 1.

TABLE 5

Example 5

The difference from example 3 is that,

The detection indexes of the sludge 5 used for the solidification in the second step are shown in Table 6.

TABLE 6

Comparative example 1

The difference with the embodiment 1 is that the curing agent in the step 3 is not added with mineral powder, and the mass percentages of the cement, the fly ash and the curing agent master batch are respectively as follows: 62.50%, 25.00% and 12.50%, the three materials are accurately weighed and evenly mixed to obtain the sludge curing agent. Other conditions were the same as in example 1.

Comparative example 2

The difference from example 5 is that the curing agent mixture ratio in step 3 is not added with the curing agent master batch, and the mass percentage ratio of cement, mineral powder and fly ash is 62.50%, 25.00% and 12.50%. Accurately weighing and uniformly mixing the three materials to obtain the sludge curing agent. Other conditions were the same as in example 5.

Effect verification

The silt solidified soil obtained in the above examples 1 to 5 was subjected to an unconfined compressive strength test using an electronic universal tester (microcomputer control) and was tested using a load-bearing ratio tester according to the test method of T0134-2019 load-bearing ratio CBR in the standard of Highway geotechnical test procedure JTG 3430-2020, and the test results at a hit number of 50 are shown in Table 7 below.

TABLE 7

Conclusion: the data show that the data such as the compressive strength, the bearing ratio and the like of the silt solidified soil in the examples 1-5 can meet the strength requirement of the construction of the highway subbase layer; the obtained silt solidified soil has high strength and good stability, and can meet the construction requirements of the highway subbase. For the sludge of 5 different working conditions of the actual construction road section, the optimal curing agent proportioning scheme required by each is developed, the final purpose of the invention is also achieved, the data is ensured for the subsequent site construction, and the invention can be applied to other civil engineering.

The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. The sludge curing agent is characterized by comprising the following raw materials in percentage by mass:

2. A sludge curative as claimed in claim 1, wherein the curative masterbatch comprises the following components: limestone, iron powder, fly ash and a composite mineralizer.

3. A sludge curing agent as claimed in claim 2, wherein the mass ratio of limestone, iron powder, fly ash and composite mineralizer is 65:2:30:3.

4. A sludge curing agent according to claim 2, wherein the composite mineralizer is desulphurized gypsum and fluorite in a mass ratio of 3:1.

5. A sludge curing agent as claimed in claim 2, wherein the preparation method of the curing agent masterbatch is as follows: and uniformly mixing the raw materials, sintering at high temperature, and ball milling to obtain the curing agent master batch.

6. A sludge curing agent as claimed in claim 5, wherein the specific conditions for the high temperature sintering are: sintering at 1400-1500 deg.c for 2.5-3.5 hr.

7. The preparation method of the sludge curing agent is characterized by comprising the following steps:

The raw materials according to any one of claims 1 to 6 are uniformly mixed, and a dry powder stirring method is used to prepare the sludge curing agent.

8. The method for preparing the sludge curing agent according to claim 7, wherein the dry powder stirring method comprises the following specific steps: stirring the raw materials for 30-40 min at a low speed of 140+/-5 r/min.

9. Use of a sludge curing agent as claimed in any one of claims 1 to 6 for curing highway construction soft soil sludge and pulp mill pulping alkali recovery green sludge.

10. The use according to claim 9, wherein the mixing amount of the curing agent is 5-10% of the total mass of the soft soil sludge for highway engineering construction and the green sludge recovered by pulp alkali from a pulp mill.