Large-volume solid waste sludge curing agent and preparation method thereof

Abstract

The invention relates to the technical field of solid waste resource utilization, in particular to a large-volume solid waste sludge curing agent which comprises the following raw materials: granulated blast furnace slag, steel slag, sulfate, lithium slag, carbonized steel slag powder and P.O 425 cement. During preparation, the raw materials are uniformly mixed and put into a planetary ball mill to be mixed and ground, and then are uniformly mixed with water according to the mass ratio of 1: 1 to obtain the sludge curing agent with the large solid waste mixing amount. According to the invention, the sludge curing agent with large solid waste content is prepared from industrial solid wastes such as steel slag, mineral slag, lithium slag and sulfate and less or even no cement, and is used for curing sludge, so that the dependence on traditional high-carbon emission materials is greatly reduced, and the curing effect is enhanced. Compared with the prior art, a high-temperature calcination process is not adopted in the curing agent preparation process, the emission of carbon dioxide can be effectively reduced, and the current low-carbon and environment-friendly trend is met.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of solid waste, and particularly to a sludge curing agent with a large amount of solid waste incorporated and a preparation method thereof. Background Art

[0002] There are numerous rivers in our country, which provide people with sufficient water resources and convenient cargo transportation routes. However, a large amount of sludge often accumulates in rivers. Currently, the annual sludge production in cities in our country is close to 30 million tons, but the treatment of sludge faces huge challenges, and about 80% of the sludge fails to be effectively stabilized. The existing sludge treatment methods are relatively crude, and most adopt landfill and open stacking. These methods are prone to random disposal, and the proportion of truly achieving safe disposal does not exceed 15%-25%.

[0003] Sludge solidification treatment is one of the important ways of sludge resource utilization. It mainly solidifies sludge by adding a curing agent. Therefore, this method has the advantages of good environmental protection, simple process, reducible pollution and stacking area, and the solidified soil after treatment can be used as recycled soil resources, etc., and is widely accepted and used on a large scale at home and abroad. Currently, inorganic curing agents in the market are widely used, mainly using traditional cementitious materials such as cement and lime, and enhancing soil stability through their hydration reaction, ion exchange and crystallization cementation. The gel structure systems formed by these reactions, such as calcium silicate hydrate, calcium aluminate hydrate and calcium sulfoaluminate hydrate, play a key role in improving soil stability.

[0004] However, there are still a series of defects and deficiencies in the existing solidification technologies in practice:

[0005] 1. The application of traditional inorganic curing agents is accompanied by the problem of high carbon emissions. For example, the production of ordinary Portland cement clinker and lime is a process with high carbon emissions. About 660-820 kilograms of carbon dioxide are generated for every ton of cement produced, and about 1200 kilograms of carbon dioxide are released during the process of calcining one ton of lime from limestone.

[0006] 2. Due to the characteristics of high water content and strong viscosity of sludge, and it also contains a relatively high amount of organic matter, there are problems such as difficult coagulation and high curing agent dosage during the solidification process. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: based on the problems of high carbon emissions and low solidification effect in the existing sludge solidification technology, to provide a sludge curing agent with a large amount of solid waste incorporated and a preparation method thereof. By using a large amount of industrial solid waste as the main component, the present invention develops a low-carbon, environmentally friendly and efficient sludge curing agent, greatly reducing the dependence on traditional high-carbon emission materials and enhancing the solidification effect.

[0008] The technical solution adopted by the present invention is: a sludge curing agent with a large amount of solid waste, comprising the following raw materials in parts by mass:

[0009]

[0010] Further, the granulated blast furnace slag is of S95 grade, the specific surface area of the blast furnace slag > 450 m 2 / kg, the sum of the mass fractions of CaO, SiO2, MgO and Al2O3 in the blast furnace slag ≥ 85%, and the 28-day activity index of the blast furnace slag ≥ 95%. The granulated blast furnace slag is a by-product in the process of blast furnace ironmaking.

[0011] Further, the steel slag is one or more of ladle furnace slag, electric arc furnace reducing slag, and basic oxygen converter slag. The steel slag is heat-soaked and magnetically separated for iron treatment, and the specific surface area of the steel slag > 500 m 2 / kg. The steel slag is an industrial solid waste generated in the steelmaking process.

[0012] Further, the sulfate is a sulfate industrial by-product generated in the industrial production process. The sulfate is one or more of phosphogypsum, desulfurized gypsum nitrate, and mirabilite gypsum, and the mass fraction of CaSO4 in the sulfate ≥ 75%.

[0013] Further, the lithium slag is an industrial solid waste generated in the process of producing lithium carbonate by the sulfuric acid method from spodumene. About 10 tons of lithium slag are generated for every 1 ton of lithium carbonate produced; the specific surface area of the lithium slag > 1000 m 2 / kg, and the sum of the mass fractions of SiO2 and Al2O3 in the lithium slag ≥ 70%.

[0014] The porous characteristics of the lithium slag can adsorb the excess water in the high-moisture-content sludge, reduce its fluidity, and help accelerate the sludge curing.

[0015] Further, the carbonized steel slag powder is obtained by pretreating the steel slag to a moisture content of 5 - 15% and then treating it with industrial waste gas of CO2 with a concentration of 10 - 40% for 6 - 24 h, and the carbon adsorption amount of the obtained carbonized steel slag powder ≥ 8%.

[0016] As a stabilizer, the carbonized steel slag powder uses its main component nano-calcium carbonate to provide carbonate ions, which can react with calcium aluminate hydrate (C-A-H) to form CO3-AFm, and the stability of the latter is higher than that of SO4-AFm. After mixing it with the curing agent and incorporating it into the sludge, it can stabilize the ettringite formed by the reaction of the curing agent.

[0017] Further, the 28-day compressive strength of the P.O 425 cement ≥ 42.5 MPa.

[0018] A preparation method of a sludge curing agent with a large amount of solid waste, comprising the following steps:

[0019] Step 1: Uniformly mix granulated blast furnace slag, steel slag, sulfate, lithium slag, carbonized steel slag powder, and P.O 425 cement to obtain a solid waste cementitious material. Put the solid waste cementitious material into a planetary ball mill and grind it until the specific surface area of the solid waste cementitious material > 800 m 2 / kg;

[0020] Step 2: By mass, mix the solid waste cementitious material and water in a mass ratio of 1:1 uniformly to obtain a sludge solidifying agent with a large amount of solid waste incorporated.

[0021] More than 90% of the raw materials in the sludge solidifying agent are industrial solid wastes, and the obtained sludge solidifying agent has the advantages of low cost and green low-carbon.

[0022] The raw materials of the sludge solidifying agent and the sludge solidifying agent are prepared by non-calcination processes such as drying, grinding, and homogenization. The whole preparation process has low energy consumption and meets the requirements of green low-carbon.

[0023] When the sludge solidifying agent with a large amount of solid waste incorporated is used to solidify sludge, its mechanical properties and impermeability are better than those of ordinary Portland cement under the same dosage. The 28-day compressive strength is increased by up to 100% at most, and the 28-day permeability coefficient is reduced by one order of magnitude.

[0024] The present invention has the following advantages compared with the prior art:

[0025] 1. The present invention prepares a sludge solidifying agent with a large amount of solid waste incorporated for sludge solidification by using industrial solid wastes such as steel slag, slag, lithium slag, and sulfate and adding little or no cement, which greatly reduces the dependence on traditional high-carbon emission materials (such as ordinary Portland cement and lime). Compared with the prior art, the present invention does not adopt a high-temperature calcination process in the preparation of the solidifying agent, which can effectively reduce the carbon dioxide emissions and conforms to the current trend of low-carbon environmental protection.

[0026] 2. Aiming at the problem of difficult coagulation caused by high water content and high organic matter content in sludge, the present invention adds lithium slag and uses its porous characteristics to adsorb the excess water in the sludge, thereby reducing the fluidity of the sludge, enhancing the effectiveness of the solidifying agent, and reducing the dosage of the solidifying agent.

[0027] 3. The present invention innovatively introduces carbonized steel slag powder as a stabilizer. The nano-calcium carbonate contained therein can react with calcium aluminate hydrate to generate CO3-AFm with higher stability, thereby inhibiting the excessive formation of ettringite and significantly improving the long-term stability of the solidified material. This improvement effectively overcomes the problem of swelling of the solidified soil caused by the instability of ettringite in the prior art.

[0028] 4. After the curing agent of the present invention cures the sludge, the mechanical properties and impermeability of the material are significantly better than those of ordinary Portland cement under the same dosage. The 28-day compressive strength is increased by up to 100%, and the 28-day permeability coefficient is reduced by one order of magnitude, effectively improving the practical performance after sludge curing.

[0029] 5. The curing agent used in the present invention is mainly made from industrial by-products, which not only has a low cost, but also can make a large amount of use of solid waste, helping to reduce the accumulation of solid waste and environmental pollution, and realizing the efficient utilization of resources. Detailed implementation mode

[0030] The following is a detailed description of the embodiments of the present invention. The embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] A preparation method of a sludge curing agent with a large amount of solid waste incorporated, comprising the following steps:

[0033] Step 1: By mass, 55 parts of granulated blast furnace slag, 30 parts of steel slag, 15 parts of sulfate, 5 parts of lithium slag, 3 parts of carbonized steel slag powder, and 5 parts of P.O 425 cement are uniformly mixed to obtain a solid waste cementitious material. The solid waste cementitious material is put into a planetary ball mill for mixing and grinding until the specific surface area of the solid waste cementitious material is 850m 2 / kg;

[0034] Step 2: By mass, the solid waste cementitious material and water are mixed evenly at a mass ratio of 1:1 to obtain a sludge curing agent with a large amount of solid waste incorporated.

[0035] During use, the sludge curing agent with a large amount of solid waste incorporated is mixed into the sludge with a water content of 60% and stirred evenly to cure the sludge; wherein, by mass, the mass ratio of the sludge curing agent with a large amount of solid waste incorporated to the sludge is 18:100.

[0036] Referring to the specifications "Soft Soil Curing Agent" (CJ / T 526—2018) and "Highway Geotechnical Test Procedures" (JTG 3430—2020), performance tests are carried out on the obtained solidified soil specimens. The unconfined compressive strength and permeability coefficient at the ages of 7d and 28d are shown in Table 1.

[0037] Example 2

[0038] Basically the same as Example 1, the difference is:

[0039] Step 1: By mass fraction, mix 40 parts of granulated blast furnace slag, 40 parts of steel slag, 15 parts of sulfate, 5 parts of lithium slag, 3 parts of carbonized steel slag powder, and 5 parts of P.O 425 cement evenly to obtain a solid waste cementitious material.

[0040] Example 3

[0041] It is basically the same as Example 1, except that:

[0042] During use, incorporate the sludge curing agent with a large amount of solid waste into the sludge with a moisture content of 65% and stir evenly to solidify the sludge; among them, by mass fraction, the mass ratio of the sludge curing agent with a large amount of solid waste to the sludge is 20:100.

[0043] Example 4

[0044] It is basically the same as Example 1, except that:

[0045] Step 1: By mass fraction, mix 40 parts of granulated blast furnace slag, 45 parts of steel slag, 10 parts of sulfate, 5 parts of lithium slag, and 3 parts of carbonized steel slag powder evenly to obtain a solid waste cementitious material.

[0046] During use, incorporate the sludge curing agent with a large amount of solid waste into the sludge with a moisture content of 45% and stir evenly to solidify the sludge.

[0047] Comparative Example 1

[0048] Comparative Example 1 is a comparative example using P.O 42.5 ordinary Portland cement as the sludge curing agent. The difference from Example 1 is that:

[0049] Use P.O 42.5 ordinary Portland cement as the sludge curing agent directly to solidify the sludge, without other raw materials.

[0050] Comparative Example 2

[0051] Comparative Example 2 is a comparative example without using lithium slag. The difference from Example 1 is that:

[0052] Step 1: By mass fraction, mix 55 parts of granulated blast furnace slag, 30 parts of steel slag, 15 parts of sulfate, 3 parts of carbonized steel slag powder, and 5 parts of P.O 425 cement evenly to obtain a solid waste cementitious material.

[0053] Comparative Example 3

[0054] Comparative Example 3 is a comparative example without using carbonized steel slag powder. The difference from Example 1 is that:

[0055] Step 1: By mass fraction, mix 55 parts of granulated blast furnace slag, 30 parts of steel slag, 15 parts of sulfate, 5 parts of lithium slag, and 5 parts of P.O 425 cement evenly to obtain a solid waste cementitious material.

[0056] Comparative Example 4

[0057] Comparative Example 4 is a comparative example for reducing the dosage of the sludge curing agent with a large amount of solid waste when solidifying sludge. The difference from Example 1 is as follows:

[0058] During use, the mass ratio of the sludge curing agent with a large amount of solid waste to the sludge is 14:100.

[0059] Table 1 Performance test results of the solidified soil obtained from Examples 1 - 4 and Comparative Examples 1 - 4

[0060]

[0061] From the results of Examples 1 to 4 in Table 1, it can be seen that the curing agent prepared by the non - calcination method and with a large amount of industrial solid waste can better solidify the sludge with a high water content (60%). The unconfined compressive strength of the 28 - day solidified soil is up to 4.1 MPa at most, and the permeability coefficient is 1.95E - 08 cm / s. In the present invention, the sludge curing agent with a large amount of solid waste can adjust the proportion and dosage of different types of solid waste to achieve different solidified soil properties. For example, when the requirement for the strength of the solidified soil is not high, the slag with a higher cost can be appropriately reduced, and the content of steel slag with a lower cost can be increased to prepare the sludge curing agent with a large amount of solid waste. When the water content of the sludge is less, on the premise of ensuring that the unconfined compressive strength and permeability coefficient of the solidified soil remain basically unchanged, the dosage of P.O425 cement in the curing agent can be reduced, and even a full - solid - waste sludge curing agent without cement can be achieved.

[0062] From the results of Comparative Example 1, it can be seen that when solidifying the sludge with the same water content, P.O 42.5 ordinary Portland cement as the curing agent, the properties of its solidified soil are much lower than those of the solidified soil of the sludge curing agent with a large amount of solid waste prepared by the present invention. This is mainly because the hydration products generated by ordinary Portland cement during the solidification process are mainly C - S - H gels, accompanied by the precipitation of more Ca(OH), which easily form larger pores and micro - cracks in the soil, resulting in insufficient overall density of the solidified soil and a higher permeability coefficient. While the large - amount - solid - waste cementitious material in the present invention, due to its complex mineral composition and reaction mechanism, can generate a variety of dense hydration products, such as C - S - H gels, ettringite, etc. These products effectively fill the micro - pores in the soil, enhance the density and water - invasion resistance of the solidified soil, significantly reduce the permeability coefficient, and thus exhibit more excellent solidified soil properties.

[0063] It can be seen from the results of Comparative Example 2 that when solidifying high water content silt, adding a certain amount of lithium slag to the solidifying agent helps to improve the early strength and reduce the permeability coefficient. Because lithium slag has a high specific surface area and high porosity, which enables it to quickly adsorb the water in the silt during the solidification process and promote the rapid hydration reaction of other active components in the solidifying agent. The lithium slag with a high specific surface area provides more reaction interfaces, accelerating the formation of C-S-H gel and other hydration products, thus significantly improving the early strength of the solidified soil. In addition, the pore structure in the lithium slag is filled with dense hydration products during the solidification process, further reducing the porosity of the solidified soil, enhancing the compactness of the material, and significantly reducing the permeability coefficient. Therefore, the solidifying agent incorporated with lithium slag exhibits a more excellent solidifying effect.

[0064] It can be seen from the results of Comparative Example 3 that when adding a certain amount of carbonized steel slag powder to the solidifying agent of solid waste cementitious material, its performance is better than that of the solidifying agent without carbonized steel slag powder when solidifying high water content silt. This is mainly because the carbonized steel slag powder is mainly composed of calcium carbonate phase, which can play the role of ettringite stabilizer during the solidification process. Ettringite, as one of the main hydration products in the solidified soil, is prone to performance fluctuations due to environmental changes. The calcium carbonate in the carbonized steel slag powder can interact with ettringite to form a more stable structure, reducing the volume change and porosity in the solidified soil, thereby improving the strength of the material and reducing the permeability coefficient. This stabilizing effect ensures that the mechanical properties and durability of the solidified soil are significantly improved under high water content conditions.

[0065] It can be seen from the results of Comparative Example 4 that reducing the dosage of the solidifying agent with a large amount of solid waste silt will significantly reduce the performance of the solidified soil. This is because the solid waste cementitious material plays a key cementitious and filling role during the silt solidification process, providing the necessary strength and compactness. When the dosage of the solidifying agent decreases, the amount of cementitious products that can be formed in the solidified soil decreases, resulting in an insufficiently dense structure and an increase in porosity, thereby causing the strength of the solidified soil to decrease and the permeability coefficient to increase. Therefore, adjusting the appropriate dosage of the solidifying agent for different silts is crucial for ensuring the comprehensive performance of the solidified soil.

Claims

1. A sludge curing agent with a high content of solid waste, characterized in that, It comprises raw materials in the following parts by mass:

2. The sludge solidifying agent for high-volume solid waste according to claim 1, characterized in that: The granulated blast furnace slag described is of S95 grade, with the specific surface area of the blast furnace slag > 450 m 2 / kg, the sum of the mass fractions of CaO, SiO2, MgO and Al2O3 in the blast furnace slag ≥ 85%, and the 28-day activity index of the blast furnace slag ≥ 95%.

3. The sludge solidifying agent for high-volume solid waste according to claim 1, characterized in that: The steel slag described above is one or more of ladle furnace slag, electric arc furnace reducing slag, and basic oxygen converter slag. The steel slag is subjected to heat soaking and magnetic separation for iron treatment, and the specific surface area of the steel slag > 500 m 2 / kg.

4. The sludge solidifying agent for a large amount of solid waste according to claim 1, characterized in that: The sulfate is a sulfate industrial by-product generated in the industrial production process. The sulfate is one or more of phosphogypsum, desulfurized gypsum nitrate, and mirabilite gypsum. The mass fraction of CaSO4 in the sulfate is ≥75%.

5. The sludge solidifying agent for high-volume solid waste according to claim 1, characterized in that: The lithium slag mentioned above is an industrial solid waste generated in the process of producing lithium carbonate from spodumene by the sulfuric acid method. The specific surface area of the lithium slag is > 1000 m 2 / kg, and the sum of the mass fractions of SiO2 and Al2O3 in the lithium slag is ≥ 70%.

6. The sludge curing agent for high-volume solid waste according to claim 3, characterized in that: The carbonized steel slag powder is obtained by treating steel slag with a moisture content of 5-15% after pretreatment with industrial waste gas of CO2 with a concentration of 10-40% for 6-24 hours, and the carbon adsorption amount is ≥8%.

7. The sludge solidifying agent for a large amount of solid waste according to claim 1, characterized in that: The 28-day compressive strength of the P.O425 cement is ≥42.5 MPa.

8. The preparation method of the sludge solidifying agent according to any one of claims 1-7, characterized in that, It comprises the following steps: Step 1. Uniformly mix granulated blast furnace slag, steel slag, sulfate, lithium slag, carbonated steel slag powder, and P.O 425 cement to obtain a solid waste cementitious material. Place the solid waste cementitious material into a planetary ball mill and grind it until the specific surface area of the solid waste cementitious material > 800 m 2 / kg; Step 2: Mix the solid waste cementitious material and water in a mass ratio of 1:1 by mass to obtain a sludge curing agent with a large amount of solid waste incorporated.

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