Resource utilization method of dredged soil and solid waste building material product

Abstract

The invention discloses a dredged soil resource utilization method and a solid waste building material product, and relates to the field of solid waste treatment. The overall water content of the material is reduced through cooperative treatment of solid waste, the property of the dredged soil is improved by using the curing agent, the activity of the dredged soil is optimized, and the treated dredged soil is applied to building material production, so that comprehensive utilization of the dredged soil is realized, and the obtained building material product has the advantages of high strength, high consumption and economic benefit and has a wide application prospect. And harmless resource utilization of the dredged soil can be realized.

Description

Technical Field

[0001] The present invention relates to the field of solid waste treatment, and in particular to a method for resource utilization of dredged soil and a solid waste building material product. Background Art

[0002] There are many rivers in my country, which provide people with sufficient water resources and also provide a new way for cargo transportation. However, a large amount of garbage and sludge can easily accumulate in rivers. At present, the annual dredged soil produced in Chinese cities is nearly 30 million tons, but the treatment of dredged soil is difficult. At present, about 80% of dredged soil has not been stabilized. The existing dredged soil treatment methods are simple, and most of them are dumped into the sea, which affects the marine ecological environment; a small part of them are landfilled and piled in the open air, which has problems such as landslides and deterioration of the surrounding ecological environment. At this stage, the requirements for reclamation are increasing, and the demand for dredged soil dumping is increasing. Dredged soil continues to accumulate, and the disposal of dredged soil needs to be dealt with urgently. With the advancement of the sustainable development strategy, the resource treatment of dredged soil has become an important direction for the subsequent comprehensive treatment of dredged soil, such as reusing dredged soil in backfill projects, embankment materials, road projects, and bricks, cement, concrete, ceramsite, etc. in building materials. However, the high water content, easy agglomeration, and low activity of dredged soil will seriously affect its utilization performance, and further treatment is needed to stimulate its activity.

[0003] In Chinese patent application CN115745332A, ballast water from ship operation is used to desalinate dredged soil. The salt content is reduced by soaking and washing. However, the moisture content of the dredged soil after washing is high and cannot be further utilized at the back end. In Chinese patent application CN115088662B, the dredged soil is dried, ground, sieved, and then pressed into shape by a mold with a cementitious material. Finally, it is fired at 1000-1500˚C. The processing process is complicated and the disposal cost is high. It is difficult to achieve large-scale comprehensive utilization and cannot truly realize the full-process resource utilization of dredged soil. Summary of the invention

[0004] Based on this, it is necessary to provide a method for resource utilization of dredged soil and solid waste building materials products to address the above-mentioned technical problems, so as to realize the full-process resource utilization of dredged soil.

[0005] A method for resource utilization of dredged soil comprises the following steps: S1. Mix 70-90% of dredged soil, 0-20% of fly ash, 0-20% of slag and 4-10% of curing agent evenly, then add 6-10% of lime, and add appropriate water according to the moisture content of the mixture to control the moisture content of the system to 17% to obtain a mixture; the mixture is sent into a mold to be pressed to form a green body, and a brick-shaped green body is obtained by pressing; wherein the sum of the weight percentages of dredged soil, fly ash, slag and lime is 100%, and the mixing ratio of the curing agent is the proportion of the mass of the mixture; S2. The green body is placed in a reactor, and water vapor is introduced to perform a hydrothermal reaction. After the hydrothermal reaction is completed, a building material product is obtained.

[0006] Preferably, the raw materials include, by weight: 60 parts of secondary fly ash, 2 parts of quicklime, 2 parts of naphthalene-based water reducer, 5 parts of calcium hydroxide, 5 parts of anhydrous calcium chloride, and 5 parts of anhydrous gypsum. They are mixed evenly and ground to an average particle size of less than 0.1 mm.

[0007] Furthermore, the mixing ratio of the curing agent is 4-6% of the mass of the mixture.

[0008] Furthermore, the pressure for pressing the green body in S1 is 5-20 MPa.

[0009] Furthermore, the pressure of the hydrothermal reaction in S1 is 1-2 MPa, and the time of the hydrothermal reaction is 2-12 h.

[0010] The present invention also provides a solid waste building material product, which is prepared by any of the above-mentioned utilization methods.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention utilizes a curing agent to effectively improve the problems of high water content, easy agglomeration, low strength, and strong water absorption of dredged soil, thereby achieving stable treatment of dredged soil raw materials. The modified dredged soil is synergistically treated with solid wastes such as slag and fly ash, and a certain amount of lime and water are added and stirred in a specific proportion to obtain a mixture. The treated dredged soil can be converted into a high-strength building material product through a hydrothermal process. The final product has high strength and excellent frost resistance.

[0012] (2) The present invention uses the synergistic treatment of multiple solid wastes and the improvement effect of dredged soil solidifier to effectively improve the strength and water resistance of the product. The modified dredged soil is used as the main raw material for hydrothermal building materials to achieve high-volume comprehensive utilization of dredged soil, further convert the dredged soil into building materials, and achieve the synergistic treatment of large amounts of solid waste while disposing of dredged soil, which is beneficial to the comprehensive treatment of industrial solid waste.

[0013] (3) The present invention combines dredged soil with hydrothermal technology, and the solid waste building materials products have the advantages of large consumption and high economic benefits. It not only realizes the high-value and efficient utilization of dredged soil, but also reduces the cost of factory production and operation, which is conducive to the engineering promotion of dredged soil preparation of building materials products. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the hydrothermal product of Example 3.

[0015] Figure 2 This is the hydrothermal product of Example 9. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with the accompanying drawings and examples, but the embodiments of the present invention are not limited thereto. The equipment not described in detail in the examples is generally general equipment or standard equipment, and can be obtained from commercial sources unless otherwise specified. In the following, the sum of the weight percentages of dredged soil, fly ash, slag and lime is 100%, and the percentage of the curing agent refers to the weight ratio of the curing agent to the mass of the mixture.

[0017] Embodiment 1: This embodiment provides a method for resource utilization of dredged soil, comprising the following steps: S1. Mix 70% of dredged soil, 10% of fly ash, 10% of slag and 1% of curing agent evenly, add 10% of lime and mix, add appropriate water according to the moisture content of the mixture to control the moisture content of the system to 17% and obtain a mixture; then send the powdered and mixed materials into a digestion system for digestion for 40 minutes; the digested materials are sent to a mechanical forming system; press in a mold to form a green body, the compaction pressure is 7MPa, and the green body with a brick shape of 200mm*95mm*53mm is obtained by pressing; S2. The green body is placed in a reactor, water vapor is introduced, and a hydrothermal reaction is carried out at a pressure of 1.2 MPa for 6 hours. After the hydrothermal reaction is completed, the reactor is opened when the temperature of the reactor drops to 50°C, and the building material product is obtained without maintenance.

[0018] Curing agent composition: Curing agent is calculated by weight, and the raw materials for preparation include: 60 parts of secondary fly ash, 2 parts of quicklime, 2 parts of naphthalene-based water reducer, 5 parts of calcium hydroxide, 5 parts of anhydrous calcium chloride, and 5 parts of anhydrous gypsum.

[0019] The curing agent is prepared by the following method: secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride and anhydrous gypsum are mixed and ground to an average particle size of less than 0.1 mm.

[0020] Embodiment 2: This embodiment provides a method for resource utilization of dredged soil, comprising the following steps: S1. Mix 70% of dredged soil, 10% of fly ash, 10% of slag and 2% of curing agent evenly, add 10% of lime and mix, add appropriate water according to the moisture content of the mixture to control the moisture content of the system to 17% and obtain a mixture; then send the powdered and mixed materials into a digestion system for digestion for 40 minutes; the digested materials are sent to a mechanical forming system; press in a mold to form a green body, the compaction pressure is 7MPa, and the green body with a brick shape of 200mm*95mm*53mm is obtained by pressing; S2. The green body is placed in a reactor, water vapor is introduced, and a hydrothermal reaction is carried out at a pressure of 1.2 MPa for 6 hours. After the hydrothermal reaction is completed, the reactor is opened when the temperature of the reactor drops to 50°C, and the building material product is obtained without maintenance.

[0021] Curing agent composition: Curing agent is calculated by weight, and the raw materials for preparation include: 60 parts of secondary fly ash, 2 parts of quicklime, 2 parts of naphthalene-based water reducer, 5 parts of calcium hydroxide, 5 parts of anhydrous calcium chloride, and 5 parts of anhydrous gypsum.

[0022] The curing agent is prepared by the following method: secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride and anhydrous gypsum are mixed and ground to an average particle size of less than 0.1 mm.

[0023] Embodiment 3: This embodiment provides a method for resource utilization of dredged soil, comprising the following steps: S1. Mix 70% of dredged soil, 10% of fly ash, 10% of slag and 4% of curing agent evenly, add 10% of lime and mix, add appropriate water according to the moisture content of the mixture to control the moisture content of the system to 17% and obtain a mixture; then send the powdered and mixed materials into a digestion system for digestion for 40 minutes; the digested materials are sent to a mechanical forming system; press in a mold to form a green body, the compaction pressure is 7MPa, and the green body with a brick shape of 200mm*95mm*53mm is obtained by pressing; S2. The green body is placed in a reactor, water vapor is introduced, and a hydrothermal reaction is carried out at a pressure of 1.2 MPa for 6 hours. After the hydrothermal reaction is completed, the reactor is opened when the temperature of the reactor drops to 50°C, and the building material product is obtained without maintenance.

[0024] Curing agent composition: Curing agent is calculated by weight, and the raw materials for preparation include: 60 parts of secondary fly ash, 2 parts of quicklime, 2 parts of naphthalene-based water reducer, 5 parts of calcium hydroxide, 5 parts of anhydrous calcium chloride, and 5 parts of anhydrous gypsum.

[0025] The curing agent is prepared by the following method: secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride and anhydrous gypsum are mixed and ground to an average particle size of less than 0.1 mm.

[0026] Embodiment 4: This embodiment is basically the same as Embodiment 3, except that: in this embodiment, the proportion of curing agent in the mixture is 6%.

[0027] Embodiment 5: This embodiment is basically the same as embodiment 3, except that the proportion of curing agent in the mixture in this embodiment is 10%.

[0028] Example 6: This example is basically the same as Example 3, except that no secondary fly ash is added to the curing agent in this example.

[0029] Embodiment 7: This embodiment is basically the same as embodiment 3, except that quicklime is not added to the curing agent in this embodiment.

[0030] Embodiment 8: This embodiment is basically the same as Embodiment 3, except that no naphthalene-based water reducer is added to the curing agent in this embodiment.

[0031] Embodiment 9: This embodiment is basically the same as Embodiment 3, except that anhydrous calcium chloride is not added to the curing agent in this embodiment.

[0032] Embodiment 10: This embodiment is basically the same as embodiment 3, except that: no calcium hydroxide is added to the curing agent in this embodiment.

[0033] Example 11: This example is basically the same as Example 3, except that anhydrous gypsum is not added to the curing agent in this example.

[0034] Performance Testing 1. Compressive strength: measured according to GBT4111-2013 "Test methods for concrete blocks and bricks"; 2. Water absorption rate: measured according to GBT4111-2013 "Test methods for concrete blocks and bricks"; Compressive strength test: The compressive strength is measured in accordance with GBT4111-2013 “Test methods for concrete blocks and bricks”, and the strength is measured after the test pieces are naturally air-dried for 24 hours.

[0035] 1. Test steps 1. Measure the length and width of each specimen’s connection surface or pressure surface twice, and take their average values, accurate to 1mm.

[0036] 2. Place 10 specimens flat in the center of the pressure plate and apply load perpendicular to the pressure surface. The load should be uniform and stable without impact or vibration. The loading speed is (5 ± 0.5) kN / s until the specimen is destroyed. Record the maximum failure load F (in N) respectively.

[0037] 2. Calculation of test results 1. Calculate the compressive strength of 10 bricks according to the following formula, accurate to 0.1MPa.

[0038]

[0039] Where f mc —compressive strength (MPa); F—maximum failure load (N); L—length of the pressure surface (connection surface) (mm); B—Width of the pressure surface (connection surface) (mm).

[0040] Calculate the average compressive strength of three to five test blocks. If the difference between the measured values ​​and their average value is no more than 15%, use the average value as the compressive strength; if the difference between a certain value and the average value is greater than 15%, this value should be discarded and the average value should be calculated with the remaining values.

[0041] Water absorption test: 1. Immerse the specimens in water at 15℃~25℃. The water surface should be at least 20mm above the specimens. After 24 hours, move them to buckets and weigh the suspended mass m1 of the specimens to an accuracy of 0.005kg. 2 Weigh the suspended mass of the test piece. Place the scale on a stable support, and place a bucket below the support at the point where it coincides with the center line of the scale. Place a hanger on the chassis of the scale, and hang the test piece on the hanger with wire. At this time, the test piece should leave the bottom of the bucket and be completely immersed in water. Subtract the mass of the hanger and wire from the scale reading to get the suspended mass m1; 3. Take the specimen out of the water, place it on a wire rack and drip water for 1 minute, then wipe off the water on the inner and outer surfaces with a wrung-out wet cloth, and immediately weigh its mass m2 in the saturated dry state, accurate to 0.005kg; 4. Place the specimen in an electric blast drying oven and dry it at 105℃±5℃ for at least 24h, then weigh it every 2h until the difference between the two weighings does not exceed 0.2% of the latter weighing; 5. After the test piece has cooled down to a temperature no more than 20°C below room temperature in the electric blast drying oven, take it out and immediately weigh its absolute dry mass m to an accuracy of 0.005kg.

[0042]

[0043] w——water absorption rate of the specimen, %; m1——the mass of the saturated surface of the specimen in dry state, in kilograms (kg); m——absolute dry mass of the specimen, in kilograms (kg); The specific test results are shown in Table 1 Table 1 Performance test results of examples and comparative examples

[0044] In Examples 1-5, as the dosage of the dredged soil solidifying agent changes, the compressive strength of the product increases rapidly and then gradually stabilizes, and the water absorption rate decreases and then gradually stabilizes; this is because the main function of the dredged soil solidifying agent is to improve the dispersion of dredged soil, improve the material state, promote hydrothermal reaction, and improve water resistance. With the increase in the dosage of the solidifying agent, the strength of the product increases significantly, the water resistance is significantly improved, and the overall water absorption rate decreases significantly. When the dosage of the solidifying agent reaches 4%, the overall product performance is good and the water absorption rate is low; further increasing the dosage of the solidifying agent will increase less, and the overall trend is stable. It may be because the curing agent initially achieves overall raw material dispersion through fly ash, and uses the dehydration performance of quicklime to achieve "crushing" and dispersion of large particles of dredged soil. At the same time, it is found that naphthalene-based water reducers can further improve the adhesion of fine particles of dredged soil to dredged soil particles to avoid further agglomeration of dredged soil; anhydrous calcium chloride can improve the unstable calcium in dredged soil, and can also quickly promote the dehydration of lime and release heat quickly. On the one hand, the water content and material state of dredged soil are controlled by combining lime with water, and on the other hand, the water content is further controlled by evaporating part of the water by increasing the temperature; calcium hydroxide and anhydrous gypsum act as active stimulants, destroying the clay particle components inside the dredged soil, releasing internal bound water, thereby releasing internal silicate minerals, and effectively improving the active composition of dredging with fly ash. While supplementing the internal silica activity of the slag, calcium hydroxide and anhydrous gypsum components are used to provide calcium components for the rear-end hydrothermal reaction, further promoting the hydrothermal reaction and achieving further improvement in product performance.

[0045] In Examples 3 and 6, with the change of the curing agent composition, under the condition of not adding fly ash, the compressive strength of the product decreases and the water absorption rate increases; under the condition of not adding fly ash, the curing agent as a whole can still play a certain dispersing and strengthening effect, but because fly ash is the main component for dispersing and supplementing the activity of dredged soil, the product cannot achieve the change of the properties of dredged soil without adding fly ash, and the improvement effect of the overall state of dredged soil is not good; and because fly ash is also used as a supplement to the siliceous component of dredged soil, under the condition of not adding fly ash, the activity of dredged soil is limited, thereby reducing the degree of hydrothermal reaction at the back end, resulting in a decrease in product performance, a decrease in water resistance, and an increase in water absorption.

[0046] In Examples 3 and 7, with the change of the curing agent composition, without adding quicklime, the compressive strength of the product decreases and the water absorption rate increases; this is because quicklime can absorb the moisture inside the dredged soil and generate heat at the same time, thereby evaporating part of the moisture in the dredged soil; without adding quicklime, the improvement of the curing agent is relatively slow, and the anhydrous calcium chloride at the back end can only play a role in removing stability without quicklime, and the overall effect of the curing agent is significantly weakened, resulting in a decrease in product performance and an increase in water absorption.

[0047] In Examples 3 and 8, with the change of the curing agent composition, the compressive strength of the product decreases and the water absorption rate increases without adding a naphthalene-based water reducer. This is because the main function of the naphthalene-based water reducer is to be adsorbed on the surface of dredged soil particles through chemical action, so that the surface of the dredged soil particles carries the same charge, forming an electrostatic repulsion effect, disintegrating the internal flocculation structure, and promoting the mutual dispersion of the dredged soil particles, thereby releasing the free water wrapped by the dredged soil, participating in the mixing of the mixture, and effectively improving the uniformity of the mixture. In addition, the naphthalene-based water reducer is more soluble in water, can quickly exert its adsorption effect within the system, improve the dredged soil charge layer, and form a thin film on the dredged soil surface, thereby effectively controlling the moisture and preventing the moisture from being further absorbed into the dredged soil, truly realizing the dispersion and locking of the moisture, and having a better improvement effect on the dredged soil, and finally the overall product performance is good.

[0048] In Examples 3 and 9, as the curing agent composition changes, without adding anhydrous calcium chloride, the compressive strength of the product decreases and the water absorption rate increases; this is because the chloride ions in the calcium chloride can react with the calcium ions to generate a soluble substance, calcium chloride, which increases the solubility of the calcium ions in the solution, accelerates the diffusion of calcium in the hydroxide ions, and thus accelerates the calcium oxide digestion process, increases the free calcium oxide digestion conversion rate, thereby improving the state of the mixture, and significantly improves the quicklime digestion effect to achieve further evaporation of water; and in Example 9, no anhydrous calcium chloride was used, resulting in cracking of the product, as shown in the attached photos. Figure 2 ; In Examples 3 and 10, as the curing agent composition changes, without adding calcium hydroxide, the compressive strength of the product decreases and the water absorption rate increases; this is because the addition of fly ash at the front end can supplement the silicon activity of the product to a certain extent, but the overall calcium activity is low. Calcium hydroxide is used to supplement part of the calcium, and at the same time, its alkalinity improves the activity of the slag soil and promotes the calcium activity inside the dredged soil, thereby achieving calcium activity supplementation.

[0049] In Examples 3 and 11, as the composition of the consolidating agent changes, without adding anhydrous gypsum, the compressive strength of the product decreases and the water absorption rate increases; this is because the anhydrous gypsum absorbs part of the moisture inside the product through calcium sulfate substances, and combines the physical stirring effect to break large particles into small particles through chemical action, thereby improving the state of the mixture; at the same time, gypsum can undergo an ettringite reaction inside the system, partially consolidating the product, improving the initial performance of the product, achieving a preliminary transition in strength, and subsequently achieving back-end performance improvement through calcium hydroxide, thereby achieving improved product strength and improved water resistance.

[0050] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. Those skilled in the art can make appropriate adjustments to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments described herein. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the scope of protection of the present invention.

Claims

1. A method for resource utilization of dredged soil, characterized in that: The steps include: S1. Mix 70-90% of dredged soil, 0-20% of fly ash, 0-20% of slag and 4-10% of curing agent evenly, then add 6-10% of lime, and add water according to the moisture content of the mixture to control the moisture content of the system to 17% to obtain a mixture; the mixture is sent into a mold and pressed to form a green body, and a brick-shaped green body is obtained by pressing; wherein the sum of the weight percentages of dredged soil, fly ash, slag and lime is 100%; the mixing ratio of the curing agent is the proportion of the mass of the mixture, and the curing agent is calculated by weight, and the raw materials for preparation include: 60 parts of secondary fly ash, 2 parts of quicklime, 2 parts of naphthalene-based water reducer, 5 parts of calcium hydroxide, 5 parts of anhydrous calcium chloride, and 5 parts of anhydrous gypsum; S2. The green body is placed in a reactor, and water vapor is introduced to perform a hydrothermal reaction. After the hydrothermal reaction is completed, a building material product is obtained.

2. The method for resource utilization of dredged soil according to claim 1, characterized in that: Secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride and anhydrous gypsum are mixed and ground to an average particle size of less than 0.1 mm.

3. The method for resource utilization of dredged soil according to claim 1, characterized in that: The pressure for pressing the green body in S1 is 5-20 MPa.

4. The method for resource utilization of dredged soil according to claim 1, characterized in that: The pressure of the hydrothermal reaction in S1 is 1-2 MPa, and the time of the hydrothermal reaction is 2-12 h.

5. A solid waste building material product, characterized in that: The dredged soil is prepared by the method for resource utilization of dredged soil according to any one of claims 1 to 4.

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