A method for the resource utilization of dredged soil and solid waste building materials

Abstract

The present invention discloses a method for the resource utilization of dredged soil and solid waste building materials products, which relates to the field of solid waste treatment. The present invention reduces the overall moisture content of the materials through collaborative treatment in the solid waste storage area, and uses a curing agent to improve the properties of the dredged soil and optimize the activity of the dredged soil. After treatment, it is applied to building materials production, so as to realize the comprehensive utilization of the dredged soil, and the obtained building materials products have the advantages of high strength, large consumption, and economic benefits, and can realize the harmless resource utilization of the dredged soil.

Description

Technical Field

[0001] The present invention relates to the field of solid waste treatment, and particularly to a method for resource utilization of dredged soil and solid waste building materials products. Background Art

[0002] A large amount of garbage and sludge is easily accumulated in rivers. The treatment of dredged soil is difficult to dispose of. The existing treatment means of dredged soil are simple. Most of them are dumped into the sea, which affects the marine ecological environment; a small part is landfilled or stacked in the open air, resulting in problems such as landslides and deterioration of the surrounding ecological environment; at present, the requirements for reclamation are increasing, and the demand for dredged soil dumping is increasing day by day. The dredged soil continues to accumulate, and the disposal problem of dredged soil needs to be urgently addressed. The resource treatment of dredged soil has become an important direction for the subsequent comprehensive disposal of dredged soil, such as reusing dredged soil in backfilling projects, embankment materials, road projects, and bricks, cement, concrete, ceramsite, etc. in building materials. However, problems such as high water content, easy agglomeration, and low activity of dredged soil will seriously affect its utilization performance and need to be further treated to stimulate its activity.

[0003] In Chinese Patent Application CN115745332A, the ballast water during ship operation is used for desalination of dredged soil. Through methods such as soaking and washing, its salt content is reduced. However, the water content of the dredged soil is relatively high after washing and it cannot be further utilized at the back end; in Chinese Patent Application CN115088662B, the dredged soil is dried, ground, sieved, and then mixed with a gelling material and formed by a mold, and finally fired at 1000-1500˚C. The treatment process is complex, the disposal cost is high, it is difficult to achieve large-scale comprehensive utilization, and the full-process resource utilization of dredged soil cannot be truly realized. Summary of the Invention

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

[0005] A method for resource utilization of dredged soil includes the following steps:

[0006] S1. Mix 70-90% of dredged soil, 0-20% of fly ash, 0-20% of slag, and 4-10% of a 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 for pressing to form a green body, and a brick-shaped green body is obtained; 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;

[0007] S2. Send the green body into a reaction kettle, introduce steam for hydrothermal reaction, and obtain building materials products after the hydrothermal reaction ends.

[0008] Preferably, by weight, 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. After mixing them evenly, grind them until the average particle size reaches below 0.1 mm.

[0009] Furthermore, the admixture ratio of the curing agent is 4 - 6% of the mass of the mixture.

[0010] Furthermore, the pressure for pressing into a green body in S1 is 5 - 20 MPa.

[0011] Furthermore, the pressure for the hydrothermal reaction in S1 is 1 - 2 MPa, and the time for the hydrothermal reaction is 2 - 12 h.

[0012] The present invention also provides a solid waste building material product, which is prepared by the utilization method described in any one of the above.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The present invention effectively improves problems such as high water content, easy agglomeration, low strength, and strong water absorption of dredged soil by using a curing agent, realizes the stable treatment of dredged soil raw materials, synergistically treats the modified dredged soil with solid wastes such as slag and fly ash, supplements a certain amount of lime and water, stirs to obtain a mixture according to a specific ratio, and can convert the treated dredged soil into high-strength building material products through a hydrothermal process. The final products have high strength and excellent frost resistance.

[0015] (2) The present invention effectively improves the strength performance and water resistance performance of the products through the synergistic treatment of multiple solid wastes and the improvement effect of the dredged soil curing agent. By using the modified dredged soil as the main raw material for hydrothermal building materials, the high-ratio comprehensive utilization of dredged soil is realized, and the dredged soil is further converted into building materials, realizing the disposal of dredged soil while synergistically disposing of large amounts of solid wastes, which is beneficial to the comprehensive disposal of industrial solid wastes.

[0016] (3) The present invention combines dredged soil with hydrothermal technology. The solid waste building material 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 operation cost of factory production, which is beneficial to the engineering promotion of preparing building material products from dredged soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the hydrothermal product of Example 3.

[0018] Figure 2 It is the hydrothermal product of Example 9. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. However, the implementation modes of the present invention are not limited thereto. The equipment not described in detail in the embodiments is usually general equipment or standard equipment, and can be obtained from commercial channels without special instructions. In the following text, 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.

[0020] Example 1: This example provides a method for resource utilization of dredged soil, including the following steps:

[0021] 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 mixed powder material into the digestion system for digestion for 40 minutes; send the digested material into the mechanical forming system; press and form a green body in a mold, with a compaction pressure of 7 MPa, and obtain a green body with a brick shape of 200 mm * 95 mm * 53 mm;

[0022] S2. Send the green body into the reaction kettle, introduce steam, and carry out hydrothermal reaction at a pressure of 1.2 MPa for 6 h. After the hydrothermal reaction is completed, open the reaction kettle when the temperature of the reaction kettle drops to 50 °C, and obtain building materials products without curing.

[0023] Composition of the curing agent: By weight, the preparation raw materials of the curing agent 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.

[0024] The curing agent is prepared by the following method: Mix secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride, and anhydrous gypsum, and then grind them to an average particle size of less than 0.1 mm.

[0025] Example 2: This example provides a method for resource utilization of dredged soil, including the following steps:

[0026] 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 mixed powder material into the digestion system for digestion for 40 minutes; send the digested material into the mechanical forming system; press and form a green body in a mold, with a compaction pressure of 7 MPa, and obtain a green body with a brick shape of 200 mm * 95 mm * 53 mm;

[0027] S2. Feed the green body into the autoclave, introduce steam, and conduct hydrothermal reaction at a pressure of 1.2 MPa for 6 hours. After the hydrothermal reaction is completed, open the autoclave when the temperature of the autoclave drops to 50 °C, and a building material product can be obtained without curing.

[0028] Composition of the curing agent: By weight, 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.

[0029] The curing agent is prepared by the following method: Mix secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride, and anhydrous gypsum, and then grind them until the average particle size reaches below 0.1 mm.

[0030] Example 3: This example provides a method for resource utilization of dredged soil, including the following steps:

[0031] 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 feed the mixed powder material into the digestion system for digestion for 40 minutes; the digested material is fed into the mechanical forming system; press in a mold to form a green body, with a compaction pressure of 7 MPa, and a green body with a brick shape of 200 mm * 95 mm * 53 mm is obtained;

[0032] S2. Feed the green body into the autoclave, introduce steam, and conduct hydrothermal reaction at a pressure of 1.2 MPa for 6 hours. After the hydrothermal reaction is completed, open the autoclave when the temperature of the autoclave drops to 50 °C, and a building material product can be obtained without curing.

[0033] Composition of the curing agent: By weight, 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.

[0034] The curing agent is prepared by the following method: Mix secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride, and anhydrous gypsum, and then grind them until the average particle size reaches below 0.1 mm.

[0035] Example 4: This example is basically the same as Example 3, the difference is: In this example, the proportion of the curing agent in the mixture is 6%.

[0036] Example 5: This example is basically the same as Example 3, the difference is: In this example, the proportion of the curing agent in the mixture is 10%.

[0037] Example 6: This example is basically the same as Example 3, except that: secondary fly ash is not added to the curing agent in this example.

[0038] Example 7: This example is basically the same as Example 3, except that: quicklime is not added to the curing agent in this example.

[0039] Example 8: This example is basically the same as Example 3, except that: naphthalene series water reducing agent is not added to the curing agent in this example.

[0040] Example 9: This example is basically the same as Example 3, except that: anhydrous calcium chloride is not added to the curing agent in this example.

[0041] Example 10: This example is basically the same as Example 3, except that: calcium hydroxide is not added to the curing agent in this example.

[0042] 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.

[0043] Performance Test

[0044] 1. Compressive strength: Measured according to GBT4111 - 2013 "Test Methods for Concrete Blocks and Bricks";

[0045] 2. Water absorption rate: Measured according to GBT4111 - 2013 "Test Methods for Concrete Blocks and Bricks";

[0046] Compressive Strength Test:

[0047] The compressive strength is measured according to GBT4111 - 2013 "Test Methods for Concrete Blocks and Bricks", and the strength is measured after the test specimens are naturally air - dried for 24h.

[0048] I. Test Steps

[0049] 1. Measure the length and width dimensions of the connecting surface or the compressed surface of each specimen twice, and take their average values respectively, accurate to 1mm.

[0050] 2. Place 10 specimens flat in the center of the pressure plate respectively, apply load perpendicular to the compressed surface, which should be uniform and stable without impact or vibration. The loading speed is (5 ± 0.5) kN / s until the specimens are damaged, and record the maximum failure load F (unit: N) respectively.

[0051] II. Calculation of Test Results

[0052] 1. Calculate the compressive strength values of 10 bricks respectively according to the following formula, accurate to 0.1MPa.

[0053]

[0054] where f mc — Compressive strength (MPa);

[0055] F — Maximum failure load (N);

[0056] L — Length of the compression surface (joint surface) (mm);

[0057] B — Width of the compression surface (joint surface) (mm).

[0058] Calculate the average compressive strength of three to five test pieces. If the difference between the measured values and their average value is not greater than 15%, use this 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 calculate the average value with the remaining values.

[0059] Water absorption test:

[0060] 1. Immerse the test piece in water at 15°C to 25°C. The water surface should be more than 20 mm above the test piece. After 24 h, move them to a water bucket respectively and weigh the suspended immersion mass m1 of the test piece, accurate to 0.005 kg;

[0061] 2. Weigh the suspended immersion mass of the test piece. Place the weighing scale on a stable support. Place a water bucket at the midline of the support below the weighing scale. Place a hanging rack on the weighing scale chassis. Hang the test piece on the hanging rack with wire. At this time, the test piece should be away from the bottom of the water bucket and fully immersed in water. Subtract the mass of the hanging rack and wire from the weighing scale reading, which is the suspended immersion mass m1;

[0062] 3. Take the test piece out of the water, place it on a wire mesh rack to drip water for 1 min, then wipe the water on the inner and outer surfaces with a wrung dry wet cloth, and immediately weigh its mass m2 in the saturated surface dry state, accurate to 0.005 kg;

[0063] 4. Place the test piece in an electrothermal blast drying oven and dry it at a temperature of 105°C ± 5°C for at least 24 h, then weigh it every 2 h until the difference between two weighings does not exceed 0.2% of the latter weighing;

[0064] 5. After the test piece is cooled in the electrothermal blast drying oven until the temperature difference from room temperature does not exceed 20°C, take it out and immediately weigh its absolute dry mass m, accurate to 0.005 kg.

[0065]

[0066] w — Water absorption of the test piece, %;

[0067] m1 — Mass of the test piece in the saturated surface dry state, in kilograms (kg);

[0068] m——The oven-dry mass of the test piece, unit: kilogram (kg);

[0069] The specific test results are shown in Table 1

[0070] Table 1 Performance test results of examples and comparative examples

[0071]

[0072] In Examples 1-5, with the change of the dosage of the dredged soil curing agent, the compressive strength of the product increased rapidly and then gradually stabilized, and the water absorption decreased and then gradually stabilized; this is because the main functions of the dredged soil curing agent are to improve the dispersion of the dredged soil, improve the material state, promote the hydrothermal reaction, and improve the water resistance. With the increase of the dosage of the curing agent, the strength of the product increased significantly, and at the same time, the water resistance performance was significantly improved, and the overall water absorption decreased significantly. When the dosage of the curing agent reached 4%, the overall performance of the product was good and the water absorption was low; further increasing the dosage of the curing agent had a smaller improvement and the overall tended to be stable. It may be because the curing agent initially realizes the overall dispersion of the raw materials through fly ash, uses the dehydration performance of quicklime to "break" and disperse the large particles of the dredged soil, and at the same time it is found that the naphthalene-based water reducer can further improve the adhesion of the fine particles of the dredged soil to the dredged soil particles to avoid further agglomeration of the dredged soil; anhydrous calcium chloride can improve the unstable calcium in the dredged soil, and can also quickly promote the dehydration of lime and rapidly release heat. On the one hand, it controls the water content and material state of the dredged soil by combining lime with water, and on the other hand, it realizes partial water evaporation through the increase of temperature to further control the water content; calcium hydroxide and anhydrous gypsum are used as activity activators to destroy the clay particle components inside the dredged soil, release the internal bound water, thereby releasing the internal silicate minerals, cooperate with fly ash to effectively improve the active composition of the dredging, supplement the silicon activity inside the muck, and at the same time use the components of calcium hydroxide and anhydrous gypsum to provide calcium components for the subsequent hydrothermal reaction, further promoting the hydrothermal reaction to achieve further improvement of the product performance.

[0073] 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 decreased and the water absorption increased; under the condition of not adding fly ash, the curing agent as a whole can still play a certain role in dispersion and strength improvement, but since fly ash is the main component for the dispersion and activity supplement of the dredged soil, without adding fly ash, the product cannot achieve the change of the properties of the dredged soil, and the improvement effect of the overall state of the dredged soil is not good; and because fly ash also serves as the supplement of the silicon component of the dredged soil, under the condition of not adding fly ash, the activity of the dredged soil is limited, resulting in a decrease in the degree of the subsequent hydrothermal reaction, leading to a decrease in the product performance and a decrease in the water resistance, and an increase in the water absorption.

[0074] In Examples 3 and 7, with the change of the curing agent composition, under the condition of not adding quicklime, the compressive strength of the product decreases and the water absorption rate increases; this is because quicklime can absorb the internal moisture of the dredged soil and generate heat at the same time, realizing the evaporation of part of the moisture in the dredged soil; without adding quicklime, the improvement of the curing agent is relatively gentle, and the anhydrous calcium chloride at the back end can only play the role of removing stability without quicklime, and the overall effect of the curing agent is significantly weakened, resulting in the decline of the product performance and the increase of the water absorption rate.

[0075] In Examples 3 and 8, with the change of the curing agent composition, under the condition of not adding naphthalene-based water reducer, the compressive strength of the product decreases and the water absorption rate increases; this is because the main function of the naphthalene-based water reducer is to adsorb on the surface of the dredged soil particles through chemical action, making the surface of the dredged soil particles carry the same kind of charge, forming an electrostatic repulsion effect, disintegrating the internal flocculent structure, promoting the mutual dispersion of the dredged soil particles, and thus releasing the free water wrapped by the dredged soil to participate in the mixing of the mixture, effectively improving the uniformity of the mixture. Moreover, the naphthalene-based water reducer is more soluble in water and can quickly play its adsorption role inside the system. While improving the charge layer of the dredged soil, it can form a thin film on the surface of the dredged soil, thus effectively controlling the moisture and avoiding further absorption of moisture by the dredged soil, truly realizing the dispersion and locking of moisture, and its improvement effect on the dredged soil is better, and finally the overall product performance is good.

[0076] In Examples 3 and 9, with the change of the curing agent composition, under the condition of not adding anhydrous calcium chloride, the compressive strength of the product decreases and the water absorption rate increases; this is because the chloride ions in calcium chloride can react with calcium ions to form soluble calcium chloride, increasing the solubility of calcium ions in the solution, accelerating the diffusion of calcium and hydroxide ions, thus accelerating the digestion process of calcium oxide and increasing the digestion conversion rate of free calcium oxide, thereby improving the state of the mixture, and at the same time significantly improving the slaking effect of quicklime to achieve further evaporation of moisture; in Example 9, the product cracked due to the non-use of anhydrous calcium chloride. For specific photos, see Appendix Figure 2 ;

[0077] In Examples 3 and 10, with the change of the curing agent composition, under the condition of not adding calcium hydroxide, the compressive strength of the product decreases and the water absorption rate increases; this is because adding fly ash at the front end can supplement the silica activity of the product to a certain extent, but the overall calcium activity is low. By adding calcium hydroxide to supplement part of the calcium, and at the same time improving the activity of the muck through its alkalinity to promote the calcium activity inside the dredged soil, the calcium activity is supplemented.

[0078] In Examples 3 and 11, with the change of the binder composition, under the condition of not adding anhydrous gypsum, the compressive strength of the product decreases and the water absorption rate increases. This is because anhydrous gypsum absorbs some of the moisture inside the product through calcium sulfate substances, and combines with 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, making part of the product consolidated, improving the initial performance of the product, achieving a preliminary transition of strength, and then improving the backend performance through calcium hydroxide, achieving an increase in the strength of the product and an improvement in water resistance.

[0079] The above description of the embodiments is to facilitate the understanding and application of the present invention by those of ordinary skill 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 effort. Therefore, the present invention is not limited to the embodiments described herein. The improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for the resource utilization of dredged soil, characterized in that, The method includes 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 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 for pressing to obtain a brick-shaped blank, and the pressure for pressing the blank is 5 - 20 MPa; among them, 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. The preparation raw materials are composed of 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. Send the blank into a reaction kettle, introduce steam for hydrothermal reaction, and obtain a building material product after the hydrothermal reaction ends.

2. The dredged soil resource utilization method according to claim 1, wherein Mix secondary fly ash, quicklime, naphthalene-based water reducer, calcium hydroxide, anhydrous calcium chloride and anhydrous gypsum and grind them to an average particle size of less than 0.1 mm.

3. The dredged soil resource utilization method according to claim 1, characterized in that In S2, the pressure of the hydrothermal reaction is 1 - 2 MPa, and the time of the hydrothermal reaction is 2 - 12 h.

4. A solid waste building material product, characterized in that, It is prepared by the method for resource utilization of dredged soil according to any one of claims 1 to 3.

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