Method for preparing baking-free brick by co-grinding mineral powder and high-water-content sand washing mud

Abstract

The invention discloses a method for preparing a baking-free brick by co-grinding mineral powder and high-water-content sand washing mud, which specifically comprises the following steps: (1) conveying the high-water-content sand washing mud into ball milling equipment, and adding the mineral powder and a drag reducer; (2) adding a curing agent and fine aggregate into the wet-ground slurry, and carrying out homogenization treatment by using forced mixing and stirring equipment; and (3) carrying out extrusion forming on the homogenized slurry, and curing to obtain the sand washing mud-based baking-free brick. The baking-free brick is prepared from the mineral powder and the high-water-content sand washing mud through common wet grinding treatment, the raw material source is wide, and the preparation process is simple; meanwhile, the repeated step of dewatering first and then adding water and resource waste are avoided, and the environment is protected while the cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of mud treatment, and in particular relates to a method for preparing unburned bricks by co-grinding mineral powder and high-water-content sand-washing mud. Background Art

[0002] With the vigorous development of modern transportation infrastructure construction, natural river sand resources are gradually decreasing in many areas. At the same time, the market share of machine-made sand as a green building material is increasing. However, limited by the relevant standards of machine-made sand and the current production process, the wet process of machine-made sand will produce a large amount of sand washing mud with a particle size of less than 75μm. According to statistics, the reserves of sand washing mud in China are as high as billions of tons and are still growing every year. At present, external stacking and landfill are the main treatment methods for sand washing mud. Given the unsustainability of current treatment methods, a large amount of land resources are wasted, and there are even potential problems such as site swamping and landfill collapse and landslide.

[0003] Using a curing agent to solidify sand-washing mud and then use it to prepare unburned bricks is one of the important ways to achieve large-scale disposal and resource utilization of sand-washing mud. Sand-washing mud has the characteristics of high water content, high viscosity, and poor engineering properties. It is difficult to directly prepare unburned bricks. It needs to be filtered and dried to reduce the water content before unburned bricks can be prepared. A process for resource utilization of sand-washing mud is disclosed in the Chinese patent with publication number CN117886550A. The combined process of "sand and gravel aggregate separation-deep dehydration-recycling-crushing-mixing and stirring-molding" is used to prepare unburned bricks from sand-washing mud. In this process, the sand-washing mud needs to be deeply dehydrated, with a water content of 15~30wt%, which increases the difficulty and cost of disposal; and the mud cake is easy to form particles when it is broken by the crushing and granulation device, which is difficult to mix evenly with the curing agent. The internal reaction products of the unburned bricks are uneven and the structure is loose, which affects the quality. At the same time, this process does not reasonably utilize some components with potential volcanic ash activity in the sand-washing mud, resulting in a waste of resources. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing unburned bricks by co-grinding mineral powder with high-water content sand-washing mud, and to realize resource utilization of the sand-washing mud through co-wet grinding, mixed stirring and extrusion molding.

[0005] The method for preparing unburned bricks by grinding mineral powder and high-water content sand washing mud comprises the following steps: Step 1: Pump the high-water content sand washing mud in the sedimentation tank into the wet grinding system through the metering and conveying equipment, and add mineral powder and drag reducer into the wet grinding system to obtain uniformly ground mud.

[0006] Step 2: The ground mud, curing agent and fine aggregate are sent to the mixing system through the metering and conveying equipment, and are mixed evenly by the mixer to form a ready-to-use mixture.

[0007] Step 3: The evenly stirred mixture is conveyed to the molding system, extruded and molded by a brick making machine to form a brick blank, and then the brick blank is cured to obtain a washed sand-mud-based unfired brick.

[0008] The bottom of the sedimentation tank is provided with a mud discharge pipe connected to the wet grinding system, and the pipe is provided with a metering and conveying device, a drag reducing agent dosing device and a mineral powder dosing device.

[0009] In step 1, the water content of the high-water content sand washing mud is 40-60 wt%.

[0010] In step 1, the grinding equipment in the wet grinding system is a ball mill, a vertical mill or a Raymond mill.

[0011] In step 1, the drag reducer is sodium stearate, polycarboxylate water reducer or a combination of sodium stearate and polycarboxylate water reducer, and the dosage range is 0.2-0.4 wt% of the dry basis mass of the sand washing mud.

[0012] In step 1, the particle size of the mineral powder is ≤0.15 mm, and the dosage range is 10 to 40 wt% of the dry mass of the sand washing mud.

[0013] In step 2, the curing agent is quicklime, sodium hydroxide or sodium silicate, and the dosage range is 0-8 wt% of the dry basis of sand washing mud and mineral powder; the particle size of the fine aggregate is continuously graded waste concrete recycled sand or iron tailings sand between 0.15 and 1.18 mm, and the dosage range is 150-280 wt% of the powder mass.

[0014] In step 3, during the curing process, the finished bricks are transferred by a forklift to a curing area in a factory shed for natural curing or constant temperature curing in a curing room.

[0015] The basic principle of the present invention is to reduce the particle size of the mineral powder and the sand washing mud through wet grinding treatment, increase the specific surface area, which can not only improve the reaction activity, but also improve the particle filling effect; the presence of water medium makes the mechanochemical reaction more likely to occur, because the ions on the surface of the solid particles will dissolve into the water, and the ions in the liquid phase can promote the dissolution of the ions on the surface of the solid particles. In addition, the sand washing mud contains minerals such as quartz, which can be used as a grinding medium with high hardness to effectively squeeze and grind the mineral powder particles, accelerate the crushing and refinement of the mineral powder, and can cause self-hydration reaction.

[0016] Compared with the prior art, the present invention has the following characteristics and beneficial effects: (1) The present invention can achieve on-site treatment of waste generated by the wet process of machine-made sand, avoid the transportation cost and pollution in other application scenarios, and solve the secondary pollution problem caused by the discharge of sand washing mud.

[0017] (2) The present invention can realize the effective utilization of water in sand washing mud. It can preset the dehydration effect according to needs and reduce the pressure of the dehydration process. At the same time, it can avoid the repeated operation of "dehydrating first and then adding water", thereby saving water resources, manpower and energy, simplifying the process flow and improving production efficiency.

[0018] (3) The slurry components of the present invention have a high degree of homogenization, and wet grinding is beneficial to improving the uniformity of the slurry components and ensuring the quality of the product.

[0019] (4) The present invention wet-grinds the sand-washing mud and the mineral powder together, which is beneficial to improving the reaction activity and dissolution rate of the mineral powder and the sand-washing mud, generating more hydration products, and further improving the structural density of the unfired bricks and their mechanical properties.

[0020] (5) The processing system of the present invention is simplified, which can realize the integration, miniaturization and skid-mounting of the equipment, simplifying the equipment installation procedure; the entire process is carried out at room temperature, with a high safety factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a process flow chart of the present invention.

[0022] Figure 2 It is a schematic diagram of the equipment flow of the present invention.

[0023] In the figure, 1 is the sand washing sedimentation tank, 2 is the delivery pump, 3 is the ball mill equipment, 4 is the drag reducer storage tank, 5 is the mineral powder silo, 6 is the aggregate bin, 7 is the curing agent, 8 is the mixing and stirring equipment, 9 is the extrusion brick making equipment, 10 is the curing room, and 11 is the transportation of unburned bricks. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific implementation modes. The specific implementation modes are further descriptions of the present invention and do not limit the present invention in any way. Technologies identical or similar to the present invention do not exceed the protection scope of the present invention.

[0025] Examples 1-3 are further illustrations of the methods provided by the present invention; the comparative example is the same as Example 1, except that the sand washing mud and the mineral powder are wet ground separately; the comparative example 2 is the same as Example 1, except that the sand washing mud and the mineral powder are not wet ground. Embodiment 1:

[0026] (1) Wet grinding of the sand washing sludge discharged from the wet sand production process: In this embodiment, the water content of the sand washing mud to be treated is 45wt%, and the median particle size is 80.6μm. 0.2wt% sodium stearate and 30wt% mineral powder are added to the sand washing mud for wet grinding of the sand washing mud. The ball mill used for wet grinding is a horizontal ball mill, and the ball milling time is 5 min. The laser particle size detection method is used. The mud particle size after wet grinding is shown in Table 1, and the median particle size is 8.0μm.

[0027] (2) Add curing agent and fine aggregate to the wet-ground slurry and mix well: 6 wt% of sodium hydroxide was added to the wet-ground slurry, the stirring time was 3 min, and the stirring speed was 120 rpm; then 205 wt% of 0.15-1.18 mm continuously graded waste concrete recycled sand was added, the stirring time was 5 min, and the stirring speed was 80 rpm.

[0028] (3) Extruding the evenly stirred slurry into a mold and curing it: The mixed slurry is conveyed by a belt conveyor to a static brick press, and the pressure of the press is controlled at 10 MPa, and the pressure is maintained for 10 s to obtain a brick. Then the brick is transferred to the curing area of ​​the factory shed by a forklift and cured for 28 days at 20℃±2℃ and 95% humidity. Embodiment 2:

[0029] (1) Wet grinding of the sand washing sludge discharged from the wet sand production process: In this embodiment, the water content of the sand washing mud to be treated is 52wt%, and the median particle size is 91.3μm. 0.4wt% of polycarboxylic acid water reducer and 30wt% of mineral powder are added to the sand washing mud for wet grinding of the sand washing mud. The ball mill used for wet grinding is a horizontal ball mill, and the ball milling time is 10 min. The laser particle size detection method is used. The mud particle size after wet grinding is shown in Table 1, and the median particle size is 9.1μm.

[0030] (2) Add curing agent and fine aggregate to the wet-ground slurry and mix well: 8 wt% of quicklime was added to the wet-milled slurry, with a stirring time of 5 min and a stirring speed of 120 rpm; then 280 wt% of 0.15-1.18 mm continuously graded iron tailings sand was added, with a stirring time of 5 min and a stirring speed of 80 rpm.

[0031] (3) Extruding the evenly stirred slurry into a mold and curing it: The mixed slurry is conveyed by a belt conveyor to a static brick press, and the pressure of the press is controlled at 11MPa and maintained for 10 seconds to obtain a brick. Then the brick is transferred to the curing area of ​​the plant shed by a forklift and cured for 28 days at 20℃±2℃ and 95% humidity. Embodiment 3:

[0032] (1) Wet grinding of the sand washing sludge discharged from the wet sand production process: In this embodiment, the water content of the sand washing mud to be treated is 48wt%, and the median particle size is 85.3μm. 0.3wt% of polycarboxylic acid water reducer, 0.1wt% of sodium stearate and 30wt% of mineral powder are added to the sand washing mud for wet grinding of the sand washing mud. The ball mill used for wet grinding is a horizontal ball mill, and the ball milling time is 10 min. The laser particle size detection method is used. The mud particle size after wet grinding is shown in Table 1, and the median particle size is 10.4μm.

[0033] (2) Add curing agent and fine aggregate to the wet-ground slurry and mix well: 8 wt% of quicklime was added to the wet-ground slurry, and the stirring time was 5 min at a stirring speed of 120 rpm; then 250 wt% of 0.15-1.18 mm continuously graded waste concrete recycled sand was added, and the stirring time was 5 min at a stirring speed of 80 rpm.

[0034] (3) Extruding the evenly stirred slurry into a mold and curing it: The mixed slurry is conveyed by a belt conveyor to a static brick press, and the pressure of the press is controlled at 12MPa, and the pressure is maintained for 10 seconds to obtain a brick. Then the brick is transferred to the curing area of ​​the factory shed by a forklift and cured for 28 days at 20℃±2℃ and 95% humidity. Comparative Example 1:

[0035] (1) Wet grinding of sand washing mud: In this example, the water content of the sand washing mud to be treated is 45wt%, and the median particle size is 80.6μm. 0.2wt% sodium stearate is added to the sand washing mud for wet grinding of the sand washing mud. The ball mill used for wet grinding is a horizontal ball mill, and the ball milling time is 5 min.

[0036] (2) Wet grinding of mineral powder: Take 30wt% of the dry weight of the washed sand mud as mineral powder, and the median particle size is 22.4μm. Add 0.2wt% of sodium stearate to the mineral powder slurry with a slurry concentration of 55wt% for wet grinding of the mineral powder. The ball mill used for wet grinding is a horizontal ball mill, and the ball milling time is 5 min. Mix the wet-ground washed sand mud and the wet-ground mineral powder in step (1) to obtain a mixed mud. The laser particle size detection method is used. The mud particle size after wet grinding is shown in Table 1, and the median particle size is 10.8μm.

[0037] (3) Add curing agent and fine aggregate to the mixed slurry and stir evenly: 6 wt% of sodium hydroxide was added to the mixed slurry, and the stirring time was 3 min at a stirring speed of 120 rpm; then 205 wt% of 0.15-1.18 mm continuously graded waste concrete recycled sand was added, and the stirring time was 5 min at a stirring speed of 80 rpm.

[0038] (4) Extruding the evenly stirred slurry into a mold and curing it: The mixed slurry is conveyed by a belt conveyor to a static brick press, and the pressure of the press is controlled at 10 MPa, and the pressure is maintained for 10 s to obtain a brick. Then the brick is transferred to the curing area of ​​the factory shed by a forklift and cured for 28 days at 20℃±2℃ and 95% humidity. Comparative Example 2:

[0039] (1) Add mineral powder, curing agent and fine aggregate to the sand washing mud discharged from the wet sand making process and mix them evenly: In this case, the water content of the sand washing mud to be treated is 45wt%, and the median particle size is 80.6μm. 30wt% of mineral powder is added to the sand washing mud, and then it is transported to the mixer and stirred for 10 minutes at a stirring speed of 120 rpm. 8 wt% of quicklime is added to the tailing mud and mineral powder mixture, and the stirring time is 5 minutes at a stirring speed of 120 rpm; then 205 wt% of 0.15~1.18 mm continuous graded waste concrete recycled sand is added, and the stirring time is 5 minutes at a stirring speed of 80 rpm.

[0040] (2) Extruding the evenly stirred slurry into a mold and curing it: The mixed slurry is conveyed by a belt conveyor to a static brick press, and the pressure of the press is controlled at 10 MPa, and the pressure is maintained for 10 s to obtain a brick. Then the brick is transferred to the curing area of ​​the factory shed by a forklift and cured for 28 days at 20℃±2℃ and 95% humidity.

[0041] The unfired bricks prepared in Examples 1-3 and Comparative Examples 1 and 2 were tested for compressive strength and water absorption, and the specific data are shown in Table 1.

[0042] According to the Test Methods for Wall Bricks (GB / T 2542-2012), the unfired bricks obtained in the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0043]

[0044] As shown in Table 1, the compressive strength of the sand-washing mud-based unfired bricks prepared by the method of the present invention in Examples 1-3 all reached more than 20 MPa, meeting the strength requirements of unfired bricks of MU 20 strength grade. The wet grinding of sand-washing mud and sand-washing mud together is conducive to regulating the size and distribution of solid particles, improving the particle filling effect, and making the microstructure of the matrix denser; benefiting from the co-grinding process, the quartz and other minerals with higher hardness in the sand-washing mud break and refine the mineral powder particles, which helps to improve the self-hydration performance of the mineral powder, generate more gel products such as C-(A)-SH, resulting in a decrease in structural porosity and an increase in strength; in addition, the co-wet grinding improves the grinding efficiency compared with the single wet grinding, reduces the production process, reduces energy consumption, and saves production costs.

[0045] On the other hand, the method provided by the present invention also includes a sand washing mud wet grinding module, a mixing and stirring module and a brick making processing module, thereby realizing the on-site harmless treatment and resource utilization of the sand washing mud.

[0046] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing unburned bricks by grinding mineral powder and high-water content sand washing mud, characterized in that The following steps are involved: Step 1: Pump the high-water content sand washing mud in the sedimentation tank into the wet grinding system through the metering and conveying equipment, and add mineral powder and drag reducer into the wet grinding system to obtain uniformly ground mud; Step 2: The ground slurry, curing agent and fine aggregate are sent to the mixing system through the metering and conveying equipment, and are mixed evenly by the mixer to form a ready-to-use mixture; Step 3: The evenly stirred mixture is conveyed to the molding system, extruded and molded by a brick making machine to form a brick blank, and then the brick blank is cured to obtain a washed sand-mud-based unfired brick.

2. The method according to claim 1, characterized in that: In step 1, the water content of the high-water content sand washing mud is 40-60 wt%.

3. The method according to claim 1, characterized in that: In step 1, the drag reducer is sodium stearate, polycarboxylate water reducer or a combination of sodium stearate and polycarboxylate water reducer, and the dosage range is 0.2-0.4 wt% of the dry basis mass of the sand washing mud.

4. The method according to claim 1, characterized in that: In step 1, the particle size of the mineral powder is ≤0.15 mm, and the dosage range is 10 to 40 wt% of the dry mass of the sand washing mud.

5. The method according to claim 1, characterized in that: In step 2, the curing agent is quicklime, sodium hydroxide or sodium silicate, and the dosage range is 0 to 8 wt% of the dry basis of sand washing mud and mineral powder.

6. The method according to claim 1, characterized in that: In step 2, the particle size of the fine aggregate is continuously graded waste concrete recycled sand or iron tailings sand between 0.15 and 1.18 mm, and the dosage range is 150 to 280 wt% of the powder mass.

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