A method for producing artificial aggregates

Abstract

The present application relates to the industrial solid waste resource utilization and artificial aggregate technical field, specifically relates to a kind of preparation method of artificial aggregate.The specific technical scheme is as follows: including the following steps: (1) the slag, fly ash, red mud are ground and sieved, after heating treatment, mixed with activator, to obtain slurry;(2) the slurry is heated to condense, then, extrusion cutting, rounding, maintenance, alkali immersion, maintenance again, to obtain artificial aggregate.The present application solves the problem of large pore of spherical particles produced by disc granulation in the prior art.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization and artificial aggregate technology, specifically to a method for preparing artificial aggregate. Background Technology

[0002] In the process of modernization, the demand for non-renewable resources such as mineral resources, energy, and soil resources is increasing, resulting in the accumulation of over 62 billion tons of various industrial solid wastes. This not only occupies a large amount of land for storage but also brings about environmental, safety, and other problems. At the same time, the demand for concrete is enormous, leading to the rapid depletion of aggregates in concrete. To reduce the mining and utilization of natural aggregates and alleviate the series of problems caused by solid waste, new technologies are urgently needed to promote the large-scale, high-value, and green application of solid waste.

[0003] Existing patented technologies for granulation using solid waste typically involve two processes: granulation and curing. In the granulation process, spherical artificial aggregates are usually produced using a disc method, while irregular artificial aggregates are typically produced through mechanical crushing. The curing process usually employs methods such as alkaline soaking, high-temperature steam curing, and accelerated carbonization. Spherical artificial aggregates better meet the requirements for stress resistance and slurry flowability in terms of morphology; however, due to the granulation method, the prepared aggregates have higher water absorption and contain more unhydrated substances, resulting in less than ideal mechanical properties.

[0004] Existing patents (such as Chinese patents with application numbers 202110484019.8, 201910611978.4, 202011103706.2, and 202311699130.4) involve placing dry powders such as industrial solid waste and cement in a disc granulator and spraying an activator or water to granulate the powder particles into spheres. This method results in insufficient compaction of the powder particles, leading to larger pores in the spheres and stronger water absorption.

[0005] Furthermore, irregular aggregates are produced through mechanical crushing, which damages the aggregates during the crushing process, resulting in numerous microcracks, a significant decrease in strength, and a high proportion of needle-like and flaky aggregates. This leads to significant disadvantages in terms of stress resistance and slurry flowability. The crushing process also generates a considerable amount of secondary fine powder. Therefore, new technological measures are needed to promote the development of artificial aggregates. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing artificial aggregates, which solves the problem of large pores in spherical particles produced by disc granulation in existing technologies.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention discloses a method for preparing artificial aggregate, comprising the following steps:

[0009] (1) Grind and sieve slag, fly ash and red mud, heat them, add activator and mix to obtain slurry;

[0010] (2) The slurry is heated at high temperature to solidify it. Then, it is extruded, granulated, rolled, cured, soaked in alkali solution, and cured again to obtain artificial aggregate.

[0011] Preferably, in step (1), by weight, the slag is ≥70 parts, the fly ash is 5-20 parts, the red mud is 5-10 parts, and the calcium-silicon molar ratio in the whole composition is greater than 1.2.

[0012] Preferably, the activator is an alkaline activator, and the dosage is 5-10%; the alkaline activator is one or a combination of sodium hydroxide, sodium silicate, sodium carbonate and water glass.

[0013] Preferably, in step (1), the heat treatment is carried out at 20-50°C for 20-50 minutes.

[0014] Preferably, in step (2), the slurry is added to the auxiliary granulation equipment after standing and coagulated at 50-90℃. After coagulation, it is extruded and granulated, and then granulated by rolling. The granules are cured for 1-3 days in an environment with a temperature of 15-25℃ and a humidity of more than 90%, and then soaked in a 5-10% sodium hydroxide solution or water glass with a modulus of 1. After being taken out, they are cured under the same conditions.

[0015] Preferably, during the rounding granulation process, the disc tilt angle is 0-20°.

[0016] Preferably, the slurry is heated by electric heating or water bath heating.

[0017] The present invention has the following beneficial effects:

[0018] 1. This invention utilizes the characteristic that the setting speed of alkali-activated gel materials is greatly affected by temperature, applying it to the preparation of artificial aggregates. The latent chemical activity of the raw materials is activated through grinding and heating, and the resulting slurry is further heated using auxiliary granulation equipment to promote slurry setting. The thermoplasticized slurry is then granulated and rolled in a disc mill. Finally, through curing and alkali soaking, artificial aggregates with high density and excellent properties are obtained. This invention uses thermoplastic slurry for granulation, resulting in a denser internal structure of the artificial aggregate, and alkali soaking further strengthens the surface layer. Compared to artificial aggregates obtained by directly using powder for disc granulation, this method avoids the phenomenon of high internal porosity and external particle strength being significantly higher than internal strength.

[0019] 2. This invention uses slurry for granulation, resulting in denser, more uniformly sized particles with a higher degree of internal hydration. It also utilizes the chemical properties of the materials, employing physical activation of the raw materials and high-temperature heating of the slurry to promote the coagulation process, reducing the slurry's fluidity for granulation, and producing spherical artificial aggregates without mechanical crushing or high-temperature sintering. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention;

[0021] Figure 2 A schematic diagram of auxiliary granulation equipment 1;

[0022] Figure 3 This is a schematic diagram of the auxiliary granulation equipment 2. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0025] refer to Figure 1 As shown, this invention discloses a method for preparing artificial aggregate, comprising the following steps:

[0026] (1) Grind and sieve slag, fly ash, and red mud, and heat them at 20-50℃ for 20-50 minutes to activate the potential activity of each component. Then, add an activator and water to mix and obtain a slurry. Slag, fly ash, and red mud are rich in silica, alumina, and calcium oxide, and are industrial solid wastes. By weight, slag ≥ 70 parts, fly ash 5-20 parts, and red mud 5-10 parts, with a calcium-silicon molar ratio greater than 1.2 in the entire composition. The activator is an alkaline activator, used at 5-10%; the alkaline activator is one or a combination of sodium hydroxide, sodium silicate, sodium carbonate, and water glass.

[0027] (2) Let the slurry stand until it is slightly fluid, then add it to the auxiliary granulation equipment and heat it to 50-90℃ to solidify it. The heating time is 5-30s. Then, extrude and cut the slurry into pellets and roll them into a disc mill. Sprinkle an appropriate amount of slag powder or a mixture of slag powder, fly ash and red mud into the disc mill (the ratio of the mixture can be the same as the ratio in step (1)). The disc tilt angle is 0-20°. The heating method is electric heating or water bath heating.

[0028] (3) Place the rounded granules in an environment with a temperature of 15-25℃ and a humidity of more than 90% for the first curing, and cure for 1-3 days.

[0029] (4) After the first curing, the particles are soaked in an alkaline solution composed of 5-10% sodium hydroxide or water glass with a modulus of 1, and then taken out to promote further hydration of the mixture adhering to the surface of the particles. The taken-out particles are then placed in an environment of 15-25℃ and humidity greater than 90% for a second curing. After a certain curing time (the curing time is determined according to the actual situation, such as 28 days), high-density artificial aggregate is finally obtained.

[0030] There are two types of auxiliary granulation equipment, including auxiliary granulation equipment 1 and auxiliary granulation equipment 2. Auxiliary granulation equipment 1 is as follows: Figure 2 The system includes a slurry storage chamber, a discharge pipe, a warm water circulation chamber, and a hot water circulation chamber. Both the warm water and hot water circulation chambers are equipped with inlet and outlet pipes. The inlet of the warm water circulation chamber is used to introduce warm water, and the inlet of the hot water circulation chamber is used to introduce hot water. Similarly, the outlet is used to discharge either warm or hot water. The temperature inside the warm water circulation chamber is at normal room temperature, 15-25℃. The temperature inside the hot water circulation chamber is 50-90℃. The warm water and hot water circulation chambers are separated from each other. The existence of the warm water circulation chamber and the separated area is to prevent heat from the heating area from being conducted to the slurry storage area, which would cause the slurry to solidify directly in the storage chamber. In use, the slurry is placed in the slurry storage chamber, and then squeezed into the discharge pipe by a pusher plate on one side of the slurry storage chamber. After passing through the water bath of the hot water circulation chamber, the slurry undergoes a brief thermoplasticization process, causing it to initially solidify before being pelletized. The discharge pipe passes through the hot water circulation chamber and the warm water circulation chamber in sequence, and is connected to the slurry storage chamber. The slurry in the slurry storage chamber is squeezed into the discharge pipe by pushing the pusher plate.

[0031] Figure 3 As shown, the auxiliary granulation equipment 2 includes a cylindrical openable mold. After the slurry is poured into the mold, it undergoes preliminary plasticization in an electric heating box. After plasticization, the mold is removed and the granules are cut.

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Example 1

[0034] A method for preparing artificial aggregate, comprising the following steps:

[0035] 70 parts slag powder, 20 parts fly ash, and 10 parts red mud were mixed, ground in a ball mill, and sieved through a 300-mesh screen. The mixed powder was then heated in an oven at 40°C for 30 minutes. A composite activator of water glass and sodium hydroxide was used to mix the powder with water. The modulus of the liquid sodium silicate was 1 (adjusted by the amount of water glass and sodium hydroxide), the alkali content was 8% (based on the mass of Na2O), and the water-cement ratio was 0.45 (wherein the water includes the water in the liquid sodium silicate solution and additional water). After the slurry was allowed to stand for a period of time, it was added to auxiliary granulation equipment 1 and heated in a water bath at 80°C to accelerate coagulation. The coagulation time was 30 seconds. The granules were then extruded and cut into pellets, which were rolled into rounds in a disc mill. After rolling, the pellets were removed, cured for 2 days, and then soaked in an 8% sodium hydroxide solution. After removal, they were further cured. The final apparent density of the pellets was 1.82 g / cm³. 3 The strength of a single particle is 9.1 MPa.

[0036] Example 2

[0037] A method for preparing artificial aggregate, comprising the following steps:

[0038] 80 parts slag powder, 10 parts fly ash, and 10 parts red mud were mixed, ground in a ball mill, and sieved through a 300-mesh screen. The mixed powder was then heated in an oven at 40°C for 30 minutes. A composite activator of water glass and sodium hydroxide was mixed with water, with a liquid sodium silicate modulus of 1, an alkali dosage of 8%, and a water-cement ratio of 0.45. After the slurry was allowed to stand for a period of time, it was added to auxiliary granulation equipment 1, and water was heated in a bath at 80°C to accelerate coagulation. The coagulation time was 30 seconds. The granules were then extruded and cut into pellets, which were rolled into rounds in a disc mill. After rolling, the pellets were removed, cured for 2 days, and then soaked in an 8% sodium hydroxide solution. After removal, they were further cured. The final apparent density of the pellets was 1.89 g / cm³. 3 The strength of a single particle is 11.3 MPa.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing artificial aggregate, characterized in that: Includes the following steps: (1) Grind and sieve the slag, fly ash and red mud, heat them, add an activator and mix them to obtain a slurry; (2) Heat the slurry to 50-90℃ to solidify it, then extrude, cut into pellets, roll into balls, cure, soak in alkali solution, and cure again to obtain artificial aggregate; In step (1), based on 100 parts by weight, there are ≥70 parts of slag, 5-20 parts of fly ash, and 5-10 parts of red mud. The molar ratio of calcium to silicon in the entire composition is greater than 1.

2.

2. The method for preparing artificial aggregate according to claim 1, characterized in that: The activator is an alkaline activator, and the amount used is 5-10% based on the mass of Na2O; the alkaline activator is one or a combination of sodium hydroxide, sodium carbonate and water glass.

3. The method for preparing artificial aggregate according to claim 2, characterized in that: In step (1), the sample is heated at 20-50°C for 20-50 minutes.

4. The method for preparing artificial aggregate according to claim 2, characterized in that: In step (2), the slurry is added to the auxiliary granulation equipment after standing and coagulated at 50-90℃. After coagulation, it is extruded and granulated, and then granulated by rolling. The granules are cured for 1-3 days at a temperature of 15-25℃ and a humidity of more than 90%. Then they are soaked in 5-10% sodium hydroxide solution or water glass with a modulus of 1. After being taken out, they are cured under the same conditions.

5. The method for preparing artificial aggregate according to claim 4, characterized in that: During the rounding granulation process, the disc tilt angle is 0-20°.

6. The method for preparing artificial aggregate according to claim 4, characterized in that: The slurry is heated by electric heating or water bath heating.

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