CN113121139A - Core-shell lightweight aggregate containing high-content sludge and preparation method thereof - Google Patents
Core-shell lightweight aggregate containing high-content sludge and preparation method thereof Download PDFInfo
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- CN113121139A CN113121139A CN202110478732.1A CN202110478732A CN113121139A CN 113121139 A CN113121139 A CN 113121139A CN 202110478732 A CN202110478732 A CN 202110478732A CN 113121139 A CN113121139 A CN 113121139A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/02—Agglomerated materials, e.g. artificial aggregates
- C04B18/023—Fired or melted materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B33/00—Clay-wares
- C04B33/02—Preparing or treating the raw materials individually or as batches
- C04B33/13—Compounding ingredients
- C04B33/132—Waste materials; Refuse; Residues
- C04B33/1321—Waste slurries, e.g. harbour sludge, industrial muds
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B33/00—Clay-wares
- C04B33/02—Preparing or treating the raw materials individually or as batches
- C04B33/13—Compounding ingredients
- C04B33/132—Waste materials; Refuse; Residues
- C04B33/138—Waste materials; Refuse; Residues from metallurgical processes, e.g. slag, furnace dust, galvanic waste
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B33/00—Clay-wares
- C04B33/32—Burning methods
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/009—Porous or hollow ceramic granular materials, e.g. microballoons
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/60—Production of ceramic materials or ceramic elements, e.g. substitution of clay or shale by alternative raw materials, e.g. ashes
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Abstract
The invention discloses a core-shell lightweight aggregate containing high-content sludge and a preparation method thereof. The core-shell lightweight aggregate comprises a core and a shell, wherein the mass ratio of the core to the shell is 2: 1-3: 1; wherein: the inner core comprises the following components in percentage by mass: 85-95% of dried sludge, 3-7% of goethite and 2-8% of hydrotalcite-like compound; the shell comprises the following components: 70-85% of sludge, 10-15% of dried sludge, 4-10% of optical fiber micro powder and 1-5% of steel slag. The powder is prepared by coating the powder of the shell on the surface of the inner core blank and then sintering the coated powder in a rotary kiln at the rotating speed of 2.5-3 r/min at the temperature of 1120-1200 ℃ for 8-12 min. The core raw material of the core-shell light aggregate is mainly sludge, has high sludge doping amount, compact shell structure, high strength, low water absorption, simple preparation process and low raw material cost, and is easy to be applied to actual production and rapid popularization.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to core-shell lightweight aggregate containing high-content sludge and a preparation method thereof.
Background
Along with the development of the country, the urbanization process is faster and faster, the sludge serving as a byproduct of the urbanization activity is correspondingly larger and larger, and the sludge has high water content and low strength and often contains pathogenic bacteria, heavy metals, toxic and harmful refractory organic matters and other harmful components. The secondary pollution is easily caused by the modes of landfill, incineration and the like, and the secondary pollution generates harmful substances such as dioxin which are extremely unfriendly to the environment, so the secondary pollution needs to be recycled.
At present, the resource utilization approaches of sludge mainly comprise composting, chemical raw material preparation and chemical raw material preparationUsed as building material, etc. The preparation of lightweight aggregate from sludge is one of the ways of resource utilization of sludge, and has been receiving wide attention since the technology of sludge firing ceramsite is proposed by Nakouzi S. For example, Wuqingren and the like perform experimental research on the formula of the sludge ingredient fired ceramsite, and the results show that: the light ceramsite which meets the national standard can be prepared by using biological sludge of different sewage treatment plants to replace partial clay, and the density is increased along with the increase of the sludge doping amount. 40 to 60 percent of water supply sludge is supplemented with fly ash, clay and glass powder to prepare the product with the bulk density of 0.7636g cm-3Ceramsite light aggregate with water absorption of 23.65 percent, but SiO in the used water supply sludge2The content is lower, only 27.30%, and other substances with high Si content need to be doped to make up for the shortage of Si content in the water supply sludge. The method is characterized in that 75% of municipal sludge is used as a raw material, glass powder is used as an auxiliary material, and the ceramsite light aggregate with the water absorption rate of 9.7% and the cylinder pressure strength of 6.8MPa is prepared, but the water content of the municipal sludge is up to 85%, the thermal weight loss of the municipal sludge reaches 45%, the actual mixing amount of the sludge is not high, and the actual mixing amount of the sludge is 30-45%.
At present, although the technology for preparing ceramsite lightweight aggregate by using sludge is mature, the sludge mixing amount of the lightweight aggregate which meets the national standard can be successfully prepared. When the sludge mixing amount is too high, due to the fact that the sludge content is large and the liquid phase is reduced, the gas in the material ball is too much to be wrapped, so that the gas overflows to form more cracks on the surface of the material ball, and the water absorption rate of the material ball is also increased rapidly. In addition, in the prior art for preparing the light aggregate from the sintered sludge, a control means for pollutants such as dioxin and the like is rarely mentioned; research shows that the incineration temperature is kept above 850 ℃ (preferably above 900 ℃) to completely decompose dioxin, and more than 99.99% of dioxin can be decomposed under the conditions that the furnace temperature is 1000 ℃ and the smoke retention time is 1 s.
Disclosure of Invention
The invention aims to provide a core-shell lightweight aggregate containing high-content sludge and a preparation method thereof, aiming at the problems in the prior art. The core raw material of the core-shell light aggregate is mainly sludge, has high sludge doping amount, compact shell structure, high strength, low water absorption, simple preparation process and low raw material cost, and is easy to be applied to actual production and rapid popularization.
In order to achieve the purpose, the invention adopts the following technical scheme:
the core-shell lightweight aggregate containing the high-content sludge comprises a core and a shell, wherein the mass ratio of the core to the shell is 2: 1-3: 1; wherein:
the inner core comprises the following components in percentage by mass: 85-95% of dried sludge, 3-7% of goethite and 2-8% of hydrotalcite-like compound;
the shell comprises the following components in percentage by mass: 70-85% of sludge, 10-15% of dried sludge, 4-10% of optical fiber micro powder and 1-5% of steel slag.
According to the scheme, the dried sludge is obtained by adding a flocculating agent into sludge, treating the sludge until the water content is 15-30%, and then drying the sludge until the sludge is completely dehydrated; the content of organic matters in the dried sludge is 60-70%.
According to the scheme, the fineness of the sludge is 0.074-0.080 mm; according to the mass percentage, the content of silicon oxide in the sludge is 60-70%, the content of aluminum oxide is 10-20%, and the total content of calcium oxide and magnesium oxide is 1-10%.
According to the scheme, the optical fiber micro powder is silicate white powder, and the average particle size is less than 2.5 microns; the fineness of the goethite is 0.01-0.1 mm; the fineness of the steel slag is 0.01-0.1 mm; the hydrotalcite-like compound is prepared from flue gas desulfurization waste residues, and the fineness of the hydrotalcite-like compound is 0.01-0.1 mm.
According to the scheme, the core-shell lightweight aggregate containing the sludge with high doping amount is prepared by sintering in a rotary kiln at 1120-1200 ℃ for 8-12 min, wherein the rotating speed of the rotary kiln is 2.5-3 r/min.
According to the scheme, the core-shell lightweight aggregate has the following cylinder pressure strength: 6-16 MPa, water absorption: 6 to 13 percent.
The preparation method of the core-shell lightweight aggregate containing the sludge with high content comprises the following steps:
(1) mixing the dried sludge, goethite, hydrotalcite-like compound and water, and then granulating to obtain a core blank;
(2) mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water to obtain shell powder;
(3) and (3) coating the shell powder obtained in the step (2) on the surface of the core blank obtained in the step (1), and sintering in a rotary kiln to obtain the core-shell lightweight aggregate containing high-content sludge, wherein the rotating speed of the rotary kiln is 2.5-3 r/min, and the sintering process is carried out for 8-12 min at the temperature of 1120-1200 ℃.
According to the scheme, in the step (1), the granulation process comprises the following steps: and granulating the mixed dried sludge, goethite, hydrotalcite-like compound and water into balls under the conditions that the rotating speed is 30-40 r/min and the rotating inclination angle is 45-60 degrees.
According to the scheme, in the step (3), the rotary kiln comprises a preheating zone and a firing zone, drying and preheating are carried out in the preheating zone, and the retention time is 42-68 min; sintering is carried out in the sintering area.
According to the scheme, in the step (3), the process for coating the powder of the shell on the surface of the core blank comprises the following steps: and coating the shell powder on the surface of the core blank under the conditions that the rotating speed is 30-40 r/min and the rotating inclination angle is 45-60 degrees.
According to the scheme, in the step (1), water accounts for 25-35% of the mass of the inner core blank body in percentage by mass; in the step (2), water accounts for 30-40% of the mass of the shell powder according to mass percentage.
The invention adopts a high-temperature rapid sintering process through a rotary kiln when roasting the core-shell lightweight aggregate, wherein the sintering temperature is 1120-1200 ℃, the rotary kiln rotating speed is 2.5-3 r/min, and the retention time is about 8-12 min. The iron substance contained in the steel slag in the shell component has a high-temperature fluidization characteristic, the shell structure can be uniformly coated on the inner core under the quick rotation of the rotary kiln, cracks possibly generated by other components during high-temperature sintering are filled, a compact shell is formed, the corresponding sintering time is shortened, oxygen is blocked before the reaction of the inner core component is carried out in a large amount, the gas amount generated inside is greatly reduced, the possibility of crack generation is reduced, and therefore the phenomenon that the core-shell light aggregate is prepared by using sludge with high organic matter content in a large mixing amount and the material ball is not cracked or melted is achieved. In addition, the core-shell light aggregate fired by the high-temperature rapid sintering process has a compact shell structure, so that harmful components such as heavy metal ions in sludge can be fully solidified inside the material, pollutant dioxin generated during high-temperature sludge incineration is avoided, the control on pollutants is realized, and the environmental safety is effectively improved.
Compared with the prior art, the invention has the following advantages:
1. the invention provides a core-shell light aggregate containing high-doping-amount sludge, wherein the core is mainly sludge, the doping amount is more than 85%, and goethite and hydrotalcite-like compound are used for assisting in fixing heavy metal ions in the sludge inside a core-shell structure; the shell takes sludge as a main material and is added with sintering aid optical fiber micro powder, steel slag and sludge, the structure is compact, the cladding performance of the core is good, and harmful components such as heavy metal ions in the sludge can be fully solidified in the material; the nuclear shell lightweight aggregate has high sludge doping amount, high strength and low water absorption rate, meets the GB17431.1-2010 nuclear shell lightweight aggregate and the test method standard thereof, and realizes the large-scale utilization of sludge.
2. The invention provides a preparation method of core-shell lightweight aggregate, which comprises the steps of sintering at high rotation speed and high temperature in a rotary kiln; the goethite and the hydrotalcite-like compound are added into the core raw material, so that heavy metal ions in the sludge can be fixed in the core-shell structure, and secondary pollution in the high-temperature sintering process is avoided; the steel slag added into the shell raw material contains a large amount of iron, can generate spinel at high temperature, is beneficial to solidifying harmful substances, heavy metal ions and the like released by sludge during high-temperature sintering in the pellet, and the sludge and sintering aid optical fiber micro powder added can form liquid-phase molten-state substances at high temperature, is beneficial to forming a specific glass phase on the shell of the pellet and better coating the inner core, so that the prepared aggregate can meet the performance requirements of light weight and high strength under the conditions of high-volume sludge and high-temperature rapid sintering; the preparation process is simple, the raw material cost is low, and the method is easy to apply to actual production and rapid popularization.
Detailed Description
The present invention is further illustrated by the following examples.
The raw material indices used in the following examples are as follows:
the dried sludge is obtained by adding a flocculating agent into sludge from a water supply plant to treat the sludge until the water content is 15-30%, and then drying the sludge until the sludge is completely dehydrated, wherein the organic matter content of the dried sludge is 65%, and the water content before the treatment by adding the flocculating agent is 80-95%; can provide skeleton support during the formation of inner core and good pore structure to control the release of internal nutrients.
The silt comes from surface soil of the place of the original factory after the removal of the metallurgical plant, the fineness of the silt is 0.074-0.080 mm, and the silt comprises 64% of silicon oxide, 14% of aluminum oxide, 2% of calcium oxide and 1% of magnesium oxide by mass percent; the method is mainly used for forming the shell with certain strength and delaying the outward diffusion speed of substances contained in the inner core.
The optical fiber micro powder is silicate white powder obtained by grinding waste vitreous optical fibers, and the average particle size is less than 2.5 mu m; it can increase the viscosity of the material for forming the shell during high-temperature sintering, and prevent the core-shell structure from cracking or deforming when the core and the shell form the core-shell structure.
The hydrotalcite-like compound is prepared from flue gas desulfurization waste residues, and the fineness of the hydrotalcite-like compound is 0.01-0.1 mm.
The goethite is commercially available goethite, and the fineness of the goethite is 0.01-0.1 mm.
The steel slag is commercially available steel slag, and the fineness of the steel slag is 0.01-0.1 mm.
Example 1
Providing a core-shell lightweight aggregate containing high-content sludge, which comprises an inner core and an outer shell; the mass ratio of the inner core to the outer shell is 2: 1;
the inner core comprises the following components in percentage by mass: 85% of dried sludge, 7% of goethite and 8% of hydrotalcite-like compound.
The shell comprises the following components in percentage by mass: 75% of sludge, 10% of dried sludge, 10% of optical fiber micro powder and 5% of steel slag.
The method for preparing the core-shell lightweight aggregate specifically comprises the following steps:
(1) according to the raw material proportion, stirring the dried sludge, goethite, hydrotalcite-like compound and water to mix uniformly, and then granulating and balling by a granulator, wherein the rotating speed of the granulator is 35r/min and the rotating inclination angle of a disc is 45 degrees in the granulating process to obtain a core blank body, and the water doping amount is 27 percent of the total mass of the core blank body;
(2) uniformly mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and the water according to the proportion of the raw materials to obtain shell powder, wherein the doping water amount is 32 percent of the total mass of the shell powder;
(3) coating the shell powder on the surface of the core blank by adopting a ball forming mill under the conditions that the rotating speed is 35r/min and the rotating inclination angle of a disc is 45 degrees, then sending the material balls into a rotary kiln with the rotating speed of 2.7r/min, staying for about 50min in a preheating section for drying and preheating, then sintering in a sintering area, sintering at 1120-1180 ℃ for 10min, and cooling to room temperature after the sintering to obtain the core-shell light aggregate.
The core-shell lightweight aggregate of the present example was tested for properties.
As can be seen from the test, the core-shell lightweight aggregate of the embodiment has the cylinder pressure strength of 8.53MPa and the water absorption of 12.15%.
Example 2
Providing a core-shell lightweight aggregate containing high-content sludge, which comprises an inner core and an outer shell; the mass ratio of the inner core to the outer shell is 2: 1;
the inner core comprises the following components in percentage by mass: 90% of dried sludge, 6% of goethite and 4% of hydrotalcite-like compound.
The shell comprises the following components in percentage by mass: 75% of sludge, 12% of dried sludge, 8% of optical fiber micro powder and 5% of steel slag.
The method for preparing the core-shell lightweight aggregate specifically comprises the following steps:
(1) according to the raw material proportion, stirring the dried sludge, goethite, hydrotalcite-like compound and water to mix uniformly, and then granulating and balling by a granulator, wherein in the granulating process, the rotating speed of the granulator is 35r/min, the rotating inclination angle of a disc is 45 degrees, so that a core blank body is obtained, and the water doping amount is 32 percent of the total mass of the core blank body;
(2) uniformly mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water according to the raw material proportion to obtain shell powder, wherein the doping water amount is 35 percent of the total mass of the shell blank;
(3) coating the powder of the shell on the surface of the core blank by adopting a ball forming mill under the conditions that the rotating speed is 35r/min and the rotating inclination angle of a disc is 45 degrees, then sending the material balls into a rotary kiln with the rotating speed of 2.7r/min, staying for about 50min in a preheating section for drying and preheating, and sintering in a sintering area, wherein the sintering process is 1120-1140 ℃, and cooling to room temperature after sintering for 10min to prepare the core-shell light aggregate.
The core-shell lightweight aggregate of the present example was tested for properties.
As can be seen from the test, the core-shell lightweight aggregate of the embodiment has the cylinder pressure strength of 9.13MPa and the water absorption of 10.63%.
Example 3
Providing a core-shell lightweight aggregate containing high-content sludge, which comprises an inner core and an outer shell; the mass ratio of the inner core to the outer shell is 2: 1;
the inner core comprises the following components in percentage by mass: 88 percent of dried sludge, 6 percent of goethite and 4 percent of hydrotalcite-like compound.
The shell comprises the following components in percentage by mass: 75% of sludge, 10% of dried sludge, 10% of optical fiber micro powder and 5% of steel slag.
The method for preparing the core-shell lightweight aggregate specifically comprises the following steps:
(1) according to the raw material proportion, stirring the dried sludge, goethite, hydrotalcite-like compound and water to mix uniformly, and then granulating and balling by a granulator, wherein the rotating speed of the granulator is 35r/min and the rotating inclination angle of a disc is 45 degrees in the granulating process to obtain a core blank body, and the water doping amount is 28 percent of the total mass of the core blank body;
(2) uniformly mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water according to the raw material proportion to obtain shell powder, wherein the doping water amount is 35 percent of the total mass of the shell blank;
(3) coating the shell powder on the surface of the core blank by adopting a ball forming mill under the conditions that the rotating speed is 35r/min and the rotating inclination angle of a disc is 45 degrees, then sending the material balls into a rotary kiln with the rotating speed of 2.8r/min, staying for about 49min in a preheating section for preheating, and then sintering in a sintering area, wherein the sintering process is sintering at 1130-1150 ℃ for 9min and then cooling to room temperature to prepare the core-shell light aggregate.
The core-shell lightweight aggregate of the present example was tested for properties.
As can be seen from the test, the core-shell lightweight aggregate of the embodiment has the cylinder pressure strength of 13.56MPa and the water absorption of 8.32%.
Example 4
Providing a core-shell lightweight aggregate containing high-content sludge, which comprises an inner core and an outer shell; the mass ratio of the inner core to the outer shell is 2: 1;
the inner core comprises the following components in percentage by mass: 90% of dried sludge, 4% of goethite and 6% of hydrotalcite-like compound.
The shell comprises the following components in percentage by mass: 75% of sludge, 10% of dried sludge, 10% of optical fiber micro powder and 5% of steel slag.
The method for preparing the core-shell lightweight aggregate specifically comprises the following steps:
(1) according to the raw material proportion, stirring the dried sludge, goethite, hydrotalcite-like compound and water to mix uniformly, and then granulating and balling by a granulator, wherein in the granulating process, the rotating speed of the granulator is 35r/min, the rotating inclination angle of a disc is 45 degrees, so that a core blank body is obtained, and the water doping amount is 32 percent of the total mass of the core blank body;
(2) uniformly mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water according to the raw material proportion to obtain shell powder, wherein the doping water amount is 35 percent of the total mass of the shell blank;
(3) coating the powder of the shell on the surface of the core blank by adopting a ball forming mill under the conditions that the rotating speed is 35r/min and the rotating inclination angle of a disc is 45 degrees, then feeding the material balls into a rotary kiln with the rotating speed of 2.7r/min, staying for about 50min in a preheating section for preheating, and then sintering in a sintering area, wherein the sintering process is 1140-1160 ℃, sintering for 10min and cooling to room temperature to prepare the core-shell light aggregate.
The core-shell lightweight aggregate of the present example was tested for properties.
As can be seen from the test, the core-shell lightweight aggregate of the embodiment has the cylinder pressure strength of 10.21MPa and the water absorption of 9.17%.
Example 5
Providing a core-shell lightweight aggregate containing high-content sludge, which comprises an inner core and an outer shell; the mass ratio of the inner core to the outer shell is 2: 1;
the inner core comprises the following components in percentage by mass: 90% of dried sludge, 5% of goethite and 5% of hydrotalcite-like compound.
The shell comprises the following components in percentage by mass: 75% of sludge, 11% of dried sludge, 10% of optical fiber micro powder and 4% of steel slag.
The method for preparing the core-shell lightweight aggregate specifically comprises the following steps:
(1) according to the raw material proportion, stirring the dried sludge, goethite, hydrotalcite-like compound and water to mix uniformly, and then granulating and balling by a granulator, wherein in the granulating process, the rotating speed of the granulator is 35r/min, the rotating inclination angle of a disc is 45 degrees, so that a core blank body is obtained, and the water doping amount is 32 percent of the total mass of the core blank body;
(2) uniformly mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water according to the raw material proportion to obtain shell powder, wherein the doping water amount is 35 percent of the total mass of the shell blank;
(3) coating the shell powder on the surface of the core blank by adopting a ball forming mill under the conditions that the rotating speed is 35r/min and the rotating inclination angle of a disc is 45 degrees, then feeding the material balls into a rotary kiln with the rotating speed of 2.9r/min, staying for about 48min in a preheating section for preheating, and then sintering in a sintering area, wherein the sintering process is 1180-1200 ℃, sintering for 8min, and cooling to room temperature to prepare the core-shell light aggregate.
The core-shell lightweight aggregate of the present example was tested for properties.
As can be seen from the test, the core-shell lightweight aggregate of the embodiment has the cylinder pressure strength of 14.43MPa and the water absorption of 7.93%.
Example 6
Providing a core-shell lightweight aggregate containing high-content sludge, which comprises an inner core and an outer shell; the mass ratio of the inner core to the outer shell is 2: 1;
the inner core comprises the following components in percentage by mass: 90% of dried sludge, 6% of goethite and 4% of hydrotalcite-like compound.
The shell comprises the following components in percentage by mass: 75% of sludge, 12% of dried sludge, 10% of optical fiber micro powder and 3% of steel slag.
The method for preparing the core-shell lightweight aggregate specifically comprises the following steps:
(1) according to the raw material proportion, stirring the dried sludge, goethite, hydrotalcite-like compound and water to mix uniformly, and then granulating and balling by a granulator, wherein in the granulating process, the rotating speed of the granulator is 35r/min, the rotating inclination angle of a disc is 45 degrees, so that a core blank body is obtained, and the water doping amount is 32 percent of the total mass of the core blank body;
(2) uniformly mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water according to the raw material proportion to obtain shell powder, wherein the doping water amount is 35 percent of the total mass of the shell blank;
(3) coating the shell powder on the surface of the core blank by adopting a ball forming mill under the conditions that the rotating speed is 35r/min and the rotating inclination angle of a disc is 45 degrees, then sending the material balls into a rotary kiln with the rotating speed of 3r/min, staying for about 46min in a preheating section for preheating, and sintering in a sintering area, wherein the sintering process is 1180-1200 ℃, sintering for 8min, and cooling to room temperature to obtain the core-shell light aggregate.
The core-shell lightweight aggregate of the present example was tested for properties.
As shown by tests, the core-shell lightweight aggregate of the embodiment has the cylinder pressure strength of 15.21MPa and the water absorption of 6.41 percent.
The above description shows and describes several preferred embodiments of the invention, but the invention is not limited to the embodiments described herein, and should not be construed as a result of screening out other embodiments, but may be implemented in combination under other conditions and capable of modifications within the scope of the inventive concept as expressed in the relevant art. Modifications of the invention by a skilled artisan are intended to be within the scope of the claims.
Claims (10)
1. The core-shell lightweight aggregate containing high-content sludge is characterized by comprising an inner core and an outer shell, wherein the mass ratio of the inner core to the outer shell is 2: 1-3: 1; wherein:
the inner core comprises the following components in percentage by mass: 85-95% of dried sludge, 3-7% of goethite and 2-8% of hydrotalcite-like compound;
the shell comprises the following components in percentage by mass: 70-85% of sludge, 10-15% of dried sludge, 4-10% of optical fiber micro powder and 1-5% of steel slag.
2. The core-shell lightweight aggregate according to claim 1, wherein the dried sludge is obtained by adding a flocculant to sludge, treating the sludge until the water content is 15-30%, and then drying the sludge until the sludge is completely dehydrated; the content of organic matters in the dried sludge is 60-70%.
3. The core-shell lightweight aggregate according to claim 1, wherein the fineness of the sludge is 0.074 to 0.080 mm; according to the mass percentage, the content of silicon oxide in the sludge is 60-70%, the content of aluminum oxide is 10-20%, and the total content of calcium oxide and magnesium oxide is 1-10%.
4. The core-shell lightweight aggregate according to claim 1, wherein the optical fiber micropowder is silicate-based white powder having an average particle size of less than 2.5 μm; the fineness of the goethite is 0.01-0.1 mm; the fineness of the steel slag is 0.01-0.1 mm; the hydrotalcite-like compound is prepared from flue gas desulfurization waste residues, and the fineness of the hydrotalcite-like compound is 0.01-0.1 mm.
5. The core-shell lightweight aggregate according to claim 1, wherein the core-shell lightweight aggregate containing high-content sludge is prepared by sintering in a rotary kiln at 1120-1200 ℃ for 8-12 min, wherein the rotation speed of the rotary kiln is 2.5-3 r/min.
6. A preparation method of the core-shell lightweight aggregate containing the sludge with high content according to any one of claims 1 to 5, which is characterized by comprising the following steps:
(1) mixing the dried sludge, goethite, hydrotalcite-like compound and water, and then granulating to obtain a core blank;
(2) mixing the sludge, the dried sludge, the optical fiber micro powder, the steel slag and water to obtain shell powder;
(3) and (3) coating the shell powder obtained in the step (2) on the surface of the core blank obtained in the step (1), and sintering in a rotary kiln to obtain the core-shell lightweight aggregate containing high-content sludge, wherein the rotating speed of the rotary kiln is 2.5-3 r/min, and the sintering process is carried out for 8-12 min at 1120-1200 ℃.
7. The preparation method according to claim 6, wherein in the step (1), the granulation process comprises: and granulating the mixed dried sludge, goethite, hydrotalcite-like compound and water into balls under the conditions that the rotating speed is 30-40 r/min and the rotating inclination angle is 45-60 degrees.
8. The preparation method according to claim 6, wherein in the step (3), the rotary kiln comprises a preheating zone and a firing zone, drying and preheating are carried out in the preheating zone, and the residence time is 42-68 min; sintering is carried out in the sintering area.
9. The preparation method according to claim 6, wherein in the step (3), the process of coating the powder of the shell on the surface of the core blank comprises the following steps: and coating the shell powder on the surface of the core blank under the conditions that the rotating speed is 30-40 r/min and the rotating inclination angle is 45-60 degrees.
10. The preparation method according to claim 6, wherein in the step (1), the water accounts for 25-35% of the mass of the inner core blank in percentage by mass; in the step (2), water accounts for 30-40% of the mass of the shell powder according to mass percentage.
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