CN114773036A - Low-density composite ceramic ball for fluidized bed and preparation method and application thereof - Google Patents
Low-density composite ceramic ball for fluidized bed and preparation method and application thereof Download PDFInfo
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- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
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- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
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- C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
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- C04B2235/34—Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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Abstract
The invention provides a low-density composite ceramic ball for a fluidized bed, and a preparation method and application thereof. The preparation method of the composite ceramic ball is a sol-gel method, and comprises the following steps: (1) preparing silicon-zirconium-aluminum sol; (2) forming and curing the silicon-zirconium-aluminum sol obtained in the step (1) to obtain gel beads, and aging the gel beads to form a precursor; (3) and (3) carrying out heat treatment on the precursor obtained in the step (2) to obtain the composite ceramic ball. The composite ceramic ball has the characteristics of high particle sphericity, moderate size, low density, high mechanical strength and long service life, and can be used in a fluidized bed.
Description
Technical Field
The invention relates to the technical field of chemical materials, in particular to a low-density composite ceramic ball for a fluidized bed, and a preparation method and application thereof.
Background
Numerous industrial heat transfer processes suffer from fouling of the heat exchanger tube walls resulting in a decrease in heat transfer coefficient and an increase in pressure drop. Proper inert solid particles are added into the heat exchanger and are uniformly fluidized, so that the heat exchanger can play a role in enhancing heat transfer and preventing and removing scale.
The solid particles currently used in heat exchangers are deficient to various degrees. For example, corundum balls have a high density and are not fluidized uniformly and are difficult to circulate when operated at low flow rates; the wear resistance of the engineering plastic particles is poor, so that the service life is short and the operation cost is high; the quartz sand has high hardness and irregular shape, so that the quartz sand can cause harmful abrasion to the wall of the heat transfer pipe; and the glass beads have low strength and weak thermal shock resistance, and are easy to break in the using process.
Alumina (Al)2O3) Because of high hardness, good chemical inertness, non-volatility, high melting point and corrosion resistance, the material is widely applied to the fields of ceramics, refractory materials, grinding materials and the like. Silicon dioxide (SiO)2) By virtue of high temperature resistance, excellent chemical stability and lower thermal expansion coefficient, the alloy can be well used for Al2O3And (3) strengthening and modifying the ceramic. With SiO2And Al2O3In contrast, zirconium oxide (ZrO)2) Not only has higher acid and alkali corrosion resistance, but also has higher strength and fracture toughness resistance. It is contemplated that SiO is used2And ZrO2Composite modified Al2O3The ceramic should have a better overall performance. In the preparation of ceramic particles, the sol-gel preparation technology has the unique advantages of simple process, controllable steps, product composition and granularity and the like, and is an important method for preparing ceramics.
Disclosure of Invention
The invention provides a preparation method of a composite ceramic ball, which is preferably a sol-gel method and comprises the following steps:
(1) preparing silicon-zirconium-aluminum sol: the method specifically comprises the following steps:
a. strongly stirring and dispersing aluminum powder in water, heating, dropwise adding an aluminum salt solution, and reacting for 2-3 hours to obtain sol A;
b1. raising the temperature of the sol A, dropwise adding a zirconium salt solution into the sol A, and reacting for 2-3 hours to obtain a sol B; adding the silica sol into the solution B, and reacting for 8-10 h to obtain silicon-zirconium-aluminum sol; or the like, or, alternatively,
b2. raising the temperature of the sol A, simultaneously adding the silica sol and the zirconium salt solution into the sol A, and reacting for 10-12 h to obtain silicon-zirconium-aluminum sol; or the like, or, alternatively,
b3. raising the temperature of the sol A, adding the silica sol into the sol A, and reacting for 2-3 h to obtain sol B'; dropwise adding a zirconium salt solution into the solution B', and reacting for 8-10 h to obtain silicon-zirconium-aluminum sol;
(2) forming and curing the silicon-zirconium-aluminum sol obtained in the step (1) to obtain gel beads, and aging the gel beads to form a precursor;
(3) and (3) carrying out heat treatment on the precursor obtained in the step (2) to obtain the composite ceramic ball.
According to an embodiment of the present invention, in the step (1), the heating is constant temperature heating. Preferably, the heating temperature is not higher than 80 ℃, preferably 50-80 ℃, for example 75 ℃.
According to an embodiment of the present invention, in the step (1), the raising of the temperature of the sol B specifically means raising the temperature of the sol B to more than 80 ℃, preferably more than 90 ℃, for example, 90 to 100 ℃, for example, 98 ℃.
According to an embodiment of the present invention, in the step (1), the molar ratio of Zr, Si, and Al in the silica-zirconia-alumina sol is 1 (0-1): (5-100), such as 1:1 (5-60), and further such as 1:1:60, 1:1:30, 1:1:15, 1:1: 5.
According to an embodiment of the present invention, in step (1), the aluminum salt solution and the zirconium salt solution may be added dropwise using a method known in the art, for example, a constant pressure funnel.
According to an embodiment of the present invention, in the step (1), the aluminum salt solution includes an aluminum salt and a solvent.
Preferably, the aluminium salt is selected from aluminium chloride and hydrates thereof, aluminium sulphate and hydrates thereof, Al (NO)3)3And at least one of its hydrates, aluminum isopropoxide, e.g. selected from AlCl3·6H2O (e.g., from Shanghai Alatin Biochemical Co., Ltd., AR, 97.0%).
According to an embodiment of the present invention, in the step (1), the zirconium salt solution includes a zirconium salt and a solvent.
Preferably, the zirconium salt is selected from ZrOCl2·2H2O、ZrOCl2·8H2O (e.g., available from showa conda industrial ceramics, ltd.).
According to an embodiment of the present invention, in step (1), the silica sol is selected from 10 to 40 wt% silica sol, such as 20 wt% or 30 wt% silica sol (e.g. available from Qingdao Mike drying agent, Inc.). The silica sol in the present invention refers to a dispersion of nano-sized silica particles in water. Preferably, the silica sol may be an acidic silica sol.
According to an embodiment of the present invention, in the step (1), the concentration of the aluminum salt in the aluminum salt solution is 1 to 5mol/L, for example, 3 mol/L.
According to an embodiment of the present invention, in the step (1), the concentration of the zirconium salt in the zirconium salt solution is 1 to 5mol/L, for example, 2.5 mol/L.
According to an embodiment of the present invention, in the step (1), the molar ratio of the aluminum powder to the aluminum salt is 1 to 8, for example, 3.5.
According to the embodiment of the invention, in the step (1), the molar ratio of the sum of the moles of the aluminum powder and the aluminum salt to the zirconium salt is (5-100): 1, such as (5-60): 1.
According to the embodiment of the invention, in the step (2), the forming and curing specifically comprises obtaining gel beads after adding a curing agent into the silicon-zirconium-aluminum sol of the step (1).
Preferably, the curing agent is selected from Hexamethylenetetramine (HMT), for example hexamethylenetetramine (AR) from the chemical industry limited, Jiangtian, Tianjin.
Preferably, the mass ratio of the silicon-zirconium-aluminum sol to the curing agent is 5 (0.1-3), for example 5: 2.
Illustratively, the forming and curing process is an oil column forming process, for example, the oil column forming process comprises the following steps: the silicon-zirconium-aluminum sol added with the curing agent is dropped into the countercurrent hot oil in spherical drops, and is rapidly cured after being heated by the hot oil under the action of surface tension to form gel beads with certain mechanical strength, such as spherical gel microbeads. Further, the hot oil is provided by an oil column forming device, the oil column forming device comprises a three-mouth flat-bottom flask and a hot oil forming column with the height of 0.4 m, the hot oil is contained in the hot oil forming column, and the hot oil flows out of the top of the forming column and circulates to the three-mouth flat-bottom flask through a buffer bottle under the driving of a peristaltic pump. The desired residence time of the pellets during curing is controlled by controlling the flow rate of the hot oil.
According to an embodiment of the present invention, in the step (3), the conditions of the aging treatment include: the aging temperature is 100-150 ℃; the aging time is 1-12 h. Illustratively, the aging process conditions include: the aging temperature is 145 ℃; the aging time is 9-10 h.
Preferably, after the aging treatment, washing and/or drying can be performed, and the washing and drying can be performed by using a method known in the art.
According to an embodiment of the present invention, in the step (3), the heat treatment includes: the temperature is raised to the heat treatment temperature, and then the heat treatment is carried out.
Preferably, the conditions of the heat treatment include: the heat treatment time is 0.5-10 h, and the heat treatment temperature is 1000-1400 ℃.
Preferably, the rate of temperature rise is 1-10 ℃/min.
Illustratively, the conditions of the heat treatment include: the heat treatment time is 2h, the heat treatment temperature is 1250 ℃, and the heating rate is 8 ℃/min.
According to an exemplary embodiment of the present invention, the preparation method includes:
(1) preparing silicon-zirconium-aluminum sol: the method specifically comprises the following steps:
a. strongly stirring and dispersing aluminum powder in water, heating, dropwise adding an aluminum salt solution, and reacting for 2-3 h to obtain sol A;
b1. raising the temperature of the sol A, dropwise adding a zirconium salt solution into the sol A, and reacting for 2-3 hours to obtain a sol B; adding the silica sol into the solution B, and reacting for 8-10 h to obtain silicon-zirconium-aluminum sol;
(2) forming and curing the silicon-zirconium-aluminum sol obtained in the step (1) to obtain gel beads, and forming a precursor after aging, washing and drying the gel beads;
(3) carrying out heat treatment on the precursor in the step (2) to obtain the composite ceramic ball;
wherein the silica sol is selected from 20 wt% silica sol; in the aluminum salt solution, AlCl3The concentration of (A) is 3 mol/L; in the zirconium salt solution, ZrOCl2The concentration of (b) is 2.5 mol/L; the molar ratio of the aluminum powder to the aluminum salt is 3.5; the molar ratio of the sum of the moles of the aluminum powder and the aluminum salt to the zirconium salt is (5-60): 1, such as 60:1, 30:1, 15:1:, and 5: 1.
According to an exemplary embodiment of the present invention, the preparation method comprises:
(1) preparing silicon-zirconium-aluminum sol: the method specifically comprises the following steps:
a. strongly stirring and dispersing aluminum powder in water, heating, dropwise adding an aluminum salt solution, and reacting for 2-3 h to obtain sol A;
b2. raising the temperature of the sol A, simultaneously adding the silica sol and the zirconium salt solution into the sol A, and reacting for 10-12 h to obtain silicon-zirconium-aluminum sol; (2) forming and curing the silicon-zirconium-aluminum sol obtained in the step (1) to obtain gel beads, and forming a precursor after aging, washing and drying the gel beads;
(3) carrying out heat treatment on the precursor in the step (2) to obtain the composite ceramic ball;
wherein the silica sol is selected from 20 wt% silica sol; in the aluminum salt solution, AlCl3The concentration of (b) is 3 mol/L; in the zirconium salt solution, ZrOCl2The concentration of (b) is 2.5 mol/L; the molar ratio of the aluminum powder to the aluminum salt is 3.5; the molar ratio of the sum of the moles of the aluminum powder and the aluminum salt to the moles of the zirconium salt is (5-60: 1), for example, 60: 1.
According to an exemplary embodiment of the present invention, the preparation method includes:
(1) preparing silicon-zirconium-aluminum sol: the method specifically comprises the following steps:
a. strongly stirring and dispersing aluminum powder in water, heating, dropwise adding an aluminum salt solution, and reacting for 2-3 hours to obtain sol A;
b3. raising the temperature of the sol A, adding the silica sol into the sol A, and reacting for 2-3 h to obtain sol B'; dropwise adding a zirconium salt solution into the solution B', and reacting for 8-10 h to obtain silicon-zirconium-aluminum sol;
(2) forming and curing the silicon-zirconium-aluminum sol obtained in the step (1) to obtain gel beads, and forming a precursor after aging treatment, washing and drying of the gel beads;
(3) washing, drying and thermally treating the precursor in the step (2) to obtain the composite ceramic ball;
wherein the silica sol is selected from 20 wt% silica sol; in the aluminum salt solution, AlCl3The concentration of (b) is 3 mol/L; in the zirconium salt solution, ZrOCl2The concentration of (A) is 2.5 mol/L; the molar ratio of the aluminum powder to the aluminum salt is 3.5; the molar ratio of the sum of the moles of the aluminum powder and the aluminum salt to the moles of the zirconium salt is (5-60: 1), for example, 60: 1.
The invention also provides a composite ceramic ball prepared by the preparation method.
Preferably, the composite ceramic balls include at least ZrO2、SiO2、Al2O3Three components.
According to an embodiment of the present invention, the composite ceramic balls are spherical particles having uniform morphology.
Preferably, the particle size of the spherical particles is 0.1-10 mm, preferably 1-5 mm, and more preferably 1-3 mm.
According to an embodiment of the present invention, the composite ceramic balls comprise: zr, Si, Al in a molar ratio of 1: 0 to 1:5 to 100, for example, 1:1:5 to 60.
According to an embodiment of the invention, the composite ceramic balls have a dry density of less than 2400kg/cm3Preferably less than 2000kg/cm3For example, 1000 to 1800kg/cm3。
According to an embodiment of the present invention, the wet density of the composite ceramic balls is less than 2600kg/cm3Preferably less than 2300kg/cm3For example, 1200 to 2300kg/cm3。
In the invention, the dry density refers to the density of the composite ceramic ball after being dried for 24 hours at 105-125 ℃; the wet density is also called saturation density, and refers to the density of the composite ceramic ball in a water absorption saturation state. The water absorption saturation state is a state when the composite ceramic ball is soaked in water and the mass change rate is less than 1 wt%.
According to an embodiment of the invention, the composite ceramic balls have a dry compressive strength of more than 45N, preferably more than 50N, such as 55-200N.
According to an embodiment of the invention, the wet compressive strength of the composite ceramic balls is more than 50N, preferably more than 60N, such as 61-200N.
In the invention, the dry compression strength is a physical quantity which represents the capability of resisting external pressure after the composite ceramic ball is dried for 24 hours at 105-125 ℃, and is expressed by a stress value (1.05Pa) when a sample is stressed; the wet compressive strength is a physical quantity representing the ability of the composite ceramic ball to resist external pressure in a state saturated with water, and is expressed as a stress value (1.05Pa) when a sample is subjected to a force. The water absorption saturation state refers to a state when the composite ceramic ball is soaked in water and the mass change rate is less than 1 wt%.
According to an embodiment of the present invention, the composite ceramic balls have good corrosion resistance. The corrosion resistance in the invention refers to the proportion of the composite ceramic ball corroded after being soaked in strong acid or strong base at room temperature (for example, 10-30 ℃) for 24 hours, which is recorded as corrosion rate, and thus represents the corrosion resistance of the composite ceramic ball, wherein the higher the corrosion rate, the worse the corrosion resistance, the lower the corrosion rate, and the better the corrosion resistance.
Illustratively, the strong acid refers to hydrochloric acid having a concentration of 1 mol/L. Illustratively, the composite ceramic balls have a corrosion rate of less than 1.5% in 1mol/L hydrochloric acid.
Illustratively, the strong base refers to a sodium hydroxide solution having a concentration of 1 mol/L. Illustratively, the composite ceramic ball has a corrosion rate of less than 0.5% in a 1mol/L sodium hydroxide solution.
According to the embodiment of the invention, the composite ceramic ball has good wear resistance. The wear resistance in the invention refers to the proportion of the composite ceramic balls which are worn after the composite ceramic balls are ball-milled in a planetary ball mill (the ball-milling conditions are that the composite ceramic balls are self-milled, the rotating speed is 250r/min, and the ball-milling time is 24 hours), and the higher the wear rate is, the poorer the wear resistance is, the lower the wear rate is, and the better the wear resistance is.
Illustratively, the composite ceramic balls have a wear rate of less than 15%.
The invention also provides the application of the composite ceramic ball, which is preferably used for a fluidized bed, such as a heat exchanger of the fluidized bed.
According to the embodiment of the invention, the heat exchanger is selected from a shell-and-tube heat exchanger (also called a shell-and-tube heat exchanger), and the composite ceramic ball can be used for preventing scaling and enhancing heat transfer.
Advantageous effects
The composite ceramic ball prepared by the invention has low density, is easy to fluidize and has better wear resistance than pure alumina. The density of the composite ceramic ball is less than 2000kg/cm3Much lower than the density of ordinary ceramics (about 2400-2900 kg/cm)3) And the density of the alumina ceramic (about 3000 kg/cm)3) The fluidized bed can be fluidized and uniformly distributed in the heat exchanger, and is easy to circulate. The composite ceramic ball has excellent wear resistance, and the engineering plastic particles have poor wear resistance although the density is low, and the wear rate of the composite ceramic ball is far higher than that of the composite ceramic ball.
According to the invention, the composite ceramic ball is prepared by researching the influence of the process conditions such as the molar ratio of Zr to Si, the adding sequence of Zr and Si and the like on the density, hardness and frictional wear performance of the composite material, so that the composite ceramic ball has lower density, higher mechanical strength, corrosion resistance and wear resistance, can be uniformly fluidized and distributed in a heat exchanger tube bundle, can fully exert the functions of enhanced heat transfer and scale prevention and removal of the composite ceramic ball in a fluidized bed, has long service life, and is a composite material with relatively superior comprehensive performance.
The composite ceramic ball prepared by the invention can be applied to a fluidized bed heat exchanger.
Drawings
FIG. 1 shows alpha-Al in comparative example 1 of the present invention2O3X-ray diffraction pattern of (a).
FIG. 2 is an X-ray diffraction pattern of the composite particle in comparative example 2 of the present invention.
Fig. 3 is an EDS diagram of the spherical composite ceramic balls of example 1 of the present invention.
FIG. 4 shows a-Al in comparative example 1 of the present invention2O3And X-ray diffraction patterns of the spherical composite ceramic spheres of examples 1 and 4 to 6.
FIG. 5 is an X-ray diffraction pattern of the spherical composite ceramic balls of examples 1 to 3 of the present invention.
FIG. 6 shows α -Al in comparative example 1 of the present invention2O3And the abrasion resistance of the spherical composite ceramic balls of examples 1 and 4 to 6.
FIG. 7 shows a-Al in comparative example 1 of the present invention2O3And the abrasion resistance of the spherical composite ceramic balls of examples 1 and 4 to 6.
FIG. 8 shows a-Al in comparative example 1 of the present invention2O3And example 1, examples 4-6, the corrosion resistance of the spherical composite ceramic balls is compared.
FIG. 9 shows α -Al in comparative example 1 of the present invention2O3And the corrosion resistance of the spherical composite ceramic balls of examples 1 to 3.
Fig. 10 is a physical diagram of the composite ceramic ball of example 1.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
Experimental drugs: aluminum powder and ZrOCl2·2H2O (e.g., from ceramics, Conda, Suzhou Co., Ltd.), aluminum trichloride hexahydrate (AlCl)3·6H2O, available from Albantin Biochemical Co., Ltd, Shanghai, AR, 97.0%), hexamethylenetetramine (i.e., hexamethylenetetramine, HMT, available from Tianjin, JiangAR), deionized water, concentrated hydrochloric acid, sodium hydroxide, 30 wt% silica sol (available from Qingdao mackerel dessicant, ltd);
an experimental instrument: BSA224S analytical balance, DFY-5/30 low-temperature constant-temperature reaction bath, CJJ79-1 magnetic heating stirrer, DF-101S heat collection type constant-temperature heating magnetic stirrer, XK-500ML hydrothermal synthesis reaction kettle, CK15 intelligent peristaltic pump, DG-202 electrothermal constant-temperature drying box, KSL-1700X-S muffle furnace, DL3-300 intelligent particle strength tester and PMQW-04 planetary ball mill.
Comparative example 1: alpha-Al2O3Preparation of spherical particles
16.5g of aluminum powder was weighed into a three-necked flask together with 84mL of deionized water while being dispersed uniformly in water with vigorous stirring, and heated to 75 ℃ in a constant-temperature oil bath. Then, 58ml of 3mol/L AlCl were added dropwise at a rate of 8 drops per minute3In solution (aluminum powder and AlCl)3The molar ratio of (a) to (b) is 3.5), and reacting for 12-16 h to obtain the hydrosol.
Curing and molding: uniformly mixing a solution containing a curing agent hexamethylene tetramine with the hydrosol, wherein the mass ratio of the hydrosol to the curing agent is 5: 2; the hydrosol is subjected to particle forming on a self-made oil column forming device, the oil column forming device consists of a three-neck flat-bottom flask and a hot oil forming column with the height of about 0.4 m, and the hot oil flows out of the top of the forming column under the driving of a peristaltic pump and circulates to a three-neck flat-bottom bottle through a buffer bottle with the capacity of 500 mL. In the curing process, hydrosol added with curing agent is dripped into hot oil by an injector to form spherical glue drops, the spherical glue drops are dripped into an inner tube of a forming column against the flowing direction of the hot oil, the residence time of the glue drops is controlled by controlling the flow rate of the hot oil, and the spherical glue drops are rapidly cured after being heated by the hot oil under the action of surface tension and fall to the bottom of a flat-bottomed flask to form spherical gel microbeads with certain mechanical strength.
After curing was complete, all the gel beads obtained were transferred to an autoclave and heat aged in an oven at 145 ℃ for 9.5 ± 0.5h to ensure complete HMT decomposition, thereby further improving the mechanical strength of the gel beads. Thereafter, in order to remove the adhesionOil and other ions, washing and soaking the gel spheres with distilled water repeatedly, and then drying in an oven at 120 ℃ for 5 h. Finally, calcining the mixture for 2 hours at 1250 ℃ in a muffle furnace at the speed of 8 ℃/min to obtain the alpha-Al2O3Spherical particles.
FIG. 1 shows α -Al in comparative example 12O3X-ray diffraction pattern of spherical particles. The results of FIG. 1 show that α -Al of comparative example 12O3Diffraction peak of spherical particle and alpha-Al2O3The standard cards were completely identical with no other miscellaneous peaks.
Test example 1
And (3) wear resistance test: 0.3g of alpha-Al is taken2O3Ball milling is carried out on the spherical particles in a planetary ball mill, and the ball milling conditions are as follows: and (4) self-milling at 250r/min for 24 hours, and then calculating the wear rate, namely the mass ratio of the mass of the worn spherical particles to the initial mass of the small balls.
And (3) corrosion resistance testing: 0.3g of the mixture is respectively soaked in 1mol/L hydrochloric acid and sodium hydroxide solution at room temperature for 24 hours. The erosion rate, i.e. the mass ratio of the eroded mass of spherical particles to the initial mass of the pellets, was calculated.
alpha-Al of comparative example 1 measured by Intelligent particle Strength tester2O3The physical properties of the spherical particles are shown in Table 1.
As shown by the above tests, the α -Al prepared in comparative example 12O3Spherical particles have good corrosion resistance, but they have too high a density, poor wear resistance and also poor mechanical strength.
Comparative example 2: ZrO (ZrO)2/Al2O3Preparation of spherical particles
Weighing 16.5g of aluminum powder and 84mL of deionized water, adding the aluminum powder and the deionized water into a three-neck flask together, stirring the mixture strongly to ensure that the mixture is uniformly dispersed in water, reacting the mixture in a constant-temperature oil bath at 75 ℃ for 2.5 +/-0.5 h, and after three minutes, dripping 58mL of 3mol/L AlCl at the speed of 8 drops per minute3In solution (aluminium powder and AlCl)3At a molar ratio of 3.5), then the oil bath temperature was raised to 98 ℃ while 5ml of 2.5mol/L ZrOCl were added2The solution was slowly dropped into the flask, AlCl3And ZrOCl2The molar ratio of 60/1, reacting with the residual aluminum powder for 2-3 h, and continuously stirring the mixture for 12-16 h to obtain the sol.
Curing and forming: the sol was cured and molded in the home-made oil column molding apparatus according to the curing and molding method of comparative example 1 to obtain gel beads.
After curing was complete, all the gel beads obtained were transferred to an autoclave and heat aged in an oven at 145 ℃ for 9.5 ± 0.5h to ensure complete HMT decomposition, thereby further improving the mechanical strength of the gel beads. Thereafter, in order to remove the attached oil and other ions, the gel spheres were repeatedly washed and soaked with distilled water, and then dried in an oven at 120 ℃ for 5 hours. Finally, the spherical composite particles are obtained by calcining the mixture for 2 hours at 1250 ℃ in a muffle furnace under the condition of 8 ℃/min.
FIG. 2 is an X-ray view of the composite particle of the comparative example, showing that the sample prepared in the comparative example includes theta-Al2O3、α-Al2O3And t-ZrO2The diffraction peak of (1).
Test example 2
Taking the spherical particles of the comparative example 2, and performing a wear resistance test and a corrosion resistance test according to the test method of the test example 1; and physical properties of the spherical composite particles of comparative example 2 were measured using an intelligent particle strength meter, see table 1 for details.
As can be seen from the above tests, the sample prepared in this comparative example has excellent wear resistance of 1.66% and corrosion resistance (0.46% corrosion rate in 1mol/L hydrochloric acid and 0.90% corrosion rate in 1mol/L sodium hydroxide solution), but it has a higher density (see Table 1), is not easy to fluidize, and is not suitable for fluidized bed operation.
Example 1:
ZrO2/SiO2/Al2O3the preparation method of the spherical composite ceramic ball comprises the following steps:
(1) 16.5g of aluminum powder was weighed into a three-necked flask together with 84mL of deionized water, and the mixture was dispersed uniformly in water in a constant temperature oil bath at 75 ℃ for three minutes with vigorous stirring8 drops of 3mol/L AlCl of 58ml are added3Solution (aluminum powder and AlCl)3The molar ratio of (3.5) is 3.5) reacting for 2-3 h, then raising the oil bath temperature to 98 ℃, and simultaneously adding 5.25ml of 2.5mol/L ZrOCl2The solution is slowly dropped into the flask, and aluminum powder and AlCl are added3Sum of molar weight of (b) and ZrOCl2The molar ratio of (1) to (2) is 60:1, the mixture reacts with the rest aluminum powder for 2-3 hours, and then the mixture is continuously stirred and reacts at the temperature of 98 ℃; finally, 4g of 20 wt% silica sol (30 wt% silica sol is diluted to 20 wt%, the same applies below) is dripped into the reactor, the mixture is continuously stirred, and the reaction is carried out for 9 +/-1 h at 98 ℃ to obtain the silicon-zirconium-aluminum sol.
(2) Curing and forming: and (3) carrying out particle forming on the silicon-zirconium-aluminum sol in the self-made oil column forming device according to the curing forming mode of the comparative example 1 to obtain gel beads.
(3) After curing was complete, all the gel beads obtained were transferred to an autoclave and heat aged in an oven at 145 ℃ for 9.5 ± 0.5h to ensure complete HMT decomposition, thereby further improving the mechanical strength of the gel beads. Thereafter, in order to remove the adhered oil and other ions, the gel spheres were repeatedly rinsed and soaked with distilled water, and then dried in an oven at 120 ℃ for 5 hours. Finally, calcining the mixture for 2 hours at 1250 ℃ in a muffle furnace at the speed of 8 ℃/min to obtain spherical composite particles, wherein the molar ratio of Zr to Si to Al is 1:1:60, and the spherical composite particles are marked as Zr1/60Si1/60Al-a。
Example 2
A spherical composite ceramic ball was prepared by the method of reference example 1, except that, in step (1), ZrOCl was used2The method comprises the following steps of adding the solution and the silica sol simultaneously, wherein the method specifically comprises the following steps: 16.5g of aluminum powder was weighed into a three-necked flask together with 84mL of deionized water, and uniformly dispersed in water in a constant temperature oil bath at 75 ℃ with vigorous stirring. After three minutes, 8ml of 3mol/L AlCl were added dropwise at a rate of 8 drops per minute3Solution (aluminum powder and AlCl)3The molar ratio of (a) to (b) is 3.5) reacting for 2-3 h; the oil bath temperature was then raised to 98 ℃ while 5ml of 2.5mol/L ZrOCl were mixed2The solution and 4g of 20 wt% silica sol are slowly dropped into a flask and reacted for 10-12 h at 98 ℃ to obtain the silicon zirconium aluminum sol. This exampleThe obtained spherical composite particles have a molar ratio of Zr to Si to Al of 1:1:60, and are marked as Zr1/60Si1/60Al-b。
Example 3
Referring to the method of example 1, a spherical composite ceramic ball was prepared, except that in step (1), silica sol was added to form a gel, and then ZrOCl was added2The solution specifically comprises: 16.5g of aluminum powder was weighed into a three-necked flask together with 84mL of deionized water, and uniformly dispersed in water in a constant temperature oil bath at 75 ℃ with vigorous stirring. After three minutes, 58ml of 3mol/L AlCl were added dropwise at a rate of 8 drops per minute3Solution (aluminum powder and AlCl)3The molar ratio of (3.5) and reacting for 2-3 h; then the oil bath temperature was raised to 98 ℃ while 4g of 20 wt% silica sol was slowly dropped into the flask, aluminum powder and AlCl3The molar ratio of the sum of the molar weight of the silica sol to the silica sol is 60:1, and then the mixture is continuously stirred and reacts for 2 to 3 hours at the temperature of 98 ℃; finally, 2.5mol/L ZrOCl is dripped into the reactor2And reacting the solution for 8-10 h to obtain the silicon-zirconium-aluminum sol. The spherical composite particles obtained in this example had a Zr/Si/Al molar ratio of 1:1:60, and were recorded as Zr1/60Si1/60Al-c。
Example 4
A spherical composite ceramic ball was prepared by the method of reference example 1, except that, in step (1), 2.5mol/L of ZrOCl2The amount of the solution added was 10.5ml and the amount of the 20 wt% silica sol added was 7.9 g. In the spherical composite particles obtained in this example, the molar ratio of Zr, Si and Al is 1:1:30, and it is noted as Zr1/30Si1/30Al-a。
Example 5
A spherical composite ceramic ball was prepared by the method of reference example 1, except that, in step (1), 2.5mol/L of ZrOCl2The amount of the solution added was 21ml and the amount of 20 wt% silica sol added was 15.8 g. In the spherical composite particles obtained in this example, the molar ratio of Zr, Si and Al is 1:1:15, and is recorded as Zr1/15Si1/15Al-a。
Example 6
Preparation of spherical composite with reference to the method of example 1Ceramic ball, except that in step (1), 2.5mol/L of ZrOCl2The amount of the solution added was 63ml and the amount of 20 wt% silica sol added was 47.2 g. The spherical composite particles obtained in this example had a Zr/Si/Al molar ratio of 1:1:5, which was recorded as Zr1/5Si1/5Al-a。
Test example 3
1. Fig. 3 is an EDS diagram of the spherical composite ceramic balls according to example 1 of the present invention, in which it can be seen that alumina, zirconia, and silica are uniformly distributed.
2. FIGS. 4 and 5 are X-ray diffraction patterns of the spherical composite ceramic balls according to examples 1 to 6 of the present invention, and the results show that the diffraction peaks of the samples prepared according to the present invention are theta-Al2O3And t-ZrO2Thus SiO2The structure of (a) is amorphous.
3. Ball-milling experiment: the spherical composite particles of examples 1 to 6 were each subjected to an abrasion resistance test in accordance with the test method of test example 1, and the test results are shown in FIGS. 6 to 7; the corrosion resistance test results are shown in fig. 8-9.
4. The physical properties of the spherical composite particles of examples 1-6 were measured using a smart particle intensity tester, see table 1.
Table 1 is a table comparing physical properties of the spherical particles prepared in comparative examples 1-2 and examples 1-6
As can be seen from Table 1, the compressive strength of the composite ceramic balls of examples 1 to 6 is much better than that of the pure Al of comparative example 12O3. Wherein, Zr of example 61/5Si1/5Al-a has the greatest compressive strength but its particle density is too great, and the dry and wet particle densities of the composite particles of examples 4-6 decrease as the molar ratio of zirconium to silicon increases. As a comprehensive comparison, the molar ratio and the addition sequence of example 1 produced Zr as compared with examples 2-61/60Si1/60Al-a has better particle density and compressive strength.
Pure oxygen as compared with comparative example 1The wear resistance of the nucleated ceramic balls of examples 1 and 4-6 was significantly improved with the addition of Zr and Si compared to aluminum, decreasing from 25.59% to about 2.68% (see fig. 6). Removing Zr with increasing molar ratio of Zr to Si1/60Si1/60In addition to the Al-a sample, the mass wear rate of the composite particles was gradually decreased, and it can be seen from comparative examples 1 to 3 that the composite ceramic balls prepared by adding Zr first in example 1 had stronger wear resistance (see fig. 7). Zr1/60Si1/60Al-a has the best abrasion resistance, Zr under strong acid and strong alkali solution conditions (FIGS. 8 and 9)1/60Si1/60The loss of Al-a in strong acid solution is only 1.26%, and the loss in strong base solution is 0.4%, which is not much different from that of pure alumina in comparative example 1, and has good corrosion resistance. As can be seen from the above, Zr in example 11/60Si1/60Al-a has the best density, mechanical strength, wear resistance and corrosion resistance.
The above description is that of the exemplary embodiments of the invention. However, the scope of protection of the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the composite ceramic ball is characterized by being a sol-gel method and comprising the following steps of:
(1) preparing silicon-zirconium-aluminum sol: the method specifically comprises the following steps:
a. strongly stirring and dispersing aluminum powder in water, heating, dropwise adding an aluminum salt solution, and reacting for 2-3 hours to obtain sol A;
b1. raising the temperature of the sol A, dropwise adding a zirconium salt solution into the sol A, and reacting for 2-3 hours to obtain a sol B; adding the silica sol into the solution B, and reacting for 8-10 h to obtain silicon-zirconium-aluminum sol; or the like, or, alternatively,
b2. raising the temperature of the sol A, simultaneously adding the silica sol and the zirconium salt solution into the sol A, and reacting for 10-12 h to obtain a silica-zirconium-aluminum sol;
b3. raising the temperature of the sol A, adding the silica sol into the sol A, and reacting for 2-3 h to obtain sol B'; dropwise adding a zirconium salt solution into the solution B', and reacting for 8-10 h to obtain silicon-zirconium-aluminum sol;
(2) forming and curing the silicon-zirconium-aluminum sol obtained in the step (1) to obtain gel beads, and aging and treating the gel beads to form a precursor;
(3) and (3) carrying out heat treatment on the precursor obtained in the step (2) to obtain the composite ceramic ball.
2. The method according to claim 1, wherein the heating in step (1) is constant temperature heating. Preferably, the heating temperature is not higher than 80 ℃.
Preferably, in the step (1), raising the sol B specifically means raising the temperature of the sol B to more than 80 ℃.
Preferably, in the step (1), the molar ratio of Zr, Si and Al in the silica-zirconium-aluminum sol is 1 (0-1) to (5-100).
3. The production method according to claim 1 or 2, wherein in step (1), the aluminum salt solution includes an aluminum salt and a solvent.
Preferably, the aluminium salt is selected from aluminium chloride and hydrates thereof, aluminium sulphate and hydrates thereof, Al (NO)3)3And at least one of a hydrate thereof and aluminum isopropoxide.
Preferably, in step (1), the zirconium salt solution comprises a zirconium salt and a solvent.
Preferably, the zirconium salt is selected from ZrOCl2·2H2O、ZrOCl2·8H2O。
Preferably, in the step (1), the silica sol is 10 to 40 wt% of silica sol.
Preferably, in the step (1), the concentration of the aluminum salt in the aluminum salt solution is 1-5 mol/L.
Preferably, in the step (1), the concentration of the zirconium salt in the zirconium salt solution is 1-5 mol/L.
Preferably, in the step (1), the molar ratio of the aluminum powder to the aluminum salt is 1-8.
Preferably, in the step (1), the molar ratio of the sum of the aluminum powder and the aluminum salt to the zirconium salt is (5-100): 1.
4. The preparation method according to any one of claims 1 to 3, wherein in the step (2), the forming and curing specifically comprises obtaining gel beads after adding a curing agent to the silica-zirconium-aluminum sol of the step (1).
Preferably, the curing agent is selected from hexamethylenetetramine.
Preferably, the mass ratio of the silicon-zirconium-aluminum sol to the curing agent is 5 (0.1-3).
Illustratively, the forming solidification is performed by an oil column forming method.
5. The production method according to any one of claims 1 to 4, wherein in the step (3), the conditions of the aging treatment include: the aging temperature is 100-150 ℃; the aging time is 1-12 h.
Preferably, the aging treatment is followed by washing and/or drying.
Preferably, in the step (3), the heat treatment includes: the temperature is raised to the heat treatment temperature, and then the heat treatment is carried out.
Preferably, the conditions of the heat treatment include: the heat treatment time is 0.5-10 h, and the heat treatment temperature is 1000-1400 ℃.
Preferably, the temperature rise rate is 1-10 ℃/min.
6. A composite ceramic ball produced by the production method according to any one of claims 1 to 5.
Preferably, the composite ceramic balls include at least ZrO2、SiO2、Al2O3Three components.
7. The composite ceramic balls of claim 6, wherein the composite ceramic balls are spherical particles of uniform morphology.
Preferably, the particle size of the spherical particles is 0.1-10 mm.
8. The composite ceramic ball according to claim 6 or 7, wherein the composite ceramic ball is made of raw materials including: the molar ratio of Zr to Si to Al is 1 (0-1) to 5-100.
Preferably, the dry density of the composite ceramic balls is less than 2400kg/cm3。
Preferably, the wet density of the composite ceramic balls is less than 2600kg/cm3。
9. The composite ceramic balls of any one of claims 6-8, wherein the composite ceramic balls have a dry compressive strength of greater than 45N.
Preferably, the wet compressive strength of the composite ceramic balls is greater than 50N.
Preferably, the composite ceramic balls have good corrosion resistance.
Preferably, the composite ceramic balls have good wear resistance.
10. Use of the composite ceramic balls according to any one of claims 6-9, preferably for fluidized bed.
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