Method for producing ultrafine short fibers using rock raw material

Abstract

This invention relates to the field of inorganic materials chemistry, and more particularly to a method for producing ultrafine short fibers from rock raw materials. In an oxidizing environment, basalt fragments are melted at a temperature of 1300±50℃-1500±50℃. The basalt is melted and homogenized, forming droplets. The temperature of these droplets in the exhaust zone is 1300-1400℃, from which primary fibers with a diameter of 100 to 150 micrometers are drawn out. These fibers are then blown at high temperature through a jet chamber nozzle. The plume temperature at the nozzle outlet is 1550-1600℃, further melting the primary fibers and drawing them into ultrafine basalt fibers by a high-speed airflow. By using a specified heating temperature, high homogenization of the basalt melt can be achieved, with a melt viscosity modulus between 1.8 and 2.3. The basalt fiber product obtained by this method has a diameter of 1.2-3.2 micrometers; the fibers have a long service life, are resistant to high temperatures, and improve the quality of the basalt fibers.

Description

Technical Field

[0001] This invention relates to the field of inorganic materials chemistry, and in particular to a method for producing ultrafine short fibers using rock raw materials. Background Technology

[0002] Currently, countries around the world are showing increasing interest in various fibers derived from basaltic rocks. These rocks are formed from the solidification and crystallization of magma (erupted volcanic rocks), and are a complex silicate system containing oxides of alkali metals and alkaline earth metals, characterized by a high iron oxide content (up to 16%).

[0003] The availability and low cost of rocks such as basalt make it possible to produce ultrafine fibers and fiber products from them. Numerous studies have shown that, in order to process them into fibers, suitable melts are those whose rheological behavior (such as viscosity, viscosity-temperature relationship, production interval, activation energy) and complex physicochemical properties (such as surface tension, wettability) correspond to certain parameters, and within the upper and lower temperature ranges of these parameters, the melt can form fibers.

[0004] In the method of producing fibers from rock melt using basalt (SU, AS No. 461909, C03B 37 / 00, 1983), crushed basalt is used, and fiber production is carried out at a melt temperature of 1200-1300°C and a viscosity of 100 psi (10 Pascals). The disadvantages of this method are process instability and short intervals between continuous fiber production, because primary crystallization occurs in the melt under the specified temperature conditions, leading to fiber breakage. Furthermore, the specified melting temperature of 1200-1300°C is relatively low because this melt contains unmelted particles.

[0005] In addition, existing technology also proposes a method for producing fibers from basalt, using basalt with the following range (%): SiO2 45-56%, Al2O3 10-19%, TiO2 0.9-2.0%, Fe2O3 and FeO 7-18%, CaO 6-15%, MgO and MnO 3-7%, Na2O and K2O 2.5-6%, with the ratio of major fiber-forming oxides and related oxides ranging from 3.2% to 1.6%; the crushed basalt is heated to a temperature of 250-400°C, loaded into a burner-loader flame with a maximum temperature of 1450-2000°C, and melted, degassed, and homogenized on a melting pad at a low melting level of 5-70 mm. Subsequently, the melting level is increased to 80-300 mm in the furnace trough, and fiber drawing is performed at a spinneret temperature of 80-300 mm. The feed temperature is 30-200°C lower than the upper limit of basalt melt crystallization temperature (RU 2421408, November 23, 2009).

[0006] The disadvantages of the above method are low fiber quality, low production ratio, and complex production process. The high-temperature preparation of basalt leads to a decrease in melt quality. The wide temperature range of the melting furnace causes rapid wear of the furnace refractory material, further increasing the possibility of melt crystallization and resulting in vitrification of the spinneret surface.

[0007] Currently, there are known methods and apparatuses for producing ultrafine short fibers from rocks ("Method for Producing Ultrafine Fibers from Rocks," Ukrainian Patent No. 27699, published November 12, 2007), and ("Apparatus for Producing Short Fibers," Ukrainian Patent No. 96308, published January 26, 2015). However, these patents mainly concern simplifying equipment design and improving equipment operating efficiency. A drawback of this equipment is that the quality of the produced basalt short fibers is low due to the presence of a large amount of non-fibrous inclusions (granules).

[0008] The method that most closely resembles the proposed short-fiber microfiber production method is the basalt microfiber production method (patent CN1281828A, published on 2001-01-31). This method involves heating basalt to 1500-1600℃, achieving a basalt melt viscosity of 110-500 poise, homogenizing the melt, and drawing it into filaments at a speed of 3500-4500 meters per minute. However, obtaining high-quality fibers under these specified parameters is difficult. A drawback of this method is the low quality of the resulting basalt short fibers due to the presence of numerous non-fiber inclusions and mechanical contact (adhesion) between fibers, which can potentially form due to the specific viscosity of the flowing melt. Summary of the Invention

[0009] In order to improve the quality of basalt fibers, this invention provides a method for producing ultrafine short fibers using rock raw materials.

[0010] This invention is achieved through the following technical solution: a method for producing ultrafine short fibers using rock raw materials, comprising the following steps: in an oxidizing environment, basalt crushed stone is melted at a temperature of 1300±50℃-1500±50℃, the basalt is melted and homogenized to form droplets, the temperature of the droplets in the exhaust zone is 1300-1400℃, primary fibers with a diameter of 100 to 150 micrometers are drawn out, and then blown at high temperature through the nozzle of the jet chamber, the plume temperature at the outlet of the jet chamber nozzle is 1550-1600℃, the primary fibers are melted, and blown by high-speed airflow into basalt ultrafine short fibers with a diameter of 1.2-3.2 micrometers and a length of 50-70 millimeters.

[0011] As a further improvement to the technical solution of the present invention, the Wuyan crushed stone is melted in a continuous furnace. Before melting, it needs to be sorted and crushed to a particle size of 3 to 10 mm, and metal particles are removed by a magnetic separator. Then it is washed, dried and filtered.

[0012] As a further improvement to the technical solution of the present invention, the chemical composition of the basalt crushed stone is as follows: silicon dioxide 49.04-54.70%, aluminum oxide 16.83-18.98%, calcium oxide 12.69-13.50%, magnesium oxide 5.15-5.49%, ferrous oxide 3.22-4.8%, iron oxide 3.9-4.41%, sodium oxide 3.51-3.78%; the acidity coefficient of the basalt crushed stone is 1.89-2.28.

[0013] As a further improvement to the technical solution of the present invention, before the basalt crushed stone is melted in an oxidizing environment, the basalt crushed stone is preheated to 90-140°C by the recovered gas discharged from the continuous furnace.

[0014] As a further improvement to the technical solution of the present invention, after obtaining the ultrafine short basalt fibers, static electricity is eliminated by using a weak aqueous acid solution with a pH value of 4-4.5.

[0015] As a further improvement to the technical solution of the present invention, the weak aqueous acid solution is an acetic acid solution or a citric acid solution.

[0016] The present invention provides a method for producing ultrafine short fibers using rock raw materials, which has the following advantages compared with the prior art: By using a specified heating temperature, the basalt melt can be highly homogenized, with a melt viscosity modulus between 1.8 and 2.3. The basalt fiber product obtained by this method has a diameter of 1.2-3.2 micrometers; the fiber has a long service life, high temperature resistance, and improved basalt fiber quality. The basalt ultrafine short fibers obtained according to this invention can be used in the aerospace industry, shipbuilding industry, automotive industry, cryogenic engineering, household appliances, thermal insulation structures (furnaces, drying drums, engines), cyclone separators, electrostatic precipitators and other thermal energy equipment, as well as refrigeration equipment in the textile, chemical, mechanical engineering, electronics and other economic sectors. Detailed Implementation

[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0019] Studies have shown that the degree of amorphization increases with increasing melt temperature. Within the temperature range of 1500-1600℃, the degree of amorphization and fiber quality indicators increase significantly when the melt is overheated for a short time (60 minutes). Within the melting temperature range of 1500-1600℃, the thickness of basalt more completely transforms from a crystalline state to an amorphous state, with a melt amorphity as high as 96%. High-quality fibers are difficult to obtain at this temperature.

[0020] Therefore, the present invention provides a specific embodiment of a method for producing ultrafine short fibers using rock raw materials, comprising the following steps: in an oxidizing environment, basalt crushed stone is melted at a temperature of 1300±50℃-1500±50℃, the basalt is melted and homogenized to form droplets, the temperature of the droplets in the exhaust zone is 1300-1400℃, primary fibers with a diameter of 100 to 150 micrometers are drawn out, and then blown at high temperature through the nozzle of the jet chamber, the plume temperature at the outlet of the jet chamber nozzle is 1550-1600℃, the primary fibers are melted, and blown by high-speed airflow into basalt ultrafine short fibers with a diameter of 1.2-3.2 micrometers and a length of 50-70 millimeters.

[0021] In one example provided by the present invention, the volcanic rock is melted in a continuous furnace. Before melting, it needs to be sorted and crushed to a particle size of 3 to 10 mm, metal particles are removed by a magnetic separator, and then it is washed, dried and filtered.

[0022] Before melting basalt crushed stone in an oxidizing environment, it is preheated to 90-140℃ by recovered gas discharged from a continuous furnace. This reduces the emission of volatile components (SO2, H2, F2, B2, etc.) from the continuous furnace, increases the melting rate of the raw material, and reduces the heat energy consumed in the melting zone to obtain the melt, thereby improving the efficiency of the method. This is because the cold material from the charging device can lower the temperature of the melting zone by 100-150℃ and also has a beneficial effect on the resistance of the refractory material, improving the safety of the furnace space. Furthermore, the exhaust gas from the continuous furnace contains almost no sulfur components that corrode metals.

[0023] Of course, existing technologies involve using residual heat to dry basalt at 150-900°C, removing crystal water and heating it (see, for example, Russian Federation Patent Nos. 2118300 and 2149841). However, these high-temperature treatments of the initial raw materials do not always have a beneficial effect on the properties of the melt and the resulting fibers, because magma is known to be a fluid silicate melt, mainly composed of non-volatile rock oxides (by volume): SiO2, TiO2, Al2O3, Fe2O3, FeO, CaO, MgO, Na2O, and K2O, totaling 90-97%. Volatile components in magma include CO2, H2, H2O, F2, and B. CO2, H2, and N2O are easily (firstly) separated from the melt. However, fluorine and other volatile components are difficult to separate from the melt and therefore accumulate in it. The presence of water significantly accelerates the recrystallization process, as even small amounts can act as a strong catalyst. The effects of N₂O on the structure and chemical properties of silicate melts are particularly pronounced. Increased N₂O pressure and its dissolution reduce the melt viscosity and transform aluminosilicate melts into silicate melts. Increased volatile (fluid) component content helps the melt remain liquid at relatively low temperatures, which is crucial for basalt fiber production.

[0024] One aspect of this invention lies in selecting a suitable melting temperature, particularly in the initial stages. Existing technology shows that the degradation rate of refractory materials begins to accelerate when the temperature rises above the critical temperature, with alkali metal oxides exhibiting the strongest corrosive effect on the lining. Therefore, within the range of 1450-1550°C, the service life of the refractory material is reduced by approximately two times for every 50°C increase in the basalt glass melting temperature, and by three times at 75°C. Lining cooling is considered one of the main factors in extending the service life of glass furnaces, but this requires significant manpower and is not always effective. Therefore, this invention uses basalt crushed stone with low corrosiveness. The chemical composition of the basalt crushed stone is as follows: silicon dioxide 49.04-54.70%, aluminum oxide 16.83-18.98%, calcium oxide 12.69-13.50%, magnesium oxide 5.15-5.49%, ferrous oxide 3.22-4.8%, iron oxide 3.9-4.41%, and sodium oxide 3.51-3.78%; the acidity coefficient of the basalt crushed stone is 1.89-2.28. Using basalt crushed stone with low corrosiveness can reduce the chemical corrosiveness of the melt, weaken the corrosive effect on the furnace refractory material, and facilitate the formation of spinel, forming a protective (decorative) layer on the furnace lining surface.

[0025] Furthermore, it has been confirmed that the amount of non-fibrous inclusions in the fiber canvas depends on the Fe2O3 content in the melt. Therefore, when the Fe2O3 content decreases while the concentrations of SiO2 and Al2O3 in the melt increase, the amount of non-fibrous inclusions ("small pieces") in the forming fiber cloth decreases. Thus, the concentration of Fe2O3 in the melt affects the quality of the resulting fiber cloth. By appropriately adjusting the composition of the raw materials, i.e., the composition of the melt, the product quality (the content of non-fibrous inclusions in the fiber cloth) can be affected.

[0026] Observations conducted at a pilot plant for basalt fiber production confirmed the presence of static charge on the ultrafine basalt yarn, negatively impacting its properties. The amount of static electricity generated on the basalt short fibers is inversely proportional to indoor humidity. Humidity cannot always be controlled in fiber production areas, leading to the accumulation of charged fibers on surrounding surfaces and workers. Therefore, this invention, after preparing the ultrafine basalt short fibers, uses a weak aqueous acid solution with a pH of 4-4.5 to eliminate static electricity. Specifically, the weak aqueous acid solution is used as an antistatic agent, sprayed in a mist form through a nozzle onto the surface of the ultrafine basalt short fibers being blown by a high-speed airflow under pressure. Specifically, the weak aqueous acid solution is an acetic acid solution or a citric acid solution.

[0027] The specific embodiments of the present invention will be described in detail below. Example 1

[0028] Weight percentage of basalt raw material: The composition is as follows: SiO2 49.04%, Al2O3 18.98%, CaO 13.50%, MgO 5.49%, FeO 4.8%, Fe2O3 4.41%, Na2O 3.78%, with an acidity coefficient of 1.89.

[0029] In an oxidizing environment, basalt fragments are melted at a temperature of 1300±50℃. The basalt is melted and homogenized, and the melt is kept for 2 hours for homogenization treatment to form droplets. The temperature of the droplets in the exhaust zone is 1350±20℃, and primary fibers with a diameter of 150 micrometers are drawn out. Then, they are blown at high temperature through the nozzle of the jet chamber. The temperature of the plume at the outlet of the jet chamber nozzle is 1550℃. The primary fibers are melted and blown into ultrafine short basalt fibers by the high-speed airflow.

[0030] Compared to other embodiments, this embodiment increases the Fe2O3 content and lowers the upper limit temperature for crystallization. Example 2

[0031] The weight percentage of basalt raw material is: The composition is as follows: SiO2 51.71%, Al2O3 17.91%, CaO 13.50%, MgO 5.49%, FeO 3.22%; Fe2O3 4.41%, Na2O 3.76%, with an acidity coefficient of 2.28.

[0032] In an oxidizing environment, basalt fragments are melted at a temperature of 1400±10℃. The basalt is melted and homogenized, and the melt is kept for 2 hours for homogenization treatment to form droplets. The temperature of the droplets in the exhaust zone is 1350±30℃, and primary fibers with a diameter of 130 micrometers are drawn out. Then, they are blown at high temperature through the nozzle of the jet chamber. The plume temperature at the outlet of the jet chamber nozzle is 1560℃. The primary fibers are melted and blown into ultrafine short basalt fibers by the high-speed airflow. Example 3

[0033] Basalt raw material weight percentage: The composition is as follows: SiO2 51.71%, Al2O3 17.91%, CaO 13.50%, MgO 5.49%, FeO 3.22%, Fe2O3 4.41%, Na2O 3.76%. The acidity coefficient is 2.28.

[0034] In an oxidizing environment, basalt fragments are melted at a temperature of 1400±50℃. The basalt is melted and homogenized, and the melt is kept for 2 hours for homogenization treatment to form droplets. The temperature of the droplets in the exhaust zone is 1350±40℃, and primary fibers with a diameter of 120 micrometers are drawn out. Then, they are blown at high temperature through the nozzle of the jet chamber. The plume temperature at the outlet of the jet chamber nozzle is 1580℃. The primary fibers are melted and blown into ultrafine short basalt fibers by the high-speed airflow. Example 4

[0035] Weight percentage of basalt raw material: The composition is as follows: SiO2 51.71%, Al2O3 17.91%, CaO 13.50%, MgO 5.49%, FeO 3.22%, Fe2O3 4.41%, Na2O 3.76%, and the acidity coefficient is 2.28.

[0036] In an oxidizing environment, basalt fragments melt at a temperature of 1450±20℃. The basalt is melted and homogenized, and then kept for 2 hours for melt homogenization treatment to form droplets. The temperature of the droplets in the exhaust zone is 1350±40℃, and primary fibers with a diameter of 110 micrometers are drawn out. These fibers are then blown at high temperature through the nozzle of the jet chamber. The plume temperature at the outlet of the jet chamber nozzle is 1580℃. The primary fibers are melted and blown into ultrafine short basalt fibers by the high-speed airflow. Example 5

[0037] Basalt raw material weight percentage: The composition is as follows: SiO2 51.71%, Al2O3 17.91%, CaO 13.50%, MgO 5.49%, FeO 3.22%, Fe2O3 4.41%, Na2O 3.78%, and the acidity coefficient is 2.28.

[0038] In an oxidizing environment, basalt fragments melt at a temperature of 1450±20℃. The basalt is melted and homogenized, and then kept for 2 hours for melt homogenization treatment to form droplets. The temperature of the droplets in the exhaust zone is 1350±40℃, and primary fibers with a diameter of 100 micrometers are drawn out. These fibers are then blown at high temperature through the nozzle of the jet chamber. The plume temperature at the outlet of the jet chamber nozzle is 1580℃. The primary fibers are melted and blown into ultrafine short basalt fibers by the high-speed airflow. Example 6

[0039] The weight percentage of basalt raw material is: The composition is 51.71% SiO2, 17.91% Al2O3, 13.50% CaO, 5.49% MgO, 3.22% FeO, 4.41% Fe2O3, and 3.78% Na2O, with an acidity coefficient of 2.28.

[0040] In an oxidizing environment, basalt fragments are melted at a temperature of 1500±50℃. The basalt is melted and homogenized, and the melt is kept for 1.5 hours for homogenization treatment to form droplets. The temperature of the droplets in the exhaust zone is 1370±20℃, and primary fibers with a diameter of 100 micrometers are drawn out. Then, they are blown at high temperature through the nozzle of the jet chamber. The plume temperature at the outlet of the jet chamber nozzle is 1600℃. The primary fibers are melted and blown into ultrafine short basalt fibers by the high-speed airflow. Test case

[0041] Then, on the mesh cylinder of the sedimentation chamber, a canvas is formed from the basalt ultrafine short fibers of each embodiment. The specific characteristics of the basalt ultrafine short fibers and the corresponding canvas are shown in the table below.

[0042] Main characteristics of basalt ultrafine short fibers and corresponding canvas

[0043] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for producing ultrafine short fibers using rock raw materials, characterized in that, The process includes the following steps: In an oxidizing environment, basalt fragments are melted at a temperature of 1300±50℃-1500±50℃. The basalt is melted and homogenized to form droplets. The temperature of the droplets in the exhaust zone is 1300-1400℃, from which primary fibers with a diameter of 100 to 150 micrometers are drawn out. These fibers are then blown at high temperature through a jet chamber nozzle. The plume temperature at the outlet of the jet chamber nozzle is 1550-1600℃. The primary fibers are melted and blown by a high-speed airflow into ultrafine short basalt fibers with a diameter of 1.2-3.2 micrometers and a length of 50-70 millimeters.

2. The method for producing ultrafine short fibers from rock raw materials according to claim 1, characterized in that, The crushed rock is melted in a continuous furnace. Before melting, it needs to be sorted and crushed to a particle size of 3 to 10 mm. Metal particles are removed by a magnetic separator, and then it is washed, dried and filtered.

3. The method for producing ultrafine short fibers from rock raw materials according to claim 1, characterized in that, The chemical composition of the basalt gravel is as follows: silicon dioxide 49.04-54.70%, aluminum oxide 16.83-18.98%, calcium oxide 12.69-13.50%, magnesium oxide 5.15-5.49%, ferrous oxide 3.22-4.8%, iron oxide 3.9-4.41%, sodium oxide 3.51-3.78%; the acidity coefficient of the basalt gravel is 1.89-2.

28.

4. The method for producing ultrafine short fibers from rock raw materials according to claim 2, characterized in that, Before the basalt crushed stone is melted in an oxidizing environment, it is preheated to 90-140℃ by the recovered gas discharged from the continuous furnace.

5. The method for producing ultrafine short fibers from rock raw materials according to claim 1, characterized in that, After obtaining ultrafine basalt fibers, electrostatic elimination was performed using a weak aqueous acid solution with a pH of 4-4.

5.

6. The method for producing ultrafine short fibers from rock raw materials according to claim 5, characterized in that, The weak aqueous acid solution is either acetic acid solution or citric acid solution.

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