Fly ash fiber and preparation method thereof

Abstract

The invention provides a fly ash fiber and a preparation method thereof, and belongs to the technical field of fly ash, the preparation method specifically comprises the following steps: firstly, mixing a fly ash raw material with a composite oxidant and a dispersant, the composite oxidant comprises a main oxidant and an auxiliary oxidant, the main oxidant is potassium permanganate, and the auxiliary oxidant is sodium hydroxide; the auxiliary oxidant is manganese dioxide; carrying out ball milling treatment on the obtained mixture, and drying to remove the dispersing agent to obtain a homogenized mixture; then placing the mixture in an air atmosphere, heating to a first preset temperature and preserving heat for a first preset time, then heating to a second preset temperature and preserving heat for a second preset time to prepare clinker liquid, and then quenching the clinker liquid to obtain glassy clinker; and finally, drawing and forming the glassy clinker through a platinum-rhodium alloy bushing plate to obtain the fly ash fiber.

Description

Technical Field

[0001] This invention relates to the field of fly ash technology, and in particular to a fly ash fiber and its preparation method. Background Technology

[0002] Fly ash is a major solid waste emitted by coal-fired power plants, and its main chemical components are SiO2, Al2O3, FeO, Fe2O3, and CaO. With increasingly stringent environmental protection requirements, the high-value utilization of fly ash is receiving growing attention. Among these efforts, the preparation of fly ash fiber from fly ash has become an effective resource recovery method. This fiber possesses excellent properties such as lightweight, heat insulation, sound insulation, and fire resistance, and is widely used in construction, environmental protection, and fireproofing materials.

[0003] The conventional process for preparing fly ash fibers involves melting fly ash and then drawing it into fibers using a platinum-rhodium alloy spinneret. However, fly ash often contains unburned residual carbon and Fe. 2+ Fe 3+ During the melting process, residual carbon produces CO in an oxygen-deficient environment, and CO will decompose the Fe. 2+ Fe 3+ When reduced to elemental iron, elemental iron readily forms a low-melting-point alloy with the platinum-rhodium alloy spinneret at high temperatures, causing the spinneret to become "poisoned." This manifests as wire breakage, hole blockage, production interruption, and damage to the spinneret, severely restricting the continuous and low-cost production of fly ash fiber. Summary of the Invention

[0004] In view of this, it is necessary to provide a method for preparing fly ash fibers to solve the problem that fly ash often contains unburned residual carbon and Fe. 2+ Fe 3+ During the melting process, residual carbon produces CO in an oxygen-deficient environment, and CO will decompose the Fe. 2+ Fe 3+ When reduced to elemental iron, elemental iron readily forms a low-melting-point alloy with the platinum-rhodium alloy spinneret at high temperatures, causing the spinneret to become "poisoned." This manifests as wire breakage, hole blockage, production interruption, and damage to the spinneret, severely hindering the continuous and low-cost production of fly ash fibers.

[0005] It is also necessary to provide a fly ash fiber.

[0006] On one hand, the present invention provides a method for preparing fly ash fibers, comprising the following steps:

[0007] Step 1: Mix fly ash raw material with composite oxidant and dispersant. The composite oxidant includes a main oxidant and an auxiliary oxidant. The main oxidant is potassium permanganate and the auxiliary oxidant is manganese dioxide.

[0008] Step 2: The mixture obtained in Step 1 is first ball-milled, and then dried to remove the dispersant, resulting in a homogenized mixture;

[0009] Step 3: Place the mixture in an air atmosphere, first heat it to a first predetermined temperature and hold it for a first predetermined time, then heat it to a second predetermined temperature and hold it for a second predetermined time to prepare a clinker liquid. Then quench the clinker liquid to obtain a glassy clinker.

[0010] Step 4: The glassy clinker is drawn into fibers using a platinum-rhodium alloy spinneret to obtain fly ash fibers.

[0011] Preferably, in step 1, the total amount of the composite oxidant added is 1%-3% of the total mass of the fly ash raw material, and the mass ratio of potassium permanganate to manganese dioxide is 1:0.5-2.

[0012] Preferably, in step 1, the mass ratio of the fly ash raw material to the dispersant is 1:1.5-2.5.

[0013] Preferably, the dispersant is anhydrous ethanol.

[0014] Preferably, in step 2, the ball milling process takes 3.5-4.5 hours and rotates at a speed of 180-220 rpm.

[0015] Preferably, in step 2, the drying temperature is 75-85℃ and the drying time is 6-8h.

[0016] Preferably, step 3 specifically involves: feeding the mixture into a tube furnace, and under an air atmosphere, firstly heating it to the first predetermined temperature at a heating rate of 3-5℃ / min, and holding it at this temperature for the first predetermined time; then heating it to the second predetermined temperature at a heating rate of 8-10℃ / min, and holding it at this temperature for the second predetermined time to prepare a clinker liquid; then removing the clinker liquid and quenching it to obtain a glassy clinker.

[0017] The first predetermined temperature is 500-700℃, the first predetermined time is 30-60 minutes, the second predetermined temperature is 1400-1450℃, and the second predetermined time is 1-2 hours.

[0018] Preferably, in step 1, the chemical composition of the fly ash raw material includes SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O, and TiO2;

[0019] The fly ash raw material comprises, by mass, 55%-60% of SiO2, 18%-21% of Al2O3, 6%-9% of Fe2O3, 4%-7% of CaO, 1%-4% of MgO, 2%-7% of Na2O, 2%-6% of K2O, and 1%-5% of TiO2.

[0020] Preferably, step 4 specifically involves drawing the glassy clinker into wires using a wire drawing furnace, wherein the number of holes in the platinum-rhodium alloy spinneret is 1-2000, the operating temperature of the platinum-rhodium alloy spinneret is 1200-1350℃, and the operating temperature of the wire drawing furnace is 1400-1550℃.

[0021] On the other hand, the present invention provides a fly ash fiber, which is prepared by the fly ash fiber preparation method described in the preceding aspect.

[0022] Compared with existing technologies, the advantages of this invention are as follows: This invention is the first to use a composite oxidant composed of potassium permanganate and manganese dioxide. Potassium permanganate acts as a "pioneer," providing initial oxidation power in the low-temperature range (200℃-300℃), while manganese dioxide maintains its oxidizing capacity continuously in the early stage of high-temperature melting (500℃-600℃). This ensures that the fly ash raw material is always in an "oxygen surplus" state during the transformation from solid to molten state, completely suppressing the reducing properties of CO. Combined with a stepped heating and heat preservation process, it can continuously release active oxygen at different temperature stages, completely oxidizing the residual carbon in the fly ash raw material, and eliminating the need for Fe2+ oxidation at the source. 2+ Fe 3+ The reducing agent CO is reduced to elemental iron, thus avoiding the "poisoning" problem caused by the formation of a low-melting-point alloy between elemental iron and the platinum-rhodium alloy sprue. This significantly extends the service life of the expensive platinum-rhodium alloy sprue and ensures the continuity of production. Specifically, by slowly heating to a first predetermined temperature and holding it for a first predetermined time, residual carbon is pre-oxidized and catalytically oxidized, effectively removing residual carbon from the fly ash raw material before melting. This prevents residual carbon from being encapsulated by the glass phase and forming difficult-to-eliminate localized reducing micro-regions during the subsequent high-temperature melting process. The temperature is then raised to a second predetermined temperature and held for a second predetermined time to completely melt the fly ash raw material into a melt. At the same time, the potassium ions introduced by potassium permanganate regulate the viscosity of the melt, generating a uniform, stable, and high-quality glass melt with very few bubble defects. This directly results in a denser fiber structure and superior mechanical properties in the final drawn fiber. Attached Figure Description

[0023] Figure 1 The flowchart illustrates the method for preparing fly ash fiber provided by this invention.

[0024] Figure 2 The image shows the X-ray photoelectron spectrum of iron in the glassy clinker obtained in Example 1.

[0025] Figure 3 The image shows the X-ray photoelectron spectrum of iron in the glassy clinker obtained in Comparative Example 1.

[0026] Figure 4 The image shows the X-ray photoelectron spectrum of iron in the glassy clinker obtained in Comparative Example 2. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0028] Please refer to Figure 1 On the one hand, the present invention provides a method for preparing fly ash fiber, comprising the following steps:

[0029] Step 1: Mix fly ash raw material with composite oxidant and dispersant. The composite oxidant includes a main oxidant and an auxiliary oxidant. The main oxidant is potassium permanganate and the auxiliary oxidant is manganese dioxide.

[0030] Step 2: The mixture obtained in Step 1 is first ball-milled, and then dried to remove the dispersant, resulting in a homogenized mixture;

[0031] Step 3: Place the mixture in an air atmosphere, first heat it to a first predetermined temperature and hold it for a first predetermined time, then heat it to a second predetermined temperature and hold it for a second predetermined time to prepare a clinker liquid. Then quench the clinker liquid to obtain a glassy clinker.

[0032] Step 4: The glassy clinker is drawn into fibers using a platinum-rhodium alloy spinneret to obtain fly ash fibers.

[0033] Compared with existing technologies, the advantages of this invention are as follows: This invention is the first to use a composite oxidant composed of potassium permanganate and manganese dioxide. Potassium permanganate acts as a "pioneer," providing initial oxidation power in the low-temperature range (200℃-300℃), while manganese dioxide maintains its oxidizing capacity continuously in the early stage of high-temperature melting (500℃-600℃). This ensures that the fly ash raw material is always in an "oxygen surplus" state during the transformation from solid to molten state, completely suppressing the reducing properties of CO. Combined with a stepped heating and heat preservation process, it can continuously release active oxygen at different temperature stages, completely oxidizing the residual carbon in the fly ash raw material, and eliminating the need for Fe2+ oxidation at the source. 2+ Fe 3+ The reducing agent CO is reduced to elemental iron, thus avoiding the "poisoning" problem caused by the formation of a low-melting-point alloy between elemental iron and the platinum-rhodium alloy sprue. This significantly extends the service life of the expensive platinum-rhodium alloy sprue and ensures the continuity of production. Specifically, by slowly heating to a first predetermined temperature and holding it for a first predetermined time, residual carbon is pre-oxidized and catalytically oxidized, effectively removing residual carbon from the fly ash raw material before melting. This prevents residual carbon from being encapsulated by the glass phase and forming difficult-to-eliminate localized reducing micro-regions during the subsequent high-temperature melting process. The temperature is then raised to a second predetermined temperature and held for a second predetermined time to completely melt the fly ash raw material into a melt. At the same time, the potassium ions introduced by potassium permanganate regulate the viscosity of the melt, generating a uniform, stable, and high-quality glass melt with very few bubble defects. This directly results in a denser fiber structure and superior mechanical properties in the final drawn fiber.

[0034] Furthermore, in step 1, the total amount of the composite oxidant added is 1%-3% of the total mass of the fly ash raw material, and the mass ratio of potassium permanganate to manganese dioxide is 1:0.5-2.

[0035] Furthermore, in step 1, the mass ratio of the fly ash raw material to the dispersant is 1:1.5-2.5.

[0036] Furthermore, the dispersant is anhydrous ethanol.

[0037] Furthermore, in step 2, the ball milling process takes 3.5-4.5 hours and rotates at a speed of 180-220 rpm.

[0038] Furthermore, in step 2, the drying temperature is 75-85℃ and the drying time is 6-8 hours.

[0039] Further, step 3 specifically involves: feeding the mixture into a tube furnace, and under an air atmosphere, firstly heating it to the first predetermined temperature at a heating rate of 3-5℃ / min, and holding it at this temperature for the first predetermined time; then heating it to the second predetermined temperature at a heating rate of 8-10℃ / min, and holding it at this temperature for the second predetermined time to prepare a clinker liquid; then removing the clinker liquid and quenching it to obtain a glassy clinker.

[0040] The first predetermined temperature is 500-700℃, the first predetermined time is 30-60 minutes, the second predetermined temperature is 1400-1450℃, and the second predetermined time is 1-2 hours.

[0041] Furthermore, in step 1, the chemical composition of the fly ash raw material includes SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O, and TiO2;

[0042] The fly ash raw material comprises, by mass, 55%-60% of SiO2, 18%-21% of Al2O3, 6%-9% of Fe2O3, 4%-7% of CaO, 1%-4% of MgO, 2%-7% of Na2O, 2%-6% of K2O, and 1%-5% of TiO2.

[0043] Furthermore, step 4 specifically involves drawing the glassy clinker into wires using a wire drawing furnace, wherein the number of holes in the platinum-rhodium alloy spinneret is 1-2000, the operating temperature of the platinum-rhodium alloy spinneret is 1200-1350℃, and the operating temperature of the wire drawing furnace is 1400-1550℃.

[0044] On the other hand, the present invention provides a fly ash fiber, which is prepared by the fly ash fiber preparation method described in the preceding aspect.

[0045] The following embodiments and comparative examples of the method of the present invention further illustrate the technical solution and technical effects of the present invention. It should be noted that the following experimental examples are only for further explanation of the present invention and do not limit the technical solution of the present invention.

[0046] The chemical composition of the fly ash raw materials used in the embodiments and comparative examples of the method of the present invention is shown in Table 1. It is understood that the fly ash raw materials used in the present invention are not limited to the following components; other fly ash raw materials can also be prepared according to the method of the present invention when preparing fly ash fibers.

[0047] Table 1 Chemical composition of fly ash raw materials <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[TiO2]]> Fly ash raw material (mass percentage) 57.91 19.14 7.85 5.80 1.89 3.09 3.09 1.23

[0048] Example 1:

[0049] The above-mentioned fly ash raw materials were mixed with composite oxidant and anhydrous ethanol, and then ball-milled and dried to obtain a homogenized mixture. In the composite oxidant, the mass ratio of potassium permanganate to manganese dioxide was 1:1, and the total amount of composite oxidant added was 1% of the total mass of fly ash raw materials. The mass ratio of fly ash raw materials to anhydrous ethanol was 1:2. The ball milling time was 4 hours, the rotation speed was 200 rpm, the drying temperature was 80℃, and the drying time was 7 hours.

[0050] The above mixture is placed in a crucible and then into a tube furnace. Under an air atmosphere, the temperature is first raised to 550°C at a rate of 4°C / min and held at this temperature for 40 minutes. Then, the temperature is raised to 1400°C at a rate of 6°C / min and held at this temperature for 1.5 hours to prepare a clinker liquid. The crucible containing the clinker liquid is then removed and placed in cold water for quenching to obtain a glassy clinker.

[0051] The glassy clinker was melt-drawn into fibers using a drawing furnace. The platinum-rhodium alloy stencil had 60 holes and operated at 1220°C. The drawing furnace operated at 1400°C and the drawing speed was 6 m / s. The final fly ash fiber sample 1 was obtained.

[0052] Example 2:

[0053] Compared with Example 1, in this example, the mass ratio of potassium permanganate to manganese dioxide in the composite oxidant is 1:1, the total amount of composite oxidant added is 2% of the total mass of fly ash raw material, and other conditions are the same as in Example 1, resulting in fly ash fiber sample 2.

[0054] Example 3:

[0055] Compared with Example 1, in this example, the mass ratio of potassium permanganate to manganese dioxide in the composite oxidant is 1:2, the total amount of composite oxidant added is 1% of the total mass of fly ash raw material, and other conditions are the same as in Example 1, resulting in fly ash fiber sample 3.

[0056] Comparative Example 1:

[0057] The fly ash raw material was directly placed into a crucible and then into a tube furnace. Under an air atmosphere, the temperature was increased to 1400℃ at a heating rate of 6℃ / min and held for 1 hour. After the holding period, the crucible was removed and placed in cold water for quenching to obtain glassy clinker.

[0058] The glassy clinker was melt-drawn into fibers using a drawing furnace. The platinum-rhodium alloy stencil had 60 holes and operated at 1220°C. The drawing furnace operated at 1400°C and the drawing speed was 6 m / s, resulting in fly ash fiber sample 4.

[0059] Comparative Example 2:

[0060] The fly ash raw material was mixed with manganese dioxide and anhydrous ethanol and then ball-milled and dried to obtain a homogenized mixture. The total amount of manganese dioxide added was 1% of the total mass of the fly ash raw material. The mass ratio of fly ash raw material to anhydrous ethanol was 1:2. The ball milling time was 4 hours, the speed was 200 rpm, the drying temperature was 80℃, and the drying time was 7 hours.

[0061] The above mixture was placed in a crucible and then placed in a tube furnace. Under an air atmosphere, the temperature was increased to 1400°C at a heating rate of 6°C / min and held for 1 hour. After the holding period, the crucible was removed and placed in cold water for quenching to obtain glassy clinker C.

[0062] The glassy clinker was melt-drawn into fibers using a drawing furnace. The platinum-rhodium alloy stencil had 60 holes and operated at 1220°C. The drawing furnace operated at 1400°C and the drawing speed was 6 m / s, resulting in fly ash fiber sample 5.

[0063] The glassy clinker obtained in Examples 1 to 3 was tested, and the results are shown in Table 1:

[0064] Table 1. Test results of glassy clinker obtained in Examples 1 to 3 Group <![CDATA[XPS results of vitreous clinker (Fe 0 content)]]> Observation of the glassy clinker melt state Glassy clinker drawing continuity Example 1 Not detected Uniform, with very few bubbles Excellent Example 2 Not detected Uniform and extremely clear Excellent Example 3 Not detected Uniform, with very few bubbles Excellent

[0065] As can be seen from Table 1, no elemental iron (Fe) was detected in the glassy clinker of all embodiments, proving that the "composite oxidant + stepped insulation" process of the present invention can completely suppress iron precipitation. At the same time, all embodiments obtained high-quality glassy clinker melt with high uniformity and very few bubble defects, thus ensuring the subsequent continuous and stable wire drawing operation (without breakage), and finally laying the foundation for the preparation of high-performance fly ash fibers.

[0066] XPS analysis was performed on the glassy clinker obtained in Example 1, Comparative Example 1, and Comparative Example 2:

[0067] Figure 2 , Figure 3 and Figure 4 The images show the X-ray photoelectron spectra of iron in the glassy clinker of Example 1, Comparative Example 1, and Comparative Example 2, respectively.

[0068] Analysis shows that, Figure 2The binding energy at ~711 eV shows that it is dominated by Fe 3+ The main characteristic peak is at ~709 eV, with a small amount of Fe present. 2+ The characteristic peaks of iron were observed, and no characteristic peaks of elemental iron were detected at ~707 eV. This result proves that the process in Example 1 of the present invention can completely suppress the precipitation of elemental iron. In stark contrast, Figure 3 and Figure 4 A distinct characteristic peak of elemental iron is visible at a binding energy of ~707 eV, while Fe is present near ~709 eV and ~711 eV, respectively. 2+ and Fe 3+ The characteristic peaks confirmed that the traditional processes of Comparative Example 1 and Comparative Example 2 could not avoid the formation of elemental iron. Elemental iron easily forms a low-melting-point alloy with the platinum-rhodium alloy spinneret at high temperatures, causing the platinum-rhodium alloy spinneret to be "poisoned". This manifests as wire breakage, plate hole blockage, production interruption and damage to the platinum-rhodium alloy spinneret, which seriously restricts the continuous and low-cost production of fly ash fiber.

[0069] Therefore, the "composite oxidant + stepped insulation" process of this invention can completely suppress the precipitation of elemental iron, thus fundamentally solving the problem of Fe being precipitated by CO. 2+ / Fe 3+ The problem of "spinning plate poisoning" caused by the reduction to elemental iron and the subsequent formation of a low-melting-point alloy with the platinum-rhodium alloy spinneret is addressed. In contrast, although Comparative Example 2 suppressed the precipitation of elemental iron to some extent, the high decomposition temperature of the manganese dioxide used in it prevented the complete removal of residual carbon during the high-temperature melting stage. Some residual carbon was encapsulated by the glass phase to form localized reducing micro-regions, which still had the potential to generate CO. Therefore, the risk of trace amounts of elemental iron precipitation could not be completely eliminated, resulting in the platinum-rhodium alloy spinneret still facing the potential threat of "poisoning".

[0070] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing fly ash fiber, characterized in that, Includes the following steps: Step 1: Mix fly ash raw material with composite oxidant and dispersant. The composite oxidant includes a main oxidant and an auxiliary oxidant. The main oxidant is potassium permanganate and the auxiliary oxidant is manganese dioxide. Step 2: The mixture obtained in Step 1 is first ball-milled, and then dried to remove the dispersant, resulting in a homogenized mixture; Step 3: Place the mixture in an air atmosphere, first heat it to a first predetermined temperature and hold it for a first predetermined time, then heat it to a second predetermined temperature and hold it for a second predetermined time to prepare a clinker liquid. Then quench the clinker liquid to obtain a glassy clinker. Step 4: The glassy clinker is drawn into fibers using a platinum-rhodium alloy spinneret to obtain fly ash fibers.

2. The method for preparing fly ash fiber according to claim 1, characterized in that, In step 1, the total amount of the composite oxidant added is 1%-3% of the total mass of the fly ash raw material, and the mass ratio of potassium permanganate to manganese dioxide is 1:0.5-2.

3. The method for preparing fly ash fiber according to claim 1, characterized in that, In step 1, the mass ratio of the fly ash raw material to the dispersant is 1:1.5-2.

5.

4. The method for preparing fly ash fiber according to claim 3, characterized in that, The dispersant is anhydrous ethanol.

5. The method for preparing fly ash fiber according to claim 1, characterized in that, In step 2, the ball milling process takes 3.5-4.5 hours and rotates at 180-220 rpm.

6. The method for preparing fly ash fiber according to claim 1, characterized in that, In step 2, the drying temperature is 75-85℃ and the drying time is 6-8h.

7. The method for preparing fly ash fiber according to claim 1, characterized in that, Step 3 specifically involves: feeding the mixture into a tube furnace, and under an air atmosphere, firstly heating it to the first predetermined temperature at a heating rate of 3-5℃ / min, and holding it at this temperature for the first predetermined time; then heating it to the second predetermined temperature at a heating rate of 8-10℃ / min, and holding it at this temperature for the second predetermined time to prepare a clinker liquid; then removing the clinker liquid and quenching it to obtain a glassy clinker. The first predetermined temperature is 500-700℃, the first predetermined time is 30-60 minutes, the second predetermined temperature is 1400-1450℃, and the second predetermined time is 1-2 hours.

8. The method for preparing fly ash fiber according to claim 1, characterized in that, In step 1, the chemical composition of the fly ash raw material includes SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O, and TiO2. The SiO2 accounts for 55%-60% of the total mass of the fly ash raw material, the Al2O3 accounts for 18%-21% of the total mass of the fly ash raw material, the Fe2O3 accounts for 6%-9% of the total mass of the fly ash raw material, the CaO accounts for 4%-7% of the total mass of the fly ash raw material, the MgO accounts for 1%-4% of the total mass of the fly ash raw material, the Na2O accounts for 2%-7% of the total mass of the fly ash raw material, the K2O accounts for 2%-6% of the total mass of the fly ash raw material, and the TiO2 accounts for 1%-5% of the total mass of the fly ash raw material.

9. The method for preparing fly ash fiber according to claim 1, characterized in that, Step 4 specifically involves drawing the glassy clinker into wires using a wire drawing kiln, wherein the number of holes in the platinum-rhodium alloy spinneret is 1-2000, the operating temperature of the platinum-rhodium alloy spinneret is 1200-1350℃, and the operating temperature of the wire drawing kiln is 1400-1550℃.

10. A fly ash fiber, characterized in that, The fly ash fiber is prepared by the method described in any one of claims 1-9.

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