CN109881467B - Ceramic long fiber microwave continuous treatment device and method - Google Patents

Abstract

The invention discloses a microwave continuous processing device and method for ceramic long fibers. The ceramic long fiber microwave continuous treatment device includes: a microwave reaction unit, which includes at least one microwave cavity for continuous passage of fibrils, and a fiber inlet and fiber outlet connected to the microwave cavity; a microwave generating unit, which includes at least one capable of A microwave generator for irradiating microwaves is provided, and the microwave output by the microwave generator can perform microwave irradiation treatment on the fibrils passing through the microwave cavity. The present invention applies microwave technology to the continuous processing of long fibers, realizing continuous operations such as cross-linking, solidification and/or firing of fibrils. At the same time, due to the use of the characteristics of microwave overall heating, it improves energy efficiency and overcomes the problem of achieving the same processing purpose. The existing technology and equipment have inherent defects such as low energy efficiency and inability to operate continuously; this device greatly shortens the processing time, improves production efficiency, saves a lot of energy, and has important practical application value.

Description

Ceramic long fiber microwave continuous treatment device and method

Technical field

The invention particularly relates to a microwave continuous processing device and method for ceramic long fibers, which belongs to the technical field of ceramic fiber preparation.

Background technique

In recent years, ceramic fiber (oxide fiber or non-oxide fiber) manufacturing technology has made significant progress. Its main driving force comes from the demand for high-performance fibers (high strength, high temperature resistance, high modulus, etc.) in the fields of aerospace and high-temperature insulation.

Although different types of ceramic fiber manufacturing processes are different, most of them first obtain fibrils from sol-gel, solution or slurry containing volatile components, or from a precursor polymer through a spinning process, and then at a certain temperature and Drying, curing, cross-linking, modification and other treatments are carried out under atmospheric conditions, and finally converted into ceramic fibers using a controllable firing process.

The price of high-performance ceramic fibers is relatively high, and highly complex processes account for a large proportion. At the same time, the complex process also makes it difficult to stably control the performance and quality of the fiber. The drying, cross-linking, curing or firing of fibrils was mostly accomplished in batches using heating equipment such as ovens and/or kilns. On the one hand, this type of method results in low energy efficiency and high cost due to the use of conduction and convection heating. On the other hand, it makes the relevant process links become intermittent or intermittent working conditions, affecting the continuity of the entire production process and the stability of product performance.

Contents of the invention

The main purpose of the present invention is to provide a microwave continuous processing device and method for ceramic long fibers. The present invention uses microwaves (single-mode microwave) to dry, cross-link and solidify and/or burn the fibrils, thereby achieving the processing of the fibrils. Efficient heating and continuous processing to overcome the shortcomings of the existing technology.

In order to achieve the foregoing invention objectives, the technical solutions adopted by the present invention include:

Embodiments of the present invention provide a microwave continuous processing device for ceramic long fibers, which includes:

A microwave reaction unit, which includes at least one microwave cavity through which fibrils can continuously pass, and a fiber inlet and fiber outlet connected to the microwave cavity;

A microwave generating unit includes a microwave generator capable of at least providing microwave irradiation, and the microwave output by the microwave generator can perform microwave irradiation treatment on the fibrils passing through the microwave cavity.

Specifically, the microwave reaction unit may be a microwave cavity, or may include two or more microwave cavities connected in series; two or more microwave cavities are connected in series, that is, two adjacent microwave cavities can pass through one microwave cavity The fiber inlet (fiber outlet) of the body is connected to the fiber outlet (fiber inlet) of another microwave cavity.

Further, the microwave cavity is a resonant cavity.

Further, the microwave cavity is a single-mode microwave resonant cavity.

Further, the shape of the microwave cavity may be cylindrical, square or other shapes.

Furthermore, the microwave cavity is made of conductive metal. For example, the microwave cavity can be made of one or more conductive metals or metal alloys, such as aluminum, stainless steel, brass, etc., but is not limited thereto.

Further, the fiber inlet and fiber outlet are arranged oppositely at both ends of the microwave cavity.

Further, the irradiation microwave is single-mode microwave.

Further, the microwave generator includes a microwave power supply and a magnetron, or the microwave generator includes a microwave oscillator, an adjustable attenuator and a solid-state microwave amplifier, and the adjustable attenuator is connected to the microwave oscillator, solid-state amplifier respectively. Microwave amplifier connection.

Specifically, the microwave generator uses electrical energy to generate microwaves of a certain frequency and power; specifically, the output power of the microwave generator can be determined based on factors such as the processing capacity requirements of the device, the composition and characteristics of the fibrils, and the dielectric loss factor.

In some more specific embodiments, the ceramic long fiber microwave continuous processing device also includes: a microwave transmission unit, the microwave transmission unit is connected to the microwave generation unit and the microwave reaction unit respectively, and is used to transmit the microwave energy provided by the microwave generator. The irradiated microwave is transmitted to the microwave reaction unit.

In some more specific embodiments, the microwave transmission unit includes a circulator, an impedance matching adjuster and a coupler that are connected to each other via waveguides (as shown in Figure 1); or the microwave transmission unit includes a circulator that is connected to each other via a coaxial line. Circulator and coupler (Figure 2).

In some more specific embodiments, the ceramic long fiber microwave continuous processing device also includes: an information collection unit, which includes at least the input of collecting and obtaining the electric field intensity in the microwave cavity, the temperature of the fibrils, and the microwave reactor. Power and output power sensors. The type and number of sensors can be determined according to the type and quantity of controllable inputs of the microwave generator, the fibrils being processed, and the reaction process variables and parameters that can be detected by the microwave reactor. For example, it can only have an infrared thermometer, or it can also include infrared thermometers. Thermometers and field strength sensors can also include infrared thermometers, incident reflected power sensors, etc.

Further, the information collection unit includes an infrared thermometer, a field strength sensor and an incident reflection power sensor.

In some more specific embodiments, the microwave continuous processing device for ceramic long fibers also includes: a control unit, which is connected to a microwave generating unit and an information collection unit.

Specifically, the control unit may include a microcomputer, memory, sensor signal input interface, control signal output interface, communication interface with the host computer and other systems of the fiber production line, and human-machine interface. The main function of the microcomputer is to determine the output control signal based on the sensor output signal and the control algorithm, and then feed the control signal to the magnetron, microwave oscillator, adjustable attenuator or preamplifier through the control signal output interface to adjust the microwave generation The working status of the device, so that the controlled variables such as temperature, microwave mode in the microwave cavity, microwave frequency, microwave power, etc. are consistent with the set value or target state; the communication interface is used to exchange information with other equipment to make the operation of the device consistent with the set value or target state. Other equipment is coordinated; the human-machine interface is used to set device operating parameters, display the control system input and output signal size and changing trends, etc.; the memory is used to save device operating data to facilitate processing process management and subsequent analysis and processing of device operating data. The program-controlled software and control programs used in the control unit can be commercial software or written by oneself, and the hardware used can be purchased commercially.

Embodiments of the present invention also provide a method for continuous microwave treatment of ceramic long fibers, which includes:

The device for continuous microwave treatment of ceramic long fibers is provided; the device works by making the fibrils continuously pass through the microwave cavity through the fiber inlet and the fiber outlet, and using single-mode microwaves to process the fibrils passing through the microwave reaction unit. Microwave irradiation treatment.

Further, the microwave irradiation treatment is performed in an air atmosphere or a protective gas (such as nitrogen or inert gas, etc.) atmosphere.

Further, the microwave irradiation treatment includes at least one of heating, drying, cross-linking and curing, and firing.

Compared with the existing technology, the present invention applies single-mode microwave technology to the continuous processing of long fibers, realizing continuous operations such as cross-linking, solidification and/or firing of fibrils. At the same time, due to the use of the characteristics of microwave overall heating, it improves It improves energy efficiency and overcomes the inherent shortcomings of existing technologies and equipment that achieve the same processing purpose, such as low energy efficiency and inability to operate continuously. The device greatly shortens the processing time, improves production efficiency, saves a lot of energy, and has important practical application value.

Description of the drawings

Figure 1 is a schematic structural diagram of a microwave continuous processing device for ceramic long fibers in Embodiment 1 of the present invention;

Figure 2 is a schematic structural diagram of a microwave continuous processing device for ceramic long fibers in Embodiment 2 and 3 of the present invention;

Figure 3 is a schematic structural diagram of multiple microwave cavities connected in series in Embodiment 4 of the present invention.

Detailed ways

In view of the deficiencies in the prior art, the inventor of this case was able to propose the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principles will be further explained below with reference to the accompanying drawings and specific embodiments.

The precursor conversion method is a common ceramic fiber manufacturing process. The general process is to first obtain raw fibers (also known as virgin silk, virgin fiber, virgin fiber, virgin fiber, raw fiber, etc.) from the precursor through melt spinning. Here We refer to them collectively as fibrils), or use the sol-gel process to obtain fibrils through an extruder; then cross-link and solidify the fibrils through heating, oxidation, etc.; and finally obtain ceramic fibers through high-temperature pyrolysis.

Whether it is oxide ceramic fiber or non-oxide ceramic fiber, reducing its production and manufacturing costs and improving product quality are two very important aspects, and realizing the continuity of production and manufacturing is an important factor in reducing costs. Cost reduction and quality The improvement will expand the application scope of ceramic fibers and open up application markets with huge demand for usage, such as chemical industry, automobiles, heat-resistant (insulation) structures, etc.

Compared with traditional processing methods, microwave processing has obvious advantages. Heat is generated directly inside the material. The material is heated from the inside to the outside without conduction and convection. The relevant devices do not need to be heated, and the fiber surface is not affected. Since the action of microwaves will bring additional translational and rotational motions to the fiber molecular motion, it increases the possibility and opportunity of intermolecular cross-linking and can promote intermolecular cross-linking.

Small changes in the ceramic fiber manufacturing process and parameters can cause major changes in the microstructure and mechanical properties of these fibers. With the help of microwave technology, the energy power acting on the reactants can be quickly controlled, eliminating traditional heat conduction and convection heating. The method is due to the temperature response hysteresis caused by the pure lag between the control volume change and the temperature response, so that rapid real-time control of the reaction temperature can be achieved. By selecting appropriate microwave parameters, not only can the reaction speed be accelerated, but also the fiber quality can be improved. The cross-linking degree, grain growth, etc. involved in the cross-linking curing and firing reaction processes can be better controlled, which is beneficial to the stability of product quality and the improvement of product performance.

Example 1

The microwave continuous processing device for ceramic long fibers in this embodiment is shown in Figure 1. It mainly consists of three parts:

The first part is the microwave generation and transmission part (the microwave generation part is the aforementioned microwave generation unit, and the microwave transmission part is the aforementioned microwave transmission unit, the same below), including magnetron 21, circulator 22, dummy load 23, and impedance matching regulator 24 and the coupler 25, the circulator 22 is respectively connected to the magnetron 21, the dummy load 23, and the impedance matching regulator 24. The impedance matching regulator 24 is also connected to the coupler 25, and the coupler 25 is also connected to the microwave cavity 1; where The magnetron 21 is a microwave generator, which is mainly used to generate fixed-frequency microwaves; the circulator 22 is mainly used to protect the magnetron 21, and introduces the microwaves reflected back from the microwave cavity 1 into the dummy load 23, so that the magnetic The control tube 21 is protected from the influence of reflected microwaves; the dummy load 23 is used to absorb the reflected microwaves, and the microwave energy absorbed by the dummy load 23 is taken away by the cooling system (the cooling system is not shown in Figure 1); the impedance matching regulator 24 is mainly used to adjust the impedance matching state between the microwave transmission part and the microwave reactor so that the microwave power reflected back is as small as possible; the coupler 25 is mainly used to couple the microwave into the microwave reactor.

The second part is the microwave reactor, which includes a microwave cavity 1, a fiber inlet 11, and a fiber outlet 12; the microwave cavity 1 is made of high conductivity metal materials (such as aluminum, brass, stainless steel, etc.). The microwave cavity is a single-mode cavity, and its internal size is determined by the microwave frequency and microwave mode required for operation. When the device is working, the electric field direction in the microwave cavity is parallel to the axis of the microwave cavity, and on the axis of the microwave cavity The upper electric field intensity takes the maximum value.

The third part is the measurement and control system (i.e., the aforementioned information collection unit and control unit), including an infrared thermometer 7 and a control system 8; among them, the infrared thermometer 7 is used to measure the temperature of the fiber and convert the temperature signal transmitted to the control system (mainly the temperature control system); the control system consists of a microcomputer, input and output interface, human-machine interface, etc. The control system receives the fiber temperature signal from the infrared thermometer, obtains the control signal according to the control algorithm, and then The control signal is fed to the magnetron to control the microwave power output by the magnetron to keep the actual temperature of the fiber consistent with the set temperature.

The working process of processing fibrils based on the ceramic long fiber microwave continuous processing device includes: after polycarbosilane (PCS) is ejected through the melt spinning nozzle, the PCS fibers (or fiber bundles composed of multiple PCS fibers) 100 enters the microwave cavity 1 of the microwave reactor through the fiber inlet, and receives microwave irradiation from the microwave generator while passing through the microwave cavity. The PCS fiber is heated to 140-210°C in the air atmosphere, and then leaves the processing through the fiber outlet. device. When the PCS fiber is in the microwave cavity, the microwave introduced into the microwave cavity by the microwave generation and transmission part interacts with the PCS fiber. At the same time, the presence of oxygen prompts the fiber to complete solidification and cross-linking. The measurement and control system continuously detects the temperature of the fiber in the microwave cavity. , and calculate the magnetron power control signal based on the error between the fiber set temperature and the actual temperature and the control algorithm, and control the microwave output power of the magnetron to keep the actual temperature of the temperature measurement point consistent with the set temperature.

Example 2

The ceramic fiber microwave continuous processing device in this embodiment is shown in Figure 2. It is similar to Embodiment 1. The entire device still consists of three parts: a microwave generation and transmission part, a microwave reactor, and a measurement and control system. The differences in Example 1 are as follows:

First, the microwave generator mainly consists of a microwave oscillator 31, an adjustable attenuator 32 and a solid-state microwave amplifier 33. The adjustable attenuator 32 is connected to the microwave oscillator 31 and the solid-state microwave amplifier 33 respectively. Among them, the output frequency of the microwave oscillator 31 is adjustable, and the frequency control signal output by the control system is used to adjust the output frequency of the microwave oscillator; the adjustable attenuator is mainly used to control the amplitude of the microwave signal output by the microwave oscillator. Within the allowable range of the microwave amplifier; the microwave amplifier is composed of solid-state devices, which amplifies the microwave signal and outputs microwave power; in this embodiment, the impedance matching regulator is not used in the transmission part of the microwave generation and transmission part, and the circulator 22 directly Connected to the coupler 25 , the solid-state microwave amplifier 33 is connected to the circulator 22 , and the circulator 22 is also connected to the dummy load 23 .

Second, in addition to measuring fiber temperature, the measurement and control system also measures the distribution of electric field intensity in the microwave cavity through field strength sensors. The control system uses the temperature signal and field strength signal to determine the frequency control signal and power control signal respectively according to the control algorithm.

The working process of processing fibrils based on the ceramic long fiber microwave continuous processing device includes: alumina sol is extruded from the spinneret, and the formed long fibers (can be understood as the aforementioned fibrils) enter the microwave cavity from the fiber inlet 1. It receives microwave irradiation when passing through the microwave cavity 1, and then leaves the processing device through the fiber outlet 12. When the fiber is in the microwave cavity, the microwave introduced into the microwave cavity by the microwave generation and transmission part interacts with the long fiber, and the lytic fiber undergoes gelation transformation; the measurement and control system continuously detects the temperature and field strength of the fiber in the microwave cavity. status, if the actual temperature deviates from the set temperature, the control system adjusts the size of the power control signal according to the control algorithm, and controls the output power of the microwave amplifier by changing the output signal of the attenuator to keep the actual temperature consistent with the set temperature; If the microwave mode in the microwave cavity deviates from the predetermined mode due to the influence of the fiber bundle, the control system 8 uses the output signal of the field strength sensor 6 and the corresponding frequency control algorithm to calculate and determine the microwave frequency control signal, and adjusts the output frequency of the microwave oscillator. Return the microwave mode in the microwave cavity to a predetermined mode.

In this embodiment, since the long fibers in the microwave cavity are always near the axis with the greatest electric field intensity, the microwave has the strongest effect on the fibers and the highest efficiency. This embodiment is suitable for both fiber materials with a small dielectric loss factor and For fiber materials with large dielectric loss factors.

Example 3

The ceramic fiber microwave continuous processing device in this embodiment is similar to Figure 2. Similar to Embodiment 2, the entire device still consists of three parts: a microwave generation and transmission part, a microwave reactor, and a measurement and control system.

The working process of processing fibrils by the ceramic long fiber microwave continuous processing device includes: alumina and silica sol containing a certain proportion are extruded from the spinneret, and the formed long fibers enter the microwave cavity from the fiber inlet. The body receives microwave irradiation when passing through the microwave cavity, and then leaves the processing device through the fiber outlet; when the fiber is in the microwave cavity, the microwave introduced into the microwave cavity by the microwave generation and transmission part interacts with the long fiber, and the lysed collagen filaments are dissolved at 80 The gelation transition occurs at -400°C and crystallizes into mullite fibers at 900-1400°C. The measurement and control system continuously detects the temperature and field strength status of the fiber in the microwave cavity. If the actual temperature deviates from the set temperature, Then the control system adjusts the size of the power control signal according to the control algorithm, and controls the output power of the microwave amplifier by changing the output signal of the attenuator to keep the actual temperature consistent with the set temperature; if the microwave mode in the microwave cavity is affected by the fiber bundle If it deviates from the predetermined mode, the control system uses the output signal of the field strength sensor and the corresponding frequency control algorithm to calculate and determine the microwave frequency control signal, adjust the output frequency of the microwave oscillator, and return the microwave mode in the microwave cavity to the predetermined mode.

In this embodiment, since the fiber in the microwave cavity is always near the axis with the greatest electric field intensity, the microwave has the strongest effect on the fiber and the highest efficiency.

Example 4

For fiber materials that require a longer reaction time or the process of cross-linking, solidifying and firing long fibers in one continuous step, multiple microwave processing devices can be used to operate in series, as shown in Figure 3, which only shows multiple microwaves. The reactors are connected in series, and the microwave generators, sensors, control systems, etc. supporting each microwave processing device can be any one of Embodiment 1, Embodiment 2, and Embodiment 3.

The microwave reactor in the present invention is composed of conductive metal materials. The internal space of the microwave reactor is a single-mode microwave resonant cavity (ie, the microwave cavity). Its shape can be cylindrical or rectangular. For different frequencies, Microwaves require resonant cavities of different sizes to form single-mode microwaves in them. This is determined by the partial differential equations and boundary conditions that describe microwaves. It is a physical constraint. The device provided by the present invention does not use any heating materials, but uses microwaves. Directly process the fibers, including cross-linking solidification, heating and sintering; due to the reflection and superposition of single-mode microwaves in the resonant cavity to form standing waves, a strong field strength can be obtained, so it can be processed Materials with poor or poor microwave absorption capabilities (such as fibers), and due to the deterministic distribution of single-mode microwave field strength in the cavity, are suitable for processing continuous materials with small or very fine cross-sections (processing materials play a major role is the electric field component in the microwave. In the cylindrical microwave cavity used in the embodiment of the invention, the electric field intensity is the strongest along the cylindrical axis. The further away from the axis, the lower the electric field intensity is.)

The present invention applies microwave technology to the continuous processing of long fibers, realizing continuous operations such as cross-linking, solidification and/or firing of fibrils. At the same time, due to the use of the characteristics of microwave overall heating, it improves energy efficiency and overcomes the problem of achieving the same processing purpose. The existing technology and equipment have inherent defects such as low energy efficiency and inability to operate continuously; this device greatly shortens the processing time, improves production efficiency, saves a lot of energy, and has important practical application value.

It should be noted that the present invention mainly provides a ceramic long fiber microwave continuous processing device, in which parts or components such as magnetrons, circulators, dummy loads, impedance matching regulators, couplers, etc. that form the device can be Existing standard parts are used, which can be purchased commercially or made by one's own. The program-controlled software and programs used in this device can be obtained commercially or made by one's own.

It should be understood that the above embodiments are only to illustrate the technical concepts and characteristics of the present invention. Their purpose is to enable those familiar with the technology to understand the content of the present invention and implement it accordingly, and cannot limit the scope of protection of the present invention. All equivalent changes or modifications made based on the spirit and essence of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A method for continuous microwave treatment of long ceramic fibers, which is characterized by including: A microwave continuous treatment device for ceramic long fibers is provided. The continuous microwave treatment device for ceramic long fibers includes: A microwave reaction unit, which includes at least one microwave cavity through which fibrils can continuously pass, and a fiber inlet and fiber outlet connected to the microwave cavity; A microwave generating unit, which includes a microwave generator that can at least provide microwave irradiation, and the single-mode microwave output by the microwave generator can perform microwave irradiation processing on the fibrils passing through the microwave cavity; And, the fibrils are continuously passed through the microwave cavity through the fiber inlet and the fiber outlet, and the microwave cavity is set to an air atmosphere containing oxygen; Use the single-mode microwave output from the microwave generator to perform microwave irradiation processing on the fibrils passing through the microwave reaction unit, and make the electric field direction in the microwave cavity parallel to the axis of the microwave cavity, and in the direction of the microwave cavity. The electric field intensity on the axis takes the maximum value, and the fibrils in the microwave cavity are always near the axis with the maximum electric field intensity, thereby heating the temperature of the fibrils to 140-210°C. 2. The method of microwave continuous processing of ceramic long fibers according to claim 1, characterized in that: the microwave cavity is a single-mode microwave resonant cavity; and the microwave cavity is made of conductive metal. 3. The method for continuous microwave treatment of long ceramic fibers according to claim 1, characterized in that: the microwave generator includes a microwave power supply and a magnetron; or, the microwave generator includes a microwave oscillator, an adjustable attenuation converters and solid-state microwave amplifiers. 4. The method for continuous microwave treatment of ceramic long fibers according to claim 1, characterized in that it also includes: a microwave transmission unit, the microwave transmission unit is connected to a microwave generating unit and a microwave reaction unit respectively, and is used to connect the microwave generator The provided irradiation microwave is transmitted to the microwave reaction unit. 5. The method for continuous microwave treatment of long ceramic fibers according to claim 1, characterized in that: the microwave transmission unit includes a circulator, an impedance matching regulator and a coupler connected to each other, the circulator, the impedance matching regulator and a coupler. Couplers are connected with waveguides or coaxial lines. 6. The method for continuous microwave processing of ceramic long fibers according to claim 1, characterized in that it also includes: an information collection unit, which includes a unit for collecting and obtaining the electric field intensity in the microwave cavity, the temperature of the fibrils, and the temperature of the microwave reactor. Sensors for input power and output power, the sensors being infrared thermometers, field strength sensors, and incident and reflected power sensors. 7. The method for continuous microwave treatment of long ceramic fibers according to claim 6, further comprising: a control unit connected to a microwave generating unit and an information collection unit.