Solid, liquid and gas separation device in polycarbosilane melt spinning process

Abstract

The utility model discloses a solid, liquid and gas separation device in a polycarbosilane melt spinning process, which is divided into a melting tank, a storage tank and a gas recovery tank which are connected through a connecting switch. Solid PCS is heated in the melting tank and stirred in the melting state for vacuum defoaming, escaped small molecules are condensed to become liquid PCS to be stored in the storage tank, and gas can enter the gas recovery tank to be recovered or stored. Separation can be carried out according to actual production requirements, solid-liquid-gas separation in the melt spinning process is achieved, and molecular weight distribution of products is better controlled. The equipment is low in investment, simple to operate and capable of effectively realizing separation and greatly improving the product quality.

Description

Technical Field

[0001] The utility model belongs to the technical field of polycarbosilane preparation, and particularly relates to a solid, liquid and gas separation device in the melting spinning process of polycarbosilane. Background Technique

[0002] At present, the main method for preparing silicon carbide (SiC) fibers is the conversion method of organic precursor polycarbosilane (PCS). This method generally includes processes such as the synthesis of organic precursor polycarbosilane (PCS), melting spinning, infusibilization treatment, and high-temperature sintering (high-temperature inorganicization). Among them, the synthesis of polycarbosilane (PCS) precursor is the basis of all research work. The composition, structure, and properties of PCS directly affect the spinnability of PCS and the reactivity of the infusibilization reaction, thus affecting the composition, structure, and properties of the final SiC fibers. As a precursor polymer, PCS needs to have a high melting point and good spinnability to meet the requirements of subsequent processes.

[0003] Research has found that PCS with a high molecular weight has a high ceramic yield and less volatile matter during the sintering process, resulting in fewer defects. Therefore, the high molecular weight part of PCS is beneficial to fiber strength, while the low molecular weight part plays the role of a plasticizer during the spinning process and is beneficial to improving spinnability. During the synthesis of PCS, it is found that with the strengthening of reaction conditions, while the softening point of PCS increases, the molecular weight increases, the molecular weight distribution gradually broadens, and the spinnability gradually decreases. It can be seen that the spinnability of PCS is also related to the molecular weight distribution (Mw / Mn). Therefore, studying the relationship between the softening point molecular weight and its distribution of PCS and the melting spinnability, and maximizing the high molecular weight part while ensuring spinnability is of great significance for preparing high-performance SiC fibers.

[0004] For the traditional melting spinning of polycarbosilane precursor, the precursor powder is loaded into the spinning cylinder and placed in a vacuum degassing furnace. It is heated to the specified degassing temperature under vacuum and kept warm for 3h, that is, the traditional vacuum degassing treatment for the precursor is directly carried out in one furnace (as Figure 2 shown). The following problems exist:

[0005] 1. It is difficult to observe or detect the molecular weight distribution of PCS in the molten state.

[0006] 2. The corresponding solid, liquid, and gas separation is not obvious or insufficient, and there is no corresponding discrimination basis.

[0007] 3. Liquid polycarbosilane (LPCS) is separated. These low molecular weight liquid polycarbosilanes (LPCS) have a low boiling point and a high vapor pressure, and are extremely volatile at room temperature; they are prone to combustion when encountering static electricity or high temperature and are a volatile and flammable liquid. The existing disposal method is to seal them in a container and transport them to a hazardous chemical treatment company for harmless treatment.

[0008] 4. It is difficult to perform subsequent processing and machining on solids, liquids, and gases in the same furnace. If the small molecules that escape are not separated, it will affect the subsequent melt spinning.

[0009] In view of this, the inventor of this case conducted in-depth research, and thus this case came into being. Utility Model Content

[0010] The purpose of the present utility model is to provide a solid-liquid-gas separation device during the melt spinning of polycarbosilane that can better control the molecular weight distribution of the product.

[0011] In order to achieve the above purpose, the technical solution of the present utility model is:

[0012] A solid-liquid-gas separation device during the melt spinning of polycarbosilane, including a melting tank, a storage tank, and a gas recovery tank, which are sequentially connected through connection switches between the melting tank, the storage tank, and the gas recovery tank;

[0013] One side wall of the melting tank is provided with a vacuum pump, an intake system, heating coils, a pressure sensor, and a temperature sensor, and the heating coils are evenly distributed along the outer wall of the tank furnace; the other side wall of the melting tank is provided with an exhaust valve, the top of the melting tank is provided with a feeding port and a stirring motor, and the bottom of the melting tank is provided with a discharging port;

[0014] One side wall of the storage tank is provided with an intake system and a pressure sensor, the other side wall of the storage tank is provided with an exhaust valve, the top of the storage tank is provided with a vacuum pump, the bottom of the storage tank is provided with a liquid discharging port, and a liquid scale is vertically arranged inside the storage tank, and the bottom end of the liquid scale is located at the bottom of the storage tank;

[0015] The side wall of the gas recovery tank is provided with an intake system and a pressure sensor, the top of the gas recovery tank is provided with a vacuum pump, and the bottom of the gas recovery tank is provided with a gas discharging port.

[0016] Further, the number of temperature sensors in the melting tank is six, which are correspondingly arranged at the upper, middle, and lower parts of the inner side walls on both sides of the tank furnace.

[0017] Further, the connection switch between the melting tank and the storage tank is a high-temperature resistant electric hard-sealed gate valve; the connection switch between the storage tank and the gas recovery tank is another high-temperature resistant electric hard-sealed gate valve.

[0018] Further, the liquid scale is a transparent scale.

[0019] The utility model relates to a solid, liquid and gas separation device in the process of polycarbosilane melting spinning. The device is divided into three areas: a melting tank, a storage tank and a gas recovery tank, and the three areas are connected through connection switches. Solid PCS is heated in the melting tank, stirred in a molten state for vacuum degassing, and the escaped small molecules become liquid PCS after condensation and are stored in the storage tank, while the gas can enter the gas recovery tank for recovery or storage. The utility model can be separated according to actual production requirements to realize the separation of solid, liquid and gaseous states in the melting spinning process. This equipment has a small investment, is easy to operate, can effectively achieve separation, and greatly improves product quality.

[0020] Specifically, a corresponding liquid scale is set to facilitate observing according to the factory inspection data of the input PCS, the amount of input PCS and the amount of overflowed small molecule liquid PCS, calculating the corresponding vacuum degassing degree, and controlling the molecular weight range of the input PCS.

[0021] Liquid polycarbosilane (LPCS) can be separated out, and after purification, it can be used for subsequent composite material preparation.

[0022] The liquid and gas are provided with their own discharge ports and can be recycled separately.

[0023] The newly added storage tank enables the removed small molecules to escape and cool, the liquid enters the storage tank, and the gas enters the gas recovery tank;

[0024] It can realize the filtration and purification treatment of liquid polycarbosilane and gas, effectively reducing resource waste. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the solid, liquid and gas separation device in the process of polycarbosilane melting spinning of the utility model;

[0026] Figure 2 It is a schematic diagram of degassing in one furnace in the process of polycarbosilane melting spinning in the background technology.

[0027] In the figure:

[0028] Melting tank a; storage tank b; gas recovery tank c; vacuum pump 1; feeding port 2; stirring motor 3; exhaust valve 4; intake system 5; heating coil 6; pressure sensor 7; temperature sensor 8; discharge port 9; gate valve 10; intake system 11; pressure sensor 13; liquid discharge port 14; liquid scale 15; exhaust valve 16; gate valve 17; intake system 18; vacuum pump 19; pressure sensor 20. Detailed Embodiment

[0029] In order to further explain the technical solution of the utility model, the utility model will be elaborated in detail through specific embodiments below.

[0030] The utility model relates to a solid, liquid and gas separation device in the process of polycarbosilane melt spinning, such as Figure 1 shown, which includes a melting tank a, a storage tank b and a gas recovery tank c. The three tanks are sequentially connected by high-temperature resistant electric hard-sealed gate valves.

[0031] The melting tank a is of a tank furnace structure and is used as a solid stirring and preheating area. One side wall of the melting tank a is provided with a vacuum pump 1, an air inlet system 5, a heating coil 6, a pressure sensor 7 and a temperature sensor 8. The heating coil 6 is evenly distributed along the outer wall of the tank furnace to uniformly heat the PCS, and it is advisable not to be in direct contact with the PCS. The number of temperature sensors 8 is six, which are correspondingly arranged at the upper, middle and lower parts of the inner side walls on both sides of the tank furnace to monitor the temperature inside the tank furnace. The other side wall of the melting tank a (the side opposite to the vacuum pump 1) is provided with an exhaust valve 4. The top of the melting tank a is provided with a feeding port 2 and a stirring motor 3. The bottom of the melting tank a is provided with a discharging port 9.

[0032] The vacuum pump 1 evacuates the inside of the melting tank a. The feeding port 2 is used for feeding. The stirring motor 3 is used to stir the molten PCS during the vacuum defoaming stage or the spinning stage to make the heating uniform. The exhaust valve 4 is used for exhausting gas and making the pressure inside the furnace consistent with the atmosphere when needed. The air inlet system 5 can be filled with inert gases such as nitrogen and argon as protective gases. The pressure sensor 7 monitors the pressure inside the tank furnace in real time. The discharging port 9 is used for discharging the molten pcs.

[0033] The storage tank b is of a tank furnace structure and is used as a liquid recovery area. One side wall of the storage tank b is provided with an air inlet system 11 and a pressure sensor 13, and the other side wall of the storage tank b is provided with an exhaust valve 16. The top of the storage tank b is provided with a vacuum pump 12. The bottom of the storage tank b is provided with a liquid discharging port 14. A liquid scale 15 is vertically arranged inside the storage tank b, and the bottom end of the liquid scale 15 is located at the bottom of the storage tank b. The liquid scale 15 is specifically a transparent scale.

[0034] The intake system 11 can be filled with inert gases such as nitrogen and argon to act as protective gases. The vacuum pump 12 can evacuate the interior of the storage tank b. The pressure sensor 13 monitors the pressure inside the storage tank b in real time. The liquid scale 15 recovers small molecules in the liquid recovery area and can monitor the volume of small molecule liquid in the cavity in real time. The content of small molecules is calculated according to the relative molecular weight of PCS input into the melting tank a furnace, the liquid scale 15 in the cavity, and the volume. Specifically, during production, under normal circumstances, about 160 ± 40 g of small molecules escape when 100 kg of PCS is input. According to the factory inspection data of the input PCS, the types and quantities of small molecules that may be contained in the PCS are understood. Through experimental or empirical data, the volatilization rate of these small molecules at specific temperatures and pressures is understood. Combining the vacuum degree, temperature, and time of the melting tank a, the removal degree of small molecules is estimated. The liquid scale 15 shows that the amount or liquid level of the liquid in the storage tank b has stabilized and there is no significant overflow of small molecule liquid. According to the calculation or estimation, the removed small molecule amount has reached the expected target value or meets the production standard.

[0035] The gas recovery tank c is used as a gas recovery tank. The side wall of the gas recovery tank c is provided with an intake system 18 and a pressure sensor 20. The top of the gas recovery tank c is provided with a vacuum pump 19, and the bottom of the gas recovery tank c is provided with a gas discharge port. The intake system 18 can be filled with inert gases such as nitrogen and argon to act as protective gases. The vacuum pump 19 can evacuate the interior of the gas recovery tank c. The pressure sensor 20 can monitor the pressure inside the gas recovery tank c in real time.

[0036] The melting tank a and the storage tank b are connected and communicated through a gate valve 10, and the storage tank b and the gas recovery tank c are connected and communicated through a gate valve 17. The gate valve 10 and the gate valve 17 are high-temperature-resistant electric hard-sealed gate valves. Electric energy is used as the power to connect the electric actuator to drive the valve to realize the opening, closing, and adjustment actions of the valve. Thus, the purpose of switching or adjusting the pipeline medium is achieved.

[0037] The control system of the device of the present utility model: It is controlled by an Omron PLC and an MCGS touch screen. The flow chart of the whole system is operated correspondingly on the touch screen, including the start and stop of each vacuum pump, coil heating, start and stop of stirring, opening and closing of each gate valve, etc., for operation, control, and interlock. Specifically, the control components for the start and stop of the vacuum pump, coil heating, start and stop of stirring, and opening and closing of the gate valve are electrically connected to the control system respectively to achieve the corresponding control.

[0038] The utility model relates to a solid, liquid and gas separation device in the process of polycarbosilane melt spinning. The device is divided into three areas: a melting tank a, a storage tank b, and a gas recovery tank c. The three areas are connected by gate valves. Solid PCS is heated in the melting tank a, stirred at a melting state for 1 min / (5 - 20 rpm) for vacuum degassing. The escaped small molecules become liquid PCS after condensation and are stored in the storage tank, while the gas can enter the next tank for recovery or storage. The utility model can be separated according to actual production requirements to achieve solid-liquid-gas separation in the melt spinning process and better control the molecular weight distribution of the product. This equipment has a small investment, simple operation, can effectively achieve separation, and greatly improve the product quality.

[0039] Specifically,

[0040] A corresponding liquid scale 15 is set to facilitate the observation according to the factory inspection data of the input PCS, the amount of the input PCS, and the amount of the overflowed small molecule liquid PCS, calculate the corresponding vacuum degassing degree, and control the molecular weight range of the input PCS.

[0041] Liquid polycarbosilane (LPCS) can be separated out and can be used for subsequent composite material preparation after purification.

[0042] The liquid and gas are provided with their respective discharge ports and can be recycled separately.

[0043] The newly added storage tank b enables the liquid to enter the storage tank and the gas to enter the gas recovery tank after the removed small molecules escape and are cooled;

[0044] The filtration and purification treatment of liquid polycarbosilane and gas can be realized, effectively reducing resource waste.

[0045] The above embodiments and drawings do not limit the product form and style of the utility model. Any appropriate changes or modifications made by those of ordinary skill in the art shall be regarded as not departing from the patent scope of the utility model.

Claims

1. A solid, liquid, and gas separation device during the melting spinning process of polycarbosilane, characterized in that: It includes a melting tank, a storage tank and a gas recovery tank, and the melting tank, the storage tank and the gas recovery tank are sequentially connected by connection switches; One side wall of the melting tank is provided with a vacuum pump, an air inlet system, heating coils, a pressure sensor and a temperature sensor, and the heating coils are evenly distributed along the outer wall of the tank furnace; another side wall of the melting tank is provided with an exhaust valve, the top of the melting tank is provided with a feeding port and a stirring motor, and the bottom of the melting tank is provided with a discharging port; One side wall of the storage tank is provided with an air inlet system and a pressure sensor, another side wall of the storage tank is provided with an exhaust valve, the top of the storage tank is provided with a vacuum pump, the bottom of the storage tank is provided with a liquid discharging port, and a liquid scale is vertically arranged inside the storage tank, and the bottom end of the liquid scale is located at the bottom of the storage tank; The side wall of the gas recovery tank is provided with an air inlet system and a pressure sensor, the top of the gas recovery tank is provided with a vacuum pump, and the bottom of the gas recovery tank is provided with a gas discharging port.

2. The solid, liquid and gas separation device during the melting spinning process of polycarbosilane according to claim 1, wherein: The number of temperature sensors in the melting tank is six, which are correspondingly arranged at the upper, middle and lower parts of the inner side walls on both sides of the tank furnace.

3. The solid, liquid, and gas separation device during the melt spinning process of polycarbosilane according to claim 1, wherein: The connection switch between the melting tank and the storage tank is a high-temperature resistant electric hard-sealed gate valve; the connection switch between the storage tank and the gas recovery tank is another high-temperature resistant electric hard-sealed gate valve.

4. The solid, liquid, and gas separation device during the melt spinning process of polycarbosilane according to claim 1, characterized in that: The liquid scale is a transparent scale.

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