A method for producing aerogel

Abstract

The present invention discloses an aerogel production method. The aerogel production method of the present invention comprises: (a) providing a mixture, wherein the mixture comprises a silicon source, an alcohol solvent and a catalyst; (b) mixing the mixture provided in step (a) in a certain proportion to prepare an alcohol gel; (c) subjecting the prepared alcohol gel to supercritical drying treatment, thereby obtaining a dry aerogel and obtaining a recovered alcohol solvent; (d) subjecting the supercritically dried aerogel to a vacuum treatment, discharging impurities and moisture in the aerogel, and obtaining a pure aerogel product. The aerogel production method of the present invention has low cost, can realize the recycling of raw materials, has low energy consumption and high production efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of aerogel production, and more particularly to an aerogel production method. Background Art

[0002] Aerogel is the lightest solid material known in the world. It has extremely low thermal conductivity, is durable, high temperature resistant, and explosion-proof. It has broad application prospects in aerospace, national defense, green buildings, new energy, environmental governance, solar thermal utilization, and other fields. It is called a magical material that changes the world and is listed as one of the top 10 popular scientific and technological achievements since the 1990s. It is a dual-use technology with great application value.

[0003] Aerogels are mainly divided into silica aerogel, alumina aerogel, zirconia aerogel and carbon aerogel due to different ingredients. At present, the thermal insulation performance of silica aerogel is the most eye-catching and the technology is the most mature. The industrial development of aerogels at home and abroad is mostly centered on the thermal insulation application of silica aerogel.

[0004] Generally, the production of aerogels follows processes such as gel preparation, aging, replacement, and supercritical drying. The overall process lasts a long time, consumes a lot of energy, and also involves the input and discharge of a large amount of alcohol solvents. The entire production process mobilizes a large amount of manpower and material resources.

[0005] There are generally two methods for preparing aerogels: atmospheric pressure preparation and supercritical preparation. Currently, the supercritical preparation method is the preferred method route. The production equipment is a reactor, and the solvent medium is generally ethanol. To reach the supercritical state, the volume of ethanol will expand by 2 times, so the filling volume ratio of the reactor needs to be controlled below 30%, and the utilization efficiency of the equipment is low; at the same time, the reactor is also a high-energy-consuming production equipment, so the traditional method of aerogel production cost is high.

[0006] Therefore, there is an urgent need to develop a new aerogel production method with low energy consumption, high output and directly usable products. Summary of the invention

[0007] The purpose of the present invention is to provide an aerogel production method with low energy consumption, large output and directly usable products.

[0008] In the present invention, a method for producing an aerogel is proposed, the method comprising the following steps:

[0009] (a) providing a mixture comprising a silicon source, an alcohol solvent and a catalyst;

[0010] (b) mixing the mixture provided in step (a) in a certain ratio to prepare an alcohol gel;

[0011] (c) subjecting the prepared alcohol gel to supercritical drying to obtain a dry aerogel and a recovered alcohol solvent;

[0012] (d) vacuuming the aerogel after supercritical drying to remove impurities and moisture in the aerogel to obtain a pure aerogel product.

[0013] The recovered alcohol solvent is used as the alcohol solvent raw material in step (a).

[0014] The mass concentration of the alcohol solvent is 90% to 98%;

[0015] Preferably, the mass concentration of the alcohol solvent is 91% to 97%; more preferably, 92% to 96%.

[0016] The silicon source is selected from the group consisting of ethyl orthosilicate, sodium silicate, methyl orthosilicate, methyltriethoxysilane, polysiloxane, water glass, silica sol and rice husk ash.

[0017] The alcohol solvent is selected from the group consisting of ethanol, methanol and isopropanol.

[0018] The working temperature of the vacuum treatment is 220-300°C.

[0019] During supercritical drying, the heating rate of the medium is controlled according to the energy input control curve, which is calculated according to the following formula:

[0020] P in =C(T)ρ(T)V(dT / dt)+V(dP a (T) / dt)

[0021] Where P in Input power for effective energy from the outside;

[0022] C(T) is the specific heat capacity of the solvent at temperature T, KJ / Kg·K

[0023] ρ(T) is the density of the solvent at temperature T, Kg / m 3 ;

[0024] V is the volume of the reactor, m 3 ;

[0025] T is the reaction temperature, K;

[0026] t is the production cycle, h;

[0027] P a (T) is the saturated vapor pressure of the solvent at the corresponding temperature, Pa.

[0028] The energy input is in the form of electric heating, thermal fluid heating, and / or induction heating.

[0029] The energy input control method is power regulation, heat flow regulation, and / or induction frequency regulation.

[0030] In another preferred embodiment, the prepared alcohol gel is subjected to a pre-forming treatment before the supercritical drying treatment.

[0031] The steps of the preforming process are:

[0032] (1) The flexible covering structure is made into a film bag with one side open;

[0033] (2) placing the prepared alcohol gel in the film bag, and placing an airbag core in the middle of the alcohol gel;

[0034] (3) the airbag core is inflated to tighten the membrane bag;

[0035] (4) inserting the film bag into a rigid support structure, and pressing the rigid support structure tightly;

[0036] (5) Deflate the airbag core and extract the airbag core.

[0037] In another preferred embodiment, the inner side of the flexible covering structure is coated with an infrared reflecting layer.

[0038] The material of the infrared reflection layer is selected from the following group: aluminum and silver.

[0039] The rigid support structure is an integral flat plate structure, a hollow structure or a wire mesh structure.

[0040] In another preferred embodiment, a heat-sealing layer is provided on the inner side of the flexible covering structure.

[0041] In another preferred embodiment, a getter is placed in the tooling.

[0042] In another preferred embodiment, a coil is arranged outside the supercritical reactor.

[0043] In another preferred embodiment, the aerogel product is packaged after the vacuum treatment.

[0044] The packaging method is:

[0045] The aerogel products are vacuum packaged and vacuum baked in batches.

[0046] In another preferred embodiment, the getter is activated during the packaging process.

[0047] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The aerogel preparation method of the present invention;

[0049] Figure 2 It is a rigid wire mesh support structure for tooling;

[0050] Figure 3 Assembly process for flexible covering film and rigid wire mesh support;

[0051] Figure 4 It is a schematic diagram of the assembly of the tooling in the supercritical reactor;

[0052] Figure 5 The relative relationship of the positions of various parts in the aerogel production tooling, that is, the position of the reflective layer and the matching diagram of the getter;

[0053] Figure 6 It is the temperature rise curve of the reactor control, that is, the relationship between the external energy input power and time;

[0054] Figure 7a , Figure 7b and Figure 7c is the average energy saving efficiency of the present invention compared with conventional production processes;

[0055] Figure 8 Schematic diagram of the aerogel workpiece packaging equipment.

[0056] The symbols in the accompanying drawings are:

[0057] 1: Vacuum transition into the warehouse;

[0058] 2: Vacuum working chamber;

[0059] 3: Vacuum transition out of the warehouse;

[0060] 4: First vacuum isolation damper;

[0061] 5: Second vacuum isolation damper;

[0062] 6: Guide rail;

[0063] 7: Heat sealing equipment;

[0064] 8: Feed inlet;

[0065] 9: Discharge port;

[0066] 10: Vacuum baking chamber;

[0067] 11: Tooling rack;

[0068] 12: The third vacuum isolation damper. DETAILED DESCRIPTION

[0069] After extensive and in-depth research, the inventors have developed a method for producing aerogels for the first time. The invention focuses on the entire process of aerogel production, fully considers aerogel preparation, supercritical treatment and subsequent product utilization, and completes the invention on this basis.

[0070] Aerogel production

[0071] (1) Preparation of alcohol gel

[0072] The preparation process of the alcohol gel includes raw material preparation and gel treatment, specifically: a certain proportion of silicon source and alcohol solvent with a concentration greater than or equal to 95% are fully stirred and mixed, reacted under the action of a catalyst, and then allowed to stand to obtain the alcohol gel. The silicon source can be selected from the following combination: tetraethyl orthosilicate, sodium silicate, methyl orthosilicate, methyl triethoxysilane, polysiloxane, water glass, silica sol and rice husk ash. The alcohol solvent can be selected from the following combination: ethanol, methanol, isopropanol, etc.

[0073] The difference between the aerogel production method of the present invention and the prior art is that: first, 95% pure ethanol is used instead of anhydrous ethanol, and the alcohol gel formed contains a certain amount of water; second, the solvent replacement link is omitted. The purpose of solvent replacement in the traditional preparation process is to replace the water in the alcohol gel, which is more conducive to the supercritical drying of the aerogel, but the solvent replacement often takes about 8 hours or more, which is the main reason for the low efficiency of aerogel production. During supercritical treatment, a small amount of anhydrous ethanol (relative to a higher filling rate) needs to be added as a heat transfer medium to dry the gel, and this anhydrous ethanol can also use recycled 98% pure ethanol. After supercritical drying, the present invention adds the steps of heating and vacuuming the aerogel, continues to heat to about 275 degrees, and performs high-temperature vacuum treatment on the reactor, which can effectively remove impurities, moisture and degassing in the aerogel, and can also retain the hydrophobicity of the aerogel, ensure the low thermal conductivity of the aerogel product, so there is no need to perform solvent replacement, and can also significantly improve the yield of aerogel and reduce the production cost of aerogel by nearly half. After eliminating the solvent replacement step, in the supercritical drying process, the input 95% concentration ethanol can still be purified and concentrated into high-concentration ethanol. The concentrated and recovered ethanol can be recycled back to the first step and used to prepare alcohol gel, making the supercritical drying process an ethanol purification process with additional benefits.

[0074] (2) Preforming

[0075] The preforming process is to design the corresponding shape of the tooling according to the final use requirements of the workpiece. The preforming tooling includes an external rigid support structure and an internal flexible coating structure. The contact surfaces of the two structures are treated accordingly to avoid adhesion. The inner side of the flexible coating structure needs to be coated with an infrared reflective layer such as aluminum or silver. The setting of the reflective layer does not affect the activation of the getter. The getter is placed before or after the supercritical is completed, and the getter needs to be activated after the product is vacuum sealed.

[0076] The external rigid support part of the tooling can be made of metal, non-metal and other materials. In order to fully and quickly exchange heat, the support part can be designed into a grid shape, which saves materials and time.

[0077] The internal flexible coating of the tooling can be made of high temperature resistant films such as PI and Teflon to adapt to the harsh conditions of supercritical fluid. The opening of the coating is 3 cm higher than the supporting part, and the filling level of the alcohol gel is 0.5 cm lower than the supporting part. After the filling is completed, 0.5 cm thick anhydrous ethanol is added to protect the alcohol gel.

[0078] The flexible film is coated with a reflective layer inside to reduce the heat radiation of the aerogel product. In order to further maintain the sealing of the vacuum system, a getter can be designed and installed. In order to avoid the shielding effect of the reflective layer on the activation of the getter, the corresponding shape can be designed when the reflective layer is coated to meet the use requirements of getters in different shapes such as strips, belts, and sheets.

[0079] Optionally, the tooling shape can be a rectangular parallelepiped, a semi-hollow cylindrical shape, a semi-elbow shape, a semi-conical tube shape, etc., to adapt to flat surfaces, cylinders, elbows, tees, valves, reducers, and other pipe fittings.

[0080] Optionally, the flexible coating material may be Teflon (polytetrafluoroethylene), PI (polyimide) or the like, and an anti-reflection layer may be coated on the inside of the material, and blank spaces may be left at specific locations to meet the requirements for activation of the getter.

[0081] Optionally, the anti-reflection layer can be made of materials such as Al and Ag.

[0082] Optionally, the flexible covering material can be used in a temperature range of -50°C to 400°C.

[0083] Optionally, the flexible covering material is molded in a design consistent with the shape of the tooling, placed inside the tooling, and fits perfectly with the inner wall of the tooling.

[0084] Optionally, the tooling material may be metal or non-metal thin plate, and the overall flat plate structure may be hollow or mesh-shaped.

[0085] Optionally, the surface of the tooling is coated with materials such as Teflon and PI to avoid adhesion to the flexible covering structure.

[0086] Optionally, a heat self-sealing layer is designed on the inner side of the coating material to meet vacuum sealing requirements.

[0087] Optionally, the getter can be in the form of a strip, a bar, a block, and the flexible covering material coating can be designed accordingly.

[0088] There are several application scenarios of aerogel insulation materials, including flat plate, circular tube, elbow, reducer or valve. Except for the flat plate, all insulation parts are curved. The high brittleness of aerogel products, especially pure aerogel, limits the use and performance of aerogel. The present invention follows the final type and near-final type design ideas, and designs the product according to the final use state of the product, which can achieve the effects of high material utilization, standardized size and convenient construction.

[0089] (3) Supercritical drying

[0090] During the supercritical drying process, the reactor is filled with preformed tooling, the temperature change of the reactor is controlled according to the temperature rise curve, and the alcohol solvent is controllably discharged from the system during the temperature rise process.

[0091] In the supercritical treatment stage, a reactor energy input control curve is proposed, through which the heating rate of the medium in the reactor can be controlled to meet the temperature requirements of aerogel supercritical production; before starting to heat up, the reactor is filled with ethanol except for the aerogel that has been gelled; when heating up, as the temperature rises, the ethanol and other media begin to expand due to the heat, and the pressure in the reactor begins to rise; a group of accurately calculated thin-diameter pipes are set outside the reactor body, and when the liquid expands, it will be discharged from the reactor body through these thin-diameter pipes, so that about 2 / 3 of the mass of the medium will be discharged from the reactor before reaching the supercritical state. The reactor body is connected to the reactor body, which reduces the energy intake accordingly; during the discharge process, the medium will rub against the inner wall of the narrow tube to generate flow resistance, which will be fed back to the liquid medium in the reactor body, which is also the internal pressure of the reactor body. The size of the resistance is related to the diameter and length of the tube, the flow rate of the medium and the temperature; by setting the energy input density, the discharge mass rate of the medium in the reactor can be controlled; by setting a narrow tube group of a certain size and length, the resistance along the tube group can be maintained within the desired range. The setting of the resistance is based on a certain value higher than the saturated vapor pressure of the medium at the corresponding temperature, maintaining the liquid properties of the medium unchanged. The energy consumed per unit volume of aerogel produced by this method is about 60% of that of the existing method, and the effective utilization space in the reactor has doubled, thereby achieving high-yield and low-energy production of aerogel.

[0092] The reactor energy control curve is calculated according to the following formula:

[0093] P in =C(T)ρ(T)V(dT / dt)+V(dP a(T) / dt)

[0094] Where P in Input power for effective energy from the outside;

[0095] C(T) is the specific heat capacity of the solvent at temperature T, KJ / Kg·K

[0096] ρ(T) is the density of the solvent at temperature T, Kg / m 3 ;

[0097] V is the volume of the reactor, m 3 ;

[0098] T is the reaction temperature, K;

[0099] t is the production cycle, h;

[0100] P a (T) is the saturated vapor pressure of the solvent at the corresponding temperature, Pa.

[0101] Optionally, the control curve equation of the reactor is obtained through theoretical calculation based on the charge amount in the reactor, the properties of the solvent, the diameter and length of the capillary tube, the production cycle requirements and the insulation condition of the reactor.

[0102] Optionally, the curve equation is used to control the energy input rate of the reactor, and the actual input energy density needs to be adjusted according to actual conditions so that the effective energy density conforms to the curve equation.

[0103] Optionally, the volume of the reactor is the effective volume, that is, the space filled with the organic solvent in the reactor, including the organic solvent in the alcohol gel, the organic solvent in the tooling room, and the organic solvent in the space before entering the coil.

[0104] Optionally, the solvent can be selected from alcohol solvents such as methanol and ethanol.

[0105] Optionally, the energy input method may be electric heating, thermal fluid heating or induction heating.

[0106] Optionally, the energy control method may be electric power modulation, heat flow modulation, induction frequency modulation, etc.

[0107] Optionally, the pressure control of the reactor is achieved by means of the flow resistance of the coil.

[0108] (4) Workpiece packaging

[0109] During the workpiece packaging process, the dried aerogel workpiece is packaged using a packaging device; the packaging device can realize batch-type continuous packaging; a getter is placed in the tooling before the workpiece is packaged, and the getter is activated after the workpiece packaging is completed.

[0110] In the traditional vacuum packaging process, packaging is completed according to the furnace. Each packaging goes through the steps of material placement, equipment shutdown, vacuum extraction, mechanical pressing, heat sealing, vacuum release and removal. The overall mechanical structure is relatively simple but the operation time is long. Especially in the steps that require vacuum heat treatment, the three steps of temperature rise, maintenance and temperature drop must be added. The work process is longer and the efficiency of product production is low.

[0111] In the vacuum packaging link, the present invention designs a batch-type continuous vacuum packaging design.

[0112] Through the above method, batch-type vacuum packaging can be realized, the packaging work is intermittent in the short distance and continuous in the long distance. The vacuum packaging work can be streamlined, greatly improving the production efficiency.

[0113] The batch-type continuous packaging equipment consists of three parts, namely, the vacuum transition inlet, the vacuum working chamber, and the vacuum transition outlet. The three chambers are isolated by vacuum doors, which are opened and closed regularly as required. Guide rails and mechanical grabbing devices are set in the chamber to complete the transfer and stacking of products. Mechanical pressing devices, heat sealing devices, and vacuum baking and aging devices are set in the vacuum chamber as required. The vacuum nozzle is designed in the vacuum working chamber. The vacuum baking and aging device can be placed in the vacuum working chamber. The vacuum working chamber can also be isolated into two chambers, which are responsible for vacuum packaging and vacuum baking and aging respectively.

[0114] During operation, the whole system maintains vacuum, the vacuum isolation damper 1 between the vacuum transition inlet and the vacuum working chamber is closed, and the two chambers are not connected to each other. The tooling with the processed aerogel inside is placed on the guide rail 1 in a certain direction to ensure that the opening of the flexible materials such as PI to be encapsulated is in the specified position. The vacuum transition inlet door is closed, the vacuum isolation damper 1 is opened, and the vacuum isolation damper 2 between the vacuum transition outlet and the vacuum working chamber is closed. Under the action of mechanical force, the tooling is horizontally moved to the specified position of the vacuum working chamber, and the vacuum isolation damper 1 is closed. The vacuum of the vacuum transition inlet is broken, and it is ready to welcome the entry of new tooling. In the vacuum working chamber, due to the design of the positioning system, the material to be heat-sealed has entered the encapsulation station, and the heat sealing system completes the heat sealing of PI and other films according to the prescribed heat sealing procedures and systems. Under the action of the manipulator or the guide rail, the heat-sealed workpiece rises or moves horizontally to the vacuum baking station, and the aging of the heat-sealed material is completed according to the baking procedure. In order to better complete the vacuum packaging and vacuum baking, a vacuum sealing door 3 can be designed between the two stations for better isolation. After the baking and aging is completed, the workpiece enters the vacuum transition warehouse through the vacuum isolation door 2 and is taken out after being cooled to a certain temperature.

[0115] Optionally, the tooling with aerogel can enter the vacuum packaging system in a horizontal or vertical state.

[0116] Optionally, the vacuum isolation damper can be configured as a vacuum gate valve or a butterfly valve, which can be remotely controlled electrically, pneumatically or hydraulically.

[0117] Optionally, the heat sealing of films such as PI follows a specific ramping and lowering pressure program and ramping and lowering and higher temperature program.

[0118] Optionally, the heat sealing tool is set at a specific position, and a positioning device is designed at the specific position, so that the aerogel tool can automatically move to the specific position along a specific track.

[0119] Optionally, after heat sealing, the aerogel tooling enters the vacuum baking section in sequence. Since the working time of the vacuum baking section is longer than the vacuum packaging time, the vacuum baking section follows the bottom-in-top-out, left-in-right-out, or right-in-left-out principle (there should be a more concise expression here, single-side in, different-side out or something else, in short, it must reflect the single-direction type).

[0120] Optionally, the aerogel workpiece can be transported by a conveyor belt, a transmission gear, a manipulator, a hydraulic rod, a guide rail, etc.

[0121] Optionally, heat sealing of flexible films such as PI can be performed by various methods such as pulse, induction, and resistance.

[0122] Optionally, the baking step after heat sealing of films such as PI can be overall baking or local baking.

[0123] Optionally, the conveying device makes corresponding interruptions according to different storage locations to meet the working space requirements of the vacuum sealing door.

[0124] The main advantages of the present invention include:

[0125] (a) The aerogel production method of the present invention uses 95% alcohol solvent as raw material, which reduces the production cost compared with using anhydrous alcohol solvent;

[0126] (b) The aerogel production method of the present invention adopts tooling preforming, has high material utilization rate, standardized workpiece size, and convenient construction;

[0127] (c) The aerogel production method of the present invention controls the temperature of the supercritical drying process according to the temperature rise curve, and has low energy consumption;

[0128] (d) The aerogel production method of the present invention has an energy saving rate of more than 40% and a productivity increase of 200% compared with the existing production method;

[0129] (e) The aerogel production method of the present invention is used to prepare aerogels, which is simple to operate and can achieve continuous batch production, avoid frequent starting and stopping of equipment, reduce energy consumption, and improve productivity.

[0130] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods for the unrecorded specific conditions in the following examples are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are weight percentages and weight parts.

[0131] It should be noted that in the claims and description of this patent, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0132] Example

[0133] Alcogel preparation

[0134] like Figure 1 As shown, a typical method for preparing aerogel of the present invention is to fully stir and mix ethyl orthosilicate and ethanol with a concentration of 95%, react under the action of a catalyst, and then stand to prepare an alcohol gel. Compared with the prior art, the alcohol gel preparation method omits the solvent replacement step, uses ethanol with a concentration of 95% instead of anhydrous ethanol, simplifies the steps, and reduces production costs.

[0135] Preform

[0136] Figure 2 It is a flat-plate tooling, which includes an external rigid support structure and an internal flexible covering structure. The rigid support structure includes a concave plate M and a convex plate N. The concave plate M and the convex plate N can be embedded together. The rigid support structure is designed as a grid structure, which saves materials and time during production.

[0137] like Figure 3 As shown, the steps of preforming a flat-plate aerogel workpiece of the present invention are:

[0138] (a) forming the flexible covering structure into a film bag with one side open;

[0139] (b) placing an alcohol gel in the film bag, and placing an airbag core in the middle of the alcohol gel;

[0140] (c) inflating the airbag core to tighten the membrane bag;

[0141] (d) inserting the membrane bag into the rigid support structure and pressing the rigid support structure;

[0142] (e) Deflate the airbag core and extract the airbag core.

[0143] The internal flexible coating of the tooling is made of PI material to adapt to the harsh supercritical conditions. The opening of the coating is 3 cm higher than the supporting part, and the filling level of the alcohol gel is 0.5 cm lower than the supporting part. After the filling is completed, 0.5 cm thick anhydrous ethanol is added to protect the alcohol gel.

[0144] The relative relationship of the positions of various parts in the aerogel production tooling is as follows: Figure 5 As shown; wherein A is a heat sealing section, B is an external rigid support structure, C1, C2 and C3 are aerogel placement positions, any one of which can be selected; D is an internal flexible coating structure, and E is a reflective layer.

[0145] Supercritical drying

[0146] During the supercritical drying process, the reactor is filled with preformed tooling. The tooling is assembled in the supercritical reactor as follows: Figure 4 shown.

[0147] The remaining space in the reactor was filled with ethanol, an alcohol solvent for preparing the alcohol gel.

[0148] The heating rate of the medium in the reactor is controlled according to the reactor energy input control curve to discharge the ethanol in the reactor.

[0149] According to the characteristics of the solvent and the specific requirements of production, the power control curve of the supercritical reactor was obtained. The specific steps are as follows:

[0150] Explanation of symbols:

[0151] ρ(T): Density of ethanol at temperature T, Kg / m 3 ;

[0152] μ(T): viscosity of ethanol at temperature T, PaS;

[0153] C p (T): specific heat of ethanol at temperature T, KJ / KgK;

[0154] P0(T): saturated vapor pressure of ethanol at temperature T, Pa;

[0155] V: Reactor volume, m 3 ;

[0156] r: Inner radius of the step-down coil, m;

[0157] r c : radius of curvature of step-down coil, m;

[0158] L: Length of step-down coil, m;

[0159] f: friction coefficient, 1;

[0160] t: heating time, S;

[0161] G(T): System mass outflow at temperature T, Kg / m2S.

[0162] The relationship between the density of ethanol and temperature is shown in formula (1):

[0163]

[0164] The relationship between the saturated vapor pressure of ethanol and temperature is shown in formula (2):

[0165]

[0166] The relationship between the viscosity of ethanol and temperature is as follows:

[0167] μ(T)=1.4248e -0.014T (3)

[0168] The relationship between the specific heat capacity of ethanol and temperature is as follows:

[0169] c p (T) = 1.9839e 0.0049T (4)

[0170] The relationship between the fluid resistance in the narrow-diameter tube and the diameter, length and mass flow rate of the medium is as follows:

[0171]

[0172] The relationship between the friction resistance coefficient and mass flow rate, medium viscosity and pipe diameter is as follows:

[0173]

[0174] The relationship between mass flow rate and temperature after selecting the pipe diameter is as follows:

[0175]

[0176] The relationship between the volume mass change of the reactor and the mass flow rate in the narrow-diameter tube is as follows:

[0177] G(T)πr 2 dt=dρ(T)V (8)

[0178] The relationship between the external energy input and the energy obtained by the medium in the reactor is as shown in formula (9):

[0179] P in dt=C(T)m(T)dT+d(PV)=C(T)ρ(T)VdT+VdP

[0180] P in =C(T)ρ(T)V(dT / dt)+V(dP / dt) (9)

[0181] The heating rate of the medium in the reactor is controlled according to the reactor energy input control curve represented by formula (9) to discharge the alcohol solvent in the reactor. A coil is arranged outside the reactor, and the alcohol solvent in the reactor is discharged through the coil. The discharged high-concentration ethanol is recovered and used for alcohol gel preparation to achieve recycling.

[0182] Figure 6 It is the relationship between external energy input power and time.

[0183] Figure 7a , Figure 7b , Figure 7c This is a comparison between the production process using this control method and the conventional production process. Compared with the conventional method, the production method of the present invention has been discharging solvent during the heating process, so Figure 7b The shaded area in the figure does not heat up to Figure 7a The temperature in the shaded area and the corresponding energy-saving data at different temperatures are the final curve. After statistical analysis, the energy-saving efficiency of the overall system is 42.78%. Figure 7c This is a curve diagram of the relationship between heating time and energy-saving efficiency. As the heating time increases, the energy-saving efficiency decreases.

[0184] Aerogel workpiece vacuum packaging

[0185] During the workpiece packaging process, the dried aerogel workpiece is packaged using a packaging device; the packaging device can realize batch-type continuous packaging; a getter is placed in the tooling before the workpiece is packaged, and the getter is activated after the workpiece is packaged.

[0186] like Figure 8 As shown, a typical packaging device of the present invention includes three parts: a vacuum transition inlet chamber 1, a vacuum working chamber 2 and a vacuum transition outlet chamber 3;

[0187] Among them, a first vacuum isolation damper 4 is provided between the vacuum transition inlet warehouse 1 and the vacuum working warehouse 2, and a second vacuum isolation damper 5 is provided between the vacuum working warehouse 2 and the vacuum transition outlet warehouse 3; the first vacuum isolation damper 4 and the second vacuum isolation damper 5 are closed when the packaging equipment encapsulates the workpiece to ensure that the overall system maintains a vacuum when the packaging equipment is working; guide rails 6 and mechanical grasping devices are provided in the vacuum transition inlet warehouse 1, the vacuum working warehouse 2 and the vacuum transition outlet warehouse 3 to complete the conveying, movement and stacking of the packaged workpieces; a heat sealing device 7 is provided in the vacuum working warehouse 2 to complete the packaging of the workpiece.

[0188] The vacuum transition inlet warehouse 1 is provided with a feed port 8. When the packaging equipment is working, the workpiece to be packaged is loaded on the tooling rack 11 and enters the packaging equipment from the feed port 8 for packaging; the vacuum transition outlet warehouse 3 is provided with a discharge port 9. After the packaging is completed, the workpiece exits the packaging equipment from the discharge port 8.

[0189] A mechanical pressing device and a vacuum baking and aging device are arranged in the vacuum working chamber 2, which cooperate with the heat sealing equipment to complete the packaging and baking and aging of the workpiece.

[0190] A positioning device and a timing device are provided in the vacuum working chamber 2. The timing device and the positioning device control the workpiece to be packaged to enter and exit the packaging equipment at a fixed time. The first vacuum isolation damper 4 and the second vacuum isolation damper 5 are closed at a fixed time, and the packaged workpiece is packaged and baked and aged at a set specific position.

[0191] The vacuum nozzle is designed in the vacuum working chamber, and the vacuum baking and aging device can be placed in the vacuum working chamber. The third vacuum isolation damper 12 is set, and the vacuum working chamber is isolated into two chambers. The vacuum working chamber is responsible for vacuum packaging, and the vacuum baking chamber 10 is responsible for vacuum baking and aging. The volume of the transition part is much smaller than the packaging working part. The opening and closing of the transition part has little effect on the overall vacuum of the system and the output of the vacuum system. Each working chamber is designed with guide rails, conveyor belts and other transport mechanisms to meet the material transportation requirements; at the same time, it is equipped with various positioning devices to ensure that the workpiece stays in the correct position; there is a vacuum baking link at the rear end of the vacuum packaging studio. The volume of the vacuum baking chamber can accommodate several sets of tooling. The tooling enters the vacuum baking chamber from one side and moves out of the vacuum baking chamber from the other side. The residence time during this period meets the time requirements of vacuum baking. The heat source for vacuum baking can use non-contact heating methods such as thermal oil and infrared. During operation, the workpieces enter the equipment from the vacuum transition chamber in batches, the entrance to the chamber is closed, the first vacuum isolation damper remains closed, and the vacuum transition chamber begins to extract vacuum. When the pressure difference on both sides of the first vacuum isolation damper meets the opening requirements of the vacuum sealing door, the first vacuum isolation damper opens, and the workpiece enters the vacuum packaging chamber through the guide rail. The first vacuum isolation damper is closed, and the vacuum transition chamber is ready to receive new workpieces. The workpieces entering the vacuum packaging chamber stay at the specified position under the action of the guide rail and the positioning system, and the part to be heat-sealed enters the working area of ​​the hot air equipment. The encapsulation of the flexible coating material is completed under the control of a certain heating and pressurizing heat sealing program. At this time, the third vacuum isolation damper is opened, and the encapsulated workpieces enter the vacuum baking chamber through the guide rail and other guiding systems. The third vacuum isolation damper is closed to avoid the influence of high temperature on the heat sealing section. The encapsulated workpieces continue to enter the vacuum baking chamber, and the workpieces pass through the working part of the vacuum baking chamber in sequence. When they reach the end of the vacuum baking chamber, the residence time in it can just meet the time requirements for vacuum baking. The rear end of the vacuum baking chamber is the vacuum transition chamber. When the second vacuum isolation damper is closed, the vacuum unit extracts the vacuum in the vacuum transition chamber, and the pressure in the vacuum transition chamber continues to decrease. When the pressure difference on both sides meets the opening requirements of the second vacuum isolation damper, the second vacuum isolation damper opens, and the workpiece after baking enters the vacuum transition chamber. The second vacuum isolation damper closes, and the vacuum transition chamber begins to be pressurized. When the external atmospheric pressure is reached, the vacuum transition chamber door opens, and the workpiece is taken out. In this way, the workpiece completes the vacuum packaging process in a batch-by-batch manner.

[0192] The aerogel production method of the invention has low cost, can realize the recycling of raw materials, has low energy consumption and high production efficiency.

[0193] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for producing aerogel, characterized in that: The production method comprises the following steps: (a) providing a mixture, the mixture comprising a silicon source, an alcohol solvent and a catalyst, wherein the mass concentration of the alcohol solvent is 95%; (b) mixing the mixture provided in step (a) in a certain ratio to prepare an alcohol gel; (c) subjecting the prepared alcohol gel to supercritical drying treatment to obtain a dried aerogel and a recovered alcohol solvent, wherein the mass concentration of the recovered alcohol solvent is 98%; (d) vacuuming the aerogel after supercritical drying to remove impurities and moisture in the aerogel to obtain a pure aerogel product.

2. The method according to claim 1, characterized in that In the supercritical treatment step, before starting to heat up, the remaining space in the reactor is filled with ethanol except for the gelled aerogel; when heating up, as the temperature rises, the ethanol begins to expand due to the heat, and the pressure in the reactor begins to rise.

3. The method according to claim 1, characterized in that The recovered alcohol solvent is used as the alcohol solvent raw material in step (a).

4. The method according to claim 1, characterized in that The working temperature of the vacuum treatment is 220-300°C.

5. The method according to claim 1, characterized in that During supercritical drying, the heating rate of the medium is controlled according to the energy input control curve, which is calculated according to the following formula: P in =C(T)ρ(T)V(dT / dt)+V(dP a (T) / dt) Where P in Input power for effective energy from the outside; C(T) is the specific heat capacity of the solvent at temperature T, KJ / Kg·K; ρ(T) is the density of the solvent at temperature T, Kg / m 3 ; V is the volume of the reactor, m 3 ; T is the reaction temperature, K; t is the production cycle, h; P a (T) is the saturated vapor pressure of the solvent at the corresponding temperature, Pa.

6. The method according to claim 1, characterized in that Before the supercritical drying process, the prepared alcohol gel is subjected to a pre-forming process.

7. The method according to claim 6, characterized in that The steps of the preforming process are: (1) The flexible covering structure is made into a film bag with one side open; (2) placing the prepared alcohol gel in the film bag, and placing an airbag core in the middle of the alcohol gel; (3) the airbag core is inflated to tighten the membrane bag; (4) inserting the film bag into a rigid support structure, and pressing the rigid support structure tightly; (5) Deflate the airbag core and extract the airbag core.

8. The method according to claim 1, characterized in that After the vacuum treatment, the aerogel product is packaged.

9. The method according to claim 8, characterized in that The packaging method is: The aerogel products are vacuum packaged and vacuum baked in batches.

10. The method according to claim 8, characterized in that Getters are activated during packaging.

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