CN106430224A - Microwave drying oven and method for preparing sodium silicate aerogel by utilizing microwave drying method - Google Patents

Abstract

The invention discloses a microwave drying oven and a method for preparing sodium silicate aerogel by utilizing a microwave drying method. The drying oven comprises a supporting table, wherein a heating box and a conveyor belt used for conveying wet gel are arranged on the table body; the conveyor belt penetrates through the whole heating box; a microwave source box is arranged above the heating box; and the top of the microwave source box is communicated with a condenser through an exhaust pipe so as to condenser and recover volatile gases produced in the wet gel heating and drying process. The microwave drying oven has the advantages that the drying oven is ingenious in structure and is capable of realizing drying and preventing explosion under normal temperature and normal pressure; the prepared aerogel has the density of 0.12-0.13g/cm<3>, the porosity of 91-94% and the heat conductivity coefficient of 0.015-0.020W/(m.K), and when powdered aerogel is prepared, the specific surface area is 550-800m<2>/g. Compared with an ordinary aerogel product, the aerogel prepared by the invention is large in specific surface area, high in porosity, low in density and low in heat conductivity coefficient of insulation products.

Description

Microwave drying oven and the method for preparing waterglass aeroge using micro-wave drying method

Technical field

The present invention relates to the preparation method of a kind of drying baker and aeroge, a kind of more particularly to microwave drying oven and using micro-The method that ripple seasoning prepares waterglass aeroge, belongs to heat insulating energy saving material technical field.

Background technology

With the fast development of global economy and society, it is a urgent need to resolve to realize building energy conservation and reduce building energy consumptionChallenge.Aeroge be a kind of new be cross-linked with each other by nano-sized particles formed with the non-of tridimensional networkCrystalline material, the features such as with light porous, ultra-low thermal conductivity, good sound insulation value and fine light transmission rate, is currentThe best solid material of heat preserving and insulating material performance, has important research and development using value in fields such as building, industry.But SiO₂The intensity of aeroge is relatively low, wear no resistance, overall aerogel material high cost, and this gives SiO₂The application band of aerogeCarry out limitation, it is difficult to large-scale promotion application.

Subsiding in order to avoid its inner skeleton structure in aeroge preparation process, will traditionally use supercritical dryingMethod.Wherein, supercritical fluid can effectively eliminate the fluid of capillary force and avoid gel in dry run as a kind ofThe contraction of skeleton, but the method needs to carry out under High Temperature High Pressure or condition of high voltage, and, energy consumption high to equipment requirements is big, operationDangerous big, it is difficult to enter Line Continuity and large-scale production.

It would therefore be highly desirable to solve the above problems.

Content of the invention

Goal of the invention：The first object of the present invention is to provide a kind of simple structure and the microwave drying oven using safety；ThisSecond purpose of invention is the method for providing a kind of utilization micro-wave drying method processing machinery waterglass aeroge of good performance.

Technical scheme：Microwave drying oven of the present invention, including supporting table, stage body is provided with heater box and for conveyingThe conveyer belt of wet gel, the conveyer belt passes through whole heater box, while microwave source case is provided with above heater box, the microwave source caseTop be connected with condenser by exhaustor, condensation reclaim wet gel heat drying process in produce escaping gas.

Preferably, heater box can realize drying at normal temperatures, and therefore its default temperature is 25～30 DEG C.The biography of conveyer beltDefeated speed is 1.0-2.0mm/s.Meanwhile, it is additionally provided with microwave drying oven for controlling conveyer belt transmission speed and microwave source temperatureController.Additionally, microwave source case is provided with metal detector.

The method that utilization micro-wave drying method of the present invention prepares waterglass aeroge, comprises the steps：

(1) silica wet gel is prepared：The deionization of 4～5 times of its volume is added under room temperature in industrial waterglassWater dilutes, and the inorganic acid for adjusting pH for adding mass concentration 10-15% is 9～10, pours mould into, be warming up to 60-80 after stirringDEG C accelerate gel, then stand.

The purpose of acid adding is to generate silicic acid precipitation i.e. gel to react with deionized water, and mineral acid here can be saltAcid, or Fluohydric acid., glacial acetic acid etc.；The time of standing is longer, reaction more abundant, formed gel structure more stable, excellentThe time of repose of choosing is 2-3h；It is possible to further place layer of glass cotton felt in mould, contribute to forming monoblockGel, makes gel not easy to crack.

(2) surface modification modification：By volume ratio 1：The mixed solution of the normal hexane of 1-2 and trim,ethylchlorosilane pours mould intoInterior, silica wet gel is flooded, is stood at room temperature.

In this step, the setting of volume ratio is particularly significant, can obtain the good aeroge of hydrophobicity.Trim normal hexane can be replacedIt is changed to hexamethyldisiloxane, but 1/3rd of normal hexane low price, about hexamethyldisiloxane；Preferred time of reposeFor 24～36h, could so react abundant；Meanwhile, recyclable waste liquid is reused.

(3) clean：Can add dehydrated alcohol in mould, drowning wet gel surface, soaking and washing 24 under room temperature～36h, collects waste liquid, then is cleaned with distilled water 1～2 time after having cleaned；May be otherwise Recycling of waste liquid to reuse.

(4) microwave drying：Silica wet gel in mould is placed in microwave drying oven, the temperature of heater box is setFor 25～30 DEG C, drying time is 30～40min, to complete drying；In the step, the purpose of normal temperature drying is to ensure wet gelInternal structure will not be destroyed, obtain the aeroge of better performances.

(5) the waterglass aeroge is obtained final product after depanning.

Beneficial effect：Compared with prior art, the remarkable advantage of the present invention is：

(1) the microwave drying oven delicate structure of the present invention, using safety, can not only abundant dried silica wet gel,And timely be passed through in condenser the volatilization gas in heating compartment by exhaustor carries out condensation recovery, reduces volatilization gasConcentration, make casing keep at normal temperatures and pressures, prevent blast.

(2) aeroge density prepared by the inventive method is 0.12～0.13g/cm³, porosity is 91～94%, heat conductionCoefficient is 0.015-0.020W/ (m K), and when making powdery aeroge, its specific surface area is 550～800m²/ g, with common gasGel product is compared, and its specific surface area is bigger, and porosity is higher, and density is lower, and heat insulating products heat conductivity is lower.

It is (3) using the aerogel plate light weight of the aeroge making of the present invention, color Bai Weihuang, surface flawless, completely hydrophobic,Fire-protection rating A1 level is not fired completely, and with fabulous sound-absorbing soundproof effect；While lumpy structure can be made, arbitrarily can cutCut, be easy to practical application.

(4) insulation material that is made using aeroge of the present invention can be widely applied to vehicle tank insulation and sound insulation, oilIt is incubated with chemical pipeline, more than -250 DEG C facility heat preservation, less than 1000 DEG C of thermal source is heat-insulated, the civil building body of wall of severe cold areaInsulation, and industrial goods are heat-insulated etc..

(5) production method cost of the present invention is relatively low, and raw material adopts cheap industrial waterglass, and equipment is set using microwave dryingStandby, expense is saved than supercritical drying device, therefore, it is possible to mass industrialized production.

Description of the drawings

Fig. 1 is the structural representation of microwave drying oven of the present invention.

Specific embodiment

Below technical scheme is described further.

As shown in figure 1, the microwave drying oven of the present invention, including supporting table 1, is provided with some legs 10, stage body below stage bodyOn be arranged side by side multiple heater boxes 3, be additionally provided with conveyer belt 2 on stage body, on the conveyer belt 2, place wet gel, conveyer belt 2 is through wholeInside individual heater box 3, while being provided with microwave source case 4 in 3 top of heater box, the microwave source case 4 is correspondingly arranged with heater box 3, andIn the top connecting tube 9 of each microwave source case 4, each connecting tube 9 is all connected to exhaustor 5, and exhaustor 5 is connected with condenser 6Logical.Controller 7 is additionally provided with the microwave drying oven, for controlling conveyer belt transmission speed and microwave source temperature.On microwave source case 4Metal detector 8 is provided with, vent 11 can also be set.Observation door 12 can be set in heater box 3.

Work process：Drying baker is opened, the wet gel that makes is put on a moving belt, the communicated band of wet gel enters heatingIn case, microwave source case radiated microwaves are dried to the wet gel for entering heater box, position of the wet gel in heater box and dryDry situation can be checked by observing door, and the transmission speed of conveyer belt and microwave source temperature can be regulated and controled by controller.CauseFor containing a large amount of ethanol in wet gel, a large amount of alcohol gas are had after heating and is evaporated, full of casing, when in casing, ethanol containsAmount is more than its explosion limit, it may occur that blast, is therefore passed through in condenser volatilization gas by exhaustor and condenses backReceive, the concentration of volatilization gas in heating compartment can be reduced in time, make casing keep at normal temperatures and pressures, preventing blast；ReclaimAlcoholic solution afterwards is repeatable to be utilized, and reduces production cost.Wet gel meeting volatilization gas in dry run, gaseous volatilization is arrivedPart dust granules can be taken away during in the air, in dust, contain part metals granule, metallic particles chance high temperature naked light can occur quick-friedFried, therefore metal detector is mounted with box house.

The performance of microwave drying aeroge is relevant with temperature when drying and transmission speed.Temperature is too high, aeroge interiorPortion's structure both shrinks are larger, destroy its internal structure, cause overall cracking, and therefore the present invention adopts normal temperature drying (25～30 DEG C),Ensure that its internal structure will not be destroyed, the aeroge of better performances can be obtained；Transmission speed is controlled to 1.0-2.0mm/s,So drying can reduce the destruction to aeroge internal structure, and porosity is higher, obtains the better performances of aeroge；Therefore permissibleTemperature and transmission speed are adjusted by controller, controller here is the common controller in this area.

Embodiment 1

The deionized water dilution of 4 times amount of volume is added under room temperature in M3.2 level industrial waterglass, adds quality denseThe salt acid for adjusting pH value of degree 10% is 10, to pour mould after uniform stirring into pH value, places one layer of pre-coated and strengthen glass in mouldGlass cellucotton felt, is warming up to 60 DEG C of acceleration gels, and standing 2h makes silica wet gel；By volume ratio 1：1 normal hexaneMould is poured into the mixed solution of trim,ethylchlorosilane, wet gel is flooded, standing 24h exchanges modified at room temperature；To in mouldDehydrated alcohol, drowning wet gel surface, soaking and washing 24h under room temperature, collection waste liquid after having cleaned is added, then is cleaned with distilled water2 times, Recycling of waste liquid；Product in mould is placed in microwave drying oven, after the completion of 25 DEG C of dryings, depanning, obtain final product waterglass airsettingGlue product.The aerogel product is made warming plate.

The major parameter situation of aerogel product obtained in 1 embodiment 1 of table

Embodiment 2

The deionized water dilution of 5 times amount of volume is added under room temperature in M3.2 level industrial waterglass, adds quality denseThe salt acid for adjusting pH value of degree 15% is 9, to pour mould after uniform stirring into pH value, places one layer of pre-coated reinforcing glass in mouldCellucotton felt, is warming up to 80 DEG C of acceleration gels, and standing 3h makes silica wet gel；By volume ratio 1：2 normal hexane andThe mixed solution of trim,ethylchlorosilane pours mould into, floods wet gel, and standing 36h exchanges modified at room temperature；Add in mouldEntering dehydrated alcohol, drowning wet gel surface, soaking and washing 24h under room temperature, collection waste liquid after having cleaned, then 2 is cleaned with distilled waterSecondary, Recycling of waste liquid；Product in mould is placed in microwave drying oven, after the completion of 30 DEG C of dryings, depanning, obtain final product waterglass aerogeProduct.The aerogel product is made warming plate.

The major parameter situation of aerogel product obtained in 2 embodiment 2 of table

Embodiment 3

The deionized water dilution of 4 times amount of volume is added under room temperature in M3.2 level industrial waterglass, adds quality denseThe salt acid for adjusting pH value of degree 13% is 9, to pour mould after uniform stirring into pH value, places one layer of pre-coated reinforcing glass in mouldCellucotton felt, is warming up to 70 DEG C of acceleration gels, and standing 3h makes silica wet gel；By volume ratio 1：2 normal hexane andThe mixed solution of trim,ethylchlorosilane pours mould into, floods wet gel, and standing 36h exchanges modified at room temperature；Add in mouldEntering dehydrated alcohol, drowning wet gel surface, soaking and washing 24h under room temperature, collection waste liquid after having cleaned, then 2 is cleaned with distilled waterSecondary, Recycling of waste liquid；Product in mould is placed in microwave drying oven, after the completion of 28 DEG C of dryings, depanning, obtain final product waterglass aerogeProduct.The aerogel product is made warming plate.

The major parameter situation of aerogel product obtained in 3 embodiment 3 of table

Reference examples 1

8 groups of parallel laboratory tests are set, and basic step is same as Example 1, and difference is baking temperature.

The major parameter situation of aerogel product obtained in 4 eight groups of control experiments of table

Claims (10)

1. a kind of microwave drying oven, it is characterised in that：Including supporting table (1), stage body be provided with heater box (3) and for convey wetThe conveyer belt (2) of gel, the conveyer belt (2) passes through whole heater box (3), while being provided with microwave source case above heater box (3)(4), the top of the microwave source case (4) is connected with condenser (6) by exhaustor (5), and wet gel heat drying is reclaimed in condensationDuring produce escaping gas.

2. microwave drying oven according to claim 1, it is characterised in that：The preset temperature of heater box (3) be 25～30℃.

3. microwave drying oven according to claim 1, it is characterised in that：The transmission speed of the conveyer belt is 1.0-2.0mm/s.

4. microwave drying oven according to claim 1, it is characterised in that：It is additionally provided with for controlling on the microwave drying ovenThe controller (7) of conveyer belt transmission speed and microwave source temperature.

5. the microwave drying oven according to claim 1 or 4, it is characterised in that：Microwave source case (4) are provided with metal spySurvey device (8).

6. a kind of method that utilization micro-wave drying method prepares waterglass aeroge, it is characterised in that comprise the steps：

(1) silica wet gel is prepared：To in industrial waterglass, add the deionized water of 4～5 times of its volume dilute under room temperatureReleasing, the inorganic acid for adjusting pH for adding mass concentration 10-15% is 9～10, mould is poured into after stirring, is warming up to 60-80 DEG C and addsRapid hardening glue, makes silica wet gel after standing；

(2) surface modification modification：By volume ratio 1：The mixing of the normal hexane/hexamethyldisiloxane of 1-2 and trim,ethylchlorosilane is moltenLiquid is poured in mould, floods silica wet gel, is stood under room temperature；

(3) silica wet gel is cleaned；

(4) microwave drying：Silica wet gel after cleaning is placed in microwave drying oven, the temperature for arranging heater box is 25～30 DEG C, the time is 30～40min, to complete drying；

(5) the waterglass aeroge is obtained final product after depanning.

7. the method for preparing waterglass aeroge using micro-wave drying method according to claim 5, it is characterised in that：Step(1), in, the mineral acid is hydrochloric acid, Fluohydric acid. or glacial acetic acid.

8. the method for preparing waterglass aeroge using micro-wave drying method according to claim 5, it is characterised in that：Step(1), in, glass fibre guard glass fibre cotton is laid in the mould in advance.

9. the method for preparing waterglass aeroge using micro-wave drying method according to claim 5, it is characterised in that：Step(1), in, the time of repose is 2-3h.

10. the method for preparing waterglass aeroge using micro-wave drying method according to claim 5, it is characterised in that：Step(2), in, the time of repose is 24～36h.