CN100552353C - The method for microwave drying of honeycomb formed bodies - Google Patents
The method for microwave drying of honeycomb formed bodies Download PDFInfo
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- CN100552353C CN100552353C CNB2005100935217A CN200510093521A CN100552353C CN 100552353 C CN100552353 C CN 100552353C CN B2005100935217 A CNB2005100935217 A CN B2005100935217A CN 200510093521 A CN200510093521 A CN 200510093521A CN 100552353 C CN100552353 C CN 100552353C
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Abstract
The present invention relates to utilize the method for microwave drying of the honeycomb formed bodies of microwave.A kind of method for microwave drying of honeycomb formed bodies is provided, and its rate of drying that can fully reduce sintered body inside in the dry run of honeycomb formed bodies is poor, and can carry out drying under the situation that does not produce the compartment distortion.This method is, by the microwave that axially is arranged at honeycomb formed bodies (1) irradiation frequency 300～30000MHz in the drying oven for above-below direction ground of compartment being made the method for honeycomb formed bodies (1) drying.In the present invention, make the moisture difference of honeycomb formed bodies (1) above-below direction in the dry run more than or equal to 0.0%/mm and smaller or equal to 0.3%/mm by irradiating microwaves.
Description
Technical field
The present invention relates to utilize the drying means of the honeycomb formed bodies of microwave.
Background technology
Honeycomb structure is extensive use in catalyst carrier and various filters etc. not only, and has recently caused also that as the diesel particulate filter (DPF) that is used for catching the particle-like substance that diesel engine discharges people gaze at.
How this type of honeycomb structure is general wants composition with ceramic main, and use following manufacture method manufacturing usually: in ceramic raw material, add entry and various additive and make the base earthy, then, be made into the sintered body (honeycomb formed bodies) of honeycomb shape with extrusion, after being dried, fire shaping to make honeycomb structure.
Drying means as honeycomb formed bodies, known have utilization to be undertaken dry lure the electric seasoning method and importing hot blast by generation such as gas burners to carry out the heated-air drying method of drying by the high-frequency energy that interelectrode electric current produced of the above and below of being located at honeycomb formed bodies, replace these drying means or share these drying means but brought into use recently, and utilize the drying means (for example, opening the 2002-283329 communique) of microwave with advantages such as rate of drying are fast with reference to patent documentation 1 spy.
In the past, the microwave drying of honeycomb formed bodies was undertaken by making the even honeycomb formed bodies that also is provided as the body that is dried therein of Electric Field Distribution in the drying oven.Have again, make the uniform means of Electric Field Distribution, used the shape of the antenna of adjusting launched microwave and the means such as adjusting fan of preparation as being used to.
But, this existing method for microwave drying, in dry run, the upper and lower end parts of honeycomb formed bodies and the drying of outer circumference portion are slower than other parts, and can not come drying honeycomb shape sintered body integral body with even speed.Honeycomb formed bodies is owing to the evaporation of moisture content is shunk, so the inner rate of drying of sintered body poor (water content is poor) has caused the distortion of the compartment of honeycomb structure.In recent years, the slimming that helps rib (dividing the spaced walls of compartment) of honeycomb structure is developed, owing to help the rib also easy more generation of distortion of leptophragmata chamber more, so the homogenising of rate of drying becomes more importantly problem.
It is generally acknowledged that influences such as the heat radiation of the honeycomb formed bodies in the dry run and evaporation latent heat are the reasons that above-mentioned rate of drying difference produces.When carrying out the microwave drying of honeycomb ceramics sintered body, steam and hot blast etc. is imported in the drying oven, and environment temperature for example risen to 80 ℃ degree to reduce heat radiation, or with increasing microwave output attempts to realize rate of drying with the method for the influence that reduces to dispel the heat homogenising, it is poor but even these methods also are difficult to fully to reduce rate of drying, nor can obtain to suppress the promising result of distortion to a certain degree, present situation that Here it is.
Summary of the invention
The present invention be in view of this type of in the past situation and the technical scheme that proposes, its purpose is to provide a kind of method for microwave drying of honeycomb formed bodies, it is poor that this method can fully reduce the rate of drying of sintered body inside in the dry run of honeycomb formed bodies, do not produce the compartment shifting ground and make its drying.
According to the present invention, this method be by to compartment axially for above-below direction be arranged at the microwave of the honeycomb formed bodies irradiation frequency 300～30000MHz in the drying oven, make the method for above-mentioned honeycomb formed bodies drying, it is characterized in that: a kind of method for microwave drying (first method for microwave drying) of honeycomb formed bodies is provided, by shining above-mentioned microwave so that the moisture difference of the above-mentioned honeycomb formed bodies above-below direction in the dry run at 0.0%～0.3%/mm.
In addition, according to the present invention, this method be by to compartment axially for above-below direction be arranged at the honeycomb formed bodies irradiation frequency 300～30000MHz in the drying oven microwave make the method for above-mentioned honeycomb formed bodies drying, it is characterized in that: the method for microwave drying (second method for microwave drying) that a kind of honeycomb formed bodies is provided, above-mentioned honeycomb formed bodies is placed tubular screen inside, the distance that makes above-mentioned honeycomb formed bodies outer circumference surface and above-mentioned screen inner peripheral surface simultaneously is more than or equal to 5mm and smaller or equal to 1/4 of above-mentioned microwave wavelength, and shines above-mentioned microwave.
Have again, according to the present invention, this method is the method that makes above-mentioned honeycomb formed bodies drying by the microwave to the honeycomb formed bodies irradiation frequency 300～30000MHz that axially is arranged in the drying oven for above-below direction ground and carries to predetermined direction of compartment, it is characterized in that: the method for microwave drying (the 3rd method for microwave drying) that a kind of honeycomb formed bodies is provided, tabular screen is set so that above-mentioned honeycomb formed bodies is sandwiched in therebetween in the setting of the both sides in the carrying path of carrying above-mentioned honeycomb formed bodies, the distance that makes above-mentioned honeycomb formed bodies and above-mentioned screen simultaneously is more than or equal to 5mm and smaller or equal to 1/4 of above-mentioned microwave wavelength, and shines above-mentioned microwave.
Also have, according to the present invention, this method is the method that makes above-mentioned honeycomb formed bodies drying by the microwave to the honeycomb formed bodies irradiation frequency 300～30000MHz that axially is arranged in the drying oven for above-below direction ground and carries to predetermined direction of compartment, it is characterized in that: the method for microwave drying (the 4th method for microwave drying) that a kind of honeycomb formed bodies is provided, under the state of arranging on the direction perpendicular to carrying, carry out the carrying of above-mentioned honeycomb formed bodies at a plurality of honeycomb formed bodies on the transportation tray, and on above-mentioned transportation tray, be provided with tabular screen, the distance that makes above-mentioned honeycomb formed bodies and above-mentioned screen simultaneously is more than or equal to 5mm and smaller or equal to 1/4 of above-mentioned microwave wavelength, and shines above-mentioned microwave.
According to the present invention, the rate of drying that can fully reduce sintered body inside in the dry run of honeycomb formed bodies is poor, and can carry out drying under the situation that does not produce the compartment distortion.
Description of drawings
Fig. 1 is the synoptic diagram of an example of having showed the embodiment of first method for microwave drying.
Fig. 2 is another routine synoptic diagram of having showed the embodiment of first method for microwave drying.
Fig. 3 has showed to be used to judge that compartment is out of shape the synoptic diagram at the position that whether takes place.
Fig. 4 is a synoptic diagram of having showed normal compartment.
Fig. 5 is a synoptic diagram of having showed an example that is judged as the compartment that has deformed.
Fig. 6 is the summary stereogram of an example of having showed the embodiment of second method for microwave drying.
Fig. 7 is the summary vertical view of an example of having showed the embodiment of second method for microwave drying.
Fig. 8 is the summary vertical view of an example of having showed the embodiment of the 3rd method for microwave drying.
Fig. 9 is another routine summary vertical view of having showed the embodiment of the 3rd method for microwave drying.
Figure 10 is the summary vertical view of an example of having showed the embodiment of the 4th method for microwave drying.
Figure 11 is the synoptic diagram that locates of having showed honeycomb formed bodies residual moisture among reference example and the embodiment.
Figure 12 is a curve map of having showed the result of reference example 1.
Figure 13 is a curve map of having showed the result of reference example 2.
Figure 14 is a curve map of having showed the result of reference example 3.
Figure 15 is a curve map of having showed the result of reference example 4.
Figure 16 is a curve map of having showed the result of embodiment 1.
Figure 17 is a curve map of having showed the result of reference example 5.
Figure 18 is a curve map of having showed the result of embodiment 2.
Figure 19 is a curve map, has showed the result of embodiment 3.
Figure 20 is a curve map of having showed the result of reference example 6.
Figure 21 is a curve map of having showed the result of embodiment 4.
Among the figure: 1-honeycomb formed bodies, 3-aluminium foil, 5-pedestal, 7-waveguide pipe, 11-outer circumference portion, 13-inside, 15-compartment, 17-screen, 18-screen, 19-screen, 20-screen, 21-transportation tray.
The specific embodiment
First method for microwave drying of the present invention is, by the microwave that axially is arranged at the honeycomb formed bodies irradiation frequency 300～30000MHz in the drying oven for above-below direction ground of compartment being made the method for above-mentioned honeycomb formed bodies drying, it is characterized in that: by shining above-mentioned microwave so that the above-mentioned honeycomb formed bodies above-below direction in the dry run moisture difference of (compartment axial) at 0.0%/mm～0.3%/mm.
The experience result that inventors according to the present invention are obtained by all experiments, as can be known, if irradiating microwaves makes the moisture difference of honeycomb formed bodies above-below direction become this value, the moisture that then can fully reduce honeycomb formed bodies inside is poor, and can carry out drying under the situation that produces the compartment distortion hardly.
In this dry run, the perfect condition of the moisture of honeycomb formed bodies above-below direction can be passed through, and for example, microwave incides the incident density (W/cm of honeycomb formed bodies from above-below direction
2) incide the incident density (W/cm of honeycomb formed bodies from horizontal direction greater than it
2), and with the output density (kW/kg) of microwave be controlled at threshold value that the compartment of honeycomb formed bodies do not deform with on obtain.
As previously mentioned, in the method for microwave drying of existing honeycomb formed bodies, the drying with the upper and lower end parts of honeycomb formed bodies and outer circumference portion is slower than the tendency of other parts.That is, on the honeycomb formed bodies above-below direction, upper end and bottom are slower with respect to the middle part drying, on the other hand, make progress in the footpath of honeycomb formed bodies, and outer circumference portion is slower with respect to inner drying.
Inventors have carried out the inner rate of drying difference of relevant this honeycomb formed bodies and have produced causal investigation, and the generation of the rate of drying of the above-below direction of known honeycomb formed bodies poor (residual moisture content is poor) is subjected to the influence of the heat radiation in the dry run to a great extent.Though the microwave energy of honeycomb formed bodies radiation is differed greatly on the energy of energy that heat radiation consumes and latent heat consumption, but because wherein the energy of heat radiation consumption is certain (fixed value), so increase the output density of microwave can reduce the to dispel the heat ratio of the energy that consumes, otherwise, increase the ratio of the energy of latent heat consumption, then reduce influence, thereby the distortion of honeycomb formed bodies is inhibited to heat radiation rate of drying difference.
Therefore, in the present invention, preferably the output density (kW/kg) of microwave is controlled at more than the threshold value that the compartment of honeycomb formed bodies do not deform.For example, the efficiency of heating surface of common microwave drier (=be used for dry energy/microwave effectively to export) be about 0.5, but the threshold value that the compartment of the honeycomb formed bodies of this microwave drier does not deform is the output density of microwave is about 3kW/kg, therefore, if the output density of microwave can be controlled at more than the 3kW/kg, preferably under the situation of considering the heating standard deviation, be controlled at (more than 120% of threshold value) more than the 3.6kW/kg, so just can the moisture difference of the honeycomb formed bodies above-below direction in the dry run be under the above-mentioned perfect condition.
And, herein, the judgment standard whether compartment of honeycomb formed bodies deforms is: be similar to Fig. 3 apart from the cross section in each 30mm scope of the top and bottom of honeycomb formed bodies 1 on, when the length on a limit of the opening portion of as shown in Figure 4 normal compartment 15 is 1 (benchmark), situation about entering with the circle of diameter 0.9 in the opening portion of compartment 15 is " not deforming ", and the situation that can not enter with as shown in Figure 5 above-mentioned circle in the opening portion of compartment 15 is " deforming ".
In addition, known, incide the incident density of honeycomb formed bodies and incide the incident density of honeycomb formed bodies from horizontal direction (side surface direction) from above-below direction (end face direction) by the control microwave, make the former greater than the latter, then can be when the rate of drying difference that makes the honeycomb formed bodies above-below direction further relax, it is poor to suppress honeycomb formed bodies rate of drying radially.Concrete grammar is, for example, as shown in Figure 1, on honeycomb formed bodies 1 side, reel and be similar to the microwave reflection article of aluminium foil 3, perhaps surround honeycomb formed bodies side configuration reflecting plate (metallic plate) etc., thereby suppress incident from the microwave of horizontal direction, as shown in Figure 2, dispose waveguide pipe 7 in the drying oven, it is used on pedestal 5 the above and below irradiating microwaves of the honeycomb formed bodies 1 that is provided with, thereby effectively from the above-below direction irradiating microwaves of honeycomb formed bodies 1.
In addition, in the present invention, microwave incides the relation that incident density B that the incident density A of honeycomb formed bodies and its incide honeycomb formed bodies from horizontal direction preferably satisfies 1.0 〉=A/ (A+B)＞0.7 from above-below direction.If inciding the incident density of honeycomb formed bodies from above-below direction, microwave satisfies this relation from the incident density that horizontal direction incides honeycomb formed bodies, just then can obtain better to suppress the effect of compartment distortion with it.
Second method for microwave drying of the present invention is, by to compartment axially for above-below direction be arranged at the honeycomb formed bodies irradiation frequency 300～30000MHz in the drying oven microwave make the method for above-mentioned honeycomb formed bodies drying, it is characterized in that: above-mentioned honeycomb formed bodies is placed tubular screen inside, the distance that makes above-mentioned honeycomb formed bodies outer circumference surface and above-mentioned screen inner peripheral surface simultaneously is at 5mm or more than the 5mm, and above-mentioned microwave wavelength 1/4 or its with under shine above-mentioned microwave.
Like this, if honeycomb formed bodies is placed tubular screen inside, then because the state that is in the covering of conductively-closed thing on every side of the outer circumference surface of honeycomb formed bodies, so the microwave incident from the horizontal direction to the honeycomb formed bodies is limited by this screen, as a result, the microwave incident density that incides honeycomb formed bodies from above-below direction incides the incident density of honeycomb formed bodies greater than it from horizontal direction.
As described in the explanation of first method for microwave drying, if the incident density of microwave from the above-below direction to the honeycomb formed bodies is greater than its incident density from horizontal direction, then can be when the rate of drying difference that makes the honeycomb formed bodies above-below direction obtains relaxing, it is poor to suppress honeycomb formed bodies rate of drying radially, the result is, the rate of drying that can fully reduce honeycomb formed bodies inside is poor, and can carry out the drying of honeycomb formed bodies under the situation that produces the compartment distortion hardly.
In addition, if the conductively-closed thing covers around the outer circumference surface of honeycomb formed bodies, then be arranged in when carrying out drying simultaneously in the drying oven, can suppress the mutual interference between adjacent cell shape sintered body, and can make the drying regime between honeycomb formed bodies be difficult to produce difference at a plurality of honeycomb formed bodies.Have, the dry steam that utilizes honeycomb formed bodies self to produce can keep near the temperature and humidity of the appropriateness in the space of honeycomb formed bodies, and can carry out drying under the situation of fold that does not generate outer circumference portion and depression again.In addition, in the prior art spy opens 2002～No. 283329 grades, though for obtain effect same with whole stove inner control in the high humidity environment of humidity 70% or more, the present invention is not carrying out just can reaching above-mentioned effect under the situation that above-mentioned environment controls.
Fig. 6 and Fig. 7 are respectively the summary stereogram and the summary vertical view of one of the embodiment of displaying second method for microwave drying example, in this example, use metal rounding cylindrical shell as tubular screen 17, and honeycomb formed bodies 1 is placed its inside.In addition, honeybee to be dried the profile of nest shape sintered body when not being cylindrical, preferably use cylindrical body to be used as screen with inner section shape identical with the cross sectional shape of this honeycomb formed bodies.And as long as can effectively suppress the intrusion of (reflection) microwave, the material of screen also can be made of the material beyond the metal.
In second method for microwave drying, the distance D of honeycomb formed bodies 1 outer circumference surface and screen 17 inner peripheral surfaces
1For more than or equal to 5mm and smaller or equal to 1/4 of microwave wavelength.For example, because in the microwave drying of honeycomb formed bodies during the general microwave that uses 2.45GHz, wavelength is 120mm, so the distance D of honeycomb formed bodies 1 outer circumference surface and screen 17 inner peripheral surfaces
1Between 5～30mm.If both distance D
1Not enough 5mm, then the water droplet that generates on the screen inner peripheral surface in the dry run also might make the rate of drying of this outer circumference surface change attached to the outer circumference surface of honeycomb formed bodies, if surpass 1/4 of microwave wavelength, then be difficult to fully shielding from the incident of the microwave of the horizontal direction of honeycomb formed bodies.
The length of screen 17 (highly) L, be maximum preferably with length as 1/2 addition of the length of the honeycomb formed bodies 1 of dry object and microwave wavelength, the length that deducts 1/2 gained of microwave wavelength with the length from honeycomb formed bodies is minimum of a value, and value is (promptly in this scope, when the position that is in sustained height when the center of the short transverse of the center of the short transverse of screen 17 and honeycomb formed bodies 1 concerns, if the upper and lower end parts of screen 17 is with respect to the upper and lower end face of honeycomb formed bodies 1 1/4 length of outstanding microwave length respectively, the length that then is in the screen 17 under this state is maximum; If the upper and lower end parts of honeycomb formed bodies 1 is with respect to the upper and lower end face of screen 17 1/4 length of outstanding microwave length respectively, the length that then is in the screen 17 under this state is minimum of a value), if identical then better with the length of honeycomb formed bodies 1.When the length L of screen 17 than the length of honeycomb formed bodies 1 in short-term, the upper end of honeycomb formed bodies 1 and/or bottom are outstanding from the upper end and/or the lower end of screen 17, in this case, if the length L of screen 17 does not satisfy above-mentioned scope, thereby then ledge will excessively be difficult to obtain sufficient shield effectiveness.On the contrary, when the length L of screen 17 is grown than the length of honeycomb formed bodies 1, the upper end of screen 17 and/or lower end are outstanding from the upper end and/or the bottom of honeycomb formed bodies 1, in this case, if the length L of screen 17 exceeds above-mentioned scope, then incessantly incide the microwave of honeycomb formed bodies 1, also may be restricted from the microwave of above-below direction incident from horizontal direction.
The 3rd method for microwave drying of the present invention is, make the method for above-mentioned honeycomb formed bodies drying by microwave to the honeycomb formed bodies irradiation frequency 300～30000MHz that axially is arranged in the drying oven and carries to predetermined direction of compartment for above-below direction ground, it is characterized in that: the both sides in the carrying path that is positioned at the above-mentioned honeycomb formed bodies of carrying set up tabular screen so that above-mentioned honeycomb formed bodies is sandwiched in therebetween, make the distance of above-mentioned honeycomb formed bodies and above-mentioned screen shine above-mentioned microwave more than or equal to 5mm and smaller or equal to 1/4 of above-mentioned microwave wavelength simultaneously.
Like this, if the both sides in the carrying path that is positioned at the above-mentioned honeycomb formed bodies of carrying set up tabular screen so that above-mentioned honeycomb formed bodies is sandwiched in therebetween, then can be by the restriction of this screen from the incident of the microwave of horizontal direction to honeycomb formed bodies, the result is that microwave incides the incident density of honeycomb formed bodies greater than its incident density from horizontal direction from above-below direction.
As previously mentioned, if microwave incides the incident density of honeycomb formed bodies from above-below direction bigger than its incident density from horizontal direction, then can be when the rate of drying difference that makes the honeycomb formed bodies above-below direction obtains relaxing, it is poor to suppress honeycomb formed bodies rate of drying radially, the result is, the rate of drying that can fully reduce honeycomb formed bodies inside is poor, and can make the honeycomb formed bodies drying under the situation that produces the compartment distortion hardly.
Fig. 8 is a summary vertical view of having showed one of the embodiment example of the 3rd method for microwave drying.The 3rd method for microwave drying carries out drying with honeycomb formed bodies in continuous drier be prerequisite, and this drying oven can carry out drying to it in the carrying by carrying mechanisms such as belt conveyor, roll-type conveyers in a predetermined direction successively at honeycomb formed bodies.Each honeycomb formed bodies 1 is handled upside down successively along the direction of arrow among the figure, and tabular screen is set so that honeycomb formed bodies is sandwiched in therebetween in the setting of the both sides in this carrying path.Though be suitable for using metallic plate to be used as this screen 18,, then also can use metal material in addition if can effectively suppress the intrusion of (reflection) microwave.In addition, as shown in Figure 9, in same drying oven, the carrying path of many honeycomb formed bodies 1 that have been arranged in parallel also can be erect in the both sides in every carrying path tabular screen 18 is set.
In the 3rd method for microwave drying, the distance D of honeycomb formed bodies 1 and screen 18
2For more than or equal to 5mm and smaller or equal to 1/4 of microwave wavelength.For example, owing to generally use the microwave of 2.45GHz in the microwave drying of honeycomb formed bodies, in this case, wavelength is 120mm, so the distance D of honeycomb formed bodies 1 and screen 18
2Between 5～30mm.If both distance D
2Not enough 5mm, then the water droplet that generates on the screen inner peripheral surface in the dry run might make the rate of drying of this outer circumference surface change attached to the outer circumference surface of honeycomb formed bodies, if surpass 1/4 of microwave wavelength, then be difficult to fully shielding from the incident of the microwave of the horizontal direction of honeycomb formed bodies.
The 4th method for microwave drying of the present invention is, make the method for above-mentioned honeycomb formed bodies drying by microwave to the honeycomb formed bodies irradiation frequency 300～30000MHz that axially is arranged in the drying oven and carries to predetermined direction of compartment for above-below direction ground, it is characterized in that: a plurality of honeycomb formed bodies on transportation tray carry out the carrying of above-mentioned honeycomb formed bodies with the state with the direction arrangement of carrying the direction quadrature, and on above-mentioned transportation tray, being provided with tabular screen, the distance that makes above-mentioned honeycomb formed bodies and above-mentioned screen simultaneously is for to shine above-mentioned microwave more than or equal to 5mm and smaller or equal to 1/4 of above-mentioned microwave wavelength.
Like this, set up tabular screen on the transportation tray of a plurality of honeycomb formed bodies if having in mounting side by side, then limited by this screen at the microwave that incides honeycomb formed bodies from horizontal direction, as a result, microwave incides the incident density of honeycomb formed bodies greater than its incident density from horizontal direction from above-below direction.
As previously mentioned, if microwave incides the incident density of honeycomb formed bodies greater than its incident density from horizontal direction from above-below direction, then can be when the rate of drying difference that makes the honeycomb formed bodies above-below direction obtains relaxing, it is poor to suppress honeycomb formed bodies rate of drying radially, the result is, the rate of drying that can fully reduce honeycomb formed bodies inside is poor, and can make the honeycomb formed bodies drying under the situation that produces the compartment distortion hardly.
Figure 10 is a summary vertical view of having showed one of the embodiment example of the 4th method for microwave drying.The 3rd method for microwave drying carries out drying with honeycomb formed bodies in continuous drier be prerequisite, and this drying oven can carry out drying to it in the carrying by carrying mechanisms such as belt conveyor, roll-type conveyers in a predetermined direction successively at honeycomb formed bodies.In addition, as its mode of transport, be on transportation tray 21, a plurality of honeycomb formed bodies 1 in turn to be carried with the state of arranging with the direction of carrying direction (direction of arrow among the figure) quadrature.Transportation tray 21 is the plate bodys that are made of ceramic porous plastid etc., and its length direction is in the direction of carrying direction quadrature and is placed on the carrying mechanism, and can load above-mentioned a plurality of honeycomb formed bodies 1 and carry.Though be suitable for using metallic plate to be used as erectting on the transportation tray 21 screen 19 that is provided with,, if can effectively suppress the intrusion of (reflection) microwave, then also can use metal material in addition.
In the 4th method for microwave drying, the distance D of honeycomb formed bodies 1 and screen 19
3For more than or equal to 5mm and smaller or equal to 1/4 of microwave wavelength.For example, because in the microwave drying of honeycomb formed bodies during the general microwave that uses 2.45GHz, wavelength is 120mm, so the distance D of honeycomb formed bodies 1 and screen 19
3Between 5～30mm.If both distance D
3Not enough 5mm, then the water droplet that generates on the screen inner peripheral surface in the dry run might make the rate of drying of this outer circumference surface change attached to the outer circumference surface of honeycomb formed bodies, if surpass 1/4 of microwave wavelength, then be difficult to fully shielding from the incident of the microwave of the horizontal direction of honeycomb formed bodies.
In addition, in the 4th method for microwave drying, shown in the example among Figure 10, except being provided with the screen 19 in setting on the transportation tray 21, if erect in the both sides that carrying is loaded into the carrying path of the honeycomb formed bodies 1 on the transportation tray 21 again and tabular screen 20 be set so that transportation tray 21 is sandwiched in therebetween, then can further limit the microwave that incides honeycomb formed bodies 1 from horizontal direction, and the rate of drying difference of honeycomb formed bodies 1 inside is more relaxed by this screen 20.
In the present invention, the microwave frequency that honeycomb formed bodies is shone is 300～30000MHz, preferably 900～5000MHz.If the not enough 300MHz of this microwave frequency, then, wavelength the volume of stove must be increased because being increased to about more than 1 meter or 1 meter, if surpass 30000MHz, then to make honeycomb formed bodies applicatory be only limited to size little owing to electric wave shoals to the penetration depth of honeycomb formed bodies.
In addition, in the present invention, be to be raw material with pottery etc. as the honeycomb formed bodies of dry object, again after wherein adding entry and additive and making the base earthy, the cellular object made from extrusion.At this, cellular referring to has the shape that axially goes up a plurality of through holes (compartment) that connect that is separated by next door (spaced walls).Though the honeycomb formed bodies that the present invention is suitable for does not have the special restriction of material and cell density, septal wall thickness, compartment shape etc.,, it is then effective especially that septal wall thickness is crossed the thin honeycomb formed bodies that makes compartment be easy to produce distortion.
Embodiment
Below will illustrate in greater detail the present invention, wait embodiment but the present invention is not limited to this according to embodiment.
Reference example 1
After talcum powder, potter's clay, alumina, adhesive, water etc. are in harmonious proportion and carry out mixing (mixing Practice), soil refining (native Practice), make diameter 120mm, length 200mm, the about 100 μ m of wall thickness, the about 300/in of compartment number by extrusion with the base soil that obtains
2(about 46/cm
2) honeycomb formed bodies.With this sintered body in batch type microwave drier (efficiency of heating surface 0.5) vertically (compartment be the state of above-below direction axially) be provided with, and be that the microwave of 2.45GHz shines 300 seconds to carry out drying with output density 1kW/kg with frequency.In addition, in this example, microwave incides honeycomb formed bodies from above-below direction incident density estimate to be about 1: 1 with its ratio from the incident density of horizontal direction (
).
After the drying, to the outer circumference portion 11 and the inside 13 of honeycomb formed bodies shown in Figure 11 1, measure the residual moisture of height 0mm (bottom)～200mm (upper end), its result shows in Figure 12.As shown in figure 12, when using the common microwave drying in the past carried out, the inside of honeycomb formed bodies is faster than outer circumference portion drying.In addition, on above-below direction, the drying of upper end and bottom (be respectively from the end face to 30mm about scope) is slower than the middle part.
Reference example 2
After talcum powder, potter's clay, alumina, adhesive, water etc. are in harmonious proportion and carry out mixing, soil refining, make diameter 120mm, length 200mm, the about 100 μ m of wall thickness, the about 300/in of compartment number by extrusion with the base soil that obtains
2(about 46/cm
2) honeycomb formed bodies.With this sintered body in batch type microwave drier (efficiency of heating surface 0.5) vertically (compartment be the state of above-below direction axially) be provided with, and be that the microwave of 2.45GHz shines 600 seconds to carry out drying with output density 0.5kW/kg with frequency.In addition, in this example, microwave incides honeycomb formed bodies from above-below direction incident density estimate to be about 1: 1 with its ratio from the incident density of horizontal direction (
).After the drying, to the outer circumference portion 11 and the inside 13 of honeycomb formed bodies shown in Figure 11 1, measure the residual moisture of height 160mm (bottom)～220mm (upper end), its result shows in Figure 13.
Reference example 3
The honeycomb formed bodies that to similarly make with above-mentioned reference example 2 in batch type microwave drier (efficiency of heating surface 0.5) vertically (compartment be the state of above-below direction axially) be provided with, and be that the microwave of 2.45GHz shines 60 seconds to carry out drying with output density 5kW/kg with frequency.In addition, in this example, the incident density of microwave from the above-below direction to the honeycomb formed bodies with its from ratio of the incident density of horizontal direction estimate to be about 1: 1 (
).After the drying, similarly measure residual moisture with Fig. 2, its result shows in Figure 14.
According to Figure 13 and Figure 14 as can be known: the little reference example 2 to 0.5kW/kg of the output density of microwave is compared to the reference example 3 of 5kW/kg greatly with the microwave output density, and the residual moisture of its above-below direction is poor, and promptly the rate of drying difference is less.This can be considered to: the microwave output density is big more, and then the catabiotic ratio of latent heat is big more with respect to the catabiotic ratio of heat radiation, and the influence of the rate of drying difference of heat radiation is reduced.But, in reference example 3, can not fully suppress the distortion of compartment.
Reference example 4
After talcum powder, potter's clay, alumina, adhesive, water etc. are in harmonious proportion and carry out mixing, soil refining, make diameter 120mm, length 170mm, the about 100 μ m of wall thickness, the about 300/in of compartment number by extrusion with the base soil that obtains
2(about 46/cm
2) honeycomb formed bodies.This sintered body side twined aluminium foil and vertically (compartment be the state of above-below direction axially) setting batch type microwave drier (efficiency of heating surface 0.5) in, and be that the microwave of 2.45GHz shines 900 seconds to carry out drying with output density 0.5kW/kg with frequency.In addition, in this example, microwave incides honeycomb formed bodies from above-below direction incident density estimate to be about 1: 1 with its ratio from the incident density of horizontal direction (
).After the drying, to the outer circumference portion 11 and the inside 13 of honeycomb formed bodies shown in Figure 11 1, measure the residual moisture of height 110mm～170mm (upper end), its result shows in Figure 15.
Aluminium foil is twined and vertically (compartment be the state of above-below direction axially) setting batch type microwave drier (efficiency of heating surface 0.5) in the side of the honeycomb formed bodies that will similarly make with above-mentioned reference example 4, and is that the microwave of 2.45GHz shines 90 seconds to carry out drying with output density 5kW/kg with frequency.In addition, in this example, microwave incides honeycomb formed bodies from above-below direction incident density estimate to be about 1: 0 with its ratio from the incident density of horizontal direction (
).After the drying, similarly measure residual moisture with above-mentioned reference example 4, its result shows in Figure 16.
Reference example 4 and embodiment 1 all are wound with aluminium foil with the microwave of reflection from horizontal direction in the honeycomb formed bodies side, though microwave incides the incident density of honeycomb formed bodies from above-below direction bigger than its incident density from horizontal direction, but the output density at microwave is in the reference example 4 of 0.5kW/kg, though the residual moisture content difference of outer circumference portion and inside is less, but the moisture difference of the above-below direction of honeycomb formed bodies is bigger, and can not fully suppress the distortion of compartment.Relative with it, output density at microwave is among the embodiment of 5kW/kg, not only the residual moisture content difference of outer circumference portion and inside is less, and the moisture difference of the above-below direction of honeycomb formed bodies is also less, and can be, and almost cannot see the distortion of compartment with the dry whole sintered body of cardinal principle even velocity.
Reference example 5
After talcum powder, potter's clay, alumina, adhesive, water etc. are in harmonious proportion and carry out mixing, soil refining, make diameter 120mm, length 200mm, the about 100 μ m of wall thickness, the about 300/in of compartment number by extrusion with the base soil that obtains
2(about 46/cm
2) honeycomb formed bodies.With this sintered body in batch type microwave drier (efficiency of heating surface 0.5) vertically (compartment be the state of above-below direction axially) be provided with, and be that the microwave of 2.45GHz shines 60 seconds to carry out drying with output density 5kW/kg with frequency.In addition, in this example, microwave incides honeycomb formed bodies from above-below direction incident density estimate to be about 1: 1 with its ratio from the incident density of horizontal direction (
).After the drying, to the outer circumference portion 11 and the inside 13 of honeycomb formed bodies shown in Figure 11 1, measure the residual moisture of height 0mm (bottom)～200mm (upper end), its result shows in Figure 17.
Embodiment 2
The honeycomb formed bodies that to similarly make with above-mentioned reference example 5 vertically (compartment axially be the state of above-below direction) is arranged on the inside of the screen of being made by metal rounding cylindrical shell (internal diameter 140mm, length 200mm) of setting in the batch type microwave drier (efficiency of heating surface 0.5).The distance of honeycomb formed bodies outer circumference surface and screen inner peripheral surface is 10mm.Under this state, with frequency be the microwave of 2.45GHz with output density 5kW/kg irradiation 60 seconds to carry out drying.In addition, in this example, microwave incides incident density A and its relation from the satisfied 1.0 〉=A/ (A+B)＞0.7 of ratio of the incident density B of horizontal direction of honeycomb formed bodies from above-below direction.After the drying, similarly measure residual moisture with above-mentioned reference example 5, its result shows in Figure 18.
Length as the metal rounding cylindrical shell of screen is 180mm, and similarly carries out the microwave drying of honeycomb formed bodies with above-mentioned use-case 2.After the drying, similarly measure residual moisture with above-mentioned reference example 5, its result shows in Figure 19.
Reference example 6
Internal diameter as the metal rounding cylindrical shell of screen is 270mm, and the distance of honeycomb formed bodies outer circumference surface and screen inner peripheral surface is 75mm, and similarly carries out the microwave drying of honeycomb formed bodies with the foregoing description 2.After the drying, similarly measure residual moisture with above-mentioned reference example 5, its result shows in Figure 20.
Embodiment 4
Will and the carrying path of honeycomb formed bodies in continuous-type microwave drying oven (efficiency of heating surface 0.5) that similarly make of above-mentioned reference example 5 on vertically (compartment axially be the state of above-below direction) 3 (being spaced apart between the honeycomb formed bodies 20mm) are set.The screen made by metallic plate (height 220mm, length 500mm, thickness 1mm) is set so that honeycomb formed bodies is sandwiched in therebetween on the both sides in carrying path.The distance of honeycomb formed bodies and screen is 20mm.Under this state, with frequency be the microwave of 2.45GHz with output density 5kW/kg irradiation 60 seconds to carry out drying.In addition, in this example, microwave incides incident density A and its relation from the satisfied 1.0 〉=A/ (A+B)＞0.7 of ratio of the incident density B of horizontal direction of honeycomb formed bodies from above-below direction.After the drying, similarly measure residual moisture with above-mentioned reference example 5, its result shows in Figure 21.
According to Figure 17 and Figure 18 as can be known: the screen that metal rounding cylindrical shell is made has limited the microwave incident from horizontal direction, microwave incides honeycomb formed bodies from above-below direction incident density is compared with the reference example 5 that does not use screen from the big use-case 2 of the incident density of horizontal direction than it, the residual moisture content difference of the residual moisture difference of above-below direction and outer circumference portion and inside is less, and the rate of drying difference of each several part is less.And, according to Figure 18 and Figure 19 as can be known: the use-case 2 identical with the length of the length of screen and honeycomb formed bodies compared, the use-case 3 that the length of screen is shorter than the length of honeycomb formed bodies, on the top from the outstanding honeycomb formed bodies in screen upper end, the residual moisture content difference of outer circumference portion and inside is big slightly.Have again, according to Figure 18 and Figure 20 as can be known: compare more than or equal to 5mm and smaller or equal to the use-case 2 of (120mm) 1/4 of microwave wavelength with the distance of honeycomb formed bodies outer circumference surface and screen inner peripheral surface, the residual moisture difference of above-below direction of reference example 6 that this distance surpasses microwave wavelength 1/4 is bigger.Also have, according to Figure 21 as can be known: even erect under the situation that the screen that metallic plate makes is set the both sides in carrying path in the continuous-type microwave drying oven, utilize this screen also can effectively limit microwave incident from horizontal direction, and the residual moisture difference and the outer circumference portion that can reduce above-below direction are poor with inner residual moisture content, also can make the rate of drying of each several part even.
The present invention can be suitable for use as the drying means of employed honeycomb formed bodies such as the catalyst carrier of exhaust gas purification catalyst for example and DPF.
Claims (2)
1. the method for microwave drying of a honeycomb formed bodies, be by the microwave that axially is arranged at the honeycomb formed bodies irradiation frequency 300～30000MHz in the drying oven for above-below direction of compartment being made the method for described honeycomb formed bodies drying, it is characterized in that: make the moisture difference of the described honeycomb formed bodies above-below direction in the dry run more than or equal to 0.0%/mm and smaller or equal to 0.3%/mm by irradiating microwaves, can make described microwave incides described honeycomb formed bodies from above-below direction incident density incide the incident density of described honeycomb formed bodies from horizontal direction, and the output density of described microwave can be controlled at more than the threshold value that the compartment of described honeycomb formed bodies do not deform greater than it.
2. the method for microwave drying of honeycomb formed bodies according to claim 1 is characterized in that: described microwave incides the relation that incident density B that the incident density A of described honeycomb formed bodies and its incide described honeycomb formed bodies from horizontal direction satisfies 1.0 〉=A/ (A+B)＞0.7 from above-below direction.
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