JP2006247484A - Method for granulating ceramic raw material and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easy-to-use granulating method capable of making structure, composition, particle size and shape unifom. <P>SOLUTION: Ceramic slurry is irradiated with ultrasonic waves from an ultrasonic wave irradiation part 142 to vibrate particles of barium titanate in a filtration chamber 140 of an ultrasonic dispersion/filtration unit 40 arranged between an agitator 34 and a spray-drying unit 42. As a result, agglomerated particles of barium titanate become single particles, which are then dispersed uniformly in a solvent. Ultrasonic dispersion and filtration for achieving such a good result are continued until the ceramic slurry is supplied to a spray nozzle 43. The ceramic slurry of such a state that particles of barium titanate are dispersed suitably in the solvent is sprayed from the spray nozzle 43, dried and sorted to produce uniform granulated particles (granules). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for granulating a ceramic raw material.

  Ceramics have been widely used in recent years as a base material for electronic devices because they have excellent electrical characteristics, thermal characteristics, durability characteristics, and excellent mechanical strength. By the way, since ceramic parts are obtained by molding and firing ceramic powder into a predetermined shape, when granulating ceramic powder (granular) suitable for molding, it is required to make the particle size and shape uniform. . In order to meet such demands, various techniques have been proposed in the granulation process (see, for example, Patent Document 1).

JP 2001-130968 A

  According to the technique of this patent document, when the ceramic powder is mixed and stirred in the dispersion medium, the slurry can be made uniform by performing ultrasonic irradiation. However, since the slurry is transported to the spray device after mixing and stirring, reaggregation of the ceramic particles can occur during this transporting process, so there remains room for improvement in homogenization and homogenization of the ceramic granules.

  An object of the present invention is to provide a granulation technique for solving the above-described problems, that is, a simple granulation technique capable of achieving homogeneity / homogenization of structure / composition and particle diameter / shape.

  In order to solve at least a part of such problems, in the method for granulating a ceramic raw material of the present invention, the pulverized ceramic raw material is suspended in a solvent and slurried, and then sprayed from a spray device to granulate the ceramic granules. In the filtration chamber of the pipe line leading to the spray device, the slurry is subjected to ultrasonic irradiation filtration while the slurry is supplied. That is, the present invention provides a method in which ultrasonic dispersion filtration is applied to a ceramic suspension slurry, and immediately after that, the slurry is supplied to a spray device.

  Since the ceramic particles suspended in the slurry are fine, they tend to agglomerate when suspended in a solvent and reagglomerate easily. However, even if the ceramic particles are strongly agglomerated, the agglomeration is released and dispersed by receiving ultrasonic irradiation in the filtration chamber of the pipe line just before reaching the spray device. Therefore, the slurry that has undergone ultrasonic dispersion filtration in the filtration chamber becomes a slurry in which single ceramic particles and a binder are uniformly dispersed, and is supplied to the spray device. In addition, coarse particles other than ceramic may be mixed in the slurry when the ceramic particles are suspended, but these coarse particles are trapped in the filtration chamber. Impurities that are harmful to the top are removed, and a high-quality and high-quality slurry can be obtained.

  The ceramic slurry that is uniformly dispersed and formed into a single particle is subjected to ultrasonic filtration in the middle of piping immediately before the spray device, so that the particles are not re-agglomerated and uniform spray drying is possible. As a result, the obtained ceramic granulated particles are homogeneous, and there is no irregularity in structure, composition, particle size or shape. Such homogenization can be achieved by performing ultrasonic dispersion filtration upstream of the spray device. In this case, in order to prevent reaggregation of the particles, it is important to arrange the ultrasonic dispersion filtration chamber and the spray device close to each other and to feed the slurry to the spray device at a high flow rate so that the particles are not re-aggregated.

  Moreover, in this invention, the excess slurry which does not pass a filtration filter can also be recirculated | refluxed to the slurry adjustment part upstream of a filtration chamber, carrying out ultrasonic dispersion filtration of the ceramic slurry in the filtration chamber provided in the piping. This has the following advantages. In general, a filtration filter is likely to be clogged due to trapped substances (so-called undissolved lumps caused by a binder) during filtration. However, as shown above, since the ceramic slurry is refluxed, the return of the slurry at this time allows the filter filter dams to be taken out of the filtration chamber and can be repeatedly irradiated with ultrasonic waves. It is possible to suppress clogging and to effectively reduce the size of the dama. Eventually, troubles during granulation (filter filter replacement, cleaning frequency) are reduced, and productivity is increased.

  Furthermore, the reaggregation of the ceramic slurry particles after passing through the filter can be further suppressed by the synergistic effect of promoting the dispersion of the ceramic particles by ultrasonic irradiation and suppressing the physical aggregation by the filter (specifically, filter filter pores). .

  In this case, if the mesh size of the filtration filter is 10 to 100 μm, the pressure rise in the filtration chamber does not become significant, and the replacement due to clogging of the filtration filter and the cleaning cycle (maintenance interval) are extended, that is, granulation. The possible period is extended, which is preferable.

  In the downstream filtration chamber where the filtration chamber is divided into an upstream filtration chamber and a downstream filtration chamber by a filtration filter, a straight pipe line downstream of the filtration filter is directly connected to a pipe line leading to the spray device. The ratio between the pipe inner diameter and the straight pipe length of the pipe line can be in the range of 1: 0.5 to 1: 5. In this way, the slurry after passing through the filtration filter can be easily flowed to the pipe line leading to the spray device, so that sedimentation and blockage of the slurry in the downstream filtration chamber can be suppressed, and an inadvertent increase in pressure in the filtration chamber can be avoided. it can. In this case, it is desirable that the ratio is 1: 1 to 1: 2 in terms of slurry retention, sedimentation, and blockage suppression.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view schematically showing a granulation step of the ceramic raw material of the example. As shown in FIG. 1, the granulation step of the present embodiment granulates barium titanate ceramic granules as a final product, and is realized by the following procedure.

  In STEP S1, high-purity titanium oxide and barium carbonate, which are ceramic raw materials, are prepared, mixed with a solvent (pure water), and stirred with a stirrer 10. At this time, titanium oxide and barium carbonate are weighed and adjusted at an optimum blending ratio with respect to pure water. Next, the mixture is finely pulverized using an appropriate pulverizer 12 (for example, a ball mill, a bead mill, etc.), and a mixed powder of titanium oxide and barium carbonate (hereinafter, mixed powder) is slurried (STEP S2). The pulverized particle size of the slurry is desirably adjusted to an average particle size of about 0.5 to 1.5 μm. The slurry thus pulverized is transferred to a downstream stirrer 16 for further uniform mixing with pure water (STEP S3).

  The slurry mixed with pure water by the stirrer 16 is sprayed from the spray nozzle of the spray dryer 18 to obtain a granular dry powder (STEP S4). Thereby, the water | moisture content of a slurry is removed almost completely, and a homogeneous dehydrated dry powder is made. Next, the dry powder is put into the vibration sieve 20 and classified (STEP S5). The dried powder after sieving is put into a calcining sheath 21 and calcined together with the sheath 21 in a calcining furnace 22 (STEP S6). By this calcining, solid phase reaction and grain growth are promoted, and a barium titanate calcined powder having a homogeneous structure and composition is obtained.

  The obtained barium titanate calcined powder is put into a stirrer 24 together with pure water and mixed and stirred (STEP S7). Also in this case, the charged barium titanate calcined powder is weighed and added at a suitable blending ratio with respect to pure water. Thereafter, coarse pulverization (STEP S8) by the pulverizer 26 and then fine pulverization (STEP S9) by the pulverizer 30 are continuously performed.

  In this coarse pulverization / fine pulverization, it is desirable to adjust the average particle diameter of coarse pulverization to about 2 to 5 μm, and fine pulverization to about 0.5 to 1.5 μm. Therefore, a pulverizer (ball mill, A bead mill or the like is used as appropriate.

  In the subsequent STEP S10, in the stirrer 34, the pulverized barium titanate calcined powder is mixed and stirred with a binder to prepare a homogeneous ceramic slurry. At this time, the binder to be added is accurately weighed and added at an optimum blending ratio with respect to the calcined powder amount in STEP S7. In this example, the binder polyvinyl alcohol (PVA), the plasticizer polyethylene glycol (PEG), the lubricant glycerin, and the dispersing agent ammonium polyacrylate were used as binders. Examples of these blends include 0.5 wt% binder, 0.1 wt% plasticizer, 0.1 wt% lubricant, and 0.3 wt% dispersant.

  In this example, the solid content concentration was set to 30 wt% when the barium titanate calcined powder was dispersed in the stirrer 34. Generally, when a binder is added to a ceramic powder to make a slurry, the solid content concentration is about 50 to 60 wt%. It carried out so that it might become the range of 30-40 wt%. That is, if the solid content concentration is in the range of 30 to 40 wt%, it is preferable that dispersion of the suspension slurry by ultrasonic dispersion filtration described later is suitably performed and reaggregation in the pipe reaching the spray nozzle 43 can be suppressed. . If the solid content concentration is too low, there is a problem that the granulation efficiency of the ceramic granule is reduced, and if it is too large, there is a problem that the propagation of the ultrasonic wave is hindered and the dispersion becomes insufficient. This results in poor reaggregation. In addition, by adjusting the slurry viscosity as low as possible (4 mPaS (= 4 CPS)), coupled with the solid content adjustment described above, the dispersion of suspended slurry is promoted and re-agglomerated by ultrasonic dispersion filtration. The effectiveness of suppression can be increased.

  After the binder addition adjustment of the ceramic slurry is performed with the agitator 34, the magnetic foreign matter in the slurry (contaminating foreign matter in the raw material mainly in iron and stainless steel and in the process) is detected by the magnetic separator 39 using a strong electromagnet. Is removed (STEP S11). In addition to such magnetic sorting, the ultrasonic dispersion filtering device 40 also performs pore filtration (STEP S12), and the spray nozzle 43 of the spray drying device 42 (STEP S13) has a purity free of impurities. A high barium titanate slurry is supplied. High quality barium titanate granules can be produced by spraying, dehydrating and granulating the slurry with this spray drying device 42. Thereafter, the barium titanate granules are put into the vibration sieve 44 and classified (STEP S14). This classified barium titanate granule can be used as a raw material for various ceramic products. In addition, between each STEP of the granulation system described above, a slurry transfer / pressure pump is appropriately disposed in the piping path.

  Next, the details of the ultrasonic dispersion filtration device 40 described above will be described. FIG. 2 is an explanatory diagram for schematically explaining the state of the slurry treatment centering on the ultrasonic dispersion filtration device 40, and FIG. 3 is a schematic cross-sectional view showing a schematic configuration of the ultrasonic dispersion filtration device 40.

  As shown in these drawings, the ultrasonic dispersion filtration apparatus 40 includes a stirrer 34 for adjusting a ceramic slurry after calcination (a slurry obtained by pulverizing and suspending a barium titanate calcined powder) and a binder, and a ceramic slurry. Is sprayed from the spray nozzle 43 to the drying tower and dried to be arranged in a pipe line between the spray drying apparatus 42 for granulating ceramic granules. The ultrasonic dispersion filtration device 40 includes a filtration chamber 140, and the ultrasonic irradiation unit 142 and the filtration filter 144 are opposed to each other in the filtration chamber 140.

  The ultrasonic irradiation unit 142 is connected to the ultrasonic oscillator 146 and irradiates ultrasonic waves to the slurry in the filtration chamber 140 (slurry supplied between the ultrasonic irradiation unit 142 and the filtration filter 144). This ultrasonic irradiation is performed while the slurry is supplied to the spray nozzle 43. The ultrasonic oscillator 146 can change its oscillation frequency in various ways, and in this embodiment, the ultrasonic irradiation unit 142 irradiates ultrasonic waves having a frequency of f = about 20 kHz.

  The ultrasonic dispersion filtration device 40 applies pressure of 0.005 to 0.1 MPa to the ceramic slurry in the filtration chamber 140 by controlling the upstream pump 145 and adjusting the inlet / outlet diameter and flow rate of the filtration chamber 140. The slurry can be irradiated with ultrasonic waves. That is, when the slurry pressure exceeds 0.1 MPa in the filtration chamber 140, the ultrasonic vibration is hindered, the ultrasonic irradiation ability is reduced, and the irradiation becomes impossible, but this apparatus has a structure that can avoid such a situation. Yes.

  The ultrasonic dispersion filtration device 40 includes a return line 148 from the filtration chamber 140 to the stirrer 34. Then, the ultrasonic dispersion filtration device 40 supplies the slurry filtered by the filtration filter 144 to the spray nozzle 43 while circulating the excess slurry that does not pass through the filtration filter 144 to the stirrer 34 via the return line 148. In addition, the ultrasonic dispersion filtration device 40 includes a water cooling jacket 150 surrounding the filtration chamber 140 at the upper portion thereof, and suppresses an increase in filtration room temperature during slurry filtration. In this example, the water cooling jacket 150 maintained the slurry temperature in the filtration chamber 140 at about 20 ° C.

  The filtration chamber 140 is divided into an upstream filtration chamber 140a and a downstream filtration chamber 140b by a filter 144. The downstream filtration chamber 140b has a straight pipe line 143a downstream of the filtration filter and a pipe line leading to the spray nozzle 43. The straight pipe line 143a is formed by a tapered connecting pipe line 143b. In this embodiment, the ratio of the pipe inner diameter and the pipe length in the straight pipe line 143a is set to about 1: 1, and the straight pipe line 143a is extended below the filtration filter 144 by a length equivalent to the filter diameter. It was decided. A pump 147 (see FIG. 2) is disposed between the tapered connecting pipe line 143b and the spray nozzle 43, and the slurry is pumped to the spray nozzle 43 by the pump, and the slurry is fed at a high flow rate. Supply to spray nozzle 43. In addition to the pumping by such a pump, in this embodiment, the pipe path is narrowed by the connecting pipe line 143b, thereby suppressing the stagnation, sedimentation, and re-aggregation of the ceramic slurry. Specifically, the straight pipe line 143a is a pipe line having a diameter of 47 mm, the pipe line having a diameter of 17.5 mm is provided downstream of the connecting pipe line 143b, and a pipe having a diameter of 8 mm is provided in front of the pump 147. The ceramic slurry is sent to the spray nozzle 43 at a high flow rate by the pump 147.

  In the present embodiment, the ultrasonic dispersion filtration apparatus 40 having the above-described configuration is installed on the upstream side of the spray drying apparatus 42, and ultrasonic dispersion filtration by the ultrasonic dispersion filtration apparatus 40 having the ultrasonic irradiation unit 142 and the filtration filter 144 is performed. Since the passed slurry is spray-dried, there are the following advantages.

  In the ceramic slurry mixed with the stirrer 34 (slurry having the binder blended and adjusted), the barium titanate particles are finely divided and highly activated, and thus aggregation of the ceramic particles is inevitable. However, even if the barium titanate particles are aggregated once, if they are irradiated with ultrasonic waves in the filtration chamber 140 in the ultrasonic dispersion filtration device, the aggregation is released and the particles are dispersed in a single state, and the particles are dispersed individually. Return to. The slurry can be continuously irradiated with ultrasonic waves while being supplied to the spray nozzle 43. As a result, the ceramic particles that have undergone ultrasonic dispersion filtration in the filtration chamber 140 are in a monodispersed state. It is sprayed from the spray nozzle 43, granulated by the spray dryer 42, and classified by the vibration sieve 44, so that uniform high-quality barium titanate granules can be produced.

  In this embodiment, since the length of the slurry supply path from the ultrasonic dispersion filtering device 40 to the spray nozzle 43 is about 0.5 m, the slurry is sprayed within a short time that does not cause reaggregation of the barium titanate slurry. Spraying from the nozzle 43 is possible. This is also advantageous in terms of the homogeneity and uniformity of granules when producing barium titanate granulated particles. In addition, in this example, the following measures were also taken in order to suppress reaggregation of the barium titanate particles.

  First, the thickness of the filtration filter 144 was about 2 mm, which was thicker than the filtration filter of a general filtration device. As a result, when the slurry passes through the filter filter pores, it can be expected that the dispersion can be promoted in the filter and the re-aggregation can be suppressed as much as the thickness increases. In addition, while adjusting the pressure applied to the ceramic slurry in the filtration chamber 140 (0.005 to 0.1 MPa), the ultrasonic vibration propagation to the slurry is performed more reliably and powerfully to further promote dispersion and re-use. The effectiveness of aggregation suppression can be enhanced. Furthermore, the reflocculation of the slurry immediately before spraying can be suppressed by adjusting the solid content concentration, adjusting the viscosity, narrowing the pipe diameter to the spray nozzle 43, and increasing the slurry flow rate by improving the pumping pump capacity. Can be increased.

  In this embodiment, since physical filtration with the filtration filter 144 in the filtration chamber 140 is also possible, coupled with the removal of magnetic foreign substances in the slurry by the magnetic separator in the stirrer 34, ultrasonic dispersion filtration is performed. In the passed slurry, coarse foreign matters can be completely removed regardless of the presence or absence of magnetism. Therefore, the quality of the barium titanate granules obtained can be further enhanced and high added value can be achieved.

  As a result, in the barium titanate granules obtained through spray drying, the structure, composition, particle size and shape of the granules can be made uniform. In addition, in order to achieve such homogeneity and uniformity, in this embodiment, it is sufficient to perform ultrasonic dispersion filtration with the ultrasonic dispersion filtration device 40 on the upstream side of the spray nozzle 43. Therefore, the structure and composition of the barium titanate granules and Uniform particle size and shape can be easily achieved.

  In this embodiment, the ceramic slurry is subjected to ultrasonic dispersion filtration in the filtration chamber 140, while excess slurry that does not pass through the filtration filter 144 is circulated to the agitator 34 on the upstream side of the filtration chamber via the return line 148. By the flow accompanying the slurry recirculation, the trapped matter (dama) in the filtration filter 144 can be pulled away from the filtration filter 144 and brought back to the stirrer 34. Therefore, clogging of the filtration filter 144 can be suppressed, and ultrasonic waves can be repeatedly irradiated to the captured matter, so that the frequency of the apparatus stop due to clogging of the filtration filter and the interruption of the granulation operation is reduced, and the production efficiency is correspondingly reduced. Can be improved.

  In this case, in this embodiment, since the mesh size of the filtration filter 144 is 10 to 100 μm, the increase in the internal pressure of the filtration chamber 140 does not become significant, and the time until filter maintenance due to clogging of the filtration filter is required, That is, the granulation execution period is extended, which is preferable.

  Moreover, the downstream-side filtration chamber 140b in which the filtration chamber 140 is divided by the filtration filter 144 has a straight pipe line 143a extending in a straight tube shape with a length equivalent to the diameter of the filtration filter. Therefore, the slurry after passing through the filtration filter can easily flow into the tapered connecting pipe line 143b on the downstream side, and then to the spray nozzle 43, and the settling and clogging of the slurry in the downstream filtration chamber 140b can be suppressed. It is preferable that the prepared pressure in the filtration chamber does not increase.

Next, the state of ultrasonic dispersion filtration in the granulation system of the above-described embodiment and the properties of the granulated barium titanate granules will be described. FIG. 4 is an explanatory view showing the state of filtration when the mesh diameter of the filter is changed and when the slurry flow rate is changed,
FIG. 5 is an explanatory view showing the particle size of the barium titanate slurry immediately before spraying, and FIG. 6 is an explanatory view showing an electron micrograph (magnification 100 × 500 times) of the obtained barium titanate granules.

  As shown in FIGS. 4A and 4B, in the ultrasonic dispersion filtration for one pass of slurry supply (about 1 liter / min), the filtration rate was practical. In addition, when the filtration filter diameter was 10 μm, an increase in the filtration chamber pressure was observed, and as a result, the filtration rate was reduced (filtration filter clogging), but there was no practical problem. In particular, when the diameter of the filter is 40 μm, the increase in the pressure in the filter chamber is small, which is preferable in terms of maintaining the filtration rate and suppressing clogging of the filter. Regarding the slurry flow rate, the lower the flow rate, the lower the filtration rate (filter filter clogging) occurred. However, there was no practical problem.

  In addition, as shown in FIG. 5, when the granules are granulated without using the ultrasonic dispersion filter 40, the particle size of the barium titanate slurry immediately before spraying is 1.5 μm in average particle size and the maximum particle size Was 5.12 μm. On the other hand, when the filtration dispersion was performed by the ultrasonic dispersion filtration apparatus 40, it was possible to achieve a fine and uniform particle size as shown in the figures.

  Furthermore, as is apparent from the photograph in FIG. 6, almost spherical spherical barium titanate granulated particles could be obtained with any filter filter diameter.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and embodiments, and can of course be implemented in various modes without departing from the gist of the present invention. is there.

It is the schematic which shows the granulation process of the ceramic raw material of an Example typically. It is explanatory drawing which illustrates the mode of the slurry process centering on the ultrasonic dispersion filtration apparatus 40 roughly. 1 is a schematic cross-sectional view showing a schematic configuration of an ultrasonic dispersion filtration device 40. It is explanatory drawing which shows the mode of filtration when the mesh diameter of a filtration filter is changed, and a slurry flow rate is changed. It is explanatory drawing which shows the particle size of the barium titanate slurry just before spraying. It is explanatory drawing which shows the electron micrograph (magnification 100 time * 500 time) of the obtained barium titanate granule.

Explanation of symbols

10 ... Stirrer 12 ... Crusher 16 ... Stirrer 18 ... Spray dryer 20 ... Vibrating sieve 21 ... Container 22 ... Calciner 24 ... Stirrer 26 .. .Pulverizer 28 ... Agitator 30 ... Crusher 34 ... Agitator 39 ... Magnetic separator 40 ... Ultrasonic dispersion filter 42 ... Spray dryer 43 ... Spray nozzle 44. .. Vibrating sieve 140 ... Filtration chamber 140a ... Upstream filtration chamber 140b ... Downstream filtration chamber 142 ... Ultrasonic irradiation section 143a ... Straight pipe line 143b ... Connection pipe line 144 ... filtration filter 145, 147 ... pump 146 ... ultrasonic oscillator 148 ... return line 150 ... water cooling jacket

Claims (5)

A method for granulating ceramic raw materials,
Obtaining ceramic powder obtained by pulverizing ceramic raw materials;
Adjusting the slurry in which the ceramic powder is suspended;
Spraying the slurry from a spray device in a spray drying device, and granulating ceramic raw material granules,
In the filtration chamber of the ultrasonic dispersion filtration device provided in the pipe line leading to the spray device, the ultrasonic filtration on the slurry is continued during the supply of the slurry to the spray device, and the filtration is performed in the filtration chamber. A method for granulating a ceramic raw material, wherein the slurry is supplied to the spray device. A method for granulating the ceramic raw material according to claim 1,
The ultrasonic filtration in the filtration chamber is
While supplying the slurry between the ultrasonic irradiation unit and the filtration filter facing each other in the filtration chamber provided in the pipe line, the slurry is irradiated with ultrasonic waves from the ultrasonic irradiation unit, and the surplus that does not pass through the filter A method for granulating a ceramic raw material, wherein the slurry is circulated to a slurry supply section to the filtration chamber. A method for granulating a ceramic raw material according to claim 2,
A method for granulating a ceramic raw material, wherein the filter has a mesh size of 10 to 100 μm. A granulating device for ceramic raw material,
A slurry adjusting unit for adjusting a slurry in which ceramic powder obtained by pulverizing ceramic raw material is suspended, and a spray drying device for granulating ceramic raw material granules by spraying the slurry from a spray device into a drying chamber and drying the slurry. ,
Furthermore, an ultrasonic dispersion filtration device is provided in a pipe line between the spray drying device and the slurry adjusting unit,
The ultrasonic dispersion filtration device
A filtration chamber provided in the pipe line;
An ultrasonic irradiation section and a filtration filter facing each other in the filtration chamber;
The ultrasonic irradiation from the ultrasonic irradiation unit to the slurry supplied between the ultrasonic irradiation unit and the filter was filtered through the filter while continuing the slurry supply to the spray device. A ceramic raw material granulator that performs supply of slurry to the spray device and slurry recirculation for circulating excess slurry that does not pass through the filter to the slurry adjusting unit. A granulating device for a ceramic raw material according to claim 4,
The filtration chamber is
The filter is divided into an upstream filtration chamber and a downstream filtration chamber,
The downstream filtration chamber is formed by a straight pipe line downstream of the filter, and a pipe line leading to the spray device is connected to the straight pipe line,
A granulation apparatus for a ceramic raw material, wherein a ratio of a pipe inner diameter and a pipe length in the straight pipe pipe is in a range of 1: 0.5 to 1: 5.

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