JP4335221B2 - Boron oxide manufacturing apparatus and manufacturing method thereof - Google Patents

Description

The present invention relates to an apparatus for producing boron oxide (chemical formula: B ₂ O ₃ ) and a method for producing the same, and more particularly to an apparatus and a method for producing high-purity boron oxide by a process of heating and dehydrating and melting boric acid. .

Boron oxide is widely used as a raw material for glass addition, steel alloying agents, amorphous alloys, and magnetic materials. In general, it is demanded that impurities can be supplied at low cost, but the allowable range of impurities and the like varies depending on applications. Non-patent document 1 discloses typical purified means of boron oxide of high purity (99% B ₂ O ₃ ) by heating and melting refined granular boric acid in an oil-fired or gas-fired glass furnace. Is described.

On the other hand, in Patent Document 1, in a method for producing a boron oxide product containing about 85 to 92% B ₂ O ₃ , boric acid is dehydrated and melted containing about 85 to 92% B ₂ O _3. A series of heating boric acid at a temperature in the range of about 220-275 ° C. for a period sufficient to form a glass, cooling the molten glass to form a solid glass product, and grinding the solid glass. A process for producing granular amorphous boron oxide comprising steps, containing about 85-92% B ₂ O ₃ and essentially free of sodium is disclosed.

The method described in Patent Document 1 aims to solve the following drawbacks of the method described in Non-Patent Document 1.
(1) Since the molten glass obtained by heating to 700-950 ° C. in the melting furnace is rapidly crushed, the product is of high quality, but energy costs are required to maintain the melting furnace at a high temperature (2) Product becomes water-absorbing by fine grinding

  However, in the method described in Patent Document 1, since the heating temperature is low, the purity of boron oxide is as low as about 85 to 92%, and a large amount of moisture remains. Therefore, there is a problem that the user has to bear energy for dehydration, and further there is a problem such as foaming due to moisture decomposed and generated during use.

Therefore, high-purity (99% B ₂ O ₃ ) boron oxide is generally produced by a method described in Non-Patent Document 1 using a glass melting furnace. However, since this glass melting furnace is a so-called direct heating facility in which combustion gas for heating is brought into direct contact with boric acid as a raw material, the combustion exhaust gas and water vapor that is a decomposition product of boric acid are the same during operation. It is discharged from the exhaust port as mixed exhaust gas. Since this exhaust gas is hot, it is desirable to reuse the exhaust heat of the above mixed exhaust gas as a heat source by heat exchange, but this exhaust gas contains boric acid dust and steam, which scales to the heat transfer surface of the heat exchanger Therefore, although the mixed exhaust gas is at a high temperature, it cannot be reused as a heat source, which causes a significant decrease in thermal efficiency.

  As a countermeasure, as shown in FIG. 6, the patent applicant installs a combustion burner 82 below the heating chamber main body 81 surrounded by the heat insulating material 80, and is made of a heat-resistant metal with a slight inclination above it. A cylindrical retort 83 is arranged, and raw material boric acid powder and / or granules are supplied from an inlet 84 above the cylindrical retort 83, and the raw boric acid is heated by indirect heating without being brought into contact with the high-temperature combustion gas. Thus, a boron oxide production apparatus that continuously performs the melting is put into practical use. In this apparatus, since the gas for heating the retort 83, in other words, the combustion gas for heating the raw material and the gas generated by pyrolysis of boric acid are completely separated, the combustion gas for retort heating is converted into the heat exchanger 85. The heat energy can be recovered through the gas and the gas generated from the retort can be processed by the exhaust gas processing device 86 to recover boric acid.

Japanese Patent Laid-Open No. 7-257921 Encyc1opedia of Chemical Technology 4th edition, volume 4, page 370

  However, the boron oxide production apparatus proposed by the above-mentioned applicant has high thermal efficiency and can produce high-purity boron oxide economically and efficiently. There was a problem that the lifetime was relatively short.

  The present invention solves the above-mentioned problems of the prior art, can continuously produce high-purity boron oxide that has high thermal efficiency and substantially does not contain moisture, and can be used stably for a long period of time. An object of the present invention is to provide a tolerable boron oxide production apparatus and a method for producing boron oxide thereby.

  The inventor of the present invention has a remarkably uniform surface temperature of a regenerative alternating combustion type radiant tube (hereinafter, simply referred to as “radiant tube”). Focusing on the fact that boron oxide can be produced very efficiently by dehydrating and further melting boric acid, the present invention has been completed.

  The boron oxide production apparatus according to the present invention comprises a regenerative alternating combustion type radiant tube installed in a heating chamber main body provided with a boric acid supply part at the upper part and a molten boron oxide discharge part at the lower part. The molten boric acid supplied into the heating chamber body from the heating section is heated by the regenerative alternating combustion type radiant tube to form molten anhydrous boron oxide, and the molten boron oxide is continuously supplied from the molten boron oxide discharge section. It will be discharged.

  In the boron oxide manufacturing apparatus, the heating chamber main body is constituted by a casing or a cylinder, and the bottom of the heating chamber main body is an inclined hearth inclined by 1 to 5 ° with respect to a horizontal plane. The end portion may be provided with a molten boron oxide discharging portion.

  In the boron oxide production apparatus, the heating chamber main body can be provided with an exhaust gas treatment facility for discharging and treating exhaust gas generated by a dehydration reaction of boric acid.

  Further, the boron oxide production apparatus may include a molten boron oxide cooling / solidifying device in the molten boron oxide discharge section.

  In the boron oxide production apparatus, the radiant tube is installed along the inclined hearth of the heating chamber body, and the molten boron oxide discharge part is provided at the end of the inclined hearth of the heating chamber. It can be.

  Further, in the boron oxide manufacturing apparatus, the heating chamber main body is constituted by a cylindrical body or a polygonal cylinder, and a plurality of radiant tubes are installed along the side wall of the heating chamber main body. be able to.

  Using the boron oxide production apparatus described in any of the above inventions, supplying raw material boric acid continuously into the main body of the boron oxide production apparatus, and storing heat in the main body of the boron oxide production apparatus The raw boronic acid is heated to form molten boron oxide by a continuous combustion type radiant tube, and boron oxide is continuously discharged by continuously flowing and discharging the generated molten boron oxide from the molten boron oxide discharge section. Can be manufactured.

  In each of the above inventions, the radiant tube is, for example, a burner in which a heat accumulator is incorporated at both ends of a tube of the type disclosed in Industrial Heating Vol. 42, No. 5, page 12, left column, lines 10-18. Is a radiant tube that repeats combustion and heat storage alternately in a short cycle of about 30 seconds, and has the characteristics that the tube temperature is made uniform by alternating combustion and the energy saving effect is obtained by high-efficiency heat exchange.

  According to the present invention, high-purity boron oxide containing substantially no water can be produced efficiently and stably for a long period of time.

  Hereinafter, embodiments of the present invention will be described based on two main embodiments.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing a boron oxide manufacturing apparatus according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA. As shown in FIGS. 1 and 2, the boron oxide manufacturing apparatus according to the first embodiment of the present invention includes a heating chamber body 10, a boric acid supply unit 30, a molten boron oxide discharge unit 15, and a radiant tube 20. ing.

  In the first embodiment shown in FIG. 1, the heating chamber body 10 is surrounded by a case surrounded by a heat insulating material 11 and the inside is lined with a material not affected by boric acid such as stainless steel or its dehydrated product. In the upper part, a raw material boric acid inlet 14 and a steam port 16 for introducing water vapor as a reaction byproduct together with dust are opened. Further, the bottom portion 12 continues to a molten boron oxide discharge portion 15 that continuously discharges the generated molten boron oxide.

  The raw boric acid inlet 14 at the upper part (ceiling side) of the heating chamber body 10 is connected to a raw boric acid supply device 30 having a hobber 31 and a screw feeder 32, and this raw boric acid supply The apparatus 30 can continuously supply boric acid as a raw material into the heating reaction chamber 13 through the boric acid inlet 14.

  The bottom surface 12 of the heating chamber body 10 is slightly inclined with respect to the horizontal plane, the lowermost end thereof is a molten boron oxide discharge portion 15, and the end thereof is partitioned by a weir 17. The inclination of the bottom surface 12 with respect to the horizontal plane is to allow the generated molten product to flow down naturally and to flow out of the molten boron oxide discharge part 15, so that the angle is 1-5 ° with respect to the horizontal plane. It is good to do.

  Inside the heating chamber main body 10 having the raw material boric acid inlet and the molten boron oxide discharge portion 15 configured in this manner, the U-shaped portion is substantially parallel to the bottom portion 12 and separated from the bottom portion 12 by a distance a. The heating unit 24 of the radiant tube 20 is located. The distance a between the lowermost end of the heating portion 24 of the radiant tube and the bottom 12 is a distance sufficient for the molten boron oxide dehydrated and melted by heating by the heating portion 24 of the radiant tube to flow down on the bottom 12. And If this distance is too large, the generated boron oxide in contact with the bottom portion 12 may not be sufficiently heated by the heating unit 24 of the radiant tube 20, and the molten / fluid state may not be maintained. It stays on top of 12 and is difficult to be discharged out of the system smoothly. In general, the separation distance a is preferably about 0.5 to 3 times the diameter of the radiant tube.

  Further, in the first embodiment shown in FIG. 1, a molten boron oxide cooling solidification crushing device 40 is provided following the molten boron oxide discharge section 15. This cooling and solidifying crushing apparatus 40 has a water-cooled W roll 42 and a demon tooth double roll crusher 44 that continuously receive molten boron oxide, and the W roll 42 and the demon tooth double roll crusher 44 are connected by a vertical air cooling duct 43. In addition, a metal container 45 with a lid is configured to be freely attached to and detached from the lower part of the demon tooth double roll crusher 44. In this embodiment, a cover 41 is installed around the upper portion of the W roll 42 from the molten boron oxide discharge part 15, and a dust collection pipe 46 is provided on the cover 41 so that generated dust can be sucked and removed. .

  A steam port 16 is provided in the upper part (ceiling side) of the heating chamber body 10 at a position away from the raw material boric acid inlet 14, and this steam port 16 is connected to the exhaust gas treatment means 50 through an exhaust gas conduit 51. ing. This exhaust gas treatment means 50 washes water vapor, boric acid vapor and dust discharged from the heating chamber body 10 to separate and recover the boric acid content as boric acid water, and the purified exhaust gas from the exhaust gas discharge pipe 52 to the atmosphere. It has a function to release. The separated and recovered boric acid water is led to an evaporation crystallization can (not shown).

  The operation of the above apparatus is as follows, whereby boron oxide can be produced from raw boric acid. First, as a preparatory stage, the raw material boric acid is filled so that the heating part 24 of the radiant tube 20 is covered, and the surface temperature of the radiant tube 20 is set to a set value of 800 to 950 ° C. and heated. The inside of the chamber reaction chamber 13 is sufficiently heated so that the generated boron oxide is in a molten state and can flow out of the discharge section 15. Here, the heating part 24 of the radiant tube 20 is heated to a high temperature excluding the heat storage body housing part of the base part of the U-shaped tube constituting the radiant tube, and heats raw material boric acid and generated boron oxide in the present invention, Or the part heated by radiant heat.

After confirming that the preheating operation is completed, the raw boric acid supply device 30 is operated, and the raw boric acid is continuously supplied from the raw boric acid inlet 14 into the heating chamber body 10. As a result, the raw material boric acid is in direct contact with the heating section 24 of the radiant tube 20 or once deposited on the bottom surface 12 and then heated to 250 to 400 ° C. by heating from the heating section 24 of the radiant tube 20, reaction formula 2H ₃ BO ₃ (s) → B ₂ O ₃ (l) + 3H ₂ O (g) −211 kJ / mol B ₂ O ₃
And the product is melted by raising the temperature to 700 ° C. or higher.

Water (H ₂ O) generated as the temperature rises and melts is completely separated from boron oxide as water vapor, and the melt becomes high-purity boron oxide. It is continuously led to the cooling and solidifying crushing device 40, formed into a sheet-like glass by the water-cooled W roll 42 of the cooling and solidifying crushing device 40, cooled by the air-cooled vertical duct 43, and then crushed by the demon double roll crusher 44 Further, even if the boron oxide produced by being directly accommodated in the metal container 45 with a lid is cut off from contact with the outside air and finely pulverized, it is possible to avoid moisture absorption.

  On the other hand, water vapor generated by the dehydration reaction, boric acid vapor generated by heating the raw boric acid, and boric acid dust inevitably generated when boric acid is charged are exhaust gas from the steam port 16 through the exhaust gas conduit 51. It is guided to the processing means 50, where it is washed with water, and the boric acid content is separated and recovered as boric acid water, and the remaining cleaned exhaust gas is discharged from the exhaust gas discharge pipe 52 into the atmosphere.

  In the above operation, as shown in FIG. 3, boric acid as a raw material is initially a powder or a granular material, but is heated and becomes a massive mass in a sintered state at the same time as the dehydration decomposition reaction starts. After that, it is further heated and reaches 400 ° C. to complete the decomposition reaction. Further, it is presumed that the generated water is volatilized as water vapor and becomes a fluid state. Therefore, it is ideal that the state of the charged material in the boron oxide production apparatus of the present invention melts and descends smoothly while in contact with the radiant tube, but sometimes it is not steady and is directly above the radiant tube. Various unsteady states can be taken, such as a shelf hanging phenomenon that occurs when the sintered product falls and falls into a molten state in the bottom hearth.

  Such an unsteady state is a phenomenon in which the object to be treated (raw material boric acid and its dehydrated product) is sintered from the powder (granular material), and in the process where the state changes from the molten / fluid state. It is presumed that this occurs because the deposits temporarily stay and hinder the flow. However, it is preferable to avoid such an unsteady state as much as possible and bring it close to the steady state. Therefore, it is important to adjust the charging speed of boric acid, which is a raw material, so that a balance with the speed at which boric acid is heated, dehydrated and melted is maintained. For example, if the boric acid charging rate temporarily exceeds the dehydration / melting rate by heating from the radiant tube, a boric acid shelf may be formed on the upper surface of the heating reaction chamber, and a cavity may be formed between the radiant tube. In such a case, it is possible to take measures such as temporarily reducing the supply rate and continuing heating, gradually melting the boric acid shelf by radiant heat, eliminating the boric acid shelf and returning to the normal operating state. is necessary.

  In order to perform such operation control, the surface temperature of the radiant tube should be measured and controlled so as to give the necessary heat input to the raw material boric acid. Such control can be performed based on the experience obtained by analyzing the relationship between the surface temperature of the radiant tube and the state of the furnace. Such heat input can be controlled by the flow rate of gas fuel supplied from the radiant tube, the combustion time, or a combination thereof.

  In performing the above control, the temperature of the radiant tube must be controlled to the maximum use temperature, for example, 950 ° C. or less. Therefore, in the present invention, industrial heating Vol.42, No.5, page 12, left column, lines 10-18, etc., a burner with a built-in heat storage material is installed at both ends of the tube, 30 seconds By using a radiant tube that alternately repeats combustion and heat storage at a short cycle, the alternating combustion cycle is shortened to about 30S, for example, so that the tube temperature can be made uniform and energy-saving effects can be obtained by high-efficiency heat exchange. Is preferred. If such a type of radiant tube is used, the surface temperature thereof becomes extremely uniform. Therefore, it is sufficient to measure the surface temperature of the radiant tube in the above control.

  The first embodiment of the present invention is as described above, but various modifications can be made without departing from the technical idea of the present invention. For example, the cooling and solidifying crushing device 40 for molten boron oxide is omitted, the molten boron oxide is directly received in the container, cooled as it is, and then crushed by a separate means, the screw of the boric acid supply device 30 It is possible to change the feeder to a vibration feeder and to remove the weir 17 from the molten boron oxide discharge part 15. Further, in this example, the radiant tube 20 has a U-shaped heating unit 24, and the U-shaped heating unit 24 is in the reaction heating chamber 13 of the box-shaped heating chamber body 10 and incorporates a heat storage body. Although both end portions are assumed to be outside the heating body main body 10, they may be positioned in the heating chamber main body 10.

  Moreover, in the said embodiment, although the bottom part 12 is inclined with respect to horizontal, this can also be made horizontal. In this case as well, molten and fluidized boron oxide stays in a certain amount at the bottom 12, but can overflow the weir 17 and be discharged out of the system. In addition, the weir 17 is not necessarily required, but its presence has the effect of depositing a certain amount of molten and fluidized boron oxide on the bottom 12 regardless of whether the bottom 12 is inclined, thereby stabilizing the operation. . The weir 17 is preferably removed, for example, at the end of the operation, and boron oxide staying on the bottom 12 is preferably discharged as much as possible.

(Second Embodiment)
FIG. 4 is a cross-sectional view schematically showing a boron oxide manufacturing apparatus according to the second embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along the line BB. As shown in FIGS. 4 and 5, the boron oxide production apparatus according to the second embodiment of the present invention includes a heating chamber body 10, a boric acid supply unit 30, a molten boron oxide discharge unit 15, and a plurality of radiant tubes 20 ( 20A-20D).

  In this second embodiment, the heating chamber body 10 is surrounded by a cylindrical body or a polygonal cylinder body surrounded by a heat insulating material 11 and lined with a material not affected by boric acid such as stainless steel or its dehydrated product. The radiant tubes 20 </ b> A to 20 </ b> D are arranged along the side wall 18 of the heating chamber body 10. In the upper part of the heating chamber body 10 constituted by the cylinder, a raw material boric acid inlet 14 is opened, and a steam port 16 leading with water vapor, boric acid vapor and boric acid dust as reaction by-products is opened. Yes. Further, the bottom portion 12 continues to a molten boron oxide discharge portion 15 that continuously discharges the molten boron oxide generated by the dehydration / melting reaction by the present apparatus.

  The raw material boric acid inlet 14 on the upper part (ceiling side) of the heating chamber body 10 is connected to the raw boric acid supply device 30 and attached thereto, as in the case of the first embodiment. Thus, boric acid as a raw material can be continuously supplied into the heating reaction chamber 13 through the boric acid inlet 14. Further, the bottom surface 12 of the heating chamber body 10 is slightly inclined with respect to the horizontal plane, and the lowermost end portion thereof is a molten boron oxide discharge portion 15 as in the case of the first embodiment. is there.

  Further, in the second embodiment shown in FIGS. 4 and 5, although not shown, the molten boron oxide having the same structure as that shown in the first embodiment is provided following the molten boron oxide discharge section 15. A cooling and solidifying crushing device is provided, and an exhaust gas processing device having the same configuration as that of the first embodiment is provided above the heating chamber body 10. These functions are not different from those in the first embodiment.

  The difference between the second embodiment and the first embodiment lies in the arrangement of the radiant tube 20 in the heating chamber body 10. In the case of the second embodiment, a plurality of radiant tubes 20 are installed along the side wall 18 of the heating chamber body 10 which is a cylindrical body (including a cylindrical body and a polygonal cylindrical body). That is, as shown in FIGS. 4 and 5, the heating of the U-shaped radiant tube 20 is performed substantially in parallel with the side wall 18 of the heating chamber body 10 which is a cylindrical body, and is separated from the side wall 18 by a predetermined distance b. Part 24 is installed.

  The separation distance b between the outer surface of the heating section 24 of the radiant tube 20 and the side wall 18 of the heating chamber body 10 is equal to the inside and outside of the space where the charged raw material boric acid is surrounded by the radiant tubes 20A to 20D. It is preferable to arrange so as to fall in quantities. As a result, the amount of heat given to the raw material boric acid from the radiant tube 20 is evenly distributed without being biased to one side, and is uniform without causing a shelf hanging in the vicinity of the side wall 18 and an insufficient heating portion in the internal space. Efficient heating can be performed. Specifically, in the cross-sectional view shown in FIG. 5, the inner area of the radiant tubes 20A to 20D may be designed to be substantially equal to the outer area.

  Further, the distance between adjacent radiant tubes, for example, the distance c between the radiant tubes 20A and 20D must be taken into consideration in the design. As shown in FIG. 4, in 2nd Embodiment, raw material boric acid is inserted from the inner center part of the space enclosed by the radiant tubes 20A-20D. Therefore, it is important that the raw material boric acid charged smoothly passes through the gap between the radiant tubes and smoothly escapes to the side wall 18 side. When the distance c is too small, the movement of the object to be processed is hindered due to the sintered product generated in the gap between the radiant tubes. On the other hand, when the distance c is too wide, the equipment diameter becomes unnecessarily large, which is not economical.

  In general, the separation distance b is preferably about 0.5 to 3 times the diameter of the radiant tube 20, and the distance c between the radiant tubes 20 is preferably about 1.5 to 3.5 times the diameter of the radiant tube 20. The number of the radiant tubes 20 may be determined depending on the production capacity of boron oxide and the like.

In the upper space of the heating chamber main body 10, a non-heating part 25, which is an installation part of the heat storage body of the radiant tube 20, is positioned. As a result, the temperature of the product gas generated in the heating chamber body 10 (mixed gas of reaction water vapor, boric acid vapor and boric acid dust generated when the raw material is charged) can be lowered in the heating chamber body. The load on the exhaust gas treatment facility can be reduced.

  The operation process of the apparatus according to the second embodiment is as follows, whereby boron oxide can be produced from the raw material boric acid. First, as a preparation stage, raw material boric acid is charged so as to cover the heating part 24 of the radiant tubes 20A to 20D. Next, the heating chamber 24 is heated so that the surface temperature of the heating unit 24 of the radiant tubes 20A to 20D becomes a set value (800 to 950 ° C.), the heating chamber body 10 is sufficiently heated, and the generated boron oxide is It is in a state where it can flow out.

  After confirming that the above preheating operation has been completed, the raw boric acid supply device 30 is continuously operated, and the raw boric acid is continuously supplied from the raw boric acid inlet 14. As a result, the raw boric acid is heated by the heating unit 24 of the radiant tube 20, and from its vicinity, the powder (granular body) becomes a sintered state, further dehydrated and melted, and the heating / temperature rise proceeds. Becomes molten boron oxide and drops onto the bottom portion 12 and flows out from the molten boron oxide discharge portion 15. The processing after flowing out from the molten boron oxide discharge unit 15 is the same as that already described in the first embodiment. Further, the processing of the reaction product gas and the like is the same as that described in the first embodiment.

  Also in the second embodiment, the state of the charge in the boron oxide production apparatus melts and descends smoothly while contacting the side wall of the radiant tube and the heating chamber body, but sometimes it is not steady, There may be various states such as a shelf hanging phenomenon occurs in the heating chamber body, and the sintered product that is collapsed falls to be molten in the bottom hearth. Such an unsteady state does not hinder the operation as long as the workpiece is lowered smoothly. However, when the unsteady state progresses and the shelf is suspended, it is preferable to temporarily stop the supply of the boric acid raw material and continue heating only from the radiant tube, thereby eliminating the shelf suspension. These measures are the same as those in the first embodiment. Further, in order to perform the operation control, the surface temperature of the radiant tube can be measured and controlled so that the necessary heat input is given to the raw material boric acid as in the first embodiment.

  The second embodiment of the present invention is as described above, but various modifications can be made without departing from the technical idea of the present invention. For example, although the number of radiant tubes is four in the above example, it can be six to eight in consideration of the necessary capacity. Further, as described in the first embodiment, the cooling and solidification crushing apparatus for molten boron oxide is omitted, and the molten boron oxide is directly stored in a receiving container, cooled, and then separately crushed. It is also possible to change to a vibration feeder or to add a weir to the molten boron oxide discharge part. Further, as in the first embodiment, the heating chamber body 10 is surrounded by a casing 11 surrounded by a heat insulating material 11, and the inside is lined with a material not affected by boric acid such as stainless steel or its dehydrated product. Although it can be configured, the inner surface can also be a heat insulating material instead.

  In the second embodiment, since the radiant tube is disposed in a bowl shape in the heating chamber body, a plurality of large-sized radiant tubes can be installed in the heating chamber body by a hanging method. As a result, in the type in which the radiant tube is installed almost horizontally as shown in the first embodiment, when the size of the radiant tube is increased, a support column must be provided in the heating chamber body to support it. The problem that it is difficult to increase the size is solved, and the construction of facilities with high productivity is facilitated.

Example 1
Boron oxide was manufactured using a boron oxide manufacturing apparatus having the basic structure shown in FIGS. 1 and 2 and having the specifications shown in Table 1. As a result, the raw material boric acid was continuously charged at a rate of 22.4 kg / h, and the product boron oxide could be produced at a rate of 12.1 kg / h. The thermal efficiency in this operation was 65%. The amount of water generated by decomposition was 9.6 kg / h, and waste water containing 2% boric acid by mass was recovered from the venturi scrubber used as the exhaust gas treatment device. In addition, in the operation process, as a result of performing surface temperature control of the radiant tube, the temperature was maintained at 700-850 degreeC.

In this operation, propane was burned at a rate of 1.76 kg / h, and the thermal efficiency η according to the following formula was 65%.
η = (effective heat × 100) / (propane consumption × true calorific value)
Here, effective heat = heating temperature of raw material + reaction endotherm + heating amount of generated boron oxide

(Example 2)
Boron oxide is manufactured using a boron oxide manufacturing apparatus having the basic structure shown in FIGS. 4 and 5 and the specifications shown in Table 2. With this facility, raw material boric acid can be continuously charged at a rate of 666 kg / h, and product oxidation borate can be produced at a rate of 360 kg / h. In addition, the amount of water generated by decomposition is 285 kg / h, and wastewater containing 2% by weight of boric acid can be recovered from the venturi scrubber used as the exhaust gas treatment device. Moreover, the surface temperature can be maintained at 700-850 degreeC by performing the surface temperature management of a radiant tube in an operation process. In this case, the combustion rate of propane is 52.4 kg / h, and the thermal efficiency η is 65%. The calculation method of the thermal efficiency is the same as that in the first embodiment.

It is sectional drawing which showed typically the boron oxide manufacturing apparatus which concerns on 1st Embodiment of this invention. It is a boron oxide manufacturing apparatus AA arrow sectional drawing which concerns on 1st Embodiment of this invention shown in FIG. It is the figure which showed typically the state change of the raw material boric acid by this invention. It is sectional drawing which showed typically the boron oxide manufacturing apparatus which concerns on 2nd Embodiment of this invention. It is a boron oxide manufacturing apparatus BB arrow sectional drawing which concerns on 2nd Embodiment of this invention shown in FIG. It is a conceptual diagram of the boron oxide manufacturing apparatus which the applicant has put into practical use.

Explanation of symbols

10: Heating chamber body
11: Insulation
12: Bottom
13: Reaction heating chamber
14: Raw material boric acid inlet
15: Molten boron oxide discharge section
16: Steam outlet
18: Side wall
20: Radiant tube
24: Heating part
25: Non-heated part
30: Boric acid feeder
31: Hopper
32: Screw feeder
40: Cooled solidification crusher (for molten boron oxide)
41: Cover
42: Water-cooled W roll
43: Vertical air cooling duct
44: Demon Double Roll Crusher
45: Metal container with lid
50: Exhaust gas treatment equipment
51: Exhaust gas conduit
52: Radiation tube
80: Insulation
81: Heating chamber body
82: Combustion burner
83: Cylindrical retort
84: Loading entrance
85: Heat exchanger
86: Exhaust gas treatment equipment

Claims (7)

  A regenerative alternating combustion type radiant tube is installed in the main body of the heating chamber provided with a boric acid supply unit at the top and a molten boron oxide discharge unit at the bottom, and supplied from the boric acid supply unit into the main body of the heating chamber. Boron oxide is produced by heating the boric acid with the regenerative alternating combustion type radiant tube to form molten anhydrous boron oxide, and the molten boron oxide is continuously discharged from the molten boron oxide discharge section. apparatus.   The heating chamber main body is constituted by a casing or a cylinder, and the bottom of the heating chamber main body is an inclined hearth that is inclined by 1 to 5 ° with respect to a horizontal plane. The boron oxide manufacturing apparatus according to claim 1, further comprising an element discharge unit.   The boron oxide production apparatus according to claim 1 or 2, wherein the heating chamber main body is provided with an exhaust gas treatment facility for exhausting and treating exhaust gas generated by a dehydration reaction of boric acid.   4. The boron oxide production apparatus according to claim 1, wherein the molten boron oxide discharge section is provided with a molten boron oxide cooling and solidifying device.   The apparatus for producing boron oxide according to any one of claims 2 to 4, wherein the regenerative alternating combustion type radiant tube is installed along the inclined hearth of the main body of the heating chamber.   The heating chamber body is constituted by a cylindrical body or a polygonal cylinder, and a plurality of regenerative alternating combustion radiant tubes are installed along the side wall of the heating chamber body. The boron oxide manufacturing apparatus in any one.   Using the boron oxide production apparatus according to any one of claims 1 to 6, while continuously supplying raw material boric acid into the main body of the boron oxide production apparatus, it is installed in the main body of the boron oxide production apparatus. Oxidation characterized in that the raw boric acid is heated to form molten boron oxide by the regenerative heat storage type alternating combustion type radiant tube, and the generated molten boron oxide is continuously discharged from the molten boron oxide discharge section. Boron manufacturing method.

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