JP7117186B2 - Spray pyrolysis equipment - Google Patents

Description

The present invention relates to a spray pyrolysis apparatus suitable for producing hollow oxide particles.

As an apparatus for producing fine particles such as oxide hollow particles, an internal combustion spray pyrolysis apparatus equipped with a combustion burner inside a pyrolysis furnace is known. Patent Literature 1 describes an apparatus in which a large number of flame injection nozzles are arranged at different heights in a cylindrical powder generation tower. Patent Literature 2 describes an apparatus in which a large number of burners are arranged in the space outside the combustion chamber. In addition, devices have been reported that directly heat spray mist with flames from single or multiple burners (Patent Documents 3 and 4).

JP 2007-84355 A Japanese Unexamined Patent Application Publication No. 2013-202603 JP-A-2001-137699 Japanese Patent Application Laid-Open No. 2004-292223

However, in the apparatus of Patent Literature 1, since a large number of burners are arranged, it is extremely difficult to control the temperature inside the furnace, and the difficulty in temperature control may lead to misfiring of the combustion burner. As described above, it is difficult to control the temperature in the furnace, and the temperature distribution in the furnace becomes non-uniform, resulting in variations in the composition. Furthermore, a misfire of the burner causes a local increase or decrease in the amount of gas, so stable operation itself is extremely difficult and impractical. In addition, in the apparatus of Patent Document 2, the structure and control are extremely complicated, and most of the heat generated from the burner is taken away by the inner wall of the external combustion chamber, resulting in poor thermal efficiency. , the scale becomes one size larger, etc., the economic efficiency is extremely poor and it is not practical. In addition, due to the structure of the furnace, the inner wall (burner portion) of the furnace tends to reach a high temperature, causing a temperature difference between the central portion of the furnace and the vicinity of the inner wall, which tends to cause non-uniformity in the particles. Moreover, since the inner wall of the furnace, which does not have a combustion gas inlet, is at a high temperature, there is a problem that particles tend to adhere to it.
In the device of Patent Document 3, the solution directly sprayed is heated by the flame of the burner, which is undesirable because it forms solid particles. In the device of Patent Document 4, the particles melted by the burner ride on the airflow of the burner, come into contact with the side surface of the burner, and adhere to each other, causing deformation and cracking of the particles, which is not preferable.

In this way, in the internal combustion spray pyrolysis apparatus, a combustion burner is arranged inside the pyrolysis furnace, and the fuel is burned as a heat source. The wind speed is high, especially near the flame of the burner, which is characterized by being much faster. For this reason, it is necessary to secure the amount of heat required to thermally decompose the sprayed solution and synthesize the fine particles, that is, the residence time in the furnace for a certain period of time, but for the reasons described above, the size of the apparatus is increased. In addition, since the vicinity of the flame part of the burner is particularly hot, the particles entering the flame part become dense, and as a result, the composite becomes a mixture of solid particles and hollow particles, resulting in non-uniformity of the composite. There are issues such as
In addition, as described above, in the internal combustion spray pyrolysis apparatus, the combustion gas generated by the combustion of the fuel significantly increases the flow velocity in the furnace, and the heat radiated from the furnace wall reduces the distance from the heat source. Since the temperature in the furnace decreases as the distance increases, it is difficult to ensure the treatment temperature and holding time necessary for synthesizing hollow particles.

Accordingly, an object of the present invention is to impart heat from a combustion burner to the spray mist in a substantially uniform manner and ensure the required treatment temperature and holding time without making a complicated structure, thereby producing homogeneous fine particles at a high temperature. An object of the present invention is to provide an internal combustion type spray pyrolysis apparatus capable of obtaining a high yield.

Therefore, the present inventor installed a spray nozzle at the bottom of a rigid cylindrical pyrolysis furnace, arranged 2 to 4 combustion burners diagonally in the tangential direction in the furnace body, and placed the combustion burner above the combustion burner By providing an auxiliary heat source, it is possible to generate a strong swirling flow in the furnace by the combustion gas of the fuel, and it is possible to take a long residence time of the spray mist in the furnace with respect to the length of the furnace. By giving the amount of heat dissipated from the body, the temperature and holding time required for synthesis of hollow particles can be stably secured with good reproducibility, the equipment is compact and simple, and the temperature inside the furnace is uniform. The present inventors have completed the present invention by finding that it is possible to achieve reduction and prevention of adhesion of powder.

That is, the present invention provides the following [1] to [10].

[1] An upward spray nozzle is provided at the bottom of a rigid cylindrical pyrolysis furnace, 2 to 4 combustion burners are diagonally positioned at approximately the same distance from the bottom of the pyrolysis furnace, and the tangential direction in the pyrolysis furnace body and one or more auxiliary heat sources are provided above the combustion burner of the pyrolysis furnace body.
[2] The spray pyrolysis apparatus according to [1], wherein the combustion burner is arranged so that the flame of the combustion burner and the spray mist do not come into direct contact with each other.
[3] The spray pyrolysis apparatus according to [1] or [2], wherein the auxiliary heat source is one or more selected from an auxiliary combustion burner, a hot air heater and an electric heater.
[4] The spray pyrolysis apparatus according to [3], wherein one or more of the combustion auxiliary burners are arranged in the tangential direction in the pyrolysis furnace body and in the swirling direction of the combustion gas.
[5] The spray pyrolysis apparatus according to [3], characterized in that one or more of the hot air heaters are arranged in the tangential direction in the pyrolysis furnace body and in the swirling direction of the combustion gas.
[6] The spray pyrolysis apparatus according to [4], wherein the combustion auxiliary burner of the auxiliary heat source is arranged so that the flame of the combustion burner and the spray mist do not come into direct contact.
[7] The spray pyrolysis apparatus according to any one of [1] to [6], wherein the residence time of the spray mist in the pyrolysis furnace is 0.1 to 600 seconds.
[8] The spray pyrolysis apparatus according to any one of [1] to [7], wherein the fuel used in the combustion burner is liquid fuel or gaseous fuel.
[9] The spray pyrolysis apparatus according to any one of [1] to [8], wherein the spray nozzle is a single or a plurality of 2- to 4-fluid nozzles.
[10] The spray pyrolysis apparatus according to any one of [1] to [9], wherein a space capable of introducing cooling air is provided at the top of the pyrolysis furnace.

By using the manufacturing apparatus of the present invention, by arranging 2 to 4 combustion burners and auxiliary heat sources, a strong swirl flow is generated by the combustion gas, and the spray mist generated from the bottom rides on the swirl flow and extends from the furnace length. Since the thermal decomposition takes a long time, the thermal decomposition time and temperature become uniform, and hollow fine particles can be obtained selectively and in a high yield.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overall schematic view of the spray pyrolysis apparatus of the present invention in which an auxiliary combustion burner is arranged (side view, cross-sectional view along line AA and cross-sectional view along line BB). Schematic overall view of the spray pyrolysis apparatus of the present invention in which combustion auxiliary burners are arranged, in which the combustion auxiliary burners are also arranged diagonally and tangentially (side view, sectional view along line AA and sectional view along line BB). is. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overall schematic view of the spray pyrolysis apparatus of the present invention in which a hot air heater is arranged (side view, AA line cross-sectional view and BB line cross-sectional view). 1 is an overall schematic diagram of a spray pyrolysis apparatus of the present invention in which an electric heater is arranged; FIG. 1 shows an example of a spray pyrolysis apparatus according to the present invention in which a swirling flow is generated in a cracking furnace by staggered arrangement of auxiliary combustion burners. 1 is an overall schematic view of a spray pyrolysis apparatus without combustion auxiliary burners; FIG. 4 shows the furnace temperature according to the example. 1 shows scanning electron microscope images of hollow particles obtained in Examples.

The spray pyrolysis apparatus of the present invention is of internal combustion type. That is, the pyrolysis furnace has a spray nozzle for spraying the raw material liquid in the pyrolysis furnace, and a combustion burner for generating combustion gas as a heat source for pyrolyzing the sprayed mist (droplets) and an auxiliary heat source. It is a spray pyrolysis device inside.

As for the shape of the pyrolysis furnace, a rigid cylindrical shape is preferable because installation of the apparatus is simple. By adopting a rigid cylindrical shape (see Fig. 1), combustion gas generated from 2 to 4 combustion burners arranged at specific positions generates a strong swirling flow in the furnace (A in Fig. 1). -A line sectional view).

The spray nozzles are arranged to spray upwards at the bottom of the pyrolysis furnace (Fig. 1). The number of spray nozzles may be one or two or more. The spray nozzle is preferably a 2- to 4-fluid nozzle, and compressed air is used as carrier air, and the spray nozzle is doubled so that an air shield is formed around the spray mist, and the solution is sprayed. can be sprayed. Also, the spray nozzle may be protected by a heat insulating material or the like as necessary in consideration of heat resistance.

The spray nozzle is arranged to spray a mist of the raw material liquid upward to the bottom of the pyrolysis furnace. The upwardly sprayed mist reaches the direction of the flame generated by the combustion burner (Fig. 1).

Two to four combustion burners are installed, preferably two. The two to four combustion burners are arranged tangentially in the pyrolysis furnace, diagonally at about the same distance from the bottom of the pyrolysis furnace (see FIG. 1A-A line cross section), but at 0° It may be placed upward at an angle of ~60°. In this case, from the viewpoint of efficiently generating a swirling flow, it is preferable to set the two to four nozzles at the same angle.
The combustion burner flame preferably does not directly contact the atomized mist to prevent overreaction of only a portion of the mist. In order to position the combustion burners so that the combustion burner flames do not come into direct contact with the atomized mist, it is preferable to keep the combustion burner flames out of the furnace (see FIG. 1). If it is desired to prevent the flame of the burner from entering the furnace, it is better to provide a mechanism for moving the burner in the front-rear direction and adjust it as necessary.
By arranging in this manner, combustion gases from opposite directions generated from two to four combustion burners create a strong swirling flow in the furnace. Since this swirling flow advances upward from the bottom of the furnace, the spray mist sprayed from the spray nozzle also rises while swirling due to this swirling flow. Therefore, the atomized mist stays in the furnace for a distance longer than the length of the furnace without directly contacting the flame generated from the combustion burner, and can undergo a long-term pyrolysis reaction.
Any combustion burner that is commercially available can be used. Considering the furnace specifications such as the furnace volume and the type of combustion, it is preferable to select a combustion burner of a type suitable for the specifications.

The residence time of the atomized mist in the furnace can be set from 0.1 seconds to 600 seconds. It is preferably set to 1 second to 300 seconds, more preferably 1.5 seconds to 60 seconds.
By setting the pyrolysis reaction time to be long in this manner, hollow microparticles can be produced stably and efficiently. In the case of spray pyrolysis using a raw material liquid as a raw material of an inorganic oxide, if the raw material droplets do not come into direct contact with a flame, the drying reaction proceeds first and the mist becomes hollow particles. Subsequently, if the thermal decomposition reaction proceeds, inorganic oxide hollow fine particles are obtained. Here, examples of inorganic oxides include metal oxides, alumina, silica, calcia, magnesia, oxides composed of aluminum and silicon, and more specifically oxides composed of alumina, silica, aluminum and silicon. oxides, titanium oxides, magnesium oxides, calcium oxides, sodium oxides, potassium oxides, lithium oxides, boron oxides, phosphorous oxides, zirconium oxides, barium oxides, cerium oxides, yttrium oxides, etc. and composite oxides in which these oxides are combined.
Solvents for dissolving or dispersing the raw materials of the elements constituting these oxides include water and organic solvents, but water is preferable from the viewpoint of environmental impact and production costs. or alkali may be added. Examples of acids that can be used include hydrochloric acid, nitric acid, sulfuric acid, and organic acids. Examples of alkalis that can be used include sodium hydroxide, calcium hydroxide, potassium hydroxide, and the like.

Both liquid fuel and gaseous fuel can be used as the fuel for the combustion burner. Specifically, gaseous fuels such as LPG, city gas, and vaporized organic matter, and liquid fuels such as kerosene, light oil, heavy oil, and recycled oil can be used.

One or more auxiliary heat sources are installed above the combustion burner of the pyrolysis furnace body (Fig. 1). Auxiliary heat sources include combustion auxiliary burners (FIGS. 1, 2, and 5), hot air heaters (FIG. 3), and electric heaters (FIG. 4). As shown in FIGS. 1 to 5, the auxiliary heat source may be installed above the combustion burner of the pyrolysis furnace body. The number of auxiliary heat sources may be one, but depending on the length of the pyrolysis furnace, it is preferable to have two to six, for example, as shown in FIGS. It may be provided on the periphery (Fig. 4).
By installing an auxiliary heat source, it is possible to provide heat equivalent to the amount of heat dissipated from the furnace body, and to stably secure the temperature and holding time necessary for synthesizing hollow particles with good reproducibility.
When a combustion auxiliary burner or hot air heater is used as the auxiliary heat source, the combustion gas generated by the combustion burner can be reduced by arranging it in the tangential direction in the furnace body in the same turning direction as the combustion burner (Figs. 2 and 3). This is preferable because the swirl flow is maintained and strengthened depending on the operating conditions of the auxiliary heat source.
The combustion auxiliary burner and the hot air heater may be installed on different surfaces and heights in order to adjust the furnace temperature and swirling flow. The surfaces to be installed may be arranged facing each other as shown in FIG. 1 or in the vertical direction of the pyrolysis furnace. The installation heights may be the same height (on the same circumference) or different levels (Fig. 5).
In addition, the flame of the auxiliary combustion burner, which is the auxiliary heat source, should not come into direct contact with the spray mist and the hollow particles that are generated. preferable. It is preferable to install the flame of the auxiliary combustion burner so that it does not enter the furnace so that the flame of the auxiliary combustion burner does not come into direct contact with the atomized mist or the generated hollow particles (see FIGS. 1 and 2). In order to prevent the flame of the auxiliary combustion burner from entering the furnace, a mechanism for moving the auxiliary combustion burner back and forth may be provided and adjusted according to the length of the flame.

Any material that is used as a furnace material can be used for the furnace body, and it is preferable to select the furnace body in consideration of the temperature to be used.
It is common to use refractory bricks, insulating bricks, castables, etc. alone, in layers, or in combination for the inner wall of the metal shell.

Particles generated by the pyrolysis reaction riding on the swirling flow from the lower part to the upper part of the pyrolysis furnace are recovered from the upper part of the pyrolysis furnace. Here, in order to collect the fine particles efficiently, it is preferable to provide a space in which cooling air can be introduced at the top of the pyrolysis furnace, and to cool and recover the fine particles by introducing the cooling air into the space. As the means for introducing the cooling air, it is possible to employ means such as installation of a cooling air suction part, means for sending the cooling air from a fan or a blower, etc., and these may be performed from a plurality of positions. Further, water cooling may be used instead of cooling air, and deionized water, tap water, or the like may be used. A bag filter or the like can be used to collect the target fine particles.
A cyclone may be placed before the bag filter in order to reduce the load on the bag filter and collect coarse particles and foreign matter.In addition, it is preferable to place a heat exchanger because residual heat can be used and the amount of exhaust gas can be reduced. .
Further, dust removal and purification equipment such as a scrubber may be arranged after the bag filter, if necessary.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.

Example 1
1992 g of tetraethyl orthosilicate, 131 g of aluminum nitrate nonahydrate, 455 g of magnesium nitrate hexahydrate, 516 g of calcium nitrate tetrahydrate, 1666 g of sodium tetraborate decahydrate, and 1 L of concentrated nitric acid were added vertically to 100 L of ion-exchanged water. It was put into the solution tank of the gas furnace and stirred. The supplied aqueous solution was turned into a mist by a liquid feed pump through a two-fluid nozzle, and was sprayed into a vertical gas furnace with the furnace temperature set at 900° C., and the synthesized hollow particles were collected with a bag filter.
The vertical gas furnace uses a vertical gas furnace with a combustion auxiliary burner (Fig. 1) and a vertical gas furnace without a combustion auxiliary burner (Fig. 6). The temperature inside the furnace was measured. FIG. 7 shows the temperature change in the furnace, and FIG. 8 shows a scanning electron microscope image of the obtained hollow particles. In FIG. 7, "with auxiliary burners" indicates the furnace temperature in the vertical gas furnace with combustion auxiliary burners (FIG. 1), and "without auxiliary burners" indicates the furnace temperature in the vertical gas furnace without combustion auxiliary burners (FIG. 6).
With this device, the retention time in the high-temperature range is long, so the strength of the particles is improved. In addition, extremely strict temperature control is possible, so the variation in the quality of the particles is extremely small.

Claims (8)

A spray pyrolysis apparatus for synthesizing inorganic oxide hollow fine particles by spraying a raw material liquid, which is a raw material for inorganic oxides, into a vertical internal combustion furnace through a fluid nozzle, and is a rigid cylindrical pyrolysis furnace. has an upward spray nozzle at the bottom of the pyrolysis furnace, 2 to 4 combustion burners are diagonally positioned at approximately the same distance from the bottom of the pyrolysis furnace, and the flame of the combustion burner and spray mist are tangentially in the pyrolysis furnace. An internal combustion type spray pyrolysis apparatus characterized by being arranged so as not to come into direct contact with each other and having one or more auxiliary heat sources above a combustion burner of a pyrolysis furnace body. 2. The spray pyrolysis apparatus according to claim 1, wherein said auxiliary heat source is one or more selected from a combustion auxiliary burner, a hot air heater and an electric heater. 3. The combustion auxiliary burner is arranged in the tangential direction in the pyrolysis furnace body and in the swirling direction of the combustion gas so that the flame of the combustion auxiliary burner and the spray mist do not come into direct contact with each other. of spray pyrolysis equipment. 3. The spray pyrolysis apparatus according to claim 2, wherein one or more of the hot air heaters are arranged in the tangential direction in the pyrolysis furnace body and in the swirling direction of the combustion gas. The spray pyrolysis apparatus according to any one of claims 1 to 4, wherein the residence time of the spray mist in the pyrolysis furnace is 0.1 to 600 seconds. The spray pyrolysis apparatus according to any one of claims 1 to 5, wherein the fuel used in the combustion burner is liquid fuel or gaseous fuel. The spray pyrolysis apparatus according to any one of claims 1 to 6, wherein the spray nozzle is a single or a plurality of 2- to 4-fluid nozzles. The spray pyrolysis apparatus according to any one of claims 1 to 7, wherein a space capable of introducing cooling air is provided at the top of the pyrolysis furnace.

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