JPH0675642B2 - Spray dryer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spray dryer for drying a solution of an inorganic acid salt or an organic acid salt to obtain a dry powder of a ceramics raw material.

[Conventional technology]

FIG. 2 shows a conventional method for obtaining this kind of powder raw material (Japanese patent
It is a block diagram which shows the spray dryer of No.1319907, British patent No. 1064484 reference). In the figure, 1 is a container for storing a solution in which a powdered solid to be dried is melted, 2 is a liquid feeding section for feeding the solution to a fluid nozzle 3, and a fluid pump or the like is used. The fluid nozzle 3 is formed as a spray nozzle that sprays two fluids, the solution and a pressurized gas described later. 4 is a compressor for generating the above-mentioned pressurized gas,
Reference numeral 5 denotes a needle valve for adjusting the pressure of the pressurized gas, and the liquid delivery unit 2, the fluid nozzle 3, the compressor 4, and the needle valve 5 constitute a nebulizing device for the solution 1. 6 is a drying container having the spray port 3a of the fluid nozzle 3 therein, 7 is an internal heating device for feeding heated gas into the drying container 6, and 8 is an air flow for controlling the flow of dry powder and gas from the drying container 6. The control container constitutes a cyclone. Reference numeral 9 is a suction device for sucking the gas from the air flow control container 8 and at the same time sucks the heated gas into the drying container 6. Reference numeral 10 is a collection container for collecting the dry powder from the air flow control container 8.

In the drying apparatus having the above structure, the solution in the container 1 is sent to the fluid nozzle 3 by the pump of the solution sending unit 2, and the pressurized gas (air or inert gas) whose pressure is adjusted by the needle valve 5 from the compressor 4 is here. It is mixed with compressed gas such as gas). Then, the mixture of the two fluids of the solution and the pressurized gas is atomized into droplets and sprayed from the upper portion of the drying container 6.

On the other hand, air (gas) enters the drying device by the suction device 9 as shown by the arrow in the figure, and when this air passes through the internal heating device 7, it is heated to become hot air. Then, the hot air is sent into the drying container 6 and comes into contact with the sprayed droplets. As a result, the droplets are instantly dried and become dry powder, which is sent to the air flow control container 8. Here, the dry powder is separated from the evaporated component and collected in the collection container 10.

[Problems to be Solved by the Invention]

The conventional spray-drying device is configured as described above, and the hot air introduced into the drying container 6 supplies evaporation energy to the sprayed droplets and heat radiation to the outside of the device is unavoidable. By the time it reaches the collecting container 10, the temperature drops significantly. This hot air contains a large amount of evaporated components, and the dry powder collected in the collection container 10 absorbs the evaporated components, so that there is a problem in that a dry powder having good dispersibility cannot be obtained. Further, there is a problem in that only the characteristic component that easily absorbs moisture is eluted from the dry powder, and a dry powder having a uniform composition cannot be obtained. In particular, it is very difficult to obtain a ceramic raw material for an oxide superconductor containing Cu (copper).

The present invention has been made to solve the above problems, and it is possible to obtain a dry powder having good dispersibility and high composition uniformity, and to obtain a chemically more stable dry powder. A spray drying device capable of performing the above is provided.

[Means for Solving the Problems]

The spray drying device of the present invention is an atomizing device for atomizing and spraying a solution to be dried, a drying container having the spray port therein, and an internal heating device for feeding heated gas to the drying container, An air flow control container for controlling the flow of the dry powder and gas from the drying container, a suction device for sucking the gas from the air flow control container, a collection container for collecting the dry powder from the air flow control container, and An external heating device for heating the collecting container from the outer side surface and the outer bottom surface is provided.

[Action]

In the spray drying apparatus of the present invention, the dry powder collected in the collecting container is heated by externally heating the collecting container by the external heating device. Therefore, the dry powder does not absorb moisture even when it comes into contact with a gas containing an evaporated component, and has good dispersibility and high composition uniformity. Also,
This dry powder that does not contain evaporation may be partially thermally decomposed by external heating at a relatively low temperature, which is the same as or higher than that of the internal heating device, and may be recovered as a more chemically stable substance. Further, because of the structure, an airflow is always introduced into the collection container, so that the dry powder is agitated and is dried uniformly without being fixed in the collection container by heating. Therefore, the dispersibility is further enhanced.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.
The same reference numerals as those shown in the drawings indicate the same parts, and a duplicate description will be omitted. In the figure, 1 is a container for a solution, 2 to 5 are liquid-feeding parts, a fluid nozzle, a compressor and a needle valve, respectively, which constitute an atomizing device for the solution, and 6 is a spray port 3a of the fluid nozzle 3 provided in the upper part. The drying container 7 is an internal heating device connected to the drying container 6, and a hot air inlet is opened around the spray port 3a. 8 is an inverted L-shaped cylindrical air flow control container attached to the side surface of the drying container 6, 9 is a suction device connected to the upper part of the air flow control container 8 via a tube, and 10 is the air flow control container 8
, 11 is an external heating device attached to the external side surface and external bottom surface of the collection container 10,
The collection container 10 is heated from the outside.

In the above-mentioned configuration, the solution in the container 1 is sent as droplets into the drying container 6 from the spray port 3a of the fluid nozzle 3 as in the conventional case. Then, in the drying container 6, it is brought into contact with the hot air introduced through the internal heating device 7 to dry instantly,
It becomes a dry powder and is guided to the air flow control container 8, where it is separated from the evaporated components and collected in the lower collection container 10. At this time, since the collection container 10 is externally heated by the external heating device 11, the dry powder in the collection container 10 is also heated and does not absorb moisture. Therefore, solute (powder solid)
Even when the hygroscopicity is high, a dry powder having good dispersibility and high composition uniformity can be obtained.

In addition, a part of the dry powder is thermally decomposed by the above heating, which makes it possible to recover it as a chemically more stable substance. Further, the dry powder is agitated by the air flow in the collection container 10, and by this and external heating by the heating device 11, the dry powder is not fixed to the inner wall of the collection container 10,
Uniform drying or thermal decomposition is performed to further enhance the dispersibility and composition uniformity. Therefore, it is possible to easily obtain the ceramic raw material of the oxide superconductor containing Cu.

Next, the experimental results of actual drying will be described.

First, in this experiment, Y ₂ O ₃ , Ba (NO ₃ ) ₂ and CuO were dissolved with concentrated nitric acid so that all components became nitrates. Further, as Y ₁ Ba ₂ Cu ₃ O _7- y, a solution was prepared so that the concentration was 0.05 mol /. Then, this solution was spray-dried by the conventional spray drying apparatus shown in FIG. 2 and the spray drying apparatus according to the present invention shown in FIG. 1, respectively.
At this time, the heater temperature of the internal heating device 7 is 160 ° C., the atomizing air pressure is 2.2 kg / cm ² , the heating air (hot air) flow rate is 0.4 m ³ / min,
A dry powder was prepared under the condition that the liquid feed rate was 7 m / min. The heater temperature of the external heating device 11 of the spray dryer according to the present invention was 250 ° C.

When a conventional spray dryer was used, a paste-like blue solute was attached to the inner wall of the collection container 10. This reached the powder collection container because the solute of the nitrate solution was dried to some extent by hot air, but was exposed to the airflow of a reduced temperature including the evaporated component and absorbed moisture, which adhered to the inner wall of the collection container 10. it is conceivable that.

On the other hand, when the spray dryer according to the present invention was used, a black dry powder having good dispersibility was recovered. Structural analysis of this powder by X-ray diffraction revealed that Ba (No ₃ ) ₂
A broad pattern of overlapping amorphous diffraction patterns was obtained. This is because in the solution, the Cu component becomes copper nitrate and exhibits a blue color, but in the dry powder,
It is considered that the black color indicates that copper oxide is in an amorphous state due to thermal decomposition.

That is, in this apparatus, not only a dry powder having good dispersibility can be obtained, but also a salt having a high hygroscopicity, such as copper nitrate, is thermally decomposed and recovered as a chemically stable compound. Therefore, it is advantageous in handling after collection. In addition, as described above, the reason why a part of thermal decomposition easily occurs is to heat the finely divided powder that does not contain the vaporized component.
Therefore, using the conventional spray dryer, the internal heating device 7
Even if the heater temperature is set to 250 ° C, thermal decomposition does not easily occur.
In this way, a good dry powder can be obtained by the synergistic effect of the internal heating device 7 and the external heating device 11.

In addition, although the two-fluid nozzle is used for the atomizing device in the above-described embodiment, the same effect can be obtained by the ultrasonic humidifier.

〔The invention's effect〕

As described above, according to the present invention, since the external heating device for heating the collection container from the outside in addition to the internal heating device is provided, it is possible to obtain a dry powder having good dispersibility and high composition uniformity, In addition, it is possible to obtain a chemically stable dry powder.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional spray dryer. 1 ... Solution container 2 ... Liquid transfer part (atomizer) 3 ... Fluid nozzle (atomizer) 3a ... Spray port (atomizer) 4 ... Compressor (atomizer) 5 ... … Needle valve (atomizer) 6 …… Drying container 7 …… Internal heating device 8 …… Air flow control container 9 …… Suction device 10 …… Collection container 11 …… External heating device Or shows a considerable part.

Claims (1)

[Claims] 1. A drying device for drying a solution, which comprises an atomizing device for atomizing and spraying the solution, a drying container having a spray port therein, and an internal heating for feeding a heating gas into the drying container. A device, an air flow control container for controlling the flow of dry powder and gas from the drying container, a suction device for sucking the gas from the air flow control container, and a collection container for collecting the dry powder from the air flow control container. A spray-drying device comprising an external heating device for heating the collection container from an outer side surface and an outer bottom surface.