JP2002143669A - Gas circulation type spray drying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas circulation type spray drying device, in which the temperature of powder and the concentration of a residual solvent in a powder product are decreased. SOLUTION: This gas circulation type spray drying device 12 is a closed type and is provided with a spray drying tower 1, a cyclone 3 and a condenser 5 from the upstream side and in which a liquid raw material containing an organic solvent as a solvent is atomized and dried in a spray device 2. The condenser 5 is constituted of at least 2 stages and the circulating gas discharged from the condenser arranged at the most downstream side is cooled to a temperature lower than -30 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a gas-circulation spray-drying apparatus used for obtaining powdered products such as raw materials for pharmaceuticals and fine chemicals.

[0002]

2. Description of the Related Art A gas circulation type spray drying apparatus mainly using nitrogen gas as a circulating gas has been put to practical use, in which a liquid raw material using an organic solvent as a solvent is atomized and dried to obtain a powder product.

FIG. 5 is a schematic diagram showing a conventional gas circulation type spray drying apparatus, in which a circulating gas such as nitrogen gas heated by a heater 9 is supplied from a stock solution pump 8 in a spray drying tower 1. The raw material is injected by the spray device 2, and the liquid raw material is instantaneously dried and pulverized, and collected as a powder product in the cyclone 3 which is a solid-gas separation device.

The exhaust gas (circulating gas) that has passed through the cyclone 3 is subjected to removal and recovery of an organic solvent contained in the exhaust gas by a solvent condensation / removal unit 14, and is returned to the heater 9 for circulating use. In the conventional apparatus, a part of the gas in which the solvent remains is discharged from the exhaust valve 13.

Conventionally, as a solvent condensing / removing device 14, for example, as disclosed in Japanese Patent No. 2791050, a device for cooling and condensing steam by indirectly contacting steam and a cooling liquid through a metal surface. And triple heat exchange condensers have been used. Among these, the latter condenser accommodates, in the main body, a first pipe for circulating the Freon-based refrigerant and a second pipe for passing the humid gas, and the first pipe and the second pipe. Has a configuration in which brine is introduced into a shell-side space as an external space.

Until now, in such a spray drying apparatus, the hot air temperature by the heater 9 has been reduced from 100 ° C. to 20 ° C.
The spray drying was performed at a high temperature of 0 ° C. and a circulating gas temperature of 0 ° C. to 50 ° C. At present, the demand for spray drying at a low temperature of a hot air temperature of 100 ° C. or lower has been increasing in the pharmaceutical and fine chemical industries. . To realize the low-temperature spray drying, it is necessary to suppress the concentration of the organic solvent in the circulating gas to an extremely low level, which will be described in detail later.

However, the conventional solvent condensation remover 1
In the gas-circulation type spray-drying apparatus using No. 4, when the condensing temperature is further reduced to remove the organic solvent, icing occurs, which makes it possible to operate continuously. However, there was a problem in low-temperature spray drying. In addition, since the temperature of the circulating gas is reduced in one stage in the condenser, a large amount of energy is required for the temperature and the size of the apparatus is also increased.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such a new demand, and an object of the present invention is to reduce the temperature by more than 30 degrees C.
By cooling the circulating gas to about ℃, the concentration of the organic solvent in the circulating gas is reduced to achieve low-temperature spraying, enabling drying and powdering of liquid materials that could not be dried up to now. It is an object of the present invention to provide a gas-circulation type spray-drying apparatus which has substantially no environmentally problematic solvent discharged to the outside.

[0009]

That is, according to the present invention, a spray-drying tower, a solid-gas separation device, and a condenser are provided from the upstream side, and a liquid raw material using an organic solvent as a solvent is provided by a spraying device. A closed type gas circulation type gas circulation type spray drying device for atomizing and drying, wherein the condenser is constituted by at least two or more stages, and a circulating gas coming out of a condenser arranged at the most downstream side is provided. A gas circulation type spray drying apparatus characterized by cooling to a temperature lower than -30 ° C is provided. At this time, it is preferable that the condenser arranged on the most downstream side is a plate heat exchanger or a plate condenser.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The gas circulation type spray drying apparatus of the present invention comprises a spray drying tower, a solid-gas separation device, and a condenser. Hereinafter, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to the following embodiments.

The configuration of the gas circulation type spray drying apparatus according to the present invention will be described with reference to the attached FIGS. 1 and 2, which schematically show the configuration of the main part.
As shown in FIG. 1, the gas circulation type spray drying apparatus of the present invention is a closed type gas circulation type spray drying apparatus 12 in which a liquid material using an organic solvent as a solvent is atomized by a spraying apparatus 2 and dried. The condenser 5 is composed of at least two or more stages, and cools the circulating gas coming out of the condenser 5 arranged at the most downstream side to a temperature lower than -30 ° C. At this time, it is preferable that a plate-type heat exchanger or a plate-type condenser be arranged in the condenser 5 arranged on the most downstream side. In addition, as shown in FIG. 2, the gas circulation type spray drying apparatus of the present invention has a drain 10 at a position behind the condenser 5 at the most downstream position, and a drain 10 at a position before the heater 9 after passing through the condenser 5. A configuration in which the blower 6 is arranged may be adopted.

In the gas circulation type spray drying apparatus, the concentration of the organic solvent in the circulating gas introduced into the heater 9 is important. When the concentration of the organic solvent is high, the temperature of the circulating gas is increased. It is necessary to raise the drying temperature and dry and solidify. However, if the solvent concentration can be kept as low as possible, the outlet temperature of the heater 9 required for drying can be lowered, and it is possible to appropriately cope with the drying of the liquid raw material that needs to keep the drying temperature low. It becomes.
Further, the concentration of the residual solvent in the powder product can be reduced.

In the present invention, the circulating gas condenser 5
Is composed of at least two or more stages to control the temperature of the circulating gas in a multi-step manner, and to provide at least the most downstream condenser, that is, the condenser that is the lowest temperature, a plate type that is resistant to freezing. A heat exchanger 21 or a flat plate condenser 22 was provided. Thereby, continuous operation at a low temperature is enabled, and an extremely low organic solvent concentration in the circulating gas introduced into the heater 9 can be achieved. As a result, the spray drying temperature can be further reduced as compared with the conventional method, and it has been realized that powder drying of pharmaceutical raw materials requiring low-temperature drying and the concentration of organic solvent in the powder dried product are reduced.

In the present invention, by the above-described configuration,
Since the temperature can be lowered to −40 ° C., the concentration of the organic solvent becomes extremely low, and a closed type spray drying apparatus which does not require an exhaust valve for lowering the concentration of the organic solvent can be obtained. This means that the solvent released to the outside of the system is practically zero, which is very effective for environmental protection.

Table 1 shows the saturation absolute humidity in nitrogen gas of an organic solvent often used as a solvent for a liquid raw material. As shown here, for example, isopropyl alcohol is 1 kg of nitrogen at −10 ° C.
0.055 kg per unit, but 0.014 kg at -30 ° C and 0.007 kg at -40 ° C, which is one-fourth of the organic solvent concentration in the circulating gas conventionally realized. It can be seen that the concentration is as low as 1/8 or less. That is, the absolute humidity of the organic solvent greatly depends on the cooling temperature, and differs greatly between -10 ° C and -40 ° C. Therefore, if an atmosphere of −40 ° C. can be realized, the organic solvent in the circulating gas can be removed to near zero.

[0016]

[Table 1]

Hereinafter, the plate heat exchanger and the flat plate condenser used in the present invention will be described. A plate-type heat exchanger has a heat exchange unit in which a plurality of corrugated heat exchange walls are stacked with a fixed volume inside, and a gas is contained in the volume between the heat exchange walls. , Heat exchange is performed from one side to the other side to cool or heat the gas. At this time, if it is desired to lower the temperature of the gas, a gas (refrigerant) having a lower temperature than the gas passes through the other volume separated by the heat exchange wall. If it is desired to raise the temperature of the gas, the opposite can be done. The plate heat exchanger of the present invention used as this condenser has a much larger contact area with the circulating gas than other condensers, and almost all the volume inside the exchanger is a heat exchange unit. Therefore, it has a feature that the heat exchange rate is very good despite its small size.

As shown in FIG. 4, the flat plate type condenser 22 contains a plurality of slip case type (outer box-like) refrigerant circulators 27 at regular intervals. A refrigerant having an appropriate temperature is introduced from the refrigerant inlet 25, circulated in the refrigerant circulating body 27, and discharged from the refrigerant outlet 26, so that the circulating gas from the circulating gas inlet 23 passes through the condenser. The temperature of the gas is lowered to condense and remove the organic solvent in the gas.

Since these two condensers easily pass the circulating gas and have a plurality of rows of gas passages, even if frost occurs on the condensation wall, the passage of the gas is not hindered so much and the condensation efficiency is reduced. It is possible to operate continuously without much lowering.

FIG. 3 shows an embodiment in which the plate-type heat exchangers are arranged in two stages. First, an organic solvent containing organic solvent is supplied from the circulating gas inlet 23 of the first-stage plate heat exchanger 21. Circulating gas at a temperature of 0 ° C.
Cool to ℃. Thereafter, the gas is introduced into the second plate heat exchanger 21 through the blower 6 and
To minus 40 ° C. And the gas is
It is discharged from the plate heat exchanger 21 and is again introduced into the first-stage plate heat exchanger 21 where the minus 40
Heat from 0 ° C to 0 ° C.

In this process, in a process in which the circulating gas is cooled to −40 ° C., the organic solvent in the circulating gas is formed into droplets and removed along the heat exchange wall which is a condensing wall. At this time, in the plate heat exchanger 21 of the first stage, the temperature of each gas is changed without using a refrigerant or a heater by performing heat exchange between the high-temperature gas and the low-temperature gas. Thus, energy consumption can be suppressed.

[0022] The realization of a low circulating gas temperature as in the gas circulation type spray drying apparatus of the present invention is necessary for drying biotechnology-related pharmaceutical raw materials that are susceptible to temperature and where necessary when necessary. It is also expected to be applied to microencapsulation of pharmaceuticals based on the concept of DDS that delivers a large amount of drug into the body. Pharmaceuticals, diagnostics,
Organic solvents such as isopropyl alcohol and methylene chloride are used for extraction, separation, and purification of enzymes and fine chemicals. However, spray drying methods are also being studied for solidification and pulverization. Is also expected.

[0023]

As described above, according to the gas circulation type spray drying apparatus of the present invention, the temperature is controlled in multiple stages by configuring the condenser in two or more stages. By arranging a plate-type heat exchanger or a plate-type condenser that is resistant to freezing as a condenser, continuous operation can be performed even when the circulating gas is cooled to a temperature lower than −30 ° C. Therefore, the concentration of the organic solvent in the circulating gas can be extremely reduced, and the spray drying temperature can be lowered. As a result, the powder temperature of the liquid raw material can be lowered, and the concentration of the residual solvent in the powder product can be reduced. As a result, the gas circulation type spray drying apparatus of the present invention has an excellent effect that a wider range of liquid raw materials can be dried and powdered.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a gas circulation type spray drying apparatus of the present invention.

FIG. 2 is a schematic diagram showing another configuration of the gas circulation type spray drying apparatus of the present invention.

FIG. 3 is a schematic diagram showing one embodiment of a plate heat exchanger used in the gas circulation type spray drying device of the present invention.

FIG. 4 is a schematic view of the internal structure of a flat plate condenser used in the gas circulation type spray dryer of the present invention.

FIG. 5 is a schematic diagram showing a configuration of a conventional gas circulation type spray drying apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Spray drying tower, 2 ... Spray apparatus, 3 ... Cyclone, 4 ...
Filter, 5: condenser, 6: blower, 7: cooling unit, 8: stock solution pump, 9: heater, 10: drain, 11: gas pressure regulating valve, 12: gas circulation type spray-drying device, 13: exhaust valve, 14 ... Solvent condensation remover, 21 ...
Plate heat exchanger, 22 flat plate condenser, 23 circulating gas inlet, 24 circulating gas outlet, 25 refrigerant inlet,
26: refrigerant outlet, 27: slip case type refrigerant circulator.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F26B 17/10 F26B 17/10 Z (72) Inventor Tatsunobu Koyama 3847 Ikebe-cho, Tsuzuki-ku, Yokohama-shi, Kanagawa Prefecture Okawara F-term in Kakoki Co., Ltd. (Reference) 3L113 AA07 AB04 AC30 AC46 AC48 AC67 AC83 BA02 CB20 DA30 4D076 AA12 AA24 BC01 BC05 DA02 DA12 EA02Z EA12Z FA01 FA11 FA22 FA34 HA11 JA01 4G004 EA03

Claims (2)

[Claims] 1. A closed-type gas circulation type sprayer comprising, from an upstream side, a spray-drying tower, a solid-gas separator, and a condenser, wherein a liquid raw material using an organic solvent as a solvent is atomized by a sprayer and dried. A gas circulation system comprising: a drying device, wherein the condenser is constituted by at least two stages, and a circulating gas coming out of the condenser arranged at the most downstream side is cooled to a temperature lower than -30 ° C. Spray drying equipment. 2. The gas circulation type spray drying apparatus according to claim 1, wherein the condenser arranged at the most downstream side is a plate type heat exchanger or a plate type condenser.