JPH01217176A - Elimination of solvent from solid - Google Patents

Abstract

PURPOSE:To eliminate solvent from a solid at a low temperature and in a short time efficiently by heating the solvent-containing solid, loaded in a drying chamber, to a prescribed temperature and by supplying steam thereto while the pressure in the drying chamber is maintained below the saturated water- vapor pressure at the prescribed temperature. CONSTITUTION:A material 11 subjected to drying which consists of a powder protein containing 6,000ppm ethanol is loaded in a drying chamber 1; water for heating whose temperature is prescribed at a point a little lower than the critical allowable temperature of the material 11 subjected to drying, for example, at 60 deg.C, is supplied into a heating jacket 3 and into a stirrer 5 by inlets 3, 7; by rotating the stirrer 5 the material 11 is preheated through the stirring and the pressure is reduced to 30Torr, a level considerably lower than the saturated water-vapor pressure at the preheating temperature by means of a vacuum pump 17; then, control valves are opened to supply superheated water vapor at 2kg/cm<2> by inlets 12, 12a. Through this procedure more than 70% of the solvent contained in the material 11 can be eliminated in about 2hours.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for drying and removing a solvent contained in a solid using a drying device.

[Prior Art] When a solvent such as ethanol contained in a solid is removed by drying using a drying device, molecular bonding and absorption between the solid component and the solvent occur in a region where the content of the solvent is extremely low. The influence of the equilibrium content due to the properties of solids cannot be ignored, and depending on the combination of the substances constituting the solid and the solvent, it is extremely difficult to remove trace amounts of residual solvent.

Conventionally, when removing residual solvent in a solid using the normal pressure drying method, the temperature of the solid charged into the drying equipment (hereinafter referred to as the material to be dried) is raised to close to the limit allowable temperature that is restricted by its quality. The sample was dried for a long time (for example, 5 to 6 hours), but if the solvent content still did not decrease to the target value, the sample was further dried by using a vacuum dryer to lower the pressure as much as possible.

[Problem to be solved by the invention] Drying of pharmaceuticals and other materials with low allowable temperatures requires an extremely long time (e.g., 20 hours or more), and depending on the material, it is necessary to reduce the solvent content to the order of PPm. There are many cases where this is impossible.

The present invention was made to solve the above problems, and
The purpose of this method is to realize a method that can efficiently remove solvents from solids in a short period of time.

[Means for Solving the Problems] A method for removing a solvent contained in a solid according to the present invention heats a drying chamber of a drying device and a solid containing a solvent charged in the drying chamber to a predetermined temperature, and then removes the solvent from the drying chamber. It is characterized by supplying water vapor to the drying chamber while maintaining the pressure of the drying chamber below the saturated water vapor pressure at that temperature.

[Embodiments of the Invention] The present invention is designed to dry and remove the solvent by sending water vapor into the drying chamber of a drying device and bringing the material to be dried into contact with the atmosphere. When the temperature is 100° C. or higher, the pressure inside the drying chamber can be maintained at normal pressure for operation.

However, if the material to be dried, such as pharmaceuticals or other materials that are sensitive to heat, can only be heated to a temperature of several tens of degrees Celsius, a drying device such as a conduction heat transfer type vacuum stirring dryer may be used to bring the material to be dried below the allowable temperature. The drying chamber is heated to a certain temperature, and superheated steam is sent into the drying chamber while maintaining the drying chamber at a pressure lower than the saturated steam pressure at the temperature of the material to be dried using a vacuum pump, condenser, etc. be. That is, the present invention incorporates a new method that can be called superheated steam drying under reduced pressure. The pressure inside the drying chamber was kept below the saturated water vapor pressure at the temperature of the material to be dried at that time, in order to avoid condensation of water vapor, and because the desolvation effect is generally greater when the pressure is reduced.

By the way, the reason why the solvent is easily removed by bringing superheated steam and a solid containing a solvent into contact is that in the presence of superheated steam, the intermolecular bonding force between the solid and the solvent, the adsorption equilibrium liquid content, or the solid This is thought to be due to a decrease in intramolecular diffusion resistance. In addition, in recent years, it has been discovered that superheated steam drying has a great bactericidal effect, and that in soybeans and the like, the n-odor components change due to the reaction and the drying becomes odorless.

The inventors of the present invention have suspected that in the presence of superheated steam, the efficiency and rate of removal of solvents contained in solids may be altered due to any of the reasons mentioned above, and furthermore, the removal efficiency and speed of solvents contained in solids may be modified in the presence of superheated steam. As a result of various experiments, we focused on the possibility that the speed of solvent removal could be accelerated by creating a low-temperature, reduced-pressure, superheated steam-like atmosphere inside the vacuum dryer as an application to heating materials. This led to the completion of the present invention.

FIG. 1 is a schematic diagram showing an example of a conductive heat transfer type vacuum agitation drying apparatus for implementing the present invention. In the figure, (+) is a cylindrical drying chamber, with heating jackets (2) on the peripheral and side walls.
is provided, and the hot water supplied from population (3) is
It passes through the heating jacket (2) and is discharged from the outlet (4). (5) is a stirrer disposed in the drying chamber (1), rotatably supported on the side wall via a bearing, and driven to rotate in the direction of the arrow by a drive source (not shown) such as a motor. (6)
is a rotary joint installed at one end of the stirrer (5), which connects the population (7) of hot water circulating inside the stirrer (5) and the outlet (
8) are connected. (9) is the input port for the material to be dried (11), (lO) is the outlet for the dried product, (12),
(12a) is a water vapor supply port that opens into the drying chamber (1) via a control valve. (13) has one end in the drying room (1)
It is a condenser that opens inward, and the other end is connected to the flocculation liquid storage tank (16) via a valve. (14) is the cooling water inlet, (15) is the outlet, (17) is the vacuum pump, (I
8) is a pressure gauge.

Next, an embodiment of the present invention using the drying apparatus as described above will be described. In addition, the drying chamber (1) of this drying device
The internal volume is 50g1, and the total heat transfer area is 1. In OM, the material to be dried (11) is 12 kg of protein powder, the solvent contained before drying is approximately 6000 PPm of ethanol, and the limit allowable temperature is approximately 65°C.
Met.

First, the material to be dried (
11). Next, the temperature of the heated hot water is set to 60°C, which is slightly lower than the limit allowable temperature (65°C) of the material to be dried (11).
heating jacket (2) from the inlets (3) and (7).
) and the stirrer (5) with hot water. and a stirrer (
5) was rotated to stir the material to be dried +4 (11), and the material to be dried (11) was preheated until the temperature of the material to be dried (11) reached 58 to 59°C. Next, the vacuum pump (17) lowers the pressure in the drying chamber (1) to the saturated water vapor pressure at this temperature (approximately 150 T
A vacuum of 30 Torr, which is significantly lower than

This state continued for 2 hours as shown in Figure 2, and a part of the material to be dried (11) was sampled every hour to measure the content of ethanol in the material to be dried (11). It didn't change. Next, increase the pressure inside the drying chamber (1) to 3
While maintaining the pressure at 0 Torr, open the control valve and transfer 2 kg/c- from the steam supply ports (12) and (12a).
When superheated steam of 1 kg/hr was supplied for 1 hour,
The ethanol content decreased slightly.

Then, when the control valve was adjusted and superheated steam of 2 kg/c- was supplied at 5 kg/hr for 45 minutes, the ethanol content was significantly reduced to about 2500 PPl11.
It became.

Next, when the regulating valve was closed and the supply of superheated steam was stopped for 30 minutes, the methanol content only slightly decreased. When the regulating valve was opened again and 2 kg/11" superheated steam was supplied at 4 kg/hr for 45 minutes, the ethanol content further decreased to about 1500 PPm.

As is clear from the above example, simply drying the material to be dried (1) hardly removes the solvent contained therein, but by blowing superheated steam into the material to be dried (11), this can be removed. It was found that 60% or more of the contained fine solvent was removed in about 1 hour and 70% or more in about 2 hours.

The solvent removed from the material to be dried (11) as described above is evaporated and led to the condenser (13), and then cooled to become a liquid and stored in the flocculation liquid storage tank (16).

In the above description, the drying apparatus shown in FIG. 1 is used to carry out the present invention, but it goes without saying that drying apparatuses having other structures may also be used.

[Effects of the Invention] As is clear from the above description, the present invention is capable of drying a solid containing a solvent by contacting it with superheated steam.
Since the solvent can be removed very efficiently at low temperatures and in a short time using a simple device, it is extremely effective in removing solvents from pharmaceuticals and other solid materials that require a reduction in residual solvent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an example of a drying apparatus for implementing the present invention, and FIG. 2 is a diagram showing experimental results of the present invention. 1: Drying room, 2: Heating jacket, 5: Stirrer, llz
12.12a: Steam supply port, 13: Condenser, 17: Vacuum pump.

Claims (1)

[Claims] A method for removing a solvent contained in a solid by drying it using a drying device, comprising: heating a drying chamber of the drying device and a solid containing a solvent charged in the drying chamber to a predetermined temperature; A method for removing a solvent contained in a solid, comprising supplying water vapor to the drying chamber while maintaining the pressure of the drying chamber below the saturated steam pressure at the temperature.