JPS58204334A - Method and apparatus for generating aerosol - Google Patents

Abstract

PURPOSE:To generate an aerosol of desired density, which makes atmospheric dust as a core and has a uniform particle diameter, without giving out a stench, by heating mixed gas of inert gas and a gasified aerosol generating liquid, and thereafter, cooling it in the air. CONSTITUTION:Gaseous CO2 A is supplied into a case 5 from a connecting port 11 having a valve 11a, from an inert gas cylinder 12. Gas A reaches a mixing nozzle 10 through a feed pipe 8, a valve 8a and a flow meter 9. On the other hand, gas A which goes into a tank 6 a dioctyl phthalate through a feed pipe 7 transfers this liquid B by pressure by a necessary quantity to the mixing nozzle 10 through a feed pipe 13, a valve 13a and a flow meter 14, and gasifies it by means of jet. In this state, the gas A and the liquid B are mixed by a necessary mixing ratio, are heated to 300 degrees or above by a heating wire 15a in a heating tube 15, and become high temperature vapor D without being oxidized. The vapor D is discharged into the air through an air port 17 from a nozzle 18, and an aerosol E is generated by a condensing operation which makes atmospheric dust as a core.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for generating an aerosol of dioctyl phthalate, which are suitable for use in verification tests of air leakage at the mounting portion of an air filter and collection efficiency.

At nuclear power facilities, radioactive dust generated in the installation environment is captured and removed using high-performance air filters, and then released to the outside world to prevent radioactive hazards from occurring. Similar measures are also taken at research facilities, such as genetic recombination experimental facilities, where the release of air in the research environment may have a significant impact on living organisms. By the way, in this case, air leaks due to poor installation of the air filter, or emissions of harmful substances in excess of the specified value due to the use of an air filter with a collection rate below the specified value, will have an extremely large and irreversible impact on the outside world. This should never happen.

Therefore, careful work is required during installation, and at the same time, after construction is complete, an aerosol generator is generally used to add aerosol, for example, dioctyl phthalate (DOP), to the upstream side of the air filter to generate a concentration difference between the upstream and downstream sides. Field verification tests are required to determine air leakage and collection efficiency. However, the test results are extremely influenced by the performance of the aerosol generator, and the aerosol of a certain particle size, which is required to measure the collection rate of the air field targeted by the aerosol generator, is extremely important. As long as the product does not have the ability to stably supply the product at a constant concentration, there can be no guarantee of sufficient performance, and verification tests will be futile. In addition, the amount of air that filters can process is increasing year by year, and the number of air filter units used is also increasing, but this requires the generation of a large amount of aerosol, and the generation device is also large. I have no choice but to do so. However, since the aerosol generator must be transported to the installation site and used, it is required to be small and capable of generating a large amount of aerosol, and its realization is a means of preventing inappropriate verification tests due to insufficient concentration. It also becomes.

However, conventionally used aerosol generators cannot be said to satisfy the above requirements.

For example, conventionally, as shown in the partial sectional view shown in FIG.
) Air is blown into the dioctyl phthalate liquid (2) in the tank (2) through one to several nozzles (3), and the thioctylphthalate (2) There are some that eject it as atomized particles.

However, in this method, the amount of aerosol generated in one air blowing amount is 200 to r'00 μg, which is small, and is not suitable for verification tests when 10 or more air filter units of standard size are used. , 100 as it is now
Application to environments with large spaces where more than one air fill unit is used is simply not possible. In addition, in devices like this that generate particles based on the force of air being blown into the air, the particle size is widely dispersed, such as a high-performance air filter, which guarantees a collection rate for aerosols with a particle size of 05 μm. However, there is a drawback in that it is difficult to guarantee sufficient performance.

Another type of device is a so-called thermal generation monodisperse aerosol generator, which heats dioctyl phthalate liquid to generate steam, cools it, and generates aerosol through condensation with atmospheric dust as the core. Since the aerosol particle size depends on the core particle concentration and has little dependence on the dispersion of the core particles, if the difference between the heating temperature and the cooling temperature is constant, an aerosol with a uniform particle size can be obtained. can be obtained stably. Further, for example, by increasing the evaporation area and increasing the heating temperature, a large amount of aerosol can be generated, which has the advantage of being able to sufficiently process even when a large amount of air is to be treated.

However, if you try to create an aerosol generator that can handle an air filter that processes a large amount of air using this method,
The disadvantage is that not only is the device large and cannot be made portable, but it also requires a large amount of electricity for heating, a large amount of cooling water for cooling, or a large amount of electricity for cooling. There is. In addition, it is difficult to control the temperature using the method of directly heating a large amount of dioctyl phthalate liquid.
Not only is it difficult to generate an aerosol with a desired particle size and a constant concentration, but it is also difficult to control the size and concentration.

In addition to this, a major drawback of this device is that the dioctyl phthalate liquid (at a boiling point of 216°C and 5g+++Hg) is heated in air at a high temperature of around 200°C, which causes the dioctyl phthalate liquid to oxidize and cause severe damage. This produces a foul odor that is strongly absorbed by the dry cough filter tested. As a result, during actual use, this strange odor fills the room and gives a great discomfort, and from this point alone, it is completely unsuitable for verification tests. For this reason, it has been difficult to obtain an aerosol generating device that is portable and capable of stably supplying aerosol having a required constant particle size at a desired concentration.

The present invention aims to provide an aerosol generating device that can satisfy the above requirements, and the details thereof will be explained below with reference to the drawings.

The present invention has been made by applying the above-mentioned principle of generating a monodisperse type aerosol called the heat generation type, and its features are as follows. That is, in the present invention, 2
A mixed gas of an inert gas such as carbon oxide (C02) or nitrogen (N2) and a gasified aerosol generating liquid such as dioctyl phthalate (DOP) gas produced by, for example, an injection nozzle is heated to a high temperature such as 500°C to 350°C. It is characterized by the fact that by heating it at a temperature of °C and then releasing it into the atmosphere and cooling it, it causes condensation and self-condensation with atmospheric dust as the core, and generates an aerosol of dioctyl phthalate. It is designed to provide various excellent effects such as the following.
That is, the most significant effect is that the oxidation of the dioctyl phthalate gas is prevented by heating it in an inert gas atmosphere, thereby preventing the occurrence of the strong odor that occurs in conventional devices.

Secondly, by adopting a heating method in an inert gas atmosphere, it is possible to heat the mixed gas that is continuously fed in at a high temperature of 300°C or more, which is much higher than conventional methods, and it is possible to generate a large amount of aerosol with a small device. This was done so that they could be obtained. Thirdly, by heating the mixed gas, the heating efficiency is improved compared to the conventional case where the dioctyl phthalate liquid is placed in a tank and heated, thereby reducing the heating power. Fourth, by releasing the gas into the atmosphere at a temperature far lower than the heating temperature (for example, 20° C.) and cooling and condensing it, the power required for cooling is completely eliminated, thereby reducing the size of the device. Fifth, when the proportion of dioctyl phthalate gas in the mixed gas is small, the particle size of the aerosol is small, and conversely, when the proportion is large, the particle size becomes small. By adjusting the flow rate of the inert gas and changing the mixing ratio, it is possible to easily obtain an aerosol with a desired uniform particle size. In addition, since the number of raw aerosol particles, that is, the concentration of dioctyl phthalate gas, is determined by the amount of mixed gas, in order to obtain aerosol with the desired particle size, the mixing ratio must be kept constant. By increasing the amount, the amount of aerosol generated is increased,
Also, by making it small, the concentration can be easily adjusted, and from the above, the dioctyl phthalate aerosol generator is small and can stably supply aerosol of the desired concentration with the required constant particle size. It has been made possible to provide the following.

Next, embodiments of the present invention described above will be described. FIG. 2 is a system diagram showing the configuration of the generator of the present invention, and FIG. 5 is a partial sectional view showing an example of use.
The case contains the following parts: (6) is a tank for dioctyl phthalate liquid, (7) is an inert gas supply pipe for liquid pressure feeding, (7 is its supply pulp, (8) is an inert gas supply pipe for adjusting concentration etc., (8α ) is its feeding pulp,
(9) is an inert gas supply pipe (7) with an inert gas flow meter opened, and one end connected to a mixing nozzle (1) through the flow meter (9) for adjusting concentration, etc. The other end of each inert gas supply pipe (8) is connected to a connection port (1) having a pulp (11α) provided so as to protrude outside the case (5).
1). During use, for example, CO□ gas A is supplied from an inert gas cylinder (12) connected to this. (16) is a dioctyl phthalate liquid supply pipe;
(13 is the supply pulp, (1 is the flow meter,
The end of the supply pipe (13) is immersed in the dioctyl phthalate liquid in the tank (6) and opened, and the other end is connected to the mixing nozzle (1) via a flow meter (10, etc.). .

Then, by blowing into the CO2 gas through the supply pipe (7), the required amount of dioctyl phthalate liquid B is forced into the mixing nozzle (1) and gasified by injection.
9) and is mixed with C02 gas A supplied in the required amount by the supply pipe (8) at the required mixing ratio.

(15) is a mixed gas heating tube, (i 5g) is a heating wire provided spirally on its inner peripheral surface, and the mixed gas is fed through the mixing nozzle (1o) at a high temperature of 500°C or more by a power source (not shown). C to produce high-temperature vapor of dioctyl phthalate that will not be oxidized. (16) is an aerosol generation tube, (17) is an air port, and (18) is a steam release nozzle, which discharges high-temperature steam into the atmosphere and cools it, and the resulting air is released from the air port (17). Aerosol E of dioctyl phthalate is created by condensation and self-condensation with dust as the nucleus. Then, this aerosol is passed through the aerosol supply pipe (20) (see Fig. 6), which is connected to the aerosol generation pipe (1) (see Fig. 6), one end of which passes through the case (5) and forms the connection port (19). As shown in the figure, the dioctyl phthalate liquid pulp is supplied to the upstream side of the air filter unit group (22) installed in the duct (2).
1 adjustment and inert gas pulp (F3IOLL
1. By adjusting with the flow meter (9). By adjusting the amount of mixed gas and the mixing ratio, an aerosol of a desired concentration with a desired uniform particle size can be obtained, facilitating the performance of valid verification tests.

Although the present invention has been explained above, in order to obtain an aerosol with a large particle size, a long growth time is required.
Since the ring-forming environment is likely to change during this period, the particle size may become non-uniform. However, this difficulty can be solved by the following means.

One means for this is to construct the aerosol generating tube (16) described above with reference to FIG. 2 as a double tube as shown in the cross-sectional view of FIG. 4, and to provide a return conduit (26) on the outer periphery. Then connect one end to the aerosol discharge port (the two communicate with the aerosol suction port).
25), and the other end is an aerosol return port (2) which opens on the downstream side of the discharge nozzle (1B), and due to the pressure difference between the installation part side of the steam discharge nozzle (18) and the aerosol discharge port (2 side), The generated aerosol is sent to the outer circumferential return path (25)
The structure is such that the steam is returned to the front part of the steam discharge nozzle (18) via the steam discharge nozzle (18). That is, a part of the primary aerosol produced by the steam discharge nozzle (18) is returned to the center of the pipe in front of the steam discharge nozzle (18) through the pipe (23). These particles are condensed and grown by the steam discharged from the steam discharge nozzle (18), flow through the center of the tube, and are discharged to the outside world. In addition, a part of the particles returns to the original state and grows, and this process is then repeated to grow particles through a multi-stage operation. Another proposal is to provide a plurality of steam discharge nozzles (1B) in series inside the aerosol generating tube (16) as shown in the cross-sectional view of FIG.
First, the first nozzle (1stL) creates a primary aerosol with particles in the atmosphere as its core. and the next nozzle (i
sb) made by the previous nozzle (18g),
In addition, by further growing the grown particles as a nucleus and performing the same growth operation using the next nozzle (18n), the particle size is made uniform, and the particle size of the aerosol particles is made uniform. .

Next, experimental results of the present invention will be explained. According to the device of the present invention, it is possible to obtain an aerosol concentration of approximately 1 g from air 1, and the amount of air released at this time is 50 tAnin.
I was able to do this. Therefore, the amount of aerosol generated per minute is 50 g/rnin.

On the other hand, in the conventional commercially available generator shown in FIG. 1, the aerosol concentration is 5 mFv/l and the emitted air amount is 85
t/min, and the amount of aerosol generated in this case is C
L 45 g/min. It can be seen from this that the generator of the present invention is capable of generating an aerosol of significantly higher concentrations of dioctyl phthalate. Moreover, as a result of prototype production, it was confirmed that a portable generator could be realized.

Furthermore, Figure 6 shows a particle size of 0.3μ (median diameter) generated using the single tube aerosol generation tube shown in Figure 3 and a double tube structure aerosol generation tube in the generator of the present invention. These are the results of comparing aerosol particle size distributions plotted on log probability paper.

As is clear from the figure, the geometric standard deviation σg with respect to the median diameter of A, which shows the case where an aerosol generating tube with a double tube structure is used.
is 1.4, whereas that of B, which shows the case of a single tube aerosol generating tube, is 1.52, which is 0.1 or more smaller, and it is possible to obtain a result closer to C, which shows monodispersity shown in the figure. I understand.

Note that although the generation of an aerosol of dioctyl phthalate has been described above, it can also be used to generate an aerosol of other liquids.

As is clear from the above explanation, according to the present invention, an aerosol of dioctyl phthalate having a uniform particle size and a desired concentration can be generated using a small device with low operating costs. It can be used not only for factory inspections of air filters, but also for on-site verification tests of air leakage and collection rate at the air filter installation part, and has great practical effects.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view showing an example of a conventional device, Fig. 2 is a system diagram showing an embodiment of the present invention, Fig. 5 is a partial sectional view showing an example of its use, Figs. 6 is a cross-sectional view showing the structure of an aerosol generating tube for promoting uniformity of aerosol particle size, and FIG. 6 is a diagram showing its particle size distribution. (1)...tank, (2)...dioctyl phthalate liquid, (5)...air blowing nozzle, (4)...porous plate, (5)...case, (6)... ...Dioctyl phthalate liquid tank, (7)...Inert gas supply pipe, (7+z)...Pulp, (8)...Inert gas supply pipe for concentration adjustment, (8... ) Kurup, (9)...flow meter, (10)...mixing nozzle, (11)...inert gas cylinder connection port, (
12)...To inert gas cylinder, (13)...Mixed gas supply pipe, (13cL)...Valve, (14)
...Flowmeter, A...Co2 gas, B...Dioctyl phthalate liquid, C...Mixed gas of dioctyl phthalate and Co2 gas, D...Steam, E
...Aerosol, (15) ...Heating tube, (
15α)...Heating source, (16)...Aerosol generation tube, (17)...Air port, (is)...Steam release nozzle, (19)...Aerosol supply pipe connection port, (20)...Aerosol supply pipe, (21)
... duct, (22) ... air filter unit group,
(25)...Outer circumference return path, (24)...Aerosol discharge port, (25)...Suction port, (26)...
Aerosol return port. Patent Applicant Oshizoku Research Institute Co., Ltd. Agent Patent Attorney Otsuka 1 person from outside the university

Claims (1)

[Scope of Claims] (1) An aerosol generation method characterized by heating a mixed gas of an inert gas and an aerosol-generating liquid, cooling the vapor, and obtaining an aerosol by condensation using atmospheric dust as a nucleus. (2) Aerosol generation device 0 equipped with a mixed gas generation mechanism of inert gas and aerosol generating liquid, each equipped with a flow rate adjustment mechanism, a heating mechanism for the mixed gas, and an aerosol generation mechanism that releases the generated steam into the atmosphere. (5) The aerosol generation mechanism according to claim 2 is placed on the aerosol discharge port side of a double pipe having an air port at one end and an aerosol discharge port at the other end, the outer circumference of which serves as a return path; An aerosol suction port communicating with one end of the return path is provided, an aerosin return port communicating with the other end of the return path is provided on the air port side, and a vapor of heated mixed gas is provided on the upstream side of the aerosol return port. An aerosol generator characterized by having a configuration including a discharge nozzle. (4) The aerosol generation mechanism according to claim 2 has a structure in which a plurality of steam discharge nozzles are arranged in series in a single pipe having an air port at one end and an aerosol discharge port at the other end. An aerosol generator characterized by: