JPH0683774B2 - Recovery method of inert organic liquid - Google Patents

Description

The present invention relates to a novel method for recovering vapor of an inert organic liquid by adsorption / desorption with an adsorbent.

[Conventional technology and problems]

As a process of heating and using an inert organic liquid, an article to be processed in which parts are arranged with solder interposed is brought into contact with vapor of the inert organic liquid, and the latent heat of the vapor melts the solder to perform soldering. Vapor-phase soldering process, thermal shock test to examine the thermal shock resistance of parts by alternately immersing the parts in heated high temperature inert organic liquid and low temperature inert organic liquid, and heated inert organic liquid For example, there is a leak test in which a hermetically sealed electronic component is dipped in to check the sealed state of the component. In these processes, in order to prevent leakage of vapor generated by heating the inert organic liquid, the vapor is recovered. For example, in the vapor phase soldering process, in order to melt the solder, an inert organic liquid having a boiling point of 200 ° C. or higher is heated to generate steam, but such steam is collected by a condenser using water as a refrigerant. Was done by.

However, in recent years, when vapor-phase soldering, deterioration due to heat of the article to be treated, strain, etc., has begun to be a problem, so low-melting solder has come to be used, and with this, the boiling point of the inert organic liquid is also increased. Those with a low boiling point of 200 ° C or less have come to be used. Therefore, in the above-described water cooling recovery method, the recovery rate of the vapor of the inert organic liquid is low, and a large amount of the inert organic liquid leaks.

Also, in the processes such as the thermal shock test and the leak test described above, an inert organic liquid having a relatively low boiling point may be used depending on the set temperature. It had the same problems as the phase soldering process.

The present inventors, as a result of repeated studies on a method of recovering such an inert organic liquid at a high recovery rate, by adsorbing and desorbing an unrecovered portion of the vapor of the inert organic liquid using an adsorbent, We have obtained the knowledge that the purpose can be achieved.

However, when desorbing the inert organic liquid from the adsorbent that has adsorbed the inert organic liquid, it is common to flow the desorption gas while heating the adsorbent to a high temperature near the boiling point of the liquid. However, there is a problem that heat is taken out by the gas. That is, the desorption gas generally adopted for increasing the desorption efficiency has an empty loading speed of 10 to 50 cm / sec, and when the desorption glass is supplied at such an empty loading speed, a large amount of heat is taken out by the desorption gas. Have the problem of being

[Means for solving problems]

The present inventors have conducted research to solve the above problems in the method of absorbing and desorbing the vapor of the above-mentioned inert organic liquid with an adsorbent and collecting the vapor. As a result, in the desorption of the inert organic liquid, by supplying the desorption gas to the adsorbent layer so that the empty flow rate is a descending flow of 5 cm / sec or less, the desorption gas has a high desorption rate, and The inventors have found that heat loss can be significantly reduced, and completed the present invention.

According to the present invention, a layer on which vapor of a fluorine-based inert organic liquid having a vapor density twice or more that of the desorption gas is adsorbed is heated and maintained at a temperature equal to or higher than the boiling point of the fluorine-inert organic liquid. In this state, the desorption gas was emptied into the adsorbent layer at a speed of 0.
005 ~ 5 cm / sec supplied as a descending flow, after desorbing the vapor of the fluorine-based inert organic liquid, cooling by desorption gas to condense the vapor of the fluorine-based inert organic liquid, inert It is a method of recovering an organic liquid.

In the present invention, the inert organic liquid to be recovered is
Although not particularly limited, it is particularly effective for a vapor density that is at least twice as large as the desorption gas.

Typical examples thereof include fluorine-based inert organic liquids such as perfluorotributylamine, perfluorotripentylamine, perfluoropolyether, and perfluoroanthracene.

Further, the adsorption of the vapor of the inert organic liquid may be carried out directly with the gas taken out from the apparatus, but in order to extend the breakthrough time of the adsorbent as much as possible, the gas is cooled in advance and the inert organic liquid is adsorbed. It is preferred to condense a portion of the liquid vapor.

The adsorbent used in the present invention is not particularly limited. Typical examples of adsorbents include activated carbon, molecular sieves, activated alumina, silica gel and the like. Among them, when the vapor is a vapor of a fluorine-based inert organic liquid, activated carbon is particularly preferably used. As the adsorption tower used for adsorption, a vertical adsorption tower or a horizontal adsorption tower is adopted, and as the adsorption method, known methods such as a fixed bed method, a moving bed method and a fluidized bed method tower are adopted without particular limitation. .

In the adsorption, the adsorption temperature is generally preferably 5 to 20 ° C. In the case of the vertical adsorption tower, it is preferable that the heat medium vapor is supplied from the lower side to the upper side. Further, it is preferable to adjust the cross-sectional area of the adsorption column, the packing density of the adsorbent, the amount of gas sucked from the device, etc. so that the empty column velocity of the gas in adsorption is about 10 to 50 cm / sec.

In the present invention, desorption of the inert organic liquid from the adsorbent, the layer consisting of the adsorbent, the empty velocity is 0.005 ~ 5 cm / sec,
It is important to carry out so that the downward flow is preferably 0.01 to 2 cm / sec. That is, in order to desorb the heating medium vapor adsorbed in the desorption layer, a high temperature of 150 ° C. or higher is generally required, and the heat loss becomes enormous according to the ordinary desorption method with a high empty space speed. In the present invention, by utilizing the large vapor density of the inert organic liquid, by flowing the desorption gas as a downward flow by utilizing the self-weight of the vapor at an extremely low empty space velocity, less heat loss, Fast desorption speed and
A desorption gas containing a vapor of an inert organic liquid at a high concentration can be obtained.

When the empty loading speed in the above desorption is slower than 0.005 cm / sec, the desorption speed does not increase sufficiently and the desorption process takes a long time. In addition, when the empty loading speed is faster than 5 cm / sec, not only the amount of heat taken out by the desorption gas increases, but also when the temperature of the adsorbent amount is adjusted by the internal heating method described later, the temperature becomes unstable and stable. It becomes difficult to perform the desorption. Further, when the flow of the desorption gas is an upward flow with respect to the adsorbent layer, if the desorption gas is caused to flow at the above-mentioned low empty loading speed, not only the non-uniform flow easily occurs, but also in the adsorbent layer. At this point, vapor recondensation occurs and the desorption rate decreases significantly.

In the present invention, the device used for desorption is not particularly limited as long as it has an adsorbent layer and can supply the desorption gas to the adsorption layer in a downward flow. For example, a vertical desorption tower provided with a fixed layer of adsorbent is commonly used. In this case, if the above-mentioned adsorption tower has such a structure, the adsorption tower may be used for desorption.

In the desorption, the desorption temperature varies depending on the boiling point of the inert organic liquid used and cannot be unconditionally limited. However, it is generally set to a temperature equal to or higher than the boiling point, preferably 10 to 50 ° C. higher than the boiling point. The method of heating the adsorbent to such a temperature is not particularly limited, but a method of heating the adsorption layer of the adsorption tower, a method of heating the supplied desorption gas, or a combination of both is generally used. Heating the adsorption layer is preferably performed by external heating or internal heating with a heat medium such as steam or a heater, and heating of the desorption gas is performed by heat exchange with a desorption gas containing vapor after desorption. .

As the above-mentioned desorption gas, a gas inert to the inert organic liquid and the adsorbent is used without particular limitation. Specifically, nitrogen, argon, steam, etc. are suitable.

The gas obtained by the above desorption is a desorption gas containing a vapor of an inert organic liquid at a high concentration, and such a gas may be cooled by a cooler to condense and recover the inert organic liquid. The waste gas after condensation is preferably purged after the remaining inert organic liquid vapor is adsorbed by the adsorbent.

The recovery method of the present invention is preferably carried out in combination with condensation by a cooler. For example, as an aspect of applying the recovery method of the present invention to the vapor phase soldering process, there is recovery of vapor of an inert organic liquid in a vapor phase soldering apparatus. That is, the gas containing the vapor of the inert organic liquid is sucked from the carry-in part and the take-out part of the object to be processed of the vapor phase soldering device for continuously supplying and soldering the object to be processed, and cooling the gas. After recovering a part of the vapor of the inert organic liquid, the remaining vapor of the inert organic liquid is recovered by the method of the present invention.

The vapor-phase soldering device is a vapor generation tank for heating an inert organic liquid to generate a heat medium vapor, a cavity for forming a vapor phase by the heat medium vapor, and carrying an article to be treated into the cavity. Generally, a unit having a carry-in unit and a take-out unit for taking out and a means for transferring an article to be processed is used.

As a method of collecting the inert organic liquid by condensing the vapor of the inert organic liquid by cooling, a method using a known condenser is adopted without particular limitation. Generally 0
It is preferable to cool to a temperature range above 10 ° C and below 10 ° C for condensation. In this case, water is generally used as the refrigerant for the condenser.

In the present invention, the inert organic liquid recovered by the above-mentioned condensation and adsorption / desorption may be purified if necessary and circulated in the vapor generation tank of the vapor phase soldering apparatus.

FIG. 1 shows a typical embodiment of an apparatus for applying the method of the present invention to a vapor phase soldering process.

An inert organic liquid is supplied to the vapor generating tank 4 of the vapor phase soldering device 1, and the heater 5 heats the inert organic liquid to generate vapor of the inert organic liquid, thereby forming a heat medium vapor phase.

The article 2 to be treated enters the apparatus from the carry-in section 9 by the conveyor 3 and is soldered in the heat medium vapor phase and then the take-out section 10
Taken out more.

On the other hand, the inert organic liquid vapor leaking toward the carry-in section 9a and the take-out section 10 of the apparatus is sucked from the lines 22-a and 22b, sent to the primary cooler 7 and cooled, and then the secondary cooler. The liquid is separated by the bubble separator 20 further cooled in 8 and sent to the adsorption tower through the line 18.

The inert organic liquid condensed and recovered in the primary cooler 7 and the secondary cooler 8 is sent to the storage tank 11.

The adsorption tower is operated in two series, 12-a and 12-b.

If one 12-a is used for adsorption, the valve 16-a and
14-a may be opened and valves 16-b and 14-b may be closed.

The waste gas 21 after the adsorption treatment may be purged 12, but may be recycled to the carry-in section 9 and the take-out section 10 if necessary.

At this time, the valves 13-a and 15-a are closed.

If the adsorption tower 12-b is saturated,
Desorption is performed during adsorption with -a.

In this case valves 13-b and 15-b are open and valve 14-b
And 16-b are closed.

The desorption gas 6 is heat-exchanged with the desorbed gas and preheated, and then supplied from the upper part of the adsorption tower 12-b through the post line 17 and taken out from the lower part. A heater or steam (not shown) for heating is generally provided in the adsorption tower.

The desorbed gas may be obtained by cooling the desorbed gas through the line 19 to the heat exchanger 23 and then cooled by the primary cooler 7 and the secondary cooler 8 to condense the inert organic liquid.

When recycling the desorption gas, the amount of gas used can be reduced by mixing the gas discharged from the primary cooler 7 with the desorption gas 6.

As described above, the mode of applying the method of the present invention to the vapor phase soldering process has been described.
The same can be applied to a process of heating an inert organic liquid such as a leak test.

〔effect〕

According to the method of the present invention, it is possible to recover the vapor of the inert organic liquid by the adsorbent with high recovery efficiency,
In the desorption, a gas having a high desorption rate, a small heat loss, and a high concentration of a vapor of an inert organic liquid can be obtained, and the desorption can be performed extremely efficiently.

(Example) The recovery method of the present invention was carried out in the process shown in FIG.

Perfluorotributylamine (hereinafter referred to as pfTBA) having a boiling point of 175 ° C. was used as the inert organic liquid. The adsorption tower was a fixed bed vertical adsorption tower, and granular activated carbon (pellets with an average particle diameter of 2 mm) was used as an adsorbent. The adsorption operation was performed as follows.

During the soldering operation, the above pfTBA vapor that diffuses to the substrate inlet and outlet was extracted from the lines 22-a and 22-b to the adsorption line by a blower (not shown).

The extracted steam is cooled from 60 ° C to 25 ° C by the primary cooler 7, the condensate is stored in the tank 11, and the exhaust gas is further cooled by the secondary cooler 8.
After cooling from 25 ° C. to 5 ° C. at 5 ° C. to condense the supersaturated pfTBA vapor, the condensate was introduced into the tank 11 through the gas-liquid separator 20 and the exhaust gas was introduced into the adsorption tower through the line 18.

At that time, the ptTBA concentration at the inlet of the adsorption tower was 1.2 mg / l, but it was below the detection limit (0.005 mg / l) on the outlet side.

In this state, after operating for about 24 hours until just before the activated carbon passed through, the adsorption tower was switched, and the desorption operation was performed on the broken adsorption tower. Nitrogen gas was used as the desorption gas 6.

The nitrogen gas at room temperature was introduced into the upper part of the desorption column after heat exchange with the desorption column exit gas. The temperature of the desorption inlet gas was raised to 50 ° C.

The desorption column was maintained at 200 ° C by the internal heating method, and the desorption gas was flowed through the adsorbent layer at a blanking speed of 0.05 cm / sec so as to descend and then extracted to the lower part of the column. The outlet gas concentration at that time was 7.6 g / l. The outlet gas of the desorption column was the nitrogen gas introduced from the top and the desorbed pfTBA vapor, which was introduced into the heat exchanger 23 and exchanged heat with the inlet gas. What had a heat exchanger inlet temperature of 150 ° C was cooled to 50 ° C. This exhaust gas was introduced into the primary cooler 7, mixed with the gas from the lines 22-a and 22-b, cooled, and discharged from the secondary cooler through the adsorption tower.

In the desorption operation, the time required for 90% desorption was 12 hours. In addition, the power required to keep the adsorption layer of the desorption column at 200 ° C. by the above operation was 44 kw, and each of the secondary coolers was 3.5 kw.

(Comparative Example 1) When the desorption gas inlet was supplied to the lower part of the desorption column under the same conditions as in Example 1, the desorption gas outlet concentration was 5.
It was 3 g / l, and it took 16 hours for 90% desorption.

The heating power required for the desorption tower is 42.5kw and the cooling power is 3.45kw.
Met.

(Comparative Example 2) The desorption gas inlet is set to the lower part of the desorption tower, and the empty loading speed in the board is set to 20.
When the conditions were exactly the same as in Example 1 except that cm / sec was used, the outlet concentration of the desorption gas was 0.038 g / l, and the time required for 90% desorption was 10 hours. The heating power required for the desorption tower is 52
It became kw and the electric power of the cooler became 8.1kw.

(Comparative Example 3) The outlet gas concentration was 0.06 g / l and the temperature was 120 ° C when operated under exactly the same conditions except that the idle speed in Example 1 was set to 15 cm / sec.
Met. The time required for 90% desorption was 11 hours.

Therefore, the heating power for the desorption tower was 48kw, and the power required for the secondary cooler increased to 6.9kw.

(Comparative Example 4) The outlet gas concentration and the temperature were 8.6 g / l when operated at exactly the same speed except that the idle speed in Example 1 was set to 0.001 cm / sec.
The temperature was 170 ° C, but the time required for 90% desorption was 25 hours. The heating power of the desorption tower was 42kw and the power of the cooler was 3.4kw.

[Brief description of drawings]

FIG. 1 shows a typical embodiment of an apparatus for applying the method of the present invention to a vapor phase soldering process. In the figure, 1 is a vapor-phase soldering device, 2 is an article to be treated, 3 is a conveyor, 4 is a steam generation tank, 5 is a heater, 6
Is a desorption gas, 7 and 8 are coolers, 9 is a carry-in section, 10 is a take-out section, 11 is a storage tank, 12-a and 12-b are adsorption towers, 13-a, 13-b and 14
a, 14b, 15-a, 15-b, 16-a and 16-b are valves, 17, 18, 19, 2
2-a and 22-b are lines, 20 is a gas phase liquid separator, 21 is waste gas, and 23 is a heat exchanger.

Claims (1)

[Claims] 1. A layer in which a vapor of a fluorine-based inert organic liquid having a vapor density twice or more that of a desorption gas is adsorbed is heated and maintained at a temperature equal to or higher than the boiling point of the fluorine-inert organic liquid. In this state, the desorption gas was added to the layer of the adsorbent at a superficial velocity.
Supplying as a downward flow of 0.005 to 5 cm / sec, desorbing the vapor of the fluorine-based inert organic liquid, cooling the desorption gas, and condensing the vapor of the fluorine-based inert organic liquid. Organic liquid recovery method