JPS62132523A - Method and device for adsorbing and removing gaseous halogenohydrocarbon - Google Patents

Abstract

PURPOSE:To efficiently adsorb and remove gaseous halogenohydrocarbon from a gaseous mixture by dry-treating the gaseous mixture before the adsorption treatment due to activated carbon and regulating the relative humidity to a specified value or below. CONSTITUTION:After sending a gaseous mixture G contg. gaseous halogenohydrocarbon to a dehumidifier 2a packed with a drying agent and drying it herein till relative humidity is made to <=50%, it is sent to an adsorption tower 1a packed with activated carbon to remove gaseous halogenohydrocarbon and discharged to the outside of a system as purified gas. When the adsorption amount of water content in the inside of the dehumidifier 2a is saturated and drying capacity is reduced, the drying agent is regenerated by changing over an adsorption removal line L to a dehumidifier 2b side and sending hot air into the dehumidifier 2a through the regeneration line Lb of the drying agent. The gaseous mixture is continuously dried by repeating such the switching of such a valve. When the absorption tower 1a reaches nearly a saturated state, the introduction line of dry gas is changed over to the adsorption tower 1b side and the gas for desorption is sent to the adsorption tower 1a side through the regeneration line La of the absorbent to regenerate activated carbon.

Description

[Detailed description of the invention] [Field of industrial application] From the mixed gas to the halogenated hydrocarbon gas (i, H full)
The present invention relates to a method and apparatus capable of efficiently adsorbing and removing Ha 1-CH gas (hereinafter referred to as Ha 1-CH gas).

[Prior Art] In industries that handle organic solvents, health problems caused by volatile solvents to workers are often a problem. For this reason, in recent years, when constructing a building that handles organic solvents, it has become mandatory to be equipped with exhaust ducts, and it has also been requested to install solvent adsorption and removal equipment to prevent the dissipation of solvent vapor into the atmosphere.

The most widely used adsorbent for solvent adsorption and removal is activated carbon.1. Normally, two or more adsorption towers installed side by side are filled with activated carbon, and adsorption and desorption regeneration are alternately repeated by valve operation, thereby continuously adsorbing and removing the solvent.

[Problems to be solved by the invention] However, Ha 1-CH gas with a low boiling point (particularly a boiling point of 100°C or less) such as Freon (trade name, manufactured by DuPont, USA), methylene chloride, carbon tetrachloride, chloroform, etc. has poor adsorption to adsorbents, and many Ha 1-CH
There is a problem that the gas is released without being adsorbed, causing pollution of the working atmosphere and air.

In other words, Hal-CH gas as mentioned above has a wide range of uses as a refrigerant, solvent, extractant, aerosol spray agent, etc., and has the advantage of not being flammable, so it can be used in a wide range of applications. However, since it is highly volatile, it tends to pollute the atmosphere, and its poor adsorption to various adsorbents makes it difficult to remove it.

Under such circumstances, the present invention seeks to provide a method and apparatus capable of efficiently adsorbing and removing Ha 1-CH gas from a mixed gas containing Ha 1-CH gas.

C. Means for Solving Problems] The configuration of the adsorption removal method according to the present invention is such that in the method of adsorbing and removing Hal-CH gas in a mixed gas containing Hal-CH gas using activated carbon, prior to the adsorption treatment, The gist is that the mixed gas is subjected to a drying process to keep the relative humidity at 50% or less. The gist of the structure of the adsorption removal equipment according to the present invention is that a dehumidifier is provided in the mixed gas introduction line to the adsorption tower filled with activated carbon.

[Function] As is well known, Hal-CH gas is difficult to adsorb and remove using an adsorbent, and this tendency is no exception even when activated carbon, which has excellent adsorption power, is used as an adsorbent.

Therefore, while various experiments were repeated to clarify the reason why Mal-CH gas is difficult to be adsorbed by activated carbon, the following facts became clear. That is, activated carbon has an excellent ability to adsorb moisture, and moisture and Hal-CH gas are antagonistic to each other as far as activated carbon adsorption is concerned. Moreover, there is a general tendency that water is more easily adsorbed. Therefore, once moisture is adsorbed on activated carbon, not only does the activated carbon's adsorption ability for Hat-CH gas decrease, but also the moisture and H
Hal-CH gas has poor affinity for at-CH gas.
The adsorption capacity for gas becomes even poorer, and Ha 1-C
The purpose of adsorption and removal of H gas cannot be achieved. In particular, our country has a warm and humid climate, and because it is surrounded by the ocean on all sides, it is extremely humid, with indoor and outdoor humidity reaching 60% or more throughout most of the year. Therefore, a considerable amount of moisture is mixed in the gas to be treated, and it is thought that this moisture preferentially adsorbs to the activated carbon and inhibits the adsorption of Ha 1-CH gas.

Therefore, the present inventors proposed that the efficiency of adsorption and removal of Ha 1-CH gas could be increased by drying and dehumidifying the mixed gas containing Hal-CH gas before adsorption and removal using activated carbon. I thought about it and proceeded with my research. As a result, if the mixed gas is dried until the relative humidity becomes 50% or less and then adsorbed on activated carbon, Hal
It was confirmed that -CH gas could be adsorbed and removed extremely efficiently.

By the way, Figure 1 shows Freon 1 as Hal-CH gas.
13 (CG12F -CClF2) gas was selected and an adsorption experiment using activated carbon was conducted, and the relative humidity of the mixed gas containing Hal-CH gas (the remaining gas is air) was found to be Freon 1.
13 and the results of an investigation to determine the effect on the equilibrium adsorption amount of water, and the experimental method was as follows.

Experimental method> (1) As shown schematically in Figure 2, a transparent airtight container V at 100°C
The following saturated aqueous solution S of inorganic salt was charged into the container, and the humidity inside the container was adjusted (a
t25°C).

K2Co3 saturated aqueous solution = 40% NLNO3 saturated aqueous solution: 61-64% (NH4)
2504 saturated aqueous solution = 81-83% (2) Absolutely dry state (1
Activated carbon (approximately 2 g) AC (after being treated at 20° C. for 3 hours or more) is placed in the sealed container V and adsorbed until it reaches a saturated moisture content.

(3) After the activated carbon AC reaches a saturated moisture content, 7.8 g/lo of Nifreon 113 is added to the sealed container V.

Freon 113 is injected into the container V and stirred with a stirrer R to uniformly disperse Freon 113 in the container V (Freon concentration 10.300
ppm) and then leave it for about 1 hour.

(4) Thereafter, the humidity and Freon 113 concentration in the sealed container V were measured, and the amount of adsorption on activated carbon AC was determined by subtracting the stabilized concentration when the concentration decreased from the initial concentration and stabilized.

(5) For comparison, the relationship between relative humidity and equilibrium adsorption amount was similarly investigated for toluene.

As is clear from Figure 1, when the relative humidity is below 50%, Hat-CH gas is adsorbed onto activated carbon preferentially over moisture, but when the relative humidity exceeds 50%, moisture is adsorbed. As the amount of Hal-CH gas increases rapidly, the amount of Hal-CH gas adsorbed decreases rapidly. As is clear from these trends, Ha 1-CH gas does not necessarily have a poor adsorption capacity for activated carbon, but it is thought that the presence of moisture above a certain amount drastically reduces the adsorption capacity for activated carbon. By drying the Hat-CH gas mixture in advance to lower the relative humidity and then performing adsorption treatment with activated carbon, it becomes possible to effectively adsorb and remove the Hal-CH gas. Regarding toluene, it can be seen that the tendency for the amount of adsorption to decrease due to relative humidity is very small.

The present invention is based on these findings, and H
This method is characterized by drying the mixed gas containing al-CH gas before it is adsorbed and removed by activated carbon, and the degree of drying is determined from the experimental results shown in Figure 1. Below the relative humidity (more preferably 40%), based on the relative humidity of 50% at which the amount of moisture adsorbed to the
% or less). Although any drying method may be used, the most preferred method from the viewpoint of continuous processing is heating drying or passing through a dehumidifier or a tower packed with a moisture absorbent.

Further, the configuration of the apparatus according to the present invention is such that a dehumidifying device is provided in the mixed gas introduction line of the activated carbon packed tower, and the above-mentioned Ha 1-
The system is designed to smoothly perform the CH gas adsorption removal method, and the specific configuration can be changed as desired depending on the overall situation of the equipment and the required processing capacity, but the basic configuration is An example of this is shown schematically in FIG. That is, in FIG. 3, Ia and lb indicate adsorption towers, the interior of which is filled with activated carbon in the form of granules, fibers, honeycombs, etc.
Further, 2a and 2b indicate dehumidifiers, the interior of which is filled with a suitable desiccant. And the solid line is Hal-
The CH gas adsorption removal line, the line indicated by the broken line La, indicates the adsorbent regeneration line, and the line indicated by the broken line Lb indicates the desiccant regeneration line, respectively. That is, mixed gas G containing Hal-CH gas
is sent from line L to one of the dehumidifiers 2a (or 2b) selected by operating the valve, and is dried in this section until the relative humidity becomes 50% or less. It is fed to adsorption tower Ia (or lb). In the adsorption tower 1a (or lb), Ha 1
The mixed gas from which the -CH gas has been removed is discharged to the outside of the system as a purified gas.

When the amount of water adsorption in the dehumidifier 2a (or 2b) becomes saturated and the drying capacity decreases, the adsorption removal line L is switched to the dehumidifier 2b side, while the dehumidifier 2a is supplied with hot air from the desiccant regeneration line Lb. (or one dry sky, :th:
s z Ancient ζ fist article + 1 + shi l→power t 1
Ki-shiLL and 4M engineer: ``The mixed gas is dried continuously by removing the Δ and waiting until the next drying process, and repeating such valve switching.Also, the Hal-CH gas adsorption in the adsorption tower Ia When the amount approaches saturation, Ha 1
-CH gas adsorption capacity is decreasing, so the drying gas introduction line is switched to the adsorption tower 1b side to continue adsorption removal, while the adsorption tower 1a side is connected to the adsorption regeneration line La from the Hat
-CH desorption gas (usually hot air) is sent in to desorb the Hal-CH gas adsorbed on the activated carbon to regenerate the activated carbon, and the desorbed exhaust gas is sent to the downstream side of the regeneration line La for Hal-CH gas adsorbed on the activated carbon. CH gas is condensed and recovered. By repeating such adsorption removal and desorption regeneration using the adsorbent, adsorption and removal of Hal-CH gas is continuously performed.

The switching timing of the adsorption towers 1a and 1b may be controlled by installing a Ha 1-CH gas concentration detector on the adsorption tower discharge line and detecting the increase in the concentration. In this case, the switching valve is a solenoid valve and the Of course, it is also possible to automatically control the first fishing λ day exclusive period by linking the fish with a 4-degree detector. It is also best to install a hygrometer on the discharge line of the dehumidifiers 2a and 2b to continuously detect the drying capacity to adjust the timing of switching to the regeneration process. Of course, it is also possible to fully automate the process. In Figure 3, a set of two adsorption towers 1
Although a structure in which the a, lb and dehumidifiers 2a and 2b are switched and operated is shown, the present invention is not limited to this type, and it is possible to use a structure in which three or more adsorption towers or dehumidifiers are installed together. In order to increase the processing capacity, or when the amount of processed gas is relatively small or the timing of generation of processed gas is not continuous, adsorption removal is performed using one adsorption tower and one dehumidifier, and non-processed gas is removed. It is also possible to perform desorption and regeneration during the period.

[Example] Using the experimental apparatus shown in Fig. 4, the Freon 113 concentration and humidity in the gas supplied to the activated carbon packed tower were variously changed, and the adsorption treatment was performed for a predetermined period of time. Changes in Freon 113 concentration were investigated. That is, as shown in FIG. 4, Freon 113 is charged into an evaporating dish 6 installed on a heater 5 in a simulated gas generator 4, heated and evaporated, and the vapor is passed along with air through a line 8 and a fan 9 to an adsorption tower 1a. (or lb). At this time, air that has been humidified or dehumidified is added to the supply gas through the humidity control device 10 and the heater 11 to variously change the humidity of the supply gas. The temperature and humidity of the supplied gas are adjusted by opening and closing the valves of the heater 11 while detecting them with the HC. And for each condition, which Freon 113 is in the gas before and after passing through the adsorption tower 1a (or lb)? The degree of a was checked using a hydrocarbon meter XI.

The experimental conditions were as follows.

Experimental conditions> Atmospheric conditions: 28°C, 90% Raw material gas feed rate: 14.48 m'/min Processing temperature: 3
5-40℃ Figure 5 shows the Freon 113 concentration in the gas passing through the adsorption tower at the end of the first patch and the Freon 113 concentration in the same gas at the end of the fifth batch. Based on these results, the following You can think in different ways.

(1) If the humidity of the supplied gas exceeds 50%, Freon 1
Not only when the 13 concentration is high, but Freon 113? Even when the degree of a is low, the Freon adsorption activity of the activated carbon decreases with a small number of treatments, and the Freon 113 concentration in the outlet gas becomes significantly high.

(2) On the other hand, if the humidity of the supplied gas is lowered to below 50%, the Freon 113 concentration in the outlet gas will be lower after 5 adsorption treatments than during the first adsorption treatment. . In other words, this experiment was conducted in an outside air atmosphere with a relative humidity of approximately 65%. Under these conditions, the activated carbon in the adsorption tower is thought to have absorbed some moisture, and during the initial adsorption treatment, the amount of adsorbed water was However, if the humidity of the supplied gas is kept below 50%, the moisture adsorbed by the activated carbon packed in the adsorption tower will be released as the supplied gas passes through the activated carbon. freon 1
It is considered that the Freon 113 adsorption activity increased and the Freon 113 adsorption removal efficiency became higher than that at the time of the initial adsorption treatment. In any case, by keeping the humidity of the supplied gas at 50% or less, Freon 113 in the supplied gas can be adsorbed and removed extremely efficiently.

[Effects of the Invention] Although the present invention is configured as described above, in short, Hat
- Dehumidify the mixed gas containing CH gas in advance to reduce its humidity to 5.
By keeping it below 0%, Hal-CH of activated carbon
Gas adsorption performance can be maximized, and Hal
-CH gas can be efficiently adsorbed and removed. Moreover, the equipment for carrying out this method requires only a dehumidifier to be installed in the treated gas introduction line of the activated carbon packed tower, and the existing activated carbon adsorption equipment can be used as is, reducing the equipment burden. If two or more activated carbon adsorption towers and two or more dehumidifiers are installed in parallel to perform adsorption and desorption regeneration and dehumidification and dry regeneration alternately, adsorption and removal of Ha 1-CH gas can be made continuous, which is faster than before. It became possible to efficiently adsorb and remove Hal-CH gas, which was considered difficult to adsorb.

[Brief explanation of drawings]

Figure 1 is a graph showing the results of investigating the influence of the relative humidity of a mixed gas on the adsorption activity of freon or toluene.
The figure is an explanatory diagram showing the adsorption activity test method, Figure 3 is a schematic flow diagram illustrating the apparatus according to the present invention, Figure 4 is an explanatory diagram showing the apparatus used in the examples, and Figure 5 is the humidity of the supplied gas. 2 is a graph showing changes in Freon concentration in adsorption tower outlet gas. Ia, lb...Activated carbon packed towers 2a, 2b...Dehumidifier L...Hal-CH gas adsorption treatment line La...Activated carbon desorption and regeneration line Lb...Dehumidifier regeneration line

Claims (2)

[Claims] (1) In a method of adsorbing and removing a halogenated hydrocarbon gas in a mixed gas containing a halogenated hydrocarbon gas using activated carbon, the mixed gas is subjected to a drying process to reduce the relative humidity to 50% prior to the adsorption process. % or less. (2) A device for adsorbing and removing halogenated hydrocarbon gas in a mixed gas containing halogenated hydrocarbon gas using activated carbon, the device being a dehumidifier to a line introducing the mixed gas to an adsorption tower filled with activated carbon. What is claimed is: 1. A device for adsorption and removal of halogenated hydrocarbon gas, characterized by comprising a device.