JP4783577B2 - Low concentration ozone gas adsorption method and adsorption device - Google Patents

Description

    The present invention relates to an adsorption method for efficiently adsorbing low-concentration ozone gas to an adsorbent and an adsorption apparatus suitable for use in the implementation of the method.

Conventionally, ozone is generated using oxygen gas as a raw material, and ozone is adsorbed by an adsorber using the obtained ozone-containing oxygen gas as a raw material gas so that oxygen and ozone can be separated and supplied to customers. Patent Document 1 is a typical prior art of this type.
As exemplified in this prior art, most of the conventional related inventions adsorb by controlling adsorption, desorption, and exhaust in the adsorber so that the ozone supply amount does not become excessive or insufficient in response to fluctuations in demand. I was trying to adjust my ability.
Japanese Patent Application Laid-Open No. 53-28570 (especially, refer to the column of claims)

  In the case of generating ozone using oxygen gas as a raw material, an ozone generator called a discharge type or ultraviolet type ozonizer has been widely used in the past, but it contains ozone gas with a low concentration of several hundred ppm to several percent. Ozone-containing oxygen gas is obtained, and if the ozone is fully adsorbed to the adsorber, the adsorption operation time becomes very long due to the low concentration, and in some cases it is as long as 10 or more hours. It was sometimes inefficient.

  For this reason, there has been a demand in the art for the development of a technology that enables efficient adsorption. However, in the past, as can be seen in Patent Document 1, most of the technologies correspond to the control of the adsorption amount and adsorption capacity. Thus, no technology relating to a technique capable of shortening the adsorption time has been provided.

  In view of the actual situation, an adsorption method capable of efficiently adsorbing the ozone gas from a raw material gas containing a low concentration of ozone gas to an adsorbent in an adsorption tower, and an adsorption device suitable for use in the implementation of the method are provided. Accordingly, the present invention has been devised here.

Therefore, in order to achieve the above-mentioned object, the present invention is characterized in that in the invention described in claim 1, the ozone generation concentration decreases as the oxygen flow rate increases, and the ozone generation concentration increases as the oxygen flow rate decreases. An adsorption method in which the ozone gas-containing oxygen released from the ozonizer is used as a raw material gas, and the ozone gas is adsorbed from the raw material gas to the adsorbent of the adsorption tower (2). In order to control the flow rate of raw material gas per unit time continuously or stepwise so that the amount of raw material gas inflow increases at the beginning of the adsorption operation and decreases at the end of the adsorption operation, the amount of raw material gas inflow per unit time is used as a parameter. When the flow rate of the raw material gas inflow is controlled, the reference concentration value of ozone gas at the adsorption tower outlet is the ozonizer. The flow rate is controlled by the inflow time starting from the starting time of inflow of the raw material gas into the adsorption tower so that it falls within the range of the ozone concentration of the raw material gas determined by the above characteristics and a half value of the ozone concentration. This is an adsorption method for low-concentration ozone gas.

Further, the present invention relates to a low-concentration ozone gas adsorbing device, wherein the ozone generation concentration decreases as the oxygen flow rate increases, and the ozone generation concentration increases as the oxygen flow rate decreases, and the ozonizer (3 An adsorber tower (2) in which an inlet is connected to a gas feed line (1) for feeding oxygen gas-containing oxygen released from the gas as a raw material gas, and an adsorbent for adsorbing ozone gas is stored therein, and an adsorber tower In (2), the flow rate controller (6) provided in the gas feed line (1) and the gas discharge line (4) connected to the outlet of the adsorption tower (2) are used to adjust the flow rate of the raw material gas. A flow rate measuring means (14) for measuring the outlet flow rate of the adsorption tower (2), and the flow rate controller (6) based on the outlet flow rate of the adsorption tower (2) measured by the flow rate measurement means (14). Control to control the flow rate continuously or in several steps Control means (11), the control means (11) is a flow rate change point at the time of the flow control, the flow rate at the outlet of the adsorption tower is the raw material gas flow rate value-"raw material gas flow rate-raw material gas flow rate x ozone concentration" A calculation / control means for controlling the flow rate of the raw material gas inflow continuously or stepwise is provided within the range of the value represented by the formula “value × ½” .

The invention described in claim 3 relates to an apparatus for adsorbing low-concentration ozone gas, and an inlet is connected to a gas supply line 1 for supplying a raw material gas containing ozone gas having a constant low concentration of about several percent. And an adsorbing tower 2 in which an adsorbent for adsorbing ozone gas is stored, and a gas discharge line 4 connected to the outlet of the adsorbing tower 2 in order to increase or decrease the gas outflow amount of the adsorbing tower 2. A pressure control valve 9, an adsorption pressure measuring means 12 provided in association with the adsorption tower 2 for measuring the adsorption pressure in the adsorption tower 2, and the adsorption pressure in the adsorption tower 2 measured by the adsorption pressure measuring means 12 Control means 13 for controlling the valve opening degree of the pressure control valve 9 based on the control means 13, the control means 13 is a constant value appropriate for the adsorption operation during the period from the initial stage to the final stage of the adsorption operation. Suck to keep Characterized in that it comprises a control means for flow control of the gas outflow tower 2.

  According to the present invention as described above, by controlling the flow rate of the raw material gas in the adsorption tower 2 continuously or stepwise from a high flow rate to a low flow rate from the initial stage to the final stage of the adsorption operation, As will be described in detail in the section “Best Mode for Carrying Out the Invention”, the adsorption amount is the same even though the adsorption amount is the same as compared with the case of the adsorption operation at a constant low flow rate that allows a large adsorption amount. The adsorption time required for mass adsorption can be shortened, for example, 1/3 to 1/2.

  In addition, the present invention provides a raw material gas to the adsorption tower 2 using a raw material gas ozone concentration per unit time as a parameter and each reference concentration value within a range of ½ of the ozone concentration as a flow rate turning point. By controlling the flow rate of the gas inflow continuously or stepwise, the adsorption time can be shortened quickly and smoothly without causing any delay.

  In addition, the present invention uses a raw material gas inflow amount as a parameter, and a reference concentration value existing within a range of a raw material gas flow rate value and a value represented by a formula of “raw material gas flow rate−raw material gas flow rate × ozone concentration value × 1/2”. By controlling the flow rate of the raw material gas in the adsorption tower 2 continuously or stepwise with the flow rate turning point, the adsorption time can be shortened efficiently.

  Furthermore, according to the present invention, the partial pressure of the supplied ozone can be achieved by controlling the adsorption pressure in the adsorption tower 2 so as to be held at a constant value appropriate for the adsorption operation during the period from the beginning to the end of the adsorption operation. As much as possible, the adsorption time can be shortened.

  In addition, the present invention can reduce the adsorption time by a simple means of increasing the amount of raw material gas flowing into the adsorption tower 2 at the beginning of the adsorption operation and gradually decreasing it with the passage of time. It has the advantage of being simple.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments according to the invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an adsorption device according to a first embodiment of the present invention.
The illustrated adsorption device is provided in connection with a feed end of a gas feed line 1 for feeding a raw material gas containing ozone gas having a low concentration of about several percent and the remainder being oxygen, for example. The controller 6, the adsorption tower 2, the gas discharge line 4, the ozone concentration measuring means 10, and the control means 11 for controlling the control flow rate of the flow rate controller 6 continuously or stepwise are provided as main components.

  As the gas supply line 1, various known gas supply systems can be applied. In this example, the oxygen supply line B, the pressure reducing valve 5, the discharge type ozonizer 3, the on-off valve 8, and the pressure gauge 14 are used to supply oxygen. A feed system for supplying a raw material gas as a main gas, which is a pressure slightly higher than atmospheric pressure, which is generated by a discharge type ozonizer 3 and typically contains 5% ozone and the remainder is oxygen. Is provided so as to be able to be fed into the adsorption tower 2.

  The adsorption tower 2 in the adsorption apparatus contains an adsorbent for adsorbing ozone gas, such as silica gel, in a tower that forms a sealed cylinder having an inlet at the top and an outlet at the bottom, and the wall material around the tower is at a low temperature. It is a device having a known structure surrounded by a cooling member of the cooling device 7, the inlet is connected to the feed end of the gas feed line 1 through an on-off valve 8 for circulating and shutting off the raw material gas inflow, The outlet is connected to the inflow end of the gas discharge line 4.

  For example, a mass flow controller is used as the flow rate controller 6. The flow rate controller 6 is disposed in the middle of the gas feed line 1 on the lower side with respect to the discharge type ozonizer 3 and on the upper side with respect to the adsorption tower 2. Is provided so as to control the flow rate of the raw material gas flowing into the.

  The ozone concentration measuring means 10 is provided at a position on the lower side with respect to the on-off valve 16 in the gas discharge line 4 and measures the ozone concentration in the gas discharged from the adsorption tower 2 outlet to the gas discharge line 4. Functions as a measuring device. The control means 11 is provided in a signal circuit connecting the measurement signal output terminal of the ozone concentration measuring means 10 and the control signal input terminal of the flow rate controller 6.

  The control means 11 will be described in detail in the description of the adsorption operation mode to be described later. The raw material gas per unit time corresponding to the continuous or stepwise control flow rate in the flow rate controller 6 shown in FIG. A calculation / storage circuit for setting and storing the ozone concentration corresponding to each raw material gas flow rate when the inflow amount is used as a parameter and the respective reference concentration values D1 to D5 within the range of ½ of the ozone concentration; A calculation / control system comprising a control output circuit for controlling the flow rate of the raw material gas flowing into the adsorption tower 2 continuously or step by step using these reference concentration values D1 to D5 as flow rate turning points is provided.

  In addition, the line provided with the on-off valve 15 in FIG. 1 is a measurement line used when measuring the ozone concentration at the entrance of the adsorption tower 2, and when measuring the ozone concentration at the entrance of the adsorption tower 2, if necessary Thus, the ozone concentration measuring means 10 can be used as a measuring instrument.

  An aspect of the adsorption operation of the adsorption apparatus having the above-described configuration will be described below with reference to FIGS. 2 to 7 in addition to FIG. 2 is an adsorption breakthrough curve diagram of the adsorption tower, FIG. 3 is an adsorption breakthrough curve diagram when the ozone concentration of the adsorption tower 2 is constant, FIG. 4 is a Langmuir adsorption theory diagram, and FIG. FIG. 6 is an outlet ozone concentration-adsorption operation time relationship graph using the gas inflow rate of the adsorption tower 2 as a parameter, and FIG. 7 is an outlet ozone due to a change in the gas inflow amount of the adsorption tower 2. The concentration-adsorption operation time relationship diagrams are respectively shown.

  In a general adsorption operation in the adsorption tower 2, it is known that the adsorption amount curve with the adsorption tower outlet ozone concentration on the vertical axis and the adsorption time on the horizontal axis exhibits a breakthrough curve as shown in FIG. When the adsorption tower outlet ozone concentration becomes equal to the raw material gas ozone concentration, it is said that it has been fully adsorbed, that is, saturated adsorption, or adsorption breakthrough, and from this, the process of comparing the raw material gas ozone concentration with the outlet ozone concentration Thus, it is possible to accurately know the saturation state of the adsorption operation in the adsorption tower.

  When the raw material gas ozone concentration during the adsorption operation is set to a constant value in the low range, the adsorption breakthrough curve using the raw material gas inflow per unit time (SLM) as a parameter is as shown in FIG. However, it is also known that if the ozone concentration is constant, the breakthrough state is delayed as the flow rate is reduced, and it takes time for full adsorption.

  According to the Langmuir adsorption theory, an adsorption amount curve with the adsorption operation temperature as a parameter and the adsorption amount as the vertical axis and the supply ozone concentration (or pressure) as the horizontal axis is shown in FIG. It is known that the amount of adsorption increases when the value is increased. It has also been found that the amount of adsorption increases with decreasing temperature. Furthermore, as represented by the following Langmuir equation, it is also clear that the supply ozone partial pressure P and the saturated adsorption amount qm are in a proportional relationship.

q = (k · qm · P) / (1 + k · P) = (1 / qm) + (1 / qm · k) × (1 / P)
∴ (1 / qm) ∝ (1 / P)
Note q: adsorption amount, P: supply ozone partial pressure, qm: saturated adsorption amount (constant) for all adsorption sites when one layer is adsorbed, k: equilibrium constant

Here, the discharge type ozonizer 3 frequently used as a device for generating ozone has a relationship between the oxygen flow rate and the ozone generation concentration as shown in FIG. As the concentration decreases and the oxygen flow rate decreases, the ozone generation concentration increases. In the adsorption operation, although it is desirable that the adsorption amount is large and the adsorption time is short, when performing the adsorption operation using the discharge type ozonizer 3, the raw material gas inflow amount (SLM) per unit time is used as a parameter. The relationship between the outlet ozone concentration and the adsorption operation time at that time is that, as shown by the respective adsorption breakthrough curves a to e in FIG. Actually, the adsorption operation is performed at a flow rate of 1 SLM or 2 SLM in the case of 5% O ₃ / remaining O ₂ source gas.

  In view of the various examination results described above, the present invention employs an operating means that changes the raw material gas inflow (SLM) per unit time in the process of adsorption starting from the initial adsorption time of the adsorption tower 2. That is, in particular, referring to FIGS. 6 and 7 in conjunction with FIG. 1, instead of fixing the inflow amount of the raw material gas fed into the adsorption tower 2 to a constant amount (for example, 2 SLM), The initial adsorption time is divided into several stages, for example, five stages within the range from the maximum amount (for example, 4 SLM) to the minimum amount (for example, 0.2 SLM) during the final time point until the adsorption saturation starts, and the initial amount of adsorption (4 SLM) The adsorption operation is performed in order, and the adsorption operation is sequentially performed while controlling the flow rate to 2 SLM, 1 SLM, 0.5 SLM, and 0.2 SLM step by step.

  By performing the adsorption operation with the flow rate controlled step by step in this way, the adsorption time can be greatly shortened compared to the case where adsorption is performed at a constant amount (2 SLM) even though the adsorption amount reaching the full amount is the same. It became clear that Note that the flow rate switching timing when controlling the flow rate can be realized by supervising so that the adsorption breakthrough curve under the actual adsorption operation becomes a steep and smooth saturation curve. In practice, the following control can be performed reliably and smoothly.

  That is, the raw material gas ozone concentration when the raw material gas inflow amount (4 SLM, 2 SLM, 1 SLM, 0.5 SLM, 0.2 SLM) per unit time in each stage determined from the characteristics of the discharge type ozonizer 3 is used as a parameter, and the ozone concentration Each of the reference concentration values D1 to D5 (see FIG. 6) existing in the range of ½ value of each is set, and the raw materials of the adsorption tower 2 are set so that these reference concentration values D1 to D5 are used as flow rate turning points. The gas inflow rate is controlled in stages.

  In order to perform the adsorption operation under the stepwise flow rate control as described above, it can be realized as follows. Referring to FIG. 1, the ozone concentration measurement means 10 measures the outlet ozone concentration of the adsorption tower 2 during the adsorption operation of the adsorption tower 2, and inputs the measurement signal to the control means 11. In the control means 11, the raw material gas inflow amount calculated and stored in advance, the information value of the reference concentration value corresponding to the raw material gas inflow amount and the input measurement signal are compared with each other as a result of comparison with the flow rate controller 6. Send flow control output. The flow rate controller 6 that has received this flow rate control output controls the flow rate of the raw material gas into the adsorption tower 2 stepwise so that the reference concentration values D1 to D5 are used as flow rate change points. 7, the adsorption operation is performed by changing the flow rate along the adsorption breakthrough curve A. The adsorption breakthrough curve A is substantially similar to the adsorption breakthrough curve C at a constant 0.2 SLM. In addition, it is in a state where it has moved greatly to the left of the horizontal axis, which clearly shows the result of the adsorption operation being performed efficiently and the adsorption completion time has been greatly shortened (about 1/2). .

  As described above, in place of the control based on the outlet ozone concentration, it is possible to perform an adsorption operation using the relationship between the amount of inflow of the source gas and the inflow time of the source gas. That is, as shown in FIG. 8, a controller that combines a flow rate adjustment and a timer is arranged, and the adsorption breakthrough curve A is obtained in advance by actual measurement or calculation, and the flow rate of the raw material gas corresponding to the adsorption time and the flow rate change timing data. Can be stored in a storage device (not shown), and the adsorption operation can be controlled without measuring the ozone concentration by controlling the flow rate based on the data stored in the storage device. In this case, since it is not necessary to use an expensive ozone densitometer, the equipment cost can be suppressed.

  In the above description, stepwise flow rate control is shown, but it is also possible to perform adsorption operation by flow rate control that is substantially continuous by setting the flow rate turning point more finely.

  Further, as a method of controlling the flow rate without measuring the ozone concentration, it is possible to use a difference between the raw material gas inflow value per unit time and the outlet gas flow rate value. That is, as shown in FIG. 9, a flow rate indicator is arranged at the outlet side of the adsorption tower, and the raw material gas flow value and the value represented by the formula of “raw material amount gas flow rate−raw material gas flow rate × ozone concentration value × 1/2”. A reference flow rate value is set as a flow rate turning point within the range of, and when the outlet flow rate value exceeds the reference flow rate value, the flow rate of the raw material gas flowing into the adsorption tower 2 is controlled stepwise. Also in this case, the flow rate control close to substantially continuous is possible by setting the flow rate turning point more finely.

  Next, FIG. 10 is a schematic configuration diagram of an adsorption device according to a fourth embodiment of the present invention. FIG. 11 is an outlet ozone concentration-adsorption operation time relationship diagram showing the pressure dependency of the adsorption tower, and FIG. 12 is an ozone adsorption amount-adsorption operation time relationship diagram due to an adsorption pressure change of the adsorption tower. In the suction device according to the fourth embodiment shown in FIG. 10, the same reference numerals are assigned to the corresponding members similar to those in the suction device shown in FIG. 1, and detailed description thereof is omitted.

  The configuration characterized in the adsorption apparatus according to the fourth embodiment includes a pressure control valve 9 provided in the gas discharge line 4, an adsorption pressure measuring means 12 for measuring the adsorption pressure in the adsorption tower 2, and the pressure. The point is that an adsorption tower gas outflow amount control system formed by the control means 13 for controlling the valve opening degree of the control valve 9 is provided.

  The pressure control valve 9 is provided in the gas discharge line 4 connected to the outlet of the adsorption tower 2 in order to increase / decrease the gas outflow amount per unit time from the adsorption tower 2. The adsorption pressure measuring means 12 is provided in association with the adsorption tower 2 in order to measure the adsorption pressure in the adsorption tower 2. The control means 13 includes a control circuit for controlling the valve opening degree of the pressure control valve 9 based on the adsorption pressure in the adsorption tower 2 measured by the adsorption pressure measuring means 12 and adsorbs the adsorption pressure in the adsorption tower 2. It has a function of controlling the flow rate of the gas outflow from the adsorption tower 2 so as to maintain a constant value suitable for the adsorption operation during the period from the beginning to the end of the operation.

  Referring to FIG. 11, when the adsorption pressure is increased in the adsorption tower 2, the adsorption saturation time increases, but the adsorption amount increases at the initial stage of the adsorption operation. However, the adsorption pressure of the discharge type ozonizer 3 can only be increased to 0.05 Mpa (1100 Torr) due to the problem of pressure resistance in the mechanism. Therefore, the adsorption operation is performed while maintaining as high a pressure as possible within the allowable range on the pressure-resistant surface, for example, a pressure around atmospheric pressure.

  As shown in FIG. 11, since the entire amount of ozone in the raw material gas is efficiently adsorbed at the initial stage of the adsorption operation, a pressure control valve is used to reduce the amount of gas flowing into the adsorption tower 2 with reference to FIG. The valve opening of 9 is throttled to keep the adsorption pressure at a constant value appropriate for the adsorption operation. For example, in the case of initial adsorption at 2 SLM and 1000 Torr with 5% ozone, the adsorption tower outlet flow rate is 1.95 SLM, but when the unadsorbed ozone begins to flow out of the adsorption tower, the outlet flow rate approaches 2 SLM and the adsorption pressure decreases. Therefore, in order to maintain 1000 Torr, the valve opening of the pressure control valve 9 is adjusted to be opened based on the command of the control means 13 that receives the measurement signal of the adsorption pressure measurement means 12. Thus, as shown in comparison in FIG. 12, if the same adsorption amount is obtained, the adsorption time can be shortened by increasing the adsorption pressure.

The schematic block diagram of the adsorption | suction apparatus which concerns on the 1st Embodiment of this invention. The adsorption breakthrough curve figure of an adsorption tower. An adsorption breakthrough curve diagram when the ozone concentration of the adsorption tower is constant. Langmuir adsorption theory diagram. The discharge ozone density | concentration diagram which shows the flow volume dependency of a discharge type ozonizer. The outlet ozone concentration-adsorption operation time relationship diagram using the gas inflow amount of the adsorption tower as a parameter. The outlet ozone concentration-adsorption operation time relationship diagram by the gas inflow change of an adsorption tower. The schematic block diagram of the adsorption | suction apparatus which concerns on the 2nd Embodiment of this invention. The schematic block diagram of the adsorption | suction apparatus which concerns on the 2nd Embodiment of this invention. The schematic block diagram of the adsorption | suction apparatus which concerns on the 4th Embodiment of this invention. The outlet ozone concentration-adsorption operation time relationship diagram which shows the pressure dependence of an adsorption tower. The ozone adsorption amount by the adsorption pressure change of an adsorption tower-adsorption operation time relationship diagram.

DESCRIPTION OF SYMBOLS 1 ... Gas feed line 2 ... Adsorption tower 3 ... Discharge-type ozonizer 4 ... Gas discharge line 5 ... Pressure-reducing valve 6 ... Flow controller 7 ... Low temperature cooling device 8 ... On-off valve 9 ... Pressure control valve 10 ... Ozone concentration measuring means 11 ... Control means 12 ... Adsorption pressure measuring means 13 ... Control means 14 ... Pressure gauge 15 ... Open / close valve 16 ... Open / close valve B ... Oxygen cylinder D1-D3 ... Reference concentration value A-E ... Adsorption breakthrough curve

Claims (3)

The ozone generation concentration decreases as the oxygen flow rate increases and the ozone generation concentration increases as the oxygen flow rate decreases. The ozone gas-containing oxygen released by the ozonizer (3) is used as the source gas. An adsorption method for adsorbing ozone gas from the raw material gas to the adsorbent of the adsorption tower (2),
The raw material gas inflow amount per unit time of the to the adsorption tower (2) to be large in the initial adsorbing operation, strikes the continuously or stepwise flow control so as to become smaller in the end, per unit time Using the raw material gas inflow as a parameter, the flow rate change point when controlling the flow of the raw material gas, the ozone concentration of the raw material gas determined by the characteristics of the ozonizer, and the ozone concentration A method for adsorbing low-concentration ozone gas, characterized in that the flow rate is controlled by the inflow time starting from the starting time of inflow of the raw material gas into the adsorption tower so as to be within a range of ½ value of the concentration. The ozone generation concentration decreases as the oxygen flow rate increases and the ozone generation concentration increases as the oxygen flow rate decreases, and the ozone gas-containing oxygen released by the ozonizer (3) is fed as a raw material gas. In order to increase / decrease the amount of raw material gas inflow in the adsorption tower (2) in which the inlet is connected to the gas feed line (1) and the adsorbent for adsorbing ozone gas is stored inside, and the adsorption tower (2) The flow rate controller (6) provided in the gas supply line (1) and the gas discharge line (4) connected to the outlet of the adsorption tower (2) are interposed to measure the outlet flow rate of the adsorption tower (2). And a control means for controlling the control flow rate of the flow rate controller (6) continuously or in several steps based on the outlet flow rate of the adsorption tower (2) measured by the flow rate measurement means (14). (11), and the control means (11) is configured to control the flow rate. The flow rate turning point at the time of adsorption is within the range of the raw material gas flow rate value and the value indicated by the formula of “raw material gas flow rate−raw material gas flow rate × ozone concentration value × 1/2”. An adsorption device for low-concentration ozone gas, comprising an operation / control means for controlling the flow rate of the raw material gas continuously or stepwise. An adsorption tower (2) in which an inlet is connected to a gas feed line (1) for feeding a raw material gas containing ozone gas having a constant low concentration of several percent, and an adsorbent for adsorbing ozone gas is stored inside A pressure control valve (9) provided in a gas discharge line (4) connected to the outlet of the adsorption tower (2) in order to increase or decrease the gas outflow amount of the adsorption tower (2), and the adsorption tower (2 ) And an adsorption pressure measuring means (12) for measuring the adsorption pressure in the adsorption tower (2), and the adsorption pressure in the adsorption tower (2) measured by the adsorption pressure measuring means (12). The control means (13) includes a control means (13) for controlling the valve opening degree of the pressure control valve (9). The control means (13) controls the adsorption pressure in the adsorption tower (2) during the period from the initial stage to the final stage of the adsorption operation. It is provided with a control means for controlling the flow rate of the gas outflow of the adsorption tower (2) so as to maintain a constant value appropriate for the adsorption operation. Adsorber low-concentration ozone gas according to symptoms.

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