Ozone supply system and ozone supply method

Abstract

This ozone supply system comprises: an adsorption tower (A, B) which contains an adsorbent that adsorbs ozone generated by an ozone generator (3) from oxygen supplied from an oxygen source (2), and in which an adsorption step for causing the adsorbent to adsorb the ozone and a desorption step for desorbing the ozone from the adsorbent are alternately repeated; a circulation path (120) through which oxygen gas not having been adsorbed onto the adsorbent in the adsorption step is discharged from the adsorption tower (A, B) and circulated to the ozone generator (3); a first supply part (4) for a first carrier gas; a carrier gas introduction path (103) for introducing, in the desorption step, the first carrier gas from the first supply part (4) into the adsorption tower (A, B); a carrier gas discharge path (104) for discharging, in the desorption step, the ozone accompanied by the first carrier gas to the outside of the adsorption tower (A, B); and a depressurization part (5) for depressurizing, in the desorption step, the interior of the adsorption tower (A, B) until the interior is lower than the atmospheric pressure.

Description

Ozone supply system and ozone supply method

[0001] The present application relates to an ozone supply system and an ozone supply method.

[0002] A conventional ozone supply system includes a high-purity oxygen gas supply source that supplies high-purity oxygen gas as an ozone raw material, an ozone generator that generates ozone using the high-purity oxygen gas supplied from the high-purity oxygen gas supply source as a raw material, an adsorption column that is filled with an adsorbent that preferentially adsorbs ozone and alternately performs an adsorption process at a relatively low temperature for the ozone generated in the ozone generator and a desorption process at a relatively high temperature for desorption, and oxygen gas that is not adsorbed by the adsorbent in the adsorption process and is discharged from the adsorption column is recycled to the high-purity oxygen gas. the ozone-containing scavenging gas introduced into the adsorption column to accompany the ozone desorbed from the adsorbent in the desorption step and then discharged from the adsorption column; an ozone discharge path for discharging the ozone-containing scavenging gas from the adsorption column in the desorption step; an ozone supply path for supplying the ozone-containing scavenging gas discharged into the ozone discharge path to an ozone consumer; and a pump for sucking in gas from the adsorption column, pressurizing it, and then introducing and mixing it with the product ozone (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2001-172004

[0004] Conventional ozone supply systems and methods use low-concentration oxygen gas for purging in order to reduce the amount of oxygen used. However, this causes nitrogen gas introduced during desorption to remain in the adsorption tower, resulting in an increase in the nitrogen concentration in the adsorption tower during the transition from ozone gas desorption to adsorption. This leads to problems such as a decrease in ozone generation efficiency and the generation of nitrogen oxides that can cause corrosion of pathways, etc.

[0005] The present application discloses a technique for solving the above-described problems, and aims to provide an ozone supply system and an ozone supply method that can suppress an increase in nitrogen concentration in an adsorption tower.

[0006] The ozone supply system disclosed in the present application includes: an ozone generator that generates ozone from oxygen supplied from an oxygen source; an adsorption tower that stores an adsorbent that adsorbs the ozone generated by the ozone generator and alternately performs an adsorption process of adsorbing ozone onto the adsorbent and a desorption process of desorbing ozone from the adsorbent; a circulation path that extracts oxygen that has not been adsorbed onto the adsorbent in the adsorption process from the adsorption tower and circulates it to the ozone generator; a first supply unit for a first carrier gas; a carrier gas introduction path that introduces the first carrier gas from the first supply unit into the adsorption tower in the desorption process; a carrier gas outlet path that extracts ozone entrained in the first carrier gas out of the adsorption tower in the desorption process; and a pressure reduction unit that reduces the pressure inside the adsorption tower to a pressure lower than atmospheric pressure in the desorption process. The ozone supply method disclosed in the present application includes an adsorption step of adsorbing generated ozone onto an adsorbent stored in an adsorption tower, and extracting oxygen that has not been adsorbed by the adsorbent from the adsorption tower and reintroducing the raw material gas into an ozone generator to regenerate ozone and supply it to the adsorption tower; a first desorption step of introducing a first carrier gas into the adsorption tower after the adsorption step is completed, desorbing the ozone adsorbed by the adsorbent together with the first carrier gas and extracting it from the adsorption tower; and a vacuum desorption step of depressurizing the inside of the adsorption tower to a pressure lower than atmospheric pressure after stopping the introduction of the first carrier gas. The ozone supply method disclosed in the present application includes an adsorption step of adsorbing generated ozone onto an adsorbent stored in an adsorption tower, and withdrawing oxygen not adsorbed by the adsorbent from the adsorption tower and reintroducing it as a raw material gas into an ozone generator to regenerate ozone and supply it to the adsorption tower; a first desorption step of, after the adsorption step is completed, introducing a first carrier gas into the adsorption tower, desorbing the ozone adsorbed by the adsorbent together with the first carrier gas, and discharging it outside the adsorption tower; and a second desorption step of, after stopping the introduction of the first carrier gas, introducing a second carrier gas having a nitrogen concentration lower than the nitrogen concentration of the first carrier gas, desorbing the ozone adsorbed by the adsorbent, and discharging it outside the adsorption tower, and replacing the first carrier gas remaining in the adsorption tower with the second carrier gas.

[0007] According to the ozone supply system and ozone supply method disclosed in the present application, an increase in the nitrogen concentration in the adsorption tower can be suppressed.

[0008] Fig. 1 is a block diagram showing the configuration of an ozone supply system according to embodiment 1. Fig. 2 is a flow chart showing steps of an ozone supply method using the ozone supply system shown in Fig. 1. Fig. 3 is a block diagram showing the configuration of an ozone supply system according to embodiment 2. Fig. 4 is a flow chart showing steps of an ozone supply method using the ozone supply system shown in Fig. 3. Fig. 5 is a flow chart showing steps of another ozone supply method using the ozone supply system shown in Fig. 3.

[0009] Embodiment 1. Figure 1 is a block diagram showing the configuration of an ozone supply system according to embodiment 1. Figure 2 is a flow diagram showing the steps of an ozone supply method using the ozone supply system shown in Figure 1. In Figure 1, the ozone supply system 1 includes adsorption towers A and B, and an ozone generator 3, an ozone introduction path 101, a circulation path 120, a first carrier gas introduction path 103, a carrier gas discharge path 104, a first supply unit 4, and a pressure reduction unit 5, all of which are connected to adsorption towers A and B.

[0010] Adsorption tower A and adsorption tower B contain adsorbents that adsorb ozone. The ozone supply system 1 alternately performs an adsorption process in which ozone is adsorbed onto the adsorbent and a desorption process in which ozone is desorbed from the adsorbent after adsorption in adsorption tower A and adsorption tower B. Ozone generator 3 introduces oxygen from oxygen source 2 via buffer tank 122 (described later), generates ozone, and supplies it to adsorption tower A or adsorption tower B in the adsorption process via ozone introduction path 101. Circulation path 120 extracts oxygen gas that is not adsorbed by the adsorbent from adsorption tower A or adsorption tower B in the adsorption process and circulates it to be introduced back into ozone generator 3 for reuse as a raw material gas. The circulation path 120 includes a circulation blower 121 that circulates the oxygen gas and a buffer tank 122 that can temporarily store the circulated oxygen gas.

[0011] The first supply unit 4 supplies a first carrier gas for desorbing ozone adsorbed by the adsorbent to the adsorption tower A or B in the desorption process via the first carrier gas inlet path 103. Dry air, for example, is used as the first carrier gas. The carrier gas outlet path 104 discharges the ozone entrained in the first carrier gas from the adsorption tower A or B in the desorption process to the pressure reduction unit 5.

[0012] The decompression unit 5 reduces the pressure inside the adsorption tower A or B in the desorption process via the carrier gas outlet path 104 until the pressure inside the adsorption tower A or B becomes lower than atmospheric pressure. The decompression unit 5 is configured, for example, by a vacuum pump. The paths 101, 120, 103, and 104 are respectively provided with switching valves 11, 12, 13, 14, 15, 16, 17, and 18 that open and close in a predetermined sequence when switching between the processes of the adsorption tower A and the adsorption tower B.

[0013] Next, an ozone supply method of the ozone supply system of the first embodiment configured as described above will be described. Note that the description will focus on adsorption tower A. Naturally, when the adsorption process is performed in adsorption tower A, the desorption process is performed in adsorption tower B. Also, when the desorption process is performed in adsorption tower A, the adsorption process is performed in adsorption tower B. Therefore, these points are the same in the following embodiments, and therefore the description thereof will be omitted as appropriate.

[0014] First, the ozone generator 3 introduces oxygen from the oxygen source 2, generates ozone, and introduces the ozone via the ozone introduction path 101 into the adsorption tower A, which is undergoing an adsorption process. Next, the introduced ozone is adsorbed by the adsorbent in the adsorption tower A. Simultaneously, oxygen gas that is not adsorbed by the adsorbent in the adsorption tower A is discharged from the adsorption tower A through the circulation path 120 and is again supplied as a raw material gas to the ozone generator 3 via the circulation blower 121 and the buffer tank 122, thereby carrying out the adsorption process (step ST01 in FIG. 2 ). At this time, the pressure in the adsorption tower A is higher than atmospheric pressure. Then, when the adsorption process in the adsorption tower A is completed, the introduction of ozone from the ozone generator 3 into the adsorption tower A is stopped.

[0015] Next, the first supply unit 4 introduces dry air as a first carrier gas into the adsorption tower A during the desorption process via the first carrier gas introduction path 103. The introduced first carrier gas sweeps the ozone adsorbed on the adsorbent of the adsorption tower A together with the first carrier gas out of the adsorption tower A via the carrier gas outlet path 104, thereby performing the first desorption process (step ST02 in FIG. 2 ). At this time, since dry air is introduced into the adsorption tower A, the pressure inside the adsorption tower A is reduced to approximately atmospheric pressure. Note that in the first desorption process, an example is shown in which the carrier gas outlet path 104, through which the ozone entrained in the first carrier gas passes, is discharged to the outside of the apparatus via the pressure reduction unit 5. However, this is not limited thereto, and the ozone may be directly discharged to the outside of the apparatus without passing through the pressure reduction unit 5 during the first desorption process.

[0016] Next, after stopping the introduction of the first carrier gas, the pressure inside the adsorption tower A is reduced by the pressure reducing unit 5 via the carrier gas outlet path 104 until the pressure inside the adsorption tower A becomes lower than atmospheric pressure (step ST03 in FIG. 2 ). During this process, components of the first carrier gas remaining inside the adsorption tower A and the carrier gas outlet path 104 are exhausted. This reduces the accumulation of nitrogen gas inside the adsorption tower A, thereby reducing the amount of NOx gas generated due to the increase in nitrogen gas in the circulation path 120 in the next adsorption step (step ST01). This prevents a decrease in the efficiency of ozone generation and reduces nitrogen oxides, which can cause corrosion of the path and other components. The depressurization by the pressure reducing unit 5 is then terminated, and the process returns to the adsorption step (step ST01 in FIG. 2 ).

[0017] As described above, the above-described effects can be obtained if the pressure inside the adsorption column A in the vacuum desorption step is lower than atmospheric pressure. However, the following can be considered to further ensure that these effects are obtained.

[0018] For example, if the nitrogen concentration in adsorption tower A during the adsorption process is C1, the pressure value in adsorption tower A is P1, the nitrogen concentration of the first carrier gas during the first desorption process is C2, and the pressure value in adsorption tower A during the vacuum desorption process is P2, the adsorption tower A is depressurized until the following relationship is met: C1 x P1 ≧ C2 x P2 (Equation 1).

[0019] By reducing the pressure in adsorption tower A until the relationship expressed by Equation 1 above is satisfied and reducing the partial pressure of nitrogen gas (concentration x pressure) in the vacuum desorption step (step ST03) to a value equal to or lower than the partial pressure of nitrogen gas in the adsorption step (step ST01), the amount of nitrogen gas adsorbed by the adsorbent in adsorption tower A at the end of the desorption step can be reliably reduced to less than that during the adsorption step. This reliably reduces the accumulation of nitrogen gas in adsorption tower A and reliably reduces the amount of NOx gas generated due to an increase in nitrogen gas in circulation path 120 in the next adsorption step (step ST01).

[0020] The ozone supply system of the first embodiment configured as described above includes: an ozone generator that generates ozone from oxygen supplied from an oxygen source; an adsorption tower that stores an adsorbent that adsorbs the ozone generated by the ozone generator and alternately performs an adsorption process of adsorbing ozone onto the adsorbent and a desorption process of desorbing ozone from the adsorbent; a circulation path that extracts oxygen that has not been adsorbed by the adsorbent in the adsorption process from the adsorption tower and circulates it to the ozone generator; a first supply unit for a first carrier gas; a carrier gas introduction path that introduces the first carrier gas from the first supply unit into the adsorption tower in the desorption process; a carrier gas outlet path that extracts ozone entrained in the first carrier gas out of the adsorption tower in the desorption process; and a decompression unit that depressurizes the inside of the adsorption tower to a pressure lower than atmospheric pressure in the desorption process. Therefore, an increase in the nitrogen concentration in the adsorption tower can be suppressed.

[0021] Furthermore, the ozone supply method of the first embodiment performed as described above includes: an adsorption step in which the generated ozone is adsorbed by an adsorbent stored in an adsorption tower, and oxygen not adsorbed by the adsorbent is extracted from the adsorption tower and reintroduced into an ozone generator as a raw material gas to regenerate ozone, which is then supplied to the adsorption tower; a first desorption step in which, after the adsorption step is completed, a first carrier gas is introduced into the adsorption tower, and the ozone adsorbed by the adsorbent is desorbed together with the first carrier gas and extracted to the outside of the adsorption tower; and a vacuum desorption step in which, after the introduction of the first carrier gas is stopped, the pressure inside the adsorption tower is reduced to below atmospheric pressure, thereby making it possible to suppress an increase in the nitrogen concentration inside the adsorption tower.

[0022] Furthermore, according to the ozone supply method of the first embodiment performed as described above, in the vacuum desorption process, the adsorption tower is depressurized until C1×P1≧C2×P2 is satisfied, where P1 is the pressure value inside the adsorption tower during the adsorption process, P2 is the pressure value inside the adsorption tower during the vacuum desorption process, C1 is the nitrogen concentration in the adsorption tower during the adsorption process, and C2 is the nitrogen concentration of the first carrier gas during the first desorption process. Therefore, by depressurizing the adsorption tower until the nitrogen partial pressure during the vacuum desorption process is equal to or lower than the nitrogen partial pressure during the adsorption process, the amount of nitrogen adsorbed to the adsorbent becomes equal to or lower than that during the adsorption process, and it is possible to prevent a large amount of nitrogen from remaining in the adsorption tower.

[0023] Embodiment 2. Fig. 3 is a block diagram showing the configuration of an ozone supply system according to embodiment 2. Fig. 4 is a flow diagram showing the steps of an ozone supply method using the ozone supply system shown in Fig. 3. Fig. 5 is a flow diagram showing the steps of another ozone supply method using the ozone supply system shown in Fig. 3.

[0024] In the figure, parts similar to those in the first embodiment are denoted by the same reference numerals, and their description will be omitted. In Fig. 3, the ozone supply system 1 includes an oxygen source 2 as a second supply unit that supplies oxygen gas as a second carrier gas having a nitrogen concentration lower than the nitrogen concentration of the first carrier gas. The oxygen source 2 introduces the second carrier gas into adsorption tower A or adsorption tower B in the desorption step via a second carrier gas introduction path 105. The system is also equipped with a carrier gas switching valve 6 that switches between supplying the first carrier gas and the second carrier gas to adsorption tower A or adsorption tower B in the desorption step.

[0025] Next, an ozone supply method of the ozone supply system according to the second embodiment configured as described above will be described. First, as in the first embodiment, the adsorption process is performed in adsorption tower A (step ST01 in FIG. 4 ). Next, in adsorption tower A, which is performing the desorption process, the first supply unit 4 introduces dry air as a first carrier gas via first carrier gas introduction path 103. The introduced first carrier gas sweeps the ozone adsorbed on the adsorbent of adsorption tower A together with the first carrier gas out of adsorption tower A via carrier gas discharge path 104, thereby performing the first desorption process (step ST02 in FIG. 4 ).

[0026] Next, after stopping the introduction of the first carrier gas, oxygen gas as a second carrier gas is introduced into the adsorption tower A from the oxygen source 2 via the second carrier gas introduction path 105. The introduced second carrier gas scavenges the ozone adsorbed on the adsorbent of the adsorption tower A and the first carrier gas remaining in the adsorption tower A together with the second carrier gas via the carrier gas discharge path 104 to the outside of the adsorption tower A, thereby performing the second desorption step (step ST04 in FIG. 4 ).

[0027] In this way, the first carrier gas remaining in the adsorption tower A and the carrier gas discharge path 104 is replaced with the second carrier gas and purged out of the adsorption tower A. This reduces the accumulation of nitrogen gas in the adsorption tower A, thereby reducing the amount of NOx gas generated due to an increase in nitrogen gas in the circulation path 120 in the next adsorption process (step ST01). This reduces nitrogen oxides, which can reduce the efficiency of ozone generation and cause corrosion of the path, etc. Then, the introduction of the second carrier gas is stopped, and the process returns to the adsorption process (step ST01 in FIG. 2 ).

[0028] Next, another example of the ozone supply method of Embodiment 2 will be described. After the second desorption step and before the adsorption step, the introduction of the second carrier gas is stopped, and then a vacuum desorption step (step ST05 in FIG. 5 ) is performed in which the pressure inside the adsorption tower A is reduced by the pressure reducing unit 5 via the carrier gas outlet path 104 until the pressure inside the adsorption tower A becomes lower than atmospheric pressure. At this time, components of the first carrier gas and the second carrier gas remaining in the adsorption tower A and not replaced by the second carrier gas are exhausted.

[0029] This further reduces the accumulation of nitrogen gas in the adsorption tower A, thereby further reducing the amount of NOx gas generated due to the increase in nitrogen gas in the circulation path 120 in the next adsorption step (step ST01). This further suppresses the decrease in ozone generation efficiency and further reduces nitrogen oxides, which cause corrosion of the path, etc. Then, after the depressurization by the depressurization unit 5 is stopped, the process returns to the adsorption step (step ST01 in FIG. 5 ).

[0030] As described above, the above-described effects can be obtained if the pressure inside the adsorption column A in the vacuum desorption step is lower than atmospheric pressure. However, the following can be considered to further ensure that these effects are obtained.

[0031] For example, if the nitrogen concentration in adsorption tower A during the adsorption process is C1, the pressure value in adsorption tower A is P1, the nitrogen concentration of the first carrier gas during the first desorption process is C2, and the pressure value in adsorption tower A during the vacuum desorption process is P2, the adsorption tower A is depressurized until the following relationship is met: C1 x P1 ≧ C2 x P2 (Equation 1).

[0032] By reducing the pressure in adsorption tower A until the relationship expressed by Equation 1 above is satisfied and reducing the partial pressure of nitrogen gas (concentration x pressure) in the vacuum desorption step (step ST03) to a value equal to or lower than the partial pressure of nitrogen gas in the adsorption step (step ST01), the amount of nitrogen gas adsorbed by the adsorbent in adsorption tower A at the end of the desorption step can be reliably reduced to less than that during the adsorption step. This reliably reduces the accumulation of nitrogen gas in adsorption tower A and reliably reduces the amount of NOx gas generated due to an increase in nitrogen gas in circulation path 120 in the next adsorption step (step ST01).

[0033] The ozone supply system of the second embodiment configured as described above has the same effects as the first embodiment, and also includes a second supply unit for a second carrier gas having a nitrogen concentration lower than the nitrogen concentration of the first carrier gas, the second supply unit being connected to the carrier gas introduction path via a carrier gas switching valve that switches between the supply of the first carrier gas and the second carrier gas to the adsorption tower, and the carrier gas discharge path discharging ozone entrained in the second carrier gas to the outside of the adsorption tower in the desorption process, thereby further suppressing an increase in the nitrogen concentration in the adsorption tower.

[0034] Furthermore, the ozone supply method of the second embodiment performed as described above includes an adsorption step of adsorbing the generated ozone onto an adsorbent stored in an adsorption tower, and extracting oxygen that has not been adsorbed by the adsorbent from the adsorption tower and reintroducing it as a raw material gas into an ozone generator to regenerate ozone and supply it to the adsorption tower; a first desorption step of, after the adsorption step is completed, introducing a first carrier gas into the adsorption tower, desorbing the ozone adsorbed by the adsorbent together with the first carrier gas, and extracting it outside the adsorption tower; and a second desorption step of, after stopping the introduction of the first carrier gas, introducing a second carrier gas having a nitrogen concentration lower than that of the first carrier gas, desorbing the ozone adsorbed by the adsorbent, and extracting it outside the adsorption tower, and replacing the first carrier gas remaining in the adsorption tower with the second carrier gas. Therefore, an increase in the nitrogen concentration in the adsorption tower can be suppressed.

[0035] Furthermore, according to the ozone supply method of the second embodiment performed as described above, a vacuum desorption step is provided in which, after stopping the introduction of the second carrier gas, the pressure inside the adsorption tower is reduced to a pressure lower than atmospheric pressure. This makes it possible to further suppress an increase in the nitrogen concentration inside the adsorption tower.

[0036] Furthermore, according to the ozone supply method of the second embodiment performed as described above, in the vacuum desorption process, the adsorption tower is depressurized until C1×P1≧C2×P2 is satisfied, where P1 is the pressure value inside the adsorption tower during the adsorption process, P2 is the pressure value inside the adsorption tower during the vacuum desorption process, C1 is the nitrogen concentration in the adsorption tower during the adsorption process, and C2 is the nitrogen concentration of the first carrier gas during the first desorption process. Therefore, by depressurizing the adsorption tower until the nitrogen partial pressure during the vacuum desorption process is equal to or lower than the nitrogen partial pressure during the adsorption process, the amount of nitrogen adsorbed to the adsorbent becomes equal to or lower than that during the adsorption process, and it is possible to prevent a large amount of nitrogen from remaining in the adsorption tower.

[0037] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are contemplated within the scope of the technology disclosed in this application. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0038] 1 Ozone supply system, 101 Ozone introduction path, 103 First carrier gas introduction path, 104 Carrier gas discharge path, 105 Second carrier gas introduction path, 11 Switching valve, 12 Switching valve, 120 Circulation path, 121 Circulation blower, 122 Buffer tank, 13 Switching valve, 14 Switching valve, 15 Switching valve, 16 Switching valve, 17 Switching valve, 18 Switching valve, 2 Oxygen source, 3 Ozone generator, 4 First supply unit, 5 Pressure reduction unit, 6 Carrier gas switching valve.

Claims

1. An ozone supply system comprising: an ozone generator that generates ozone from oxygen supplied from an oxygen source; an adsorption tower that stores an adsorbent that adsorbs the ozone generated by the ozone generator and alternately performs an adsorption process in which ozone is adsorbed by the adsorbent and a desorption process in which ozone is desorbed from the adsorbent; a circulation path that extracts oxygen that is not adsorbed by the adsorbent from the adsorption tower in the adsorption process and circulates it to the ozone generator; a first supply unit for a first carrier gas; a carrier gas introduction path that introduces the first carrier gas from the first supply unit into the adsorption tower in the desorption process; a carrier gas outlet path that extracts ozone entrained in the first carrier gas to the outside of the adsorption tower in the desorption process; and a pressure reduction unit that reduces the pressure inside the adsorption tower to a pressure lower than atmospheric pressure in the desorption process.

2. An ozone supply system as described in claim 1, comprising a second supply unit for a second carrier gas having a nitrogen concentration lower than the nitrogen concentration of the first carrier gas, the second supply unit being connected to the carrier gas introduction path via a carrier gas switching valve that switches the supply of the first carrier gas and the second carrier gas to the adsorption tower, and the carrier gas discharge path discharging ozone entrained in the second carrier gas to outside the adsorption tower in a desorption process.

3. An ozone supply method comprising: an adsorption step of adsorbing the generated ozone into an adsorbent stored in an adsorption tower, and extracting oxygen not adsorbed by the adsorbent from the adsorption tower and reintroducing it into an ozone generator as a raw material gas to regenerate ozone and supply it to the adsorption tower; a first desorption step of introducing a first carrier gas into the adsorption tower after the adsorption step is completed, desorbing the ozone adsorbed by the adsorbent together with the first carrier gas and extracting it out of the adsorption tower; and a vacuum desorption step of reducing the pressure inside the adsorption tower to a pressure lower than atmospheric pressure after stopping the introduction of the first carrier gas.

4. An ozone supply method comprising: an adsorption step of adsorbing the generated ozone into an adsorbent stored in an adsorption tower, and withdrawing oxygen not adsorbed by the adsorbent from the adsorption tower and reintroducing it into an ozone generator as a raw material gas to regenerate ozone and supply it to the adsorption tower; a first desorption step of introducing a first carrier gas into the adsorption tower after the adsorption step is completed, desorbing the ozone adsorbed by the adsorbent together with the first carrier gas and discharging it to the outside of the adsorption tower; and a second desorption step of introducing a second carrier gas having a nitrogen concentration lower than that of the first carrier gas after stopping the introduction of the first carrier gas, desorbing the ozone adsorbed by the adsorbent and discharging it to the outside of the adsorption tower, and replacing the first carrier gas remaining in the adsorption tower with the second carrier gas.

5. The ozone supply method according to claim 4, further comprising a vacuum desorption step of reducing the pressure inside the adsorption tower to a pressure lower than atmospheric pressure after stopping the introduction of the second carrier gas.

6. An ozone supply method as described in claim 3 or claim 5, wherein, in the vacuum desorption process, the adsorption tower is depressurized until C1×P1≧C2×P2 holds, where P1 is the pressure value in the adsorption tower during the adsorption process, P2 is the pressure value in the adsorption tower during the vacuum desorption process, C1 is the nitrogen concentration in the adsorption tower during the adsorption process, and C2 is the nitrogen concentration of the first carrier gas in the first desorption process.