JP2000203807A - Supply of high-concentration ozone and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of nitrogen oxides while scarcely increasing the consumption of a high-purity oxygen gas by using a low-purity oxygen gas as a scavenging gas in a desorbing step for ozone in an adsorption cylinder, releasing the pressure of the interior of the adsorption cylinder after the desorption and then purging the interior of the adsorption cylinder with the high-purity oxygen gas. SOLUTION: Oxygen gas containing ozone generated in an ozonizer 1 is introduced into an adsorption cylinder A or B cooled to a low temperature to adsorb the ozone on an adsorbent. The oxygen gas led out of the adsorption cylinder A or B is passed through passages 12a or 12b and 15, mixed with a high-purity oxygen supply source 2 which is a raw material, introduced into the ozonizer 1 and reutilized. A low-purity oxygen gas as a scavenging gas is introduced from a pressure swing adsorption type oxygen generator (an oxygen PSA) 3 through passages 17 and 13a or 13b while heating the adsorption cylinder A or B after completing the adsorption to desorb the ozone. Thereby, the ozone is accompanied by the scavenging gas and supplied through passages 14a or 14b and 20 to the destination of consumption. After desorbing the ozone, the pressure of the adsorption cylinder A or B is released to then carry out a pressure releasing and purging step of the interior of the adsorption cylinder A or B with the high-purity oxygen gas from the supply source 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for supplying high-concentration ozone, and more particularly to a method and apparatus for supplying high-concentration ozone to equipment utilizing relatively high-concentration ozone, such as pulp bleaching or water treatment. Method and apparatus.

[0002]

2. Description of the Related Art Ozone is generated by high-voltage silent discharge in an ozone generator using air, oxygen-rich gas or oxygen gas as a source gas. However, the ozone concentration obtained by high-voltage silent discharge is 15% by mass or less even when oxygen gas is used as a raw material gas.
In consideration of efficiency, the ozone is supplied to the user at an ozone concentration of 6 to 7% by mass, at most about 10% by mass.

On the other hand, where ozone is used, higher concentration ozone is desired in order to improve the efficiency of treatment with ozone. For this reason, means for supplying ozone at a high concentration by concentrating the ozone-containing gas generated by the ozone generator has been devised.

[0004] For example, ozone has a property of adsorbing to an adsorbent such as silica gel at a low temperature. Therefore, using this property, ozone and oxygen are separated by a temperature fluctuation adsorption separation (TSA) method. However, a relatively high concentration of ozone is obtained. Further, oxygen separated from ozone is not exhausted, but is recycled as an ozone raw material by circulating it to an ozone generator.

[0005] The concentration of ozone by the TSA method is generally performed using a plurality of adsorption cylinders filled with an adsorbent such as silica gel that preferentially adsorbs ozone, and the ozone generated by an ozone generator is removed. The oxygen gas contained is introduced into the adsorption column cooled to a low temperature to cause the ozone in the oxygen gas to be adsorbed by the adsorbent in the adsorption column, and the oxygen gas derived from the adsorption column is converted into a high-purity oxygen gas as a raw material. Ozone adsorbing / oxygen reusing step of mixing and introducing into the ozone generator, and introducing a scavenging gas while heating the adsorbing cylinder after the step to desorb ozone adsorbed on the adsorbent,
The high concentration ozone is supplied by alternately repeating the ozone desorption / supply step of supplying the scavenging gas with ozone and supplying it to the ozone consuming destination.

[0006]

However, the scavenging gas used in the desorption step is a low-purity oxygen gas, such as oxygen PS, which is cheaper and easier to obtain than a high-purity oxygen gas.
In many cases, low-purity oxygen gas generated by A (pressure fluctuation adsorption type oxygen generator) was used. However, oxygen P
The low-purity oxygen gas from SA usually contains several percent of nitrogen gas.
The low-purity oxygen gas remains in the adsorption column after the ozone desorption / supply step has been completed. For this reason, when the ozone-containing oxygen gas is introduced into the adsorption cylinder in the next ozone adsorption / oxygen recycle process,
The low-purity oxygen gas remaining in the adsorption cylinder is led out of the adsorption cylinder and mixed with the high-purity oxygen gas as the raw material, and the nitrogen gas flows into the ozone generator to generate nitrogen oxides.

[0007] Since this nitrogen oxide causes deterioration of the adsorbent and significantly lowers the performance of the apparatus, conventionally,
A nitrogen oxide removing device is provided between the ozone generator and the adsorption column to prevent nitrogen oxides from being introduced into the adsorption column. However, the nitrogen oxide removing device is not only complicated and expensive in structure, but also requires labor and cost for maintenance, which greatly affects equipment cost and operating cost.

On the other hand, by using high-purity oxygen gas as the scavenging gas, the above-mentioned generation of nitrogen oxides can be almost completely suppressed. However, since high-purity oxygen gas is consumed in large quantities, In this case, too, the operation cost becomes large.

Therefore, the present invention provides a method for supplying high-concentration ozone, which can suppress the generation of nitrogen oxides without increasing the consumption of high-purity oxygen gas, and can reduce the equipment cost and operation cost. And a device.

[0010]

In order to achieve the above object, a method for supplying high-concentration ozone according to the present invention comprises introducing an ozone-containing oxygen gas generated by an ozone generator into an adsorption column cooled to a low temperature. The ozone in the oxygen gas is adsorbed by the adsorbent in the adsorption cylinder by means of the oxygen gas, and the oxygen gas discharged from the adsorption cylinder is mixed with the high-purity oxygen gas of the raw material and introduced into the ozone generator. A recycling process,
An ozone desorbing / supplying step of introducing a scavenging gas while heating the adsorption column after the step to desorb ozone adsorbed on the adsorbent, and accompanying the scavenging gas with ozone and supplying it to an ozone consuming destination; Is alternately repeated to supply high-concentration ozone, using a non-high-purity oxygen gas as a scavenging gas in the ozone desorption / supply step, and releasing the inside of the adsorption cylinder after the ozone desorption / supply step. A pressure release purge step of purging the interior of the adsorption cylinder with high-purity oxygen gas after the pressure is applied is performed. In particular, the pressure release is performed on the scavenging gas introduction side of the adsorption cylinder.

The high-concentration ozone supply apparatus of the present invention includes a high-purity oxygen gas supply source for supplying a high-purity oxygen gas as an ozone raw material, and a high-purity oxygen gas supplied from the high-purity oxygen gas supply source. Generator that generates ozone by using ozone as a raw material and an adsorbent that preferentially adsorbs ozone are filled, and the ozone generated by the ozone generator is adsorbed in a relatively low-temperature adsorption process, and desorbed at a relatively high temperature. The desorption operation is alternately performed in the adsorption column, and the oxygen gas derived from the adsorption column without being adsorbed by the adsorbent in the adsorption step is mixed with the high-purity oxygen gas supplied from the high-purity oxygen gas supply source. An oxygen circulation path, a scavenging gas introduction path for introducing a scavenging gas for deriving from the adsorption cylinder along with the ozone desorbed from the adsorbent in the desorption step, and a non-high-purity oxygen gas as a scavenging gas. To A non-high-purity oxygen gas supply source for supply, an ozone supply path for supplying an ozone entrained scavenging gas derived from the adsorption cylinder to an ozone consuming destination, and a pressure release path for releasing gas in the adsorption cylinder, A high-purity oxygen introduction path for introducing high-purity oxygen gas into the cylinder is provided.

[0012]

FIG. 1 is a schematic system diagram showing one embodiment of a high-concentration ozone supply apparatus according to the present invention. This high-concentration ozone supply device is configured to alternately switch two adsorption columns A and B filled with an adsorbent such as silica gel to an adsorption step and a desorption step to concentrate ozone, and generate ozone. Generator 1, a high-purity oxygen supply source 2 for supplying a high-purity oxygen gas as an ozone raw material, and a non-high-purity oxygen gas used as a scavenging gas, for example, a low-purity oxygen gas. An oxygen PSA 3 and a circulation pump 4 for circulating and recycling oxygen gas are provided.

Each of the adsorption tubes A and B has an ozone-containing oxygen introduction path 11a, 11b and a circulating oxygen derivation path 12
a, 12b, the scavenging gas introduction paths 13a, 13b, and the concentrated ozone derivation paths 14a, 14b, which are connected to the respective paths by a predetermined procedure when switching the process of the adsorption cylinders A, B. Valves 21a, 21 which open and close with pressure
b, 22a, 22b, 23a, 23b, 24a, 24b
Are provided respectively.

The circulating oxygen outlet paths 12a and 12b are
After merging with the oxygen circulation path 15 provided with the circulation pump 4, it is connected to a raw oxygen supply path 16 for supplying a high-purity oxygen gas from the high-purity oxygen supply source 2 to the ozone generator 1. Further, a low-purity oxygen introduction path 17 for introducing low-purity oxygen gas generated by the oxygen PSA 3 as a scavenging gas, and a pressure release (blow) in the adsorption tubes A and B are provided to the scavenging gas introduction paths 13a and 13b. And a high-purity oxygen introduction path 19a, 19b connected to the raw oxygen supply path 16 from the high-purity oxygen supply source 2 is provided in each of the ozone-containing oxygen introduction paths 11a, 11b. Have been. Further, the low-purity oxygen introduction path 17,
The pressure release path 18 and the high-purity oxygen introduction path 19 are provided with valves 27, 28, 29a, and 29b that are opened and closed in a predetermined order.

Although not shown, each of the adsorption tubes A and B
Is provided with a cooling means for cooling the adsorbent, for example, a cooling jacket using liquid oxygen or liquid nitrogen as a cooling source, and a heating means, for example, an electric heater. Further, a concentration stabilizer for stabilizing the ozone concentration can be provided in the ozone supply path 20 for supplying the concentrated ozone led to the concentrated ozone deriving paths 14a and 14b to the ozone consuming destination. Further, three or more adsorption cylinders can be used.

The thus-formed high-concentration ozone supply apparatus switches the above-mentioned valves in a predetermined order and opens and closes them, and cools or heats the respective adsorption cylinders, thereby causing the adsorption cylinders A and B to generate ozone. Oxygen gas containing ozone generated in the reactor 1 is introduced into an adsorption column cooled to a low temperature to adsorb ozone to the adsorbent, and oxygen gas not adsorbed by the adsorbent is mixed with high-purity oxygen gas and circulated. The ozone adsorption / oxygen recycle process for reuse, and the scavenging gas is introduced while heating the adsorption column to desorb ozone adsorbed on the adsorbent in the above process, and the scavenging gas is accompanied by ozone to consume ozone. By alternately switching to the ozone desorption / supply step to be supplied first, concentrated ozone can be supplied continuously.

Next, an operation procedure for concentrating and supplying ozone to a predetermined concentration by using the above apparatus will be described. In the first stage, it is assumed that the adsorption column A is in the ozone adsorption / oxygen recycle step and the adsorption column B is in the desorption / supply step.

At this time, the switching valve 21a of the ozone-containing oxygen introducing path 11a and the switching valve 22a of the circulating oxygen deriving path 12a of the adsorption cylinder A in the ozone adsorption / oxygen recycle process.
, The switching valve 23b of the scavenging gas introduction path 13b, the switching valve 24b of the concentrated ozone derivation path 14b, and the switching valve 27 of the low-purity oxygen introduction path 17 in the adsorption cylinder B in the open, desorption / supply process.
Is open, and all other switching valves are closed. The adsorption cylinder A is cooled to a predetermined temperature and the adsorption cylinder B
Is heated to a predetermined temperature in a predetermined temperature rising pattern.

The high-purity oxygen gas that has passed from the high-purity oxygen supply source 2 through the raw material oxygen supply path 16 and merged with the circulating oxygen from the oxygen circulation path 15 is used as an ozone raw material by the ozone generator 1.
The oxygen is partly converted to ozone by the high-voltage silent discharge in the ozone generator 1, and becomes ozone-containing oxygen gas. The ozone-containing oxygen gas is passed through the ozone-containing oxygen introduction path 11a of the adsorption cylinder A and the switching valve 21a. It is introduced into the adsorption column A in the circulation reuse step. As a result, the ozone in the oxygen gas is adsorbed by the adsorbent such as silica gel kept cooled at -80 ° C, for example.

The oxygen gas that has been drawn out of the adsorption column A without being adsorbed by the adsorbent is supplied to the circulation oxygen deriving path 12a and the switching valve 22.
a, through the oxygen circulation path 15 and the circulation pump 4, merge with the high-purity oxygen gas in the raw material oxygen supply path 16, and are circulated and reused as the ozone raw material. The ozone concentration of the ozone-containing oxygen gas generated by the ozone generator 1 is arbitrary,
In consideration of the efficiency of the ozone generator 1, usually 6 to 7% by mass is appropriate.

On the other hand, in the adsorption cylinder B in the desorption / supply step, the adsorbent is heated by a heater or the like, and the low-purity oxygen introduction path 17, the switching valve 27, the scavenging gas introduction path 13b, and the switching valve 23b are supplied from the oxygen PSA 3 to the low purity oxygen introduction path. The low-purity oxygen gas that has passed through is introduced as a scavenging gas, and the ozone desorbed from the adsorbent is condensed with the scavenging gas from the adsorption column B to the concentrated ozone deriving path 14.
b, and is supplied to the ozone consuming destination through the ozone supply path 20 via the switching valve 24b.

This desorption / supply step is performed for a predetermined time set beforehand, usually until the ozone concentration of the ozone-enriched gas discharged from the adsorption column B decreases to a predetermined concentration. The switching valve 24b and the switching valve 27 of the low-purity oxygen introduction path 17 are closed and detached.
The supply step ends. Subsequently, a pressure release purge step is performed as a preparatory operation for entering the next adsorption step. In the pressure release purge step, first, the switching valve (blow valve) 28 of the pressure release path 18 is opened, and a pressure release operation (blow) for releasing the gas in the adsorption tube B is performed. Thereafter, the switching valve 29b is opened, and the high-purity oxygen gas from the high-purity oxygen supply source 2 is introduced into the adsorption column B, which has been reduced to a predetermined pressure by the pressure release operation through the high-purity oxygen introduction path 19b and the switching valve 29b. Then, the operation of discharging the low-purity oxygen gas (scavenging gas) existing in the adsorption cylinder B from the adsorption cylinder B to the outside through the scavenging gas introduction path 13b, the switching valve 23b, the pressure release path 18, and the switching valve 28, that is, A purge operation is performed. In addition, it is desirable to install an ozone decomposer 30 for removing ozone contained in the exhaust gas downstream of the pressure release path 18.

Thus, the gas in the adsorption cylinder B, that is, the low-purity oxygen gas containing nitrogen introduced as a scavenging gas in the desorption / supply process is purged from the adsorption cylinder B by the newly introduced high-purity oxygen gas. Then, the interior of the adsorption cylinder B is filled with the newly introduced high-purity oxygen.

FIG. 2 is a schematic diagram showing the flow of gas in the adsorption cylinder and the ozone concentration distribution in the cylinder. The hatched portion indicates a portion having a high ozone concentration. First, FIG.
Shows the state at the end of the adsorption step. In the figure, the ozone-containing oxygen gas (G1) is introduced from the ozone-containing oxygen introduction path 11 on the cylinder inlet side and circulated from the circulating oxygen outlet path 12 on the cylinder outlet side. Oxygen (G2) is discharged, and the adsorbent in the cylinder has ozone O up to near the cylinder outlet side.
₃ is saturated.

When the mode is switched to the desorption step, as shown in FIG. 2B, low-purity oxygen gas (G3) is introduced as a scavenging gas from the scavenging gas introduction path 13 on the cylinder outlet side, and the ozone desorbed from the adsorbent is discharged. With this, it is led out as an ozone-enriched gas (G4) to the concentrated ozone outlet path 14 on the cylinder inlet side.
When the desorption step is completed, as shown in FIG. 2 (C), the pressure is released from the pressure release path 18 via the scavenging gas introduction path 13 on the cylinder outlet side, and the gas (low-purity oxygen) in the cylinder is released. Gas (G3)) is discharged to a predetermined pressure. Further, FIG.
As shown in (D), high-purity oxygen introduction route 1 on the cylinder inlet side
By introducing the high-purity oxygen gas (G5) into the cylinder from step 9, the low-purity oxygen gas (G3) remaining in the cylinder is purged.

By performing the purging operation by introducing the high-purity oxygen gas for a predetermined time, the low-purity oxygen gas in the cylinder can be removed.
That is, nitrogen contained in the low-purity oxygen gas can be discharged outside the cylinder. Therefore, even if the gas in the cylinder is circulated and reused in the ozone generator 1 in the next ozone adsorption / oxygen recycle process, no nitrogen oxide is generated in the ozone generator 1.

This eliminates the need for installing a conventional nitrogen oxide removing apparatus, and can reduce equipment costs and maintenance costs. Further, the consumption of the high-purity oxygen gas can be reduced as compared with the case where the high-purity oxygen gas is used for all of the scavenging gas, so that the operation cost can be reduced.

The pressure release operation of the adsorption cylinder may be performed immediately after the completion of the desorption step, but ozone remaining adsorbed on the adsorbent in the cylinder is discharged outside the cylinder by the pressure release operation. Therefore, it is preferable to perform the pressure release operation after cooling to a temperature at which ozone can be kept adsorbed by the adsorbent. At the end of the desorption step, the ozone concentration on the cylinder inlet side to which the concentrated ozone deriving path 14 is connected is high, so that the pressure release operation is performed from the cylinder outlet side to which the scavenging gas introduction path 13 is connected. Ozone emissions during operation can be minimized.

Further, the operating conditions of the pressure release operation and the purge operation can be appropriately set according to the volume and shape of the adsorption column, and the flow rates of the pressure release gas and the purge gas can be arbitrarily set. Usually, it is preferable to perform the pressure release operation until the pressure in the cylinder becomes close to the atmospheric pressure. Also, the flow rate of the depressurized gas and the flow rate of the purge gas (high-purity oxygen gas) may be set as large as possible without adversely affecting the adsorbent, so that the nitrogen gas can be purged from the adsorption cylinder within an appropriate time. Just set it.

The adsorption cylinder after the pressure release purge step is switched to the above-mentioned ozone adsorption / oxygen circulation / reuse step, and the ozone adsorption / oxygen circulation / reuse step, desorption / supply step, and discharge step are performed in each adsorption cylinder. The pressure purge step is performed repeatedly.

[0031]

EXAMPLES Using the adsorption column having an internal volume of 0.09 m ³ filled with silica gel as an adsorbent, 0.5 MPa cylinder pressure
a, the flow rate of each gas was set to 0.05 Nm ³ / min, and the desorption time was set to 100 minutes. In this case, if high-purity oxygen gas is used for all of the scavenging gas, the required amount is 5N.
the m ^3.

Under the above conditions, the amount of low-purity oxygen gas used as a scavenging gas in the desorption step is the same 5 Nm ³
Becomes Then, as a result of examining the time of the pressure release purge step, it was confirmed that the low-purity oxygen gas in the cylinder could be reliably purged by setting the time of the purge operation for introducing high-purity oxygen to 20 minutes. Therefore, the consumption of the high-purity oxygen gas used in the purge operation is reduced to 5 Nm ³
From 1 to ³ Nm ³ .

[0033]

As described above, according to the present invention,
Even if a nitrogen-containing gas is used as a scavenging gas in the desorption step, nitrogen does not flow into the ozone generator, so there is no need to install a nitrogen oxide removing device, which requires a large facility cost and operating cost, and purifies the gas. The consumption of high-purity oxygen gas can be significantly reduced as compared with the case where high-purity oxygen gas is used for all of the gases. In addition, since simple piping and a switching valve can be added to the conventional apparatus, high-concentration ozone can be supplied at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing one embodiment of a high-concentration ozone supply device of the present invention.

FIG. 2 is a schematic diagram showing a gas flow in an adsorption cylinder and an ozone concentration distribution in the cylinder.

[Explanation of symbols]

A, B: adsorption cylinder, 1: ozone generator, 2: high-purity oxygen supply source, 3: oxygen PSA, 4: circulation pump, 11a, 11
b: ozone-containing oxygen introduction path, 12a, 12b: circulating oxygen derivation path, 13a, 13b: scavenging gas introduction path, 14
a, 14b: a concentrated ozone deriving route, 15: an oxygen circulation route, 16: a raw material oxygen supply route, 17: a low-purity oxygen introduction route, 18: a pressure release route, 19a, 19b: a high purity oxygen introduction route, 20: ozone supply Routes, 21a, 21b, 22
a, 22b, 23a, 23b, 24a, 24b, 27,
28, 29a, 29b: switching valve, 30: ozone decomposer

Continued on the front page F term (reference) 4D012 CA13 CB06 CD01 CG01 CJ02 CJ06 4D050 AA01 AA12 BB02 BD04 BD06 BD08 4G042 AA07 CB12 CB15 CB16 CE04 4L055 AD08 BB18 CB47

Claims (3)

[Claims] 1. An oxygen gas containing ozone generated by an ozone generator is introduced into an adsorption column cooled at a low temperature, and the ozone in the oxygen gas is adsorbed by an adsorbent in the adsorption column. An ozone adsorption / oxygen recycle step of mixing the oxygen gas leading out of the cylinder with the high-purity oxygen gas of the raw material and introducing the mixture into the ozone generator; and introducing a scavenging gas while heating the adsorption cylinder after the step is completed. A method of supplying high-concentration ozone by alternately repeating the ozone desorbing / supplying step of desorbing ozone adsorbed on the adsorbent and supplying the ozone consuming destination with the scavenging gas accompanied by ozone. A non-high-purity oxygen gas is used as a scavenging gas in the desorption / supply step, and after the ozone desorption / supply step, the pressure in the adsorption cylinder is released, and then the interior of the adsorption cylinder is purged with high-purity oxygen gas. Pressure The method of supplying the high-concentration ozone and performs di step. 2. A method for supplying high-concentration ozone, wherein the pressure release is performed on a scavenging gas introduction side of an adsorption column. 3. A high-purity oxygen gas supply source for supplying high-purity oxygen gas as an ozone raw material, and an ozone generator for generating ozone using the high-purity oxygen gas supplied from the high-purity oxygen gas source as a raw material. , Adsorbent that preferentially adsorbs ozone is filled, and the operation of adsorbing ozone generated by an ozone generator in a relatively low temperature adsorption process and desorbing in a relatively high temperature desorption process is performed alternately. A cylinder, an oxygen circulation path for mixing oxygen gas derived from the adsorption cylinder without adsorbing the adsorbent in the adsorption step with high-purity oxygen gas supplied from the high-purity oxygen gas supply source, and adsorbing in the desorption step A scavenging gas introduction path for introducing scavenging gas into the adsorption cylinder to accompany ozone desorbed from the adsorbent, and a non-high-purity oxygen gas supply source for supplying non-high-purity oxygen gas as a scavenging gas. , Adsorption cylinder An ozone supply path for supplying an ozone-conducting scavenging gas derived from the ozone consuming destination, a pressure release path for releasing gas in the adsorption cylinder, and a high-purity oxygen for introducing high-purity oxygen gas into the adsorption cylinder. An apparatus for supplying high-concentration ozone, comprising an introduction path.