JP5058107B2 - NOx purification device - Google Patents

Description

  The present invention relates to a NOx purification device that purifies room temperature gas containing NOx in a tunnel or an underground parking lot where an automobile travels, and relates to a NOx purification device that can be stably and easily managed for a long period of time, for example.

  In recent years, surrounding environmental pollution due to acid rain has become serious. Against this backdrop, there are regulations on the emission of harmful substances such as NOx (nitrogen oxides) contained in ventilation gas in tunnels and underground parking lots where automobiles travel, and exhaust gas along roads at intersections where there is a large amount of automobile travel. It has been strengthened.

  A conventionally used NOx purification catalyst in combustion exhaust gas is not activated when the gas temperature is low. However, the current ventilation gas for automobile driving tunnels or the like is air at normal temperature. Therefore, the conventional NOx purification catalyst cannot be used for NOx purification of ventilation gas.

  Thus, two purification methods have been proposed as methods for removing NOx and the like contained in ventilation gas in the presence of oxygen at room temperature.

One purification method is a dry NOx adsorption removal method in which NOx in the ventilation gas is adsorbed and removed by an adsorbent. Here, the constituent components of NOx are NO (nitrogen monoxide) and NO ₂ (nitrogen dioxide). In particular, since the NO ₂ in NOx has a property of easily adsorbed on the adsorbent, it is possible to easily adsorb and remove NO ₂ in the ventilation gas. In this NOx adsorption removal method, the NOx removal performance can be maintained by exchanging a new adsorbent before the adsorption saturation of NO ₂ .

However, NOx in the ventilation gas is usually because about 90% of NO and the remaining 10% of NO ₂ and the component, is very poor removal efficiency of NOx is only adsorption removal of NO ₂ by the adsorbent.

Therefore, in this dry NOx adsorption removal method, before adsorbing NOx to the adsorbent, O ₃ (ozone) is added to the ventilation gas and converted to NO ₂ by an oxidation reaction of NO and O _3. NOx removal efficiency is increased.

The dry NOx adsorption / removal method allows the used adsorbent, which has sufficiently adsorbed NO _2, to be brought into a state where it can be reused by carrying it to another recycling plant and then performing high-temperature heat treatment or chemical cleaning. A method of reproducing and newly reusing is considered (for example, see Patent Document 1).

Another purification method is a wet NOx absorption and removal method in which NOx is absorbed and removed with an alkaline solution. This wet NOx absorption / removal method absorbs and removes NOx, which is an acidic gas, by spraying an alkali solution into a ventilation gas or by bubbling a ventilation gas sent into the alkali solution (for example, Patent Documents). 2).
JP-A-8-24579 Japanese Patent Laid-Open No. 6-99030

  The above-described purification method using the dry NOx adsorption removal method is being put into practical use because an adsorbent can be used relatively easily.

However, the purification method using the dry NOx adsorption / removal method requires a new regeneration process of the adsorbent by the regeneration factory and the replacement process of the adsorbent before the NO ₂ adsorption saturation. In addition, there is a problem that the cost is high. Moreover, in order to purify the ventilation gas over a long period of time, it is necessary to install a large number of adsorbents, and there are problems such as the burden of equipment costs and an increase in installation space.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a NOx purification device that can be stably and easily managed for a long period of time.

In order to solve the above-mentioned problems, the present invention supplies an adsorbing device that is installed in a ventilation gas flow path and contains an adsorbent that physically adsorbs NOx (nitrogen oxide) contained in the ventilation gas, and air gas. an air supply device, the discharging process air gas supplied from the air supply device generates O _3, and means for injecting O ₃ that is the product to the ventilation gas flow path, O _3, which is the injection By means of oxidizing NO contained in the ventilation gas to generate NO ₂ and when the adsorbent has adsorbed a preset amount of NOx, a reducing gas is supplied and the inside of the adsorption device is A substitution means for substituting with a reducing gas atmosphere; and a desorption means for depressurizing the adsorption apparatus and desorbing NOx adsorbed on the adsorbent when the inside of the adsorption apparatus is substituted with a reducing gas atmosphere; Release in the reducing gas atmosphere And a means for eliminating the desorbed NOx by performing an electrical treatment.

<Action>
Therefore, according to the present invention, by taking the above-described means, NOx adsorbed on the adsorbent is desorbed and decomposed, the adsorbent is regenerated on the spot, and the regenerated adsorbent is used for ventilation gas. Since NOx in the inside can be adsorbed and removed, it is possible to provide a NOx purification device that can be stably and easily managed over a long period of time.

  According to the present invention, it is possible to provide a NOx purification device that can be stably and easily managed over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
(Configuration of NOx purification device)
FIG. 1 is a schematic diagram showing a configuration of a NOx purification device 1 according to the first embodiment of the present invention.

The NOx purification device 1 purifies harmful substances such as NOx (nitrogen oxide) contained in the ventilation gas X coexisting with oxygen, and includes an adsorption device 10, a discharge device 20, an intake device 30 (desorption means). Air supply device 40 (NO ₂ generation means), reducing gas supply device 50 (replacement means), switching valves 61 to 65, and control device 70. Moreover, each apparatus 10-50 is connected by the gas pipe 80, and the inflow and outflow of gas are controlled by opening and closing of the switching valves 61-65.

  Ventilation gas X is a ventilation gas in tunnels where automobiles run and underground parking lots where many cars are parked, exhaust gas along roads at intersections where there is a lot of automobile traffic, and other harmful substances at normal temperature and low concentration. Various gases containing certain NOx.

  The adsorption device 10 is installed at an appropriate location of the ventilation gas flow path 81 that takes in the room temperature gas in which oxygen coexists, and removes NOx (nitrogen oxide) from the ventilation gas X to make the purified gas Y. . Specifically, the adsorbent 15 is accommodated in the adsorption device 10, and the adsorbent 15 has a function of physically adsorbing NOx under a ventilation gas atmosphere.

Supplementally, O ₃ is supplied from the discharge device 20 described later, and NO (nitrogen monoxide), which is a constituent component of NOx contained in the ventilation gas, is oxidized to NO ₂ (nitrogen dioxide). The NO ₂ is physically adsorbed by the adsorbent 15 to remove NO x.

  In addition, as the adsorbent 15, a material in which zeolite, noble metal, activated carbon, alkali metal, alkaline earth metal, activated alumina, silica, manganese oxide or the like is laminated is used. . Of these adsorbents, it is particularly desirable to use zeolite or activated alumina.

The discharge device 20 discharges the air gas supplied from the air supply device 40 to generate ozone gas (O ₃ ). Then, the discharge device 20 injects the generated O ₃ into the ventilation gas flow path 81 on the inflow side of the adsorption device 10. Although not shown, the discharge device 20 includes a discharge unit and a discharge power source. The discharge unit 20 supplies a desired discharge voltage to the discharge unit via the high-voltage cable line from the discharge power source. To do.

  Further, when NOx desorbed from the adsorbent 15 is introduced from the adsorbing device 10 by the process described later, the discharging apparatus 20 decomposes and eliminates the NOx by the discharging process.

  The intake device 30 sucks the inside of the adsorption device 10 and depressurizes it. For example, the intake device 30 is controlled by the control device 70, and when it is determined that the inside of the adsorption device 10 has been replaced with a reducing gas atmosphere, the adsorption device 10 is decompressed. Thereby, NOx adsorbed on the adsorbent 15 is desorbed.

Supplementally, as shown in FIG. 2A, NO ₂ is pressed against the adsorbent 15 by atmospheric pressure. When the pressure is reduced in this state, as shown in FIG. 2B, the force for suppressing NO ₂ to the adsorbent 15 is reduced, so that NOx is desorbed. The desorbed NOx flows into the discharge device 20.

  The air supply device 40 supplies air gas to the discharge device 20.

The reducing gas supply device 50 extracts nitrogen gas (N ₂ ), which is a reducing gas, from the air gas and supplies it to the adsorption device 10. For example, when the reducing gas supply device 50 is controlled by the control device 70 and it is determined from the concentration of NOx flowing into the adsorption device 10 that the allowable amount of NOx adsorbed to the adsorbent 15 has been exceeded, N is added to the adsorption device 10. _Two gases are supplied. Thereby, the inside of the adsorption device 10 is replaced with a reducing gas atmosphere. As the reducing gas supply device 50, for example, a PSA (Pressure Swing Adsorption) nitrogen generator can be used. Further, the reducing gas supply device 50 is appropriately filled with an adsorbent having a pore size, and only N ₂ gas is separated and extracted from the gas components in the air, thereby supplying N ₂ gas as the reducing gas. .

  The switching valves 61 to 65 are valves that open and close in response to a valve opening / closing control command from the control device 70, and control the gas supplied to the devices 10 to 50.

  The control device 70 is controlled by each device, and performs switching of operation modes shown in FIGS.

(Operation of NOx purification device)
FIG. 3 is a flowchart for explaining the operation of the NOx purification device 1 according to this embodiment.

  When the power is turned on, the NOx purification device 1 starts the adsorption operation (S1). When the NOx adsorption amount adsorbed on the adsorbent 15 exceeds the allowable amount (S2-Yes), the NOx purification device 1 starts the adsorption operation again after performing the replacement operation and the regeneration operation (S3, S4). To do. Thereafter, the NOx purification device 1 sequentially repeats these processes.

  FIG. 4 is a schematic diagram showing a state during NOx adsorption operation.

When NOx is adsorbed, a valve opening / closing control command is sent from the control device 70, the switching valves 61, 62, 64 are opened, and the other switching valves 63, 65 are closed. Thereby, the room temperature ventilation gas X containing NOx (NO, NO ₂ ) which is a harmful substance taken in from the ventilation gas flow path 81 is introduced into the adsorption device 10.

Subsequently, under the control of the control device 70, the air supply device 40 and the discharge device 20 are activated and O ₃ gas is introduced into the adsorption device 10. Specifically, air gas containing O ₂ (oxygen) is taken into the discharge device 20 from the air supply device 40. And in the discharge device 20, a discharge process is performed, O ₂ is dissociated from the air gas by the discharge reaction, and O ₃ is generated. The generated O ₃ is injected into the ventilation gas flow path 81 on the inflow side of the adsorption device 10.

In the ventilation gas flow path 81, the injected O ₃ reacts with NO in the ventilation gas X, and NO, which is a constituent component of NOx, is oxidized to NO ₂ . The oxidized NO ₂ is adsorbed by the adsorbent 15 in the adsorption device 10.

In short, NO, which occupies about 90% of the ventilation gas X, is converted to NO ₂ by oxidative decomposition, so that it can be reliably adsorbed by the adsorbent 15 in the adsorption device 10. As a result, NOx can be efficiently removed from the room temperature ventilation gas X. The injection concentration of O ₃ is preferably the same mole number concentration as the NO concentration in the NOx concentration.

  FIG. 5 is a schematic diagram showing a state during the replacement operation with the reducing gas.

When the required period has elapsed after the start of the adsorption process of the NOx purification device 1, it can be considered that the adsorption amount of NOx adsorbed on the adsorbent 15 exceeds the allowable amount. In this case, the control device 70 sends a valve opening / closing control command to replace the inside of the adsorption device 10 with the reducing gas atmosphere, opens the switching valves 63, 65, and closes the other switching valves 61, 62, 64. . Here, the required period is set to a period before the adsorbent 15 undergoes NO ₂ adsorption saturation. For example, it is determined from the amount of traffic of the automobile, the state of contamination in the air, the type of the adsorbent 15, the amount of NOx generated, etc., and is set in advance in a setting memory (not shown) of the control device 70 so as to be appropriately variable.

Subsequently, under the control of the control device 70, the reducing gas supply device 50 and the intake device 30 are activated (ON), and the discharge device 20 is stopped (OFF). At this time, the reducing gas supply device 50 takes in the air gas as it starts up, and separates and extracts only the N ₂ gas from the gas components in the air. Then, a reducing gas is supplied from the downstream side of the adsorption device 10, and the inside of the adsorption device 10 is replaced with a reducing gas atmosphere.

  Note that whether or not the amount of NOx adsorbed by the adsorbent exceeds the allowable amount may be determined from the concentration of NOx flowing into the adsorption device 10, for example.

  FIG. 6 is a schematic diagram showing a state during the regeneration operation of the adsorbent 15.

When the controller 70 determines that the inside of the adsorption device 10 has been sufficiently replaced with the reducing gas atmosphere state, the regeneration process for the adsorbent 15 is executed. At this time, the control device 70 detects the O ₂ gas concentration in the adsorption device 10 with an oxygen sensor, and determines whether or not the reducing gas atmosphere state is sufficiently substituted. This is because if the O ₂ gas concentration is low, it can be considered that the N ₂ gas concentration is high.

  When executing the regeneration process, the control device 70 sends a valve opening / closing control command for executing the regeneration process. Thereby, after the switching valve 65 is opened and the switching valves 61, 62, 63, 64 are closed, the intake device 30 and the discharge device 20 are activated (ON).

  As the intake device 30 is activated, the suction device 10 is inhaled. Here, since the switching valves 61, 62, 63, 64 are closed, the inside of the adsorption device 10 is depressurized in a reducing gas atmosphere. When the intake device 10 is depressurized in a reducing gas atmosphere, NOx adsorbed on the adsorbent in the adsorption device 10 is desorbed.

The desorbed NOx is introduced into the discharge device 20. In the discharge device 20, the discharge process is performed in a reduced reducing gas (N ₂ ) atmosphere. Thus, NO is a NOx flowing desorbed from the adsorbent 15 to the discharge device 20, NO ₂ is reduced and decomposed into harmless N ₂ by the action of the discharge reaction, disappear.

(Effect of NOx purification device)
As described above, the NOx purification device 1 according to this embodiment includes the adsorber 10 that stores the adsorbent 15 that physically adsorbs NOx (nitrogen oxide) contained in the ventilation gas X, and the ventilation gas X. When the adsorbent 15 adsorbs a preset amount of NOx by oxidizing NO contained therein to generate NO ₂ , a reducing gas is supplied to reduce the inside of the adsorber 10. A replacement gas supply device 50 that replaces with a gas atmosphere, and an intake device 30 that depressurizes the adsorption device 10 and desorbs NOx adsorbed on the adsorbent 15 when the adsorption device 10 is replaced with a reducing gas atmosphere; Since the discharge device 20 for eliminating the desorbed NOx by performing discharge treatment in a reducing gas atmosphere is provided, the operation can be stably and easily managed over a long period of time.

  That is, in the NOx purification device according to this embodiment, the operation modes of FIGS. 4 to 6 are sequentially repeated based on the command of the control device 70, so that NOx adsorbed on the adsorbent 15 is desorbed and decomposed. The adsorbent 15 can be regenerated on the spot, and NOx in the ventilation gas X can be adsorbed and removed using the regenerated adsorbent 15. In short, since the adsorbent 15 in the adsorbing device 10 can be regenerated while the installation state is fixed, it is not necessary to replace the adsorbent 15 with a new adsorbent, and it is not necessary to remove and carry it into the regenerating facility.

  In addition, although the NOx purification apparatus 1 in this embodiment is one example of use, since the adsorbent 15 can be regenerated on the spot in a short time, for example, even when there is a lot of NOx emissions from a car in the daytime, etc. The NOx purification process and the adsorbent regeneration process can be performed alternately with almost no effect on the NOx purification.

  In addition, according to the NOx purification device 1 of the present embodiment, it is possible to achieve a reduction in size and price compared to a general NOx purification device 2 that does not perform the regeneration process of the adsorbent.

  Supplementally, the NOx purification device is installed in a semi-closed place such as a tunnel where toxic gas accumulates. Here, the general NOx purification device 2 is packed with a large number of adsorbents so that it can be operated from half a year to one year. Therefore, as shown in FIG. 7, there is a problem that the installation space is vast and the construction burden is great. On the other hand, the NOx purification device 1 according to the present embodiment can reuse the adsorbent 15 and reduce the size of the device. Therefore, the installation space is small, and the construction work can be reduced. Has a remarkable effect.

<Second Embodiment>
FIG. 8 is a configuration diagram showing the configuration of the NOx purification device 1S according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the part same as the already demonstrated part, and the overlapping description is abbreviate | omitted unless there is particular description.

  In the NOx purification device 1S according to the present embodiment, the NOx purification device 1 according to the first embodiment further includes a resistance heater heating device 90. This resistance heater heating device 90 covers the adsorption device 10 and heats the adsorbent 15.

  In the NOx purification device 1S according to the present embodiment, the resistance heater heating device 90 is also activated simultaneously during the decompression operation by the intake air of the intake device 30. As a result, the NOx adsorbed on the adsorbent 15 can be desorbed in a shorter time than simply reducing the pressure, and the adsorbent 15 can be regenerated with higher efficiency. As a merit of using not only the decompression means but also the heating means in this way, the heating temperature is low because it is under reduced pressure compared to the case of the heating means alone. As compared with, NOx desorption is possible in a short time because the heating means is used in combination.

  As long as the adsorbent 15 can be heated, a device other than the resistance heater 90 may be used. For example, as shown in FIG. 9, the high frequency heating device 91 may cover the adsorption device 10. Even with such a configuration, it has been confirmed that NOx can be more efficiently desorbed according to the study by the present inventors.

<Other embodiments>
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine a component suitably in different embodiment.

It is a mimetic diagram showing composition of NOx purification device 1 concerning a 1st embodiment of the present invention. It is a schematic diagram for demonstrating the effect of pressure reduction by the intake device 30 according to the embodiment. It is a flowchart for demonstrating operation | movement of the NOx purification apparatus 1 which concerns on the same embodiment. It is a mimetic diagram showing the state at the time of NOx adsorption operation of NOx purification device 1 concerning the embodiment. It is a mimetic diagram showing the state at the time of substitution operation to reducing gas of NOx purification device 1 concerning the embodiment. It is a flow figure at the time of regeneration operation of adsorption agent 15 of NOx purification device 1 concerning the embodiment. It is a schematic diagram for demonstrating the installation state of a common NOx purification apparatus. It is a block diagram which shows the structure of 1 S of NOx purification apparatuses which concern on the 2nd Embodiment of this invention. It is a schematic diagram which shows the other example of the NOx purification apparatus which concerns on the same embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... NOx purification apparatus, 10 ... Adsorber, 15 ... Adsorbent, 20 ... Discharge device, 30 ... Intake device, 40 ... Air supply device, 50 ... Reducing gas Supply device, 61-65 ... switching valve, 70 ... control device, 80 ... gas pipe, 81 ... ventilation gas flow path, 90 ... resistance heater heating device, 91 ... high frequency heating Device, X ... ventilation gas, Y ... purified gas.

Claims (5)

An adsorption device installed in a ventilation gas flow path and containing an adsorbent that physically adsorbs NOx (nitrogen oxide) contained in the ventilation gas;
An air supply device for supplying air gas;
It means for discharging treated air gas generates O _3, injects O ₃ that is the product to the ventilation gas flow path supplied from the air supply device,
The O ₃ that is the injection, and means for generating NO ₂ by oxidizing NO contained in the ventilation gas,
When the adsorbent adsorbs a preset amount of NOx, a replacement means for supplying a reducing gas and replacing the inside of the adsorption device with a reducing gas atmosphere;
Desorption means for depressurizing the adsorption device and desorbing NOx adsorbed on the adsorbent when the inside of the adsorption device is replaced with a reducing gas atmosphere;
Means for eliminating the desorbed NOx by performing a discharge treatment in the reducing gas atmosphere;
A NOx purification device comprising: In the NOx purification device according to claim 1,
The NOx purification device, wherein the desorption means depressurizes and heats the adsorption device to desorb NOx adsorbed on the adsorbent. The NOx purification device according to claim 2,
The NOx purification device, wherein the desorption means heats the adsorption device with a resistance heater. The NOx purification device according to claim 2,
The NOx purification device, wherein the desorption means heats the adsorption device with high frequency. The NOx purification device according to any one of claims 1 to 4,
The NOx purification device, wherein the reducing gas is nitrogen gas.

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