WO2016147792A1

WO2016147792A1 - Air purifier

Info

Publication number: WO2016147792A1
Application number: PCT/JP2016/054885
Authority: WO
Inventors: 木内　正人
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2015-03-19
Filing date: 2016-02-19
Publication date: 2016-09-22
Also published as: JPWO2016147792A1

Abstract

Provided is an air purifier capable of removing intermediate products produced in a process of decomposition of volatile organic compounds (VOCs) using a photocatalyst. The air purifier is provided with an enclosure, a blower, a VOC removal unit, and a corona discharge unit. The enclosure has a wind tunnel formed in the interior and has an air inlet for taking air into the wind tunnel and an air outlet for discharging purified air from inside the wind tunnel. The blower generates an air flow from the air inlet toward the air outlet within the wind tunnel. The VOC removal unit is arranged within the wind tunnel and has a photocatalyst filter and a light source for irradiating the photocatalyst filter with light. The corona discharge unit is arranged downstream of the VOC removal unit in the wind tunnel.

Description

Air cleaner

The present invention relates to an air cleaner.

Conventionally, an air cleaner that decomposes a volatile organic compound (VOC) using a photocatalyst is known. VOC means a highly volatile organic compound such as ketones, alcohols, organic acids, etc., and when it is contained in the air, it induces allergic symptoms in some people and causes atopy, urticaria Cause asthma, etc. Also, dust suspended in the air, mainly organic and inorganic substances, particles of micrometer or less can induce allergic symptoms, and can cause pneumoconiosis and lung cancer. And the air cleaner which collects such dust by corona discharge is also known. Patent document 1 is disclosing the air cleaner which combined the deodorizing function by a photocatalyst, and the dust collection function by corona discharge.

JP-A-11-179118

However, when an attempt is made to remove VOC using a photocatalyst, sufficient oxidation may not be performed depending on environmental conditions such as temperature and humidity, and harmful intermediate products may still be generated. For example, in the case of ethanol, acetaldehyde is generated.

The present invention provides an air purifier capable of removing intermediate products generated in the decomposition process in addition to the removal of dust in the air and the decomposition of volatile organic compounds (VOC) using a photocatalyst. Objective.

The air cleaner which concerns on the 1st viewpoint of this invention is provided with a housing | casing, an air blower, a VOC removal part, and a corona discharge part. The casing has a wind tunnel formed therein, and has an intake port for sucking air into the wind tunnel and an exhaust port for discharging the cleaned air from the wind tunnel. The blower generates an air flow from the intake port toward the exhaust port in the wind tunnel. The VOC removal unit is disposed in the wind tunnel and includes a photocatalytic filter and a light source that irradiates light to the photocatalytic filter. There are no particular limitations on the characteristics of the light source, but any light source that emits light that effectively drives the above-described photocatalyst may be used, and a mercury-filled quartz lamp may be considered. The corona discharge part is disposed downstream of the VOC removal part in the wind tunnel.

The air cleaner which concerns on the 2nd viewpoint of this invention is an air cleaner which concerns on a 1st viewpoint, Comprising: The said photocatalyst filter is formed in the tunnel shape in which many holes were formed, and has an opening in one end. In addition, the other end has a shielding member that shields the airflow, and the airflow flows into the photocatalytic filter through the opening, and flows out of the photocatalytic filter through the numerous holes. ing.

The air cleaner according to a third aspect of the present invention is the air cleaner according to the second aspect, wherein the shielding member shields transmission of ultraviolet rays irradiated from the light source. The corona discharge part is located on the opposite side of the light source with respect to the shielding member.

The air cleaner according to a fourth aspect of the present invention is the air cleaner according to the second aspect or the third aspect, wherein the light source is disposed in the photocatalytic filter.

The air cleaner according to a fifth aspect of the present invention is the air cleaner according to any one of the second to fourth aspects, wherein the photocatalytic filter is at least partially formed in a mesh shape.

The air cleaner which concerns on the 6th viewpoint of this invention is an air cleaner which concerns on either of the 2nd viewpoint from the 2nd viewpoint, Comprising: The said air blower sends the said air current in the said photocatalyst filter through the said opening. Are arranged as follows.

The air cleaner according to the seventh aspect of the present invention is the air cleaner according to any one of the first to sixth aspects, further comprising an ozone decomposing unit. The ozone decomposing unit is disposed downstream of the corona discharge unit in the wind tunnel.

According to the present invention, an air cleaner provided with a VOC removal unit and a corona discharge unit is provided. Therefore, VOC in the air can be removed and dust in the air can be removed. By the way, during corona discharge, ozone having a strong oxidizing power can be generated. However, according to the present invention, the corona discharge part is arranged downstream of the VOC removal part. Therefore, the intermediate product remaining without being decomposed by the VOC removal unit can be decomposed by ozone generated during corona discharge. Thereby, the intermediate product produced in the decomposition process of VOC using a photocatalyst can also be removed.

The side sectional view of the air cleaner concerning one embodiment of the present invention. The top view of the air cleaner in the state which removed the top | upper surface.

Hereinafter, an air cleaner according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side sectional view of an air cleaner 1 according to this embodiment, and FIG. 2 is a plan view of the air cleaner 1. However, in FIG. 2, the top surface is removed so that the internal structure of the air cleaner 1 can be seen. The air cleaner 1 can be installed in a living environment of a human being such as indoors or in a vehicle, and purifies and activates air in the environment. In particular, even if the air purifier 1 having the characteristics described below is small and lightweight, it can exhibit a sufficient air cleaning capability and is convenient for carrying.

As shown in FIGS. 1 and 2, the air purifier 1 has a housing 2 that forms a wind tunnel S1 therein. The housing | casing 2 which concerns on this embodiment is a rectangular parallelepiped shape. In the following description, “up and down” and “lateral direction” are defined with reference to FIG. 1 unless otherwise specified. The “width direction” is a direction orthogonal to the “lateral direction” in FIG. The internal space of the housing 2 is divided in the vertical direction by the partition plate 3, the space above the partition plate 3 is a machine room forming the wind tunnel S1, and the space below the partition plate 3 is the electric chamber S2. is there. A power supply circuit 4 and a control board 5 are accommodated in the electric chamber S2. The power supply circuit 4 supplies electric power to the electrical components of the air cleaner 1, and the control board 5 controls the operation of these components. The partition plate 3 is substantially equal to the shapes of the top surface 2c and the bottom surface 2d of the housing 2.

An air inlet H1 and an air outlet H2 are formed on the

side surfaces

2a and 2b at both ends in the lateral direction of the housing 2, respectively. The intake port H1 and the exhaust port H2 are both openings that connect the wind tunnel S1 and the external space, and do not face the electric chamber S2. In FIG. 1 and FIG. 2, the intake port H1 and the exhaust port H2 do not appear originally, but their positions are shown for reference. As shown in the figure, the intake port H1 and the exhaust port H2 are located on the same straight line extending substantially in the lateral direction.

In the wind tunnel S1, the dust collection filter 10, the blower 20, the partition plate 21, the VOC removal unit 30, the corona discharge unit 40, and the ozone decomposition unit 50 are arranged in this order from the side surface 2a to the side surface 2b. Has been. When the blower 20 is driven by receiving power supply from the power supply circuit 4, an airflow A1 is generated in the wind tunnel S1 from the intake port H1 on the side surface 2a to the exhaust port H2 on the side surface 2b. The air sucked into the wind tunnel S1 through the air inlet H1 is removed from harmful substances while proceeding in the wind tunnel S1 in the lateral direction, and then discharged from the air outlet H2.

The dust collection filter 10 is disposed so as to face the air inlet H1. Therefore, the air taken into the wind tunnel S1 through the intake port H1 first passes through the dust collection filter 10. Although the performance of the dust collection filter 10 is not particularly limited, it is possible to remove relatively large dust, for example, a diameter of about 500 micrometers. For example, the dust collection filter 10 can be a sponge material filter that entangles dust.

A blower 20 is disposed downstream of the dust collection filter 10. The blower 20 is disposed adjacent to the dust collection filter 10 so that the air suction port contacts the dust collection filter 10. Therefore, the air that has passed through the dust collection filter 10 is efficiently taken into the blower 20 and flows further downstream via the air discharge port of the blower 20. The blower 20 is fixed on the partition plate 3 by a support member (not shown).

The structure of the blower 20 is not particularly limited as long as an airflow having an appropriate air volume can be generated in the wind tunnel S1, and can be appropriately selected from various forms such as a sirocco fan and a crossflow fan. However, it is preferable to use a small size, light weight, low noise and long life. From the viewpoint that it can be used continuously for a long time, it is preferable to select one using a brushless motor. If the air volume is too small, the air purification function in the environment where the air purifier 1 is installed may not be sufficiently exhibited, which may be undesirable. If the air volume is too large, the VOC removal unit 30 described later may be used. In this case, the time during which VOC acts on the photocatalyst is shortened, which is not preferable. From such a viewpoint, the air volume of the blower 20 is preferably 1 liter or more and 500 liters or less per minute, and more preferably 10 liters or more and 100 liters or less per minute. Further, the arrangement of the blower 20 can be selected as appropriate, and, for example, on the downstream side of the VOC removal unit 30 as long as the airflow A1 from the intake port H1 to the exhaust port H2 can be generated in the wind tunnel S1. It may be arranged.

The VOC removal unit 30 is disposed adjacent to the blower 20 on the downstream side of the blower 20. However, a partition plate 21 is disposed between the VOC removal unit 30 and the blower 20. The partition plate 21 stands on the partition plate 3 and extends to the top surface 2 c of the housing 2. Further, the partition plate 21 is formed with an opening so as to face the air discharge port of the blower 20, and as a result, the air discharged from the blower 20 passes through the partition plate 21 to the VOC removal unit 30. Reach.

The VOC removal unit 30 is a device that oxidatively decomposes VOC contained in air by causing a photocatalyst excited by ultraviolet rays (UV light) to act on the air. Specifically, the VOC removal unit 30 includes a photocatalytic filter 31 and an ultraviolet (UV) lamp 32 that irradiates the photocatalytic filter 31 with ultraviolet light. The photocatalytic filter 31 has a tunnel member 33 that is open at both ends and extends substantially in the lateral direction. The tunnel member 33 does not have a bottom surface (a surface on the side of the partition plate 3) as a whole or has a certain rectangular tube shape, and is fixed on the partition plate 3. The tunnel member 33 according to the present embodiment is made of an inorganic material, and a photocatalyst is applied to the entire surface of the tunnel member 33. Although the kind of photocatalyst is not specifically limited, In this embodiment, it is titanium dioxide. The tunnel member 33 according to the present embodiment is entirely formed in a mesh shape. In other words, the tunnel member 33 is formed with a large number of holes through which air can pass.

The UV lamp 32 is driven by receiving power supply from the power supply circuit 4. The structure of the UV lamp 32 is not particularly limited as long as it has sufficient light emission characteristics to excite the photocatalyst. In the present embodiment, it is a mercury lamp with a quartz tube. However, of course, other modes such as an LED lamp can be used. The wavelength of ultraviolet rays emitted from the UV lamp 32 is typically about 260 nanometers. As long as the photocatalyst can be excited, a visible light lamp can be used instead of the UV lamp 32. Further, the UV lamp 32 according to the present embodiment has a substantially cross-sectional center of the tunnel member 33 in the tunnel member 33 so that the photocatalyst applied to the surface of the tunnel member 33 can be efficiently irradiated with ultraviolet rays. It arrange | positions so that it may extend in a horizontal direction substantially. However, the arrangement of the UV lamp 32 is not particularly limited as long as the photocatalyst can be excited.

The opening on the upstream side of the tunnel member 33 is arranged adjacent to the opening of the partition plate 21 facing the air discharge port of the blower 20, and the air flowing out from the air discharge port is large in size. The portion flows into the tunnel member 33 through the opening on the upstream side. On the other hand, the opening on the downstream side of the tunnel member 33 is closed by a plate-shaped airflow shielding member 34. For this reason, the air that has flowed into the tunnel member 33 cannot escape from the tunnel member 33 through the opening on the downstream side of the tunnel member 33, and passes through a large number of holes formed in the mesh-shaped tunnel member 33. Then, it flows out of the tunnel member 33. The shielding member 34 can make it difficult for the airflow from the blower 20 to flow, thereby reducing the wind speed and ensuring a sufficient time for the VOC to act on the photocatalyst.

In the present embodiment, the air that has flowed into the tunnel member 33 follows the flow path, so that almost all of the air taken into the wind tunnel S1 comes into contact with the photocatalyst. Thereby, VOC in the air efficiently contacts the photocatalyst and is oxidatively decomposed. However, even if the VOC is efficiently decomposed by the photocatalyst, the effect of the photocatalyst does not completely decompose the VOC to a harmless substance, and a certain amount of harmful intermediate products may still remain. Moreover, the VOC removal part 30 cannot exhibit the dust collection effect, and dust in the air is not removed. Therefore, on the downstream side of the VOC removal unit 30, a corona discharge unit 40 for removing these harmful airborne substances is disposed.

More specifically, the corona discharge part 40 is disposed on the opposite side of the UV lamp 32 with respect to the shielding member 34. The corona discharge unit 40 is a device that generates corona discharge. The structure of the corona discharge part 40 is not particularly limited as long as corona discharge can be generated. In the present embodiment, the corona discharge part 40 includes a needle-like discharge electrode 41 and a ring-like counter electrode 42. A positive voltage is applied to the discharge electrode 41 from the power supply circuit 4, and the counter electrode 42 is grounded. The discharge electrode 41 is disposed upstream of the counter electrode 42. Further, the needle-like discharge electrode 41 is located substantially on the central axis of the ring-shaped counter electrode 42, and the needle tip of the discharge electrode 41 is spaced from the ring-shaped counter electrode 42 by a certain distance. This distance is preferably 5 mm or more and 20 mm or less. In this case, the voltage is preferably 1 kV or more and 30 kV or less.

With the above configuration, when a high voltage is applied between the discharge electrode 41 and the counter electrode 42, corona discharge occurs between the

electrodes

41 and 42. Thereby, in the air near the corona discharge part 40, while being able to shower an intermediate product with an electronic shower, ozone generate | occur | produces. The ozone generated here can decompose the intermediate product by its strong oxidizing power. Therefore, the corona discharge unit 40 can detoxify the VOC that could not be removed by the VOC removal unit 30 and the intermediate product (particularly the latter) during the decomposition by the action of the electron shower and ozone described above. it can.

Further, when corona discharge occurs, dust in the air near the corona discharge portion 40 is charged, and the charged dust is collected on the counter electrode 42 by Coulomb force and burned out here. Thereby, dust in the air is also removed.

By the way, it is preferable that the shielding member 34 described above is made of a material that shields transmission of ultraviolet rays, or an ultraviolet absorbent is applied to the surface. In this case, the ultraviolet rays generated by the UV lamp 32 do not easily reach the

electrodes

41 and 42 of the corona discharge unit 40, and the

electrodes

41 and 42 can be prevented from being deteriorated. If the shielding member 34 is not provided, the floating organic substance is carbonized by ultraviolet rays, and when used for a long period of time, it may adhere to the insulating portion and cause dielectric breakdown. Further, from the above viewpoint, the shielding member 34, particularly the surface on the tunnel member 33 side, is preferably configured in a dark color, particularly black, so that ultraviolet rays can be efficiently absorbed. Moreover, in this embodiment, it is preferable that the inner surface facing the wind tunnel S1 of the housing | casing 2, the partition plate 3, and the partition plate 21, especially these

members

2, 3, and 21 is also comprised by dark color, especially black. .

The central axis of the ring-shaped counter electrode 42 is generally aligned with the central axis of the exhaust port H2 of the housing 2. And the ozone decomposition | disassembly part 50 is arrange | positioned between the counter electrode 42 and the exhaust port H2 so that both may be contacted. The ozone generated by the corona discharge is used for decomposition of the intermediate product, but surplus ozone remains. The ozonolysis unit 50 is a device for removing the remaining ozone. The structure of the ozone decomposing unit 50 is not particularly limited as long as ozone can be decomposed, but in this embodiment, an ozone decomposing element using graphite which is a nonmetallic catalyst is used. Further, the ozonolysis section 50 according to the present embodiment has a structure in which a catalyst having ozone decomposability is configured in a honeycomb (honeycomb) shape, and the honeycomb passage extends from the ring-shaped counter electrode 42 to the exhaust port H2. Are arranged as follows.

As Example 1, an air cleaner similar to the air cleaner according to the above embodiment was manufactured. The air volume of the blower was 35 liters per minute.

When the air cleaner according to Example 1 was placed indoors and the number of ions contained in the air was measured near the outside of the exhaust port, the number of negative ions was 300,000 / cc and the number of positive ions was 200 / cc. Results were obtained. For the measurement of the number of ions, an air ion counter “ITC-201A” manufactured by Andes Electric Co., Ltd. was used. In the air cleaner according to Example 1, it was confirmed that negative ions having a preferable concentration were generated by the excited air.

Moreover, when the amount of particles of each size contained in the air was measured and the dust collection rate was calculated under both the driving and stopping conditions of the air cleaner according to Example 1, the following results were obtained. Obtained. The measurement was performed near the outside of the exhaust port of the air cleaner using a particle counter “KC-51” manufactured by Rion Corporation. From the following results, it was confirmed that dust in the air was removed at a high dust collection rate.

In addition, when air containing 10 ppm formaldehyde was supplied to the air intake of the air cleaner according to Example 1 and the concentration of formaldehyde in the air discharged from the exhaust was measured, it was 500 ppb, confirming a 95% decomposition efficiency. It was done. The concentration was measured using a portable VOC monitor “ppbRAE PGM-7240” manufactured by RAE SYSTEMS.

Further, when the atmosphere was supplied to the air inlet of the air cleaner according to Example 1 and the concentration of ozone in the air discharged from the air outlet was measured, a result of 0.2 ppm was obtained.
Here, the steady state ozone concentration in the sealed space can be estimated by the following calculation.
ρ (t): concentration of ozone at time t (ppm)
N (t): number of ozone at time t V: volume of the room where the air purifier is operating (l)
T _1/2 : half-life of ozone (min)
λ: damping constant (min ^-1 )
n _p : Ozone generation rate (ppm · min ⁻¹ ) released from the air cleaner
ρ _p : Concentration of ozone released from the air cleaner (ppm)
V _p : wind speed of air discharged from the air purifier (l · min ⁻¹ )
Then,
N (t) = ρ (t) · V
n _p = ρ _p · V _p
λ = 0.693 · T _1/2 ^-1
It is.

The differential equation describing the decay phenomenon when there is a constant inflow of ozone is expressed as follows.
dN (t) / dt = n _p −λN (t)
Therefore, since tN → ∞, dN (t) / dt = 0,
N (∞) = n _p · λ ⁻¹
ρ (∞) = n _p · λ ^-1 · V ^-1
= Ρ _p · V _p · (T _1/2 /0.693) · V ^-1
It becomes. Here, the volume of the room where the air cleaner is used is V = 8000 l, the ozone half-life is T _1/2 = 30 min, and the measured values are used as ρ _p = 0.2 ppm and V _p = 35 l · min ⁻¹ . To calculate ρ (∞) = 0.038 ppm.

Therefore, if it is a room of 8 cubic meters (between two tatami mats), it will be well below the environmental standard (0.05 ppm). The ozone concentration before driving the air cleaner was 0.01 ppm or less, which is the detection limit of the measuring device. For the measurement of ozone concentration, an ozone monitor “EG-2001” made by Sugawara Jitsugyo was used.

Next, the UV lamp was removed from the air cleaner according to Example 1, and this was designated as Comparative Example 1. And when the air containing 10 ppm formaldehyde was supplied to the inlet of the air cleaner which concerns on the comparative example 1, and the density | concentration of formaldehyde of the air discharged | emitted from an exhaust port was measured, the result of 5 ppm was obtained. In this case, the decomposition efficiency was 50%, which was confirmed to be insufficient as an air cleaning effect. The concentration was measured using a portable VOC monitor “ppbRAE PGM-7240” manufactured by RAE SYSTEMS.

Moreover, the corona discharge part was removed from the air cleaner according to Example 1, and this was designated as Comparative Example 2. And when the air containing 10 ppm formaldehyde was supplied to the air inlet of the air cleaner which concerns on the comparative example 2, and the density | concentration of formaldehyde of the air discharged | emitted from an exhaust port was measured, the result of 8 ppm was obtained. In this case, the decomposition efficiency was 20%, which was confirmed to be insufficient as an air cleaning effect. The concentration was measured using a portable VOC monitor “ppbRAE PGM-7240” manufactured by RAE SYSTEMS.

Furthermore, the ozone decomposition part was removed from the air cleaner according to Example 1, and this was designated as Example 2. And when air | atmosphere was supplied to the inlet port of the air cleaner which concerns on Example 2, and the density | concentration of the ozone in the air discharged | emitted from an exhaust port was measured, the result of 20 ppm was obtained. This result exceeded the environmental standard (0.05 ppm), and it was confirmed that the air cleaner according to Example 1 is more suitable for indoor use than the air cleaner according to Example 2. . The ozone concentration before driving the air cleaner was 0.01 ppm or less, which is the detection limit of the measuring device. For the measurement of ozone concentration, an ozone monitor “EG-2001” manufactured by Sugawara Jitsugyo was used.

From the above, the air purifying effect of the air purifier according to Example 1 was confirmed. In addition, compared with Example 1, when there is no VOC removal unit (Comparative Example 1) or when there is no corona discharge unit (Comparative Example 2), sufficient air compared to the air cleaner according to Example 1 is obtained. It was confirmed that the cleaning effect was not exhibited.

Further, the photocatalyst filter having the mesh-shaped tunnel member and the shielding member is removed from the air cleaner according to the first embodiment, and instead, the photocatalyst is provided at the same position with no holes on the side surfaces and openings at both ends. A cylindrical tunnel member coated on the entire surface was disposed, and this was taken as Example 3. The cross-sectional shape of the tunnel member of the air cleaner according to Example 1 was a square of 20 mm × 25 mm, whereas the diameter of the circular cross-section of the tunnel member according to Example 3 was 24 mm. And the air containing 10 ppm formaldehyde was supplied to the air inlet of the air cleaner which concerns on Example 3, and when the density | concentration of the formaldehyde of the air discharged | emitted from an exhaust port was measured, the result of 6 ppm was obtained. In this case, the decomposition efficiency was 40%, which was lower than the air cleaning effect (95%) according to Example 1. Thereby, the superiority of the photocatalytic filter having a structure having a mesh-shaped tunnel member and a shielding member was confirmed.

DESCRIPTION OF SYMBOLS 1 Air cleaner 2 Case 20 Blower 30 VOC removal part 31 Photocatalyst filter 32 UV lamp (light source)
33 Tunnel member 34 Shield member 40 Corona discharge part 50 Ozone decomposition part S1 Wind tunnel H1 Intake port H2 Exhaust port A1 Wind flow S2 Electrical room (electric circuit and control board installation part)
2a Upstream side surface 2b Downstream side surface 21 Partition plate (wall separating the blower and the photocatalyst chamber. There is a hole through which air passes.)
41 Discharge electrode (corona discharge needle electrode)
42 Counter electrode (Installation electrode for corona discharge)

Claims

A casing having a wind tunnel formed therein, an intake port for sucking air into the wind tunnel, and an exhaust port for discharging the cleaned air from the wind tunnel;
A blower for generating an air flow from the intake port toward the exhaust port in the wind tunnel;
A VOC removal unit that is disposed in the wind tunnel and includes a photocatalytic filter and a light source that irradiates light to the photocatalytic filter;
A corona discharge section disposed downstream of the VOC removal section in the wind tunnel;
An air purifier.
The photocatalytic filter is formed in a tunnel shape having a large number of holes, and has an opening at one end and a shielding member that shields the airflow at the other end, and the airflow passes through the opening. It is configured to flow into the photocatalytic filter and to flow out of the photocatalytic filter through the numerous holes.
The air cleaner according to claim 1.
The shielding member shields transmission of ultraviolet rays emitted from the light source,
The corona discharge part is located on the opposite side of the light source with respect to the shielding member.
The air cleaner according to claim 2.
The light source is disposed in the photocatalytic filter,
The air cleaner according to claim 2 or 3.
The photocatalytic filter is at least partially formed in a mesh shape,
The air cleaner according to any one of claims 2 to 4.
The blower is arranged to send the airflow into the photocatalytic filter through the opening.
The air cleaner according to any one of claims 2 to 5.
An ozone decomposing unit disposed downstream of the corona discharge unit in the wind tunnel;
The air cleaner according to any one of claims 1 to 6.