JPS586529B2 - air deodorization equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a deodorizing device for air containing malodorous components.

Conventionally, deodorizing equipment using ozone injects ozone into air containing malodorous components, or injects ozone after washing the air to be treated with water, oxidizes malodorous components with ozone through a gas phase reaction, and removes ozone. The odor contained in the product neutralizes the odor of malodorous components, resulting in a deodorizing effect.

In this case, deodorization by ozone oxidation may proceed effectively depending on the concentration of malodorous components, reaction temperature, and reaction time.

However, for air to be treated that contains malodorous components at a concentration of ppm or less, the oxidation reaction is slow at room temperature even if ozone is injected at a concentration similar to the total concentration of malodorous components, and the deodorizing effect is ineffective. They must mainly rely on ozone odor to mask the odor.

However, ozone is the main component of photochemical smock, and several
Exposure to ozone at a concentration of pm or higher for a long period of time is harmful to the human body and plants.

Therefore, no matter how effective the odor reduction effect is, it is not preferable to release a large amount of the main reaction ozone.

In other words, the ozone deodorizing device should exhibit its deodorizing effect through the oxidizing action of ozone.

An object of the present invention is to provide a novel ozone deodorizing device (hereinafter simply referred to as the device) that is capable of increasing the ozone oxidation efficiency of malodorous components without releasing high concentrations of unreacted ozone.

FIG. 1 is a system diagram of an embodiment of an air deodorizing apparatus according to the present invention.

In the figure, air 1 to be treated containing malodorous components is sent to an ozone oxidizer 7 by a blower 2.

At this time, a predetermined amount of ozonized air 5 generated by an ozone generator 4 is injected from a diffuser 3 provided in the duct and uniformly mixed with the seated air 1 to be treated. The air becomes air 6 and is introduced into the ozone oxidizer 7.

In this ozone oxidizer 7, the air 6 to be treated passes through a packed bed 71 filled with oxidation-promoting particulate matter, and contains sulfur-based malodorous components such as hydrogen sulfide, methyl mercaptan, and methyl sulfide, or trimethylamine and dimethylamine. The malodorous components containing ammonia nitrogen are oxidized and decomposed to become treated air 8 from which the malodor has been removed, and are introduced into the cleaning tower 9.

In this cleaning tower 9, the air 8 to be treated is transferred to a gas-liquid contact section 91.
Unreacted ozone is decomposed and removed by countercurrent contact with the reducing circulating fluid 95 sprayed by the spray 92 while passing through.

Furthermore, the gas to be treated 8 passes through a demister 93 made of stainless steel or plastic fibers, etc., where the mist is separated, and the treated air 10 becomes almost odorless and clean, and is discharged out of the system.

The particulate material for promoting ozone oxidation of malodorous components filled in the packed bed 71 includes transition metal oxides such as tri-iron tetroxide, manganese dioxide, nickel oxide, and copper oxide, or mixtures thereof; An adsorbent such as activated carbon, α-alumina, or zeolite, or a mixture of the above-mentioned transition metal oxide alone or a mixture thereof and the above-mentioned adsorbent is applied.

It is presumed that the ozone oxidation reaction of hydrogen sulfide, which is a typical malodorous component, proceeds as follows.

Here, the symbol (ad) indicates a state in which the substance is physically or chemically adsorbed on the surface of the granular filler, and a substance expressed by a simple chemical symbol indicates that it is in a gaseous state.

The ozone oxidation reaction of hydrogen sulfide proceeds with at least one of hydrogen sulfide and ozone being adsorbed on the surface of the packing in the packed bed 71, in other words, captured and concentrated on the surface of the packing. do.

As is clear from the above reaction equation between hydrogen sulfide and ozone, in order to completely oxidize and decompose hydrogen sulfide into sulfur dioxide and water, hydrogen sulfide and ozone in a molar concentration or higher are required.

In addition, since ozone partially self-decomposes on the surface of the filling, if a filling other than activated carbon is used, at least one chemical equivalent of ozone is required to ozone oxidize all malodorous components.
．． It is preferable to add ozone in an amount of 1 to 1.5 times or more, and at least 3 times the stoichiometrically required amount of ozone, since self-decomposition of ozone actively proceeds when activated carbon is used as a filler.

The smaller the size of the filler, the better from the viewpoint of ozone oxidation promoting ability, while the larger the size is, the better, in order to reduce ventilation resistance.

Usually molded pellets with a diameter of 2 to 6 mesh, or spherical products with a diameter of 4 to 12 mm, or diameter and height of 6 to 6 mm.
A cylindrical piece with a diameter of 15 mm and a wall thickness of 2 to 4 mm is used.

The size of the packed bed 71 is set so that the space velocity of the air to be treated 6 passing therethrough is about 2,000 to 6,5000 hr-1.

A general description of the deodorizing reactions of typical malodorous components other than hydrogen sulfide in the ozone oxidizer 7 is as follows.

Methyl mercabumene and methyl disulfide mainly result in methyl thiosulfonate and methyl sulfonate anhydride.

methyl sulfide becomes dimethyl sulfoxide and dimethyl fluorone.

trimethylamine Primarily nitromethane.

Although it has poor reactivity with ammonia and ozone, it is removed by a neutralization reaction with acidic substances accumulated on the surface of the packing.

For example, aldehydes It is oxidized to a carboxylic acid.

nitrogen oxides Eventually it becomes nitric acid.

Among the ozone oxidation products of the above-mentioned malodorous components, sulfuric acid, nitric acid, carboxylic acid, ammonium sulfate, etc., which have low vapor pressure at room temperature, gradually accumulate on the surface of the packing in the packed bed 71, and their weight becomes the weight of the packing. When the amount exceeds 1.5 to 4%, the ozone oxidation promotion reaction of malodorous components is inhibited.

Therefore, it is necessary to periodically wash the packed bed 71 with water to remove them.

A spray 72 and a pump 76 in FIG. 1 are devices for cleaning the packed bed 71 with a cleaning liquid 76.

The frequency varies depending on the concentration of malodorous components in the air to be treated, but for example, when targeting dilute malodorous air such as ventilation air of a sewage treatment plant or garbage treatment plant building, the frequency is 1,500~
The packed bed 71 is washed once every 3,000 hours until the pH of the circulating water 74 for washing the packed bed 71 becomes about 5 or higher.

The maximum number of p
The cleaning solution 94 in the cleaning tower 9 contains unreacted ozone at a concentration of at least 2.0 pm to remove it.
5 mmol/l or more of sodium thiosulfate or 7 mmol
An aqueous solution containing one or more types of water-soluble reducing agents such as sodium sulfite or more and adjusted to a pH of 7 or more, or 100
An aqueous solution containing at least mmol/l of hydrogen peroxide and whose pH is adjusted to at least 9 is used.

At this time, if a packed tower is used as the cleaning tower 9, 1~
For ozone contained at a concentration of 10 ppm, the gas side standard overall capacity coefficient KGa, which is a parameter that expresses the likelihood of gas absorption, is 250 to 800 kg.
-mol/m3・hr・atm.

That is, when KGa is 400 and the ozone concentration is 3 ppm, the mass flow rate of the gas to be treated 8 at the gas-liquid contact part 91 of the cleaning tower 9 is 160 kgmol/m3·hr·atm, and the height of the gas-liquid contact part 91 is 2 m. This will reduce the ozone concentration at the outlet of the cleaning tower to 0.02 ppm, which is one-third of Japan's environmental standard for oxidant concentration of 0.06 ppm, and there is no need to worry about secondary pollution due to emitted ozone.

FIG. 2 is a characteristic diagram showing the performance of the air deodorizing apparatus according to the present invention, and shows the results of measurement of the hydrogen sulfide removal ability carried out under the severe processing conditions shown in the table.

In the figure, curve A is the change in hydrogen sulfide removal ability over time until the 8th day after the start of operation, and curve B is the hydrogen sulfide removal curve after washing the packed bed 71 with water after being subjected to the test of curve A. C is a hydrogen sulfide removal curve after repeating the above ozone oxidation and water washing regeneration operations a total of four times.

For comparison, curve D shows the change over time in the hydrogen sulfide removal rate when ozone is not added to the air to be treated containing hydrogen sulfide.

Furthermore, when the packed bed 71 of the ozone oxidizer 7 was removed and hydrogen sulfide was ozone oxidized for 5 seconds in a gas phase reaction, the hydrogen sulfide removal rate was about 12%.

As explained in detail above, the air deodorizing device according to the present invention has a much superior ozone oxidation efficiency of malodorous components compared to the conventional ozone oxidation of malodorous components in the gas phase, and also uses activated carbon etc. to absorb malodors. This method has the advantage that the lifespan of the filling is significantly longer than that of other methods.

Furthermore, since a cleaning tower for excess ozone is provided to prevent discharge of unreacted ozone, there is no risk of secondary pollution occurring due to the use of ozone, which is useful in practice.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure is a characteristic diagram for explaining the performance of the air deodorizing device according to the present invention. In the figure, 1, 6, 8 are air to be treated, 2 is a blower, 3 is a diffuser, 4 is an ozone generator, 5 is ozonized air, 7 is an ozone oxidizer, 71 is a packed bed, 72, 92 are sprayers ,
73 and 93 are demisters, 74 is washing water, 75 is circulating water, 76 and 98 are pumps, 9 is a washing tower, 91 is a gas-liquid contact section, 94 is a washing liquid, 95 is a circulating liquid, and 10 is processing air.

Claims (1)

[Claims] 1. Ozone generator, means for adding and mixing the ozonized gas generated by this device to the air to be treated containing malodorous components, ozone oxidation accelerating device made of transition metal oxides, adsorbents, or mixtures thereof. An ozone oxidation device that has a built-in filler and is brought into contact with the introduced ozone-added air to be treated to cause an oxidation reaction between malodorous components in the air to be treated and ozone, and the air to be treated that has passed through the ozone oxidation device is reduced. An air deodorizing device comprising means for cleaning with a cleaning liquid containing an ozone oxidizing agent, and a cleaning device for cleaning a filling built in the ozone oxidation device with water.