JPS5933011B2 - Ozone deodorization equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement in an ozone deodorizing device.

Conventionally, in sewage treatment plants, human waste treatment plants, etc., ammonia, methyl mercaptan, hydrogen sulfide, methyl sulfide, tolumethylamine, and other substances with unpleasant odors are released into the atmosphere, and when their concentrations are high, they worsen the living environment. Therefore, the emission limit is regulated by the Offensive Odor Prevention Act.

Methods used to deodorize and remove these malodorous substances include adsorption removal with an adsorbent, cleaning with a chemical solution, ozone oxidation and water washing, ozone oxidation and chemical washing, and a combination of water washing and catalyst-oxidation. There is.

The reaction between a typical malodorous substance and ozone is shown by the following chemical formula.

Hydrogen sulfide Methyl mercaptan Sulfide Methyl trimethylamine In this way, malodorous substances undergo ozone oxidation and change into odorless compounds or substances with a weak odor, and their solubility in water increases (so that washing with water and ozone oxidation must be used together). A considerable removal effect can be expected.

In particular, when the concentration of sulfide-based malodorous substances is high, it is more effective to use alkaline cleaning and ozone oxidation together than to wash with water and ozone oxidation (furthermore, if powdered activated carbon coexists in the form of a slurry, it will give a relatively weak alkaline effect. It was found that a hydrogen sulfide removal rate of 60 to 90% could be obtained even when the pH was 8 to 9.

In addition to the chemical formula below that reacts with alkali and then reacts with ozone, 2NaOH + H2S- + Na2S + 2H2ONa S + H2S- → 2NaH8 Na S +03 → Na2SO3 NaH8+0 → NaH803 h Na2SO3+03->Na2SO4+02N
aH8O3+03→NaH8O4+02 Due to the solid catalytic action of the activated carbon, after being dissolved in the absorption liquid, it is oxidized by atmospheric oxygen in the following order, which is why a relatively high removal rate was obtained even with a weakly alkaline solution.

The fact that this weak alkalinity can absorb and remove hydrogen sulfide-based malodorous components means that the amount of alkali consumed is small and can be used to deodorize exhaust gas containing a lot of carbon dioxide gas that has been treated with aerobic microorganisms at sewage treatment plants, human waste treatment plants, etc. In addition, since ammonia, which hardly reacts with ozone and is detected in large quantities, has a washing effect with water, it has a great effect when acidic gases and alkaline gases coexist.

However, in an operation in which activated carbon slurry containing a weak alkaline aqueous solution is applied to the absorption tower by spraying or the like, there are disadvantages such as uneven adhesion or sedimentation of the activated carbon to the absorption tower filling material, clogging of pipes, etc.

The present invention has been made to solve the above-mentioned drawbacks.
The object of the present invention is to provide an ozone deodorizing device that uses a carbonaceous material such as coal or charcoal as an absorption tower filler, and cleans and deodorizes a gas to be treated to which ozone has been added with a weak alkaline aqueous solution.

An embodiment of the present invention will be described below based on the drawings.

In FIG.
In the treatment gas supply device having a gas to be treated gas, first, the ozonized gas sucked by the blower 1 and generated by the ozone generator 2 is added and mixed, and then sent into the lower space of the container for the cleaning tower 3.

Trimethylamine and mercaptans, which are highly reactive with ozone in the exhaust gas at sewage and human waste treatment plants, are partially oxidized in the gas phase, but hydrogen sulfide, which is detected at relatively high concentrations, is hardly oxidized in the gas phase and remains unreacted. It ascends the cleaning tower 3 together with ozone.

A carbonaceous material 4 serving as a solid catalyst is housed in the intermediate part of the cleaning tower 3 on a holding shelf 5 as a filler in order to increase the gas-liquid contact efficiency, and when the gas to be treated rises,
It is absorbed as sulfide ions in the weakly alkaline aqueous solution continuously sprayed from the spray 6, and is catalyzed by the surface of the carbonaceous material 4. Oxidized.

This oxidation lowers the pH of the solution and also absorbs and removes malodorous components such as amines and ammonia.

The carbonaceous material in the present invention is a natural carbonaceous material such as coal, charcoal, etc., and may be coke with a high porosity, but also lignite, brown coal, black coal, white coal, etc., which retain the porous wood structure. charcoal is better.

These have a specific surface area of activated carbon of 15,000 to 2,000 m'/
250~40077+3/ for lignite and brown coal
350-400 m/? ,200~2 with white charcoal
Although it is as low as 50 m'/g, if it is filled in a certain mass, appropriate voids can be formed, so it can be used as a filler to improve the gas-liquid contact efficiency.

In addition, on the surface of carbonaceous materials, the reaction is not with gas but with the solution passing through the cleaning liquid and solid, so black charcoal leaves the sapwood and causes radial cracks in the heartwood compared to pine, maple, etc., which absorb a lot of water. Sawtooth oak, oak, chestnut, etc., which have large pores, reduce resistance to air blowing and are more convenient for the movement and distribution of the cleaning solution.

The treated gas is subjected to mist removal in a demister 7 and is released into the atmosphere.

On the other hand, the cleaning liquid flowing down from the lower drainage port provided in the container for the cleaning tower 3 enters the sedimentation tank 8, and the finely discharged carbonaceous material is precipitated and then enters the adjustment tank 9.

This adjustment tank 9 constitutes a weak alkaline aqueous solution supply device together with a pump 10 which will be described later.

The pump 10 sucks the weak alkaline aqueous solution in the adjustment tank 9,
Spray again from spray 6.

That is, the weak alkaline aqueous solution supply device operates continuously while the gas to be treated is being supplied to the cleaning tower 3, and continues to supply the weak alkaline aqueous solution into the cleaning tower 3 via the spray 6.

Here, in the adjustment tank 9, the pH is measured by a pH meter 11, and when the pH drops below a predetermined value, a concentrated solution such as caustic soda or soda carbonate is automatically added from the alkaline storage tank 12 to maintain a constant pH. .

Further, a certain amount of the cleaning liquid is discharged from the overflow pipe 13, and water is replenished from the replenishment water pipe 14 to compensate for the amount of discharged water and the evaporated water.

In the same figure, 15 is a pH adjustment device, 16 is a valve for replenishing alkaline solution from the alkaline storage tank 12 to the adjustment tank 9, and a plurality of holding shelves 5 are used as shown in FIG. 2 to maintain a high porosity. Furthermore, as shown in FIG. 3, the cleaning liquid may be sprayed from the spray 6 onto each carbonaceous material 4 on a plurality of holding shelves 5.

As explained above, according to the present invention, since a solid catalyst similar to activated carbon is used as a filler, there is no clogging due to suspension, sedimentation separation, piping damage, etc. using powdered activated carbon as in the past, resulting in stable operation. can be ensured.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram showing an outline of one embodiment of the present invention, Fig. 2 is a block diagram showing main parts of another embodiment of the present invention, and Fig. 3 is a block diagram showing an outline of an embodiment of the present invention. It is a block diagram which shows the principal part of yet another different Example. 3... Container, 4... Carbonaceous material, 6.
...Spray, 8... Sedimentation tank.

Claims (1)

[Claims] 1. A container with a bottom drain and a spray on the top,
A solid carbonaceous material housed in an intermediate portion of the container; a gas supply device for supplying a gas to be treated mixed with ozonized gas into a lower space of the container; An ozone deodorizing device comprising: a weak alkaline aqueous solution supply device that supplies a weak alkaline aqueous solution into the container through the spray while the gas to be treated is supplied to the container by the supply device.