JP2820824B2 - Biological treatment of digestive gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for biologically treating digestive gas, and more particularly to a sulfur-based odorant such as hydrogen sulfide generated from a human waste treatment plant, a sewage treatment plant and various other factories, ammonia, and the like. The present invention relates to a biological treatment method effective for treating digestive gas containing carbon dioxide and the like.

[0002]

2. Description of the Related Art Digestion gas generated when performing anaerobic treatment of high-concentration organic matter-containing waste liquid, such as in a human waste treatment plant or a sewage treatment plant sludge treatment system, is subjected to decarboxylation for the purpose of volume reduction for storage and energy saving. Corrosiveness of combustion gas and 2
Desulfurization treatment is applied due to the problem of secondary pollution (SOx).

[0003] In these decarboxylation and desulfurization treatments, a washing method and an adsorption method are usually employed.

[0004] In recent years, research on applying biological techniques to gas treatment has been advanced, and in the field of deodorization, in particular, some of them have been implemented.

[0005]

However, in the above-mentioned decarboxylation and desulfurization treatments by the conventional cleaning method and adsorption method, any of the methods requires a high chemical cost and an adsorbent replacement cost, and also has a considerable maintenance and management aspect. Requires human labor.

[0006] The biological treatment method has the advantage that the reaction is carried out by the mediation of microorganisms that grow in nature, so that there is little operating cost. However, the methods developed so far usually use aerobic microorganisms. When an anaerobic gas as described above is treated, supply of oxygen is required. Therefore, for a gas such as a digestive gas which may be ignited due to the mixing of excess air, it is necessary to treat the gas under completely anaerobic conditions or microaerobic conditions because supply of excessive oxygen is dangerous.

[0007] In the natural world, there are microorganisms that can be desulfurized (oxidize hydrogen sulfide and decompose as sulfuric acid from the gas) under anaerobic conditions, but when anaerobic microorganisms are used, they may give off odor, However, there is a problem in maintenance and economics, such as the need to provide energy instead of oxygen (for example, light in the case of purple sulfur bacteria).

[0008] The main components of the digested gas are methane, carbon dioxide, hydrogen sulfide, ammonia and the like. When burning this, it is necessary to remove hydrogen sulfide and ammonia in order to reduce SOx and NOx. There is. These components are easily oxidized by microorganisms, but since the microorganisms involved in the reaction are aerobic bacteria, it is necessary to keep the growth environment of the microorganisms aerobic.

The present invention has been made in view of the above points, and has as its object to provide a biological treatment method for digested gas that solves the problems of the conventional biological treatment method. .

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is to form a packed bed filled with a microorganism-grown filler in a processing unit, The digestive gas is introduced into the tank and brought into contact with the absorbent circulating in the aeration tank to absorb hydrogen sulfide and carbon dioxide in the gas into the absorbent, and decomposed by microorganisms while the absorbent flows down the packed bed. In addition, there is provided a method for biologically treating digestive gas, wherein an odor component mainly emitted from the aeration tank, such as hydrogen sulfide or ammonia, is biologically treated in another treatment device.

[0011]

The digestion gas introduced into the treatment vessel is passed through a packed bed filled with a packing material on which microorganisms have formed, and is brought into contact with a large amount of an absorbent saturated with oxygen by aeration, whereby the microorganisms in the packed bed are removed. Uses the dissolved oxygen to produce hydrogen sulfide in the gas,
Ammonia and the like can be oxidized.

A part of the hydrogen sulfide or the like absorbed in the absorbing solution is oxidized by microorganisms settled on the surface of the filler while passing through the packed bed and mixed into the absorbing solution as sulfuric acid or the like.

Since the carbon dioxide in the digestion gas is dissolved in the absorption solution by bringing the digestion gas into contact with the absorption solution, the gas volume is reduced, and as a result, the calorific value per unit volume increases. is there.

The absorbing liquid that has fallen into the liquid reservoir at the bottom of the processor is
It is circulated and used as an absorbent after aeration and saturation of oxygen. Aeration also serves to dissolve oxygen and degas carbon dioxide dissolved in the absorbing solution.

Odor components such as hydrogen sulfide and ammonia remaining in the absorbing solution upon aeration are dispersed, and these odor components are biologically decomposed and removed under aerobic conditions in another deodorization tower to remove odor. Exhausted as gas.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of an apparatus applied to carry out the present invention on an industrial scale.

The embodiment includes a washing tower A for absorbing a target component in digestion gas into an absorbing solution, and a deodorizing tower for removing odorous components that are separated when the absorbing solution is aerated to circulate the absorbing solution. The case where B is added is shown.

In FIG. 1, reference numeral 1 denotes a processor constituting the washing tower A, and reference numeral 2 denotes a packed bed formed in the middle of the processor 1, which is filled with a filler on which microorganisms have grown. Reference numeral 3 denotes a water sprinkler disposed above the packed bed 2 in the processor 1, and is connected to the liquid supply pipe 4. Reference numeral 5 denotes an air supply port provided on the side wall of the processing unit 1 below the packed bed 2, 6 denotes an exhaust port provided on the top of the processing unit 1, and 7 denotes an exhaust port 6.
An eliminator 8 disposed near the water sprinkler 4 nearby is a liquid reservoir formed at the bottom of the processor 1.

Reference numeral 9 denotes a processor constituting the deodorization tower B provided in parallel with the washing tower A. Reference numeral 10 denotes a packed bed formed in the middle of the processor 9 and is filled with a filler on which microorganisms have formed. Reference numeral 11 denotes a sprinkler disposed above the packed bed 10 in the processing unit 9, and is connected to the liquid supply pipe 12. 13 is a packed bed 1 in the processor 9
0 The draining plate disposed below receives the absorbing liquid falling from the packed bed 10, collects water in a water collecting groove 14 provided on the inner wall surface of the processor 9, and discharges the water to the outside via a drain pipe 15. It is like that. Reference numeral 16 denotes an exhaust port provided at the top of the processor 9;
7 is an eliminator provided near the exhaust port 16 above the sprinkler 11, and 18 is a liquid reservoir formed at the bottom of the processor 9.
The liquid reservoir 18 is separated from the liquid reservoir 8 of the washing tower A by a partition wall 19, and aeration gas from the deodorization tower B side is supplied to the washing tower A.
The two reservoirs 8 and 18 are communicated by a through hole 20 provided below the partition wall 19 so as not to leak to the side.
Reference numeral 21 denotes an aeration diffuser provided in the liquid reservoir 18 and connected to the air supply pipe 22. Reference numeral 23 denotes a liquid discharge pipe connected to the liquid reservoir 18, and this liquid discharge pipe 23 is connected to the common circulation pump 2
4 are connected to the liquid supply pipes 4 and 12 of the sprinklers 3 and 11. Numerals 25 and 26 are watering valves respectively inserted into the two liquid supply pipes 4 and 12 for watering amount adjustment. Reference numeral 27 denotes a replenisher supply pipe connected to the liquid reservoir 18, and reference numeral 28 denotes an overflow pipe connected to the liquid reservoir 8, for keeping the liquid level of both the liquid reservoirs 8 and 18 constant.

In the above configuration, the digestion gas is supplied to the air supply port 5
The gas is introduced into the treatment device 1 of the washing tower A, and the gas-liquid contact is efficiently performed in the packed layer 2 with the absorbing liquid sprinkled from the water sprinkler 4, and hydrogen sulfide, ammonia, carbon dioxide, etc. in the gas are absorbed. Transfer to liquid. After the treated gas is removed of water by the eliminator 7, it is discharged from the discharge port 6 and guided to a gas holder or a combustion facility.

The absorbing solution having absorbed the component to be removed comes into contact with microorganisms that grow on the surface or inside the packed bed while flowing down the packed bed 2, and a part of the hydrogen sulfide and the like in the absorbing solution is oxidized to sulfuric acid and the like. And falls into the liquid reservoir 8 together with the absorbing liquid falling from the packed bed 2. The stored liquid that has fallen into the liquid storage section 8 in this way passes through the through hole 20 of the partition wall 19 and the liquid storage section 18 of the deodorization tower B.
And is here aerated by the sprinkler tube 21. During this aeration, the absorbed gas component is diffused from the liquid stored in the liquid reservoir 18. The released gas contains odor components such as hydrogen sulfide and ammonia, and these are efficiently decomposed by aerobic microorganisms while passing through the packed layer 10, and the deodorized treated gas is removed by the eliminator 17. The water is removed and discharged to the atmosphere from the discharge port 16 or a finishing process is performed as necessary. The absorbing liquid that has fallen from the packed bed 10 is collected in the collecting groove 14 by the draining plate 13 and is collected by the drain pipe 1.
It is discharged out of the vessel via 5. The stored liquid in the liquid storage section 18 is again saturated with oxygen by aeration, and is sent to the water sprayers 3 and 11 by the circulation pump 24 for circulating use. By circulating the absorbing solution by aerating and saturating oxygen in this way, the decomposition by microorganisms can be performed under microaerobic conditions. In addition, a part of this liquid is used as water necessary for growing organisms in the packed layers 2 and 10.

However, in carrying out the above-mentioned method, the following are specific items.

(A) As the packing material used for the packed bed 2 of the washing tower A, it is desirable to use a material on which organisms can easily form and have high gas-liquid contact efficiency. Usually, a corrugated plate is used. Ceramic, granulated slag, peat, sponge, or the like may be used, or a polymer gel or the like in which a microorganism group that decomposes the component to be removed is activated or adhered. As the filler used for the packed bed 10 of the deodorization tower B, any filler suitable for biological deodorization may be used, and an adsorbent, porous ceramic, peat, sponge, granulated slag, or the like is used. Further, it may be a polymer gel or the like in which a microorganism group that decomposes the component to be removed is enclosed or adhered.

(B) In the above embodiment, the liquid reservoirs 8 and 18 of the washing tower A and the deodorization tower B are configured to be separated by the partition wall 19, but both the liquid reservoirs 8 and 18 are separated. The configuration may be such that they are independently connected by a communication pipe.

(C) As the absorbing liquid used for watering, secondary sewage water is usually used, but it may be industrial water, groundwater, or well water. In addition, since microorganisms that oxidize hydrogen sulfide and the like are aerobic, the oxygen required for microorganisms is obtained by aerating the absorbing solution with an oxygen-containing gas in advance and saturating the oxygen to form dissolved oxygen in the water spray. Give in. This watering may be intermittent, but is usually performed continuously.

(D) The sprinkling liquid in the deodorization tower B can be recycled. However, since the pH is lowered by sulfuric acid generated by the biodegradation of hydrogen sulfide, the complexity and economy of the neutralization operation are taken into consideration. It is preferable to use a one-time system in which water is collected by the draining plate 13 and discharged outside the vessel.

(E) In the deodorization tower B, since the aerated gas released from the stored liquid at the time of aeration is deodorized, the gas used for aeration may be an odorous gas as long as it contains oxygen. When an aerobic odor gas generated in a place is used, deodorization of the aerobic odor can be performed at the same time.

(F) The replenishment of the liquid reservoirs 8 and 18 may be performed by detecting the water level of the stored liquid. However, normally, a constant amount is continuously supplied from the replenisher supply pipe 27 and the overflow pipe is supplied. Overflow from 28.

(G) The packed bed 10 of the deodorization tower B may be of a single-layer type as in the embodiment, but may be of a multi-layer type in which a plurality of packed layers are provided in multiple stages. By setting conditions favorable for the growth of microorganisms that decompose odor components, more effective deodorization can be achieved. Also, other formats may be used.

(H) In the above embodiment, a biological deodorization tower is used in terms of maintenance, management and economy, but it may be a conventional physicochemical deodorization tower.

[0032]

As described above, according to the present invention, the following effects can be obtained.

(A) Since the digestion gas is processed without using a chemical, the operating cost is low. (b) No secondary pollution occurs because the absorbed gas components are further biologically treated.

(C) As the gas for aeration, an aerobic odor gas generated from other sources can be used. In this case, the odor gas can be deodorized at the same time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a processing apparatus to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Processor (washing tower) 2 ... Packing layer 3 ... Sprinkler 8 ... Liquid reservoir 9 ... Processor (deodorization tower) 10 ... Packing layer 11 ... Sprinkler 18 ... Liquid reservoir 21 ... Air diffuser 24 ... Circulation pump A: Cleaning tower B: Deodorization tower

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI C02F 3/04 (58) Field surveyed (Int.Cl. ⁶ , DB name) B01D 53/34

Claims (1)

(57) [Claims] 1. A packed bed filled with a filler on which microorganisms have been grown is formed in a treatment device, and a digestion gas is introduced into the treatment device, and the digested gas is brought into contact with an absorbing solution circulating in an aeration tank to form a gas. Hydrogen sulfide and carbon dioxide gas are absorbed by the absorbing solution, and the absorbing solution is decomposed by microorganisms while flowing down the packed bed, and another odor component of hydrogen sulfide and ammonia mainly emitted from the aeration tank is separated. A biological treatment method for digestive gas, comprising biological treatment in a vessel.