CN1194796C - Biologic cleaning method for low-concentration organic waste gas - Google Patents

Abstract

The present invention discloses a biological purification treating method for organic waste gas, which comprises the following steps that the waste gas is added into an organic filtering tower by the way that the flow direction of the waste gas is parallel to the spraying direction or is opposite to the spraying direction, organic matters in the waste gas are captured by microorganisms to be degraded into carbon dioxide and water, and the purified gas is discharged into the atmospheric air. The present invention has the advantages of simple technology, convenient operation, high removing rate and no secondary pollution.

Description

Biological Purification Method of Low Concentration Organic Matter Waste Gas

technical field

The invention relates to a biological purification treatment method of organic waste gas. More specifically, the present invention relates to the biological purification treatment method of low-concentration organic waste gas such as aromatic hydrocarbons (benzene, toluene, xylene), aliphatic hydrocarbons, halogenated aromatic hydrocarbons, etc. The exhaust gas treatment method that the membrane filter material is in contact with each other and is purified under the action of microorganisms.

Background technique

In recent years, mankind's awareness of environmental protection has been increasing, and stricter requirements have been put forward for the treatment of organic waste gas pollution. In the past, people put forward some treatment methods of organic waste gas after long-term research. To sum up, there are mainly (catalytic) combustion method, adsorption method and absorption method. The main characteristics of these methods are briefly listed in the table below.

Table 1 Organic waste gas treatment method and performance comparison table method (catalytic) combustion method Adsorption absorption method High concentration Processing efficiency high middle high cost high middle high Low concentration Processing efficiency high high middle cost high high high final product CO ₂ , H ₂ O Desorbed organics for recycling or further processing Desorbed organics for recycling or further processing scope of use High concentration Low concentration High concentration other Incomplete combustion, producing toxic intermediate products high operating costs When the operating pressure is low, the absorption rate is very low, and the absorption solution needs to be recovered

The domestic technology of using microbial membranes to purify organic waste gas is still in the research stage, and there are no reports of patent applications. The inventor has found through long-term research that under certain conditions, the microorganisms that eat organic matter are fixed on the filter material to form a microbial film, and then the organic gas is degraded into carbon dioxide and water through the microbial film, and the gas is purified. The present invention has thus been accomplished.

Contents of the invention

Therefore, the object of the present invention is to provide a method for degrading organic waste gas by using a filter material with biofilm, especially using the microorganisms with film, so that the organic matter in the waste gas is captured and degraded by microorganisms into carbon dioxide and water, and the gas is purified. . The method of the invention has simple process, convenient operation, high removal rate and no secondary pollution.

In the present invention, the total concentration of organic matter is usually below 2000PPm, the rest is oxygen, nitrogen, etc., the temperature is ambient temperature, and the pressure is ambient pressure.

In the present invention, the biological filter material used is formed by carrying microorganisms on the surface of the filter material. Activated carbon is used as a carrier without special limitation. It can be commercially available activated carbon, or it can be made of coal, walnut shell , coconut shell, wood, aggregate or natural organic matter and other raw materials prepared by known methods.

The microorganisms used in the present invention are not particularly limited, mainly bacteria such as bacillus, breviphyte, mold, actinomycetes and the like.

In the present invention, in addition to maintaining the humidity of the biological filter material, the spray liquid used also provides the microorganisms with the required nitrogen, phosphorus, trace elements and moisture. A feature of the present invention is to use the effluent of domestic sewage treatment equipment and/or the effluent of petrochemical industry wastewater treatment equipment and/or activated sludge as spray liquid to provide nitrogen, phosphorus, trace elements, moisture and bacterial sources required by microorganisms. The general composition of the effluent from these treatment plants is as follows:

Table 2 Treatment water quality composition (mg/l) nutrients pH Ammonia nitrogen PO ₄ ^2- (calculated as P) concentration 6.5～7.5 15 1

If artificially configured nutrient solution is used, the composition and formulation can be configured in the following table.

Table 3 nutrient solution composition (mg/l) nutrients K ₂ PO ₄ Na ₂ HPO ₄ KH ₂ PO ₄ NH ₄ Cl _FeCl3 MnSO _{4 MgSO4 CaCl2} concentration 28.5 33.4 8.5 5.0 0.25 39.9 46.13 36.4

In the present invention, asynchronous film-hanging method is used to prepare biological filter material. Put the activated sludge in the sewage treatment plant into a culture tank, add nutrients and water, and cultivate. When the physical and biochemical properties of the sludge reach the required value, add an organic solution to the tank to start acclimatization. After the requirements are met, put the activated carbon into the culture tank and fully contact with the solution in the tank, remove it and let it stand still. When no liquid drops flow down, put it into the filter tower, pass in the gas containing organic matter, and adjust the pH to 7 , Add nutrient solution to start film hanging. After the air tightness check is made to confirm that there is no air leakage, the air is continuously fed, and the nutrient solution is added regularly to ensure the growth of the biofilm and complete the preparation of the biofilm.

In the following, the present invention will be described in more detail with reference to the accompanying drawings. These descriptions are for the purpose of illustration only, and do not limit the invention, the scope of which is set forth in the appended claims.

Description of drawings

Fig. 1 shows the single-stage or multi-stage spraying system of parallel air intake for implementing the biological filter material purification method of the present invention.

Fig. 2 shows a single-stage or multi-stage spraying system of one-point air intake and gas-liquid countercurrent flow for implementing the biological filter material purification method of the present invention.

Fig. 3 shows a single-stage or multi-stage spraying system with one-point air intake and gas-liquid parallel flow for implementing the biological filter material purification method of the present invention.

Figure 4 shows a biological filter tower with a humidifier.

Detailed ways

As shown in Figure 1, the organic waste gas enters the single-stage and/or multi-stage biological filter tower in parallel in the direction indicated by the arrow, and the organic matter in it is captured and degraded by microorganisms, and the nutrient solution is sprayed on the biological filter material in parallel as shown in the figure , to supply microbial nutrients and maintain the conditions for microbial survival.

As we all know, during the operation of the biological filter tower, it is not only necessary to provide the microorganisms with the nutrients they need, but also to provide the microorganisms with a suitable living environment, such as temperature, oxygen and pH value. Therefore, during the operation of the biological filter tower, the pH value, temperature and humidity are mainly controlled.

The humidity of the biological filter tower is maintained by spraying liquid. Usually, the relative humidity of the filter tower is controlled at 40-60%. When the humidity of the filter tower is greater than 60%, the water fills the pores of the filter material, which reduces the specific surface area of the filter material, shortens the residence time of the gas, reduces the transfer of oxygen and organic matter, and increases the area of the anaerobic zone and anaerobic zone. It causes the metabolic rate of organic substances such as benzene series to decrease, and also causes the increase of filter tower resistance and the loss of nutrients; when the humidity of the filter tower is less than 40%, the protein denaturation in the microorganism body is reduced, the activity is reduced, and the metabolism is slowed down or even stopped. activities directly affect the utilization rate of organic matter. At the same time, it will cause the filter material to dry and crack, causing gas short-circuit flow, and reducing the purification efficiency of organic matter.

The temperature of the biological filter tower is suitable for the growth of microorganisms, usually controlled at 20-40°C. When the temperature is lower than 20°C, the synthesis of microbial proteins is prevented, the microorganisms are in a dormant state, and their growth and metabolism are slow. When the temperature is higher than 40°C, it will cause the inactivation of key cell organs of microorganisms and the coagulation of proteins, resulting in the death of microorganisms.

The pH value of the filtrate liquid and/or solid phase in the biofiltration tower is a key factor in determining the removal of organic matter, and its change strongly affects the activity of microorganisms. Observing the microbial phase, it is found that the microorganisms in the filter tower are mainly bacteria and actinomycetes, and their most suitable pH value is 7-9. Therefore, the pH value of the biological filter tower is generally controlled at 7.5-8.5, preferably around 8. This can be controlled by methods known in the art such as adding buffers.

Figure 2 shows another spray system for the method of the present invention. The organic waste gas enters the tower from a point at the bottom of the filter tower, and passes through the single-stage and/or multi-stage biofilm-activated carbon bed countercurrently with the nutrient solution from the nutrient solution circulation tank, where the organic matter is captured by microorganisms and degraded into carbon dioxide and water , the purified gas is discharged from the top of the tower.

Figure 3 shows co-current flow of gas and liquid through a single and/or multi-stage sprinkler system. In this system, the organic matter waste gas and the nutrient solution from the nutrient solution circulation tank flow side by side and enter the filter tower from the top of the filter tower, and pass through single-stage and/or multi-stage biofilm-activated carbon beds, where the organic matter is absorbed Microorganisms capture and degrade into carbon dioxide and water, and the purified gas is discharged from the bottom of the tower.

Figure 4 shows a single and/or multi-stage sprinkler system with humidifiers. A humidifier is installed outside the spray system. The organic waste gas enters the humidifier first, and then enters the single-stage and/or multi-stage biofilm-activated carbon filter bed. The gas is captured and degraded by microorganisms during the flow process, purifying the gas discharged from the top of the tower.

In the method of the present invention, when the total concentration of "triphenyl" in the exhaust gas is 2000 mg/m ³ and the empty tower residence time is t>20 seconds, the organic matter removal rate is above 95%, and the organic matter concentration in the purified gas is less than 60 mg/m ^3. The final products are carbon dioxide and water, with high removal rate and no secondary pollution.

Claims (6)

1. A biological purification method for organic waste gas, characterized in that: the method makes the waste gas flow through the biological filter material in the biological filter tower, and the biodegradable organic matter is captured and decomposed into harmless substances by microorganisms; the biological filter The material is a biofilm attached to the surface of natural materials such as peach shells, coconut shells, sawdust, cow dung or wood chips, or porous materials based on activated carbon; One or more than two kinds; the organic matter is aromatic hydrocarbon, aliphatic hydrocarbon or halogenated aromatic hydrocarbon; the relative humidity of the biological filter tower is 40-60%; the temperature of the biological filter tower is 20-40°C; The pH value of the filtrate liquid and/or solid phase in the biological filter tower is 7.5-8.5; the spray liquid provides nutrients for microorganisms, and the composition of the spray liquid: K ₂ PO ₄ : 28.5mg/l, Na ₂ HPO ₄ : 33.4 mg/l, KH ₂ PO ₄ : 8.5 mg/l, NH ₄ Cl: 5.0 mg/l FeCl ₃ : 0.25 mg/l, MnSO ₄ : 39.9 mg/l, MgSO ₄ : 46.13 mg/l, CaCl ₂ : 36.4mg/l; the total concentration of said organic matter is usually below 2000PPm. 2. The method according to claim 1, characterized in that the waste gas passes through the single-stage and/or multi-stage biological filter material in a countercurrent direction to the spraying direction of the spraying liquid. 3. The method according to claim 1, characterized in that the exhaust gas passes through the single-stage and/or multi-stage biological filter materials in a direction parallel to the spraying direction of the spraying liquid. 4. The method according to claim 1, characterized in that the exhaust gas is fed into the biological filter tower at the bottom or top of the biological filter tower. 5. The method according to claim 1, characterized in that: the biological filter tower has multiple stages. 6. The method according to claim 1, characterized in that: before the waste gas is fed into the biological filter tower, it is first passed into a humidifier for humidification.

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