CN100376312C - A plate type biological filter tower and its waste gas treatment process - Google Patents

Abstract

The present invention provides a plate type biological filtration tower and a waste gas treatment process thereof. Tower plates are arranged according to the ratio of layer thickness and tower diameter from 2.0 to 0.5, the whole biological filtration tower is composed of a plurality of tower plates, and a plate type biological filtration system for waste gas is formed. Nutrient liquid directly sprayed on every tower plate reversely contacts with waste gas from the bottom of the tower in order to remove pollutant in the waste gas, and the pollutant is oxidized into CO2, H2O and other simple compounds. The tower plate at a top layer is used as a dehydrater for gas current to spray cleaning liquid interstitially (usually 1% diluted alkaline liquor). The plate type biological filtration tower and a waste gas treatment process thereof of the present invention has sufficient and uniform gas and liquid contact, the spraying strength of every tower plate can be flexibly controlled according to the load of pollution treatment, the spraying strength of nutrient is greatly reduced, the total pressure drop of the tower is lowered, a filler layer has low supporting intensity, a dewatering system is built inside, and a biological filtration layer system realizes modular design. The present invention has important market application prospect.

Description

A plate type biological filter tower and its waste gas treatment process

(1) Technical field

The invention relates to a plate type biological filter tower and a process method for treating waste gas by using it.

(2) Background technology

Due to the incomparable advantages of low cost and environmental friendliness compared with traditional methods (such as absorption, adsorption, combustion, etc.), waste gas biological oxidation treatment technology is becoming a high-tech that is rapidly promoted in the field of waste gas pollution control, especially at low concentrations. , Large volume of organic waste gas and malodorous gas treatment. So far, the biological treatment of waste gas has expanded from the initial odor and simple organic compounds to the control of gaseous pollutants such as aromatic hydrocarbons, halogenated hydrocarbons and even inorganic substances.

According to the form of microorganisms, exhaust gas biological treatment technology can be divided into two types: suspension type and attachment type. The attachment type is the first to be popularized and applied in the field of exhaust gas purification due to the small pressure drop of the system, such as biological filtration, biological trickling filter, biological drum, etc. These technologies have their own characteristics, but there is a common problem that the thickness of the packing layer (the height of a single layer is usually about 2m), the uneven distribution of pollution load, nutrients, moisture and biomass on the packing layer, and the packing bed layer The channeling phenomenon caused by blockage is serious, which directly affects the treatment efficiency of the system. Numerous practices and studies have shown that 75% of the reasons for poor operation of attached biological filtration systems are due to uneven distribution of airflow, biomass, and nutrients.

In the past 10 years, domestic and foreign published literature searches have shown that uneven control of nutrients (including water) and excessive local biomass are the main reasons for the plugging of packing beds, and the occurrence of channeling phenomenon leads to uneven gas-liquid contact. , further deteriorating the overall effect of the system. Therefore, the uniform control of nutrients in the filler layer is a key. A large number of research results show that the nutrients and biomass of the attached biological filtration system are unevenly distributed along the height (axial direction) of the packing layer. When studying the biological filtration of toluene exhaust gas, it is found that the moisture content of the packing layer gradually decreases with the passage of time. The sub-reduction area gradually extends from the air inlet to the entire packing layer, and the pollution load of the packing layer per unit height varies greatly. In addition, practical applications have found that the outlet air flow of the biological trickling filter system is seriously water-carrying (in order to make the nutrient distribution uniform, nutrient atomization and spraying are required), the pipeline dehydrator is often blocked (biological blockage), and the cleaning intensity is high.

Patent application number 200420037051.3, patent name Self-control exhaust gas purifier provides a multi-layered exhaust gas purification device, the device achieves the purpose of removing acid pollutants in exhaust gas by spraying lye. Due to the particularity of biological treatment, the installation of the device needs to consider various factors such as biofilm adhesion, microbial nutrient supply, and exhaust gas composition, temperature, concentration, humidity and other physical parameters. The structure of the multi-layer packing layer has not yet been applied to biological oxidation treatment. in the device.

(3) Contents of the invention

In order to solve the shortcomings of the existing biological oxidation treatment equipment, such as the thickness of the packing layer, the uneven distribution of pollution load on the packing layer, nutrients, water and biomass, and the easy blockage of the pipeline dehydrator, the present invention provides a fully and uniform gas-liquid contact , The support strength of the packing layer is small, and the plate structure waste gas biological filter tower and its waste gas treatment process are integrated with the dehydration system.

For achieving the purpose of the invention, the technical scheme adopted by the present invention is:

A plate-type biological filtration tower mainly includes a tower body, an air inlet at the bottom of the tower body, an air outlet at the top of the tower, a biofilm carrier packing layer placed in the tower, and a nutrient circulation system. The biofilm carrier packing layer is set in multiple layers, and the ratio of layer thickness to tower diameter is 0.2 to 0.5, and the tower diameter refers to the inner diameter of the tower body; the top biofilm carrier packing layer is a dehydrator, and the upper part is provided with a cleaning liquid spray Shower pipe; the upper part of other biofilm carrier packing layers except the top layer is provided with a nutrient spray pipe and a nutrient collection pipe at the bottom; the nutrient spray pipe is provided with a flow control meter; the nutrient spray pipe and the nutrient collection pipe are respectively It is connected with the nutrient circulation tank located at the bottom of the tower body, and forms a nutrient circulation system through a circulation pump.

In this way, each layer of biofilm carrier packing layer is a "tray", and the whole biological filtration tower is composed of several "trays", forming a plate structure waste gas biological filtration system, and the nutrient solution is directly sprayed on each "tray" On the top, it is in reverse contact with the exhaust gas entering from the bottom of the tower to remove the pollutants in the exhaust gas, so that the pollutants are oxidized and decomposed into CO ₂ , H ₂ O and other simple compounds. The top "tray" is used as an air flow dehydrator (plate), instead of spraying nutrients, it is changed to spray cleaning liquid. Depending on the pressure drop of the dehydration "tray", the biofilm carrier packing "tray" is cleaned intermittently. The nutrient refers to the substance that maintains the growth activity of microorganisms, and its composition varies with the biological species that decompose the pollutants; the cleaning solution refers to the solution for cleaning the biofilm attached to the surface of the solid filler, usually a dilute alkali with a concentration of 1% by mass Solution, such as sodium hydroxide solution, potassium hydroxide solution, etc.; biofilm carrier filler refers to the carrier for the microbial layer to attach to. Usually, the biofilm carrier filler layer is 3-6 layers. Preferably, the biofilm carrier packing layer has 4 layers, and the ratio of layer thickness to column diameter is 0.2-0.5.

The biofilm carrier filler is one of the following: ① natural compost, ② natural broken wood, ③ plastic filler, ④ ceramic filler.

A waste gas biological treatment process using the plate-type biological filter tower, the biofilm carrier packing layer is attached with microbial dominant bacteria, the process is: the air velocity in the empty bed is 0.05 ~ 0.2m/s, the empty bed residence time is 10 ～30s, under the conditions of packing layer temperature 25～35℃ and liquid phase pH value 3.0～7.5, the waste gas is passed into the plate type biological filter tower through the inlet, and the treated waste gas is discharged through the gas outlet.

Specifically, when the waste gas to be treated is a gas pollutant containing 0.1 to 1.0 g/ ^m3 of toluene, the microbial dominant bacteria is Pseudomonas sp., the air velocity in the empty bed is 0.05m/s, the empty bed residence time is 20s, and the filler Under the conditions of layer temperature of 25-30°C and liquid phase pH value of 6.5-7.5, the exhaust gas is passed into the plate-type biological filter tower through the inlet, and the treated exhaust gas is discharged through the outlet.

When the exhaust gas is a gas pollutant containing H ₂ S0.1-0.5g/m ³ , the dominant microbial bacterium is Thiobacillus genus, the gas velocity in the empty bed is 0.05m/s, the residence time in the empty bed is 20s, and the packing layer Under the conditions of temperature 25-30°C and liquid phase pH value 3.0-4.0, the exhaust gas is passed into the plate-type biological filter tower through the inlet, and the treated exhaust gas is discharged through the outlet.

The beneficial effects of the plate structure waste gas biological tower and its technology of the present invention are mainly reflected in: (1) the packing layer is a "plate structure", and the nutrient intensity of each "tray" can be controlled independently according to the processing load, which improves the unit packing. Handling load; (2) Improve the plugging problem of the packing layer, avoid the channeling phenomenon, and the gas-liquid contact is uniform and sufficient; (3) The thickness of the single layer packing is reduced, and the strength requirement of the packing support frame is reduced; (5) The top packing "tray" As a dehydrator, the built-in dehydrator of the biological filtration system is realized, and no additional pipeline dehydrator is required; (6) Due to the "tray type" structure, the replacement of packing is more convenient.

(4) Drawings of the instruction manual

Fig. 1 is the structural representation of biological filtration tower of the present invention;

Figure 2 is a schematic diagram of the structure of a biological filtration tower with different packing layers; a is one packing layer, b is two packing layers, and c is four packing layers.

(5) Specific implementation methods

The focus of the present invention is a waste gas biological filter tower with a plate structure, which is versatile for different waste gases and applicable to waste gas pollutants that can be decomposed by microorganisms; it is also common for different fillers, as mentioned above, any that can be used for biological treatment Bulk packing is suitable. Therefore, the embodiment is tested with two types of representative pollutants. These two types of substances are respectively H ₂ S (representing sewage station odor) and toluene (representing VOCs); for the comparability of different test results, the fillers are all selected from plastic flat triangle.

The structure of the plate-type biological filtration tower is shown in Figure 1, mainly including a tower body, an air inlet 1 at the bottom of the tower body, an air outlet 2 at the top of the tower, a biofilm carrier packing layer 3 placed in the tower, and a nutrient circulation system , the biofilm carrier packing layer is arranged in multiple layers, the ratio of layer thickness to tower diameter is 0.2 to 0.5, and a cleaning liquid spray pipe 4 is arranged on the top of the top biofilm carrier packing layer, and the top of other biofilm carrier packing layers except the top layer A nutrient spray pipe 5 and a nutrient collection pipe 6 are arranged at the bottom, and the nutrient spray pipe is provided with a flow control meter 7, and the nutrient spray pipe and the nutrient collection pipe are respectively connected to the nutrient circulation tank 8 located at the bottom of the tower body , constitute the nutrient circulation system by circulation pump 9.

When the system is started, it is necessary to hang film on the filler to obtain biological filler. The pre-prepared bacterial suspension (mass concentration is about 10%) is sprayed on each packing layer in a mist form by the nutrient solution spray system, and is in reverse contact with the exhaust gas, and the pollutants in the exhaust gas are used as microbial carbon sources or energy sources. During the start-up period, the exhaust gas pollution load (controlled by concentration and gas volume) gradually increases from low (the specific value depends on the type of pollutant), the temperature of the packing layer is 25-30°C, and the pH range of the liquid phase depends on the type of microorganisms. For natural fillers, the bacterial suspension is sprayed intermittently (a cycle of 3 days, each time is subject to water penetration at the bottom of the filler layer), and the humidity of the filler layer is kept above 55%; for artificial fillers (plastics and ceramics), Due to the large pores of the filler, it is recommended to use continuous spraying. When the pollutant removal rate is maintained above 85%, it shows that the system is stable.

The present invention is further described in connection with specific examples below. For the convenience of description, it is more appropriate to point out the specific thickness of the test packing layer, which should be determined by the ratio of layer thickness to tower diameter in actual engineering:

Example 1:

The embodiment and working principle of the present invention are: plate-type biological filtration treatment process of waste gas containing toluene 0.75-1.00g/ ^m3 , empty bed gas velocity 0.05m/s, empty bed residence time 20s, packing layer temperature 25-30°C, The pH value of the liquid phase ranges from 6.5 to 7.5 (the dominant microbe is Pseudomonas spp., and the biofilm carrier filler is a plastic flat triangle). The inner diameter of the tower is 800mm, and the biofilm carrier filler is placed in three ways: one layer (thickness 1.0m), two layers (each thickness 500mm), and four layers (thickness each 250mm). Nutrients and toluene exhaust gas are in reverse contact, and nutrients are sprayed The strength control is the same, that is, 20L/m ² .h, as shown in Figure 2. The exhaust gas treatment results are shown in Table 1.

Table 1 Toluene waste gas treatment results

The results in Table 1 show that under the same operating conditions, the plate-type packing layer structure is beneficial to the removal of exhaust gas pollutants, and the unit packing pollution load of the four-layer "tray" biological filtration tower is the highest (average 152g/m ³ .h). In addition, under the same nutrient spraying intensity, the total pressure drop of the "plate structure" biological filtration tower is basically the same as that of the single packing structure.

Example 2:

The embodiment and working principle of the present invention are: plate type biological filtration treatment process containing H ₂ S 0.175-0.228g/m ³ waste gas, empty bed gas velocity 0.05m/s, empty bed residence time 20s, packing layer temperature 25-30 °C, the pH value of the liquid phase ranges from 3.0 to 4.0 (the dominant microbe is Thiobacillus genus, and the biofilm carrier filler is a plastic flat triangle). The inner diameter of the tower is 800mm, and the biofilm carrier filler is still placed in three ways: one layer (thickness 1.0m), two layers (each thickness 500mm), and four layers (each thickness 250mm). The nutrients and H ₂ S waste gas are in reverse contact. The nutrient spraying intensity is controlled the same, that is, 20L/m ² .h, as shown in Figure 2. The exhaust gas treatment results are shown in Table 2.

Table 2 H ₂ S waste gas treatment results

The results in Table 2 show that under the same operating conditions, the plate-type packing layer structure is also beneficial to the purification of H ₂ S waste gas, and the pollution load per unit packing of the four-layer "tray" biological filter tower is still the highest (average 35.2g/m ³ .h), The total pressure drop remains the same (11 _mmH2O ).

Example 3:

The embodiment and working principle of the present invention are as follows: the operating conditions are the same as in Example 1, the inner diameter of the tower is 800 mm, and there are four layers of biofilm carrier packing trays, each layer thickness is 250 mm, and the nutrient spray is controlled by three modes: Mode 1 , the spray intensity of the four layers is the same, both are 20L/m ² .h; mode 2, the top tray is not sprayed, and the spray intensity of the other three layers is the same, that is, 20L/m ² .h; mode 3, the top tray is not sprayed Spraying, the remaining three layers start from the air inlet of the bottom layer, and the spray intensity decreases by 30% in turn, that is, the bottom layer is 20L/m ² .h, the second layer is 14L/m ² .h, and the third layer is 9.8L/m ² .h. The exhaust gas treatment results are shown in Table 3.

Table 3 Toluene waste gas treatment results

The results in Table 3 show that the exhaust gas biological filter tower with plate structure is beneficial to the removal of exhaust gas pollutants, and the nutrient spray intensity of each "tray" can be adjusted reasonably, which will basically not affect the pollutant removal effect, and the total spray The amount can be effectively reduced, and the total pressure drop of the tower can also be effectively controlled, which once again verifies that the role of nutrients is mainly to maintain biological activity. Excessive nutrients will lead to a large number of organisms, causing the pressure drop of the packing layer to increase.

Example 4:

The embodiment and working principle of the present invention are as follows: plate type biological filtration treatment process for waste gas containing toluene 1.8-2.0g/ ^m3 , empty bed gas velocity 0.05m/s, packing layer temperature 25-30°C, liquid phase pH range 6.5 ～7.5 (Pseudomonas spp. is the dominant microorganism, and the biofilm carrier filler is plastic flat triangle). The inner diameter of the tower is 800mm, and the number of biofilm carrier packing trays is four layers (each layer thickness 250mm), five layers (each layer thickness 250mm), six layers (each layer thickness 250mm), and the corresponding empty bed residence time is 20s , 25s, 30s, the nutrient is sprayed and controlled according to the third mode of the embodiment, that is, the top floor tray is not sprayed, and the remaining three to five layers start from the bottom air intake end, and the spray intensity is successively decreased by 20%, that is, the bottom 20L/ m ² .h, second floor 16L/m ² .h, third floor 12.8L/m ² .h, fourth floor 10.2L/m ² .h, fifth floor 8.2L/m ² .h. The exhaust gas treatment results are shown in Table 4.

Table 4 Toluene waste gas treatment results

The results in Table 4 show that for higher concentration exhaust gas (exhaust gas concentration greater than 1500mg/m ³ ), the removal effect can be improved by increasing the number of trays. In this example, when the number of packed trays increases to six, the removal efficiency reaches 98.5%, and the outlet toluene concentration is maintained between 27.7 and 30.7 mg/ ^m3 , meeting the requirements of GB16297-96 "Comprehensive Emission Standard of Air Pollutants" , that is, the organized emission concentration of toluene is less than 40mg/m ³ , while the total spray intensity is only 67.2L/m ² .h. Of course, as the number of trays increases, the total pressure drop of the column also increases accordingly.

Note: The gas-phase toluene and H ₂ S concentration monitoring methods involved in the present invention adopt the corresponding methods specified in "Air and Waste Gas Monitoring and Analysis Methods" compiled by the State Environmental Protection Administration.

To sum up, the waste gas biological filtration tower with plate structure according to the present invention is beneficial to the removal of waste gas pollutants. The packing layer has a "plate structure", and the nutrient spraying intensity of each "tray" can be flexibly controlled according to the pollution treatment load. The nutrient spray intensity is greatly reduced, the overall pressure drop of the tower is reduced, and the modular design of the biological filtration layer system is realized. Compared with the prior art, the waste gas biological filtration tower with plate structure of the present invention has sufficient and uniform gas-liquid contact, low packing layer support strength, built-in dehydration system, and broad market application prospects.

Claims (8)

1. A plate type biological filtration tower mainly includes a tower body, an air inlet positioned at the bottom of the tower body, an air outlet positioned at the top of the tower, a biofilm carrier packing layer placed in the tower, and a nutrient circulation system, characterized in that: The biofilm carrier packing layer is set in multiple layers, and the ratio of layer thickness to tower diameter is 0.2 to 0.5; the top biofilm carrier packing layer is a dehydrator, and a cleaning liquid spray pipe is arranged on the upper part; other biofilm carrier packings except the top layer The top of the layer is provided with a nutrient spray pipe, and the bottom is provided with a nutrient collection pipe; the nutrient spray pipes are all provided with a flow control meter; The circulation pump constitutes the nutrient circulation system. 2. The plate-type biological filtration tower according to claim 1, characterized in that the biofilm carrier packing layers are 3 to 6 layers. 3. The plate-type biological filtration tower according to claim 1, characterized in that the biofilm carrier packing layer has 4 layers, and the ratio of layer thickness to tower diameter is 0.2-0.5. 4. The plate-type biological filter tower as claimed in claim 1, wherein the biofilm carrier filler is one of the following: ① natural compost, ② natural broken wood, ③ plastic filler, ④ ceramic filler. 5. The plate-type biological filter tower as claimed in claim 1, characterized in that said cleaning solution is a dilute alkaline solution with a concentration of 1% by mass. 6. A waste gas biological treatment process using the plate-type biological filter tower as claimed in claim 1, the biofilm carrier packing layer is attached with microbial dominant bacteria, it is characterized in that the process is: at an empty bed gas velocity of 0.05 to 0.2 m/s, the empty bed residence time is 10-30s, the packing layer temperature is 25-35°C, and the liquid phase pH value is 3.0-7.5, the waste gas is passed into the plate type biological filter tower through the inlet, and the treated waste gas passes through the gas outlet discharge. 7. The waste gas biological treatment process as claimed in claim 6, characterized in that the waste gas is a gaseous pollutant containing 0.1 to 1.0 g/ ^m of toluene, and the microbial dominant bacterium is Pseudomonas spp. Under the conditions of 0.05m/s, empty bed residence time of 20s, packing layer temperature of 25-30°C, and liquid phase pH of 6.5-7.5, the exhaust gas is passed into the plate-type biological filter tower through the inlet, and the treated exhaust gas is discharged through the outlet. . 8. The exhaust gas biological treatment process as claimed in claim 6, characterized in that the exhaust gas is a gas pollutant containing H ₂ S0.1-0.5g/m ³ , and the dominant microbial bacterium is Thiobacillus genus. The gas velocity is 0.05m/s, the empty bed residence time is 20s, the packing layer temperature is 25-30°C, and the liquid phase pH value is 3.0-4.0. The waste gas is passed into the plate-type biological filter tower through the air inlet, and the waste gas after treatment is passed through Exhaust air outlet.

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