Method for purifying malodorous exhaust gas

Abstract

The application discloses a foul-smelling waste gas purification method and belongs to the technical field of waste gas treatment. The method comprises the following steps: step 1, foul-smelling waste gas is sucked into an alkali washing tower through a fan; step 2, the waste gas treated by the alkali washing tower is subjected to water washing treatment in a prewashing tower, a spraying device is arranged in the prewashing tower, and the relative humidity of the waste gas reaches more than 95% after spraying washing; step 3, the waste gas treated by the prewashing tower is introduced into a biological filter tank from the bottom, a biological filler layer is arranged in the biological filter tank, and a spraying water device is arranged at the top of the biological filter tank; and step 4, the gas treated by the biological filter tank is discharged through an exhaust pipe. The bacterial agent in the biological filter tank performs biochemical conversion on the odor substances in the waste gas, adsorbs the foul-smelling substances, decomposes the foul-smelling substances into simple inorganic substances such as CO2, H2O, H2SO4 and HNO3, effectively removes foul-smelling components such as NH3 and H2S, and greatly reduces the odor concentration in the waste gas.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment technology, and specifically relates to a method for purifying odorous waste gas. Background Technology

[0002] With the improvement of social and economic levels, the problem of malodor pollution has received increasing attention from the public. Malodor pollutants refer to all gaseous substances that irritate the olfactory organs, cause unpleasantness, and affect the living environment. To date, tens of thousands of malodorous substances have been discovered. Using air as a medium, there are about 4,000 kinds of malodorous substances that can be perceived by the olfactory organs. These malodorous gases are almost all volatile, hydrophilic, and lipophilic. According to the different chemical components of the gases, they are divided into 5 categories: (1) sulfur-containing compounds such as thiols, H2S, and thioethers; (2) nitrogen-containing compounds such as NH3, indole, and amines; (3) halogenated hydrocarbons, chlorine, and other halogens and their derivatives; (4) hydrocarbons such as alkenes, alkanes, and aromatic hydrocarbons; and (5) oxygen-containing organic compounds such as phenols, aldehydes, and ketones.

[0003] Odor pollution, as a form of sensory pollution, is characterized by numerous sources and a wide impact. It not only harms the ecological environment but also poses significant risks to human health. Odor pollution not only irritates the olfactory organs, causing psychological aversion, but also adversely affects the digestive, endocrine, and nervous systems, leading to physical discomfort. Among the more harmful odorous substances are H2S, NH3, formaldehyde, styrene, and phenols. For example, H2S has a strong irritant effect on mucous membranes; high concentrations can cause suffocation and damage the central nervous system. NH3 has an irritant and corrosive effect on the respiratory tract mucosa; high concentrations can lead to anemia, tissue deficiency, and reduced immunity.

[0004] Currently, physical, chemical, and biological deodorization methods are mainly used to treat odorous gases, altering their phases and structures to achieve deodorization. Among these, biological deodorization refers to methods that utilize microbial metabolism to degrade or convert odorous substances into less harmful or harmless substances. Compared to physical and chemical methods, biological deodorization offers advantages such as high treatment efficiency, no secondary pollution, ease of operation, and low cost, and has been widely applied in odor control.

[0005] However, in biological deodorization technology, fillers are needed as a medium for microbial attachment, growth, and fixation. Ideally, fillers should have characteristics such as large specific surface area, high porosity, strong stability, and good durability. According to their material characteristics, they can be divided into inorganic and organic types. Inorganic types include quartz sand, ceramsite, and slag, while organic types include agar, sodium alginate, and chemically synthesized materials such as polyethylene and polyurethane foam. Among them, polyurethane foam is a polymer foaming material with low density and high open-cell ratio. Using it as a growth carrier for deodorizing microorganisms can greatly improve the deodorization effect. However, when polyurethane foam is used as a biological carrier, the biofilm formation efficiency is low, and the biofilm is unstable and easily falls off, resulting in an unsatisfactory deodorization effect. Summary of the Invention

[0006] This invention provides a method for purifying malodorous waste gas, which can solve the problem of poor deodorization effect in existing malodorous waste gas treatment processes.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for purifying malodorous waste gas includes the following steps:

[0009] Step 1: The malodorous waste gas is drawn into the alkaline scrubbing tower by a fan;

[0010] Step 2: The exhaust gas after being treated by the alkaline scrubbing tower enters the pre-scrubbing tower for water washing. The pre-scrubbing tower is equipped with a spray device. After spray washing, the relative humidity of the exhaust gas reaches more than 95%.

[0011] Step 3: The exhaust gas after pre-washing tower enters the biological filter from the bottom. The biological filter is equipped with a biological packing layer with a height of 0.5-1m. A spray water device is installed at the top of the biological filter to maintain the moisture content of the biological packing between 30-80% through water spraying.

[0012] Step 4: The gas treated by the biological filter is discharged through the exhaust stack.

[0013] In some embodiments, the alkaline solution in the alkaline washing tower is a sodium hydroxide solution with a concentration of 20-40%, which absorbs acidic gases and pretreats odorous waste gases.

[0014] The biological packing material is prepared through the following steps:

[0015] Lactic acid bacteria inoculant, Bacillus inoculant and yeast inoculant were mixed in a certain proportion to form a compound bacterial solution; modified polyurethane foam particles were added to the compound bacterial solution, placed on a shaker, and cultured at 35°C under natural light for 24 hours. After that, the modified polyurethane foam particles were removed to obtain the biological filler.

[0016] The mass ratio of modified polyurethane foam particles to composite bacterial solution is 1g:10-50mL.

[0017] The flow rate of the odorous waste gas is 100-250 L / min.

[0018] The operating temperature of the biological filter is 20-35℃.

[0019] The raw materials for preparing the modified polyurethane foam particles include oxidized polyurethane foam, amino acids, aminated magnetic particles, and glutaraldehyde.

[0020] The amino acid is at least one selected from alanine, glycine, arginine, L-cysteine, L-glutamic acid, lysine, methionine, and taurine.

[0021] The oxidized polyurethane foam particles are polyurethane foam particles treated with acidic potassium permanganate solution.

[0022] The aminated magnetic particles are polyethyleneimine-grafted iron tetroxide particles.

[0023] In some embodiments, the mass ratio of lactic acid bacteria, Bacillus, and yeast in the compound bacterial solution is 5-7:3-5:3-5.

[0024] In some embodiments, the lactic acid bacteria content in the lactic acid bacteria inoculant is 2.3 × 10⁻⁶. 8 CFU / mL -3.1×10 8 CFU / mL, the lactic acid bacteria is Lactobacillus acidophilus.

[0025] In some embodiments, the Bacillus content in the Bacillus inoculant is 3.7 × 10⁻⁶. 8 CFU / mL -5.8×10 8 CFU / mL, the Bacillus is Bacillus coagulans.

[0026] In some embodiments, the yeast content in the yeast inoculum is 2.3 × 10⁻⁶. 8 CFU / mL -4.5×10 8 CFU / mL, the lactic acid bacteria is abnormal Hansenula polymorpha.

[0027] In some embodiments, the modified polyurethane foam particles are prepared as follows:

[0028] The oxidized polyurethane foam particles were soaked in a glutaraldehyde solution at 37°C for 24 hours and then removed. They were then soaked in a mixture of amino acids, aminated magnetic particles and deionized water and reacted at 35-40°C for 24 hours. After filtration, the filter cake was rinsed and air-dried to obtain modified polyurethane foam particles.

[0029] In some embodiments, the glutaraldehyde solution has a mass fraction of 5%.

[0030] In some embodiments, the mass ratio of amino acids, aminated magnetic particles, and deionized water in the mixture is 0.5-1:0.5-1:100.

[0031] In some embodiments, the method for preparing the oxidized polyurethane foam particles is as follows:

[0032] Potassium permanganate was added to sulfuric acid solution and stirred until homogeneous to obtain acidic potassium permanganate solution. Polyurethane foam particles were then immersed in the acidic potassium permanganate solution at 45-55℃ for 4-6 hours under continuous aeration. After removal, the particles were washed with hydrochloric acid solution to remove the brown layer on the surface, and then washed with PBS phosphate buffer solution until the washing solution was neutral. The particles were then air-dried to obtain oxidized polyurethane foam particles.

[0033] In some embodiments, the ratio of potassium permanganate to sulfuric acid solution in the acidic potassium permanganate solution is 0.5 g: 10 mL, and the sulfuric acid solution is composed of concentrated sulfuric acid and deionized water in a volume ratio of 1:9.

[0034] In some implementations, the concentrated sulfuric acid has a mass fraction of 95-98%.

[0035] In some implementations, the concentration of the hydrochloric acid solution is 4-6 mol / L, the concentration of the PBS phosphate buffer solution is 0.01 mol / L, and the pH value is 7.2-7.4.

[0036] In some embodiments, the method for preparing the amination magnetic particles is as follows:

[0037] S1. Preparation of carboxylated iron oxide particles: FeCl3·6H2O and FeCl2·4H2O were added to deionized water, and sodium hydroxide solution containing sodium citrate was added under stirring. Under nitrogen protection, the reaction was stirred at 80°C for 1 hour. The black product was collected by magnetic separation. The black product was then washed three times with ultrapure water and freeze-dried to obtain carboxylated iron oxide particles.

[0038] S2. Preparation of Aminated Magnetic Particles: Carboxylated iron oxide particles were ultrasonically dispersed in deionized water, acetic acid was added to adjust the pH to 6, EDC·HCl and NHS were added, and the mixture was stirred for 1 h under nitrogen protection at room temperature. Hydroxide solution was added to adjust the pH to 7, and then water-soluble polyethyleneimine was added. The mixture was stirred for 24 h under nitrogen protection at room temperature. After the reaction was completed, the black product was collected by magnetic separation. The black product was then washed three times with ultrapure water and freeze-dried to obtain aminated magnetic particles.

[0039] First, carboxylated iron tetroxide particles were prepared using FeCl3·6H2O and FeCl2·4H2O as iron sources and sodium citrate as an additive. Then, polyethyleneimine was grafted onto the surface of the carboxylated iron tetroxide particles by utilizing the amide reaction between carboxyl and amino groups to obtain aminated magnetic particles.

[0040] In some embodiments, the ratio of FeCl3·6H2O, FeCl2·4H2O, deionized water, and sodium hydroxide solution containing sodium citrate in S1 is 2.7g:1.0g:100-200mL:40mL, and the sodium hydroxide solution containing sodium citrate is composed of a 1.5mol / L sodium hydroxide solution and sodium citrate in a ratio of 40mL:0.01mol.

[0041] In some embodiments, the stirring speed in S1 is 1000-1500 rpm.

[0042] In some embodiments, the ratio of carboxylated iron oxide particles, deionized water, EDC·HCl [1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride], NHS (N-hydroxysuccinimide) and polyethyleneimine in S2 is 3.0g:60-100mL:3.8g:2.3g:6-10g, and the polyethyleneimine solution is composed of polyethyleneimine and deionized water at a ratio of 1g:6-10mL.

[0043] In some embodiments, the polyethyleneimine is branched polyethyleneimine with a Mw of 600-1800.

[0044] In some embodiments, the concentration of sodium hydroxide solution in S2 is 1 mol / L.

[0045] The beneficial effects of this invention are:

[0046] This invention provides a method for purifying odorous waste gas. First, the odorous gas is pretreated with an alkaline solution. Then, in a pre-washing tower, water spraying is used to initially remove heavily water-soluble odorous substances such as ammonia and organic odorous substances from the air, adjusting the physicochemical properties of the air, such as temperature and pH, and increasing humidity to create conditions for subsequent biological filtration. The waste gas treated in the pre-washing tower enters a biological filter, where it comes into full contact with the moistened biological packing material. Odorous substances are first absorbed by the packing material and then oxidized and degraded by the microorganisms within, eliminating the odor and completing the deodorization process. The microbial agents in the biological filter biochemically transform the odorous substances in the waste gas, using them as a direct energy source or part of their energy chain. After biochemical transformation, the odorous substances are adsorbed and decomposed into simple inorganic substances such as CO2, H2O, H2SO4, and HNO3, effectively removing odorous components such as NH3 and H2S, resulting in a significant reduction in the odor concentration in the waste gas.

[0047] To address the issue of poor performance of polyurethane foam as a biological carrier, this invention first uses an acidic potassium permanganate solution to oxidize it, increasing the roughness of the polyurethane foam and introducing hydrophilic groups. Based on this, amino acids and amination-modified magnetic particles are used for chemical modification, further increasing the number of hydrophilic groups such as hydroxyl, amino, and carboxyl groups on the polyurethane foam, thereby increasing its specific surface area and absorption rate, and ultimately improving the microbial loading capacity. Amino acids not only enhance the hydrophilicity of the polyurethane foam but also bind to ammonia molecules, enhancing the deodorizing performance of the biological carrier and acting as nutrients to accelerate microbial reproduction. The amination-modified magnetic particles carry numerous positively charged amino groups, which interact with the negatively charged surface of microorganisms, reducing the repulsive force between the microorganisms and the carrier, accelerating the attachment and immobilization process of microorganisms, and promoting their proliferation, thus improving the odor treatment effect. Furthermore, the magnetic properties of the amination-modified magnetic particles also have a positive impact on the growth, reproduction, and degradation capabilities of microorganisms.

[0048] The abundant amino groups on the amination magnetic particles in this invention can react with hydrogen sulfide gas, enhancing the deodorization effect of the biological filler. It combines the advantages of polyethyleneimine and iron oxide, and solves the problem of iron oxide's tendency to agglomerate. Detailed Implementation

[0049] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0050] The technical solution of this application will be illustrated below through specific embodiments and comparative examples. In the following embodiments, the polyurethane foam particles are cuboid blocks of 2cm×2cm×6cm, which are from Lanzhou Polyurethane Foam Processing Plant, and the branched polyethyleneimine (BPE I, Mw=1800) is purchased from Gongbike New Material Technology (Shanghai) Co., Ltd.

[0051] Preparation Example 1

[0052] The method for preparing the modified polyurethane foam particles is as follows:

[0053] 10g of oxidized polyurethane foam particles were soaked in 100mL of 5wt% glutaraldehyde solution at 37℃ for 24h, and then removed and soaked in a mixture of 0.5g alanine, 0.5g aminated magnetic particles and 100mL deionized water. The mixture was reacted at 35℃ for 24h, filtered, the filter cake was rinsed and air-dried to obtain modified polyurethane foam particles.

[0054] The method for preparing the oxidized polyurethane foam particles is as follows:

[0055] Add 5g of potassium permanganate to a sulfuric acid solution consisting of 10mL of 95wt% concentrated sulfuric acid and 90mL of deionized water, and stir until homogeneous to obtain an acidic potassium permanganate solution. Soak 10g of polyurethane foam particles in the acidic potassium permanganate solution at 45℃ for 4 hours under continuous aeration. Remove the particles and wash them with a 4mol / L hydrochloric acid solution to remove the brown layer on the surface. Then wash them with a 0.01mol / L PBS phosphate buffer solution with a pH of 7.2 until the washing solution is neutral. Allow them to air dry to obtain oxidized polyurethane foam particles.

[0056] The method for preparing the amination-modified magnetic particles is as follows:

[0057] S1. Add 2.7g FeCl3·6H2O and 1.0g FeCl2·4H2O to 100mL of deionized water, and add 40mL of sodium hydroxide solution containing sodium citrate while stirring. The sodium hydroxide solution containing sodium citrate is composed of 1.5mol / L sodium hydroxide solution and sodium citrate in a volume ratio of 40mL:0.01mol. Under nitrogen protection, stir and react at 1000rpm and 80℃ for 1h. Collect the black product by magnetic separation, then wash the black product three times with ultrapure water and freeze dry to obtain carboxylated iron tetroxide particles.

[0058] S2. 3.0 g of carboxylated iron oxide particles were ultrasonically dispersed in 60 mL of deionized water. Acetic acid was added to adjust the pH to 6. 3.8 g of EDC·HCl and 2.3 g of NHS were added. The mixture was stirred for 1 h under nitrogen protection at room temperature. 1 mol / L hydroxide solution was added to adjust the pH to 7. Then, a solution consisting of 6 g of branched polyethyleneimine and 60 mL of deionized water was added. The mixture was stirred and reacted for 24 h under nitrogen protection at room temperature. After the reaction was completed, the black product was collected by magnetic separation. The black product was then washed three times with ultrapure water and freeze-dried to obtain aminated magnetic particles.

[0059] Preparation Example 2

[0060] The method for preparing the modified polyurethane foam particles is as follows:

[0061] 10g of oxidized polyurethane foam particles were soaked in 100mL of 5wt% glutaraldehyde solution at 37℃ for 24h, and then removed and soaked in a mixture of 0.8g glycine, 0.8g aminated magnetic particles and 100mL deionized water. The mixture was reacted at 38℃ for 24h, filtered, the filter cake was rinsed and air-dried to obtain modified polyurethane foam particles.

[0062] The method for preparing the oxidized polyurethane foam particles is as follows:

[0063] Add 5g of potassium permanganate to a sulfuric acid solution consisting of 10mL of 95wt% concentrated sulfuric acid and 90mL of deionized water, and stir until homogeneous to obtain an acidic potassium permanganate solution. Soak 10g of polyurethane foam particles in the acidic potassium permanganate solution at 50℃ for 5 hours under continuous aeration. Remove the particles and wash them with a 5mol / L hydrochloric acid solution to remove the brown layer on the surface. Then wash them with a 0.01mol / L PBS phosphate buffer solution with a pH of 7.2 until the washing solution is neutral. Allow them to air dry to obtain oxidized polyurethane foam particles.

[0064] The method for preparing the amination-modified magnetic particles is as follows:

[0065] S1. Add 2.7g FeCl3·6H2O and 1.0g FeCl2·4H2O to 150mL of deionized water, and add 40mL of sodium hydroxide solution containing sodium citrate while stirring. The sodium hydroxide solution containing sodium citrate is composed of 1.5mol / L sodium hydroxide solution and sodium citrate in a volume ratio of 40mL:0.01mol. Under nitrogen protection, stir and react at 1200rpm and 80℃ for 1h. Collect the black product by magnetic separation, then wash the black product three times with ultrapure water and freeze dry to obtain carboxylated iron tetroxide particles.

[0066] S2. 3.0 g of carboxylated iron oxide particles were ultrasonically dispersed in 80 mL of deionized water. Acetic acid was added to adjust the pH to 6. 3.8 g of EDC·HCl and 2.3 g of NHS were added. The mixture was stirred for 1 h under nitrogen protection at room temperature. 1 mol / L hydroxide solution was added to adjust the pH to 7. Then, a solution consisting of 8 g of branched polyethyleneimine and 100 mL of deionized water was added. The mixture was stirred and reacted for 24 h under nitrogen protection at room temperature. After the reaction was completed, the black product was collected by magnetic separation. The black product was then washed three times with ultrapure water and freeze-dried to obtain aminated magnetic particles.

[0067] Preparation Example 3

[0068] The preparation of modified polyurethane foam particles differs from that in Example 1 only in that the method used in this example is as follows:

[0069] 10g of oxidized polyurethane foam particles were soaked in 100mL of 5wt% glutaraldehyde solution at 37℃ for 24h, and then removed and soaked in a mixture of 1g arginine, 1g aminated magnetic particles and 100mL deionized water. The mixture was reacted at 40℃ for 24h, filtered, the filter cake was rinsed and air-dried to obtain modified polyurethane foam particles.

[0070] Compare with Example 1

[0071] The modified polyurethane foam particles were prepared in the same manner as in Preparation Example 1, except that alanine was removed from the particles in Example 1.

[0072] Compare with Example 2

[0073] The modified polyurethane foam particles were prepared in the same manner as in Preparation Example 1, except that the aminated magnetic particles in Example 1 were replaced with an equal mass mixture of polyethyleneimine and carboxylated iron tetroxide particles in a mass ratio of 1:1. The mixture was mixed in a mixer at a speed of 60 rpm for 5 min.

[0074] Compare with Example 3

[0075] The modified polyurethane foam particles were prepared in the same manner as in Preparation Example 1, except that the aminated magnetic particles in Example 1 were replaced with an equal mass of branched polyethyleneimine.

[0076] Compare with Example 4

[0077] The preparation of modified polyurethane foam particles differed from that in Preparation Example 1 only in that the aminated magnetic particles in Example 1 were replaced with an equal mass of carboxylated iron tetroxide particles. The preparation of the carboxylated iron tetroxide particles was the same as in Preparation Example 1.

[0078] Example 1

[0079] A method for purifying malodorous waste gas includes the following steps:

[0080] Step 1: The odorous waste gas is drawn into the alkaline scrubbing tower by a fan. The flow rate of the odorous waste gas is 100L / min. The alkaline solution in the alkaline scrubbing tower is a 20% sodium hydroxide solution.

[0081] Step 2: The exhaust gas after being treated by the alkaline scrubbing tower enters the pre-scrubbing tower for water washing. The pre-scrubbing tower is equipped with a spray device. After spray washing, the relative humidity of the exhaust gas reaches 96%.

[0082] Step 3: The exhaust gas after pre-washing tower treatment enters the biological filter from the bottom. The operating temperature of the biological filter is 20℃. The biological filter is equipped with a biological packing layer with a height of 0.5m. A spray water device is installed at the top of the biological filter to maintain the moisture content of the biological packing at 30% through water spraying.

[0083] Step 4: The gas treated by the biological filter is discharged through the exhaust stack.

[0084] The biological packing material is prepared through the following steps:

[0085] Lactic acid bacteria inoculant, Bacillus inoculant and yeast inoculant were mixed in a mass ratio of 5:3:3 to form a composite bacterial solution; 10g of the modified polyurethane foam particles from Preparation Example 1 were added to 100mL of the composite bacterial solution, placed on a shaker, and cultured at 35℃ under natural light for 24h. After that, the modified polyurethane foam particles were taken out to obtain the biological filler.

[0086] The lactic acid bacteria content in the lactic acid bacteria inoculant is 2.3 × 10⁻⁶. 8 CFU / mL, the lactic acid bacteria is Lactobacillus acidophilus.

[0087] The Bacillus content in the Bacillus inoculant is 3.7 × 10⁻⁶. 8 CFU / mL, the Bacillus is Bacillus coagulans.

[0088] The yeast content in the yeast inoculum is 2.3 × 10⁻⁶. 8 CFU / mL, the lactic acid bacteria is abnormal Hansenula polymorpha.

[0089] Example 2

[0090] A method for purifying malodorous waste gas includes the following steps:

[0091] Step 1: The odorous waste gas is drawn into the alkaline scrubbing tower by a fan. The flow rate of the odorous waste gas is 150 L / min. The alkaline solution in the alkaline scrubbing tower is a 30% sodium hydroxide solution.

[0092] Step 2: The exhaust gas after being treated by the alkaline scrubbing tower enters the pre-scrubbing tower for water washing. The pre-scrubbing tower is equipped with a spray device. After spray washing, the relative humidity of the exhaust gas reaches 96%.

[0093] Step 3: The exhaust gas after pre-washing tower enters the biological filter from the bottom. The operating temperature of the biological filter is 25℃. The biological filter is equipped with a biological packing layer with a height of 0.5m. A spray water device is installed at the top of the biological filter to maintain the moisture content of the biological packing at 50% through water spraying.

[0094] Step 4: The gas treated by the biological filter is discharged through the exhaust stack.

[0095] The biological packing material is prepared through the following steps:

[0096] Lactic acid bacteria inoculant, Bacillus inoculant and yeast inoculant were mixed in a mass ratio of 6:4:4 to form a compound bacterial solution; 10g of the modified polyurethane foam particles of Preparation Example 1 were added to 200mL of the compound bacterial solution, placed on a shaker and cultured at 35℃ under natural light for 24h. After that, the modified polyurethane foam particles were taken out to obtain the biological filler.

[0097] The lactic acid bacteria content in the lactic acid bacteria inoculant is 2.5 × 10⁻⁶. 8 CFU / mL, the lactic acid bacteria is Lactobacillus acidophilus.

[0098] The Bacillus content in the Bacillus inoculant is 4.0 × 10⁻⁶. 8 CFU / mL, the Bacillus is Bacillus coagulans.

[0099] The yeast content in the yeast inoculum is 3.5 × 10⁻⁶. 8 CFU / mL, the lactic acid bacteria is abnormal Hansenula polymorpha.

[0100] Example 3

[0101] A method for purifying malodorous waste gas includes the following steps:

[0102] Step 1: The odorous waste gas is drawn into the alkaline scrubbing tower by a fan. The flow rate of the odorous waste gas is 250 L / min. The alkaline solution in the alkaline scrubbing tower is a 40% sodium hydroxide solution.

[0103] Step 2: The exhaust gas after being treated by the alkaline scrubbing tower enters the pre-scrubbing tower for water washing. The pre-scrubbing tower is equipped with a spray device. After spray washing, the relative humidity of the exhaust gas reaches 96%.

[0104] Step 3: The exhaust gas after pre-washing tower enters the biological filter from the bottom. The operating temperature of the biological filter is 35℃. The biological filter is equipped with a biological packing layer with a height of 1m. A spray water device is installed at the top of the biological filter to maintain the moisture content of the biological packing at around 80% through water spraying.

[0105] Step 4: The gas treated by the biological filter is discharged through the exhaust stack.

[0106] The biological packing material is prepared through the following steps:

[0107] Lactic acid bacteria inoculant, Bacillus inoculant and yeast inoculant were mixed in a mass ratio of 7:5:5 to form a composite bacterial solution; 10g of the modified polyurethane foam particles from Preparation Example 1 were added to 500mL of the composite bacterial solution, placed on a shaker, and cultured at 35℃ under natural light for 24h. After that, the modified polyurethane foam particles were taken out to obtain the biological filler.

[0108] The lactic acid bacteria content in the lactic acid bacteria inoculant is 3.1 × 10⁻⁶. 8 CFU / mL, the lactic acid bacteria is Lactobacillus acidophilus.

[0109] The Bacillus content in the Bacillus inoculant is 5.8 × 10⁻⁶. 8 CFU / mL, the Bacillus is Bacillus coagulans.

[0110] The yeast content in the yeast inoculum is 4.5 × 10⁻⁶. 8 CFU / mL, the lactic acid bacteria is abnormal Hansenula polymorpha.

[0111] Example 4

[0112] A method for purifying malodorous waste gas, which differs from Example 1 only in that the modified polyurethane foam particles in Example 1 are replaced with the product obtained in Preparation Example 2 in equal mass.

[0113] Example 5

[0114] A method for purifying malodorous waste gas, which differs from Example 1 only in that the modified polyurethane foam particles in Example 1 are replaced with the product obtained in Preparation Example 3 in equal mass.

[0115] Example 6

[0116] A method for purifying malodorous waste gas, compared with Example 1, differs only in that the height of the biological packing layer in the biological filter of this local example is 0.5m.

[0117] Example 7

[0118] A method for purifying malodorous waste gas, which differs from Example 1 only in that the height of the biological packing layer in the biological filter of this local example is 1m.

[0119] Example 8

[0120] A method for purifying malodorous waste gas, which differs from Example 2 only in that the modified polyurethane foam particles in Example 2 are replaced with an equal mass of the product obtained in Preparation Example 2.

[0121] Comparative Example 1

[0122] A method for purifying malodorous waste gas, which differs from Example 1 only in that the modified polyurethane foam particles in Example 1 are replaced with the product obtained in Control Example 1 of equal mass.

[0123] Comparative Example 2

[0124] A method for purifying malodorous waste gas, which differs from Example 1 only in that the modified polyurethane foam particles in Example 1 are replaced with the product obtained in Control Example 2 of equal mass.

[0125] Comparative Example 3

[0126] A method for purifying malodorous waste gas, which differs from Example 1 only in that the modified polyurethane foam particles in Example 1 are replaced with the product obtained in Control Example 3 of equal mass.

[0127] Comparative Example 4

[0128] A method for purifying malodorous waste gas, which differs from Example 1 only in that the modified polyurethane foam particles in Example 1 are replaced with the product obtained in Control Example 4 of equal mass.

[0129] The odorous waste gas purification methods described in Examples 1-8 and Comparative Examples 1-4 were used to treat the waste gas emitted from a kitchen waste treatment plant in Yangzhou. After 7 days of use, the hydrogen sulfide content in the waste gas before treatment was measured to be 2.35 mg / m³. 3 The content of methanethiol is 0.75 mg / m³. 3 The ammonia content is 2.0 mg / m³. 3 The hydrogen sulfide, methanethiol, and ammonia contents in the treated waste gas were recorded, and the hydrogen sulfide removal rate, methanethiol removal rate, and ammonia removal rate were calculated. The results are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] As can be seen from the data recorded in Table 1, compared with Comparative Examples 1-4, the odor purification process of Examples 1-8 has a higher removal rate of hydrogen sulfide, methanethiol and ammonia odors. Therefore, the deodorization effect is better and it is more suitable for practical application.

[0134] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0135] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for purifying malodorous waste gas, characterized in that, Includes the following steps: Step 1: The malodorous waste gas is drawn into the alkaline scrubbing tower by a fan; Step 2: The exhaust gas after being treated by the alkaline scrubbing tower enters the pre-scrubbing tower for water washing. The pre-scrubbing tower is equipped with a spray device. After spray washing, the relative humidity of the exhaust gas reaches more than 95%. Step 3: The exhaust gas after pre-washing tower enters the biological filter from the bottom. The biological filter is equipped with a biological packing layer and a spray water device is installed at the top of the biological filter to maintain the moisture content of the biological packing between 30-80% through water spraying. Step 4: The gas treated by the biological filter is discharged through the exhaust stack; The biological packing material is prepared through the following steps: Lactic acid bacteria inoculant, Bacillus inoculant and yeast inoculant were mixed in a certain proportion to form a compound bacterial solution; modified polyurethane foam particles were added to the compound bacterial solution, placed on a shaker, and cultured at 35°C under natural light for 24 hours. After that, the modified polyurethane foam particles were removed to obtain the biological filler. The raw materials for preparing the modified polyurethane foam particles include oxidized polyurethane foam, amino acids, aminated magnetic particles, and glutaraldehyde; The method for preparing the modified polyurethane foam particles is as follows: The oxidized polyurethane foam particles were soaked in a glutaraldehyde solution at 37°C for 24 hours and then removed. They were then soaked in a mixture of amino acids, aminated magnetic particles and deionized water and reacted at 35-40°C for 24 hours. After filtration, the filter cake was rinsed and air-dried to obtain modified polyurethane foam particles. The oxidized polyurethane foam particles are polyurethane foam particles treated with acidic potassium permanganate solution; The method for preparing the amination-modified magnetic particles is as follows: S1. Add FeCl3·6H2O and FeCl2·4H2O to deionized water, add sodium hydroxide solution containing sodium citrate while stirring, and stir the reaction at 80°C for 1 hour under nitrogen protection. Collect the black product by magnetic separation, then wash the black product three times with ultrapure water and freeze dry to obtain carboxylated iron oxide particles. S2. Carboxylated iron oxide particles were ultrasonically dispersed in deionized water, and acetic acid was added to adjust the pH to 6. EDC·HCl and NHS were added, and the mixture was stirred for 1 h under nitrogen protection at room temperature. Sodium hydroxide solution was added to adjust the pH to 7, and then an aqueous solution of polyethyleneimine was added. The mixture was stirred for 24 h under nitrogen protection at room temperature. After the reaction was completed, the black product was collected by magnetic separation. The black product was then washed three times with ultrapure water and freeze-dried to obtain aminated magnetic particles.

2. The method for purifying malodorous waste gas according to claim 1, characterized in that, The height of the biological packing layer is 0.5-1m.

3. The method for purifying malodorous waste gas according to claim 1, characterized in that, The mass ratio of modified polyurethane foam particles to composite bacterial solution is 1g:10-50mL.

4. The method for purifying malodorous waste gas according to claim 1, characterized in that, The amino acid is at least one selected from alanine, glycine, arginine, L-cysteine, L-glutamic acid, lysine, methionine, and taurine.

5. The method for purifying malodorous waste gas according to claim 1, characterized in that, The mass ratio of amino acids, aminated magnetic particles and deionized water in the mixture is 0.5-1:0.5-1:100.

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