Biochemical enhanced treatment method for non-methane hydrocarbon in waste gas

Abstract

The invention discloses a biochemical enhanced treatment method for non-methane hydrocarbon in waste gas. The method comprises the steps of waste gas activation and aggregate formation, molecular sieve adsorption and enrichment, efficient degradation of biological bacteria, tail gas emission and material circulation. By optimizing process parameters, an activation-adsorption-degradation cooperative treatment system is constructed, the non-methane total hydrocarbon degradation rate is increased by 30%-50% compared with that of a traditional process, the concentration of non-methane total hydrocarbon in treated tail gas is lower than the national emission standard, the process is low in operation cost and free of secondary pollution, and efficient purification and resource recycling of oil field waste gas are achieved.

Description

Technical Field

[0001] This invention relates to the field of oilfield waste gas treatment technology, specifically to a biochemically enhanced treatment method for non-methane total hydrocarbons in waste gas, applicable to the purification and treatment of waste gas containing non-methane total hydrocarbons generated during oilfield extraction and gathering processes. Background Technology

[0002] Oilfields generate large amounts of waste gas during extraction, oil and gas gathering and transportation, and processing. Non-methane hydrocarbons (NMHC, the sum of all volatile organic compounds (VOCs) excluding methane) are a major pollutant, characterized by high volatility, complex composition, flammability, explosiveness, and significant environmental and human health hazards. Currently, methods for treating NMHC in oilfield waste gas mainly include adsorption, combustion, and biodegradation. However, existing technologies have several drawbacks: adsorption methods, when used alone, easily saturate the adsorbent, require frequent regeneration, and have limited treatment efficiency; combustion methods have high energy consumption and operating costs, and may generate secondary pollution; traditional biodegradation methods suffer from insufficient contact between waste gas and microorganisms, low microbial activity, and slow degradation rates, resulting in generally low NMHC degradation rates that fail to meet increasingly stringent environmental emission standards.

[0003] In existing technologies, some processes attempt to improve treatment efficiency by adding nutrients or surfactants. However, these methods suffer from problems such as unreasonable component combinations, poor activation effects, and the failure to form a synergistic "gas-liquid-solid-bacteria" system. Consequently, the degradation rate of non-methane total hydrocarbons is not significantly improved, making it difficult to achieve efficient and stable treatment. Therefore, developing a synergistic treatment process that can enhance waste gas activation, improve adsorption efficiency, and enhance microbial degradation activity is crucial for solving non-methane total hydrocarbon pollution in oilfield waste gas. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing oilfield waste gas non-methane total hydrocarbon treatment processes and provide a biochemically enhanced treatment method for non-methane total hydrocarbons in waste gas. Through the synergistic effect of activation liquid activation, molecular sieve adsorption and microbial degradation, the degradation rate of non-methane total hydrocarbons is significantly improved, achieving efficient purification of waste gas.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A biochemically enhanced treatment method for non-methane total hydrocarbons in waste gas includes the following steps: (1) Waste gas activation and aggregate formation: Oilfield waste gas is introduced into a spray tower, and activation liquid is atomized and sprayed simultaneously. The activation liquid and waste gas are mixed in countercurrent contact to form waste gas-activation liquid aggregates. The gas-liquid volume ratio in the spray tower is 1000:1-3000:1, the spray pressure is 0.3-0.8MPa, and the tower temperature is 25-35℃. The activation liquid is obtained by mixing surfactant and nutrient. The surfactant is selected from one or a mixture of sodium dodecyl sulfate and sodium dodecyl sulfonate. The nutrient is selected from one or a mixture of meat and bone meal and urea. The mass concentration of surfactant in the activation liquid is 0.1%-0.5%, the mass concentration of nutrient is 0.3%-1.0%, and the remainder is deionized water. (2) Molecular sieve adsorption and enrichment: The waste gas-activated liquid aggregate is passed into an adsorption tower filled with NA molecular sieves. The NA molecular sieves adsorb and enrich non-methane total hydrocarbons at an adsorption space velocity of 500-1500 h⁻¹. -1 The pressure inside the adsorption tower is 0.1-0.3 MPa; the specific surface area of ​​the NA molecular sieve is 800-1200 m². 2 / g, with a pore size of 0.5-1.2nm; (3) Highly efficient degradation by microorganisms: The NA molecular sieves of the adsorbed aggregates are fed into the bioreactor, and Pseudomonas aeruginosa (CGMCC No. 14412) is introduced. Pseudoalteromonas sp. The degradation is carried out using BJQ-112 bacterial agent; the pH in the bioreactor is 6.5-7.5, the dissolved oxygen content is 2-5 mg / L, the reaction temperature is 28-32℃, and the hydraulic retention time is 4-8 h; (4) Tail gas emission and material recycling: The tail gas after degradation meets the emission standards, and part of the reaction liquid is recycled back to the spray tower for reuse.

[0006] Preferably, the formulation of the activation solution in step (1) is: sodium dodecyl sulfonate 0.1%-0.5%, urea 0.5%-0.8%, and the remainder is deionized water.

[0007] Preferably, the formulation of the activation solution in step (1) is: sodium dodecyl sulfonate 0.4%, urea 0.6%, and the remainder is deionized water.

[0008] Preferably, the NA molecular sieve described in step (2) is pretreated before use: soaked in 3%-5% hydrochloric acid solution for 2-3 hours, rinsed with deionized water until neutral, and dried at 100℃-110℃ for 4-5 hours.

[0009] Further preferably, the NA molecular sieve described in step (2) needs to be pretreated before use: soak the NA molecular sieve in a 5% hydrochloric acid solution for 2 hours, rinse it with deionized water until neutral, and then dry it at 110°C for 4 hours. After cooling, it is ready for use.

[0010] Furthermore, the bioreactor described in step 4 is equipped with an aeration device and a stirring device, with an aeration intensity of 0.5-1.0 m³ / s. 3 / (m 2 •h), with a stirring rate of 50-100 r / min to ensure that the microorganisms are in full contact with the adsorbed non-methane total hydrocarbons.

[0011] Compared with the prior art, the present invention has the following advantages: This invention prepares an activation liquid by compounding a specific surfactant with nutrients. The surfactant reduces the interfacial tension between the waste gas and the liquid, promoting the emulsification and dispersion of non-methane total hydrocarbons (NMRs) and achieving pre-activation of the waste gas. Simultaneously, the aggregates formed by the activation liquid and the waste gas improve the stability of NMRs, laying the foundation for subsequent adsorption and degradation. Furthermore, the nutrients in the activation liquid provide sufficient carbon, nitrogen, and trace elements for subsequent biodegradation, enhancing the metabolic activity of microorganisms and further increasing the degradation rate.

[0012] Using NA molecular sieves with strong adsorption properties to adsorb and enrich waste gas-activated liquid aggregates can significantly increase the local concentration of non-methane total hydrocarbons, solving the problems of low pollutant concentration and low microbial degradation efficiency in waste gas; the specific pore size and specific surface area of ​​NA molecular sieves ensure the selectivity and capacity of adsorption, and extend the adsorption cycle.

[0013] This invention optimizes process parameters to construct a synergistic treatment system of "activation-adsorption-degradation". The degradation rate of non-methane total hydrocarbons is significantly improved compared with traditional processes. The concentration of non-methane total hydrocarbons in the treated exhaust gas is lower than the national emission standard. Moreover, the process has low operating costs and no secondary pollution, realizing efficient purification and resource recycling of oilfield waste gas. Detailed Implementation

[0014] Example 1 A biochemically enhanced process for treating non-methane total hydrocarbons in oilfield waste gas includes the following steps: Preparation of activation solution: Take 0.2% sodium dodecyl sulfate, 0.1% sodium dodecyl sulfonate, 0.5% meat and bone meal, 0.3% urea, and the remainder is deionized water by mass concentration. Mix them and stir at 30°C for 30 minutes until completely dissolved to obtain the activation solution.

[0015] Waste gas activation and aggregate formation: Oilfield waste gas with a non-methane total hydrocarbon concentration of 800 mg / m³ is introduced into a spray tower. The activation liquid is atomized by the spraying device and sprayed countercurrently. The gas-liquid volume ratio is 2000:1, the spraying pressure is 0.5 MPa, and the temperature inside the tower is controlled at 30℃. The waste gas and activation liquid are fully mixed to form waste gas-activation liquid aggregates.

[0016] Molecular sieve adsorption enrichment: The aggregates are passed into an adsorption tower filled with pretreated NA molecular sieves at an adsorption space velocity of 1000 h⁻¹. -1 The pressure inside the adsorption tower is 0.2 MPa; NA molecular sieve (specific surface area 500-800 m²) 2 / g, pore size approximately 5 angstroms) pretreatment method is as follows: soak in 5% hydrochloric acid solution for 2 hours, rinse with deionized water until neutral, and dry at 110℃ for 4 hours.

[0017] High-efficiency degradation by microorganisms: NA molecular sieves containing adsorbed aggregates are fed into a bioreactor, and a bacterial agent of *Pseudomonas alterniflora* BJQ-112 is introduced at an inoculum concentration of 5 × 10⁻⁶. 7 CFU / mL; pH in the reactor was controlled at 7.0, dissolved oxygen content at 3 mg / L, reaction temperature at 30℃, hydraulic retention time at 6 h, and aeration intensity at 0.8 m. 3 / (m 2 •h), with a stirring rate of 80 r / min. *Pseudomonas alterniflora* BJQ-112 was cultured in LB medium at 30℃ and 200 rpm on a shaker for 24 hours. Then, 5% of the culture medium was inoculated into the fermentation medium and cultured at 30℃ and 200 rpm with stirring, an air volume of 1:0.4-0.5, and a pressure of 0.05 MPa for 36 hours. Fermentation medium (g / L): glucose 10, liquid paraffin 15, yeast extract 3.0, magnesium sulfate 0.2, potassium chloride 0.2, potassium dihydrogen phosphate 2.0, urea 1.0, ammonium nitrate 1.5, Tween-80 0.5 mL, trace salt solution 1.0 mL, pH natural. Each liter of trace salt solution contained 11.0 g zinc sulfate, 6.0 g manganese sulfate, 1.0 g ferrous sulfate, 27.3 g EDTA-Na, 0.3 g cobalt sulfate, 40 mg copper sulfate, 60 mg boric acid, and 1 mg potassium iodide.

[0018] Exhaust gas emissions and material recycling: The concentration of non-methane total hydrocarbons in the exhaust gas after degradation is 28 mg / m³. 3 The degradation rate was 96.5%, meeting emission standards; 30% of the reaction liquid was recycled to the spray tower for the preparation of activation liquid.

[0019] Example 2 The difference from Example 1 is that the activation solution formula is 0.3% sodium dodecyl sulfate, 0.8% meat and bone meal, and the balance is deionized water; the gas-liquid volume ratio of the spray tower is 1500:1, the spray pressure is 0.4 MPa, and the adsorption space velocity is 800 h⁻¹. -1 The hydraulic retention time in the bioreactor is 5 hours. The concentration of non-methane total hydrocarbons in the treated tail gas is 35 mg / m³. 3 The degradation rate was 95.6%.

[0020] Example 3 The difference from Example 1 is that the activation solution formula is 0.4% sodium dodecyl sulfonate, 0.6% urea, and the balance is deionized water; the gas-liquid volume ratio of the spray tower is 2500:1, the spray pressure is 0.6 MPa, and the adsorption space velocity is 1200 h⁻¹. -1 The hydraulic retention time in the bioreactor was 7 hours. The concentration of non-methane total hydrocarbons in the tail gas after treating the same amount of NMHC was 22 mg / m³. 3 The degradation rate was 97.2%.

Claims

1. A biochemically enhanced treatment method for non-methane total hydrocarbons in waste gas, characterized in that, Includes the following steps: (1) Waste gas activation and aggregate formation: Oilfield waste gas is introduced into a spray tower, and activation liquid is atomized and sprayed simultaneously. The activation liquid and waste gas are mixed in countercurrent contact to form waste gas-activation liquid aggregates. The gas-liquid volume ratio in the spray tower is 1000:1-3000:1, the spray pressure is 0.3-0.8MPa, and the tower temperature is 25-35℃. The activation liquid is obtained by mixing surfactant and nutrient. The surfactant is selected from one or a mixture of sodium dodecyl sulfate and sodium dodecyl sulfonate. The nutrient is selected from one or a mixture of meat and bone meal and urea. The mass concentration of surfactant in the activation liquid is 0.1%-0.5%, the mass concentration of nutrient is 0.3%-1.0%, and the remainder is deionized water. (2) Molecular sieve adsorption and enrichment: The waste gas-activated liquid aggregate is passed into an adsorption tower filled with NA molecular sieves. The NA molecular sieves adsorb and enrich non-methane total hydrocarbons at an adsorption space velocity of 500-1500 h⁻¹. -1 The pressure inside the adsorption tower is 0.1-0.3 MPa; the specific surface area of ​​the NA molecular sieve is 800-1200 m². 2 / g, with a pore size of 0.5-1.2nm; (3) Highly efficient degradation by microorganisms: The NA molecular sieves of the adsorbed aggregates are fed into the bioreactor, and Pseudomonas aeruginosa (CGMCC No. 14412) is introduced. Pseudoalteromonas sp. The degradation is carried out using BJQ-112 bacterial agent; the pH in the bioreactor is 6.5-7.5, the dissolved oxygen content is 2-5 mg / L, the reaction temperature is 28-32℃, and the hydraulic retention time is 4-8 h; (4) Tail gas emission and material recycling: The tail gas after degradation meets the emission standards, and part of the reaction liquid is recycled back to the spray tower for reuse.

2. The biochemically enhanced treatment method according to claim 1, characterized in that, The formula of the activation solution in step (1) is: sodium dodecyl sulfonate 0.1%-0.5%, urea 0.5%-0.8%, and the remainder is deionized water.

3. The biochemically enhanced treatment method according to claim 2, characterized in that, The formula of the activation solution in step (1) is: sodium dodecyl sulfonate 0.4%, urea 0.6%, and the remainder is deionized water.

4. The biochemically enhanced treatment method according to claim 1, characterized in that, The NA molecular sieve described in step (2) is pretreated before use: soaked in 3%-5% hydrochloric acid solution for 2-3 hours, rinsed with deionized water until neutral, and dried at 100℃-110℃ for 4-5 hours.

5. The biochemically enhanced treatment method according to claim 4, characterized in that, The NA molecular sieve described in step (2) needs to be pretreated before use: soak the NA molecular sieve in a 5% hydrochloric acid solution for 2 hours, rinse it with deionized water until neutral, dry it at 110°C for 4 hours, and cool it for later use.

6. The biochemically enhanced treatment method according to claim 1, characterized in that, In step (3), the inoculum concentration of *Pseudomonas alterniflora* BJQ-112 is 10. 6 -10 8 CFU / mL.

7. The biochemically enhanced treatment method according to claim 1, characterized in that, In step (3), the aeration intensity in the bioreactor is 0.5-1.0 m. 3 / (m 2 •h), with a stirring rate of 50-100 r / min.