NO_x空气氧化与碱液吸收工艺实验研究.pdf

烟 气 污 染 治 理 NOx空气氧化与碱液吸收工艺实验研究 乔军师 胡金榜 宗润宽 常明坤 天津大学化工学院, 天津 300072 摘要 根据我国NOx废气治理技术的特点与现状, 分析了用空气氧化 NO, 用烧碱溶液对氧化后的气体进行吸收工艺 的可行性。并对该工艺中模拟废气中NOx的浓度、氧化时间、氧化度以及吸收率之间的关系进行了实验研究和分析, 为其工业应用提供了实验依据。 关键词 空气氧化法 NOx 氧化度 吸收率 1 前言 NOx主要由 NO 和 NO2组成, 此外还包括 N2O、 N2O3等, 统称为氮氧化物。现在全世界 NOx年排放 量约为 8610 6 t [ 1] , 从而引起了酸雨 、 光化学烟雾等 破坏地球生态环境和损害人体健康的一系列问题 。 NOx中NO2的体积百分数称为NOx的氧化度,含 NOx废气是一种较难处理的工业废气 ,其中的 NOx的 氧化度一般都很低,NO 除了生成络合物外,几乎不被 水或碱液吸收。为了有效地治理含 NOx废气 , 需将 其中的 NO 氧化为 NO2,调节NOx的氧化度至 50～ 60,然后再用吸收剂进行吸收。在低浓度下 ,NO 的 氧化速率是非常缓慢的, 因此提高 NO 的氧化速率就 成为脱除 NOx的决定性因素。对于治理 NOx废气, 以提高环境质量为目的, 综合考虑各种氧化方法的氧 化效率和成本, 本实际研究选用空气氧化法 [ 2] 。 利用空气作为氧化剂氧化 NO, 空气来源丰富且 成本低 ,通过氧化提高 NOx到一定的氧化度 ,能促进 含NOx废气的脱除。 根据我国经济技术的现状 , 吸收法治理含 NOx 废气 ,是化学工业生产过程中普遍采用的方法 。在众 多的吸收方法中 ,碱液吸收法较为常用 。但综合考虑 原料价值 、操作费用和吸收效率等因素, 工业上以 NaOH 和 Na2CO3使用较多,其中 NaOH 溶液的吸收效 果更好些 。因此本实验选用NaOH 作为吸收剂。 当NOx废气的氧化度为 50～ 60时 , 吸收速 率最大,吸收效率也最高 [ 3] 。 2 实验设计 2. 1 实验流程与设备 实验流程如图 1 所示。 图1 实验流程图 1氮气钢瓶; 2NO 钢瓶; 3流量计; 4气体混合器; 5氧化塔; 6采样点; 7吸收塔; 8碱液罐; 9碱液泵; 10抽气泵。 实验中使用的主要设备参数为 吸收塔直径为 30. 5 mm, 高为 1 200 mm ; 氧化塔直径为 200 mm ,塔高 为750 mm 。 2. 2 实验与检测方法 实验时, 采用转子流量计来控制 N2和 NO 的流 量,进而得到所需的模拟工业废气。N2和NO 经气体 混合器充分混合后 ,从氧化塔顶端进入 , 与同样从氧 化塔顶端进入的空气进行混合。在氧化塔内停留一 定时间,NO 与空气中的氧气发生氧化反应生成 NO2, 从而提高NOx的氧化度 。氧化后的气体由底部进入 吸收塔 ,NaOH 水溶液从塔顶由计量泵送入 。在吸收 塔内完成NaOH 水溶液对 NOx的吸收操作 ,处理后的 废气从吸收塔顶由抽气泵排出。为了测试氧化塔对 NO 的氧化效果以及检测吸收塔的吸收效率 ,分别在 吸收塔的进口和出口处设置采样点 ,采用盐酸萘乙二 胺分光光度法, 对NOx废气进行浓度监测 ,其优点在 于能同时准确测量NO2和NOx的浓度。 2. 3 实验条件 实验条件如表 1所示。 37 环 境 工 程 2005年 4 月第23 卷第2 期 表 1 实验条件 N2流量 m3h- 1 氧化时间 s 操作温度 ℃ 补充空气与模拟 废气摩尔流量比 NaOH 溶液 质量分数 0 . 76016. 2～ 18. 91∶ 16 0 . 67016. 2～ 18. 91∶ 16 0 . 58416. 2～ 18. 91∶ 16 3 实验数据分析与讨论 3. 1 氧化时间对NO 转化率的影响 实验测得当 NO 的浓度在 3 500～ 5 500 mg m 3 范 围内变化时,氧化时间与 NO 的转化率的对应关系如 图2 所示。 图 2 NO 转化率与 NO 浓度及氧化时间的关系 由图 2可知, 当NO 浓度一定时,NO 的转化率随 着氧化时间的延长而增大 。 3. 2 氧化度对NOx吸收效率的影响 实验测得当吸收塔进口的 NOx浓度 [ NOx]进口 为3 700 mg m 3 时 统计值 3 700 mg m 3 10 ,NOx 氧化度和NOx吸收率的关系曲线, 如图 3 所示 。 图 3 NOx吸收率和 NOx氧化度的关系 在此还对一定 NOx进口浓度下 NOx氧化度对 NOx吸收率的影响进行了实验研究,实测数据见表2。 由图 3和表2 可知 ,当[NOx]进口一定时, 随着NOx 氧化度的升高,NOx吸收率也相应提高 。 3. 3 NOx进口浓度对NOx吸收效率的影响 实验测得当 NOx氧化度一定时 NOx吸收率和 [NOx]进口的关系如表 3所示。 表 2 [ NOx] 进口一定时 NOx吸收率和 NOx氧化度的关系 [ NOx]进口 mgm- 3 NOx氧化度NOx吸收率 2 00015. 1～ 16. 544. 8～ 51. 4 2 50016. 2～ 24. 851. 5～ 63. 5 3 00019. 2～ 25. 856. 4～ 67. 9 3 70023. 1～ 32. 565. 5～ 74. 4 4 50027. 5～ 34. 669. 7～ 76. 5 5 50030. 3～ 42. 170. 3～ 85. 2 表3 NOx氧化度一定时 NOx吸收率和[ NOx]进 口的关系 NOx氧化度 [ NOx]进口 mgm- 3 NOx吸收率 151 860～ 2 28044. 8～ 53. 2 202 248～ 3 02355. 1～ 60. 6 252 748～ 4 42863. 5～ 69. 7 303 588～ 5 10669. 7～ 74. 4 353 992～ 5 80171. 9～ 81. 3 405 801～ 6 14075. 8～ 85. 2 由 表 3 可知 , 当 NOx氧 化度 一定 时, 随 着 [NOx]进口的升高,NOx吸收率也相应提高 。 由此可见, 用吸收法治理 NOx废气时, 对于 NOx 氧化度较低的工业 NOx废气 , 提高 NOx的氧化度对 NOx废气的治理是十分必要而且非常有效的。 4 结论 使用空气作为NO 的氧化剂, 把氧化后的气体用 NaOH 溶液进行吸收 。该工艺成本低, 经济性好 , 工 艺流程简单, 对 NOx浓度较大的工业废气还可对副 产品亚硝酸钠进行回收利用。本实验为该工艺的工 业应用提供了实验依据。 参考文献 1 郑惠榕. 简析氮氧化物的污染及工业治理. 福州师范高等专科学校 化学系, 2000. 1 28～ 30. 2 常明坤, 胡金榜, 宗润宽, 王晋刚. 利用空气氧化 NOx的技术探讨. 化学工业与工程,2003. 20 6 518～ 522. 3 童志权. 工业废气净化与利用. 北京 化学工业出版社, 2001. 297～ 314. 作者通讯处 乔军师 300072 天津大学化工学院化机系 电话 022 27408812 E -mail qiaojunshi sina. com 2004- 06-17 收稿 38 环 境 工 程 2005年 4 月第23 卷第2 期 APPLIATION OF UPFLOW ANAEROBIC SLUDGE BED -CONTACT OXIDATION PROCESS IN TREATMENT OF ETHANOL WASTEWATERFan Xinsheng et al 21 Abstract The application of UASB -contact oxidation process in treating ethanol wastewater is presented. The operating results have shown that when the influent CODCr, BOD5and SS are in range of 18 000 ～ 21 000 mg L, 10 500 ～ 12 000mg L and 16 000 ～ 18 500 mg L respectively , the effluent of the system is good enough to meet the class Ⅱguided by NationalWastewater IntegratedDischarge Standard GB8978- 96 . Keywords ethanolwastewater, UASB reactor and contact oxidation STUDY ONTREATMENT OF PHOSPHORIC COATING WASTEWATERWu Juzhen et al 23 Abstract The defatted wastewater was pretreated by heating or demulsified by acidification;then the phosphorized wastewater was expreienced advanced treatment by coagulation -flocculation -sedimentation -airfloat process. The combination of suitable chemicals, inorganic coagulant and high polymer flocculant can reduced remarkably the contents of CODCr, oil and SS of the wastewater. The tests show that the process can reduce CODCrfrom 900～ 2 200 mg L to below 50 mg L, the oil content from 300～ 800 mg L to below 5 mg L and SS less than 45 mg L. All the inds meet the second -order of “National Wastewater Discharge Standard” GB8978 -1996. Keywords flocculant, phosphorized wastewater, wastewater treatment, emulsified oil-bearing wastewater and demusification APPLICATION OF LKM TYPE FLOCCULANT IN TREATMENT OF OILY WASTEWATER Song Yongji et al 26 Abstract LKM type flocculant possesses of high-anti-emulsificaton ability , good water solubility , good stability and usability. The cost of its multiple prescription LKM -5715 is low and its flocculation result is perfect. The insitu industrial experiments indicated that at similar deoiling efficiency, its consumption was 1 2～ 1 5 amount of poly -aluminum chloride. The production of scum was little and easy to dispose and utilize. Instead of poly -alminum chloride, LKM -5715 type flocculant can be widely utilized in the treatment of oily wastewater. Keywords wastewater treatment, flocculant and application study ENGINEERING EXAMPLE OF TREATING HOTEL SEWAGE BY A2 O PROCESS Yu Xiuhua et al 28 Abstract The designed treating capacity of a wastewater treatment plant for a hotel was 800 m3 d. The A2 O process was used and the running results of two years showed that when CODCr, BOD5, SS, NH3-N and animal plant oil of the influent were 250～ 300 mg L, 100 ～ 150 m L, 120～ 140 mg L, 25 mg L and 50 mg L respectively, the quality of the effluent could meet the first -order during second period of “ Discharge Limits of Water Pollutants” DB44 26 -2001in Guangdong Province. Keywords hotel wastewater, A2 O process and fully embedded structure OPERATION MANAGMENT OF A-A O PROCESS IN COKING WASTE WATER TREATMENT SYSTEMXing Xiangjun et al 29 Abstract According to the actual circumstance of construction and operation of wastewater treatment project in Bei Gang Group Company, biological denitrogenation theory , A -A O technological process, domestication sludge and operation managment were discussed in this paper. The factors influencing the biological denitrogenation and nitrogenation were also explored. Keywords coking waste water, nitrification-denitrification process and operation managment APPLICATION OF SIMPLIFIED ACTIVATED SLUDGE MODEL TO URBAN WASTEWATER TREATMENT PLANTLiu Fang et al 33 Abstract Simplified activated sludge model ASM -CNis proposed based on the activated sludge model No. 1 ASM1. This model describes the carbon oxidation process and nitration process. The amount of components, processes and parametersof ASM -CN isfewer thanthat of ASM1, so the practicability of ASM -CN model is enhanced. The measurement of components and parameters is also studied. Finally, ASM-CN model is applied to simulate the operation of actualwastewater treatent plants and good results are achieved. Keywords activated sludge model, simplificaiton, urban wastewater treatment plant and simulation EXPERIMENTAL RESEARCH ON PROCESS OF AIR OXIDATION AND ABSORPTION OF NOX WITHALKALINE SOLUTIONQiao Junshi et al 37 Abstract According to the characteristics of current technology of disposing NOXinwaste gas in China, the possibility of the process of air oxidation of NO and absorption of NOXwaste gas with sodium hydroxide solution is analyzed. For the simulated waste gas in this process, the relation of NOXconcentration, oxidation time, ratio of oxidation and NOXabsorptivity was studied and analyzed, which provides an experimental basis for its industrial application. 3 ENVIRONMENTAL ENGINEERING Vol. 23, No. 2,Apr. ,2005 Keywords air oxidation, NOX, ratio of oxidation and absorptivity DENITRIFICATION OFNO IN WASTE GASSTREAMS USING AGED -REFUSE -BASED BIOREACTORZhang Hua et al 39 Abstract Stabilized or aged refuse is a good media for bioreactor and can be used to treat NOXinwaste gas streams. Laboratory study shows that an aged -refuse -based bioreactor can effectively remove NO fromwaste gas streams. The empty bed retentiontime EBRTis the key parameter effecting the removal efficiency of NO which decreases with the shortening of EBRT. The removal efficiency of NO is 90with the EBRT of 3. 8 min and 96at 7. 5min. The removal efficiency of NO under anaerobic condition is better than that of aerobic condition. Denitrification of NO is preferable to the biological nitrification of NO. Keywords aged refuse, nitrogen oxides, nitric oxide, biofiltration and denitrification TREATINGVOLATILE ORGANIC COMPOUNDS-BEARINGEXHAUSTGAS IN PACKING PRINTING HOUSEQiaoHuixian et al 42 Abstract The paper introduced that VOCs exhaust gas in packing printing house was treated by FCJ organic gas purification equipment, which is based on adsorption and catalytic combustion principle. The technical process and detecting result on treating VOCs exhaust gas were described in detail. The results showed that it is efficient to treating VOCs exhaust gas in packing printing house by FCJ technique and equipment. The treating result meets the second-order of the national emission standard. Keywords printing, VOCs, adsorption, catalytic combustion and treatment of exhaust gas NEW EXPLORATION OF CLEANING TECHNIQUE FOR CATERING OIL FUME Zhang Jinping et al 45 Abstract On the basis of comparing conclusionof various cooking oil fume decontaminationtechnology, a new cleaning technique combined an atomization wet witha filtration adsorptionisdeveloped and a cooking fume decontamination is searchedaccording to cooking oil fume constituents and contamination characteristics of catering. The results in the laboratory showed that the removing efficiency of oil fume by the new cleaning technique is above 92. The released cooking fume consistency by the technique can meet the national standard. The new technique is suited to medium and small restaurants. Keywords oil fume cleaning, atomization wet , filtration adsorption and removal efficiency INVESTIGATION OF TRAFFIC NOISE ATTENUATION PROVIDED BY GREEN BELTS Zhou Jingxuan et al 48 Abstract This study investigates the noise attenuation of 8 green belts, and a quantitative relationship between the total noise attenuation, excess attenuation, width and visibility is obtained. The spectrum analysis of the noise attenuation is also done, which provides a basis for the design of forest belts of highway for noise reduction. Keywords traffic noise, green belts, effect of noise attenuation and design of forest belts RESEARCH ON ACOUSTIC DESIGN AND CALCULATION OF RESISTANCE LOSS OF NOISE CONTROL FOR COLLIERY AIR SHAFTZhang Chi 52 Abstract Due to a high air flow rate and a strong moise radiation in a colliery air shaft, it is the key to controlling noise successfully that the right and reasonable acoustic design for muffler and the calculation of resistance loss. Keywords colliery air shaft, centrifugal fan, noise control, acoustic design and resistance loss CHARACTERIZATION OFRIVER DREDGING SILTAND ITS FEASIBILITY STUDYAS COVERING MATERIALS FOR REFUSE LANDFILLZhao Aihua et al 56 Abstract It is studied systematically that various parameters, such as penetration coefficient, leaching toxicity and the content of heavy metals etc of river dredging silt, aswell as its feasibility of a covering material for refuse landfill. The results show that it possesses of better slope stability when used as a covering material for refuse landfill, which can basically meet the technical requirements of the covering material. There is no extra burden to the treatment of the leachate. So this sort of use can not only solve the problem of lackings of soil for a plain type landfill, but also make a way out for the dredging silt. Keywords dredging silt, covering material and research EXPERIMENTALSTUDYONPRODUCINGMASONRYCEMENTBYFLY-ASHOF CIRCULATING FLUIDIZED BED BOILERZhao Ming et al 59 Abstract Because circulating fluidized bed combustion CFBis the advanced technology of combustion, it is developing widely at home 4 ENVIRONMENTAL ENGINEERING Vol. 23, No. 2,Apr. ,2005