【作者】 徐姣；

【导师】 张卫江；

【作者基本信息】 天津大学 ， 化学工程， 2009， 博士

【摘要】 化石燃料(包括石油及煤炭)中含有硫氮物质,在燃烧过程中以SO2和NOx气体的形式排放出来,是形成“酸雨”的主要污染物,给人类的生存带来严重危害。NO气体是NOx气体的主要存在形式,本论文着重讨论SO2和NO气体的净化处理。SO2和NOx气体污染问题受到了世界范围的普遍关注,许多国家都制定了严格的限排控制措施。目前,我国在SO2先期治理的基础上,又出台了对NOx的限排政策。SO2和NOx的治理已成为世界领域的研究热点,各种治理技术百花齐放层出不穷,正在全球范围内深入研究与开展。传统的SO2和NOx气体治理技术主要采用物理化学方法,应用较广的有湿式烟气脱硫(Wet?FGD)和NH3选择性催化还原(SCR)技术脱氮组合、活性焦吸附法和等离子体法等,这些方法在SO2和NOx的污染治理中起到了重要作用,但也都不同程度地存在成本高、工艺复杂、二次污染及吸附剂、催化剂或吸收液等再生的问题。生物法脱硫脱氮是近年来的新兴技术,它的主要优势在于工艺设备简单,管理维护方便,能耗低,运行费用低,二次污染少,去除有害成分的效率也比较高,因此具有广阔的工业应用前景。论文采用生物滴滤工艺进行SO2和NO气体的净化处理。总体分为四部分:(1)采用异养反硝化菌进行NO气体的脱除实验,并考察了最佳工艺操作条件。通过在生物滴滤塔中进行填料挂膜,利用反硝化菌处理模拟的NO工业废气。实验表明:当气体空塔停留时间为80s,液体喷淋密度为16?20 m3/(m2·h),进气浓度为30?500 mg/m3时,NO平均去除率可达到98.4%。同时,在液相中只能检测到微量的NO3?,说明塔内发生了较为彻底的反硝化作用,采用生物反硝化是处理含NO废气的可行途径。(2)采用硫酸盐还原菌(SRB) +脱氮硫杆菌(TD)两级生物滴滤塔串联工艺进行SO2和NO气体的脱除实验,并考察了最佳工艺操作条件。分别在两个生物滴滤塔中进行SRB和TD的填料挂膜,模拟的SO2工业废气进入SRB生物塔,并在厌氧条件下进行SO2和NO气体脱除实验。实验表明:操作平稳后,当气体空塔停留时间为30s,喷淋密度为26 m3/(m2·h),SO2进气浓度为500—1500 mg/m3时,SO2气体去除率可达99%以上,生成的H2S气体平均去除率达到90.5%。当停留时间为180s,喷淋密度为16 m3/(m2·h),NO进气浓度为500—2000 mg/m3时,NO去除率最高可达到98%,平均去除率为73.3%。采用SRB处理SO2气体和采用TD处理NO气体的生物法可行。(3)采用SRB + TD +异养反硝化菌的单级生物滴滤塔进行SO2和NO气体同步脱除实验,并考察了最佳工艺操作条件。在一个生物滴滤塔中进行SRB + TD +异养反硝化菌三种优势菌的混菌填料挂膜,处理含SO2和NO的模拟工业废气。实验表明:维持喷淋液pH值7?8,S2O32?浓度3g/L左右,当气体空塔停留时间为135s,喷淋密度为18 m3/(m2·h),SO2进气浓度为200—5000 mg/m3时,NO进气浓度为20—500 mg/m3时,SO2气体平均去除率为97.6%,NO气体平均去除率为51.4%。生物法同步脱除SO2和NO气体还需深入研究,解决SRB与TD对S2O32?的底物竞争与其它矛盾问题,进一步提高NO气体的去除效率。(4)生物法脱除SO2和NO气体的机理研究。探讨了生物膜的形成机理与菌落构成,分析了单级生物滴滤塔中几种优势菌的相互关系。在传统生物膜理论的基础上,结合实验过程改进了生物膜理论,主要根据含水量的多少将塔生物膜区分为水膜型生物膜、固膜型生物膜和活性生物膜。并阐述了适合处理SO2和NO气体的最佳生物膜形式。论述了同步脱除SO2和NO气体的生物反应机理。找出了制约生物法同步脱除SO2和NO气体去除效率的不利因素,提出了新的研究方向。同时讨论了本课题研究将面对工业化应用的实际问题。更多还原

【Abstract】 Fossil fuels such as petroleum and charcoal contain sulfur and nitrogen which can convert into SO2 and NOx let off after burning. SO2 and NOx can bring sour rain on the earth and detroy the health of mankind. NO is the main exist material of NOx, so the removal of SO2 and NO from industry waste gases are investigated in this paper.The pollution of SO2 and NOx catch the worldwide attention, and many countries are taking some effective measures to control the pollution. Now, the regulation of controlling NOx is established while the pollution of SO2 is being controlled. And the treatment of the pollution of SO2 and NOx is a hot research in the world, all kinds of techniques are developed to solve the problem of the pollution of SO2 and NOx.Traditional disposal techniques of SO2 and NOx mainly adopt physical and chemical methods. The common ones are wet flue gas desulfurization and NH3 election catalyse reduction combined technique, active char adsorption and plasma method and so on. These techniques have taken the important roles in the process of controlling the pollution of SO2 and NOx, but they have some problems such as high cost, complex technics, secondary pollution and the reborn problem of sorbents and catalyzers. Biological one is a new technique and applied wildly by virtue of its simple apparatus, convenient maintenance, low energy consumption, less secondary contamination and high removal efficiency.In this paper bio-trickling towers were established to purify SO2 and NO gases. The whole paper included four parts as follows:(1) Heterotrophic denitrificans were adopted to purify NO simultation waste gases, and the optimal operation conditions were investigated.Biological trickling tower with biofilm carrier was used to investigate the process of purifying the simulating nitric-oxide-containing waste gas by denitrifiers. The experiment demonstrated that rod bacillus denitrifyers can be gotten by dynamic cultured and tamed for carrying on the packing materials. Nitric oxide removal efficiency is up to 98.4%, with empty-bed residence time(EBRT)80 s, inlet nitric oxide concentration 30～500 mg/m3 and circulating liquid flux 90-100L/h. In addition, only little NO3- could be detected in the liquid. The way of purification of nitric-oxide-containing waste gas by denitrifying is feasible.(2) SRB + TD two bio-trickling towers in series were developed to purify SO2 and NO simulation waste gases respectively, and the optimal operation conditions were investigated.Biological trickling technique is usually carried out to purify those biodegradable waste gases. In this experiment, Sulfate-Reducing Bacteria(SRB) and Thiobacillus denitrificans(TD) were cultured for carrying on the packing materials in the two bio-trickling towers respectively to treat the waste gases of sulfur dioxide and nitric oxide under the anaerobic conditions. The experiment demonstrated that sulfur dioxide removal efficiency can reach over 99%, with empty-bed residence time(EBRT)30s, inlet concentration 500?1500mg/m3 and circulating liquid spraying density 26m3/(m2·h), and the average removal efficiency of hydrogen sulfide produced by SRB is 90.5%; Nitric oxide removal efficiency can reach 98%at its maximum and average removal efficiency was 73.3% , with empty-bed residence time(EBRT)20s, inlet nitric oxide concentration 500?2000mg/m3 and circulating liquid spraying density 26m3/(m2·h). So, conclusion can be drawn that the way of purification of sulfur dioxide and nitric oxide waste gases by microorganism is worth investigating.(3) SRB + TD + heterotrophic denitrificans cultured in one bio-trickling tower was developed to purify SO2 and NO simulation waste gases, and the optimal operation conditions were investigated.SRB + TD + heterotrophic denitrificans were cultured in one bio-trickling tower to simlutaneous remove SO2 and NO simulation waste gases. The experiment demonstrated that sulfur dioxide average removal efficiency can reach 97.6% and nitric oxide average removal efficiency can reach 51.4%, with pH 7?8,the concentration of S2O32? 3g/L, empty-bed residence time(EBRT)135s, circulating liquid spraying density 18m3/(m2·h), sulfur dioxide inlet concentration 200?5000mg/m3 and nitric oxide inlet concentration 20?500mg/m3. To elevate gases removal efficiency, the further study on simultaneous biological removal of SO2 and NO gases need to solve some problems such as the competition between SRB and TD on S2O32?.(4) The study on biological mechanism of removal of SO2 and NO gasesIn the four part of this paper, the mechanism of biofilm forming and the structure of microorganism in the biofilm was discussed. On the basis of tradition biofilm theory and experiment, a transformed biofilm theory was brought forward which divides biofilm in the bio-trickling tower into three kinds: liquid biofilm, solid biofilm and active biofilm according to different containing water quantity. And the suitable biofilm to biological removal of SO2 and NO were analyzed. In addition, biological removal mechanism were discussed in this part. Some disadvantages of biological removal of SO2 and NO wrer found and next research goals were brought forward and some practical problems which will be confronted in the process of indutrial application of this subject were also discussed in this part.更多还原