氮化制度对Si3N4-SiC复合材料性能的影响

详细地研究了氮化制度对Si3N4-SiC复合材料性能的影响,研究结果表明:经过单一的氮化高峰反应后,材料的力学性能、物相和显微结构均较差,而经过2个连续的氮化高峰的反应烧结能够得到较好的力学性能、物相和显微结构,继续通过高温后处理,复合材料的性能随反应时间的延长逐步提高.     

含生物毒性物质的化工污水对硝化作用的影响

针对某大型化工企业新建的污水生物脱氮处理系统,研究了含有生物毒性物质的化工污水对硝化作用的影响。研究结果表明来源于个别排放点的染料生产污水、橡胶生产污水、助剂生产污水对硝化作用有显著的影响,一些特征污染物如苯胺,硝基苯,苯酚及Zn2+,Mn2+,Ni2+均对硝化作用有明显的抑制作用,从而导致生化处理系统的硝化反应速率明显降低,而且以Ni2+最为显著。     

MBBR中HRT与pH对短程硝化反硝化的影响

为了开发经济高效的生物脱氮工艺,在MBBR中进行了短程硝化反硝化的研究,考察了HRT与pH对短程硝化反硝化的影响。结果表明,在短程硝化反硝化过程中,在室温、不控制溶解氧的条件下,NH_4~+-N与COD去除率随着HRT的延长而增大,出水NO_2~--N随着HRT的延长先增大后减少,当HRT为8h时出水NO_2~--N最高;当pH由5增加到10时,COD去除率的变化较小,NH_4~+-N去除率和出水NO_2~--N则随着pH的增大先增大后减小,pH在8~9时对NH_4~+-N的处理效果最好,出水NO_2~--N最高。     

生物膜厚度对膜曝气生物膜反应器硝化性能的影响

在设定的膜内压力下(2 k Pa)启动并运行膜曝气生物膜反应器(MABR),对生物膜生长过程中的硝化性能及生物膜组成变化进行了分析。实验结果表明,在生物膜厚度增长到(293.3±5.8)μm的过程中,生物膜内的总氧通量先增加后减少,最高可达21.3 g O2?m?2?d?1,证实了生物膜的存在可增强MABR的氧传质能力。在生物膜厚度增长的过程中,氨氮表面去除负荷也是先增加后减少,最高可达4.91 g N?m?2?d?1,表明在MABR硝化过程中存在最佳的生物膜厚度,根据所研究最佳生物膜厚度为(119.0±3.0)μm,此时MABR具有最高的氧通量和氨氮表面去除负荷,硝化性能最好。生物膜内胞外聚合物(EPS)成分分析结果表明,随着生物膜厚度的增加,生物膜内层紧密型EPS的含量增加,导致氧传质阻力增加,这是生物膜内氧通量及氨氮去除负荷随生物膜厚度先增加后下降的内在原因。     

Nitrification and denitrification derived N2O production from a grassland soil under application of DCD and Actilith F2

The relative contribution of nitrification and denitrification to N₂O production was investigated by means of soil incubations with acetylene in a mixed clover/ryegrass sown sward 5 days after application of a mineral fertiliser (calcium ammonium nitrate) or an organic one (cattle slurry) with and without the addition of the nitrification inhibitor dicyandiamide (DCD) and the commercial slurry additive Actilith-F2. At this time, maximum field N₂O emissions were taking place. N₂O production by the slurry amended soil was twice as high as that of the mineral amended one. N₂O came in a greater proportion from nitrification rather than from denitrification in the slurry treatment, while for the mineral fertilisation most N₂O came from denitrification. The addition of DCD to slurry produced a decrease in N₂O production both from nitrification and denitrification. No reduction in N₂O losses was observed from addition of DCD to the mineral fertilisation, although DCD resulted effective in reducing the nitrification rate by 53% both in the slurry and the mineral fertilisation. Actilith F2 induced a high nitrification rate and N₂O production from denitrification was reduced while that from nitrification was not. This revised version was published online in August 2006 with corrections to the Cover Date.     

微米级硝化纤维素的制备及性能研究

为了使硝化反应在近似均相的条件下进行,采用对精制棉进行水解处理,用稀酸水解法制得结晶度较为一致的微晶纤维素,再用硝硫混酸进行硝化得到微米级硝化纤维素。用扫描电镜和红外光谱对其微观形貌和结构进行了表征。用DSC分析了其热性能,并测试了其撞击感度和黏度。结果表明,制备微米级硝化纤维素的最佳条件为:硝硫混酸体积比为1∶3,硝化时间30min,硝化温度为35℃。制得的微米级硝化纤维素样品粒度均匀,其特性落高为57.466cm,黏度为478mPa·s,分解峰温达到211.20℃,硝化均匀,含氮量可达12.8%。     

微生物燃料电池处理丙酮和氨氮废水及同步产电性能研究

本研究利用阴离子交换膜作为分隔膜构建了生物阴极微生物燃料电池（Microbial fuel cell, MFC），通过硝化反硝化过程去除氨氮、降解丙酮同时产电。实验探究了不同丙酮浓度（50 mg/L、100 mg/L、300 mg/L、500 mg/L、700 mg/L）对MFC产电及氨氮（200 mg/L）的去除效果。结果表明，在选定的丙酮浓度范围内，丙酮的去除率均高达96%以上；当丙酮浓度高于300 mg/L时，氨氮的去除开始受到抑制，氨氮最高去除率为73.7%，且丙酮浓度为300 mg/L时，对应的MFC的产电性能最佳，最高输出功率密度可达49.7 mW/m2。高通量测序技术分析了阳极及阴极微生物群落结构，从门级分类上看，阳极中的优势微生物群落主要为变形菌，拟杆菌门及厚壁菌门；阴极上的优势微生物群落为拟杆菌门、放线菌门、变形菌门及酸杆菌门。从属级分类上看，阳极主要的优势菌种为Comamonas, Acetoanaerobium，Stenotrophomonas。阴极主要的优势菌种为Rhodococcus，Aridibacter, Thauera，Ignavibacterium。     

不同运行方式对微生物燃料电池处理氨氮废水的影响

微生物燃料电池(MFC)是一种既能去除污染物又能产电的新型污水处理技术,由于其具有利用生物转化能量的节能优势,MFC废水脱氮处理技术引起了更多的关注。本实验在启动MFC的同步硝化与反硝化(SND)后,首先研究了通路与断路条件对MFC产电脱氮的影响,结果表明:断路时有利于硝化反应的发生,氨氮去除率有最大值95.17%;而通路更有利于COD和总氮的去除,表明氮的去除主要依靠阴极接受电子进行。随后分析了曝气阶段+停曝阶段运行方式对MFC产电和脱氮的影响,结果显示:曝气8.5h(DO为4.0mg/L)后停止曝气,停曝阶段为11.5h,DO逐渐降低到2.0mg/L,输出电压由无曝气运行的31mV提高到120mV左右,氨氮去除率最高达到86.42%、总氮去除负荷由无曝气运行的0.064g/(L·d)升高到0.46g/(L·d)。说明曝气阶段+停曝阶段运行方式既能有效提高MFC脱氮产电性能又可以减少维持高浓度DO的能量输入。     

Multilevel surrogate modeling of an amine scrubbing process for CO2capture

Surrogate models provide a powerful method for simplifying calculations within complex simulations. While surrogate models are broadly applied within chemical engineering, little research exists investigating the level of surrogacy's impact on a simplified process model. In this work, artificial neural networks (ANN) and Kriging models are used as surrogate models at the process, process unit, and thermodynamic levels for a CO₂ amine scrubbing process. The surrogated models are evaluated against an Aspen Plus simulation for accuracy, convergence behavior, computational cost, and ability to extrapolate. The thermodynamic and process unit models can better handle discontinuous, non-smooth behavior, and convergence issues in the surrogated truth model, but poor conditioning in the final system of equations results in a lower accuracy and convergence rate than the process level surrogate. Beyond model accuracy, availability of diverse data, intended re-usability, and the desired outputs must be considered when selecting a level of abstraction.     

Nitrous oxide emissions from fertilized upland fields in Thailand

Nitrous oxide (N₂O) emission from fertilized maize fields was measured using a closed chamber at four experimental sites in Thailand. The average measured N₂O flux from unfertilized plots through crop season was 4.16 ± 1.52, 5.05 ± 1.65, 5.25 ± 1.68 and 6.74 ± 2.95 g N₂O-N m^-2 h^-1, at Nakhon Sawan, Phra Phutthabat, Khon Kaen and Chiang Mai, respectively. Increased N₂O emissions by the application of nitrogen fertilizer were 0.22–0.44, 0.19–0.38%, 0.12–0.24 and 0.08–0.15% of the applied N, respectively. Compared to other data, N₂O emission rate to applied nitrogen was not significantly different between the data of Thailand and the Temperate Zone.