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1.
《Calphad》2021
Existing alumina extraction and material production methods result in the formation of harmful ammonia gas or ammonia water originating from aluminum nitride (AlN) in dross. Therefore, in this study, aluminum dross was used as a denitration reagent to eliminate nitrogen oxides in flue gas and AlN in dross. Based on the proposed scheme, thermodynamic calculations were performed to investigate the denitrification effect and reduction of aluminum dross in flue gas. The results show that equilibrium concentrations of NO, NO2, and HF in the flue gas were influenced mainly by temperature; their concentrations increased with an increase in the temperature, reaching 4.4 × 10−20, 1.7 × 10−38, and 7.0 × 10−8 g/m3, respectively, at 923 K. The Gibbs free energy corresponding to the reaction of CO2 with Al/AlN in aluminum dross was −377/–120 kJ/mol. HF, originating from the reaction of NaF and water vapor, maintained an extremely low concentration of 6.99 × 10−8 g/m3 at 923 K. These results indicate that aluminum dross processing may clean the flue gas and increase the calorific value while eliminating the hazards of AlN. The results obtained herein will provide theoretical guidance toward new avenues of aluminum dross utilization. 相似文献
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3.
Yang Li Defu Che Chenglong Yang Mingyu Yao Tingwen Zhao Kangli Fu Hanchen Zhao 《中国化学工程学报》2021,29(1):401-408
SO2 and NO emitted from coal-fired power plants have caused serious air pollution in China. In this study, a test system for NO oxidation using O3 is established. The basic characteristics of NO oxidation and products forms are studied. A separate test system for the combined removal of SO2 and NOx is also established, and the absorption characteristics of NOx are studied. The characteristics of NO oxidation and NOx absorption were verified in a 35 t·h-1 industrial boiler wet combined desulfurization and denitrification project. The operating economy of ozone oxidation wet denitrification technology is analyzed. The results show that O3 has a high rate and strong selectivity for NO oxidation. When O3 is insufficient, the primary oxidation product is NO2. When O3 is present in excess, NO2 continues to get oxidized to N2O5 or NO3. The removal efficiency of NO2 in alkaline absorption system is low (only about 15%). NOx removal efficiency can be improved by oxidizing NOx to N2O5 or NO3 by increasing ozone ratio. When the molar ratio of O3/NO is 1.77, the NOx removal efficiency reaches 90.3%, while the operating cost of removing NOx per kilogram is 6.06 USD (NO2). 相似文献
4.
对放脉冲电脱除烟气中的NO和NOx的实验研究与分析结果表明 ,烟气中的飞灰对NOx具有 2 %~ 4 %的吸附脱除作用 ,同时 ,对脉冲放电产生抑制导致脱除率降低。增加烟气含水量增强了飞灰粒子表面的化学吸附能力 ,使得在烟气含水量为 15 % (V V)和单位体积烟气注入能量小于 3W·h Nm3时 ,NO和NOx的脱除率提高 5 %~ 15 % ,烟气在反应器中停留时间 5 .9s、单位体积注入能量小于 4W·h Nm3时 ,NO和NOx的脱除率分别为 4 2 %和 2 9%。 相似文献
5.
Desislava Bögner Frederike Schmachtl Björn Mayr Christopher P. Franz Sabine Strieben Gregor Jaehne 《臭氧:科学与工程》2019,41(2):105-117
Recirculating Aquaculture Systems (RAS) reduce water consumption by efficient filtration to maintain appropriate levels of accumulating compounds and sludge. Sludge is mechanically separated by drum filters and disposed of to the detriment of overall system water budgets. Dissolved nitrogen compounds are reduced via nitrification–denitrification filters, requiring commercial external carbon sources. The reuse of sludge after ozone pre-treatment may represent the next step in RAS optimization. The present study analyzes the content of sludge from RAS and tests ozonation as a pre-treatment for recycling as carbon source. The dissociative effect of ozone and the physicochemical changes due to ozonation lead to a significant increase in soluble carbon availability. Predominantly long-chain fatty acid (FA) (saturated and unsaturated) with 16 and 18 carbon atoms independently of the treatment were found in the profiles. Saturated FA concentrations in solution increased after 20, 40, and 60 min ozonation. The solid content of the sludge was practically unaffected by ozonation in terms of FA profile: only saturated FA slightly increases after 40 min treatment. The implications of these findings for denitrifying bacteria are discussed.
Abbreviations: Recirculating Aquaculture Systems (RAS); Advanced Oxidation Processes (AOPs) 相似文献
6.
研究为在炼油污水的CAST工艺的主反应区中 ,通过恰当控制pH值和DO(污水中溶解氧含量 )值 ,可以使硝化与反硝化反应同步进行 ,在去除COD ,BOD的同时 ,也可提高其脱氮效果 ,从而得出DO的最佳值为 0 .8mg/L ,pH为 7.3~ 7.7之间。 相似文献
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8.
Sungyoun Kim Hyejung Jung Kwang-Soo Kim In S. Kim 《Canadian Metallurgical Quarterly》2004,130(12):1475-1480
The treatment performance of sequential heterotrophic and autotrophic denitrification process was evaluated using synthetic wastewaters containing high nitrate concentrations. The effluents from two sequentially connected reactors, for heterotrophic denitrification and sulfur-based autotrophic denitrification, were analyzed for more than 200 days. Experimental results indicated that higher than 95% of the nitrate removal could be achieved with volumetric nitrate loading rates of 2.16, 3.24, and 4.32 kg/m3?d. The maximum denitrification rates, with 1,000 mgN/l influent nitrate concentrations, for the heterotrophic and sulfur-packed autotrophic reactors, were found to be 2.47 and 3.61 kg/m3?d, respectively. A sequential heterotrophic and autotrophic denitrification process is considered a good alternative for the sole autotrophic denitrification process, providing excellent nitrate removal, especially for nitrate-rich wastewaters with very low organic contents. 相似文献
9.
A two-dimensional, particle-based biofilm model coupled with mass transport and computational fluid dynamics was developed to simulate autotrophic denitrification in a spiral-wound membrane biofilm reactor (MBfR), where hydrogen is supplied via hollow-fiber membrane fabric. The spiral-wound configuration consists of alternating layers of plastic spacer net and membrane fabric that create rows of flow channels, with the top and bottom walls comprised of membranes. The transversal filaments of the spacer partially obstruct the channel flow, producing complex mixing and shear patterns that require multidimensional representation. This study investigated the effect of hydrogen and nitrate concentrations, as well as spacer configuration, on biofilm development and denitrification fluxes. The model results indicate that the cavity spacer filaments, which rest on the bottom membranes, cause uneven biofilm growth. Most biofilm resided on the bottom membranes, only in the wake of the filaments where low shear zones formed. In this way, filament configuration may help achieve a desired biofilm thickness. For the conditions tested in this study, the highest nitrate fluxes were attained by minimizing the filament diameter and maximizing the filament spacing. This lowered the shear stress at the top membranes, allowing for more biofilm growth. For the scenarios studied, biomass limitation at the top membranes hindered performance more significantly than diffusion limitation in the thick biofilms at the bottom membranes. The results also highlighted the importance of two-dimensional modeling to capture uneven biofilm growth on a substratum with geometrical complexity. 相似文献
10.