浓硝盐水的钙法脱硝工艺研究

介绍了以氯化钙作脱硝剂脱除浓硝盐水中的硫酸根,并用单因素实验和正交实验法研究钙硫比、反应时间、反应温度、硫酸钠浓度对浓硝盐水的脱硝率和残余钙离子浓度的影响。

容错控制在浓硝酸高压反应釜中的应用研究

介绍了直硝法生产浓硝酸工艺的关键工序,并分析了对高压反应釜生产进程的质量与产量影响较大的“管道化配料新工艺”。针对浓硝生产系统的变参数、强耦合、多变量、高腐蚀、非线性等工艺特征,利用“动态系统故障检测与诊断技术”与“PSBE算法”,建立了高压反应釜运行的数学模型,并提出了多个传感器同时发生故障时的容错控制策略,给出了高压反应釜管道化混合装置容错控制方法。

浓硝水制取芒硝工艺分析

芒硝(十水合硫酸钠Na_2SO_4·10H_2O)是轻工、化工工业原料。在化学工业中主要用来制取无水硫酸钠和硫化碱,它不仅可用来制取泡花碱、硫酸钡等化学材料,还可用于生产元明粉(无水硫酸钠)。近几年国内外对元明粉的需求量越来越大,元明粉广泛用于可用于维尼纶、泡花碱、漂染、合成洗涤剂、玻璃、造纸、制革、输油气管道防腐、金属冶炼、表面处理、填充剂等行业。可见芒硝的生产工艺对我国的生活起着重要的影响,所以需要对芒硝的生产工艺进行研究,主要论述了浓硝水制取芒硝的工艺流程。

一、二类容器换热器、塔器、浓硝塔罐等产品

安徽淮化集团化机厂妨建于1958年．至今已有40年化工机械设备与配件加工安装历史。四十年来，企业规模不断扩大，生产能力不断提高，现有固定资产原值1600余万元，在用设备200余台，生产设备齐备，技术力量雄厚，是淮南市重要的机械加工制造企业。

浅谈硝镁法浓硝酸装置防冻措施

硝镁法浓硝酸装置生产过程中，由于浓硝酸镁的易结晶性、高硅铸铁的脆性，对该工艺控制提出严格的防冻要求。

浅议硝酸工业的发展概况及浓稀硝酸生产方法

在化工生产行业中，浓稀硝酸工业，经过了120多年的发展，—个集设计合理，技术成熟、能源综合利用，产品齐全，环保达标的化工工业体系，用双加压法工艺生产稀硝酸，用间硝法中的硝酸镁法工艺生产浓硝酸，提高产品浓度，合理提高系统压力，降低能量的消耗及原材物料，降低了尾气排放浓度标准，从而减少对环境大气的污染，确保安全环保符合国家标准。

CF表面处理对SLS用PA12/CF复合材料性能的影响

利用热空气处理法和浓硝酸处理法分别对碳纤维(CF)进行表面处理,然后与尼龙(PA)12粉末按量比3∶7通过机械混合法制备PA12/CF复合粉末材料。将复合粉末材料进行注塑成型,考察了热处理温度及浓硝酸处理时间对复合材料力学性能和热性能的影响。结果表明,浓硝酸处理时间为1 h处理效果最好,与未处理的CF复合材料相比,注塑样条拉伸强度提高23%,弯曲弹性模量提高133%,维卡软化点提高6.2℃;扫描电子显微镜分析表明,经过热处理后的CF在PA12基体中分散均匀,两者的界面相容性良好。

高压釜管道化配料装置容错控制设计

分析“管道化配料新工艺”和“动态系统故障检测与诊断技术” ,针对浓硝生产系统的变参数、强耦合、多变量、高腐蚀、非线性等工艺特征 ,给出高压反应釜管道化混合装置容错控制方法。

Cu与浓、稀硝酸反应实验的改进与创新

针对人教版新(2019年版)、旧(2004年版)两版教材中Cu与浓、稀硝酸反应两个实验中存在的不足,采用配套的密封性良好的胶头滴管和滴瓶,或者生活中易得的5 mL注射器和小西林瓶组合设计实现Cu与浓、稀硝酸实验的微型化、绿色化、系列化改进.其中在铅笔芯上缠绕铜丝和稀硝酸反应的实验,利用原电池原理加快反应速率,无须加热,节约能源.创设全封闭的、无氧环境可以清楚地观察到无色气体NO的生成.改进后的实验仪器和操作步骤更为简单,在缩短反应时间的同时强化呈现了实验现象,环保安全,适合学生分组实验.

The influence of urbanization on karst rivers based on nutrient concentration and nitrate dual isotopes： an example from southwestern China

China is experiencing rapid urbanization that has changed the water quality of rivers, especially nutrient loads. In this study, a typical urban river located in a karst area, Chengguan River, was chosen to explore the influence of urbanization on river ecosystems based on nutrient concentration and nitrate isotopes. The results show monthly variability of water chemistry and nutrient concentration. Nutrient concentration in two tributaries and the mainstem showed significant spatial variability, with heavy N and P pollution in one tributary near a suburban area,indicating a response to different levels of urbanization.Measurements of nitrate dual isotopes suggest thatvolatilization, assimilation, nitrification, and denitrification all occur in the polluted river. Water chemistry and nitrate isotopes show that major nitrogen sources included domestic waste and agricultural input, such as chemical fertilizer and manure. The results suggest that urbanization increases nutrient concentrations and accelerates the riverine nitrogen dynamic, and point to the need to manage point sources of sewage effluents to improve the water quality of urban rivers in southwestern China.

Impact of the water-sediment regulation and a rainstorm on nutrient transport in the Huanghe River

Dissolved nutrient concentration in the Huanghe （Yellow） River at Lijin was monitored during a water-sediment regulation period and a subsequent rainstorm from 14 June to 19 July, 2005. This study provides detailed information on nutrient concentrations in the Huanghe River during the water-sediment regulation and rainstorm periods, and is of significance for the downstream area of the Huanghe River and the Bohai Sea. The average concentrations of nitrate, nitrite and ammonia were 304.7 μmol/L, 0.19 μmol/L, and 1.10 μmol/L, respectively, while the average concentrations of dissolved inorganic phosphorus （DIP） and dissolved silicate （DSi） were 0.23 gmol/L and 122.9 ktmol/L, respectively. Nutrient concentrations during the water-sediment regulation period were mainly influenced by the dilution effect, floodplain effect and sediment resuspension while dilution and erosion effects were the main factors during the rainstorm. The fluxes of dissolved inorganic nitrogen （DIN）, DIP and DSi during the water-sediment regulation and rainstorm periods accounted for 20.4%, 19.5%, 16.7% and 4.97%, 6.45%, 5.47% of the annual nutrient fluxes, respectively. Discharge was the main factor influencing the fluxes of nutrients during both the water- sediment regulation and the rainstorm periods.

Effects of Nitrate Concentration in Main Anoxic Zone on Denitrifying Dephosphatation

The effects of nitrate concentration in the main anoxic zone on denitrifying dephosphatation capability were conducted based on modified University of Cape Town （MUCT） process. Meanwhile the relation between optimal nitrate concentration （Nopt） and influent C/N ratio was evaluated, in which the influont chemical oxygen demand （COD） concentration was stabilized at （2905：10）mg/L, the influent total phosphorus （TP） concentration was stabilized at （7.0±0. 5）mg/L. The results indicated that： （1） the nitrate concentration in the main anoxic zone had an effect on denitrifying dephosphatation capability, and the average percentages of anoxic phosphorus uptake in total phosphorus uptake （ηa） increased with nitrate cancentration increasing, i.e., increasing from 62.1% at2.0 mg/L to63.7%, 65.6%, 68.1%, and 72.3% at 2.2, 2.4, 2.6 and 2.8mg/L, respectively; （2） the Nopt as function of influent C/N ratio could be calculated by the equation： y = 0.67x^2-7.79x ＋ 22. 21; the maximum percentages of anoxic phosphorus uptake in total phosphorus uptake （ηa,max） as function of the Nopt could be calculated by the equation： y=0.77-0.33e^-（x/1.52）. The Nopt was the important control parameter that must be optimized for operation of conveational biological nutrieat removal activated sludge （BNRAS） system.

Cleavage of catalytic ally grown carbon nanofibers into hydrophilic segments by oxidation in a mixture of concentrated HNO3-H2SO4 in an autoclave

The catalytically grown carbon nanofibers were treated by a mixture of concentrated nitric aid and sulfuric aid in an autoclave at temperature 333, 363 and 423 K. It was found that the samples treated at 363 K and 423 K were still well dispersed in water 15 hours later, indicating that carbon nanofibers can be made hydrophilicy. It was also found that the dispersion was destroyed when the pH value was lowered by adding acid. The results are significant when the carbon nanofibers are used as enhancing component in polymer composite material because several hundreds of nm are perfect size and the hydrophilicity controls the dispersion of CNFs in the polymer media. It is concluded that the amount of the oxygen-containing groups on the surface and the hydrophilicity of the carbon nanofibers can be controlled by the treatment temperature, and that the carbon nanofibers can be cleaved into uniform segments.

The δ^15N response and nitrate assimilation of Orychophragmus violaceus and Brassica napus plantlets in vitro during the multiplication stage cultured under different nitrate concentrations

Natural nitrogen isotope composition(δ^(15)N) is an indicator of nitrogen sources and is useful in the investigation of nitrogen cycling in organisms and ecosystems. δ^(15)N is also used to study assimilation of inorganic nitrogen. However, the foliar δ^(15)N of intact plants, which is a consequence of nitrate assimilation occurring in the roots and shoots, is not suited for studying nitrate assimilation in cases where nitrate is the sole nitrogen source. In this study, Orychophragmus violaceus(Ov) and Brassica napus(Bn) plantlets, in which nitrate assimilation occurred in the leaves, were used to study the relationship between foliar δ^(15)N and nitrate assimilation.The plantlets were grown in vitro in culture media with different nitrate concentrations, and no root formation occurred for the plantlets during the multiplication stage.Nitrogen isotope fractionation occurred in both the Ov and the Bn plantlets under all treatments. Furthermore, the foliar nitrogen content of both the Ov and Bn plantlets increased with increasing nitrate concentration. Foliar nitrogen isotope fractionation was negatively correlated with foliar nitrogen content for both the Ov and Bn plantlets. Our results suggest that the foliar nitrogen isotope fractionation value could be employed to evaluate nitrate assimilation ability and leaf nitrate reductase activity.Moreover, high external nitrate concentrations couldcontribute to improved foliar nitrogen content and enhanced nitrate assimilation ability.

Measurement of trace nitrate concentrations in seawater by ion chromatography with valve switching

An ion chromatographic method with a valve switching facility was developed to determine trace nitrate concentrations in seawater using two pumps, two different suppressors, and two columns. A carbohydrate membrane desalter was used to reduce the high concentrations of sodium salts in samples. In this method, trace nitrate was eluted from the concentrator column to the analytical columns, while the matrix fl owed to waste. Neither chemical pre-treatment nor sample dilution was required. In the optimized separation conditions, the method showed good linearity( R >0.99) in the 0.05 and 50 mg/L concentration range, and satisfactory repeatability(RSD<5%, n =6). The limit of detection for nitrate was 0.02 mg/L. Results showed that the valve switching system was suitable and practical for the determination of trace nitrate in seawater.

Simulated Impacts of Sulfate and Nitrate Aerosol Formation on Surface-Layer Ozone Concentrations in China

The authors quantify the impacts of sulfate and nitrate aerosol formation on surface-layer 03 concentrations over China using the one-way nested-grid capa- bility of the global three-dimensional Goddard Earth Ob- serving System chemical transport model （GEOS-Chem）. Chemical reactions associated with sulfate formation are simulated to generally increase 03 concentrations in China. Over the North China Plain （NCP） and the Si- chuan Basin （SCB）, where simulated sulfate concentra- tions are the largest, ozone concentrations show maximum increases in spring by 1.8 ppbv （3.2%） in the NCP and by 2.6 ppbv （3.7%） in the SCB. On the contrary, nitrate formation is simulated to reduce 03 concentrations by up to 1.0 ppbv in eastern China, with the largest reduc- tions of 1.0 ppbv （1.4%） in summer over the NCE Ac- counting for the formation of both sulfate and nitrate, the surface-layer O3 concentrations over a large fraction of eastern China are simulated to increase in winter, spring, and autumn, dominated by the impact of sulfate forma- tion, but to decrease in summer because of the dominant contribution from nitrate formation.

Simultaneous heterotrophic nitrification and aerobic denitrification at high initial phenol concentration by isolated bacterium Diaphorobacter sp. PD-7

A strain capable of phenol degradation, hetemtrophic nitrification and aerobic denitrification was isolated from activated sludge of coking-plant wastewater ponds under aerobic condition. Based on its morphology, physiology, biochemical analysis and phylogenetic characteristics, the isolate was identified as Diaphorobacter sp. PD-7. Biodegradation tests of phenol showed that the maximum phenol degradation occurred at the late phase of exponential growth stages, with 1400 mg·L^-1 phenol completely degraded within 85 h. Diaphorobacter sp. PD-7 accumulated a vast quantity of phenol hydroxylase in this physiological phase, ensuring that the cells quickly utilize phenol as a sole carbon and energy source. The kinetic behavior ofDiaphorobacter sp. PD-7 in batch cultures was investigated over a wide range of initial phenol concentrations （0-1400mg·L^-1） by using the Haldane model, which adequately describes the dynamic behavior of phenol biodegradation by strain Diaphombacter sp. PD-7. At initial phenol concentration of 1400mg· L^-l, batch experiments （0.25 L flask） of nitrogen removal under aerobic condition gave almost entirely removal of 120.69mg· L^- 1 ammonium nitrogen within 75 h, while nitrate nitrogen removal reached 91% within 65 h. Moreover, hydroxylamine oxidase, periplasmic nitrate reductase and nitrite reductase were successfully expressed in the isolate.

Chemical and Organic Contamination of Phreatic Aquifer of Sidi Bouzid （Center West of Tunisia）

An understanding of the long-term changes in the nitrate and microbial contamination pattern of the groundwater of Sidi Bouzid （Centre West of Tunisia） is critical to conservation of drinking water in rural areas supporting mixed land-use activities such as cropping, livestock farming, and residence. The phreatic aquifer was revealed polluted by domestic disposals of the wastewaters in the urban zone. The average nitrate concentration in the groundwater of the east of the mioplioquaternary aquifer of Saddaguia （Sidi Bouzid） rose from 50 mg NO3- during 1996 to over 100 mg in 2003, which represents an increase of some 10 mg per year. Nitrate groundwater pollution during the period 1996-2003 was the result of the abusive use of fertilizers.In the cultivated zone, we must reduce the effects of the excessive use of the nitrogen fertilizers on the basis of monitoring soil once a year, managing water resources, rationalizing the use of the chemical substances. In urban zones, most of lost wells located in the perimeter reveal the gravity of the state of the aquifer. This last is organically polluted and requires an immediate action for the generalization of the purification network. We need to take into account the reality of under soil in all future planning＇s and arrangements. A scheme of sanitation seems necessary before all plans of arrangement. The extension of the sewer network must give the priority to the most vulnerable zones.