MASS TRANSFER IN MEMBRANE ABSORPTIONDESORPTION OF AMMONIA FROM AMMONIA WATER

Hydrophobic membrane can provide fast mass transfer for absorption-desorption of gasesform liquid to absorbent.The removal of ammonia from ammonia water and absorption with dilutesulphuric acid was studied in a pilot plant with polypropylene hollow fiber column,The removalrate and influences of operation temperature,flow rate and concentration on mass transferperformances were discussed mathematically.Experimental results and computer calculation show thatthe ammonia removal rate is not affected by the feed concentration for a given system.Both partialand overall mass transfer coefficients vary along the axis of the fiber,and the mass transfer for themembrane process is controlled by membrane resistance.

Preparation and stability of zinc ferrite nano-particle suspension of ammonia-water solution

In order to apply nano-particles to the ammonia-water absorption refrigeration, the zinc ferrite nano-particles suspension of ammonia-water solution with the mixed surfactants of sodium dodecyl benzene sulfonate （SDBS） and cetyl trimethyl ammonium bromide （CTAB） is prepared. A series of experiments is performed to investigate the stability of the prepared nanofluid with different contents and proportions of surfactants, different durations of ultrasonic wave vibration and different durations of illumination. The optimal dispersion conditions are 1.5% SDBS, 0. 015% CTAB（mass fraction）, 30 min of ultrasonic vibration and over 72 h of illumination. Finally, based on double electrode layer theory, the influences of the content of the surfactants on the stability of nanofluid are analyzed. The existence of the optimal surfactant content is proved, which is in accordance with the experimental results.

water460 MW燃气-蒸汽联合循环机组SCR脱硝氨水稀释系统的优化改造

广东惠州LNG电厂二期扩建热电联产工程为3×460 MW燃气蒸汽联合循环机组,机组配套烟气脱硝装置,调试投产后,4号、5号机先后出现脱硝氨水倒流进入机组水汽系统,导致炉内水汽品质劣化的事件,给机组运行和对外供汽带来了安全、环保和社会效益风险。文章对脱硝系统运行方式和氨水稀释用水水源进行了优化改造,以提高二期机组脱硝系统和水汽系统运行的稳定性和可靠性。

Performance Evaluation of Heat Exchangers in OTEC Using Ammonia/Water Mixture as Working Fluid

The ocean thermal energy conversion (OTEC) system is a promising solution to provide stable electricity supply. Although the available temperature difference in OTEC systems is small, an ammonia/water mixture as working fluid is expected to decrease irreversible losses in the heat exchangers and to improve system performance. However, in actual heat exchangers, an adequate temperature crossing does not occur in the condenser but in the evaporator. Therefore, clarification of this characteristic is important. To date, the logarithmic temperature difference (LMTD) method is used in performance evaluations of OTEC heat exchangers. This method is of limited use if physical properties of fluids vary. A generalized mean temperature difference (GMTD) method is introduced to perform this evaluation. As changes in fluid property values can be considered in the GMTD method, method dependencies on heat exchanger characteristics, effectiveness, and system characteristics can be studied. In particular, GMTD and LMTD using a pure substance were found to be almost equal. Mean temperature differences using mixtures as working fluid were higher in the evaporator, but lower in the condenser, from the GMTD method than from the LMTD method. For higher ammonia concentrations in ammonia/water mixtures, the mean temperature differences from both methods are different.

Thermodynamic and Experimental Analysis of an Ammonia-Water Absorption Chiller

A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.

Irrigation water salinity and N fertilization:Effects on ammonia oxidizer abundance, enzyme activity and cotton growth in a drip irrigated cotton field

Use of saline water in irrigated agriculture has become an important means for alleviating water scarcity in arid and semi-arid regions. The objective of this field experiment was to evaluate the effects of irrigation water salinity and N fertilization on soil physicochemical and biological properties related to nitrification and denitrification. A 3×2 factorial design was used with three levels of irrigation water salinity（0.35, 4.61 and 8.04 d S m-1） and two N rates（0 and 360 kg N ha^（-1））. The results indicated that irrigation water salinity and N fertilization had significant effects on many soil physicochemical properties including water content, salinity, p H, NH_4-N concentration, and NO_3-N concentration. The abundance（i.e., gene copy number） of ammonia-oxidizing archaea（AOA） was greater than that of ammonia-oxidizing bacteria（AOB） in all treatments. Irrigation water salinity had no significant effect on the abundance of AOA or AOB in unfertilized plots. However, saline irrigation water（i.e., the 4.61 and 8.04 d S m-1 treatments） reduced AOA abundance, AOB abundance and potential nitrification rate in N fertilized plots. Regardless of N application rate, saline irrigation water increased urease activity but reduced the activities of both nitrate reductase and nitrite reductase. Irrigation with saline irrigation water significantly reduced cotton biomass, N uptake and yield. Nitrogen application exacerbated the negative effect of saline water. These results suggest that brackish water and saline water irrigation could significantly reduce both the abundance of ammonia oxidizers and potential nitrification rates. The AOA may play a more important role than AOB in nitrification in desert soil.

Computer study of the formation of water-ammonia clusters and their dielectric properties

The absorption of one to six ammonia molecules by the （H2O）50 cluster is studied by the molecular dynamics method under near-atmospheric conditions. The capture of NH 3 molecules by a water cluster produces an increase in the integrated intensity of IR absorbance, substantially decreases emission power in the frequency range of 0≤ω≤3500cm-1,and transforms a continuous reflectance spectrum into a banded one. Adsorption of ammonia molecules by water clusters greatly diminishes the number of electrons that are active with respect to electromagnetic radiation. The present results are also compared with the experimental findings wherever available.

Computer Simulation of an Ammonia-Water Absorption Cycle for Refrigeration: Using a Distillation Tower to Replace the Generator

By using a distillation tower as the regenerator, the coefficient of performance (COP) of the ammonia-water absorption refrigeration cycle is calculated in this work. Two types of distillation towers, namely an equilibrium-stage tower with a total condenser and a packed-bed tower with a partial condenser, are used in the cycle. From the simulation results, it is found that both types of distillation towers can successfully increase the COP of the cycle due to increased ammonia concentration in the vapor phase of the ammonia-water refrigerant. It was also found that the tower equipped with a partial condenser provides higher COP than that of the tower equipped with a total condenser. The value of COP can be further increased when the generator is replaced by the packed-bed tower in this water-ammonia absorption cycle. The effects of the mass flow rate ratio of NH3/H2O, stage number, reflux ratio and energy duty of the tower on the COP of the cycle are also studied in the present paper.

Simultaneous removal of ammonia and N-nitrosamine precursors from high ammonia water by zeolite and powdered activated carbon

When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products（DBPs） may form. If N-nitrosamine precursors are present, highly toxic N-nitrosamines, primarily N-nitrosodimethylamine（NDMA）, may also form. Removing their precursors before disinfection should be a more effective way to minimize these DBPs formation. In this study, zeolites and activated carbon were examined for ammonia and N-nitrosamine precursor removal when incorporated into drinking water treatment processes.The test results indicate that Mordenite zeolite can remove ammonia and five of seven N-nitrosamine precursors efficiently by single step adsorption test. The practical applicability was evaluated by simulation of typical drinking water treatment processes using six-gang stirring system. The Mordenite zeolite was applied at the steps of lime softening, alum coagulation, and alum coagulation with powdered activated carbon（PAC） sorption. While the lime softening process resulted in poor zeolite performance, alum coagulation did not impact ammonia and N-nitrosamine precursor removal. During alum coagulation, more than67% ammonia and 70%–100% N-nitrosamine precursors were removed by Mordenite zeolite（except 3-（dimethylaminomethyl）indole（DMAI） and 4-dimethylaminoantipyrine（DMAP））. PAC effectively removed DMAI and DMAP when added during alum coagulation. A combination of the zeolite and PAC selected efficiently removed ammonia and all tested seven N-nitrosamine precursors（dimethylamine（DMA）, ethylmethylamine（EMA）, diethylamine（DEA）, dipropylamine（DPA）, trimethylamine（TMA）, DMAP, and DMAI） during the alum coagulation process.

Magnetic Field Enhancement in Ammonia-Water Absorption Refrigeration Systems

Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively.

Analysis of Ammonia Nitrogen Content in Water Based on Weighted Least Squares Support Vector Machine (WLSSVM) Algorithm

Determination of ammonia nitrogen content in water is the basic item of the environmental water pollution, and is the key index to evaluate the water quality. This article designs a water quality monitoring system based on the on-line automatic ammonia nitrogen monitoring system, and establishes a forecasting model based on the weighted least squares support vector machine algorithm. The weighted least squares support vector machine algorithm increases the weight parameter setting, improves the speed and accuracy of prediction learning, and improves the robustness. In this article, a comparison between neural network model and weighted least square support vector machine model is made, which shows that the weighted least squares support vector machine model has better prediction accuracy.

Removal of Ammonia from Drinking Water by Clinoptilolite

The removal of ammonia of low concentration from driking water by clinoptilolite is studied with such factors as particle size and amount of clinoptilolite, inihal concentration of ammonia and sodium, pH in influent, attrition looses and regeneration. Langmuir and Freundrich ion exchange isotherms are used to represent experimental isotherm data and experimental results indicate that clinoptilolite is an attractive and promising agent for removal of ammonia of low concentration from drinking water, and the ion exchange process is suitable for Freundlich isotherm.

Effect of Water Ammonia Nitrogen Concentration on Survival of Mosquitofish Gambusia affinis

In this study, the relationship of the growth of invasion fish with water eutrophication processes was explored in Yangtze estuary, China. High water ammonia nitrogen concentration produced high effects on the growth and survival of mosquitofish Gambusia affinis. When the ammonia nitrogen was higher than 51.75 mg/l, the fish death rate obviously increased with days, and at the 4th day fish presented the highest mortality, while 23.72 mg/l ammonia nitrogen conditions have been able to ensure fish survival for two days in experiment treatment. Therefore, ammonia nitrogen of Grade V polluted water (national water quality criteria) is just 3 mg/l, and the water can be enough to support fish normal survival. Our results suggest mosquitofish was a suitable pioneer species for restoring polluted water ecology and purify water.

Ion Selective Electrode Determination of Ammonia Nitrogen in Passaic River Waste Water in New Jersey Essex County Area

The percent ammonia nitrogen was determined in Passaic River waste water using Ion-Selective Electrode EPA Method 350.3. The intelligent ammonia sensor integrates ammonia electrode, pH electrode and Ammonia Ion electrode together to realize the in situ detection of ammonia. The test results have shown that the sensor is easy operation, low cost and no pollution. The ammonia is determined potentiometrically using an ammonia ion selective electrode and a pH/mV meter, having an expanded millivolt scale. The ammonia selective electrode uses a hydrophobic gas-permeable membrane to separate the sample solution from an electrode internal solution of ammonium chloride. Dissolved ammonia is converted to NH3 gas by raising the pH to above 11.0 with a strong base. NH3 gas diffuses the membrane and changes the internal solution pH that is sensed by the electrode. In single laboratory test results have been found 1.001 NH3-/L and 0.897 mg NH3-N/L, recoveries were 77.3% and 83.1%, respectively.

热泵精馏耦合吸收处理含盐氨水

针对含盐氨水的回收与处理,利用蒸发除盐、精馏脱氨并耦合吸收制备一定浓度的氨水。采用一系列节能技术对蒸发和精馏进行计算优化,即双效蒸发与塔顶蒸汽直接压缩热泵精馏耦合吸收工艺(SchemeⅠ)、热泵蒸发与塔顶蒸汽直接压缩热泵精馏耦合吸收工艺(SchemeⅡ)和热泵蒸发与塔底闪蒸再压缩热泵精馏耦合吸收工艺(SchemeⅢ)。选用ELECNRTL电解质模型计算物系的热力学数据和相平衡数据,并以年总费用、综合能耗和热力学效率等作为工艺评价指标,对提出的以上3种处理工艺进行模拟与优化。研究结果表明,与SchemeⅠ相比,SchemeⅡ和SchemeⅢ可分别节省年总费用22.18%和31.66%;节约能耗47.56%和57.87%;而热力学效率则分别提高了8.59%和2.28%。显然,SchemeⅢ在年总费用与能耗方面更具优势,SchemeⅡ在热力学效率方面更具优势。

氨型碱性水化学对690TT腐蚀特性的影响

为探索氨型碱性水化学对传热管材料690TT腐蚀行为的影响,开展传热管材料690TT合金在B-Li-NH_4OH和NH_4OH两种水质下的腐蚀特性研究,分析690TT腐蚀产物释放特性,综合评价氨型碱性水质对690TT腐蚀特性的影响。研究结果表明,690TT材料与两种氨型碱性水质均具有较好的相容性。690TT在两种水质中均形成了致密的氧化膜,氧化膜由NiFe_(2)O_(4)尖晶石氧化物和少量的铁氧化物Fe_(2)O_(3)组成,相对而言690TT在NH_(4)OH型水质条件下的总腐蚀失重量、总腐蚀产物释放量略低于在B-Li-NH_(4)OH水质下,但690TT向水质释放的Ni元素总量与上述规律相反,这可能与Ni元素和氨形成络合物[Ni(NH_(3))_(m)]^(2+)有关,Ni元素释放量增加对反应堆一回路辐照场控制有不利影响。本研究结果可为氨型碱性水化学技术的设计和应用提供数据支撑。

气化装置外排废水氨氮高分析与处理

气化装置外排灰水中氨氮含量较高会造成水处理装置SBR活性污泥失活,造成分公司水处理装置处理气化废水难度增加,为了实现水处理装置长周期平稳运行,气化装置外排灰水量需要降低。从而加剧气化系统水的恶性循环,水质逐渐变差,最终影响气化装置的长周期平稳运行。文章通过分析外排废水中氨氮高的形成原因,针对性的进行生产优化调整,减少外排废水氨氮含量,保障装置平稳运行。

鄱阳湖季节性氨氮水生生物生态风险评估

基于生态环境部颁布的《淡水水生生物水质基准—氨氮》提供的有限离散基准值,对鄱阳湖内6个测站在2018年的氨氮水生生物生态风险(RQ)进行量化评估,进一步讨论了水温和pH值对氨氮水生生物毒性的影响,提出了一种《淡水水生生物水质基准—氨氮》的运用思路,对鄱阳湖地区氨氮的治理提供了数据支撑和经验借鉴。结果表明:氨氮平均浓度最高出现在冬季,平均浓度最低出现在秋季;鄱阳湖夏季的短期水生生物水质基准(SWQC)和长期水生生物水质基准(LWQC)最低,春季的SWQC和LWQC最高;鄱阳湖夏季的长期水生生物生态风险LRQ>1,表明在夏季鄱阳湖的氨氮长期水生生物生态风险超过环境容许值;鄱阳湖夏季存在因水温和pH值的升高导致SWQC和LWQC降低,进而引发水生生物生态风险提高的问题。加强对鄱阳湖的pH值监控和预警应作为水资源管理的重点。

系统中水含量对锂介导合成氨的性能影响

针对锂介导合成氨(LM-NRR)过程中存在的水污染问题,通过对比实验及扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)等表征手段,探讨了含水量对LM-NRR体系的性能影响及其在反应界面中的作用机理。结果表明,无水条件下的LM-NRR体系具有较好的氨合成性能,在反应时间为120 min、N2流速为4 m L·min^(-1)、电流密度为3 m A·cm^(-2)条件下的氨合成速率可达0.0124μg·s^(-1)·cm^(-2),法拉第效率为7.05%。含水量对LM-NRR体系的影响显著,会极大地降低体系的氨合成速率及法拉第效率。这主要是由于反应界面上的水会加剧竞争性析氢反应(HER)、促进电解质中Li BF_(4)的水解以及钝化表面活性锂位点,进而降低了体系的氨反应活性。