Effect of Nonsteady state H2O2 Tests on Oxygen Transfer Rate in Enhanced Biological Phosphorus Removal Process

A laboratory scale enhanced biological phosphorus removal process was operated in the University of Cape Town configuration to study the variations in alpha and oxygen transfer efficiency (OTEf) under different process conditions. As part of this investigation, process oxygen transfer parameters were determined using the steady state oxygen uptake rate (OUR) and the nonsteady state hydrogen peroxide addition (HPA) methods, as per the American Society of Civil Engineers guidelines. The results indicated that the oxygen transfer parameters [volumetric mass transfer coefficient (KLaf), oxygen transfer rate (OTRf), α and OTEf)] were higher when both methods were applied on the same day, compared to the subsequent period, when only the steady state OUR method was employed, under similar operating conditions. The difference in the oxygen transfer parameters appears to be due to the addition of H2O2 that generates reactive oxygen species in the nonsteady state HPA test. Based on the findings, it was concluded that the HPA test was not a suitable technique to measure oxygen transfer under process conditions. Further, a conceptual model hypothesizing the impacts of H2O2 addition on activated sludge process is presented.     

Atmospheric Oxygen Transfer During In Situ Oxygen Uptake Rate Measurements

In situ apparent oxygen uptake rate (OUR) measurements of laboratory bioreactors open to atmospheric air are practical and useful, but atmospheric oxygen transfer into the reactor may significantly underestimate the actual values of OUR. The effects of the atmospheric oxygen transfer were quantitatively assessed using an oxygen mass transfer model. A factor Ψ representing the degree of underestimation of actual OUR by the in situ apparent OUR (OURa) technique was introduced. The Ψ factor for the primary settling tank effluent of a local water pollution control plant was found to be unity in the beginning of reaction period when the microbial activity was high (OURa = 27 mg/L?h), but decreased to 76% at the end of reaction period when the microbial reaction rate was low (OURa = 2 mg/L?h).     

Oxygen Transfer Model for a Flow-Through Hollow-Fiber Membrane Biofilm Reactor

A mechanistic oxygen transfer model was developed and applied to a flow-through hollow-fiber membrane-aerated biofilm reactor. Model results are compared to conventional clean water test results as well as performance data obtained when an actively nitrifying biofilm was present on the fibers. With the biofilm present, oxygen transfer efficiencies between 30 and 55% were calculated from the measured data including the outlet gas oxygen concentration, ammonia consumption stoichiometry, and oxidized nitrogen production stoichiometry, all of which were in reasonable agreement. The mechanistic model overpredicted the oxygen transfer by a factor of 1.3 relative to the result calculated from the outlet gas oxygen concentration, which was considered the most accurate of the measured benchmarks. A mass transfer coefficient derived from the clean water testing with oxygen sensors at the membrane-liquid interface was the most accurate of the predictive models (overpredicted by a factor of 1.1) while a coefficient determined by measuring bulk liquid dissolved oxygen underpredicted the oxygen transfer by a factor of 3. The mechanistic model was found to be an adequate tool for design because it used the published diffusion and partition coefficients rather than requiring small-scale testing to determine the system-specific mass transfer coefficients.     

气体保护电渣重熔过程氧传递的动力学研究

基于渗透理论建立了气体保护电渣重熔过程渣-钢间氧传递的动力学模型,并在50 kg电渣炉进行模具钢S136(/%:0.39C、0.26Si、0.43Mn、0.020P、0.018S、13.37Cr、0.21Mo、0.34V)的重熔实验,得出渣中FeO含量-0～2.0%(FeO),电极端部钢液中原始氧含量-0～0.010 0%[O],自耗电极半径-40～300 mm和重熔速率-(0.5～5.0)×10^-6 m³/s对熔渣和钢液间传氧速率的影响。结果表明,熔渣中FeO含量-(FeO)存在一个临界值,(FeO)小于此临界值时,氧的传递过程为电极端部钢液向渣中传递;反之,氧的传递过程为渣中FeO向电极端部钢液内传递。随自耗电极半径的增加,钢-渣间传氧速率减小;随着重熔速率和钢液中原始氧含量增加,钢-渣间传氧速率增加。     

基于深度学习的人体低氧状态识别

通过低氧实验提出一种快速识别人体低氧状态的方法.通过搭建深层神经网络训练实验数据识别氧气体积分数(16%~21%)与人体可耐受极端低氧气体积分数(15.5%~16%)条件下光电容积脉搏波(photoplethysmography, PPG)信号, 获得人体生理状态的模式识别网络.经测试该网络的识别正确率可达92.8%.利用混淆矩阵及接受者操作性能(receiver operating characteristic, ROC)曲线分析, 混淆矩阵的训练集、验证集、测试集、全集识别正确率分别达到97.9%、94.8%、92.8%和96.3%, AUC (area under curve)值接近1, 认为该网络分类性能优良, 并且可在4 s内完成整个识别过程.      

Cold Simulation of Oxygen Transfer Rate in BOF

 By measuring the mass transfer coefficient of between water and oil, the oxygen transfer rate of bath in the BOF smelting process is researched, and the influence of top and bottom blowing gas flow rate on the mechanism of mass transfer between metal and slag is discussed. The results show that when the bottom blowing gas flow rate increases on the conditions of top blowing, the mass transfer rate evidently increases, and the influence ratio of top blowing on the mass transfer is 10 percent of bottom blowing; The relation among top gas flow rate, bottom gas flow rate and lance height are established by the stirring power density. The equation between the mass transfer coefficient between metal and slag is formed, which furnishes reference for optimizing process parameters of BOF. The relation between the emulsification ratio between water and oil and the bottom blowing gas flow rate on the condition of top and bottom blowing is obtained. The result shows that with the increase of the bottom blowing gas flow rate the emulsification ratio increases in linearity, which increases the mass transfer rate of benzoic acid between water and oil.     

基于Excel的稳态传热计算

根据稳态下多层炉衬传热原理,采用Excel进行辅助计算,建立各种耐火材料的热传导系数数据表.计算时输入热面温度及各层炉衬厚度,便可快速、准确地计算出相应的传热参数.     

Dynamic Oxygen Storage Capacity Measurements on Ceria-Based Material

The constant increase in the number of environ-mental protection regulations worldwide has broughtabout significant restrictions onthe nature and quantityof exhaust gases originating from mobile sources suchas automobile emissions .These increasingly dema…     

高富氧喷煤对高炉冶炼影响的分析

 通过分析高富氧喷煤后焦炭在高炉中的作用及炉内冶炼参数的变化,在富氧、喷煤、风温、装料制度、上下部调剂等方面合理配合条件下,可提高煤粉燃烧率,维持较高的风口理论燃烧温度,减少炉腹煤气量,提高生产效率。高富氧喷煤达到焦比和煤比各占一半时,焦炭量能够满足直接还原和渗碳需求。为了满足焦炭骨架作用,需要使用反应性差和耐磨性好的焦炭。     

烟气循环烧结过程风氧平衡

 与普通烧结相比,烟气循环烧结工艺拥有节能减排和清洁生产的优势。为此,重点研究了烟气循环烧结过程风氧平衡规律,旨在保证烧结产质量指标的前提下,进一步提高烟气循环率,根据理论计算结合实测对烟气循环烧结过程风氧平衡进行了研究。研究结果表明：烧结机的中前部和尾部几个风箱的烟气具有低硫、氧含量高、温度较高的特点,可以作为循环烟气,与部分高温环冷废气均匀混合后,在保证烧结进风氧气体积分数18%以上的前提下,通过优化调节主抽风量、漏风率和烧结耗氧量等,可以实现烟气循环率达到43%,为烟气循环烧结工艺的发展提供了理论指导。     

CexZr1-xO2储氧材料制备方法研究进展

本文综述了共沉淀法、溶胶-凝胶法、水热法、高能球磨法等常用CexZr1-xO2储氧材料的合成方法,并进行了比较.阐述了CexZr1-xO2的基本改性机制,详述了稀土元素、碱土元素以及过渡金属对CexZr1-xO2的改性效果及原理.相关研究结果表明,CexZr1-xO2晶体结构、形貌、比表面积与其合成方法有很大关系,从而...     

Experimental Assessment of Bacterial Storage Yield

An experimental procedure was developed for the respirometric determination of bacterial storage yield as defined in the Activated Sludge Model No. 3. The proposed approach is based on the oxygen utilization rate (OUR) profile obtained from a batch test and correlates the area under the OUR curve to the amount of oxygen associated with substrate storage. Model simulation was used to evaluate the procedure for different initial experimental conditions. The procedure was tested on acetate. The same storage yield value of 0.76 gCOD/gCOD was calculated for two experiments, starting with different F/M ratios of 0.12 and 0.64 gCOD/g cellCOD.     

Nitrification in Pure Oxygen Activated Sludge Systems

Mixed liquor pH and temperature are two parameters that affect the growth rate of nitrifying bacteria and therefore the minimum solids retention time required to achieve nitrification. The objective of this study was to determine the consequence of low mixed liquor pH, and to determine if pH depression could be alleviated by recovering alkalinity through denitrification in a pure oxygen activated sludge system. The study was conducted at the University of Manitoba using laboratory scale, pure oxygen activated sludge reactors, fed with primary effluent. The results indicated that when denitrification was not included in the process, the concentration of CO2 in the headspace of the pure oxygen reactors increased to as high as 15% due to carbon oxidation and endogenous respiration. The high CO2 concentration in the headspace combined with low alkalinity caused by nitrification resulted in bulk mixed liquor pHs below 5.5. In order to maintain complete nitrification at a temperature of 24°C and a mixed liquor pH of 5.5, a solids retention time (SRT) of 12 days was required. In comparison, when denitrification was included in the process the pH of the mixed liquor was increased to 6.4 allowing for full nitrification at an SRT of 5.6 days at a temperature of 24°C. The increase in pH in the denitrification trains was attributed to three factors: recovery of alkalinity through the denitrification process, the conversion of influent carbon to CO2 in the anoxic reactor allowing the CO2 to escape to the atmosphere, and the recycle of mixed liquor super saturated with CO2 from the pure oxygen reactor to the anoxic reactor allowing the CO2 to escape to the open atmosphere. It was determined that the nitrifier growth rate at 12°C was approximately 50% of the rate measured at 24°C. At mixed liquor pHs between 6.0 and 6.3 at a temperature of 12°C, the specific nitrifier growth rate was between 0.12 and 0.15?d?1, while at 24°C, the specific nitrifier growth rate was between 0.25 and 0.30?d?1 at pHs ranging from 5.0 to 6.1     

80t顶底复合吹炼转炉的冶金效果

对比了包头钢铁（集团）公司炼钢厂80t顶底复合吹炼转炉和顶吹氧化转炉的冶金效果,结果表明,底吹气体对钢水的搅拌作远大于顶吹氧化。采用顶底复合吹炼工艺后,不仅钢水成分和温度更均匀,吹炼更平稳,而且钢水终点残余锰点含量提高。由于吹炼时间、氧化消耗量及炉渣中的FeO含量都有所降低,因此金属收得率提高,另外,通过适当提高炉渣碱度,该工艺还可取得较好的脱磷效果。     

氧气顶吹转炉脱磷工艺分析

对鞍钢100t氧气顶吹转炉进行了单渣法和双渣法脱磷过程分析,在脱磷反应热力学和动力学分析的基础上,进行了有针对性的试验。分析了工艺参数对脱磷反应的影响,总结出转炉出钢磷含量、脱磷率等与各主要工艺参数的定量关系,提出了优化顶吹转炉脱磷工艺的操作方法。     

常压富氧浸出在黄金氰化生产中的应用

针对某氰化厂金精矿,为进一步提高氰化浸出率,采用常压富氧浸出工艺,进行了小型、半工业、工业3种规模的试验研究。小型试验结果表明,富氧浸出工艺能提高金浸出率0.30%;半工业试验结果表明,采用富氧浸出工艺后,金浸出速度明显高于空气浸出工艺组。通过3个月工业试验结果表明,与现场空气浸出工艺组对比,富氧浸出工艺能明显提高浸出速度,提高金浸出率0.18%,浸渣中银品位降低5×10-6～6×10-6,年增加经济效益490.10万元,取得了良好经济技术指标,该研究成果为在黄金企业推广应用提供借鉴,推动了氰化浸出技术的发展。     

底吹炉氧枪喷口形式对气泡形态及混合状况的影响

针对4种不同的氧枪喷口结构进行了冷态试验研究，采用高速相机获得了不同喷口下的炉内气泡形态，采用电导率法测试了不同喷口下炉内流体的混合状况。试验结果表明，在相同的气体流量下，不同的气体喷口时炉内气泡的形态十分相似，当采用结构最复杂的喷口时，炉内的混合状态是最好的，结构最简单的喷口混合效果最差，其最小响应时间较最复杂喷口增加约11%，均混时间增加约4.7%。     

富氧底吹炼铜炉关键技术研究

对目前国内关于底吹熔炼炉的文献进行了总结,并对比了几种先进熔炼方法的技术特点,还对长径比、隔墙和氧枪等关键部位的设计进行了分析和讨论。结果表明,底吹熔炼炉在流动、传质、单位床能力和单位能耗等方面有着一定的优势。     

Transferring Characteristics of Momentum/Energy during Oxygen Jetting into the Molten Bath in BOFs: A Computational Exploration

This paper presents a numerical study of transferring characteristics of momentum/energy during oxygen jetting into the slag–metal molten bath in basic oxygen furnaces by a multi‐fluid volume of fluid model. The evolution of the momentum/energy and turbulence of jets along their axial travel were studied. The results were quantitatively compared within a wide range of oxygen supply pressures, at which the jets may be at under‐ or over‐expanding state. The efficiency of the momentum/energy transfer from the jets to the molten bath was also assessed with respect to lance height and operation pressure. The numerical results show that the momentum and kinetic energy for the jets suffering from shock waves likely cause more intensive damping compared to the jets with expansion waves. The turbulence kinetic energy and turbulence dissipation rate are observed to firstly increase and then decrease. This effect is more pronounced at a lower operation pressure. Based on these results, the optimum lance height was identified for a rapid slagging operation. It is also shown that the efficiency of the energy transfer from the jets to the molten bath is very low. Decreasing lance height or increasing operation pressure promotes the efficiency of the momentum transfer from the jets to the molten bath but lowers the efficiency of the kinetic energy transfer.