Synergistic Treatment of Low-concentration Organic Waste Gas by Micro-nano Bubble Coordinated with Peroxymonosulfate

Continuous dynamic experiment was conducted for the treatment of low-concentration organic waste gas with xylene as a representative, using micro-nano bubble and peroxymonosulfate working in synergy. The degradation rule of xylene under different conditions such as the ORP value of the spray liquid, pH value of the spray liquid, liquid-gas ratio of the spray liquid, residence time of xylene, and initial concentration of xylene was investigated. The results showed that at a low concentration, the pH value of the spray liquid had little effect on the degradation rate of xylene. The degradation rate of xylene rose with the increase of the ORP value of the spray liquid, the liquid-gas ratio of the spray liquid, the residence time of xylene, and the initial concentration of xylene.

Adhesion forces for water/oil droplet and bubble on coking coal surfaces with different roughness

Surface roughness plays a significant role in floatability of coal.In the present paper,coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements.The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness.The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning.Maximum adhesion forces between water and surfaces were 111.70,125.48,and 136.42μN when the roughness was 0.23,0.98,and 2.79 μm,respectively.In contrast,under a liquid environment,the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water.Maximum adhesion forces of increasing roughness were 97.14,42.76,and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48,145.84,and 121.02 lN between oil droplet and surfaces,respectively.Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.

Numerical simulation of bubble chaotic motion in a cavitating water jet

A computational fluid dynamics (CFD) method is developed to investigate the radical motion of single cavitating bubble in the oscillating pressure field of a cavitating water jet. Regarding water as a compressible fluid, the simulation is performed at different oscillating frequencies. It is found that the bubble motion presents obvious nonlinear feature, and bifurcation and chaos appear on some conditions. The results manifest the indetermination of the cavitating bubble motion in the oscillating pressure field of the cavitating water jet.

Experimental assessment of two-phase bubble pump for solar water heating

The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat could be transferred downward from the collector to a hot water storage tank.The designed system consists of two sets of heat-pipe evacuated tube collectors,a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level.Discharge heads of 1 and 5 m were tested.The bubble pump could operate at the collector temperature of about 90-100 ℃ and vapor gage pressure of 80-90 kPa.It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head.Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly,daily and long-term performance tests.The thermal performance of the proposed system is compared with conventional solar water heaters.The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account.And the former is a zero carbon system.

Observation and theoretic analysis of gas-bubble formation and growth in water-model

The behavior of bubbles is observed with high-speed digital camera in water-model. It is found that each bubble has three processes: bubble formation, bubble coalescence and bubble division. Bubble shape is spherical firstly, then elliptical and spherical crown after coalescence, and spherical again after division. These phenomena are explained theoretically. And the bubble size is defined newly. The so-defined bubble size is measured through digital camera and LECO graphical analyzer. And the measured results are compared with those in literatures.

A novel multi-channel porous structure facilitating mass transport towards highly efficient alkaline water electrolysis

An advantageous porous architecture of electrodes is pivotal in significantly enhancing alkaline water electrolysis(AWE)efficiency by optimizing the mass transport mechanisms.This effect becomes even more pronounced when aiming to achieve elevated current densities.Herein,we employed a rapid and scalable laser texturing process to craft novel multi-channel porous electrodes.Particularly,the obtained electrodes exhibit the lowest Tafel slope of 79 mV dec^(-1)(HER)and 49 mV dec^(-1)(OER).As anticipated,the alkaline electrolyzer(AEL)cell incorporating multi-channel porous electrodes(NP-LT30)exhibited a remarkable improvement in cell efficiency,with voltage drops(from 2.28 to 1.97 V)exceeding 300 mV under 1 A cm^(-1),compared to conventional perforated Ni plate electrodes.This enhancement mainly stemmed from the employed multi-channel porous structure,facilitating mass transport and bubble dynamics through an innovative convection mode,surpassing the traditional convection mode.Furthermore,the NP-LT30-based AEL cell demonstrated exceptional durability for 300 h under 1.0 A cm^(-2).This study underscores the capability of the novel multi-channel porous electrodes to expedite mass transport in practical AWE applications.

Numerical Modelling and Simulation of Chemical Reactions in a Nano-Pulse Discharged Bubble for Water Treatment

A zero-dimensional model to simulate a nano-pulse-discharged bubble in water was developed. The model consists of gas and liquid phases corresponding to the inside and outside of the bubble, respectively. The diffusions of chemical species from the gas to the liquid phase through the bubble interface was also investigated. The initial gas is Ar, but includes a little H20 and 02 in the bubble. The time evolution of the OH concentration in the liquid phase was mainly investigated as an important species for water treatment. It was shown that OH was generated in the bubble and then diffused into the liquid. With the application of a continuous nano-pulse discharge, more OH radicals were generated as the frequency increased at a low voltage for a given power consumption.

Effect of supercritical water shell on cavitation bubble dynamics

Based on reported experimental data, a new model for single cavitation bubble dynamics is proposed considering a supercritical water （SCW） shell surrounding the bubble. Theoretical investigations show that the SCW shell apparently slows down the oscillation of the bubble and cools the gas temperature inside the collapsing bubble. Furthermore, the model is simplified to a Rayleigh-Plesset-like equation for a thin SCW shell. The dependence of the bubble dynamics on the thickness and density of the SCW shell is studied. The results show the bubble dynamics depends on the thickness but is insensitive to the density of the SCW shell. The thicker the SCW shell is, the smaller are the wall velocity and the gas temperature in the bubble. In the authors＇ opinion, the SCW shell works as a buffering agent. In collapsing, it is compressed to absorb a good deal of the work transformed into the bubble internal energy during bubble collapse so that it weakens the bubble oscillations.

Effect of bubbles addition on teetered bed separation

To improve the separation efficiency of a conventional Teetered Bed Separator(TBS) in beneficiation of fine coal with a wide size range,an Aeration TBS(A-TBS) was proposed in this investigation.The bubbles were introduced to A-TBS by a self-priming micro-bubble generator.This study theoretically analyzed the effect of bubbles on the difference in hindered settling terminal velocity between different density particles,investigated the impact of superficial water velocity(V_(SW)) and superficial gas velocity(V_(Sg)) on bed fluidization,and compared the performance of the TBS and A-TBS in treating 1-0.25 mm size fraction particles.The results show that the expansion degree of fluidized bed which was formed by different size particles or has different initial height,is increased by the introduction of bubbles.Compared with the TBS,at the same level of clean coal ash content,the A-TBS shows an increase in the combustible recovery of clean coal,ash content of tailings,and practical separation density by 5.26%,6.56%,and 0.088 g/cm3 respectively,while it shows a decrease in the probable error(E_p) and V_(SW) by 0.031 and 3.51 mm/s,respectively.The addition of bubbles at a proper amount not only improves the separation performance of TBS,but also reduces the upward water velocity.

Dispersive bubble wall—a new method of flow control in tundish

Tundish is the last refractory vessel in the steelmaking process. The fluid flow phenomena in tundish have a strong influence on the separation of non-metallic inclusions. The dispersive bubble wall （DBW） is a new method in tundish metallurgy. A water model of a multi-strand tundish has been set up based on the Froude number and Reynold number similarity criteria. The effect of DBW＋weir on the flow pattern has been studied. The results show that this new structure of DBW＋weir is beneficial not only to uniform the temperature among different submerge entry nozzles but also to separate non-metallic inclusions from liquid steel. The DBW can capture the particles of non-metallic inclusions and make them float up to the surface.

Flow Properties of Ultra-Fine Bubble Mixtures Passing through Micro-Apertures

The flow properties of fine bubble mixture flows are investigated and reported. Few previous studies have focused on ultra-fine bubble (UFB) mixtures, which contain sub-micrometer sized bubbles. In this study, UFB mixtures of water and glycerol solution are passed through micro-sized slits and capillaries, and the resultant pressure drops are evaluated in comparison with those for water and aqueous glycerol alone. The experimentally measured pressure drop for slits (≤51 μm) and capillaries (≤81 μm) is less for UFB mixtures than for water and aqueous glycerol alone. This phenomenon is considered in terms of interface behavior and attributed to the electric interaction between an electric double layer and the UFBs. Furthermore, numerical observation for slip wall conditions is conducted, and the results for UFB mixtures agree with the predicted values for slip wall conditions.

Liquid mean velocity and turbulence in a horizontal air-water bubbly flow

The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes oriented in different planes, and local liquid-phase velocities and turbulent stresses were simultaneously obtained. Systematic measurements were conducted covering a range of local void fraction from 0 to 11.7%. The important experiment results and parametric trends are summarized and discussed.

气水两相下降流中泡状流与段塞流转换边界研究

针对塔河油田气水混注驱替“阁楼油”过程中泡状流与段塞流转换边界不清的问题,利用数值模拟方法对气水两相下降流中泡状流与段塞流进行了模拟分析。结果表明:在气相表观流速为0.01~1.00 m/s、液相表观流速为0.03~2.00 m/s、管径为76 mm的模拟条件下,管道中主要为泡状流和段塞流;与模拟结果相比,Barnea、Kokal、薛玉卿模型预测的转换边界偏小,Bhagwat和Yijun模型预测的转换边界偏大;随着气相表观流速增加,泡状流向段塞流转换时所需液量逐渐增大;在低液量条件下,越靠近管道中心,气泡数量越多,空隙率越大;随液量增加,单个小气泡体积减小,气泡在整个管道横截面上分布越均匀。基于漂移模型,考虑气泡群滑脱速度,建立了新的泡状流与段塞流转换边界模型,216组文献数据验证结果显示,新模型准确率为95.37%,准确度较高。建立的泡状流—段塞流转换边界模型,不仅可提高井筒压力、温度模型的计算精度,同时对塔河油田现场注入井井口参数优化、注入设备优选和提高“阁楼油”驱替效率有很好的理论指导意义。

Effect of Micro-electrolysis and Micro-nano Bubbles Coupled with Peroxymonosulfate Treatment of Rural Domestic Sewage

With the continuous deepening of rural revitalization strategy and the increasingly strict sewage discharge standards,rural domestic sewage treatment technology is facing higher challenges and requirements.The combined process of micro-electrolysis+micro-nano bubbles coupled with peroxymonosulfate was constructed in this study,and the treatment effect and application value of this technology were explored with the actual rural domestic sewage as the treatment object.The experimental results showed that under the conditions of HRT of 120 min,PMS dosage of 0.15 mmol/L,pH=7,MBs air intake of 15 ml/min,current intensity of 15 A,and Fe/C mass ratio of 1:1,the removal rates of COD,ammonia nitrogen and total phosphorus can reach 88.55%,77.18%and 74.67%,respectively.Under the condition that the pH value of sewage was not adjusted,the non-biochemical simultaneous decarbonization,denitrification and phosphorus removal of rural domestic sewage can be achieved by micro-electrolysis and micro-nano bubbles coupled with peroxymonosulfate.The concentrations of effluent COD,ammonia nitrogen and total phosphorus met the requirements of the first level standard of the Discharge Standard of Water Pollutants for Rural Domestic Sewage Treatment Facilities(DB45T2413-2021).And the comprehensive operating cost was about 1.15 yuan/m 3.

面向大电流密度电解水的碳基催化剂研究进展

电解水体系可以在温和条件下制备氢气。得益于高比表面积、高电子传输性和原料丰富等优点,碳基电催化剂备受关注。商业用电解水装置需要在较低过电位下实现较大交换电流,进而实现氢气的持续快速生产。然而当前实验室研究的重心大多放在小电流服役工况,对于大电流工况下的系列问题关注较少。研究表明,电解水体系在不同电流密度下表现出的问题差异较大,其影响因素包括气泡、电催化剂局域微环境和电极稳定性等。本综述,首先对碳基电解水催化剂的发展现状进行了总结,大电流模式下暴露出的问题与挑战进行了讨论,并提出可能有效的解决方法,以实现能满足大电流密度要求的高活性高稳定性碳基电催化剂的研发。

电解水过程中微电极制备研究进展

电解水过程中产生的气泡会影响电解槽的稳定运行,了解气泡的成核、生长和脱离的规律是对气泡进行有效管理的前提。气泡生长是一个通过相界面的传质过程,从单气泡尺度模拟其演化行为,可以帮助深入理解电极表面气液传质过程,以及气泡的生成对局部流场和浓度场的影响关系,从而实现控制电解槽稳定运行、降低能耗以及提高电流效率等目的。实现单气泡生长行为的可视化,微电极的制备是必不可少的,微电极能够稳定且呈周期性的产生单个气泡。目前制备微电极的方法主要为铂丝嵌入环氧树脂法、光刻和电化学共沉积法、纳米盘电极法和印刷电路板法等,本文对这几种微电极制备方法的研究现状进行了阐述分析,不同学者制备微电极的实验结论存在差异,需要实验进行验证;目前微电极制备技术仍然无法对气泡的成核阶段进行可视化研究。未来,研究在电化学控制下气泡成核过程的可视化,并使用更快的电化学仪器来研究气泡的成核动力学将是重点。

质子束水量热计中量热芯的超纯水制备与预辐照

针对质子束的水吸收剂量绝对测量中化学热缺陷的修正问题,本研究基于热敏电阻研制水量热计,并进行气体饱和超纯水系统的设计。通过向量热芯内的超纯水充入高纯气体形成饱和状态,最大程度减少辐射化学反应的产额。在量热芯封装后通过预辐照,使量热芯超纯水中O2充分发生辐解反应,使量热芯内水环境达到无热损的稳定状态,成功研制了稳定的零热损水量热计,减少了量热芯热损对水吸收剂量绝对测量结果的影响,可为后续水吸收剂量的绝对测量提供技术支持。

受限空间内水下爆轰燃气射流发展特性

为探索脉冲爆轰水冲压发动机水下工作时导水器内燃气射流发展特性,利用可燃气体的爆轰在水下受限空间内产生脉动气泡,对爆轰管在圆筒形受限空间内的水下爆轰燃气射流进行了数值仿真与实验验证。基于雷诺时均基本方程组与k-ε两方程模型耦合流体体积气液界面追踪方法的相输运方程建立受限空间中水下单次燃气射流流场流动模型,使用OpenFOAM中的Compressible Inter Foam求解器对受限空间中脉冲爆轰燃气射流进行数值求解。结果表明:受限空间对水下爆轰的前导激波的影响较小,前导激波幅值与自由空间相比变化不大,由爆轰燃气射流所引起的压力扰动大幅升高且持续时间明显增加,受限空间中各处压力显著高于受限空间之外;受限空间中燃气泡的脉动周期延长至60 ms左右,然而受限空间径向尺寸对燃气泡的脉动周期影响较小。可见,受限空间可提高水下爆轰管出口近场压力并延长燃气射流作用时间,研究结果对脉冲爆轰水冲压发动机推力性能提升方法研究具有重要指导作用。

大兴安岭多年冻土区两种水体温室气体浓度动态与冬季储存特征

北方内陆水体是温室气体排放的热点,对量化区域碳收支起重要作用,但其排放的季节变化尚不清楚。观测了大兴安岭多年冻土区府库奇河及其改道形成的牛轭湖(演替晚期)冻结期冰层中储存的二氧化碳(CO_(2))和甲烷(CH_(4))浓度,并比较了两种水体中CO_(2)和CH_(4)浓度在三个不同时期(冻结期、非冻结期、春季融化)的差异。结果表明:两种水体CO_(2)和CH_(4)浓度季节变化存在差异。牛轭湖在冻结期水体中CO_(2)和CH_(4)浓度最高,有明显的冰下积累现象,其中CH_(4)浓度平均值为(2.21±0.54)μmo/L,分别是非冻结期和春季融化期水体CH_(4)浓度的5倍和14倍。河流水体中CO_(2)和CH_(4)浓度最高出现在春季融化期,显著高于非冻结期和冻结期(P<0.05)。水中CO_(2)和CH_(4)浓度受多种环境因子的影响,与可溶性有机碳(DOC)正相关(P<0.05),与溶解氧(DO)、水温为负相关(P<0.05)。冻结期冰层形成后,温室气体会以冰气泡的形式存储在冰层中,气泡的主要成分是CO_(2)和CH_(4),其中CO_(2)占90%以上。由于冰气泡中CO_(2)和CH_(4)浓度约为冰下水体浓度的1%—30%,忽略冰层中储存的温室气体将会增加北方水体碳排放的不确定性。研究明确了大兴安岭多年冻土区两种水体溶解性CO_(2)和CH_(4)的季节变化特征与冬季温室气体储存能力,为深入认知该区域水体碳循环过程提供重要数据支持。