Quadrature Method of Moments for Nanoparticle Coagulation and Diffusion in the Planar Impinging Jet Flow

A computational model combining large .eddy simulation with quadrature moment method was em-ployed to study nanoparticle evolution in a confined impinging jet. The investigated particle size is limited in the transient regime, and the particle collision kernel was obtained by using the theory of flux matching. The simulation was validated by comparing it with the experimental results. The numerical results show coherent structure acts to dominate particle number intensity, size and polydispersity distributions, and it also induce particle-laden iet to be diluted by .the ambient.The evolution of particle dynarnics in.the impinging jet flow are strongly related to the Rey-nolds number and nozzle-to-plate distance, and their relationships were analyzed.

Nanoparticle Transport and Coagulation in Bends of Circular Cross Section via a New Moment Method

Transport of nanoparticles and coagulation is simulated with the combination of CFD in a circular bend. The Taylor-expansion moment method(TEMOM)is employed to study dynamics of nanoparticles with Brownian motion,based on the flow field from numerical simulation.A fully developed flow pattern in the present simulation is compared with previous numerical results for validating the model and computational code.It is found that for the simulated particulate flow system,the particle mass concentration,number concentration,particle polydispersity, mean particle diameter and geometric standard deviation over cross-section increase with time.The distribution of particle mass concentration at different time is independent of the initial particle size.More particles are concen-trated at outer edge of the bend.Coagulation plays more important role at initial stage than that in the subsequent period.The increase of Reynolds number and initial particle size leads to the increase of particle number concentration.The particle polydispersity,mean particle diameter and geometric standard deviation increase with decreasing Reynolds number and initial particle size.

Nanoparticle coagulation in a planar jet via moment method

Large eddy simulations of nanoparticle coagulation in an incompressible planar jet were performed. The particle is described using a moment method to approximate the particle general dynarnics equations. The time-averaged results based on 3000 time steps for every case were obtained to explore the influence of the Schmidt number and the Damkohler number on the nanoparticle dynamics. The results show that the changes of Schmidt number have the influence on the number concentration of nanoparticles only when the particle diameter is less than 1 nm for the fixed gas parameters. The number concentration of particles for small particles decreases more rapidly along the flow direction, and the nanoparticles with larger Schmidt number have a narrower distribution along the transverse direction. The smaller nanoparticles Coagulate and disperse easily, grow rapidly hence show a stronger polydispersity. The smaller coagulation time scale can enhance the particle collision and coagulation. Frequented collision and coagulation bring a great increase in particle size. The larger the Damkohler number is, the higher the particle polydispersity is.

Simulation of the Brownian coagulation of nanoparticles with initial bimodal size distribution via moment method

The Brownian coagulation of nanoparticles with initial bimodal size distribution, i.e., mode i and j, is numerically studied using the moment method. Evolutions of particle number concentration, geometric average diameter and geometric standard deviation are given in the free molecular regime, the continuum regime, the free molecular regime and transition regime, the free molecular regime and continuum regime, respectively. The results show that, both in the free molecular regime and the continuum regime, the num- ber concentration of mode i and j decreases with increasing time. The evolutions of particle geometric average diameter with different initial size distribution are quite different. Both intra-modal and inter-modal coagulation finally make the polydispersed size distribution become monodispersed. As time goes by, the size distribution with initial bimodal turns to be unimoda/and shifts to a larger particle size range. In the free molecular regime and transition regime, the inter- modal coagulation becomes dominant when the number concentrations of mode i and j are of the same order. The effects of the number concentration of mode i and mode j on the evolution of geometric average diameter of mode j are negligible, while the effects of the number concentration of mode j on the evolution of geometric average diameter of mode j is distinct. In the free molecular regime and continuum regime, the higher the initial number concentration of mode j, the more obvious the variation of the number concentration of mode i.

Direct Monte Carlo Method Simulation of the Synthesis of Carbon Particle Through Coagulation in the Detonation of Explosives

A model is constructed and used in computing the coagulation probability of free carbon during the detonation of explosives. A direct simulation Monte Carlo (DSMC) program is constructed to simulate the coagulation of free carbon particles. The evaluation of the distribution spectrum of particles in the system is obtained. The simulation result is consistent with the experimental curve.

Properties and coagulation mechanisms of polyferric silicate sulfate with high concentration

Polyferric silicate sulfate （PFSS） with high concentration was prepared using the composite-poly method. The coagulation properties and mechanisms of this new complex were probed using TEM, Fe-Ferron timed complex-colorimetric method, and infrared spectrum method. The results showed that the flocculating effect of polyferric silicate sulfate had an advantage over polyferric sulfate （PFS）, as the optimum coagulation effect could be obtained when the Si/Fe mole ratio was 0.75 in accordance with its macrostructure of PFSS. According to the Fe-Ferron timed complex-colorimetric method, the Si species was mainly Sic, whereas, the Fe species were Fea and Fec in the copolymerization system. The infrared spectra indicated that the structure of these new flocculants was formed by polymers, mainly by olation, which was different from polyferric sulfate, and the vibration of M-OH-M of around 1100 cm^-1, also proved that there existed Fe-OH-Fe and its polymers in some forms.

Nanoparticle nucleation and coagulation in a mixing layer

Numerical simulation of nanoparticle nucleation and coagulation in a mixing layer with sulfuric acid vapor binary system is performed using the large eddy simulation and the direct quadrature method of moment. The distributions of number concentration, volume concentration, and average diameter of nanoparticles are obtained. The results show that the coherent structures have an important effect on the distributions of number concentration, volume concentration and average diameter of nanoparticles via continuously transporting and diffusing the nanoparticles to the area of low particle concentration. In the streamwise direction, the number concentration of nanoparticles decreases, while the volume concentration and the average diameter increase. The distributions of number concentration, volume concentration and average diameter of nanoparticles are spatially inhomogeneous. The characteristic time of nucleation is shorter than that of coagulation. The nucleation takes place more easily in the area of low temperature because where the number concentration of nanoparticles is high, while the intensity of coagulation is mainly affected by the number concentration. Both nucleation and coagulation result in the variation of average diameter of nanoparticles.

新型聚镧混凝剂的制备及其在低温低浊水中的深度除磷性能

针对铁铝盐混凝剂在低温低浊水中深度除磷性能欠佳的问题,基于镧和磷酸根具有特异性亲和力的特性,选用溶胶-凝胶法以不同镧源、有机配体和原料(酸、碱、醇、水)配比制备了一系列聚镧混凝剂(LXC),所得材料中镧的质量分数均为30%~33%,混凝絮体颗粒尺寸达1600μm,且在5 min内即可完成沉降过程。以LaCl_(3)和聚氯化铝(PAC)为对照样品,评估了LXC对学校河水[温度为4~6℃,磷质量浓度为(1.0±0.1)mg/L]、阳澄湖水[温度为4~6℃,磷质量浓度为(0.1±0.3)mg/L]和石湖水[温度为4~6℃,磷质量浓度为(0.8±0.2)mg/L]的深度除磷、除浊性能。结果表明,相同投加量下LXC对不同水样的除磷效果均优于LaCl_(3)和PAC,适宜条件下混凝出水中残余磷质量浓度低于0.02mg/L,均达到深度除磷效果。该研究为深度除磷、缓解水体富营养化提供新的解决思路。

凝固方式对天然橡胶脂肪酸含量及性能的影响

脂肪酸是天然橡胶(NR)中重要的非胶组分之一。文中通过2种品系(热研73397和IAN873)、3种凝固方式(甲酸凝固、硫酸凝固、自然凝固)和2种标准胶工艺(全乳标准胶工艺(WF)、凝胶标准胶工艺(TSR))制备样品,研究了凝固方式对天然橡胶中脂肪酸含量的影响,探明脂肪酸含量变异性对NR力学性能的影响。结果表明,凝固方式会对非胶组分带来明显影响,其中硫酸凝固方式下样品脂肪酸含量保持效果最佳,而自然凝固方式下样品的下降幅度最为明显。在力学性能方面,在WF工艺下,非胶组分的适当降解有利于硫化反应的进行,这对应于自然凝固方式硫化胶具有最高的力学性能,而硫酸凝固的力学性能最低;在TSR工艺下,随熟化时间的延长,自然凝固硫化胶的力学性能降低。相同工艺下,IAN 873品系的重均分子量和凝胶含量均高于热研73397,而经过凝块熟化后甲酸和自然凝固样品的凝胶含量均不同程度的增加,但硫酸凝固的凝胶含量几乎没有变化,其TSR工艺样品的凝胶含量最低,这说明硫酸凝固阻碍了熟化过程中橡胶分子链发生结构化。

剪切增稠液微胶囊的制备与性能研究

本研究以壳聚糖材料为壁材,剪切增稠液(STF)为芯材,通过单凝聚法制备了STF微胶囊(STF MCs)。通过单因素实验研究,确定了微胶囊的制备工艺参数:司盘80(Span 80)与吐温80(Tween 80)作为分散剂,复配比例为3∶1;乳化剂用量为11%,核壳比为2∶1,搅拌速度为600 r/min,反应温度为60℃;体系的油水比为1∶2。在此条件下制得的STF MCs呈较为规整的球形,粒径分布较为均匀,且主要集中在3μm左右。结果表明,碳纳米管的引入有效改善了STF的流变性能。掺杂CNTs的STF体系具有更小临界剪切速率,更快的黏度突变,并且峰值黏度增加近一倍;芯材和微胶囊乳液的红外光谱大部分都一致,表明壳聚糖成功吸附在芯材液滴表面,实现了对STF的包封。壁材对芯材STF起到了保护作用,提升了芯材STF的热稳定性。

混凝沉淀法处理冶金含氟废水工艺研究

水中氟含量超标会对环境造成巨大影响,目前冶金行业普遍采用混凝沉淀法处理含氟废水。因此,针对混凝沉淀法除氟工艺中影响因素多、除氟效果缺少综合评估的问题,以某钢铁公司生产过程中产生的含氟废水为对象进行研究。首先通过正交实验考察pH、聚氯化铝(PAC)投加量、聚丙烯酰胺(PAM)投加量、PAC搅拌时间、PAM搅拌时间对含氟废水除氟效率影响的主次关系。研究结果表明,影响除氟效率的主次因素排序依次为pH、PAC搅拌时间、PAC投加量、PAM搅拌时间、PAM投加量。此外,对上述因素及温度等单因素变化对除氟效率的影响进行了研究。结果表明,最佳条件:pH为7、PAC投加量为70 mL、PAM投加量为2.5 mL、PAC搅拌时间为15 min、PAM搅拌时间为30 min、温度为30℃,在此最佳条件下除氟效率最高,可以达到99.3%。实际工程应用中,混凝沉淀法对氟离子总去除率在80%~90%,出水氟含量保持在7 mg/L左右,能够满足氟离子达标排放的要求。

凝固浴对湿法制备聚氨酯微孔膜结构和性能的影响

为了探讨厚度方向上呈非对称异质结构聚氨酯(PU)微孔膜的成型条件和性能表现,采用湿法成膜方法制备了PU微孔膜,通过改变凝固浴组分及配比,观察分析其对微孔膜微观结构的影响,探讨微孔结构对薄膜透气性、吸湿率、孔隙率、力学性能的影响机制。结果表明:在水系凝固浴中,同时添加钠盐和N,N-二甲基甲酰胺(DMF)可以塑造微孔膜具备相对致密的“皮膜层”,有利于提高力学性能;仅添加DMF制得的薄膜内部虽无明显孔室,但凹凸起伏的褶皱结构能够形成贯通微细通道,透气性能突出;仅添加钠盐参与凝固的样品,膜体内呈海绵状蜂窝多孔结构,且膜皮层和底层具备尺寸相对较大的明显孔眼结构,因而吸湿率较高;乙醇凝固的样品,呈典型闭孔泡沫结构特征,透气、透湿和力学性能适中。

混凝动力学存在问题与研究趋势

对混凝动力学的研究和应用现状中存在问题进行了较为全面的分析,重点阐述了混凝动力学理论、混凝动力学控制指标等在应用研究中存在的问题;并在此基础上阐述了混凝动力学研究方法的发展趋势,以期推动混凝动力学研究的发展。

植物叶蛋白提取工艺及蛋白肽制备技术研究进展

随着社会发展水平的提升,食物来源日益多元化,人们对优质蛋白质食物消费量不断增加,促使植物蛋白资源的开发和提取技术兴起。植物蛋白有动物蛋白无可比拟的优势,通过对叶蛋白深加工制备的蛋白肽,可以进一步提升植物蛋白的营养价值。因此,植物叶蛋白的提取及精深加工备受人们关注,植物叶蛋白的提取方法更是多种多样,最佳提取工艺参数也有深究。本文在前人研究的基础上对不同的叶蛋白经典提取方法及精深加工生产蛋白肽的方法进行整理综述,从主要的叶蛋白提取环节着手,回顾了各提取方法的原理知识、操作注意事项并进行优缺点评价,以期为后续植物叶蛋白提取研究及蛋白肽的制备提供理论依据及指导意见。

益气温阳活血利水法在膜性肾病中的疗效及对相关抗体、凝血纤溶系统的影响

目的:探究益气温阳活血利水法在膜性肾病(MN)中的疗效及对相关抗体、凝血纤溶系统的影响。方法:选择2020年6月-2022年6月北京市昌平区中医医院收治的83例MN患者,根据随机数表法分为对照组(n=41)和观察组(n=42)。对照组进行常规MN治疗,观察组则在对照组的基础上加用益气温阳活血利水法进行治疗。比较两组的MN治疗总有效率、治疗前后的症状体征积分(颜面肢体水肿、神疲乏力及畏寒肢冷)、相关抗体指标[血清抗磷脂酶A2受体抗体(PLA2R-Ab)及磷脂酶A2-ⅠB(PLA2-ⅠB)]及凝血纤溶指标[组织纤维溶酶原激活物(t-PA)、纤溶酶原激活抑制剂(PAI-Ⅰ)及活化部分凝血活酶时间(APTT)、凝血酶时间(TT)]。结果:观察组治疗总有效率显著高于对照组,差异有统计学意义(P<0.05)。治疗前,两组症状体征积分、相关抗体指标及凝血纤溶指标比较,差异无统计学意义(P>0.05);治疗1个疗程及2个疗程后,观察组各项症状体征积分均低于对照组,差异有统计学意义(P<0.05)。治疗1个疗程及2个疗程后,观察组PLA2R-Ab、PLA2-ⅠB及PAI-Ⅰ显著低于对照组,t-PA高于对照组,APTT、TT长于对照组,差异有统计学意义(P<0.05)。结论:益气温阳活血利水法应用于MN中的疗效较好,且可有效改善患者相关抗体及凝血纤溶状态。

复凝聚法制备泡椒香精微胶囊及工艺优化

本研究探讨壁材浓度、壁材比、芯壁比、固化剂添加量对微胶囊的包埋率和有效载量的影响。经单因素实验和响应面优化实验,确定最佳包埋条件为壁材浓度1.06%,芯壁比2.1∶1 g/g,壁材比2.2∶1 g/g,固化剂添加量0.17%,在此条件下获得的泡椒香精微胶囊包埋率达81.1%。

生乳稳定性快速评价方法体系研究

目的建立用于生乳稳定性快速评价的方法。方法通过对设计的不同新鲜程度的生乳,进行热凝聚时间法检测生乳稳定性的研究,以及与磷酸盐添加方法、氯化钙添加方法、盐酸添加方法相结合,通过降低生乳稳定性,进行有效识别生乳的稳定性。结果通过实验确定热凝聚时间法最佳取样量120 mL,油浴时间40min,并开发了一种热凝聚时间法检测装置,包含锥形瓶,油浴锅,冷凝管装置,有效解决生乳加热过程中糊管和溢出容器的问题;同时确定了最优的添加浓度,磷酸盐添加方法为0.5mol/L磷酸二氢钾溶液1.1mL,氯化钙添加方法为0.09 mol/L氯化钙溶液0.66 mL,盐酸添加方法为0.1 mol/L盐酸溶液0.7 mL,并与热凝聚时间方法相关联,建立了快速测试生乳稳定性的方法。结论本研究建立了快速、批量、重复性好的生乳稳定性检测方法,用于生乳质量监控管理,为探索牛乳稳定性评价指标和检测方法提供理论参考依据。

响应面法优化焦化废水生化尾水混凝药剂投加量研究

采用聚合氯化铝(PAC)+聚丙烯酰胺(PAM)混凝处理焦化废水生化尾水,通过单因素实验考察了混凝剂PAC、PAM投加量对混凝处理效果的影响。基于单因素实验开展响应面混凝实验,构建PAC、PAM投加量为自变量,出水残留浊度和出水过余电导率组成的加药控制系数为响应量的数学模型并对其参数进行了响应面优化。结果表明,混凝处理最佳药剂投加量PAC为2546.96 mg/L,PAM为10.90 mg/L,此条件下出水平均浊度残留率为4.24%、电导率过余率为2.77%、加药控制系数为7.01,与模型预测值相对误差<5%,进一步证明该响应面模型合理有效,对同时实现处理过程混凝充分反应和盐分有效控制具有指导作用,并可为相关自动化加药模型开发提供思路。

总磷应急去除工艺研究

目前污水处理除磷工艺主要以厌氧-缺氧-好氧(A^(2)/O)为主,然而A^(2)/O工艺仅能实现正磷酸盐的去除。当非正磷酸盐浓度过高时,采取应急措施去除污水中的非正磷酸盐以确保出水水质达标是非常必要的。基于此,开展了污水中总磷的应急去除的工艺研究。通过对传统芬顿氧化、臭氧-传统芬顿氧化、次氯酸钠(NaClO)氧化等方式对比,确定了NaClO氧化为最佳氧化方式,通过进一步的探索,得出了混凝法去除正磷酸盐的最佳条件:加入10 mL质量分数为5.5%的NaClO、氧化时间为30 min、氧化搅拌转速为60 r·min^(-1)、混凝剂体积为0.2 mL、混凝时间为20 min、搅拌速度为300 r·min^(-1)、慢速搅拌时间10 min、慢速搅拌速度60 r·min^(-1)、质量分数0.1%的聚丙烯酰胺体积为0.2 mL、助凝时间为30 min、助凝搅拌速度为60 r·min^(-1)。在上述条件下,非正磷酸盐的氧化去除率最高。该实验的开展可作为A^(2)/O工艺的重要辅助手段,当总磷浓度过高引起水质冲击时可确保出水水质达标。

血浆稀释回归法消除脂肪血标本对凝血结果干扰的应用价值研究

目的:探讨血浆稀释回归法消除脂肪血标本对凝血结果干扰的应用价值。方法:选择2021年1月至2023年2月在本院行健康体检的84例正常血浆标本设为对照组,用脂肪乳配制呈不同程度模拟脂肪血,其中轻度脂肪血标本28例,中度脂肪血标本27例,重度脂肪血标本29例。检测患者凝血功能指标,同期选择在本院门诊和住院患者脂肪标本68份设为观察组(重度脂肪血标本31例,中度脂肪血标本37例),行高速离心法、血浆稀释回归法处理,比较不同程度脂肪血血浆稀释回归法与高速离心法处理前、后凝血功能差异。结果:模拟脂肪血中:中、重度脂肪组凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)值高于对照组,D-二聚体(DD)值低于对照组,有统计学差异(P<0.05);轻度脂肪组PT、DD、APTT值与对照组相比,无统计学差异(P>0.05);脂肪血标本中:中度脂肪血标本经血浆稀释回归法、高速离心法处理后PT、APTT值均低于处理前,DD值均高于处理前,有统计学差异(P<0.05);血浆稀释回归法、高速离心法处理后PT、DD、APTT水平比较,无统计学差异(P>0.05)。重度脂肪血标本经血浆稀释回归法、高速离心法处理后PT、APTT值均低于处理前,DD值均高于处理前,有统计学差异(P<0.05);血浆稀释回归法、高速离心法处理后PT、DD、APTT水平比较,无统计学差异(P>0.05)。结论:血浆稀释回归法、高速离心法均可消除中、重脂肪血标本对凝血结果造成的干扰,但前者无需离心操作,操作更简便。