二次除尘器除尘效率的影响因素

介绍了二次除尘器除尘效率的影响因素和改进措施,以及在设计过程中需要完善的问题,实践表明,二次除尘器能够满足干熄焦工艺的除尘要求,相对稳定,且性价比较高。     

限域传质分离机制初探：界面吸附层的“二次限域”效应

限域传质分离膜主要面向分子/离子水平的高精度分离过程,对解决CO2分离、共沸物分离、盐湖提锂、海水淡化等重大应用需求具有重要意义。然而目前,这类膜的限域传质机制研究滞后,理论模型缺乏,已不能满足材料和化工等学科高速发展的需求。用介科学观点思考限域传质分离膜同时具有高通量和高选择性这一反常现象,即突破Trade-off效应,这是选择性机制与通量机制之间的竞争与协调导致的。纳微固液界面处流体分子在界面处会优先吸附,形成稳定的吸附层,基于此本文提出了"二次限域"的假说,即界面诱导的类固态新界面会对中间流体再次产生限域效应。通过对比限域传质分离膜的孔道尺寸与二次限域尺寸,进一步认知了二次限域的选择性机制,并结合选择性机制与通量模型对膜通量和选择性的定量预测进行了初探,以期为精密构建限域传质膜提供理论基础。     

传质控制下宽分布石膏颗粒群溶解特性

烟气CO₂直接与工业固废磷石膏矿化反应生成碳酸钙与硫酸铵的控速步骤是磷石膏的溶解。在传质控制下,准确表达溶解特性是矿化反应器设计的理论依据。采用种群平衡模型预测传质控制下粒径宽分布石膏颗粒群溶解特性,采用矩积分法和特征线法对模型进行数值求解并与传统的平均粒径模型表达进行对比。结果显示：种群平衡模型反映了粒径分布对溶解速率的影响,计算得到溶解过程中总容积传质系数的变化,与实验结果吻合良好,证实了种群平衡模型预测的可靠性。与之相比,平均粒径模型预测溶解速率值比实验值偏大,由此解释了工业反应器中物料实际停留时间大于模型计算值的原因。     

二次交联凝胶颗粒堵水体系的研制

针对裂缝性油藏堵水成功率低、堵剂漏失严重且容易误堵的问题,研制了一种凝胶颗粒类堵剂,该堵剂通过凝胶颗粒在地层下的二次交联进行堵水。以丙烯酰胺(AM)和不稳定易分解酯类单体J-1为主要原料,通过本体聚合的方法合成凝胶颗粒,由于J-1中含有双键结构使其聚合成具有三维网状结构的凝胶颗粒;凝胶颗粒和二次交联剂J-2在地层下再次交联形成高强度凝胶体。凝胶颗粒成胶时间随J-1加量不同其分解时间不同,使得颗粒成胶时间可控。堵剂成胶时间为1～4 d,凝胶颗粒质量分数为1%～3%,初始黏度接近注入水黏度,在油相中基本不成胶,在水相中能够形成高黏度凝胶体,在高矿化度下能够形成黏度220 000 m Pa·s以上的高强度凝胶;在70℃条件下,90 d内黏度变化较小,性能保持良好,具有良好的抗盐性和热稳定性。填砂管实验结果表明,堵水体系突破压力在31. 25 MPa/m以上,封堵率在92%以上,具有很好的封堵性能。     

长期运行期间微孔曝气系统氧传质效率的影响因素及污染控制

微孔曝气因其较高的氧传质效率成为城镇污水处理厂好氧生物处理系统中最常用的曝气技术之一.文中综述了影响微孔曝气氧传质效率的因素,包括工艺条件、污水水质条件、环境因素等.但是,在长期运行过程中,微孔曝气器的污染成为对氧传质效率影响最大的因素.文中对累积于微孔曝气器表面及气孔内的生物污染、有机污染和无机结垢的形成原因进行了总...     

双溢流立体传质塔板上液相流场CFD研究

采用计算流体力学方法对直径为2 600 mm的工业规模双溢流立体传质塔板板上气液二相流动进行了模拟研究。计算了不同工况下收缩流和扩张流2种流型的液相流场分布,得到了双溢流塔板收缩流和扩张流2种流型的板上气液二相流场分布规律。通过将清液层高度的CFD结果和经验公式的计算结果进行对比,验证了所建模型的正确性。模拟计算结果表明:边降液管收缩流板面液相流动较均匀,近似于均匀的收缩流,不存在回流区;中降液管扩张流板面液相流动不均匀,靠近塔板中心流速较快,塔板弓形区存在着回流现象;板孔处的帽罩区液层较其他地方小,液相体积分数较其他地方低,扩张流受气相的影响较收缩流大。     

塔板上流型变化对板效率影响的计算传质学

利用能够描述塔板上气液两相错流过程的流体力学模型,建立了同时模拟气液两相流动与传质过程的数学模型;通过对气液两相传质方程和流体力学模型方程的联立求解,计算得到了塔板上液相速度分布和气液两相浓度分布的数值解,考察了气相完全混合和气相部分混合两种条件下塔板上的气液两相浓度分布,同时考察了气相完全混合时流型变化对塔板效率的影响.     

高浓度絮状颗粒污泥流化床的半工业化实验

研制开发了高浓度絮体化好氧颗粒污泥流化床装置,针对生活废水进行了半工业性实验.3个月的连续运行结果表明,高浓度絮体化好氧颗粒污泥流化床具有较高的生物降解效率,且能够稳定运行.实验表明,该装置内MLSS达到14g/L,是AA/O氧化沟(MLSS为3～4 g/L)的4倍.其水力停留时间为1h时的出水COD是45 mg/L,...     

新型气体分布器对非牛顿流体中氧传质的影响

研究了环状气体分布器、微孔型气体分布器一号、微孔型气体分布器二号3种型式的气体分布器对非牛顿流体中氧传质的影响。着重考察了微孔型分布器对同一组合桨的功耗、气含率ε、氧传质系数KLα以及比功耗传氧系数Eo2的影响,并与传统的环状气体分布器的结果进行了对比。结果表明:在相同条件下,微孔型气体分布器条件下所得KLα和Eo2均高于环状气体分布器的对应值,可以取得较好的传质混合效果,有利于提高非牛顿流体中的溶氧水平。     

第二液相对气液二相体系传质的影响

以CO2气体-K2CO3/KHCO3水溶液吸收过程为研究体系,用酸解法测量气体被吸收的速率,通过对比试验考察了加入第2液相(有机相)对体系传质速率的影响。经过试验研究证明,第2液相的加入对气液传质过程的影响程度与加入的物质有关,在试验条件下甲苯对体系强化作用高于异辛醇和庚烷对体系的强化作用。当第2液相加入量较小时,随加入量的增加,其对气液传质过程的促进作用增强,但当第2液相加入量较大时,这种作用则不明显。同时第2液相对传质作用的影响与流动场有关,增加流动场的搅动有助于强化气液传质作用。     

MASS TRANSFER IN RECIRCULATING BLOOD FLOW

An experimental investigation was done on oxygen transfer into laminar flows of whole blood and saline downstream of an abrupt pipe expansion. This was used as the experimental model for regions of separated flow in the arterial system. The flow was fully-developed prior to the tube expansion with Reynolds numbers between 160 and 850. The results showed high transfer rates over most of the region downstream of the step, with maximum transfer occurring near the reattachment point. In addition, oscillations of the transfer rate were measured at the larger Reynolds numbers of 450 and 850.     

浓度对传质系数的影响及多元物系传质

在筛板塔中对甲醇-乙醇-水三元物系进行精馏传质过程实验,考虑浓度对传质系数的影响建立了一个数学模型,对各组分在塔中的浓度分布进行模拟计算,计算结果能正确反映各组分在塔中浓度分布的变化规律.实验与计算结果都表明在某些浓度范围内乙醇呈现出比较复杂的变化规律.     

传质系数与浓度的关系

在含 6块塔板的板式塔中选择 2个非理想性较大的二元物系进行全回流蒸馏传质实验 ,同时从描述多组分扩散过程的普遍化方程———Maxwell-Stefan(MS)方程出发建立一个求算传质系数的数学模型 .数据处理和计算的结果表明 ,传质系数不仅与该塔板的浓度有关 ,还与相邻塔板的浓度有关 .对于非理想程度大的醇水物系 ,在不同浓度下的传质系数最大值与最小值相差可达约 1个数量级 .因此 ,对于非理想物系 ,在设计计算中将传质系数当作常数的处理将会产生较大误差 .     

高浓度电除尘器入口封头气固两相流动的近流线数值模拟

利用近流线数值模拟方法,采用与大型高浓度电除尘器入口封头原型完全相同的1∶1的几何模型,详细真实地模拟了入口封头及其内部具有复杂结构的预除尘角钢和两层开孔达数万个的气流分布板.采用可实现性k-ε模型和随机颗粒轨道模型,对其气固两相流动进行了数值计算,得出了气相速度分布、颗粒浓度分布和流动阻力分布特性.计算结果与工业性试验数据进行了比较,两者吻合较好,提出并证明了利用近流线数值模拟方法可以详细真实地模拟高浓度电除尘器入口封头内部结构及其气固两相流动.计算和试验结果均表明,所研究的高浓度电除尘器入口封头,其出口处气流分布为中间区域偏低,四周区域偏高;其预除尘效率约为27.6%左右,其流动阻力高达766Pa.     

CONVECTIVE MASS TRANSFER WITH PULSATILE FLOW IN STRAIGHT RIGID TUBES

This work is a numerical study of mass transport with laminar pulsatile flow through a straight rigid tube with no backflow. Convective oxygen transport is analyzed for a reactive fluid (blood) and nonreactive fluids. The literature contains several experimental and theoretical studies of this problem; however, the conclusions drawn from these investigations are contradictory. The results of this study can be used to explain many of these contradictions.     

次毫米过滤组件分区高含量污泥试验研究

采用次毫米过滤(SMF)组件实现高含量污泥(MLSS)分区(A区和B区),为膜生物反应器(B区)的稳定高效运行提供适宜的污泥质量浓度(5.0～10.0 g.L-1)。研究了回流体积比≥2.0条件下SMF组件(孔径0.47 mm)分离高含量污泥的运行特征及分区效果,对比分析了两区微生物实测与理论含量的差异,并考察了SMF组件耦合A区对营养物的去除效果。结果表明,在分离高含量污泥时,目标B区的污泥的质量浓度为2.0～10.0 g.L-1,对膜生物反应器是适用的;对应A区的污泥的质量浓度在15.5～33.5 g.L-1。SMF组件滤出液MLSS的质量浓度在1.4～4.2g.L-1,平均通量可达192 L.m-.2h-1。此外,SMF组件耦合A区对COD的去除率在82%以上。     

MASS TRANSFER FROM FLAT PLATES TO POWER-LAW FLUIDS IN LAMINAR FLOW

Mass transfer from vertical flat plates to water and 0.5 to 1.5% aqueous CMC solutions is measured in the Reynolds number range of 10^{- 2}to 6.0 x 10₃. Blasius analysis has been found to be valid only up to a Reynolds number of 100, below which Graetz-Leveque solution is more appropriate.     

MASS TRANSFER ENHANCEMENT BY SMALL FLOW OBSTACLES IN ELECTROCHEMICAL CELLS

Mass transfer enhancement by small obstacles attached to the cathode in electrolytic flow cells of 5x5 mm cross-section and 500 mm length was investigated. Double beam laser interferometry was used to observe the local mass transfer boundary layer thicknesses preceding and following rod-shaped dielectric obstacles placed normal to the direction of electrolyte flow. Flow patterns have been visualized by use of suspensions of small inert particles and dark field photography. For the evaluation of the effectiveness of mass transport enhancement, pressure drops, and limiting currents for the reduction of ferricyanide have been measured in the range of Reynolds Number 80 to 3200. The degree of enhancement increases with decreasing obstacle spacing until an optimal spacing of approximately 15 times the obstacle size is reached. A three to five-fold increase in the average mass transfer coefficient is achieved by the use of obstacles with a small fraction of the pumping power required to obtain the same limiting current by increasing the flow rate in the unobstructed channel. Small obstacles produce efficient mixing near the electrode surface, and corresponding improvement in uniformity and magnitude of mass transport rates, without increasing the energy dissipation in the bulk fluid.     

MASS TRANSFER IN TURBULENT PULSATING FLOWS

The effect of flow oscillation to the mass transfer between turbulent fluid and solid wall was investigatedby measuring the mass transfer rate between fluid and pipe wall with imposed oscillating flow usingelectrochemical method.The velocity and concentration field in the viscous sublayer which controls the mass trans-fer in such a process was simulated by a simple wave model of single harmonics.Experimental results confirmthat the flow oscillation has no influene on time averaged mass transfer rate,but the phase difference betweenphase averaged velocity field and concentration field shifts with the frequency of imposed oscillating flow.Numeri-cal analysis reveals that the concentration boundarylayer which is responsible for the mass transfer is muchthinner than the viscous sublayer which greatly weakens the influence of imposed oscillating flow on mass transfer.     

MASS TRANSFER ENHANCEMENT BY SMALL FLOW OBSTACLES IN ELECTROCHEMICAL CELLS

Mass transfer enhancement by small obstacles attached to the cathode in electrolytic flow cells of 5x5 mm cross-section and 500 mm length was investigated. Double beam laser interferometry was used to observe the local mass transfer boundary layer thicknesses preceding and following rod-shaped dielectric obstacles placed normal to the direction of electrolyte flow. Flow patterns have been visualized by use of suspensions of small inert particles and dark field photography. For the evaluation of the effectiveness of mass transport enhancement, pressure drops, and limiting currents for the reduction of ferricyanide have been measured in the range of Reynolds Number 80 to 3200. The degree of enhancement increases with decreasing obstacle spacing until an optimal spacing of approximately 15 times the obstacle size is reached. A three to five-fold increase in the average mass transfer coefficient is achieved by the use of obstacles with a small fraction of the pumping power required to obtain the same limiting current by increasing the flow rate in the unobstructed channel. Small obstacles produce efficient mixing near the electrode surface, and corresponding improvement in uniformity and magnitude of mass transport rates, without increasing the energy dissipation in the bulk fluid.