液幕式脱硫吸收塔中气液传质特性的实验研究

对液幕式吸收塔脱硫性能进行了实验研究,分析了烟气流量、循环浆液量、浆液pH值等参数对脱硫性能的影响,合理选择装置结构和运行参数时,脱硫效率可达95%;提出了液幕式吸收塔中传质面积的计算方法,建立了液幕式吸收塔的传质模型,发现传质系数在pH=5～10之间变化不明显,得到了液幕式吸收塔的传质系数关于气相和液相雷诺数的经验关系式.     

槽型芯湿法烟气脱硫的实验研究

湿法烟气脱硫是一个化学反应和传质同时进行的过程，其影响因素众多，如液体浓度、液体流动状况、气体流动状况、液气比、浆液pH值等。本文提出一种横向冲刷槽形芯湿法脱硫技术，通过试验的方法，研究了影响脱硫效率的诸多因素并进行了分析。     

气液双流程烟气脱硫塔内脱硫效率与传质性能的研究

实验采用电石渣做为脱硫剂,对气液双流程液幕式脱硫塔的脱硫性能以及传质特性进行了相关的实验研究。通过实验测试,提出了烟气流量、浆液循环量、液气比值等主要影响参数对液幕式脱硫塔的脱硫性能的影响。同时本研究提出了一个相关气液双流程脱硫塔的传质模型,其形式如:Sh=16.226Reg0.863Rel-1.64和Sh=27.126Reg-0.77(L/G)-1.64。基于气液传质模型,双流塔内浆液与烟气间复杂的气液传质过程可以通过烟气雷诺数,浆液雷诺数以及液气比描述的经验关系式进行定量计算。这些参数的影响规律为研究液幕式湿法烟气脱硫系统中二氧化硫的反应特性及实际工程的应用提供了重要的指导数据。实验发现,浆液循环量增加时,总的脱硫效率相应会提高,液气比增加时,总的脱硫效率也相应会提高。而烟气流量增加时,相应的脱硫效率却随之降低。通过实验研究发现:当液气比大于20L/m3时,脱硫率可达90%以上;然而pH值对传质的影响作用很小。     

大型燃煤电站锅炉脱硫塔脱硫效率的数值模拟

利用双膜理论建立了脱硫过程的理论模型,以国内某百万千瓦级火电机组烟气脱硫系统的脱硫塔为例进行了数值计算,分析了浆液pH值、入口SO2质量浓度、液气比、锅炉负荷、浆液液滴粒径、喷淋层投运方式及吸收塔塔径等参数对脱硫效率的影响,并与工程实际数据进行了比较.结果表明:数值计算结果与生产现场运行数据比较吻合;各喷淋层的脱硫能力不一样,第3喷淋层的脱硫能力最强,第2喷淋层和第1喷淋层的脱硫能力次之;脱硫效率随浆液pH值和液气比的增大而提高,随入口SO2质量浓度、锅炉负荷和浆液液滴粒径的增加而逐渐降低.     

降膜—浅层鼓泡烟气脱硫除尘系统的实验研究

提高烟气脱硫除尘技术水平是从源头防治尘肺病、硫化物中毒等职业病的重要一环。结合降膜法脱硫和鼓泡法除尘的优点,设计了新型的降膜—浅层鼓泡烟气脱硫除尘一体化实验系统,并采用十二烷基苯磺酸钠作为表面活性剂改性氢氧化钠吸收液,对模拟电厂烟气的除尘脱硫性能进行了研究。结果表明:添加表面活性剂能同时促进溶液脱硫和除尘效率;随SO2初始浓度的增大,反应器脱硫效率减小(尤其是SO2浓度增大到1 756 mg/m3以上时),但除尘效率略有增加。     

湿法脱硫的传质与化学平衡模型研究

采用喷淋式吸收塔的石灰石-石膏湿法脱硫技术是目前燃煤电站使用最广的脱硫工艺.在吸收塔内,喷淋的液滴在上升的烟气中逆向下落,吸收烟气中的SO2.基于稳态假设,分析了液滴内的化学反应过程和液相成份的平衡关系,以及固体CaCO3的溶解速率模型.采用总的传质系数,建立了液滴吸收气相成份的传质速率模型.通过气液两相之间各个成份的物量平衡分析,建立了吸收区的控制容积平衡方程.该模型对工程应用具有指导意义,也可以进一步应用于吸收塔的仿真计算和流场数值模拟计算.     

湿法烟气脱硫存在SO32-时石灰石的活性研究

利用定pH值滴定法研究了SO32-存在时石灰石的溶解特性.结果表明,当SO32-存在时,石灰石的溶解过程受石灰石颗粒表面和液相主体之间的传质及石灰石颗粒的表面反应速度共同控制.表面反应速率常数不仅仅与石灰石种类有关,且随浆液的pH值增大而减小,随温度、搅拌速率和CO2分压的升高而增大.     

锅炉对流受热面错列管束相对节距对其对流换热的影响分析

计算并分析了横向冲刷错列管束中管子横向与纵向相对节距修正系数的影响因素,给出了它们之间的变化规律,为横向冲刷错列管束的设计提供了必要的参考依据.     

新型双循环降膜湿法脱硫方式的试验研究

提出了一种新型横向冲刷式双循环降膜湿法脱硫方式,研究了串联给浆工况主要运行参数对脱硫效率的影响规律.通过串联给浆和并联给浆的对比试验表明:串联给浆方案具有最佳的脱硫性能.试验发现:本脱硫装置能够缓解系统结垢和堵塞,且出口烟气不携带液滴,烟温高于绝热饱和温度,在实际应用中能够省去烟气再热系统和除雾器装置.     

湿法烟气脱硫存在SO3^2-时石灰石的活性研究

利用定pH值滴定法研究了SO3^2-存在时石灰石的溶解特性．结果表明,当SO3^2-存在时,石灰石的溶解过程受石灰石颗粒表面和液相主体之间的传质及石灰石颗粒的表面反应速度共同控制．表面反应速率常数不仅仅与石灰石种类有关,且随浆液的pH值增大而减小,随温度、搅拌速率和CO2分压的升高而增大．     

降膜反应法氢氧化钠烟气脱硫的实验研究

基于降膜反应法,采用氢氧化钠溶液进行烟气脱硫的实验研究,重点考察了气液在不同工况下的脱硫效果。实验表明:脱硫效率随SO2初始浓度的增大而减小;液气比越高,系统的脱硫效率越高,但到一定程度后提高不明显;在pH=8～13.3范围内,pH值越大脱硫效率越高,较低的pH值时液气比对脱硫效率的影响更明显;脱硫效率随着吸收液温度的上升而呈下降趋势;NaOH吸收液的脱硫效果要比CaO吸收液脱硫效果更好。实验研究旨在为探讨绿色低碳的脱硫技术提供参考。     

Numerical and Experimental Investigations of Heat Removal Performance of Sodium-to-Air Heat Exchanger Used in Fast Reactors

Sodium-to-air heat exchangers (AHX) are used in fast breeder reactors for removal of decay heat generated in the core after a reactor shutdown. The AHX is an important component of the safety-grade decay heat removal system in a fast reactor. Decay heat removal critically depends on the performance of the AHX, which is essentially a cross-flow heat exchanger with liquid sodium flowing on the tube side and air flowing across finned tubes in the cross-flow mode. In this paper, a three-dimensional numerical study is carried out to investigate the flow and heat transfer characteristics when air flows over a representative bank of finned tubes in an AHX. The computational model has been validated against published experimental benchmarks. Based on parametric studies, appropriate correlations for the Nusselt number and fin effectiveness are derived. A computationally efficient porous body model is then developed and an integrated thermal hydraulics study of AHX is carried out using the derived heat transfer correlation. The numerical predictions of the porous body model are compared with the results of an experimental AHX tested at the Indira Gandhi Centre for Atomic Research; Kalpakkam, India. A good agreement between the results is seen.     

运行参数对喷雾干燥烟气脱硫效率影响的数值模拟

以计算流体力学为基础,结合浆滴脱硫的双膜模型,以Euler/Lagrange方法建立了喷雾干燥烟气脱硫的数值计算模型及程序,在较广的参数变化范围内,模拟结果与Hill和Zank的试验数据符合较好;同时对影响脱硫效率的运行参数如雾化浆滴粒径、出口饱和温距、入口SO2浓度和钙硫摩尔比进行了模拟。相对于常用的一维平推流模型,能够方便地跟踪单个浆滴的运动轨迹及脱硫和蒸发经历,直观的显示出整个反应器内的流场、温度场及组分的空间分布。     

Heat transfer characteristics of falling film evaporation on horizontal tube arrays

A falling film heat transfer test facility has been built for the measurement of falling film evaporation in a vacuum of about 1000 Pa. At this condition, only convective evaporation occurred in the liquid film. The Reynolds numbers of falling film over a range from 21.6 to 108.1 were tested on six-tube arrays made of enhanced or smooth tubes. Results show that the tubes with both enhanced outer and inner surfaces give high heat flux. Besides, as the Reynolds number increases, the heat transfer enhancement ratio of falling film evaporation decreases. A semi-analytical correlation is established to predict the heat transfer coefficients of falling film evaporation on smooth tube arrays, considering the contributions of partially dryout and fully wet regimes, respectively. For enhanced tubes, the heat transfer enhancement ratios to the smooth tubes were also correlated.     

Experimental Study on Heat Transfer of Heated Falling Film Under Gas–Liquid Cross-Flow Condition

With the influence of the different gas Reynolds numbers and liquid Reynolds numbers on heated falling film heat transfer, an experiment was performed by noncontact thermal infrared imaging technology under the gas–liquid cross-flow condition. The results indicated that during the increase of liquid Reynolds number the thickness and thermal resistance of liquid film increased in the determined temperature of the heating water, which weakened the heat transfer of the liquid film. However, the increase of liquid Reynolds number strengthened liquid film turbulence and therefore enhanced heat transfer. Under the synergistic effect of these two factors, there should be an optimal liquid Reynolds number that minimizes thermal resistance and maximizes the heat transfer coefficient of the liquid film. Temperature plays an important role in heat transfer of laminar liquid film flow. However, the heat transfer of turbulent liquid film flow is not sensitive to liquid film inlet temperature.     

EDV湿法烟气脱硫装置的优化措施

辽河石化0.8Mt/a重油催化裂化装置采用EDV湿法烟气洗涤脱硫技术,可以有效脱除装置排放的烟气中的SO2、催化剂颗粒等污染物。应用该技术,可将SO2含量从313.1mg/m3(标准)降到31.1mg/m3(标准),脱除率达到90.37%;催化剂固体颗粒从363.1mg/m3(标准)降到30.6mg/m3(标准),脱除率达到91.58%,均优于国家排放标准。为解决装置运行中存在的耗电量高、新鲜水用量大和装置排水中TSS含量高等问题,分别采取洗涤塔吸收区喷管分层可选洗涤功能、降低入塔烟气温度,以及废液处理单元选用絮凝剂-助凝剂组合加注方式,代替絮凝剂单一加注等优化措施。优化后,装置排放烟气中SO2、固体颗粒等污染物含量仍优于国家排放标准,装置每小时节电176kW·h,新鲜水用量从15t/h减少到12t/h,排水中TSS含量从101mg/L降到43mg/L。     

沿垂直壁面气-液降膜流动传质过程的数值研究

在考虑气-液两相间质量源项和能量源项的条件下,基于VOF算法,建立了水和空气沿竖直平板壁面两相降膜流动传热传质的CFD模型。利用该模型研究了水和空气两相间的传质特性,分析了液膜波动、进气进液速度以及温度对传质的影响,计算结果表明:一定程度的液膜波动、进气速度和进液速度的提高、气-液之间的温差的增加,都能强化气-液之间的传质过程。     

A study on flow and heat transfer characteristics for saturated falling-film evaporation of liquid oxygen in a vertical channel

In this study, a mathematical model for the laminar falling film is presented in order to simulate the evaporation heat transfer characteristics in falling liquid oxygen films. The model takes into account the effect of the interfacial shear. The values of the film thickness, the heat transfer coefficient as well as the interfacial shear are obtained under given conditions by solving the model with an iteration method. The influences of the inlet Reynolds number, channel length and the interfacial shear on the flow and heat transfer characteristics of the falling film evaporation are analyzed in detail. Effects of key factors on the circulation ratio of the inlet fluid mass flow rate to the generated vapor mass flow rate, an important design parameter for reboilers/condensers, are particularly analyzed. In addition, the variations of the average vapor velocity and interfacial film velocity are also discussed. The analysis results could provide theoretical guidance for the simulation and design of downflow reboilers/condensers applied in air separation units.     

富氧燃烧烟气加压脱硝的实验与模拟研究

为了解决富氧燃烧烟气中NOx对CO2资源化利用的影响问题,实验研究了加压条件下鼓泡与液膜反应器中液体对NOx的吸收作用。建立了高压下NOx吸收的传质及动力学耦合模型,利用该模型对鼓泡吸收和液膜吸收进行了模拟,获得了不同压力下气液相产物的浓度,并与实验结果进行了对比。结果表明:气液相产物的实验结果与模拟结果吻合,且模型的氮元素守恒率高于90%;最佳吸收压力为1.5 MPa;吸附在反应器壁面的液膜对于NOx有较强的吸收作用,液膜的成分主要是HNO3。