木家具中挥发性有机物的散发传质特性

建立了新的木家具挥发物散发完全解析模型,全面考虑了各种传质机理和污染物阻力,同时适用于有无换气的模拟. 经分析模型提出了一套简捷的新实验方法,利用同一家具在密封箱中若干释放周期的稳态和实时浓度,同时求取目标污染物的4个重要传质参数：可散发量C0、扩散系数D、分配系数K和对流传质系数h. 测定了(23±0.5)℃、相对湿度45%±5%下某家具中甲醛和总挥发物的传质参数,甲醛C0=4994 mg/m3, D=4.05′10-10 m2/s, K=499, h=1.4′10-3 m/s;总挥发物C0=19939 mg/m3, D=2.12′10-10 m2/s, K=1001, h=5.0′10-4 m/s,均落于常见范围,与其他方法所得对应参数的变异系数小于0.5%. 将参数代入数值算法预测有无换气条件下气候箱中的散发浓度,与实验值的平均偏差小于3.5%.     

建材VOC散发过程模拟与传质参数测定新方法

建材中挥发性有机化合物(VOC)的散发是一个复杂传质过程。为准确把握传质特性,首先建立了一套描述干建材散发行为的显性完全解析模型,适用于模拟对人体最不利的无换气情况;代入有关文献中的传质参数预测了环境舱浓度,与文献中对应的实验数据及数值算法预测值吻合良好。然后基于对模型的分析提出一套简便快捷的实验方法,能够利用不同VOC背景值下干建材在密闭舱中散发的平衡浓度或逐时浓度,求取预测散发过程的4个重要的传质参数:可散发浓度C₀、扩散系数D、分配系数K和对流传质系数h_m;实验部分测算了两类密度板中甲醛散发的C₀、D、K、h_m,代入数值算法预测了密闭舱和直流舱的环境舱浓度,与实验数据吻合良好。该套模型和测定方法能够应用于建材散发的模拟研究。     

封存CO2裹挟可挥发性污染物的迁移模型分析

为了研究封存CO₂注入过程可挥发性污染物的释放和迁移特性,本文建立了CO₂-水-残余油多相流驱替过程中的污染物迁移模型。采用数学模拟方法分析了多相驱替过程和污染物迁移过程,并研究了相间传质特性、初始油相分布和CO₂注入速率等对污染物迁移过程的影响。研究表明:CO₂驱替过程将促使可挥发污染物进入CO₂相并随之在地层中迁移,逐渐形成相间传质区域。相间传质区域的演化反映了污染物释放和CO₂裹挟污染物迁移的特性。可挥发污染物的传质系数越大,相间传质区域越窄,油相饱和度衰减越快;油相初始饱和度较大时,其饱和度衰减相对缓慢,对应的相间传质区域也较窄。当CO₂注入速率增大时,相间传质区域增大,油相饱和度衰减变快。本文模型可用于不同地质储层环境下封存CO₂时可挥发性污染物的迁移特性分析,并用于封存CO₂的风险分析与评价。     

水力喷射-空气旋流器用于湿法烟气脱硫及其传质机理

在一种新型高效的气液传质设备--水力喷射-空气旋流器(WSA)中,以Ca(OH)₂料浆为吸收剂进行了模拟烟气湿法脱硫的实验研究。结果表明:脱硫率随进口气速增加而增加;随液体喷射速度增加先增加,增加到一定程度后几乎不变;随烟气中SO₂的进口浓度增加而减小,存在一适宜的Ca(OH)₂浓度和回流比。在气体流量24～72 m³·h^-1、循环液体量0.4～0.8 m³·h^-1、料浆中Ca(OH)₂浓度7500 g·m^-3时,对SO₂浓度为1891～6373 mg·m^-3的烟气进行湿法脱硫,脱硫率达88.9%～97.7%,且WSA的旋流气体和喷射液体在湿法脱硫中具有自清洁能力,未发现内部结垢和喷孔堵塞现象。总体积传质系数K_Ga、有效相界面积a均随进口气速u_G增大而增大,而总传质系数K_G随u_G增加变化较小;当液体喷射速度 u_L≤0.26 m·s^-1时,K_Ga和K_G随u_L增加快速增大,之后增加缓慢,而a随u_L几乎线性增加,K_Ga和K_G随吸收剂中Ca(OH)₂浓度c_L增加有一最大值。结合实验数据拟合得到了相关的经验公式,这些关联式能较好地预测WSA的湿法脱硫传质性能。气体旋流场强度对总体积传质系数K_Ga和有效相界面积a起支配作用,脱硫传质过程同时受气膜和液膜阻力控制,但以液膜控制为主。     

不同形状方向性型孔液体润滑端面密封性能对比

表面微孔的方向性可以改变密封间隙中流体的流向,在孔区末端汇聚产生明显的流体动压效应,使摩擦副端面打开,形成全膜润滑。以不同开孔形状（圆形、菱形、椭圆形、长方形）型孔端面密封为研究对象,考虑润滑液膜中的空化现象,基于质量守恒JFO空化算法建立数值模拟模型,采用有限差分法求解Reynolds控制方程,获得端面膜压分布。对比分析了在不同操作参数和几何结构参数下不同开孔端面密封性能。结果表明：相比于圆孔,在低速或高压下,方向性型孔都具有较好的动压效应,且长方形孔的动压开启力最好,菱形孔泄漏率较小。当膜厚h₀=1.5～2.5 mm,孔深h_p=2～3 mm,长短轴比γ=3～4,反向开孔比β=0.5,倾斜角α₁=30°～50°、α₂=120°～140°时,不同形状方向性型孔可获得最佳的动压密封性能。     

直流舱测定材料VOC散发关键参数的浓度轨迹法

室内及车内环境中材料散发的挥发性有机化合物(VOC)是造成空气品质低劣的重要因素之一, 显著影响着人们的舒适度和身体健康。材料VOC散发特性由3个关键参数表征:初始可散发浓度C₀、扩散系数D_m和分配系数K。测定上述散发关键参数是研究材料VOC散发规律进而预测人体暴露和健康风险的基础。基于目前应用最广泛的直流舱中材料VOC的散发过程, 提出了同时测定C₀和D_m的浓度轨迹法。该方法通过预设K值, 然后对环境舱浓度的对数进行线性拟合, 根据斜率和截距获得关键参数C₀和D_m。敏感性分析表明, 不同的K值对测定的C₀和D_m值影响很小。通过对文献中的直流舱散发实验数据进行处理, 结果表明该测定方法具有较高的精度。     

响应面法优化β-Co(OH)2的合成

以硫酸钴、氢氧化钠为原料,氨水为络合剂,抗坏血酸为保护剂合成β-Co(OH)₂。实验研究了反应温度、氢氧化钠溶液浓度、络合剂与硫酸钴中Co²⁺的摩尔比和保护剂对产品收率的影响。采用三因素三水平的响应面分析法对工艺条件进行优化,得到了β-Co(OH)₂合成的最优工艺条件。实验结果表明：在反应温度为79 ℃、氢氧化钠溶液浓度为2.89 mol/L、络合剂与硫酸钴中Co²⁺的摩尔比为2.19等条件下,合成的β-Co(OH)₂最高收率为97.40%,同时通过X射线衍射对产物进行了结构表征。     

微通道内离子液体/乙醇混合溶液吸收CO2的传质特性

采用高速摄像仪对微通道内离子液体/乙醇混合溶液吸收CO₂的传质行为进行了实验研究。考察了弹状流型下气液两相流量比和离子液体浓度对液侧体积传质系数k_La和液侧传质系数k_L的影响。当离子液体浓度不变时,k_La、k_L均随气液流量比的升高而增大并逐渐趋于恒定。当液相流量不变时,对于不同浓度的离子液体溶液,液侧体积传质系数k_La和液侧传质系数k_L随气液流量比的变化曲线出现了交叉点。在交叉点之前,k_La和k_L均随着离子液体浓度的增大而减小;在交叉点之后,k_La和k_L均随着离子液体浓度的增大而增大。提出了用于预测液侧体积传质系数k_La的新的量纲1经验关联式,预测效果良好。     

纳米b-Ni(OH)2的制备及其储锂性能

以Ni(NO₃)₂·6H₂O和NaOH为原料采用化学沉淀法制备了Ni(OH)₂电极材料。采用X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)表征了样品的微观结构,结果表明该样品是具有片状纳米次级结构的β-Ni(OH)₂。采用循环伏安(CV)和电化学充放电测试研究了该β-Ni(OH)₂样品的储锂性能,结果发现该样品作为锂离子电池负极材料具有非常高的储锂活性,在50 mA·g^-1电流密度下其第3次循环放电比容量高于1550 mA·h·g^-1;样品电极中的碳含量对其循环性能和倍率性都有显著影响,通过交流阻抗(EIS)测试分析了样品电极中碳含量的作用机理。     

臭氧复合钼酸铵促进剂对金属铝磷化的影响

利用臭氧的强氧化性和环境友好性,研究将其用作铝材磷化过程中的氧化促进剂。采用SEM、极化曲线等测试手段,确定了磷化液的最佳配比为：ρ(Zn²⁺)=5.0 g/L、ρ(PO^3-₄)=20 g/L、ρ(F^-)=1.5 g/L、ρ(钼酸铵)=1.0 g/L、ρ（臭氧）=0.5~0.9 mg/L,pH控制在3.5~3.7。在此条件下加入臭氧复合钼酸铵促进剂,制得磷化膜的主要成分为Zn₃(PO₄)₂•4H₂O,并含少量锌,膜质量可达4.95 g/m²。在质量分数为3％的氯化钠溶液中测定磷化膜的电极化曲线,其腐蚀电位相对于其他条件下形成的磷化膜发生正移,腐蚀电流密度仅为3.0 μA/cm²,说明磷化膜的耐腐蚀性能好。     

A unified conjugate mass transfer model of VOC emission

This paper develops a unified conjugate mass transfer model for VOC (Volatile Organic Compound) emission, which implies conjugate boundary condition for mass transfer at the material-air interface. Thus, no special treatment is needed at the material-air interface and numerical methods for conjugate heat transfer problem can be applied directly. The material-air partition coefficient has been taken into account and its effect is the same as specific heat in the energy equation. The equivalent diffusion coefficient in the material K_maD_m instead of D_m characterizes the rate of mass transfer. The ratioK _ma D _m /D _a indicates whether VOC emission is controlled by the internal diffusion or not. The equivalent air-phase initial concentration C₀/K_ma determines the order of maximum concentration in the air. VOC emission contains two stages: the initial stage and the pseudo-steady stage when the emission rate nearly equals mass rate through the outlet of the air. Diffusion coefficient of VOC in the material has a significant effect on VOC emission in the two stages. The effect of partition coefficient on VOC emission depends on the value of K_maD_m/D_a.     

湿建筑材料中VOC释放规律

湿建筑材料中挥发性有机物（volatile organic compound,VOC）释放过程是一个非常复杂的物理过程,其中包括材料本身的干燥过程以及质量传递过程。为探讨湿建筑材料中VOC的释放机理,本文建立了描述湿建筑材料中VOC释放过程的物理模型,模型考虑了湿建筑材料中VOC释放过程中的干燥过程,并用该模型分析了VOC的饱和蒸气压在整个VOC释放过程中的作用机理。把该模型的计算结果与VB模型求解结果、Yang等建立的模型求解结果以及实验结果进行了对比,得出干燥模型计算结果与Yang等建立的模型计算结果以及实验数据吻合较好,较VB模型能更准确地描述VOC的扩散过程。通过不同工况下环境小室的实验数据,对温度与相对湿度对湿建筑材料中VOC释放过程的影响规律进行了分析。     

Experimental investigation and mathematical modelling of wood combustion in a moving grate boiler

The use of biomass to generate energy offers significant environmental advantages for the reduction in emissions of greenhouse gases. The main objective of this study was to investigate the performance of a small scale biomass heating plant: i.e. combustion characteristics and emissions. An extensive series of experimental tests was carried out at a small scale residential biomass heating plant i.e. wood chip fired boiler. The concentrations of CO, NO_x, particulate matter in the flue gas were measured. In addition, mathematical modelling work using FLIC and FLUENT codes was carried out in order to simulate the overall performance of the wood fired heating system. Results showed that pollutant emissions from the boiler were within the relative emission limits. Mass concentration of CO emission was 550-1600 mg/m³ (10% O₂). NO_x concentration in the flue gas from the wood chips combustion varied slightly between 28 and 60 ppmv. Mass concentration of PM₁₀ in the flue gas was 205 mg/m³ (10% O₂) The modelling results showed that most of the fuel was burnt inside the furnace and little CO was released from the system due to the high flue gas temperature in the furnace. The injection of the secondary air provided adequate mixing and favourable combustion conditions in the over-bed chamber in the wood chips fired boiler. This study has shown that the use of wood heating system result in much lower CO₂ emissions than from a fossil fuel e.g. coal fired heating system.     

Evaluation of VOC emission and sorption characteristics of low-VOC adhesive-bonded building materials

To reduce the risk of indoor air pollution caused by synthetic building materials, low-volitile organic compounds (VOC) building materials, including adhesives, are commonly used in building construction. Although adhesives do not directly contact indoor air, they affect VOC mass transfer at the surface of finishing materials by diffusion. This study investigates VOC emission and sorption behaviors of building materials with low-VOC adhesives. Small chamber emission and sorption experiments were designed in parallel to field measurements to examine the onsite VOC emission and sorption rates of adhesive-bonded building materials. It was found that the onsite emission rates from a wallpaper composite (polyvinyl chloride wallpaper?+?paper adhesive?+?gypsum board) were higher than the emission rates detected in the small-scale chamber, which demonstrates the possible sorption effect of the wallpaper composite. The results of the sorption chamber experiment confirm that the wallpaper is a sorptive building material and that the bonding of wallpaper to gypsum board increases the sorption and re-emission rates. These results indicate that even though low-VOC adhesive-bonded materials are used, additional indoor air quality control techniques should be applied to minimize re-emission by sorption processes over long periods of time.     

The external mass transfer of basic and acidic dyes on wood

The parameters affecting the initial adsorption rates of Astrazone Blue dye (Basic Blue 69) on to wood have been studied. A simple model has been proposed to determine the external mass transfer coefficients and these have been compared with values obtained using a more complex procedure. The external mass transfer coefficient, β, has been shown to vary linearly with agitation and initial dye concentration using log-log coordinates; furthermore β is independent of particle size. The effect of temperature has been studied and the activation energy for the process is 44 ± 2 kJ mol^?1. Similar correlations were obtained for the adsorption of Telon Blue dye (Acid Blue 25) on wood. Using log-log correlations, the external mass transfer coefficient was found to vary with (rev min^?1)^0.14, C₀^?0.27; and a small dependence on particle size was also observed. The activation energy for the external mass transfer process was 25 ± 2 kJ mol^?1.     

溶剂型木器涂料中挥发性有机化合物释放规律

小型气候箱模拟典型室内空气条件，不同时间用椰子壳活性炭吸附管收集一定体积硝基、多组分聚氨酯清漆涂膜释放出的VOC与空气的混合气体，气相色谱法测定二硫化碳提取液中VOC组分浓度的实验方法，研究了溶剂型木器涂料成膜后VOC的气相浓度由迅速衰减、过渡和缓慢衰减三个过程构成并受液-气界面压力差和解吸的控制，基于数据分析建立定量描述涂料涂装后气相浓度与涂膜中VOC组分量、空气交换率、实验仓容积相互关系的数学模型。气相浓度的衰减率R，可表征VOC释放特性，温度、湿度、空气交换率条件对气相浓度衰减率影响研究表明其与温度、组分的色谱保留时间存在函数关系。     

Fuel and emissions properties of Stirling engine operated with wood powder

From viewpoints of the environment and fuel cost reduction, small-scale biomass combined heat and power (CHP) plants are in demand, especially wood-waste fueled system, which are simple to operate and maintenance-free with high thermal efficiency similar to oil fired units. These are requested by wood and other industries located in mountainous region. To meet these requirements, a Stirling engine CHP system combined with simplified biomass combustion process with pulverized wood powder was developed.In an R&D project started in 2004 considering wood powder properties as a fuel, combustion performance and emissions in combustion flue gas were tested using combustion test apparatus with commercial size units. The wood powder combustion system was modified and optimized during the combustion test results, and the design of the demonstration plant combined with 55 kW_e Stirling engine power unit was considered. The demonstration plant was finally completed in March of 2006, and test operation has been progressed for the future commercial CHP system.In the wood powder combustion test, wood powder of less than 500 μm is mainly used, and a combustion chamber length of 3 m is applied. In these conditions, the air ratio can be reduced to 1.1 without increasing CO emission of less than 10 ppm and combustion efficiency of 99.9%. In the same conditions, NO_x emission is estimated to be less than 120 ppm (6% O₂ basis). Wood powder was confirmed to have excellent properties as a fuel for Stirling engine CHP system. This paper summarizes the wood powder combustion test, and presents the evaluation of the burner design parameters for the biomass Stirling engine system.