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。     

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。     

建材内甲醛散发参数处理方法及实验研究

提出了一种新型的建筑板材内甲醛散发关键参数的处理方法,并进行了不同温度场作用下的实验研究。结果表明,温度可以明显促进板材内甲醛的散发,根据实验数据拟合得到Km、C0和Dm,三大参数随温度的变化规律验证了本文提出的新型处理方法;实验过程中,舱内浓度对甲醛挥发速率的抑制作用比温度对其的促进作用更加明显;本文提出的新型处理方法被证实是可行并且可靠的,可为板材内其他VOC气体散发参数的处理提供依据和参考。     

建材内甲醛散发参数处理方法及实验研究

提出了一种新型的建筑板材内甲醛散发关键参数的处理方法,并进行了不同温度场作用下的实验研究。结果表明,温度可以明显促进板材内甲醛的散发,根据实验数据拟合得到K_m、C₀和D_m,三大参数随温度的变化规律验证了本文提出的新型处理方法;实验过程中,舱内浓度对甲醛挥发速率的抑制作用比温度对其的促进作用更加明显;本文提出的新型处理方法被证实是可行并且可靠的,可为板材内其他VOC气体散发参数的处理提供依据和参考。     

袋式法测试车用塑料VOC散发量的方法研究

采用聚丙烯(PP)和聚甲醛(POM)塑料为实验样品,使用袋式法进行VOC(挥发性有机化合物)测试,考察不同采样袋体积和取样量对VOC散发量的影响。结果表明,在同样采样袋体积和散发空间下,改变样品的取样量,散发量和取样量相关系数大于0.7;等比例改变采样袋体积和取样量时,对各物质的散发浓度影响较小,相对偏差在30%以内;采用袋式法测试PP和POM塑料中VOC散发量相对标准偏差均小于15%,方法的重复性较好。     

涂料VOC检测方法现状分析及涂料消费税关于VOC检测建议

将我国现行涂料VOC检测方法作了梳理和比较,将现行的19项标准分为通用型标准和专用型标准两类,并将现行标准中的方法归纳为6种,分别为:差值法(扣除沸点大干250℃的VOC)、差值法(不扣除沸点大于250℃的VOC)、差值法(不扣除沸点大于250℃的VOC,扣除水分)、气相色谱法(不扣除水分)、气相色谱法(扣除水分)和顶空气相色谱法。分析了我国涂料VOC检测现行标准体系中存在的不足,并针对涂料消费税的VOC检测提出了建议。     

ICP-MS法和WD-XRF法测定地质样品中稀土元素的方法研究

针对分析大批量的区域地质调查和多金属勘查任务,分别建立了过氧化钠碱熔-ICP-MS、高压密闭消解-ICP-MS和粉末压片-WD-XRF 3种分析方法测定土壤、水系沉积物和岩石样品中15种稀土元素。3种方法的检出限分别为0.011～0.173、0.001 2～0.009 7、0.06～5.42μg/g,高压密闭消解-ICP-MS法的检出限明显优于碱熔ICP-MS法和粉末压片WDXRF法; 3种方法测定的国家标准物质稀土元素的相对误差(RE%)分别为-6.5～6.6、-11.2～3.6、-9.7～12.7,精密度(RSD%)分别为2.4～8.8、2.8～8.2、2.4～9.4,均满足DZ/T 0258—2014《多目标区域地球化学调查规范(1∶250 000)》的要求。实验表明,粉末压片-WD-XRF法受到检出限高的限制,不能应用于测定稀土含量极低的地质样品,高压密闭酸溶-ICP-MS法测定矿物结构复杂的岩石样品时,个别测定结果严重低于标准值。验证了碱熔ICP-MS法在实际工作中的可行性,测定值最接近真实值,最适合进行分析大批量的区域地质调查和多金属勘查任务。     

酸溶方法对电感耦合等离子体质谱法测定岩石中稀土元素的影响

基于电感耦合等离子体质谱仪(ICP-MS)测定稀土元素的优势,在选择仪器最佳工作参数的基础上,探究了敞口混合四酸溶样法和密闭酸溶法对ICP-MS测定岩石中稀土元素的影响。并对密闭酸溶法的前处理步骤进行了优化。结果表明:敞口混合四酸溶样法(HNO3-HCL-HCLO4-HF)、优化密闭酸溶法(HNO3-HCL-HCLO4-HF)和密闭酸溶法(HNO3-HF)均通过岩石成分分析国家一级标准物质的验证,可以实现ICP-MS对岩石中稀土元素的测定;优化密闭酸溶法结合ICP-MS测定稀土元素的方法检出限为0.00029～0.023μg/g,相对标准偏差为1.56%～8.11%,相对误差在-8.24%～10.52%范围内,加标回收率为89%～106%;密闭酸溶法的检出限为0.00015～0.014μg/g,相对标准偏差为1.17%～4.84%,相对误差在-5.42%～5.78%范围内,加标回收率为92%～103%。敞口混合四酸溶样法的检出限为0.00034～0.030μg/g,相对标准偏差为2.46%～10.20%,相对误差在-21.04%～25.68%范围内,加标回收率为85%～109%。敞口混合四酸溶样法前处理流程最短,但样品消解不完全,准确度较低,适用于大批量样品前处理;密闭酸溶法检出限低,精密度、准确度高及用酸量少等特点,但处理流程较长,不适用于大批量样品前处理;优化密闭酸溶法相比于密闭酸溶法做了改进,具有操作简便、处理流程短的优点,适用于高精度要求的大批量样品前处理。     

色谱测UNIFAC参数的方法研究

UNTFAC参数通常从汽液平衡数据回归得出.鉴于汽液平衡实验繁琐且不经济,而气液色谱实验简单、迅速、经济、可靠,近年来巳用于测UNIFAC参数,其中又有两种方法:一种用单体系无限稀释活度系数γ~∞,加上单参数Flory-Huggins方程回归;另一种由几个体系的γ~∞联立回归.前者仅适用于分子大小悬殊的体系,后者则相对来说精度较差、工作量较大.本工作采用了单体系γ~∞与无限稀释条件下活度系数-组成曲线斜率结合回归(简称斜率法).斜率测定用Valentin-Guiochon公式.比较了三种方法,工作表明:多γ~∞法一般较差,斜率法结果较为满意.分析了UNIFAC参数对γ~∞及((?)γ)/(?)x)_x=0的灵敏度,发现γ~∞的影响比((?)γ/(?)x)_x=0大.用极大似然法讨论了参数估计与置信区间.     

模拟人居环境中合成材料老化挥发物的试验方法

综述了模拟人居环境中合成材料老化挥发物的试验方法,包括环境试验装置、模拟人居环境试验、挥发性有机化合物(VOC)的分析方法和室内人居环境中的VOC散发模型.在此基础上,指出今后值得注重的若干研究课题.     

Development of a test method using a VOC analyzer to measure VOC emission from adhesives for building materials

A volatile organic compound (VOC) analyzer is a portable device to measure the four main aromatic hydrocarbon gases: toluene, ethylbenzene, xylene and styrene. With the VOC analyzer, a semiconductor gas sensor eliminates the need for the carrier gas which is required for conventional gas chromatography. In addition, since the semiconductor gas sensor is supersensitive to gas components, it is not necessary to use a conventional gas concentrator or other complicated equipment. Compared with other measurement methods, the VOC analyzer is useful for measuring toluene, ethylbenzene, xylene and styrene in new buildings because of its ease in obtaining field results and repeating the test. For easy, fast and economic testing of total (TVOC) emission from adhesives used for building materials, we developed a test method using the VOC analyzer and compared its measurement of VOC emissions from building materials such as adhesives, paints and wood-based panels with that of the 20-l chamber method, which is the standardized test method in Korea. There was a good correlation between the TVOC emission concentrations determined by the VOC analyzer and the TVOC emission factor (EF) by the 20-l chamber. Based on this good correlation, the VOC analyzer is expected to gain widespread use in the manufacturing field application where a quick and easy test for VOC emission from adhesives for building materials is required. Furthermore, the VOC analyzer offers the potential to become an easier, faster and more economical technique than the currently used standard methods.     

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.     

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。     

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%.     

Influence of VOC and formaldehyde emission from tile adhesives on their indoor concentrations in buildings

Volatile organic compounds (VOC) and formaldehyde emitted from building materials are considered to be one of the main causes of indoor air pollution in buildings. To reduce indoor pollutant concentrations, new installation methods for wall papers and flooring materials have been widely introduced to the construction field, including a nonadhesive floating method. However, adhesives are still widely used to install wall tiles or floor tiles on areas such as kitchens, bathrooms, and showers. The objective of this study was to investigate the influence of tile adhesive emissions on indoor air quality. The VOC and formaldehyde emission rates from two different types of tile adhesives, a conventional adhesive and a low-VOC emission adhesive, were measured using small emission test chambers. Full scale experiments were also carried out in three identical test rooms in a building. One wall of each room was finished with wallpaper in Test Room 1 and with tiles in Test Rooms 2 and 3. The other walls and ceilings were finished with wall papers in all test rooms. Wall tiles of Test Room 2 were installed with the conventional adhesive, while those of Test Room 3 were installed with the low-VOC emission adhesive. The indoor VOC concentrations in Test Room 2 were significantly higher than those in Test Room 3 due to a significantly higher VOC emission from the conventional tile adhesive. Even though the adhesives were applied under the finishing materials, investigation revealed that the adhesives were the most dominant contributor of indoor VOC concentration.     

木家具表面挥发性污染物散发传质特性

木家具表面挥发性污染物的散发是一类污染环境的复杂传质行为。为准确把握传质特性,首先建立了一套更完善的新式完全解析模型,综合考虑了两大传质机理(扩散、对流)、气候箱中污染物阻力、背景浓度和进气浓度,同时适用于无换气或换气条件下的模拟研究;例如,预测气候箱或木家具中污染物浓度变化,评价传质速率或散发量,以及估算室内浓度达标时限。然后通过对模型的分析提出了一套简便快捷的新式实验法,利用木家具在换气箱中散发的逐时浓度,一并求取目标污染物的3个重要传质参数:可散发量ρ₀、扩散系数δ和分配系数β。实验部分使用该换气箱法测算了某密度板家具中甲醛和总挥发性有机化合物的ρ₀、δ和β,与文献中基于密封箱的数据处理方法所得结果的变异系数小于5%,并有效避免了出现负压等密封箱采样可能导致的潜在问题。将传质参数代入数值算法预测了密封箱和换气箱中木家具散发挥发性污染物的浓度变化,与实验测量的数据吻合良好。该模型和方法能够准确预测或测定木家具表面挥发性污染物传质特性。     

The importance of reducing the systematic error due to non-linearity in N2O flux measurements by static chambers

Closed (non-steady state) chamber measurements are often used to determine the gas exchange of N₂O. Many researchers have addressed the underestimation of the emission estimates obtained from closed chamber measurements when using linear regression methods. However, the linear regression method is still usually applied to derive the flux. The importance of using non-linear regression methods is demonstrated with data from four fertilizing events each consisting of 1 month of automatic chamber measurements at Cabauw in the Netherlands in the period from July 2005 to July 2006. It is presented that the cumulative emission estimates with the exponential regression method are close to the cumulative emissions estimates with the intercept method. The linear estimates differ by up to 60% of the estimates with the exponential method. The performance of each method is validated using a C₂H₆ tracer and a goodness-of-fit analysis. The goodness-of-fit is much better for the exponential than the linear regression method. The systematic error due to linear regression is of the same order as the estimated uncertainty due to temporal variation. Therefore, closed-chamber data should be tested for non-linearity and an appropriate method should be used to calculate the flux. An erratum to this article can be found at     

A multi-phase model for VOC emission from single-layer dry building materials

A multi-phase model for the emission of VOC from dry building materials is developed. Dry building materials are viewed as porous media. A general adsorption isotherm is used to construct the concentration equation in the porous media. The boundary conditions at the material-air interface are presented for both CFD model and one compartment model. With the use of Henry’s law for the adsorption isotherm, an analytical solution is obtained and further is validated with the comparison of the experiment performed by Yang et al. [1], yielding a relatively good agreement. The effects of the model parameters on the emission are investigated in detail. Increasing the effective diffusion coefficient and the partition coefficient tends to promote the emission and increase the peak value of the concentration in the air. The effect of the porosity depends on the degree of the dependence of the effective diffusion coefficient on the porosity. When a weak dependence exists, the increase of the porosity tends to suppress the emission and decrease the peak value of the concentration in the air. However, when a strong dependence exists, the increase of the porosity tends to promote the emission and increase the peak value of the concentration in the air.