Numerical investigation of tube furnace toxicity measurement method (ISO 19700)

ISO TS 19700 describes a test method for the generation of fire effluent and the identification and measurement of its constituent combustion products. The method has been previously accepted as a British Standard (BS 7990:2003) and as an IEC Standard (IEC 60695‐7‐50), which involves the decomposition of materials or products under various decomposing conditions occurring in different types and stages of real fires. It uses a moving test specimen and a tube furnace at different temperatures and air flow rates as the fire model. Simulations of flow and combustion conditions inside the tube (Purser) furnace were carried out and validated with the measurements. The objective of the present study is to demonstrate the validity of using computational fluid dynamics (CFD)‐based fire field modelling techniques to predict the fire environment inside the tube furnace. These numerical investigations are also used to verify critical experimental operating parameters that affect the performance of the tube furnace and understand the modus operandi of the tube furnace toxicity method. Copyright © 2011 John Wiley & Sons, Ltd.     

从燃烧温度分析套筒窑燃烧高炉煤气的可行性

计算了传统工艺下套筒窑燃烧高炉煤气时下燃烧室的燃烧温度并分析了其不可行性,并就采用燃气预热技术、高效喷射技术及无焰燃烧技术对下燃烧室燃烧温度的影响进行计算分析,从而得出套筒窑燃烧高炉煤气的可行性,并给出若干措施及建议。     

Predicting toxic gas concentrations at locations remote from the fire source

A toxicity model capable of predicting toxic gas concentrations within fire enclosures utilizing the concept of the local equivalence ratio (LER) was recently developed. This paper describes an enhancement of the original model that improves its accuracy in predicting species concentrations at remote locations from the room of fire origin. The enhanced technique involves dividing the CFD computational domain into two regions for species calculation, a control region (CR) and a transport region. Toxic gas concentrations in the CR are calculated using the formulation developed in the earlier study whereas in the transport region, gas concentrations are determined as a result of the mixing of hot combustion gases with fresh air. The concept of a critical equivalence ratio, which is derived from the effective heat release rate (or combustion efficiency) of the fire scenario being simulated, is introduced to perform the domain division. Predictions of temperatures and species concentrations at various locations made by the new model are compared with the results from two experiments. Compared with the earlier model, the modified model provides considerable improvements in the predictions of toxic species levels. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of burning temperature on the structural changes of Woodceramics

Woodceramics are new porous carbon materials obtained by burning wood or woody material impregnated with thermosetting resin in a vacuum furnace. In this paper, the effect of burning temperature on the structural changes of Woodceramics is analyzed experimentally.Woodceramics were prepared using medium density fiberboard which was burned at temperatures less than 1000°C in a charcoal kiln. A drastic decrease in dimensions and weight was observed at temperatures lower than 600°C but they decreased gradually at temperatures higher than 600°C. Reproducibility of dimensions and weight by burning is possible.When Woodceramics were prepared by burning at higher than 1600°C by high frequency induction furnace, dimensions and weight decreased due to transformation of amorphous carbon to graphite, but the porous structure of wood remains unchanged.The distribution of glassy carbon and amorphous carbon was difficult to decipher after graphitization by observation with SEM and X-ray diffraction analysis.     

The effect of high-intensity ultrasound on solid polymers

Powders of polyethylene, polypropylene, poly(vinyl chloride) and poly(methyl methacrylate) have been subjected to irradiation with high-intensity ultrasound while suspended in water. Changes in the particle sizes and the surface morphology were noted and the pattern of the results was correlated with the physical properties of the materials. In anticipation of sonochemically enhanced reactions at polymer surfaces, the effect on a polyethylene sheet was also examined. The implications of the results for preparative methods as well as surface reactions are discussed.     

Stark effect on persistent spectral hole burning and dipole moment characteristics of anthraquinone derivatives doped in polymers

We have investigated the Stark effect on the spectral hole characteristics in the photochemical hole burning reaction in systems of anthraquinone derivatives, such as 1,4-dihydroxyanthraquinone (DAQ) and 4-amino-2,6-bis(4-butylphenoxy)1,5-dihydroxyanthraquinone (ABDAQ) as guest molecules embedded in host polymers such as 2-hydroxyethyl methacrylate (PHEMA) or poly(vinyl butyral) (PVB). The hole broadening and refilling were observed by applying an external electric field to the samples. Thus, the dipole moment differences of the guest molecules between the ground state and the excited state were estimated as follows: 0.38, 0.51 and 0.26 D in the DAQ/PHEMA, ABDAQ/PHEMA and ABDAQ/PVB systems, respectively. These material dependent characteristics of have been able to be explained qualitatively by Hammett's substituent constant and the Taft's polar substituent constant. Furthermore, from the application view point, 5 × 5 multiple spectral holes could be formed in both the wavelength and the electric field dimensions at 4.2 K in the ABDAQ/PVB system. This result indicates that high-density data multiplexing can be achieved in both the wavelength and the electric field dimensions using the Stark effect on the spectral holes.     

The effect of variation in polymer properties on the rate of burning

The sensitivity of the burning rate to variations in physical and chemical properties of synthetic polymers has been examined in order to understand the relative importance of the knowledge of these properties. The sensitivity analysis was performed using a numerical pyrolysis model called ThermaKin, which was employed to compute the rate of burning (expressed in terms of mass loss) of a one‐dimensional material object exposed to steady radiative heat. The results of the calculations indicate that the knowledge of decomposition reaction parameters (including the Arrhenius pre‐exponential factor, activation energy, heat, and char yield) is of key importance for prediction of the peak and average burning rates. Copyright © 2009 John Wiley & Sons, Ltd.     

The effect of oxygen concentration on CO and soot yields in fires

In addition to global ventilation effects on fires, vitiation of air can also affect the generation of chemical species in a built environment. Experiments were performed at lab‐scale with the Fire Propagation Apparatus (ASTM E2058) in order to study the effect of air vitiation on CO and soot yields. Results regarding the fuel burning rate are also presented. Both carbon dioxide and nitrogen were used as diluents in the inlet air flows. The oxygen concentration was decreased stepwise until the extinction point was reached. A first set of experiments was performed in well‐ventilated fire conditions (equivalence ratio between 0.1 and 0.25). A second set of experiments was carried out in under‐ventilated fire conditions (equivalence ratio equal to 1.1). A procedure is proposed for experimental data reduction. The results revealed themselves useful for improving combustion sub‐model predictions. Copyright © 2007 John Wiley & Sons, Ltd.     

电场和提取剂对提取胞外聚合物的影响

本文研究了电场和提取剂对胞外聚合物提取效果的影响,实验测定了在交流电场下不同的提取剂如：NaOH、EDTA、Tris和硫酸对提取液中的多糖含量,结果表明,电场和提取剂对提取效果有明显影响。     

聚合物在高温高盐油藏中的应用

随着油田的不断开发,油藏条件不断恶化,高温高盐油藏不断增加,如何提高这类油田的采收率成为油田稳产的基础。本文论述了聚合物在高温高盐油藏调驱中应用现状和发展趋势,得出了聚合物弱凝胶体系是高温高盐油藏提高采收率的一种具有前景的重要技术。     

Effects of temperature on elastic behavior of short compact polymers

In this paper, we study further to explore the effects of temperature on the elastic behavior of short compact polymers. Average conformations and thermodynamics statistical properties at various temperatures T are calculated here. Different chain lengths N and elongation ratio λ are also considered simultaneously. From the plots of f and f_U vs. elongation ratio at low temperature, we can know that compact polymers are more close to the native states. With temperature decreasing deeply, polymer chains have the tendency to form globular structures. The results are concluded from: the ratio of 〈L₁²〉/〈L₂²〉 increase abruptly with temperature decreasing at low temperature, and both characteristic ratio 〈R²〉/Nb² and average energy per bond 〈U〉 decreases abruptly with temperature decreasing at low temperature, here L₁², and L₂² are the eigenvalues of the radius of gyration tensor S (L₁²≤L₂²). We also analyze the relationship between the heat capacity C_V and temperature T for different chain lengths in the process of tensile elongation. The coil-to-globule transition temperature T_c can be estimated from the location of the peak on the heat capacity plot as a function of temperature. The plots of 〈R²〉 as a function of chain length N at different temperatures are also shown, and the correlation 〈R²〉∼N^α is obtained at T>T_c or T<T_c, while at T=T_c, the plots are irregular, here α depends on temperature and elongation ratio simultaneously. Elastic force (f), energy contribution to elastic force (f_U), and the ratio f_U/f are also discussed at various temperatures. These investigations may provide some insights into elastic behaviors of compact polymers at different temperatures, especially at low temperature.     

The effect of polymerisation methods on the adsorption capacity of HEMA based molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are generally synthesised either by thermal initiation or by photo polymerisation methods. Recently we used a gamma irradiation method for the preparation of MIPs. In this communication we compare three different methods for the synthesis of 2-hydroxy ethyl methacrylate (HEMA) based MIP imprinted for hydrocortisone in terms of its capacity to adsorb the print molecule. Our results show that MIP prepared by the gamma irradiation method has a better adsorption capacity than the thermally initiated polymer. It is interesting to note that its adsorption capacity is comparable or marginally better than the photo polymerised MIP.     

The effect of disperse dyes on the glass transition temperature of polymers

The lowering of the glass transition temperature (T_g) of a polymer produced by the incorporating various concentrations of azo disperse dyes has been investigated, and the effects of the structure and concentrations of the dyes were examined. The T_g values were lowered with increasing dye concentrations in the polymer, and the lowering of T_g produced by the dyes was influenced not only by the molecular structure of the dyes but also the dye-polymer interactions.     

The effect of confinement in nanoporous polymers on the glass transition temperature

The glass transition temperature (T_g) of nanoporous polyetherimide (PEI) and PEI thin films was investigated. The T_g decreased from its bulk value in both of these confined systems. Monte Carlo simulations were performed to calculate the nearest neighbor pore-to-pore distances in the nanoporous PEI. A quantitative analogy between the nanoporous PEI and PEI thin films is proposed through an equivalence of nearest neighbor pore-to-pore distances and thin film thickness. The effect of confinement is believed to be due to the interface regions, which possess higher chain mobility than the bulk. When these high mobility interface regions are sufficiently close together, the excess mobility at the interface region affects the dynamics of the system by restraining percolation of the slow domains resulting in the observed decrease in T_g.     

高温石墨炉法测定痕量金属的条件选择

高温石墨炉法测定痕量金属对工作条件的要求非常严格,影响分析准确度和精密度的原因较多。从干燥温度和时间,灰化温度和时间,原子化温度和时间,高温除残温度和时间的选择,自动进样器的调整,试样处理等几个方面,合理、正确地选择工作条件能够得到最佳吸收灵敏度和测量精密度。     

Analysis of work on smoke component yields from room‐scale fire tests

Smoke Component Yields from Room‐Scale Fire Tests (NIST Technical Note TN 1453) has recently been published. This was expected to be an important work in developing concentrations and yields of toxicants that could be used for evaluating the usefulness of small scale smoke toxicity apparatuses (or fire models) for use in the prediction of the toxicity of materials and products in real fires. However, the work has a number of uncertainties that limit its potential for use as a reference. There are three major problems with this work. First, the post‐flashover concentrations of CO are too low (as recognized by the authors who recommend that this part of the data not be used). Second, the post‐flashover concentrations of the main toxicants measured (HCN and HC1) were much higher than found in most studies. Third, the precision of the data was inadequate. The consequence of the first two issues is that the work seriously overestimates the toxicological importance of gases known to have only minor effects in post‐flashover fires, such as HCN and HCl. The very low concentrations of toxicants measured at pre‐flashover conditions might have a value not discussed by the authors: an indication that pre‐flashover fires of the type conducted here do not generate extremely toxic atmospheres. Accordingly, the report does not provide reliable characteristic room scale combustion gas data that can be used for validating small‐scale furnaces. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of molding temperature and pressure on properties of soy protein polymers

Because of the worldwide environmental pollution problem with petroleum polymers, soy protein polymers have been considered as alternatives for biodegradable plastics. The objective of this research was to study the curing behavior of soy protein isolates (SPIs) for that application. The molding variables of temperature, pressure, and time and curing quality factors of tensile strength, strain, and water resistance were evaluated. The maximum stress of 42.9 MPa and maximum strain of 4.61% of the specimen were obtained when SPI was molded at 150°C and 20 MPa for 5 min. The water absorption of the specimen decreased as molding temperature and time increased. Glycerol greatly improved the flexibility of the specimen but decreased its strength. For SPI with 25% glycerol added, the maximum stress and strain of about 12 MPa and 140%, respectively, were achieved when the specimen was molded at 140°C for 5 min. Molding temperature, pressure, and time are major parameters influencing the curing quality of soy protein polymers. At fixed pressure, the molding temperature and time had significant interactive effects on curing quality. At high temperature (e.g., at 150°C) it took about 3 min to reach optimum curing quality; however, at low temperature (120°C) it took about 10 min to reach optimum curing quality. The maximum strength and strain of the cured protein polymer occurred at the molding temperature close to its phase transition temperature or about 40°C below its exothermic temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2595–2602, 1999     

基于迁移学习工况划分的裂解炉收率PSO-LS-SVM建模

乙烯裂解炉收率的实时预测对于生产的先进控制及节能降耗具有重要意义。实际生产过程中,不同工况的收率具有较大差别,采用单一工况、单一模型无法满足生产需要。考虑到裂解炉不同运行过程中的相似性,同时为了减小建模过程中典型样本的采集成本,有效利用历史数据,辅以迁移学习算法实现工况的高精度划分。不同工况采用泛化能力强、训练速度高的最小二乘支持向量机建模,并利用粒子群算法对LS-SVM的参数寻优,进一步提高模型精度,从而实现了多工况、多模型的高精度收率预测。基于某乙烯厂现场数据的实验结果表明,多工况、多模型的预测效果更准确合理,PSO优化LS-SVM建立的裂解炉收率模型预测精度更高,趋势跟踪性能良好。