Polycyclic aromatic hydrocarbons emitted by power stations,and influence of combustion conditions

Polycyclic aromatic hydrocarbons (PAH) were measured in the emissions of seven power stations. For the first time, all measurements were made with standard sampling and uniform analysis procedures. The influence of effective power of the station, nature of fuel (coal, oil, diesel oil) and kind of furnace was determined. The relations between PAH emission and excess oxygen in flue gas, NO_x concentration, calorific value and composition of the fuel and amount of ash were established. Very fast reactions, at high temperature, between PAH and gaseous pollutants are possible in the furnace or during the passage of flue gas through the stack. The gas-particle ratio of the PAH also depends on all combustion parameters. The PAH emitted are unburnt matter, numerous light compounds (with two or three rings) or heavy compounds or after demethylation of alkyl PAH. The impact of power stations on the amount of PAH in the atmosphere cannot exceed 5% in large cities.     

Generating a representative signal of coal moisture content to anticipate combustion control in thermal power stations

This article describes the possibilities of continuously measuring coal moisture in the boiler feeding circuit of a thermal power station so that the measurement can be used as a signal for the boiler combustion control system. To do so, in the first place, the point through which coal would be fed into the boiler was chosen. After studying the different parts of the circuit, the feeder was selected. Then, an installation was designed, at semi-industrial scale, faithfully reproducing the operation of a belt conveyor. In order to measure the moisture content, a microwave system was installed, and a large number of coal samples with different ranks and grain sizes was tested showing eventually the likelihood of the objective.     

用氧化锌晶须改善稠油冷采中螺杆泵定子的耐磨性能

随着采油工艺技术的不断发展，螺杆泵采油技术在稠油出砂冷采中得到了普遍应用。并取得了巨大的经济效益。但在生产过程中，螺杆泵易因砂磨而失效。这主要是由于砂子的存在。使得泵中的元件发生缓慢的剪切作用。从而造成螺杆泵持续使用寿命平均为10～12月。通过螺杆泵的工作原理，分析了定子在工作过程中的受力状况，列出了造成螺杆泵磨损的因素。得出了螺杆泵的磨损分布规律，进而分析了螺杆泵橡胶定子在稠油携砂冷采中的磨损机理，最后提出了在传统的螺杆泵生产材料丁腈橡胶的基础上，用氧化锌晶须对其进行改性来提高螺杆泵在稠油冷采工况下的耐磨性。     

用氧化锌晶须改善稠油冷采中螺杆泵定子的综合性能研究

螺杆泵采油已成为油田开采常用的举升方式,特别是在普通稠油带砂冷采中有较重要的应用。现今所用的螺杆泵绝大部分是国产的,普遍存在的一个较严重的问题:定子橡胶材料的性能问题。使用螺杆泵开采的稠油中,常常含有较多的细粉砂,这就要求定子的橡胶材料具有较强的耐磨性,但同时又不能太硬,否则将影响转子的转动。目前国产泵寿命在3~5个月左右。针对影响丁腈橡胶存在的力学性能、耐磨性和尺寸稳定性不高等问题,讨论了氧化锌晶须对NBR硫化胶综合性能的补强效应,探讨了ZnO晶须在不同添加量下的综合性能,得出氧化锌晶须最佳添加量为10份时,复合丁腈橡胶的综合性能最好。     

Improvements in thermal,mechanical, and dielectric properties of epoxy resin by chemical modification with a novel amino-terminated liquid-crystalline copoly(ester amide)

We used a novel amino end-capped aromatic liquid crystalline copoly(ester amide) (LCP) to improve the thermal and mechanical properties of glycidyl end-caped poly(bisphenol A-co-epichlorohydrin) (DGEBA) cured with 4,4′-diaminodiphenylsulfone (DDS). The thermal and mechanical properties of the blends were investigated as a function of LCP loading. Upon addition of 10 phr of LCP, the impact strength of the modified epoxy was dramatically increased from 35.8 J/m to 51.8 J/m, which is an approximately 30% improvement compared to the un-modified system. In addition, an increase in the fracture toughness and decreases in the dielectric constant and the dielectric loss were found with increases in LCP loading in the blend. These improvements were achieved even when LCP was dispersed in an epoxy network within a homophase structure.     

Improvements in morphology,mechanical and thermal properties of films produced by reactive blending of poly(lactic acid)/natural rubber latex with dicumyl peroxide

The effect of dicumyl peroxide (DCP) as a free-radical cross-linking agent on the morphology, thermal and mechanical properties, and gas permeation of blown films prepared by reactive blending of poly(lactic acid) (PLA) and natural rubber latex was investigated. In comparison to the blown films without DCP, SEM micrographs revealed that the amount of debonded rubber domains from the cryofractured surface reduced considerably. This was when DCP at 0.003 phr was incorporated and the free radicals from thermally decomposed DCP reacted with PLA and NR chains, generating PLA–NR copolymers and cross-linked NR as confirmed by FTIR spectra. These PLA–NR copolymers acted as compatibilizers, which increased the strength at the PLA/NR interfaces, leading to the improvement in tensile strength, elongation at break, tensile toughness, impact strength, and tear strength. Although DCP did not influence the cold crystallization of PLA, TGA thermograms showed that thermal stability slightly increased owing to the enhanced interfacial adhesion. However, the addition of DCP at 0.005 and 0.010 phr resulted in a high content of cross-linked NR gel, by consuming the free radicals instead in copolymer formation. Therefore, the compatibilization efficiency was significantly reduced and the mechanical properties of reactive PLA/NR blown films finally dropped. Also, this poor interfacial adhesion facilitated the microvoid formation at the polymer–rubber interface as a result of mechanical stretching upon the film blowing process, increasing the permeation of water vapor and oxygen molecules. According to our study, it can be summarized that to optimize the morphology, mechanical properties, and gas permeation property of the free radical-assisted reactive blends, it is of great concern to carefully balance reactive compatibilizer formation and gel formation by adjusting the DCP content.     

Predictive equations for CO2 emission factors for coal combustion, their applicability in a thermal power plant and subsequent assessment of uncertainty in CO2 estimation

The emission of carbon dioxide varies systematically with the rank and type of coal combusted. Hence use of a single default emission factor proposed by IPCC (Inter Governmental Panel on Climate Change) for entire categories coals may not be appropriate option to obtain a reliable estimate of carbon dioxide emission level or towards the preparation of national carbon dioxide inventory. Even predictive equations developed based on the coals of different origin may not work well with coals of a specific origin. Several linear predictive equations were thus developed separately for coking and non-coking coals of Indian origin for the estimation of carbon dioxide emission utilizing basic coal parameters such as VM, FC, GCV and NCV on different basis. Large numbers of authenticated data set were used for multiple regression analysis and good correlations were obtained. Those equations were also validated with different data sets of Indian coals. Its applicability towards estimation of CO₂ emission from power plant was also studied and uncertainty in CO₂ estimation is revealed. The developed equations may be utilized to get a realistic estimate of carbon dioxide emission with specific cases where Indian coals are mostly used.     

Thermodynamics,a good theory for the study of electrochemistry in non-isothermal systems. A specific application: thermal diffusion

We present here a short survey on general non-equilibrium thermodynamics when the external forces are especially of electrostatical nature. Such a development provides a very well-adapted frame to analyse many irreversible processes as thermal diffusion in ionic media. This phenomena, so-called Soret effect in fluid mixtures, has greatly been studied by various experimental methods. Among these, the electrochemical ones give valuable information on quantities such as entropies and heats of transfer.     

In situ,quantitative characterization of gelation and fusion mechanism in poly(vinyl chloride) plastisols by small angle light scattering (SALS)

The present paper explores an effective means of characterizing structural changes of poly(vinyl chloride) (PVC) particles during gelation and fusion of PVC plastisols with small angle light scattering (SALS). The SALS method was shown to provide an in situ observation of swelling of PVC particles as well as quantitative information of average size of swollen particles while they are in progress of gelation and fusion. In addition, the SALS method enabled one to evaluate the relative solvent power of plasticizers from the manner of increase in the correlation distances.     

Characterization of polynuclear aromatic hydrocarbons in bitumen,heavy oil fractions boiling above 350 °C by g.c.-m.s.

The separation and characterization of polynuclear aromatic hydrocarbons of five fractions of bitumen, heavy oils and synthetic fuels boiling > 350 °C were performed using a combination of Chromatographic techniques. The polynuclear aromatic hydrocarbon fractions were obtained by liquid-solid chromatography and prior to the high performance liquid chromatography and gas chromatography/mass spectrometry techniques, the fractions were subjected to an acid/base extraction procedure to remove polar material. In total, 97 polynuclear aromatic hydrocarbons were tentatively identified by a correlation of their mass spectra and retention indices with those of 25 model polynuclear aromatic compounds.     

Effect of copolymers modifying PVC on its physical and mechanical properties and its UV-radiation resistance. III. Changes in thermal stability of PVC films modified by MMA/MA,VC/VAC,MBS or ABS induced by UV-irradiation

The influence of UV-radiation on thermal stability of PVC films, depending on the type and quantity of modifying copolymers, was studied. It was found that UV radiation can induce various changes in thermal stability of PVC decreasing its dehydrochlorination temperature T⁰₁ while increasing temperature of decomposition T⁰₂. Particularly distinct changes in sampels containing VC/VAC indicate that even 1% of this copolymer accelerates the photodehydrochlorination and the processes which decrease the temperature of decomposition of PVC. Smaller changes than in pure PVC in thermal parameters in samples containing ABS after irradiation show that this copolymer increases the PVC resistance to UV radiation. Films containing MBS, ABS, MMA/MA reveal the largest changes in T⁰₁ after irradiation in the case of a content of 1% of these copolymers in the samples. In the case of bigger quantity (3 to 10%) the changes are smaller and may even diversify their direction. These copolymers, contrary to VC/VAC, make PVC films a little turbid indicating the limited compatibility of both components. Hence, the conclution is that the structure of a film, depending on compatibility of components and changing with their differing concentration, has decisive influence on the thermal and photochemical processes.     

Pd/Ce0.6Zr0.4O2/Al2O3 as advanced materials for three-way catalysts: Part 1. Catalyst characterisation, thermal stability and catalytic activity in the reduction of NO by CO

Pd-loaded Ce_0.6Zr_0.4O₂ solid solutions supported on Al₂O₃ are investigated as catalysts for the reduction of NO by CO. The attention is focused on the role of the Ce_0.6Zr_0.4O₂ and of the Pd dispersion on the catalytic activity. The system shows a very high activity below 500 K, which is almost independent on the Pd dispersion. The high activity is attributed to a promoting effect of the Ce_0.6Zr_0.4O₂ on the NO conversion. Investigation of the influence of high temperature treatments disclosed a thermal stabilisation of both Ce_0.6Zr_0.4O₂ and Al₂O₃ in the Ce_0.6Zr_0.4O₂/Al₂O₃ system.