In this study, a commercially available nano-sized silica (SiO 2 ) was surface-modified via esterification with oleic acid (OA), a relatively inexpensive and hydrophobic modifier, and characterized by FTIR, NMR, SEM, EDS, and TGA measurements. Various amounts of the surface-modified silica nanoparticles (SiO 2 -OA) were dispersed in a poly(amic acid), which were then cyclized at high temperatures to form a series of PI/SiO 2 -OA nanocomposite films (PISA). The effect of the addition of the SiO 2 -OA nanoparticles on the properties of the as-prepared polyimide nanocomposite was studied. The results indicated that, comparing with pure PI and PI/pristineSiO 2 composite film (PISI), the as-prepared PISA films had enhanced dynamic mechanical properties and thermal stability, as well as reduced water absorption and thermal expansion. The as-prepared PI/SiO 2 -OA nanocomposites have potential for applications in high performance microelectronic devices.

Some confusion still exists in the literature regarding the simultaneous absorption of SO2 and HCl by calcined limestone in hot flue gases. Therefore, further efforts to understand and clarify the absorption behaviors of SO2 and HCl are presented in this study. Experiments were carried out under conditions that simulated combustion in a fixed-bed reactor coupled with an online Fourier transform infrared spectrometer. The fixed-bed reactor used was specially designed to be capable of handling high-temperature operations involving gas–solid reactions. This paper described and explained the phenomena of variations in the concentration profiles of SO2 and HCl during the simultaneous absorption process. This work suggested possible heterogeneous and homogeneous reactions that may occur under the conditions being studied. Particular emphasis is placed on elucidating why concurrent sulfation enhancement and chlorination suppression occurs; experimental evidence confirmed that these processes were caused because of the behavior of the sulfation process of chloride. In the present study, to continuously monitor SO2 and HCl discharged during reaction processes plays a crucial role in observing particular phenomena, providing important information regarding absorption characteristics. From the experimental results, it was observed that, upon increasing the temperature from 650 to 700 °C, chlorination was considerably suppressed because chloride started to vigorously react with SO2, leading to the indirect enhancement of sulfation and the re-release of HCl into the gas phase. It was also surprising to find that, at or above 700 °C, the overall uptake efficiency remained nearly unchanged despite the difference in reactivity of SO2 and HCl. Besides, the importance and impact of the gas atmosphere on the uptake efficiency was also analyzed and compared.

This work aimed to elaborate on the influence of CO 2 on the reactivity of CaO with HCl under conditions similar to combustion environment. This study was conducted in an innovated fixed-bed reactor to investigate the influences of simulated CO 2 concentrations on the chemistry of CaO with HCl at varied temperatures. Tests of sole CaO carbonation and chlorination were performed in a thermogravimetric analyzer and fixed-bed reactor, respectively, to provide fundamental information for the CaO chlorination experiments in the presence of CO 2 . The HCl concentrations were continuously monitored in a Fourier Transform Infrared (FTIR) cell and the repeatability tests yielded good results. These results indicated that the presence of CO 2 was beneficial for the apparent reaction rates of CaO chlorination performed at 650 ˚C and 700 ˚C, compared with the case of only chlorination; nevertheless, this benefit accompanied a slight reduction of HCl capture capacity. The results were related to the CaO carbonation behavior. On the © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 other hand, further increased CO 2 concentrations had no effect on the extent of the chlorination reaction.

Experimental study of dry HCl removal from simulated combustion flue gases using calcined limestone (CaO) is reported. The study was conducted in a unique fixed-bed reactor coupled with an online Fourier transform infrared (FTIR) spectrometer to investigate the effects of the presence of SO 2 , CO 2 and O 2 on the chlorination reactivity of calcined limestone. The dechlorination efficiency, defined by the effluent HCl concentration, would be used to describe the HCl absorption history to gain a better understanding of the chlorination behavior. The experimental results indicated that the HCl uptake capacity remains less affected under various gas atmospheres at 650 °C although the chlorination is found to be faster when CO 2 is present. At temperatures of 750 or 850 °C, the presence of SO 2 or O 2 significantly decreases the reactivity of the calcined limestone toward HCl. The concurrent sulfation of chlorides, such as CaCl 2 •H 2 O and/or CaClOH, causes the subsequent rerelease of HCl to the gas phase, thus reducing the attainable extent of the chlorination reaction. The presence of O 2 impedes the conversion of calcined limestone to chlorides, presumably through some type of reaction involving the dechlorination of the sorbent particles.

The focus of this study is the effects of sulfur and calcium compounds on reducing dioxins in fly ash collected from the baghouse of a pilot-scale fluidized bed combustor. Pelletized sawdust with various amounts of polyvinyl chloride (PVC), pyrite, and calcium hydroxide was used as the feeding material. The experimental results indicated an extremely low concentration of dioxin in the fly ash from the cyclone (0.025 to 0.284 ng g -1 ), and the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the fly ash collected from the baghouse increased by 27.4% as the chlorine content increased from 0.568 to 1.136 wt%. The inhibition of PCDD/Fs by sulfur is not clear and can be attributed to the low content of copper (average 387 ppm), which serves as the catalyst for the Deacon reaction. Octa-chlorinated dibenzofuran (OCDF) was the major congener of the PCDD/Fs. The highest toxicity-equivalent (I-TEQ) of 2,3,7,8substituted congeners was 2,3,4,7,8-PeCDF, which accounted for 37% of the total congeners (average value). The correlation between the I-TEQ values and 2,3,4,7,8-PeCDF concentration of fly ash is also discussed.