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21.
Wittaya Chuajiw Mitsuru Nakano Kazumasa Takatori Toshiya Kojim Yoshiki Wakimoto Yoshiaki Fukushima 《环境科学学报(英文版)》2013,25(12):2507-2515
The amount of carbon dioxide (CO2) absorption and calcium ion (Ca^2+) concentration besides the pH of aqueous solution were observed during the COz absorption to precipitate calcium carbonate (CaCO3) from calcium hydroxide (Ca(OH)2). A reaction rate-limiting effect of an amount of CO2 absorption without any organic additives in the early stage of the precipitation was observed, which was attributed to an interruption effect of bicarbonate ion (HCO3) on the precipitation of CaCO3. The improvement for the reaction rate was achieved not only by amine additives but also by neutral additives such as ε-caprolactam or amine salt. When the hexamethylene diamine was dissolved in the solution, successive change of crystal forms of CaCO3 aragonite to calcite in aqueous suspensions, confirmed by Ca^2+ concentration change and X-ray diffraction, was concluded that a local environment around the amine group in aqueous solution and an interaction of the diamine with precipitated CaCO3 particles were important factors for these reactions. 相似文献
22.
Toshiro Tsuji Yoshiki Tanaka Hironori Itoh 《Journal of Material Cycles and Waste Management》2001,3(1):2-7
Plastic pellets of polyethylene (PE), polypropylene (PP), and polystyrene (PS) were gasified in a two-stage thermal degradation
process. The first stage is the conversion of polyolefins to distilled oils using a melting vessel. In the second stage, the
oils from the first stage are gasified using a tubular reactor. The distilled oil yields of PE, PP, and PS in the first stage
were 84, 89, 92 wt%, respectively, each at 470°C. The total gas yields of PE, PP, and PS in the second stage were 80, 74,
and 6.2 wt%, respectively, each at 800°C. The main components of the product gas for PE and PP were methane and olefins such
as ethene and propene. Some aromatic oils, including benzene, toluene, and xylene, were also produced as by-products. The
amount of carbonaceous residue, or coke, was very low (less than 1 wt%). By dividing the process into two stages, the coking
rate was considerably reduced compared with direct gasification of the polyolefins.
Received: July 19, 2000 / Accepted: September 17, 2000 相似文献