Effects of Temperature and [S] on the Kinetics of Nitrogen Removal from Liquid Steel

The kinetics of denitrogenation from liquid steel was studied by using an oxygen-nitrogen analysis system(LECO TC-436) under 1600 degreesC similar to 2813 degreesC conditions. The results show that when [S]=0.005%, nitrogen removal was controlled by nitrogen transfer in liquid diffusion layer, when [S]=0.012% and 0.140%, it was controlled by both nitrogen transfer in liquid diffusion layer and the chemical reaction at the liquid-gas interface below 2250 degreesC, and by nitrogen transfer in liquid diffusion layer under 2250 degreesC similar to 2813 degreesC conditions. The activation energy E-a was 57 kJ/mol for 0.0050%[S], 95 kJ/mol for 0.012%[S], 165 kJ/mol for 0.140%[S]. The resistance of sulphur on nitrogen removal decreased with the temperature rose, and disappeared at 2630 degreesC. Based on the results obtained, it has been answered why the nitrogen in liquid steel can be decreased rapidly by carbon-oxygen reaction under very high oxygen and sulphur content conditions during the BOF, EAF, VOD and AOD steelmaking processes.

Study on Purification Efficiency of Vertical Flow Wetlands on Domestic Wastewater

The combination method of intermittent influent and vertical flow wetlands （VFW） was used in the test to treat the domestic wastewater. Four artificial wetlands including Typha latifolia wetland,Phragmites australis （P.H.） wetland,polyculture wetlands （Typha latifolia and Phragmites australis） and non-vegetation wetland were established in the test. The effects of hydraulic retention time （HRT） and plant species on pollutants removal efficiencies were studied. The results showed that when HRT=7,the treatment efficiencies of wetlands with plants for the removal of TN and NH＋4-N were up to 99.65% and 99.58%,respectively. For the control wetland,TN removal efficiency was up to 87.9% when HRT were 6 days,and NH＋4-N removal efficiency was up to 91.8% when HRT were 5 days. TP removal efficiencies of four wetlands were higher than 93% when HRT was 6 days. Through the studies on different plants,it was found that vegetation wetlands had better nitrogen removal efficiency than non-vegetation wetland. The treatment efficacy of Phragmites australis wetland and polyculture wetland was better than Typha latifolia wetland.

Influence of sulfation on CeO_2-ZrO_2 catalysts for NO reduction with NH_3

CeO2‐ZrO2 (CeZr) and sulfated CeO2‐ZrO2 (S‐CeZr) catalysts were prepared for the selective catalytic reduction of NO with NH3. The CeZr catalysts exhibited higher activity at low temperatures (< 200°C) and lower activity at high temperatures (> 200 °C) than the S‐CeZr catalysts. The sulfation ofCeZr was studied in terms of surface acidity, redox properties and NO adsorption‐desorption bytemperature‐dependent experiments and in situ infrared spectroscopy. S‐CeZr displayed high concentrationsof acidic sites and increased surface acidities, but poor reducibility compared with CeZr.The high acidity of S‐CeZr was attributed to the presence of Br?nsted acid sites, arising mainly fromthe surface sulfates. Because the surface was covered with sulfate species, S‐CeZr showed lower NOadsorption and weaker oxidation ability than CeZr. The adsorption of NH3 on the Br?nsted acid sites restricted the reaction with NO at low temperatures, but the selective catalytic reduction cycle occurred easily at relatively low temperatures (150 °C), and the weakly bound nitrite was partially activated on the S‐CeZr catalyst at relatively high temperatures (300 °C). The catalytic mechanisms for the CeZr and S‐CeZr catalysts at 150 and 300 °C were also studied.

NO reduction by CO over TiO_2-γ-Al_2O_3 supported In/Ag catalyst under lean burn conditions

TiO2/γ-Al2O3 supported In/Ag catalysts were prepared by impregnation method,and investigated for NO reduction with CO as the reducing agent under lean burn conditions.The microscopic structure and surface properties of the catalysts were studied by N2 adsorption-desorption,X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,ultraviolet-visible spectroscopy,H2 temperature-programmed reduction and Fourier transform infrared spectroscopy.TiO2/γ-Al2O3 supported In/Ag is a good catalyst for the reduction of NO to N2.It displayed high dispersion,large amounts of surface active components and high NO adsorption capacity,which gave good catalytic performance and stability for the reduction of NO with CO under lean burn conditions.The silver species stabilized and improved the dispersion of the indium species.The introduction of TiO2 into the γ-Al2O3 support promoted NO adsorption and improved the dispersion of the indium species and silver species.