Effectiveness of SO2 sorbents by thermogravimetry-combustion with coal

A new experimental method is described for non-isothermal thermogravimetry (TG) involving combustion of mixtures of sieved coal with sieved calcium-containing sorbents. This rapid TG method utilizes a baseline for TG combustion of coal alone, derives an equation that gives a semi-quantitative measure (±10% repeatability) of the coal's reactive sulphur retained by the sorbent, the extent of retention of S0₂ generated in situ during combustion varying with different sorbents. The method permits direct variation in separate experiments of the calcium-to-sulphur ratio during combustion and relative ranking of different sorbents by retention of reactive sulphur in combustion. Relative rankings are presented for three pre-calcined natural stones (two limestones and one dolomite); these results correlate with relative rankings from another TG method reported in the literature. It is suggested that this new method is useful for pre-screening the effectiveness of S0₂ sorbents considered for use in fluidizedbed combustion of coal.     

Conductivity of nanometer TiO2 thin films by magnetron sputtering

The conductivity of nanometer TiO₂ thin films was presented in this paper. The dependence of the conductivity of TiO₂ thin films on the thickness of the film and the substrate material were educed. The TiO₂ films were deposited by reactive magnetron sputtering of a Ti targets in an Ar+O₂ mixture in a conventional sputtering reactor. The thickness of the films deposited on Ti varied in the range from 15 to 225 nm. The resistivity of the films was measured at room temperature in the air. It was found that the conductivity of TiO₂ thin films varies in the range from conductor, semiconductor to nonconductor. This was attributed to electrons transfer at the interface between the TiO₂ and substrates, and the depth of electrons transfer was determined by the difference of work function.     

Natural working fluids for solar-boosted heat pumps

The option of using natural working fluids as a substitute of R-22 for solar-boosted heat pumps depends not only upon thermal performance and hazardous rating but also on potential impacts on the environment. This paper presents the comparative assessment of natural working fluids with R-22 in terms of their characteristics and thermophysical properties, and thermal performance. Some justification is given for using natural working fluids in a solar boosted heat pump water heater. The results show that R-744 is not suitable for solar-boosted heat pumps because of its low critical temperature and high operational pressures. On the other hand, R-717 seems to be a more appropriate substitute in terms of operational parameters and overall performance. However, major changes in the heat pumps are required. R-290 and R-1270 are identified as candidates for direct drop-in substitutes for R-22.     

Effect of Cobalt Precursors on the Dispersion of Cobalt on MCM-41

The photocatalytic activity of titanium dioxide supported on zeolites HZSM-5, HY and H was evaluated for a novel intermolecular cyclization of ethylenediamine with propylene glycol leading to dihydropyrazine. Titanium dioxide supported on zeolites has been prepared with 2 and 5 wt% of TiO₂ by solid-state reaction, impregnation and sol impregnation methods. From the characterization by XRD, BET, EDAX and TPD of NH₃, it is deduced that in all cases titanium dioxide is in small particles of anatase on zeolites. The highest photocatalytic activity was obtained with 2 wt% TiO₂/H prepared by solid-state reaction. The acidity determined by TPD of NH₃ was found to be lower for TiO₂/H than for TiO₂/HZSM-5 and TiO₂/HY. From the above observations, it can be concluded that adsorption, acidity and structure of zeolites have an influence on the activity of supported TiO₂.     

天然气等离子体法制氢技术

传统的天然气蒸汽转化制氢方法在制取氢气的同时,伴随着大量的"温室气体"二氧化碳排放。本文介绍了等离子体技术及其在裂解天然气制氢气和炭黑方面的应用。由分析可知,高温下天然气裂解为氢气和炭黑是一个在热力学上有利的过程,该工艺减少了二氧化碳排放,减轻了环境污染;在产品成本和能耗方面也有竞争力。     

过渡金属硫化物催化剂上NH3还原SO2的反应

采用沉淀法制备过渡金属硫化物与TiO2的复合硫氧化物催化剂样品,考察了该催化剂上NH3选择性还原SO2反应。与相应的氧化物催化剂相比,过渡金属硫化物催化剂上NH3选择性还原SO2的反应活性增高,单质硫选择性增加。催化剂的活性与其自身的氧化还原能力、硫化物的比表面积及所属结构有一定的关系。过渡金属离子的电负性与催化剂活性呈明显的“火山型”曲线,电负性适中的CoS2—TiO2催化剂的活性较高。根据以上研究提出了硫化物催化剂上NH3还原SO2的反应机理,催化剂活性来源于硫化物物相和TiO2的双组分协同作用。     

Effect of formate and methanol on photoreduction/removal of toxic cadmium ions using TiO2 semiconductor as photocatalyst

Photoreduction/removal of cadmium was studied at pH 7 using TiO₂ Degussa as photocatalyst, and either formate or methanol as hole scavengers. In the absence of organic additives, approximately 60% of cadmium was found to be removed from the solution by adsorption. Addition of formate resulted in the photoreduction of cadmium to its metallic form. No cadmium reduction was observed when methanol was added as the hole scavenger. Zeta potential measurements of the catalyst suspensions and studies on the extent of organic additive adsorption and mineralisation were used to prove the photoreduction process. It was found that the adsorption of both cadmium and the organic hole scavenger is crucial for the photoreduction of cadmium. It is postulated that to be an effective hole scavenger the organic additive needs to be easily photooxidised under an anoxic environment. In addition, the presence of formate radicals could be responsible for the Cd photoreduction.     

Effects of carbon dioxide on bacterial growth parameters in milk as measured by conductivity

Inhibition of bacterial growth by dissolved carbon dioxide (CO2) has been well established in many foods including dairy foods. However, the effects of dissolved CO2 on specific growth parameters such as length of lag phase, time to maximum growth rate, and numbers of organisms at the stationary phase have not been quantified for organisms of concern in milk. The effect of dissolved CO2 concentrations of 0.6 to 61.4 mM on specific bacterial growth parameters in raw or single organism inoculated sterile milk was determined at 15 degrees C by conductance. Commingled raw or sterile milks were amended to a final concentration of 0.5 mg/ml each of urea and arginine HCl. Sterile milks were inoculated singly with one of six different microorganisms to a final concentration of approximately 10(2) to 10(3) cfu/ml; raw milk was adjusted to a final indigenous bacterial population of approximately 10(3) cfu/ml. Conductivity of the milk was recorded every 60 s over 4 to 5 d in a circulating apparatus at 15 degrees C. Conductivity values were fit to Gompertz equations and growth parameters calculated. Conductance correlated with plate counts and was satisfactory for monitoring microbial growth. Data fit the Gompertz equation with high correlation (R2 = 0.96 to 1.00). In all cases, dissolved CO2 significantly inhibited growth of raw milk bacteria, influencing lag, exponential, and stationary growth phases as well as all tested monocultures.     

四川省土壤有效硫状况及硫肥效应研究

通过对四川省 6类 32 9个土壤样品的有效硫的分析 ,结果表明缺硫及潜在性缺硫土样占总样本的 2 3 1 % .但结合田间试验 ,在四川盆地特定环境条件下 ,即使土壤耕层有效硫处于缺乏范围 ,增施硫肥对玉米、小麦、油菜产量无明显增加 ,并就产生的原因作了初步分析 .通过对土壤硫素平衡的测算 ,预测在近期内 ,四川盆地主要农耕地不会发生大面积缺硫问题     

Reference Values of the Dielectric Constant of Natural Gas Components Determined with a Cross Capacitor

A novel toroidal cross capacitor was used to measure accurately the dielectric polarizability(p) (i.e., the dielectric constant as a function of the pressure) of helium, argon, nitrogen, methane, and carbon dioxide atT=50°C. The data extend up to 7 MPa (5 MPa for CO₂) and may be useful for calibrating on-line, capacitance-based systems that are designed to measure the heating value of natural gas. The uncertainties ofandpare 4×10^–6and (3.0×10^–5 p+84 Pa), respectively. The properties of helium that had been calculatedab initiofrom quantum mechanics were used to verify that the cross capacitor deformed in a predictable manner under hydrostatic (gas) pressure. Thus, a common cause of systematic errors in measuring the dielectric constant of gases was avoided. For helium, the rms deviation of(p) from the calculations was only 2.7×10^–7. This suggests that the estimated uncertainty is very conservative.