Experimental Research and Mathematical Modelling for Coal Reburning in Furnace

1 Introduction Coal combustion is one of the main sources of forming NOx in the atmosphere. To reduce NOx emissions, various NOx reduction strategies have been investigated. Among recent developments for reducing NOx emissions, reburning technology is considered to be one of the most cost-effective ones for coal combustion systems, capable of reducing 50%–70% of NOx [1]. In the past several years, many investigators have worked on laboratory-scale measurements, kinetic mechanisms and nume…     

氯化物浸出黄铜矿的试验研究

研究了硝酸催化氧化、氯化物浸出黄铜矿的机理，考察了氧化和浸出反应的影响因素。研究结果表明：硝酸催化氧化的优化条件是酸度。0．50mol／L、温度95℃、硝酸量0．5％～1．0％。采用浸出、氧化分离式新工艺，4．5h铜的浸出率达97％，氧化除铁率97％，可实现黄铜矿浸出的综合优化。     

用超声波速度方法测试硝酸溶液浓度

用超声波分析溶液浓度的方法是基于声速与溶液相份的关系，这种关系还受到温度的较大影响，本文报道了超声速度与硝酸溶液浓度、温度关系的测量工作，实验结果显示，在质量百分比浓度为５０￣１００％范围内，声速随浓度增加而降低；在温度为１０￣５５℃范围内，声速也随温度升高而降低。根据实验结果计算了纯ＨＮＯ３液体的声速－浓度关系，本文还给出了声速法测硝酸浓度的智能仪器原理。     

A modified method of nitric acid pulping of bagasse

Pulping of bagasse by a rapid and mild nitric acid process was successfully carried out to produce different grades of pulp. Nitric chemimechanical bagasse pulp was produced in a high yield of 91 % on pulping depithed bagasse with 4% HNO₃ for a period of 30 min at 80°C, followed by alkali pulping with 2% NaOH at 95°C for 30 min. The pulp had a satisfactory strength and high opacity. On increasing the strengths of nitric acid to 7% and alkali to 7% a nitric semichemical pulp of 65% yield was obtained. The pulp had a superior strength and high opacity. The pulp was easily bleached to 71% general electric brightness (GE) with the chlorination-alkali-extraction-hypochlorite (CEH) sequence. With 15% HNO₃ and 8% NaOH, nitric chemical bagasse pulp was produced. The pulp was easily bleached to a high brightness of 82% GE with one stage hypochlorite. The pulp had a higher strength than kraft bagasse pulp. A satisfactory newsprint paper was produced on an experimental paper machine with a furnish composed of 80% bleached nitric semichemical bagasse pulp, 10% bleached softwood pulp and 10% clay.     

Hydration Model for Evaluation of Thermodynamic Activities in Nitric Acid-Nitrate-Water System

Modeling was carried out on activities of components in the nitric acid-nitrate-water ternary system in order to examine details of the chemical reactions in reprocessing solutions. To modify our earlier “Hydration Model”, the ternary system was regarded as the mixed solution of two kinds of cluster molecules which were dominant associated molecules in the nitric acid-water system and nitrate-water system, respectively. Activities in the ternary system were calculated from those in the two binary systems taking into account the change of entropy and enthalpy during mixing. The entropy term was calculated assuming ideal mixing. The enthalpy term was calculated assuming that the nitric acid cluster would be influenced by one nitrate cluster as if there were m _s /m _na numbers of nitric acid clusters, where m _s and m _na were the numbers of water molecules in nitrate and nitric acid cluster molecules, respectively.

The model was able to predict activities of nitric acid, water and nitrate. Its use was verified for the activities of nitric acid and water provided phase separation did not occur. The verification for nitrate activity was not carried out, however, the model should be suitable.     

Characterization and Comparison of Cellulose Extraction from Ginger Stalk by Two Different Chemical Treatments

Agricultural residues are important renewable biomass resources that have not received much research attention. Ginger stalk is a major agricultural waste in China.The extraction of cellulose from ginger stalk would convert this waste into a high value-added product and, simultaneously, contribute to environmental protection. This research studied the characteristics of cellulose extracted from ginger stalk by two different treatments:(i) potassium hydroxide(KOH) treatment and(ii) nitric acid-ethanol(NAE) treatment. The optimal condition for the KOH treatment was obtained, it was at 1∶30 solidto-liquid ratio(SLR) for 5 h extraction time with 14 wt% KOH. The optimal condition for the NAE treatment was as follows: 1∶40 SLR, 4 h extraction time, and a reaction temperature of 90℃. However, the cellulose obtained by NAE treatment was severely degraded than that by KOH treatment. The Fourier-transform infrared(FT-IR) spectroscopy analyses revealed that both treatments successfully dissolved the lignin and hemicellulose. Two treatments showed a higher cellulose yield, and the extracted cellulose had more crystal structure.     

硝酸尾气高效组合处理工艺及应用

采用延伸吸收法和非选择性催化还原法高效组合成一种硝酸尾气处理新工艺，具有流程简单成熟、自动化程度高、装置投资少、氨转化率高、增产硝酸等特点。经最终处理后的排放尾气中的NOx体积分数小于400×10^-6，排放量小于22kg／h，大大低于国家规定的相关大气污染物排放标准。     

Characterization and activity of copper-on-carbon catalysts for low-temperature selective reduction of nitric oxide with ammonia

The activities for NO reduction with ammonia in the presence and absence of O₂ have been examined over copper salts supported on activated carbon (AC) and carbon black (CB) which have been characterized by application of X-ray diffraction and scanning electron microscopy before and after use in the reduction process. The beneficial effects of increases in loading and the introduction of oxygen are demonstrated. On the most active catalyst and under optimum conditions 100% reduction of the NO to N₂ occurs at 180 °C and Cu, Cu₂O and CuO on the catalyst are shown to be present at various stages of the preparation and reduction process with large crystallites of metallic copper detected on the AC catalyst of optimum loading. Deactivation and regeneration of the catalysts is also examined. A mechanism for the redox process is proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural Perspectives on the Mechanism of Soluble Guanylate Cyclase Activation

The enzyme soluble guanylate cyclase (sGC) is the prototypical nitric oxide (NO) receptor in humans and other higher eukaryotes and is responsible for transducing the initial NO signal to the secondary messenger cyclic guanosine monophosphate (cGMP). Generation of cGMP in turn leads to diverse physiological effects in the cardiopulmonary, vascular, and neurological systems. Given these important downstream effects, sGC has been biochemically characterized in great detail in the four decades since its discovery. Structures of full-length sGC, however, have proven elusive until very recently. In 2019, advances in single particle cryo–electron microscopy (cryo-EM) enabled visualization of full-length sGC for the first time. This review will summarize insights revealed by the structures of sGC in the unactivated and activated states and discuss their implications in the mechanism of sGC activation.