Advanced Materials Research Vol. 1023

Abstract: Treatment of nucleoside phosphoropiperidates with 0.5 equiv of water in the presence of 4,5-dicyanoimidazole (DCI) provides an efficient method for one-pot synthesis of symmetrical P¹,P²-dipyrimidine-nucleoside diphosphates under mild conditions.

Abstract: Two natural pyrimidine-nucleoside 5′-monophosphates have been synthesized from the corresponding nucleoside 5′-H-phosphonate monoesters via a one-pot reaction in high yields. ³¹P NMR tracing experiments revealed that after H₂O was added, iodophosphate intermediates were hydrolyzed immediately to generate nucleoside 5′-monophosphates almost quantitatively. Unlike the reaction in pyridine, the iodine oxidation reaction in DMF followed by immediate hydrolysis formed only a very small amount of dinucleoside diphosphate self-condensation byproduct.

Abstract: A facile and efficient method for the synthesis of dinucleoside triphosphates with pyrimidine bases (Up₃U, Cp₃C, and Up₃C) from the corresponding nucleoside 5′-phosphoropiperidates has been developed. The experimental results indicated that the employment of 4,5-dicyanoimidazole (DCI) as the activator could notably promote the coupling reaction.

Abstract: A practical solvent-free method for the preparation of 1,8-diaminooctanes functionalized with phosphonate esters has been developed. The synthetic conditions based on the Kabachnik-Fields reaction were investigated with different reactant ratios and temperatures. The experimental results showed that the solvent-free condition with moderately elevated reaction temperature was optimal for the synthesis of this type of compounds.

Abstract: For the retrofit of precipitation and flue gas desulfurization (FGD) system, stalling issue of the boiler axial-flow induced draft fan (IDF) was analyzed. By testing the running characteristic parameter of IDF at the scene, and combining with its characteristic: curve, it was discovered that the actual working point of IDF nears its theory stall line, and stalling issue would appear during running. In order to make the actual working point of IDF keeping away from its theory stall line and avoid the stalling issue of IDF, KSE ( the steady implement of function ) equipment was installed at the entrance of the IDF' to changing the position of IDF theory stall line. The stalling issue of IDF was analyzed and probed, and the problem that the stall margin selection should be considered carefully in IDF retrofit and type selection was presented, which gives some useful suggestion for the similar retrofit in power plant.

Abstract: This paper presents the analysis on the periodic fluctuation of pressure in flue and air system of a 660MW supercritical boiler, firing high sulfur coal. The analysis shows that the fluctuation is resulted from a blockage in its air pre-heater, especially in winter. Just as the temperature of flue gas lower than its acid dew point, corrosion occurs and induces the blockage furthermore. This paper exhibits a typical case in boiler firing high sulfur coal.

Abstract: This paper presents the experimental investigation on the operational performances of a Boiler after a Low NOx burner retrofit. After the retrofit, several operational performances emerge a major change, including the unburned combustible in flying ash raise under higher load, the temperature of reheat steam drop greatly under lower load. As a result, the changes have an influence on the economy of boiler. As for it, a special experimental study was carried out to obtain the best operating mode, and the law of change on the several parameters. The research results are a significant reference to retrofit involved in Low NOx burner utilized to a boiler.

Abstract: This paper presents a research on the problem of catalyst failure in a selective catalytic reduction (SCR) system. The preliminary analysis indicates that the catalyst failure is caused by abrasion. For this, firstly, the mechanism of abrasion is analyzed through a field experiment. Secondly, according to the results from the field experiment, a scheme is put forward to optimize the flow field. Finally, the application results show that the uniformity of fly ash distribution in the flue gas are improved prominently, the reliability of the SCR system is enhanced at the same time.

Abstract: As a result of incorrect operation causing the stall of primary fan, the pressure of primary air continuously decreased. Therefore, the combustion stability in boiler has been disturbanced greatly, and the generation unit trips due to water-coal ratio imbalance. In this paper, the stall accident resulted from incorrect operation have been analyzed, and correct operation for the fan have been put forward. Namely, the precursory phenomena of stall can be found and eliminated. Correct operations can keep the pressure of primary air stable. It is concluded that adopting the suitable water-coal ratio and air-coal ratio are helpful to keep the unit on safe.

Abstract: Effects of a metal oxide structure on the oxygen sensing properties are investigated. In the existence of the etched V-groove gallium oxide geometry, its electrical and sensing properties, i.e., high sensitivity and response time areinvestigated. Grain sizes of the material are dependent on different sputtering conditions and investigated by AFM. Under the partial-voltage circuit measurement, it can be confirmed that the increase of temperature will result in the increase of resistance for the Ga₂O₃ oxygen sensor. From experiment, good stability and repeatability of the oxide sensor are demonstrated when tested under oxygen concentration. These properties show that the oxide structure has a good potential for high sensitivity oxygen sensor.