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61.
Furnace sorbent injection (FSI) is used to remove SO2 formed during coal combustion by injecting sorbent into the high temperature zone of a furnace above the fireball. FSI is cost effective for older coal-fired boilers, especially when space or capital budgets are limited. To optimize the design and performance of FSI, an SO2/sorbent modeling scheme that simultaneously considers calcination (or dehydration), sintering, and sulfation has been developed and implemented. It is coupled with a three-dimensional combustion model based on computational fluid dynamics to determine the most desirable locations for sorbent injection and to optimize the amount of sorbent needed to achieve a targeted SO2 removal efficiency. A sensitivity analysis was conducted to determine the effect of flue gas temperature, particle diameter, and SO2 concentration on the extent of sulfation. This SO2/sorbent sub-model was applied to a 126-MW front-wall fired boiler firing eastern bituminous coal. The SO2 removal efficiencies predicted by the model agreed well with those measured in the field. The modeling results indicated that sorbent injected directly into the furnace through boosted over-fired air ports is more effective at removing SO2, due to longer residence time and better mixing, relative to ports higher in the furnace with poor mixing. This modeling approach is optimized for full-furnace application to facilitate the design process. 相似文献
62.
Cover Picture: Discovery of MK‐8970: An Acetal Carbonate Prodrug of Raltegravir with Enhanced Colonic Absorption (ChemMedChem 2/2015) 下载免费PDF全文
Dr. Abbas M. Walji Dr. Rosa I. Sanchez Dr. Sophie‐Dorothee Clas Dr. Rebecca Nofsinger Dr. Manuel de Lera Ruiz Dr. Jing Li Dr. Amrithraj Bennet Christopher John Dr. David Jonathan Bennett Dr. John M. Sanders Christina N. Di Marco Somang Hope Kim Dr. Jaume Balsells Scott S. Ceglia Dr. Qun Dang Kimberly Manser Becky Nissley Dr. John S. Wai Dr. Michael Hafey Junying Wang Gene Chessen Dr. Allen Templeton Dr. John Higgins Dr. Ronald Smith Dr. Yunhui Wu Dr. Jay Grobler Dr. Paul J. Coleman 《ChemMedChem》2015,10(2):213-213
63.
Two new methods for preparing submicrometer powders of M2(WO4)3, M = Sc, In, and Al via combustion synthesis are reported. Stoichiometric combinations of trivalent metal nitrates, ammonium metatungstate, and either urea or carbohydrazide as the fuel were reacted at 550°C, producing amorphous or poorly crystallized powders with an average particle size ranging from 164 to 350 nm. Calcining the powders at 800°C for 1 h produced well‐crystallized, phase‐pure powders with an average particle size ranging from 210 to 711 nm. Powders sintered at 1000°C for 14 h resulted in pellets that were 87%–95% of the theoretical density, which is notably higher than typically obtained from powders prepared by solid‐state reaction. Whereas there was little difference in the microstructure of Al2(WO4)3 pellets prepared with the two different powders, the carbohydrazide‐derived powders resulted in In2(WO4)3 and Sc2(WO4)3 pellets with a larger grain size than those prepared with urea‐derived powders. The electrical conductivity of the sintered pellets, while comparable to that reported for polycrystalline M2(WO4)3 prepared by solid‐state reaction, was strongly influenced by grain‐boundary effects. 相似文献
64.
S. Arepalli H. Fireman C. Huffman P. Moloney P. Nikolaev L. Yowell K. Kim P. A. Kohl C. D. Higgins S. P. Turano W. J. Ready 《JOM Journal of the Minerals, Metals and Materials Society》2005,57(12):26-31
Electrochemical double-layer capacitors, or supercapacitors, have tremendous potential as high-power energy sources for use
in low-weight hybrid systems for space exploration. Electrodes based on single-wall carbon nanotubes (SWCNTs) offer exceptional
power and energy performance due to the high surface area, high conductivity, and the ability to functionalize the SWCNTs
to optimize capacitor properties. This paper will report on the preparation of electrochemical capacitors incorporating SWCNT
electrodes and their performance compared with existing commercial technology. Preliminary results indicate that substantial
increases in power and energy density are possible. The effects of nanotube growth and processing methods on electrochemical
capacitor performance is also presented. The compatibility of different SWCNTs and electrolytes was studied by varying the
type of electrolyte ions that accumulate on the high-surface-area electrodes.
For more information, contact W.J. Ready, Georgia Tech Research Institute, 925 Dalney St., Atlanta, GA 30332; (404) 385-4497;
fax (404) 894-0580; e-mail jud.ready@gtri.gatech.edu. 相似文献
65.
A genetic algorithm controlled multispot transmitter is proposed as an alternative approach to optimizing the power distribution for single element receivers in fully diffuse mobile indoor optical wireless communication systems. By specifically tailoring the algorithm, it is shown that by dynamically altering the intensity of individual diffusion spots, a consistent power distribution, with negligible impact on bandwidth and rms delay spread, can be created in multiple rooms independent of reflectivity characteristics and user movement patterns. This advantageous adaptability removes the need for bespoke system design, aiming instead for the use of a more cost effective, optimal transmitter and receiver capable of deployment in multiple scenarios and applications. From the simulations conducted it is deduced, that implementing a receiver with a FOV=55deg in conjunction with either of two notable algorithms, the dynamic range of the rooms, referenced against the peak received power, can be reduced by up to 26% when empty, and furthermore to within 12% of this optimized case when user movement perturbs the channel. 相似文献
66.
A steady-state, axi-symmetric, numerical model was developed to investigate the agglomeration of molten particles of sulphide ore in the reaction shaft of a flash smelting process used for extracting copper. The turbulent, particle-laden, gas flow was simulated in conjunction with a population balance model to account for agglomeration. The agglomeration was found to depend primarily on the particle to gas mass loading ratio, and the particle size and turbulence intensity at the shaft inlet. Predictions compared well with the limited experimental data in the literature. Increasing the angle at which the flow enters the shaft from the burner was found to increase agglomeration up to a critical angle at which the flow behaviour changes. The results have implications for the control and reduction of dust levels in the waste gas stream. 相似文献
67.
Users and providers of recycled water in Queensland, Australia, were canvassed to ascertain concerns about recycled water quality and directions for applied research. Some 79% of respondents had concerns about recycled water quality including microbiological components, such as viruses, parasites and bacteria, salinity related components, aggregate components, such as pH and solids, nutrients, organic components, including pesticides and endocrine disruptors, as well as quality variability. Relative differences in the proportion of concern for some quality characteristics were observed between the areas of different population density with those from the low population areas being more concerned than those from medium or high areas. Some users and providers observed changes in recycled water quality during distribution including nutrients, chlorine, solids, colour and odour. Some 52% of providers and 19% of current users propose to expand their usage and 30% of non-users propose to commence doing so in the next 5 years. Recycled water quality characteristics identified for applied research included microbiological components, organic components, nutrients and salinity. 相似文献
68.
A set of words X over a finite alphabet A is said to be unavoidable if all but finitely many words in A* have a factor in X. We examine the problem of calculating the cardinality of minimal unavoidable sets of words of uniform length; we correct an error in [8], state a conjecture offering a formula for the minimum size of these so called n-good sets for all values of n, and show that the conjecture is correct in an infinite number of cases. 相似文献
69.
Polyadenylation contributes to the destabilization of bacterial mRNA. We have investigated the role of polyadenylation in the degradation of RNA by the purified Escherichia coli degradosome in vitro. RNA molecules with 3'-ends incorporated into a stable stem-loop structure could not readily be degraded by purified polynucleotide phosphorylase or by the degradosome, even though the degradosome contains active RhlB helicase which normally facilitates degradation of structured RNA. The exoribonucleolytic activity of the degradosome was due to polynucleotide phosphorylase, rather than the recently reported exonucleolytic activity exhibited by a purified fragment of RNase E (Huang, H., Liao, J., and Cohen, S. N. (1998) Nature 391, 99-102). Addition of a 3'-poly(A) tail stimulated degradation by the degradosome. As few as 5 adenosine residues were sufficient to achieve this stimulation, and generic sequences were equally effective. The data show that the degradosome requires a single-stranded "toehold" 3' to a secondary structure to recognize and degrade the RNA molecule efficiently; polyadenylation can provide this single-stranded 3'-end. Significantly, oligo(G) and oligo(U) tails were unable to stimulate degradation; for oligo(G), at least, this is probably due to the formation of a G quartet structure which makes the 3'-end inaccessible. The inaccessibility of 3'-oligo(U) sequences is likely to have a role in stabilization of RNA molecules generated by Rho-independent terminators. 相似文献
70.