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Chen G.,State Key Laboratory of Coal Combustion | Xia J.,State Key Laboratory of Coal Combustion | Yan Z.,Guangdong Red Bay Generation Co. | Jiang J.,Guangdong Red Bay Generation Co.
American Society of Mechanical Engineers, Power Division (Publication) POWER | Year: 2011

Blended-coal-firing is an effective method to reduce pollutant emissions and increase boiler efficiency when lack of designed coals. In order to improve the technical level of coal blending, a intelligent decision system of whole coal-utilizing process was developed in this work. For the entire life course of coals in power plant, this system could provide automated decisions for coal stacking, coal blending, taking coal, pulverizing and combustion optimization, and built a platform for information management and coal dispatching. The database and expert system theories were bases of the system, while the optimize blending theory and intelligent multi-objective optimization were the core algorithm. To make the boiler operation safety, economic and environmental was the ultimate goal. During the development of system, a technique of dynamic monitoring of coal bunker and a two-level coal blending optimization method were proposed, which could provide feasible solutions for accurate blending and the entire process tracking of coals. After the completion of system, in December 2009, it was installed and running in the Guangdong Red Bay power plant which equipped 600MW boiler. The software can help improving the efficiency and decision-making level of coal blending work, enhancing the boiler's full load capacity of stable combustion, and reducing emissions. It has achieved good economic and social benefits until now. Copyright © 2011 by ASME. Source

Feng G.,State Key Laboratory of Coal Combustion | Zhao W.,State Key Laboratory of Coal Combustion | Cummings P.T.,Vanderbilt University | Li S.,State Key Laboratory of Coal Combustion
Science China Chemistry | Year: 2016

Room temperature ionic liquids (RTILs) with dispersed carbon pieces exhibit distinctive physiochemical properties. To explore the molecular mechanism, RTILs/carbon pieces mixture was investigated by molecular dynamics (MD) simulation in this work. Rigid and flexible carbon pieces in the form of graphene with different thicknesses and carbon nanotubes in different sizes were dispersed in a representative RTIL 1-butyl-3-methyl-imidazolium dicyanamide ([Bmim][DCA]). This study demonstrated that the diffusion coefficients of RTILs in the presence of flexible carbons are similar to those of bulk RTILs at varying temperatures, which is in contrast to the decreased diffusion of RTILs in the presence of rigid carbons. In addition, interfacial ion number density at rigid carbon surfaces was higher than that at flexible ones, which is correlated with the accessible external surface area of carbon pieces. The life time of cation-anion pair in the presence of carbon pieces also exhibited a dependence on carbon flexibility. RTILs with dispersed rigid carbon pieces showed longer ion pair life time than those with flexible ones, in consistence with the observation in diffusion coefficients. This work highlights the necessity of including the carbon flexibility when performing MD simulation of RTILs in the presence of dispersed carbon pieces in order to obtain the reliable dynamical and interfacial structural properties. © 2016 Science China Press and Springer-Verlag Berlin Heidelberg Source

Xia J.,State Key Laboratory of Coal Combustion | Zhang C.,State Key Laboratory of Coal Combustion | Chen G.,State Key Laboratory of Coal Combustion
American Society of Mechanical Engineers, Power Division (Publication) POWER | Year: 2011

In china, many thermal power plants have to burn blended coals forced by the complexity of coal type and market tension and transportation pressure of coal purchasing. As a engineering implementation method of coal blending," different coals grinding in different mills and then mixed burning in the furnace" has many advantages such as low investment, easy to control milling system parameters and can be optimized online, etc, compared with traditional coal blending methods. But it is limited by the number of mills and cannot achieve high-precision ratio of blending. To remedy this shortcoming, a model of two-level optimization of coal blending for the thermal power plant with direct blowing pulverizing system was established in this paper. The tradional coal blending was regarded as first step of optimization. The secondary optimization was implemented by adjusting the outputs of different mills, then the blend was changed to accurate ratio. Furthermore, since the existence of coal bunker, it made a time lag from coal discharge to combustion, meanwhile, the real-time load was unpredictable and the coal utilization rate was inconsistent of each bunker. The three reasons make it uncertain of the current coal of bunker. To identify each coal in the mill(equivalent to bunker) correctly was the basis of achieving the second blending optimization. Therefore, a soft-sensing model of coal moisture based on the heat balance equation was used to take this work. At last, a intelligent coal blending system by the two-level optimization model was developed for a power plant and achieved good results. Copyright © 2011 by ASME. Source

Zhao Y.,State Key Laboratory of Coal Combustion | Zhao Y.,Huazhong University of Science and Technology | Zhang J.,State Key Laboratory of Coal Combustion | Tian C.,State Key Laboratory of Coal Combustion | And 3 more authors.
Energy and Fuels | Year: 2010

To understand the formation mechanism of high-calcium fly ashes, the mineralogical, physical, and chemical properties of several high calcium fly ashes and their different density fractions (<1.0, 1.0-2.5, 2.5-2.89, and >2.89 g/cm3) from a coal-fired power plant were characterized by X-ray diffractometry (XRD), field scanning electron microscopy equipped with energy dispersive X-ray analysis (FSEM-EDX), and X-ray fluorescence spectroscopy (XRF). The occurrence of calcium in coal was determined using sequential extraction tests. The results show that the carbonate-bonded calcium is the dominant species in Xiaolongtan coal, and the ionexchangeable calcium only occupies 19.2% of total calcium. The major calcium-bearing minerals in low temperature ash (LTA) of the feed coal, lignite from the Yunnan province, include calcite, bassanite, and dolomite. The fly ashes examined contained aluminosilicates with a high concentration of calcium oxide. The major minerals includemullite, quartz, lime, anhydrite, and gehlenite, and theminor minerals are comprised of hematite, magnetite, akermanite, portlandite, and larnite. Minerals in the density faction less than 1.0 g/cm3 consist of lime, calcite, anhydrite, and clay; between 1.0-2.5 g/cm3, quartz, mullite, anhydrite, and gehlenite; between 2.5-2.89g/cm3, anhydrite, lime, gehlenite, hematite, and quartz; and greater than 2.89 g/cm3, larnite, gehlenite, anhydrite, brownmillerite, and some heavy minerals. In accordance with the microstructural characteristics of the fly ash particles, high-calcium fly ash can be classified into several groups, namely hollowed smooth particles, dense particles, agglomerate particles, porous particles, plerosphere, and other particles with complex surface characteristics. On the basis of chemical composition, high-calcium fly ashes can be classified into four groups namely: calcium oxide, calcium sulfates, Ca-Al-Si compounds, and Ca-S-X (X: Fe, Al, Si, Mg, etc.) compounds.Calcium oxide and calcium sulfates aremainly derived fromthe original calcium-bearingminerals in coal, whereas Ca-Al-Si and Ca-S-X compounds are formed by the secondary reaction of CaO and CaSO4. Copyrigh © 2009 American Chemical Society. Source

Wu H.,State Key Laboratory of Coal Combustion | Qiu Y.,State Key Laboratory of Coal Combustion | Liu H.,State Key Laboratory of Coal Combustion | Luo G.-Q.,State Key Laboratory of Coal Combustion | And 2 more authors.
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2013

Mercury in oxy-coal combustion flue gas must be removed before CO2 recovery as it can cause liquid metal embrittlement and material failure of aluminum heat exchangers during CO2 purification and compression. Experiments about NO and SO2 influence on homogeneous Hg0(g) oxidation by HCl were conducted under simulated O2/CO2 atmosphere at 200~1000°C. Results showed that CO2, N2, O2/CO2 and O2/N2 atmospheres exhibited similar Hg oxidation trend, while generally Hg oxidation in O2/CO2 was higher than CO2 atmosphere and a little bit lower than O2/N2 atmosphere. Hg0(g) oxidation by NO/HCl was enhanced at 200~600°C and inhibited at 800~1000°C. At the temperature of 1000°C, a minimum Hg oxidation rate existed as the NO concentration varied. SO2 strongly inhibited Hg0(g) oxidation by HCl. Source

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