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[en] The advantages of using fluidized bed heat recovery units with diesel engines are well documented. Two of those are: significantly less tube fouling and heat transfer coefficient four to five time higher than that of conventional shell and tube heat exchangers. The high concentration of soot in the exhaust gases of diesel engines make fouling a major concern in design of any kind of heat recovery unit. In the experiment a conventional fluidized bed heat exchanger was connected to the exhaust of a diesel engine mounted on a dynamometer. With this arrangement it was possible to test the heat recovery unit under a wide range of operating conditions. The main objective of this experiment was the determination of the performance characteristics of the heat recovery unit, especially with reference to its heat transfer and fouling characteristics. (author)
[en] In order to study the various health influencing parameters related to particulate as well as to gas-phase pollutants emitted by Diesel engine exhaust, there is an urgent need for appropriate sampling devices and methods for cell exposure studies and associated biological and toxicological tests. In a previous paper , a specific concept for a cell culture exposure chamber was introduced to allow the uniform exposure of cell cultures to diesel aerosols. In the present work, this cell culture exposure chamber is evaluated and characterized with state-of-the-art nanoparticles measurement instrumentation to assess the local deposition of soot aggregates on the cell cultures and any losses due to particle deposition on the cell culture exposure chamber walls, and in addition an upgraded Multiculture Exposure Chamber (MEC) for in vitro continuous flow cell exposure tests is introduced with improved, compared to the previous version, features. Analysis and design of the MEC employs CFD and true to geometry representations of soot particle aggregates.
[en] Because of its adaptability over a wide range of environments in North America, the U.S. Department of Energy has chosen switchgrass as a model species for developing herbaceous energy crops. The suitability of energy crops as a feedstock for fuels or power is reflected in their energy content and conversion, and in their ease of handling, which also ultimately determine the type of potential and uses. Analyses indicate that switchgrass is versatile. Its energy content (when the initial moisture content is considered) is similar to wheat straw's and greater than wood's. Early analysis of ethanol production by enzymatic hydrolys/fermentation indicates that it produces high yield with current technology. Earlier reports of its high ash and alkaline contents have increased attention to harvesting, storage, and handling techniques to reduce soil contamination. With proper methods, ash and alkaline can be maintained at a relatively low level, and problems of slagging in conventional combustion systems can be avoided. (au) 18 refs
[en] The Advanced Staged Fluidized-Bed Coal Combustion System (ASC) is a novel clean coal technology for either coal-fired repowering of existing boilers or for incremental power generation using combined-cycle gas turbines. This new technology combines staged combustion for gaseous emission control, in-situ sulfur capture, and an ash agglomeration/vitrification process for the agglomeration/vitrification of ash and spent sorbent, thus rendering solid waste environmentally benign. The market for ASC is expected to be for clean coal-fired repowering of generating units up to 250 MW, especially for units where space is limited. The expected tightening of the environmental requirements on leachable solids residue by-products could considerably increase the marketability for ASC. ASC consists of modular low-pressure vessels in which coal is partially combusted and gasified using stacked fluidized-bed processes to produce low-to-medium-Btu, high-temperature gas. This relatively clean fuel gas is used to repower/refuel existing pulverized-coal, natural gas, or oil-fired boilers using bottom firing and reburning techniques. The benefits of ASC coal-fired repowering include the ability to repower boilers without obtaining additional space while meeting the more stringent environmental requirements of the future. Low NOx, SOx, and particulate levels are expected while a nonleachable solid residue with trace metal encapsulation is produced. ASC also minimizes boiler modification and life-extension expenditures. Repowered efficiencies can be restored to the initial operating plant efficiency, and the existing boiler capacity can be increased by 10%. Preliminary cost estimates indicate that ASC will have up to a $250/kW capital cost advantage over existing coal-fired repowering options. 4 figs., 4 tabs
[en] Rice husk ash (RHA) which contains more than 90 percent silica is proven to be an active silica source in zeolite synthesis. In this study, nano sodalite has been successfully synthesized hydrothermally at 60 degree Celsius using RHA as silica source in alkaline medium at various crystallization times. Commercial fumed silica was used as comparison for the silica source. Analysis by XRD has shown that pure nano sodalite was formed in 3 hours and stable up to more than 24 hours when using RHA as silica source. On the other hand, fumed silica produced pure nano sodalite only at 4 hours while a mixture of zeolites was observed outside this time range. FESEM shows a worm-like morphology of nano sodalite in the size range of 50-100 nm while FTIR shows the formation of aluminosilicates bonds. Analysis on the dissolved silica in the gel reaction mixture demonstrates the decreasing mass of silica after prolong time of crystallization which indicates the consumption of the dissolved silica in crystal growth of nano sodalite. This study shows that RHA is a better silica source in stabilizing the nano sodalite phase in oxide gel reaction mixture as compared to fumed silica. (author)
[en] Solutions are proposed for enhancement of the in-service safety of hydraulicked ash-slag dumps with consideration of their hydrothermal regime. An assessment is given for the minimum dimensions of the settling basins and top surface of ash-slag dumps.
[en] Highlights: ► Fire/explosions are undesirable events in-process safety of matchhead composition. ► DSC and ARC were used to analyze the thermal decomposition of a matchhead composition. ► ARC studies evidence of onset of exothermic activity at 115.5 °C. ► Reactive potential was compared under adiabatic and isothermal conditions. ► Kinetic parameters were estimated for the thermal process observed in DSC and ARC. - Abstract: From the process safety point of view, irrespective of the kind of stimulus (friction, impact, heat), the final event is “thermal” in nature. Differential Scanning Calorimetry (DSC) and Accelerating Rate Calorimetry (ARC) were performed to understand thermal characteristics and kinetics of a matchhead composition. A single sharp and narrow exothermic transition occurred at 200, 210, 215 and 220 °C at different heating rates (5, 10, 15 and 20 °C min−1) suggesting that the matchhead composition was vulnerable to thermal hazard. ARC studies depicted onset temperature at 115.5 °C and a sharp rise in exothermic reaction at 127.64 °C within the time span of 14 s with the maximum heat release rate of 598.4 °C min−1. The exothermic activity resulted in rapid pressure rise (50.45 bar) confirming the vulnerability of this mixture to undergo catastrophic explosion. Kinetic parameters were estimated for the thermal process observed in DSC and ARC. Such data were validated
[en] This document qualitatively evaluates the FR-equency and consequences of DST and SST representative flammable gas accidents and associated represented hazardous conditions without controls. Based on the evaluation, it was determined that safety-significant SSCs and/or TSRs were required to prevent or mitigate flammable gas accidents. Controls were selected and the accidents re-evaluated taking credit for the controls
[en] After the law by decree of the 12. June 2003, N 233 (ATEX Directive) and REACH regulation (Regulation EC n. 2907/2006 of the European Parliament), several industrial fields, also not chemical, need the flammability data for the substances used. Perhaps, many of these data, especially for compounds with not common uses, are not easy to collect. It would be helpful to provide prediction methods in order to calculate these data without any experimentation that sometimes results time consuming, expensive and practically impossible for all the commercial compounds. In this research the ASTM software CHETAH (CHEmical Thermodynamic And Hazard evaluation) has been used in order to compute the lower flammability limit (Li), the limiting oxygen concentration (LOC, using nitrogen as inert gas) as a function of temperature, the adiabatic flame temperature Tflame, the fundamental burning velocity (Su), the quenching distance (Qd), the minimum ignition energy (MIE) for esters and ethers, substances highly used in industry.
[it]Con il recepimento del Decreto Legislativo 12 giugno 2003, N. 233 (Direttiva ATEX) e del regolamento REACH (Regolamento CE n. 1907/2006 del Parlamento Europeo) e sorta la necessita per i responsabili di molte attivita industriali, anche non chimiche, di disporre dei dati di infiammabilita per le sostanze utilizzate. Purtroppo, molti di questi dati, soprattutto per i composti d'impiego non comunissimo, non sono facilmente reperibili. Sarebbe quindi auspicabile poter disporre di idonei metodi previsionali per ricavare, gia sulla carta, questi dati senza ricorrere necessariamente alla sperimentazione, talvolta lunga e costosa e praticamente irrealizzabile per tutte le sostanze in commercio. In questo lavoro e stata utilizzata la versione 8 del software CHETAH (CHEmical Thermodynamic And Hazard evaluation) comercializzato dall'ASTM per calcolare il limite inferiore di infiammabilita Li dell'ossigeno di sicurezza MOC (con azoto come gas inerte) in funzione della temperatura, la temperatura adiabatica di fiamma Tfiamma, la velocita di propagazione della fiamma Su, la distanza di estinzione Qd, l'energia minima di innesco MIE di esteri ed eteri, importanti sostanze di notevole interesse industriale.