Combustion systems, direct

Boilers may be direct fired or indirect fired. Energy supply designs account for various combustion methods using fossil fuels, municipal waste, process residues, waste heat, and by-products. Special boiler combustion systems to reduce pollution or improve efficiency include fluidized-bed and combined cycle. 

LIF has been used in a multitude of studies to measure the concentrations of some important radicals, most frequently of OH, CH, and NO. While OH is an important contributor to the fuel degradation and oxidation pathways and an indicator of hot areas in flames, CH has often been used to trace the flame front location, whereas the direct investigation of NO formation is of importance with regard to NO, being a regulated air toxic. Species including other elements, such as sulfur, phosphorus, alkali, etc., can be detected by LIF in combustion systems, and often, an indication of their presence may already be a useful result, even if quantification is not possible. 

The direct combustion of wood and other plant matter has been a primary energy source in the past. Any type of biomass can be burned to produce heat or steam to turn a generator or perform mechanical work. Direct combustion is used in large power plants that produce up to 400 megawatts. Most direct combustion systems can use any type of biomass as long as the moisture content is less than 60%. Wood and wood residues are commonly used along with a number of other agricultural residues. 

Much of the discussion of oxygen flame calorimetry presented in section 7.3 is directly applicable to fluorine flame calorimetry. As in the case of bomb calorimetry, however, the special properties of fluorine combustion systems and problems associated with handling fluorine require a somewhat different experimental method [109,115,116]. Thus, for example, a metal burner should be used. Also, the fact that the mixing of many gases with F2 may lead to spontaneous ignition hinders the use of a premixed flame. Fluorine combustion calorimetry has been used to study the thermochemistry of important reactions, such as... 

Hantschk, C., J. Hermann, and D. Vortmeyer. 1996. Actively instability control with direct-drive servo valves in liquid-fueled combustion systems. 26th Symposium (International) on Combustion Proceedings. Pittsburgh, PA The Combustion Institute. 2835-41. 

Assuming most PAH are stable in the atmosphere, which we feel is an excellent assumption, we ask what happens to these compounds after they are released from combustion systems throughout the world. We suggest that PAH are transported to a-quatic sediments either by direct airborne transport or by sediment resuspension and redeposition. 

A variety of fuel performance problems can be directly linked to the presence of olefinic compounds in a fuel. Problems such as darkening of fuel color, gum and sludge formation, and combustion system deposits can be directly linked to the presence of olefins. 

In addition to what appears to be a heterogeneous chemical source for HONO, it has also been shown to be emitted directly from combustion systems. For example, it has been measured in the exhaust of noncatalyst-equipped automobiles (Pitts et al., 1984b), from natural gas combustion in a kitchen stove, and in the emissions from kerosene and propane space heaters (e.g., Pitts et al., 1985, 1989 Brauer et al., 1990 Febo and Perrino, 1991,1995 Spicer et al., 1993 Vecera and Dasgupta, 1994). 

The reaction time for direct partial oxidation of methane is of the order of tenths of seconds, which is much longer than the gas residence time in most combustion systems, and the low temperature chemistry for methane is seldom significant in combustion. One exception is the so-called NOv-sensitized oxidation, where presence of nitrogen oxides significantly enhances the oxidation rate of hydrocarbons at lower temperatures. This phenomena is discussed in Section 14.3.1.3. 

Fluorescence measurements of HO have been a common feature of laboratory kinetics studies of the reaction-rate coefficients of HO with various molecules and of studies of this free radical in combustion systems (24). In fact, although direct tropospheric fluorescence HO measurements were first... 

Our third area of combustion research involved magnetohydro-dynamic or MHD power generation and the combustor development of such a system. Our work in MHD combustion is directed toward a part of a larger program which will result in an entire MHD system being operated in Butte, Montana sometime in Fiscal 1982. To support our MHD work, we have a one-megawatt atmospheric pressure combustor and a five-megawatt pressurized (6 atmospheres) combustor test facility. 

Although gas turbine combustion systems operate with overall air/fuel ratios which are quite fuel-lean, perhaps three times stoichiometric, stabilization of the combustion process requires that a portion of the combustor, the primary zone, operate stoichiometric or fuel-rich. Under fuel-lean conditions, fuel-bound nitrogen can be converted directly to N0X. Under fuel-rich conditions, fuel-bound nitrogen can be converted to HCN and NH3 in addition to N0X. Of course, in either case, the most desirable product of converted fuel nitrogen would be molecular nitrogen,... 

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