Metal combustion temperatures

Dry chlorine reacts with most metals combustively depending on temperature alurninum, arsenic, gold, mercury, selenium, teUerium, and tin react with dry CI2 in gaseous or Hquid form at ordinary temperatures carbon steel ignites at about 250°C depending on the physical shape and titanium reacts violendy with dry chlorine. Wet chlorine is very reactive because of the hydrochloric acid and hypochlorous acid (see eq. 37). Metals stable to wet chlorine include platinum, silver, tantalum, and titanium. Tantalum is the most stable to both dry and wet chlorine. 

Furnaces for Oil and Natural Gas Firing. Natural gas furnaces are relatively small in size because of the ease of mixing the fuel and the air, hence the relatively rapid combustion of gas. Oil also bums rapidly with a luminous flame. To prevent excessive metal wall temperatures resulting from high radiation rates, oil-fired furnaces are designed slightly larger in size than gas-fired units in order to reduce the heat absorption rates. 

Applicability/Limitations Fluidized beds require frequent attention for maintenance and cleaning purposes. This treatment is ideal for slurries and sludges but not for bulky or viscous wastes. The waste particles should be of a certain size and be homogeneous. Wastes must have a low sodium content and a low heavy metal content. Some refractory wastes may not be fully destroyed since these units operate at low combustion temperatures (750 to 1000°C). 

The choice of these values is arbitrary. In practice, the cooling fraction will depend not only on the combustion temperature but also on the compressor delivery temperature (i.e. the pressure ratio), the allowable metal temperature and other factors, as described in Chapter 5. But with ip assumed for the first nozzle guide vane row, together with the extra total pressure loss involved (k = 0.07 in Eq. (4.48)), the rotor inlet temperature may be determined. These assumptions were used as input to the code developed by Young [11] for cycle calculations, which considers the real gas properties. 

The results of calculations for the cooling air flow fractions in the first (nozzle guide vane) row of the turbine, ba.sed on the assumptions outlined in Section 5.2 for film cooled blading, are illustrated in Fig. 5.1. The entry gas temperature Tgi was taken as the combustion temperature Tcoi = Ty and the cooling air temperature as the compressor delivery temperature T2. The cooling air required is. shown here as a fraction of the exhaust gas flow, i.e. as ip/( 1 + ip), plotted against compressor pressure ratio and combustion temperature for an allowable blade metal temperature, Tpi = 800°C. Also shown are... 

At very high combustion temperatures, it is not sufficient that the first blade row alone needs to be cooled. In practice, up to half a dozen rows may be cooled in an industrial gas turbine, if the combustion temperature is high and the allowable blade metal temperature is low. The cooling fractions for each of the cooled rows must be estimated and u.sed in the cycle calculations, which now become complex. 

Baffles and combustion area tile, brickwork, and other refractory surfaces are subject to risks of thermal breakdown perhaps as a result of severe local overheating caused by poor flame control. Where baffles are missing or broken, this adds to the risk of local overheating (especially of superheater tubes) due to excessive gas combustion temperatures. As a result, intact baffles and fireside boiler-metal surfaces may suffer from spalling. Check for missing or broken tube hangers and unsupported tubes. 

Direct reaction of transition metals (Ti, Ta, Nb, Zr) or A1 or Si results in adiabatic combustion temperatures of 2500-A500 C. 

The combustion temperature of soot particulates can be lowered by the addition of an oxidation catalyst in the form of fuel additives[2], by spraying metal salt solution on an accumulated soot or by the impregnation of filter walls with an oxidation catalyst. For the last option, oxides of supported metals are considered to be... 

FIGURE 9.1 Adiabatic combustion temperature of various metal-oxygen/nitrogen systems as a function of equivalence ratio . Initial conditions 298 K and 1 atm. 

The combustion temperature of metallized pyrolants is high due to the high heat of combushon of metal parhcles, and the molecular mass of the combustion pro-... 

Metal particles, most commonly aluminum particles, are also known as additives for propellants and pyrolants that increase the combustion temperature and hence also the specific impulse. However, a heat-transfer process from the high-tempera-ture gas to the aluminum particles is required to melt the particles and then a subsequent diffusional process of oxidizer fragments toward each aluminum particle... 

The molecular mass of the combustion products in the ramburner is increased by the formation of the oxidized metal particles. However, the temperature in the ramburner is also increased by the oxidation. The results of thermochemical calculations indicate that the specific impulse generated by the combustion in the ramburner is more dependent on the average combustion temperature than the average molecular mass of the products when metal particles are added. Table 15.4 shows the heats of combustion and the major oxidized products of the soHd particles used in ducted rockets. 

The electric infrared incineration technology is a mobile thermal processing system that is suitable for soils or sediments contaminated with organic compounds, polychlorinated biphenyls (PCBs), and metals. Liquid organic wastes can be treated after mixing with sand or soil. Electrically powered silicon carbide rods heat organic wastes to combustion temperature while any remaining combustibles are incinerated in an afterburner. 

A promising alternative for reducing heavy metal concentrations and leachability are the several emerging advanced thermal treatment technologies. Operated at high combustion temperatures (i.e., between 900 and 1400 C), these... 

The metals also present an additional problem in that the product oxide, fluoride, or nitride species may be a solid phase at the combustion temperature or condense during expansion through the rocket nozzle. Figure 2 presents a graphical comparison of the phase properties of the... 

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