Reducing flame

Solutions of these fire retardant formulations are impregnated into wood under fliU cell pressure treatment to obtain dry chemical retentions of 65 to 95 kg/m this type of treatment greatly reduces flame-spread and afterglow. These effects are the result of changed thermal decomposition reactions that favor production of carbon dioxide and water (vapor) as opposed to more flammable components (55). Char oxidation (glowing or smoldering) is also inhibited. 

Flue Gas Recirculation Flue gas recirculation, alone or in combination with other modifications, can significantly reduce thermal NO. Recirculated flue gas is a diluent that reduces flame temperatures. External and internal recirculation paths have been applied internal... 

Water or steam injection reduces flame temperatures and thus thermal NO,. Water injection is especially effective for gas turbines, reducing NO, emissions by about... 

There is a need to have all accepted test standards require that deflagration testing he done with a restricted outlet. More research is needed to evaluate the effect of restriction size and location on flame arrester effectiveness. Not all test standards require this for deflagration testing. This is important since protected side restrictions severely reduce flame arrester capability. 

Chan et al. (1983) studied flame propagation in an obstructed channel whose degree of confinement could be varied by adjustment of exposure of the perforations in its top. Its dimensions were 1.22 m long and 127 x 203 mm in cross section. Results showed that reducing top confinement greatly reduced flame acceleration. When the channel s top confinement was reduced to 10%, the maximum flame speed produced for methane-air mixtures dropped from 120 m/s to 30 m/s. 

Spraying conditions make hardness values so variable that unless they are accurately known no comparisons are possible. Brinell hardness figures for sprayed molybdenum vary from 350 when produced with a reducing flame to 725 with an oxidising flame, and while a thick sprayed deposit of 0-8% carbon steel can give a figure of 330, the hardness of a particle obtained by micro hardness methods will be about 550. 

Since NO is a precursor in NDMA formation and high combustion temperatures (usually from 1500 to 1800 0) yield high reaction rates between oxygen and nitrogen, a decrease in NDMA formation can also be achieved by lowering the flame temperature. Excess air seems to be the most economic way to reduce flame temperature and NO synthesis. In a new type of burner developed on this principle the resulting air had only 0.05 - 0.1 mg NO /m as compared with 14 mg/m in conventional burners. Accordingly, malt dried with such burners contains only 1 to 3 mg/kg NDMA, a 15-30 fold reduction of the NDMA concentration. 

To guard against incomplete reduction of ore fines which would be elutriated prematurely during preheating, the midsection combustion was adjusted to produce a mildly reducing flame containing approximately 4%... 

Variable fuel flow is used in burners to throttle or cut back the fuel flow rate, reducing flame size, as the system heating load varies. These burners have conventional steady-state efficiencies and higher seasonal efficiencies. They are available for large apartment boilers and furnaces. 

Flue gas recirculation Flue gas recirculation, alone or in combination with other modifications, can significantly reduce thermal NO,. Recirculated flue gas is a diluent that reduces flame temperatures. External and internal recirculation paths have been applied internal recirculation can be accomplished by jet entrainment using either combustion air or fuel jet energy external recirculation requires a fan or a jet pump (driven by the combustion air). When combined with staged-air or staged-fuel methods, NO emissions from gas-fired burners can be reduced by 50 to 90 percent. In some applications, external flue-gas recirculation can decrease thermal efficiency. Condensation in the recirculation loop can cause operating problems and increase maintenance requirements. 

Low-NO burners are designed to delay and control the mixing of coal and air in the main combustion zone. A typical low-NO air-staged burner is illustrated in Fig. 24-16. This combustion approach can reduce NO emissions from coal burning by 40 to 50 percent. Because of the reduced flame temperature and delayed mixing in a low-NO burner, unburned carbon emissions may increase in some apphcations and for some coals. Overfire air is another technique for... 

Some manufacturers of internal cooling tower components, specifically fill material and drift eliminators, have products produced from less easily ignited plastic that have been tested by a nationally recognized testing laboratory and determined to have sufficient fire resistance or reduced flame spread ratings that when, and only when, used in an otherwise noncombustible cooling tower, do not require fixed automatic fire protection. 

Interactions between the flame and the surrounding wall (in a combustion chamber) could influence the contaminant production. This is examined by Dionisios Vlachos and his group at the University of Delaware (formerly at the University of Massachusetts at Amherst) using numerical bifurcation techniques (Chapter 26). For the first time, oscillatory instabilities have been found and control methodologies have been proposed to reduce flame temperatures and NO2 emissions. 

Manganese produces violet color in an oxidizing flame on a microcosmic or borax bead. The color disappears in a reducing flame. 

In most similar activities in petroleum refineries, the vapors from stripping "sour water" are processed in a Claus plant. With care in design and operation of the stripper, the vapors typically consist of equal volumes of H2S, NH3 and H2O. Such a mixture can support high-temperature reducing flame in which NH3 is destroyed. 

Before the blowpipe, salts of nickel, give, in the oxidating flame, with biborate of soda, a reddish-yellow glass, which becomes much paler as it cools. In the reducing flame, greyish particles of reduced nickel are disseminated through the bead.. . 

Bromine compounds reduced flame speeds in all cases, but chloroform increased them in most cases. Although the promoting effect of chloroform has not been reported before and the view generally is that chlorine compounds reduce flame speeds, a close examination of previous data (4, 6,7,9) reveals that under certain conditions, chlorine and methyl chloride had increased flame speeds. 

B. Dry Reactions.—When heated in the reducing flame a bead of microcosmic salt assumes a blue, violet, or brown colour with increasing quantities of niobic acid the heated bead becomes red on the addition of ferrous sulphate. With tantalic acid under these conditions the bead remains colourless. 

---