Flameless burning

Since the reaction involving NO is termolecular in nature, the oxidation of gaseous fuel species by NO is very slow at low pressures and the reaction only occurs when the temperature is well above 1000 K. It is for this reason that flameless burning of nitropolymer pyrolants occurs in the low-pressure region. 

V.V. Aleksandrov S.S. Khlevnoi, Surface Temperature During the Flameless Burning of Nitroglycerin Propellant , FizGoreniyaVzryva 6 (4), 438-43 (1970) (Russ) CA 75, 89714 (1971) [Prior exptn by these authors on a pro-pint consisting of NC, NG and DNT indicated that the surface temp, T, in nameless combustion does not depend on the initial temp. Other prior work to explore Tg involved measurement of the mean heat of vapn of NG and other propint volatiles at elevated temps and pressures. These measurements provided an estimate of... 

Flameless gas-air heaters also have been designed. They have a cylindrical body made of porous refractory ceramic material. After the ignition of the air-gas mixture, a flameless combustion takes place within the pores of the heater s ceramic body. The flameless burning has two advantages (a) the fuel combustion is very complete, and (b) the bottomhole zone does not become fouled with soot. During the combustion process, the body of the heater becomes red hot, radiating the heat into the oil-bearing bed. In another variant, the porous ceramic piece is placed direcdy on the wellbottom in such a manner that it encloses the perforated body of the heater like a jacket. 

Catalytic or flameless combustion of hydn en exhibits many advantages in comparison with flame combustion. It occurs at low temperatures (ambient - 800 K), is safe and leads to a very high conversion of the burning gas (99.9 %). The NOX formation which usually occurs in conventional combustion at temperatures of about 1700 K, is here almost completely suppressed. The catalytic combustion in diffusion burners (Fig. 7-2) occurs in the presence of small amounts of Pt or Pd catalysts. It is adequate, e.g., for kitchen appliances such as cooker, oven, water heater, space heater. Drawbacks are the possible non-uniformity of the temperature distribution at die catalyst surface, rapid changes in the operational state, and relatively small heat flux densities [47]. 

The test for mercury (ASTM, 201 ly) consists of burning the sample in an oxygen bomb with dilute nitric acid and determination of the mercury by flameless cold vapor atomic absorption. 

Smouldering n. A slow, flameless, smoking burning of a fabric. 

Catalytic Combustion. Catalytic combnstion is a process by which a lean fuel-air mixture is passed over a catalyst to flamelessly initiate combustion. The air and fuel are premixed upstream of the catalyst. A portion of the fnel is burned in the catalyst and the balance is burned downstream of the catalyst. This technique allows combustion temperatures to remain below 2730°F (1500°C), which is below the optimum temperature for production of thermal NO r (the nitrogen and oxygen in the air react to form NO r). The result is very low NO r emissions, on the order of 3 ppm. The technology is being demonstrated on a gas turbine and has been deemed by EPA to have proven that the reductions have been achieved in practice. 

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