Burning particle size

Another method iavolves an electric-arc vaporizer which is >2000° C before burning (25,32). One of the features of the process is a rapid quench of the hot gas flow to yield very fine oxide particles (<0.15 nm). This product is quite reactive and imparts accelerated cure rates to mbber. Internally fired rotary kilns are used extensively ia Canada and Europe and, to a limited extent, ia the United States (24). The burning occurs ia the kiln and the heat is sufficient to melt and vaporize the ziac. Because of the lower temperatures, the particles are coarser than those produced ia the other processes. In a fourth process, ziac metal which is purified ia a vertical refining column is burned. In essence, the purification is a distillation and impure ziac can be used to make extremely pure oxide. Also, a wide range of particle sizes is possible (33). 

Portiand cement clinker structures (18,19) vary considerably with composition, particle size of raw materials, and burning conditions, resulting in variations of clinker porosity, crystallite sizes and forms, and aggregations of crystallites. Alite sizes range up to about 80 p.m or even larger, most being 15—40 )J.m. 

Burning times for coal particles are obtained from integrated reaction rates. For larger particles (>100 fim) and at practical combustion temperatures, there is a good correlation between theory and experiment for char burnout. Experimental data are found to obey the Nusselt "square law" which states that the burning time varies with the square of the initial particle diameter (t ). However, for particle sizes smaller than 100 p.m, the Nusselt... 

Antimony trioxide (SbaOj). It is produced from stibnite (antimony sulphide). Some typical properties are density 5.2-5.67 g/cm- pH of water suspension 2-6.5 particle size 0.2-3 p,m specific surface area 2-13 m-/g. Antimony trioxide has been the oxide universally employed as flame retardant, but recently antimony pentoxide (SbaOs) has also been used. Antimony oxides require the presence of a halogen compound to exert their fire-retardant effect. The flame-retarding action is produced in the vapour phase above the burning surface. The halogen and the antimony oxide in a vapour phase (above 315 C) react to form halides and oxyhalides which act as extinguishing moieties. Combination with zinc borate, zinc stannate and ammonium octamolybdate enhances the flame-retarding properties of antimony trioxide. 

It calculates one-dimensional heat conduction through walls and structure no solid or liquid ciMiibustion models are available. The energy and mass for burning solids or liquids must be input. It has no agglomeration model nor ability to represent log-normal particle-size distribution. 

When a flammable liquid is sprayed as fine droplets into the air, a flammable mixture can result, which may burn or explode. The mist or spray may be formed by condensation of saturated vapors or by mechanical means [40]. As the particle sizes of the liquid become greater than 0.01 mm diameter, the lower flammability limit of the material becomes lower while above 0.01 mm, the LEL is about the same as the vapor. Mechanical engine crankcase explosions of oil mist in air are hazardous, and current practice is to apply explosion relief valves to the crankcase. 

It is reported that beryllium powder, of unspecified particle size, will burn in air at 1 200°C and react with nitrogen at 500 C Fluorine appears to attack beryllium at room temperature, and the other halogens, nitrogen dioxide and hydrogen sulphide are said to attack it at elevated temperatures ... 

Dwiggins, Particle Size Measurement and the Effect of Particle Size on The Burning Time of Chemical Delay Compositions , NAVWEPS 7304... 

Andreev Chuiko (Ref 35) observed stable burning in PETN of 5 micron particle size and relative density 6 = 1.17, up to 60 atm pressure. At higher pressures (up to 100 atm) burning rate increased rapidly. The pressure at which transition from stable to accelerating... 

Ultrafine Ammonium Perchbrate (UFAP). For high burning rate propints a fine particle size AP is required and is produced by 3 processes ... 

Baldwin (Ref 65) also synthesized a copolymer from acrylic acid and carboranylmethyl acrylate which was used to make the proplnts in Table 36. Composition A has the burning rates shown in the table for the AP particle sizes indicated. Composition B had an average AP particle size of 15 microns and a burning... 

Particle Size of Ammonium Perchlorate and Burning Rate at 2000psi... 

N. E. Cohen, 13th Symp (Int) Combust (Proc) (1970), 1019—29 CA 76, 61471 (1972) To analyze and explain the mechanism of combustion of powdered metals in contact with a solid oxidizer (AP) with the powdered metal dispersed in solid AP (I), the combustion of various compressed I-Al and I-Mg mixts in N2 under various conditions in a high-pressure window bomb was studied. The regression-rate laws of the mixts at high and low pressures, the pressure limits for deflagration, and the structures of the combustion zone and of the surface were detd. The burning rate of various I-Al mixts, as a function of pressure, I particle size, and mixt ratio was determined by cinematography. The combustion was difficult to achieve... 

A recent review relating the pyrotechnic reaction mechanism, particle size, stoichiometry, temp and compaction density to burning rate is Ref 66, and a study of the effect of multidimensional heat transfer on the rate of flame propagation is Ref 120, which showed that the material of the delay body has no effect on the performance of most delay compns, a finding which agrees with test data... 

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