Explosion concentrations

Any hydrogen contained within the chlorine from the electroly2er is concentrated in the residual gas from the Hquefaction process and must not be allowed to exceed the explosive concentration limit of 5%. Although hydrogen concentration can be controUed by adding dry air to the process. 

The majority of the cyanuric acid produced commercially is made via pyrolysis of urea [57-13-6] (mp 135°C) primarily employing either directiy or indirectly fired stainless steel rotary kilns. Small amounts of CA are produced by pyrolysis of urea in stirred batch or continuous reactors, over molten tin, or in sulfolane. The feed to the kilns can be either urea soHd, melt, or aqueous solution. Since conversion of urea to CA is endothermic and goes through a plastic stage, heat and mass transport are important process considerations. The kiln operates under slight vacuum. Air is drawn into the kiln to avoid explosive concentrations of ammonia (15—27 mol %). 

Minimum Explosible Concentration (MFC) The lowest concentration of combustible dust necessary to produce an explosion. 

Dust Minimum ignition temperature (°C) Minimum explosible concentration (g/l)... 

Material Median particle size, pm Minimum explosive concentration g/m= p max bar ga (dp/dt)max> ba r/sec Ksi bar-m sec Dust Hazard Class... 

Material Median particle size, Mm Minimum explosive concentration g/m3 P oux bar ga (dP/dl)max, bar/sec KSt Dust bar-m Hazard sec Class ... 

Minimum ignition Minimum temperature (°C) explosible ------------------ concentration... 

Dost Minimum ignition temperature (°C) Minimum explosible concentration (g/l) Minimum ignition energy (m)) Maximum explosion pressure Maximum rate of pressure rise (psi/s) Maximum Notes oxygen cor>centration to prevent ignition (% by volume)... 

Under normal conditions, solutions of sodium (and other) chlorites when acidified do not evolve chlorine dioxide in dangerous amounts. However, explosive concentrations may result if acid is dropped onto solid chlorites. 

Table 5. Representative ignition temperatures, minimum explosion concentration, and minimum ignition energy for selected dusts, from NFPA Fire Protection Handbook (National Fire Protection Association, 1986) and other sources.

Explosive concentrations of chemicals, dusts, and vapors Noise levels of equipment Types and degree of radiation... 

Minimum explosive concentration for explosive and pyrotechnic dusts have been reported in the range of 40 to 1000 gm/mm, (40 to 1000 oz/ft ). With the exception of location 5 in Building 1619 at Louisiana AAP, all the dust concentrations determined for the various plants were below the maximum average concentrations. 

The lower explosive limit and minimum explosive concentrations of flax, wool, cotton, jute, hemp and sisal fibres are of the same order of magnitude as those of highly explosive dusts [15], The explosibility of pyrites dusts with sulfur contents above 20% was evaluated experimentally. Dusts of 30% sulfur content gave explosion pressures of 3 bar at pressure rise rates of 16 bar/sec. Mixtures of 60% pyrites and 40% powdered limestone still showed significant pressure effects, and the proportion of limestone actually needed to suppress explosions was considerably above the values currently accepted by mining industries [16], Effects of mixtures of particle sizes in combustible dusts upon minimum ignition temperature (T ") and upon presence or absence of explosion were studied. Presence of 30% of fines in a coarse dust lowers Tf significantly [17], Experimental explosions of polyethylene,... 

Three pulp mill workers died after inhalation of fumes for approximately 10-15 minutes from a nitric acid tank explosion (concentrations not available). No significant respiratory complaints were apparent during initial examination. However, 4—6 hours later they became cyanotic with frothy fluid escaping from the nose and mouth. All died in less than 24 hours. Necropsy showed bronchiolar epithelial necrosis, marked capillary engorgement, and slight interstitial edema of alveoli the lungs were five times heavier than normal and released abundant frothy fluid from all lobes. The delayed manifestations of lung injury were consistent... 

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