The elements of group 7 (7B) are the halogens, fluorine, chlorine, bromine and iodine, whose atoms have outer shells with one electron short of a full set. They react strongly with atoms with surplus electrons, to form negative ions. This activity decreases from fluorine to iodine. Atoms which need two electrons to complete their outer [...]
Thewelements of group 1 (1A) are the alkali metals – lithium, sodium, potassium, rubidium and caesium. Their atoms have a single electron in their outer shells, which they part with very readily to form positive ions. Because of this they react violently with water and most non-metals. The affinities of the alkali metals for most [...]
Nitrogen is commonly used as an inert gas as it will not react with most materials. Nitrogen may not be suitable in some instances, as in processing some metal dusts, with which it can react. Magnesium dust is such a material. Similarly, carbon dioxide and water vapor can serve as oxidizers in metal dust systems. [...]
There are many cases where the presence of flammable vapors or explosible dusts cannot be practically maintained outside the flammable limits. In such instances it is essential that the concentration of oxygen, or other oxidant, be maintained below the minimum oxidant concentration that will support combustion, LOC. When continuous oxidant monitoring instrumentation is used the [...]
The first of the several considerations in explosion prevention design is the identification and management of potentially combustible materials in the process environment. Specifically, such materials should be managed to maintain their airborne concentration outside the limits of flammability, preferably below the LFL. An extensive tabulation of flammability limits for gases and vapors is given [...]
FlashPoint Flash point (FP) is the temperature, as determined by test, at which a liquid (or solid) emits sufficient vapor to form combustible mixtures with air. The FP may be estimated from vapor pressure data for pure species. The FP of mixtures are best determined using any of several test methods. An extensive listing of [...]
Inert components in a fuel-air mixture limit the temperature and pressure rise on ignition or prevent ignition completely. Nitrogen is commonly employed as an inert gas. Water vapor and carbon dioxide are somewhat more effective inerting gases due to their higher molar heat capacities. This is evidenced by the effect of these gases on minimum [...]
The limiting oxidant concentration (LOC) is that concentration of oxidant below which a deflagration (flame propagation in the gas, mist, suspended dust, or hybrid mixture) cannot occur. For hydrocarbons where oxygen is the oxidant and nitrogen is the diluent the LOC is approximately 9 to 11 vol % oxygen. The LOC for dusts is dependent [...]
Mixtures containing both a flammable gas and suspended flammable dust are called hybrid mixtures. The LEL of a hybrid mixture is reduced in proportion to the gas concentration up to its LFL value (Bartknecht 1989). This may not be true for a hybrid mixture in which the flammable gas has a high LEL, such as [...]
Dusts suspended in air will support combustion when a minimum mass concentration, designated the lower explosible limit, or LEL, is achieved and sufficient ignition energy is provided. The value of the LEL depends on the composition of the solid phase, its particle size distribution and to some extent on the strength of the ignition source. [...]