Limiting oxidant concentration

This example shows how to calculate the limiting oxidant concentration of a vapor if an experimentally determined value is not available. 

Limiting Oxidant Concentration (LOG) The concentration of oxidant below which a deflagration cannot occur in a specified mixture. 

Limiting oxidant concentration of a given dust cloud is dependent on the type of the inert gas that is used to replace the oxidant of the atmosphere as well as some process conditions such as temperature. Therefore, LOC testing should simulate the process conditions and be performed by using an inert gas that is representative of the inert gas used in practice. 

Limiting oxidant concentration for combustion is dependent on the type of dust and type of inert gas used. Once the LOC of the dust has been determined for the inert gas that will be used, the inert gas needs to be introduced into the vessel. Successful inert gas blanketing will only be possible if the entire volume of the vessel is inerted and the inert atmosphere is maintained throughout even when the vessel is opened during the addition of solids and/or liquids to the vessel. 

Oxidation. There are 10 types of oxidative reactions in use industriaHy (80). Safe reactions depend on limiting the concentration of oxidi2ing agents or oxidants, or on low temperature. The foUowing should be used with extreme caution salts of permanganic acid hypochlorous acid and salts sodium... 

The Phalaborwa complex ia the northeastern Transvaal is a complex volcanic orebody. Different sections are mined to recover magnetite, apatite, a copper concentrate, vermicuhte, and baddeleyite, Hsted in order of aimual quantities mined. The baddeleyite is contained in the foskorite ore zone at a zirconium oxide concentration of 0.2%, and at a lesser concentration in the carbonatite orebody. Although baddeleyite is recovered from the process tailings to meet market demand, the maximum output could be limited by the requirements for the magnetite and apatite. The baddeleyite concentrate contains ca 96% zirconium oxide with a hafnium content of 2% Hf/Zr + Hf. A comminuted, chemically beneficiated concentrate containing ca 99% zirconium oxide is produced also. 

The limitation for chemical oxidation is that oxidation is frequently not completed to the final products C02 and H20. This can be due to a number of factors, including oxidant concentration, pH, redox potential, or the formation of stable intermediate toxic oxidation products. 

In homogeneous reactions, the upper limits of concentration are determined by the (limited) solubility of the salts of periodic acid and by the low pH values produced by periodic acid itself. Apart from these considerations, the concentration conditions to be selected are governed by the type of information desired. A very dilute solution having a high oxidant substrate ratio is used in the exploratory or preliminary phase defined earlier (see p. 13), but a more concentrated solution, in which the oxidant is only slightly in excess of the theoretical, is recommended for the preparative phase. 

The sulfonium dimer can in turn be oxidized at a higher potential, which is the diffusion-limited oxidation current of Ph2S. For this reason, the concentration of the latter in the reaction layer closer to the electrode is practically zero, so a dimeric dication radical formed from [(Ph)2S-C6H4SPhj can only react with this cation. Thus, no trimers but only tetramers are obtained under such conditions (Scheme 12) [52, 54, 55]. 

Field Observations Canadian workers using ambient oxidant dose have correlated meteorologic variables with plant injury.A correlation was discovered when an empirical relationship involving evapotrans-piration (the coefficient of evaporation) was developed and used to modify the dose information. This empirical relationship has been used on a limited basis to predict damaging oxidant concentrations from monitored meteorologic conditions. 

Field surv have confirmed oxidant injury to ponderosa pine and associated species at numerous locations in the Sierra Nevada foothills east and southeast of Fresno. Oxidant measurements at ground stations and by instrumented aircraft show late-aftemoon peaks of transported oxidant on the western slopes of the Sierras. Limited measurements by instrumented aircraft suggest the development of a layer of oxidant approaching the forested mountain slopes between 610 and 1,829 m during the late afternoon. A very weak inversion or isothermal layer may serve as a reservoir of oxidant, which is advected to the mountain slope in the southern coastal air basin, as suggested by Edinger. Considerable concern has been registered about air quality in the Lake Tahoe basin, where local development may cause adverse oxidant concentrations. ... 

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