Pentanes flammability limits

The behavior of flammability limits at elevated pressures can be explained somewhat satisfactorily. For simple hydrocarbons (ethane, propane,..., pentane),... 

Pentane is considered nontoxic at concentrations below its lower flammability limits (15,000ppm). Human subjects exposed to SOOOppm for 10 minutes did not experience mucous membrane irritation or other symptoms. In early reports topical application of pentane to volunteers caused painful burning sensations accompanied by itching after 5 hours, blisters formed on the exposed areas. More recent studies showed that 2.0ml applied to the skin of volunteers for 24 hours was not irritating. ... 

In this example the use of foam, which was described in Section 3.3.1, will be demonstrated as a postrelease mitigation agent. An accidental release of n-pentane, a flammable material, from a storage tank into a diked area, and a hazard zone to a concentration of one half the lower flammable limit (LFL/2) will be evaluated. For n-pentane the LFL is 1.4% by volume in air. Then the LFL/2 will be 0.7% by volume in air (GPSA, 1972). 

The behavior of flammability limits at elevated pressures can be explained somewhat satisfactorily. For simple hydrocarbons (ethane, propane,..., pentane), it appears that the rich limits extend almost linearly with increasing pressure at a rate of about 0.13 vol%/atm the lean limits, on the other hand, are at first extended slightly and thereafter narrowed as pressure is increased to 6 atm. In all, the lean limit appears not to be affected appreciably by the pressure. Figure 25 for natural gas in air shows the pressure effect for conditions above atmospheric. 

Calculate the upper and lower flammability limits of a gas mixture tliat consists of 30% metliane, 50% etliane, and 20% pentane by volume. 

A gas mixture of methane, ethane, and pentane entering an adsorber has an upper flammability limit of 12.5% and a lower flammability limit of 2.85%. Given a methane concentration of 30%, calculate the concentrations of the other two components of the gas mixture. Flammability limits for methane, ethane, and propane at various concentrations are given in the following table. 

There are two composition limits of flammability for air and a gaseous fuel under specified conditions [76]. The lower limit is the minimum concentration of combustible gas that will support combustion, while the higher limit is the maximum concentration. Table 5.1 shows the lower and higher limits for pure hydrocarbons in air at room temperature and atmospheric pressure (RTP) [76]. For methane in air, the flammability limit is 5—15 mol%. For ethane in air, the limits are 2.9—13.0 mol%. The limits become lower with increasing molecular weight. It also is interesting to note that the limits are the same for n-pentane and isopentane, and also for -butane and isobutane. 

A flammable gas detector is designed to measure the amount of flammable gas in the atmosphere and relate it to the upper and lower flammable limits. The gas mixture is drawn over a catalytic surface where oxidation, i.e. combustion, takes place. The combustion causes a rise in temperature of the surface which is measured by a decrease in its electrical resistance. The instruments have to be calibrated for the particular gas of interest but for petrol vapours pentane or heptane are used as the reference gas. The readings are usually displayed in terms of percentage of the lower explosive limit. 

N-Pentane (CgHij) is a flammable gas with a molecular weight of 72.17. ACGIH lists the threshold limit values for airborne concentrations at 600 ppm, or 1800 mg/m NIOSH lists the lowest lethal concentration at an estimated 130,000 ppm for an inhalation exposure to a human subject. 

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