Lower explosive level

Solvent vapor emissions from a coating operation are diluted with air to bring the solvent concentrations below the lower explosive level. As a pollution prevention measure you are asked to consider nitrogen as an alternative for air to transport the solvent vapor. What are the advantages of the nitrogen system over the air system ... 

Hazard Lower explosive level in air 1.2% by volume. Moderate fire risk. 

Hazard Flammable, dangerous fire risk lower explosive level 1.4%, upperexplosivelevel8.6%. May be narcotic in high concentrations. 

Hazard Flammable, moderate fire risk. Toxic by ingestion, inhalation, and skin absorption. Lower explosion level 1.8%. TLV 0.15 mg(Pb)/m3. Toxic by skin absorption. 

Control of lower explosive level (LEL) In a multiple zone dryer... 

If the solvent concentration of a zone exceeds certain level, then the system becomes to be in danger of explosion due to the flammability of organic solvent vapor. This level of solvent concentration is called as lower explosive level (LEL), and the dryer should be operated below the LEL prior to any constraints. Thus each zone needs sufficient airflow rate to meet these needs. However, too much airflow rate results in waste of energy to heat the excess air, and it increases the load ofwaste gas facilities (e.g., VOC emission control units). Therefore the airflow rate of each zone and the ratio of recycled to fresh air should be optimized. The typical airflow system for a multiple zone dryer is shown in Figure 7.3.32. The supplying air of each zone is consisted of fresh and recycled (used or returned from the exit gas) air as shown in the figure. LEL can be calculated if we know the evaporation rate of solvent of a zone. The evaporation rate of solvent can be measured or calculated as we explained in previous sections. Thus we can distribute the fresh air to each zone to meet the LEL safety without substantial increase in the total exhaust air. 

Methane has a GHS flammability rating of 1 (NFPA rating of 4), putting it in the extremely flammable category. A methane leak in a lab is extremely dangerous. The lower explosive level (LEL) is 4.5% and the upper explosive level (UEL) is 16.5%. A sulfur compound, often ethyl mercaptan or a mixture of mercaptans, is added to natural gas to give it an unpleasant odor and allow for easy detection. The complete combustion of methane produces carbon dioxide and water ... 

The vapour pressure from which combustion is possible (= lower explosion level, LEL)... 

Table 26.11 Flash points and the lower explosion levels (LEL) of some common organic solvents...

The saturated vapour pressure of ethanol is 58.5 mbar and the lower explosion level is 3.4 vol.%. 

The solution would be to monitor the atmosphere with a gas detector. If a flammable or combustible gas exceeds 10 percent of the lower explosive level, the work must be stopped. Next, identify the source of the gas and repair the leakage. 

At the stoichiometric ratio of ammonia to oxygen, the ammonia/air mixture is explosive. Therefore lower levels of ammonia are used. The lower explosion level (LEL) declines with pressure so low pressure systems can use a higher level of ammonia than high pressure systems [29]. There are other potential explosive hazards. For example, formation of ammonium nitrite or ammonium nitrate is a concern and precautions must be taken in order to avoid explosions. 

HDT heat distortion (deflection) temp. lei lower explosive level... 

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