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From Environmental Management: Wastewater and Groundwater Treatment

Worldwide regulations are requiring greater capture efficiencies and destruction rates for operations that handle volatile organic compounds (VOCs). Many furnaces, dryers, reactors, and other process equipment will need improved monitoring or add-on pollution controls to meet these evolving rules.

To reduce the total exhaust volume from operations handling solvents or VOCs, many such systems use internal recirculation or exhaust-gas recycle. Steps to minimize exhaust gas volumes create energy savings and translate to smaller equipment requirements. However, they increase the VOC concentration inside the process equipment, which may increase the risk of fire or explosion.

Beyond threshold concentrations, organic vapors yield potentially explosive conditions. Unless valid information is available regarding the specific composition of the gas stream, safe design and operation is a challenge.

Described below is a technique for estimating the lower explosive limit (LEL) of a vapor stream that contains a mixture of organic compounds. LEL is defined as the lowest concentration of organics in a homogenous mixture of air and organic(s) that is sufficient to allow an explosion or fire to occur when an ignition source is present.

The estimation procedure will give the engineer valuable insight into gas compositions for safe equipment design and operation. However, it...


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© 2014 Chemical Engineering

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