Demystifying the selection of mist eliminators; Part 2: The applications

Entrainment of liquid droplets in vapor streams often results in loss of valuable products. Entrainment may also cause operational problems: contaminating the overhead gaseous products; damaging downstream equipment by accelerating corrosion, erosion and fouling; and aggravating air pollution by carrying liquid pollutants into the atmosphere. Mist eliminators -- such as cyclones, impingement separators, gravity settlers, venturi scrubbers and electrostatic precipitators -- are used to separate the entrained droplets from the gaseous streams. This separation often allows increases in the throughput rates of various process equipment. Consequently, when selecting new equipment, one can specify smaller sizes by including entrainment separators, which can be installed inside the new unit. This article focuses on the layout, installation and troubleshooting of these units in various operating environments in the chemical process industries (CPI). Discussions include special design considerations of mist eliminators for such commonly encountered CPI equipment as packed and trayed columns, evaporators, steam drums and condensing heat exchangers.