TECHNICAL ANALYSIS

Mist Eliminators

The most important purposes of a mist eliminator system are to:

1. Protect in-line stack gas reheater tubes from plugging
2. Prevent corrosion and/or erosion of the exhaust-stack lining
3. Protect the induced-draft fan from damage
4. Limit the emissions of particulates from the scrubber to the  atmosphere
5. Reduce reheater energy requirements by removing water droplets from the flue gas stream

The configuration of the mist eliminator, whether horizontal (vertical gas flow) or vertical (horizontal gas flow), is important to the efficiency of collection, reentrainment, and susceptibility to plugging.

Two types of material are used in the industry for mist eliminator construction: stainless steel and, predominantly, plastics. Each material has both advantages and disadvantages. Stainless steel, usually 316L, is strong and rigid (therefore allowing high-pressure washing), has acceptable corrosion resistance, provides a smooth collection surface (to limit scale formation), and is not sensitive to sudden temperature increases. It is, however, heavy and more expensive for both raw material and fabrication. Mist eliminators are also constructed with fiberglass reinforced plastics (FRP), corrugated plastic, and/or polypropylene. These materials of construction have excellent corrosion resistance, are lightweight, and are relatively inexpensive (compared with stainless steel). Their main disadvantage is poor strength (they can become embrittled after long exposure to scrubbing slurry) and temperature sensitivity.