Sieve plate tower extractors are liquid - liquid extractors. Sieve type extractor is the multistage, counter current sieve tray tower. They are very effective for system of low surface tension, which does not require mechanical agitation for dispersion. The stage type extractor can operate in batch or continuous basis. Small droplets of liquids are formed as the light phase flows through a perforated sieve plate, these droplets rise through the continuous heavy phase and coalesce underneath the next plate. The heavy phase flows downward from plate to plate through one or more downspouts or weirs depending on the column diameter. By turning the sieve plates upside down, heavy liquid becomes the dispersed phase. These multistage counter current columns feature a simple design with no moving parts while providing high mass transfer rates, little axial mixing between stage and overall extraction efficiency.

The sieve tray tower is a highly effective contacting device for applications requiring a low gas-to-liquid ratio. The design consists of a number of perforated trays in a vertical cylindrical tower. Liquid flows horizontally across the trays while gas flows up through the perforated tray at high velocity creating a frothing effect where the gas absorption takes place. The liquid then flows through down comer pipes to the lower trays. The number of trays can vary depending on the application and efficiency required. Sieve trays are best suited for absorption of highly soluble but volatile compounds such as alcohols and other soluble organics as well as some acid gases. This type of configuration minimizes water usage while achieving maximum contaminant removal.

Sight flow indicator is used for visually indicating fluid flow through a conduit including a housing that has an inlet and an outlet and defines a flow passage between the two. The flow passage consists of a sighting region and a downstream restricted region that has a smaller flow area than said sighting region. The window in the housing provides viewing of the sighting region. The elongated member that is located in the sighting region which is too long to move from the sighting region into the restricted region and is sufficiently smaller than the sighting region.