Fractionating tower: Several types of reflux available
Thread Content
As the title suggests, there are several types of reflux in distillation columns; please explain all the different forms
There are mainly two types of reflux in a distillation column: internal reflux and external reflux. 1. **Internal reflux**: This is the reflux that forms naturally inside the distillation column. Inside the tower, the lighter components evaporate upward, while the heavier components flow downward due to condensation. During this process, some of the condensed liquid is sent back into the tower as reflux to enhance the separation effect. 2. **External reflux**: This type of reflux involves the deliberate reintroduction of a portion of the product that comes out of the top of the tower – usually a condensed liquid – back into the distillation tower. Doing so can help regulate operating conditions and optimize the efficiency and effectiveness of the distillation process, and it is commonly used in industrial applications. Each reflux method plays a key role in improving the material separation efficiency within the tower as well as the operational flexibility of the tower. .
Top circulation, No.1 refinery, No.2 refinery, re-refining, oil slurry
Under normal circumstances, there is tower top reflux and side stream reflux. Side stream reflux is further divided into mid-section reflux (external reflux) and internal reflux; external reflux usually involves cooling the liquid before returning it to the upper part of the extraction trays or packing, while internal reflux involves returning hot liquid to the lower part of those trays or packing sections.
The three types of reflux refer to the three methods of reflux: cold reflux, hot reflux, and cyclic reflux. Cold reflux (subcooled liquid reflux) – After the vapor phase distillate at the top of the tower is completely condensed in a condenser, it is further cooled below its bubble point temperature, resulting in a subcooled liquid. Using this subcooled liquid as reflux is referred to as cold reflux. Hot reflux (saturated liquid reflux) – The vapor distillate from the top of the tower is condensed to its bubble point temperature, and this saturated liquid is used as reflux; this is known as hot reflux. Circulating reflux involves extracting a portion of the liquid fraction from the side stream of the tower; after being cooled through heat exchange, it is sent back to one or several trays above the extraction tray as reflux, which is what is known as circulating reflux.