Column Operation

The operation of a batch rectifier only will be considered in here. The most popular operating modes are: constant reflux ratio (with variable distillate composition), constant distillate composition (with variable reflux ratio) and total reflux (no product take-off). The former two operations are in fact semi-batch operations; the latter one is truly a batch operation. Operation at optimal reflux ratio should be mentioned too, but - since it is often accomplished through a series of constant reflux ratio sequences - this operating mode will not be considered here. In the following, the components are numbered in order of decreasing ease of separation (i.e. component 1 is the most volatile one, component 2 is the second most volatile, and component Nc is the least volatile).

From a practical point of view, regardless of the operating policy, the operation of a multicomponent column is carried out in three steps: (i) a start-up phase; (ii) a main cut production phase; and (iii) a slop cut removal phase. The last two steps are repeated sequentially. The following actions take place during the start-up phase: the column and receivers are possibly cleaned from the materials processed in the previous batch; cooling of the condenser is started; steam is fed to the reboiler, so that the material to be processed is heated up to its bubble point and starts to vaporize; as soon as the overhead vapour has been condensed and has filled the reflux drum, liquid is returned to the top of the column, and the column is run at total reflux; consequently, the column trays are sequentially filled with liquid.

The start-up procedure is very general, and goes on until either the steady state is approached, or the lighter product purity specification is reached in the reflux drum. The other two phases vary according to the operating policy employed.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment