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Distillation is the method of separating the components of a solution which depends upon the distribution of the substances between a gas and a liquid phase.Distillation may be done in two ways :
1. Production of vapor by boiling the liquid mixture to be separated and condensing the vapor without allowing any to return to the still,there is no reflux.
2. Returning a part of condensate to the still under such conditions that this returning liquid is brought into intimate contact with on their way to condenser.
The distillation column consists of several trays, which allow the simultaneous travel of liquid down the tray and vapor up the tray, allowing mixing of the two phases and therefore equilibrium.
The liquid mixture that is to be processed is known as the feed. The feed-tray divides the column into a top (enriching or rectification) section and a bottom (stripping) section.
The vapour moves up the column,and as it exits the top of the unit, it is cooled by a condenser. The condensed liquid is stored in a holding vessel known as the reflux drum.Some of this liquid is recycled back to the top of the column and this is called the reflux.
The condensed liquid that is removed from the system is known as the top product or distillate.
The aim of this experiment is determination of boiling range characteristics of petroleum product by using ASTM distillation.ASTM Distillation is a standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure.
Working Principle :
It is based on the principle of differential or simple distillation.A batch of liquid is charged to a still fitted with some sort of heating device.The charge is boiled slowly and the vapors are withdrawn as rapidly as they form to a condenser where they are liquified and the condensate is collected in the reciever.