Crude Methanol contains approximately 18% of water at this stage (along with other impurities). It is transferred to the Crude Methanol storage tank where it will become the feed to the next part of the operation i.e. Purification by distillation
Purification of Crude Methanol to the required methanol product quality (IMPCA or US Federal Grade AA spec) is achieved in two separate distillation columns.
The first column is designed to remove low boiling impurities, also called ‘Light Ends’. These ‘light ends’ are simply materials that will boil at a lower temperature than the boiling point of Methanol. Traditionally, this process is called ‘topping’ and the equipment is called a ‘Topping Column’ or ‘Light Ends Column’.
After the ‘topping’ process, the crude is transferred to the ‘Refining Column or Heavy Ends Column’. It is in this next step of purification that the liquid is again constantly boiled until the water (which boils at a higher temperature) is separated from product methanol (which leaves the top of the column).
Good quality methanol vapor separates and rises to the top of this column. From here it is changed back to liquid, (condensed). Part of this condensed liquid methanol, (called distillate) is taken to the storage tanks called Check Tanks.