Production of anhydrous alcohol from rectified spirit (Industrial Ethanol) with molecular sieve dehydration utilizing pre concentration column:
The rectified spirit before sending in for dehydration process, it is heated and portion of water is stripped in the pre concentration column through a pre-heater. The mixture of alcohol and the remaining portion of water are sent to molecular sieve in the form of vapour.
The molecular sieves are hard granular substances, cylindrical extrudates manufactured from clay like silica gel material such as potassium alumino silicates. They are grated according to the nominal diameter of the myriad of internal pores, which make up the interstitial free volume found within their structure. A typical sieve used in ethanol dehydration is Type 3A. This designation means that the average diameter of the interstitial passageways is 3 Angstroms (One Angstroms: 1A is unit of measures equivalent to 10-8 centi meters). Thus the passageways in the structure have a diameter that is molecular scale. The water molecule has a mean diameter less than 3A, while the ethanol molecule has a mean diameter greater than 3A.