In the continuous shell still process, several shell stills are linked in series to form a battery. Fresh feed continuously enters the first still, which is kept at the lowest temperature for the lightest overhead product.
- Bottoms from the first still are fed to the second still, which is kept at the temperature for the next higher boiling overhead product and so on.
- The number of still required depends on the number of products needed.
- If the feed and the temperature of each still remain constant, the finished product is of satisfactory quality.
Following figure depicts the continuous shell still process, which is an improvement over the batch shell still process.