Column length effects, industrial

There are some factors affecting the choice of column equipment in order to obtain a good separation. The length of column is necessary more than 30 times the diameter of column, because the resolution increases at the square root of column length. That is why a longer column is used for gel filtration especially for an analytical fractionation. A bed length of more than 1 m is not useful and effective for industrial separation. 

An effective flow rate for resolution is the order of 5 mL/cm2h and up to about 25 mL/cm2h is allowed for industrial preparations. The length of the column and flow rate are basically in an inverse relation. 

---