Pulsed extraction columns fall into two main categories and both are very similar in construction. The only difference is that the first type incorporates packed column sections fitted with sieve plate assemblies. In both cases, there are separator vessels at the top and bottom of the column.
- The two phases are fed into the column by means of a twin-headed dosing pump which can be adjusted to set the exact throughput required for the particular process.
- A pulsing unit is connected to the bottom of the column and pulses the head of liquid through a column.
- The stainless steel sieve plate inserts normally have a plate spacing of 100 mm and they are pre-assembled to form complete units before being fitted into the column sections. if the process requires plates constructed from other materials or the free-plate areas greater than the approximate 20 % normally used, the assemblies can be easily exchanged.
- When temperature control of the extraction process is required, heating jackets can be provided for the column and immersion heaters for the separator vessels.
To meet the requirements of the processes involved in liquid/liquid extraction, a wide range of packings are available in various sizes and in different materials of construction.
To complete the extraction column, the following ancillary equipment is recommended :
- Dosing pumps or metering pumps.
- Pulsation pumps.
- Interface detector using the principle of capacitance change.
Pulsed columns are suitable for liquid extraction processes where the specific gravity (S.G) difference between light and heavy phases is in the range from 0.05 to 0.6