what are the necessary equipments or instruments used for safety in distillation column? Do distillation column need protection from lightening or thunder?

Debashis,

You will need to ground the column to a buried ground loop to protect against lightening. Typical you have two conncections from the vessel to the ground loop, incase one ground connection gets cut.

As far as instruments, you will level transmitters and level shut downs. It is also typical to have pressure differentail pressure trasmitters around sections or pack, so that you can tell if the pack if fouled for some reason.

Hope this helps,

Steven

Guidance to lightening protection of civil structures can be found in standard EN62305 (parts 1-4).
Regarding protection and instrumentation - this depends to some extent on the chemicals being separated and size of the column. The reboiler may require a safety valve on the steam side of the heating coil (assuming steam is the heat source); commonly flow and pressure instruments are fitted to measure energy input. The product side may also require a safety valve or bursting disc. Pressure temperature and level sensors may also be required. Bottom product will normally require flow measurement/control.
At the top of the column pressure and temperature sensors are normal, similarly instrumentation is commonly included in the condenser (flow and inlet/outlet temperature) on the coolant side to warn of fouling. Vacuum relief may also be necessary to prevent damage during the shutdown procedure. Flow is required for top product and reflux.
Feed flow and temperature are also normally instrumented. Temperature sensors are also usually included at various points up the column to check performance, particularly if there are side streams.
Interlocking and control will normally be associated with the measurements.

Thanks a lot sir. It really helped me. I have another question, for azotropic distillation and for distillation of viscouse feed,what kind of tray is used?and purpose of using those type of trays.