Shell and tube heat exchanger with split shell and method of using

A method of heating a feed stream for a reaction zone using reactor effluent comprising:

• providing a shell and tube heat exchanger comprising:
• a shell side having a separation plate dividing the shell into at least two compartments, each of the compartments having a feed inlet and a feed outlet;
• and
• a tube side comprising a plurality of tubes in the shell, at least one tube in each compartment, the tube side having an effluent inlet and an effluent outlet;
• dividing the feed stream into at least two portions;
• passing the two portions of the feed stream from the feed inlets to the feed outlets of each compartment and passing the reactor effluent from the effluent inlet to the effluent outlet to pre-heat the two portions of the feed stream;
• heating the two pre-heated portions of the feed stream in a charge heater;
• and
• introducing the two heated portions of the feed stream from the charge heater into the reaction zone.