Vapor feed is heated in a furnace by fuel gas. Draw an instrumentation and control diagram that accomplishes the following objectives:

a. Feed is flow controlled

b. Fuel gas is flow controlled and ratioed to feed rate

c. The fuel to feed ratio is adjusted by a furnace exit temperature controller

d. High furnace stack-gas temperature (>75%) pinches the fuel gas control valve

e. Specify all control valve actions and provide a detailed over-ride scheme