The HDA process begins with mixing fresh toluene with a stream of recycle unreacted toluene, the mixing is achieved in a storage tank. The toluene is then pumped to combine it with a stream of mixed hydrogen and fresh hydrogen gas. The mixture of hydrogen and toluene is preheated before it is introduced to the heater or furnace. In the furnace the stream is heated to 600 C, the reaction temperature, then introduced into the reactor. The reactor is where the main reaction happens: