Page 146 - Design of Simple and Robust Process Plants
P. 146
4.2 The Methodology of Process Synthesis 131
LOW
HEAT
RECOVERY
MEDIUM
HIGH
REACTION
SECTION
FUEL
AIR
Fig. 4.39. High-temperature endothermic reactor in furnace
with heat recovery system.
STACK
LOW
HEAT
RECOVERY
MEDIUM
HIGH
REACTION
SECTION
FUEL
AIR
Fig. 4.40. High-temperature endothermic reactor in furnace
with gas-turbine and heat recovery.
This structure is characterized by crossing flows of similar heat capacity (mass
sensible heat), and consists of:
. feed effluent heat exchanger for process flows; and
. feed effluent heat exchange of flue-gas with air inlet (air preheat).
In this case the choice is the temperature level of air preheat. In principle, we prefer
to preheat to maximal level, as the saving is on primary energy. The constraint is
determined economically, as higher temperatures ask for more durable, expensive
materials to construct the air pre-heater and radiation sections.
