Page 178 - Design of Simple and Robust Process Plants

5.3 Combination of Process Functions 163
In case a gas turbine is not foreseen, the cascade cooling follows the following steps:
(i) high-temperature process heating; (ii) medium-temperature process heating; and
(iii) air and fuel preheating.
In the above process, heating might include steam generation to achieve a correct
energy balance. One design for a furnace for high-temperature reactions is that of a
calcination reactor (Figure 5.18). The furnace, which is of a staged, fluidized bed

Flue Gases
Solids inlet

Solids preheating
and drying sections

Calcination section
Fuel
Air preheating
sections

Solids outlet
Air inlet

Fig. 5.18. Calcination furnace: multi-stage fluidized beds.

concept, starts at the cold air side with air preheating stages, and this is followed by
calcination with fuel as energy source, together with several preheating zones where
the feed material is preheated and dried. Clearly, this design is an example of inte-
grated functionality. An overview of the different functions in a furnace are shown
in Table 5.4.

Table 5.4. Combination of functions in a furnace.

Furnace Application(s)

Reaction Steam cracker, syngas production
High process temperature > 250 C Process superheater, steam superheater
Medium process temperature, Process heater, evaporator
Medium pressure steam
Low process temperature < 150 C, Process heater, condensate heater
Low temperature steam
Air/fuel preheating Flue gas cooling
Gas turbine Power generation