Figure 5.9 presents the fl owsheet prior to heat integration. Fresh and recycled
phenol is evaporated and mixed with hydrogen in the evaporator (Ev - 1) at about
2 bar. The gas mixture enters the catalytic hydrogenation reactor (R - 1). The inlet
temperature should be kept strictly constant, in this case at 150 ° C, to avoid the occurrence of a “ hot spot ” . Therefore, the placement of a small heat exchanger
(H - 1) in front of the reactor is recommended for control reasons. Reactor cooling
is ensured by steam generation at 140 – 150 ° C (3.6 – 4.7 bar). The reaction mixture
is separated in gas and liquid streams in the fl ash (S - 1) after cooling at 33 ° C by
passing through the exchanger (H - 2 ). The gas containing hydrogen is recycled to
the reactor via the compressor (Comp - 1), while the liquid phase is sent to
separation.