Page 207 - Fluid Catalytic Cracking Handbook

Unit Monitoring and Control 175

The pressure in the regenerator dome is:

22. J - 0,2 = 21.9 psig (151.0 K P)

The static pressure head in the regenerator is:

3
2
2
(18 ft) x (25 lb/ft ) x (1 ft /!44 in ) = 3.1 psig (21.4 K p)
The pressure above the regenerated catalyst standpipe is:
22.1 + 3.1 = 25.2 psig (173.7 K p)

The pressure buildup in the regenerated catalyst standpipe is:

30.5 - 25.2 = 5.3 psi (36.5 K p)
The pressure below the regenerated catalyst slide valve is:

30.5 - 5.5 = 25 psig (172.4 K p)

The pressure drop in the vertical riser is:

25 - 19 = 6 psi (41.4 K p)

The catalyst density in the spent catalyst standpipe is:

2
2
3
2
(2.0 lb/in ) x (144 in /ft )/(14.4 ft) = 20 lb/ft = 320 kg/m 3
The catalyst density in the regenerated catalyst standpipe is:
2
2
3
2
(5.3 lb/in ) x (144 in /ft )/(30 ft) = 25.4 lb/ft = 407 kg/m 3
Figure 5-10 shows the results of the above pressure balance survey.
Analysis of the Findings
The pressure balance survey indicates that neither the spent nor the
regenerated catalyst standpipe is generating "optimum" pressure head.
3
3
This is evidenced by the low catalyst densities of 20 lb/ft (320 kg/m )
3 3
and 25.4 lb/ft (407 kg/m ), respectively. As indicated in Chapter 8,
several factors can cause low pressure, including "under" or "over"