Question 10.9: Determine the steam requirements of a fixed-bed regenerative...
Determine the steam requirements of a fixed-bed regenerative carbon adsorption system for air emission control.
The given data are as follows:
RE = 95\%
HAP_{o} = 50 ppmv
St = 0.3 lb steam/ lb carbon (see Table 3)
θ_{reg} = 2 h (see Table 3)
A_{bed} = 181 ft²
| Table 3 Carbon Adsorber System Efficiency Variables |
||
| Steam requirement for regeneration, St (lb steam/lb carbon) | ||
| 0.3 | 1.0 | |
| Outlet HAP concentration, HAP_{o} (ppmv) | 70 | 10–12 |
| Adsorption cycle time,^{a} θ_{ad} (h) | 2 | 2 |
| Regeneration cycle time,^{a} θ_{reg} (h) | 2 | 2 |
_{}^{a}\textrm{In } some instances, cycle times may be considerably longer than the values given here. The values in this table are approximate, not definitive.
Assume θ_{dry-cool} = 0.25 h.
Use Eq. (10):
Q_{s} = NA [St(C'_{req})/(θ_{req} − θ_{dry-cool})]/60 (10)
Q_{s} = 1[0.3(2,390)/( 2 − 0.25)]/60
Q_{s} = 6.84 lb steam/min
Q_{s}/A_{bed} = (6.84 lb steam/min)/181 ft²
Q_{s}/A_{bed} = 0.0378 lb steam/min ft²
Because Q_{s}/A_{bed} is less than 4 lb steam/min-ft², fluidization in the carbon bed is not expected.