Fig. 8 shows the total number removal efficiency of fine particles
by the WFGD system with different amount of steam addition
in the particle growth region. The liquid-to-gas ratio (L/G) was
10 L Nm3. The temperature of inlet flue gas and desulfurization liquid
are 90 C and 15 C, respectively. Due to the formation of sulfates and sulfites aerosol particles during the desulfurization process
when CaCO3 is used as the reagent, the removal efficiency is
negative without steam addition. The removal efficiency can improve
significantly by adding steam in the particle growth region.
For example, when the amount of steam added in the phase transition
chamber is 0.08 kg Nm3, the removal efficiency can improve
from 29% to 42% in comparison to that of without steam
addition. These experimental results are consistent with the calculated
results which are illustrated in Figs. 9 and 10. Fig. 9 shows the
calculated supersaturation of flue gas as a function of the amount
of steam added. The steam added in the particle growth region is
dry and saturated water vapor with the temperature being
100 C. And the initial relative humidity of desulfurated flue gas
is 95% with the temperature being 45 C, 50 C and 55 C respectively.
It can be seen that, with increasing the amount of steam
added the supersaturation of flue gas rise, leading to the amount
of condensable water vapor increasing. Then both the growth rate
of fine particles diameter and the final diameter of grown droplets
increase with the supersaturation (S) of flue gas, which can be seen
in Fig. 10. What’s more, the diameter of fine particles hardly alters
with time while the supersaturation of flue gas is lower than the
critical supersaturation (Scr) necessary for particle nucleation.
And fine particles can’t be activated and grow up to droplets. While
the supersaturation rises from 1.5 to 2.0, the final diameter of
grown droplets increases from 2.8 lm to 6.0 lm accordingly. And
this is propitious to enhance the removal efficiency of fine particles.
Therefore, particle removal efficiency would improve with
increasing the amount of steam added for both ways. On the one
hand, the critical supersaturation necessary for particle nucleation
would decrease and then more fine particles could be activated and
grown up to droplets. On the other hand, the amount of condensable
water vapor increases greatly and the grown droplets would
be larger. Consequently, the more steam that is added, the larger
the condensational droplets will be and the easier they can be removed
by inertial forces.
Fig. 8 shows the total number removal efficiency of fine particles
by the WFGD system with different amount of steam addition
in the particle growth region. The liquid-to-gas ratio (L/G) was
10 L Nm3. The temperature of inlet flue gas and desulfurization liquid
are 90 C and 15 C, respectively. Due to the formation of sulfates and sulfites aerosol particles during the desulfurization process
when CaCO3 is used as the reagent, the removal efficiency is
negative without steam addition. The removal efficiency can improve
significantly by adding steam in the particle growth region.
For example, when the amount of steam added in the phase transition
chamber is 0.08 kg Nm3, the removal efficiency can improve
from 29% to 42% in comparison to that of without steam
addition. These experimental results are consistent with the calculated
results which are illustrated in Figs. 9 and 10. Fig. 9 shows the
calculated supersaturation of flue gas as a function of the amount
of steam added. The steam added in the particle growth region is
dry and saturated water vapor with the temperature being
100 C. And the initial relative humidity of desulfurated flue gas
is 95% with the temperature being 45 C, 50 C and 55 C respectively.
It can be seen that, with increasing the amount of steam
added the supersaturation of flue gas rise, leading to the amount
of condensable water vapor increasing. Then both the growth rate
of fine particles diameter and the final diameter of grown droplets
increase with the supersaturation (S) of flue gas, which can be seen
in Fig. 10. What’s more, the diameter of fine particles hardly alters
with time while the supersaturation of flue gas is lower than the
critical supersaturation (Scr) necessary for particle nucleation.
And fine particles can’t be activated and grow up to droplets. While
the supersaturation rises from 1.5 to 2.0, the final diameter of
grown droplets increases from 2.8 lm to 6.0 lm accordingly. And
this is propitious to enhance the removal efficiency of fine particles.
Therefore, particle removal efficiency would improve with
increasing the amount of steam added for both ways. On the one
hand, the critical supersaturation necessary for particle nucleation
would decrease and then more fine particles could be activated and
grown up to droplets. On the other hand, the amount of condensable
water vapor increases greatly and the grown droplets would
be larger. Consequently, the more steam that is added, the larger
the condensational droplets will be and the easier they can be removed
by inertial forces.
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