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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