Synergistic Removal Of Dust Using The WFGD(wet Flue Gas Desulfurization) Scubber

The wet flue gas desulfurization?WFGD?technology is widely used to control the SO₂ emission in power plants.Using the WFGD system to control the SO₂ emission and improve the synergistic dust removal efficiency is an economical way for the power plants to reveal the ultra-low pollutant emission.The existing application results implicated that the WFGD system have a certain effect of removing dust,and the efficiency can be improved by adding some strengthened mass transfer components,but the mechanism of the strengthened effect is still not clear,and there are no studies on the influence mechanism of connected impact parameters.In this paper,the mass transfer and synergistic dust removal characteristics of WFGD systems were investigated for the sieve-tray spray scrubber and spray scrubber.For the sieve-tray spray scrubber,the enhanced efficiency is increased with the gas flowrate,slurry flowrate and pH value.At the same liquid-gas ratio,it also increases with the increase of flue gas flow.With the increases of SO₂ concentration,it decreases.The pore diameter and porosity of the sieve-tray spray scrubber can significantly enhance the absorption of SO₂.With the decrease of porosity,the enhancement efficiency was obviously improved by different influencing factors.Compared to the porosity,pore diameter has relatively less influence.For small pore diameter of 5mm,the enhancement effect is more significant,while for large pore diameter of 15mm and25mm,the enhancement effect is relatively small.For the spray scrubber,the influence of parameters,including dust particles diameter and inlet concentration of dust particles,and the flow rate of flue gas and slurry,on the dust removal efficiency were investigated.For the sieve-tray spray scrubber,the influence of parameters such as the pore diameter and porosity of sieve trays on the dust removal efficiency were examined.In the spray scubber,the dust removal efficiency for small particles is relatively low,and it increases with particles diameter increases.For particles diameter of 20?m,the removal efficiency can reach more than 90%.In the sieve-tray spray scubber,the dust removal effect is similar to that of the spray scubber.However,the overall dust removal efficiency of the sieve-tray spray scubber is slightly higher than that of the spray scubber.Under the same pore diameter,the overall dust removal efficiency of the sieve-tray spray scubber decreases with the increase of porosity and pore diameter.When the porosity increased from 21.2%to 40.82%,the dust removal efficiency decreased from 96.1%to 91.2%.Under the same porosity,the dust removal efficiency decreased from 99.3%of 5mm aperture to 93.3%of 25mm.Based on the dust parameters and operating parameters of a scrubber,a novel droplets swarm model for dust removal efficiency was developed from the single droplet model.The model resovled the tranditional model can not reflect the influence of complex gas-liquid flow on dust removal.The enhanced dust removal efficiency of sieve tray was expressed by introducing a strength coefficient to an inertial collision model.The dust removal efficiency model for the sieve-tray spray scrubber was developed by combining the droplets swarm model for spray scrubber with the modified inertial collision model for the sieve tray.The model effectively reflects the enhanced dust removal effect of the foam layer and provides a basis for calculating the dust removal efficiency of sieve-tray spray scrubber.The chemical composition and morphology of particles emitted from a WFGD system were analyzed.The inlet particles diameter,inlet particles concentration and liquid/gas ratio?L/G?,were all found to affect particles emissions.Smaller diameter particles and higher inlet particles concentrations resulted in S_i and total particles mass concentrations increases.The particles emitted from WFGD were mainly fine particles,with up to 96%of particles being below 2.5?m,and the removal efficiency is seldom effective for particles of 1?m and 0.5?m.the particles elements concentration is less than the sieve-tray spray scrubber,the mean diameter of the particles decreased from1.15?m in the spray scubber to 0.94?m in sieve-tray spray scubber.