Theoretical And Experimental Research On Flue Gas Desulfurization By Two-fluid Electrostatic Spray Of Lime Slurry

Based on series fundamental experiments and theoretical analyses, the charged spray theory, flue gas absorption mechanism, the two-fluid electrostatic spray characteristics of the limewater, flue gas desulfurization by the electrostatic spray, charged multiphase turbulent flow are studied systematically and comprehensively in this paper, which established a research foundation for flue gas desulfurization by the electrostatic spray. Based on the WFGD systems, the desulfurization efficiency is improved by improving the limewater droplets movement characteristics, charging characteristics and surface absorption characteristics through making uses of the charged spray. The research work involves the limewater droplets charging characteristics, the two-fluid electrostatic spray structure of the limewater and the droplets space distributing, the model and experiment of flue gas desulfurization by the electrostatic spray, charged multiphase turbulent flow theory and numerical simulation in the tower. This research work is supported by the University Natural Science Foundation of Jiangsu Province.1. The medium conductance and polarization mechanisms are analyzed in theory, the limewater droplets electrification and non-excess charge polarization mechanisms are discussed. The annular electrode and droplets troop inducement voltage distributing are gained. Dipole moments of limewater droplets and SO₂ are analyzed in theory. The model of charge to mass ratio of limewater droplets is established, the calculation results is in accord with the experimental data.2. The experimental equipments have been designed and produced. The limewater droplets charging characteristics are tested. The experimental data indicate the pole distance, liquid to gas ratio and the slurry consistence are the important factors for the droplets electrification effect.3. Flue gas desulfurization of electrostatic charged spray system have been designed and produced. The experimental data show the efficiency by limewater electrostatic spray could improve 5-12% than the traditional spray. The improvement of efficiency is relation to the electrification droplets movement characteristics and surface absorption characteristics. And the minishing of the droplets and space distributing uniformity are important factors to improve the efficiency. The effects of Ca/S ratio, temperature, revolving flow, inlet SO₂ consistence to efficiency are test and discussed. The efficiency is proved when the Ca/S mol ratio increase. The temperature could improve the efficiency under the some range. Revolving flow could improve the time of the droplets and flue gas, and revolving flow enhances the gas turbulent fluctuation, and could conduce to the contact gas and droplets. Inlet SO₂ consistence is big, and the efficiency is small.4. The two-fluid electrostatic spray of the limewater is tested by the PIV. The spray flow images, velocity vector graphs and nephograms are gained. There are the distinctness convolution structures in the two-fluid electrostatic spray. The idiographic flow structures are analyzed. The two-fluid electrostatic spray flow structures involve main jet flow section, up convolution section, down convolution section and influence section.5. The two-fluid electrostatic spray of the limewater is tested by the PDA. The droplets diameter, droplets velocity and droplets turbulent fluctuation intensity are obtained under the different voltages and liquid to gas ratios. The limewater droplets diameter minish, the dimension distributing uniformity improve and the droplets velocity increase at first and decrease later while the high voltage increasing. The possibility of atomization of droplets is analyzed on base of the Rayleigh Limitation. The experimental data on the charged two-fluid flow show that the charged droplets are provided with follows. The droplets turbulent fluctuation intensity is concerned with the droplets velocity and the droplets themselves are provided with strong turbulent fluctuation.6. Based on the microcosmic function between electrification droplets and SO₂ molecules, the electrification and non-excess charge polarization for SO₂ absorption mass transfer process are important factors and are know from the conventional spray. The electrostatic force and polarization force between droplets and SO₂ molecules for the electrification and non-excess charge polarization. The mass transfer velocity increases. Combined with the spray reactor FGD process, the high electrostatic field reaction section, droplets inducement electric field reaction section and tower wall film reaction section are taken into account. The model of flue gas desulfurization by the electrostatic spray reactor is inextenso established.7. Based on the electrostatic spray, adopting assumption that the droplets are regarded as fluid, the charged multiphase flow is established. Applied the Reynolds time-average method, a k-ε-k_p model of Reynolds time-average equations for gas and chargeddroplets are set up. The heat and mass transfer of gas and droplets are advised. The simulation of limewater electrostatic spray flow is carried through in the tower. The simulations indicate the charged droplets distribute uniformity and the droplets inlet velocity is different under the different voltage.