Numerical Simulation Of Flow Field And SO₂ Concentration Distribution In Lime Slurry Electrostatic Spraying Desulphuration Process

Wet flue gas desulphurization system has been the main technology among flue gas desulphurization industry in the world, as its high desulfurization degree and mature theory. But there are some problems discourage its wild application China, such as the large spraying quantity, the big size droplet and the high cost. Lime slurry charging spraying desulfurization is a new desulfurization method bringing electrostatic spraying into wet flue gas desulphurization system, with a lower investment and operating cost through atomization quantity and SO2 absorption situation improved.In this paper, numerical simulation for charged gas-liquid two phase flow field and SO2 concentration field in experimental lime slurry charging spraying desulfurization tower has been carried out, based on charged two phase flow theory and knowledge about SO2 absorption. From the result, it has been known the affection of charging voltage, slurry flow rate, injection direction and position on flow field and SO2 concentration field. This will make contribuition on extensive application of lime slurry charging spraying desulfurization.1. Electrostatic field generated by ring-like electrode has been simulated, based on Laplace equation, through extending commercial Fluent 6.3 function. The result shows that the electrostatic field is symmetry about z-axis, with the highest electrostatic field strength on nozzle, but electrostatic field strength is weakened quickly away from electrode; electrostatic field strength is strengthened as the charging voltage increased or the distension between electrodes decreased, while electrostatic field around nozzle electrode changes obviously, and it is the main part for lime slurry droplet induction charging.2. Charged two phase flow field in Lime slurry charging spraying desulfurization tower has been simulated based on Euler-Lagrange method, trajectories of lime slurry droplet using discrete random walk (DRW) model, and coupled simulation between electrostatic field and flow field has been achieved through adding electrostatic force procedure to computing process by UDF function in Fluent 6.3. The result shows gas velocity gradient decreases in jet flow zone after lime slurry charged, and gas entrainment is enhanced on bondary of the jet flow zone, which is obviously enhanced while the lime slurry flow rate increased, this will strengthen SO2 absorption process.3. SO2 absorption process has been simulated, adding SO2 absorption model through UDF function in Fluent, the result indicates that SO2 concentration is affected by the gas-liquid two phase flow field, and desulfurization degree calculated has a good agreement with the experimental data, while with the same tendency; desulfurization degree is increased as lime slurry charged; desulfurization performance is better when lime slurry injection and gas motion is in the same direction.