Modeling flue gas desulfurization by spray-dry absorption

摘要

A detailed model for flue gas desulfurization by spray-dry absorption with a lime slurry is presented.The model combines a steady state one-dimensional spray-dryer model with a single-drop model for SO_2 absorption with instantaneous irreversible reaction in a rigid droplet containing uniformly dispersed fine lime particles.The fate of the droplets is followed from atomization until formatin of a porous coherent shell around the dyring droplets.the model results wee vailated against vaailable experimental spray-dry FGD results,showing excellent agreement at low to medium Ca/S feed ratios.The model was then used to study the relevance of the different resistances to SO_2 absorption and to predict the influence of the main operating ariables on the spray-dryer desulfurizatin performance.Analysis of variables profiles along the spray-dry column showed that the initial droplet velocity has no influence on model results and that the initial drosplets decelerating phase a always accounts for negligible SO_2 captures.Results further showed that the controlling resistances to SO_2 absorptio shifts from a liquid-phase one near the atomizer to a gas-phase one at the column exit.The operating variables that exert the largest influence on the overalldesulfurizatin efficiency are the Ca/S molar feed ratio,the mean initial droplet size and the mean lime particles size.In particular,careful control of the last two variables in critical in order to obtain a good spray-dryer performance.