engleski

Flue Gas Desulfurization by Absorption in Water Droplets

Flue gas desulfurization in spray towers is an efficient sulfur dioxide removal method for marine and stationary applications. It is based on the absorption mechanism of sulphur dioxide in droplets falling in the stream of flue gases, removing the pollutants due to concentration differences. More stringent legislature limiting the pollutant emissions is expected both for the coal-fired power plants and for marine engines, and detailed numerical modelling is one way of tackling the need for improving the efficiency and the design of the spray towers. In order to satisfactorily describe all the pertinent phenomena, a lumped-parameter absorption model, for the falling pure water droplet has been implemented. The main factors limiting the absorption are the mass transfer of pollutants through the gas-droplet interface and the droplet aqueous phase chemistry. Mass transfer coefficient modelling is the most significant parameter regulating the absorption dynamic into the droplet. It depends on the residence time, droplet size, velocity, flow field, and is difficult to model correctly for a wide range of conditions. On the other hand, the in-droplet chemistry regulates the maximum quantity of dissolved pollutants. It is limited by Henry’s law for gas dissolution and the dissociation and reactions of sulphur dioxide in the aqueous solution. Further, using the seawater as the absorbing solution further enhances the absorption potential due to salinity, alkalinity and the ionic strength. The implemented model was used on the single droplet compared with the available literature data. The model can be used for prediction of sulfur dioxide uptake on a single droplet scale and as a basis for further development of the more complex sulfur dioxide absorption models.

flue gas desulfurization, pure water absorption, sulfur dioxide – water chemistry

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