Dynamics of wet flue gas desulphurization in spray absorber
A concise one dimensional thermal-hydraulic two-fluid model is presented for the numerical prediction of sulphur dioxide absorption from the flue gas onto drops of the water-limestone slurry in the vertical spray tower absorber. The model is based on mass, momentum and energy balance equations for each phase separately, i.e. downward falling droplets of water-limestone slurry and upward flowing flue gas. The sulphur dioxide content in the flue gas is predicted by a balance equation of the sulphur dioxide mass fraction in the flue gas. Interface transfer processes between the flue gas and the droplets are determined by closure laws. The obtained steady-state balance equations are transformed in a form suitable for a direct application of the numerical integration method for the system of ordinary differential equations. The developed thermalhydraulic model is validated by comparing numerical results with available measured data at the large utility absorber. The presented results clearly show the dynamics of flue gas and droplets thermal-hydraulic processes and their influence on the absorption process.
Multiphase Euler–Lagrange CFD simulation applied to Wet Flue Gas Desulphurisation technology
Abstract The gas and liquid hydrodynamics inside an Open Spray Tower has been simulated using a commercial CFD code, while a model that treats the absorption process of SO2 has been developed and implemented in the software through dedicated modules. Besides SO2 absorption also evaporation of slurry droplets and droplet-wall interaction are considered, the latter modeled with an empirical correlation and implemented in a sub-module. The continuous gas phase has been modeled in an Eulerian framework, while the dispersed liquid phase with a Lagrangian approach by tracking a large number of particles through the computational domain. Physical absorption of SO2 has been modeled using dual-film theory and appropriate empirical and semi-empirical correlations. The model for aqueous phase chemistry considers instantaneous equilibrium reactions of eight dissolved species into a slurry droplet, namely: SO 2 ,aq , CO 2 ,aq , H + , OH - , HSO 3 - , SO 3 2 - , HCO 3 - , CO 3 2 - . The empirical droplet-wall interaction model handles impact, deposition and splashing events occurring when a liquid particle hits an internal element of the scrubber. A pilot plant OST has been simulated and the numerical results show good agreement with the experimental values of pressure drop, temperature and sulphur dioxide removal efficiency.
Point-to-point and point-to-multipoint communications
A network, such as wired and/or wireless LAN, is configured to have both point-to-point and point-to-multipoint connections. The point-to-multipoint connection(s) is used to communicate information between a plurality of the stations (or modem, or transceivers) in the network, whereas the point-to-point connection(s) are used to communicate information between only 2 stations in the network with the ability to, for example, maximize performance (rate/reach/BER/latency/etc) between those two stations. A master station allocates one or more frequency bands to the various point-to-multipoint and point-to-point connections.