Laser Optical Flow Measurements and Computational Fluid Dynamic Calculation of Spray Tower Hydrodynamics

Spray towers for gas scrubbing and similar separation technology applications often show complicated three-dimensional gas flow patterns. Due to non-optimal inlet duct configuration and nozzle arrangement inhomogeneous gas distributions in the tower cross-section may result with a fraction of the gas stream bypassing the dense spray region. Thereby, the axial gas flux locally may reach a multiple of the towers superficial velocity. To maintain the efficiency of the spray tower the maldistribution effects are counterbalanced by the amount of the liquid throughput implying increased operating costs. In the current investigation the mechanisms of the non-ideal gas and spray motion are analysed with the help of Laser Doppler and Phase Doppler measurements in single spray cone experiments as well as in a pilot-sized spray tower. In addition to the gas velocity profiles and the spray's size distribution, the gas phase pressure drop and the spray's wall deposition flux was also measured for the countercurrent spray/gas operation. The experimental pilot-plant data were used to evaluate the results of computational fluid-dynamics simulations, based on the particle-in-cell (PIC) methodology for the polydispersed spray/gas-flow. The spray-nozzle flow is demonstrated to influence the gas motion to a considerable extend on the scale of the near nozzle region as well as in the overall spray tower flow field. A substantial amount of the total liquid injected is lost in form of spray/wall deposition.