A novel drying tower technology for zero liquid discharge of desulfurization technology

The wet limestone/gypsum flue gas desulfurization (WFGD) technology has been attracting much interest, while handling with wastewater produced in WFGD is indispensable but difficult. Zero liquid Discharge (ZLD) technology is to recycle water content and reuse salt content of wastewater, which has becoming developing trend because of the strict wastewater emission regulation in China. However, existing ZLD technology cannot realize low investment and low power consumption. Therefore, in this paper, a novel drying tower applied in ZLD system was proposed. Wurster fluidized bed was introduced into drying of desulfurization wastewater and high gas-liquid heat transfer can be achieved with inert particles as immediate heat carrier. Industrial experiment and numerical simulation were applied to verify the feasibility of this novel drying tower, research flow structure in tower and offer optimization for future operation. The results indicate that this novel drying tower applied for a 300 MW power plant performs well in ten-day pilot run. Through numerical simulation applying computational particle fluid dynamics (CPFD), gas-solid-liquid flow structure of inner circulation is detected. With the increase of particle size, the evaporation efficiency increases firstly and then decreases while power consumption increases. The working condition with particle size of 1.6 mm performs best. With more bed material in dryer, higher efficiency and pressure drop can be obtained. Overall considering working effect, bed material of 380 kg is recommended for future operation. In simulation range, high efficiency and low power consumption can be obtained with higher wind supply ratio of central part. With the work of experiment and simulation, the novel drying tower is proved to be applicable and recommended operating parameters for future operation are offered through simulation results.