Study on the Removal of Heavy Metals From Wastewater by Ultra High Lime With Aluminum Precipitation Coupling Activated Carbon Adsorption in 300 MW Coal-Fired Units

Abstract

ObjectivesThe wet flue gas desulphurization of coal-fired power plants generates a large amount of wastewater containing heavy metals, the removal of heavy metals from wastewater by coupling of limestone and sodium metaaluminate precipitation and activated carbon adsorption were studied.MethodsThe optimized feed ratio, temperature, and pH value for the precipitation method were obtained, and the experimental parameters for the type of adsorbent and adsorption layer height were optimized. Based on this, engineering tests were conducted on the 300 MW unit of Sanhe coal-fired power plant. Field experiments were conducted with an additional precipitator feeder and adsorption device, and effect was investigated.ResultsThe optimal feeding rate is 160 kg/h, the flow rate is 1 m3/h, and the adsorption height is 10 cm. Under the experimental conditions, the overall heavy metal removal efficiency is significantly improved. Compared with the heavy metal content in the original export of the power plant, the removal efficiency of lead, chromium, copper, and nickel from the export increase by 33.24%, 81.93%, 35.22%, and 57.52%, respectively, after installing a mixed precipitation and adsorption device.ConclusionsThe method of coupling of limestone and sodium metaaluminate precipitation and activated carbon adsorption can effectively promote the removal of heavy metals from desulfurization wastewater, providing guidance for the deep removal of heavy metals in the wastewater from coal-fired power plants.

Keywords

• coal-fired units
• desulfurization wastewater
• heavy metal
• ultra-high lime with aluminum
• activated carbon
• adsorption