Utilizing titanium-containing pickling sludge to prepare raw meal for clinker production

Abstract

The titanium-containing pickling sludge (TS sludge) was regarded as one hazardous waste due its Cu, Zn and Ni leaching pollution, and there were hardly any effective treatments on the TS sludge. The feasibility of utilizing TS sludge to prepare raw meal was discussed by a series of experiments. The results revealed that 1.0% addition of the TS sludge effectively improved the burnability of the calcined clinker, and forwarded the formation of alite with more amounts and smaller size, while 5.0% addition of the TS sludge led to more formation of interstitial phases, and further hindered the formation of alite and belite. The optimal workability of produced cement at different calcination temperatures was acquired as the addition reached 1.0%, and the highest unconfined compressive strength of produced mortars was attained as 49.37 MPa (28 days) when 1.0% addition of the TS sludge was incorporated at 1450 °C. Fluorine in TS sludge mainly distributed in the silicate phases, and mostly accumulated on the boundary of alite and belite phases. The preferential distribution of titanium was detected in the interstitial phases, but the distribution of Cu, Ni and Zn was stochastic. This had a positive effect on the prevention of corrosion of steel, by free fluorine ions, when used in reinforced concrete, and it provides a feasible direction for the comprehensive utilization of titanium-containing pickling sludge with limited proportions in cement raw materials. The immobilization ratios of F, Cu, Zn and Ni were higher than 99.50%, and the hazardous elements leaching under different leaching environments incorporating 5.0% addition of the TS sludge would not provoke the second leaching pollution.