Enhancing Burnability Characteristics of Low-Temperature Burnt-Cement Clinker by Recycling Phosphogypsum Wastes

Abstract

In the present study, the effect of phosphogypsum, a byproduct from the phosphoric acid production industry, on the clinkerization process was researched in order to improve the burnability of clinkers at lower burning temperatures. Raw meal samples containing phosphogypsum at 0%, 1%, 3%, and 5% by weight were burned at 1,350°C, 1,400°C, 1,450°C, and 1,500°C. The introduction of phosphogypsum reduced the presence of unbounded (free) CaO relatively up to 43%. Thus, the mineralization effect of phosphogypsum promotes lower burning temperatures. The free CaO content of the 5% phosphogypsum containing clinker decreased to 0.94% at 1,400°C after 120 min of burning time. The free CaO content was found to be almost identical (0.75%) to that of industrial clinker burned in a rotary kiln at 1,500°C. Due to the low free CaO content (<1%) and the burnability index (73), the recycling of phosphogypsum wastes was found to be suitable for the production of eco-efficient clinkers. The reduced energy consumption and energy-related CO2 emissions in such modified clinkers can contribute to the economic and ecological goals of the cement industry.