Abstract
Cement kiln dust (CKD) is a major by-product of cement manufacturing and has the potential to be recycled as a raw material if the high concentrations of chlorine and potassium are removed. This study tested four leaching solutions (distilled water and three organic acids) and determined the optimum reaction conditions. At a liquid/solid (L/S ratio) of 10, the removal efficiency of formic, citric, and oxalic acid was higher than that of distilled water, but at L/S 20, distilled water also achieved a high removal efficiency of Cl (≥90%) and K (≥70%). In addition, to minimize the discharge of wastewater after leaching, the efficiency of ion-exchange resins for the recovery of leaching solution was tested. When the cation- and anion-exchange resins were arranged together, more than 95% of both Cl and K contained in the leaching solution could be removed. Leaching solution without Cl and K was found to have a high leaching efficiency even after being recycled three times, resulting in a significant reduction in wastewater emissions.
Highlights
Cement kiln dust (CKD) is a by-product of the cement manufacturing process and has traditionally been considered as an industrial waste product
The removal efficiencies were highest for formic acid, followed by oxalic acid, citric acid, and distilled water (DW); the reaction time
This study assessed the use of different leaching solutions for removing chloride and potassium
Summary
Cement kiln dust (CKD) is a by-product of the cement manufacturing process and has traditionally been considered as an industrial waste product. Global cement production capacity in 2017 was. ~4.99 billion tons per year [1,2], while the CKD production rate ranged from 54 to 200 kg per ton of produced cement clinker [3]. CKD is composed of fine, powdery solids and highly alkaline particulate material, and is similar in appearance to Portland cement. Its size distribution and chemical composition depends on production factors such as raw material, processing method, fuel, kiln type, cement type, and dust collection method (e.g., cyclones, bag filters, or electrostatic precipitators). Finer particles tend to exhibit a higher sulfate and alkali content.
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