Improved slagging characteristics of low-value solid waste fuel asphalt rock by mineral additives of CaCO3, MgO, and Kaolin under fluidized bed condition

Abstract

As a low-value solid waste fuel, asphalt rock is prone to slagging even under fluidized bed condition. The purpose of this study is to improve the slagging characteristics of asphalt rock by adding the mineral additives CaCO₃, MgO, and Kaolin. The results showed that the K, Al, Ca salts in asphalt rock ash will evolve at different temperatures and exist mainly as K₂SO₄, KAlSiO₄, Al₂O₃·SiO₂, Al₂O₃, CaSO₄, and CaSiO₃. The CaSO₄ formed from sulfur oxides and calcium-containing compounds is the main factor in asphalt rock slagging and can be facilitated by CaSiO₃ with a small amount of CaCO₃. The MgO can form MgCa(SiO₃)₂ with a high melting point and helps raise the ash fusion temperatures. In addition, the Kaolin will promote the formation of low-temperature eutectics, resulting in a slight decrease in ash fusion temperatures. Through optimization, it was found that with the addition of 9.0% MgO+9.0% Kaolin+2.0% CaCO₃ (in weight), the slagging ratio and pressure difference of asphalt rock under fluidized bed conditions decreased from 6.5% to 4.2% and from 6.0 Pa to 4.0 Pa, respectively. By combining simulation and experimental methods, it has been shown that appropriate mineral additives of CaCO₃, MgO, and Kaolin can effectively improve the slagging characteristics of asphalt rock.

Graphical abstract