Kinetic and thermodynamic analysis on preparation of belite-calcium sulphoaluminate cement using electrolytic manganese residue and barium slag by TGA

Electrolytic manganese residue (EMR) is a solid filter residue obtained from manganese carbonate ore during the production of metal manganese. A potential avenue towards large-scale utilisation of EMR is its use in cement preparation. However, the preparation of cement materials using EMR requires high-temperature calcination. In this study, the thermal properties and pyrolysis kinetics of belite–calcium sulfoaluminate cement raw meal were systematically studied using a multiple-heating-rate method based on thermogravimetric analysis and a kinetic model. The kinetic and thermodynamic parameters was studied using non-isothermal Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Friedman and Kissinger methods. The results showed that from 30 to 1300°C, the pyrolysis reaction of cement raw meal was mainly divided into four steps: the crystalline water removal from calcium sulphate dihydrate and bauxite, the ammonia nitrogen removal from ammonium salts and the calcium sulphate crystal transformation; the decomposition of calcium carbonate and carbon-containing organic matter; the sulphate and carbonate substance decomposition and the clinker mineral phase formation. The average activation energies calculated when using the non-isothermal FWO, KAS, Friedman and Kissinger methods were 244.49, 240.7, 239.24 and 380.60 kJ/mol and the average pre-exponential factors were 1.75 × 10 20 , 3.65 × 10 20 , 7.11 × 10 21 and 1.55 × 10 13 s −1 , respectively. Herein, the pyrolysis kinetics of the cement raw meal was divided into two main stages: In stage 1 ( α : 0.15–0.8, 524°C–754°C), the mechanism of P2/3 accelerated nucleation in the Mampel Power rule, and the reaction mechanism function was G( α )= α 3/2 . In stage 2 ( α : 0.80–0.95, 754°C–1165°C), during the local conversion of α = 0.2–0.8, when α was 0.5, a random nucleation and subsequent growth mechanism of A6 was noted and the mechanism function was G( α ) = [−ln(1 − α )] 2/3 .