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

Abstract

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 × 10²⁰, 3.65 × 10²⁰, 7.11 × 10²¹ and 1.55 × 10¹³ 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, the chemical reaction mechanism of the R3 phase boundary was noted and the mechanism function was G(α) = 1 - (1-α)^1/3; however, 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.

Keywords: Barium slag; Electrolytic manganese residue; Isoconversional method; Thermal property; Thermogravimetric analysis.