Evolution of heat during the synthesis of ­hydrosilicates in aerated concrete

The heat evolved during the synthesis of 11.3 Å tobermorite from lime and quartz is 125 kJ/kg and the synthesis of xonolite is 50 kJ/kg, which raises the pressure and temperature in the autoclave. Recommendations are given below for controlling the composition of the hydrate and for reducing the consumption of steam during the autoclaving.

1 Introduction

It is well known that heat is evolved during the reactions when calcium silicate hydrates are formed from calcium hydroxide and finely ground quartz in an autoclave. The exact values for the heat evolution of this process are very difficult to determine so at first the problem was approached theoretically. The results of these theoretical calculations are given by Babuschkin et al. [1]. The reaction for the formation of tobermorite from calcium hydroxide and quartz at a temperature of 179 °C has a reaction enthalpy of ΔHP = 30–31 kcal/mol. However, an enthalpy of ΔHP = 20–25 kcal...

Related articles:

Issue 2010-06

Thermophysical properties of limestone as a function of origin (Part 2): Calcination enthalpy and equilibrium temperature

1 Introduction For the energy evaluation of the calcination process in kilns two enthalpy values are required: the enthalpy at normal temperature and the enthalpy at decomposition temperature. The...


Influence of material properties on the decomposition time of limestone under shaft kiln conditions

1 Introduction The decomposition of limestone is an endothermic topochemical reaction: CaCO3    +           ?HR  =            CaO   +   CO2 (solid)     (reaction enthalpy) ...


Lime production experience 4.0

1 The calcination process The calcination of limestone is a chemical process of decomposition in which heat applied to carbonates decomposes them into oxides. Decomposition takes place at a...

Issue 2018-5 KR101832105 (B1)

Method for manufacturing milk of lime using waste heat recovery line

(22) 05.09.2017 (43) 26.02.2018 (57) The present invention relates to a waste heat recovery line capable of recovering waste heat generated in the production of liquid limestone oil and transferring...

Issue 2010-02

Thermophysical properties of limestone as a func­tion of origin (Part 1): Specific heat capacities

1 Introduction The calcination of limestone is a complex process, due to the variety of parameters which exert an influence on it. These parameters are related not only to the type of kiln and its...