Development of porous refractory materials for rotary cement kilns

Nowadays, researchers of cement industry, as other researchers, has been focused on energy efficiency related subjects. The first step of energy efficiency is to prevent heat losses in production process. Refractory porous structures are preferred as thermal insulation materials due to their heat conduction mechanisms. Mechanical properties, especially strength values, decrease significantly in highly porous materials. Regarding many studies, the increase in porosity will increase the insulation performance and decrease mechanical properties (strength, impact resistance, fracture toughness). The size and distribution of pores are crucial parameters concerning mechanical properties. Evidence suggests that small pores have negligible effect on fracture strength where larger and connected pores can greatly affect mechanical properties and fracture strength in particular. In this study, the effects of different additives were investigated to find the ideal additive(s) that could reduce the negative impact of the increased porosity of the magnesium-spinel refractory on mechanical properties. For this purpose, MgOH, Electrode fracture, Activated carbon, Polyvinyl alcohol, Coke, Calcined magnesite, and SiC were chosen for further investigation. Aiming to increase the amount of porosity (in order to reduce the density), it is intended to fabricate a refractory with minimum fracture strength of 45,8 N/mm2 to use in the process. Finally, by meeting these two criteria, other expected technical properties such as water absorption, density and thermal conductivity were considered to optimize the properties of the fabricated refractory.