Reducing energy losses in industrial processes with high-efficiency thermal insulation of microporous castable calcium silicate produced from elements of biomass: eggshells and rice husk ash

Abstract

This research project aims to find a common and integrated solution to two problems of great impact in Brazil. The first is to find a sustainable destination for the millions of tons of rice husks and eggshells from chickens generated in the industrial production of these foods. As they are biological materials of low degradability, these barks cannot simply be used as fertilizer in plantations or fully absorbed by the production chains. Currently, a significant proportion of such materials are disposed of in landfills or outdoor piles. The second problem is the loss of thermal energy that occurs in all industrial processes that have high-temperature operations (200-1200ºC) due to the lack of appropriate thermal insulators. The compound known as hydrated calcium silicate (CaSiO3.3H2O) is a synthetic material widely used in this application because it is highly porous, chemically inert, and less toxic than ceramic fiber blankets. Currently, it is produced from the hydrothermal reaction between sources of calcium oxide (CaO) and silica (SiO2) using mineral raw materials such as calcined limestone rocks and quartz sand, respectively. Considering that chicken eggshells are mainly formed by calcium carbonate (CaCO3) and rice shells contain high levels of silica, it is reasonable to assume that these wastes can be combined to produce thermal insulators based on full-biomass-formed hydrated calcium silicate. In addition to providing an adequate destination for biological waste, this new material would strongly contribute to minimizing the carbon footprint of other industrial processes by reducing thermal losses and fuel consumption. Other residential and building applications for this material, which involve passive protection of doors, electrical cables, and beams against fire and thermo-acoustic insulation of roofs and floors, indicate a great potential for immediate consumption in civil and automotive construction. (AU)