To blend is a good solution to improve the heat insulation applicability of diatomite ores

Abstract

Background: The idea of mixing different grades of diatomite ores with certain ratios to obtain blends with tailored minerals constitution that can help on improving their thermal insulation applicability is introduced in this study. In this respect, three diatomite samples were collected for investigation from El-Masakheet, Kasr El-Sagha, and Demia deposits, El-Fayoum, Egypt. Complete chemical and phase analyses of these samples were carried out. The analyses showed that El-Masakheet sample was of low-grade diatomite with excess calcite content. In addition, Kasr El-Sagha and Demia samples were of high-grade diatomite with minor calcite contents. By firing the dried Kasr El Sagha and Demia yellow samples specimens at different temperatures for 1 h, they showed complete destruction at 900°C. Different amounts of El-Masakheet sample was blended with Kasr El-Sagha and Demia yellow samples. The specimens were subjected to firing at different temperatures for 1 h. The physical properties of the fired mixed specimens were followed up. Results: Results showed that by blending El-Masakheet sample with 50% mass ratio with Kasr El-Sagha or Demia yellow samples, a pronounced increase in the thermal applicability of the fired blends from 900 to 1100°C was achieved. In addition, a notable increase in their open porosity was recorded. This improvement was attributed to the change in the minerals constitution ratios in the blends due to the increase in their calcite contents after El Masakheet addition, especially the Ca/Si and Ca/(Al + Si) atom ratios. This change served in forming high melting points minerals like αwollastonite and akermanite on firing the blends specimens instead of low melting point minerals like cristobalite and alkali aluminosilicate which were formed on firing the high-grade ores alone. Consequently, an increasing in the porosity and the thermal applicability of the new specimens from 900 to 1100°C was achieved. Conclusions: The idea of mixing different grades of diatomite ores with certain ratios to obtain blends with tailored minerals constitution can help on improving their thermal insulation applicability and their open porosity. Besides, this concept gave a good solution to get use of the unexploited low-grade diatomite ores, especially of high calcite content.