Preparation Of Lightweight Porous Thermal Insulation Material From Coal Fly Ash

In the past 20 years,with the rapid development of China’s economy,the building area of China has increased sharply,which has brought a huge negative impact on the resources and environment.Using thermal insulation material on the exterior wall of the building can effectively reduce the heat exchange between the inside and outside of the building and reduce energy consumption.At present,the general use of organic insulation materials on the market,but it is flammable,easy to cause fire risk.In recent years,inorganic thermal insulation materials have been widely studied for their safety and reliability.In China,the accumulation of coal fly ash occupies a large amount of land,causing a variety of negative effects on the atmosphere,water system,agriculture and other aspects,and has great harm to the environment and society.In view of the problems of high density and poor heat insulation performance of inorganic thermal insulation materials,this paper considers that the foaming agent method is suitable for preparing porous materials with inorganic materials as raw materials,small density,uniform porosity and good heat insulation effect.The lightweight porous insulation material with high porosity was fired by adding Si C foaming agent,Na₂CO₃ and Mg O flux at high temperature.In the preliminary experiment,the reaction conditions were determined by thermogravimetric analysis and ash melting point analysis,and the experimental conditions were optimized by means of electron microscope analysis,density determination,compressive strength analysis,thermal conductivity analysis,etc.,and the influence of foaming agent addition amount and firing conditions on the performance of the sample was investigated.The results show that when the amount of Si C is 0.8 wt.%,the amount of Na₂CO₃ and Mg O is 6.0 wt.%,the firing temperature is 1200°C,and the holding time is 10 min,the apparent density of the sample is only 0.30 g/cm³,and the thermal conductivity is as low as 0.16 W/（m·K）.The compressive strength is 0.67 MPa,and the size and distribution of pores in the interior are very uniform,which can be used as the insulation material of the external walls of buildings.Steel slag contains abundant Fe₂O₃,which can decompose to produce oxygen at high temperature.In order to further improve the performance of porous materials fired with Si C as foaming agent and provide sufficient oxygen environment in the foaming process,this experiment investigated the effect of adding gravity slag and gravity ash on the firing of porous materials.The experimental results show that the addition of two kinds of steel slag does not significantly affect the porosity of the sample,because the foaming ability of Fe₂O₃ is relatively general,which can not be compared with the foaming ability of Si C.The addition of gravity slag improves the uniformity of air bubbles in the firing materials,but compared with the gravity slag,the porosity uniformity of the fired samples after adding gravity slag does not improve,which is speculated to contain more Ca O and Mg O in the steel making gravity slag.According to the analysis of heavy metal leaching experiment,the safety of porous thermal insulation material can be guaranteed whether steel slag is added or not.This study provides experimental data support for the preparation of lightweight porous inorganic thermal insulation materials,and provides a new way for the utilization of high-value coal fly ash resources.This study provides experimental data support for the preparation of lightweight porous inorganic thermal insulation materials,and provides a new way for the utilization of high-value fly ash resources.