Recycling of waste coal dust for the energy-efficient fabrication of bricks: a laboratory to industrial-scale study

In this study, an optimal mixture of loess brick clays and waste coal dust in laboratory hollow blocks production is determined with the aim of promoting sustainable development in terms of saving resources and energy. The novelty of the work lies in the first-time utilization of waste coal dust in combination with loess soil brick-making thus bolstering European effort on waste utilization. The mentioned is also in line with UN sustainable development goals, SDG 12 and 9. The chemical and mineralogical contents of the clays were obtained using various chemical characterization methods, and thermal behavior by using dilatometry and simultaneous DSC/TG analysis. The important ceramic and technological characteristics of the extruded brick clay and waste coal dust composite samples during molding, drying, and firing were obtained. The chosen mixture of 70 % calcareous clay and 30 % plastic clay to 3 % of high-calorie waste coal dust is found optimal. Industrial-scale optimal blocks (250x190x190 mm3) with 60 % of vertical voids were fired in a tunnel kiln, and the firing regime was recorded. It is determined that the regime must be corrected in the firing and cooling zone since the differences measured by thermo-couples were up to 180 °C. The industrial prototype was found to be of satisfactory quality meeting the requirements of water absorption and compressive strength as per European and other international standards. The study was first of a kind detailed characterization of the industrial size bricks encompassing waste coal dust and loess brick clays, with the emphasis on the usability in the industry, and additionally recording and correcting of the firing regime in a tunnel kiln. The product is recyclable and can be disposed of safely after the end of life.