Paste Backfilling Used for Coal Fire Control in Thailand

Abstract

The environmental effects of spontaneous combustion coal seam fires in Mae Moh Lignite Mine in Thailand are subject to a wide array to land surfaces disturbance and air pollution. Air pollution in coal fire is mainly due to the fugitive emission of particulate matter and gases including sulphur dioxide (SO2) and oxides of nitrogen (NOx). The traditional methods, executed by fire fighting teams by covering the coal fire areas with soil, excavated burning coal outcrops and injecting water in the coal seam fires are continuously improved. Initiatives to introduce modern techniques, such as backfill placement at fracture and coal seam to cool down the burning coal and cut off air supply. This study is being conducted to investigate the properties of cement and cement kiln dust as backfill materials. As part of this investigation, mixture of materials were prepared by combining cement and cement kiln dust in various ratios of 0.35, 0.4, 0.45, 0.5, 0.55 and 0.6, to determine their optimal mix proportions for compressive strength development and permeability. The compressive strength of the mixtures of cement and cement kiln dust specimens continued to increase with increasing curing time. It was found the maximum compressive strength of the mixture of 20 % cement and 80 % cement kiln dust was 6.74 MPa mixing a water to solid ratio 0.46. The permeability of mixtures were decreases when cement kiln dust increases.