The Use of Non-Conventional Sensors to Monitor and Evaluate the Quality of Coal During the Cleaning Process

Coal is one of the most important sources for energy generation. In order to reach buyer or legislation requirements, and prevent environmental pollution, coal must be washed by processes such as froth flotation to remove mineral matter and to increase the coal quality. Different techniques such as X-ray diffraction and artificial vision are employed to monitor coal flows during the washing process; nevertheless, these techniques require high-cost equipment and qualified personnel to perform the analysis; also, data interpretation is a time-consuming task. The use of non-conventional sensors, such as a solid–liquid electrical conductivity sensor, to forecast the quality of coal offers an easy to employ method to monitor the process in real time, take corrective actions and improve the resulting coal grade, reduce the loss of valuable material and reduce pollution, increasing the sustainability of the process. For this research, coal samples from Región Carbonífera in Coahuila, Mexico were analyzed to obtain their intrinsic characteristics and their electrical conductivity. It was found that the electrical conductivity value is directly proportional to the calorific value and inversely proportional to the ash content. A conductivity value increase from 25 to 30 µS/cm was obtained when using a surfactant modified coal pulp.