Characterisation of coal and its combustion ash: recognition of environmental impact and remediation

Abstract

Energy generation from coal poses an environmental drawback due to the abundance of some potential hazardous elements (PHEs). A few PHEs (As, Sb, Cu, Mn and Zn) are noticed in the coal collected from thermal power plants of India. Among them, As and Sb are depleted while Cu, Mn and Zn are enriched in fly and bottom ash. The short- and long-term exposure of these PHEs into the ecosystem by emission, deposition and leaching causes environmental contamination as well as pollution and health hazards. The water-leaching experiment shows that these elements have feeble mobilisation tendency and low risk. The bioavailability test reflects that bio-uptake of these PHEs into the human system may be the origin of several diseases. Proper storage and recycling of the large amount of fly and bottom ash are a serious concern of thermal power plants. Chemical characterisation of ash, including elemental mapping by scanning electron microscope, calculated enrichment ratio (ER) and relative enrichment index (REI) values, as well as lab-scale water-leaching experiments predict that combustion residues of the studied power generating unit are safe for utilisation in construction, geotechnical and even in agricultural sectors. Chemical characterisation and pre-treatment of ashes before utilisation are urgently required to prevent any possible contamination. Regular scrutiny of emission control device, proper management of ash disposal and frequent utilisation are the keys for clean energy generation. A deep chemical and physical analysis of coal from power plants prior to utilisation is the primary task for sustainable energy generation from environmental aspect.

Keywords: Ash utilisation; Coal combustion; Environmental consequence; Potential hazardous elements.