Characterization and washability of Pakistani bituminous coal from Punjab

Abstract

ABSTRACT Pre-combustion cleaning techniques are used to remove unwanted impurities and environmentally harmful constituents in coal. In this study, gross samples collected from seven zones of Punjab coalfield were separately subjected to sizing into coarse (+25 mm), intermediate (–25 + 1.168 mm), fine (–1.168 + 0.147 mm), and ultrafine (–0.147 mm) fractions. Proximate and ultimate components, forms of sulfur and gross calorific value of all size fractions and the composite sample of each zone coal were determined. Float-sink tests were conducted on coarse, intermediate and fine fractions. The results show that Punjab coal contains moisture, ash, volatile matter, and fixed carbon in the range of 2.28–4.61%, 34.13–51.59%, 26.72–34.25%, and 18.17–28.92%, respectively, belonging to high volatile bituminous B and C categories. The large proportion of mass lies in the intermediate size range for Chambel (63.10%), Dandot (60.27%), Trans-Indus (54.83%), Dalwal (52.20%), and Ara-Basharat (47.22%) coals whereas coarse particles constitute the major proportion of Padhrar (47.92%) and Jhelum (45.83%) coals. At 16% target ash content, the overall clean coal yield achievable for Jhelum, Ara-Basharat, Dandot, Dalwal, Padhrar, Chambel, and Trans-Indus zone coals were found as 16.32%, 20.76%, 37.20%, 48.59%, 46.29%, 70.43%, and 67.40% with sulfur contents of 2.89%, 2.80%, 2.90%, 3.57%, 4.28%, 3.89%, and 4.21%, respectively. The extent of coal cleaning was found higher for the Central Salt Range (Padhrar and Chambel zone) and Western Punjab (Trans-Indus zone) coals than the Eastern Salt Range (Jhelum, Ara-Basharat, Dandot and Dalwal zone) coals based on their degrees of washing and S-values. Padhrar coal exhibits the best washing characteristics as revealed by its highest S-value of 78.5.