Relationship between random reflectance of ulminite B/collotelinite and technological parameters of Polish low-rank coal Barbara Bielowicz ⇑ AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, al. Mickiewicza 30, 30-054 Cracow, Poland highlights  Correlation between Rr and GCV and Rr and C daf is very high.  It is possible to determine Rr of ulminite B from M t af , GCV maf , and C daf .  The suborder of Polish lignite can be determined with use of Rr.  The boundary between lignite C and lignite B should be set at Rr equal to 0.35%. article info Article history: Received 27 October 2012 Received in revised form 26 March 2013 Accepted 16 April 2013 Available online 9 May 2013 Keywords: Low-rank coal Classification of coal Random reflectance of ulminite B/ collotelinite abstract The main objective of the study is to determine the correlation between random reflectance of ulminite B/collotelinite and chemical and technological parameters in Polish low-rank coals. The study includes results from 284 samples of humic low-rank coal from Polish deposits tested by the author and supple- mented with data from the literature. Research on the properties of different types of coal include: tech- nical analysis, physico-chemical and petrographic analysis. Among the studied deposits, the average random reflectance (Rr) is 0.28, with a standard deviation of 0.06 and the coefficient of variation at 20%. Gross calorific value in the tested coal varies from 7.25 MJ/kg to 26.30 MJ/kg, with average value of 12.46 MJ/kg. Average total moisture in Polish low-rank coal deposits is 47.8% and ranges from 15% up to 60%. Carbon content in the tested coal recalculated to dry ash-free basis varies from 56.4% to 79.0% while on average it is 68.1%. Basic parameters of Polish low-rank coal are characterized by low var- iability, while gross calorific value and carbon content are of very low variability. The highest variability is observed in case of ash content and sulphur content. The correlation between random reflectance, gross calorific value and carbon content is very high. There is high correlation between moisture, net calorific value and random reflectance. The analysis shows that it is possible to calculate random reflectance of ulminite B/collotelinite from gross calorific value, carbon content and total moisture with a correlation coefficient equal to 0.97. By analyzing the correlation between the measures of the degree of coalification and using multiple regression, it has been found that the suborder of Polish lignite can be determined with use of the random reflectance of ulminite B/collotelinite. Based on the results of multiple regression, it is proposed that the boundary between low-rank C (soft brown coal) and low-rank B (dull brown coal) for Polish low-rank coal should be set at a random reflectance of ulminite B equal to 0.35%. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Random reflectance of huminite or vitrinite is one of the param- eters used to determine the degree of coalification. Coalification is the alteration of vegetation to peat and then to lignite, subbitumi- nous coal, bituminous coal and anthracite [1]. The degree of coali- fication determines the rank of coal. To understand the rank of coal, physical and chemical parameters were given [1–5] (Table 1). Increasing coalification is accompanied by decreasing moisture and hydrogen content, while carbon content and calorific value are increasing. The change in vitrinite reflectance – along with the increase of coalification – is linked to the increase in aromati- zation [1,3,6]. Currently, there is no single classification parameter for low-rank coal and in order to assess the degree of coalification, the following parameters are being used: huminite/vitrinite ran- dom reflectance, bed moisture and the gross calorific value calcu- lated on a moist, ash-free basis. According to Standard ISO 11760/2005 [7], the boundary be- tween low- and medium-rank coal is set at vitrinite reflectance equal to 0.50%. The low-rank category is divided into three subcat- egories: low-rank C (lignite C, soft brown coal), low-rank B (lignite B, dull brown coal) and low-rank A (Sub-bituminous coal). The 0016-2361/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fuel.2013.04.034 ⇑ Tel.: +48 88 556 51 82; fax: +48 12 633 29 36. E-mail address: bielowicz_barbara@o2.pl Fuel 111 (2013) 229–238 Contents lists available at SciVerse ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel