Stefan Marinov

Sulfur functionalities and physical characteristics of the Maritza Iztok Basin lignite

Abstract The use of selective functional group modification procedures has been investigated for the determination sulfur forms in low-rank coals. A Bulgarian lignite from the Maritza Iztok Basin was submitted to a variety of chemical treatments. The fresh lignite and residues were studied by atmospheric pressure temperature-programmed reduction (AP-TPR) and sulfur K-edge X-ray absorption near-edge structure (XANES) analysis to investigate the distribution of sulfur forms. The impact on the physical characteristics of the lignite following each treatment was studied by thermal analysis (d.t.a.) and scanning electron microscopy (SEM-EDX). The results have demonstrated the ability of selective procedures to simplify sulfur functionality determination by AP-TPR and have provided a clear insight into the impact of treatments on the thermal characteristics of the lignite.

Modelling the structure of a coking coal

Abstract A high-vitrinite coking coal (87%C,daf) is subjected both to reductive butylation by treatment with potassium and butyl iodide in tetrahydrofuran and to non-reductive butylation by treatment with butyl lithium and butyl iodide. The yields of chloroform extracts (butylated coal basis) are 67.2 and 17.1% respectively. The extracts are separated by adsorption and gel-permeation chromatography into a few fractions in a way to be in “equimolar” ratios (considering the average molecular masses). A specific method for modelling the average structure of butylated coal products is used based on elemental and average molecular mass analysis and data derived from 1 H and 13 C NMR spectra. The constructed fraction models are corrected with respect to the introduced butyl groups and pieced together in an assembled model of the initial coal structure. The designed model visualizes some coking coal structural features.

Study of the sulphur functionalities and physical characteristics of a bulgarian lignite by desulphurization techniques

Abstract A complete knowledge and understanding of the thermal reactivety of sulphur forms in coal is crucial for the development of new, efficient desulphurisation techniques. This contribution reports on seven selective desulphurization treatments of a Bulgarian lignite. The impact of individual treatments on the sulphur distribution was monitored by AP-TPR and XANES techniques. Complementary data concerning the physical impact of the treatments was obtained by DTA and SEM-EDX.

Atmospheric Pressure Temperature Programmed Reduction (AP-TPR) as a tool to investigate the changes in sulphur functionalities in solid fuels

This research contribution reports the preliminary interpretation of the results of selective desulphurization procedures of a Bulgarian lignite, Maritza-Iztok. The AP-TPR profiles can be explained in view of the selective treatments used. In addition, the importance of heat recovery for the products obtained is discussed.