Helena Machnikowska

Microbial degradation of low rank coals

Abstract The strain of Pseudomonas putida was tested in terms of the degradation ability of organic matter of lignites and subbituminous coals. The conversion degree to water soluble products and structural characteristics of bioextracts and bioresidues by elemental analysis and infrared spectroscopy were assessed. Oxidizing pretreatment with nitric acid essentially enhanced the biodegradability resulting in ∼90% solubilization of lignites and ∼40% of subbituminous coals. The bioextracts precipitated from supernatants were solids of high contribution 40–70% of oxygen functionalities and increased nitrogen content. The extent of bioresidue organic matter alteration increased with conversion depth. The enhanced hydrogen content was most characteristic feature of the residues.

The characterization of coal macerals by diffuse reflectance infrared spectroscopy

Abstract Diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy was applied to study the structure of vitrinites, liptinites and fusinites isolated from different rank coals (77.0–91.5%C) using a centrifugal float–sink procedure. Among the macerals separated from a given coal, liptinites are characterized by the highest proportion of aliphatic CH groups, occurring principally as CH 2 , and fusinites by the most aromatic structure. Macerals separated from the low rank coals show comparable content of hydroxyl groups that occur as free OH or form similar types of hydrogen bonds. Carbonyl groups appear not only as conjugated ketones and quinones in vitrinites, but also as carboxylic groups in liptinites and low rank fusinites. CH ar /CH al ratio does not vary with carbon content in liptinites, but increases in vitrinites and fusinites. In the case of liptinites and vitrinites, a linear relationship between CH ar /CH al and reflectance is observed up to vitrinite R 0 value of 1.80%. For all macerals, the ratio CH ar /CC increases with reflectance, but at different rates. Structural parameters CH ar /CH al and CH ar /CC calculated from DRIFT spectra are very helpful in monitoring the differences among macerals of given coal and following structural rearrangement occurring with rank.

Rank dependence of organic sulfur functionalities in coal

Organic sulfur functionalities were characterized and quantified by atmospheric-pressure temperature-programmed reduction (AP-TPR). Nine coals were chosen to cover the entire rank range from subbituminous coal to anthracite. To be able to study the organic sulfur groups, the vitrinite concentrates were separated from each coal sample. The results confirm the larger amount of sulfide in low-rank coals. The amount of thiophenes generally increases with rank. Nevertheless, sulfur functionality distribution can vary from coal to coal even at the same rank.

Modification of coking behaviour of coal blends by plasticizing additives

Abstract Commercial coal-tar pitch (CTP) and pitch-like residue (RP)—a waste by-product of coking plants—were used as an additive to two coal blends in metallurgical coke production. The additives were characterized in terms of chemical composition, solvent analysis, 1 H NMR spectroscopy, extrographic fractionation, hydrogen transfer properties, thermogravimetric analysis and plastic properties. Both the thermal behaviour and hydrogen transfer properties of the additives are crucial for the coal plastic phase modification during co-carbonization. CTP improves the coking properties of coal blend, i.e. coking and swelling abilities, dilation and fluidity, whereas RP leads only to a fluidity enhancement. This is reflected in different yields, anisotropic carbon, microstrength and reactivity to carbon dioxide of the cokes produced at two different laboratory scales. The beneficial effect of the additives on the metallurgical coke quality not only depends on the properties of the additives themselves, but also the coking properties of the coal blend to which the plasticizing agent was added is a critical factor.

Solvolysis of three Polish coal samples by treatment with N-methyl-2-pyrrolidinone and an NaOHCH3OH mixture☆

Abstract This study concerns the extractable materials obtained by solvolysis of three Polish coals. N-methyl-2-pyrrolidinone extraction and NaOH CH 3 OH treatment of these coals were compared using several analytical procedures (extrography, sonication, gas capillary column chromatography, and i.r. and 1H n.m.r. spectroscopy). Thermodesorption, on line with gas chromatography and mass spectrometry, was also applied to these coal samples.

Structural characterization of residues from supercritical gas extraction of brown coal

Abstract Residues from supercritical gas extraction of brown coal with toluene and butanol were studied by proximate and ultimate analyses, optical microscopy and X-ray diffractometry. The type of solvent appeared to have a decisive influence on the yield, properties and structure of the residues produced in the range 380–440 °C. The residues from extraction with toluene had a microstructure and structural ordering similar to those of the raw coal. Extraction with butanol gave caked and optically anisotropic residues with a relatively high degree of structural ordering.

Sulfur characterization of Polish coals, their lithotypes and macerals

Three coals of different rank (Ro = 0.58–1.01%), and the lithotypes and macerals separated from these coals, were analysed in this study. The wet chemical technique was used to determine the distribution of sulfate, pyritic and organic sulfur forms in the coals and lithotypes. The morphology, size and mode of occurrence of pyrite were examined by optical microscopy and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis. An oxidative technique was developed to study the organically bound sulfur in the maceral microsamples. Pyritic and organic sulfur accounted for nearly all the sulfur in the coals examined and their lithotypes. In comparison with the coals, the lithotypes had a higher proportion of very fine pyrite. Pyrite was most abundant in fusain. The organic sulfur content in the lithotypes decreased in the order: clarain > vitrain > durain > fusain. An analysis of the SO2 evolution profile from temperature programmed oxidation (TPO) of the maceral concentrates indicated that exinite showed the most distinct changes in the chemical structure of sulfur compounds with coal rank. Based on the TPO study a new parameter describing the reactivity of organic sulfur of macerals is proposed.