Krzysztof Stańczyk

Transformation of nitrogen structures in carbonization of model compounds determined by XPS

Abstract Nitrogen-containing chars were prepared by low-temperature carbonization (460 °C) of compounds containing pyrrolic, pyridinic, amino and cyano groups. The changes of precursor functionalities and transformation of nitrogen structures at 600 and 800 °C were determined by X-ray photoelectron spectroscopy. From all precursors, at low-temperature carbonization, three types of nitrogen structure were obtained: pyrrolic, pyridinic and quaternary, but from a precursor containing cyano groups this group was also observed. The concentration of pyrrolic and pyridinic structures decreases with increasing calcination temperature, whereas the amount of quaternary nitrogen increases. Quaternary nitrogen is the most stable form of the observed nitrogen structures, but an additional peak appeared at 403 eV for chars calcined at 800 °C.

Inhibiting effect of incorporated nitrogen on the oxidation of microcrystalline carbons

Abstract Nitrogen-containing carbons were prepared by carbonization of sucrose with additions of urea, glucosamine hydrochloride, uracil, hydroxymethyl pyridine, or picolylamine. The development of their nitrogen content during charring, carbonization at 1100°C, and subsequent activation with CO2 at 850°C was followed by chemical analysis as a function of the quantity of nitrogen additive. The time needed to reach a constant burn-off during activation with CO2 was considerably longer than with a nitrogen-free sucrose carbon. A similar inhibition of oxidation was also observed in the oxidation with 5% O2-95% Ar. Kinetic data were obtained from thermogravimetric experiments. The nitrogen contained in the carbons was liberated during combustion largely as NOx.

Elimination of nitrogen from coal in pyrolysis and hydropyrolysis: a study of coal and model chars

Abstract To determine the changes in coal nitrogen structures during pyrolysis and hydropyrolysis, model chars from defined nitrogen compounds were prepared and subjected to further heating under pyrolysis and hydropyrolysis conditions. Elimination of nitrogen from such model chars as well as from coal chars was investigated by pyrolysis-mass spectrometry.

Chemometric Study of the Ex Situ Underground Coal Gasification Wastewater Experimental Data.

The main goal of the study was the analysis of the parameters of wastewater generated during the ex situ underground coal gasification (UCG) experiments on lignite from Belchatow, and hard coal from Ziemowit and Bobrek coal mines, simulated in the ex situ reactor. The UCG wastewater may pose a potential threat to the groundwater since it contains high concentrations of inorganic (i.e., ammonia nitrogen, nitrites, chlorides, free and bound cyanides, sulfates and trace elements: As, B, Cr, Zn, Al, Cd, Co, Mn, Cu, Mo, Ni, Pb, Hg, Se, Ti, Fe) and organic (i.e., phenolics, benzene and their alkyl derivatives, and polycyclic aromatic hydrocarbons) contaminants. The principal component analysis and hierarchical clustering analysis enabled to effectively explore the similarities and dissimilarities between the samples generated in lignite and hard coal oxygen gasification process in terms of the amounts and concentrations of particular components. The total amount of wastewater produced in lignite gasification process was higher than the amount generated in hard coal gasification experiments. The lignite gasification wastewater was also characterized by the highest contents of acenaphthene, phenanthrene, anthracene, fluoranthene, and pyrene, whereas hard coal gasification wastewater was characterized by relatively higher concentrations of nitrites, As, Cr, Cu, benzene, toluene, xylene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene.

HDN of 1–4 tetrahydroquinoline over MoNxOy and NbNxOy: effect of transition metal, solvent and ammonia

Oxynitrides of early transition metals are bifunctional catalysts active in hydrodenitrogenation (HDN). The strength of the hydrogenating function and the acidic properties of molybdenum and niobium oxynitrides were investigated, as well as the inhibiting effect of ammonia and the effect of solvent (cyclohexane or tetradecane) on HDN of 1,2,3,4‐tetrahydroquinoline (1–4 THQ). Even under high hydrogen pressure (4.5 MPa) the reaction was found to be able to proceed without hydrogenation of the aromatic cycle of 1–4 THQ before C–N bond scission, which is not the case over sulfided NiMo supported catalysts in HDN. Experiments in presence of ammonia permitted to support a bifunctional dual site concept.

Chemical and toxicological evaluation of underground coal gasification (UCG) effluents. The coal rank effect.

The effect of coal rank on the composition and toxicity of water effluents resulting from two underground coal gasification experiments with distinct coal samples (lignite and hard coal) was investigated. A broad range of organic and inorganic parameters was determined in the sampled condensates. The physicochemical tests were supplemented by toxicity bioassays based on the luminescent bacteria Vibrio fischeri as the test organism. The principal component analysis and Pearson correlation analysis were adopted to assist in the interpretation of the raw experimental data, and the multiple regression statistical method was subsequently employed to enable predictions of the toxicity based on the values of the selected parameters. Significant differences in the qualitative and quantitative description of the contamination profiles were identified for both types of coal under study. Independent of the coal rank, the most characteristic organic components of the studied condensates were phenols, naphthalene and benzene. In the inorganic array, ammonia, sulphates and selected heavy metals and metalloids were identified as the dominant constituents. Except for benzene with its alkyl homologues (BTEX), selected polycyclic aromatic hydrocarbons (PAHs), zinc and selenium, the values of the remaining parameters were considerably greater for the hard coal condensates. The studies revealed that all of the tested UCG condensates were extremely toxic to V. fischeri; however, the average toxicity level for the hard coal condensates was approximately 56% higher than that obtained for the lignite. The statistical analysis provided results supporting that the toxicity of the condensates was most positively correlated with the concentrations of free ammonia, phenols and certain heavy metals.

Imaging the Underground Coal Gasification Zone with Microgravity Surveys

The paper describes results of microgravity measurements made on the surface over an underground geo reactor where experimental coal gasification was performed in a shallow seam of coal. The aim of the research was to determine whether, and to what extent, the microgravity method can be used to detect and image a coal gasification zone, especially caverns where the coal was burnt out. In theory, the effects of coal gasification process create caverns and cracks, e.g., zones of altered bulk density. Before the measurements, theoretical density models of completely and partially gasified coal were analysed. Results of the calculations of gravity field response showed that in both cases on the surface over the gasification zone there should be local gravimetric anomalies. Over the geo reactor, two series of gravimetric measurements prior to and after gasification were conducted. Comparison of the results of two measurement series revealed the presence of gravimetric anomalies that could be related to the cavern formation process. Data from these measurements were used to verify theoretical models. After the experiment, a small cavern was detected at the depth of the coal seam by the test borehole drilled in one of the anomalous areas.

Influence of hydropyrolysis parameters on char yield, properties and combustion reactivity

Abstract The effects of temperature and hydrogen pressure on the yield, properties and reactivity of chars from fixed-bed hydropyrolysis of a subbituminous coal and a lignite were determined. The chars were compared with those obtained by pure pyrolysis. With increasing temperature and pressure, both the yield and the reactivity of the char decreased. Hydropyrolysis char was more reactive than pyrolysis char.

Sensing underground coal gasification by ground penetrating radar

The paper describes the results of research on the applicability of the ground penetrating radar (GPR) method for remote sensing and monitoring of the underground coal gasification (UCG) processes. The gasification of coal in a bed entails various technological problems and poses risks to the environment. Therefore, in parallel with research on coal gasification technologies, it is necessary to develop techniques for remote sensing of the process environment. One such technique may be the radar method, which allows imaging of regions of mass loss (voids, fissures) in coal during and after carrying out a gasification process in the bed. The paper describes two research experiments. The first one was carried out on a large-scale model constructed on the surface. It simulated a coal seam in natural geological conditions. A second experiment was performed in a shallow coal deposit maintained in a disused mine and kept accessible for research purposes. Tests performed in the laboratory and in situ conditions showed that the method provides valuable data for assessing and monitoring gasification surfaces in the UCG processes. The advantage of the GPR method is its high resolution and the possibility of determining the spatial shape of various zones and forms created in the coal by the gasification process.

XPS evidences for changes in the nitrogen forms in result of hydropyrolysis of model chars

Publisher Summary This chapter presents work to establish the influence of the reducing hydrogen atmosphere on the state of nitrogen forms in the course of hydropyrolysis. Determination of the nitrogen forms in coals increased the significance resulting from many attempts to find relationships between given nitrogen functionalities and NOx emission during coal combustion. Nondestructive techniques determine the forms of nitrogen in coals and chars and show that most of the nitrogen in coal is present in a form of ring compounds as pyrrolic, pyridinic, and quaternary structures. Carbonization of the nitrogen compounds is carried out in a fixed-bed reactor in the argon or hydrogen flow. The chapter discusses the chars pyrolized under argon, and the amount of quaternary nitrogen increases with the increase of pyrolysis temperature. With the increase of pyrolysis temperature, the amount of pyridinic and pyrrolic forms decreases.