Jan Yperman

Sulphur group analysis in solid matrices by atmospheric pressure-temperature programmed reduction

The atmospheric pressure-temperature programmed reduction (AP-TPR) has become an established and reliable method amongst the different sulphur characterisation techniques for solid materials, like coal and coal derived products, rubber and clay. The analytical method is based upon the fact that specific sulphur functional groups are hydrogenated at specific temperatures. During the last few years, several adjustments have been made to the hard- and software as well as to the experimental parameters. The changes and the reliability of the method are extensively discussed in this paper.

Characterisation of adsorbents prepared by pyrolysis of sludge and sludge/disposal filter cake mix

Copper and zinc removal from water (pH = 5.0) using adsorbents produced from slow and fast pyrolysis of industrial sludge and industrial sludge mixed with a disposal filter cake (FC), post treated with HCl, is investigated in comparison with a commercial adsorbent F400. The results show that a pseudo-second order kinetics model is followed. The Langmuir-Freundlich isotherm model is found to fit the data best. The capacity for heavy metal removal of studied adsorbents is generally better than that of commercial F400. The dominant heavy metal removal mechanism is cation exchange. Higher heavy metal removal capacity is associated with fast pyrolysis adsorbents and sludge/FC derived adsorbents, due to enhanced cation exchange. Improvement of Zn(2+) removal via 1 N HCl post-treatment is only effective when exchangeable cations of the adsorbent are substituted with H(+) ions, which boost the cation exchange capacity. Increase of temperature also enhances metal removal capacity. Fast pyrolysis sludge-based adsorbents can be reused after several adsorption-desorption cycles.

AP-TPR study of sulphur in coals subjected to mild oxidation. Part 1. Demineralised coals

Abstract Five samples of coal characterised by different degree of coalification and different content of sulphur have been subjected to oxidation in the dry phase and in aqueous media in order to determine the effect of oxidation on the sulphur groups. The transformations were studied by the classical chemical methods and by atmospheric pressure–temperature programmed reduction. It has been shown that the greatest changes in sulphur groups occurs in the case of the oxidation with HNO3 and peroxyacetic acid, while the air oxidation and the oxidation in the O2/Na2CO3 system is much less effective. The oxidation leads to formation of sulphoxides, sulphones and sulphonic acids. The non-thiophene groups have been found much more susceptible to oxidation than the thiophene ones.

Low rank coals sulphur functionality study by AP-TPR/TPO coupled with MS and potentiometric detection and by XPS

Abstract Atmospheric pressure-temperature programmed reduction (AP-TPR) and X-ray photoelectron spectroscopy (XPS) techniques were applied to low rank coals sulphur study. Coal samples were pyrolysed in a flow of water vapor (WV). It was demonstrated that this treatment influenced mainly aliphatic sulphur. Samples were characterised by two methods and data were interpreted within the limits of the techniques. XPS measurements registered sulphur 2p spectra with two main signals for organic and inorganic sulphur compounds. The AP-TPR set-up, with potentiometric detection of the formed H2S as S2− using an ion selective Ag2S-electrode, gives quantitative data about the presence of different sulphur species. The AP-TPR equipment on-line coupled with a mass spectrometer (MS) gives extra qualitative information about different reductive and oxidative organic sulphur forms. Using MS not only H2S but also SO2, COS, CS2, and all other volatile sulphur and organic compounds can be monitored, giving more information for the initial presence of the different sulphur forms and to the mechanisms involved in the pyrolytic process. This AP-TPR-MS experiment is subsequently followed by AP-TPO-MS measurement (in an oxidated atmosphere) to study sulphur presence in the residue (tar and char) in the reactor. Comparing all these AP-TPR profiles results in a better assignment of the different signals to specific sulphur functionalities.

Economic assessment of flash co-pyrolysis of short rotation coppice and biopolymer waste streams.

The disposal problem associated with phytoextraction of farmland polluted with heavy metals by means of willow requires a biomass conversion technique which meets both ecological and economical needs. Combustion and gasification of willow require special and costly flue gas treatment to avoid re-emission of the metals in the atmosphere, whereas flash pyrolysis mainly results in the production of (almost) metal free bio-oil with a relatively high water content. Flash co-pyrolysis of biomass and waste of biopolymers synergistically improves the characteristics of the pyrolysis process: e.g. reduction of the water content of the bio-oil, more bio-oil and less char production and an increase of the HHV of the oil. This research paper investigates the economic consequences of the synergistic effects of flash co-pyrolysis of 1:1 w/w ratio blends of willow and different biopolymer waste streams via cost-benefit analysis and Monte Carlo simulations taking into account uncertainties. In all cases economic opportunities of flash co-pyrolysis of biomass with biopolymer waste are improved compared to flash pyrolysis of pure willow. Of all the biopolymers under investigation, polyhydroxybutyrate (PHB) is the most promising, followed by Eastar, Biopearls, potato starch, polylactic acid (PLA), corn starch and Solanyl in order of decreasing profits. Taking into account uncertainties, flash co-pyrolysis is expected to be cheaper than composting biopolymer waste streams, except for corn starch. If uncertainty increases, composting also becomes more interesting than flash co-pyrolysis for waste of Solanyl. If the investment expenditure is 15% higher in practice than estimated, the preference for flash co-pyrolysis compared to composting biopolymer waste becomes less clear. Only when the system of green current certificates is dismissed, composting clearly is a much cheaper processing technique for disposing of biopolymer waste.

Interaction of the organic matrix with pyrite during pyrolysis of a high-sulfur bituminous coal

Abstract High-sulfur bituminous coal containing 4.17 wt% of pyritic sulfur and the pyrite concentrate separated from this coal were used to examine the interaction between pyritic sulfur and the organic part of coal during pyrolysis. At 330–500°C, as a result of the reaction of sulfur derived from pyrite decomposition with the coal organic matrix, a significant increase in the organic sulfur in the char is observed, from 1.47 to 3.17 wt%. The enrichment in sulfur is most pronounced between 400 and 450°C, corresponding to the most intensive thermal degradation of this coal. At these temperatures, some of the pyrite is converted to pyrrhotite. The organic sulfur content is a maximum at ∼ 500°C, when all the pyrite is reduced to pyrrhotite. The pyrite in the coal undergoes conversion to troilite via pyrrhotite at lower temperatures than does pure pyrite. Compared with the thermal decomposition of pure pyrite, the pyrite present in coal starts to decompose at a lower temperature (330 vs. 400°C). The conversion to troilite also proceeds to completion at a much lower temperature. This demonstrates that the decomposition of pyrite is markedly affected by the presence of the organic coal substance.

AP-TPR investigation of the effect of pyrite removal on the sulfur characterization of different rank coals

Abstract The effect of pyrite removal on the determination of organic sulfur functionalities of different rank coals by atmospheric pressure-temperature-programmed reduction (AP-TPR) method was studied. The nitric acid treatment and sink–float separation were performed to reduce the content of pyritic sulfur in the samples. Microscopic examination of raw coals was performed to determine the mode of pyrite occurrence and to estimate the possibility of its removal using high-density liquids, i.e. ZnCl 2 and CHBr 3 /CCl 4 mixture. The AP-TPR investigation showed a different impact of nitric acid treatment and sink–float separation on the distribution of organic sulfur functionalities in coal. The evolution of sulfur dioxide observed by AP-TPR-mass spectrometry (MS) confirmed the formation of oxidized sulfur compounds during nitric acid treatment. Organic sulfonic groups are nearly totally decomposed to SO 2 without reduction of the latter to H 2 S under AP-TPR conditions. Some sulfur species remained in the TPR residue which was proven by AP-TPO-MS analysis through SO 2 monitoring.

A study of the reductive pyrolysis behaviour of sulphur model compounds

Abstract The difficulties inherent in the direct determination of sulphur functionalities in complex solid matrices by various techniques often make the need for reference compounds indispensable. One of the pyrolysis techniques used for sulphur determination is atmospheric pressure–temperature programmed reduction (AP-TPR). Experiments on sulphur model compounds have served successfully as a reference for both the temperature region in which the reduction or hydrogenation occurs and the efficiency of the reduction reaction. In this study, the pyrolysis behaviour of several organic and inorganic sulphur model compounds is investigated by AP-TPR using a mass spectrometer detector interfaced with the pyrolysis reactor (AP-TPR-MS). This technique permits a more complete description of the competitive and successive reactions that are occurring during the pyrolysis of the model compounds, providing new information regarding the reduction efficiency of oxidised and non-oxidised sulphur compounds.

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.

Effect of calcium and calcium minerals in coal on its thermal analysis

Abstract The effect of the presence of limestone and dolomite in coal, and calcium in lignite, on atmospheric-pressure temperature-programmed reduction (AP-TPR) analysis was studied. AP-TPR experiments were carried out on a bituminous coal with added limestone and dolomite and on a demineralized lignite. The results showed that both calcium minerals captured the gaseous H 2 S formed under AP-TPR conditions and produced CaS. Consequently the sulfur recovery monitored was too low and the AP-TPR kinetograms were deformed. The study also showed that the influence of dolomite is greater than of limestone. AP-TPR analysis of lignite demineralized and then loaded with calcium ions again showed a clear lowering of sulfur comparable with that of dolomite, but starting at a higher temperature.