Presence Of Mineral Matter Research Articles

Multi‐proxy climate and environmental records from a Holocene eutrophic mire, southern taiga subzone, West Siberia

Palaeoenvironmental reconstructions from peat are strongly focused on ombrotrophic mires, but this study demonstrates that eutrophic mires can also be used. A multi‐proxy approach was applied to a eutrophic mire on a floodplain terrace in the southern taiga of West Siberia. The results of the reconstruction were considered in the wide geographic context of the surrounding regions, including Siberia and Central Asia. Different palaeoecological proxies (analysis of plant macrofossils, testate amoebae, oribatid mites, molluscs, peat humification, ash content and spectral characteristics of humic acids) were used in this study. The results of different proxies showed a high level of consistency among themselves, which allowed for a robust interpretation of Holocene mire development. Throughout the ~7800 years history of the mire, there was a high level of surface wetness. The presence of mineral matter in the peat between 7800 and 5100 cal. a BP indicates regular flooding caused by the intensive fluvial activity, apparently resulting from increased precipitation. This was followed by a trend towards a gradual decrease in surface wetness from conditions of high surface moisture (stagnant water) between 5100 and 3000 cal. a BP to present day conditions of moderate surface moisture with a water table slightly below the mire surface. This pattern is consistent with the well‐documented long‐term trend from palaeoecological records throughout the taiga and arctic zones in West Siberia and central arid Asia. Our data further support the idea that the westerlies were the dominant driver of climate for the southern taiga of West Siberia during the Middle to Late Holocene.

Empirical Kinetic Models for the CO2 Gasification of Biomass Chars. Part 1. Gasification of Wood Chars and Forest Residue Chars.

The gasification kinetics of charcoals and biomass chars is complicated by several factors, including chemical and physical inhomogeneities, the presence of mineral matter, and the irregular geometry of the pore structure. Even the theoretically deduced gasification models can only provide empirical or semiempirical descriptions. In this study, an empirical kinetic model from the earlier works of the authors was adapted for the CO2 gasification of biomass chars. It is based on a versatile polynomial approximation that helps to describe the dependence of the reaction rate on the progress of the conversion. The applicability of the model was tested by the reevaluation of 24 thermogravimetric analysis (TGA) experiments from earlier publications. The adjustable parameters of the model were determined by the method of least squares by evaluating groups of experiments together. Two evaluation strategies were tested. In the regular evaluations, the same kinetic parameters were employed for all the experiments with a given sample. The use of experiments with modulated and constant reaction rate (CRR) temperature programs made it possible to employ another approach too, when the preexponential factor was allowed to vary from experiment to experiment. The latter approach allows a formal kinetic description of the differences in the thermal deactivation of the samples caused by different thermal histories as well as of some inevitable systematic errors of the TGA experiments. The evaluations were carried out by both approaches, and the results were compared. The evaluations were based on 12 experiments. As a test, each evaluation of the study was repeated with only 8 experiments. The results of the latter test calculations indicated that the information content of the employed experiments is sufficient for the evaluation approaches of this work.

Pyrolysis kinetic behavior and Py-GC–MS analysis of waste dahlia flowers into renewable fuel and value-added chemicals

To explore the bioenergy potential, kinetic and pyrolysis behavior of waste dahlia flowers (DF), model-free methods and Py-GC–MS were used. Kinetic characteristics of DF biomass were estimated by adopting four model-free methods, Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), Friedman, and Distributed Activation Energy (DAEM). Further, functional groups, the presence of mineral matter in DF biomass, and mineral compounds present in the inorganic residue were analyzed using FTIR, EDX, and XRF. Physicochemical analysis results confirmed its bioenergy potential for conversion into renewable fuel and valuable chemicals. The kinetic results of DF biomass showed that activation energy varied with conversion value, and the thermodynamic analysis indicated multiple step pyrolysis. FTIR analysis confirmed the presence of hemicellulose, cellulose, and lignin in biomass. EDX and XRF analysis also revealed the presence of various useful mineral matter, which had a positive effect during pyrolysis. Py-GC–MS results confirmed that at a lower temperature (500 °C), the formation of ester, nitrogen containing compounds and acid were higher, while at higher temperatures (550 °C and 600 °C), the formation of oxygenated compounds were reduced and the production of hydrocarbons and alcohols increased.

Effect of mineral matter on structure and dielectric properties of chars

The study was undertaken to investigate the changes of mineral matters in coal during heat treatment and its effect on structure and dielectric properties of generated chars. An acid treatment method was adopted to remove mineral matters in coal for preparing chars at 850–1600 °C using an electric furnace. Dielectric properties of coal chars were determined with the transmission/reflection method. Also, phase structure of coal chars was examined by X-ray diffraction (XRD). Significant transformation was found in the presence of mineral matters during heat treatment. Especially the process of creating silicon carbide (SiC) above 1300 °C in carbothermal reduction played a catalytic role on char structure. Consequently, dielectric properties were improved with the increase of structural ordering. These results could be instructive for the application of mineral matters in microwave technique at higher temperatures.

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

Pyrolysis of lignocellulosic materials typically form carbonaceous residues (chars) with structures similar to the starting material. However, previous studies reported in the literature have shown that fast pyrolysis of cellulose and lignin form a molten intermediate liquid resulting in chars with smooth surfaces and evidences of intense bubbling. The fraction responsible for morphology conservation during pyrolysis is not known. In this article, pyrolysis visualization studies were carried out with a fast camera on cellulose, xylan, Organosolv lignin (OL), milled wood lignin (MWL), and lignocellulosic sugarcane bagasse to identify the component responsible for morphological conservation. The materials were heated using a modified Pyroprobe with measured sample heating rates close to 100°C/s. Our studies confirm that cellulose, lignin, and deashed xylan are completely transformed into an intermediate liquid; the intensity of bubbling for lignin was far superior that of cellulose. Xylan as received, however, only forms a small amount of intermediate liquid; it does not fully melt and maintains its general shape during pyrolysis. These results suggest that the presence of mineral matter is critical for lignocellulosic materials to retain their original morphology. We repeated the studies on raw bagasse and acid washed bagasse. The raw bagasse retains its morphology; the acid washed bagasse shrank dramatically, but was not completely converted into a liquid. Our results suggest that in addition to hemicellulose with the presence of ash, other biomass fractions or the different temperatures at which the different fractions melt and solidify could also be contributing to maintain the structure of the lignocellulosic material during pyrolysis.

Microscopic Past of Poutwater Pond

Poutwater Pond Bog is a National Natural Landmark located in Holden, MA. As present-day species inhabiting this bog have been described, this study presents an insight into earlier inhabitants of the area during the mid- to late Holocene. A 5-m coring of peat was collected 10 m from the pond edge. Radiocarbon analysis of 10 sections of the core shows a nearly linear accumulation rate of peatland from 8500 years ago to the present. The presence of mineral matter at the base of the core suggests paulidification as the mechanism for formation of the bog. Microfossils were isolated from sections of the peat core by density-buoyant centrifugation, and examined using a scanning electron microscope. High-resolution images of pollen, sponge remains, and algae are presented. Circumneutral and acidobiontic diatoms were found at different depths of the core, indicating a changing water environment over time. Arboreal pollen grains were documented spanning 8500 years of vegetative history, permitting insight into the biodiversity that once existed.

Bisphenol A Removal from Water by Activated Carbon. Effects of Carbon Characteristics and Solution Chemistry

The present study aimed to analyze the behavior of different activated carbons in the adsorption and removal of bisphenol A (2-2-bis-4-hydroxypheniyl propane) from aqueous solutions in order to identify the parameters that determine this process. Two commercial activated carbons and one prepared in our laboratory from almond shells were used; they were texturally and chemically characterized, obtaining the surface area, pore size distribution, mineral matter content, elemental analysis, oxygen surface groups, and pH of the point of zero charge (pH(PZC)), among other parameters. Adsorption isotherms of bisphenol A and adsorption capacities were obtained. The capacity of the carbons to remove bisphenol A was related to their characteristics. Thus, the adsorption of bisphenol A on activated carbon fundamentally depends on the chemical nature of the carbon surface and the pH of the solution. The most favorable experimental conditions for this process are those in which the net charge density of the carbon is zero and the bisphenol A is in molecular form. Under these conditions, the adsorbent-adsorbate interactions that govern the adsorption mechanism are enhanced. Influences of the mineral matter present in the carbon samples and the solution chemistry (pH and ionic strength) were also analyzed. The presence of mineral matter in carbons reduces their adsorption capacity because of the hydrophilic nature of the matter. The presence of electrolytes in the solution favor the adsorption process because of the screening effect produced between the positively charged carbon surface and the bisphenol A molecules, with a resulting increase in adsorbent-adsorbate interactions.

The distribution of mineral matter in pulverised coal particles in relation to burnout behaviour

The presence of mineral matter in a pulverised coal particle may affect the behaviour of the particle during combustion, and could influence the level of unburnt carbon in ash experienced in power stations. This paper presents details of a computer-controlled scanning electron microscopy (CCSEM) method of characterising the mineral content of individual pulverised coal particles and describes the distribution of mineral matter in pulverised coal samples. The possible influences of the mineral matter distribution on levels of unburnt carbon are discussed in the light of burnout measurements for the same coal samples. Pulverised coal particles may be divided into three types on the basis of their mineral content: organic-rich particles, organic particles with included minerals, and excluded mineral particles. The relative proportions of these different particle types have been characterised for a suite of 18 power station coals from around the world. Organic-rich particles are the most abundant, and particles containing included minerals form a greater mass fraction of the coals than excluded mineral particles. The excluded mineral particles have a considerably finer size distribution than the particles containing organic material, and the organic-rich particles are generally slightly larger than the organic particles with included minerals. Ranking the coals by degree of mineral-organic association shows a strong separation of coals on a geographical basis. Australian and South African coals show higher levels of mineral-organic association than British and North American coals. Although there are a number of possible mechanisms by which included minerals might modify the combustion behaviour of pulverised coal particles, comparison between the mineral distribution and the combustion performance of these coals does not favour any particular mechanism for influencing levels of unburnt carbon.

97/02674 Evaluation of Mo catalyst precursors for hydrotreating coal derived liquids

Numerous studies have examined the use of dispersed catalysts for promoting the dissolution of coal and upgrading high-boiling and residual liquids. Catalysts have been added in various forms, including oil soluble organometallics and carbonyls, with industrial interest for application to a spectrum of residual feedstocks, and demonstration in coal liquefaction at the pilot plant scale. Dispersed catalysts offer certain advantages over supported catalysts for hydroprocessing such feedstocks. Because of their large molecular size, many of the feed constituents cannot access the internal pore structure of supported catalysts, and hence upgrading must proceed by an indirect process, probably involving H-transfer via lower molecular weight species. Another major deficiency of supported catalysts is their susceptibility to deactivation by reactions which cause the deposition of carbon and metals. Dispersed catalysts can overcome the first of these obstacles and may be less susceptible to deactivation. At the same time, there are also difficulties in the utilization of dispersed catalysts. These include: attaining and maintaining adequate dispersion; and converting the precursor to the active phase. Moreover, the effective catalyst metals, such as Mo, are expensive and their application is only economically viable if they can be used at very low concentrations or efficiently recycled. Inmore » direct coal liquefaction, the presence of mineral matter and undissolved coal in the products of coal solubilization mean that a solids separation step is necessary and, inevitably, catalyst will be removed with the reject stream. This program studied the effectiveness of dispersed Mo catalysts for hydroprocessing solids-free residual coal liquids.« less

Composition of turfgrass thatch

In many intensively cultured turfs, thatch, an organic layer of leaves, stems, and roots, that develops above the soil surface, is recognized as a potentially serious problem. This study evaluated the constituents of turfgrass thatch in terms of organic matter (OM), cellulose, and lignin content. Ten samples were analyzed containing two or three layers of 2‐cm thick for a total of 30 layers. As thatch layers may often include mineral matter, a technique was developed to separate the OM from any mineral particles in the samples. An important loss of OM was observed during the separation process. Despite problems encountered during the constituent analyses due to the heterogeneity of the samples and the presence of mineral matter, results showed a significant increase in lignin content with depth.

A review of the kinetics of the nitric oxide-carbon reaction

The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from studies in which catalysis played no role and from studies in which catalysts were present as a result of addition or as natural inclusions (i.e. in coals). It is concluded that there generally exist three distinct reaction regimes, defined in terms of reaction temperatures. There is a near-ambient-temperature chemisorption regime, in which steady gasification is not possible. In this regime, both reversible and irreversible chemisorption processes are observed. A low-temperature gasification regime is observed at temperatures above ∼ 500 K, but below ∼ 1000 K. A high-temperature gasification regime is observed above this transition temperature. The low-temperature gasification regime is characterized by low activation energies, and the high-temperature regime by high activation energies. These two distinct gasification regimes however are not observed in all cases, and there is as yet no clear understanding of what determines this. In the reaction of pure NO with carbons, the order of reaction with respect to NO appears to be near unity in the gasification regimes and two in the low-temperature chemisorption regime. The apparent order in gasification is strongly influenced by the presence of CO in the reactant gas stream, and in certain reaction configurations the CO may be self-generated. In the presence of CO, the apparent order with respect to NO decreases, and there are several reports of apparent fractional order. Other oxidizing gases (e.g. O 2, H 2O) can also influence the kinetics and course of the NO-carbon reaction. The thermal history of the carbon can have a significant effect on its reactivity in NO. It appears however that the annealing of carbons towards NO cannot be reliably predicted from the annealing behaviour of the carbons towards other oxidizing gases (i.e. O 2). Reaction rates of NO with carbon can also be influenced by the presence of mineral matter. There is no general agreement on the quantitative importance of mineral catalysis in the reaction of carbons with NO.

96/00293 Oil shale as a feedstock for carbon materials

The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from studies in which catalysis played no role and from studies in which catalysts were present as a result of addition or as natural inclusions (i.e. in coals). It is concluded that there generally exist three distinct reaction regimes, defined in terms of reaction temperatures. There is a near-ambient-temperature chemisorption regime, in which steady gasification is not possible. In this regime, both reversible and irreversible chemisorption processes are observed. A low-temperature gasification regime is observed at temperatures above ∼ 500 K, but below ∼ 1000 K. A high-temperature gasification regime is observed above this transition temperature. The low-temperature gasification regime is characterized by low activation energies, and the high-temperature regime by high activation energies. These two distinct gasification regimes however are not observed in all cases, and there is as yet no clear understanding of what determines this. In the reaction of pure NO with carbons, the order of reaction with respect to NO appears to be near unity in the gasification regimes and two in the low-temperature chemisorption regime. The apparent order in gasification is strongly influenced by the presence of CO in the reactant gas stream, and in certain reaction configurations the CO may be self-generated. In the presence of CO, the apparent order with respect to NO decreases, and there are several reports of apparent fractional order. Other oxidizing gases (e.g. O2, H2O) can also influence the kinetics and course of the NO-carbon reaction. The thermal history of the carbon can have a significant effect on its reactivity in NO. It appears however that the annealing of carbons towards NO cannot be reliably predicted from the annealing behaviour of the carbons towards other oxidizing gases (i.e. O2). Reaction rates of NO with carbon can also be influenced by the presence of mineral matter. There is no general agreement on the quantitative importance of mineral catalysis in the reaction of carbons with NO.

Characterization of trace amounts of aluminium in biological reference materials by electrothermal atomic absorption spectrometry.

The homogeneity of aluminium at the ppm level in a set of reference materials provided by Agriculture Canada was determined by electrothermal atomic absorption spectrometry. The materials included bran, wheat flour, gluten, whole egg powder, whole milk powder, meat powder, starch, cellulose, corn kernel and corn stalk. Reproducible values were obtained, which indicated that all of the materials studied can be considered to have a homogeneous distribution of aluminium between samples at test portion sizes of 250 mg. All of the materials, except milk, egg and meat, required HF in addition to HNO3 to effect complete dissolution, indicating the presence of mineral matter.

The interactions of carbons with potassium

This paper describes an investigation of the interaction of a wide range of carbons with potassium. In particular, the relationships between reaction temperature, potassium adsorption, carbon structural characterisation data (macroporosity, surface area, X-ray crystallographic parameters and microstrength), and size degradation are considered in detail. For isotropic, high surface area carbons, high potassium uptakes occurred, but no size degradation was observed. Needle-coke with flow domain optical texture and low surface area had comparatively little size degradation and potassium uptake. For anisotropic metallurgical cokes with a range of types of optical textures and low surface area, significant size degradation was observed. The results suggest that size degradation is probably associated with the heterogeneity and varying orientation of anisotropic components in the structure and the presence of mineral matter. The mechanism proposed for size degradation involves adsorption with swelling during potassium uptake occurring in non-uniform ways, resulting in high stresses and size degradation of the coke lumps. The stresses set up at the interface between the carbon and mineral particles may also be significant in size degradation. However, carbon structural changes were observed as a result of potassium uptake irrespective of the size degradation.

Infrared optical constants of coal slags - Dependence on chemical composition

The results of an experimental study of the infrared optical constants of coal slags are presented. The real and imaginary parts of the refractive index were determined from transmittance and reflectance measurements carried out on thin polished glassy slag wafers at room temperature from visible wavelengths to 13 jun. The dependence of the optical constants on slag chemical composition was investigated, and correlations were developed based on the measured data to allow estimation of the optical constants as a function of wavelength and composition. HE presence of mineral matter in coal has several conse- quences for radiative heat transfer in coal combustion systems. The fly-ash particles dispersed in the combustion gases may absorb, emit, and scatter radiation, with possibly signifi- cant effects on heat transfer.1'2 Also, the slag layers formed on the walls alter the wall radiative properties. To estimate the effects of either fly ash or slag layers (which may be semitransparent3) on radiative heat transfer, one needs data on the complex refractive index m = n — ik of the ash/slag at infrared wavelengths. For calculations of radiant emission by the fly ash, the imaginary part k of the refractive index is of particular importance. At present, the available data on the optical constants (i.e., n and k) are fairly sparse and uncertain, particularly on k. Although there have been several reported measurements of n and k for fly ash,4'9 in each case, experimen- tal problems were encountered that appear to have significantly affected the measured values. The earliest reported optical constants for fly ash by Willis4 were later shown by Gupta and Wall10 to be in error from the use of incorrect data-reduction procedures. Similarly, the experimental technique used by Volz5 to measure k for fly ash was later shown by Toon et al.11 to be inapplicable for particles in the size range of fly-ash particles as a result of neglect of scattering. Lowe et al.6 and Gupta and Wall8 measured k for fly ash in situ in an operating pulverized coal utility boiler. In both studies, however, the measured values were biased by the presence of up to 10% residual carbon in the ash at the measure- ment location.8 Co wen et al.7 found similar effects of residual carbon in their measurements of k on sampled submicron ash. Finally, Wyatt9 has reported optical constants for fly-ash par- ticles at a wavelength of 0.6328 jLim, measured using a single- particle light-scattering technique. A later sensitivity analysis of the technique by Marx,12 however, concluded that the method cannot be used reliably to measure k for values below 0.01 (which is greater than the values reported by Wyatt) although it can be used to measure n accurately. In light of the problems encountered in the studies to date, it is clear that there is a need for improved data on the optical constants of fly ash in the infrared. Unfortunately, consider-

Effect of mineral matter of coals on the microporosity of charcoals

Coals are associated with inorganic impurities that may affect several reactions occurring during the carbonization process, namely the formation of volatiles and tars and their subsequent pyrolysis reactions. Two types of low rank coals with different mineral matter content (3.9 and 22.4 wt %, respectively) have been selected. Removal of the inorganic matter was carried out by hydrochloric acid treatment followed by extraction with a mixture of hydrochloric and hydrofluoric acid. After demineralization, the micropore volume of both coals increased due to the opening of pores, which were blocked by mineral impurities. The micropore volume of chars from unwashed as well as from demineralized coals reached a maximum with pyrolysis temperature. Below 875 K the presence of mineral matter only slightly affects the microporosity of chars by partial blockage of apertures. This blockage disappears after demineralization of the carbonized char. At a higher temperature, however, chars prepared from unwashed coals have a smaller micropore volume than those obtained from demineralized coals. It is suggested that the silica-alumina compounds associated with the coals are responsible for the observed decrease in micropore volume of chars.

A TPD study of coal chars in relation to the catalysis of mineral matter

The steam gasification mechanism of brown coal was studied by a temperature-programmed desorption (TPD)technique. A Morwell coal was devolatilized in N 2 and then gasified in steam at 1100 K. During the TPD of a partially gasified char, H 2O, CO 2 and CO evolved approximately at 640, 870 and 1020 K, respectively. The presence of mineral matter was found to be responsible for these gas evolutions, since essentially no gas evolution was observed during the TPD of the demineralized coal char. The comparison of the above TPD pattern with those determined for the cation-exchanged samples revealed which inorganic species is responsible for each TPD peak: H 2O evolution was due to Ca; CO 2 evolution to Ca and Mg; CO evolution to Na and/or Fe. The exchanged metal species like Ca and Na significantly catalysed the gasification reaction. The relation between the catalytic activity and TPD pattern was discussed in terms of surface oxygen complexes.

Hydrogen/deuterium transfer in coal liquefaction

Reactions have been made with deuterium-labelled solvent (d 4- and d 12-tetralin) and both Powhatan bituminous (Pittsburgh Seam) coal and model compounds under coal liquefaction conditions to study hydrogen transfer mechanisms. Powhatan coal liquefies quickly. Hydrogen transfer from the solvent to the reaction products continues throughout the heating period (up to 60 min). Significant hydrogen/deuterium exchange occurs and this strongly affects the distribution of deuterium in the products and also affects the extent of conversion as measured by the amount of THF-insoluble material. Increased deuteration of the solvent leads to decreased conversion. This exchange is enhanced by heavy aromatic species and by the presence of mineral matter and unconverted coal solids.

Graphitization of carbon under high pressure

A review of the recent work on acceleration of graphitization under high pressure by electric spark shock and in the presence of mineral matter is presented.

Petrographic and sporological studies of some coals from Talcher coalfield, Orissa, India

The present paper outlines petrographic and sporological studies of coals from Nandira and South-Balanda mines of Talcher coalfield in the Mahanadi Coal Basin, Orissa, India. No previous knowledge exists about petro-palynological characters of these coals although general microstructural details of Talcher coals have been   established.
 The coals investigated are dull in appearance and non-banded. They are composed of Durain, Vitrain and Fusain components. Durain forms the main component with narrow short black lenticles of Fusain. The microscopic study of Durain component indicates Vitrinite, Exinite, and Inertinite as main macerals. Exinite constitutes microspores, megaspores and microsporangia. Vitrain and Fusain components under microscope show Vitrinite and Fusinite macerals showing woody structure. Trimacerites form the bulk of the microlithotypes.
 Sporological studies of these coals reveal a large variety of miospores. The miospore assemblage in the coals comprises of trilete, monolete, monosaccate and disaccate forms. Genera Punctatisporites, Parasaccites, Virkkipollenitcs, Sulcatisporites, Lunatisporites, Stotersporites, Faunipollenites and Cuneatisporites are well represented. Saccate sporomorphs constitute a large group in the miospore assemblage. Among saccate forms the genus Parasaccites dominates in miospore distribution.  Petro-palynological characters of the coals investigated indicate that by and large they are of non-banded Durain component composed mostly of saccate forms. (predominated by monosaccates), resembling the main seam of Talcher coalfield in palyno-petrographic composition. Presence of mineral matter, high proportion of Inertinite and Exinite constituted by spores, and less amount of vitrain and Clarain indicate high moisture content and low grade quality coals.