Lignite Surface Research Articles

Wettability modification and restraint of moisture re-adsorption of lignite using cationic gemini surfactant

Adsorption of surfactants onto lignite surface may result in wettability changes and slow the re-adsorption of moisture onto dried lignite. In this work, a cationic gemini surfactant, ethanediyl-1,2-bis(dimethyl dodecyl ammonium bromide) (12-2-12), was chosen, and its adsorption characteristics and the influence on the surface wettability of lignite were investigated. The results suggest that a strong attraction takes place between the negatively charged lignite surface and a gemini surfactant with positively charged head groups to form a monolayer adsorption in low surfactant concentration. Electrostatic forces play a dominant role in the adsorption of a cationic gemini surfactant on the lignite surface while hydrogen bonding does not. The adsorption density of a gemini surfactant on coal surfaces increased with an enhancement in the amount of polar oxygen containing functional groups and the addition of KCl. A decrease in wetting heat indicated that the lignite treated with the gemini surfactant led to a significant decrease in the hydrophilicity of lignite. The high concentration of oxygen-containing functional groups increased the negative charge of the coal surface, which is beneficial for adsorption of the cationic gemini surfactant adsorption onto the coal surface that decreased the hydrophilicity of lignite effectively. The lignite wettability surface modification results were compared with the traditional cationic surfactant cetyltrimethyl ammonium bromide (CTAB); these results suggested that the unique chemical structure of the gemini surfactant with two hydrophilic and two hydrophobic groups had a more prominent impact on lignite surface hydrophilicity. The gemini surfactant adsorbed on lignite surface also had a significant improvement in resisting moisture re-adsorption and could create pathways toward utilizing lignite industrially.

Theoretical Investigation of Noncovalent Interactions between Low-Rank Coal and Water

The high moisture content of low-rank coals (LRCs) is associated with the noncovalent interactions between coal and water, such as hydrogen bonding and van der Waals attraction. In this study, the molecular model of lignite was constructed and its electrostatic potential (ESP) on a van der Waals surface was analyzed. The mechanism of water absorption on the hydrophilic or hydrophobic sites of the lignite surface was investigated based on the atoms in molecules analysis and reduced density gradient analysis of seven typical lignite···water complexes. The regions with the most negative and positive ESP values were associated with oxygen in oxygen functional groups, and hydrogen was associated with smaller electronegativity. The typical hydrogen bonds O–H···O were formed between water and oxygen functional groups, whereas the weaker hydrogen bonds C–H···O were formed between water and the skeleton components of lignite, such as the benzene ring and methyl and methylene groups. Oxygen functional groups were r...

Effects of lignite application on ammonia and nitrous oxide emissions from cattle pens

Beef cattle feedlots are a major source of ammonia (NH3) emissions from livestock industries. We investigated the effects of lignite surface applications on NH3 and nitrous oxide (N2O) emissions from beef cattle feedlot pens. Two rates of lignite, 3 and 6kgm−2, were tested in the treatment pen. No lignite was applied in the control pen. Twenty-four Black Angus steers were fed identical commercial rations in each pen. We measured NH3 and N2O concentrations continuously from 4th Sep to 13th Nov 2014 using Quantum Cascade Laser (QCL) NH3 analysers and a closed-path Fourier Transform Infrared Spectroscopy analyser (CP-FTIR) in conjunction with the integrated horizontal flux method to calculate NH3 and N2O fluxes. During the feeding period, 16 and 26% of the excreted nitrogen (N) (240gNhead−1day−1) was lost via NH3 volatilization from the control pen, while lignite application decreased NH3 volatilization to 12 and 18% of the excreted N, for Phase 1 and Phase 2, respectively. Compared to the control pen, lignite application decreased NH3 emissions by approximately 30%. Nitrous oxide emissions from the cattle pens were small, 0.10 and 0.14gN2O-Nhead−1day−1 (<0.1% of excreted N) for the control pen, for Phase 1 and Phase 2, respectively. Lignite application increased direct N2O emissions by 40 and 57%, to 0.14 and 0.22gN2O-Nhead−1day−1, for Phase 1 and Phase 2, respectively. The increase in N2O emissions resulting from lignite application was counteracted by the lower indirect N2O emission due to decreased NH3 volatilization. Using 1% as a default emission factor of deposited NH3 for indirect N2O emissions, the application of lignite decreased total N2O emissions.

Analysis of Wellbore Skin Samples-Typology, Composition, and Hydraulic Properties.

The presence of a wellbore skin layer, formed during the drilling process, is a major impediment for the energy-efficient use of water wells. Many models exist that predict its potential impacts on well hydraulics, but so far its relevant hydraulic parameters were only estimates or, at best, model results. Here, we present data on the typology, thickness, composition, and hydraulic properties obtained from the sampling of excavated dewatering wells in lignite surface mines and from inclined core drilling into the annulus of an abandoned water well. Despite the limited number of samples, several types of skin were identified. Both surface cake filtration and particle straining in the aquifer occur. The presence of microcracks may be a determining feature for the hydraulic conductivity of skin layers. In the case of the well-developed water supply well, no skin layer was detected. The observed types and properties of wellbore skin samples can be used to test the many mathematical skin models.

Effective Flotation of Lignite Using a Mixture of Dodecane and 4-Dodecylphenol (DDP) as a Collector

ABSTRACTLignite is difficult to float using common oily collectors, for example, diesel and kerosene. In this investigation, a mixture of dodecane and 4-dodecylphenol (DDP) was used as a collector. The flotation performance using the mixture of dodecane and DDP as a collector is much better than that using dodecane or DDP solely. The concentrate yield using the mixture as a collector is much higher than that using dodecane or DDP solely. However, concentrate ash is lower than that using dodecane or DDP solely. The mixture of dodecane and DDP was proven to be an effective collector for lignite flotation. FTIR was used to indicate the changes in surface properties of lignite before and after the adsorption of different collectors. The improvements in flotation performance of lignite by the mixture are discussed and the adsorption mechanism of the dodecane and DDP on lignite surface was also obtained. Using the mixture of DDP and dodecane as the collector, the dodecane primarily covers the hydrophobic sites on the lignite surface while the DDP primarily covers the hydrophilic sites on the lignite surface.

Effect of moisture on dehydration and heat transfer characteristics of lignite in low temperature carbonization furnace

Dehydration of lignite primarily occurs in two stages, namely, removal of surface moisture and decrease in oxygen-containing functional groups and moisture stage. Moisture on the lignite surface could be removed at temperatures below 100°C. However, parts of oxygen-containing functional groups were removed first followed by the removal of the adsorbed moisture at temperatures in the range 100–300°C. Dehydration time increased with an increase in the dehydration load and heat transfer distance. At surface moisture of 7wt.%, temperature of lignite increased rapidly. Higher temperature of combustion chamber yielded shorter removal times for surface moisture and oxygen-containing functional groups. Based on the rate of increase of lignite temperature and associated heat transfer process, coking chamber could be divided into three zones: the near, middle, and remote zones. The near zone temperature curve was determined to be a convex function ∂2T∂τ2≤0; however, the middle zone temperature curve was determined to be a concave function ∂2T∂τ2≥0⋅∂2T∂τ2=0 and ∂T∂τ=k were the boundary indices of the middle and remote zones. 100°C isothermal surface movement rate was found to be affected by the heat transfer capacity and dehydration load. Center temperature distribution of coking chamber was made uniform by steam, and temperature of HM7% was the most uniform distribution.

Laboratory Study on the Spontaneous Combustion Propensity of Lignite Undergone Heating Treatment at Low Temperature in Inert and Low-Oxygen Environments

This laboratory study investigated the spontaneous combustion propensity of coal undergone heating treatment at low temperature (<200 °C) in N2, CO2, and the air of 10% O2 environments. The investigations include the changes in the emission of carbon oxides, oxygen consumption, activation energy, infrared spectroscopy, and pore structure before and after the treatment of lignite. The results show that in comparison to the original coal, the treated lignite is more easily oxidized, produces more carbon oxides at low temperature, and has more C–O structure, less heteroatoms substitution structure and free OH content, larger pore volume, and high porosity and permeability. Porous structure analysis reveals that the treated lignite produces a variety of pores larger than 10 nm, and these pores are conductive to the movement of the oxygen molecules in lignite and the chemical reaction between oxygen molecules and active groups on the surface of lignite. This study concludes that lignite undergoing heating trea...

The effect of organic solvent thermal treatment on the physicochemical properties of lignite

AbstractTwo organic solvents (ethanol and n‐hexane) were selected to dewater and upgrade Indonesian lignite under high pressure and moderate temperature. The solid products yield of lignite upgraded by ethanol and n‐hexane are 65.1% and 74.4% at 300 °C, 17 MPa and 300 °C, 12 MPa, respectively. In addition, the organic solvents upgrading significantly reduced the moisture content, increased the fixed carbon content, decreased the atomic ratios of O/C and H/C, and considerably increased the calorific value of lignite. Numerous porous and large holes were created on the surface of the upgraded lignite due to the extraction of absorbed water and organic matter in raw lignite. Because of the extraction and decomposition of functional groups in the process of upgrading, the content of carboxyl, carbonyl, hydroxyl, and other oxygen‐containing functional groups is significantly decreased. Also, the condensation degree of the aromatic ring increased, and the quality of lignite upgraded by n‐hexane was better than that of lignite upgraded by ethanol. The content of carbonyl in the lignite decreased from 19.42% to 5.72% after ethanol upgrading and to 2.04% after n‐hexane upgrading at 300 °C, but the carboxyl groups were decomposed at 300 °C. © 2015 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Development of a GIS-based information system for mining activities: Afsin-Elbistan lignite surface mine case study

In this study, it was aimed to monitor mining activities and product movements by establishing a mine information system and to give the optimum decision by conducting the necessary inquiries and analyses. For this purpose, at first the map materials used in the mining activities in Afsin-Elbistan lignite basin were converted to digital maps by means of GIS techniques, and after that the lignite deposit was modelled in 3D, by utilising drill holes data and geostatistical methods. With the integration of the table and graphical data obtained in this way in GIS environment, performance of location-dependent analysis, such as the determination of reserve-quality distributions, was made possible. Within this scope, it was demonstrated that the reserve quantities and statistical information of all attributes included in the databases selected from the screen or of any other databases generated through inquiries are accessible, and also thematic maps can be generated.

Method for Location of An External Dump in Surface Mining Using the A-Star Algorithm

Abstract The construction of a surface mine always involves the necessity of accessing deposits through the removal of the residual overburden above. In the beginning phase of exploitation, the masses of overburden are located outside the perimeters of the excavation site, on the external dump, until the moment of internal dumping. In the case of lignite surface mines, these dumps can cover a ground surface of several dozen to a few thousand hectares. This results from a high concentration of lignite extraction, counted in millions of Mg per year, and the relatively large depth of its residual deposits. Determining the best place for the location of an external dump requires a detailed analysis of existing options, followed by a choice of the most favorable one. This article, using the case study of an open-cast lignite mine, presents the selection method for an external dump location based on graph theory and the A-star algorithm. This algorithm, based on the spatial distribution of individual intersections on the graph, seeks specified graph states, continually expanding them with additional elementary fields until the required surface area for the external dump - defined by the lowest value of the occupied site - is achieved. To do this, it is necessary to accurately identify the factors affecting the choice of dump location. On such a basis, it is then possible to specify the target function, which reflects the individual costs of dump construction on a given site. This is discussed further in chapter 3. The area of potential dump location has been divided into elementary fields, each represented by a corresponding geometrical locus. Ascribed to this locus, in addition to its geodesic coordinates, are the appropriate attributes reflecting the degree of development of its elementary field. These tasks can be carried out automatically thanks to the integration of the method with the system of geospatial data management for the given area. The collection of loci, together with geodesic coordinates, constitutes the points on the graph used during exploration. This is done using the A-star algorithm, which uses a heuristic function, allowing it to identify the optimal solution; therefore, the collection of elementary fields, which occupy the potential construction area of a dump, characterized by the lowest value representing the cost of occupation and dumping of overburden in the area. The precision of the boundary, generated by the algorithm, is dependent on the established size of the elementary field, and should be refined each time by the designer of the surface mine. This article presents the application of the above method of dump location using the example of “Tomisławice,” a lignite surface mine owned by PAK KWB Konin S. A. The method made it possible to identify the most favorable dump location on the northeast side of the initial pit, within 2 kilometers of its surrounding area (discussed further in chapter 3). This method is universal in nature and, after certain modifications, can be implemented for other surface mines as well.

Externalities from lignite mining-related dust emissions

During the last three decades, several studies have been conducted in order to assess the external costs of electricity production from fossil fuels, especially coal and lignite. Nevertheless, these studies usually ignore the impacts generated by the upstream mining works. This paper contributes to existing literature and attempts to fill this gap by exploring the externalities of lignite mining owing to the emission of suspended particulate matter. To this end, a ‘bottom-up’ approach is implemented, using as case study the largest operational lignite surface mine at the Lignite Center of Western Macedonia (Greece). The results indicate that annual air pollution externalities of lignite mining are of the order of 3€/ton of lignite, which corresponds to around 5.0 €/MWh. The estimated costs are significantly lower, i.e. up to 80%, when dust deposition is considered in air dispersion models. In any case, these findings should be seen as a starting point for discussion owing to the lack of specific emission rates for Greek lignite mines.

Removal of methylene blue from aqueous solution using by untreated lignite as potential low-cost adsorbent: Kinetic, thermodynamic and equilibrium approach

The adsorption mechanism of the cationic methylene blue dye to the abundant and inexpensive lignite as an adsorbent from aqueous solutions was investigated as a function of ionic strength, pH, temperature, initial dye concentration, contact time and stirring speed. The adsorption capacity increased with the increasing temperature, initial dye concentration, pH and ionic strength, although it was not affected by the stirring speed. The value of zeta potential decreased with the increasing pH. Experimental adsorption data were modelled by different equilibrium isotherms such as Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (D–R), BET, Halsey, Harkins–Jura, Smith and Henderson isotherms. The adsorption process fitted well to pseudo-second-order kinetics and the Langmuir model. Activation energy of the adsorption processes was found to be 49.81kJmol−1 initial dye concentration of 80mgL−1 using the Arrhenius equation, indicating the strong electrostatic interactions between the adsorbent and dye. The isosteric enthalpy and entropy changes were calculated as 58.19kJmol−1 and −0.186kJmol−1K−1, respectively, indicating that the adsorption process was endothermic and the orderliness of the adsorption system slightly decreases with adsorption of methylene blue molecules to the lignite surface. FT-IR results revealed that several functional groups on the coal surface are responsible for methylene blue adsorption. The observed differences in the reflection of the SEM images of lignite and methylene blue adsorbed lignite are due to the presence of methylene blue, which was adsorbed. BET isotherm and nitrogen-adsorption–desorption isotherms analysis results implied that lignite is a heteroporous material exhibiting microporous properties.

Surface restructuring of lignite by bio-char of Cuminum cyminum – Exploring the prospects in defluoridation followed by fuel applications

Recently, there has been an interest in the areas of developing new carbon materials for fluoride removal applications. The development of new carbon materials is of recent choice which involves the synthesis of hybrid carbon from various sources. In this context, the present contribution is made to focus on the study the restructured surface of lignite using a bio-material called Cuminum cyminum. The restructured lignite (RSL) was synthesized with an improved carbon content of 13% and its BET surface area was found to be 3.12 times greater than lignite (L). The amorphous nature of lignite and RSL was quite explicable from XRD studies. SEM studies exhibited a fibrous and finer surface of lignite which was well restructured into a semi-melt (5μm) surface for RSL. Defluoridation potential of Restructured Lignite (15.8mgg−1) was greater than the lignite (13.8mgg−1) at pH 7.93±0.03. Kinetic and isotherm parameters derived from various models helped in comprehending the nature and dynamics of fluoride sorption. Both the normal and the restructured lignite were found to be consistent with its fluoride uptake of 57% and 60% respectively even after fifth cycle of regeneration. High heating values of 22.01MJkg−1 and 26.90MJkg−1 respectively for lignite and RSL deemed their additional application as fuel materials.

Contribution of electrical tomography methods in geotechnical investigations at Mavropigi lignite open pit mine, Northern Greece

In this paper, the application of 2D and 3D electrical resistivity methods in geotechnical investigations is explored through a case study in Northern Greece. These two methods were employed at a lignite surface mining operation where fracture zones and discontinuities have been recently observed close to the pit boundaries. The main aim of the geophysical survey was to estimate the inclination of the contact between the Neogene and Schist/Carbonate formations near the southern limits of the pit, as well as to estimate the thickness of the carbonate rocks on top of the Schist formations to evaluate the stability of the southern slopes. Synthetic data were initially generated to help plan an efficient electrical tomography survey, in a region with complex geology and irregular terrain. Three configurations (Wenner–Schlumberger and dipole–dipole or pole–dipole) proved essential in such conditions and helped improving the resolution of the resistivity section. The sections were then calibrated by boreholes. Finally, the geophysical survey provided invaluable data regarding the geometry of the bedrock and possible faults, which was essential for the slope stability calculations.

Flotation of lignite pretreated by sorbitan monooleate

In this study, sorbitan monooleate was used to pretreat lignite prior to flotation tests. First, the lignite sample and water were mixed with 0%, 0.5%, 1%, 1.5% and 2% (on the basis of the weight of the coal) of sorbitan monooleate to produce five types of flotation slurries. FTIR, XPS and SEM were used to analyze the surface properties of the lignite sample. The flotation tests were used to indicate the improvements in flotation of lignite after the sorbitan monooleate pre-treatment. FTIR and XPS results showed that there are many oxygenated functional groups in lignite such as carboxyl group and hydroxyl groups. Furthermore, SEM results showed that there are many holes on the lignite surface. These holes will be filled with water in the flotation pulp. The flotation results indicated that sorbitan monooleate can improve the lignite flotation at low concentrations of sorbitan monooleate. However, the flotation behavior of lignite deteriorated at higher concentrations of sorbitan monooleate.

Local community opinions regarding the socio-environmental aspects of lignite surface mining: Experiences from central Poland

Surface lignite mining covers large areas and usually generates social conflicts which pose one of several energy security threats to certain states. Therefore, defining the social conditions determines the success of a mining project. Two communes were chosen for a public opinion study: Kleszczów, where the Bełchatów mine is located, and Złoczew, where a lignite deposit will soon be developed. The analysis shows, as opposed to other areas in Poland that have been projected for development, that both local communities are characterised by a high level of acceptance for lignite mining. In both cases, awareness about the profits was stronger than anxiety about the investment's negative effects. However, most inhabitants could not assess the mining company's diligence concerning its responsibility for mining damages as well as the diligence of external experts assessing the environmental impacts of excavation. Most respondents also could not assess if the legal regulations of public participation in the decision process were sufficient, but the negative opinions outweighed the positive ones. From the perspective of the energy policy, dialogue-type social communication is needed for every case of a new energy-mining project. Research on local public opinion should be the first step to opening up a social debate.

Local communities' knowledge of lignite surface mining – sources and level of satisfaction: examples from central Poland

Abstract Developing of large-scale lignite excavation can often generate socio-environmental conflicts between mining-energy companies and various stakeholders, such as local communities or ecological organizations. In this context indication of potential channels of communication with local communities’ is needed to increase the level of their satisfaction with own knowledge and to optimize the social dialogue. The paper presents the results of a questionnaire survey conducted in selected communities of the Łódź voivodeship where surface mining exists at present (Kleszczów) or will be developed soon (Złoczew). They were realized with the Computer Assisted Telephone Interviewing on the representative groups of adults. The paper contains analysis of two selected closed-type questions: the first one concerned self-assessment of knowledge level of lignite mining, the second one - sources of information on mining activity. Previous media reports on mining activity in the examined areas were analysed, too. As it seems, various means of social communication should be used: television and radio are the major source of information for local communities, printing press and the Internet are important as well. A detailed set of communication channels and the content of individual messages should be carefully selected for specific target groups (depending on gender, age and education). It should be emphasized that a properly conducted public debate may prove to be one of the factors determining the success of mining-energy investments and sustainable development of some regions.

Catalysis and compensation effect of K2CO3 in low-rank coal — CO2 gasification

Abstract The CO2 gasification of a low rank coal catalysed by K2CO3 was studied, at 700–950°C and 1 atm. A two level full factorial design revealed that the gasification reaction was sensitive to the solid residence time, reaction temperature, CO2 partial pressure and catalyst load. K2CO3 was an efficient catalyst at all temperatures studied, particularly during the second stage when the Boudouard reaction dominates. The gasification rate was increased continuously with increasing catalyst load up to a load of ∼20% w/w K2CO3 concentration, following a sigmoid curve. Above this point, limited catalytic effect was observed, possibly due to the saturation of the lignite surface by K+. A correlation was found to exist between the catalytic gasification rate and the Alkali Index, which increased with the impregnation of the inorganic K2CO3 salt. When K2CO3 load increased, the Arrhenius parameters, E and k 0, increased simultaneously exhibiting a compensation effect. The isokinetic temperature was found about 600 to 650°C corresponding to the minimum temperature required for the formation of catalytic active intermediates. At temperatures studied, the catalytic active intermediates seemed to be always present and the catalysis progresses unhindered due to the redox cycle, resulting in high rates and conversion.

Comparison of Gamma Irradiated and Raw Lignite in Bioliquefaction Process by Fungus T5

The bioliquefaction of coal is a processing technology for converting solid coal to liquid oil at ambient temperature by helping microorganism. The pretreated of lignite is important to decrease the hydrofobic of lignite surface. One of pretreated method was irradiation by gamma rays. Aim of this research was to compare the gamma irradiated lignite and raw lignite in bioliquefaction process by selected fungus T5. The fungus was identified by molecular method using 18S rDNA. Treatments were A (MSS + gamma irradiated lignite 5% + T5) and B (MSS + raw lignite 5% + T5) and culture type was sub-merged. The parameters observed were colonization, bacterial and fungal enumeration, identify of dominant bacteria using 16S rDNA and characterization of bioliquefaction product by UV-Vis spectroscopy dan gas chromatography – mass spectrometry (GCMS). The results showed that fungus T5 belongs to Ascomycota, Trichoderma asperellum . Fungus has the ability to growth and liquefy gamma irradiated and raw lignite. Bacteria were detected in raw lignite treatment and dominant bacteria were identified as Bacillus megaterium and Bacillus thuringensis . UV-Vis analysis showed that boliquefaction product mainly contained naphtacene, naphthalene, and anthracene for gamma irradiated lignite, but anthracene and benzene for raw lignite. For GCMS analysis, 22 and 38 compounds were identified for gamma irradiated and raw lignite. Both treatment had different number of hydrocarbon, i.e. C 6 – C 35 (A) and C 10 – C 35 (B) and dominated by aromatic acids, aliphatic and phenylethers. Percent area of gasoline (C 7 – C 11 ) and diesel (C 10 – C 24 ) fractions on the treatment B was 7.23% and 62.35%, while in treatment A was 7.22% and 44.27%. Based on the results, pretreated of lignite by gamma irradiation could be increased the bioliquefaction product. Received: 5 December 2011; Revised: 21 May 2012; Accepted: 11 June 2012

Characterisation of lignite as an industrial adsorbent

An alternative use of the abundant and inexpensive lignite (also known as brown coal) as an industrial adsorbent has been characterised. The adsorptive properties of two Victorian lignite without any pre-treatment were investigated using the cationic methylene blue dye as a model compound in aqueous solutions. Two commercial activated carbon products were also studied for comparison. The adsorption equilibrium of the four adsorbents was better described by the Langmuir isotherm model than the Freundlich model. The adsorption capacities of the two untreated lignite adsorbents, Loy Yang and Yallourn, calculated using Langmuir isotherms were 286 and 370mg/g, respectively, higher than a coconut shell-based activated carbon (167mg/g), but lower than a coal-based activated carbon (435mg/g). Surface area results suggested that larger micropores and mesopores were important for achieving good methylene blue adsorption by the activated carbons. However, FTIR and cation exchange capacity analyses revealed that, for the lignite, chemical interactions between lignite surface functional groups and methylene blue molecules occurred, thereby augmenting its adsorption capacity.