Alberta Subbituminous Coal Research Articles

Potential of Air Dense Medium Fluidized Bed Separation of Mineral Matter for Mercury Rejection from Alberta Sub-Bituminous Coal

In this study, three basic conditions for efficient dry separation of mineral matter from coal by an air dense medium fluidized bed (ADMFB) separator were assessed. The optimal fluidization air velocity for ADMFB separation was found to be insensitive to particle sizes of feed examined. The suitability of using an ADMFB separation to co-reject mercury with mineral matter was demonstrated. A strong linear relationship between mercury content and mineral matter content was confirmed for two of the three actively mined seams of this sub-bituminous coal. Following ADMFB separation, the linear fit of mercury rejection and ash rejection led to a coefficient of determination ranging from 0.98 to 0.86. In one of the coal seams studied, a mercury rejection of 58% and a mineral matter rejection of 60% were achievable at a total combustible recovery of 87% at optimized fluidization air velocity.

Mercury Removal Characteristics during Thermal Upgrading of Fractionated Alberta Subbituminous Coal

In response to mercury emission control from coal combustion flue gases, coal cleaning and thermal upgrading are being considered as precombustion mercury emission control options. In our previous study, dry coal cleaning using an air dense medium fluidized bed (ADMFB) was shown to reject a substantial fraction of mercury in original coal while retaining acceptable combustible recovery. In this study, mercury removal characteristics by thermal upgrading were studied using Alberta subbituminous coals fractionated by a air dense medium fluidized bed (ADMFB). It was found that the bottom 28% of the run-of-mine coal cleaned by ADMFB separator contained over 57% ash-forming mineral matters and 46% mercury. Mercury removal from this fraction of coal increased rapidly at temperatures over 206–329 °C. During thermal upgrading, the mass of coal decreased and the calorific values increased with increasing upgrading temperature. The observed weight loss and increase in the calorific value of upgraded coal at temperatures between 106 and 329 °C were attributed mainly to the evaporation of moisture which does not contribute to calorific value, with a small amount to the loss of combustible volatiles.

Comparison of calculated mercury emissions from three Alberta power plants over a 33 week period – Influence of geological environment

Feed coals and fly ashes from two coal-fired power plants burning Alberta subbituminous coal were analyzed for C, Cl, Hg, and S and calorific values (for feed coal only), every week for a period of 33 weeks. The feed coals used in this study were deposited in brackish water and are compared to the coals deposited in a freshwater environment. The Hg and char (unburnt carbon) content of the fly ash was monitored to determine the variation of Hg and its possible relationship to the char types in the fly ash. The feed coals have Hg content of 0.026–0.089 mg/kg and their fly ash contains 0.02–0.243 mg/kg of Hg. The C content of the fly ashes ranges from 0.15% to 0.51%. The carbon/char was separated from the fly ash using HF and HCl. Reactive vitrinitic (formed from woody part of plants) and less reactive inertinitic (natural char) chars were separated by density separations of various specific gravities using ZnBr 2. The char is mostly reactive vitrinitic (67–80 vol.%). Both stations have similar range of C content for their respective fly ashes. However, station 2 shows a much wider range of Hg in fly ash compared to station 1. In general, the fly ash from coal deposited under brackish water environment (stations 1 and 2) appears to have same or higher Hg content for lower C content compared to the fly ash from coal deposited under fresh water environment. The calculated emitted Hg for the period of 33 weeks for station 1 is estimated to be 64–90% of the total input of Hg with an average of 74%. The calculated emitted Hg shows a more complex pattern for station 2 and falls into two groups; with group (a) showing higher enrichment index for both Hg and S. The calculated emitted Hg for this group is 43–74% with an average of 57%, indicative of more Hg being captured by fly ash, possibly due to interaction between Hg and S. In the second group (b) the emitted Hg is calculated to be 74–95% with an average of 85%. The relative enrichment of both Hg and S in group (b) is low compared to group (a), indicative of possible slight paleo-weathering of the feed coal. The present study indicates that geological parameters such as paleo weathering and also depositional environment of the feed coal may influence the Hg content of fly ash.

An Investigation on Mercury Association in an Alberta Sub-bituminous Coal

There are various mercury species in nature. Understanding mercury association with coal components could play a critical role in controlling mercury emission from coal utilization. In this study, an Alberta sub-bituminous coal was fractionated into various size and density fractions. The mercury and sulfur contents in each fraction were determined. To identify mercury association with coal components, the fractionated coal samples before and after low-temperature ashing were characterized by an X-ray diffractometer. Our study showed a clear correlation between the mercury and ash contents of coal. Such a relation was not observed between the mercury and sulfur contents. The potential to remove mercury prior to coal utilization by ash rejection using an air dense medium fluidized bed separator was demonstrated. At a combustible recovery of 81%, an ash rejection of 55% was achieved, leading to a mercury rejection of 56%.

Parameters influencing the variation in mercury emissions from an Alberta power plant burning high inertinite coal over thirty-eight weeks period

Feed coals and fly ashes from a coal-fired power station burning Alberta subbituminous coal were examined for a period of thirty-eight weeks to determine the variation in emitted mercury. Feed coal samples were analyzed for proximate, calorific value and Hg content, while fly ash samples were examined for C and Hg contents. The maceral content of the feed coal was also determined. The emitted mercury was calculated and compared to mercury emitted from the stack according to a mass-balance calculation from a previous study for the same station. Mercury contents ranged from 0.029 to 0.066 mg/kg for feed coal, and from 0.069 to 0.112 mg/kg for fly ash. The carbon/char in fly ash was separated into reactive (vitrinitic/bimacerate) and less reactive (inertinitic) chars using ZnBr 2 at specific gravities of 1.7, 2.0, and 2.25 to 2.4. The result shows that there is a positive correlation between the carbon and mercury content of the fly ash. The reactive char particles in the fly ash may be responsible for the capture mercury in fly ash. The percentage of estimated captured mercury by fly ash increases with increasing carbon content (%) in fly ash. The percentage of emitted mercury for the period of 38 weeks is estimated to be within the range of 49% to 76% of the total input of mercury.

Fundamental Study on Mercury Release Characteristics during Thermal Upgrading of an Alberta Sub-bituminous Coal

An Alberta sub-bituminous coal was tested for the level of mercury removal obtained by a low-temperature thermal upgrading. The mercury removal characteristics, relative to increasing temperature and upgrading time, were determined. Rapid thermal upgrading at 400 °C released ∼72% of the mercury in the original coal, with a negligible total thermal energy loss. A corresponding increase in the calorific value of the upgraded coal was observed, from ∼20 900 kJ/kg to 25 900 kJ/kg. A further increase in the upgrading temperature, from 400 °C to 600 °C, produced only a minimal further increase in mercury removal. Rapid thermal upgrading at 400 °C resulted in a higher mercury removal efficiency than the temperature-programmable thermal upgrading. Thermal upgrading of sub-bituminous coal could be considered to be a viable option for mercury emission control. A volume reaction model of a first-order process was applied to simulate mercury removal from coal during the thermal upgrading. A comprehensive time constan...

Steady-State Gasification of An Alberta Subbituminous Coal in a Microfluidized Bed

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSteady-State Gasification of An Alberta Subbituminous Coal in a Microfluidized BedZ.-G. Zhang, D. S. Scott, and P. L. SilvestonCite this: Energy Fuels 1994, 8, 3, 637–642Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/ef00045a019RIGHTS & PERMISSIONSArticle Views133Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (662 KB) Get e-Alerts Get e-Alerts

Alberta's Sub-Bituminous Coal – Building on its Strengths

The 1973 decision to base Alberta's electrical generation on sub-bituminous coal has provided a balance between economic, environmental and social goals in the province. Presently six strip mines produce more than 22 million tonnes of low-sulphur coal for 6 thermal stations that generate 90% of the province's electricity needs. Alberta has relatively low-cost power, high coal-related job creation and an industry meeting the goals of sustainable development.

Evidence for methane reactivity during coal pyrolysis and liquefaction

Experiments were conducted to determine whether or not methane (natural gas) is an active hydrogenation gas for pyrolysis and liquefaction of Highvale (Alberta subbituminous) coal. Reactions were done under pressure in methane, hydrogen and argon gases in order to compare the toluene-soluble conversions. Tubing bomb micro-reactors were employed at 450 °C and 19–24 MPa. Tetralin was used as the donor solvent for the liquefaction runs and iron oxide was employed as the catalyst for the catalytic experiments. For comparison, a separate set of studies were conducted with standard samples of Illinois no. 6 bituminous coal under similar reaction conditions. The toluene soluble products were analysed by 1H n.m.r., g.c. and elemental analysis and the gases by g.c. The data for both coals show that under pyrolysis and non-catalytic liquefaction conditions, coal conversions to toluene soluble products were higher for the runs with hydrogen gas than the corresponding methane runs. However, coal conversions under methane gas pressures were higher than those observed in the runs under inert gas (argon) atmospheres, indicating some hydrogenation activity for methane. In the catalytic runs, methane conversions of Highvale coal were consistently higher than the hydrogen conversions while conversions of Illinois no. 6 coal were equivalent. The 1H n.m.r. analysis of the liquid products from both coals showed that the compositions of the oils observed in the hydrogen and methane runs are similar. G.c. analysis of the liquid products showed alkylation of the donor solvent in the presence of methane to give methyl and dimethyl products.

Agglomeration and coprocessing of Alberta subbituminous coal

Coal/oil agglomerates have been prepared from Alberta subbituminous coal and Alberta heavy oils. Pulverized coal, partially dried agglomerates and steam-stripped agglomerates showed similar process performance when subjected to coprocessing with a supported catalyst. The properties of the process derived non-distillable oils were similar irrespective of the feed pretreatment procedure. Clay and silica mineral matter in the coal had no observable catalytic effect.

The liquefaction of an Alberta subbituminous coal with hydrogenated bitumen

A series of experiments was conducted to examine the effectiveness of hydrogenated Athabasca bitumen for the liquefaction of an Alberta subbituminous coal. Hydrogenated bitumens were prepared by treatment with hydrogen and an alumina supported Ni/Mo catalyst under a variety of process conditions. Bitumen hydrogenated at 440 °C was shown to be a better coal liquefaction solvent, both in terms of coal conversion and distillate yields, than bitumen hydrogenated at 400 °C. Over 90 wt% of an Alberta subbituminous coal was solubilized at 440 °C using a 30 min residence time and a hydrogen pressure of 6.9 MPa in bitumen solvent that had been prepared by hydrogenation at 440 °C. Of the 72 wt% (based on total feed) distillate obtained from this experiment, 76% boiled below 343 °C and had S and N contents of 860 and 2300 ppm, respectively. Coal solubilization temperature was shown to have a significant effect on coal conversion.

Co‐processing of alberta subbituminous coal and bitumen in a semi‐continuous hot charge‐discharge unit

AbstractLiquefaction of an Alberta subbituminous coal (Highvale) with bitumen was studied using a semi‐continuous, two stage, hot charge‐discharge (HCD) unit. Experiments were performed using a CO/steam atmosphere in the first, and H2 atmosphere in the second stage. The second stage (hydrogenation) reactor input and output gas temperatures, compositions, reactor gas and liquid temperatures were measured during the reaction. In the numerical solutions of the mass and energy balance equations experimental data were used, and hydrogen consumption, heteroatom (O and S) removal, hydrocarbon gas production kinetic rate constants, and hydrogenation reaction enthalpy were determined.

SEPARATION OF MACERALS FROM SUBBITUMINOUS COALS AND THEIR RESPONSE TO LIQUEFACTION

ABSTRACT Separation of macerals from three Alberta subbituminous coals was investigated using float-and-sink method with dense liquids followed by the density gradient technique proposed by Dyrkacz and co-workers at Argonne National Laboratory, U.S.A. Resolutions of 90 percent or greater purity were obtained in some fractions in quantities sufficient to study their response to liquefaction. The ease of liquefaction of macerals isolated from subbituminous coals was, in descending order, liptinite, vitrinite, inertinite. Liquefaction of inertinite occurred at somewhat higher temperatures compared to that of vitrinite macerals which initiated between 350° and 400°C. Analysis of the chemical makeup of macerals from a subbituminous coal indicated that liptinite was relatively rich in hydrogen, whereas vitrinite and inertinite were relatively rich in oxygen and carbon respectively. The average densities were 1.285, 1.345 and 1.458 g/cc for liptinite, vitrinite, and inertinite respectively. X-ray diffraction and...

MASS TRANSFER LIMITATIONS IN COAL LIQUEFACTION

ABSTRACT In a number of contributions to coal liquefaction, gas–liquid mass transfer limitation has been referred by neglecting mass transfer limitation of solvent Into solid coal. Reported apparent activation energies of coal liquefaction reactions are In the range of 10–20 kCal/g–mole, which are too low for thermal reactions, Imply that diffusion Is the rate controlling step. In this study, the solvent diffusion effect on solvolysis of vitrinitic macerals In Alberta subbituminous coal has been studied, by performing petrographlc analyses of original coal and liquefaction residues. Quasi–steady state and transient coal–solvent diffusion-chemical reaction models are developed to Interpret the experimental data. Results indicate that solvent diffusion into the reactive maceral most likely be a rate limiting step In coal liquefaction.

Contribution of vitrinite macerals to the liquefaction of subbituminous coals

Four Alberta subbituminous coals were selected to investigate the contribution of vitrinite macerals to liquefaction. There are indications of a rectilinear correlation between conversion yields of different density fractions of coal and their vitrinite content, but it is too early to discern any conversion factor by which any maceral group may be used to predict the liquefaction behaviour of a subbituminous coal. Contrary to common belief, not all the vitrinite fraction of the feed coal is reactive. There seems to be a definite positive correlation between the percent vitrinite reacted and the liquefaction conversion yield. Much more research work is needed to further understand the contribution of vitrinite macerals to liquefaction of a subbituminous coal.

CO-PROCESSING OF ALBERTA SUBBITUMINOUS COAL WITH OIL SAND BITUMEN

Co-processing of six Alberta subbituminous coals and Suncor bitumen (Athabasca deposit) by using H/sub 2/ (Fe/sub 2/O/sub 3/ catalyst) and CO/steam (K/sub 2/CO/sub 3/ catalyst) as reducing atmospheres have been studied. Results show that CO/steam gives significantly higher overall conversion compared to H/sub 2/ with certain coals. However, the quality of products (as determined by distillation and subsequent extraction) are better when H/sub 2/ was used in the co-processing of coal with bitumen. A second stage catalytic hydrogenation is required to upgrade heavy hydrocarbons (extracts) which form almost 50% of the product.

COAL LIQUEFACTION RATE CONSTANTS MEASUREMENT

ABSTRACT Liquefaction data from tests on three Alberta sub-bituminous coals (Smoky Tower, Highvale, Vesta) using 130 ml autoclave have been used to predict the rate constants of various proposed models. Calculated rate constants are correlated with Arr-henius law. Results indicated that only coal to gas conversions are purely thermal reactions, while toluene and tetrahydrofuran (THF) extracts conversions are associated with gas-solvent-coal solvolysis.

MANAGEMENT OF COAL MACERALS IN THE LIQUEFACTION OF LOW RANK COALS

ABSTRACT Three Alberta subbituminous coals were selected to investigate the contribution of different macerals to liquefaction. These coals represent the full range of geographic, rank and geological variations present In the Alberta Plains Coal Region. In addition, for comparison, two U.S. lignites (Texas and North Dakota) were included in these investigations. To enhance maceral concentration, density fractionation was carried out on these samples. Though liquefaction yields appear to increase with increase in vitrinite (huminite) content, a clear-cut correlation between conversion and maceral content is not established because of (a) uncertain behaviour of semi-inert macerals and (b) differences in behaviour within the vitrinite (huminite) macera1 group.

Low Temperature Carbonization of Alberta Subbituminous Coal - Results of Preliminary Tests of the New Stansfield Report

Low Temperature Carbonization of Alberta Subbituminous Coal - <i>Results of Preliminary Tests of the New Stansfield Report</i>