Pyrite Removal Research Articles

The effect of acid treatment on the removal of pyrite in coal

The effect of acid treatment on the removal of pyrite in coal

00/03067 Pyrite removal from Illinois #6 coal by CrCl 2 reduction and effect of pyrite on the coprocessing of Illinois #6 coal with waste automotive

00/03067 Pyrite removal from Illinois #6 coal by CrCl 2 reduction and effect of pyrite on the coprocessing of Illinois #6 coal with waste automotive

00/01766 PET coprocessing with Yallourn brown coal under hydroliquefaction conditions

Pyrite was removed from Illinois #6 coal by HF/HCl washes and by CrCl2 reduction. The effect of pyrite on the coprocessing of Illinois #6 coal with waste automotive oil was investigated. ICP results show that the standard HF/HCl treatment still leaves about 65% of the pyrite in the Illinois #6 coal, but acidic CrCl2 reduction can remove 95.9% of the pyrite from the same coal without causing significant alteration of the organic matter as shown by examination of samples before and after treatment by infrared and 13C NMR spectroscopy as well as by atomic ratios (H/C, N/C and Sorganic/C). XPS results show that compared to untreated Illinois #6 coal, the inorganic composition on the surface of CrCl2 treated Illinois #6 coal changes very little except for loss of pyrite, whereas the inorganic composition of HF/HCl treated Illinois #6 coal changes substantially. A comparison between untreated coal and CrCl2 treated Illinois # 6 coal was made by TOF-SIMS (Time-of-Flight Secondary-Ion Mass Spectroscopy). Nearly total removal of pyrite from Illinois #6 coal by CrCl2 decreases the conversion yield of the coal to THF solubles to 16.2%, compared to 60.9% for untreated Illinois #6 coal and 53.4% for HF/HCl treated Illinois #6 when each of these coals is coprocessed with waste automotive oil under the same reaction conditions. This comparison of conversion yields of the coal further supports the conclusion reached previously that pyrite functions as a catalyst aiding in dissolution of the coal to form gas, oil, asphaltenes and char.

Biochemical removal of HAP precursors from coal — INEEL slurry column testing

A combined physical/biochemical process for the precombustion removal of 13 inorganic hazardous air pollutant (HAP) precursors, i.e., Sb, As, Be, Cd, Cr, Cl, Co, F, Pb, Hg, Mn, Ni and Se, from coal was tested. Biochemical processes for removal of HAP precursors from coal potentially offer advantages of deeper cleaning, more specificity and less coal loss. The slurry column is a second-generation process for the beneficiation of fine (60-mesh × 10µm) coal by a combination of physical separation of mineral matter and biooxidation of pyrite. Sixty-seven percent removal of pyrite from a 60-mesh Pittsburgh #8 coal was achieved at a 35% (w/w) slurry concentration and a five-day reactor residence time. Ninety percent of the heating value of the feed coal was recovered. Among the HAP precursors of most concern, over half of the Se, As and Hg were removed from the feed coal. From 40% to 70% of most HAP precursors were removed from the feed coal. Hg in the feed coal was reduced from 0.12 to 0.054 µg/g in the product coal, while waste coal contained 0.24 µ/g.

Pyrite removal from Illinois #6 coal by CrCl2 reduction and effect of pyrite on the coprocessing of Illinois #6 coal with waste automotive oil

Abstract Pyrite was removed from Illinois #6 coal by HF/HCl washes and by CrCl 2 reduction. The effect of pyrite on the coprocessing of Illinois #6 coal with waste automotive oil was investigated. ICP results show that the standard HF/HCl treatment still leaves about 65% of the pyrite in the Illinois #6 coal, but acidic CrCl 2 reduction can remove 95.9% of the pyrite from the same coal without causing significant alteration of the organic matter as shown by examination of samples before and after treatment by infrared and 13 C NMR spectroscopy as well as by atomic ratios (H/C, N/C and S organic /C). XPS results show that compared to untreated Illinois #6 coal, the inorganic composition on the surface of CrCl 2 treated Illinois #6 coal changes very little except for loss of pyrite, whereas the inorganic composition of HF/HCl treated Illinois #6 coal changes substantially. A comparison between untreated coal and CrCl 2 treated Illinois # 6 coal was made by TOF-SIMS (Time-of-Flight Secondary-Ion Mass Spectroscopy). Nearly total removal of pyrite from Illinois #6 coal by CrCl 2 decreases the conversion yield of the coal to THF solubles to 16.2%, compared to 60.9% for untreated Illinois #6 coal and 53.4% for HF/HCl treated Illinois #6 when each of these coals is coprocessed with waste automotive oil under the same reaction conditions. This comparison of conversion yields of the coal further supports the conclusion reached previously that pyrite functions as a catalyst aiding in dissolution of the coal to form gas, oil, asphaltenes and char.

Reduction of high-sulphur coal in the potassium–liquid ammonia system

Polish high-sulphur coal was twice subjected to reduction in the potassium–liquid ammonia system. The process was carried out on both raw and demineralised coal. Elemental and spectral analyses of the initial coal and the reduction products were performed. Different forms of sulphur found in the samples were studied by the classical chemical methods and by atmospheric pressure–temperature programmed reduction (AP–TPR). The effect of reduction on particular sulphur compounds is discussed. It was found that reduction in the potassium–liquid ammonia system led to cleavage of C–S bonds, appearance of thiol groups, and the partial removal of pyrite and sulphates from the coal whereas the content of elemental sulphur did not change significantly.

Desulfurization of pittsburgh coal by microbial column flotation

Microbial column flotation usingThiobacillus ferrooxidans was applied for desulfurization of Pittsburgh coal of CWM (Coal-Water Mixture) size between 38 μm and 75 μm. The coal contained ferrous ion which would interfere separation of pyrite from coal by microbial flotation. The wash-out of ferrous ion with 0.5N HC1 solution enabled pyrite removal from coal. The coal was divided into two parts, the small-size coal between 38 μm and 53 μm, and the large-size coal between 53 μm and 75 μm. The pyritic sulfur content was decreased from 2.88% of the feed coal to 0.98% of the product coal for the largesize coal and from 2.77% of the feed coal to 1.12% of the product coal for the small-size coal by microbial flotation. The decrease was based on removal of liberated pyrite particles (between 20 μm and 70 μm). However, the fine particles (less than 20 μm) could not be removed even though the pyrite particles were liberated from coal particles. The microbial column flotation was more effective for desulfurization of the large liberated pyrite particle than that of the small. It was not effective for desulfurization of the locked pyrite particles that were buried in coal particles. Both the pyrite liberation from coal and its particle size are important factors for the pyrite removal by microbial column flotation.

97/03506 Electrostatic apparatus for cleaning of coal powder with removal of pyrite, ash, and toxic minerals

97/03506 Electrostatic apparatus for cleaning of coal powder with removal of pyrite, ash, and toxic minerals

97/03512 Flotation of oil-agglomerated coal for ash and pyrite removal—simultaneous grinding and agglomeration

97/03512 Flotation of oil-agglomerated coal for ash and pyrite removal—simultaneous grinding and agglomeration

97/02594 Pyrite removal from coal by microbial leaching

97/02594 Pyrite removal from coal by microbial leaching

96/03547 Flotation of oil-aggiomerated coal for ash and pyrite removal

Low-rank/oxidized coals respond poorly to oil agglomeration. Emulsification of kerosene in the presence of surfactants dramatically reduces the size of the kerosene droplets, lowering the consumption of kerosene needed to agglomerate oil down to 0.25–0.5%. Surfactants can also entirely change the interaction between oil droplets and coal particles. Consequently, kerosene cationic emulsions can efficiently agglomerate oxidized coal particles. The agglomerates obtained in such a process can still be recovered by screening.

Refinement of low-grade clay by microbial removal of sulfur and iron compounds using Thiobacillus ferrooxidans

The refinement of low-grade clay, of which impurities are mainly sulfur and iron compounds, is required because of the recent shortage of high-grade clay for manufacturing of structural ceramics. The major impurity compound contained in the low-grade clay we treated was identified as pyrite by X-ray powder diffraction and inductively coupled plasma analyses. The well-formed crystals of pyrite had a framboidal form of 1 μm–20 μm diameter. The microbial removal of pyrite from the low-grade clay was investigated by using a sulfur and iron-oxidizing bacterium, Thiobacillus ferrooxidans. About 82–90% of the pyrite was removed in 5–12 d for pulp densities up to 70% (w/v). The removal rate of pyrite ranged from 270 to 914 mg-pyritic sulfur/ l·d depending upon clay pulp density. The rate of pyrite removal (r) could be expressed as a function of pyritic sulfur concentration (S): r (mg-pyritic sulfur/ l·h) = 1.96 × 10 −2 S (mg-pyritic sulfur/ l). The logarithm of the amount of oxidized pyrite per unit volume and the final pH in the reaction medium were found to have a linear relationship which could be expressed as pH = 2.43–0.55 log [FeS 2 (mM)]. With the refined clay no red color due to the presence of pyrite was developed after firing, and its whiteness was similar to that of a high-grade clay.

Combined physical/microbial beneficiation of coal using the flood/drain bioreactor

The flood/drain reactor consists of a bed of intermediate-sized coal (roughly 0.5 to 5 mm) periodically fluidized by pumping in a mixed bacterial culture. Metabolic products and coal fines are washed out of the bed, and large pyritic inclusions and other dense mineral matter tends to settle to the base of the bed. Draining the bed then draws in fresh air for subsequent pyrite removal by microorganisms. Experiments on a laboratory-scale bed, 10.2 cm diameter with two 12 × 30 mesh Illinois # 6 coals and a 1 4 in. × 28 mesh Pittsburgh # 8 coal showed that up to 80% pyrite removal could be achieved in four weeks by this combination of physical separation and microbial activity. Operational problems included removal of fines from the bed during start-up and the appearance of acidophilic protozoa grazing on the pyrite-oxidizing bacteria. Significant improvement in performance is anticipated by eliminating the lag-phase of the sulfur-oxidizing bacteria and optimizing the timing of the flood/drain cycles.

The Porto Torres biodepyritization pilot plant: Light and shade of one year operation

The nominal 50 kg h −1 dry coal biodepyritization pilot plant was built at Porto Torres (Sassari, Italy) in the area of EniChem S.p.A. Chemical Works, with financial support of the Commission of European Communities and with the participation of the DMT of Essen (Germany), the Mining and Mineral Processing Department of the University of Cagliari (Italy), the Technical University of Delft (The Netherlands) and the Warren Spring Laboratory of Stevenage (UK). The plant went on stream in early September 1992. Test runs were carried in the range 6.5–41.5% solids concentration. For every solids concentration the steady state was attained in about 10 d. For all the test runs the assays showed that more than 90% pyrite removal is achieved in the first five bioreactors; for a pulp flow rate of 6.94 × 10 −2 dm 3 s −1, (250 l h −1) and useful bioreactor volume of 7.5 m 3, this corresponds to a residence time of 540 345 s, i.e., 6.254 d, and to a pyritic iron biosolubilization rate of 36 mg dm −3 h −1. The pyrite biosolubilization rate constant is 1.53 × 10 −2 h −1. The power input per bioreactor operating on a 40% solids pulp is 4 kW with cos Φ = 0.76. Hence, the power required for processing 100 kg h −1 coal at 40% solids in the bioreactor section is 4 × 5 = 20 kW h, i.e. 200 kW h per tonne dry coal.

Desulfurization of coal by microbial column flotation

Twenty-three strains capable of oxidizing iron were isolated from coal and ore storage sites as well as coal and ore mines, volcanic areas, and hot spring. Four strains were found to have high iron-oxidizing activity. One strain (T-4) was selected for this experiment since the strain showed the fastest leaching rate of iron and sulfate from pyrite among the four strains. The T-4 strain was assigned for Thiobacillus ferrooxidans from its cultural and morphological characteristics.Bacterial treatment was applied to column flotation. An increase of cell density in the microbial column flotation resulted in the increase of pyrite removal from a coal-pyrite mixture (high sulfur imitated coal) with corresponding decrease of coal recovery. The addition of kerosene into the microbial column flotation increased the recovery of the imitated coal from 55% (without kerosene) to 81% (with 50 microL/L kerosene) with the reduction of pyrite sulfur content from 11% (feed coal) to 3.9% (product coal). The kerosene addition could reduce the pyritic sulfur content by collecting the coal in the recovery. However, the addition could not enhance separation of pyrite from the coal-pyrite mixture, since pyrite rejection was not affected by the increase of the kerosene addition. An excellent separation was obtained by the microbial flotation using a long column which had a length-diameter (L/D) ratio of 12.7. The long column flotation reduced the pyritic sulfur content from 11% (feed coal) to 1.8% (product coal) when 80% of the feed coal was recovered without the kerosene addition. The long column flotation not only attained an excellent separation but also reduced the amount of cells for desulfurization to as little as one-tenth of the reported amount.

Managing hazardous air pollutants: state of the art

Managing hazardous air pollutants: state of the art

Microbial coal desulfurization in an airlift bioreactor by sulfur-oxidizing bacterium thiobacillus ferrooxidans

Microbial desulfurization of a domestic anthracite coal by using an acidophilic, sulfuroxidizing bacterium, Thiobacillus ferrooxidans has been studied in an airlift slurry reactor of 12 L volume. Effects of coal slurry density and CO 2 supplement on microbial pyrite removal have been evaluated. High sulfur removal rates have been obtained even for very high coal slurry densities (up to 70% w/v). About 90 ∼ 95 % of the sulfur in the coal could be removed in 15 ∼ 20 days. The efficiency of microbial desulfurization was significantly improved with CO 2 enriched air supply for high coal slurry densities.

Determination of organic/inorganic associations of trace elements in kerogen of the New Albany shale

The inorganic and organic associations of trace elements in the kerogen of the New Albany shale were studied by analysis of kerogen fractions and a mineral residue (~85% FeS 2) obtained by density separations. The degree of association of As, Co, Mn, Ni, Sb and Se with pyrite and/or marcasite (FeS 2) was determined by the analysis of individual mineral grains by electron microprobe X-ray fluorescence (EMP-XRF) analysis and by analysis of the mineral residue treated with dilute HNO 3 to remove pyrite and marcasite. The association of several other elements in minerals which are insoluble in dilute HNO 3, such as rutile and chalcopyrite, were also determined. The results of these studies indicate an essentially total organic association for V and approximately 95% organic association for Ni in New Albany kerogen. Methods to correct for inorganic contributions based on low-temperature ashing, chemical removal of pyrite, EMP-XRF and physical methods of separation are compared.

Pyrite removal from kerogen without altering organic matter: the chromous chloride method

The standard hydrochloric/hydrofluoric acid treatment used to remove most minerals in kerogen preparation often leaves abundant pyrite. This pyrite is a major obstacle to establishing elemental composition and functional group distributions in kerogen by both chemical and spectroscopic techniques. Quantitative pyrite removal by other conventional means such as nitric acid, lithium aluminum hydride, and sodium borohydride has not been possible without objectionable alterations of the organic matter. Experiments reported here demonstrate that acidic chromous chloride reduction can remove pyrite quantitatively without causing significant alteration of the organic matter

Mechanism of microbial flotation using Thiobacillus ferrooxidans for pyrite suppression

Microbial desulfurization might be developed as a new process for the removal of pyrite sulfur from coal sluries such as coal-water mixture (CWM). An application of iron-oxidizing bacterium Thiobacillus ferrooxidans to flotation would shorten the periods of the microbial removal of pyrite from some weeks by leaching methods to a few minutes. The floatability of pyrite in flotation was mainly reduced by T. ferrooxidans itself rather than by other microbial substances in bacterial culture as additive of flotation liquor. Floatability was suppressed within a few seconds by bacterial contact. The suppression was proportional to increasing the number of cells observed between bacterial adhesion and the suppression of floatability. If 25% of the total pyrite surface area covered with the bacteria, pyrite floatability would be completely depressed. Bacteria that lost their iron-oxidizing activities by sodium cyanide treatment were also able to adhere to pyrite and reduced pyrite floatability as much as normal bacteria did. Thiobacillus ferrooxidans ATCC 23270, T-1, 9, and 11, which had different iron-oxidizing abilities, suppressed floatability to similar-levels. The oxidizing ability of bacteria did not influence the suppressing effect. These results showed the mechanism of the suppression of pyrite floatability by bacteria. Quick bacterial adhesion to pyrite induced floatability suppression by changing the surface property from hydrophobic. The quick adhesion of the bacterium was the novel function which worked to change the surface property of pyrite to remove it from coal.