Article

Laboratory and Semi-Pilot Bioreactor Feasibility Tests for Desulphurization of Turkish Lignite using Leptospirillum ferriphilum

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Abstract

The low rank coal lignite stands out to be a profuse source of energy in Turkey and accounts for nearly 43% of its total fossil fuel production. However, the high sulfur content associated with lignite averts its application in several sectors due to various health and environmental issues. In the present work, biodesulphurization of Turkish lignite was studied in 1 and 20 L aerated bioreactors using an iron oxidizing acidophile, Leptospirillum ferriphilum (L. ferriphilum). Additionally, the effect of Span 80 (S80) on biodesulphurization of the sample was studied, under the optimum concentration derived from our previous shake flask study, in order to notice its effect under scale-up aerated bioreactor conditions. Under lab scale (using 1 L bioreactors), in the absence of S80, L. ferriphilum could desulphurize a maximum of 65.6% sulfur from the lignite sample, while 56% desulphurization was achieved in the presence of 0.05% (v/v) S80. Further scale-up studies under semipilot conditions (in 20 L reactors) indicated a maximum desulphurization of 63% from the sample in absence of S80. The pH, oxidation–reduction potential (ORP), and Fe2+ iron and total iron concentrations were periodically monitored in all the reactors during the course of the experiments. XRD and FTIR characterization of the lignite samples pre and post biodesulphurization provided valuable information on the structural and phase changes due to the microbial action.

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... Mesophilic acidophiles can grow at optimum conditions of temperature ranging 20-40ºC and at a pH range of 1.5-2.5. This group of microorganisms include (to name a few) Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans and Leptospirillum ferriphilum, that have been widely used in bioleaching studies (Mishra et al. 2018c;Panda et al. 2013;Sukla et al. 2014). The genus Acidithiobacillus is comprised of gram-negative, rod-shaped, autotrophic bacteria with a size of about 0.4 × 2 µm. ...
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The effects of surfactant Tween-80 on the growth, sulfur oxidation, and expression of selected typical sulfur metabolism relevant genes of Acidithiobacillus ferrooxidans ATCC 23270 were investigated. The results showed that in the presence of 10−2 g/L Tween-80, the growth of A. ferrooxidans and its metabolism on the insoluble substrate S0 and CuFeS2 were promoted. After 24 d of bioleaching, the copper extraction yield of chalcopyrite at 10−2 g/L Tween-80 increased by 16% compared with the bioleaching experiment without Tween-80. FT-IR spectra analysis revealed that the result was probably caused by the extracellular polymeric substances whose composition could be changed by the surfactant addition. RT-qPCR was used to analyze the differential expressions of 17 selected sulfur metabolism relevant genes in response to the addition of Tween-80. Down-regulation of the extracellular protein genes indicated the influence of Tween-80 on bacteria-sulfur adsorption. Variation of the expression level of the enzymes provided a supplement to sulfur metabolism investigation.
Article
The biodesulfurization capability of a strain having sulfur and iron metabolism isolated from acidic mine drainage of Balya (Balikesir, Turkey) was studied. Molecular identification of the 16S rRNA gene showed that this bacterium was a strain of Acidithiobacillus ferrivorans. Desulfurization optimization experiments were performed by Taguchi’s method. Statistical experimental arrangement L16 (45) was prepared to determine optimum sulfur removal. The optimum conditions for these parameters were found to be pH of 2.5, inoculum amount of 2%, pulp density of 1%, particle size of −500 + 250 μm, and incubation time of 14 days. A value of “Prob > F” less than 0.0500 indicates that model terms are significant. The obtained yields of total sulfur removal were approximately 33%. According to variance analysis, it was seen that all parameters were effective in removal of total sulfur. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses also indicated a modification of the coal surface after biodesulfurization. The redox potential was measured as 818 mV (7 days) and 788 mV (14 days) during the biodesulfurization experiment by the Pt–Ag/AgCl system of cyclic voltammetry, which suggested that the Fe3+/Fe2+ redox pair could be thermodynamically competitive with the O2/H2O couple as the electron acceptor during bacterial sulfur oxidation, demonstrating that S0 oxidation was coupled with Fe3+ reduction. Thermogravimetry, differential thermal analysis, and differential thermogravimetry curves for untreated and biotreated coal showed the differences in combustion profiles, possibly relating to structural alterations derived from biotreatments.
Article
A total of 48 samples, feed (run-of-mine) coals and their combustion residues (fly ash and bottom ash) were systematically collected twice a week over a 4 week period (June 1998) from two boiler units (I and II) of the Cayirhan power plant (630 MW) that burns zeolite-bearing coals of late Miocene age. The feed coals are high in moisture (22.8% as-received) content and ash (44.9%) yield and total S content (5.1%), and low in calorific value (2995 kcal/kg). The mineralogy of the feed coals contains unusually high contents of the zeolites (clinoptilolite/heulandite and analcime), which are distributed within the organic matter of coal. Other minerals determined are gypsum, quartz, feldspar, pyrite, dolomite, calcite, cristobalite and clays. Common minerals in the crystalline phase of the combustion residues are anhydrite, feldspar, quartz, hematite, lime and Ca–Mg silicate. Minor and trace amounts of magnetite, cristobalite, maghemite, gehlenite, calcite and clinoptilolite/heulandite are also present in the combustion residues. Trace element contents of the feed coals, except for W, fall within the estimated range of values for most world coals; however, the mean values of Mn, Ta, Th, U and Zr are near maximum values of most world coals. Elements such as As, Bi, Ge, Mo, Pb, Tl, W and Zn are enriched more in the fly ash compared to the bottom ash.
Article
This study has two aims: to improve the biodesulphurization of a semi-anthracite by packed-column leaching by reducing the insoluble sulphate on the coal surface, and to determine whether after the combustion of treated and untreated coal, sulphate sulphur is transformed completely into sulphur dioxide or part remains in the ashes without reacting. Combustion tests were analysed by TG-MS. To reduce the precipitation of salts, two parameters are worked on: solution pH, which is reduced to 1.3, and the idle time between washes (ITBW), which is altered. After 125 days of treatment, comparison with the results of previous studies showed that the precipitated salt content was reduced pyritic desulphurization was increased up to 43%, and total desulphurization to 24%.
Article
The biodesulphurisation of coal carried out in pile could be an interesting option to clean coal. In view of the good results obtained in biodesulphurisation test column at lab scale on a sample of semianthracite coal that proceed of an industrial plant with a high sulphur content, mainly pyritic sulphur, the feasibility of the process at pilot plant scale was studied. The pile was formed with 6ton of gravity middlings coal sample with a grain size −12+0.5mm from S.A. Hullera Vasco-Leonesa industrial plant. The coal has a total sulphur content of 3.78% and a pyritic sulphur content of 2.88%, the rest of sulphur is organic sulphur. The biodesulphurisation process in pilot plant follows three stages: stabilization of the pile, biodesulphurisation and washing. Heap was sampled twice during stabilisation stage, at the end of desulphurisation process and finally once washed. A pyritic sulphur removal of 39% and total sulphur removal of 23% was obtained. To complete the bioleaching process, the treatment of purge of leachate was carried out with the objective to recycling to head of process. The best treatment was a pre-treatment of the leachate until pH 4, and further treatment by reverse osmosis of the clarified water. Comparing this process with conventional precipitation to reach disposal limits, the reagents consumption and sludges were reduced considerably and due to the high quality of permeate it permits to recycle it to head of process.
Article
The effects of inoculum percentage, initial pH, growth temperature, shaking rate, substrate type and initial substrate concentration on the growth kinetics of Rhodococcus rhodochrous, a sulfur-removing bacterium, were investigated. The optimum value for each parameter that favoured the maximum specific growth rate was calculated from models established through linear of non-linear regression of the relevant data. Around these optima, biodesulfurization experiments were performed with sterile lignite. An increase in sulfate, pyritic and organic sulfur reduction with increasing reaction time were observed. The highest decreases in the total (30.2%) and organic sulfur (27.1%) contents were obtained with Mengen lignite at 75 h of biodesulfurization.
Article
With an increase in environmental degradation, the environmental norms are becoming more and more stringent day by day. Research work is currently being undertaken around the world to bring about deeper desulfurization of crude oils. Presently, two crude oil samples, i.e., heavy crude oil (HCO, 1.88% S) and light crude oil (LCO, 0.378% S) were procured from a local petroleum refinery. Bio-desulfurization (BDS) of LCO using Pantoea agglomerans D23W3 resulted in 61.40% removal of sulfur, whereas HCO showed 63.29% S removal under similar conditions. The use of P. agglomerans D23W3 under anaerobic conditions showed marginally better results than those under aerobic conditions. However, the use of thermophile Klebsiella sp. 13T resulted in 62.43% S removal from LCO and 68.08% S removal from HCO. Studies have also been extended on the use of reactive adsorption techniques for the removal of sulfur from crude oils. Among all of the different adsorbents studied, residual coal obtained after the solvent extraction of Samla coal showed the maximum removal of sulfur, i.e., 78.90% from LCO and 74.46% from HCO. Hydro-desulfurization is an established technology for the deep desulfurization of petroleum and its products. Widening the choice and exploring further developments in deeper desulfurization of petroleum alternative technologies may also be developed. Comparative studies were extended on the use of BDS, reactive adsorption, oxy-desulfurization, photo-desulfurization, and solvent extraction for the removal of sulfur from HCO and LCO. Among all of these techniques, oxy-desulfurization was found to be the best. To study the deep desulfurization of LCO and HCO, two- and three-step integrated processes were developed for the removal of sulfur from HCO and LCO. BDS under anaerobic conditions followed by oxy-desulfurization followed by reactive adsorption integration resulted in maximum removal, i.e., 95.21% removal of sulfur from HCO and 94.30% removal of sulfur from LCO.
Article
In this paper, a two-step desulfurization process for high-sulfur coal was investigated. Two Chinese coals with the addition of 10 wt % potassium hydroxide or sodium hydroxide were pyrolyzed under an atmosphere of nitrogen or hydrogen in a fixed-bed reactor at 600 °C, and then the obtained chars were washed with hot water. The results indicated that, without the addition of an alkali component, the sulfur removal of these two coals by pyrolysis and hydropyrolysis is 40%−50% and the sulfur content of chars is reduced only slightly, in comparison with the original coals; with the addition of 10 wt % potassium hydroxide or sodium hydroxide into the original coals and the chars being washed with hot water, the sulfur removal is 70%−80% and the sulfur content in chars is reduced dramatically. The combustion behavior of chars was also investigated, using thermogravimetric analysis. The results showed that those chars that had an added alkali component and were subjected to water-washing were more reactive and can be burned more easily than those without added alkali, which was also confirmed by a kinetics analysis of char combustion.
Article
Chars and activated carbons were produced from raw, HCl-washed, and HCl/HF-washed Elbistan lignites at 700 °C, 800 °C, 900 °C, and 1000 °C. The pyrolysis and activation reactions increased the BET areas (m2/g carbon) of the acid-washed samples almost 10-fold. The increase of the BET areas (m2/g carbon) by increasing the temperature of pyrolysis or activation from 700 °C to 1000 °C was explained with the burn-out of carbon which led to the development of porosity. The values of the stacking heights, Lc of HCl/HF-washed samples seemed to increase from 1.0 nm to 1.5 nm, the average number of graphene sheets increased from 2.8 to 4.4, and the lateral size of the crystallites, La, increased very faintly from 5.0 nm to 5.5 nm when the pyrolysis temperature was increased from 700 °C to 1000 °C. Activation reactions performed at the same temperature range did not change the stacking heights. The values of Lc for activated HCl/HF-washed samples stayed almost constant in the same range as for the carbonized samples within 1.0−1.5 nm. This indicated that oxidative reactions during activation did not alter the stacking heights of the crystallites significantly in the temperature range of 700−1000 °C. The results presented in the present work can be considered as indications for the development of turbostratic (fully disordered) structures in the temperature range of 700−1000 °C.
Article
Experiments have been carried out to determine the effects of biodesulfurization time on the removal of sulfur constituents of six Turkish lignites by Sulfolobus solfataricus. The changes in sulfur content of Tuncbilek, Karliova, Beypazari, Can, Elbistan, and Mengen lignites are shown as functions of time. A decrease in all sulfur forms with increasing time was observed for each coal. The highest total and organic sulfur reductions were observed with Beypazari lignite as 57.1 and 47.8%, respectively. The influence of analyses of the original samples on total and organic sulfur reductions has been investigated through multiple linear regression analysis. The resulting determination coefficients are compared to obtain the beat fitting parameter set. For the six lignites the experimental values of total and organic sulfur reductions appeared to agree with the values calculated for the models.
Article
The purpose of the present work was to investigate the effect of the concentration of HI and reaction time in the chemical desulfurization of Cayirhan lignite in a microwave energy set up and to compare the results with those obtained in a thermal heating system. As the concentration of the HI was increased, the extent of desulfurization was also increased in all the experiments done for all of the samples of lignite. The main difference between the thermal and microwave heating was the extremely short times for desulfurization in the case of microwave experiments. After desulfurization experiments Stotal/C ratio of all of the samples decreased to a lower value than that of the raw lignite which was 0.034. The loss of the sulfur containing bands in the FTIR spectra of the desulfurized lignite showed that the HI treatment was effective in the cleavage of dithioethers and thioetheric groups. Sulfur containing functionalities like thioethers and thiols although usually requiring strong reducing agents could be removed in significant amounts with concentrated hydroiodic acid from the coal matrix. The rapidity of the desulfurization reactions with microwave heating in concentrated HI was probably due to localized superheating which made HI more effective in the reactions such as with thioethers and thiols that normally resisted to cleavage by HI under thermal heating conditions.
Article
Organic matter present in lignite samples collected from different depths (i.e. top, mid and bottom) of lignite source, Ilgın, Konya province, was examined by using subtractive-FTIR-ATR spectroscopy. FTIR spectra were recorded on (i) original samples, (ii) the samples dried at 105°C and (iii) the samples acid-treated and dried. After a combustion process performed for each sample at 650°C for 15min, the spectra of samples were recorded and subtracted from the spectra of untreated samples. Hence, a software-based subtraction made it possible to acquire a representative spectra related with organic matter. As the contribution of the bands related with inorganic constituents in lignite samples were eliminated after spectrum-subtraction procedure, difference-spectra led analyzing the spectra related with organic matter in lignite samples, reasonably. Furthermore, the bands related with acidic functional groups, aromatic and aliphatic structures were analyzed on the basis of difference-spectra, easily. From the difference-spectra it was shown that an acid-treatment process under mild conditions caused shift in some specific bands related with carbonyl groups of carboxyls so that the band at around 1710cm(-1) arisen, while the intensity of the band at around 1420cm(-1) was diminished. Through the acid-treatment process, acidic groups in lignite samples from different depths were thought to be turned into similar forms by protonation and/or stripping of metal ions originally bonded. Difference-spectra acquired for acid-treated samples made it possible to evaluate the form of carboxylic acid groups present in the studied samples under specific environmental conditions. Hence, a facile and environmentally-friendly methodology was used to analyze organic matter in lignite by using FTIR spectra, and valuable information was acquired about the aliphatic, aromatic and acidic character of the studied lignite samples collected from different depths. The proposed methodology seems to be promising in acquiring approximate representative spectra for lignite organic matter by using little or no chemicals.
Article
This study focuses on the determination and concentration of twelve elements (Na, K, Ca, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn and Cd) occurring in sub-bituminous Assam coals and their geochemical association. Distribution of these elements between organic and mineral matters was studied. Comparison of the results of three coals has shown that three elements (Mg, Ca and Mn) are significantly organic bound, while five elements (Fe, Co, Ni, Cu and Zn) are significantly mineral bound; Cd is 50% bound to either organic or mineral matter. FTIR and XRD studies reveal qualitative information about the bonding pattern and nature of components of the mineral matters. The results obtained in this study have considerable geochemical and technological interests.
Article
Effects of two typical surfactants, Tween-80 and sodium isobutyl-xanthate (NaIBX), with different concentrations on the growth and sulfur-oxidizing activities of a new strain Acidithiobacillus albertensis BY-05, an acidophilic sulfur-oxidizing bacterium, were investigated. The results indicate that both surfactants can enhance the growth and sulfur-oxidizing activities of A. albertensis BY-05 only at some special concentrations, e.g., 10−4–10−8 g/L for NaIBX and lower than 10−8 g/L for Tween-80, but were inhibited and even harmful at higher concentrations. Both surfactants can not be metabolized by A. albertensis BY-05. The contact between the bacteria and the sulfur particles may be dependent upon both the extracellular substance and the surfactants, both of which provide the amphiphilic environment improving the attachment for bacteria to the sulfur particles surface. These data could be significant for enlarging the applications of both A. albertensis BY-05 and some typical surfactants for industrial bioleaching of sulfides minerals.
Article
In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish lignites with crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH, and also lignite source on the desulphurization have been examined. The values for incubation period, pulp density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 degrees C, and pH 5.0, respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29% reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided from Tuncbilek with crude laccase was found to be relatively higher than the other examined coal samples. Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur, sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 mu m under optimal conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison tests and ANOVA were performed.
Article
The oxidation of ferrous iron by Acidithiobacillus ferrooxidans in the pH range 2.5-7.0 was characterized. In order to measure the rate of bacterial oxidation of ferrous iron with A. ferrooxidans in this high pH range, a novel experimental methodology was developed. The results showed that the inhibition of ferrous iron oxidation activity by A. ferrooxidans observed at pH values above 3.0 is partially linked to the formation of ferric iron precipitates, which apparently hinder transport processes on the cell surface. By carefully controlling the amount of iron precipitates formed during the oxidation of ferrous iron in this pH range, enhanced bacterial activity was obtained.
Article
Iron and sulfur oxidation by Thiobacillus ferrooxidans as well as growth on ferrous iron were inhibited by a variety of low molecular weight organic compounds. The influences of chemical structure of the organic inhibitors, pH, temperature, physical treatment of cells, and added inhibitory or stimulatory inorganic ions and iron oxidation suggest that a major factor contributing to the inhibitory effects on iron oxidation is the relative electronegativity of the organic molecule. The data also suggest that inhibitory organic compounds may (i) directly affect the iron-oxidizing enzyme system, (ii) react abiologically with ferrous iron outside the cell, (iii) interfere with the roles of phosphate and sulfate in iron oxidation, and (iv) nonselectively disrupt the cell envelope or membrane.
Article
The stringent new regulations to lower sulfur content in fossil fuels require new economic and efficient methods for desulfurization of recalcitrant organic sulfur. Hydrodesulfurization of such compounds is very costly and requires high operating temperature and pressure. Biodesulfurization is a non-invasive approach that can specifically remove sulfur from refractory hydrocarbons under mild conditions and it can be potentially used in industrial desulfurization. Intensive research has been conducted in microbiology and molecular biology of the competent strains to increase their desulfurization activity; however, even the highest activity obtained is still insufficient to fulfill the industrial requirements. To improve the biodesulfurization efficiency, more work is needed in areas such as increasing specific desulfurization activity, hydrocarbon phase tolerance, sulfur removal at higher temperature, and isolating new strains for desulfurizing a broader range of sulfur compounds. This article comprehensively reviews and discusses key issues, advances and challenges for a competitive biodesulfurization process.
Global Perspective on the Use of Low Quality Coals
  • S J Mills
Mills, S. J. Global Perspective on the Use of Low Quality Coals; IEA Clean Coal Centre: London, 2011; pp 1−80 (available online at: h t t p s : / / w w w. u s e a. o r g / s i t e s / d e f a u l t / fi l e s / 0 1 2 0 1 1 _ Global%20perspective%20on%20the%20use%20of%20low%20quali ty%20coals_ccc180.pdf).
Depyritization of US coal using iron-oxidizing bacteria: batch stirred reactor study
  • A Pathak
  • D J Kim
  • H Srichandan
  • B G Kim
Pathak, A.; Kim, D. J.; Srichandan, H.; Kim, B. G. Depyritization of US coal using iron-oxidizing bacteria: batch stirred reactor study. Int. J. Chem. Mol. Nucl. Mater. Metallurg. Eng. 2013, 7, 839−842.
3147−3155. (26) Panda, S.; Akcil, A.; Pradhan, N.; Deveci, H. Current scenario of chalcopyrite bioleaching: A review on the recent advances to its heap leaching technology
  • P An-An
  • L Hong-Chang
  • N Zhen-Yuan
  • X Jin-Lan
An-an, P.; Hong-chang, L.; Zhen-yuan, N.; Jin-lan, X. Effect of surfactant Tween-80 on sulfur oxidation and expression of sulfur metabolism relevant genes of Acidithiobacillus ferrooxidans. Trans. Nonferrous Met. Soc. China 2012, 22, 3147−3155. (26) Panda, S.; Akcil, A.; Pradhan, N.; Deveci, H. Current scenario of chalcopyrite bioleaching: A review on the recent advances to its heap leaching technology. Bioresour. Technol. 2015, 196, 694−706.