Extraction Of Lignite Research Articles

Microbial pretreatment of coals: A tool for solubilization of lignite in organic solvent – quinoline

A method was developed for the conversion of low rank coals to products soluble in an organic solvent (quinoline). A selected group of polynuclear aromatic-compound-degrading and lignin-degrading facultative pure cultures and enriched anaerobic mixed microbial cultures developed for this purpose were used separately as well as together under co-culture conditions for stepwise treatment of Neyveli lignite (NL). This aerobic-anaerobic co-metabolic (co-culture) biodegradation (AACB) process resulted in the enhancement of quinoline extractability of the lignite, thereby yielding clean coal substance (the extract). The residual lignite obtained after quinoline extraction was subjected to a second step of AACB fermentation treatment. This resulted in further extraction of lignite in quinoline. The conditions were optimised for AACB fermentation treatment. The two-step AACB fermentation process under optimum conditions, resulted in an overall enhancement of yield of extract from 18% for the original lignite sample to 56% for the treated sample. The changes in the filtrate were evaluated using UV spectra, those in the residue were evaluated using FTIR spectroscopy and UV-reflectance and those in the extract using proton NMR spectra of the chloroform soluble fraction. The results indicated a decreased absorption in the carbonyl region in the AACB-treated residue and also a decrease in the overall mineral matter in the lignite samples. The mechanism of the AACB fermentation process is discussed. The process affords biosolubilization of lignite in organic solvent (quinoline) under milder conditions along with a simultaneous removal of a part of the mineral matter present in the coal. Uses for the clean coal extract obtained are suggested.

Rheinbraun's concept for power generation based on biotechnologically converted lignite

The main objective of Rheinbraun's research activities with respect to biotechnological lignite upgrading is the large-scale production of liquid and gaseous products in particular for the energy and chemical/refinery sectors. This report outlines Rheinbraun's technical concept for electricity production on the basis of biotechnologically solubilized lignite. Starting out from conventional lignite extraction (opencast mining technology), this concept includes, inter alia, solubilization of the ground coal in bioreactors located near the deposits. The liquid coal reduced in terms of moisture, ash (mainly slag-forming minerals) and inorganic sulphur content is transported via pipeline to the power stations. Power generation is performed in oil-based or gas and steam turbine power plants. A first rough cost estimate based on the assumptions described here and compared with the latest power plant generation shows the general cost-efficiency of this technology despite the additional costs in respect of coal solubilization. The main reasons are: low-cost process techniques for coal conversion (mild reaction condition, low pressure and temperature) on the one hand and cost reductions mainly in power plant technologies (more efficient combustion processes and simplified gas clean-up) but also in coal transport (easy fuel handling) on the other hand. Moreover it is hoped that an extended range of products will make it possible to widen the fields of lignite application. In 1995 Rheinbraun started a research project, 1 1 The research project is financially supported by the North Rhine-Westphalian Ministry of Economics, Medium-Sized Enterprises, Technology and Transport, Germany. in which various leading biotechnological companies and institutes in Germany and the USA are involved. The positive results obtained during the first 10 months of the current project are very promising. So, the first difficult step has been taken: several liters of microbially solubilized Rhenish lignite have been produced. This pre-product with a water content of approximately 95% will now be used to select efficient and low-cost preparation techniques and to perform the first suitability investigations (combustion tests, tests analogous to crude oil preparation). However, it is much too early to determine whether biotechnological lignite upgrading is the ultimate solution or a dead end.

EXTRACTION KINETICS OF COALS AT SUBCRITICAL AND SUPERCRITICAL CONDITIONS

ABSTRACT The extraction kinetics of two lignites and one bituminous coal with benzene, toluene and pyridine were studied at both sub and supercritical conditions in a batch reactor equipped with a coal basket. The time-extract yield data of lignites at supercritical conditions could'nt be treated due to severe thermal decomposition and heating-up effects. The data for Zonguidak coal and those for subcritical extraction of Cizre lignite could be fitted into a first order rate equation with the rate constants changing 0·02-0·05 min−1 range.

95/05876 Effect of preswelling on soxhlet and supercritical gas extraction of a Turklsh lignite

95/05876 Effect of preswelling on soxhlet and supercritical gas extraction of a Turklsh lignite

95/06016 Supercritical-gas extraction of some Turkish lignite with different solvents

95/06016 Supercritical-gas extraction of some Turkish lignite with different solvents

95/04589 Comparison of oils and asphaltenes from extraction of bituminous coal and lignite with hydrogenated anthracene oil

95/04589 Comparison of oils and asphaltenes from extraction of bituminous coal and lignite with hydrogenated anthracene oil

95/03482 The European transmission grid

Extraction residue (ER) from ultrasonic extraction of Xinghe lignite (XL) was subjected to sequential thermal dissolution (TD) in cyclohexane from 200 °C to 320 °C and subsequently in benzene, methanol, ethanol, and isopropanol at 320 °C. The yields of soluble portions (SPs) in methanol and ethanol are much higher than those in cyclohexane and benzene, and the total SP yield is ca. 48.3%. According to gas chromatography/mass spectrometric analysis, the most abundant group components are arenols in cyclohexane-soluble portion obtained at 290 °C and methanol-soluble portion obtained at 320 °C, arenes in both cyclohexane- and benzene-soluble portions obtained at 320 °C, alkanoates in ethanol-soluble portion obtained at 320 °C, and alkenones in isopropanol-soluble portion obtained at 320 °C. Anthracene was used as hydrogen acceptor to probe hydrogen transfer (HT) from ER in terms of the formation of 9,10-dihydroanthracene (DHA) and 1,2,3,4-tetrahydroanthracene (THA) during TD. As a result, both DHA and THA were detected in all the SPs except benzene-soluble portion obtained at 320 °C and the yields of both DHA and THA increased with raising temperature in cyclohexane, indicating that raising temperature enhances HT from ER to anthracene. Compared to TD in cyclohexane, alkanols, especially isopropanol, enhance the HT more significantly at 320 °C.

Comparison of oils and asphaltenes from extraction of bituminous coal and lignite with hydrogenated anthracene oil

The application of 1H n.m.r. spectroscopy and g.c.-m.s. to the analysis of aromatic fractions obtained in the liquefaction of two coals of different rank is described. The conversion and the yield of asphaltenes have been related to the proportion of aliphatic hydrogen in the extraction oils after liquefaction. The n.m.r. bands for asphaltenes are similar to those of recovered anthracene oils, but mass spectra show that a substantial amount of high-molecular-weight compounds is produced during the extraction of a bituminous coal, compounds not encountered in lignite liquefaction.

95/03473 The use of blended coals in direct coal liquefaction

Extraction residue (ER) from ultrasonic extraction of Xinghe lignite (XL) was subjected to sequential thermal dissolution (TD) in cyclohexane from 200 °C to 320 °C and subsequently in benzene, methanol, ethanol, and isopropanol at 320 °C. The yields of soluble portions (SPs) in methanol and ethanol are much higher than those in cyclohexane and benzene, and the total SP yield is ca. 48.3%. According to gas chromatography/mass spectrometric analysis, the most abundant group components are arenols in cyclohexane-soluble portion obtained at 290 °C and methanol-soluble portion obtained at 320 °C, arenes in both cyclohexane- and benzene-soluble portions obtained at 320 °C, alkanoates in ethanol-soluble portion obtained at 320 °C, and alkenones in isopropanol-soluble portion obtained at 320 °C. Anthracene was used as hydrogen acceptor to probe hydrogen transfer (HT) from ER in terms of the formation of 9,10-dihydroanthracene (DHA) and 1,2,3,4-tetrahydroanthracene (THA) during TD. As a result, both DHA and THA were detected in all the SPs except benzene-soluble portion obtained at 320 °C and the yields of both DHA and THA increased with raising temperature in cyclohexane, indicating that raising temperature enhances HT from ER to anthracene. Compared to TD in cyclohexane, alkanols, especially isopropanol, enhance the HT more significantly at 320 °C.

A spectroscopic study of structural changes occurring in supercritical gas extraction of a Spanish lignite with alcohols

Supercritical gas (SCG) extraction of a Spanish lignite was conducted with methanol and ethanol in a semicontinuous mode at temperatures between 250 and 350 °C and pressures up to 15.2 MPa. The resultant extracts and residues were characterized principally by FT-i.r. spectroscopy and n.m.r. to specifically provide information on the mode and extent of solvent incorporation via secondary reactions. FT-i.r. and n.m.r. revealed that alkylation and esterification reactions both occur to a significant extent. The extent of alkylation increases with increasing temperature and SCG extractions with 13C-labelled methanol demonstrated that the incorporated methyl groups are mainly bound to C atoms but also to O, S and N atoms. The extent of esterification is incomplete, as indicated by the presence of free carboxylic acids in both the chars and extracts, and decreases with increasing temperature due to the competing effect of decarboxylation reactions.

Hydrogenating supercritical coal extraction with toluene, tetralin, molecular hydrogen and their mixtures

Hydrogenating extraction of bituminous coal and lignite was investigated using toluene as extracting solvent, and molecular hydrogen and/or tetralin as hydrogenating agent. In non-isothermal experiments a fixed bed of coal was slowly heated from ambient temperature to 550 °C in a stream of pressurized toluene/H 2/tetralin mixture, and the extraction rates were continuously measured over the entire temperature range. The measured extraction rate profiles showed characteristic differences depending on the combination of solvent and hydrogenating agent. These differences were interpreted and compared with the thermodynamic phase behaviour of the solvent-H 2 system, to understand the physical and chemical steps involved in the complex mechanism of hydrogenating coal extraction. The fact that the addition of hydrogen during extraction had a negative effect on coal conversion and extract yield was also explained.

Desulphurisation of a spanish lignite via low temperature supercritical gas extraction

Supecritical gas (SCG) extraction of a high sulphur Spanish lignite with methanol has been conducted at temperatures between 250 and 350°C and the resultant extracts have been characterised by GC/MS and other appropriate techniques. Char prepared at 350°C contained 40% less organic sulphur than the initial coal but a similar reduction in organic sulphur content was achieved by pyrolysis at 500°C. Thus the extent of desulphurisation is influenced primarily by thermal processes rather than by the nature of the SCG. Nevertheless, the methanol had a significant impact on product distribution; it was incorporated into the extracts and residues as both methyl ethers and esters and decomposed to generate hydrogen in situ, some of which was transferred to the lignite.

Comparative studies of solvent extraction of Neyveli lignite and Assam coal through alkaline treatment and acidic depolymerization

Alkaline treatment of Neyveli lignite resulted in the enhanced extraction of lignite in aqueous alkaline medium. Treated lignite was recovered from the aqueous alkaline medium, by neutralization with acid. Alkaline treatment of coal in phenol resulted in enhanced extraction of quinoline (68%, compared with 41% from alkaline treatment in aqueous media). Acidic depolymerization of lignite in phenol was also performed. Comparative studies of the solvent extraction of lignite through alkaline treatment and acidic depolymerization have been reported. Depolymerized lignite resulted in an enhanced devolatilization yield through pyrolysis at 723 K in steam.

Alkyl aryl ethers in lignite solubilization: 2. Analysis of oil fractions

The FT-i.r. and 1H n.m.r. spectroscopic analyses of oils or maltenes from a Spanish lignite (Utrillas, Teruel), are reported. These oils were obtained by depolymerization with alkyl aromatic ethers (anisole, 3-methylanisoleand 1,3-dimethoxybenzene) catalyzed by Lewis acids ZnCl 2, AlCl 3, SbCl 3and BF 3 (as boron trifluoride etherate), at atmospheric pressure and temperatures <220 °C. Bands due to aromatic ethers in the i.r. and n.m.r. spectra of the oils obtained by depolymerization indicate solvent incorporation. Oils obtained by direct lignite extraction showed 25% aromatic H and some H α (≈3%) without OH groups. These appeared in some oils obtained by depolymerization with AlCl 3 and were due to secondary reactions with the aromatic extract. Oils derived from processes with good yields showed increases in aromaticity. The extent of substitution of aromatic rings in oils obtained by depolymerization was less than for oils directly extracted. All the oils studied show a low degree of condensation.

Solvent Extraction of Lignite and Carbonization of Lignite Extracts

Solvent Extraction of Lignite and Carbonization of Lignite Extracts