Shengli Lignite Research Articles

Suppression of crosslinking combination of carboxyl functional groups with NaOH on combustion performance of Shengli lignite

It is important to inhibit the spontaneous combustion of lignite for its safe transportation and efficient utilization. Shengli lignite was treated with a NaOH solution and the as-prepared coal samples were extensively characterized by SEM-EDS, XRD, FT-IR, XPS, and Raman spectra techniques. The combustion properties of NaOH treated lignite were determined by TGA. The results show that NaOH treatment played a significant inhibitory effect on the combustion performance of Shengli lignite. The NaOH treated lignite showed two weight loss temperature regions. The temperature corresponding to the maximum combustion rate of Shengli lignite after the NaOH pretreatment was about 350–400 °C, higher than that of untreated sample, indicating that NaOH treatment significantly decreased the combustion reactivity of Shengli lignite. FT-IR and XPS analyses identified the analogous sodium polycarboxylic acid, originating from the crosslinking combination of carboxyl functional groups with NaOH. It is deduced that the suppressing effect of NaOH treatment on the combustion performance of lignite maybe attributed to the higher stability of analogous sodium polycarboxylic acid.

Bioliquefaction of the extracts from Shengli lignite

Shengli lignite was sequentially extracted with aqueous NaOH solution, n-hexane, dichloromethane (DCM), isometric benzene and ethanol (IMBE), and acetone to obtain extracts 1–5 (E1–E5). Each extract was biotreated by an isolated fungus WF8 under the same conditions. The results show that E1 is much more susceptible to the bioliquefaction (BL) than other extracts. The BL of E1 proceeded via the cleavage of C–O–C and Si–O bonds to some extent, while most of the methylaromatic and –COOH-containing moieties in E1 are inert toward BL by WF8. E1 has largely similar molecular mass distribution (MMD) to unliquefied E1, but quite different MMD from bioliquefied E1, further indicating that the BL of E1 proceeded via biochemical reactions by WF8.

Drying and Moisture Readsorption Characteristics of Lignite

ABSTRACT The physical and chemical changes of three different types of lignite during drying at temperatures from 80 to 180°C were investigated using a moisture meter and an infrared spectroscopy system. The results showed that the drying of lignite could be classified into two stages, namely, a fast upgrading stage where surface moisture was lost, and a slower moderating stage where internal moisture diffused to the surface and evaporated. Some unstable oxygen-containing polar groups in the lignite decomposed during the drying process, resulting in an increased contact angle and reduced wettability. With increasing temperature, the size of the micropores decreased and the number of mesopores increased. The decrease in the specific surface area and the increase in the pore size and pore volume were observed. In addition, the moisture readsorption characteristics of lignite were closely related to the previous drying process. The reabsorption capacity of the treated lignite increased with increasing pre-drying temperature, while an extremely high drying temperature degraded the pore structure of partial lignite, such as Shengli lignite, reducing its ability to reabsorb moisture.

Estimation of Pores Distribution in Lignite Utilizing Hg, H2O, CO2, and N2 as Molecular Probes

Pores size distribution (PSD) and surface area (SA) analysis are so important for the description of porous materials, so selection of different pore characterization methods is emphasized, especially nondestruction methods. In this study, N2, H2O, CO2, and Hg were utilized as molecular probes to estimate the PSD in Shengli lignite (SL). In the N2 adsorption, traditional degassed sample and wet samples freezing by liquid N2 were combined to obtain the PSD and moisture distribution in SL. The pores of degassed samples were mainly located in the range of 5–100 nm, and most of the moisture was in the larger macropores in the range of 26–100 nm, peaking at 37 nm. We used two methods of H2O as molecular probe: H2O dynamic adsorption and low-field nuclear magnetic resonance (LFNMR). The saturation concentration of H2O in the pore of SL was 0.29 cm3/g from H2O adsorption, and the pores located in the range of 1–154 nm and peaked at 42.4 nm from LFNMR. The comparison and combination of different molecule probes w...

Co-gasification of thermally pretreated wheat straw with Shengli lignite for hydrogen production

Abstract Wheat straw (WS) was thermally pretreated at 200, 300 and 400 °C in a muffle furnace, respectively, before co-gasified with Shengli lignite (SL). The results from thermogravimetric analyzer (TGA) experiments showed that interaction of solid phases between SL and the pretreated WSs occurred at the gasification stage rather than the pyrolysis stage and the synergy varied with the biomass pretreatment temperature. Co-gasification of WS-200/SL had an inhibitory effect, and there was no synergy effect during WS-300/SL co-gasification. In contrast, co-gasification of WS-400/SL had a positive effect in the gasification stage. The investigation of co-gasification in a fixed-bed reactor, however, found synergies in product gas yields and carbon conversion for both WS-200/SL and WS-400/SL. The (H 2 +CO) yield and carbon conversion increased by 3.95% and 18.32%, respectively, for co-gasification of WS-400/SL blends compared with the calculated values based on individual materials. From the results of both the TGA and fixed-bed experiments, it is concluded that 400 °C of pyrolysis temperature for WS is the best to produce hydrogen for co-gasification with SL. The maximum synergetic effect was explained by the relatively high surface area and high content of alkali metals in WS-400.

Preparation of porous carbons by hydrothermal carbonization and KOH activation of lignite and their performance for electric double layer capacitor

A series of porous carbons (PCs) were obtained from Shengli lignite (SL) via hydrothermal carbonization (HTC) pre-treatment and followed by chemical activation with KOH. The effects of preparation parameters including HTC temperature, KOH-hydrochar ratio and activation temperature on pore structure and the electrochemical performances of PCs were investigated in details. The PCs are mainly micropores structure according to the N2 adsorption-desorption isotherms test and the highest specific surface area (SSA) is up to 3162m2g−1. The SSA and total pore volume of PCs with HTC pre-treatment are larger than that without HTC treatment. The electrochemical performances of the symmetric electric double layer capacitor (EDLC) fabricated from these PC electrodes were tested by galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy. All the PCs as electrode for EDLC exhibit ideal capacitive behaviors in 6M KOH electrolyte. The specific capacitance of 200-HTC-800-3 can reach as high as 295Fg−1 at the current density of 40mAg−1 and still retained 210Fg−1 at the current density of 10Ag−1. It also shows excellent electrochemical cycle performance that after 15000 cycles the specific capacitance value almost not decay. The processes used to produce the PCs can reduce the energy consumption compared to the traditional carbonization-activation method.

Construction of the molecular structure model of the Shengli lignite using TG-GC/MS and FTIR spectrometry data

The molecular structure model of the Shengli lignite was determined via TG-GC/MS for the analysis of the pyrolysis products’ structure and contents, in combination with ultimate analysis and FTIR for the determination of its structure parameters. Then the model was constructed by hand referring to references, optimized and revised on the basis of quantum chemistry by semi-empirical and the second derivative force field. It was estimated that the cross-links were comprised of ether bond (O), aliphatic bond (CH2, CH2CH2), ester bond, SS, etc., and heterocyclic compounds were mainly furan, indole, quinoline, etc., while its oxygen-containing functional groups were primarily carboxyl, hydroxyl, and ether. The molecular formula for the lignite structure model was C169H140O44N3S2. A FTIR spectrum calculated based on the model is consistent with that of the experimental data.

Preparation of high-dispersion Ni/C catalyst using modified lignite as carbon precursor for catalytic reforming of biomass volatiles

Lignite is rich in oxygen-containing species (OCSs) and able to load Ni via ion exchange to prepare Ni/C catalyst. However, the OCSs usually exists in the form of organic salts, which can reduce the capacity of Ni ion exchange. In this paper, Shengli lignite (SL) was treated with HCl and HCl/HF to selectively remove the organic salts and insoluble minerals, respectively, and the modified lignite was oxidized by H2O2 to further increase the carboxyl content. The treated lignite was used to prepare Ni/C catalyst and the activity for biomass volatile reforming was evaluated. The results show that demineralization (DM) caused the corrosion of pore structure of SL and gave a Ni/C catalyst with a low specific surface area (SSA) of 222.1m2/g. Oxidation with H2O2 further destroyed the structure of DMSL and provided a Ni/C with the lowest SSA of 141.1m2/g. Acid wash (AW) with HCl resulted in the increase of ion exchange capacity of SL and gave a Ni/C catalyst with larger SSA, higher loading, lower particle size and well dispersion of Ni particle in comparison with SL and DMSL. H2O2 treatment of AWSL significantly increased the amount of carboxyl group to 3.8mmol/g and gave a Ni/C with the largest SSA of 291.1m2/g, highest Ni loading of 17.3% and smallest Ni crystallite size of 3.4nm, as well as most active for corncob volatile reforming.

Identification of oxygen-containing organic compounds from thermally dissolved Shengli lignite in toluene/ethanol

ABSTRACTIn order to efficiently use low rank coals, thermal dissolution (TD) of Shengli lignite (SL) was carried out in a mixed solvent toluene/ethanol with synergistic effect and the TDSL was analyzed with gas chromatography/mass spectrometry (GC/MS). Seventy one oxygen-containing organic compounds (OCOCs) including alcohols, phenols, ethers, ketones, acids, and esters were detected. Among the OCOCs, the relative content of phenols and esters is higher, and their possible formation mechanisms are discussed. Hence, understanding the structure of OCOCs in lignite at the molecular level is more promising to convert the low calorific fuel into high-valued organic compounds.

Catalytic effect of sodium components on the microstructure and steam gasification of demineralized Shengli lignite char

The catalytic effect of sodium on the demineralized Shengli (SL+) lignite char microstructure and the performance of steam gasification were studied. Various sodium compounds including NaNO3, CH3COONa, Na2CO3 and NaOH were loaded on the demineralized coal samples, respectively, and the steam gasification was tested on the fix-bed reactor. The char samples were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy. Experimental results showed that sodium hydroxide loaded samples exhibited the highest gasification reactivity among the coal samples prepared. With the increase of the alkalinity of sodium compounds, the carbon crystallite structure tended to be disordered. In the process of pyrolysis, the introduction of sodium species promoted the ring-opening and polycondensation process of the chemicals in the coal samples. The possible reaction mechanism might be inferred that the sodium ions may replace the hydrogen ions in the oxygen-containing functional groups to form sodium phenolate intermediate, which may be critical for the catalytic effect of sodium species during gasification. It was speculated that the ring-opening of the condensation aromatic nucleus was the rate-limiting step in the whole process of gasification.

Direct production of high hydrogen syngas by steam gasification of Shengli lignite/chars: Remarkable promotion effect of inherent minerals and pyrolysis temperature

The steam gasification of Shengli (SL) lignite and the demineralized lignite/chars were tested on a laboratory fixed-bed micro reactor system. The evolution rates of syngas, carbon conversions to gas, yields of gaseous products, and H2/CO molar ratios of SL lignite/chars were systematically investigated. Meanwhile, the gasification performance of SL lignite/chars was compared with the corresponding demineralized samples. The results showed that the inherent minerals in SL lignite/chars not only effectively promoted the steam gasification reaction but also considerably improved the gasification selectivity towards the production of H2 and CO2. Further characterizations by the scanning electron microscope (SEM-EDS) and X-ray fluorescence (XRF) demonstrated that it became more difficult for the minerals in SL lignite being eluted by hydrochloric acid solution with the temperature increasing of pyrolysis process. The results confirmed that the inherent minerals and lignite formed metals-lignite intermediate complex during pyrolysis process. The formed metals-lignite intermediate complex works as the active sites which effectively promote the steam gasification performance of SL lignite/chars, especially in favor of the direct generation of high hydrogen syngas.

Extension of catalyst lifetime by doping of Ce in Ni-loaded acid-washed Shengli lignite char for biomass catalytic gasification

Preparation and lifetime extension of modified lignite char loaded with Ni by doping of Ce using a co-impregnation method for biomass gasification.

Effect of metal ions on the steam gasification performance of demineralized Shengli lignite char

Lignite is considered to be a promising coal to obtain H2 or H2-rich synthesis gas. In order to investigate which metal ions promote its high H2 production, Shengli lignite after partial demineralization followed by addition metal ions were mainly studied. The steam gasification reaction with temperature programmed was tested by using fixed-bed reactor. XRD, Raman, XPS and FTIR were used to do the research on microcrystalline structure changes of the Shengli lignite. The results proved that the gasification reactivity of HCl treatment samples were poor. The addition of alkali metal and alkaline earth metal had a distinguished catalytic effect on the steam gasification. Nevertheless, transition metal had a slight catalysis. The metal ions added into the acid treatment lignite decreased initiating gasification temperatures, increased H2 cumulative yield and H2/CO ratio in the syngas from the steam gasification, especially for Ca, K and Na. The XRD and Raman results revealed that the addition of alkali metal and alkaline earth metal made the char structure disorderly, and hindered chemical structure of coal changes towards graphitization. The XPS results indicated that the content of CO increased significantly after adding metal ions, which could contribute to opening the loop of aromatic nucleus. The reaction mechanisms about how metal ions catalyzed low-rank coals in steam gasification were proposed.

Effects of demineralization on the structure and combustion properties of Shengli lignite

Investigation of the effects of demineralization of inherent minerals in Shengli lignite (SL) on its structure and combustion property in the field of coal conversion is an extremely important and interesting topic. In this study, inherent minerals in SL were demineralized by hydrochloric acid (HCl) treatment. Further, the metals cations Na+, Al3+, K+, Ca2+, Mn2+ and Fe3+, corresponding to the inherent metal ions in lignite were added into the demineralized samples by the impregnation method in order to compare their effects. The surface morphology and structure parameters of the raw and demineralized lignite samples were characterized by SEM, nitrogen adsorption–desorption, FTIR, XPS, XRD and Raman spectroscopy. The combustion properties of lignite samples were investigated by thermogravimetric analysis. Demineralization led to an improvement in the amount of side chains in SL and destroyed the pore structure and aromaticity; however, it did not have obvious effects on the surface morphology of SL and the main forms of carbon and oxygen. Moreover, demineralization increased the ignition temperature and apparent activation energy, and decreased the combustion stability index of SL. Added aluminum ions resulted in a decrease in the combustion stability and reactivity of the HCl treated sample; however, the added metals cations such as Na+, K+, Ca2+, Mn2+ and Fe3+, exhibited opposite effects.

Characterization of the oxidation products of Shengli lignite using mass spectrometers with “hard”, “soft” and ambient ion sources

Shengli lignite (SL) was oxidized and depolymerized in aqueous sodium hypochlorite under mild conditions followed by sequential extraction with ethoxyethane and ethyl acetate. The extracts were analyzed by Fourier transform infrared spectroscopy, gas chromatograph/mass spectrometry (GC/MS), time-of-flight mass spectrometry (TOF-MS) equipped with electrospray ionization (ESI), and direct analysis in real time (DART) to understand the structural features of SL. In total, 130, 272, and 818 compounds were identified by GC/MS, ESI-MS, and DART-MS, respectively, and the corresponding molecular mass distributions are between 70 and 322, 114 and 664, 113 and 753u, respectively. GC/MS detected molecules with low molecular mass and polarity, and the major species include aliphatic acids, benzene polycarboxylic acids, chloro-substituted species and nitrogen-containing compounds. A large number of heteroatom-containing compounds (oxygen, nitrogen and sulfur) with relatively high molecular mass and unsaturation degree were determined using ESI-MS. As an ambient ionization technique, DART speeded up the analysis time with little or no sample pretreatment. Compared to the other two MS techniques, DART-MS broadened the measurement range, and OxN5, and OxN6 classes were only detected by DART-MS.

Characterization of Oxygenates, Nitrogenates, and Sulfonates in Shengli Lignite Extracts by Orbitrap Mass Spectrometry

ABSTRACTA series of carbon disulfide/acetone mixtures were used to extract organic species from Shengli lignite, a Chinese coal. Orbitrap mass spectrometry coupled with electrospray ionization was used to characterize the molecules in the extracts. Heteroatomic species, including oxygenates, nitrogenates, and sulfonates, were determined. Pure carbon disulfide or acetone had the lowest extraction for oxygenates while the mixtures increased the relative abundance of oxygenates. From the value of the double bond equivalence, the compounds with 1 oxygen contained the highest concentrations of aromatics and aliphatics, but compounds with 6 were aliphatic with a double bond equivalence of 3. For compounds containing 2 oxygens, aromatics with one ring were present at the highest concentrations in the 1:1 carbon disulfide:acetone extract. For compounds containing 3, 4, and 5 oxygens, most aromatic species were identified with double bond equivalence values between 4 and 6, showing the presence of an aromatic ring. The results indicated that the solvent mixtures enhanced the extraction of oxygenates from Shengli lignite.

Characterization of the Oxygenated Chemicals Produced from Supercritical Methanolysis of Modified Lignites

Lignites are promising as feedstocks for producing value-added oxygenated chemicals (OCs) due to their high contents of oxygen-containing organic species. Two modified lignites were produced from Xiaolongtan lignite and Shengli lignite via sequential ultrasonic extraction and subsequent supercritical methanolysis to produce OCs. Solid-state 13C nuclear magnetic resonance analysis reveals the differences in carbon skeleton structures and oxygen-functional groups between the two modified lignites. The molecular compositions of OCs from the methanolysis were characterized with Fourier transform infrared spectrometer (FTIRS), gas chromatograph/mass spectrometer (GC/MS), and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FTICRMS). Six types of hydrogen bonds and distribution of >C═O groups in the OCs were analyzed with FTIRS. Alkylphenols with C1−C6 in alkyl group(s) dominate in the GC/MS-detectable organic species and methyl is the major alkyl group. The ...

Shengli lignite liquefaction under syngas and complex solvent

The liquefaction of Shengli lignite (SL) were studied in the system of syngas (H2+CO) and complex solvent (H2O+THN) and the system of hydrogen (H2) and tetralin (THN). Asphaltene (AS) and preasphaltene (PA) from the two systems were characterized by FT-IR. The results show that both conversion and oil yield of Shengli lignite liquefaction in the (H2+CO)/(H2O+THN) system are significantly higher than those in the H2/THN system. The conversion and oil yield under syngas (H2:CO (volume ratio)=1:1) and complex solvent (THN:H2O (volume ratio)=1:1) reach respectively 88.79% and 55.47% at 400°C, 4 MPa and 30 min. The differences in the conversion and oil yield between the (H2+CO)/(H2O+THN) and H2/THN systems are 8.00% and 7.54%, respectively. This suggests that the water-gas shift reaction can produce active hydrogen in the (H2+CO)/(H2O+THN) system, which benefits the hydrogenation of SL and PA. Meanwhile, THN can stabilize the free radicals from SL pyrolysis and dissolve the products (AS and PA) from SL liquefaction. The synergistic effect of two factors results in the improvement of conversion and oil yield. This study shows that it is a new lignite liquefaction technology using the (H2+CO)/(H2O+THN) system.

Effect of ionic liquid 1-butyl-3-methyl-imidazolium dihydrogen phosphate pretreatment on pyrolysis of Shengli lignite

The pyrolysis behaviors of Shengli lignite (SL) pretreated with ionic liquid 1-butyl-3-methyl-imidazolium dihydrogen phosphate ([Bmim]H2PO4) was studied in this paper. The effect of pretreatment temperature and the ratio of [Bmim]H2PO4 to SL on the pyrolysis behaviors of lignite were mainly investigated. Also the mechanism of the influence of [Bmim]H2PO4 pretreatment on the pyrolysis of lignite was investigated by FTIR analysis. It is found that [Bmim]H2PO4 pretreatment results in the drastical increase of the yield of tar, especially the yield of oil fraction. The yield of tars obtained from pyrolysis of SL treated in [Bmim]H2PO4 at 200°C with the ratio of [Bmim]H2PO4 to SL at 1 increases by 1.7 times compared to that of SL. [Bmim]H2PO4 pretreatment results in the increase of yield of oil fraction, especially the yield of arenes and phenolics. The FT-IR analysis shows that [Bmim]H2PO4 pretreatment results in the increase of the content of carbonyl group and ether bond in SL.

Macerals of Shengli Lignite in Inner Mongolia of China and Their Combustion Reactivity

The macerals, including fusinitic coal containing 72.20% inertinite and xyloid coal containing 91.43% huminite, were separated from Shengli lignite using an optical microscope, and their combustion reactivity was examined by thermogravimetric analysis. Several combustion parameters, including ignition and burnout indices, were analyzed, and the combustion kinetics of the samples were calculated by regression. Fusinitic coal presented a porous structure, while xyloid coal presented a compact structure. The specific surface area of fusinitic coal was 2.5 times larger than that of xyloid coal, and the light-off temperature of the former was higher than that of the latter. However, the overall combustion reactivity of fusinitic coal was better than that of xyloid coal. The combustion processes of fusinitic and xyloid coals can be accurately described by both the homogeneous model and the shrinking core model. The features of xyloid coal agree with the shrinking core model when its conversion rate is 10%–90%. The activation energy of fusinitic coal during combustion can be divided into three phases, with the middle phase featuring the highest energy. The activation energy of xyloid coal is lower than that of fusinitic coal in the light-off phase, which may explain the low light-off temperature of this coal.