Yaoli Peng

Separation and analysis of aromatic hydrocarbons from two Chinese coals

Abstract Separation and analysis of aromatic hydrocarbons (AHs) from coals is of considerable significance for both fuel and non-fuel use of the coals. In present work two Chinese bituminous coals were selected for separation of AHs by ultrasonic extraction with CS 2 followed by column chromatography using hexane as eluent. A series of AHs were separated from the two coals and analyzed by GC/MS. FTIR was employed to characterize the raw coals and the extracted residues. The results of GC/MS analysis show that the separated AHs are mono- to tetracyclic arenes, among which the principle AHs are alkyl naphthalenes and phenanthrenes. Obvious differences in the composition and the structure of AHs exist between the two coals, i.e., the AHs from Tongting coal tend to be higher rings compared to those from Pingshuo coal both from the variety and from the abundance of the AHs. FTIR analysis shows that the raw and extracted coals are similar in terms of functional groups, suggesting that the composition and structure of CS 2 extract, especially the AHs, from coals can be used to interpret the coal structure to some extent.

Solid Superacid-catalyzed Hydroconversion of Demineralized Shengli Coal Liquefaction Residue under Microwave Irradiation

Abstract Shengli coal liquefaction residue was demineralized; the demineralized Shengli coal liquefaction residue (DMSCLR) was then subject to non-catalytic and SO4 2−/ZrO2- or SO4 2−/TiO2-catalyzed hydroconversion in methanol under microwave irradiation. The results show that both, SO4 2−/ZrO2 and SO4 2−/TiO2, significantly catalyzed DMSCLR hydroconversion. The MESs of hydrogenated DMSCLR were analyzed with gas chromatography/mass spectrometer. The MESs and methanol-inextractable fractions of hydrogenated DMSCLR were characterized with Fourier transform infrared spectrometer.

Convenient synthesis ofn-methylpyrrolidine-2-thione and some thioamides

The synthesis of thioamides and thiolactams, which are used as important organic intermediates, has attracted great attention. However, expensive reagents, severe reaction conditions and low yields of the target products made conventional methods inconvenient and economically infeasible. To overcome these disadvantages, we investigated a new process for synthesizing thioamides and thiolactams. We examined thermal reactions of CS2 withN- methyl-2-pyrrolidinone, formylamide, acetamide andN,N-dimethylformylamide, respectively. The results show that under optimum conditionsN-methylpyrrolidine-2-thione and the corresponding thioamides can be obtained in good to excellent yields by the above thionation reactions.

Improving the Recovery of Coarse-Coal Particles by Adding Premineralization Prior to Column Flotation

ABSTRACT A premineralization process, a pipe flow mineralization method adopted by adding a self-aspirated bubble generator in the feed pipe, was developed to improve the recovery of coarse-coal particles using a flotation column. The recoveries of various size fractions, including -700+600, -600+500, -500+250, -250+74, and -74 μm, using a conventional column (CC), a premineralization column (PMC), and a conventional column combined with the premineralization process (PM-CC) were investigated. According to the results, the CC showed a good performance in recovering coal particles with sizes below 250 μm, but a poor recovery of particles of sizes above 250 μm. The PM-CC presented advantages in recovering coal particles in contrast with the CC, especially coarse coal particles. Compared with the CC, the combustible recovery of -700+600, -600+500, -500+250, -250+74, and -74 μm size fractions obtained with the PM-CC was increased by 17.69, 17.15, 10.37, 0.58, and 4.07 percentage points, respectively, and the combustible recovery of the clean coal increased by 9.29 percentage points. The ash content of clean coal obtained with the PM-CC was almost identical to that of the CC. It was an effective way that adding the premineralization process prior to column flotation to strengthen the recovery of coarse-coal particles.

The role of polyaluminum chloride in kaolinite aggregation in the sequent coagulation and flocculation process.

The role of polyaluminum chloride (PAC) in kaolinite aggregation is studied in this paper by the aggregation of kaolinite with the single and combined use of PAC and polyethylene oxide (PEO). The sequent coagulation and flocculation pattern with the combined use of PAC and PEO shows higher aggregation efficiency than that with the single use of PAC or PEO. In the sequent coagulation and flocculation pattern, the settling velocity and the Zeta potential of kaolinite steadily increase with the PAC concentration, which indicates that the role of PAC is to render the interaction between kaolinite and PEO rather than charge neutralization. This conclusion is supported by the X-ray photoelectron spectroscopy analysis, which shows steady increase of Al-OH group on kaolinite with the PAC concentration.

Separation of 0.75-0.125 mm Fine Coal Using the Cylindrical Section of a 710/500 mm Three-Product Dense Medium Cyclone

ABSTRACT Dense medium cyclone is effective in beneficiation of fine coal with great separation precision. Small-diameter cyclones (usually 150 mm to 350 mm) are preferred in industrial applications. But the handling capacity of a small cyclone is low, which brings about the problems of maintain and operation. The separation efficiency of large-diameter cyclones with greater handling capability in fine coal treatment is questionable. In this study, the cylindrical section of a 710/500 mm three-product cyclone was adopted to treat 0.75–0.125 mm fine coal, where the cylinder-cone cyclone was a surge section. Influence of inlet pressure and feed rate were studied in an industrial environment. According to the results, the separation efficiency was sharp at relatively low feed pressures (110 KPa to 160 KPa). The separation effect increased with the feed rate. The favorable Ecart probable (Ep) value of 0.054 was obtained at an inlet pressure of 120 KPa and a feed rate of 42 t/h. Results of the studies showed that large-diameter cyclones will be applicable for fine coal treatment. These results will be significant for fine coal with a high content of near-density material.

Interaction of fine, medium, and coarse particles in coal fines flotation

ABSTRACT This study is concerned with the interaction among fine, medium, and coarse particles in coal flotation. Flotation tests for fine, medium, and coarse particles and the artificial ternary-particle mixtures were executed in a lab flotation cell. Flotation results were evaluated by the modified flotation rate constant (Km) according to the classical first-order flotation model. A parameter called interaction degree was developed to estimate the interaction among fine, medium, and coarse particles. It was observed that the modified flotation rate constant of medium particles was significantly faster than fine and coarse particles. The interaction among of fine, medium, and coarse particles was stronger with a relatively higher proportion of medium particles compared with the proportions of fine and coarse particles. Meanwhile, the gap for flotation rate constant between fast (medium particles) and slow (coarse/fine) fractions narrowed in the ternary-particle mixture flotation.

Intensified Ash Rejection in Coal Flotation by the Aggregation of Gangue Minerals Induced by Polyaluminum Chloride

ABSTRACT It is difficult to obtain a low-ash clean coal from a coal sample containing a high proportion of gangue minerals by traditional flotation methods due to the severe gangue contamination of the concentrate. In this article, a novel flotation method, using polyaluminum chloride (PAC) is described that showed better ash rejection. The aggregation due to PAC addition was verified with a concentration around 20 mg/L, and PAC selectively aggregated the high-ash gangue minerals (> 2.0 g/cm3) but did not aggregate the low-ash coal (< 1.4 g/cm3). With higher concentrations of PAC, both coal and gangue minerals were dispersed. The scanning electron microscope pictures of the flotation concentrate indicated that the contamination of gangue minerals was reduced using a low concentration of PAC. The zeta-potential measurements showed that charge neutralization with a low PAC concentration was the main aggregation mechanism of the gangue minerals. The zeta potential of the low-ash coal was highly positive when PAC was added, which means that the coal particles were dispersed due to the electrostatic double-layer repulsion.

Flotation Optimization of Ultrafine Microcrystalline Graphite Using a Box-Behnken Design

ABSTRACT In this investigation, emulsified kerosene and high-shear agitation were used to improve flotation performance of microcrystalline graphite. The flotation conditions were determined first and then optimized through a Box-Behnken design to minimize the concentrate ash content and to maximize the concentrate yield. Two quadratic models were developed to correlate the flotation variables, including agitation speed, agitation time, and collector dosage. As a result, both responses and the predicted optimal results were obtained. The lowest ash content of 7.81% and the highest yield of 91.00% were achieved by using an agitation speed of 27,173 rpm, an agitation time of 20 min, and a collector dosage of 79 kg/t. The analysis of variance indicated that the models of concentrate ash content and concentrate yield were significant terms to both responses.

Comparative study of conventional cell and cyclonic microbubble flotation column for upgrading a difficult-to-float Chinese coking coal using statistical evaluation

ABSTRACT Investigations were executed to upgrade a difficult-to-float coking slime (38.40°Contact angle and 40.14% ash content) by conventional flotation cell and cyclonic microbubble flotation column technologies. Firstly, flotation performance of conventional cell considering interactions of collector dosage, pulp density, and frother dosage was estimated by statistical evaluation. The conventional cell results indicated that clean coal with 11.89% ash content was obtained at 53.94% yield and 79.40% combustible recovery. Secondly, the effects of controlling factors (froth depth and circulating pulp pressure) on the flotation performance of cyclonic microbubble flotation column technology (FCMC) were investigated according to the earlier conventional cell studies. The combustible recovery of the clean coal could be further increased to 90.54% at 62.78% yield and 11.67% ash content by using the FCMC. Finally, the flotation performance in the conventional flotation cell and FCMC was compared with that of the release analysis data. It was concluded that, in general, the performance of the conventional flotation cell was poorer, while the flotation performance of the FCMC was better than that of the release analysis data. Therefore, this difficult-to-float coking coal can be concentrated to a qualified product with minimal usage of reagent and low cost by using the cyclonic microbubble flotation column technology.