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Efficient enrichment of macerals improves the liquefaction efficiency of low-rank coal. The paper studied the characteristics of Shendong low-rank coal, including proximate and ultimate analyses, size and density compositions, and petrographic analysis, as well as the migration regularity of narrow particle size of low-rank coal macerals in the enhanced gravity field. On this basis, a novel classification separation process for low-rank coal macerals using Krebs hydrocyclone and enhanced gravity separator was proposed. The classification size was determined to be 0.074 mm and Krebs hydrocyclone achieved a satisfactory classification effect with a classification efficiency of 84.72%. Based on the enhanced gravity separation results of macerals from hydrocyclone underflow and overflow, the optimal sorting solutions for underflow and overflow were obtained through response surface analysis, respectively. Through the novel classification separation process, the vitrinite content of clean coal has been increased from 46.60% to 61.33% with an outstanding recovery of 77.40%. The novel classification separation process using hydrocyclone and enhanced gravity separator develops an excellent enrichment effect for low-rank coal macerals, which also provides a prospective approach for the cleaner utilization of low-rank coal. [ABSTRACT FROM AUTHOR]

High-efficiency separation of low-grade collophane becomes an inevitable trend with the depletion of high-grade phosphate ore. The work innovatively introduced enhanced gravity separation technology into the pre-separation process of low-grade collophane and discussed the influences of various factors on the enhanced gravity pre-separation effect. The influential significances of parameters, parametric interactions, and performance optimization were investigated using the RSM (Response Surface Methodology). The results showed that the P2O5 grade of the low-grade collophane could be increased from 14.84% to 20.26% with a recovery of 79.55%, and the P2O5 grade of tailings could be reduced to 7.27% under the optimal conditions—f of 44.50 Hz, P of 0.02 Mpa, and V of 22.04 ml/s. Compared with conventional gravity separation, the P2O5 recovery significantly increased by nearly 30%, and the P2O5 grade of tailings has been reduced remarkably. The response surface analysis showed that the influential significances of parameters could be ranked as P > f > V, and parametric interactions could be ranked as fP > PV > fV. The results of verification experiments agreed with the optimization results, which proved the reliability of the prediction model. The enhanced gravity separation technology developed an excellent pre-separation effect of low-grade collophane. [ABSTRACT FROM AUTHOR]

High-efficiency deashing and desulfurization of fine coal is an inevitable trend in the comprehensive utilization of coal resources. This work introducing heavy-medium into the enhanced gravity field to examine the effect of each parameter on the performance of fine coal separation. On this basis, the Response Surface Methodology (RSM) was conducted to study the influential significance of parameters, parametric interactions, and performance optimization of fine coal separation in the heavy-medium enhanced gravity field. The feed dosage and heavy-medium density influence the separation indexes obviously by changing the sorting environment, while the rotational frequency and recoil water pressure affect the separation effect apparently by adjusting the force on particles. The performance optimization results showed that the desired separation indexes – ηt of 81.11%, ηa of 80.00%, β of 44.93%, and λ of 44.76% can be obtained under the optimal combination of parameter levels – M of 27.23 g, ρ of 1.4 g/cm3, f of 30 Hz, and P of 0.03 Mpa. The verification experiments were carried out and the results were consistent with the results of performance optimization. The introduction of heavy-medium provides a new efficient way for the deashing and desulfurization of fine-grained high-sulfur coal in the enhanced gravity field. [ABSTRACT FROM AUTHOR]

The enhanced gravity concentrator with water medium has been used for the low-rank coal maceral enrichment and achieved a favorable effect. This study utilized the magnetite powder as the separation medium in the enhanced gravity separation test. The enhanced gravity separation with different medium was contrasted, the heavy medium separation possessed a more excellent separation mechanism and better effect, and the vitrinite content and recovery of concentrates was increased to 80.40 vol.% and 54.85%. In addition, the results of float–sink test and enhanced gravity separation with heavy medium were compared under the same separation density, the difference of vitrinite content and between the two methods was below 5%, and the vitrinite recovery of enhanced gravity separation was increased to 77.9% with the separation medium of 1.40 g/cm3. The density difference of macerals was proved by the EDS and XRD measurement, the more quantity of polycondensation aromatic rings and tighter microcrystalline structure leads to the higher density of inertinite. [ABSTRACT FROM AUTHOR]

In this paper, the enhanced gravity separation of maceral components was studied based on the characteristics of maceral components for low-rank coal from Shendong. Vitrinite and ash content were only 48.42 and 8.77%, respectively. Rod mill grinding showed that the optimal grinding time was 10 min based on the vitrinite content and vitrinite recovery which reached maximum 81.34 and 80.85%, respectively. Maceral separation test conducted with the Falcon concentrator showed that using optimal conditions of rotary frequency 30 Hz, feed dosage 15 ml/s and recoil water pressure 0.03 Mpa, the best vitrinite content, benefication ratio and vitrinite recovery were 67.25%, 1.16, and 72.48%, respectively. With the increase of rotary frequency or decrease of recoil water pressure, the finer particles in each particle fraction became more underflow products, and these finer particles in underflow products were all high-density products with density higher than 1.35 g/cm3. Because the content of vitrinite was higher in the coarser particles, the average particle size of the original overflow product was directly reduced by these fine particles entering the overflow product, which caused the decrease of vitrinite content and the increase of vitrinite recovery. [ABSTRACT FROM AUTHOR]

Flow field characteristics of Falcon separator are studied by CFD simulation based on Euler-Euler model as multiphase flow model and Reynolds stress model as turbulence model, including particle movement state in delamination area and separation area, three phase (Tangential, radial and axial directions) velocity distribution and turbulence field distribution. Simulation results show that particle movement trajectory is a three-dimensional helical structure with circular motion in groove, which can be regarded as "a circular harmonic motion of a roller coaster"; velocity distribution in the delamination area is almost same as other centrifugal separators but it is quite different in the groove; with feeding of recoil water, the turbulence intensity in the separation area is increased obviously, but it has a lower influence on the disturbance at upper layer of convective membrane, which enhanced the separation effect. [ABSTRACT FROM AUTHOR]

The liberation characteristics of long flame coal from the Chinese Shenhua were studied by comparison of ball grinding and rod grinding. First, the effects of grinding time on maceral liberation under the different particle size range, including vitrinite content (VC), vitrinite liberation degree (VLD) and vitrinite monomer content (VMC) were researched. Then, the influence of different grinding methods on maceral liberation were compared under same grinding fineness. Test results showed that the vitrinite in rod mill grinding is more concentrated in coarser particles compared with ball mill grinding, which provides favorable conditions for subsequent maceral beneficiation. In addition, in the range of +0.125 mm, all indexes with rod grinding are better than that of ball grinding. Especially, in the range of −0.045 mm, the vitrinite yield obtained by rod mill is always higher than that obtained by ball mill when ash content in each particle size range is almost the same. Analysis results show that the stress area of particles is small for ball grinding to result in random cracks. But rod mill crushes particles by slowly increasing squeeze force greater than stress intensity of particles, the force area of particles is larger to protect particle size decrease to a extent. [ABSTRACT FROM AUTHOR]

This paper studies particle motion and flow field characteristics with fly ash as an example and combine the experiments to analyze the separation process of rotary triboelectric separator in detail. Under boundary reference conditions of 22 kV plate voltage, 3 m/s feed flow, and 1815 r/min (189.95 rad/s) friction wheel speed, it simulated single-particle and particle group movement with different plate voltages and different feeding positions. Simulation of particle movement shows that particles may collide with a plate to cause serious particle mixing when plate voltage is higher. The initial velocity direction of particles is vertical downward and particles enter the separation chamber from the middle of the feeding port as much as possible to achieve better separation. The analysis of the flow field shows that the increase of the feeding airflow speed leads to a higher flow velocity inside the friction chamber and increases turbulence intensity; increases in friction wheel speed enhances flow field uniformity in the friction chamber and it is accompanied by an increase in velocity gradient; The co-flow speed mainly affects airflow field in the sorting room, the increase of co-flow speed within a certain range effectively stabilizes airflow field in the sorting room. [ABSTRACT FROM AUTHOR]