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1

Pretreatment of coking wastewater by an adsorption process using fine coking coal

Gao L., Li S., Wang Y., Gui X., Xu H.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 1

422--436

EN

A new technique for pretreatment of coking wastewater is introduced based on the concept of circular economy. Coal is fed into a coking system after adsorption. This study validates the feasibility of using coking coal to adsorb organic pollutants in coking wastewater. The sorption kinetics and equilibrium sorption isotherms of coking coal for removal of chemical oxygen demand (COD) and phenol from coking wastewater was also discussed in this paper. Gas chromatograph/mass spectroscopy (GC/MS) was used to detect changes in the quality of coking wastewater. The results showed that when coking coal dosage was 120 g/dm3, 65% of COD and 34% of phenol in waste water can be removed after 40 min of agitation. The surface functional groups of coking coal before and after adsorption were observed with a Fourier transform infrared spectrometer. The kinetics of COD and phenol adsorption from coking wastewater by coking coal fitted the pseudo second-order model. The adsorption process of coking coal can be classified into two categories, namely, rapid and slow. The Freundlich isotherm provided a better fit with all adsorption isotherms than the Langmuir isotherm. Coking coal could be a suitable low-cost adsorbent for recalcitrant organic pollutants.

2

Flotation behavior of hard-to-separate and high-ash fine coal

Xing Y., Gui X., Liu J., Cao Y., Zhang Y., Li S.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 2

703--717

EN

The flotation behavior of hard-to-separate and high-ash fine coal was investigated using conventional flotation with constant power input. A new flotation process, based on energy input and distribution, was designed to lower the ash content of concentrate. The results obtained using Fourier transform infrared (FTIR) analysis show that the coal samples have good floatability because of many hydrophobic and few hydrophilic functional groups. Under a constant power input, a large number of ash-forming materials floated into a froth product at the start of flotation. Based on the Fuerstenau upgrading curves, it was determined that the 0.25-0.074 mm size fraction range showed the worst selectivity when compared with 0.50-0.25 mm and -0.074 mm size fractions. The desired concentrate with an ash content of 13.98%, 27.59% of ash recovery, and 80.01% combustible matter recovery could be obtained by transferring the excess energy of the flotation-conditioning stage to the pre-conditioning stage and increasing the power input step-by-step in the flotation-conditioning stage at equal total energy consumption.

3

Effect of intergrown particle liberation on difficult-to-separate coking coal flotation

Gui X., Liu J., Cao Y., Xing Y., Deng Y., Li S.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 1

279--294

EN

Flotation tests with intergrown particle liberation were conducted to explore a separation method of difficult-to-separate coking coal from the Tangshan Kailuan mine in China. The particle size distribution, density and coal petrography were investigated. The difficult-to-separate coking coal sample resulted in intergrown particles, such as non-liberated coal and rocks. Thus, intergrown coal particle liberation and re-separation tests were conducted. The results showed that grinding time had a great effect on the flotation performance. Grinding prompted coal to dissociate and improve the surface hydrophobic properties of minerals. However, heterogeneous fine silt covered the surface of coal particles when coal was ground too long. The inorganic mineral particles were over-ground and reduced the contact angle of coal. The results of coal rock dissociation and laboratory re-separation tests showed that clean coal combustible recovery increased through intergrown particle liberation and re-separation.

4

Effect of two-stage stirred pulp-mixing on coal flotation

Gui X., Wang Y., Zhang H., Li S.

Physicochemical Problems of Mineral Processing

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2014

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Vol. 50, iss. 1

299--310

EN

Stirred pulp-mixing is performed before coal flotation. In this study, a two-stage stirred pulpmixing tank was designed based on the single-stirred process to intensify the mixing effect of pulp and flotation reagents. A tank has a pitched-impeller opening-type turbine. Stirred pulp-mixing and flotation experiments were conducted on a sample of anthracite fine coal (-0.5mm) from the Xuehu Coal Preparation Plant in Henan Province, China. The results of the two-stage stirred pulp-mixing were compared with those of a single-stage stirred pulp-mixing in terms of flotation performance. Compared with the single-stage stirred pulp-mixing, two mixing areas and double-layer impeller were able to strengthen the energy input to the stirred system, thereby improving the mixing efficiency of flotation reagents and coal particles in the pulp. The two-stage stirred pulp-mixing significantly increased the flotation feed rate of the cyclone-static micro-bubble flotation column and concentrate yield, enhanced the combustible matter recovery effect of coarse particles at a suitable flotation feed rate, and ensured the recovery effect of fine particles at high flotation feed rate.

5

Flotation kinetics and separation selectivity of coal size fractions

Li Y., Zhao W., Gui X., Zhang X.

Physicochemical Problems of Mineral Processing

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2013

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Vol. 49, iss. 2

387--395

EN

Flotation recovery and kinetics for three size fractions of coal were investigated. Flotation of combustible matter recovery was approximated with the first order kinetic equation while flotation of the ash forming minerals with the second order equation. Next, the equations for each size fraction were combined and a formula was obtained which was used for approximation of the experimental results using the so-called Fuerstenau upgrading curve, which relates the recovery of combustible matter recovery and recovery of ash forming minerals, both in concentrate. The Fuerstenau upgrading plot showed that the best selectivity was obtained for the middle size fraction of 0.25–0.075 mm, while the flotation selectivity of larger 0.5–0.25 mm and smaller –0.075 mm particles was diminished. This finding agrees with many other investigations.

6

Two-Way Relaying Cooperative Wireless Networks : Resource Allocation and Performance Analysis

Abrar M., Gui X., Punchihewa A.

International Journal of Electronics and Telecommunications

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2013

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Vol. 59, No. 3

229-235

EN

Relay-based cooperative wireless networks have been widely considered one of the cost-effective solutions to meet the demands in future wireless networks. In order to maximize the overall sum-rate while maintaining proportional fairness among users, we investigate different resource allocation algorithms in two-way relay networks with analog network coding (ANC) protocol and time division broadcast (TDBC) protocol. The algorithms investigated are different from traditional proportional fairness schemes in terms of fairness and computational complexity as we have applied Access Proportional Fairness (APF) and Minimum Rate Proportional Fairness (MRPF) along with load balancing at the relays. A MATLAB simulation has been performed and simulation results show the effectiveness of these algorithms.