Using microwave pretreatment to improve the high-gradient magnetic-separation desulfurization of pulverized coal before combustion

Zhang, Zhenxing; Gao, Yan; Zhu, Guangqing; Zhao, Peng; Ma, Zhijun; Zhang, Bo

doi:10.1016/j.fuel.2020.117826

Cited by 37 publications

(11 citation statements)

References 21 publications

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“…To seek the key factors affecting the performance of the waterjet propulsion device, the orthogonal test is formulated. e orthogonal method is mature and widely used in many fields such as energy [28], chemistry [29], pharmacy [30], and environment [31]. e hydraulic performance and flow characteristics of the selected and original schemes are compared, and the suppression mechanism is analyzed.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Rotating Stall Phenomenon and Optimization in Mixed‐Flow Waterjet Propulsion Device

Luo

Zhang

et al. 2020

Advances in Materials Science and Engineering

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The rotating stall is a kind of flow phenomenon in the impeller harming the navigation speed of vessels propelled by a waterjet propulsion device when the waterjet propulsion device operates at the small flow rate conditions. The numerical simulated hydraulic performance was compared with experimental results so that the reliability of the CFD method was verified. The grooves are proposed before the inlet of an impeller to suppress the rotating stall. The orthogonal experiment is designed to seek the appropriate values of the parameters such as the length, width, depth, and number of the groove. The results show that the width of groove has the greatest influence on the performance of the device, followed by the number, the depth, and the length. The width, number, depth, and length of the selected groove scheme are 3.10 × 10−2D, 72, 3.10 × 10−2D, and 7.75 × 10−2D, respectively. At the rotating stall conditions, the selected groove scheme is numerically calculated. In contradistinction to the original scheme, it is found that the groove can improve the flow in the impeller and enhance the head of valley point condition, but the efficiency drops due to the increasing local hydraulic loss near the groove. When the groove is installed, the positive slop region on the flow rate-head curve disappears related to the static pressure difference on the blade, especially depending on the static pressure on the suction side. The flow pattern on the span surface of the vortex core is smooth, and then, the head increases. On the contrary, the head decreases. The outcome is beneficial to improve the performance of the waterjet propulsion device and enrich the rotating stall theory.

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Section: Introductionmentioning

confidence: 99%

Investigation of Rotating Stall Phenomenon and Optimization in Mixed‐Flow Waterjet Propulsion Device

Luo

Zhang

et al. 2020

Advances in Materials Science and Engineering

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“…The Box-Behnken response surface methodology was utilized to analyse the interaction between the three parameters. The quadratic model was recommended to fit the orthogonal results, which the value of Prob > F lower than 0.0001 [ 36 ]. In this case A, B, BC and B 2 are significant terms in the metals recovery with Prob > F values under 0.05.…”

Section: Resultsmentioning

confidence: 99%

“…The goodness of the recommended quadratic model is analyzed in Table 3 , where the value of the prediction R 2 was 0.8988, which means that the second-order polynomial model was accurate. The predicted residual sum of squares measures the signal to noise ratio, which is desirable to be greater than 4 [ 35 , 36 ]. The value of 22.825 indicates an adequate signal, which can be used to navigate the design space.…”

Section: Resultsmentioning

confidence: 99%

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Recovery of Metals from Heat-Treated Printed Circuit Boards via an Enhanced Gravity Concentrator and High-Gradient Magnetic Separator

Xian

Tao

et al. 2021

Materials

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The recovery and reuse of waste printed circuit boards (PCBs) has attracted more and more attention from global researchers, as recycling of waste PCB metals is of great significance to the rational utilization of metal material resources. This study puts forward a clean and economical method in which enhanced gravity separation and wet high-gradient magnetic separation were combined to recover waste PCBs with heat treatment at a temperature of 240 °C. The heat treatment could improve the metal liberation effect of the PCBs, and the thermal behavior was measured by thermogravimetric analysis (TGA). The pyrolysis of the non-metal fraction (NMF) began around 300 °C, and the glass transition temperature of epoxy resin was 135.17 °C. The enhanced gravity separation technique was used for the separation of metals and NMF under the compound force field. The metals grade of the gravity concentrates fraction (GRF) was 82.97% under the optimal conditions, and the metals recovery reached 90.55%. A wet high-gradient magnetic separator was applied to classify the GRF into magnetic (MA) and non-magnetic (NMA) fractions, which could achieve iron and copper enrichment. After the three stages combined process, the copper and iron grades of the NMA and MA fractions were 70.17% and 73.42%, and the recovery reached 74.02% and 78.11%, respectively.

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“…These two methods are widely useful in particular for the removal of organic fluorine [4,14,20,26]. For coal with a higher content of inorganic fluorine, the defluorination of pulverized coal before combustion using various physical or physicochemical methods has a low operating cost compared to the other two processes [27]. As mentioned previously, the majority of fluorine in coal is in association with inorganic minerals, indicating that most of the fluorine has a strong affinity for ash materials (i.e., gangue).…”

Section: Coal Samplementioning

confidence: 99%

Characterization and Removal Potential of Fluorine in Lignite from a Mine in Shaanxi Province, China: A Case Study

Zhou

et al. 2022

Minerals

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Fluorine appears in coal and is released into the atmosphere upon combustion, resulting in harmful impacts on the environment and life, which needs to be removed from coal before utilization. Coal can be processed by flotation and gravity separation to reduce its fluorine content. In this study, a lignite sample from a mine in Shaanxi Province, China, was characterized using the float–sink test, sieving test, X-ray diffraction (XRD), and polarized light microscopy. Mineralogical analysis indicated that the fluorine in coal is mainly contained in Muscovite and polylithionite, and partly in pyrite. The washability and floatability analyses were employed to evaluate the extent of fluorine removal from >0.5 and <0.5 mm size fractions of lignite, respectively. Compared to the raw sample that contained 347.74 μg/g fluorine content, the proposed combination of gravity-flotation separation process decreased the fluorine content to 90.14 μg/g, which meets the requisites of coal standards.

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Using microwave pretreatment to improve the high-gradient magnetic-separation desulfurization of pulverized coal before combustion

Cited by 37 publications

References 21 publications

Investigation of Rotating Stall Phenomenon and Optimization in Mixed‐Flow Waterjet Propulsion Device

Investigation of Rotating Stall Phenomenon and Optimization in Mixed‐Flow Waterjet Propulsion Device

Recovery of Metals from Heat-Treated Printed Circuit Boards via an Enhanced Gravity Concentrator and High-Gradient Magnetic Separator

Characterization and Removal Potential of Fluorine in Lignite from a Mine in Shaanxi Province, China: A Case Study

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