Zhenfu Luo - Academia.edu (original) (raw)
Papers by Zhenfu Luo
The Canadian Journal of Chemical Engineering, 2015
ABSTRACT A vibrated gas-solid fluidized bed was proposed and tested to improve and upgrade fine l... more ABSTRACT A vibrated gas-solid fluidized bed was proposed and tested to improve and upgrade fine lignite. A broad particle size (0.074–0.3 mm) of magnetite powder was prepared and used as main separating medium solids for coal improvement. The fluidization stability of the bed, including the fluidization index, fluctuations of bed pressure drop, and uniformity of bed density, was greatly enhanced by introducing the vibration energy to the static bed. The vibrated separation shows positive effects to improve the surface morphology of lignite and upgrade its quality to a certain degree. Ash-content segregation of fine lignite samples obviously occurs by the joint effects of fluidized gas and vibration. The optimal segregation degree Sash values of 0.73 and 0.70 were achieved with suitable operating factors. The density-dependent separation performance indicates that the ash and sulfur contents of lignite were sharply reduced with the probable error E values of 0.060 and 0.065 g/cm3. However, the overall E value for 6–1 mm sized fine lignite increases to 0.12 g/cm3 due to the shift in the D50 with particle size. The products of low-ash clean coal, middlings, and high-ash gangue were effectively obtained by successive separations. The dry coal improvement technology provides an alternative approach for the clean utilization of fine coal. This article is protected by copyright. All rights reserved
Powder Technology, 2015
ABSTRACT A separating fluidized bed (SFB) with magnetic powders as the heavy medium was used for ... more ABSTRACT A separating fluidized bed (SFB) with magnetic powders as the heavy medium was used for dry coal separation. However, during the continuous separation process in the modularized dry coal separation system, the bed density under the coal inlets was found to fluctuate seriously. In this study, the effect of feed with different densities on the fluidization of the SFB was investigated using pressure time series and image analyses. The pressure measured at different bed heights severely fluctuated when particles run into the bed, and the bed surface sunk locally. After feeding, the SFB returned to the previous status, being a “separating fluidized bed”. However, for large particles, the stability of the SFB was severely damaged, and the “separating fluidized bed” acted as a “bubbling fluidized bed”, after feeding. Therefore, particles large enough to damage the stability of the SFB should not be fed into the bed.
Energy Conversion and Management, 2015
ABSTRACT The comparative study between the high-ash lignite (HAS) and low-ash lignite (LAS) demon... more ABSTRACT The comparative study between the high-ash lignite (HAS) and low-ash lignite (LAS) demonstrated great effects of mineral matter on physico-chemical properties, inherent moisture and drying kinetics of Chinese lignite. The physico-chemical properties were characterized by X-ray diffraction (XRD), N2 physisorption, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and thermoanalytical methods. Raw and treated samples (screening, dry beneficiation, and flotation) were analyzed for inherent moisture content. Drying kinetic experiments were performed by isothermal thermogravimetry in combination with thin-layer models. In comparison with LAS, HAS had less cohesive features with higher amounts of heterogeneous crystalline minerals, less quantity of O-containing functional groups, and smaller surface areas as well as lower pore volumes, as evidenced by characterization analysis. Less cohesive features could allow the moisture to move easily through the lignite, which thus resulted in a lower inherent moisture contained in HAS. On the other hand, due to higher thermal conductivity and poorer holding-moisture structures resulted from the presence of abundant minerals, HAS revealed more promising drying kinetics with lower activation energies, which were determined by the combination of isothermal experiments and Page model analyses.
Particuology, 2015
ABSTRACT To improve the separation efficiency of air dense medium fluidized beds for dry coal pre... more ABSTRACT To improve the separation efficiency of air dense medium fluidized beds for dry coal preparation, a gas-vibro fluidized bed has been proposed in which magnetic powder is used as the heavy medium. Pressure fluctuations in the gas-vibro fluidized bed were investigated using time- and frequency-domain analysis methods. The relationship between pressure fluctuations, bubble behavior, and separation efficiency was established. The low amplitude of the standard deviation, the power spectral density (PSD), the incoherent-output PSD, and the high amplitude of the coherent-output PSD, which corresponds to the bubble behavior in the bed, were improved for coal preparation. The coal ash content was reduced from 42.55% to 16.54% by using the gas-vibro fluidized bed.
Fuel Processing Technology, 2014
ABSTRACT The drying performance of Chinese lignite particles in a laboratory scale vibration flui... more ABSTRACT The drying performance of Chinese lignite particles in a laboratory scale vibration fluidized bed dryer was investigated under various operating conditions: inlet air temperature (120–200 °C), superficial air velocity (1.5 Umf (the minimum fluidization velocity)–2.2 Umf,), frequency (10–50 Hz), amplitude (1–5 mm), particle size (0.5–6 mm) and bed height (20–60 mm). The drying results showed that higher temperature, larger air velocity, higher frequency and higher amplitude (not too high), smaller particle size and lower bed height were favorable for drying. The Midilli–Kucuk model provided the best fit of these drying results and further implied that the moisture transfer of lignite was mainly controlled by internal diffusion. In comparison with the case of an ordinary fluidized bed, the gas-vibro fluidized bed dryer exhibited improvement of drying characteristics. Moreover, the drying kinetics was largely dependent on the frequency and amplitude of vibration.
Energy & Fuels, 2014
ABSTRACT Fine coal dry separation technology has been one of the international research hotspots ... more ABSTRACT Fine coal dry separation technology has been one of the international research hotspots in the field of coal preparation. This article proposes the shallow bed dense-phase gas-solid fluidized bed separation technology to remove gangue from the high ash fine coal. According to the criterion of center pressure drop, the C-P, value can be finally reduced by reducing the bed height, H, to decrease the bed pressure drop, Delta P-B, under the condition of a fixed gas distributor pressure drop, Delta P-D. A fluidized bed of uniform and stable density was formed. The medium of 33% fine particles showed a better performance in -6+3 mm, -3+2 mm, and -2+1 mm fine coal separation than the medium of different fine particles content by ash segregation. A 100 nun bed height with a medium of 33% fine particles was selected to separate -6+3 mm fine coal. The ash content of cleaned coal reached 9.66% under the optimized conditions, whereas the clean coal yield reached more than 77.75%. For -3+2 mm fine coal, the cleaned coal yield was 82.59%, the ash content of clean coal was 10.93%, and the deash rate could reach 51.96%. The shallow bed dense-phase gas-solid fluidized bed exhibited poor liquidity and high viscosity under conditions of low gas velocities. The shallow bed dense-phase gas-solid fluidized bed (100 mm bed height) with medium containing 33% fine particles can separate the -6+2 mm fine coal.
International Journal of Mining Science and Technology, 2012
ABSTRACT In order to study the settling mechanism of particles in an air–solid magnetically stabi... more ABSTRACT In order to study the settling mechanism of particles in an air–solid magnetically stabilized fluidized bed (MSFB) for separation, we carried out free settling and quasi-zero settling tests on the tracing particles. The results show that the main resistance forces as the tracing particles settled in an air–solid MSFB were motion resistance force and yield force. The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles. The acceleration decreased from 3022.62 cm/s2 to zero in 0.1 s, and in the end, the particles stopped in the air–solid MSFB. The yield force on particles increased with increasing the magnetic field intensity, resulting in decrease of the quasi-zero settling displacement. However, the yield force on particles decreased with increasing the fluidized air velocity, leading to increase of the quasi-zero settling displacement. When the structure and operating parameters of the air–solid MSFB were set up, the yield stress on particles stopped in an air–solid MSFB was a function of diameter and density of particles. The settling displacements of equal diameter particles increased with increasing their densities, and the settling displacements of equal density particles increased with increasing their diameters.
International Journal of Mining Science and Technology, 2015
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology
ABSTRACT
The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed wa... more The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed was investigated with coal from South Africa. The coal used for the study has a low inherent moisture content, a moderate ash content, a moderate volatile content, a low sulphur content and a high calorific value. Its washability is moderate. Experimental results show that the separating quality of the fluidized bed drops gradually as the feedcoal particle size decreases. The probable error, E, values for 50-25 mm, 25-13 mm and 13-6 mm coals were 0.04 g/cm3, 0.06 g/cm3 and 0.09 g/cm3, respectively. The cause of the differences in separating characteristics was analysed by particle dynamics and numerical modelling. Furthermore, the pilot fluidized bed was employed to separate 50-6mm coal. In this experiment the coal ash content was reduced from 23.74% to 11.79%, with a probable error, E, value of 0.07 g/cm3 and a recovery efficiency of 98.26%. This indicates that the fluidized bed is applic...
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology
The transition and dissipation of vibration in a gas-solid fluidized bed with coarse particles (&... more The transition and dissipation of vibration in a gas-solid fluidized bed with coarse particles (>1 mm) was studied experimentally. The mechanism for the enhancement of fluidization peformance due to vibration was analyzed, from which a model for the separation fine coal particles in the bed was proposed. Finally, two types of feed coal from Wuhai region, 6-3 mm and 3-1 mm in diameter, were tested to evaluate the separation capability of the vibrated fluidized bed, and demonstrated that it can effectively discharge the gangue with high ash content and get clean coal product with low ash content. The separation efficiency, i.e. possible error E value of these two feed coal was 0.175-0.195 and 0.19-0.225, respectively.
International Journal of Mining Science and Technology, 2013
ABSTRACT Bed stability, and especially the bed density distribution, is affected by the behavior ... more ABSTRACT Bed stability, and especially the bed density distribution, is affected by the behavior of bubbles in a gas solid fluidized bed. Bubble rise velocity in a pulsed gas–solid fluidized bed was studied using photographic and computational fluid dynamics methods. The variation in bubble rise velocity was investigated as a function of the periodic pulsed air flow. A predictive model of bubble rise velocity was derived: ub=ψ(Ut+Up-Umf)+kpgdb. The software of Origin was used to fit the empirical coefficients to give ψ = 0.4807 and kp = 0.1305. Experimental verification of the simulations shows that the regular change in bubble rise velocity is accurately described by the model. The correlation coefficient was 0.9905 for the simulations and 0.9706 for the experiments.
International Journal of Mineral Processing
Coal consumption accounted for 70.48% of the primary energy consumption and coal preparation is u... more Coal consumption accounted for 70.48% of the primary energy consumption and coal preparation is used in clean coal technology. Dry separation of a high-density phase fluidized bed has gained widespread attention because of its high precision, stability, and efficiency of separation. The effects of a high-density coarse-particle layer on a gas-solid fluidized bed for coal preparation are necessary. Theoretical analysis of single particle packing structure shows that the pore of a high-density coarse layer has a decisive role in the uniform dispersion of airflow. The porosity rate of a high-density coarse layer is determined mainly by the stack height of particles, followed by the size of the particles in the layer. A mathematical model on bed pressure drop Delta P, height of high-density coarse layer H-CS and fluidizing gas velocity nu was established based on a dense phase gas-solid separation fluidized bed experiment. Density and distribution of coarse-particle layers combined to f...
Energy & Fuels
The combined dewatering process and dry separation in a vibration fluidized-bed dryer was develop... more The combined dewatering process and dry separation in a vibration fluidized-bed dryer was developed to upgrade Chinese lignite in terms of moisture and ash for effective utilization in power plants. The influence of operational parameters (fluidizing gas velocity, vibration strength, bed height, and drying temperature) and lignite properties (particle size and moisture content) on the drying or separation characteristics of −6-1 mm lignite was examined in a laboratory-scale vibration fluidized-bed dryer. Both operational parameters and lignite properties had a significant effect on the drying and separation performance. The drying and separation behaviors of a vibration fluidized bed were both enhanced in comparison to the case without vibration under the same operating conditions. Moreover, with the change in gas velocity, the drying and separation processes could be combined in the same vibration fluidized-bed dryer. Both processes achieved promising results compared to those of t...
Procedia Engineering, 2015
ABSTRACT Coal plays a dominant role in China's energy consumption structure. The efficien... more ABSTRACT Coal plays a dominant role in China's energy consumption structure. The efficient and clean utilization of coal sources has great significance to protect China's energy supply and environmental protection. Coal beneficiation is the primary technology of coal cleaning and recently, wet beneficiation of coal is the predominant method of purification in the world. However, the worldwide water shortage limits the development of wet beneficiation technologies. Then, it is urgent to develop efficient dry beneficiation theories and technologies. More than 2/3 China's coal resources are distributed in drought coal regions. In addition, China also has a large amount of low-rank coal which can be slimed easily. China needs to develop efficient dry coal beneficiation technology. In the gas-solid fluidized bed system, the shape of coal is of vital importance to the particle's sedimentation movement and it also has significant effect on the result of gravity concentration. In this essay, zingg index is cited to describe the shape of coal to distinguish the columnar particles from flaky ones, as a consequence of this, the equation of different particle's motion can be deduced. The experiment covers the columnar coal, flaky coal and lump ones; the result shows that separation efficiency for lump coal was the best, with EP reaching 0.055. As for columnar coal, the result was less satisfactory, reaching 0.11. In contrast, the distribution curve of flaky coal cannot be drawn because its shape affected the separation process.
Fuel, 2015
ABSTRACT Coal is one of the most important primary energy sources worldwide. With the shortage of... more ABSTRACT Coal is one of the most important primary energy sources worldwide. With the shortage of water resources and increasing acid rain, the studies on dry coal beneficiation have become more and more important. In this study, a gas-vibro fluidized bed introducing active pulsing gas into an air-dense medium fluidized bed was used for the deash and desulfurization of fine coal. The effects of gas velocity and pulsation frequency on the separation efficiency were investigated. The results show that acted by the active pulsing air flow the separation efficiency was enhanced when the pulsation frequency (f) ranged from 3.49 Hz to 5.24 Hz. Inorganic sulfur species such as pyrites and sulfate were removed efficiently. The SO2 emission during coal combustion could be reduced evidently after separation.
The Canadian Journal of Chemical Engineering, 2015
ABSTRACT A vibrated gas-solid fluidized bed was proposed and tested to improve and upgrade fine l... more ABSTRACT A vibrated gas-solid fluidized bed was proposed and tested to improve and upgrade fine lignite. A broad particle size (0.074–0.3 mm) of magnetite powder was prepared and used as main separating medium solids for coal improvement. The fluidization stability of the bed, including the fluidization index, fluctuations of bed pressure drop, and uniformity of bed density, was greatly enhanced by introducing the vibration energy to the static bed. The vibrated separation shows positive effects to improve the surface morphology of lignite and upgrade its quality to a certain degree. Ash-content segregation of fine lignite samples obviously occurs by the joint effects of fluidized gas and vibration. The optimal segregation degree Sash values of 0.73 and 0.70 were achieved with suitable operating factors. The density-dependent separation performance indicates that the ash and sulfur contents of lignite were sharply reduced with the probable error E values of 0.060 and 0.065 g/cm3. However, the overall E value for 6–1 mm sized fine lignite increases to 0.12 g/cm3 due to the shift in the D50 with particle size. The products of low-ash clean coal, middlings, and high-ash gangue were effectively obtained by successive separations. The dry coal improvement technology provides an alternative approach for the clean utilization of fine coal. This article is protected by copyright. All rights reserved
Powder Technology, 2015
ABSTRACT A separating fluidized bed (SFB) with magnetic powders as the heavy medium was used for ... more ABSTRACT A separating fluidized bed (SFB) with magnetic powders as the heavy medium was used for dry coal separation. However, during the continuous separation process in the modularized dry coal separation system, the bed density under the coal inlets was found to fluctuate seriously. In this study, the effect of feed with different densities on the fluidization of the SFB was investigated using pressure time series and image analyses. The pressure measured at different bed heights severely fluctuated when particles run into the bed, and the bed surface sunk locally. After feeding, the SFB returned to the previous status, being a “separating fluidized bed”. However, for large particles, the stability of the SFB was severely damaged, and the “separating fluidized bed” acted as a “bubbling fluidized bed”, after feeding. Therefore, particles large enough to damage the stability of the SFB should not be fed into the bed.
Energy Conversion and Management, 2015
ABSTRACT The comparative study between the high-ash lignite (HAS) and low-ash lignite (LAS) demon... more ABSTRACT The comparative study between the high-ash lignite (HAS) and low-ash lignite (LAS) demonstrated great effects of mineral matter on physico-chemical properties, inherent moisture and drying kinetics of Chinese lignite. The physico-chemical properties were characterized by X-ray diffraction (XRD), N2 physisorption, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and thermoanalytical methods. Raw and treated samples (screening, dry beneficiation, and flotation) were analyzed for inherent moisture content. Drying kinetic experiments were performed by isothermal thermogravimetry in combination with thin-layer models. In comparison with LAS, HAS had less cohesive features with higher amounts of heterogeneous crystalline minerals, less quantity of O-containing functional groups, and smaller surface areas as well as lower pore volumes, as evidenced by characterization analysis. Less cohesive features could allow the moisture to move easily through the lignite, which thus resulted in a lower inherent moisture contained in HAS. On the other hand, due to higher thermal conductivity and poorer holding-moisture structures resulted from the presence of abundant minerals, HAS revealed more promising drying kinetics with lower activation energies, which were determined by the combination of isothermal experiments and Page model analyses.
Particuology, 2015
ABSTRACT To improve the separation efficiency of air dense medium fluidized beds for dry coal pre... more ABSTRACT To improve the separation efficiency of air dense medium fluidized beds for dry coal preparation, a gas-vibro fluidized bed has been proposed in which magnetic powder is used as the heavy medium. Pressure fluctuations in the gas-vibro fluidized bed were investigated using time- and frequency-domain analysis methods. The relationship between pressure fluctuations, bubble behavior, and separation efficiency was established. The low amplitude of the standard deviation, the power spectral density (PSD), the incoherent-output PSD, and the high amplitude of the coherent-output PSD, which corresponds to the bubble behavior in the bed, were improved for coal preparation. The coal ash content was reduced from 42.55% to 16.54% by using the gas-vibro fluidized bed.
Fuel Processing Technology, 2014
ABSTRACT The drying performance of Chinese lignite particles in a laboratory scale vibration flui... more ABSTRACT The drying performance of Chinese lignite particles in a laboratory scale vibration fluidized bed dryer was investigated under various operating conditions: inlet air temperature (120–200 °C), superficial air velocity (1.5 Umf (the minimum fluidization velocity)–2.2 Umf,), frequency (10–50 Hz), amplitude (1–5 mm), particle size (0.5–6 mm) and bed height (20–60 mm). The drying results showed that higher temperature, larger air velocity, higher frequency and higher amplitude (not too high), smaller particle size and lower bed height were favorable for drying. The Midilli–Kucuk model provided the best fit of these drying results and further implied that the moisture transfer of lignite was mainly controlled by internal diffusion. In comparison with the case of an ordinary fluidized bed, the gas-vibro fluidized bed dryer exhibited improvement of drying characteristics. Moreover, the drying kinetics was largely dependent on the frequency and amplitude of vibration.
Energy & Fuels, 2014
ABSTRACT Fine coal dry separation technology has been one of the international research hotspots ... more ABSTRACT Fine coal dry separation technology has been one of the international research hotspots in the field of coal preparation. This article proposes the shallow bed dense-phase gas-solid fluidized bed separation technology to remove gangue from the high ash fine coal. According to the criterion of center pressure drop, the C-P, value can be finally reduced by reducing the bed height, H, to decrease the bed pressure drop, Delta P-B, under the condition of a fixed gas distributor pressure drop, Delta P-D. A fluidized bed of uniform and stable density was formed. The medium of 33% fine particles showed a better performance in -6+3 mm, -3+2 mm, and -2+1 mm fine coal separation than the medium of different fine particles content by ash segregation. A 100 nun bed height with a medium of 33% fine particles was selected to separate -6+3 mm fine coal. The ash content of cleaned coal reached 9.66% under the optimized conditions, whereas the clean coal yield reached more than 77.75%. For -3+2 mm fine coal, the cleaned coal yield was 82.59%, the ash content of clean coal was 10.93%, and the deash rate could reach 51.96%. The shallow bed dense-phase gas-solid fluidized bed exhibited poor liquidity and high viscosity under conditions of low gas velocities. The shallow bed dense-phase gas-solid fluidized bed (100 mm bed height) with medium containing 33% fine particles can separate the -6+2 mm fine coal.
International Journal of Mining Science and Technology, 2012
ABSTRACT In order to study the settling mechanism of particles in an air–solid magnetically stabi... more ABSTRACT In order to study the settling mechanism of particles in an air–solid magnetically stabilized fluidized bed (MSFB) for separation, we carried out free settling and quasi-zero settling tests on the tracing particles. The results show that the main resistance forces as the tracing particles settled in an air–solid MSFB were motion resistance force and yield force. The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles. The acceleration decreased from 3022.62 cm/s2 to zero in 0.1 s, and in the end, the particles stopped in the air–solid MSFB. The yield force on particles increased with increasing the magnetic field intensity, resulting in decrease of the quasi-zero settling displacement. However, the yield force on particles decreased with increasing the fluidized air velocity, leading to increase of the quasi-zero settling displacement. When the structure and operating parameters of the air–solid MSFB were set up, the yield stress on particles stopped in an air–solid MSFB was a function of diameter and density of particles. The settling displacements of equal diameter particles increased with increasing their densities, and the settling displacements of equal density particles increased with increasing their diameters.
International Journal of Mining Science and Technology, 2015
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology
ABSTRACT
The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed wa... more The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed was investigated with coal from South Africa. The coal used for the study has a low inherent moisture content, a moderate ash content, a moderate volatile content, a low sulphur content and a high calorific value. Its washability is moderate. Experimental results show that the separating quality of the fluidized bed drops gradually as the feedcoal particle size decreases. The probable error, E, values for 50-25 mm, 25-13 mm and 13-6 mm coals were 0.04 g/cm3, 0.06 g/cm3 and 0.09 g/cm3, respectively. The cause of the differences in separating characteristics was analysed by particle dynamics and numerical modelling. Furthermore, the pilot fluidized bed was employed to separate 50-6mm coal. In this experiment the coal ash content was reduced from 23.74% to 11.79%, with a probable error, E, value of 0.07 g/cm3 and a recovery efficiency of 98.26%. This indicates that the fluidized bed is applic...
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology
The transition and dissipation of vibration in a gas-solid fluidized bed with coarse particles (&... more The transition and dissipation of vibration in a gas-solid fluidized bed with coarse particles (>1 mm) was studied experimentally. The mechanism for the enhancement of fluidization peformance due to vibration was analyzed, from which a model for the separation fine coal particles in the bed was proposed. Finally, two types of feed coal from Wuhai region, 6-3 mm and 3-1 mm in diameter, were tested to evaluate the separation capability of the vibrated fluidized bed, and demonstrated that it can effectively discharge the gangue with high ash content and get clean coal product with low ash content. The separation efficiency, i.e. possible error E value of these two feed coal was 0.175-0.195 and 0.19-0.225, respectively.
International Journal of Mining Science and Technology, 2013
ABSTRACT Bed stability, and especially the bed density distribution, is affected by the behavior ... more ABSTRACT Bed stability, and especially the bed density distribution, is affected by the behavior of bubbles in a gas solid fluidized bed. Bubble rise velocity in a pulsed gas–solid fluidized bed was studied using photographic and computational fluid dynamics methods. The variation in bubble rise velocity was investigated as a function of the periodic pulsed air flow. A predictive model of bubble rise velocity was derived: ub=ψ(Ut+Up-Umf)+kpgdb. The software of Origin was used to fit the empirical coefficients to give ψ = 0.4807 and kp = 0.1305. Experimental verification of the simulations shows that the regular change in bubble rise velocity is accurately described by the model. The correlation coefficient was 0.9905 for the simulations and 0.9706 for the experiments.
International Journal of Mineral Processing
Coal consumption accounted for 70.48% of the primary energy consumption and coal preparation is u... more Coal consumption accounted for 70.48% of the primary energy consumption and coal preparation is used in clean coal technology. Dry separation of a high-density phase fluidized bed has gained widespread attention because of its high precision, stability, and efficiency of separation. The effects of a high-density coarse-particle layer on a gas-solid fluidized bed for coal preparation are necessary. Theoretical analysis of single particle packing structure shows that the pore of a high-density coarse layer has a decisive role in the uniform dispersion of airflow. The porosity rate of a high-density coarse layer is determined mainly by the stack height of particles, followed by the size of the particles in the layer. A mathematical model on bed pressure drop Delta P, height of high-density coarse layer H-CS and fluidizing gas velocity nu was established based on a dense phase gas-solid separation fluidized bed experiment. Density and distribution of coarse-particle layers combined to f...
Energy & Fuels
The combined dewatering process and dry separation in a vibration fluidized-bed dryer was develop... more The combined dewatering process and dry separation in a vibration fluidized-bed dryer was developed to upgrade Chinese lignite in terms of moisture and ash for effective utilization in power plants. The influence of operational parameters (fluidizing gas velocity, vibration strength, bed height, and drying temperature) and lignite properties (particle size and moisture content) on the drying or separation characteristics of −6-1 mm lignite was examined in a laboratory-scale vibration fluidized-bed dryer. Both operational parameters and lignite properties had a significant effect on the drying and separation performance. The drying and separation behaviors of a vibration fluidized bed were both enhanced in comparison to the case without vibration under the same operating conditions. Moreover, with the change in gas velocity, the drying and separation processes could be combined in the same vibration fluidized-bed dryer. Both processes achieved promising results compared to those of t...
Procedia Engineering, 2015
ABSTRACT Coal plays a dominant role in China's energy consumption structure. The efficien... more ABSTRACT Coal plays a dominant role in China's energy consumption structure. The efficient and clean utilization of coal sources has great significance to protect China's energy supply and environmental protection. Coal beneficiation is the primary technology of coal cleaning and recently, wet beneficiation of coal is the predominant method of purification in the world. However, the worldwide water shortage limits the development of wet beneficiation technologies. Then, it is urgent to develop efficient dry beneficiation theories and technologies. More than 2/3 China's coal resources are distributed in drought coal regions. In addition, China also has a large amount of low-rank coal which can be slimed easily. China needs to develop efficient dry coal beneficiation technology. In the gas-solid fluidized bed system, the shape of coal is of vital importance to the particle's sedimentation movement and it also has significant effect on the result of gravity concentration. In this essay, zingg index is cited to describe the shape of coal to distinguish the columnar particles from flaky ones, as a consequence of this, the equation of different particle's motion can be deduced. The experiment covers the columnar coal, flaky coal and lump ones; the result shows that separation efficiency for lump coal was the best, with EP reaching 0.055. As for columnar coal, the result was less satisfactory, reaching 0.11. In contrast, the distribution curve of flaky coal cannot be drawn because its shape affected the separation process.
Fuel, 2015
ABSTRACT Coal is one of the most important primary energy sources worldwide. With the shortage of... more ABSTRACT Coal is one of the most important primary energy sources worldwide. With the shortage of water resources and increasing acid rain, the studies on dry coal beneficiation have become more and more important. In this study, a gas-vibro fluidized bed introducing active pulsing gas into an air-dense medium fluidized bed was used for the deash and desulfurization of fine coal. The effects of gas velocity and pulsation frequency on the separation efficiency were investigated. The results show that acted by the active pulsing air flow the separation efficiency was enhanced when the pulsation frequency (f) ranged from 3.49 Hz to 5.24 Hz. Inorganic sulfur species such as pyrites and sulfate were removed efficiently. The SO2 emission during coal combustion could be reduced evidently after separation.