Shulei Song

Utilizing an Air-Dense Medium Fluidized Bed Dry Separating System for Preparing a Low-Ash Coal

An industrial-scale air-dense medium fluidized bed was used to prepare a low-ash coal from a feed coal that was difficult to wash. The low-ash coal provided raw material for preparing low-ash activated carbon. A new fluidized bed density control method for preparing a low-ash coal was proposed, which effectively reduced bed density fluctuation, thus maintaining the uniformity and stability of the bed density. A separation density of 1.42 g/cm3 was maintained in the air-dense medium fluidized bed to produce a clean coal with an ash content of 3.71%, with an E P value of 0.055. Results showed that the air-dense medium fluidized bed system is an efficient dry separation method for difficult-to-wash coal.

Fluidization Characteristics of a Gas-Paigeite-Powder Bed to be Utilized for Dry Coal Beneficiation

The physical properties of paigeite powder were investigated and the characteristics of a gas-solid fluidized bed using the powder were studied. The intent was to expand the choice of medium solids appropriate for fluidized bed dry coal beneficiation. Experimental results show that paigeite powder has a low density, a high saturation magnetization, and a small coercivity. Under suitable technical and operating conditions the fluidization performance of paigeite powder with either a narrow, or a specified wide, size range is good. A gas-paigeite fluidized bed, formed from 0.074–0.3 mm paigeite, was used to separate 6–13 mm, hard-to-wash coal at a separating density of 1.5 g/cm3. The ash content of this coal was reduced from 22.37% to 9.88%, with a clean coal recovery of 60.64% and a probable error, E, value of 0.075 g/cm3. This indicates good separation performance of the fluidized bed.

Fluidization Characteristics of a Fine Magnetite Powder Fluidized Bed for Density-Based Dry Separation of Coal

Gas-solid fluidized bed separation technique is very beneficial for saving water resources and for the clean utilization of coal resource. The hydrodynamics of 0.15–0.06 mm fine Geldart B magnetite powder were experimentally and numerically studied to decrease the lower size limit. The results show that the static bed height should be controlled near 300 mm (e.g., 300–350 mm). The bubble size, amount, and frequency of the fine particle bed are smaller than those of the bed containing 0.3–0.15 mm large Geldart B particles, thus leading to a higher bed activity. The pressure drop and density of the fine particle bed are uniform and stable, which indicates a good fluidization quality. Furthermore, simulated results are consistent with experimental data, which indicates the correctness and effectiveness of the simulations. The superficial gas velocity should be adjusted to not more than 1.8U mf for the fine particle bed. Additionally, wide size range magnetite powder, which contains 94.23 wt% < 0.3 mm particles with a 0.3–0.06 mm particles content of 91.38 wt%, was used in an industrial scale modularized demonstration system for 50-6 mm coal density separation. The ash content of feed coal was reduced from 55.35% to 14.67% with a probable error, E, value of 0.06 g/cm3.

Brown coal drying processes-a review

Brown coals become increasingly important in energy consumption with the deposits of other energy resources decreasing every year. The direct utilization of moist brown coals without drying brings many problems such as low combustion efficiency, high greenhouse gas emissions, and it is not acceptable for coal gasification or liquefaction. Pre-drying brown coal is necessary and meaningful. Various drying processes, mainly classified into evaporative and non-evaporative drying, are summarized in this paper, introducing the principles and analyzing the advantages and disadvantages.

The fundamental study on the reutilization of electronic scrap by passive pulsed air classifiers

As the electric and electronic technology being developed so quickly, the amount of electronic scrap (ES) becomes more and more enormous. The reutilization of ES is an urgent and challenging task achieved by adopting high efficiency, environmental friendly separation methods for reuse and recycle of electronic scrap. A practical and efficient separation method using passive pulsed air classifiers is introduced in this paper. In the pulsing air classifier, expansions and contractions separation of the throats impose a distance-varying airflow which alternately accelerates and decelerates the particles. Dynamics of the moving particles were analyzed by applying of advanced high-speed dynamic analyzing equipment. The ANSYS simulation results show that the accelerating region and symmetrical vortexes in the passive pulsed air separator are the basic reasons to achieve excellent separation based on density-dominant difference in passive pulsed air classifier. The results of the laboratory experiments indicate that the pulsing classifiers achieve more effective results of separation and get a wider range of operating velocities of the airflow than the non-pulsing ones. The acceleration and deceleration phenomenon of the air currents in the column of the passive pulsed separator provides a density dominant separation. It is concluded that this is favorable for electronic scrap processing.

Triboelectric Coal Beneficiation: A Potential Pollution Control Technique for Power Plant

The purpose of coal preparation is to reduce sulfur and other pollutants for utility application. The triboelectric dry beneficiation can work effectively for ultrafine coal particles of <200 mesh, and provide a unique opportunity for treating pulverized coal in power plants. High grade steam coal with low ash, low sulphur and high heat value can be obtained by this process, and then the pollution will be controlled before coal fired. Mineral impurities and coal matrixes can be tribocharged differently, and thus can be separated when an external electrostatic field is applied. This is implemented in triboelectric beneficiation. As a dry process, triboelectric separation has many advantages over traditional wet processes, notably the ability to operate in areas where water resources are scarce, and no need for dewatering. Triboelectric dry beneficiation well adapts to the large-scale pithead power station, especially in arid northwest area where coal resources are abundant. Additionally, triboelectric dry beneficiation has great potential to produce ultra-low ash coal for injection metallurgy and yielding such material of coal-based carbon as high-quality active carbon, etc.

Mercury Removal and Ash Reduction from Coal by an Air Dense Medium Fluidized Bed

ABSTRACT This study focused on the occurrence of mercury in coal and the effectiveness of mercury and ash removal by an air dense medium fluidized bed (ADMFB). Results of the study revealed that there was a linear correlation between the mercury content, ash content and density of coal. This was attributed to the fact that mercury mainly exists in high density minerals containing elements with a certain affinity for mercury such as silicon, aluminum, iron, titanium, potassium, sodium, chloride, zinc, and magnesium. There is therefore a good correlation between the separation efficiency of ADMFB and the quality of the clean coal, as well as the overall removal of mercury. By optimizing the operating conditions based on the fitting models, clean coal with a mercury content of 0.0841 ppm and a separation efficiency exceeding 99.8% was obtained. The desirability of the separation effect optimized by fitting models was 0.999. Based on these results, it was concluded that ADMFB is an effective way to remove mercury from coal and reduce its ash content.

Basic Research on the Separation of Electronic Scraps with an Active-Pulsed Airflow Classifier

The separation mechanism with the active-pulsed airflow was studied fundamentally in this paper. The displacement, velocity and acceleration of the equal settling particles within the active-pulsed airflow were observed by a Memrecam Ci3 motion particle analyzer. Result of the research shows that in the active-pulsed airflow the acceleration of low-density particles is greater than that of high-density particles, which leads to a distinct difference of the velocity and the displacement of the equal settling particles. Therefore, a density-dominant separation of particles was achieved owing to the difference of the acceleration. The separation experiments of +2-0.5 mm electronic scraps show that the active-pulsed airflow has higher separation efficiency than the conventional classification with an upward and steady airflow. In addition, when the pulsated frequency is 2.0 Hz, the separation efficiencies with the active-pulsed airflow classifier are about 5-10% higher than that of the steady airflow ones.