周恩会,赵跃民,董良,等. 振动重介质分选流化床流化质量改善机理与细粒煤高效分选[J]. 煤炭学报,2023,48(12):4559−4570. DOI: 10.13225/j.cnki.jccs.2023.1201
引用本文: 周恩会,赵跃民,董良,等. 振动重介质分选流化床流化质量改善机理与细粒煤高效分选[J]. 煤炭学报,2023,48(12):4559−4570. DOI: 10.13225/j.cnki.jccs.2023.1201
ZHOU Enhui,ZHAO Yuemin,DONG Liang,et al. Mechanism of improving fluidization quality and efficient dry fine coal separation in vibrated dense medium fluidized bed for separation[J]. Journal of China Coal Society,2023,48(12):4559−4570. DOI: 10.13225/j.cnki.jccs.2023.1201
Citation: ZHOU Enhui,ZHAO Yuemin,DONG Liang,et al. Mechanism of improving fluidization quality and efficient dry fine coal separation in vibrated dense medium fluidized bed for separation[J]. Journal of China Coal Society,2023,48(12):4559−4570. DOI: 10.13225/j.cnki.jccs.2023.1201

振动重介质分选流化床流化质量改善机理与细粒煤高效分选

Mechanism of improving fluidization quality and efficient dry fine coal separation in vibrated dense medium fluidized bed for separation

  • 摘要: 煤炭清洁高效利用是国家重大战略需求。随着我国煤炭工业重心战略西移和综采技术的普及,所开采的原煤尤其是动力煤日趋“贫、细、杂”化,迫切需要细粒煤高效干法分选技术。细粒煤具有迎风面积小、重力效应弱的特点,风力分选时介质密度与分选密度差异大,传统的干法重介质分选时气泡大、返混严重,均无法在有限时间和空间内实现细粒煤有效分离。将简谐振动与上升气流协同输入气固重介质流化床,通过振动能量强化气固接触、抑制气泡兼并、改善流化质量。着重研究了振动能量在床层中的传递过程与床层响应规律,发现床层密度的扰动程度主要取决于上升气流与振动能量的竞争协调结果,气泡引发床层密度的随机性波动,振动能量将颗粒由无规律的随机运动转变为周期性振荡,沿床层轴向挤压破碎气泡;基于经典两相理论,结合床层塌落过程中气泡相与乳化相的逸出规律,计算得到了振动激励下气体在气泡相与乳化相中的分布比例,表明振动能量可以有效驱使气体由气泡相迁移至乳化相,气泡体积减少19.23%,削弱了气泡引起的床层波动,改善了流化质量,形成了均匀稳定的流态化分选环境。建立了振动对流化质量改善效果的量化评价模型,明确了适合细粒煤高效分选的振幅、频率、气速3因素协同操作范围,将新疆黑山矿薄煤层6~1 mm精煤发热量相较于原煤提高了4 571 kJ/kg。

     

    Abstract: Clean and efficient utilization of coal is a major strategic demand in China. With the strategic transfer of China’s coal industry to the western region and the wide application of comprehensive mining technology, the raw coal, especially steam coal, is becoming increasingly “poor, fine, and miscellaneous”. There is an urgent need for an efficient dry fine coal separation technology. Fine coal has the characteristics of small windward area and weak gravity effect. Wind separation methods have large differences in medium density and separation density, as well as large bubbles and severe backmixing when using traditional air dense medium separation technology. These methods cannot achieve an effective separation of fine coal in a limited time and space. In this study, simple harmonic vibration and upward airflow were synergistically inputted into a gas-solid fluidized bed, aiming to enhance gas-solid contact, suppress bubble merging, and improve fluidization quality through vibration energy. The transfer process of vibration energy in the bed and the response law of the bed particles were studied. It was found that the disturbance degree of bed density mainly depends on the competition and coordination between the upward airflow and vibration energy. The bubbles cause random fluctuations in bed density, and the vibration energy transforms particles from irregular random motion to periodic oscillation. The bubbles are compressed and broken axially along the bed. Combining the classical two-phase theory and the escape law of bubble phase and emulsified phase during bed collapse, the distribution ratio of gas in the bubble phase and emulsion phase under vibration excitation was calculated. It was found that vibration energy can effectively drive the gas from the bubble phase to the emulsified phase, reducing the bubble volume by 19.23%, effectively weakening the bed wave caused by bubbles. The fluidization quality has been improved. A uniform and stable fluidized separation environment is formed. A quantitative evaluation model for the effect of vibration energy on fluidization quality improvement has been established. The synergistic operation ranges of amplitude, frequency, and gas velocity suitable for an efficient separation of fine coal have been clarified. A series of separation experiments were conducted, which increased the calorific value of 6-1 mm clean coal from the Heishan Coal Mine in Xinjiang by 4 571 kJ/kg compared to raw coal.

     

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