Wang Guangming, Ma Zhijun, Zhou Zhijing, Zheng Yunsheng, Cheng Liang
College of Mining, Liaoning Technical University, Fuxin 12300, China.
College of Materials Science & Engineering, Liaoning Technical University, Fuxin 12300, China.
Molecules. 2024 Aug 6;29(16):3729. doi: 10.3390/molecules29163729.
In order to reduce the content of sulfur and ash in coal, improve the desulfurization and deashing rates, a combined experiment method of microwave magnetic separation-flotation was proposed for raw coal. The desulfurization and deashing rates of three experiment methods, namely, single magnetic separation, microwave magnetic separation, and microwave magnetic separation-flotation, were compared. Taking the microwave magnetic separation-flotation experiment method as the main line, the effects of the microwave irradiation time, microwave power, grinding time, magnetic field intensity, plate seam width, foaming agent dosage, collector dosage, and inhibitor dosage on desulfurization and deashing were discussed, and the mechanism of microwave irradiation on magnetic separation and flotation was revealed. The results show that under the conditions of a microwave irradiation time of 60 s, a microwave power of 80% of the rated power (800 W), a grinding time of 8 min, a plate seam width (the plate seam width of a magnetic separator sorting box) of 1 mm, a magnetic field intensity of 2.32 T, a foaming agent dosage of 90 g/t, a collector dosage of 2125 g/t, and an inhibitor dosage of 1500 g/t, the desulfurization and deashing effect is the best. The desulphurization rate is 76.51%, the sulfur removal rate of pyrite is 96.50%, and the deashing rate is 61.91%. Microwaves have the characteristic of selective heating, and the thermal conductivity of organic matter in coal is greater than that of mineral. Microwave irradiation can improve the reactivity of pyrite in coal, pyrolyze pyrite into high-magnetic pyrite, improve the magnetic properties, and improve the magnetic separation effect. Therefore, microwave irradiation plays a role in promoting magnetic separation. Through microwave irradiation, the positive and negative charges in coal molecules constantly vibrate and create friction under the action of an electric field force, and the thermal action generated by this vibration and friction process affects the structural changes in oxygen-containing functional groups in coal. With the increase in the irradiation time and power, the hydrophilic functional groups of -OH and -COOH decrease and the hydrophilicity decreases. Microwave heating evaporates the water in the pores of coal samples and weakens surface hydration. At the same time, microwave irradiation destroys the structure of coal and impurity minerals, produces cracks at the junction, increases the surface area of coal to a certain extent, enhances the hydrophobicity, and then improves the effect of flotation desulfurization and deashing. Therefore, after the microwave irradiation of raw coal, the magnetic separation effect is enhanced, and the flotation desulfurization effect is also enhanced.
为降低煤中硫和灰分的含量，提高脱硫率和脱灰率，提出了一种针对原煤的微波磁选 - 浮选联合实验方法。比较了单一磁选、微波磁选和微波磁选 - 浮选三种实验方法的脱硫率和脱灰率。以微波磁选 - 浮选实验方法为主线，探讨了微波辐照时间、微波功率、研磨时间、磁场强度、板缝宽度、起泡剂用量、捕收剂用量和抑制剂用量对脱硫和脱灰的影响，并揭示了微波辐照对磁选和浮选的作用机理。结果表明，在微波辐照时间为60 s、微波功率为额定功率（800 W）的80%、研磨时间为8 min、板缝宽度（磁选机分选箱的板缝宽度）为1 mm、磁场强度为2.32 T、起泡剂用量为90 g/t、捕收剂用量为2125 g/t、抑制剂用量为1500 g/t的条件下，脱硫和脱灰效果最佳。脱硫率为76.51%，黄铁矿的脱硫率为96.50%，脱灰率为61.91%。微波具有选择性加热的特性，煤中有机质的热导率大于矿物质的热导率。微波辐照可提高煤中黄铁矿的反应活性，将黄铁矿热解为高磁性黄铁矿，改善其磁性，提高磁选效果。因此，微波辐照对磁选起到促进作用。通过微波辐照，煤分子中的正负电荷在电场力作用下不断振动并产生摩擦，这种振动和摩擦过程产生的热作用影响煤中含氧官能团的结构变化。随着辐照时间和功率的增加， -OH和 -COOH等亲水性官能团减少，亲水性降低。微波加热使煤样孔隙中的水分蒸发，削弱表面水化作用。同时，微波辐照破坏煤和杂质矿物的结构，在交界处产生裂纹，在一定程度上增加煤的表面积，增强疏水性，进而提高浮选脱硫和脱灰效果。因此，原煤经微波辐照后，磁选效果增强，浮选脱硫效果也增强。
