胜利提质褐煤表面含氧基团亲水位点的微波钝化

发布时间：2018-07-31 10:05

【摘要】：国内外开发了许多褐煤脱水提质技术,存在的主要问题是脱水提质后易回吸水分而浪费大量脱水能量,大量文献报道干燥褐煤回吸水分的主因是其表面含氧基团与水分存在较强相互作用。目前关于褐煤的研究集中于干燥对其理化性质的影响,很少有从本质上去研究如何钝化褐煤表面含氧基团,从而达到抑制回吸水分的目的。课题组成员微波干燥褐煤的研究结果表明微波对褐煤表面含氧基团有脱除作用,但针对低价值褐煤而言,高品质微波能量仅用于褐煤脱水不经济,因此在课题组成员研究的基础上,为了抑制脱水褐煤复吸水分和能源浪费,在常规脱水提质的基础上结合微波对表面含氧基团进行钝化。本文主要研究了胜利褐煤热空气、热真空脱水提质过程中微波辐照对含氧基团的钝化作用规律。通过微观含氧基团含量的变化来体现微波的钝化作用,并用宏观的水蒸汽吸附、接触角及Zeta电位等实验数据来进一步证明微波的钝化作用,从而为脱水提质过程中亲水含氧基团的钝化和常规褐煤干燥技术与微波钝化结合奠定理论基础。褐煤脱水实验结果表明,脱水率50%之前,热真空脱水优势明显强于热空气,微波脱水整个脱水过程都明显要优于前两者。含氧基团研究结果表明,胜利褐煤中含氧基团主要为羟基、羰基、羧基。提质褐煤微波辐照后,含氧基团含量有所变化,不同脱水程度热空气样品微波辐照后含氧基团总量的变化规律为先增加后减小再增加,不同脱水程度热真空样品微波辐照后含氧基团总量的变化规律为先增加后减小再增加再减小。对于热空气脱水及热真空脱水,脱水率达到50%左右时引入微波能进行表面亲水含氧基团钝化是较合适的。水蒸汽吸附实验结果表明,同一脱水率条件下微波脱水样品平衡复吸量远小于热空气样品的平衡复吸量,略小于热真空样品的平衡复吸量,微波脱水样品的总含水量也小于热空气和热真空样品的总含水量。脱水样品微波辐照后其复吸量的变化趋势和含氧基团变化趋势基本上一致。微波脱水样品接触角与相同脱水程度下的热空气和热真空样品接触角相比要远大于后两者的接触角。孔结构特性研究可知微波对褐煤热空气干燥煤样具有扩孔作用,微波的扩孔作用使得部分微孔向中孔转化,结合水蒸汽吸附数据可知孔结构对褐煤复吸及其持水能力影响不大。提质褐煤微波辐照后Zeta电位绝对值变小。综合含氧基团、水蒸汽吸附、接触角及Zeta电位的分析可得出:微波能在脱水率达50%~65%间加入能够起到较好的钝化作用。
[Abstract]:Many lignite dehydration and quality technologies have been developed at home and abroad. The main problem is that dehydration is easy to absorb water and waste a lot of dehydration energy. It is reported in a large number of literatures that the main reason for the moisture absorption of dry lignite is the strong interaction between oxygen groups and moisture on the surface of lignite. At present, the research on lignite is focused on the effect of drying on its physical and chemical properties, and few studies have been done on how to passivate oxygen-containing groups on the surface of lignite in order to restrain the absorption of water. The results of microwave drying of lignite show that microwave can remove oxygen-containing groups on lignite surface, but for low-value lignite, it is not economical to use high quality microwave energy only for lignite dehydration. Therefore, in order to restrain the water and energy waste of dehydrated lignite, the surface oxygen-containing groups were passivated on the basis of conventional dehydration and extraction combined with microwave. In this paper, the law of passivation of oxygen containing groups by microwave irradiation in the process of hot air and hot vacuum dehydration of Shengli lignite is studied. The effect of microwave passivation is reflected by the change of the content of oxygen group in microcosmic, and the experimental data of water vapor adsorption, contact angle and Zeta potential are used to further prove the passivation effect of microwave. The results provide a theoretical basis for the passivation of hydrophilic oxygen-containing groups and the combination of conventional lignite drying and microwave passivation. The experimental results show that before the dehydration rate of 50%, the superiority of thermal vacuum dehydration is obviously stronger than that of hot air, and the whole dehydration process of microwave dehydration is obviously better than that of the former two. The results show that the oxygen groups in Shengli lignite are mainly hydroxyl, carbonyl and carboxyl groups. After microwave irradiation of lignite, the content of oxygen-containing groups changed, and the total amount of oxygen groups in hot air samples with different dehydration degree increased first, then decreased, then increased. After microwave irradiation, the total oxygen content of hot vacuum samples with different degree of dehydration is increased first, then decreased and then decreased. For hot air dehydration and thermal vacuum dehydration, when the dehydration rate is about 50%, it is more appropriate to introduce microwave energy to passivate the hydrophilic oxygen-containing groups on the surface. The experimental results of water vapor adsorption show that the equilibrium reabsorption of microwave dehydrated samples is much smaller than that of hot air samples and slightly smaller than that of hot vacuum samples under the same dehydration rate. The total moisture content of microwave dehydrated samples is also smaller than that of hot air and hot vacuum samples. After microwave irradiation, the re-absorption of dehydrated samples is basically the same as that of oxygen-containing groups. The contact angle of microwave dehydrated sample is much larger than that of hot air and thermal vacuum sample under the same dehydration degree. The study of pore structure characteristics shows that microwave has the effect of pore expansion on lignite hot air drying coal sample. The effect of microwave repore expansion makes part of micropore to mesopore transform. Combined with the data of water vapor adsorption, the pore structure has little effect on the absorption of lignite and its water holding capacity. The absolute value of Zeta potential of extracted lignite decreased after microwave irradiation. From the analysis of oxygen group, water vapor adsorption, contact angle and Zeta potential, it is concluded that microwave can play a better role in passivation when the dehydration rate reaches 50% or 65%.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD849.2

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