煤泥滤饼结构特性的研究

发布时间：2018-03-16 04:26

本文选题：煤泥　切入点：脱水特性　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着选煤技术的发展,在大多数选煤厂中,湿法选煤占据主要地位,由此带来的问题便是最终煤炭产品中的水分需要脱除。煤泥脱水往往伴随着滤饼的生成,而滤饼结构在很大程度上影响着脱水效果,一方面,滤饼结构受煤泥特性、煤浆性质的影响,另一方面,药剂制度也与滤饼结构有着密切的联系。本文主要研究了煤泥在不同条件下的脱水试验,分析了各种条件下的滤饼结构特性及其对脱水效果的影响机理,同时探索了煤泥脱水过程中,滤饼的动态生长规律,并利用灰色关联法分析了各因素对滤饼水分的影响程度,结果表明:(1)煤的变质程度对煤泥的脱水效果影响显著,中等变质程度的煤样脱水效果最好,变质程度过高或过低,都将不利于脱水的进行。煤泥粒度越大,所形成的滤饼比阻越小,孔隙率越大,水分在滤饼中的流动更加通畅,脱水速度越大,同时滤饼的分形维数随着煤泥粒度的增大而减小,孔隙内表面积减小,水分更易排出,使得最终的滤饼水分降低。由于黏土矿物在1.4-1.6g/cm~3密度级的煤泥中的富集使得滤饼比阻增大,孔隙率降低,脱水效果变差。(2)随着煤浆浓度的增加,滤饼的孔隙率降低,不利于的脱水的进行,同时分形维数变大,孔隙内表面更加粗糙,使得水分的排出难度加大。p H越小,煤浆中的H~+离子浓度越大,降低了颗粒表面对水分子的吸引力,使得二者更容易分离,同时随着pH的减小,滤饼的上表面的孔隙率增大,分形维数有所减小,滤饼比阻降低,更有利于脱水。(3)随着脱水过程的进行,滤饼孔隙的分形维数有所增加,滤饼的孔隙率先稍有增大后减小,在表面水消失之后继续进行脱水,又可以使得孔隙率有所增大。其中滤饼上表面的孔隙率随脱水时间变化的数学模型为:y=0.673x~2 9.982x+40.37,滤饼纵剖面的孔隙率随脱水时间变化的数学模型为:y=0.291x~2 4.223x+45.15。(4)通过比较各种价态及阴阳离子对煤泥脱水效果的影响可知,在阴离子为Cl~-时,一价阳离子K+和Na~+可以有效降低滤饼水分;二价阳离子Mg~(2+)和Ca~(2+)降低滤饼水分、提高脱水速度的效果更明显,其中Ca~(2+)的效果优于Mg~(2+);三价阳离子Fe~(3+)和Al~(3+)的助滤效果最好,Al~(3+)的稳定性高于Fe~(3+)。阳离子为Na~+时,阴离子Cl-的脱水效果最好,SO_4~(2-)次之,NO_3~-最差。(5)通过对不同药剂制度下的煤泥脱水效果对比分析可知,阳离子聚丙烯酰胺的助滤效果最佳,最佳药剂用量为150g/t,脱水速度为0.09mL/s.cm~2,此时的滤饼比阻最小,滤饼上表面的孔隙率最大为31%,分形维数小,最有利于脱水的进行。(6)利用灰色关联分析得到,各因素对滤饼水分影响程度从大到小排序依次为:颗粒粒度、煤浆浓度、煤浆pH、阳离子聚丙烯酰胺用量、煤样变质程度、AlCl_3用量。
[Abstract]:With the development of coal preparation technology, wet coal preparation occupies the main position in most coal preparation plants, which brings about the problem that the moisture in the final coal products needs to be removed. On the one hand, the structure of filter cake is affected by the characteristics of coal slime, coal slurry, on the other hand, The medicament system is also closely related to the structure of filter cake. In this paper, the dewatering tests of coal slime under different conditions are mainly studied, and the structural characteristics of filter cake under various conditions and its influence mechanism on the dehydration effect are analyzed. At the same time, the dynamic growth law of filter cake in the process of coal slime dehydration is explored, and the influence of various factors on moisture content of filter cake is analyzed by using grey correlation method. The results show that the degree of metamorphism of coal has a significant influence on the dehydration effect of coal slime. Coal samples with medium metamorphic degree have the best dehydration effect, too high or too low degree of metamorphism will be unfavorable to dewatering. The larger the particle size of coal slime, the smaller the specific resistance of the filter cake, the larger the porosity, and the more smooth the flow of water in the filter cake. With the increase of dehydration rate, the fractal dimension of filter cake decreases with the increase of coal particle size, the internal surface area of pore decreases, and the water is discharged more easily. Due to the enrichment of clay minerals in the coal slime of 1.4-1.6 g / cm ~ 3 density grade, the specific resistance of filter cake increases, the porosity decreases, and the dehydration effect becomes worse. 2) with the increase of coal slurry concentration, the porosity of filter cake decreases. At the same time, the fractal dimension becomes larger and the inner surface of the pore becomes rougher. The smaller the water excretion is, the smaller the H ~ + concentration in the coal slurry is, which reduces the attraction of the particle surface to the water molecules. At the same time, with the decrease of pH, the porosity of the upper surface of the filter cake increases, the fractal dimension decreases, and the specific resistance of the filter cake decreases, which is more favorable to the dehydration process. The fractal dimension of filter cake pore increased, the pore of filter cake increased slightly and then decreased, and then dehydrated after the surface water disappeared. The porosity of the upper surface of the filter cake varies with the dehydration time, and the mathematical model of the change of porosity with dehydration time of the filter cake is:: yyong 0.673xf2, 9.982x 40.37. the mathematical model of the variation of porosity with dehydration time of the filter cake profile is:: yyyong 0.291xf2 / 4.223x 45.15.4) by comparison, the porosity of the filter cake is 0.291x2 / 2 and 4.223x / 45.15.4 respectively. The effect of species valence and anion on the dewatering effect of coal slime is known. When the anion is Cln-, monovalent cations K and Na ~ can effectively reduce the moisture of filter cake, and the divalent cations Mg~(2) and Ca~(2) decrease the moisture of filter cake, and the effect of increasing dehydration rate is more obvious. The effect of Ca~(2) is better than that of Mg~(2, and that of trivalent cations Fe~(3) and Al~(3) is better than that of Fe~(3. The dehydration effect of anionic Cl- is better than that of SOS _ 4N _ 2) followed by No _ 3- worst. (5) by comparing and analyzing the dewatering effect of coal slime under different medicament systems, we can see that cationic polyacrylamide is the best filter aid. The optimum dosage is 150g / t, the dehydration rate is 0.09mL / s 路cm-2, the filter cake has the smallest specific resistance, the maximum porosity on the surface of the filter cake is 31g / t, the fractal dimension is small, and the dehydration is most favorable. The order of influencing factors on the moisture content of filter cake is: particle size, coal slurry concentration, coal slurry pH, cationic polyacrylamide content, coal sample metamorphism degree and AlCl3 consumption.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD94

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