Study On Modification Of Macerals In Shenfu Coals And Its Flotability

This paper aims to increase macerals surface differences by surface modification for improving the effect of macerals flotation separation. The influence of microwave milling on the crushing and dissociation of macerals were investigated. The effect of microwave in hydrogen and methane atmosphere and ultraviolet radiation under organic matters atmosphere on surface properties of macerals were studied. And the influence of the variation of maceral surface properties on its flotability were anlysized which provides the important datas and guidance for the development of coal maceral separation techniques.Taking Shenfu coal as the research object, the effect of microwave-assisted mechanical-chemical activation on the performance of float-sink of Shenfu coal were researched. The effect of treatment time and treating method on particle distribution of treated coal powder and its float-sink properties were explored. The relationship of coal particle distribution and float-sink properties were analyzed. The results showed that combined treatment by microwave and mechanical-chemical activation has obvious effect on coal particle distribution and the float-sink properties of Shenfu coal. The yields increase in fine fraction coal and decrease in coarse fraction coal as the microwave treatment time extension; the contents of light component decrease as the grain size of screening decrease in the process of float-sink testing; and accordingly the heavy component increase which indicate that macerals will generate enrichment respectively in the process of grinding and screening, vitrinite (the contents of light component is higher) likely enrich in the coarse fraction and inertinite (mainly is fusinite and semifusinite, and the contents of heavy component is higher) tend to consist in the fine fraction of coal samples; the same size and components coal samples with different microwave treatment time have different results of float-sink which reavealed that microwave in the process of grinding have cleavage-assisted effect. The effect of grinder type and reagents on flotation results were researched. The results showed that the minimum yield of float and the maximum yield of sink were appeared in microwave irradiation for 2min, moreover, vitrinite and inertinite had the highest enrichment rates, 92.57% and 57.74% respectively. The enrichment rates of vitrinite of float and inertinite of sink were higher relatively when cationic reagents were used and the pH was 7, 85.04% and 47.34% respectively. And because of the weaker influences of surface electric properties of mineral particle when flotation used nonionic reagents, the recovery and maceral enrichment rate almost were not effected by the pH values of the pulp.The modification of Shenfu coal by a microwave treatment in hydrogen and methane atmosphere and maceral separation by flotation were investigated. The results indicate that the vitrinite and inertinite had the highest enrichment rates when the microwave treated in hydrogen atmosphere for 1min (92.71% and 54.35% respectively) and methane for 5min (89.98% and 52.99% respectively). Hand-picked samples, fusain (SFF) and vitrain (SFV) were modified using same way and the variation of contact angle and zeta potential were analyzed. The study found that the surface contact angles and zeta potentials of SFF and SFV have irregular changes with the extention of microwave treatment time. There were the biggest differences of PZC between SFF and SFV under the microwave treatment in hydrogen atmosphere for 1min and methane atmosphere for 2min. The enrichment rates of inertinite and vitrinite after separation by flotation increased with the enlargement of the wettability differences of SFF and SFV. The above results indicated that it is an effective method to enlarge the differences of surface properties of macerals via microwave modification to separate fusain and vitrain.A photocatalysis reactor was designed to reseach the effect of small organic moleculars modification under potocatalysis on maceral surface, and searching another approach to enlarge the wettability differences of macerals. The nitrogen that carried the small organic molecular substances reacted with coal samples under ultraviolet irradiation and the wettability of modified were analyzed . The results showed that the modification could obviously improve the differences of surface properties of macerals.The FTIR analysis showed that the maceral surface functional groups such as -OH,NH2,-NH,-COOH and C=C of aromatic hydrocarbons varied with different treatment methods and time. The XPS analysis indicated that the mainly changing surface groups in the process of modification were C-C, C-H, C-O, C=O, COO-, etc. Moreover, the change of the contents of C=O and COO- on the surface of SFF were more obviously than SFV. The wettability of the modified coal samples were effected by the cooperation of–OH and–COOH which resulted in the irregular changes of the wettability of SFF and SFV under different modified conditions.