Experimental Study On Microwave Removal Of Low Rank Coal Polar Functional Groups

Low rank coal has high internal water content, which not only makes it have low combustion efficiency and high transportation cost, but also increases the CO2 emission in the process of combustion and utilization. However, the low rank coal has a strong ability to absorb moisture and high spontaneous combustion tendency after drying, so it is difficult to completely solve the existing problems of low rank coal in the simple dehydration process.Oxygen functional groups is the primary sites and chemisorption sites of moisture adsorption and spontaneous combustion in the low rank coal. It is hopeful that by reduced oxygen containing polar functional groups content in coal samples method solve the plight of application caused to the strong ability to absorb moisture and high spontaneous combustion tendency of low rank coal. The microwave can be used to selectively act on polar molecules or groups, to evaporate or break down by absorb a large amount of energy. It has been studied that the oxygen containing polar functional groups in low rank coals can be decomposed effectively under microwave irradiation. However, there are few studies on the removal mechanism of the polar functional groups in low rank coal under microwave irradiation.In order to separately study the effect of microwave power, reaction time, reaction temperature on the removal of polar groups, in this paper we design microwave upgrading low rank coal characteristic experiment contrapuntally. The research shows that the thermal effect of microwave has an important influence on the removal of polar groups, and the polar group content in low rank coal is greatly decreased with the increase of the reaction temperature. It is also found that the removal of polar groups under microwave conditions is controlled by the reaction thermodynamics. In the same reaction temperature, the reaction time is difficult to achieve the purpose of improving the removal efficiency. And the study confirmed that the microwave power can be used as a single impact conditions directly affect the very radical removal effect in the first time. Under the same reaction temperature conditions, with microwave power improve poor stability of low rank coal in the carboxyl group decomposition rate increased gradually. On this basis, in this research speculated the correlation mechanism of the low rank coal polar groups decomposion by comparing the conventional / microwave treatment under the conditions of the same heating process, and microwave treatment experiments under near room temperature conditions. The results show that the same temperature conditions, microwave control compared to the conventional heating method has better results for the oxygen polar functional groups removal efficiency. Its action principle can be attributed to microwave selective heating effect or the nonthermal effect of microwave on polar groups(without the effect of electromagnetic energy to the transformation of the heat energy directly by high frequency electromagnetic fields caused by microwave); Upgrading experiments under normal temperature conditions, found in very low temperature also has certain removal effect for oxygen containing polar functional groups in low rank coal under microwave irradiation, and with the removal of increasing microwave power, irradiation time polar groups gradually increased. In this paper, the first experimental study confirmed that microwave irradiation for low rank coal in the oxygen containing polar functional groups of the removal of non thermal effect.