Promoting Mechanism Of Microwave Irradiation On Slurryability Of Lignite

Through the coal water slurry (CWS) gasifying efficiently in entrained-flow with high temperature and high pressure, gas, liquid fuels and other chemical products can be produced. It is a hot topic in the field of clean coal technology at home and abroad. Lignite is very abundant which accounts for a third of the world’s coal reserves. However, it includes high moisture which results in high transportation costs and low efficiency. Modified lignite and made it into CWS is an effective way before utilizing it. Meanwhile, it has important significance for energy conservation and emission reduction by promoting clean coal technology progress.In this paper, microwave irradiation technique was employed to improve the slurryability of lignite. A preliminary research of the moisture removal process was studied firstly. Through calculation with the six different thin layer drying mathematical models, it was found that the Page model was the most appropriate model to describe the drying process of lignite. Comparing with the smaller reactor and fewer samples, bigger reactor and more samples result in lower dehydration energy consumption per unit. Moreover, the dehydration energy consumption decreased with the increasing of microwave power.Microwave irradiation can improve the slurryability of lignite effectively. With the increasing of the microwave power and time, the maximum solid concentration of Shengli CWS increased to51.65%(700W for10min) from46.67%. Meanwhile, Microwave irradiation also has a good suitability for different lignite. After being microwave irradiation at1000W for4min, the maximum concentration of five different CWSs made from Baiyinhua, Dongwuqi, Mengyuan, Shiguai and Gushan all increased. The CWS prepared from lignite which before or after microwave irradiation both shows pseudoplastic fluid.The fourier transform infrared spectrometer, N2adsorption porometer, contact angle measurement apparatus, micro electrophoresis and other instruments were employed to text the physical and chemical properties of lignite, and the promoting mechanism of microwave irradiation on slurryability of lignite was analysed. After microwave treatment, the oxygen-containing groups reduced, the pore structure changed, the contact angle and the Zeta potential increased. All above lead to a decrease of hydrophilicity of coal surface and the free moisture holding capacity of coal, which increase the free moisture in the same solid concentration of coal water slurries. Consequently, the slurryability of lignite was improved.