Influence Of Ultrasound/Electrochemical Pretreatment On The Dewatering Perfomance Of Fine-grained Lignite

With the tension of the global energy demand and the development of green economy demands, more and more people began to pay attention to the efficient use of coal resources, especially the technology research of use of low-level lignite became a focus and hot spot, but the high content of water of the lignite coal, which directly increased the transportation cost, even influenced the normal operation of production device, and reduced the coal to these as the raw power generation or the economy of the Efficient use. For the viscous slurry, low filter speed and high moisture of fine-grained lignite, to develop a reasonable set of fine-grained lignite dewatering, seeking an effectively fine-grained lignite vacuum dewatering technology method is a Premise of effective use of lignite, having an important practical significance.The raw material of this thesis was derived from the Zhalainuoer North mines in Mongolia. On the basis of the determination of fine lignite surface properties and pore structure, pretreatment of fine lignite coal slurry by electrochemistry, ultrasound, ultrasound-electrochemical. Examine the vacuum performance impact of dewatering of fine-grained brown coal and obtained optimum conditions of dewatering. Using XRD, SEM, FTIR, contact angle and so on to characterize the sample in order to elaborate the interaction mechanism of ultrasound-electrochemical. The following conclusions were drawn:1.In the vacuum filtration test of coal slurry, the total moisture of cake increased with the increasing of concentration of coal slurry, but totally had removal effect which is not obvious. When the concentration of coal slurry is 150g/L, and the total moisture of cake is 45.73%, the inherent moisture of cake is 18.85%.2.Using of graphite-the iron electrode. Investigated the electrolysis time, the electrolytic current and electrolyte type, dosage, to the effect of fine lignite dehydration. When the concentration of coal slurry is 150g/L, the electrolysis time is 30 min, the electrolytic current is 0.5A, the electrolyte is A12 (SO4) 3, and when electrolyte amount is 1000g/t, the lowest inherent moisture of cake content decreased from 18.85% to 7.15%. It explained that after the electrochemical pretreatment of fine lignite coal slurry, can significantly removal the inherent moisture.3.Respectively using 20kHz,59kHz frequency ultrasound pretreatment to fine lignite coal slurry. Under the effect of 20kHz frequency ultrasound, total moisture of the cake have decreased from 45.73% to 43.2%, but inherent moisture of the cake have no obvious changes. Under the effect of 59kHz frequency ultrasound, total moisture and inherent moisture and respectively decreased from 45.73% and 18.85% to 42.8% and 16.54%. The ultrasonic pretreatment of 59kHz frequency can affect the nature of the particle surface and internal pore structure through cavitations, change the surface hydrophobic, prompt the more developed fine pores particles collapse within the particles, increase the aperture and promote the removal of inherent moisture.4.Investigated the effect of different combinations of electrochemical pretreatment and ultrasonic pretreatment on the role of fine-grained brown coal vacuum dewatering. Ultrasound under the conditions of the electrochemical late. The total moisture and inherent moisture in the cake were lower than other pretreatment, were 6.5%and 36% respectively. Relative to the single-filter blank test was reduced by 12.35% and 9.73%.5.Analysis the result by Fourier Transform infrared spectroscopy (FTIR) found that the hydrophilic oxygen-containing groups of particles surface after the pretreatment reduced. At the same time, contact angle measurements on the surface of coal particles found after ultrasound-electrochemical pretreatment the fine lignite contact angle increased by 16° and coal sample wet ability decreased, thereby enhancing the effect of fine-grained brown coal dewatering. Scanning electron microscopy (SEM) observed that after pretreatment the average area of pores gradually increased, and inherent moisture occurred in the pore was easier removable, promoting the enhance of dehydration efficiency; Determination of fine-grained brown coal particle size distribution by laser particle size analyzer, after a large particle proportion decreased significantly after pretreatment, particle size distribution becomes more uniform, and promote effect of dehydration in a certain extent, but Intensity is too large can lead to fine smaller grain size content increasing, so that the cake moisture removable difficult. Therefore rational conditions of pretreatment should be chosen.