Study On Drying Characteristics Of Lignite In Vibration Fluidized Bed

In china the brown coal accounted for about13%of the total coal, and with theenvironmental problems and energy crisis intensified, processing and utilization of low-qualitycoal need to be explored and studied deep step by step. mostly,the brown coal that used in browncoal utilization technologies are dried, therefore how to dry the brown coal fastly and effectively isan important task to the utilization of the brown coal.This article studied the characteristics of the brown coal drying, and it is built on the flow anddrying experiments of the brown coal, combined with its dynamic characteristics.This paper give an brief introduction of the distribution of the brown coal in domestic andoverseas and drying technology, and give a detailed description of the internal structure of thebrown coal and the form of moisture in it. Also the vibration mechanism of the vibration fluidizedbed, bed characteristics and drying characteristics are introduced and explained, at last the dryingmethod of the fine-grained brown coal that used in this paper is confirmed.The comparative study give an qualitative description and analyze on the changes anddifferences in fluidization characteristics at different moisture content, different size, different ashcontent and different vibration parameters, by the bed pressure drop and minimum fluidizationvelocity. Also the effects of frequency and gas velocity on particle mixing degree of brown coaland the effect of frequency and amplitude on the degree of mixing are observed. As for theMongolia1st brown coal, With the decrease of the moisture content of lignite, particle size andash, minimum fluidization velocity decreases, as fluidized, the fluidized bed are more stable. Withthe increases of the amplitude and decrease of frequency, the initial fluidization velocity of theparticles increases, the fluidized bed become unstable. When the gas velocity is low, the action ofvibrating is to dense the bed. At higher gas velocity, bed expansion becomes positive, but, withincreasing frequency, the bed expansion become lower until the bed height does not change. Withincreasing frequency, the degree of mixing of the bed weaker after inhancing. As the amplitudeincreases, the the mixed bed occurs decreasing tendency.Through the drying experiment system platform, we studied the drying variationcharacteristics of brown coal at different particle size, moisture content, vibration parameters, inlettemperature, air speed, etc. At last we drew a conclusion that as for the Mongolia1st brown coalAs the particle size decreases, the reduction in height of the bed, the increase of inlet temperatureand wind speed, the drying time becomes shorter, the drying rate is increased. As the frequencyincreases, the drying rate increases. Drying rate increases and then decreases with the amplitudeincreasing. the drying effect is the best when the vibration frequency f=30HZ,the vibration amplitude=2mm,the height of the bed H=40mm, the inlet temperature T=160℃, the fluidizationnumber N=2, and by established regression mathematical model we get the equation to fit theeffect characteristics of different factors perfect, correlation coefficients were above0.99. Studingon the mechanism of vibration to the fluidized bed, the vibration can reduced draw bubbles, thusensuring the stability of the bed; in the inner water drying stage a low flow rate is more energyefficient.