Research Of Fluidized Lignite Drying Technology

Lignite coal with the characteristics of high water and low calorific value,which is used directly to generate electricity will lead to problems such as insufficient output of the milling system,low thermal efficiency of the boiler and low net efficiency of the power plant.It can be seen that drying and upgrading of lignite coal has important theoretical and practical significance.Combined with the rich gas of power plant and the high efficiency heat and mass transfer of gas-solid two-phase in fluidized bed.In this paper,the technology of fluidized lignite coal drying under low temperature flue gas is deeply studied.Based on the unsteady boundary conditions,established the lignite coal particle unsteady drying and temperature raising process model under fluidization state,in the model,the changes of flue gas temperature are considered,and the changes of lignite coal properties with its moisture content and the changes of flue gas with its temperature are taken into accout.This model is used to analyze the changes of water content,flue gas temperature and particle temperature in the drying process of lignite.The analysis shows,with the increase of particle size,the decrease of flue gas temperature,the decrease of flue gas velocity and the increase of bed thickness,the drying rate decreases,and the flue gas temperature has the greatest influence on the drying rate.For the lignite coal with an initial moisture content of 36.7 and a particle size of 3mm,The bed thickness is 300-450 mm.When the flue gas initial temperature is 200?,the drying time of lignite is recommended about 5-6min;When the gas initial temperature is 300?,the drying time of lignite coal is recommended about 4-5min.The better target water content of lignite coal is not less than 10%.Through the calculation of mass;heat balance;and the calculation of the relevant parameters of the fluidized bed,the fluidized bed drying system of Lignite dryness 200t/h under different flue gas temperature is designed and calculated,including the calculation of the size and structure of the drying equipment,and the calculation of drying system auxiliary equipment selection parameter.Taking a 600 MW boiler unit as the research object,the thermal calculation was carried out.The influence on the boiler unit operating parameters,economy and pollutant emission due to different water content lignite coal combustion was studied,it will provide some reference significance for designing of lignite coal dry system in burning lignite coal power plant.The results showed that compared with the burning the original lignite coal with water content of 36.7%,when burning lignite coal of the moisture content was 30%,25%,20%,15%,10%,the exhaust gas temperature respectively decreased 4.5?,7?,9?,11?and1.5?.The boiler thermal efficiency is respectively increased by 0.55%,0.84%,1.1%,1.3% and 1.5%.when the boiler thermal efficiency is increased by 0.55%,the power generation standard coal consumption will be reduced by 6.5g / kW·h,the purchasing coal will reduced 12.92 million yuan Per year,and the power consumption of pulverizer decrease by 12.9%,the fan power is reduced by 9.5%.And at the same time,combustion of dried lignite also reduces pollutant emissions,the greatest impact on the emission reduction of NOx.