Study On Synergistic Upgrading Of Fine Lignite By Drying And Separating In Pulsed Gas-solid Fluidized Bed

As a low rank coal,lignite has huge reserves in the world,and the realization of efficient utilization of lignite resources has become the research focus of today’s society.It is an effective method to use lignite directly as steam coal after drying and separation.Compared with wet coal preparation technology,Fluidization dry coal preparation technology does not use water in the separation process,which can not only realize the effective ash reduction and desulfurization of lignite resources,but also has the advantages in the separation process The potential of drying,dehydration and quality improvement.In this paper,the heating air and air flow pulsation mechanism are introduced into the gas-solid fluidized bed,and Geldart is used to study the effect of the heating air and the flow fluctuation mechanism on the gas-solid fluidized bed As a kind of heavy matter,Geldart B magnetite powder is used to form a hot pulsating air heavy medium fluidized bed.By heating the air bed,the drying rate of lignite is improved,the agglomeration of wet particles is restrained.Through the forced vibration of pulsating air flow on the bed layer,the granular activity of bed layer is enhanced,the contact efficiency of gas-solid is improved,the process of mass transfer and heat transfer is accelerated,and the gravity separation of fine brown coal is strengthened,and fine brown coal can be finally realized The process of coal drying and sorting is integrated.In this paper,the influence of temperature and frequency of air flow on the minimum fluidization velocity,The density and density stability of the bed are systematically examined by the fluidization test of the medium-heavy fluidized bed with pulsed hot air.The results show that the minimum rate of fluidization of the bed can be effectively lowered by increasing the air temperature and can be further lowered by introducing a forced air flow.The minimum value appears at f=3.5 Hz.As the temperature increases,the influence of the fluctuation frequency on the minimum velocity of the fluidizing gas in the bed layer gradually decreases;in a certain range,the air temperature and pulsation frequency decrease the bed density,and improve the bed density stability The synergistic effect of the property is favorable for the stable separation of lignite particles in the range of 120℃and pulse frequency of 2.62Hz-4.36Hz.The drying characteristics of fine brown coal were studied by drying experiments of-6+3mm and-3+1mm fine brown coal in a pulsating fluidized bed.The results show that the increase of air velocity,temperature and pulsation frequency and the addition of medium have significant effect on the removal of external water from lignite,which can effectively improve the drying rate of lignite.With the decrease of water,the drying rate is mainly affected by the pore structure inside the brown coal particles.Based on the study of fluidization characteristics of hot pulsating air dense medium fluidized bed and drying characteristics of fine lignite,the test of drying separation and synergistic upgrading of fine lignite was carried out,and the separation degree of bed ash,moisture,ash content and calorific value of clean coal product were taken as evaluation indexes,The results show that the optimum conditions for drying and separating-6+3 mm lignite in hot pulsating gas-solid fluidized bed are as follows:air velocity is 8.17 cm/s-8.80 cm/s,pulsating frequency is 3.50 Hz-4.36 Hz,temperature is 120℃-150℃,drying and separating time is 5min-8min.the ash content of clean coal product is 7.85%-9.95%,which is 62.9%-70.7%lower than that of raw coal,and the possible deviation e is 0.12 g/cm~3;The total moisture content is 12.38%-13.86%,which is 54.61%-59.46%lower than that of raw coal;Compared with the raw coal,the calorific value increased by 2419.25cal/g.This paper has 53 pictures,22 tables and 96 references.