Energy & Fuels, Vol.32, No.1, 936-953, 2018
Separation and Upgrading of Fine Lignite in a Pulsed Fluidized Bed. 2. Experimental Study on Lignite Separation Characteristics and Improvement of Separation Efficiency
A pulsed fluidized bed system was established, targeting the analysis of the drying and separation characteristics of fine lignite. Experiments, involving factors of air velocity, pulsating frequency, and bed height were conducted under room temperature to analyze the influence of each factor on the separation characteristics of -6 + 3 mm lignite and -3 + 1 mm lignite in a pulsed fluidized bed, respectively. The combustible recovery and standard deviation of ash content were implemented to evaluate the separation efficiency. Results show three factors have a significant impact on the separation efficiency of fine lignite. Afterward, the thermal energy characterized by inlet temperature was imported into the pulsed fluidized bed system to study the influence of inlet temperature, air velocity, pulsating frequency, and bed height on the separation efficiency of fine lignite under thermal conditions. Results show that the ash content of the top layer product decreases significantly from 14.44% to 9.82% and from 15.52% to 7.31% when the pulsating frequency increases from 0 Hz to 3.93 Hz under room temperature and thermal conditions for 6 + 3 mm lignite, respectively. For 3 + 1 mm lignite, the ash content of the top layer product decreases from 17.22% to 10.25% and from 16.77% to 10.01% under room temperature and thermal conditions, respectively. Optimal operation parameters were determined. With the air velocity of 1.09 m/s, inlet temperature of 80 degrees C, pulsating frequency of 3.93 Hz, and bed height of 120 mm, the optimal separation efficiency was achieved for 6 + 3 mm lignite. For -3 + 1 mm lignite, the optimal is achieved when air velocity, inlet temperature, pulsating frequency, and bed height are 0.55 m/s, 100 degrees C, 3.49 Hz, and 80 mm. The separation efficiency of lignite with a pulsed fluidized bed was dramatically improved.