Reasearch On Synergetic Upgrading Of Lignite Separating And Drying By A Column-type Pulsating Airflow Classifier

Lignite is featured as high moisture, low calorific value, easy to sliming, self-igniting, and difficult to sort and transport. As a result, developing the coal chemical project to carry out its on-site conversion is a sound choice. The lignite gasification technology can synthesize gas to produce the downstream products. At present, Ash removing and drying are the two main pretreatment techniques before lignite gasification. Based on the collected 3-1 mm and 6-3 mm Inner Mongolia lignite sample, the sorting-drying synergetic upgrading was carried out on the column-type pulsating airflow classifier established in the laboratory, so as to determine the scope of processing parameters, such as the airflow rate, pulsation frequency, feeding rate, and air temperature. In addition, research on the processing optimization was carried out and the Fluent Software was adopted to simulate the sorting and drying process, thus providing theoretical basis for the lignite sorting and drying theory, as well as reference for the future semi-industrial tests and industrial tests.This paper combines the theoretical knowledge of mineral processing, particle science, fluid mechanics, and heat and mass transfer theory, and makes dynamic analysis of the solid particles in pulsating hot airflow. Through the single factor test, the optimal single factor parameters of the 3-1 mm and 6-3 mm lignite fractions were determined.In condition when the airflow rate is 9.39m/s, thepulsation frequency is 2.07 Hz, the material delivery rate is 250.00g/s and the air temperature is 80.0℃, as to the 3-1 mm lignite, the test system can get a recovery of combustible object of 48.34%, a clean coal ash of 27.89% which is 10.19 percents lower than the raw coal ash, as well a total moisture of clean coal of 11.23%; in condition when the airflow rate is 11.61m/s, thepulsation frequency is 1.60 Hz, the material delivery rate is 200.00g/s and the air temperature is 80.0℃, as to the 6-3 mm lignite, the test system can get a recovery of combustible object of 73.91%, a clean coal ash of 21.43% which is also 10.12 percents lower than the raw coal ash, and a total moisture of clean coal of 12.43%. The sorting effect of the column-type pulsating airflow sorting-drying synergetic upgradingexperiment system on the6-3 mm particle-level lignite is better than that on the 3-1 mm lignite, but the drying effect of the test system on the 3-1 mm particle-level lignite is better than that on the6-3 mm particle-level lignite. After sorting and drying, the 6-3 mm lignite can meet the requirements of lignite gasification, and used for the pretreatment before the lignite fluidized gasification.Based on the single factor test, the Design-Expert Software was applied to carry out four-factor three-level orthogonal test on the 6-3 mm lignite fraction, getting a interactive(2FI) model influencing the recovery rate of combustible object and the moisture of light products. Among them, the interaction between the airflow rate and the feeding rate has the biggest impact on the recovery rate of combustible object, and the between the feeding rate and the air temperature has the biggest impact on the total moisture of light products. A mathematical model of the relationship between the recovery of combustible object, the total moisture of light products and each practical factor. Through optimizing the test was obtained, it reaches the optimal conditions for the sorting-drying synergetic upgrading of 6-3 mm lignite.In condition when the airflow rate is 11.28m/s, thepulsation frequency is 1.83 Hz, the feeding rate is 150.00g/s and the air temperature is 80.0℃, it can reduce the clean coal ash of the 6-3 mm lignite to 20.25% and the clean coal moisture to 11.21%, realizing a clean coal productivity of 63.21% and a recovery of 73.64%, which can effectively reduce the clean coal ash and moisture. In the optimal test conditions, the recovery efficiencyηof the column-type pulsating airflow sorting-drying synergetic upgrading device used to sort and dry the 6-3 mmlignite is 78.04%, the probable error EP is 0.15, and the imperfection value, I, is 0.28.The Eulerian-Eulerian model for gas-solid two-phase flow of the Fluent Software is suitable for the sorting and drying simulation of the 6-3 mm lignite, as well as to solve the sorting-drying residence time coupling problem, and the synergetic mechanism between sorting and drying dehydration heat transfer. In condition of selecting the optimal test parameters, while giving the pulsating hot airflow at a temperature of 354 K for 1.267 s, the coal and minerals can be effectively separated. After 2.503 s, the mineralswere basically concentrated at the aggregate port at the bottom of the sorting and drying column. After 2.968 s, the coal particles are basically distributed at the top of the device and escape from the exit. The coal particles stay in the sorting and drying column for about 2.968 s. When t is 2.503 s, the temperature of most coal particles is distributed between 310~337K. Within the drying time t is 2.968 s, the heat efficiency η of the 6-3 mm lignite keeps decreasing with time.