Research On Selective Grinding Mechanism And Separating Enrichment Of Macerals In Shenfu Coal

With the optimization of China’s energy structure, high-efficiency and low-carbon clean utilization of coal has been greatly emphasized. Grading utilization is an important way to achieve clean and efficient conversion of coal. Currently, grading utilization is limited to pyrolysis polygeneration conversion of low rank coal, few researches were focused on the grading utilization from perspective of coal petrography. Jurassic low rank bituminous coals are rich in inertinite, which severely restricts their efficient conversion. The key to solve this problem is to clarify the characteristics of macerals separation. Therefore, maceral separation technology of high inertinite Jurassic coal not only has important theoretical significance for efficient and clean conversion and utilization, but also has good prospects for development.Shenfu coal is a typical Jurassic coal. Coals collected from Shenmu Wangjiagou mine were used as coal samples. Distribution characteristics, grindability, wettability and surface structure of Shenfu coal macerals were investigated systematically by means of optical microscopy, infrared spectroscopy and low-temperature nitrogen adsorption methods, as a result, interface interaction model was obtained. On the other hand, reseaches on selective grinding mechanism, heavy medium cyclone separation, and flotation separation and enrichment of the macerals were carried out comphensively.(1) Vitrain ash is lower than fusain, while total sulfur content in fusain is twice as that of vitain. Vitrinite contains more alkyl side chains and-NH2,-NH- and other cationic groups. Inertinite contains more aromatic structural units and the oxygen-containing functional groups. Different coal interface effects mainly consist of Van der Waals force, ?-? interaction between aromatic rings and hydrogen bonding. There are many medium and large holes in inertinite, with larger surface area than vitrinite.(2) Mohs hardness and Hardgrove grindability index of inertinite were significantly higher than vitrinite. The initial contact angle difference between vitrain and fusain is very little, while the equilibrium contact angle of fusain is far less than that of vitrinite. Water has good diffusion on fusain surface, which results in high wetting heat. Obvious difference in hydrophobicity between vitain and fusain can be observed.(3) Dissociation degree of coal macerals increases with the decrease of particle size. When particle size of the pulverized coal is 0.075~0.045 mm, dissociation degree of the coal macerals reached 92.3%. Distribution behaviors of coal macerals from microwave-assisted ball milling, impact grinding and airflow pulverizing treatements were considered, relationships between dissocciation degree and different grinding forces were dicussed, achieving the selective grinding model and mechanism. It was discovered that selective dissociation degree during airflow pulverization is higher.(4) Heavy medium cyclone separtion behavior of 1~0.2mm Shenfu fine coal was studied in laboratory with high density in first section and low density in second section. The maximum vitrinite enrichment ratio of vitrain is 79.73% when the cyclone’s cone ratio is 0.85, feeding pressure is 0.06 MPa, and ratio of solid to liquid is 1:4. The maximum inertinite enrichment ratio in the fusain is is 72.50% when the cyclone’s cone ratio is 0.65, ratio of solid to liquid is 1:4, feeding pressure is 0.10 MPa.(5) Average vitrinite recovery ratio in vitain, average inertinite recovery ratio in fusain, and minerals recovery ratio in coal can get 92.17%, 39.49%, 76.78%, respectively. Heavy liquid cyclone separation simulation analysis shows maceral continuous separation enrichment can be achieved through this method.(6) Slurry p H value and surfactant have effects on maceral electric potential based on single-trough flotating machine experiments. Matching principles between coal surface modification and collector was revealed. The parameters of coal separation and enrichment through flotation are optimized.(7) 86.96% enrichment ratio of vitrinite in vitrain and 70.80% enrichment ratio of inertinite in fusain were obtained by flotation with Al Cl3 dosage is 154mg/L, Beth octanol dosage is 120g/t, Dodecyl Trimethyl Ammonium Bromide is 100 mg/L, slurry concentration is 100g/L, air flow is 0.30m3/(m2·min), contact time is 3.5min, rotational speed of impeller is 1800r/min.(8) Collector flotation mechanism based on UV spectrum, infrared spectrum, electric potential measurements stated that cationic collector and anionic collector concentrated on the surface of pulverized coal mainly by electrostatic adsorption, dispersion force is another factor.