| Coal is one of the most important energy in our country, and wet coal preparation which could produce a large number of slime water can affect output of preparation plants. With the increas ing of mineral mechanization, the content of gangue in raw coal is more. Clay mineral in the gangue may is one important reason that generate much more difficultly settled coal slurry. Therefore, with the development of society and awareness of environmental protection, the clean utilization of coal is focused on in the society.By us ing industrial analys is, infrared spectroscopy, laser particle size and XRD, the mud properties, occurrence modes, particle size and mineral composition of 2# raw coal at Malan coal preparation plant, Shanxi coal & electron group is analyzed. The results show that the compositions of this mineral are mainly montmorillonite, kaolin, pyrite and quartz, and among these, kaolin and sand are at larger proportion. Coal particle surface has a large number of active functional groups such as-OH,-C=O and-COOH.After studying the properties of raw coal, by changing the p H value, hardness of water, static and dynamic mixing time, the single factor experiments are designed to study the influence on the electric potential changes of different particle size and different density of raw coal, coal, kaolin, quartz sand and mixed mineral particles. The results show as below:(1) The change trends of coal particle surface potential at different size and denis ity is similar to the raw coal change. The smaller p H value, greater water hardness and less mixing time with water, the Zeta potential of raw coal particle is bigger and surface charge is less.(2) When the p H value increased, Zeta potential of mineral particles will change as follows: Mix the raw coal and kaolin, with a high content of kaolin, the mixture paticles Zeta potential will decrease, and potential is 0 when C:K=1:1 at p H is 7.22, C:K=1:3 at p H is 8.36. Raw coal and quartz sand mixed mineral particles charged negatively,Zeta potential will increase. The Zeta potential of kaolin and quartz sand mixture paticles will increase. When the p H value is 7, the particle surface has the least charge, they are –28.92mV、–26.73 m V、–27.22 mV. As the hardness of water, the Zeta potential of mineral particle surface will increase, the particle surface charge is determinted by the charge property.(3) With the increase of static and dynamic mixed time, the mixture paticles Zeta potential of raw coal and kaolin will increase over time. The mixture paticles Zeta potential of raw coal and quartz sand will increase first and then decrease, and the surface has the least charge as time infinitly, they are –18.57 m V、–24.40 m V、–30.77 mV. The paticles Zeta potential of kaolin and quartz sand is nagetive, and decrease first and then increase as the static mixing time, when the time is 24 hours, paticles has the least charge which are –30.64 m V、–29.60mV、–23.73 mV. Charge will increase first and then decrease as the dynamic mixing time, and the surface has the least charge as time infinitly, they are –19.05mV、–22.07mV、–22.58 m V.The above experiment results provide a good theoretical basis to collpidal dispersion theory, determination of reagent system of coal preparation plant and realization of closed circuit technique of slime water. The results also have great industrial value. |
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