Minerals in most cases are to be preparated in water or heavy environment, that is why the products of preparation contain water in an amount from 30 to 90% (non-condensed). For the subsequent metallurgical, thermal, chemical processing or transporting of such whey must be dewatered by one of the processes of dewatering.
Today traditional methods of mechanical dewatering of grainy materials is screening, drainage filtration, centrifugation, besieging in water with the compression of sediment have mainly exhausted them selves. Their development goes on mainly extensively due to multiplying centrifugal force, vacuum, etc. At the same time for achieving standard humidity considerable volumes of the treated mountain raw material are thermally dried which is one of the most expensive processes of technological chain in preparation of coal, in addition, ecologically dirty and fire- dangerous.
Mechanical and thermal dewatering of shallow products of enriching of coal is foreseen in the technological charts of modern domestic and oversea coal dressing plants.
For reduction of prices and deeper dewatering of shallow products of coal preparation different methods of intensification, both mechanical and thermal methods are developed which include different physical and chemical influence (superficially active matters, aquatic steam, vibration and centrifugal forces, temperature of gases and etc). One of such methods of intensification of dewatering is mechanical derangement of water film from the surface of coal particles by a high-speed stream of air.
For the study of effect of blowing off water film from the surface of coal particles analytical and comparative resonance methods were used and as well as methods of speed filming and nuclear magnetic resonance. Researches showed that this process has a certain sequence: period of induction, basic process of derangement and period of small speed of moisture delete. Duration of periods is calculated by the hundredth fraction of a second and depends mainly on the speed of blast. General duration of moisture delete from one corn at speed of air of 30-60 m/s makes 0,1 s, at the speed of air of 160-170 m/s all three periods are closed in the thousandth fraction of a second.
THE PURPOSE AND TASKS OF WORK
One of the most actual issues of modern technologies of preparation of minerals that is effective dewatering of fine materials is examined in this master's degree work. Traditional methods of dewatering are centrifugation, filtration, dewatering screening does not provide the necessary level of humidity of the finished product in a number of cases.
The purpose of this work is to explore the basic constituents of the process of dewatering of fine material by means of method of blowing off the water film in the speed stream of air.
Taking into account existent experience of coal preparation it is possible to formulate the range of basic requirements of modern perspective technology. They are economy, ecological cleanness, fire-proof, simplicity of realization, technologicalness, universality. The class of mechanical methods meets the requirements in coal dewatering, because thermal, physical and chemical processes are expensive and often do not meet the modern requirements of safety and ecological cleanness, that has recently been especially actual.
The principle of mechanical derangement of water film from the surface of material was applied for grainy mineral raw material [2]. The researches, carried out at the Institute of enriching of hard fuel (Russia, Lyubertsi), showed, that using a gas stream speed of 40-160 m/s it is possible to decrease humidity of coal of 0,25-1,0 mm size to 9-12%. Thus 70-80% of primary superficial moisture of coal is deleted. The effect of dewatering is fixed at speed of gas higher than30 m/s. The time of delete of moisture is at the level of 0,1 s are hundredth fraction of a second [2].
The industrial variant of application of dewatering by derangement method of water film by means of high-speed stream of air has been proposed by the Ukrainian scientists of the Donetsk National Technical University headed by V.Beletskiy. It consists in application of ejecting of moist coal which makes the continuous process of dewatering by a simple serial vehicle possible. The author group of scientists has done the approbation of the method of blowing off water film by ejecting only [3].
CONCLUSIONS
A new highly effective mechanical method of dewatering of shallow material by blowing off water film at the speed stream of air is studied and analyzed in this paper, which provides the delete of primary superficial moisture of coal to 70-80%. Dewatering of coal by the method of “blowing off water film” makes it possible to obtain eventual to 7-13%. Practically all types of moisture are thus deleted: gravitation, hygroscopic, pellicle, capillary, except for chemically linked. The method of dewatering of water film from the surface of minerals by mechanical derangement meets the requirements, of a modern perspective method. They are economy, ecological cleanness, fire-proof, simplicity of realization, technologicalness, universality.
Development of theoretical idea of this perspective process of dewatering and its experimental research is an actual task in the modern enriching of minerals.
|
LIST OF REFERENCES
- Кваша В.Б., Чижов В.В., Айнштейн В.Г. Срыв влаги с поверхности частиц в инжекторном слое //Инженерно-физический журнал. - 1976, - т.ХХХ, № 3. - С.411-415.
- Филиппов В.А., Подлуцкий Л.Д. Интенсификация обезвоживания мелких продуктов обогащения // Уголь. - 1981. -№ 12, С.47-48.
- Скибенко В.М., Білецький В.С., Сергєєв П.В. Закономірності течії води в поверхневих плівках при аеромеханічному зневодненні дисперсних матеріалів//Збагачення корисних копалин, вип. 12 (53), 2001. с.80-89.
- Chattopadhyay J., Sarkar G.G. Dewatering of of coal fines by the use of additives/ of J. Inst.Eng/(India). Vining of and of Met.Div, 1983, 64. ? 2, 53-57.
- High-sulfur of coal upgrading by improved oil agglomeration / W.Pavlak, K.Szymocha, Y.Briker, B. Ignasiak of //Processing and utilization of high-sulfur coals. - Amsterdam - Oxford - New York - Tokyo.-1990, P. 279-287.