High prices on petrol and gas stipulated the increase of interest in coal as priority type of fuel and raw material in chemical industry. At the same time, the hydraulic transport is most advantageous for the transmission of plenties of coal on considerable distances.

A hydrotransport system of coal includes:

Flash-animation, Macromedia Flash Basic 8, 16 frames, 22 KB.

1. Main terminal is the beginning of the system. Coal is crushed and ground down there. Coal-water slurry is prepared from ground coal and loaded in the line. The master pump station are also includes the main terminal.
2. Pipeline with the pump stations are used for creation of necessary pressure in the line and for moving of product on a pipeline. Blocking devices for defence of pipeline are also included here.
3. A receiving terminal - complex for dewatering and subsequent use of the product.

Basic descriptions of the large hydrotransport systems are summarized in a table. The table shows that length of workings pipelines achieves 440 kilometres, and the size of maximal piece of material is not exceeded by 3 mm.

System	Leight, km	Diameter, mm	Productivity, bln. t./year	Amount of the pumps stations	Max. diameter of pieces, mm	Level of introduction
Kadis -- East-Lake (USA - Ohio)	174	254	1,3	4	4,4	Worked in 1957-1963.
Black-Mesa -- Mohave (USA, Arizona)	440	457	4,4	3	1,2	Worked in 1970-2006
Belovo -- Novosibirsk (Russia)	252	500	3,0	-	2,0	Worked in 1990-1994.
Freiling -- Emile (France)	9	386	2,5 - 3,0	-	2,0	Working from 1952.
Porto-Torres (Italy)	4	406	3,5 - 4,1	-	3,0	Working from 1970

The hydrotransport systems of coal has a number of advantages: minimum economic expenses and losses of product; the small terms of building of pipelines; high reliability; possibility of complete automation; ecological cleanness; independence from weather conditions.

However researches and practice of exploitation of hydrotransport systems exposed a number of technical and technological problems, arising up at the hydraulic transport of coal:

1. difficulties with dewatering of coal. Process of dewatering in the existing hydrotransport systems include the thermal drying – expensive and inflammable process, which contaminates the atmosphere;
2. properties of coked coals are worsened in the distant hydraulic transport;
3. promoted destruction of low metamorphisated coals and concomitant factions of wastes, that sharply complicate the process of dewatering.

The task of the real work is development of technological bases of effective dewatering of coals in hydrotransport at long distances (200-500 km and more). Combination of processes of hydrotransport and oil granulation is offered for this purpose.

In area of theoretical researches:

- I have made the analysis of coal fines as an object of dewatering with the use of oil aggregation;
- I have explored the theoretical bases of mechanism of coal-oil aggregates receipt in conditions of the reduced expenses of oil reagent;
- I have examined the adhesion contact «coal - oil» and elementary act of oil aggregation.

The phenomenological model of coal dewatering with use of oil aggregation, which was developed by our university, include a number of subprocesses. Successive consideration of this subprocesses gives a possibility to understand the phenomenal mechanism deeper and to expose its characteristics.

Hydrodynamic factors have influence at the subprocess of rapprochement and meeting of objects (piece of coal and drop of reagent) in a water environment. Near and distant hydrodynamic cooperation are basic among this factors.

Near hydrodynamic cooperation is determined by properties of thin superficial layers of water. Distant hydrodynamic cooperation consist in that the large piece of coal (3-6 mm) or large oil drop oil change the lines of water flow and the trajectory of motion of small particles. The form of coal pieces also haves an influence at cooperation of hard objects in water. Probability of capture of «awkward» hydrophobic pieces of coal by aggregates is multiplied because the thickness of anomalous layer of water is thinner on verges and ribs.

The process of adhesion determines cooperation of coal with oil reagents. Ousting of water layer with oil from coal surface depends on nature of adhesion connection «coal – oil» and areas of border layer connective on the surface of particles.

Image 1. Phenological model of dewatering (L. 4, p. 39)

а) coal К of Karagandinskaya mine;
б) boіler oil М100;
в) aggregate "boіler oil - coal";
г) МОS;
д) aggregate "МОS - coal";
е) benzol polymer of Avdeevskiy CHP;
ж) aggregate "polymer - coal"

Experimental information, which was received by the methods of molecular spectroscopy, shows that adhesion contacts in the area «coal – oil» are conditioned not only by adsorption, but also by forces of chemical nature (changing of intensity of peaks of absorption at 3460 and in the area of 3200-3100 sm-1 confirms the presence of hydrogen connection). It is instrumental in an origin of adsorbing layer on the coal surface – border film of oil-binder, which is the first stage of dewatering.

The process of formation of «kernel - shell» structures takes place at transportation and simultaneous interfusion of slurry in a pipeline. The concentration of water phase in slurry considerably exceeds the concentration of oil phase, so emulsion of kind «oil - water» first appears during agitation. The initial stage of receipt of emulsion is accompanied by diminishing of emulsive drops diameter and high dispergation speed. After reaching the dynamic equilibrium of the system the process is completed.

Image 2. Coal-water aggregates (L. 4, p. 39)

а, б) conglomeration structures, х65;
в, г) «kernel - shell» structures, х55;
д, е) microaggregates, х100

Autohesion contacts of coal pieces covered with binder layer are carried out like the adhesion contacts. The chronological sequence of phases of contact is as follows: meeting – rapprochement – a breach of water tape – coupling of coal pieces. A primary coal-oil aggregate unites a few pieces and has a radius, considerably exceeding the radii of his separate constituents, therefore meeting with it of yet unrelated pieces is possible using diffusive and inertia mechanisms.

Descriptions of the products	Without oil aggregation	With oil aggregation
Humidity of cake at the Frud factor = 2000, %	34	17
Ash content, %	50 - 55	79 - 85
Mass concentration of slurry, %	50	50
Relative hydraulic losses of pressure in the pipeline	1	0,85 - 0,9
Content of remaining oil, %	-	tracks -- to 5-10 mg/l

Wide range of particle dimensions of hard phase forming the aggregates, of the hydrotransport systems determines different probability of meeting for a pair of pieces of different radii. The structure of primary and secondary aggregates also depends on correlation of these probabilities.

Dewatering of aggregated coal by centrifugation is substantially more effective in comparison to non aggregated coal. Thus, application of the special process of dewatering and coal fines preparation – oil aggregation, in combination with the hydraulic transport allows, at first, radically reduce humidity of filter cake (from 34 to 17 %); secondly, substantially decrease the loss of organic mass with water and multiply ash content of hard component in water to 79-85%; thirdly, save the coking properties of the hydraulically transported coal.

Literature

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