Essence of problem of salt coals
World experience of processing of salt coals
Processes and methods of the direct processing of salt coals
Home researches in area of demineralization of coals
Experimental researches in area of demineralization of coal
Technology of DonNTU "washing–agglomeration"
Review of results. Conclusions
Actuality of work is conditioned by importance of providing of fuel and energy base of country on a prospect. The structure of fuel and energy complex in our country is mainly oriented to thermal power–station. In 2000 from 52,8 million kW to general power of power–stations in Ukraine, 36,3 millions kW was on thermal power–stations. At the same time the supplies of home coal present 95,4 % from the general volume of organic block fuels in Ukraine. Oil and gas are largely exported. Therefore the searching of new high-efficiency and ecologically more clean technologies of the using of coal as a fuel on thermal power–station is the issue of present time.
One of perspective directions of preparation of coal to incineration on thermal power–station is the use of technologies of demineralization of the so–called salt coal, that in general balance of supplies of coal in Ukraine makes 10%. (picture 1)
The beds of salt coal with enhance able maintenance of NaCl and KCl are concentrated in Western and North Donbas and developed partly. At the same time, his incineration is related to the problems; firstly, substantial increase of wear of caldron aggregates of thermal power–station, secondly, by an ecological danger by the conditioned possibility of origin at incineration of dioxins and hit of them in an environment. It sharply puts the question of demineralization of the indicated coal before the using.
The idea of work is complex approach to the problem of enriching of coal on salt that includes combination of it with technologies of washing during the hydraulic transporting, oily aggregating of coal, effective mechanical dehydration.
The aim of work is an improvement of technology of enriching of coal on salt in the process of his main hydraulic transporting.
The researching tasks: 1.Study of process of enriching of coal on salt by his washing. 2. Research of demineralization of coal washing in the process of the hydraulic transporting. 3. Development of rational sequence of operations of technology of demineralization of coal that includes: washing of coal in the process of his hydraulic conveying — oily aggregating of coal is dehydration of coal. 4. Development of the technical decisions that sent to intensification of the oily aggregating of hydrophilization of salt coal and diminishing of charges of reagent.
Basic difficulties constrained with the using of deposits of alkaline coals consist in the following. Firstly, they are conditioned by enhance able scarifying ability of salt coals [7].
By the second negative phenomenon, taking place at incineration of salt coals, there is intensive corrosion of metal that increases with the increase of temperature and increase of maintenance in coal of chlorous natrium [7].
In our view, there is very necessary an ecological estimation of salt coals as an object of the thermal processing. It is important to mark large probability of education at heat treatment of salt coals of dioxins the toxic action of that is great [20]. The substances of dioxin row possess mutagen properties, repress immune possibilities of organism, accumulating in an organism cause various illnesses and even stipulate curvature of spiral of molecule of DNA [20 –23].
The researches of effective and ecologically acceptable methods of processing of salt coals are conducted in two fundamentally different directions: the first one supposes development of new methods of the direct using of salt coals without moving away natrium– and chlorcontain admixtures; the second one foresees a preliminary demineralization with the subsequent use of standard product in heating (or other processes). (picture 2)
First direction includes incineration of salt coals, gasification, fluidizing, half coking, and also their complex processing with the selection of gumates.
In Germany and England incineration is approved of salt coal [3, 6]. Thus it's added clay. Such decision is one of most simple.
Technical decisions [9–11] foresee the special additions to salt coals that neutralize negative influence of alkaline salts at their incineration. However application of additions worsens the technological indexes of process of incineration. For deployment in industry this is considered uneconomical way [1].
The row of decisions is sent to the search and development of new rational technical equipments and methods of incineration of salt coals. So Lissner A. suggested burning these coals in the special stratified heating with the reverse serve of smoke gas and introduction to him aquatic steam. However, this method is acceptable only to the caldrons of the small productivity [1, 4].
In Germany the researching works are executed on half coking of salt coals. It is set that at processing by this method coal of deposit Meseburg–east the about 50 % of natrium and 60–80 % passes to the semi coke.
In the USA, Ukraine and Germany experiments are executed on fluidizing of salt coals [5, 12, 13]. On the whole, the got results are appraised by researchers as positive, and processing of salt coals is confessed hydrogenization by perspective direction.
It is noticed in the USA that at storage of salt coal outdoors under influence of natural factors there is his natural washing from salt [17]. This fact deserves attention, however at all simplicity of such reception it has a row of defects: firstly, seasonal character; secondly, the results of demineralization strongly depend on amount of falling out fallouts and difficult forecast. Main defects are: from one side, degradation of coal at the protracted storage, worsening of his technological properties because of oxidization and, with other, is the necessary active salting of soils in the district of warehousing of salt coal.
The second direction foreseeing the preliminary enriching of coal on salt (demineralization) is worked out in a number of research centers. Thus most part of the offered solutions is based on the different variants of the water washing of salt coal. It, in particular, technologies of the State institute of mineral resources of Ukraine (SIMR), SHO "Haymek", Donetsk national technical university (DonNTU).
Thus, the conducted review shows that the problem of processing of salt coals is actively studied by the scientists of row of countries and certain successes are attained both in areas of their direct use and in enriching on salt.
1. Technologies of gasification of salt coal
The Dnepropetrovsk chemical–technological institute (DCTI) is execute researches of fitness of salt coals of the Novomoskovsk deposit for the receipt of the ennobled fuel the method of gasification. Thus as the base method of gasification of coals is using in a boiling layer under constraint.
The approbation of technology, conducted on salt coals Novomoskovsk and Starobelsk of deposits of Donbas, showed the fitness of these coals for gasification in a boiling layer [14, 15]. Considerable corrosion of steel of different brands is fixed at the same time. This circumstance is substantial obstacle retentive industrial introduction of this technology.
2. Technology of incineration of salt coal
Technology sent to the decline of maintenance of chlorcontain gases in foods of combustion of salt coals to the size got on in unsalt coals and corresponding diminishing of corrosion of surfaces of heating of caldrons [8].
Verification of the offered method of incineration of salt coals is preliminary carried out on the experience–industry setting created on the experimental base of Institute of coal energytechnologies of NAN of Ukraine.
Experiments on a pilot plant showed efficiency of such process the productivity.
3. Technology of the complex processing of salt coals
Institute of physical–organic chemistry and coal chemistry NAN of Ukraine researches are conducted on the alkaline hydrolysis of salt coals [16]. On the basis of laboratory researches the chart of the complex processing and use of salt coals of Donbas is offered. A technical decision includes three stages of processing. The tests of technology showed her perspective.
The brought directions over of researches are perspective; their development can result in creation of new high–efficiency industrial technologies of processing of salt coal.
1. Technology of SIMR of demineralization of coal the water washing
Deep complex researches of demineralization and ennoblement of salt coal of Donbas were conducted in Ukraine. The state institute of mineral resources is work out technology of demineralization of coal by the water washing [25].
2. Technology of SHO "Haymek" the hydraulic "demineralization–conveying"
This technology supposes combination of processes of the hydraulic conveying and demineralization. The lacks of technology it is been, firstly, educed effect of secondary concentration of salts in coal after 50 kilometers of his hydro transportation [24], and, secondly, intensive growing of salt coal shallow in the process of the hydraulic conveying a stipulating increase of maintenance of class is a 0,074 mm to 35–40% [18].
Experimental researches are development of the researches of process of demineralization of coal in oil produced before by planning of experiment. A research object coal of layer of С12 of the Novomoskovsk deposit of Western Donbas. Coal before a demineralization initially it was in oil on the offered technology.
The Donetsk national technical university on the base of foregoing technologies is work out the improved technology of demineralization of coal, removing their defects [25]. The basic idea of this method consists of combination of processes the "water washing is an oily agglomeration". (picture 3)
A flow sheet includes the two stadia crushing of initial coal with preliminary grohochenie on every stage. A key difference is a fractional serve of reagent in a process.
The ground tests of new technology of the Novomoskovsk deposit of Western Donbas DonNTU and SHO of "Haymek" conducted on salt coals, showed her efficiency. Due to application organic reagent–connective, the flow sheet of dehydration of coal is substantially simplified and diminishes amount equipment.
The conducted theoretical researches allowed setting basic conformities to law and specific features of process of demineralization of coal on different technologies. The worked out DonNTU elements of theory of process of demineralization of coal in a water environment are taken to the following:
1. The offered phenomenological models of process of demineralization of coal washing allowed identifying all elementary processes, set their sequence and intercommunication.
2. Analysis of elementary act of contact "coal is water" showed that most hydratation of salt coal is possible on an external surface and in the macro pores of coal phase.
3. 3. The fundamental chart is worked out of exchange of mass processes, taking place at the demineralization of coals, that includes warm exchange of mass processes and extracting.
4. The analysis of exchange of mass processes at the demineralization of coal allowed to set that the structure of border layer of dissolution includes zones:
– to superficial (chemical) hydratation;
– to by volume (physical) hydratation;
– zone of the locally—saturated solution.
5. The effective extracting of salts is possible only from macro pores and cracks of coal substance. For engaging in the process of dissolution of the salt components contained in mezo– and micro pores opening of internal surface of coal is needed.
6. Theoretical interpretation is out the phenomenon of secondary accumulation of salt in a coal phase in the combined process hydraulic "washing—conveying".
7. The theoretical ground of the combined technology is "demineralization of coal washing is an oily agglomeration ". In particular:
– two stadia’s serve of connective in a process demineralization is reasonable;
– principles are set forth and a formula is given for determination of rational expense of connective reagent on the first stage of his serve;
– it is set that contacts in zone "salt coal — connective" for oily coal agglomerates conditioned along with simple physical adsorption by the display of forces of chemical nature.
8. The theoretical ground of substantial increase of efficiency of dehydration of oily coal agglomerate is mechanical derangement of water tape. The results of theoretical researches served basis of new technological decisions.
During the writing of this abstract master's degree work is not yet complete. Final completion: December of 2011. Complete text of work and materials on the topic can be got for an author or his leader after the named date.