COMPOSITION AND STRUCTURE OF COAL ORGANIC MASS. 3. DINAMICS OF COAL CHEMICAL STRUCTURE DURING METAMORPHISM

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1 CHEMISTRY & CHEMICAL TECHNOLOGY Vol. 5, No. 3, 2011 Chemistry Vaim Barsky 1, Gennay Vlasov 2 an Anriy Runitsky 1 COMPOSITION AND STRUCTURE OF COAL ORGANIC MASS. 3. DINAMICS OF COAL CHEMICAL STRUCTURE DURING METAMORPHISM 1 Ukrainian State Chemico-Technological University, Dnepropetrovsk, Ukraine 2 JSC Aveevskiy KHZ, Aveevka, Ukraine Receive: January 28, 2011 / Revise: March 15, 2011 / Accepte: May 26, 2011 Barsky V., Vlasov G., Runitsky A., 2011 Abstract. Dynamics of coal chemical structure uring metamorphism has been evaluate using mathematical moel of metamorphism kinetics attache to the time axis in accorance with artificial coalification ata. Keywors: metamorphism, coal, chemical structure. 1. Introuction The result of generalization of actual facts an theoretical positions concerning moern conceptions of soli fuels chemical structure is that peculiarities of carbon physico-chemical properties of various geologic age are consiere as one of the major criteria of their objectivity. Thus in the polyconjuction theory [1], where the ratio between its implementers is the main element (hyrogen bons in younger coals an EDA-interaction in ol coals), three jumps in the coal properties are emphasize. The first jump is a caking capacity which takes place uring LF G transition (from long-flame coal to gas coal). The amount of carbonyl groups essentially ecreases, an consequently the hyrogen bons strength that ensures the high strength an porosity for young coals ecreases too. The secon jump is achieving of maximum caking an solubility. It takes place uring G F transition (from gas coal to fat coal). The polyconjunction system is eveloping towar eclining in hyrogen bons an increasing in onor-acceptor interaction. It weakens interactions between macromolecules, ecreases coals porosity an strength, create liqui-like structure. The thir jump is isappearance of caking an ability to transfer into soluble state. It takes place uring C LB L transition (coke coal lean-baking coal lean coal). The extensive polyconjunction system is forme an strong C C bons appear between macromolecules. The coal strength an porosity increase. In the theory of self-associate multimer [2] the ratio between EDA-interactions is the main one. These interactions are stimulate by heteroatoms (mainly by oxygen atoms) in young coals an byaromatic fragments in ol coals. Using self-association factor χ [3] the mentione secon jump is foun as a proof of ientity of eveloping conception. However, to our opinion, more groune approach exists to explain the mentione peculiarities of physicochemical properties of soli fuel. It has to inclue the average but practically observe kinetics, stoichiometry an material balance of metamorphism. Moreover, the inispensable conition must be preservation of equality between a form (structure an strength of bons between atoms) an a content (fuel elemental structure). We use such approach to etect the jumps of physico-chemical properties of soli fuel an realize it by means of mathematical moel efinition an analysis of artificial coalification kinetics [4]. 2. Experimental To ascertain parameters of kinetic moels an special points etecte by means of the moel, we carrie out experiments with all types of coal using stanar proceure. The results are represente in Tables 1-3.

2 286 Vaim Barsky et al. Investigation object Petrographic an elemental composition of investigate objects Rank of Average coal by value of DSTU vitrinite reflectance, Petrographic composition (without mineral aitives), % R 0, % V t S V I L V t +L Sum of mineral fillers, ΣMF, % Elemental composition (ry ashless state), % C H N O S t α 1, mas % Alexanrine eposit B Truovska mine LF Kurakhovska mine LFG Dopropolska Proletarska G F C LB Mospinska mine L Komenantska А Notes: 1 O H α = 100% ; 2 brown coal; 3 anthracite C Investigation object Dopropolska Proletarska Rank of coal by DSTU G F C LB Yiel an quality of coal estruction proucts in centrifugal fiel Destruction proucts Yiel of estruction proucts in centrifugal fiel (γ), % W f а Technical analysis A f S tf V f Table 1 Table 2 Elemental composition (ry ashless state), % C f H f N f O f liqui soli phase gas phase* liqui soli phase gas phase* liqui soli phase gas phase* liqui soli phase gas phase* l l s s g g * Defining the elemental composition of gas phase we issue from the mass balance: q = q γ + q γ + q γ, where i an j are numbers of coal an elements, respectively. Hence, foun elemental composition of a gas-vapor phase. q q q γ q γ i i S tf l l s s g i i =. Using experimental ata we 2 λi i

3 Composition an Structure of Coal Organic Mass. 3. Dinamics of Coal Chemical Results an Discussion Table 3 Characteristics of soli fuel using IR-spectroscopy ata Rank of coal Parameter β* η 1 = D 3040 /D 2920 η 2 = D 2920 /D 1690 η 3 = D 2920 /D 1600 B LF LFG Initial G Liqui phase Soli phase Initial F Liqui phase Soli phase Initial C Liqui phase Soli phase Initial LB Liqui phase Soli phase L А η * 2 ( l) β = η ( s) 3.1. Metamorphism Jumps Accoringly to Artificial Coalification Data 2 The analysis of kinetic moels of soli fuel coalification showe the following: 1. Bright brown coal formation is a completion of lignite stage corresponing to the maximum of mass loss rate (r max(1) = % per year) at τ 1 = 2.93 year. Bright brown coal is ientifie in accorance with stanar values of carbon mass content (75 mas %) an reflectance (0.55 %). Accoringly to artificial coalification ata 5 hyrogen atoms are for every oxygen atom. We may suppose that so high value of mass loss rate is achieve ue to the reactions of carbon ioxie formation an partially ue to water formation [cf. 4, Table 1]. These assumptions are in agreement with the scheme of fuel aliphatic part ecomposition by the reactions of ehyration, ecarboxylation an cyclization suggeste by V. Rakovsky at the analysis of coking chemism. We took it as a hypothesis when we consiere the chemism of natural metamorphism [5]. Table 3 also represents β parameter, which we introuce as a measure of intermolecular interaction between structures of liqui an soli phases. Accoringly to the guest-master conception it is necessary to ifferentiate them as mobile component an filtering lattice. The same ifferentiation of coal structural fragments (but in less efinite form) is the basis for selfconjunction theory an theory of self-associate multimer [3]. 2. The beginning of metamorphism lignite stage correspons to the maximum of rate of carbon mass content increase in the soli resiue (r max(2) = % per year) at τ 2 = 3.61 year. This beginning is in the view of transition of fuel composition, structure an properties from LF to LFG rank (C (τ 2 ) = 81 % an 8 hyrogen atoms are for every oxygen atom). The fact that the maximum change of carbon content is achieve after the maximum of mass loss (τ 2 > τ 1 ) confirms once more that at the examine stages of metamorphism the soli resiue coalification takes place ue to the primary proceeing of ehyration reactions an ecarboxylation reactions particularly. 3. The crossing of curves of hyrogen an oxygen mass changes epening on time points to the completion of chemical structures metamorphic formation. Such structures ensure the goo caking of coal resiue uring its coking. Taking into account the ata of artificial coalification the curves crossing is in τ 3 point at time axis, between G an F coals. The peculiarity of fuel chemical structure an composition is a parameter α(τ 3 ) = 0 (cf. (12) in [4]). Therefore, the chemical structures esignating the coal properties are characterize by the atomic ratio between hyrogen an oxygen inversely proportional to their atomic masses. In accorance with artificial coalification ata, τ 3 = 4.51 an C (τ 3 ) = Thus, the atomic ratio hyrogen:oxygen is approximately 16.

4 288 Vaim Barsky et al. 4. The minimum of the curve α(τ 4 ) correspons to the bounary between baking coals an anthracites an falls on metamorphism stage of free-burning coal of L rank. The approaching to this minimum is etermine by chemical structures transformation towar the increase of hyrogen atoms number (> 16) per one oxygen atom with continuous ecrease of their total amount. At the same time the carbon mass content increases, τ 4 6 years, α(τ 4 ) = 2.89, C (τ 4 ) = an 50 hyrogen atoms are for every oxygen atom. 5. The reversion of α(τ) curve to α(τ 5 ) = 0 characterizes the transition of L coal to graphite across the anthracites area. Taking into account that equality α(τ 5 ) = 0 is a conition of complete loss of hyrogen an oxygen by the soli resiue, the upper limit of this interval is α(τ 5 ) = with corresponing C (τ 5 ) = Regularities of Physico-Chemical an Structural Properties Changes for Soli Fuel uring Metamorphism One can see from Table 1 that there are jumps (change of irection or rate of changes) in metamorphism row by the sum of baking (an free-burning) microcomponents from B to LF, from G to F, from LB to L, from L to A. For R 0 only L A transition has a jump. The change of sign of parameter α is observe for G F transition. Comparing the ata concerning elemental compositions an vitrinite reflectance presente in Table 1 an results of artificial coalification we see their agreement. From Table 2 one can see that yiels of liqui an gas phases of F coal are equal. Moreover, coals form a group by gas phase yiel: G an F coals from the one sie, an C an LB coals from the other. Obviously these facts explain the jump between F an C coals by V. The ifference between G an F coals is the interchange between yiels of yiel an gas phases. The same ifference is between C an LB coals but with other numerical values. We restricte our investigations only by these coals because LF an LFG coals have a very low yiel of liqui phase; the yiels of B, L an A coals practically are absent. Carbon is the main element of all phases though its content is minimal in the gas phase of all coals. Hyrogen an oxygen are mainly in the gas phase; nitrogen is present in all phases. The greatest content of sulphur is in the gas phase, except LB coal. To confirm the possibility of artificial coalification use as an experimental moel of natural metamorphism we compare corresponing epenencies between carbon content C an vitrinite reflectance R 0. Fig. 1 shows the full agreement between curves of artificial coalification an natural metamorphism. Therefore, kinetic equations obtaine by us, nee only changes in τ scale. Averaging the coals geologic age given in literature, the transition perio from brown coals to anthracites is 300 ions years. Hence, the unit if conventional time τ in (11) (see [4]) is 50 ions years. As istinct from volatile components yiel, the thickness of plastic layer irectly shows the G F transition (the thir jump ) as a maximum of the curve (Fig. 2). The beginning of curve sharp raise foune itself at the transition from brown ull coal to long-flame coal coincies with the preicte secon jump. The crossing of its escening branch with C axis points to the beginning of L A transition (the forth jump ). The jumps which were etermine using the thickness of plastic layer, are also on the curves of metamorphic change of baking microcomponents sum. The fact that the same peculiarities of natural metamorphism are ientifie by the values base on phenomena of ifferent nature reveals the foune kinetic regularities. Fig. 1. Depenence of C on R 0 in accorance with the ata of artificial coalification (o) an natural metamorphism ( ) y, mm Fig. 2. Plastic layer thickness vs carbon content

5 Composition an Structure of Coal Organic Mass. 3. Dinamics of Coal Chemical 289 Taking into account the results of coal elemental analysis the values of α parameter (see Table 1) were calculate. The change of parameter uring metamorphism is shown in Fig. 3: the curve crosses X-axis in the point correspone to G F transfer (the thir jump ) an its minimum inicates the en of coal an beginning of anthracite stage of metamorphism, the same as uring artificaial coalification. these structures ecreases while the perio before the stage of gas coals, but then this tenency is not vali. The transfer from gas colas to fat ones is accompanie by the ecrease of aromatic structures part. The minimum of η 1 locate between states is the beginning of the new perio of OMC intensive aromatization, the rate of which oes not ecrease uring the perio till anthracite formation. initial coal β Fig. 3. Elemental-structural parameter α vs carbon content The stuy of the changing character of phases elemental composition (accoring to the pyrolysis ata in a centrifugal fiel) uring metamorphism at the stage of caking coals shows that structure transformation of coal in the area of the thir jump is influence by the change of elemental character of the gas phase. At the stage before F coal there is an active loss of oxygen mainly with CO 2 compouns; at the stage after F coal active loss of hyrogen mainly with CH 4 an oxygen (boune with more heavy coal structures) with H 2 O. Fig. 5. Change of η 2 parameter with the increase of metamorphism egree initial coal liqui phase initial coal liqui phase Fig. 6. Change of η 3 parameter uring metamorphism Fig. 4. Change of η 1 parameter with the increase of carbon content Assuming that the change of spectral parameter η 1 (Fig. 4) uring metamorphism inicates the change of ratio between aromatic an aliphatic structures, the latter ones preominate over others in young coals. The part of The changes of parameter η 2 uring metamorphism (Fig. 5) are connecte with the change of ratio between amounts of strong aliphatic C H bons an C=O bons, taking into account that such parameter characterizes the egree of intermolecular interaction [1]. In accorance with experimental ata we may assume that the intensive oxygen loss at the stage incluing B-ull, B-bright an C coals is accompanie by the formation of new C=O bons with participation of resiual oxygen at practically constant amount of aliphatic C H bons. The increase of η 2 value at the stage of C F transfer is connecte with further oxygen loss but with C=O bon rupture. Here the atomic ratio hyrogen:oxygen is approximately 16. Uner

6 290 Vaim Barsky et al. mentione conitions the reactions leaing to the accelerate ecrease of hyrogen mass content are ominant ue to the rupture of aliphatic C H bons. Obtaine ata concerning η 3 (Fig. 6) inicate the ominant rupture of aliphatic C H bons uring the perio till the stage of caking coals. In the area of F coal the rupture rate of C=C bons is preominant over that of C H bons. It means the minimum at the η 3 curve not only for original coals but for liqui phase too. Such treatment of the experimental ata supposes that C=C bons refer to aliphatic fragments of coal, that is in agreement with the ata concerning its aromatization uring the same perio. 4. Conclusions The en of lignite stage is the formation of brown bright coal (5 hyrogen atoms for every oxygen atom). The beginning of metamorphism coal stage is a LF LFG transfer (8 hyrogen atoms for every oxygen atom). Both phenomena take place ue to ecarboxylation leaing to the hyrogen loss in the form of molecular hyrogen an methane. While transferring from G to F coal the metamorphic formation of chemical structures ensuring the goo caking of resiual coal at coking leas to the atomic ratio hyrogen:oxygen 16 ue to the ominant ehyration reactions. The transfer from caking to free-burning coals is etermine by the reactions of methane an water formation which increase the atomic ratio H/O ( 50) at the constant ecrease of their total amount. The transformation of chemical structures at the stage of noncaking coals (L graphite transfer) takes place only ue to the hyrogen loss of soli fuel aromatic structures. References [1] Rusianova N., Maksimova N., Ignashev V. et al.: Koks i Khimiya, 1991, 3, 8. [2] Gagrin S. an Krichko A.: Khimiya Tverogo Topliva, 1984, 4, 3. [3] Barsky V., Vlasov G. an Runitsky A.: Chem. & Chem. Techn., 2009, 3, 315. [4] Barsky V., Vlasov G. an Runitsky A.: Chem. & Chem. Techn., 2011, 2, 139. [5] Barsky V., Vlasov G. an Runitsky A.: Koks i Khimiya, 2004, 1, 6. ПРО СКЛАД І БУДОВУ ОРГАНІЧНОЇ МАСИ ВУГІЛЛЯ. 3. ОЦІНКА ДИНАМІКИ ХІМІЧНОЇ БУДОВИ ВУГІЛЛЯ В ХОДІ МЕТАМОРФІЗМУ Анотація. За допомогою математичної моделі кінетики метаморфізму, що прив язана до осі часу за даними штучної вуглефікації, виконана оцінка динаміки хімічної будови вугілля в ході метаморфізму. Ключові слова: метаморфізм, вугілля, хімічна будова.