Changes in the Composition and Properties of the Alcohol-Benzene Extract of Peat during Thermal Briquetting
Abstract Generated abstract
This study examines how heating and thermal briquetting alter the alcohol-benzene extract of peat, with attention to the role of extract components in forming the strong structure of thermobriquettes. Peat was analyzed in its initial state, after heating to 250°C and rapid cooling, and after briquetting at 250°C, comparing extract yields, group composition, melting point, iodine number, acid number, and ester number. Heating increased the total extract yield through formation of all bitumen fractions to varying degrees and enriched the extract in more low-molecular and unsaturated compounds. During pressing, increases in asphaltenes and in oils and resins, together with changes in melting point and iodine number, were interpreted as evidence that extract components participate in compaction and polycondensation reactions during briquette structure formation.
Full Text
Changes in the Composition and Properties of the Alcohol–Benzene Extract of Peat During Thermal Briquetting
S. G. Maslov, S. I. Smolyaninov, E. A. Kurakolova, O. F. Puseva
(Presented by the scientific-methodological seminar of the organic departments)
One of the main reasons for the formation of the strong structure of a thermobriquette is the chemical interaction of the group constituents of peat. Certain ideas about this can be obtained by studying the composition and properties of the alcohol–benzene extract (ABE) extracted from the initial peat, from peat heated to 250°C and rapidly cooled, and from thermobriquettes obtained at a temperature of 250°C.
The initial peat had the following characteristics: degree of decomposition 35%, $W^a$ — 11.11%, $A^c$ — 8.7%, $V^r$ — 68.42%, $S^c$ — 0.10%, $C^r$ — 59.27%, $H^r$ — 6.10%, $N^r$ — 2.74%, $O^r$ — 31.90%.
In the literature [1–6], the fact of an increase in the yield of ABE during heating of solid peat fossil fuels has been repeatedly noted. From the data presented in Table 1, it follows unambiguously that this increase is due to the formation of all constituent parts of the ABE, but to different extents.
Table 1
Yields and composition of the alcohol–benzene extract, %
| Object of study | ABE yield | Asphaltenes | Non-asphaltene fraction | Losses I | Waxes | Paraffins | Oils and resins | Losses II |
|---|---|---|---|---|---|---|---|---|
| Initial peat | 6.4 | 51.6 | 44.8 | 3.6 | 29.3 | 2.7 | 7.5 | 5.3 |
| Peat after heating to 250°C | 17.0 | 48.4 | 35.8 | 15.8 | 21.9 | 6.8 | 3.9 | 3.2 |
| Thermobriquette | 16.0 | 53.5 | 35.3 | 11.2 | 17.5 | 4.3 | 9.5 | 4.0 |
| Yields based on the initial peat | ||||||||
| Initial peat | 6.4 | 3.30 | 2.87 | 0.23 | 1.88 | 0.17 | 0.48 | 0.34 |
| Peat after heating to 250°C | 11.9 | 5.76 | 4.26 | 1.88 | 2.60 | 0.81 | 0.47 | 0.38 |
| Thermobriquette | 11.2 | 6.00 | 3.95 | 1.25 | 1.96 | 0.48 | 1.06 | 0.45 |
It should be noted that the method used was designed for the separation of bitumens isolated from natural peat. The ABE from heated peat should be enriched with resinous compounds (this is emphasized by N. M. Karavaev and Yan Huang [6]), which is not observed in our case. Apparently, here, as has repeatedly been pointed out in methods for separating similar mixtures in the analysis of petroleum produc-
during the precipitation of waxes and paraffins there is co-precipitation of resins, and the results for the yield of all the indicated components are distorted: for waxes and paraffins toward an increase, and for resins toward a decrease.
In the composition of the alcohol-benzene extract (ABE) from thermobriquettes there is an increase in the content of asphaltenes, oils, and resins, and a corresponding decrease in the proportion of other components. This fact indicates that compaction reactions occur during the briquetting of heated peat.
To characterize the ABE, the melting point and the iodine, acid, and ester numbers were determined (Table 2). These data provide additional information on the nature of the processes occurring during thermal briquetting of peat.
Table 2
Characteristics of the alcohol-benzene extract
| Object of study | Melting point, °C | Iodine number, mg iodine per 1 g of extract | Acid number, mg KOH per 1 g of extract | Ester number, mg KOH per 1 g of extract |
|---|---|---|---|---|
| Initial peat | 81.5 | 25.4 | 58.9 | 126.4 |
| Peat after heating to 250°C | 58.0 | 59.7 | 37.1 | 139.0 |
| Thermobriquette | 65.0 | 31.7 | 49.5 | 165.4 |
Thus, the increase in the iodine number of the ABE upon heating of peat indicates an increased unsaturation of the chemical bonds of the extract components and their increased chemical activity. The simultaneous lowering of the melting point indicates enrichment of the ABE with low-molecular-weight compounds. Conversely, the increase in the melting point and the decrease in the iodine number of the ABE from thermobriquettes is direct evidence of the participation of its components in compaction reactions and, ultimately, in the formation of the strong structure of the thermobriquette.
Conclusions
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It has been established that the increase in the yield of ABE after heating of peat occurs through the formation of all constituent parts of the bitumens, but to different extents.
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It has been found that, during pressing of heated peat, the yield of asphaltenes and of the sum of oils and resins increases, which indicates the occurrence of polycondensation reactions.
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It has been shown that, during the heating of peat, the ABE from it is enriched with low-molecular-weight compounds, which actively participate in compaction reactions during briquetting.
Literature
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E. V. Kondrat’ev, S. K. Kupichev. Chemistry of Solid Fuel. Vol. VI, issue 5, 403, 1935.
-
G. E. Fridman. DAN SSSR. Vol. XXVII, No. 5, 875, 1951.
-
G. L. Stadnikov. Origin of Coals and Petroleum. Publishing House of the Academy of Sciences of the USSR, Moscow, 1937.
-
A. I. Khrisanfova. Proceedings of IGI, Academy of Sciences of the USSR. 2, 278, 1950.
-
D. P. Zverev, Yu. V. Pushkarev. Chemistry of Solid Fuel. 4, 55, 1967.
-
N. M. Karavasev, Yan Khuan. Izv. Academy of Sciences of the USSR, Department of Technical Sciences, “Metallurgy and Fuel”, 4, 151, 1961.