Yield and Composition of Products from the Bertination of Itat Brown Coal under Rapid Heating
Abstract Generated abstract
This study examines preliminary thermal treatment, or bertination, of Itat brown coal under rapid heating as a means of improving products from subsequent thermal processing. Dried coal of 200 to 250 micrometers was treated in a rapid heating apparatus at 220, 280, and 340°C, with product yields, gas composition, and solid residue properties measured and compared with semicoking at 450°C. Increasing temperature reduced solid residue yield and increased gas and pyrogenetic water formation, with tar appearing at 340°C and combustible gas components rising as carbon dioxide declined. The treatment increased the calorific value of the solid residues relative to the initial coal, slightly raised carbon and ash contents, reduced volatile yield, and removed part of the carbon dioxide and pyrogenetic water associated with thermal destruction.
Full Text
YIELD AND COMPOSITION OF PRODUCTS FROM BERTINATION OF ITAT BROWN COAL UNDER RAPID HEATING
Ya. A. Belikhmaer, K. K. Stramkovskaya
(Presented by the scientific-methodological seminar of the Faculty of Chemical Technology)
One of the ways of improving the quality of products from the thermal processing of coals may be their preliminary thermal treatment (bertination). It is known from the literature that bertination improves the composition of the gas during gasification [1] and has a positive effect on the yield and quality of coke [2].
The aim of the present work is to determine the yield and composition of the products of bertination of brown coals from the Itat deposit under conditions of rapid heating. The study was carried out on an installation whose schematic diagram is shown in Fig. 1.
Fig. 1. Rapid-heating installation for solid fuels: 1 — fuel bunker, 2 — screw feeder, 3 — distributing cone, 4 — plug, 5 — reactor, 6 — CHTR, 7 — cyclone, 8 — cyclone receiver, 9 — cooler, 10 — cooler receiver, 11 — electrostatic precipitator, 12 — electrostatic-precipitator receiver, 13 — tube with CaCl₂, 14 — adsorber, 15 — gas meter, 16 — lower screw feeder, 17 — solid-residue bunker, 18 — electric furnaces.
The bertination procedure was as follows. Coal preliminarily dried to 3–4%, of the 200–250 μm fraction, was charged into hopper 1 in an amount of 1.5 kg. After this, the apparatus was checked for tightness and heating of the reactor and of the KTR was switched on. Upon reaching the specified reactor-wall temperature, the drives of both screw feeders were switched on simultaneously. The temperature to which the coal particles were heated was recorded with a thermomagnetic pyrometer, whose thermocouple was installed at the outlet from the KTR. At a constant reactor-wall temperature, the temperature of the coal particles remained unchanged throughout the experiment. The KTR wall temperature was maintained equal to the temperature of the coal particles.
The duration of each experiment was 25 min. Ten minutes after the start of the experiment and at the end of the experiment, gas samples were taken. The gas was analyzed on a VTI-2 apparatus and an KhT-2M chromatograph. The solid residue was subjected to technical and ultimate analyses. Bertination was carried out at temperatures of 220, 280, and 340°C.
The experimental results are presented in Table 1, from which it is evident that, with increasing bertination temperature, the yield of solid residue decreases, while the yields of gas and pyrogenetic water increase. At a temperature of 340°C, tar evolution is observed. This indicates
Table 1
Yields of products from bertination of Itat brown coal
under rapid heating
| No. | Process temperature, °C | Solid residue | Gas | Pyrogenetic water | Tar |
|---|---|---|---|---|---|
| 1 | 220 | 98.48 | 1.52 | — | — |
| 2 | 280 | 97.84 | 1.80 | 0.36 | traces |
| 3 | 340 | 95.24 | 2.74 | 1.62 | 0.40 |
| 4 | 450 | 69.20 | 17.80 | 5.62 | 7.38 |
that, at this temperature, reactions of the main process of thermal destruction of the organic mass of the coal are already proceeding appreciably. Table 1 also gives the results of semicoking of the coal in the same apparatus at a temperature of 450°C. From comparison of these data it is evident that, during bertination, 29% of the pyrogenetic water is removed
Table 2
Composition of the gas from bertination of Itat brown coal
under rapid heating
| No. | Process temperature, °C | CO₂ | CO | H₂ | CH₄ | CₘHₙ | γ, kg/nm³ | Gas yield, nm³/t o.m. | CO₂ yield, nm³/t o.m. |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 220 | 97.1 | 2.9 | — | — | — | 1.954 | 7.8 | 7.6 |
| 2 | 280 | 85.2 | 9.7 | 3.2 | 1.9 | — | 1.818 | 10.0 | 8.5 |
| 3 | 340 | 74.6 | 17.2 | 2.0 | 5.8 | 0.4 | 1.735 | 18.0 | 13.4 |
| 4 | 450 | 33.2 | 32.3 | 12.3 | 22.0 | 0.2 | 1.230 | 146 | 48.6 |
at a temperature of 450°C. From comparison of these data it is evident that, during bertination, 29% of the pyrogenetic water ...
from the amount that is formed as a result of thermal destruction at 450°C.
The results of the gas analysis are given in Table 2. As the temperature rises, the content of combustible components in the gas increases and the content of CO₂ decreases from 97.1% to 74.6%. As a result, the specific gravity of the gas decreases from 1.954 kg/nm³ to 1.735 kg/nm³. At a temperature of 340°C, unsaturated hydrocarbons appear in the gas.
Table 3
Characteristics of solid residues
| No. | Process temperature, °C | \(W^p\) | \(A^c\) | \(V^r\) | \(C^r\) | \(H^r\) | \((O + N + S)^r\) | \(Q_n^p\), kcal/kg |
|---|---|---|---|---|---|---|---|---|
| 1 | Initial coal | 38.0 | 4.80 | 48.2 | 70.70 | 5.10 | 24.20 | 3890 |
| 2 | 220 | — | 4.90 | 47.6 | 70.90 | 4.95 | 24.15 | 6280 |
| 3 | 280 | — | 4.96 | 46.9 | 71.30 | 4.86 | 23.84 | 6286 |
| 4 | 340 | — | 5.10 | 42.7 | 72.00 | 4.80 | 23.20 | 6310 |
According to the elemental-analysis data, an increase is observed in the solid residues in the content of \(C^r\) from 70.7 to 72% and a decrease in \(H^r\) from 5.1% to 4.8% at 340°C. The calorific value of the solid residues varies from 6280 to 6310 kcal/kg and is considerably higher than the calorific value of the initial coal, 3890 kcal/kg (on working fuel). A consequence of bertination is also an increase in the ash content of the solid residues from 4.8 to 5.1% and a decrease in the yield of volatiles from 48.2 to 42.5%.
Conclusions
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Bertination of Itat brown coal makes it possible to remove 22.7% of ballast gases (CO₂) and 29% of pyrogenetic water.
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The calorific value of the solid residues increases from 6280 kcal/kg to 6310 kcal/kg and is considerably higher than the calorific value of the initial coal, 3980 kcal/kg (on working fuel).
Literature
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B. M. Derman, V. A. Nikolaeva, Effect of preliminary thermal treatment on the composition of gas during gasification of Moscow-region coal in a filtration channel. Proceedings of IGI, Academy of Sciences of the USSR, 13, 1960.
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E. P. Starke, D. M. Lisin. On the causes of the positive effect of thermal preparation of coals on coke quality. Proceedings of KhMI, Siberian Branch of the Academy of Sciences of the USSR, issue 16, 1961.