Prospective Evaluation of Peat from Several Deposits in Tomsk Oblast as a Raw Material for Metallurgical Processing of Bakchar Iron Ores
Abstract Generated abstract
This paper evaluates peat deposits in Tomsk Oblast as a potential fuel and fuel-smelting raw material for metallurgical processing of Bakchar iron ores. Ten peat samples from major nearby deposits were characterized by botanical composition, decomposition degree, proximate and elemental analysis, ash, sulfur, and phosphorus content, and were tested in machine-molded fuel-smelting materials and thermobriquettes under selected processing regimes. The results indicate that most samples meet relevant sulfur and phosphorus requirements, although ash content varies, and that strong metallurgical fuel can be produced from the studied peats, especially through thermobriquetting or use of more decomposed lower layers. The authors conclude that the regional peat reserve base appears sufficient and qualitatively suitable to support a large metallurgical complex producing up to about 3 million tons of pig iron annually.
Full Text
PROCEEDINGS
of the Tomsk Order of the Red Banner of Labor Polytechnic Institute
named after S. M. Kirov
Volume 163 1970
PROSPECTIVE EVALUATION OF PEAT FROM A NUMBER OF DEPOSITS IN TOMSK OBLAST AS A RAW MATERIAL FOR THE METALLURGICAL PROCESSING OF BAKCHAR IRON ORES
S. I. SMOLYANINOV, G. G. KRINITSYN, S. G. MASLOV
(Recommended by the Scientific-Methodological Seminar of the Chemical-Technological Faculty
of the Tomsk Polytechnic Institute)
Owing to the favorable combination of the inexhaustible reserves of iron ores of the Bakchar deposit, unique in their chemical composition, and the large peat resources located in the immediate vicinity of the iron-ore deposit, the possibility arises of organizing a metallurgical–energy–chemical combine, where peat will serve as a metallurgical fuel, while the by-products of the combine will be used as raw materials for chemical synthesis, mineral fertilizers, toxic chemicals, etc. In addition, gas may become a source of energy.
From the point of view of the location of peat deposits, all peat bogs situated within a radius of 60–70 km from the Bakchar–Melnikovo road should be regarded as promising for industrial use in organizing a chemical-metallurgical combine on the basis of the Bakchar iron ores and peat. Taking the yield of air-dry peat from one cubic meter of raw peat as 0.12 t, and the recovery coefficient as 0.3, the total reserves of air-dry peat in the indicated base, according to data from the institute “Giprotorfrazvedka,” are estimated at 116 million t. The possible scale of peat extraction is 22 million t, calculated as air-dry peat. This amount is sufficient to support the production of up to 3 million t of pig iron when air-dry peat or fuel-smelting materials are used as blast-furnace fuel.
From the five largest sections of this base, 10 peat samples were taken. The characteristics of the sampling points, the degree of decomposition, and the botanical composition of the peat are given in Table 1, and its proximate analysis and elemental composition in Tables 2 and 3, respectively.
In fuel intended for metallurgical needs, state standards limit ash content, sulfur content, and, in some cases, phosphorus content. These indicators for all the peat samples studied, in comparison with the basic requirements of standards for metallurgical hard-coal coke for various designated purposes and with the values of these indicators recommended by VNIITP for peat coke and semicoke, are given in Table 4. In calculating the sulfur content in coke, it was conventionally assumed that the fraction of volatile sulfur is 50%. The data in Table 4 show that the ash content of peat coke in samples 1, 2, and 4 lies beyond the permissible values. Samples 3, 5, and 7 are especially clean with respect to ash content. With respect to sulfur content, practically all the tested peat samples satisfy the strictest—
…to the requirements of GOST standards. The same also applies to phosphorus content. However, this latter indicator, when peat is used in the metallurgical processing of the iron ores of the Bakchar deposit, which are phosphorous, cannot be considered limiting.
Table 1
Sampling points, degree of decomposition, and botanical composition of the peat
| Sample No. | Sampling point, km from the Bakchar district center | Sampling depth interval | Degree of decomposition | Botanical composition, % | Peat type |
|---|---|---|---|---|---|
| 1 | 30 km to the southeast | 0–1 | 35 | Sedge limosa—50, sedge lasiocarpa—40, sphagnum fuscum—10 | sedge lowland |
| 2 | 30 km to the southeast | 1–2 | 45 | Sedge lasiocarpa and diandra—70, horsetail, buckbean—15, grass residues—15 | sedge lowland |
| 3 | 70 km to the east-southeast | 0–1 | 5–7 | Sphagnum fuscum—100 | fuscum |
| 4 | 70 km to the east-southeast | 1–2 | 25 | Sphagnum magellanicum—50, fuscum—25, angustifolium—20, cotton grass—5, fir bark—single specimens | magellanicum |
| 5 | 30 km to the east | 0–1 | 5 | Sphagnum fuscum—70, angustifolium—15, magellanicum—15 | fuscum |
| 6 | 30 km to the east | 1–2 | 20 | Sphagnum magellanicum—75, angustifolium—15, sedge lasiocarpa—5, woody remains—5 | magellanicum |
| 7 | 70 km to the east | 0–1 | 15 | Sphagnum angustifolium—75, magellanicum—20, cotton grass—5 | angustifolium |
| 8 | 70 km to the east | 1–2 | 55 | Cotton grass—35, sphagnum magellanicum—45, angustifolium—10, pine bark—10 | cotton-grass–sphagnum |
| 9 | 50 km to the southeast | 0–1 | 5 | Sphagnum fuscum—85, fuscum–magellanicum—15 | fuscum |
| 10 | 50 km to the southeast | 1–2 | 50 | Sedge—60, sphagnum magellanicum—10, angustifolium—5, cotton grass—15, birch and pine bark—10 | sedge lowland |
In order to determine the conditions for obtaining the strongest fuel-and-smelting materials, batches of moldings were prepared from all peat samples (the procedure was described earlier [1]) with the following parameters. The initial moisture content of the peat was 85, 80, and 75%; the conditional degree of processing was 0.5, 1.0, and 3.0; the carbon:iron ratio was 0.7:1.0, 1.0:1.0, and 1.5:1.0. Based on tests of the moldings and the coke obtained from them for crushing strength and abrasion resistance, preliminary technical conditions were determined for the recommended regime for producing fuel-and-smelting materials based on machine-molded peat. In selecting the conditions, preference was given to the strength of the iron-coke,
Table 2
Proximate analysis and heating value of peat
| Sample No. | $W^p$ | $W^a$ | $A^c$ | $V^r$ | $Q^b$ |
|---|---|---|---|---|---|
| 1 | 84,98 | 9,75 | 7,83 | 71,41 | 4800 |
| 2 | 84,00 | 8,75 | 12,33 | 68,44 | 4557 |
| 3 | 91,64 | 9,08 | 2,04 | 77,37 | 4138 |
| 4 | 90,90 | 7,91 | 6,01 | 74,68 | 4433 |
| 5 | 90,00 | 8,96 | 1,85 | 76,44 | 4454 |
| 6 | 88,00 | 9,12 | 3,35 | 73,32 | 4921 |
| 7 | 91,00 | 8,48 | 1,97 | 78,35 | 4549 |
| 8 | 91,00 | 8,09 | 3,87 | 72,34 | 4980 |
| 9 | 89,00 | 6,39 | 2,44 | 76,52 | 4565 |
| 10 | 89,00 | 8,12 | 4,02 | 69,16 | 5199 |
Table 3
Elemental composition of peat
| Sample No. | $C^r$ | $H^r$ | $N^r$ | $O^r$ | $S^c$ | $P^c$ |
|---|---|---|---|---|---|---|
| 1 | 57,33 | 6,12 | 3,03 | 33,52 | 0,28 | 0,012 |
| 2 | 57,44 | 6,16 | 2,97 | 33,43 | 0,29 | 0,009 |
| 3 | 51,34 | 5,86 | 0,76 | 42,04 | 0,06 | 0,001 |
| 4 | 54,67 | 5,95 | 1,55 | 38,83 | 0,09 | 0,005 |
| 5 | 50,75 | 5,83 | 0,85 | 42,57 | 0,04 | 0,001 |
| 6 | 65,61 | 6,12 | 1,83 | 35,44 | 0,12 | 0,006 |
| 7 | 51,30 | 6,05 | 0,98 | 41,67 | 0,04 | 0,003 |
| 8 | 57,92 | 6,27 | 1,99 | 33,82 | 0,12 | 0,007 |
| 9 | 53,09 | 5,97 | 1,26 | 39,68 | 0,08 | 0,004 |
| 10 | 59,21 | 6,45 | 2,42 | 31,92 | 0,18 | 0,008 |
Table 4a
Recommendations of VNIITP for peat coke and semicoke
| For agglomeration | For ferroalloys | For pellets | For charging | For blast-furnace processes | For foundry purposes |
|---|---|---|---|---|---|
| 12 | 10 | 12 | 8 | 10 | 12 |
| 0,3 | 0,3 | 0,3 | 0,3 | 0,3 | 0,3 |
| 0,015 | 0,010 | 0,015 | 0,015 | 0,015 | 0,015 |
Table 4b
Content of ash, sulfur, and phosphorus in peat coke (according to technical and elemental analysis data for peat samples)
| Peat sample number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| 23.0 | 30.8 | 8.2 | 19.9 | 7.4 | 11.2 | 7.0 | 12.5 | 9.6 | 11.9 | |
| 0.41 | 0.36 | 0.12 | 0.15 | 0.08 | 0.20 | 0.07 | 0.20 | 0.15 | 0.26 | |
| 0.035 | 0.022 | 0.004 | 0.016 | 0.004 | 0.021 | 0.011 | 0.024 | 0.016 | 0.024 |
In this, consideration was given to the desirability of obtaining molded pieces with the maximum possible content of iron ore. The recommended regime for each given peat sample is presented in Table 5. The final moisture content—
Table 5
Preliminary technical conditions for the recommended regime for obtaining fuel-flux materials based on machine-molded peat
| No. of peat sample | Initial moisture content of peat, % | Conventional degree of peat processing | Ratio between peat and ore: carbon-to-iron ratio | Ratio between peat and ore: ore content in the mixture with raw (working-moisture) peat, % | Ore characteristics: iron content, % | Ore characteristics: degree of grinding, mm | Final moisture content of fuel-flux materials, % |
|---|---|---|---|---|---|---|---|
| 1 | 75 | 3 | 0.7:1.0 | 13.6 | 60 | not more than 0.15 | 20–25 |
| 2 | 75 | 3 | 0.7:1.0 | 14.1 | 60 | —“— | 20–25 |
| 3 | 80 | 3 | 1.0:1.0 | 6.9 | 60 | —“— | 20–25 |
| 4 | 75 | 3 | 0.7:1.0 | 12.3 | 60 | —“— | 20–25 |
| 5 | 75 | 3 | 1.0:1.0 | 8.8 | 60 | —“— | 20–25 |
| 6 | 75 | 3 | 0.7:1.0 | 13.3 | 60 | —“— | 20–25 |
| 7 | 75 | 3 | 1.0:1.0 | 11.4 | 60 | —“— | 20–25 |
| 8 | 85 | 3 | 0.7:1.0 | 11.0 | 60 | —“— | 20–25 |
| 9 | 85 | 3 | 0.7:1.0 | 10.4 | 60 | —“— | 20–25 |
| 10 | 85 | 3 | 0.7:1.0 | 10.4 | 60 | —“— | 20–25 |
—of the fuel-flux materials was defined conditionally as the limiting value possible under natural drying. When fuel-flux materials are used in the blast-furnace process, artificial drying to the lowest possible moisture content must be organized.
The strength of peat thermal briquettes is influenced by the following factors: the temperature of peat heating before briquetting, the briquetting pressure, the degree of peat grinding, and the holding time of the peat in the heated state before application of pressure and under pressure. Of all these factors, the briquetting temperature is of decisive importance. Preliminary experiments established the following optimal values for a number of factors [2]: briquetting pressure 250 kg/cm², degree of grinding 0.5–0 mm, holding before application of pressure 1 min and under pressure 2 min. With these parameters, the influence of temperature on strength was determined.
thermobriquettes for all peat samples. On the basis of the tests carried out and the data obtained earlier, technical conditions were formulated for the recommended thermobriquetting regime (Table 6), ensuring the production of thermobriquettes of maximum strength with optimal energy expenditure.
Table 6
Technical conditions for the recommended thermobriquetting regime
| Sample no. | Peat heating temperature, °C | Briquetting pressure, kg/cm² | Holding of peat in the hot state before filling the mold, sec. | Holding under pressure, sec. | Peat particle size, mm | Note |
|---|---|---|---|---|---|---|
| 1 | 255 | 250 | 60 | 120 | 0.5–0 | For high-speed heating |
| 2 | 255 | —"— | —"— | —"— | —"— | —"— |
| 3 | 260 | —"— | —"— | —"— | —"— | For slow heating |
| 4 | 260 | —"— | —"— | —"— | —"— | For high-speed heating |
| 5 | 260 | —"— | —"— | —"— | —"— | For slow heating |
| 6 | 250 | —"— | —"— | —"— | —"— | For high-speed heating |
| 7 | 255 | —"— | —"— | —"— | —"— | For slow heating |
| 8 | 255 | —"— | —"— | —"— | —"— | For high-speed heating |
| 9 | 265 | —"— | —"— | —"— | —"— | For slow heating |
| 10 | 255 | —"— | —"— | —"— | —"— | For high-speed heating |
The characteristics of the mechanical strength of fuel-smelting materials and thermobriquettes given in Table 7 show that a strong metallurgical fuel can be obtained from all the peat samples studied.
It should be noted, however, that the mechanical strength of coke from fuel-smelting materials obtained on the basis of machine-formed peat of low degree of decomposition is unsatisfactory. These samples were prepared from peat taken from a depth of up to one meter. The lower-lying peat layers in all areas have a high degree of decomposition and, as a rule, exhibit significantly higher strength. Consequently, when exploiting a peat deposit and extracting peat to the full depth, it is possible to obtain a metallurgical fuel of considerably higher strength than that provided by samples from only one upper peat layer. It should also be noted that, for peat samples 3, 4 and 5, 6, the strength of iron coke for the upper and lower peat layers differs little and is noticeably lower in comparison with the best samples (samples 1, 8, 10).
This drawback of peats of low degree of decomposition, when determining directions for obtaining metallurgical fuel from peats of the deposits studied, can be eliminated by organizing the production of thermobriquettes or fuel-smelting materials on the basis of
milled peat. The thermobriquettes we tested have high strength regardless of the degree of decomposition.
Thus, the preliminary metallurgical evaluation of peat from deposits promising for the industrial development of the Bakchar iron-ore deposit shows that, in terms of peat reserves and quality, the indicated deposits can serve as a reliable base for organizing a large metallurgical complex for the production of cast iron of up to 3 million tons per year.
Table 7
Some characteristics of fuel-smelting materials, coke made from them, and thermobriquettes obtained under optimal conditions
| Peat sample No. | Air-dry fuel-smelting materials: Crushing resistance, kg/cm² | Air-dry fuel-smelting materials: Abrasion, % | Iron-coke fuel-smelting materials: Crushing resistance, kg/cm² | Iron-coke fuel-smelting materials: Abrasion, % | Thermobriquettes: Crushing resistance, kg/cm² | Thermobriquettes: Abrasion, % |
|---|---|---|---|---|---|---|
| 1 | 176 | 1.5 | 107 | 1.4 | 800 | 7.2 |
| 2 | 211 | 1.5 | 193 | 12.6 | 763 | 2.7 |
| 3 | 203 | 8.9 | 187 | 37.0 | 782 | 4.5 |
| 4 | 277 | 2.6 | 132 | 22.1 | 950 | 2.9 |
| 5 | 168 | 2.0 | 88 | 17.6 | 735 | 5.5 |
| 6 | 36 | 5.3 | 94 | 14.1 | 605 | 0.7 |
| 7 | 81 | 6.5 | 53 | 81.0 | 682 | 4.0 |
| 8 | 251 | 1.8 | 93 | 5.4 | 911 | 1.2 |
| 9 | 53 | 0.9 | 26 | 67.1 | 519 | 2.4 |
| 10 | 290 | 2.6 | 144 | 9.8 | 440 | 2.7 |
LITERATURE
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I. V. Gebler, S. I. Smolyaninov. Fuel-smelting materials based on peat. Izv. TPI, vol. 126, 1964.
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S. I. Smolyaninov, V. E. Voronin. Production of peat thermobriquettes under conditions of high-speed heating. Torfyanaya promyshlennost’, No. 4, 1962.