PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
named after S. M. Kirov

Vol. 126　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1964

FUEL-SMELTING MATERIALS BASED ON PEAT

I. V. GEBLER, S. I. SMOLYANINOV

Peat could be an excellent metallurgical fuel, since it contains only a small amount of harmful impurities—ash and sulfur. Smelting pig iron on peat can yield results, in terms of metal quality, close to the smelting of this metal on charcoal, which is still used for producing high-quality steel.

In the Soviet Union, mainly in the 1930s, successful smelts of pig iron were carried out in blast furnaces at the Vyksa and Kosogorsk plants and at the Chernorechensk Chemical Combine, using peat coke and air-dry (uncoked) formed peat as blast-furnace fuel [1, 2, 3, 4].

At approximately the same time, engineer P. M. Vavilov advanced the idea of the gas-blast-furnace process, that is, the idea of conducting blast-furnace smelting on air-dry peat with simultaneous production of pig iron, high-calorific gas, and peat tar. This idea enjoyed broad support until very recently [5, 6, 7, 8].

Serious attention is still being paid to the question of using peat as a metallurgical fuel. This is confirmed by the conference held in Moscow in 1958 on the use of peat in the metallurgical industry [9], and by other evidence.

The following methods of using peat as a metallurgical fuel are known:

1. Production of blast-furnace coke from peat:
   a) coking of machine-formed peat;
   b) obtaining blast-furnace coke from milled peat through intermediate production of thermobriquettes;
   c) obtaining blast-furnace coke from milled peat through intermediate semicoking followed by briquetting of the semicoke (with a binder) and coking of the briquettes;
   d) obtaining blast-furnace coke by coking briquettes pressed under high pressure from milled peat.

2. Production of semicoke from milled peat, using this semicoke to replace lean coals in the coal charge and for ore agglomeration.

3. Use of air-dry formed peat.

Methods were also proposed for producing peat–iron-ore briquettes (peat, ore, fluxes) by thermobriquetting methods [4].

All these methods have a number of substantial shortcomings. Coke made from machine-formed peat of a low degree of processing possesses

comparatively low mechanical strength, at best 60–80 kg/cm². In addition, at present there are no high-capacity peat-coking furnaces.

The production of blast-furnace coke from milled peat, suitable for large-volume furnaces, is possible only with considerable complication of the technological process and a sharp increase in its cost.

We propose a method for obtaining fuel-smelting materials from peat, i.e., materials containing in their composition fuel, iron ore, and fluxes in the proportions required for the blast-furnace process, which consists in the following.

Raw peat with working moisture content (not less than 80–85%) is subjected to processing (grinding), after which, with thorough mixing, finely ground ore and fluxes are added to it in the required proportion. The ore and fluxes must be ground to grain sizes of no more than 0.15 mm, and preferably finer, down to 0.07 mm and less. The mixture is molded under a pressure of 1–5 kg/cm² into molds of the required size and shape. After natural drying to a moisture content of no more than 15–20%, the fuel-smelting materials are suitable for use in blast furnaces in the air-dry state or after coke has been obtained from them; the former is preferable.

Under laboratory conditions, we obtained, on the basis of peat and ore containing 40% iron, with the calculated amount of flux—limestone—fuel-smelting materials with a carbon-to-iron ratio (in the sample coked at 800°) of up to 0.9:1.

For the laboratory samples, the indices of mechanical strength were determined (abrasion, crushing resistance, strength index according to K. I. Syskov—the work of destruction per unit increase in surface area), porosity, and the percentage of reduced iron.

The table below gives data on determining the indices of mechanical strength of fuel-smelting materials with additions, to the raw mass of peat (working moisture content 85%), of 6 and 10% iron ore and the corresponding amount of fluxes (degree of grinding 0.088 mm). For comparison, the same table gives the indices determined by us under equivalent conditions for metallurgical cokes produced by the Kemerovo Coke-Chemical Plant and the Kuznetsk Metallurgical Combine, as well as for charcoal (birch-retort) and molded peat without additives.

A fuel-smelting material with an addition of 10% ore to the raw mass of peat has, after removal of volatiles at 800°, a ratio between carbon and iron of approximately 0.9:1, and with an ore addition of 6%—1.6:1. In the first case, the indicated ratios are normal for the modern blast-furnace process; in the second, they are quite permissible, since in smelting certain special grades of pig iron the coke consumption even exceeds this value.

As can be seen from the table, fuel-smelting materials in the air-dry state are equal to good metallurgical coke in crushing resistance and strength index, and surpass it in abrasion resistance. This circumstance is of particular importance when charging air-dry materials into the blast furnace, since a considerable share of the destructive forces is applied to the fuel during its transportation and charging into the bell.

For the gas permeability of the blast-furnace burden, the abrasion resistance of the burden components is of great importance. This index of fuel-smelting materials noticeably exceeds the abrasion resistance of hard-coal coke only in samples with an addition of 10% ore heated to 800°. However, this gives no grounds for believing that such materials cannot be used in large blast furnaces. The gas permeability of the column of peat-

fired fuel-smelting materials, even those having somewhat higher abrasion than coal coke, may, owing to the homogeneity of the material, prove to be much higher than for a multicomponent charge in the usual blast-furnace process.

The successful use of peat fuel-smelting materials in furnaces of smaller volume is all the more unquestionable. This is clearly seen from a comparison of the mechanical strength of the indicated materials and charcoal (Table 1), which, as is known, is still used at the present time.

It is interesting to note that fuel-smelting materials have, in comparison with pure peat, increased mechanical strength in the temperature range of 400°, where the latter, as a rule, has a mini-

Table 1

Fuel-smelting materials based on peat

mum strength. This is important both when these materials are used in the blast furnace in the air-dry state and when they are coked in continuous-action furnaces.

In specimens heated to a temperature of 800°, the percentage of iron reduced to metal is 60–70%, and the porosity is 45–60%.

It should also be noted that specimens with the addition of ore and fluxes dry under natural conditions 20–25% faster than molded peat without additives, and the final moisture content is 4–5% lower.

Since, at the moment of molding, such an amount of ore can be added to raw peat as will ensure normal ratios between ore and fuel in the blast-furnace process, the above-described method for producing fuel-smelting materials may also be regarded as a method for lumping dusty ores and ore fines.

The production of such fuel-smelting materials can apparently be carried out on ordinary peat-molding machines; moreover, the additional costs will be minimal and will most likely be offset by the acceleration of the natural drying of peat under the action of the ore and fluxes.

Conclusions

1. It is proposed to use peat in the form of fuel-smelting materials in the gas-blast-furnace process.

2. Fuel-smelting materials obtained in the course of the production of machine-molded peat, in the air-dry state, exceed bituminous-coal metallurgical coke in strength.

References

1. N. N. Bogdanov. Coking of Peat. GNTI, Moscow–Leningrad, 1931.

2. M. A. Pavlov. Metallurgy of Pig Iron. Vol. 1, Publishing House of the Academy of Sciences of the USSR, Moscow–Leningrad, 1948.

3. A. A. Myagkov. Peat Coke. ONTI Publishing House, Moscow–Leningrad, 1936.

4. K. Klimov. New Methods of Thermal Processing of Peat. GONTI Publishing House, Moscow–Leningrad, 1939.

5. A. P. Vavilov. A Forgotten Problem (the Problem of the Comprehensive Use of Peat in Blast Furnaces). VNITO Metallurgists Publishing House, 1939.

6. V. V. Kondakov. Blast-furnace smelting on peat and oxygen blast. Kislorod, No. 1, pp. 35–47, 1945.

7. A. K. Fanbushov. Smelting pig iron in cupola furnaces on peat. Peat Industry, No. 5, pp. 28–32, 1957.

8. B. D. Sysoev. The use of peat for gasification by employing it as a metallurgical fuel. Peat Industry, No. 1, pp. 13–15, 1959.

9. A. G. Born. Conference on the use of peat in the metallurgical industry. Coke and Chemistry, No. 2, pp. 56–58, 1959.