Testing Peat Fuel-Fluxing Materials in a Laboratory Blast Furnace

S. I. Smolyaninov, V. S. Arkhipov, G. G. Krinitsyn

(Presented by the Scientific-Methodological Seminar of the KhTF)

The largest in the world West Siberian iron-ore basin may play a major role in supplying the third metallurgical base of the USSR with iron ore. The enormous peat reserves in Western Siberia create favorable technical and economic conditions for the comprehensive use of this raw material in the metallurgical and chemical industries. The idea of using air-dry lump peat and peat coke in blast furnaces has long attracted the attention of a number of researchers [1, 2].

At Tomsk Polytechnic Institute, a fundamentally new technology has been developed for obtaining blast-furnace monoburden (fuel-fluxing materials) based on peat [3].

The accepted methods for testing coal coke cannot be directly transferred to metallurgical fuel of another type, since they do not reflect the actual behavior of the fuel in a blast furnace [4].

Many questions concerning the behavior of the burden under blast-furnace smelting conditions can be resolved by tests in large laboratory blast furnaces, which, however, make it possible to work with such a quantity of experimental material as can practically be obtained on bench-scale installations. Such installations have been used more than once in studies of blast-furnace production [5, 6].

The laboratory blast furnace installed at Tomsk Polytechnic Institute during 1965–1967 was designed on the basis of an installation operating at the A. A. Baikov Institute of Metallurgy [7], but, unlike the latter, it is equipped with a system for condensing volatile pyrolysis products. The gas leaving the furnace at a temperature of 400–600°C is freed from dust in a cyclone and cooled in a water cooler, where tar condenses. The furnace makes it possible to test small quantities of materials under conditions of counterflow of burden and gas at temperatures sufficient for smelting pig iron.

In November 1967, the first smelting was carried out for the purpose of testing fuel-fluxing materials (TFM). The materials were prepared in an amount of 1200 kg by the peat problem laboratory of TPI in the summer of 1967. The initial components for obtaining TFM were Tagan peat and iron-ore concentrate from the Abagur factory. The analysis of the burden materials is given in Tables 1 and 2.

The carbon-to-iron ratio in the fuel-fluxing materials is 0.5, i.e., it corresponds to the fuel consumption in industrial blast furnaces. Since the laboratory blast furnace, owing to large heat losses, operates with a carbon consumption of 6–7 kg per 1 kg of pig iron, in

Technical analysis of charge materials

Chemical composition of the mineral part

coke, amounting by weight to 63% of the entire charge, is introduced into the experimental charge.

The campaign lasted two days and 15 hours. During the first and second periods the furnace was heated up and brought to the operating regime. Operation on the experimental charge continued for 27 hours 30 min. During this time, 545,5 kg of fuel-fluxing materials were charged and 43,3 kg of metal and 158 kg of slag were obtained. The average blast consumption was 91 m\(^3\)/h of air under normal conditions. The principal smelting indices by periods are given in Table 3. During the last 2 hours 25 min the furnace was charged only with FFM, in order to obtain as large an amount of material as possible under dis-

Table 3

Smelting indices

briquettes. After cooling, the furnace was dismantled and samples of the material were taken along the height, with subsequent screening and weighing. Measurements of the briquettes showed that they decrease in volume by approximately a factor of 2 as they move from the throat to the tuyeres. Beginning at a level 400 mm above the tuyeres, intense disintegration of the briquette takes place, and 91% of the briquettes reach the tuyeres in the form of fines of 5–0 mm.

Despite the low strength of the TFM in the lower zones of the furnace, the removal of iron with dust was small—about 10% of the balance amount of iron. The furnace operation remained smooth during the tests. Judging by the coefficient

Table 2

charge materials, %

CIPO, utilization of the useful volume of the furnace even improved somewhat, despite the fact that the volume of charge materials per unit of metal increased considerably. The increased rate of descent of the materials of the experimental charge is apparently explained by shrinkage of the briquettes. The intensity of coke combustion decreased slightly in comparison with operation on the standard charge (186.3 kg/m²·h versus 189.5 kg/m²·h).

Under the conditions of a laboratory blast furnace, the iron does not have time to be completely reduced and partially passes into the slag in the form of ferrous oxide; therefore the calculated amount of slag is less than the actual amount. The composition of the pig iron obtained is close to foundry iron (silicon content 1–2%). It should be noted that the amount of top gas when operating on the experimental charge increases due to gases from peat pyrolysis, and at the same time its temperature decreases (from 520 to 450°C). This indicates cooling of the furnace shaft due to heat consumption for the coking of peat.

The small dimensions of the laboratory blast furnace create specific features in pig-iron smelting: 1—high rate of conversion of the charge into liquid products and gas; 2—high fuel consumption per 1 kg of metal; 3—low rate of charge movement.

Thus, material placed in a laboratory blast furnace undergoes heat-exchange processes and chemical transformations under counterflow conditions at a more accelerated rate and under more severe conditions than in an industrial furnace. At the same time, the mechanical loads of crushing and abrasion do not reach the values characteristic of industrial furnaces, either in magnitude or in duration of action.

Therefore, the test results cannot be transferred directly to industrial furnaces. Smelting in the laboratory blast furnace convincingly showed that obtaining pig iron from a single charge of the above composition raises no doubts. The question is in what quantities and in what unit TFMs can be used. Clarification of this question should be the aim of further investigations.

Conclusions

1. The possibility of smelting pig iron from a single charge based on peat has been demonstrated.

1. The use of fuel-fluxing materials in the burden leads to an increase in the rate of descent of the burden, an increase in the volume of bosh gases, and a decrease in temperatures in the furnace shaft.

2. Studies should be carried out to determine the optimal conditions for the use of FFM in industrial units.

References

1. V. V. Kondakov. Kislorod, 1, 35–47, 1945.

2. M. N. Grachevskii. Gasification of Local Fuels and Long-Distance Gas Supply. ONTI Publishing House, 70–78, 1936.

3. I. V. Gebler, S. I. Smolyaninov. Izv. TPI, vol. 126, 8–12, 1964.

4. K. I. Syskov. Theory of Coke Behavior in the Blast-Furnace Process. Publishing House of the Academy of Sciences of the USSR, 176–177, 1949.

5. Taylor, Lowny, Huy. Problems of Modern Metallurgy. Collection of articles. IL Publishing House, 2, 38, 1958.

6. I. F. Koval. Stal’, 6, 497–506, 1959.

7. A. M. Chernyshev et al. Proceedings of IGI. Publishing House of the Academy of Sciences of the USSR, vol. XXII, 70–78, 1963.