DETERMINATION OF OPTIMAL CONDITIONS FOR THE EXTRACTION OF HUMIC ACIDS FROM PEAT AND BROWN COALS BY THE DISPERSION METHOD

A. F. KARPOVICH, V. M. VITYUGIN, I. N. LANTSMAN

(Submitted by the scientific seminar of the Department of OChT)

Technical progress in the field of metallurgical production is imposing increasingly high requirements on the preparation of ore fines and concentrates for metallurgical processing, on improving the quality of granulated fine-grained materials, and on further intensifying the processes by which they are obtained.

At present, bentonite is used as a binding additive in the granulation of iron-ore concentrate. However, in the blast-furnace process the latter is a ballast component; therefore its presence in the iron-ore burden is undesirable.

Sodium humates may be used as additives that do not introduce ballast components into the pelletized burden. It has been shown that the introduction of 0.2–0.3% of a carbon-alkali reagent into the moist cake of iron-ore concentrate increases the strength and improves the granulometric composition of the granules obtained.

Selection of a method for obtaining sodium humates

A literature review of existing methods for extracting humic acids and sodium humates from peat and brown coal [1–4] for specific production applications showed that the most economical method is the continuous high-speed dispersion method [5], suitable for continuous industrial production of sodium humates.

Selection of the object of study

As sources for obtaining humic acids, the following were selected:

a) brown coals (Irsha-Borodino and Nazarovo) from the Kansk-Achinsk basin, which are the cheapest open-pit mined coals in the USSR;

b) peat from the Vasyugan deposit in Tomsk Oblast. The peat was selected for a comparative study of the efficiency of humic-acid extraction.

Characteristics of the objects of study

Humic-acid content:

    in Irsha-Borodino brown coal — 20.84%,
    in Nazarovo brown coal — 26.25%,
    in Vasyugan peat — 39.00%.

Experimental part

The studies were carried out in a laboratory single-stage disperser of the Khotuntsev–Pushkin design. Determination of the concentration

of the sodium humate solution was carried out by measuring their optical densities [6]. For measurements of optical densities, an FEK-M photoelectric colorimeter was used, with a working face length of 1.080 mm and a blue light filter. The main factors on which the yield of humic acids from solid fuels depends are: alkali concentration, the ratio of solid to liquid in the suspension, and the number of treatments of the latter in the disperser.

The dependence of the yield of humic acids from peat and brown coals on the concentration of the alkaline solution used for extraction, the percentage content of solids in the suspension, and the number of treatments of the suspension in the disperser is presented in Fig. 1.

When determining the yield of humic acids from peat and brown coals as a function of the concentration of the alkaline solution, peat and brown coals were treated three times at a 6% solids content in the suspension (Fig. 1a).

When determining the yield of humic acids as a function of the concentration of peat and coal in the suspension, the concentration of the alkaline solution was taken as 1% for peat and 2% for brown coals, with threefold treatment (Fig. 1b).

When determining the dependence of the yield of humic acids on the number of treatments of the suspension, the concentration of the alkaline solution was taken as 1% for peat and 2% for brown coal; the concentration of peat in the suspension was 6%, and that of brown coals 10% (Fig. 1c). The extraction conditions for humic acids from Irsha-Borodino and Nazarovo brown coals are identical. The curves coincide.

Thus, the optimal conditions for isolating humic acids are as follows: solids content in the suspension: 10–15% for brown coals and 6% for peat; concentration of the alkaline solution: 2% for brown coals and 4–10% for peat. Here the maxima for brown coals are 10–15, and for peat 4–10. The maximum yield of humic acids from Vasyugan peat is 38%, and from Irsha-Borodino and Nazarovo brown coals 85–90%.

Fig. 1. Dependence of the yield of humic acids from Nazarovo (1), Irsha-Borodino (2) brown coals and Vasyugan peat (3) on the concentration of the alkaline solution (a), the concentration of coal and peat in the suspension (b), and the number of treatments of the suspension (c).

Discussion of Results

The continuous dispersion method for obtaining humic acids, according to G. M. Volkov, with replacement of the operations of centrifugation and precipitation

of humic acids by evaporating a dispersed coal–alkali suspension can successfully meet the needs of ferrous metallurgy for sodium humates. According to our calculations, the cost of 1 ton of humates, calculated on a dry-matter basis, is 77 rubles 45 kopecks. The greater effect of adsorptive reduction in the strength of brown-coal particles, compared with peat, during dispersion promotes more efficient extraction of humic acids from brown coals (85–90% versus 38%).

Table 1

Technical analysis and calorific value of peat and brown coals

Taking into account the less favorable conditions for extraction and transportation of peat than of brown coal, preference in use should be given to brown coal.

REFERENCES

1. T. A. Kukharenko, S. A. Shapiro. Fundamentals of the technology of humic acid production. In: Humic Fertilizers, Theory and Practice of Their Application, Moscow, 1957.

2. V. S. Baranov. Humic solutions for drilling wells under complicated conditions. Gostoptekhizdat, Moscow, 1955.

3. V. A. Demyanova. Treatment of clay solutions with coal-alkali preparations. Razvedka nedr, No. 4, 1952.

4. I. V. Gebler. On the use of alkaline humates in in-boiler water treatment. Izv. TPI, vol. 64, 1948.

5. G. M. Volkov. On the technology of humic acid production. Transactions of the Institute of Fossil Fuels, No. 12, 1961.

6. E. M. Aleksandrova, N. G. Lidina. Optical properties of solutions of humates and sols of humic acids. Khimiya i tekhnologiya topliva, No. 8, 1956.