Study of Ore from the Rozhdestvenskoye Deposit in Tomsk Oblast as a Hydrogen Sulfide Absorbent

K. K. Stramkovskaya, A. S. Pozhitnaya

(Presented by Professor, Doctor I. V. Gebler)

The Rozhdestvenskoye deposit of bog ore is located on the southwestern outskirts of the village of Rozhdestvenka, six kilometers northeast of the village of Sergeevo and 40 km northwest of the district center, the village of Pyshkino-Troitskoye.

The geological-lithological section of the deposit, according to the available data, is as follows: 1) soil-vegetation layer—0.05–0.40 m; 2) ore horizon—0.15–1.10 m; 3) light-yellow clay with a visible thickness of 1.45 m.

The ore deposits occur as separate lenses elongated along the right and left banks of the Tatunaika River. The length of the lenses varies from 100 to 800 m. The thickness of the ore horizon varies from 0.05 to 1.1 m, averaging 0.4 m. The deposits of bog ore at the deposit are overlain by a dark-gray, almost black, soil-vegetation layer with a thickness of 0.4 m.

In studying the chemical composition of the ore of this deposit, it was found that the CaO content in the samples varied from 5.60 to 30.0%; \(\mathrm{Fe_2O_3}\) from 15.39 to 39.00%; \(\mathrm{Al_2O_3}\) from 3.63 to 13.31%; \(\mathrm{SiO_2}\) from 10.1 to 37.95%; \(\mathrm{Na_2O}\) and \(\mathrm{K_2O}\) from 0.5 to 1.37%. Loss on ignition ranged from 13 to 33.72%.

In granulometric composition the ores consist of 25–29% aleuritic fraction and 4 to 12% sandy fraction. Mineralogically, the heavy fraction is represented 70–80% by iron hydroxides. The remaining minerals are characterized by a clearly expressed ore-epidote-hornblende association. In addition, the presence here of pyroxene, garnet, and tourmaline is characteristic. In the light fraction, before treatment with a ten-percent hydrochloric acid solution, up to 98% consisted of fine grains of calcite, colored dark brown and brown by iron hydroxides. After treatment with hydrochloric acid, in the light fraction quartz constituted 38–45%. Feldspar occupies a subordinate position relative to quartz and amounts to 10–20%. The ore reserves at the deposit amount to 31,000 t [1].

To determine the technological qualities of the ore as a hydrogen sulfide absorbent, the samples listed in Table 1 were studied.

Table 1

In addition, average samples were prepared proportional to the thickness of the seams (a) and proportional to the ore reserves in the deposit sections (b). For comparison, ore from the Kudinovskoye deposit, taken from the warehouse of the Kemerovo nitrogen-fertilizer plant, was studied. The location from which one of the samples was taken was not indicated by the geologists; therefore we called it the zero (0) sample.

The absorbing mass consisted of ore with a particle size of 0.25–1 mm and wood sawdust, fraction 0.5–3 mm, in a 1:1 ratio by volume. The mass was alkalized with unslaked lime in an amount of 0.5% by weight and moistened to a moisture content of 35–45 wt.%.

To determine the possibility of increasing the activity of the absorbing mass, an absorbing mass was prepared from the average sample (a) and peat in a 1:1 ratio by volume.

The moisture content of the purifying mass was determined by drying it to constant weight at a temperature of 100–105°.

The absorptive capacity was determined on an apparatus assembled according to the following scheme: hydrogen sulfide, obtained in a Kipp apparatus, was passed through a bottle with water, a column with spent bog ore, and dryers with CaCl₂, and then, after passing through a rheometer, entered the column with the mass under investigation. After the column with the mass, moisture carried out of the absorbing mass was trapped in two calcium-chloride tubes. The increase in weight of the tube with the mass and of the calcium-chloride tubes gave the amount of hydrogen sulfide retained by the absorbing mass [2]. The absorptive capacity of the mass was expressed in weight percent based on the dry mass (ore and sawdust). To guarantee complete absorption of hydrogen sulfide, it was passed for an additional two hours after heating of the column ceased as a result of the dying out of the exothermic absorption reactions.

The study of the regeneration process of the absorbing masses was carried out in order to determine the maximum sulfur capacity of the masses after several cycles of absorption and regeneration. The sulfur-containing masses were regenerated with moist air. The rate of passage of air was 6–7 l/hr. The end of regeneration was determined by constant weight and by the change in color from black to brown, after which the mass was again saturated with hydrogen sulfide. The time required for regeneration varied from 2 to 4 hours.

For most samples five regenerations and six absorptions were carried out, while for the average samples eight regenerations and nine saturations were carried out. The data obtained are given in Table 2 and in Fig. 1.

Table 2

In plotting the graph, the total absorptive capacity and the total absorption time after each regeneration of the ore were laid off on the coordinate axes.

Fig. 1. Absorptive capacity as a function of saturation time. 1—Kudinov ore; 2—Rozhdestvenskoye ore—sample 21; 3—Rozhdestvenskoye ore—sample 144; 4—Rozhdestvenskoye ore—sample 2; 5—Rozhdestvenskoye ore—sample 0.

From the results obtained it follows that, after the very first regeneration, the absorptive capacity of samples 0 and 2 proved to be considerably higher than that of the Kudinov ore; and after the third and fourth regenerations the Kudinov ore showed a lower absorptive capacity not only in comparison with samples 0 and 2, but also with samples 144, 21, and the average prepared in proportion to the reserves. Although the amount of iron in samples 0 and 2 is considerably less than in the Kudinov ore, the initial absorptive capacity of these samples is almost equal to the absorptive capacity of the Kudinov ore. This is apparently explained by the fact that the iron in the Rozhdestvenskoye ore is more hydrated than in the Kudinov ore. In addition, this ore contains manganese oxide (from 0.5 to 2%). The Rozhdestvenskoye ore also has a higher alkalinity than the Kudinov ore, and this improves the process of hydrogen sulfide absorption, since in an alkaline medium the reaction proceeds with the formation of ferric oxide sulfide, \(Fe_2S_3\), which is readily regenerated by atmospheric oxygen in a moist medium. In the absence of alkali, or when its amount is insufficient, the reaction proceeds with the formation of ferrous sulfide. The latter can react with elemental sulfur to form disulfide \(Fe_2S_2\)—a compound that is completely nonregenerable.

In addition, the conversion of the ferric form of iron into the ferrous form is disadvantageous for the purification process, since each iron atom binds only one molecule of hydrogen sulfide. Iron sulfide can also be oxidized by oxygen to iron sulfate—a nonregenerable compound.

The lower absorptive capacity of samples 28, 29, 105, and 9 is explained not only by the low content of iron oxides, but also by the excessively high alkalinity of these samples, which reduces the activity of the iron, since the solubility product of ferric oxide hydrates decreases with increasing alkalinity. The most hydrated form

iron in samples 0 and 2 naturally indicates a high reactivity toward hydrogen sulfide after regeneration of the ore with air. In addition, it is evident that the alkalinity in these samples is optimal for the formation of sulfides of the ferrous form.

The maximum absorptive capacity of many ore samples from the Rozhdestvenskoye deposit is considerably higher than, or equal to, the maximum absorptive capacity of Kudinovskaya ore.

Conclusions

1. The absorptive capacity for hydrogen sulfide of bog ore from the Rozhdestvenskoye deposit before regeneration is lower than the absorptive capacity of Kudinovskaya ore.

2. When cycles of saturation and regeneration are alternated, the total absorptive capacity of most samples of Rozhdestvenskoye ore is higher than that of Kudinovskaya ore, owing to its mineralogical composition, which is more favorable for this purpose.

3. Ore from the Rozhdestvenskoye deposit can be successfully used for fine purification of gas from hydrogen sulfide.

References

1. V. M. Zhukov. Report of the Non-ore Party of the Tomsk Complex Expedition for 1958, Tomsk.

2. Berl-Lunge. Chemical-Technological Methods of Investigation, vol. IV, issue 2, Moscow, 1940.

3. Yu. D. Kernos, N. I. Brodskaya, V. P. Teodorovich. Gas Industry, No. 10, 1956.