PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
OF THE ORDER OF THE OCTOBER REVOLUTION AND THE ORDER OF THE RED BANNER OF LABOR
NAMED AFTER S. M. KIROV

Volume 254 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 1975

INDUSTRIAL TESTS OF THE CRYSTALLIZATION OF AMMONIUM SULFATE IN THE PRESENCE OF MANGANESE SULFATE ADDITIVES

I. N. NOZHKINA, V. M. VITYUGIN, A. L. SHTEIN, G. I. TRONDINA

(Presented by the scientific seminar of the Department of General Chemical Technology)

Earlier laboratory studies and short-term pilot-plant tests [1] established the fundamental possibility of enlarging ammonium sulfate crystals in saturators of coke-chemical production by means of additives of salts of magnesium, chromium, and manganese.

In connection with the wide use of microelements in agriculture [2] and taking into account the importance of the element manganese as a micronutrient fertilizer, in November–December 1961, employees of the Department of General Chemical Technology of the Tomsk Polytechnic Institute, together with workers of the Central Factory Laboratory of the Kemerovo Coke-Chemical Plant, carried out long-term industrial tests of the method using technical manganese sulfate salt as a microadditive. It was important to establish the effectiveness of the additive on the crystallization of ammonium sulfate in the presence of temporary deviations from the normal operating regime of the saturators. The procedure for conducting the tests was as follows: manganese sulfate salt was dissolved in water in an amount of 10 kg (calculated as the ion Mn$^{+2}$), which amounted to 0.2% of the hourly output of the shop in ammonium sulfate; the additive was fed through the circulation vessel into each operating saturator. During the first two days of the tests, a corrective additive in the amount of 0.5 kg (as the ion Mn$^{+2}$) was introduced into the cycle hourly to maintain the optimum concentration of the manganese ion in the solution. Samples of solid ammonium sulfate were taken just as often from each saturator and dryer. In the subsequent days of the tests, the corrective additive was introduced into the cycle once per shift, and an average salt sample was taken for the shift. The samples taken were studied for particle-size composition and for their manganese content.

The data from these tests indicate an improvement in the granulometric composition of ammonium sulfate crystallized in the presence of manganese salt.

After the saturators, the yield of the \(+0.25\ \mathrm{mm}\) class, averaged over two shifts before introduction of the additive, was 50–60%. Throughout the entire testing period the yield of the \(+0.25\ \mathrm{mm}\) class fluctuated within the range 70–88%. It is interesting to note that, beginning with the second shift on November 18, the feeding of manganese salt to the saturators was temporarily stopped, and the yield of the coarse \(+0.25\ \mathrm{mm}\) class on November 19 decreased to 57%, with a simultaneous decrease in the manganese content in the crystalline product. The effectiveness of the additive’s influence on the crystallization process of ammonium sulfate became apparent on the fourth day after manganese was introduced into the cycle, when its content in the solution reached a certain concentration. In the solid product it amounted to 0.007%. The feeding of the additive to the saturators was practically stopped after December 5, and on December 9–10 a clear decline in the effect of the manganese ion on the crystallization process of ammonium sulfate was observed. Although the manganese content in the crystalline product remained equal to 0.007%, in the solution it had decreased considerably; the additive can exert an effect on the crystallization process only from the solution at a definite concentration of manganese ion in it. This fact also indicates that the crystalline product removes from the solution a strictly definite amount of manganese, while the portion remaining in the solution regulates the process of crystal growth and crystallization. During the nucleation of a new ammonium sulfate crystal, manganese enters into its composition at any content of the latter in the solution. Taking into account the possibility that fine crystals remain in the saturator bath for a long time, an important fact is that even after the feeding of the additive is stopped, the crystalline product contains a certain amount of manganese. In addition, when the same amount of additive is present in the solution, the fine fractions of the crystalline product should contain more manganese owing to the larger specific surface area of the finely crystalline product.

Thus, the industrial tests carried out at the Kemerovo Coke-Chemical Plant showed that, under shop operating conditions, in the presence of temporary deviations from the normal operating regime of the saturators, an additive of manganese sulfate promotes improvement of the granulometric composition of ammonium sulfate. It should be noted that the tests were conducted under process conditions unfavorable for obtaining a coarse-crystalline product: the temperature of the mother liquor was 65–68°C, and the ammonia load was above \(20\ \mathrm{kg}/\mathrm{m}^{2}\cdot\mathrm{h}\) (when operating with two saturators).

According to research data (3), when the temperature of the mother liquor is lowered from 55.8 to 51.7°C, the yield of the \(+0.25\ \mathrm{mm}\) class increases by 7%; when the load with respect to \(\mathrm{NH}_{3}\) is reduced from 14–16 \(\mathrm{kg}/\mathrm{m}^{2}\cdot\mathrm{h}\) to 11 \(\mathrm{kg}/\mathrm{m}^{2}\cdot\mathrm{h}\), the yield of the \(+0.25\ \mathrm{mm}\) class increases by 7%.

REFERENCES

1. V. M. Vityugin, I. N. Nozhkina, O. A. Fuks. Purification and crystallization of ammonium sulfate.—Proceedings of the 1st Scientific Conference of the Tomsk Branch of the D. I. Mendeleev All-Union Chemical Society, Tomsk University Press, 1969.

2. M. V. Katalymov. Trace Elements and Microfertilizers. Moscow—Leningrad, 1965.

3. Central Laboratory of the Kemerovo Order of Lenin Coke-Chemical Plant. Report on the topic: “Improvement of the Quality of Ammonium Sulfate,” Kemerovo, 1967.