PURIFICATION AND THERMOCHEMICAL CONVERSION OF AMMONIUM SULFATE: A PATHWAY TO SUSTAINABLE WASTE RECYCLING
Ammonium sulfate obtained from the coke-chemical production of JSC “QARMET” (Kazakhstan) is contaminated with tarry substances and pyridine-based sulfates. The presence of these impurities leads to adverse effects, including a strong odor, caking, and an atypical commercial appearance of the product. The presence of pyridine sulfate (a weak alkali) also increases acidity (pH < 5). As a result, the manufacturer has faced marketing difficulties with this by-product since the company’s inception. The only potential consumer in Kazakhstan – the rice-growing sector of the Kyzylorda region – currently imports this fertilizer from Uzbekistan.
This paper presents the results of a study on the purification of substandard ammonium sulfate from coke-chemical production. To expand its potential applications, the mechanisms for producing complex fertilizers based on this product were investigated.
The newly obtained data serve as a fundamental theoretical and technological basis for the development of new production lines for chemical products such as synthetic sodium carbonates and compound fertilizers.
The mechanism of topochemical interaction between potassium carbonate and molten ammonium bisulfate was studied, and the following reaction pathways were established:
At equimolar ratios of 2NH₄HSO₄ to K₂CO₃, ammonium potassium sulfate (NH₄KSO₄) forms in the temperature range of 157-260 °C.
Above 260 °C, potassium sulfate and ammonium sulfate are formed, with simultaneous pyrolysis of the latter to ammonium bisulfate and ammonia.
Upon cooling, various double bisulfates are formed, depending on the ratio of potassium sulfate to ammonium bisulfate produced in the reaction.