عنوان مقاله [English]
On the basis of environmental and safety reasons, hardness of agricultural sulfur granules should be high enough to have minimum dust formation during transportation and storage. On the other hand, by using agricultural sulfur, soil indigenous thiobacillus bacteria can oxidize elemental sulfur to sulfuric acid and decrease the soil pH. Sulfur particle size is one of the most important parameters, which affect the oxidation rate. Thus, hardness of sulfur granules should be low enough to be easily crushed to fine particles. In this research, first, hardness and electromicroscopic structure of elemental sulfur granules, solidified at different medium temperatures were investigated and the optimum temperature was determined. The results indicated that the optimum temperature is 30°C. At higher temperatures, the percent of dust formation was considerably increased. In the next stage, the agricultural sulfur and the enriched sulfur with Fe, Zn and Mn were prepared at optimum medium temperature. Mechanical strength, abrasion resistance and dispersion percent of the prepared granules were measured. The data indicated that sulfur fertilizer granules were harder than elemental sulfur ones probably due to their inorganic content. In addition, their dispersion in contact with water was significantly increased compared with elemental sulfur granules so that more than 94 percent of granules crushed to fine particles during 2 hours.