【作者】 陈德明； 王亭杰； 王轶； 金涌；

【Author】 CHEN De-ming, WANG Ting-jie, WANG Yi, JIN Yong (Department of Chemical Engineering, Tsinghua University, Beijing 100084, China)

【机构】 清华大学化工系；

【摘要】 硝酸铵钙是优良的土壤营养性复合化肥,其造粒方法主要是油浸造粒和喷淋塔造粒,特点是先形成液滴再冷却结晶,产品粒径小、强度低,造粒过程污染严重.包覆造粒方法是将原料液雾化成液滴在晶种表面逐层包覆,使颗粒逐渐增大,能够克服上述缺点.本文研究硝酸铵钙包覆造粒的可行性和特殊性,测定了硝酸铵钙复盐的熔点和熔融热,考察了硝酸铵钙熔融液的结晶特性,实验表明,在没有晶种和搅拌条件下,硝酸铵钙容易形成过冷溶液,很难结晶.在造粒过程中颗粒强度会发生变化.实验确定,硝酸铵钙包覆造粒过程的操作温度上限为95℃.更多还原

【Abstract】 Calcium ammonium nitrate (CAN) is a type of excellent soil nutritional complex fertilizer. There are two granulation techniques for CAN, which include oil-immersion granulation and spray-tower granulation. They have the same processes, i.e., formation of CAN liquid drops by spraying, and then crystallization by cooling in oil/air with existence of crystal seeds. But the CAN granuled produced by the above-mentioned methods has small particle sizes, low strength, severe environmental pollution in the granulation process, and other shortcomings. However, coating granulation can overcome the above-mentioned shortcomings. In coating granulation process, feed is atomized and coated on the surface of the seed, and crystallize by cooling for achieving particle enlargement gradually. In this paper, the feasibility and basic properties for the coating granulation of’CAN are studied. The melting point and melting heat of CAN are determined. The experimental result shows that the crystallization of melted CAN is very difficult without the inducement of seed or agitation because melted CAN easily form over-cooled solution. In the crystallization process, the strength of CAN particles varies along with time and becomes stable after a certain time. The highest operating temperature in the stable granulation process of CAN is 95℃.更多还原