The Modification Studies Of Granular Ammonium Nitrate

Granular ammonium nitrate is widely used in industrial explosives because of its good fluidity and its ANFO (ammonium nitrate fuel oil) can be achieved by highly mechanized mixed in blast site. But their applications were restricted due to their gross hygroscopicity and low detonators sensitivity. In this paper, vacuum-dehydration method (ZK method) was used to modify granular ammonium nitrate to obtain one kind of ammonium nitrate with better performances.Granular ammonium nitrate were treated by ZK method and heating-cooling method with laboratorial rotary drum. And the granular ammonium nitrate were characterized by oil absorption rate, SEM, pore diameter analyzer, detonators sensitivity. The experiment results showed that the granular ammonium nitrate treated by two methods all have certain promotion in oil absorption rate, specific surface, the number of pore and detonators sensitivity. In several aspects of performances mentioned above, the granular ammonium nitrate treated by ZK method were superior to the ones treated by heating-cooling method. But, moisture absorption rate of granular ammonium nitrate treated by two methods were all increased significantly.The influences of the amount of foaming agent solution, type of foaming agent, concentration of foaming agent solution, heating temperature of rotary drum and rotary drum technology on oil absorption or moisture absorption rate of granular ammonium nitrate were studied. The optimum conditions of ZK method were obtained as follows:foaming agent solution is4wt%ZK composite foaming agent solution, the amount of ZK composite foaming agent solution is3.0%of the mass of granular ammonium nitrate, the rotary drum was heated to85℃and rotation speed was increased to40r·min-1while removing moisture. Under these conditions, oil absorption, specific area, mean pore size and detonators sensitivity of the granular ammonium nitrate treated by ZK method have been further improved. At the same time, its performance of anti-hygroscopic was improved significantly. In addition, its temperature of transition of Ⅲ(?)Ⅳ was increased to54.57℃and its transition of Ⅱ(?)Ⅲ was eliminated basically.The performances of the modified ammonium nitrate were compared with one kind of porous granular ammonium nitrate with a high degree of market acceptance. The experiment results showed that the modified granular ammonium nitrate were superior to this porous granular ammonium nitrate in performances of oil absorption, specific area and charge critical diameter.In this thesis, a simple device and method of testing charge critical diameter of granular ammonium nitrate was established. The results showed that charge critical diameter of modified granular ammonium nitrate was31mm.Several kinds of additives were added into ammonium nitrate solution to study their effects on decomposition temperature of ammonium nitrate solution. The results indicated that1%NH4Cl, HNO3and stearylamine would decrease the decomposition temperature of ammonium nitrate solution. And within1%NH4Cl and HNO3mixtures, the decomposition temperature of ammonium nitrate solution was advanced to152℃. ZK composite foaming agent had no impact on the decomposition temperature of ammonium nitrate solution when its mass was not more than0.25%of ammonium nitrate solution.