Comprehensive Research On Ammonium Nitrate Thermal Hazard

Ammonium nitrate is a sort of compound that we are very familiar with,which has a broad use.Not only is it the agricultural fertilizer of high quality,it is also the raw materials in chemical industry.In industrial production,not only solid ammonium nitrate is used,but ammonium nitrate aqueous solution at high temperature is used.Thus it is necessary to conduct safe research on ammonium nitrate in solid-liquid two states,especially research on the impurity influence on the thermal stability,and it has critical practical significance on the safe production and use of ammonium nitrate.In this paper,ammonium nitrate thermal hazard is the main line.Researches on the solid and liquid states ammonium nitrate are conducted.For the solid ammonium nitrate,firstly,the decomposition process of ammonium nitrate was analyzed by thermal analysis technology during the temperature raising period;secondly,thermal hazard of the packing state ammonium nitrate was discussed by dust layer ignition temperature device and solid combustion point tester;then the thermal hazard of the cloud state ammonium nitrate was studied by dust ignition temperature device;at the same time,the danger of oxidized ammonium nitrate was researched using solid oxidizing tester.As for ammonium nitrate solution,firstly,thermal analysis was conducted using C600 micro calorimetric instrument;secondly,the critical explosion temperature was tested and studied using small capacity thermal insulation tester.The specific research contents and conclusions are as follows:(1)Ammonium nitrate was endothermically decomposed in the open air,and the main products are H2 O,NH3,N2 O and NO.When ammonium nitrate is mixed with wood powder,it was exothermically decomposed,and the initial decomposition temperature was lower.When wood powder’s mass fraction increases,decomposition temperature moves to high temperature,and heat quantity increase.(2)When the ammonium nitrate in packing state was heated under high temperature surface heating,there was no ignition burning before melting point;when mixed with wood powder,after severe burn in around 220℃,with the increase of the content of wood powder,the ignition temperature was on the decline.(3)When the ammonium nitrate in packing state was under high temperature,there was no spontaneous combustion before melting.When mixed with wood powder,there was spontaneous combustion at about150℃ and the spontaneous temperature decreased with the increase of the wood powder mass fraction.(4)Ammonium nitrate dust cloud combusts in 410℃.When the wood powder was added,the ignition temperature moved down to about 330℃,and with the increase of wood powder content,ignition temperature lowered.(5)Ammonium nitrate oxidizing is classified as category 2.The tag symbol of solid ammonium nitrate is "flame in the ring",the signal word is "risk",and the risk illustration is “possible fuel combustion improver;antioxidant”.(6)Through C600 micro calorimetric instrument testing,solid ammonium nitrate had exothermic decomposition at 271.6℃ in a closed environment.When the water was added,the initial decomposition temperature is lower than that of pure ammonium nitrate when concentration of 80%.When the concentration was 90%,heat quantity was greater than the pure ammonium nitrate.When ammonium nitrate solution mixed with Cl-,the decomposition temperature was decreased obviously,and the temperature increased with the content of Cl-.(7)When the critical explosion temperature of ammonium nitrate solution with concentration of 70%,80%,90%,the critical explosion temperature was lowest with concentration of 80%.When Cl-was added,the critical explosion temperature was reduced,and it increased with the increase of Cl-content.