Test And Research On Minimum Ignition Temperature And Minimum Ignition Energy Of KNO₃/S/C Mixed Dust

As one of the four greatest inventions of China,black powder is widely applied on weapons ignition system and civilian blasting,which is composed of KNO₃/S/C mixture.Due to the specificity,it is of high possibility to combust and explode as soon as being excited by external energy.In this paper,the mixture dust of KNO₃/S/C is viewed as the research object,the minimum ignition temperature of mixed dust cloud,the minimum ignition energy and the minimum ignition temperature of dust layer tested and studied via Godbert-Greenwald test device,1.2-L Hartmann tester and dust layer constant temperature heating device.In addition,the influence of blow pressure,different proportion,concentration of dust cloud,granularity of niter on the minimum ignition temperature of mixed dust cloud and the influence of different proportion,concentration of dust cloud,granularity of niter on the minimum ignition energy of mixed dust was studied.It can be concluded that:?1?When the granularities of KNO₃/S/C are d50=45/75/58?m,respectively,concentration is 1.136g/L,the mixed dust with mass ratio ??KNO₃?:??S?:??C?=75:10:15,the minimum ignition temperature of mixed dust cloud showed a tendency of decrease firstly and increase later with the increase of blow pressure,and the optimum blow pressure value is 0.3bar.When the content of charcoal is constant,with the increase of sulphur dust concentration and the reduction of potassium nitrate,the minimum ignition temperature showed a decreasing trend.When the mass ratio was ??KNO₃?:??S?:??C?=75:10:15,65:20:15,55:30:15,45:40:15,35:50:15,the corresponding minimum ignition temperature was 309,300,290,285,282°C,respectively.The minimum ignition temperature of mixed dust cloud showed a tendency of decrease firstly and increase later with the increase of concentration,for which there was sensitive concentration.It was found that the mixed dust sensitive concentration with three different portion ??KNO₃?:??S?:??C?=75:10:15,65:20:15,35:50:15 are all 1.136g/L,and the corresponding minimum ignition temperature was 309,300,282°C,respectively.The minimum ignition temperature of mixed dust cloud showed a tendency of gradual increasewith the increase of potassium nitrate granular.It can be concluded that when the potassium nitrate granular was d50=45,53,90?m,with the mass ratios of ??KNO₃?:??S?:??C?=75:10:15,65:20:15,35:50:15,the corresponding minimum ignition temperature was 309,315,320°C;300,308,315°C;282,290,300°C,respectively.?2?When the ignition energy was 2240 mJ,the two kind of mixed dust with mass ratios??KNO₃?:??S?:??C?=75:10:15,65:20:15 were all not burning and exploded.When the mass ratios are ??KNO₃?:??S?:??C?=55:30:15,45:40:15,35:50:15,the minimum ignition energy of burning and explosion were 2240,1141,410 m J.Within certain range of ignition energy,the two kind of mixed dust concentration with mass ratios ??KNO₃?:??S?:??C?=75:10:15,65:20:15 have low sensitivity to the electrostatic spark.When the concentration range from0.417 to 2.917g/L,it would not burn and explode with the minimum ignition energy 2240 mJ.Concentration portion of dust cloud has obvious influence on the mixed dust with mass ratio??KNO₃?:??S?:??C?=35:50:15.And with the increase of concentration,the minimum ignition energy decreased first and increased later.When potassium nitrate granular were d50=45,53,90?m,and the ignition energy was 2240 mJ,concentration was 0.833g/L,mass ratio was??KNO₃?:??S?:??C?=75:10:15,65: 20:15,there was no burning and explosion.The potassium nitrate granular has obvious influence on the mixed dust cloud burning explosion with mass ratio ??KNO₃?:??S?: ??C?=35:50:15.Under the three kinds of potassium nitrate granular,the corresponding minimum ignition energy were 410,272,220 mJ,respectively.And the minimum concentration under the portion was between 0.083 and 0.167g/L.?3?With the increase of heating plate,the internal mixed dust minimum ignition temperature with bulking thickness,mass ratio ??KNO₃?:??S?:??C?=75:10:15 showed a tendency of gradual increase.It was measured that the minimum ignition temperature of the mixed dust layer under the specific mass ratio was 280°C.