Experimental Study On Ignition Characteristics Of Tobacco Dust

Cigarette production in tobacco processing enterprises is the process of processing tobacco leaves into tobacco products through tobacco processing system.It includes tobacco leaf's primary processing,leaf beating,shredding,tobacco expansion,slice processing and rolling technology.In this process,the tobacco dust also exists in every link of the processing technology.This paper designs an improved testing instrument for the minimum ignition temperature of the dust layer and the test equipment table,and carries out the smoldering test on the tobacco dust layer under different conditions on the test bench,compares the differences of the test results,studies the smoldering combustion process of the tobacco dust layer on the metal hot surface,and analyzes the factors which influence the smoldering of the tobacco dust;By using a high-speed video camera to capture the tobacco dust flame's propagation in Hartmann tube pipe and analyzing different concentration,different flame propagation rules of jet pressure and different ignition energy conditions,to reveal the tobacco dust cloud combustion's characteristics,and put forward corresponding preventive measures.The results show that the peak of heat release rate of picadura dust,sliced tobacco dust and rolled tobacco powder are 90 kw/?,91 kw/? and 75 kw/? respectively,and the flame propagation rate of sliced tobacco dust is the fastest.The rolled tobacco powder with the lowest peak value was first released around 50 s,and the picadura dust and sliced tobacco dust were released around 75s?80 s respectively.The smoldering on the surface of different sizes of tobacco dust can be analyzed in periods.The temperature of exothermic oxidation phase mutation,so to control the smoldering,we must control its development trend before oxidation stage and make the corresponding effective early warning scheme,reduce the probability of occurrence of tobacco smoldering.Tobacco dust first smoldering in the top layer and then spreads down gradually until the dust completely burns out.Oxygen is the decisive factor affecting the production and development of tobacco dust smoldering.When the dust layer reaches the smoldering temperature,the temperature rise rate of the top layer is the highest,and the temperature rise rate of the top layer is relatively slow when there is no smoldering in the middle layer for the top layer smouldering has a preheating effect.The larger the particle size is,the longer the duration of smoldering will be and the duration of the test will also become longer.The smaller the particle size is,the shorter the duration of each stage of smoldering will be and the smoldering become more rapid and harder to control.Twokinds of high-energy electric fire electrodes failed to ignite the picadura dust and rolled tobacco powder which in the large particle size,which indicated that the large particle size of tobacco dust had low spark sensitivity and low risk of igniting the dust cloud.In tobacco dust cloud flame stage,the dust gradually develops into sparks,because of dust is not uniform in diameter during the slicing process,so the sparks in the end of combustion phase are the tobacco powder combustion residue fragments.Under the same conditions,the relatively high concentration of dust cloud is more likely to catch fire,and the flame propagation time is longer.For sliced tobacco dust,the longest flame propagation duration of sliced powder is 600 Ms when the mass is 1.0 g,the ignition energy of electric spark is 200 J and the press is 6.0bar.It is about three times of the flame propagation time when the ignition energy of the same mass and the same powder injection pressure is 100 J,which indicates that the ignition energy directly determines the combustion effect of the dust cloud.Corn starch is different from tobacco dust in essence,and the flame propagation time is about 900 ms under the condition of 1.0 g powder spray pressure of 4.0 bar EDM ignition energy 100 J.Far exceeds the burning time of cloud flame of tobacco dust under the same conditions.Through the experimental study of smoldering characteristics of tobacco dust layer and flame propagation characteristics of dust cloud combustion,an effective early warning scheme can be put forward for restraining tobacco dust smoldering in industrial production,and the probability of tobacco smoldering can be reduced to avoid the conversion of smoldering to open fire;The flame propagation characteristics of tobacco dust were further understood through the experimental study,and the evolution process and characteristics of tobacco dust cloud ignition were revealed,which provided the basis for the prevention and control of fire accidents in tobacco processing enterprises.