Font Size: a A A

Study On The Effect Of Mold On The Fire Risk Of Storage Rice

Posted on:2020-08-09Degree:MasterType:Thesis
Country:ChinaCandidate:X JinFull Text:PDF
GTID:2393330572979024Subject:Safety science and engineering
Abstract/Summary:PDF Full Text Request
In recent years,China's grain reserves have reached about 600 billion kilograms with the gradually increased stock reserves.Rice is the most important staple food for the Asians,especially in China.The rice storage issue as national paln has vital bearing on the social stability and national safety.A large amounts of storage rice wihich is combustible increase the risk of fire and cause huge disasters and losses when the fire broke out.During the process of storage,the mold not only affected the quality of storage rice,but also released lots of heat and changed the characteristics of rice,causing a higer fire risk.Therefore,the study on the effects of mold on storage rice fire risk is of great importance.Firstly,the effets of moisture content and moldy degree on the smoldering of storage rice were validated.Then,the different combustion behavior of storage rice caused by mold also were discussed.Finally,the effects of mold on the characteristics of gas phase and solid phase products under low temperature heating were studied.The main research work is as follows:1.The effect of moisture content(three kinds of water content),moldy degree(two kinds of mildew degree)and ventilation on the vertical smoldering characteristics of storage rice was studied,using a bench-scale smoldering experimental apparaturs.Under natural ventilation conditions,the moisture content and the moldy degree has no significant effect on the smoldering temperature field.In the case of forced ventilation,ventilation can not only promote the smoldering because the oxygen enhances the oxidation reaction of residue carbon.Meanwhile,the air flow which takes away lots of heat has an inhibition on the smoldering.The samples with moisture content is 9.5%cannot propagate downward with the 5 L/min and 7.5 L/min air flow with a compact carborn layer.When the ventilation volume is 5 L/min,the average velocity of the smoldering front and the average velocity of the carborn oxidation front increase with the increase of moisture content and moldy degree.The conversion time from smoldering to combustion reduces a lot under this conditions.When the air flow rate is 7.5L/min,with the moisture content increases,this two kinds of velocities slightly reduce,but the conversion time from smoldering to combustion reduces.However,this two kind of speed increase with the moldy degree increased.Meanwhile,the smoldering of severly moldy samples quickly converted into combustion.The Raman and BET test results showe that the carbon residue of the severely moldy samples is looser and has a higher specific surface area.It can be seen that mold promotes the smoldering and cuts down the conversion time to falming combustion,thereby increasing the fire hazard of storing rice.2.The fatty acid value of rice increases sharply after storage of rice mold.The thermostability of rice samples with different moldy degrees has been studied by thermogravimetric analysis.The results showes that the initial pyrolysis temperature of rice samples significantly advances with the increase of mildew under nitrogen and air conditions.The effect of mold on the combustion behavior of storage rice was studied by a cone calorimeter test.The results find that the ignition time of storage rice decreases with the increase of external heating radiation.And as the degree of mildew increased,the ignition time of the sample decreased,and the moldy rice could be ingited at lower heat flux.Meanwhile,the fire performance index decreases,and the fire growth rate index increases,indicating that the fire hazard of stored rice increases with the degree of mildew.The results of steady-state tubular furnace combustion experiments show that under the condition of full combustion,the release of combustion heat and toxic fumes is mainly affected by the amount of intake air and the injection rate,and the effect of mold isnot of great significance.3.The contents of carbon,hydrogen,oxygen,nitrogen and sulfur do not change much when the rice is moldy.The results of differential scanning calorimeter showeds that the moldy sample had a higher endothermic enthalpy value in the low temperature region(40-100 ?).Besides,the gas chromatography-mass spectrometer was used to investigate gaseous substance released in the endothermic process.Gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy were used to study the low temperature(below 200 ?)oxidative decomposition characteristics of storage rice.With the increase of temperature,the kinds of gas phase pyrolysis products of storage rice samples increases from ten to forty,indicating the breakage of molecular chains such as rice starch,fat,protein and lignin.The intensity of mainly functional groups in solid phase have little change,indicating that the basic framework of matter did not change much.The strength of the hydroxyl functional group significantly reduces as the temperature increases.This is cuased by the precipitation of water and the oxidation of alcohols.The intensity of hydrocarbons unctional group slightly decreases,indicating that the carbon-hydrogen bond between the end chain and the side chain of molecule are subjected to thermal oxidative decomposition.The strength of the hydroxyl functional group of the mildew sample is significantly larger than that of the unmold sample at room temperature,slightly lager at 100 ?,and almost uniform at 150 ?,and finally less than the unmold sample at 200 ?.This not only indicates that the process of mold produces substance with hydroxyl groups,but also indicates that the mold accelerates the thermal oxidative decomposition of the stored rice.
Keywords/Search Tags:storage rice, mold, fire risk, thermal oxidationl pyrolysis characteristics, smoldering characteristics, combustion behavior
PDF Full Text Request
Related items