粮食储备库中不同品种稻谷的火灾危险性研究

Study on the fire risk of different varieties of rice in granary

粮食是人类的生存之本,是各国经济发展的基础,是国家安全的重要保证。中国是粮食的生产和消费大国,也是粮食的储备大国。因此,保证粮食储备安全对于国家发展与安全具有重要的战略意义。储粮由碳、氢、氧、氮和硫等元素组成,易燃烧。并且,储粮燃烧过程中会产生大量热及有毒烟气,火灾危害巨大。针对我国安徽地区不同品种的稻谷样品,利用锥形量热仪和激光拉曼光谱仪研究不同样品燃烧行为差异。锥形量热仪由五个主要部分构成:分析天平、样品托盘、打火器、锥形加热器、氧分析仪。实验时用锡箔纸放置于样品容器底部与侧面,暴露出100mm×100mm的上表面,保持样品容器距锥形量热仪底部约25mm处。电火花装置置于样品上方约15mm处以点燃样品。分别在几种热辐射强度(25,35,45,55kW/m^(2))下测试样品的燃烧行为,得到样品的热释放速率、热释放速率峰值、总热释放量、总生烟量、点燃时间、火灾性能指数和火灾蔓延指数等热参数。激光拉曼光谱仪由514.5nm氩激光线提供反向散射激发。拉曼光谱中的强度比I_(D)/I_(G)用来表征样品的石墨化程度。研究结果表明,在热辐射强度相同的情况下,糯稻的燃烧危险性最小,烟气危险性最大,而粳稻与籼稻的燃烧危险性及烟气危险性差别不大。在25kW/m^(2)的热辐射强度下,糯稻的火灾性能指数最大,为2.1s·m^(2)/kW,分别比粳稻与籼稻高185.1%与106.9%。同时,糯稻的火灾蔓延指数最小,为0.31kW/(m^(2)·s),分别比粳稻与籼稻低64.0%和55.7%。并且,糯稻的总生烟量最大,分别高出粳稻与籼稻23.9%与15.1%。随着热辐射强度增加(25~55kW/m^(2)),不同样品引燃时间差值缩小,同时,稻谷样品的热释放速率峰值也从最初的100kW/m^(2)持续增加至约180kW/m^(2)。糯稻的I_(D)/I_(G)值为3.1,远高于籼稻和粳稻,表明糯稻燃烧后残炭的石墨化程度较低。糯稻被点燃前热辐射能积聚更多,点燃后积聚的热能被释放,反向促进其充分燃烧。研究结果揭示了不同品种稻谷燃烧及烟气危险性,并为粮食储备库火灾风险防控提供理论及数据参考。值得注意的是,不同种类粮食(如玉米、小麦和大豆等)由于物理结构及化学成分的差异,可能存在不同的燃烧机制及演化规律。并且,由于不同地区的气候、环境等存在差异,不同地区粮食的成分及燃烧行为可能也不同。建议不同地区和品种粮食储备库建立恰当的储粮火灾安全评价标准,为构建全国范围内的储粮火灾安全评价体系提供参考。

Food is the foundation of human survival,the basis of economic development of all countries,and an important guarantee for national security.China is a big country in food production,consumption,and reserve.Therefore,ensuring the safety of grain reserves is of great strategic significance for the development and security of China.Stored grain consisting of carbon,hydrogen,oxygen,nitrogen,and sulfur is easy to burn,and the burning process of stored grain produces a lot of heat and toxic smoke,capable of causing huge fire disaster.A cone calorimeter was used to study the combustion behavior of rice samples of different varieties in Anhui province,China.The cone calorimeter is mainly composed of five parts:analysis balance,sample tray,ignitor,conical heater,and oxygen analyzer.A tinfoil paper was placed at the bottom and side of a sample container to expose the upper surface of 100 mm×100 mm,and the sample container was kept 25 mm away from the bottom of the cone calorimeter.The combustion behavior of the samples was tested at different heat radiation intensities(25,35,45 and 55 kW/m^(2))to obtain the heat release rate,peak heat release rate,total heat release rate,total smoke production,time to ignition,fire performance index,and fire growth index.The laser Raman spectrometer was excited by the backscattering of 514.5 nm argon laser line,and the intensity ratio I_(D)/I_(G) in Raman spectroscopy was used to characterize the graphitization degree of the sample.The results showed that under the same thermal radiation intensity,the glutinous rice with the lowest flamer had highest smoke risk,whereas there was no significant difference between the japonica rice and indica rice at both risks.Under 25 kW/m^(2) of thermal radiation,the fire performance index value of glutinous rice was 2.1 s·m^(2)/kW,which was 185.1%and 106.9%higher than that of japonica rice and indica rice,respectively.Meanwhile,the fire spread index value of the glutinous rice was the lowest(0.31 kW/(m^(2)·s)),which was 64.0%and 55.7%lower than that of japonica rice and indica rice,respectively.Additionally,the total smoke production of glutinous rice was 23.9%and 15.1%higher than that of japonica rice and indica rice,respectively.With the increase in thermal radiation intensity(from 25 to 55 kW/m^(2)),the time of ignition difference between samples decreased,and the peak heat release rate of rice samples increased from 100 to 180 kW/m^(2).The I_(D)/I_(G) value of glutinous rice was 3.1,which was much higher than that of indica and japonica,indicating that the graphitization degree of char residue for glutinous was low after combustion.The thermal radiation energy of glutinous rice accumulated a lot before ignition,and the accumulated heat energy was released after ignition,which promoted its full combustion in return.Those results reveal the flame and smoke hazards of rice with different varieties,and provide theory and data reference for fire risk prevention and control of grain storage depots.It is worth noting that the differences in physical structure and chemical composition for different kinds of grains(such as corn,wheat,and soybean,etc.)may also have different combustion mechanisms and evolution rules.Additionally,due to the differences in climate and environment of different regions,the composition and burning behavior of grain may also be different.We suggest that appropriate fire safety evaluation standards should be established for grain storage in different regions and varieties,which can provide an important reference for constructing a fire safety evaluation system for grain storage in China.