电缆内部材料高温热解产生的可燃气体是促进燃烧的关键因素,但现有研究多针对典型的电缆材料热解,缺乏对实际较为复杂组分热解气体燃烧的系统探究。为此,基于反应力场(reactive force field,ReaxFF)分子动力学(molecular dynamics,MD)...电缆内部材料高温热解产生的可燃气体是促进燃烧的关键因素,但现有研究多针对典型的电缆材料热解,缺乏对实际较为复杂组分热解气体燃烧的系统探究。为此,基于反应力场(reactive force field,ReaxFF)分子动力学(molecular dynamics,MD)模拟方法,搭建电缆热解气体(含CO、CH_(4)、C_(2)H_(2)、H_(2)、O_(2))燃烧模型,在3000~3800 K温度范围内开展反应动力学研究,分析燃烧过程中的粒子分布规律,研究不同燃料分子的燃烧反应网络。结果表明:温度显著影响燃烧反应进程,高温加速CH_(4)、C_(2)H_(2)等可燃气体的分解及中间产物转化。CH_(4)主要通过脱氢和氧化反应生成CH_(3)·、CH_(3)OH_(2)·等中间产物,最终生成H_(2)O;C_(2)H_(2)反应路径与CH_(4)类似,但C≡C键断裂更为关键;H_(2)氧化生成OH·、H_(2)O等产物;CO在高温下通过HOCO·等中间态转化为CO_(2)。该研究从微观层面揭示了电缆火灾中可燃气体促燃的本质,为更精准的电缆火灾演化模型构建提供理论支撑,并基于热解气体燃烧时的特征产物浓度变化,给出优化火灾早期预警传感器阈值的量化参考。展开更多
It is important to understand the effects of demineralization on the reactivity of coal pyrolysis for demineralization coal in OCCSS systems.The molecular dynamics of the pyrolysis of ZD-R and ZD-D was investigated us...It is important to understand the effects of demineralization on the reactivity of coal pyrolysis for demineralization coal in OCCSS systems.The molecular dynamics of the pyrolysis of ZD-R and ZD-D was investigated using the ReaxFF MD method.It is indicated that the pyrolysis reactivity of ZD-D is enhanced.Acid demineralization treatment helps to enhance the cross-linking reaction of light tar C5-14 molecules in the main pyrolysis stage,generating light tar fragments with higher molecular mass.In the polycondensation pyrolysis stage,the acid demineralization treatment promotes the polycondensation reaction at high temperatures.The generation of H2 in ZD-R pyrolysis is primarily attributed to the N-H bond breaking in pyrrole at low temperatures.At high temperatures,it is predominantly associated with the hydrogen abstraction reaction between carboxyl functional groups and the dehydrogenation reaction of hydrogen bond breaking in the aliphatic hydrocarbon structures.H2O is primarily attributed to the reaction of the hydroxyl group on the carboxyl group.CO_(2) is always related to the carboxyl group.CO is mainly related to the reduction reaction of carbonyl group,carboxyl group,and CO_(2).During the initial pyrolysis stage of ZD-D after acid demineralization treatment,the hydrogen abstraction reaction of the carboxyl functional group and the generation of CO molecules by the methoxy group are enhanced.The generation of H2 by the aliphatic structure is enhanced in the main pyrolysis stage.The ring-opening reaction of the phenoxy group to generate CO in the polycondensation pyrolysis stage is also facilitated.展开更多
To accurately investigate the evolution characteristics and generation mechanism of retained oil,the study analyzed organic-rich lacustrine shale samples from the Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay...To accurately investigate the evolution characteristics and generation mechanism of retained oil,the study analyzed organic-rich lacustrine shale samples from the Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay Basin.This analysis involves Rock-Eval pyrolysis,pyrolysis simulation experiments,Gas Chromatograph Mass Spectrometer(GC-MS),and reactive molecular dynamics simulations(ReaxFF).The results revealed the retained oil primarily consisted of n-alkanes with carbon numbers ranging from C14 to C36.The generation of retained oil occurred through three stages.A slow growth stage of production rate was observed before reaching the peak of oil production in Stage Ⅰ.Stage Ⅱ involved a rapid increase in oil retention,with C12-C17 and C24-C32 serving as the primary components,increasing continuously during the pyrolysis process.The generation process involved the cleavage of weak bonds,including bridging bonds(hydroxyl,oxy,peroxy,imino,amino,and nitro),ether bonds,and acid amides in the first stage(Ro=0.50%-0.75%).The carbon chains in aromatic ring structures with heteroatomic functional groups breaks in the second stage(R_(o)=0.75%-1.20%).In the third stage(R_(o)=1.20%-2.50%),the ring structures underwent ring-opening reactions to synthesize iso-short-chain olefins and radicals,while further breakdown of aliphatic chains occurred.By coupling pyrolysis simu-lation experiments and molecular simulation technology,the evolution characteristics and bond breaking mechanism of retained oil in three stages were revealed,providing a reference for the for-mation and evolution mechanism of retained oil.展开更多
The experiment explored the Fe_(2)O_(3) reduction process with H_(2)/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850℃.The ReaxFF molecular dynamics(MD)simul...The experiment explored the Fe_(2)O_(3) reduction process with H_(2)/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850℃.The ReaxFF molecular dynamics(MD)simulation method was used to observe the reduction process and provide an atomic-level explanation.The accuracy of the parameters used in the simulation was verified by the density functional theory(DFT)calculation.The simulation shows that the initial reduction rate of H_(2) is much faster than that of CO(from 800 to 950℃).As the reduction proceeds,cementite,obtained after CO participates in the reduction at 850℃,will appear on the iron surface.Due to the active properties of C atoms in cementite,they are easy to further react with the O atoms in Fe_(2)O_(3).The generation of internal CO may destroy the dense structure of the surface layer,thereby affecting the overall reduction swelling of Fe_(2)O_(3).However,excess CO is detrimental to the reaction rate,mainly because of the poor thermodynamic conditions of CO in the temperature range and the molecular diffusion capacity is not as good as that of H_(2).Furthermore,the surface structures obtained after H_(2) and CO reduction have been compared,and it was found that the structure obtained by CO reduction has a larger surface area,thus promoting the sub sequent reaction of H_(2).展开更多
To obtain detailed information on the potential energy, the evolution of species, the initial reaction paths, and thermal decomposition products, we conducted simulations on pyrolysis process of CL20/BTF co-crystal us...To obtain detailed information on the potential energy, the evolution of species, the initial reaction paths, and thermal decomposition products, we conducted simulations on pyrolysis process of CL20/BTF co-crystal using the ReaxFF/lg reaction force field, with temperature set at 2000 K to 3000 K. With the analysis of evolution curves of potential energy based on exponential function, we obtain the overall characteristic time. Via a description of the total package reaction with classical Arrhenius law, we obtain the activation energy of CL20/BTF co-crystal： Ea=60.8 kcal/mol. Based on the initial path of CL20/BTF co-crystal thermal decomposition we studied, we conclude that N-NO2 bond of CL20 molecules breaks first, working as a dominant role in the initial stage of thermal decomposition under the condition of different temperatures, and that all CL20 molecules completely decompose before BTF molecular regardless of different temperatures. We also find that the main products of CL20/BTF co-crystal are NO2, NO, NO3, HNO, O2, N2, H2O, CO2, N2O, and HONO, etc., on which the temperature forms certain influence.展开更多
文摘电缆内部材料高温热解产生的可燃气体是促进燃烧的关键因素,但现有研究多针对典型的电缆材料热解,缺乏对实际较为复杂组分热解气体燃烧的系统探究。为此,基于反应力场(reactive force field,ReaxFF)分子动力学(molecular dynamics,MD)模拟方法,搭建电缆热解气体(含CO、CH_(4)、C_(2)H_(2)、H_(2)、O_(2))燃烧模型,在3000~3800 K温度范围内开展反应动力学研究,分析燃烧过程中的粒子分布规律,研究不同燃料分子的燃烧反应网络。结果表明:温度显著影响燃烧反应进程,高温加速CH_(4)、C_(2)H_(2)等可燃气体的分解及中间产物转化。CH_(4)主要通过脱氢和氧化反应生成CH_(3)·、CH_(3)OH_(2)·等中间产物,最终生成H_(2)O;C_(2)H_(2)反应路径与CH_(4)类似,但C≡C键断裂更为关键;H_(2)氧化生成OH·、H_(2)O等产物;CO在高温下通过HOCO·等中间态转化为CO_(2)。该研究从微观层面揭示了电缆火灾中可燃气体促燃的本质,为更精准的电缆火灾演化模型构建提供理论支撑,并基于热解气体燃烧时的特征产物浓度变化,给出优化火灾早期预警传感器阈值的量化参考。
文摘It is important to understand the effects of demineralization on the reactivity of coal pyrolysis for demineralization coal in OCCSS systems.The molecular dynamics of the pyrolysis of ZD-R and ZD-D was investigated using the ReaxFF MD method.It is indicated that the pyrolysis reactivity of ZD-D is enhanced.Acid demineralization treatment helps to enhance the cross-linking reaction of light tar C5-14 molecules in the main pyrolysis stage,generating light tar fragments with higher molecular mass.In the polycondensation pyrolysis stage,the acid demineralization treatment promotes the polycondensation reaction at high temperatures.The generation of H2 in ZD-R pyrolysis is primarily attributed to the N-H bond breaking in pyrrole at low temperatures.At high temperatures,it is predominantly associated with the hydrogen abstraction reaction between carboxyl functional groups and the dehydrogenation reaction of hydrogen bond breaking in the aliphatic hydrocarbon structures.H2O is primarily attributed to the reaction of the hydroxyl group on the carboxyl group.CO_(2) is always related to the carboxyl group.CO is mainly related to the reduction reaction of carbonyl group,carboxyl group,and CO_(2).During the initial pyrolysis stage of ZD-D after acid demineralization treatment,the hydrogen abstraction reaction of the carboxyl functional group and the generation of CO molecules by the methoxy group are enhanced.The generation of H2 by the aliphatic structure is enhanced in the main pyrolysis stage.The ring-opening reaction of the phenoxy group to generate CO in the polycondensation pyrolysis stage is also facilitated.
基金financially supported by the National Natural Science Foundation of China (Grant No. 42072150)
文摘To accurately investigate the evolution characteristics and generation mechanism of retained oil,the study analyzed organic-rich lacustrine shale samples from the Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay Basin.This analysis involves Rock-Eval pyrolysis,pyrolysis simulation experiments,Gas Chromatograph Mass Spectrometer(GC-MS),and reactive molecular dynamics simulations(ReaxFF).The results revealed the retained oil primarily consisted of n-alkanes with carbon numbers ranging from C14 to C36.The generation of retained oil occurred through three stages.A slow growth stage of production rate was observed before reaching the peak of oil production in Stage Ⅰ.Stage Ⅱ involved a rapid increase in oil retention,with C12-C17 and C24-C32 serving as the primary components,increasing continuously during the pyrolysis process.The generation process involved the cleavage of weak bonds,including bridging bonds(hydroxyl,oxy,peroxy,imino,amino,and nitro),ether bonds,and acid amides in the first stage(Ro=0.50%-0.75%).The carbon chains in aromatic ring structures with heteroatomic functional groups breaks in the second stage(R_(o)=0.75%-1.20%).In the third stage(R_(o)=1.20%-2.50%),the ring structures underwent ring-opening reactions to synthesize iso-short-chain olefins and radicals,while further breakdown of aliphatic chains occurred.By coupling pyrolysis simu-lation experiments and molecular simulation technology,the evolution characteristics and bond breaking mechanism of retained oil in three stages were revealed,providing a reference for the for-mation and evolution mechanism of retained oil.
基金financial support from the National Natural Science Foundation of China(Nos.52204335 and 52374319)the National Nature Science Foundation of China(No.52174291)the Central Universities Foundation of China(No.06500170)。
文摘The experiment explored the Fe_(2)O_(3) reduction process with H_(2)/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850℃.The ReaxFF molecular dynamics(MD)simulation method was used to observe the reduction process and provide an atomic-level explanation.The accuracy of the parameters used in the simulation was verified by the density functional theory(DFT)calculation.The simulation shows that the initial reduction rate of H_(2) is much faster than that of CO(from 800 to 950℃).As the reduction proceeds,cementite,obtained after CO participates in the reduction at 850℃,will appear on the iron surface.Due to the active properties of C atoms in cementite,they are easy to further react with the O atoms in Fe_(2)O_(3).The generation of internal CO may destroy the dense structure of the surface layer,thereby affecting the overall reduction swelling of Fe_(2)O_(3).However,excess CO is detrimental to the reaction rate,mainly because of the poor thermodynamic conditions of CO in the temperature range and the molecular diffusion capacity is not as good as that of H_(2).Furthermore,the surface structures obtained after H_(2) and CO reduction have been compared,and it was found that the structure obtained by CO reduction has a larger surface area,thus promoting the sub sequent reaction of H_(2).
文摘To obtain detailed information on the potential energy, the evolution of species, the initial reaction paths, and thermal decomposition products, we conducted simulations on pyrolysis process of CL20/BTF co-crystal using the ReaxFF/lg reaction force field, with temperature set at 2000 K to 3000 K. With the analysis of evolution curves of potential energy based on exponential function, we obtain the overall characteristic time. Via a description of the total package reaction with classical Arrhenius law, we obtain the activation energy of CL20/BTF co-crystal： Ea=60.8 kcal/mol. Based on the initial path of CL20/BTF co-crystal thermal decomposition we studied, we conclude that N-NO2 bond of CL20 molecules breaks first, working as a dominant role in the initial stage of thermal decomposition under the condition of different temperatures, and that all CL20 molecules completely decompose before BTF molecular regardless of different temperatures. We also find that the main products of CL20/BTF co-crystal are NO2, NO, NO3, HNO, O2, N2, H2O, CO2, N2O, and HONO, etc., on which the temperature forms certain influence.
