天然气等离子体裂解的研究

【作者】 苏斌；

【导师】 高爱华；

【作者基本信息】 西北大学 ， 凝聚态物理， 2007， 硕士

【摘要】 本论文研究了在直流和交流辉光放电条件下等离子体裂解甲烷的规律和自由基——氢（H·）、甲基（CH₃·）、亚甲基（CH₂·）、次甲基（CH·）的形成规律。实验采用红外光谱分析技术检测甲烷的裂解过程，甲烷气体在3.3μm附近有一条较强的吸收带v₃，选择v₃作为探测对象对甲烷气体的裂解程度进行在线测量。研制了用于激光吸收光谱测量的光源——3391nm He-Ne红外激光器；设计了测量甲烷裂解规律的激光吸收光谱系统；为探测器设计了检波电路，抑制噪声，提高测量稳定性。分别采用直流和交流辉光放电等离子体来进行甲烷裂解变化规律的实验研究。在实验条件下，研究发现：在50Pa到300Pa之间，激光透过率与甲烷气体的压强成对数关系，拟合实验数据得到激光透过率曲线：η=226.6exp（-0.0179P）；在天然气气压低于100Pa的情况下，裂解过程最快能在0.5s内完成；实验获得的直流和交流放电甲烷最大裂解率分别为96％和98％。甲烷裂解随放电电流和气压变化的基本规律是：在相同气压情况下，放电电流越大，甲烷完全裂解所需要的时间越短；在相同电流情况下，放电气压越高，甲烷完全裂解所需要的时间就越长。实验分别测量了直流和交流放电过程中H·（656.3nm）、CH₃·（724.6nm）、CH₂·（341.9）及CH·（431.42nm）自由基发射光谱强度的变化，并对其发射光谱强度随时间的变化规律进行了描绘和分析。由于不同自由基达到极值和动态平衡的时间不尽相同，因此可以通过选择合适的放电条件来控制反应的方向，从而实现目的产物的选择性和产率的最大。更多还原

【Abstract】 The laws of methane decomposition and formation of free radicals such as hydrogen （H）, methyl （CH₃）, methane （CH₂） and methyne （CH） were studied under the DC and AC glow discharge plasma condition.The process of methane decomposition was detected by infrared spectral analysis technology in the experiment. Because methane has sensitive absorbable v₃ spectral band near 3.3μm,the v₃ spectral band is selected as the working spectral lines to detect the extent of methanedecomposition. The 3391nm He-Ne Infrared laser was developed as the light source of laser absorbable spectra. The filter circuit was designed for suppressing detection noise and enhancing measure stability.The experiment of methane decomposition was conducted under DC and AC glow discharge plasma condition respectively. The experiment results show: between 50Pa and 300Pa, the laser’stransmission rate and pressure of natural gas accords with the logarithm relation. The laser’s transmission rate curve whereη= 226.6 exp（-0.0179P） was obtained through fit experimentdata. The shortest time that decomposing process of natural gas was accomplished is 0.5 second below 100Pa condition. The highest decomposition rate of methane could be reached 96% and 98% respectively in DC and AC glow discharge. The basic rule of methane decomposes along with the change of discharge current and discharge pressure is: on the same discharge pressure condition, time of completely decomposing methane decrease when discharge current increase; on the same discharge current condition, time of completely decomposing methane increase when discharge pressure increase.The H·（656.3nm）, CH₃·（724.6nm）, CH₂·（341.9） and CH·（431.42nm） free radicals’ change of PL intensity were detected in DC and AC discharge process respectively, and their change rule were described and analyzed. Because the time of different free radical achieved the intensity extreme value and the dynamical equilibrium is different, therefore through the appropriate discharge condition is choice to control response direction so as to realize the goal product selectivity and production rate are biggest.更多还原