Gas Plasma Pyrolysis

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.