PFC recycling system by continuous gas chromatography

We propose a new system to reduce emissions of Perfluorocompounds (PFCs) from semiconductor industries by continuous gas chromatography technology. For example, the recycling technology that was suggested before, such as cryogenic distillation, has some problems in its repurification step. It needs a huge distillation tower and much power for refrigeration. The continuous gas chromatography technology is a compact alternative to the conventional technology. This system is composed of the series of separation columns, vacuum pumps, and sequentially controlled valves. The mixture of PFCs is separated by the difference of the affinity for the filling material in the column. Only pure PFCs separated perfectly are outputs and the others are injected to the next column. By recycling the mixture of PFCs, which was not separated by single column, the continuous gas chromatography outputs the pure PFCs continuously. Moreover, it can experimentally separate CF₄-NF₃, which cannot be separated by a cryogenic distillation. Based on the accumulation and consideration of experimental data, we realized the continuous efficient separation of CF₄/C₂F₆ with the large-scale pilot plant of the continuous gas chromatography. In this method, a high recovery rate of more than 99% was obtained and residual C₂F₆ in recovered CF₄ and residual CF₄ in recovered C₂F₆ were less than 0.01%. This recycling system is compact and it can operate with low-energy consumption.