A STREAMLINED, PORTABLE MID-IR TDL BASED SYSTEM FOR ON-SITE MONITORING OF PFC'S FROM POTROOM EXHAUST DUCTS

摘要

Monitoring perfluorocarbons (PFCs) emitted from potroom exhaust ducts is an issue of outstanding concern to primary producers of aluminium worldwide. Mid-IR tunable diode laser spectroscopy has been used successfully to obtain detailed, time resolved, accurate data on emissions of both CF_4 and C_2F_6. Data of this quality is extremely valuable for providing information on the process itself, and for providing CF_4 and C_2F_6 emission factors consistent with the IPCC "tier 3b" method. This paper presents an alternate approach to determining the environmental impact of PFC emissions. This method involves acquiring "tier 3b" quality data for CF_4, then estimating the C_2F_6 emission factor based on the CF_4 results and default CF_4/C_2F_6 weight ratios published by the IPCC. The error factors introduced to the total impact on global climate, calculated from emission factors and the global warming potential (GWP) in CO_2 equivalents for each species, are less than +-10%. Unisearch has recently introduced a line of mid-IR instruments based on their earlier TAMS-150, used in previous studies of PFC emissions. The EMS-150 is more streamlined and more portable than the TAMS-150, and is also capable of monitoring both CF_4 and C_2F_6. The EMS base model is even smaller and much less expensive, and is capable of acquiring "tier 3b" quality data for CF_4. Using the above approach, this data can be used to obtain near-"tier 3b" quality emission factors at a much reduced cost.