Results of a comparative pilot field test study of a first generation Quantitative Optical Gas Imaging (QOGI) system
Report no. 23/20: Quantitative optical gas imaging (QOGI) is a new system to detect fugitive emission sources and quantify their mass release rates. This report presents an evaluation of QOGI technology compared to other techniques (Sniffing/EPA Method 21 and high flow sampling (HFS)), during a field study in a European petro-chemical manufacturing site.
A sample of 33 leaks from those detected during a Leak Detection and Repair (LDAR) campaign were surveyed during the field study. The QOGI system was able to quantify 18 in the field. A further 10 leaks were quantified following the field test after processing of the leak images by the system manufacturer. Unstable imaging of the background was the main reason for not being able to quantify emissions from the other 5 leaks. For the portion of the leaks that could not be quantified, there is no procedure envisaged which can overcome this limitation with the generation of QOGI system tested at the time of this field study (2016).
When comparing the quantification between HFS and QOGI, the most accurate QOGI results were obtained with leak rates > 60 g/h. QOGI was shown to be as accurate as using Sniffing/Method 21 to estimate total VOC fugitive emissions. The results from the evaluation of the QOGI technology, showed that QOGI is a promising technology for detecting fugitive emission sources and quantifying the mass release rate for each individual leak. Sniffing/Method 21 also provide emissions quantification but only at the level of the facility, using statistical-derived factors. This field trial has identified issues with the use of the first generation of QOGI system in a refinery process plant environment which should be further assessed before any recommendation for using it in such an environment can be made. A second generation has been developed and the vendors state that some of the issues have been overcome. However, further field testing is required to evaluate these developments.