Optical methods for remote measurement of diffuse VOCs: their role in the quantification of annual refinery emissions

Report no. 6/08: This report provides a review of the techniques which are currently commercially available for remotely monitoring VOCs from both point and area diffuse emission sources. The use of recently developed optical gas imaging (OGI) equipment is a relatively simple and cost-effective method to identify fugitive point emission sources. An OGI camera can scan all potential sources on a process plant, which is not possible using conventional hydrocarbon leak detection instruments.

Emission factors have been developed to permit quantification of annual emissions using OGI techniques. For refinery area diffuse emission sources, the use of emission factor methodologies is concluded to be very effective in combination with a procedure to detect any ‘significant emitters’. Complex remote sensing techniques can only provide short-term emission measurements. Extrapolation of these can lead to very large errors in the projected annual inventory values due to the temporal variability of refinery emissions.

The OGI technique permits the cost-effective identification of any tank equipment components causing significant emissions. The complex techniques at best allow the identification of tanks with significant emissions but do not have the capability of pinpointing the equipment components in need of maintenance.