Development of Real-Time Flare Combustion Efficiency Monitor

There are approximately 7,000 flares in operation at industrial facilities across the U.S. Flares are one of the largest Volatile Organic Compounds (VOC) and air toxics emissions sources. Based on a special emission inventory required by the Texas Commission on Environmental Quality in 2007, highly reactive VOC emissions from 28 flares located in 11 facilities in Harris County, Texas, where 1,469.5 tons in a year, which accounted for 60% of the emissions from the 11 facilities. Unlike stack emissions, there are no practical methods available to measure emission rate or control efficiency of flares. For air emission inventories, flares are assumed to have and efficiency of 98% when their operations meet the conditions codified in federal regulation (40 CFR§60.18). Many studies have shown that this 98% efficiency assumption may not be valid even when flares meet the regulatory requirements. This has been a critical issue facing regulatory agencies and industry because VOC and air toxics emission s from flares can make up more than 50% of emissions,assuming the 98% efficiency. If the actual flare efficiency varies, the emission inventory will be drastically different, causing large errors in air quality planning, compliance, health impact assessments, and associated decision making. §The proposed method uses a 4-band infrared (IR) imagerto determine relative concentrations of CO2, CO and hydrocarbons (HC) in the flare plume, and calculate flare efficiency in real-time. It would not only solve the problem of not being able to measure flare efficiency, but is will provide facility operators with real-time performance information needed to improve flare operations and minimize flare emissions. §The proposed Phase I work includes (1) using a laboratory hyper-spectral imager with video frame rate capabilities to image actual flares and select the best spectral windows for the proposed 4 band camera, and (2) performing a benchscale test using the same hyper-spectral imager as a surrogate to the 4-band camera and conventional analyzers for CO2, CO and hydrocarbons (HC) to validate the proposed method. The results of Phase I will prove the concept and determine design parameters for the proposal flare efficiency monitorto be constructed during Phase II. §Anticipated results of the proposed project will fill the void in flare efficiency monitoring for the estimated 7,000 flares in the United States. Potential environmental benefits include a reduction in VOC and air toxics emissions by tens of thousands of tons annually.