Laboratory testing of a continuous emissions monitor for hydrochloric acid

Abstract

Continuous monitoring of exhaust flue gas has become a common practice in power plants in response to Federal Mercury and Air Toxics Standards (MATS) standards. Under the current rules, hydrochloric acid (HCl) is not continuously measured at most plants; however, MATS standards have been proposed for HCl, and tunable diode laser (TDL) absorption spectroscopy is one method that can be used to measure HCl continuously. The focus of this work is on the evaluation and verification of the operation performance of an HCL TDL over a range of real-world operating environments. The testing was conducted at the University of California at Riverside (UCR) spectroscopy evaluation laboratory. Laboratory tests were conducted at three separate temperatures, 25ºC, 100ºC, and 200ºC, and two distinct moisture levels for the enhanced temperatures, 0%, (2 tests) and 4%, over a concentration range from 0 ppmv to 25 ppmv-m at each of the elevated temperatures. The results showed good instrument accuracy as a function of changing temperature and moisture. Data analysis showed that the average percentage difference between the ammonia concentration and the calibration source was 3.33% for varying moisture from 0% to 4% and 2.69% for varying temperature from 25 to 100/200ºC. An HCl absorption line of 1.742 μm was selected for by the manufacturer for this instrument. The Hi Tran database indicated that CO₂ is probably the only major interferent, although the CO₂ absorption is very weak at that wavelength. Interference tests for NO, CO, SO₂, NH₃, and CO₂ for a range of concentrations typical of flue gasses in coal-fired power plants did not show any interference with TDL HCl measurements at 1.742 μm. For these interference tests, CO₂ was tested at a concentration of 11.9% concentration in N₂ for these tests. Average precision over the entire range for all 10 tests is 3.12%.

Implications: The focus of this study was an evaluation of the operation performance of a tunable diode laser (TDL) for the measurement of hydrochloric acid (HCl) over a range of real-world operating environments. The results showed good instrument accuracy as a function of changing temperature from 25ºC to 200ºC and moisture from 0% to 4%. Such as an instrument could be used for continuous monitoring of exhaust flue gas in power plants once the Federal Mercury and Air Toxics Standards (MATS) standards have been fully implemented.

Additional information

Notes on contributors

Chuck Dene

Chuck Dene is a senior program manager at the Electric Power Research Institute, Palo Alto, CA.

John T. Pisano

John T. Pisano and Kurt Bumiller are senior development engineers, and Thomas D. Durbin is a research engineer at the Bourns College of Engineering–Center for Environmental Research and Technology at the University of California at Riverside, CA.

Thomas D. Durbin

John T. Pisano and Kurt Bumiller are senior development engineers, and Thomas D. Durbin is a research engineer at the Bourns College of Engineering–Center for Environmental Research and Technology at the University of California at Riverside, CA.

Kurt Bumiller

John T. Pisano and Kurt Bumiller are senior development engineers, and Thomas D. Durbin is a research engineer at the Bourns College of Engineering–Center for Environmental Research and Technology at the University of California at Riverside, CA.

Keith Crabbe

Keith Crabbe is a vice-president of CEMTEK Environmental, Santa Ana, CA.

Lawrence J. Muzio

Lawrence J. Muzio is a vice-president at the Fossil Energy Research Corp., Laguna Hills, CA.