John T. Pisano

A passive flux denuder for evaluating emissions of ammonia at a dairy farm.

Abstract Passive samplers have been shown to be an inexpensive alternative to direct sampling. Diffusion denuders have been developed to measure the concentration of species such as ammonia (NH3), which is in equilibrium with particulate ammonium nitrate. Conventional denuder sampling that inherently requires air pumps and, therefore, electrical power. To estimate emissions of NH3 from a fugitive source would require an array of active samplers and meteorological measurements to estimate the flux. A recently developed fabric denuder was configured in an open tube to passively sample NH3 flux. Passive and active samplers were collocated at a dairy farm at the California State University, Fresno, Agricultural Research Facility. During this comparison study, NH3 flux measurements were made at the dairy farm lagoon before and after the lagoon underwent acidification. Comparisons were made of the flux measurements obtained directly from the passive flux denuder and those calculated from an active filter pack sampler and wind velocity. The results show significant correlation between the two methods, although a correction factor needed to be applied to directly compare the two techniques. This passive sampling approach significantly reduces the cost and complexity of sampling and has the potential to economically develop a larger inventory base for ambient NH3 emissions.

A UV differential optical absorption spectrometer for the measurement of sulfur dioxide emissions from vehicles

A differential optical absorption spectrometer for measurements of low-level sulfur dioxide (SO2) emissions from vehicles in real time was developed and employed. With a time resolution of 3 s and an optical path length of 19.6 m, a minimum detection limit of 75 ppbv SO2 (three times the standard deviation) was achieved. The wavelength region covered, UVB, was chosen to include the major SO2 absorption feature at 300 nm, while avoiding wavelength regions in which other components of vehicle exhaust are known to absorb. However, formaldehyde was found to be present in vehicle exhaust in high enough concentrations to be a major interferent. The analysis software was modified to account for the formaldehyde interferent using a two-dimensional fitting routine. The application of the instrument to real vehicle exhaust demonstrated that it was capable of measuring the contribution to SO2 emissions from lubricant oil sulfur over the range of current and future oil sulfur levels.

Application of near infrared TDLAS systems to HF measurements in aluminum smelters

The LASIR system of instruments provide a way of measuring specific pollutants with no interferences form other gases. Since they are based on laser diodes operating in the communication region of the near infrared, they are rugged, easy to operate and relatively small and inexpensive. The instrument can be located in any desired location where it is free of environmental constraints and is readily available for servicing if required. The monitoring beam is transmitted to the measuring location by fiber optics. In some configurations the delivery optics contain no electrical components and can be placed in explosive or hazardous locations. These measurements locations can be up to several kilometers distant from the control. Three versions of the LASIR are available, (1) the LASIR-R for perimeter or area ambient air monitoring, (2) the LASIR-P for point source measurements, and (3) the LASIR-S for in stack monitoring. Multiplexing can be used to operate, simultaneously, a combination of a number of these versions for mt he same instrument at a number of locations, and if desired, with a variety of different lasers. Examples of the application of these system for measuring HF in aluminum smelters have shown that there is ample sensitivity to measure HF both in the stacks and in the pot-rooms of these smelters.

Laboratory testing of a continuous emissions monitor for hydrochloric acid

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.

The LasIR: a tunable diode laser system for environmental and industrial applications

Tunable Diode Laser Absorption Spectroscopy, operating in the near IR, is the best method available for making continuous measurements of many gases. The measurements are interference free and can be made with high sensitivity in fractions of a second. Sensitivities in the parts per billion range can be achieved for a number of gases such as CO, CO2, HF, HCl, CH4, C2H4, C2H2, O2, NH3, HCN, H2S.

Laboratory investigation of three distinct emissions monitors for hydrochloric acid.

ABSTRACT The measurement of hydrochloric acid (HCl) on a continuous basis in coal-fired plants is expected to become more important if HCl standards become implemented as part of the Federal Mercury and Air Toxics Standards (MATS) standards that are under consideration. For this study, the operational performance of three methods/instruments, including tunable diode laser absorption spectroscopy (TDLAS), cavity ring down spectroscopy (CRDS), and Fourier transform infrared (FTIR) spectroscopy, were evaluated over a range of real-world operating environments. Evaluations were done over an HCl concentration range of 0–25 ppmv and temperatures of 25, 100, and 185 °C. The average differences with respect to temperature were 3.0% for the TDL for values over 2.0 ppmv and 6.9% of all concentrations, 3.3% for the CRDS, and 4.5% for the FTIR. Interference tests for H2O, SO2, and CO, CO2, and NO for a range of concentrations typical of flue gases from coal-fired power plants did not show any strong interferences. The possible exception was an interference from H2O with the FTIR. The instrument average precision over the entire range was 4.4% for the TDL with better precision seen for concentrations levels of 2.0 ppmv and above, 2.5% for the CRDS, and 3.5% for the FTIR. The minimum detection limits were all on the order of 0.25 ppmv, or less, utilizing the TDL values with a 5-m path. Zero drift was found to be 1.48% for the TDL, 0.88% for the CRDS, and 1.28% for the FTIR. Implications: This study provides an evaluation of the operational performance of three methods/instruments, including TDL absorption spectroscopy (TDLAS), cavity ring down spectroscopy (CRDS), and FTIR spectroscopy, 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 temperature and no strong interferences for flue gases typical to coal-fired power plants. The results show that these instruments would be viable for the measurement of HCl in coal-fired plants if HCl standards become implemented as part of the Federal Mercury and Air Toxics Standards (MATS) standards that are under consideration.

Optimization of SNCR NOx Control on a Wood-Fired Boiler

Selective noncatalytic reduction (SNCR) is a postcombustion technique for reducing NOx emissions from power generation facilities. The optimization of the SNCR system involves maximizing NOx reduction while minimizing NH3 slip. This requires optimization of both the SNCR system as well as the combustion, as their performances are interrelated. This work discusses the results of an optimization study of SNCR systems on a wood-fired boiler. This included measurements of NH3, which was measured with a tunable diode laser, as well as temperature, O2, CO, and NOx. The results clearly showed the interrelationship between the SNCR process and combustion. Marked improvement in SNCR performance was possible on this boiler due in part to the availability of instrumentation that allowed the operators to optimize combustion and maintain these conditions once they were defined.

LasIRTM‐R ‐ the New Generation RoHS‐Compliant Gas Analyzers Based on Tunable Diode Lasers

The laser-based optical gas sensor using Tunable Diode Laser Absorption Spectroscopy (TDLAS) is rapidly gaining favor wherever high sensitivity, real-time measurement and freedom from interferences are required [1, 2], specifically for the measurement of HF in primary aluminum smelters and other process gases at various metal smelters. It eliminates the problems associated with extractive gas sampling techniques. A first generation of equipment designed by Unisearch Associates and based on the near-IR TDLAS appeared on the market in the mid-90s. It has since been improved significantly by employing fast scan measurement techniques. Now, the system is more compact, robust, easier to operate and calibrate, and it can be simply audited. The utilization of fast scan measurement techniques with the state-of-the-art high speed electronics and sophisticated software optimization algorithms not only provides enhanced stability and sensitivity but expands the dynamic range of the measurements to five orders of magnitude. This new generation RoHS-compliant instrument (Restriction of Hazardous Substances) is also very inexpensive compared to other gas analysis instruments. The technology has found applications in many industries that require fast, accurate measurement of trace emissions for both process control and environmental regulatory requirements. These include, but not limited to, HF emissions in aluminum smelters, NH3 slip measurements for DeNOx scrubbers in the Power Industry, HCl and HF emissions monitoring in the Cement Industry and in Incinerators and for process control in Steel Smelting. This paper describes the new generation TDLAS-based gas analyzer and, as an example, its use in primary aluminum smelters.

Impact of Engine Lubricant Properties on Regulated Gaseous Emissions of 2000-2001 Model-Year Gasoline Vehicles

Abstract The impact of the sulfur (S) content in lubricating oil was evaluated for four ultra-low-emission vehicles and two super-ultra-low-emission vehicles, all with low mileage. The S content in the lube oils ranged from 0.01 to 0.76%, while the S content of the gasoline was fixed at 0.2 ppmw. Vehicles were configured with aged catalysts and tested over the Federal Test Procedure, at idle and at 50-mph cruise conditions. In all testing modes, variations in the S level of the lubricant did not significantly affect the regulated gas-phase tailpipe emissions. In addition to the regulated gas-phase emissions, a key element of the research was measuring the engine-out sulfur dioxide (SO2) in near-real-time. This research used a new methodology based on a differential optical absorption spectrometer (DOAS) to measure SO2 from the lubricants used in this study. With the DOAS, the contribution of SO2 emissions for the highest-S lubricant was found to range from less than 1 to 6 ppm on a gasoline S equivalent basis over the range of vehicles and test cycles used. The development and operation of the DOAS is discussed in this paper.