Current Technology for Continuous Monitoring of Particulate Emissions

Particulate matter is characterized by its physical and chemical properties. Federal and state emission standards identify two important physical properties, opacity (visible emissions) and particulate mass concentration. In addition, particle size and particle composition are characteristics that play a significant role in the assessment of health effects, visibility, and control strategy. Systems to monitor these particle characteristics are in various stages of development. Opacity monitors have the longest history of commercial availability and of applicability to various source emissions. Particulate mass monitors have a short history as commercially available systems and are under evaluation in various source applications. Particle size monitors are mainly in the advanced prototype development stage undergoing evaluation. Particle composition monitors are in the early stages of development as research prototypes. Real time size monitoring systems will eventually be wedded to real time particle composition analyzers to give a monitoring system for particle size distributions of chemical constituents.     

Current Technology for Continuous Monitoring of Gaseous Emissions

The purpose of this paper is to present a discussion of the latest developments in continuous gaseous emissions measurement. Subject areas include extractive and in-situ measurement. An exhaustive discussion of all instrumental methods currently available for use is neither appropriate nor productive in that several reviews have already been published in this area. Current needs for the development of new instrumentation in support of pending EPA regulations will be noted.     

Development of Instrumentation for Continuous On-line Monitoring of Non-Methane Organic Carbon in Air Emissions

ABSTRACT

Non-methane organic carbon (NMOC) is a measure of total organic carbon in an air emission, excluding that from methane. Thus, it measures the total amount of carbon, irrespective of the structure and functional groups in the molecule. The U.S. Environmental Protection Agency (EPA) Method 25 is used for quantification of NMOC in emission sources and in ambient air. This method involves laboratory analysis of collected air samples and cannot be used for real-time measurements. It is prone to interferences from CO₂, CH₄, and CO, as well as moisture. In this paper, a novel method for continuous, on-line monitoring of NMOC in air emissions and ambient air is presented. Detection limits are at ppb levels, and interference of permanent gases have been eliminated.     

Continuous Measurement of Diesel Particulate Emissions

Evaluation of emerging diesel particulate emissions control technology will require analytical procedures capable of continuous or “real-time” measurement of transient organic and elemental carbon emissions. Procedures based on the flame ionlzation properties of organic carbon and the opacity or light extinction properties of elemental carbon are described, and applied for measurement of particulate emissions from diesel engines. The Instrumentation provided adequate sensitivity and time resolution for observation of the transient emissions associated with typical automobile urban driving conditions. Analytical accuracy is evaluated by comparing Integrated average results to measurements using classical gravimetric filtration and solvent extraction procedures. Mass specifc extinction coefficients are evaluated using the Beer-Lambert law. A simplified linear model relating elemental carbon concentration to opacity is also evaluated.     

Using Continuous PM2.5 Monitoring Data to Report an Air Quality Index

Abstract

As stated in 40 CFR 58, Appendix G (2000), statistical linear regression models can be applied to relate PM_2.5 continuous monitoring (CM) measurements with federal reference method (FRM) measurements, collocated or otherwise, for the purpose of reporting the air quality index (AQI). The CM measurements can then be transformed via the model to remove any bias relative to FRM measurements. The resulting FRM-like modeled measurements may be used to provide more timely reporting of a metropolitan statistical area’s (MSA’s) AQI.¹ Of considerable importance is the quality of the model used to relate the CM and FRM measurements. The use of a poor model could result in misleading AQI reporting in the form of incorrectly claiming either good or bad air quality.

This paper describes a measure of adequacy for deciding whether a statistical linear regression model that relates FRM and continuous PM_2.5 measurements is sufficient for use in AQI reporting. The approach is the U.S. Environmental Protection Agency’s (EPA’s) data quality objectives (DQO) process, a seven-step strategic planning approach to determine the most appropriate data type, quality, quantity, and synthesis for a given activity.² The chosen measure of model adequacy is r², the square of the correlation coefficient between FRM measurements and their modeled counterparts. The paper concludes by developing regression models that meet this desired level of adequacy for the MSAs of Greensboro/Winston-Salem/High Point, NC; and Davenport/Moline/Rock Island, IA/IL. In both cases, a log transformation of the data appeared most appropriate. For the data from the Greens-boro/Winston-Salem/High Point MSA, a simple linear regression model of the FRM and CM measurements had an r² of 0.96, based on 227 paired observations. For the data from the Davenport/Moline/Rock Island MSA, due to seasonal differences between CM and FRM measurements, the simple linear regression model had to be expanded to include a temperature dependency, resulting in an r² of 0.86, based on 214 paired observations.     

Performance Testing of a Multimetals Continuous Emissions Monitor

ABSTRACT

A prototype instrument, designed for continuous monitoring of hazardous air pollutant metal emissions in the stack gases of waste incinerators and industrial furnaces, has undergone a performance evaluation that included a relative accuracy test audit. The test results confirmed the instrument's ability to accurately measure stack gas metal concentrations and thus validate the applicability of the candidate technique for compliance assurance monitoring for the specific source involved. The analytical accuracy of this system, documented during the recent test exercise, represents a significant improvement in performance relative to that previously achieved, and can be attributed with certainty to the recent implementation of a shrouded nozzle sampling system. By reducing deposition losses of particulate matter in the extracted stack gas stream to acceptable levels, presentation of a more representative sample stream to the elemental analyzer has been accomplished. The present paper discusses the design and operation of the multimetals continuous emissions monitor (MMCEM), the shrouded nozzle sampling system, and the results of recent performance testing.     

Measurement of Exhaust Emissions in Piston And Diesel Engines by Dispersive Spectroscopy

A versatile but simple, reliable, rugged, and compact vehicle exhaust monitoring system has been developed, allowing detection of carbon monoxide (CO), carbon dioxide (COo), high and low hydrocarbons (HHC and LHC), and nitric oxide (NO). The analysis is performed by dispersive absorption spectroscopy with instrumentation designed and fabricated for this demanding industrial environment. The operation of the instrumentation is described here, as well as results for both diesel and piston engine emission testing. This equipment has been used for California 7 mode-7 cycle hot start and cold start tests, the California heavy-duty engine test cycles, EPA CVS tests reading bag samples and also continuous dilute, and finally it has been used for idle checks. Testing has been performed on production automobiles, as well as those equipped with thermal reactors or catalytic mufflers, and also both heavy-duty gasoline and diesel. engines. The instrumentation has shown very good correlation with other established techniques, and because of its sensitivity, selectivity, ruggedness, and simplicity, has been shown to be suitable for vehicle emission analysis. Applications include assembly-line testing, engine testing, certification testing, quality audit testing, emission lab testing, and research.     

Continuous Emission Monitoring: Objectives and Requirements

Regulations were recently proposed by the Environmental Protection Agency which, when promulgated, will require existing and new sources within certain specified source categories to install, operate, and maintain continuous emission monitoring systems. Major comments received on these proposed regulations are discussed as are the overall benefits that can be derived from the utilization of continuous emission monitoring systems.     

Continuous Monitoring of FGD Wet Scrubber Corrosion

This article describes an electrochemical corrosion monitoring system developed in England that offers utilities the capability of continuously measuring power plant corrosion activity for a wide range of operating conditions.     

Evaluation of the Potential of Laser-Induced Breakdown Spectroscopy for Detection of Trace Element in Liquid

Abstract

The analytical figure of merit of the potential of laser-induced breakdown spectroscopy (LIBS) has been evaluated for detection of trace element in liquid. LIBS data of Mg, Cr, Mn, and Re were studied. Various optical geometries, which produce the laser spark in and at the liquid sample, were tested. The calibration curves for Mg, Cr, Mn, and Re were obtained at the optimized experimental conditions with bulk liquid and in liquid jet. It was found that measurements using a liquid jet provide better detection limits than bulk liquid measurements. The limits of detection (LOD) of Mg, Cr, Mn, and Re in the present liquid jet measurement are found to be 0.1, 0.4, 0.7, and 8 ppm, respectively. The LOD of Mg using Mg 279.55 nm was compared with the values found in other liquid work.     

Identification and Control of NOx Emissions Using Neural Networks

ABSTRACT

We investigate the application of two classes of artificial neural networks for the identification and control of discrete-time nonlinear dynamical systems. A fully connected recurrent network is used for process identification, and a multilayer feedforward network is used for process control. The two neural networks are arranged in series for closed-loop control of oxides of nitrogen (NO_x) emissions of a simplified representation of a dynamical system. Plant data from one of Commonwealth Edison's coal-fired power plants are used for testing the approach, with initial results indicating that the method is feasible. However, further work is required to determine whether the method remains feasible as the number of state variables and control variables are increased.     

The Value of Continuous Monitoring to the User

Potential benefits of a continuous monitoring program are presented in the form of questions that can be asked in connection with the information gained from the program. These questions are:

1. Are there process problems of which we are unaware?

2. Will this information be useful in the design of the next plant?

3. Can the information be used for improved process control?

4. Are we losing valuable material?

5. Can we use this information to modify our process for reduced pollution?     

On-Road Measurement of Vehicle Tailpipe Emissions Using a Portable Instrument

Abstract

A study design procedure was developed and demonstrated for the deployment of portable onboard tailpipe emissions measurement systems for selected highway vehicles fueled by gasoline and E85 (a blend of 85% ethanol and 15% gasoline). Data collection, screening, processing, and analysis protocols were developed to assure data quality and to provide insights regarding quantification of real-world intravehicle variability in hot-stabilized emissions. Onboard systems provide representative real-world emissions measurements; however, onboard field studies are challenged by the observable but uncontrollable nature of traffic flow and ambient conditions. By characterizing intravehicle variability based on repeated data collection runs with the same driver/vehicle/route combinations, this study establishes the ability to develop stable modal emissions rates for idle, acceleration, cruise, and deceleration even in the face of uncontrollable external factors. For example, a consistent finding is that average emissions during acceleration are typically 5 times greater than during idle for hydrocarbons and carbon dioxide and 10 times greater for nitric oxide and carbon monoxide. A statistical method for comparing on-road emissions of different drivers is presented. Onboard data demonstrate the importance of accounting for the episodic nature of real-world emissions to help develop appropriate traffic and air quality management strategies.     

Atmospheric Particulate Emissions from Dry Abrasive Blasting Using Coal Slag

Abstract

Coal slag is one of the widely used abrasives in dry abrasive blasting. Atmospheric emissions from this process include particulate matter (PM) and heavy metals, such as chromium, lead, manganese, nickel. Quantities and characteristics of PM emissions depend on abrasive characteristics and process parameters. Emission factors are key inputs to estimate emissions. Experiments were conducted to study the effect of blast pressure, abrasive feed rate, and initial surface contamination on total PM (TPM) emission factors for coal slag. Rusted and painted mild steel surfaces were used as base plates. Blasting was carried out in an enclosed chamber, and PM was collected from an exhaust duct using U.S. Environment Protection Agency source sampling methods for stationary sources. Results showed that there is significant effect of blast pressure, feed rate, and surface contamination on TPM emissions. Mathematical equations were developed to estimate emission factors in terms of mass of emissions per unit mass of abrasive used, as well as mass of emissions per unit of surface area cleaned. These equations will help industries in estimating PM emissions based on blast pressure and abrasive feed rate. In addition, emissions can be reduced by choosing optimum operating conditions.     

Extractive Continuous Emission Monitoring at San Juan Generating Station

Continuous emission monitors at San Juan have had very high availability and reliability over the past two years. Three extractive systems are in service on two 350 MW units and one 515 MW unit. Another 515 MW unit is scheduled for startup in 1982. All units are coal-fired with electrostatic precipitators and Wellman-Lord desulfurization systems, and all units will have the same extractive emission monitor systems utilizing microprocessors for control and data acquisition.

This paper discusses the design of and operating experience with the extractive systems and microprocessors, including their problems, advantages, and disadvantages. It will also outline system costs and describe certification experience for two units.

Secondly, this paper describes five years of history on operating and maintaining two early in-situ analyzer systems, a temporary system, and the present extractive systems. Finally, the development of dedicated daily maintenance will be summarized as a major reason for successful emission monitor systems.     

Characterization of Emissions from Vehicles Using Methanol and Methanol-Gasoline Blended Fuels

Exhaust and evaporative emissions were examined from vehicles fueled with methanol or a gasoline-methanol blend. Regulated automobile pollutants, as well as detailed hydrocarbons, methanol, and aldehydes were measured, and exhaust emission trends were obtained for vehicle operation over five different driving cycles. Results indicated that use of the blended fuel does not generally have any significant effect on base-line exhaust emission rates of regulated pollutants; however, emission rates of aldehydes increased during the Federal Test Procedure. Aldehyde emissions from the methanol-fueled car were roughly an order of magnitude higher than those resulting from blended fuel usage. The hydrocarbon composition of evaporative emissions with the blended fuel was similar to that with the base-line fuel except when canister breakthrough occurred. Evaporative emissions during breakthrough were comprised chiefly of N-butane.     

Evaluation of Continuous Performance Monitoring Techniques for Hazardous Waste Incinerators

This paper discusses monitoring the waste destruction efficiency of hazardous waste incinerators. The particular problem is to ensure that incinerators do not release, without detection, significant quantities of waste as a result of operating fluctuations or equipment degradation. To detect these conditions, continuous, automated, and real-time source monitoring is required. Detection of degraded performance by monitoring and measuring waste compounds directly is not presently possible on a continuous basis. An alternative is to use commercially available continuous monitors to measure combustion intermediates (e.g., CO or hydrocarbons) and thereby infer waste destruction efficiency. Required, however, is a correlation between the emission of intermediates and the emission of waste. In this paper, the response of a number of these continuous monitors is compared with waste destruction efficiency measurements from a laboratory scale, liquid-spray incinerator operated on fuel oil doped with model waste compounds: benzene, chlorobenzene, acrylonitrile, and chloroform. Total hydrocarbon and CH₄ measurements are found to vary with waste emission in a nearly linear manner; however, a substantial increase in CO emission occurs before a significant amount of waste is released. These results suggest that CO may serve as an indicator of the approach of waste release, while total hydrocarbons may provide an indicator of immediate waste release.     

Continuous Monitoring of Methane and Other Hydrocarbons In Urban Atmospheres

Continuous measurements of total hydrocarbons (and other organic substances) and of methane were made in Cincinnati and Los Angeles for three-month periods. Some of the measurements were made during episodes of photochemical air pollution. Two instruments, one for measurement of total hydrocarbons and the other for methane, were operated in parallel. Both incorporated flame ionization detectors having greater sensitivity than commercial flame ionization instruments. The flame ionization analysis for methane was made specific by use of an adsorbent carbon column preceding the analyzer to retain all organic substances except methane. Subtracting the methane concentration values from those for total hydrocarbons gave nonmethane hydrocarbon concentrations. The data showed diurnal patterns of concentrations of methane and nonmethane hydrocarbons in the atmosphere. Average hourly values for methane were strikingly similar in Los Angeles and in Cincinnati (2.6 and 2.4 ppm, respectively); those for nonmethane hydrocarbons were four times as high in Los Angeles (3.0 and 0.8 ppm, respectively). A bimodal frequency distribution pattern of the concentrations suggested that atmospheric ventilation was either good or poor, with less than a random amount of time in intermediate stages. The width of the methane frequency distribution peak was about half the width of that for nonmethane hydrocarbons, indicating a different and more constant source for the former.