Minnesota Power’s Operating Experience with Integrated Particulate and SO2 Scrubbing

Minnesota Power currently has in commercial operation a 500 MW gas cleaning system consisting of a venturi particulate scrubber, integrated with a spray tower SO₂ absorber. The system was designed to achieve 99.7% particulate removal and 90% SO₂ removal based upon burning a 2.8 % sulfur coal.

Initially the concept of using a venturi for wet particulate collection was selected based upon a significant cost saving of $25 million compared to dry particulate collection devices. Subsequently, the Interaction of particulate collection with SO₂ removal provided additional operating cost benefits. Prior to start-up of the commercial system, a pilot plant was used to evaluate various modes of operation. Results showed that alkali contained in the fly ash removed with the venturi was sufficient to meet the alkali requirement for SO₂ removal.

Clay Boswell Station Unit No. 4 was started up during March 1980. Since initial start-up the system has exhibited almost 100% availability. EPA compliance testing has confirmed that the system Is meeting its emission standards. The unit is operating with fly ash as the only source of alkali. Since commercial operation started, no external alkali has been purchased.

This paper will discuss the design details of the system and performance of the commercial system.     

Roof Monitor Emissions: Test Methodology

Studies of roof monitor emissions are conducted for two reasons: (1) to obtain design data necessary to engineer control systems to meet existing regulations, and (2) to determine projected control costs which can influence present day proposals for process change. Heated wire anemometers and rotating vane anemometers have been selected for velocity measurements, and high-volume air samplers have been selected to collect the particulate sample. Evaluation of other types of velocity sensing devices are described in the paper.

Roof monitor studies must be preceded by a preliminary survey to allow the project engineer to determine the test sampling locations and specific methodology necessary for the given study, and to allow the engineer to determine the type of safety equipment, scaffolds, and power requirements necessary to complete the study.

Field tests are conducted by operating a number of high-volume air samplers simultaneously while at the same time measuring the velocity of the gas through the monitor opening. Curves of particulate concentration and velocity as a function of monitor length are constructed. The concentration and velocity curves are then integrated together and the resultant curve is multiplied by the monitor width to determine a curve of mass emission rate as a function of monitor length. The total mass emission rate is represented by the area under the mass emission rate curve.

Procedures for calibrating the anemometers and correcting for the effect of power fluctuation on the high-volume sampler operation are described. Data evaluation procedures and discussion of test error are also described.

A study can cost between 10 and 20 thousand dollars, including the cost of manpower and the cost of scaffolds, power, cables, etc. It can take four months or more to conduct a study, from the preliminary survey phase through the report phase.     

Advanced Concepts in FGD Technology: The SHU Process with Cooling Tower Discharge

The growing awareness of ecological issues in Europe, reinforced by the public debate surrounding acid rain, has led to the enactment of laws and regulations in West Germany relating to emissions from large coal fired combustors.

Flue gas desulfurization (FGD) units have been compulsory for new coal fired power plants in West Germany for about 12 years. The new legislation enacted in 1983, to be met by the middle of 1988, applies not only to new plants but, unlike in the United States, also to. existing power plants (>30MW).

The law currently specifies a residual SO2 emission level of 400 mg/Nm³ (0.311b MM/BTU) for large power plants (>100 MW), but a level of 200 mg/Nm³ (0.15 lb MM/BTU) is already under discussion in some cases. The legally binding emission standards stipulate that none of the daily averages, calculated on the basis of half hour averages may exceed the concentration allowed. SO2 removal efficiencies of 90 percent to 95 percent are normally provided. Since 1983, more than 35,000 MW of retrofit FGD units have been installed in Germany to meet this SO₂ standard.

The regulations also do not allow for the ponding of calcium sulfite scrubber sludge, but stipulate the production of gypsum from limestone slurry processes. Additionally the regulations require flue gases to have a minimum temperature in the stack of 72° C (162°F) after desulfurization. Treated flue gases do not have to be reheated if discharged via a cooling tower.     

Energy consumption and energy-saving potential analysis of pollutant abatement systems in a 1000-MW coal-fired power plant

Pollutant abatement systems are widely applied in the coal-fired power sector, and the energy consumption is considered an important part of the auxiliary power. An energy consumption analysis and assessment model of pollutant abatement systems in a power unit was developed based on the dynamic parameters and technology. The energy consumption of pollutant abatement systems in a 1000-MW coal-fired power unit that meets the ultra-low emission limits and the factors of operating parameters, including unit load and inlet concentration of pollutants, on the operating power were analyzed. The results show that the total power consumption of the pollutant abatement systems accounted for 1.27% of the gross power generation during the monitoring period. The wet flue gas desulfurization (WFGD) system consumed 67% of the rate, whereas the selective catalytic reduction (SCR) and electrostatic precipitator (ESP) systems consumed 8.9% and 24.1%, respectively. The power consumption rate of pollutant abatement systems decreased with the increase of unit load and increased with the increase of the inlet concentration of pollutants. The operation adjustment was also an effective method to increase the energy efficiency. For example, the operation adjustment of slurry circulation pumps could promote the energy-saving operation of the WFGD system.

Implications: The application of pollutant abatement technologies increases the internal energy consumption of the power plant, which will lead to an increase of power generation costs. The real-time energy consumption of the different pollutant abatement systems in a typical power unit is analyzed based on the dynamic operating data. Further, the influence of different operating parameters on the operating power of the system and the possible energy-saving potential are analyzed.     

VOC Recovery through Microwave Regeneration of Adsorbents: Comparative Economic Feasibility Studies

ABSTRACT

Microwave regeneration of adsorbents facilitates the recovery of volatile organic compounds (VOCs) by decoupling the bed heating from the stripping gas. This makes possible the creation of a highly-concentrated regeneration effluent from which the VOCs can be recovered by condensation at near-ambient temperatures. The economic feasibility of two novel microwave-regenerated adsorption systems was evaluated by systematically comparing the capital and operating costs of the proposed systems with 10 conventional VOC control technologies. The microwave systems were found to have similar capital and operating costs to conventional steam regeneration systems and, therefore, may present an attractive alternative for recovering water-miscible solvents. In general, the cost of the microwave subsystem is a relatively small component of the overall system costs, and the microwave power requirements are within the range of commercially available generators, even for large emission streams.     

interpretation of air quality data with respect to the national ambient air quality standards

San Diego Gas &; Electric has developed a quality assurance program for continuous emission monitors (CEM). Extractive, rather than in situ, monitors were selected as a result of an in-house evaluation program. Two extractive systems have been certified and a good operating and maintenance record has been established on these systems. A successful program requires the involvement and support of all affected personnel. It is desirable to have one or two key personnel coordinate the development of the program. It is also highly desirable to have good in-house source testing capabilities.     

Pennsylvania’s Compuiterized Air Monitoring System

The Pennsylvania Air Pollution Commission has developed a regulatory program based upon the control of local air pollution problems and reduction of pollutant levels in air basins. The geographical boundaries of 10 air basins have been established. The Commission’s air basin regulations will provide for the reduction of over-all pollutant levels and for emergency procedures in the event of adverse meteorological conditions. The paper discusses the format and objectives of the program.

In order to effectively enforce the air basin regulations and maintain the necessary surveillance of the state’s air quality, a "computerized real time on-line integrated air monitoring-data handling system" has been designed. The system will incorporate a network to constantly monitor the air in each air basin.The primary objectives of the system are: 1. Constant surveillance of air pollution in the air basins.

2. Provide information on air pollution potential alerts.

3. Aid in further development of air quality criteria and regulations.

The air monitoring network is estimated to include approximately 25 remote stations. Each remote will contain air pollution and meteorological sampling equipment and hardware to telemeter to a central station. The data will be transmitted over leased telephone lines. The central station in Harrisburg will contain the necessary hardware to receive and process data, calculate and display results and permit supervisory control of the network. Output options will include immediate display of edited data, command and alarm information, and presentation of statistical results.

Although the air monitoring system is one of the principle ingredients of the program, the air basin concept encompasses other component systems designed to knit together the entire air pollution control program in Pennsylvania.     

A Feasibility Study on the Predictive Emission Monitoring System Applied to the Hsinta Power Plant of Taiwan Power Company

Abstract

The continuous emission monitoring system (CEMS) can monitor flue gas emissions continuously and instantaneously. However, it has the disadvantages of enormous cost, easily producing errors in sampling periods of bad weather, lagging response in variable ambient environments, and missing data in daily zero and span tests and maintenance. The concept of a predictive emission monitoring system (PEMS) is to use the operating parameters of combustion equipment through thermodynamic or statistical methods to construct a mathematic model that can predict emissions by a computer program. The goal of this study is to set up a PEMS in a gas-fired combined cycle power generation unit at the Hsinta station of Taiwan Power Co. The emissions to be monitored include nitrogen oxides (NO_x) and oxygen (O₂) in flue gas. The major variables of the predictive model were determined based on the combustion theory. The data of these variables then were analyzed to establish a regression model. From the regression results, the influences of these variables are discussed and the predicted values are compared with the CEMS data for accuracy. In addition, according to the cost information, the capital and operation and maintenance costs for a PEMS can be much lower than those for a CEMS.     

Fans and Fan Systems

Abstract

There is a need for robust and accurate techniques for the measurement of ammonia (NH₃) and other atmospheric pollutant emissions from poultry production facilities. Reasonable estimates of NH₃ emission rate (ER) from poultry facilities are needed to guide discussions about the industry’s impact on local and regional air quality. The design of these facilities features numerous emission points and results in emission characteristics of relatively low concentrations and exhaust flow rates that vary diurnally, seasonally, and with bird age over a considerable range. These factors combine to render conventional emissions monitoring approaches difficult to apply. Access to these facilities is also often restricted for biosecurity reasons. The three objectives of this study were (1) to compare three methods for measuring exhaust NH₃ concentrations and thus ERs, (2) to compare ventilation rates using in situ measured fan characteristics versus using manufacturer sourced fan curves, and (3) to examine limitations of the alternative measurement technologies. In this study, two open-path monitoring systems operating outside of the buildings were compared with a portable monitoring system sampling upstream of a primary exhaust fan. The position of the open-path systems relative to the exhaust fans, measurement strategy adopted, and weather conditions significantly influenced the quality of data collected when compared with the internally located, portable monitoring system. Calculation of exhaust airflow from the facility had a large effect on calculated emissions and assuming that the installed fans performed as per published performance characteristics potentially overestimated emissions by 13.6–26.8%. The open-path measurement systems showed promise for being able to obtain ER measurements with minimal access to the house, although the availability of individual fan characteristics markedly improved the calculated ER accuracy. However, substantial operator skill and experience and favorable weather conditions were required to obtain good quality results.     

Correlating Emissions with Time and Temperature to Predict Worst-Case Emissions from Open Liquid Area Sources

Abstract

The two primary factors influencing ambient air pollutant concentrations are emission rate and dispersion rate. Gaussian dispersion modeling studies for odors, and often other air pollutants, vary dispersion rates using hourly meteorological data. However, emission rates are typically held constant, based on one measured value. Using constant emission rates can be especially inaccurate for open liquid area sources, like wastewater treatment plant units, which have greater emissions during warmer weather, when volatilization and biological activity increase. If emission rates for a wastewater odor study are measured on a cooler day and input directly into a dispersion model as constant values, odor impact will likely be underestimated. Unfortunately, because of project schedules, not all emissions sampling from open liquid area sources can be conducted under worst-case summertime conditions. To address this problem, this paper presents a method of varying emission rates based on temperature and time of the day to predict worst-case emissions. Emissions are varied as a linear function of temperature, according to Henry’s law, and a tenth order polynomial function of time. Equation coefficients are developed for a specific area source using concentration and temperature measurements, captured over a multiday period using a data-logging monitor. As a test case, time/temperature concentration correlation coefficients were estimated from field measurements of hydrogen sulfide (H₂S) at the Rowlett Creek Wastewater Treatment Plant in Garland, TX. The correlations were then used to scale a flux chamber emission rate measurement according to hourly readings of time and temperature, to create an hourly emission rate file for input to the dispersion model ISCST3. ISCST3 was then used to predict hourly atmospheric concentrations of H₂S. With emission rates varying hourly, ISCST3 predicted 384 acres of odor impact, compared with 103 acres for constant emissions. Because field sampling had been conducted on relatively cool days (85–90 °F), the constant emission rate underestimated odor impact significantly (by 73%).     

Techniques and Procedures for the Measurement of Aircraft Gas Turbine Engine Emissions

In 1968 the Society of Automotive Engineers formed the Committee on Aircraft Exhaust Emissions Measurement (E-31) whose charge was the development of acceptable standards of measurement for the characterization of aircraft engine exhaust. This committee’s efforts have resulted in the issuance of two Aerospace Recommended Practices, ARP 1179 “Aircraft Gas Turbine Exhaust Smoke Measurement” and ARP 1256 “Procedure for the Continuous Sampling and Measurement of Gaseous Emissions from Aircraft Turbine Engines.” These Recommended Practices have in large part been adopted by the Environmental Protection Agency and promulgated in Federal Register Volume 38, Number 136, Tuesday, July 17, 1973.

For the past three years Pratt & Whitney Aircraft has been measuring emissions from aircraft gas turbine engines using on-line instrumentation systems designed both in accordance with these Aerospace Recommended Practices and in response to the operational needs of a large experimental engineering test facility. In addition to a discussion of these systems this paper describes the experience derived from continuous testing programs in support of this test facility with consideration being given to the specific problems of sampling, sample handling, system accuracy, and data recording and reduction. Comment is made as to the practical limitations of the recommended methods and procedures as applied to emission control technology programs and suggestions are presented for improving the measurement technology.     

Operating History and Current Status of Fabric Filters in the Utility Industry

Electric utilities have made significant progress in recent years in designing and operating baghouses for collection of coal fly ash. As a result, early concerns with high operating and maintenance requirements and short bag lives are no longer an issue. With increasingly stringent air emissions regulations and imminent revision of the Clean Air Act, baghouses have become an attractive particulate collection option for utilities.

In order to keep its member utilities apprised of the latest design and operation and maintenance experience with baghouses, the Electric Power Research Institute has been conducting surveys of utility baghouse user experience. This paper presents results from the latest survey, conducted in 1989. A previous survey was conducted in 1985. The 1989 survey was conducted using questionnaires mailed to the utilities, telephone inquiries, and plant visits. This paper discusses the general trends observed in baghouse design, performance, operation and maintenance.     

The Cost of Stack Gas Cleaning in New York State

A cost estimating methodology has been applied to an emission point inventory to estimate the capital and operating costs of stack gas cleaning in the manufacturing sector of New York State. The study represents the first major attempt to estimate control costs on a source by source basis for a large region. The various control cost components are presented for each of the twenty manufacturing industry groups and the usefulness of the estimates for an abatement planning model is outlined.

In recent years a number of heroic efforts have been made to estimate the cost of air pollution abatement on a national or regional basis. Unfortunately, these studies have relied almost entirely upon emission factors, cost engineering functions, pilot plant operations, and average or ideal firms, because of the paucity of primary data.^1-6

In the estimates of capital and operating costs presented below, an attempt has been made to improve on previous research by making extensive use of primary data. The data were taken from an emission inventory of over 20,000 sources of air contamination in New York State. A cost estimating methodology was applied to engineering parameters of existing control operations on a source by source basis. The results have been aggregated to the two-digit SIC level.     

Extractive Sampling and Optical Remote Sensing of F100 Aircraft Engine Emissions

Abstract

The Strategic Environmental Research and Development Program (SERDP) has initiated several programs to develop and evaluate techniques to characterize emissions from military aircraft to meet increasingly stringent regulatory requirements. This paper describes the results of a recent field study using extractive and optical remote sensing (ORS) techniques to measure emissions from six F-15 fighter aircraft. Testing was performed between November 14 and 16, 2006 on the trim-pad facility at Tyndall Air Force Base in Panama City, FL. Measurements were made on eight different F100 engines, and the engines were tested on-wing of in-use aircraft. A total of 39 test runs were performed at engine power levels that ranged from idle to military power. The approach adopted for these tests involved extractive sampling with collocated ORS measurements at a distance of approximately 20–25 nozzle diameters downstream of the engine exit plane. The emission indices calculated for carbon dioxide, carbon monoxide, nitric oxide, and several volatile organic compounds showed very good agreement when comparing the extractive and ORS sampling methods.     

Thermal and Catalytic Incinerators for the Control of VOCs

Abstract

The emission of Volatile Organic Compounds (VOCs) is attracting increasing concern both from the public and by government agencies. Among the many available control technologies for the treatment of VOC containing waste streams, incineration offers an ultimate disposal strategy rather than a means for collecting or concentrating the offending compounds. This paper describes the major, commercially available thermal and catalytic incinerator systems that are designed to treat dilute, VOC containing gas streams. Qualitative guidelines are presented whereby the technologies can be compared. In addition, an example waste stream is used to illustrate a simplified procedure for calculating the material and energy balances for each of the incinerators. The resulting parameters will be used in a companion paper to estimate the capital and operating costs associated with each design. In this manner, a first estimate can be obtained of the costs of cleaning a waste stream containing low levels of VOCs.     

Assessment of Dry Sorbent Emission Control Technologies Part I. Fundamental Processes

The utility and industrial sectors continue to come under pressure from both national and local regulatory groups to reduce sulfur dioxide emissions. With a trend in the utility industry for life extension, retrofit technologies are likely to play an important role in any SO₂ emission reduction strategy. Potential retrofit technologies include, singly and in combination: coal switching or cleaning, wet or dry FGD, conversion to fluidized bed, and dry sorbent injection. The diversity within the utility industry in terms of unit size, unit age, fuel use, financial base, and geographic location dictates the need for a variety of technologies to address SO₂ emission control. Dry injection processes involving the injection of dry powders into either the furnace or post-furnace region offer the potential for low capital cost retrofitable technologies. However, compared to wet FGD processes, the dry calcium based processes will likely have lower SO₂ removal efficiencies and may pose more plant-wide integration issues that need to be addressed from both an applications and R&D perspective.

This paper provides a critical assessment of dry injection technologies, in two parts. Part 1 focuses on sorbent processes and science. An assessment of the different dry sorbent processes and the effect of process parameters is provided. Emphasis is placed on process limitations and potential avenues to enhance SO₂ removal. Part 2 will deal with applications of the technology, addressing cost, scale-up, and integration issues.

Much of the data included in this paper was presented at the 1986 Joint Symposium on Dry SO₂ and Simultaneous SO₂/NO_x Control Technologies, sponsored by the Electric Power Research Institute and the Environmental Protection Agency and held in June 1986. This paper provides both an overview and an evaluation of the technology, based largely on our analysis of the data and interpretations discussed at this symposium.     

Estimated Validity and Reliability of On-Board Diagnostics for Older Vehicles: Comparison with Remote Sensing Observations

ABSTRACT

Based on requirements under the Clean Air Act Amendments of 1990, most state vehicle inspection and maintenance (I/M) programs have, since 2002, replaced the tailpipe emission testing with the on-board diagnostic (OBD) II testing for 1996 model and newer vehicles. This test relies on the OBD II system to give the pass or fail result, depending on certain conditions that might cause the vehicle to emit pollution 1.5 times higher than the regulated standard. The OBD II system is a computer and sensors installed in the vehicle to monitor the emission control units and signal if there is any malfunction. As a vehicle ages, its engine, pollution control units, and OBD II system deteriorate. Because the OBD II system's durability directly influences the test outcome, it is important to examine the fleetwide trend in the OBD II test results in comparison with an alternative measure of identifying high emitting vehicles. This study investigates whether the validity and reliability of the OBD II test is related to the age of the OBD II system installed in the fleet. Using Atlanta's I/M testing records and remote sensing device (RSD) data collected during 2002–2005, this research establishes the convergent validity and interobserver reliability criteria for the OBD II test based on on-road emissions measured by RSDs. The study results show that older vehicles exhibit significantly lower RSD–OBD II outcome agreement than newer vehicles. This suggests that the validity and reliability of the OBD II test may decline in the older vehicle fleets. Explanations and possible confounding factors for these findings are discussed.

IMPLICATIONS This research demonstrates the potential worsening validity and reliability of the on-board diagnostic (OBD) II test in old vehicles. If the main source of low validity and reliability comes from the OBD II system malfunction, we expect this malfunctioning OBD II fleet will continue to grow in the future. If unchecked, the deterioration of OBD II system may impair the effort of the inspection and maintenance (I/M) program to identify high-emitting vehicles and the ultimate objective of reducing the air pollution from automobiles. This result is especially important in a regulatory context where technological and emissions standards dominate environmental policy and yet little attention is paid to the possible degradation of environmental monitors themselves.     

Developments In Sampling And Analysis Instrumentation For Stationary Sources

The body of information presented in this paper is provided as an orientation to instrument developers and users, and those individuals concerned with the measurement of pollutant emissions from stationary sources.

A system concept is presented and shows six unit operations comprising a complete measurement system. These operations include sample site selection, sample transport, sample treatment, sample analysis, data reduction and display, and data interpretation.

Five measurement approaches are discussed. The first two involve sample extraction from within the stack. The remaining three are new techniques using conventional and advanced electro-optical methods. The new approaches include in situ monitoring, remote sensing, and long-path sensing.

Attention is focused on the performance requirements of interface systems required to couple analyzers to sources for sample extraction. Current status of instrumentation is summarized in terms of commercially available systems, research and prototype developments, and feasibility studies for each of the five approaches.