Stack Emissions Research Articles

Evaluating the health impacts of incinerator emissions

Before a municipal solid waste incinerator (MSWI) can be operated, it is generally required that a health risk assessment be performed and that human health risks predicted fall below permissible levels. There are several components to the risk assessment paradigm, including: (1) determination of stack emissions for potentially toxic chemicals, (2) calculation of atmospheric dispersion and exposure point concentrations, (3) development of scenarios by which humans become exposed to airborne chemicals, (4) identification of dose-response functions for carcinogenic and noncarcinogenic effects, and (5) prediction of the probability of health impacts. Typical MSWI air contaminants of concern are metals (e.g., Ag, As, Be, Cd, Cr, Hg, Ni, Pb, Sb) and organic compounds (e.g., benzene, PCBs, B(a)P, polychlorinated dioxins/furans). MSWI risk assessments include both direct exposure pathways (air inhalation, incidental ingestion of soil), and indirect pathways (food-chain exposures such as human consumption of produce, beef, fish, and milk). To perform a risk assessment for direct and indirect routes of exposure, both atmospheric concentration and deposition rate are required; assumptions need to be made about toxicity as a function of route of exposure. Interpretation of risk-assessment results requires understanding how some of the conservative assumptions made in the risk-assessment process play out relative to real-world health hazards. Some attempts have been made to verify that predicted concentrations of airborne contaminants are reflected by measured levels, but in most cases the predicted air and soil concentrations fall below limits of detection and always within background variability. In summary, health risk assessments are useful for regulatory guidance, but it has not been possible to verify that health risks of MSWI emissions contribute measurably to population health risks.

Quantitative risk assessment of stack emissions from municipal waste combustors

Multi-pathway risk assessment (MRA) is a tool for evaluating the possibility of adverse effects to human health that may result from contaminant releases from municipal solid waste combustors (MWCs) and other sources of air pollution. An MRA attempts to model the movement of pollutants within the environment to various points at which they may be contacted by people, beginning with inhalation of contaminated air and continuing with indirect pathways such as food chain exposures that entail contaminant transfer and accumulation through several media. MRAs of MWCs date back to the mid-1980s, and are rooted in methods developed to assess the consequences of radionuclide releases from nuclear power generation. A detailed example of a typical MRA is presented that follows the classic four-stage risk assessment paradigm (Valberg et al., 1995). MRA methods, however, continue to be enhanced and refined by recent research. A number of current risk assessment topics are explored that are new to traditional MRAs and may serve to re-focus our collective efforts. The purpose of and demands on MRAs must be considered. A philosophical shift toward placing greater realism in MRAs underscores the importance of uncertainties inherent to risk estimates. Tools such as probabilistic risk assessment techniques must be developed and endorsed so that decision-makers may intelligently utilize the information provided by MRAs.

Overview of municipal waste incineration industry in west Europe (based on the German experience)

This paper presents an overview of the current status of the waste-to-energy activities in the west European countries, outlining the demand for municipal waste incineration and the development in the design of the combustion system as well as in the air pollution control system. Trend setter in the technical development over the last 10 years have been the emissions regulations for waste incinerators. As an example the Dutch, Austrian, Swiss, German and EC-legislation is compared with the current state-of-the-art flue gas treatment technology and its achievable emission values. The boost of new technologies was mainly created by the dramatic tightening of these emissions legislation. The second part of the paper details the status of air pollution control technologies currently being used. Various four to five stage flue gas cleaning processes, including the recovery of marketable products from the residuals, are covered. Hence not only the minimization of stack emissions is politically pursued. The requirement of resource recovery from residuals has become more and more a major criteria for the design of flue gas treatment processes. This paper explores the process technologies used in achieving this goal as well as giving an outlook on novel concepts aiming for even higher rates of recovery and better quality products. The paper concludes with a listing of the major technology vendors and with some economical/ecological aspects of waste incineration plants equipped with modern combustion and air pollution control technology.

An accurate Predictive Emissions Monitoring System (PEMS) for an ethylene furnace

AbstractThe Predictive Emissions Monitoring System (PEMS) has been recently proposed as an alternative to hardware continuous emissions monitors (CEM). PEMS has two distinct advantages over hardware CEM: much lower costs to install and maintain, and ability to provide information on emissions under various conditions. Using a state‐of‐the‐art computer program, an accurate PEMS was developed for an ethylene furnace at Exxon Chemical Company's Baytown Olefins Plant, Baytown, Texas. First, a test plan was carefully designed to collect furnace process and stack emissions data over the total operating range of the furnace. The emissions data (NOx, O2 and CO) were collected and measured by an independent company for 5 days. The related process data were recorded in the DCS system during the same 5‐day period. A dataset with some 7,000 patterns of related process and emissions data was generated. The PEMS system contains 2 parts: emissions prediction and sensor validation models. The main purpose of the sensor validation model is to validate the input sensor's raw data and reconstruct new sensor values, if necessary, before they are used in the prediction model. Its usage provides a high degree of confidence for the PEMS system. Two separate emissions prediction models were built, one for NOx and O2, and the other for CO. Both final models have the same 9 input sensors. A PEMS relative accuracy test audit (RATA) was performed by an independent company to test the PEMS system under the three firing rate conditions (low, medium, and high). Test results indicate that the PEMS system satisfied both the relative accuracy (RA) and the stringent statistical test requirements including the F‐test, t‐test and r‐correlation.

MHD-steam thermal power plant electrical stations with zero stack emission

A system study of a combined cycle MHD-steam thermal power plant electrical station with zero stack emission through recirculation of CO/sub 2/, is presented. The design of the MHD generator of the topper is done by means of a quasi-one dimensional optimization model. The technology of the components is conventional. An overall efficiency larger than 40% for power plants with thermal power inputs above 1000 MWth, is obtained.

Determination of Total Organic Emissions from Hazardous Waste Combustors

U.S. Environmental Protection Agency risk assessment guidance currently under development for evaluation of permitting information from hazardous waste combustors requires a quantity referred to as "total organic carbon". The risk guidance does not define this term precisely, nor does it explain how it should be determined. This paper discusses basic principles of sampling and analysis of stack emissions for "total organics", best currently available technology, and the status of two ongoing projects designed to provide guidance and to improve analysis procedures. Determination of total organics from stack emissions is much more complicated than might be expected, and more published guidance is badly needed. The best scheme available for analysis of stack emissions for total organics to be used in material balance style "bookkeeping" includes determination of organics content in three boiling point ranges: <100 °C, 100 °C-300 °C, and >300 °C. Total organic carbon is not a useful quantity, since it includes soot, polymeric material, and other nonextractable organic materials. Total organics has been found to be an imperfect but less misleading term. Various calculations can be made and conclusions can be drawn on the basis of the contents of the individual boiling point ranges, as determined by the recommended methodology. The analysis strategy is complicated and difficult, and it contains limitations and compromises. It does not, however, require exotic analysis instrumentation, nor is it very expensive. Each of these facets of the methodology is discussed in this paper, and a status report is provided on development of a guidance document and a research project intended to produce improved methods.

Compact incinerator afterburner concept based on vortex combustion

A design concept for a compact incinerator afterburner based on actively controlled vortex combustion was developed and tested at ≈ 5 kW and ≈ 50 kW. Acoustic control of fluid dynamics was used to enhance mixing and increase the DRE (destruction and removal efficiency) for a waste surrogate. A detail study of the concept of utilizing vortex combustion for incineration was undertaken in a small-scale flame using advanced laser diagnostics to elucidate and optimize the fluid dynamic mechanisms. The system was then scaled up by ≈ 10, optimized, and evaluated for performance. The open loop active control methodology is based on the concept of combustion in periodic axisymmetric vortices. Acoustic excitation was, used both to stabilize coherent vortices in the central jet air flow and to control circumferential gaseous fuel and waste injection into the shear layer at the right time during vortex formation. The gaseous-fueled actively controlled 4.5 kW incinerator was able to surpass 99.997% DRE even when the gaseous benzene waste surrogate constituted 66% of the total combustible content and the combustible to total air ratio (ø) was 0.974; lowering ø below this increased the DRE to beyond our detection limit. The DRE for gaseous benzene exceeded 99.999% in the 50-kW system when combustible to air ratios were kept below 0.78. Parameters found critical to maintenance of high DRE at both energy scales were the fraction of circumferentially entrained air, the entrainment geometry, the forcing levels, and the phase angle of fuel injection with respect to the vortex roll-up. The 50-kW combustor was also evaluated for stack emissions and combustion efficiency. The controller improved combustion efficiency and lowered emissions: CO dropped from 2900 ppm to as low as 2 ppm. Unburned hydrocarbons were also reduced. Under some conditions the controller also reduced NO x levels down to as low as 12 ppm.

Validation of a Test Method for Collection and Analysis of Chloroform Emissions From Stationary Sources.

A test method based upon the adsorption of chloroform onto charcoal was evaluated for the collection and analysis of chloroform emissions from stationary sources. In this method, a source gas sample is pulled through adsorption tubes containing activated charcoal (to adsorb the chloroform), and chloroform is extracted from the charcoal with a hexane/methanol mixture. The extract is analyzed by gas chromatography with an electron capture detector. Procedures in Environmental Protection Agency (EPA) Method 301 were utilized to test the suitability of the method under field conditions at two sampling sites (paper mills). EPA Method 301 requires that four separate trains ("quad train") operate simultaneously in each run. During each run, two of the four sampling trains were spiked with a known amount of gaseous chloroform. The quad train sampling was performed six or more times. In the first field test, the stack emissions of chloroform were approximately 300 ppm, the mean spike recovery was 82%, the precision of the method for unspiked samples was within 5%, and the sampling bias was -43 ppm. Modifications were made to the sampling method and the spike gas introduction system. The revised method was then tested at a second field site which had chloroform emissions of approximately 220 ppm. The mean spike recovery improved to 95%, the unspiked sample precision was within 5%, and the sampling bias improved to -8.5 ppm.

TFTR D-T Experience with Tritium Radioactivity during Maintenance

The Tokamak Fusion Test Reactor (TFTR) facility began operations with trace tritium in July 1993. These operations consist of the delivery, storage, injection, and subsequent processing of tritium gas in support of the D-T fusion program. The tritium is transferred throughout the facility using vacuum pumping systems and expansion volumes. These systems have manipulated and processed 14.4 PBq (388,983 Ci) of tritium from July 1993 through December 1994. This paper discusses the operational health physics program with regard to the performance of maintenance on tritium contaminated systems. Data and findings are provided from maintenance situations ranging from work on small volume piping to large volume neutral beam systems. Results and comparisons of tritium contamination levels, airborne radioactivity levels, and oil concentrations are presented for these systems. Descriptions of the maintenance tasks are provided for the entire scope of work and include general information toward conceptual understanding of the maintenance conduct of operations. General procedural requirements, job planning, pre-job briefing topics, control mechanisms, techniques to reduce exposure, and lessons learned are discussed. A complete description of various types of tritium monitoring and sampling equipment is also discussed. Several types of air monitoring equipment were used during these tasks to identify the most consistent and reliable methods for detection and radiological assessments. The results of radiological measurements are described in relation to the differentiation of elemental tritium to tritium oxide in worker's breathing zones and the associated general work area. A comparison is provided to process system monitoring, system moist air purges, system contamination levels and subsequent stack emission sampling for both elemental and oxide tritium. A summary is provided to describe the relationship between elemental and oxide tritium as a result of properly planned and performed maintenance on tritium process systems.

The use of health risk assessment to estimate desirable sampling detection limits.

The inclusion of non-detected chemicals in a health risk assessment may lead, in some cases, to estimated risks that exceed regulatory thresholds, because one must use the detection limit or half of the detection limit. This study presents a methodology which will allow one to estimate appropriate detection limits by conducting a health risk assessment prior to the source sampling program. The advantages and shortcomings of various levels of detail in the risk assessment to determine those detection limits are discussed. The application of the methodology is demonstrated with a case study of the potential health effects of power plant stack emissions.

Thermal Encapsulation of Metals in Superfund Soils

Abstract Superfund sites frequently contain both heavy metals and organic hazardous waste. If not properly controlled, the metals may be changed to a more leachable form and may also be emitted to the atmosphere via the exhaust stack. This paper documents a batch kiln R&D test program to solve these metal-related problems. It was performed under the U.S. EPA’s SITE (Superfund Innovative Technology Evaluation) Emerging Technology Program. Allis Mineral Systems has developed the Thermal Encapsulation Process. Metals with limits set by EPA’s TCLP (Toxicity Characteristic Leaching Procedure) test and BIF (boiler and industrial furnace) stack emission regulations, such as cadmium, chromium, and lead, are the initial target of this process. This process, while unproven in these areas, may also apply to mixed waste (EPA hazardous waste/low-level radioactive wastes) and may also benefit commercial hazardous waste or Superfund thermal treatment systems. The results of the SITE tests were positive: strong, durable ...

Elemental characterization of coal ash and its leachates using sequential extraction techniques

Over 50 million tons of coal ash are produced annually in North America. Technological improvements in air pollution control have decreased stack emissions but have also increased contaminant concentrations in the ash of coal-fired boiler applications. The leaching of heavy metals and other elements during regulatory tests may cause coal ash ro be classified as hazardous waste, complicating land disposal. The hazardous nature of coal ash remains unclear because current toxicity tests fail to effectively characterize the elemental distribution and chemical solubility of trace metals in the landfill environment. Leaching characteristics of ash samples can be investigated with various laboratory extraction procedures in association with multi-elemental analytical techniques (e.g., neutron activation analysis and inductively coupled plasma-atomic emission spectroscopy). Such methods provide more thorough analyses of coal ash leaching dynamics than the regulatory assessments can demonstrate. Regulatory elements including Ag, As, Ba, Cd, Cr, Hg, Pb, and Se were shown to remain in largely insoluble forms while elements such as B and S leached at higher levels. Experimental results may assist operators of coal-fired boiler industries in selecting coal types and disposal options to curtail the leaching of potentially toxic inorganic contaminants.

First industrial experience with partial waste gas recirculation in a sinter plant

Hoogovens will have to satisfy very strict requirements for the stack emission from the sinter plant. Reduction of the amount of stack gas to be cleaned could be one of the step : a concept developed by Lurgi. As pot grate trials can only provide limited information, one of these sinterstrands has been covered with a hood into which a part of the stack gas is recycled. The first operating experience will be described.

Mercury stack emissions from U.S. electric utility power plants

Mercury stack emissions from U.S. electric utility power plants

The role of multiple regression and exploratory data analysis in the development of leukemia incidence risk models for comparison of radionuclide air stack emissions from nuclear and coal power industries

Risks associated with power generation must be identified to make intelligent choices between alternate power technologies. Radionuclide air stack emissions for a single coal plant and a single nuclear plant are used to compute the single plant leukemia incidence risk and total industry leukemia incidence risk. Leukemia incidence is the response variable as a function of radionuclide bone dose for the six proposed dose response curves considered. During normal operation a coal plant has higher radionuclide emissions than a nuclear plant and the coal industry has a higher leukaemia incidence risk than the nuclear industry, unless a nuclear accident occurs. Variation of nuclear accident size allows quantification of the impact of accidents on the total industry leukemia incidence risk comparison. The leukemia incidence risk is quantified as the number of accidents of a given size for the nuclear industry leukemia incidence risk to equal the coal industry leukemia incidence risk. The general linear model is used to develop equations that relate the accident frequency required for equal industry risks to the magnitude of the nuclear emission. Exploratory data analysis revealed that the relationship between the natural log of accident number versus the natural log of accident size is linear.

Use of Fourier transform infrared spectrometry as a continuous emission monitor

This paper describes the use of a Fourier transfer infrared (FTIR) spectrometer, integrated with a sampling system and a control software, as a continuous emission monitor (CEM) for on-line measurement of most volatile organic and some inorganic compounds from various gas emissions. The time response of the system was tested experimentally, and can be approximated by a complete mixing model. In order to validate the measurement accuracy of the system, spiking tests are suggested. This paper discusses considerations in designing the spiking test and analyzing the spiking results. Field test results show that the FTIR-CEM has a stable performance and can be applied to stack emission monitoring, process monitoring, and unknown HAPs identification in many thermal treatment processes.

The role of multiple regression of exploratory data analysis in the development of leukemia incidence risk models for comparison of radionuclide air stack emissions from nuclear and coal power industries

The role of multiple regression of exploratory data analysis in the development of leukemia incidence risk models for comparison of radionuclide air stack emissions from nuclear and coal power industries

Arc plasmatrons for burning fuel in industrial installations

The problem of energy consumption/energy efficiency in industrial processes, particularly at thermotechnical installations, is discussed. The method of plasma thermochemical preparation and combustion of fuel is discussed as an effective means of utilizing energy resources and reducing emissions of nitrogen oxides in stack gases. Energy consumption could be reduced by up to 20% by th above method by ensurong complete combustion of fuel. Stack emissions could be reduced up to 30-40%

Mortality at an automotive stamping and assembly complex

Mortality among workers with 2 or more years employment at an automotive stamping and assembly complex was analyzed using standardized mortality ratio (SMR), proportional mortality ratio (PMR), and mortality odds ratio (MOR) methods. The stamping plant all-cause SMR was considerably less than expected (for white men, SMR = 0.65, 95% confidence interval [CI] = 0.54, 0.79; for black men, SMR = 0.73, 95% CI = 0.45, 1.13), indicating a strong "healthy worker effect." However, six stomach cancer deaths produced an SMR of 4.4 (95% CI = 1.62, 9.6) and a PMR of 6.8 (95% CI = 2.5, 15). Based on small numbers of cases, stomach cancer risk increased with duration in stamping and tool and die departments where exposures included drawing compound and other metalworking fluids. Stamping plant lung cancer mortality was elevated among production welders (MOR = 2.7, 95% CI = 1.2, 6.3), and increased with duration. Welding was performed on sheet metal sometimes coated with drawing compound, primer, or epoxy resin adhesive. As was observed for the stamping plant, the all-cause SMR for the two assembly plants was unusually low (for white men, SMR = 0.64, 95% CI = 0.56, 0.73; for black men, SMR = 0.57, 95% CI = 0.43, 0.75). The lung cancer SMR was not elevated but the MOR was (MOR = 1.58, 95% CI = 1.1, 2.4) and increased with assembly plant duration (MOR = 1.78, 95% CI = 1.02, 3.1, at mean duration of cases). In the assembly plants, paint oven stack emissions had been reintroduced into the plant by the ventilation system.

Trace elements in coal and their dispersal during combustion

This is partly a review and partly the results of some experimental work. Results for concentrations of trace elements in samples of coal from 9 mines in about 100 km of one seam show the variability in terms of variance ratios, namely, maximum divided by minimum values. The dispersal of trace elements during combustion is dealt with in detail, the stress being on the fate of trace elements in stack emissions and in residues (flyash and bottom ash). Results of a 4 yr investigation of the deposition of trace elements in the environs of an Australian power plant showed decreasing amounts with distance from the stack and variations at different locations with time. In general, the amounts of trace elements collected were mostly less than the amounts contributed by rock weathering, litter decay and fertilisers. Results are given for the use of germanium to indicate the variations in proportions of flyash in deposition. It is proposed that more information should be obtained for trace elements in deposition and for the leachability of residues at particular power plants. A positive approach to environmental aspects of trace elements in coal is espoused and it is considered unlikely that harmful effects should arise from trace elements in coal if proper care is taken.